AC.2000.J33.0202.R02 Revision 0 3 April 2002

AMOG Consulting A.C.N. 065 475 818

Sea Technology House A.B.N. 12 065 475 818

Monash Business Park Telephone: + 61 3 9558 9077

19 Business Park Drive Facsimile: + 61 3 9558 9880

Notting Hill Victoria 3168 Email: amogmel@amog.com.au

Australia Internet: www.amog.com.au

Hull Fouling as a Vector for the 

Translocation of Marine Organisms

PHASE 3

THE SIGNIFICANCE OF THE 

PROSPECTIVE BAN ON TRIBUTYLTIN 

ANTIFOULING PAINTS ON THE 

INTRODUCTION & TRANSLOCATION 

OF MARINE PESTS IN AUSTRALIA

Report No. 2

April 2002

Submitted to: DEPT OF AGRICULTURE, FISHERIES

AND FORESTRY - AUSTRALIA

Strategic Ballast Water R&D Program

GPO Box 858

Canberra ACT 2601

Attention: Peter Cassells
Phase 3 - The Significance of the Prospective Ban on Tributyltin Antifouling Paints on the Introduction & Translocation of Marine 

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DOCUMENT ISSUE AND DISTRIBUTION

Document Number AC.2000.J33.0202.R02

Document Title Phase 3 - The Significance of the Prospective Ban on Tributyltin 

Antifouling Paings on the Introduction & Translocation of 

Marine Pests in Australia

Client Dept. of Agriculture, Fisheries and Forestry (AFFA)

Job Number AC.2000.J33

Job Title Hull Fouling Research

Copy Number 1

Issue Date Issued Author Checked Authorised

Revision 0 03.04.02

J. Lewis H. Houridis Dr A. Potts

DISTRIBUTION OF COPIES

Number of Copies Location

1 AMOG Consulting (Melbourne office)

1 Marine Science & Ecology

1 AQIS/AFFA

REVISION REGISTER

Page Revision Date Comments
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PREAMBLE

Hull Fouling as a Vector for the Translocation of Marine Organisms is a project initiated by the 

Australian Strategic Ballast Water Research and Development Program (Department of 

Agriculture, Fisheries and Forestry - Australia) to review the current state of knowledge 

concerned with the fouling of ships’ hulls and the potential for marine organisms to be 

transferred, both domestically and internationally, by this pathway. Further, the intent is to 

institute a strategy to develop and implement a hull fouling management module into the 

Australian Ballast Water Decision Support System. The ‘‘Hull Fouling’’ project is divided into 

four phases.

Phase 1 to prepare a definitive report on the status of research into hull fouling as a pathway for 

the introduction of invasive marine species has been completed (AMOG Consulting, 2001).

The main objectives specified for phase three of the project were to conduct a review of the likely 

current and future significance of the proposed IMO ban on tributyltin (TBT) and consider the 

risk of vessels visiting Australian waters with depleted levels of antifoulant. The approach 

specified was to:

• Consult with paint companies and other organisations conducting research into this area in 

order to provide a review of possible alternatives to TBT and their relative costs and 

effectiveness.

• Consider the risk of introduction to Australian waters of invasive marine species via vessels 

with depleted levels of antifoulant.

• Identify gaps in knowledge and therefore risk associated with the proposed TBT ban.

• Identify gaps in knowledge and make recommendations for future research.

The purposes of the other two phases proposed for the project were to:

• Carry out a review of the data available for the Australian Port Surveys and other related 

research and evaluate whether hull type organisms present have resulted from the 

organisms likely to be on ships’ hulls (Phase 2); and

• Develop a strategy to develop an implement a hull management module into the Australian 

Ballast Water Decision Support System (Phase 4). 
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EXECUTIVE SUMMARY

The attachment and growth of marine organisms on the hulls of vessels imposes significant 

operational and economic costs on the vessel operator and antifouling measures are therefore 

needed. Since the mid-18th century, antifouling paints have been the primary method of control 

fouling. These prevent fouling attachment by continuously releasing a biocide from the coating 

surface, which either kills or deters the settling spores or larvae. Up until the 1970s, most 

antifouling paints were based on copper, and the effective life of these paints rarely exceeded 24 

months. At that time the vessel would need to be docked, the spent antifouling coating and 

attached fouling removed, and a new coating applied. 

In the 1960s, organotin compounds were found to be highly effective antifouling biocides and 

subsequent developments led to the formulation of self-polishing copolymer (SPC) antifouling 

paints based on tributyltin (TBT) copolymers. These paint systems could provide effective 

antifouling performance for more than 5 years, and the self-polishing effect generated additional 

operational and fuel savings. However, TBT released from antifouling paints has been found to 

have adverse effects in the marine environment and the International Maritime Organization 

(IMO) recently adopted a new convention to globally ban the application of TBT antifouling 

paints form 1 January 2003.

Hull fouling has been recognised as a significant vector for the introduction of marine species to 

Australia and concerns have been expressed that the ban on TBT antifouling paints may 

heighten the risk of introduction if less effective antifouling systems are used.

The available alternatives to TBT antifouling products are: 

• Conventional copper-based (copper metal, cuprous oxide or cuprous thiocyanate) 

antifouling paints, often containing a secondary biocide such as diuron, chlorothalonil, 

thiram or zineb;

• ‘‘New technology’’ self-polishing copper-based antifouling paints, likely to contain a ‘‘new’’ 

secondary biocide such as zinc pyrithione, copper pyrithione or Sea-Nine 211;

• Silicone-based, ‘‘non-toxic’’ fouling-release coatings;

• Novel coatings based on new ‘‘natural’’ biocides, or having fibrous surfaces; and

• Physical, electronic and chemical deterrents. 

Conventional copper-based coatings do not provide the reliability or effective life of TBT, and 

antifouling protection only for periods up to 36 months is claimed. ‘‘New technology’’ 

copper-based systems have resin systems, which are claimed to self-polish in a similar manner 

to TBT SPC systems and to provide similar performance. Such systems are based on copper 

acrylate, zinc acrylate or silyl polymers. The results from trials and ship applications support 

these claims, and these products should provide antifouling protection matching that provided 

by TBT SPC paints. The ‘‘new technology’’ coatings are more expensive that TBT or conventional 

coatings, but savings in performance should offset this initial expense.
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Fouling release coatings do not prevent fouling by release of a biocide, but instead have surface 

characteristics that minimise the strength of adhesion of attaching organisms. They therefore 

pose no chemical threat to the environment. The most effective fouling release coatings found to 

date are based on silicone compounds. Fouling organisms will attach and grow on these coatings 

under static conditions, but are relatively easy to dislodge. Self-cleaning has been seen on vessels 

which exceed 15 knots. For slower, less active vessels, in-water cleaning is necessary if the hull is 

to be kept fouling-free for when it leaves port. If this is not done, there is a risk of organism 

translocation.

In many countries antifouling paints must be registered, and in Australia this role is performed 

by the National Registration Authority for Veterinary and Agricultural Chemicals (NRA). Every 

antifouling product that contains an ‘‘active’’ must be registered, and all ‘‘actives’’ must be 

approved to ensure they pose no risk to the environment or to public health. Ten actives are 

currently approved for use in antifouling formulations. The registration process can take up to 

15 months or more if a new ‘‘active’’ is used in a formulation. Silicone and other fouling release 

coatings, fibrelock coatings and construction materials such as copper cladding do not require 

registration as they are not considered to contain an ‘‘active’’ antifouling agent. Only one of the 

‘‘new technology’’ copper-based coatings, of which 17 or more are commercially-available for 

application overseas, is registered and therefore available for application to vessels docked in 

Australian shipyards.

In the short to medium term, ship owners will turn to copper-based coatings to replace TBT 

antifouling paints. ‘New technology’’ coatings are expected to provide the necessary 

performance and to be generally applied to vessels with long docking cycles. Vessels with 

shorter docking cycles (< 3 years) may utilise cheaper, conventional copper-based systems, but 

application of ‘‘new technology’’ products to these vessels would still provide operational and 

economic advantages and also reduce the risk of organism translocation. 

Cuprous oxide based systems cannot be safely applied to aluminium hulls, and this sector of the 

maritime industry could be greatly affected by the TBT ban as TBT and cuprous oxide free 

coatings have an effective life of rarely more than two years. Silicone, fouling release coatings 

offer an alternative for this sector, and seem particularly suitable for high-speed catamarans. As 

more antifouling biocides come under scrutiny and are banned or restricted, as seen with the 

recent banning of diuron in the UK and the raising of concerns with respect to copper, fouling 

release coatings may become increasingly the most effective method of fouling control.

The significant research gaps identified related to:

• The limited number of independent, comparative studies of antifouling efficacy and 

performance; and 

• The limited number of viable, environmentally-acceptable antifouling biocides, coatings and 

processes.

The following series of recommendations were seen as ways of improving fouling control on 

vessels and therefore reducing the incidence and risk of translocation and introduction of exotic 

marine species to Australia in hull fouling communities. 
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With respect to antifouling registration in Australia, it is recommended that:

• The registration process be reviewed with respect to allowing new, potentially safer and 

more effective commercial products to be granted interim approval, or use under permit, 

until the full registration process can be completed. Such approval or use would be subject 

to availability of certain data, most likely from overseas, that indicates the product is both 

safe and effective, or on the basis of overseas approval; and

• The need to register ‘‘active’’-free antifouling products be investigated to provide some 

warranty of efficacy

With respect to the evaluation and validation of antifouling product performance, it is 

recommended that:

• The current antifouling patch trial project be reviewed to determine how future, similar 

programs can be introduced to ensure best available antifouling products are available and 

promoted for use by all ship and boat owners; and

• An education program is established to ensure boat and ship operators are fully cognisant of 

the options, performance and efficacy of different antifouling products to ensure optimum 

fouling control. 

In anticipation of increases use of fouling release coatings, it is recommended that attention be 

directed to the development of hull management practices including:

• Development of mechanised, non-abrasive cleaning technology for use in-water;

• Clearer understanding of performance with respect to optimum application techniques, 

vessel speeds, and surface degradation; and

• Development of cleaning regimes to ensure vessel hulls are maintained fouling-free both to 

optimise ship performance and to minimise the risk of organism translocation. 

With the limited options currently available for antifouling control, and continuing concerns on 

the environmental impact of antifouling biocide and the likelihood that more stringent 

restrictions are likely, it is also recommended that active support be provided to:

• Australian research on biofouling processes and new methods of fouling control; and 

• Studies on the environmental fate and ecotoxicology of antifouling agents relevant to the 

Australian marine environment.

A recommendation of the Phase 1 Report (AMOG Consulting 2001) was the creation of a 

cooperative research program or centre, which would bring together universities, paint 

companies, shipping companies, boating organisations and other research organisations with a 

specific interest in hull fouling and its prevention. This would facilitate research with outcomes 

offering economic benefits to the maritime industry, while at the same time reducing the risks of 

marine pest introductions and translocations in Australia. A number of the programs 

recommended in this Phase 3 report could be successfully undertaken or coordinated from such 

as program or centre. 
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TABLE OF CONTENTS

1. PREVENTION OF FOULING ON VESSELS: A BRIEF HISTORY. . . . . . . . . . . . . . . 1

2. ANTIFOULING COATING TYPES. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.1 BIOCIDAL ANTIFOULING COATINGS . . . . . . . . . . . . . . . . . . . . . . . 5

2.1.1 Metal Sheathing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

2.1.2 Conventional Antifouling Paint Types . . . . . . . . . . . . . . . . . . . . . . . . 6

2.1.2.1 Soluble Matrix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2.1.2.2 Contact Leaching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

2.1.3 Self-Polishing Copolymer (SPC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

2.1.4 Controlled Depletion Polymer (CDP) . . . . . . . . . . . . . . . . . . . . . . . . 10

2.1.5 ‘‘New Technology’’ Tin-Free Antifouling Paints . . . . . . . . . . . . . . . . . . 10

2.2 FOULING-RELEASE COATINGS . . . . . . . . . . . . . . . . . . . . . . . . . . 11

2.3 NON-TOXIC AND NON-LEACHING ACTIVE COATINGS. . . . . . . . . . . 11

3. ANTIFOULING BIOCIDES & OTHER ACTIVE COMPONENTS . . . . . . . . . . . . . 13

 3.1 ORGANOTIN COMPOUNDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

3.2 COPPER AND COPPER COMPOUNDS . . . . . . . . . . . . . . . . . . . . . . 14

3.2.1 Cuprous Oxide . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

3.2.2 Metallic Copper. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

3.2.3 Copper Thiocyanate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

3.2.4 Copper Pyrithione . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

3.2.5 Other Copper Compounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

3.3 OTHER METALS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

3.4 ORGANIC BIOCIDES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

3.4.1 Diuron . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

3.4.2 Dithiocarbamates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

3.4.3 Chlorothalonil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

3.4.4 Irgarol 1051 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
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3.4.5 Sea-Nine 211 (C-9211, Kathon 5287, RH-287) . . . . . . . . . . . . . . . . . . . . 20

3.4.6 Zinc Pyrithione . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

3.4.7 Other Booster Biocides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

3.5 NATURAL BIOCIDES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

3.5.1 Natural Antifouling Defences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

3.5.2 Natural Antifouling Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

3.6 PAINT ADDITIVES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

4. FOULING RELEASE COATINGS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

4.1 FLUORINATED POLYMER COATINGS . . . . . . . . . . . . . . . . . . . . . . 29

4.2 SILICONE COATINGS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

5. NOVEL COATINGS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

5.1 FIBRE COATINGS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

5.2 Electromagnetic Coatings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

6. CURRENT AND PROSPECTIVE LEGISLATION ON ANTIFOULING PAINT USAGE. 39

6.1 STATE CONTROLS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

6.2 NATIONAL REGULATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

6.2.1 NRA Registration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

6.2.2 ANZECC Code of Practice. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

6.2.3 Australian Government Policy . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

6.2.4 International Regulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

6.3 ANTIFOULING REGULATION & REGISTRATION IN OTHER COUNTRIES 42

6.3.1 United Kingdom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

6.3.2 Europe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

6.3.3 United States/Canada . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

6.3.4 Asia/ New Zealand/South Africa . . . . . . . . . . . . . . . . . . . . . . . . . . 45
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6.4 PROSPECTIVE RESTRICTIONS AND REGULATIONS ON ANTIFOULING 

COATINGS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

7. ALTERNATIVES TO TBT ANTIFOULING COATINGS. . . . . . . . . . . . . . . . . . . 48

7.1 REQUIREMENTS OF THE BOATING & SHIPPING INDUSTRY . . . . . . . . 48

7.2 TBT-FREE ANTIFOULING COATINGS. . . . . . . . . . . . . . . . . . . . . . . 49

7.2.1 Conventional TBT-Free Antifouling Coatings. . . . . . . . . . . . . . . . . . . . 51

7.2.2 ‘‘New Technology’’ Antifouling Coatings . . . . . . . . . . . . . . . . . . . . . . 52

7.3 BIOCIDE-FREE ALTERNATIVES . . . . . . . . . . . . . . . . . . . . . . . . . . 60

7.3.1 Fouling-Release Coatings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

7.3.2 Fibre Coatings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

7.3.3 Biocide-Free Self-Polishing Coatings . . . . . . . . . . . . . . . . . . . . . . . . . 67

7.3.4 Scrubbable and Inert Coatings . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

7.4 METALLIC COATINGS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

7.5 PROSPECTS FOR OTHER ANTIFOULING TECHNOLOGIES. . . . . . . . . . 69

7.5.1 New Biocides . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

7.5.2 Minimally Adhesive Surfaces and Surface Micro-topography . . . . . . . . . . 70

7.5.3 Natural Antifoulants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

7.5.4 Physical, Electronic & Chemical Deterrents . . . . . . . . . . . . . . . . . . . . . 74

8. THE IMPACT OF THE BAN ON TBT COATINGS AND ITS IMPACT ON THE 

INTRODUCTION OF EXOTIC MARINE SPECIES . . . . . . . . . . . . . . . . . . . . . 76

9. CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

10. RESEARCH GAPS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84

11. RECOMMENDATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
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11.1 Registration and Approval of Antifouling Products . . . . . . . . . . . . . . . . 85

11.2 Evaluation and Validation of Antifouling Product Performance . . . . . . . . 85

11.3 Hull Maintenance Practices for Fouling Release Coatings . . . . . . . . . . . . . 86

11.4 Research and Development of New Antifouling Technologies . . . . . . . . . . 86

11.5 Cooperative Research on Fouling Prevention . . . . . . . . . . . . . . . . . . . . 87

12. REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

13. PERSONAL CONTACTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113

APPENDIX 1 114

Antifouling Products Registered by the National Registration Authority in Australia . . . . . 115

APPENDIX 2 117

List of ‘‘New Technology’’ Copper-based Antifouling Coatings . . . . . . . . . . . . . . . . . . 117

APPENDIX 3 1

List of Commercial, Biocide-Free, Fouling Release Coatings . . . . . . . . . . . . . . . . . . . . . 1
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LIST OF TABLES

Table 1 The registration status of antifouling biocides in Australia (L. Cahill, pers. comm.)

40

Table 2 List of NRA approved antifouling actives and their usage in registered antifouling 

products.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Table 3 List of UK approved antifouling actives and their usage in registered antifouling 

products. (* approval of products containing diuron has since been revoked) . 50

Table 4 List of US approved antifouling actives and their usage in registered antifouling 

products.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

Table 5 List of ‘‘new technology’’ copper-based antifouling coatings.. . . . . . . . . . . 53

Table 6 Percentage of all vessels with respective antifouling ratings. . . . . . . . . . . . 56

Table 7 Percentage of vessels within scheme life with respective antifouling ratings.. . 57

Table 8 Comparative costs per tanker of TBT-based paints and TBT-free alternatives 

(Source: ORTEPA)) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59

Table 9 Fouling release coatings available on the world market . . . . . . . . . . . . . . 60

Table 10 Fouling release systems applied as test patches to USN ships . . . . . . . . . . 62

Table 11 Pros and cons of different antifouling types (from Chapman, 1998) . . . . . . . 78
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LIST OF FIGURES

Figure 1 Diagrammatic representation of soluble matrix copper antifouling paint (from 

Callow, 1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Figure 2 Diagrammatic representation of contact leaching copper antifouling paint (from 

Callow, 1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Figure 3 Diagrammatic representation of self-polishing copolymer (SPC) antifouling paint 

(1-3 represent coats of paint) (from Callow, 1990) . . . . . . . . . . . . . . . . . . 9

Figure 4 DWT and dry-dock interval for the 1980’s vs. 1990’s (from Anderson, 1998) . . 48

Figure 5 Percentage of ships satisfactory vs. in-service period (from Anderson, 1998) . . 51

Figure 6 Percentage of ships satisfactory for copper acrylate SPC vs. TBT SPC (from 

Anderson, 1998). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
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ABBREVIATIONS & ACRONYMS

AHMV Automated hull maintenance vehicle

AMOG AMOG Consulting

ANZECC Australian and New Zealand Environment and Conservation 

Council

AQIS Australian Quarantine Inspection Service

ASTM American Society for Testing and Materials

BCL Benzalkonium chloride

BP British Petroleum

BPD Biocide Products Directive

CAEP Copper Antifouling Environmental Program

CDC Controlled depletion copper

CDP Controlled depletion polymer

CPT Copper pyrithione

DBTDL Dibutyltin dilaurate

DRA Defence Research Agency (UK)

DSTO Defence Science and Technology Organisation (Australia)

DWT Dead weight tonnage

EPA Environmental Protection Agency (US)

EQS Environmental quality standard

EU European Union

FIFRA Federal Insecticide, Fungicide and Rodenticide Act (US)

FR Fouling release

FRP Fibre reinforced plastics

HEMA Hydroxyethyl methacrylate

HSE Health and Safety Executive (UK)

IMO International Maritime Organization

ISO International Standards Organization

LNG Liquid natural gas

LPG Liquid petroleum gas

MER Marine Engineers Review

MFO Mixed function oxygenase

NOEC No effect concentration

NRA National Registration Authority for Agricultural & Veterinary 

Chemicals

NSWC Naval Surface Warfare Center (US)

OECD Organisation for Economic Cooperation and Development

ORTEPA Organotin Environmental Program Association

PDMDPS Polydimethyldiphenylsilicone

PDMS Polydimethylsiloxane

PEC Predicted environmental concentration

PHEMA Polyhydroxyethyl methacrylate

PNEC Predicted no effect concentration

PNIPAAM Poly(N-isopropylacrylamide)

PSA Pyridine sulphonic acid

PTFE Polytetrafluoroethylene

PVC Polyvinyl chloride

RAN Royal Australian Navy

RTV Room temperature vulcanisation
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SPC Self-polishing copolymer

TBT Tributyltin

TBTO Tributyltin oxide

TCMC Pyridine Tetrachloromethylsulphonyl pyridine

TMTB Thiocyanomethylthiobenzothiazole

UNSW University of New South Wales

VOC Volatile organic compound

VOHAP Volatile organic hazardous air pollutants

WWF World Wildlife Fund

ZPT Zinc pyrithione
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1. PREVENTION OF FOULING ON VESSELS: A BRIEF HISTORY

The history of practices to prevent the growth of fouling organisms on ship and boat 

hulls and the development of antifouling paints has been reviewed by a number of 

authors (Laidlow, 1952; Lunn, 1974; Callow, 1990, 1996, 1999; Bennett, 1996; Lewis, 

1998). However, this will be briefly recounted here as background to the ban on 

antifouling systems containing tributyltin (TBT) and the availability of alternatives.

Until the latter part of the eighteenth century, the only effective method of controlling 

fouling was to regularly beach vessels to allow manual removal of the fouling growth. 

The first authenticated protective treatment applied to a vessel was the experimental 

attachment of copper sheet to the frigate HMS Alarm in 1758. This experiment was a 

success and, by 1780, copper sheathing was in general use throughout the British Navy 

(Laidlow, 1952). However, copper sheathing could not be used on the iron-hulled ships 

constructed in the early nineteenth century because of the corrosive action of copper on 

iron.

The weight of fouling on unprotected hulls made the ships unmanoeuvrable and 

unseaworthy and various alternatives to copper sheathing were tried, including 

sheathings of zinc, lead, nickel, galvanised iron and alloys of antimony, zinc and tin 

(Callow, 1996). Antifouling paints offered a solution and, by 1865, more than 300 

patents for antifouling compositions had been issued in England alone, most of which 

were utterly useless (Hare, 1993). The first practical compositions to be widely used 

were hot soap compositions containing copper sulphate. Subsequently antifouling 

paints incorporating cuprous oxide, mercuric oxide or arsenic in shellac varnish or a 

resin matrix with turpentine, naphtha or benzene as solvents were developed (Callow, 

1996). 

Although many non-chemical methods, including ultrasonics, electric currents, 

magnetic fields, and optical methods have been proposed as means of preventing 

fouling attachment (Fischer et al, 1984), toxic antifouling coatings are recognised as the 

most cost effective means of fouling control (Little & DePalma, 1988; Callow, 1996; 

Hare, 2000). Advantages include ease of manufacture, high speed and low cost 

application, durability, and applicability to a variety of structural forms and substrates. 

Despite continuous research seeking effective antifouling biocides, relatively few were 

found. In the early 1950s mercury and arsenic were considered alongside copper as 

primary antifouling biocides for use in coatings. However, these were subsequently 

banned on occupational health and safety grounds (Fischer et al., 1984). Then, in the 

mid-1950s, organotin compounds were found to have broad-spectrum biocidal 

properties and, by the early 1960s, their excellent antifouling properties were being 

commercialised (Evans, 1981; Gitlitz, 1981). 

When first introduced, organotin compounds were thought to be environmentally safe 

because they degraded rapidly to harmless inorganic forms of tin (Evans & Hill, 1983). 

In the sea, tributyltin is broken down microbially, first to the much less toxic dibutyltin, 

then to monobutyltin, and ultimately to inorganic tin. However, in the late 1970s, 

Pacific oysters grown commercially near small boat harbours and marinas in France 

were found to have a high incidence of shell malformation that affected their 

marketability and survival (Alzieu et al, 1980). The oysters were found to contain 

elevated tin levels and the malformations were subsequently confirmed to be due to 
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low levels of TBT in the water. As a result, in 1982, the French government became the 

first authority to legislate to restrict the use of organotin paints. 

Since that time, substantial research has been undertaken worldwide to document 

levels of TBT in the marine environment, to evaluate its environmental effects, to assess 

its toxicity to a broad range of marine organisms, and to determine more closely its fate 

and the process of degradation (Champ & Seligman, 1996; de Mora, 1996). In summary, 

TBT contamination was found to occur almost universally in inshore regions with 

shipping or boating activity. Highest levels were commonly associated with high 

densities of recreational craft or near boat and ship repair facilities, particularly in 

semi-enclosed waters such as small boat harbours and marinas that had limited water 

exchange with more open waters. 

Malformed oysters were found to occur in a number of countries, and the growth and 

survival of a number of different types of shellfish were also affected. Perhaps the most 

sensitive indicator of TBT contamination is the incidence of a condition known as 

imposex in various species of gastropod molluscs, such as the European mud whelk 

(Gibbs & Bryan, 1996a, 1996b). Imposex is the development of male characteristics in 

female individuals and in its most severe form can lead to sterility in some species. It 

has been postulated that levels of TBT in seawater as low as 1 ng l

-1

 (1 part per trillion) 

can induce imposex in the European mud whelk. In Australia malformed Pacific 

oysters were found in Tasmania, similar abnormalities were found in Sydney rock 

oysters (Batley & Scammell, 1991) and imposex has been observed in shellfish in NSW, 

Victoria, South Australia, Western Australia and Queensland (Kohn & Almasi, 1993; 

Nias et al., 1993; Foale, 1993; Wilson et al., 1993: Reitsema & Spickett, 1999; Rees et al., 

2001). 

Many other marine organisms were affected by TBT, but none was as sensitive as the 

shellfish. Differences in the toxicity of TBT between various animal and plant species 

have been attributed to the varying abilities of organisms to metabolise the compound. 

For instance, finfish and crabs are able to metabolise accumulated TBT relatively 

effectively via the mixed function oxygenase (MFO) system, and this system may confer 

some resistance to TBT toxicity. However, shellfish have very low MFO activity and 

this correlates well with their limited ability to metabolise TBT (Lee, 1996).

Studies on the degradation of TBT in marine waters confirmed that it does sequentially 

debutylise to ultimately form inorganic tin. In San Diego Bay waters, the half-life for 

TBT was determined to be between 6 and 19 days with microbial metabolism 

implicated as the principal degradation pathway (Seligman et al., 1986). Degradation 

within sediments appears to be much slower, with a half-life of 162 days estimated for 

San Diego Bay (Stang & Seligman, 1986) and up to 1.85 years in New Zealand (de Mora 

et al., 1989).

The above studies suggested that the marine environment has the capacity to cope with 

some TBT input, as long as input levels were not too high. However, it is apparent 

from many surveys and observations on shellfish malformations that the unrestricted 

use of TBT paints caused this capacity to be exceeded, particularly in inshore areas with 

high concentrations of small craft and poor water exchange. As a consequence, 

management actions to restrict the input of TBT into the marine environment were 

widely introduced. Three approaches were taken: 
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• To restrict or prohibit the use of TBT paints on small craft;

• To prevent or control the release of TBT wastes from dockyards and slipway; and

• To impose a maximum permissible TBT release rate on antifouling paints applied 

to large vessels. 

Such restrictions included bans on the use of TBT on vessels less than 25 m in length in 

Norway, Finland, South Africa and countries of the European Union, a 4 μg TBT cm-2

day-1 release rate limit in addition to a < 25 m ban in the United States, Canada and 

Sweden, a 5 μg TBT cm-2 day-1 release rate limit in addition to a <25 m ban in most 

States of Australia, and a total ban on all TBT use in Japan and New Zealand.

These controls proved effective in many regions. For example, in France tin levels in 

areas of concern were 5 to 10 times lower in 1985 than in 1982, and there was a 

concomitant decrease in organotin levels within oyster tissues. Over the same period 

the percentage of oysters with shell abnormalities dropped from 100% to less than 40%, 

while the incidence of acute form abnormalities dropped from a peak of 91% to less 

than 5% (Alzieu, 1986). The incidence of imposex declined (Evans et al., 1996; Evans, 

1999), and in Australia oyster growth returned to normal, with TBT barely detectable in 

their tissues (Batley, 1995). 

Restrictions imposed on the use of TBT on small craft were clearly justifiable. Marinas 

and moorings for small craft were often close to shell fisheries or native marine 

communities sensitive to TBT effects. Furthermore, the high boat densities in shallow 

and sheltered waters with poor water exchange often led to elevated TBT levels in 

surrounding waters. Practices in shipyards and slipways also contributed significantly 

to environmental contamination. Paint wastes, from both blasting and painting 

processes, were invariably washed into the sea and, particularly where paint chips or 

flakes incorporated into sediments, contamination is likely to persist for many years. 

For large shipping arguments for and against controls on antifoulings containing TBT 

were less clear-cut, from both an environmental and economic viewpoint (ORTEPA, 

1990). TBT paints continued to be used on large vessels as tin-free alternatives were not 

considered to provide equivalent performance in terms of effective life, polishing 

characteristics, or coating durability (Anderson, 1993). However the search for 

alternative, more environmentally acceptable biocide and antifouling systems and other 

means of controlling fouling continued in earnest, and the research has appeared to be 

successful. 

While, as noted above, the negative impacts of TBT were observed to diminish in many 

inshore regions, impacts attributable to TBT became more widely reported in offshore 

regions and significant levels measured in animals high in the food chain such as seals 

and dolphins (Tanabe, 1999; Takahashi et al., 1998, 2000). In Canada, a recent review of 

the persistence, bioaccumulation and toxicity of TBT in aquatic environments 

concluded it met all criteria for designation as a Track 1 substance under Canada’s 

Toxic Substances Management Policy. This requirement required that measures be 

introduced to virtually eliminate it from the Canadian environment (Maguire, 2000). 

However, because of the long persistence of TBT in sediment, it was predicted that 

there could be a ‘‘legacy problem’’ in some locations in Canada for perhaps 30 to 40 

years after a total ban on TBT use was introduced. 
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In 1999, the Marine Environment Protection Committee of the International Maritime 

Organisation resolved to develop an instrument to reduce the use and impact of 

harmful antifouling coating systems. The first action was to be a global ban on the use 

of TBT antifouling coatings on shipping. In 1998, within its Oceans Policy, the 

Australian Government declared proactive support for the IMO action. Over the years 

from 1999 to 2001, the MEPC developed a Convention to facilitate controls on harmful 

antifouling systems and, in October of this year a Diplomatic Conference approved this 

convention. The Convention bans the application of TBT antifouling paints to shipping 

from 1 January 2003. 

With respect to the phase-out of TBT paints, authors have variously claimed that 

alternatives to TBT are available, but not proven and accepted on a global basis 

(Champ, 2000) or, more strongly, that ‘‘there are no substitutes currently available 

which are as effective as TBT’’ (Abel, 2000), and that a phase-out of TBT-containing 

antifouling paints would have serious economic consequences for the shipping industry 

because no available tin-free antifouling paint could match the 5-year dry-docking 

interval enabled by TBT copolymer paints (Maguire, 2000). If future antifouling 

practices were as ineffective as claimed, the risk of translocation of exotic species as hull 

fouling species would increase and is a concern that warrants serious consideration. As 

a consequence, the alternatives to TBT as an antifouling biocide, to TBT-containing 

antifouling paints, their availability, performance, and potential for use by the shipping 

industry will be explored in the remainder of this report, and an assessment of how 

their use will impact on the risks of introduction and translocation of marine pests in 

Australian waters. 
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2. ANTIFOULING COATING TYPES

2.1 BIOCIDAL ANTIFOULING COATINGS 

Biocidal antifouling coatings prevent or minimise fouling growth by the release of 

active agents from or through the surface of the coating. Until the advent of 

fouling-release coatings, all successful antifouling applications were based on delivery 

of toxins into the very thin (lamella) zone in the vicinity of the paint film (Hare, 2000). 

The thickness of the toxic layer is reduced as the speed of the vessel increases; at 2 knots 

it is about 500 μm, at 20 knots, about 10 μm. 

To be effective the agent must be released continuously, and at a rate sufficient to 

maintain toxic or inhibitory agent concentrations at the surface for all potential fouling 

organisms. The life of a biocidal antifouling coating is therefore limited by the content 

and mechanism for delivery of the biocide. An effective biocidal antifouling coating 

therefore depends on both having a broad-spectrum biocide or biocide package and a 

paint or coating vehicle able to deliver biocide continuously at the required rate over an 

extended period of time. 

2.1.1 Metal Sheathing

Sheathing of vessels with lead was practiced as far back as 700 BC, but lead only 

provided barrier protection against wood borers and had no antifouling effect. Of the 

metals, only copper and its alloys, and silver and zinc were found to resist fouling to a 

degree greater than that of other hard smooth surfaces. Extensive observations 

undertaken in the course of corrosion studies enabled the common metals and alloys to 

be grouped on the probability that they would foul when exposed to the sea (LaQue, 

1948). All the metals and alloys classified as least likely to foul contained more than 64% 

copper. Zinc resisted fouling only temporarily and the protective action of galvanising 

was lost as the surface becomes coated with corrosion products (Redfield, 1952). Silver 

similarly had limited resistance to fouling.

Pure copper, and 70/30 and 90/10 copper-nickel alloys have been demonstrated to 

exhibit long-term antifouling activity (Efird & Anderson, 1975; Efird, 1976; Wildsmith, 

1984). Copper-nickel alloys are less prone to impingement corrosion than pure copper 

and, as a result, have become widely used, particularly for seawater pipework and 

condenser tubing where low pitting attack and resistance to erosion corrosion are 

essential (Chamberlain & Garner, 1988). 90/10 copper-nickel has also become widely 

used because of its antifouling performance, for example as splash-zone sheathing on 

the legs of oil and gas platforms, and as expanded mesh for fish cages and intake 

screens at power stations (Moreton & Glover, 1980; Chamberlain & Garner, 1988). As 

cladding, composite plates are manufactured by hot rolling a thin layer of 

copper-nickel, 1.5-2 mm thick, with a steel backing plate. Sheathing methods have been 

developed to provide a more economical method of hull protection and for retrofit 

situations. Techniques include welding panels of copper-nickel sheet to a steel hull and 

adhesive bonding of copper-nickel foil (Boulton et al., 2001). 
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2.1.2 Conventional Antifouling Paint Types

Antifouling paints can be classified into a number of different types on the basis of the 

way the biocide is dispersed and subsequently released from the paint matrix (Callow, 

1990; Bennett, 1996; Lewis, 1998; Hare, 2000). Conventional, or ‘‘free association’’ paints 

have biocide particles physically dispersed through the paint matrix or binder. When 

the painted surface is immersed, seawater penetrates the paint film and contacts the 

biocide, which dissolves and migrates to the coating surface by simple diffusion. 

Conventional coatings can be of two types: ‘‘soluble matrix’’ and ‘‘contact leaching’’.

2.1.2.1 Soluble Matrix

In soluble matrix antifoulings, the binder is slightly soluble in alkaline seawater and 

fresh biocide is continually released as the binder dissolves. The primary film-forming 

component of conventional soluble matrix antifoulings is gum rosin, a natural product 

obtained from the tree Pinus elliottii (Callow, 1996). Rosin consists of a mixture of acids, 

primarily abietic acid. The acidic rosin slowly dissolves in seawater exposing the 

particles of cuprous oxide and other biocides, which are then released. The rate of 

binder dissolution is a critical aspect for effectiveness. If binder dissolution is too slow, 

the coating will not provide sufficient biocide to be effective; if too fast, the biocide 

reservoir will be too rapidly exhausted, limiting the effective life of the coating (Hare, 

2000).

Soluble matrix systems based on natural rosin are often found to be too soluble at the 

pH of seawater (Hare, 2000). Limed rosin, in which rosin was reacted with lime at high 

temperature to neutralise some of its acidity and decrease solubility, or phenolic 

varnishes or chlorinated rubber have therefore been used to crudely regulate the rate of 

binder dissolution. Unmodified rosin was also very soft, and films made from it were 

quite weak. Modern soluble matrix paints generally contain more rosin and plasticizer, 

and less insoluble polymer, than traditional soluble matrix paints. These deplete more 

consistently, and longer effective lives can be achieved.

However, rosin is also brittle, has limited resistance to UV, and is unstable to oxidation. 

Rosin-based antifoulings can therefore physically degrade if they experience prolonged 

exposure to the atmosphere, such as during ship construction, dockings and along the 

wind and water line (boot top) of vessels. If dried out, the resin becomes hard and 

insoluble in seawater, allowing fouling attachment on re-immersion until solubility is 

regained (Foster, 1994). For similar reasons, traditional soluble matrix antifoulings need 

to be immersed within 24 hours of application. Insoluble co-film forming materials are 

often added to improve the film forming properties, but the presence of these materials 

also leads to the formation of a large leached layer on the surface of the coating after the 

release of the soluble components, resulting in an inefficient polishing action, problems 

in recoating and less controlled release. 
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Figure 1 Diagrammatic representation of soluble matrix copper antifouling paint 

(from Callow, 1990)

Conventional, soluble matrix types of antifouling have been in use since the early 1930s 

but were rarely effective for more than 12-18 months. The relative short lifetime of such 

conventional antifouling coatings is a result of the low mechanical strength of the rosin 

and the ability to build up only relatively thin systems (Kjaer, 1992). The reliance on 

mechanical dissolution, rather than a chemically controlled process, meant that the rate 

of dissolution was not as well controlled and, even for the most modern systems, the 

effective life was considered to be a maximum of 3 years (Anderson, 1998). Also, the 

longer the systems were immersed, the thicker the leached layer that formed at the 

surface as a consequence of the surface erosion not matching the rate of copper 

dissolution from within the film. As the leached layer grew in thickness, the biocide 

release rate at the surface decreased, and effectiveness was compromised.

2.1.2.2 Contact Leaching

Contact leaching antifoulings, also known as insoluble matrix or diffusion coatings, are 

based on insoluble resins, such as chlorinated rubber, acrylic and vinyl. Rosin can also 

be added if a degree of solubility is required (Hare, 2000). The biocide content needs to 

be high enough to ensure that biocide particles are in contact throughout the dry film. 

As biocides and other soluble ingredients are dissolved from the surface layers, 

underlying biocide particles are exposed. These polymer resins had higher mechanical 

strength than rosin, which enabled thicker systems to be applied (Kjaer, 1992). Contact 

leaching antifoulings are hard, mechanically tough antifoulings that do not erode at all 

over time (Anderson, 1998). They have a maximum life of 2 years since, after this time, 

there is too little biocide reaching the surface to be effective. 
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Figure 2 Diagrammatic representation of contact leaching copper antifouling paint 

(from Callow, 1990)

The principle drawbacks with contact leaching coatings were the initially excessive 

biocide release rate, diminishing exponentially with time, and the residual paint matrix 

remaining on the hull surface which contributed to progressive development of hull 

roughness and reduction in ship performance.

2.1.3 Self-Polishing Copolymer (SPC)

A significant advance in antifouling technology took place in the mid-1970s with the 

development of organotin copolymer paints, commonly known as self-polishing 

copolymer (SPC) coatings. In the first organotin paints, the organotin biocide was freely 

associated in the binder of soluble matrix and contact leaching paint types (Hare, 2000) 

but the organotin copolymer provided both the biocide and the acrylic binder for the 

paint. In tributyltin (TBT) copolymer paints, tributyltin methacrylate was usually 

copolymerised with methyl methacrylate (Anderson, 1993; Hunter & Cain, 1996). 

When TBT SPC coatings are immersed, the reaction between seawater and TBT occurs 

rapidly but is confined to the top few nanometres of the surface layer. This is because of 

the hydrophobic nature of the paint film and the bulky nature of both the TBT and the 

copolymer. The TBT is released as result of the hydrolysis of the ester groups that link 

the TBT moiety to the acrylic backbone of the binder (Hare, 2000). The reaction occurs in 

the presence of an alkaline pigment with slight seawater solubility. Zinc oxide is often 

used, but cuprous oxide is another option. Removal of the TBT causes an increase in the 

glass transition temperature of the copolymer, making it brittle, and a change from 

insoluble to soluble. Solubilisation then allows the entangled copolymer chain to be 

removed from the surface, providing both the self-polishing effect and further exposure 

of biocide. Beneath the immediate surface of the film, the non-hydrolysed polymer 

remains quite hydrophobic until it is eventually exposed to the seawater by the 

dissolution of the hydrolysed material above it.
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Figure 3 Diagrammatic representation of self-polishing copolymer (SPC) 

antifouling paint (1-3 represent coats of paint) (from Callow, 1990)

The hydrolysis reaction of the TBT polymer with seawater is confined to a surface layer 

approximately 20 μm thick, which stays thin even with prolonged immersion 

(Anderson, 1998) This proffers an advantage at recoating and repair, as only a high 

pressure fresh water wash is needed to remove this ‘‘leached’’ layer as preparation for 

recoating. The acrylic nature of the coatings also provided strength and durability and 

the coatings could survive wet/dry cycling stresses on boot tops and during ship 

construction and maintenance.

The polishing rate of TBT copolymers is directly proportional to vessels speed, so 

products with different polishing rates could be tailor-made for specific vessel types 

(Anderson, 1998): a slow polishing product could be used on high activity, high speed 

ships, whereas slow vessels, or vessels that remain stationary for long periods, could 

use a fast polishing product.

The advantages of SPC coatings were: 

• An effective life of 5 or more years, proportional to coating thickness; 

• Controlled and constant biocide release rates, unlike the exponential decline of 

biocide release from conventional coatings; 

• Recoat ability; 

• Continuous replacement of active surface; and 

• A self-smoothing or polishing action that results from peaks of roughness eroding 

faster than surrounding areas. 

On fuel savings alone, the economic benefits of organotin copolymer antifoulings were 

substantial and, when considered along with the extended docking intervals and lower 

maintenance costs, shipowners benefited significantly from this new technology. 

Compared with the traditional soluble matrix paints, SPC paints allowed an 

improvement of 300% in dry-docking intervals and an estimated saving to the marine 
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industry in fuel, dry-docking and other costs of some $2500M per annum (Milne, 1991; 

Callow, 1996).

2.1.4 Controlled Depletion Polymer (CDP)

Tin-free polishing/ablative type antifoulings commercialised in the later 1980s utilised 

a dissolution/erosion process for biocide delivery by combining a large proportion of 

seawater-soluble binder with high-performance polymeric ingredients to physically 

control the dissolution rate (Kjaer, 1992). When in contact with seawater the biocides, 

the soluble binder, and the ingredients controlling dissolution, dissolve together and are 

washed away as micro-lumps. The process of ablation is a physical process and as such 

CDP systems are a type of soluble matrix coating. However, the technology enabled 

application of high build systems, which provided an effective life of up to 36 months. 

However, polishing rates of these systems were found to be inconsistent and the active 

surface layer was relatively thick, predisposing the coatings to premature failure by 

formation of insoluble surface precipitates (Lewis, 1998).

2.1.5 ‘‘New Technology’’ Tin-Free Antifouling Paints

A range of ‘‘new technology’’ tin-free coatings offers the promise of effective life and 

polishing performance approaching or matching that of TBT copolymer coatings. These 

coatings are claimed to provide controlled rates of biocide release, reduced thickness of 

active surface layers, and coating stability. These coatings are based on several different 

polymer systems, including copper acrylate, zinc acrylate and silyl polymers. They have 

in a common an acrylic backbone polymer, similar to that in TBT copolymer systems, 

with an ester linkage that undergoes hydrolysis in seawater (Anderson, 1998). 

Copper acrylate polymers act through a chemical hydrolysis mechanism similar to TBT 

copolymer systems (Hunter & Cain, 1996; Ohsugi et al., 1989). The copper acrylate 

polymers react in seawater to release the copper ion and produce an outer soluble layer, 

which dissolves at a constant rate. The result is constant controlled release of the 

biocide. The copper released through hydrolysis of the polymer is, however, 

insufficient to control fouling on its own. All therefore also contain copper oxide as the 

main biocide, and usually an organic booster biocide such as Sea-Nine 211 or ZPT (see 

Sections 3.4.3, 3.4.5).

Similarly, in zinc acrylate copolymers, zinc ions exchange with sodium ions and the 

resulting structure then dissolves in a controlled manner (Taki et al., 2001). The 

dissolution rate can be controlled by varying the concentration of the functional group 

and the hydrophilicity of the polymer. Rotor tests demonstrated that surface roughness 

was similar to organotin self-polishing coatings and smoother than other tin-free 

antifouling paints.

The copper acrylate, zinc acrylate and silyl polymer systems are considered to be true 

self-polishing copolymer systems, in the sense of TBT SPC systems, in that:

• The leached layer remains thin after prolonged immersion;

• There is a characteristic polishing pattern on ships;

• Vessel speed and polishing rate are proportional; and
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• They provide long-term performance on ships (Anderson, 1998).

An alternative approach is the use of hydrolysable zinc carboxylate salt binder 

technology with micro fibre reinforcement (Hempels in Anon., 1999b). The polishing is 

said to be controlled by the reaction of the binder with seawater through ion exchange. 

The zinc carboxylate polymer salt binder has a low hydrophilic level but, through 

exchange of the zinc ions for sodium ions from the seawater, a thin reactive surface 

layer becomes water soluble. When this hydrolysed surface layer is subsequently 

dissolved, the biocides are released. The polishing rate can be adjusted by 

modifications within the polymer chains. The micro fibres make the coating more 

flexible and impact resistant, addressing the poor mechanical properties often exhibited 

by conventional tin-free coatings that crack and peel.

Kuo et al. (1999) report on the development and testing of surface-fragmenting, 

self-polishing tin-free antifouling coatings. In these coatings, instead of side chains of 

the copolymer hydrolysing, the hydrolysable group is built into the backbone of the 

cross linked copolymer. When the copolymer hydrolyses at the film/water interface, it 

fragments into small pieces to effect polishing. 

2.2 FOULING-RELEASE COATINGS

Considerable attention in recent decades has focused on the concept of a non-biocidal 

and non-toxic coating system which has surface properties that prevent the secure 

adhesion and attachment of fouling organisms; i.e. non-stick coatings. The objective for 

these ‘‘fouling release’’ or ‘‘minimally adhesive’’ surfaces was to create surface 

characteristics which reduce the adhesion strength of attaching organisms to the point 

where the organism detaches under its own weight as it grows, or is dislodged by water 

movement as, for example, when a ship moves through the water. Significant 

developments have occurred in this field and, in 1997, there were about 40 patents 

registered (Watermann et al., 1997). A number of these products are now commercially 

available.

The major class of candidate fouling release coatings is a group of synthetic polymers 

and copolymers generally called low surface energy (Baier & Meyer, 1994). The surfaces 

of these are free of groups which, at oceanic ionic strengths, are charged either 

positively or negatively. The initial focus in the development of fouling release coatings 

was on fluorinated coatings, but interest subsequently moved to silicone polymers 

(Brady et al., 1987; Bultman & Griffith, 1994).

Fouling release coatings are discussed in more detail in Section 4.

2.3 NON-TOXIC AND NON-LEACHING ACTIVE COATINGS

Biocide-free self-polishing coatings have been developed which utilise similar 

chemistry and technology to the TBT and tin-free, copper-based self-polishing coatings 

(Watermann et al., 2001a, 2001b). In non-toxic SPCs, a non-toxic compound is 

substituted for the copolymer bound biocide (i.e. the TBT monomer in the TBT 

copolymer). The hydrolysis process is identical. Methacrylate and several specially 

designed epoxies have been used to create non-biocidal self-polishing coatings. The 
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objective of these is to create an active, polishing surface that would be too unstable for 

fouling to remain attached.

Biological and biochemical processes with potential for preventing fouling settlement 

have been proposed as an alternative to using toxic compounds. These include the 

dissolution of adhesive substances by enzymes, intervention in metabolic processes, 

adhesive synthesis or calcium transport, competitive inhibition of receptors, and 

negative chemotaxis (Abarzua & Jakubowski, 1995) The potential of non-leaching 

biocides has also been suggested (Clarkson & Evans, 1993). These are attached to a 

surface and exert a toxic effect on organisms that contact the surface, but without the 

biocide being released into the surrounding environment. If this approach proved 

effective, the total quantity used would be small, and the amount released into the 

environment greatly reduced compared to conventional antifoulants, thus creating a 

cost-effective, environmentally acceptable system. 

Non-leaching biocides (NLBs) are toxins held onto the surface to deter fouling 

organisms, and are not leached into the surrounding environment (Clarkson & Evans, 

1993). The antifouling potential of quaternary ammonium salts as NLBs has been 

investigated (Mellouki et al.. 1989). The salts were grafted on to a vinyl copolymer by 

means of a covalent non−hydrolysable bond, and did not diffuse into the environment.

After four months immersion only bacteria were present in the microbial films; diatoms 

and cyanobacteria were absent. 

Clarkson & Evans (1993, 1995b) assessed DC5700 as a potential non-leaching biocide. 

However, the compound leached from the surfaces, whether bonded via a silane 

coupling agent or incorporated into a silicone elastomer. These authors concluded that, 

with the current state of knowledge, the concept of NLBs, although theoretically 

desirable, was found in practice impossible to achieve. 

The use of non-toxic organic repellents as antifoulants has been proposed. Sodium 

benzoate has been found to be effective in preventing barnacle settlement on soluble 

matrix paints (Vetere et al., 1999). The compound also retarded the growth of the green 

macroalga Enteromorpha, and diminished the settlement of tube building amphipods. 

The effect of barnacles was considered to be the larvae either being repelled and 

swimming away, or a narcotic effect of the benzoate causing the larvae to become 

sluggish. 

Some promising research has also been undertaken on neurotransmitter blockers to 

prevent the settlement and metamorphosis of barnacles and mussels (Yamamoto et al., 

1998). Larval attachment and metamorphosis is influenced by a range of environmental 

factors and larval signal transduction and neurotransmission systems are integral to 

this process. Interference with neurotransmission is seen as a potential non-toxic 

antifouling mechanism.
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3. ANTIFOULING BIOCIDES & OTHER ACTIVE COMPONENTS

Despite intensive research for more than a century, relatively few effective antifouling 

biocides have been found to have the necessary combination of physical, chemical and 

toxicological properties to make them effective antifoulants. Biocides must react with 

seawater in such a way to enable consistent, controlled release from the paint film of the 

active component; they must also be toxic, or have a deterrent effect on the immense 

diversity of potential fouling organisms, yet not cause toxic effects to non-target species 

after release. The characteristics of an ideal antifouling agent were summarised by 

Jacobson (1998) as:

• Efficacy in the control of organisms on a ship’s submerged hull;

• Rapid degradation in the environment;

• Rapid partitioning in the environment resulting in limited bioavailability to 

non-target organisms;

• Minimal bioaccumulation of toxicologically significant compounds; and

• Minimal toxicity to non-target organisms at concentrations present in the 

environment.

3.1 ORGANOTIN COMPOUNDS

As previously mentioned, organotin compounds were found to have broad-spectrum 

biocidal properties in the mid 1950s and, by the early 1960s, their excellent antifouling 

properties were being commercialised (Evans, 1981; Gitlitz, 1981). The first organotin 

antifoulings were free-association paints, containing tributyltin oxide, tributyltin 

fluoride or triphenyltin fluoride (Evans, 1987).

Of the organotins, tributyltin compounds were considered to offer the widest 

separation between antifouling properties and mammalian toxicity. Tributyltin tin 

oxide is a liquid and was initially used mainly in coatings where relatively short-term 

protection was required as its leaching rate was high. Tributyltin fluoride, a white solid, 

was used in longer life paints. Triphenyltin compounds, including the fluoride, chloride 

and hydroxide, were also used, as were tripropyltin compounds. The latter are excellent 

fungicides and broad-spectrum bacteriocides and were used in combination with TBTO 

to broaden the spectrum of effectiveness (Evans & Hill, 1983). 

Both soluble matrix and contact leaching antifouling coatings were formulated using 

free-association trialkyltin compounds. However, these all had relatively high TBT 

release rates and were widely banned by the introduction of regulations restricting 

permissible release rates to 4 or 5 μg cm-2 day-1.

Long-term performance of organotin antifouling paints was achieved through the 

development of organometallic copolymer systems. The most successful of these was 

tributyltin methacrylate/methyl methacrylate and, in 1974, the first commercial 

organotin copolymer antifouling paint was based on this system (Evans & Hill, 1983). 

TBT copolymer systems frequently also contain copper compounds and an organic 
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booster as co-biocides to provide effective protection against the whole spectrum of 

fouling organisms, and under all operating conditions (Voulvoulis et al., 1999).

The environmental impact of TBT is now widely acknowledged (see Section 1) and has 

led to the imminent global ban on application and use of antifouling paints containing 

organotins as active biocides. 

In response to the impending ban on tributyltin compounds as antifoulants, Abbott et 

al. (2000) discussed the opportunities for using alternative tributyltin compounds which 

may have had useful biological activity but less of the harmful side-effects. Examples 

quoted included tri-cyclohexyl tin, used as a miticide on apples, and triphenyl 

compounds used on potatoes against blight. The possibility of substituting organic 

moeties to formulate, for example, pentyl butyl octyl tin, in a process analogous to that 

used in the pharmaceutical industry to eliminate harmful side effects was also raised. 

However legislation, such as that in the UK, was already in place to proscribe the use of 

all triorganotins as antifoulants, although hundreds of potential triorganotins have 

never been synthesized and less than half a dozen ever tested or used.

3.2 COPPER AND COPPER COMPOUNDS

Copper, in the form of copper salts, was the first antifouling biocides to be incorporated 

into antifouling paints and continues to be used widely today, both as a co-biocide in 

TBT copolymer paints and as the primary alternative to TBT. Copper is an essential 

element, required for the growth of all plants and animals, and occurs commonly in the 

environment (Lewis & Cave, 1992). However, high concentrations can be deleterious to 

marine organisms. The most bioavailable, and thus the most toxic form of ionic, 

unbound copper, is the free hydrated ion, Cu(H2O)6

2+ (Voulvoulis et al., 1999). The 

antifouling effect of the copper is achieved through dissolution and release of free 

cupric ions from the coating surface, which have a toxic effect on settling fouling 

organisms. 

After release organic ligands in seawater bind the cationic copper species to form 

anionic, hydrophilic and kinetically inert copper chelates, which reduces the toxicity. 

Speciation studies in coastal waters indicate that more than 99% of the total copper is 

strongly bound or chelated with organic ligands, leaving the concentration of free 

cationic copper at levels that are non-toxic to most organisms. There is also strong 

evidence that strong copper chelators are synthesized and excreted by microorganisms 

in response to gradual and potentially toxic increases in copper concentrations in the 

water column (Ahsanullah & Florence, 1984; Donat et al., 1994; Voulvoulis et al., 1999). 

However, when some booster biocides, including dithiocarbamates, are used with 

copper, synergistic effects can occur as a result of the formation of lipophilic organic 

copper complexes that can diffuse across plasma membranes (Bonnemain & Dive, 

1990). The copper levels in oysters harvested near marinas and mooring areas in 

France increased between 1979 and 1991 and this was attributed to increasing use of 

copper-based antifouling paints following the ban on TBT use on small craft (Claisse & 

Alzieu, 1993). 

Although copper is broad spectrum in action, it is particularly effective in controlling 

animal fouling (Callow, 1996). Copper leaching rates of 10 and 20 μg cm-2 day-1 are 

required to prevent settlement of barnacles and diatom slimes respectively (Banfield, 

1980). Several significant algal foulers also show marked copper tolerance, including 
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the green alga Enteromorpha, the brown alga Ectocarpus, and the diatom Achnanthes. 

When release rates decline, animal foulers such as species of the encrusting bryozoan 

Watersipora and the serpulid tubeworm Hydroides are also able to colonise the paint 

surface. A booster biocide is therefore usually incorporated in copper-based 

antifoulings to broaden the spectrum of control. 

Some concern has been raised about the loading of copper in the marine environment 

from the use of copper-based antifouling paints on recreational and commercial vessels 

(Hall & Anderson, 1999). The contribution of copper from antifouling paints has been 

estimated as 2% of the total copper load in New York New Jersey Harbour, and 10% or 

less of anthropogenic input in the UK, whereas antifouling coatings from Navy, 

commercial, and pleasure craft are considered major sources of copper loading in San 

Diego Bay in the US. 

A deterministic ecological risk assessment for copper in European saltwater 

environments demonstrated the probability of ecological risk from acute dissolved 

copper exposures to be generally low (Hall & Anderson, 1999). Available data from 

copper monitoring studies formed the basis of the assessment, and 31 studies 

encompassing 101 sites were used. In only two studies (marina/harbour sites in France 

and Greece) did the mean observed environmental concentration exceed the predicted 

no effect concentration. The chemistry of copper in natural saltwater was considered a 

key in assessing this risk. Generally over 99% of the toxic form of copper, Cu(II), is 

bound to naturally occurring organic ligands, such as humic substances, leaving only a 

very small fraction of Cu(II) bioavailable to biota in saltwater aquatic environments. 

3.2.1 Cuprous Oxide

Cuprous oxide (Cu2O), a red powder, is the most widely used antifouling biocide in 

tin-free coatings. Alternative copper compounds were often used only when 

compositions coloured other than red or red-brown were required, such as using 

cuprous thiocyanate (white), copper acetoarsenite (green) or metallic copper flake 

(copper bronze), or for application to aluminium substrates.

The wide use of cuprous oxide is a consequence of its low-cost and broad spectrum 

activity against fouling organisms. However, antifouling formulations based on 

cuprous oxide often contain booster biocides to enhance performance (N. Blossom in 

1999b). Some proprietary lines of cuprous oxide are claimed by the manufacturer 

Chemet to have lower initial release rates than competitive materials and a new line, 

called Controlled Depletion Copper (CDC), is claimed to further reduce initial, and yet 

maintain steady, release rates. Antifouling products based on this material were 

claimed to achieve significantly lower release rates when tested by the new ASTM 

copper release test method.

3.2.2 Metallic Copper

Fouling prevention on copper and copper alloy sheet was initially considered to be due 

to gross exfoliation (Redfield, 1952). Oxidation of the copper surface produced a loosely 

attached or slightly soluble oxide layer, which caused attached fouling to be sloughed. 

However, exfoliation alone could not be considered responsible, as the corrosion rate 

was too low when compared to other metals such as iron and zinc. A toxic effect was 

therefore implicated, and this was attributed to dissolution of the copper, not to an 

inherent toxic quality of the copper surface (Redfield, 1952). The long-term antifouling 
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performance of copper-nickel alloys is now considered to result from a combination of 

the release of toxic material together with sloughing of fouling attached to loosely 

adherent layers of corrosion product (Efird & Anderson, 1975; Efird, 1976; Chamberlain 

& Garner, 1988; Powell, 1994; Blunn, 1986).

Copper nickel alloys have been observed to have a self-cleaning property, and velocities 

of 3-8 knots have effectively removed fouling accumulations (Powell, 1994). Under 

static conditions accumulated fouling has been easily removed by wiping or light 

scraping (Blunn, 1986). Copper-nickel alloys, particularly 70/30 and 90/10 with small 

additions of iron, can be more susceptible to fouling by copper tolerant organisms. This 

fouling may only be a microbial slime of copper tolerant diatom species, which may not 

significantly affect vessel performance, but in some regions fouling by copper tolerant 

macrofouling species, such as the brown alga Ectocarpus or the tubeworm Hydroides 

may cause significant problems (Lewis & Smith, 1991; Hall & Baker, 1986).

3.2.3 Copper Thiocyanate

Copper thiocyanate is not as effective an antifoulant as cuprous oxide (J. Lewis, pers. 

obs.), but is less aggressive in its corrosive effect on aluminium. It is therefore widely 

used as the primary or co-biocide in antifouling paints for aluminium vessel hulls and 

other aluminium components such as stern drives. Use of cuprous thiocyanate also 

permits paint formulation in different colours, as it does not have the strong red 

pigmentation of cuprous oxide. Available TBT-free antifouling coatings for aluminium 

surfaces have a much shorter effective life than those containing cuprous oxide, often as 

short as twelve months. 

White cuprous thiocyanate is considered to have, in many ways, similar properties to 

those of cuprous oxide (Vetere et al., 1997). Both dissolve in seawater principally as 

CuCl2

1- and have the same solubility, although cuprous thiocyanate is less oxidisable. 

Barnacle larval bioassays found cuprous thiocyanate to be more toxic than cuprous 

oxide, with the toxic action demonstrated to be due to the free copper ion, and not the 

thiocyanate anion. Cuprous oxide based antifouling pigments contain 3.32 times more 

copper per unit volume than the cuprous thiocyanate based material. However, the 

higher toxicity of the latter means that pigment content did not need to be increased to 

match the same copper per unit volume as cuprous oxide (Vetere et al., 1997).

3.2.4 Copper Pyrithione

Copper pyrithione (Copper Omadine ®) is manufactured alongside zinc pyrithione (see 

Section 3.4.5) by Arch Chemicals (formerly Olin Corporation) and was introduced as an 

antifouling biocide in 1996. It is claimed to have similar activity against soft fouling 

organisms as zinc pyrithione, and to have similar rapid degradation and to neither 

bioaccumulate nor persist in the marine environment (Turley & Waldron, 1999; Turley 

et al., 2000). Copper pyrithione (CPT) is not yet registered for use by the U.S. EPA, but a 

registration application has been filed (R. Martin in Anon., 1999b). A similar situation 

exists in Australia, with use of copper pyrithione dependent on acceptance and 

registration by the NRA.

The efficacy of CPT was tested in experimental paints immersed in Biscayne Bay, 

Florida (Turley & Waldron, 1999). Prototype paints containing combinations of 

cuprous oxide and CPT were tested alongside a biocide-free blank, an antifouling paint 
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containing TBT and cuprous oxide, and a commercial copper-based antifouling paint. 

Key findings were:

• Combinations of CPT and cuprous oxide were more effective than either biocide 

alone;

• Relative low levels of CPT (~ 3%) were effective; and 

• CPT/cuprous oxide paints preformed better than commercial controls.

3.2.5 Other Copper Compounds

Copper napthenate, copper resinate, copper sulphate and cuprous sulphide are also 

used as active copper sources in some antifouling paints approved for use in the United 

Kingdom (Health & Safety Executive, 2001). 

3.3 OTHER METALS

In the early 1950s, mercury and arsenic were considered alongside copper as primary 

biocides in antifouling paints, but were subsequently banned on occupational health 

and safety and environmental grounds (Fischer et al., 1984).

Zinc oxide is commonly added to copper-based antifouling paints, primarily as a filler 

(Callow, 1996). The zinc not only enhances the performance of the antifouling paint 

(French et al., 1984), but is also economically advantageous with respect to raw material 

costs; zinc oxide being less expensive than the cuprous oxide it replaces.

3.4 ORGANIC BIOCIDES

As mentioned in Section 3.2, although copper is effective against the majority of fouling 

organism, several significant algal biofoulers show marked physiological tolerance to 

copper (Voulvoulis et al., 1999). A booster biocide is therefore usually incorporated in 

copper based antifoulings to control copper-resistant species. In the United Kingdom, 

for example, twelve booster biocides are used as active ingredients in approved 

antifouling products (Voulvoulis et al., 1999; Health and Safety Executive, 2001): Irgarol 

1051, diuron, Kathon 5287 (Sea-Nine 211), maneb, zineb, thiram, ziram, chlorothalonil, 

dichlofluanid, TMTB, TCMS pyridine and zinc pyrithione. The activities of these 

booster biocides can be quite different; for example the fungicides thiram and nabam 

are active against diatom slimes (Hunter & Cain, 1996) and Irgarol 1051 against 

macroalgae (de Nys et al, 1996), whereas chlorothalonil and Sea-Nine 211 show more 

broad-spectrum activity (de Nys et al., 1996). Biodegradability of these biocides can also 

vary considerably, ranging from readily biodegradable (Sea-Nine 211) to 

non-biodegradable (diuron and Irgarol 1051) (Callow & Willingham, 1996). 

The unforeseen impact of persistent antifouling biocides in the marine environment, 

particularly in relation to TBT but again highlighted by the recent detection of residual 

Irgarol in inshore waters (Readman, 1996), has seen a general strengthening of 

registration requirements for new antifouling biocides. In the United States, for 

example, information must be provided to satisfy the Environmental Protection Agency 

(EPA) that the benefits of the new pesticide outweigh any risks (see Section 6.3.3). The 

review and approval process can typically take 3-5 years and requires submission of a 
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database and the absence of any evidence that the active ingredient will pose any 

significant risk to human health or the environment (Bingaman & Willingham, 1994). 

3.4.1 Diuron 

- dichlorophenyl dimethylurea

Diuron inhibits photosynthesis and is one of the major urea herbicides used in 

agriculture since the 1950s for weed control on no-crop areas (Voulvoulis et al., 1999). In 

2001, 89 approved antifouling products in the UK contained diuron (Health & Safety 

Executive, 2001). In one survey, diuron was present in 73.4% of antifouling paints sold 

by chandlers in one region of the UK (Voulvoulis et al., 2000), and another survey 

estimated that 45-52% of recreational craft were painted with antifoulings containing 

diuron (Boxall et al., 2000).

In the United Kingdom, diuron is one of the pesticides that most frequently exceeds the 

Environmental Quality Standard (EQS) of 1 mg l

-1 in controlled waters. This is 

predominantly attributed to its use in agriculture, although some inputs have been 

related to its antifouling use (Voulvoulis et al., 1999). On the Mediterranean coast of 

Spain, diuron, together with Irgarol 1051, was the most ubiquitous antifouling biocide 

detected. It was found in every marina and harbour sampled (Martinez et al., 2001). The 

highest concentration measured was 2.19 μg l

-1

. Diuron has not been found to be readily 

degraded in seawater (Callow & Willingham, 1996). 

In one study in an estuary in Essex, UK, diuron was not traced in any of the samples 

collected although, from a market survey, it was present in 74% of all antifouling paints 

sold in the region (Voulvoulis et al., 2000). However, in a second study, both diuron and 

Irgarol 1051 were found in water samples from areas of high yachting activity and 

diuron was measured at the highest concentrations (Thomas et al., 2001). In a survey of 

sediments, diuron was detected in samples at one site, a marina in Southampton Water 

(Thomas et al., 2000). Its presence was thought to be associated with paint chippings, 

emphasising the importance of environmental management of shore-side practices. 

Both amateur and professional use of diuron in antifouling products was revoked in the 

UK in 2000 (Health & Safety Executive, 2000; Nash, 2001d).

Concentrations of diuron measured in sediments on the Queensland coast are 

considered sufficiently high to result in ecosystem impacts (Haynes et al., 2000a, 2000b). 

However, this contamination was attributed to the widespread use of diuron as a 

herbicide by the sugarcane industry rather than use in antifouling paints. In the marine 

environment, diuron can inhibit photosynthesis and growth in periphyton, 

phytoplankton and seagrasses (Molander et al., 1992; Mayer, 1987; Ralph, 2000; Haynes 

et al., 2000b). 

3.4.2 Dithiocarbamates

Thiram (bis(dimethylthiocarbamoyl)disulphide), ziram (zinc bis(dimethyl 

thio-carbamate), zineb (zinc ethylene bisdithiocarbamate), and maneb (manganese 

ethylene bisdithiocarbamate) have a wide range of action against a number of 

organisms (Voulvoulis et al., 1999). In agriculture they are used as protective fungicides, 
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particularly for fruit and vegetable crops or, in the case of maneb, as a leaf and seed 

treatment. 

Zineb is the only dithiocarbamate still used as a cobiocide in the UK and is currently a 

component of ten approved tin-free and 33 TBT-based antifouling products (Health & 

Safety Executive, 2001). Zineb is highly effective in antifouling paints as it is strongly 

synergistic with copper and enables the amount of copper to be reduced without loss of 

antifouling effect (Hunter & Evans, 1991a., 1991b). After its review of booster biocides in 

2000, the UK Advisory Committee on Pesticides recommended that the approval of 

zineb in antifouling products for professional use by all application methods, and 

approval of amateur products by brush and roller, should continue (Advisory 

Committee on Pesticides, 2000).

3.4.3 Chlorothalonil 

 - 2,4,5,6-tetrachloroiso-phthalonitrile

Chlorothalonil, also known as Nopcocide N-96 ® (Henkel), is used in agriculture as a 

fungicide and in paints and adhesives as a preservative. It is highly toxic to fish and 

aquatic invertebrates, but not phytotoxic (Ernst et al., 1991; Caux et al., 1996). Fifteen 

antifouling coatings approved for use in the UK contain chlorothalonil (Health & Safety 

Executive, 2001).

A study of the degradation of chlorothalonil in seawater found degradation to become 

apparent after four weeks and to proceed more rapidly in seawater supplemented with 

cultured marine bacteria (Callow & Willingham, 1996).

High concentrations of chlorothalonil were measured in water and sediment in the 

Blackwater estuary in the UK, but the cause appeared more likely to be agricultural 

run-off than to its use in antifouling paints (Voulvoulis et al., 2000).

In 2000, the UK Advisory Committee on Pesticides recommended that all amateur uses 

of antifouling products containing chlorothalonil should be revoked because 

information on humans indicated that the risk of skin sensitisation in humans was 

unacceptable (Advisory Committee on Pesticides, 2000).

3.4.4 Irgarol 1051 

- 2-methylthio-4-t-butylamino-6-cyclopropylamino-s-triazine

Irgarol 1051® (Ciba-Geigy) is an agricultural herbicide that is highly effective against 

freshwater and marine algae (Voulvoulis et al., 1999). It belongs to the s-triazine group 

of compounds that act as photosystem-II inhibitors, by inhibiting photosynthetic 

electron capture transport in chloroplasts (Dahl & Blanck, 1996; Voulvoulis et al., 1999; 

Hall et al., 1999). Irgarol is primarily used as a booster biocide to improve a coating’s 

resistance to slime and algae (J. Windus in 1999b).

Irgarol 1051 has been commercially available and sold for more than a decade in Europe 

and the Far East. In 2001, one hundred and three antifouling products containing 

Irgarol were approved for use in the UK (Health & Safety Executive, 2001) and, in one 

region of the UK, 20.3% of antifouling paints sold by chandlers contained Irgarol 

(Voulvoulis et al., 2000). The US EPA registered Irgarol as an antifouling biocide in 1994 
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(US Federal Register, November 2, 1994). Additional ecological effects data and 

environmental fate data were required to be submitted by end-use formulators of 

antifouling paint containing Irgarol, and in 2001 7 antifouling paints containing Irgarol 

were registered for use in the US (J. Bloom, pers. comm.).

Readman (1996) expressed concerns, and raised the question as to whether coastal 

ecosystems were at risk from Irgarol. Irgarol has now been detected in marine and 

estuarine water and sediment samples from areas associated with boating activity in the 

United Kingdom (Gough et al., 1994; Scarlett et al. 1997; Voulvoulis et al., 2000; Thomas 

et al., 2000, 2001), France (Tolosa et al., 1996), Spain (Ferrer et al., 1997; Ferrer & Barcelo, 

1999; Martinez et al., 2001), Germany (Biselli et al., 2000), Japan (Liu et al., 1999), 

Bermuda (Connelly et al., 2001) and Australia (Scarlett et al., 1999). The highest levels 

detected in Plymouth Sound, UK, (> 120 ng l

-1) significantly inhibited the growth of 

Enteromorpha spores under laboratory conditions and the no effect concentration on 

photosynthetic activity in adult Enteromorpha fronds was 22 ng l

-1 (Scarlett et al., 1997). 

Available data suggests that Irgarol is more toxic to algae than other trophic levels, and 

can inhibit algal growth at concentrations between 10 and 100 μg l

-1 (Rogers et al., 1996; 

Voulvoulis et al., 1999). A probabilistic risk assessment of the use of Irgarol indicated 

low ecological risk in estuaries, coastal areas and various open-type marinas (Hall et al., 

1999). However 10% or more of the plant species in enclosed marinas with low flushing 

rates were determined to be possibly exposed to levels that would reduce 

photosynthetic activity and growth over summer. Studies in Japan similarly found that 

both Irgarol 1051 and its degradation product (2-methylthio-4-

tert-butylamino-6-amino-s--triazine) could influence the primary producer community 

in the aquatic environment. The NOEC (0.3 μg/l) of Irgarol to the brown macroalga 

Eisenia bicyclis was the same as the maximum concentration (0.296 μg/l) detected in 

Japanese coastal waters.

Irgarol is not readily degraded in seawater (Callow & Willingham, 1996). White rot 

fungus, Phanerochaete chrysosporium, appears to biotransform Irgarol, but does not 

cleave the heterocyclic ring, suggesting that degradation products may accumulate in 

the environment (Liu et al., 1997; Voulvoulis et al., 1999).

A number of countries have recently imposed restrictions on the use of Irgarol as an 

antifouling biocide because of its persistence in the marine environment (see Section 

6.4). Irgarol has been considered, but not approved, by the NRA for use as an 

antifouling biocide in Australia (L. Cahill, pers. comm.).

3.4.5 Sea-Nine 211 (C-9211, Kathon 5287, RH-287)

- 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one

Sea-Nine 211® (Rohm and Haas Company) is a highly effective, broad-spectrum 

antifouling biocide (Willingham & Jacobson, 1993). Its antifouling efficacy was 

recognised more than 20 years ago (Miller & Lovegrove, 1990), but it was only 

commercialised after concerns were raised on the environmental impact of organotins 

(Callow, 1996). The performance of copper paints is improved by the addition of 

Sea-Nine, which can be used in all types of paint matrices (Harrington & Willingham, 

1993). The controlled release of Sea-Nine 211 from a monolithic, non-ablative coating 

based on vinyl chloride/vinyl acetate copolymer resin indicated many species were 

inhibited at release rates of 5 μg cm-2 day-1, but that fluxes of up to 20 μg cm-2 day-1 could 
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be needed to completely prevent barnacle attachment and diatom slimes when the 

biocide was used alone (Vasishtha et al., 1995; Callow, 1996).

Rohm and Haas obtained U.S. EPA registration for Sea-Nine 211 in 1994 and this was 

the first organic biocide registered for use in antifouling paints within the United States 

(Bingaman & Willingham, 1994, 1995). On the basis of its lower persistence in the 

environment and its lower toxicity towards humans in comparison to TBT, Rohm & 

Haas won the United States Presidential Green Chemistry Ward in 1996, and was 

Chemical Engineering’s Environmental Champion in 1997.

The major features of Sea-Nine 211 claimed to meet current and prospective criteria for 

antifouling biocides are (L. Graziano & J. Harrington in Anon., 1999b):

• It has a wide spectrum of activity against fouling organisms including slime, 

grasses, and barnacles;

• It has a short half-life in seawater and sediment and therefore does not accumulate 

in the environment; and

• It imposes minimal risk to non-target organisms due to its rapid degradation, the 

lack of accumulation in organism tissues, and because it is not a chronic or 

reproductive toxin.

Studies on the degradation of Sea-Nine in seawater have estimated half-lives of 8.5 days 

in natural coastal seawater (Callow & Finlay, 1995; Callow & Willingham, 1996) and less 

than 1 hour in aerobic and anaerobic microcosms of marine sediment and seawater 

(Jacobson et al., 1993; Jacobson & Willingham, 2000). In seawater, Sea-Nine binds 

strongly and essentially irreversibly to sediment, and in both seawater and sediment it 

is rapidly degraded by microorganisms to ring opened structures with greatly reduced 

toxicity (Willingham & Jacobson, 1993). Jacobson (1998) reviewed the environmental 

chemistry and environmental toxicity of Sea-Nine 211 and zinc pyrithione (ZPT) in 

comparison to TBT. He concluded that both were environmentally preferable to TBT as 

they both degraded extremely rapidly under environmental conditions, bound tightly 

to sediment, thus limiting bioavailability, and did not bioconcentrate. Although 

Sea-Nine 211, ZPT and TBT were all acute toxicants, the former two are not chronic 

toxicants and metabolites of Sea-Nine and ZPT are 4-5 orders of magnitude less toxic 

than the parent. Predicted environmental concentrations for both Sea-Nine and ZPT 

were also 60-4000 times less toxic than the lowest chronic toxicity value. This contrasts 

to TBT where predicted environmental concentrations were 4 to more than 100 times 

greater than the chronic effect level.

Outside of the United States, Sea-Nine 211 is licensed, as Kathon 5287, for use as an 

active component in antifouling products in the United Kingdom (Voulvoulis et al., 

1999) and 27 tin-free products containing the biocide are currently approved for use in 

that country (HSE, 2001). In all of these it is used as a booster biocide to cuprous oxide 

or as a co-biocide with other active agents. Sea-Nine 211 has been fully assessed by 

Environment Australia for use as an antifouling biocide (L. Cahill, pers. comm.) and one 

product containing Sea-Nine (Jotun Seavictor 50) is registered by the NRA. In Sweden, 

Sea-Nine is subject to some restrictions and the biocide has the same regulatory status 

as diuron (Ranke & Jastorff, 2000). 
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Sea-Nine 211 was recently reported to be present at concentrations of up to 3700 ng l

-1 in 

marina waters in Spain (Martinez et al., 2001). This appears to be the first positive 

report of this biocide in marine waters, and may reflect its increasing use as a substitute 

for the more persistent biocides Irgarol 1051 and diuron. 

Sea-Nine 211 is a skin sensitiser and is predicted to also be a skin and eye irritant 

(Advisory Committee on Pesticides, 2000). Amateur use of products containing 

Sea-Nine biocide were revoked in the UK in 1999 for this reason and, in 2000, the 

Advisory Committee on Pesticides recommended that although professional use should 

be permitted to continue, this should be subject to the use of additional personal 

protective equipment and further data requirements.

3.4.6 Zinc Pyrithione

- zinc 2-pyridinethiol-1-oxide

Zinc pyrithione, sold as Zinc Omadine ® (Arch Chemicals, formerly Olin Corporation) 

is used in agriculture as a bacteriocide and fungicide, and in shampoos as an 

antidandruff treatment. It has been used for the latter during the past 35 years and no 

environmental effects have been noted in this time, suggesting that pyrithione does not 

persist in the environment (Turley et al., 2000). Zinc pyrithione (ZPT) has low solubility 

in water, which contributes to its effectiveness as an antifouling pigment. It acts 

especially well in combination with cuprous oxide and cuprous thiocyanate, and forms 

stable complexes with copper, mercury and silver (Ranke & Jastorff, 2000). The copper 

complex is considered to be of particular interest as it is formed during release from 

copper-containing antifouling coatings. Zinc and Copper Omadine ® are said to be 

dependable biocides for the control of soft fouling organisms and to complement the 

hard fouling control of cuprous oxide (R. Martin in Anon. 1999b).

Zinc pyrithione has been used in antifouling formulations in Japan since 1991. ZPT was 

registered by the US EPA for use as an antifouling biocide in 1997, and five antifouling 

coatings containing the biocide are now approved for use (J. Bloom, pers. comm.). ZPT 

has recently been approved by Environment Australia for use in antifouling paints (L. 

Cahill, pers. comm.), and the first product containing this biocide has recently been 

registered in Australia (NRA, 2001, 2002). Twenty-nine approved antifouling products 

in the UK contain ZPT (Health & Safety Executive, 2001).

Thomas et al. (2000) summarised knowledge on the fate of ZPT in the marine 

environment. ZPT has a short half-life in natural seawater (t1/2=<4 h; Turley et al., 2000) 

and low aqueous solubility (Fenn & Alexander, 1988). The most effective degradation 

pathway is photodegradation with a reported half-life of less than 20 minutes in the 

presence of UV light (Neihof et al., 1979). In waters were UV degradation is likely to be 

poor or non-existent, it has been hypothesized that the pyrithione would accumulate in 

the sediment as the stable Mn2+- pyrithione complex (Galvin et al., 1998). However, 

other studies have shown the Cu2+ complex to be the most stable (Nakajima et al., 1990) 

and in areas such as marinas where copper concentrations are relatively high 

(Matthiessen et al., 1999), Thomas et al. speculate that the pyrithione may accumulate as 

the copper pyrithione complex (CPT). In other work by these authors (Thomas, 1999; 

Thomas et al., 2001), ZPT and CPT were found to be below the level of detection (<20 

ng/l) in marina water samples. They were unaware of any studies on the accumulation 

of ZPT on suspended particulate matter. 
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Turley et al. (2000) further discuss fate and degradation pathways for pyrithiones. They 

observe that pyrithione chelates many transition metal ions to complexes with different 

dissociation constants. Whether introduced into the marine environment as zinc or 

copper pyrithione, copper pyrithione, with the lowest dissociation constant, would 

become the predominant complex and follow the one fate pathway. Degradation rates 

were found to be rapid whether due to photolysis, biodegradation or redox, and in 

aerobic and anaerobic water and sediments. 

As pyrithione has yet to be detected in the marine environment, models have been used 

to predict environmental concentrations under various conditions (Turley et al., 2000). A 

preliminary predicted environmental concentration (PEC) in the water column was 

estimated to be < 0.04 μg l

-1

, which compares to acute toxicity values for aquatic 

organisms of 2.6 to 400 μg l

-1

. The chronic no effect toxicity concentration (NOEC) is 1.5 

μg l

-1

. Applying a safety factor of 10 based on OECD guideline, Turley et al. (2000) 

calculated the predicted no effect level (PNEC) to be 0.15 μg l

-1

, and the worst case risk 

quotient (PEC/PNEC) to be <1. The major stable degradation product of zinc and 

copper pyrithione, 2-pyridine sulfonic acid (PSA) was considered to be at least four 

orders of magnitude less toxic than the parent compound. 

A comparison of the environmental chemistry and aquatic toxicology of ZPT and 

Sea-Nine 211 with TBT is discussed above (Section 3.4.3). The review concluded that 

both ZPT and Sea-Nine 211 were environmentally preferable alternatives to TBT 

(Jacobson, 1998).

In 2000, the UK Advisory Committee on Pesticides recommended continued approval 

of zinc pyrithione in antifouling products for professional use by all application 

methods, and amateur use by brush and roller (Advisory Committee on Pesticides, 

2000).

3.4.7 Other Booster Biocides

Other booster biocides used in antifouling applications include dichlofluanid 

(N-dimethyl-N-phenylsulphamide), TCMTB (2-(thiocyanomethylthio)benzothiazole), 

and TCMS pyridine (2,3,5,6-tetrachloro-4-(methylsulphonyl)pyridine) (Voulvoulis et al., 

1999). Dichlofluanid is used as an agricultural fungicide and TCMTB as an agricultural 

fungicide, as a wood preservative, and in the leather industry. TCMS pyridine has no 

other applications. 

In the UK, 38 approved antifouling products contain dichlofluanid, five TCMTB, and 

nine TCMS pyridine (Health & Safety Ecxecutive, 2001). Dichlofluanid was present in 

only 0.6% of antifouling paint sold by chandlers surveyed in a UK study, but was 

nevertheless detected in relatively high concentrations at several localities in the region 

after a boating season (Voulvoulis et al., 2000). Dichlofluanid has also been detected in 

marina waters in Spain (Martinez et al., 2001). The presence of dichlofluanid was not 

assessed in the study of antifouling biocide contamination of sediments in Southampton 

Water (Thomas et al., 2000). Dichlofluanid is much less soluble in water than both 

Irgarol 1051 and diuron, which may allow it to become associated with particulate 

matter and thus have the potential to bioaccumulate. Thomas et al. (2000) also comment 

that although dichlofluanid has been used extensively on various crops, very little is 

known about its environmental fate and effects. 
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In 2000, the UK Advisory Committee on Pesticides recommended that approvals for 

dichlofluanid in professional products (all application methods) and in amateur 

products (for application by brush, roller and spreader) continue. However, it also 

recommended that approvals for amateur use by airless/conventional spraying and 

aerosol application be revoked (Advisory Committee on Pesticides, 2000). Amateur use 

of TCMTB was revoked in 1999 due to concerns on skin irritation and sensitisation 

potential. In 2000, the ACP recommended that approval for professional use of TCMCT 

in antifouling products could continue subject to additional requirements for use of 

personal protective equipment.

3.5 NATURAL BIOCIDES

3.5.1 Natural Antifouling Defences

The search for new methods of fouling control have extended to looking at the marine 

organisms themselves. The surface of any organism in the sea, like any artificially 

immersed surface, is the potential attachment site for fouling species. Whales and 

turtles, for example, often carry a healthy population of barnacle species. However, the 

majority of marine species do not readily foul, and understanding the way that they do 

this is seen to potentially provide novel solutions for the prevention of fouling.

Marine organisms have evolved three major classes of adaptation to fouling pressure: 

tolerance, avoidance and defence (Wahl, 1989). These are not necessarily exclusive, and 

a given organism may use several adaptations or adopt different strategies at different 

life stages. Tolerance can be seen in organisms, such as some bivalves, tubeworms, 

ascidians and barnacles, which secrete an outer shell or tube that is able to foul almost 

completely leaving only the essential orifices clean. Avoidance can include accelerated 

growth rates to produce new tissues at a rate higher than the local fouling rate, 

avoidance in time by investing energy in reproduction rather than antifouling defences, 

or retreat into less vulnerable habitats. 

Defence mechanisms can be divided into three types: mechanical, physical and 

chemical (Wahl, 1989). Mechanical defence can include the development of special 

surface structures such as spicules which hinder attachment, intense production of 

mucous to impede adhesion, periodic sloughing of outer shells, cuticles or epidermis, 

friction against sediment, and active removal of attached larvae by scraping and picking 

with specialised appendages. 

Wahl (1989) speculated that organisms may utilise minimally adhesive outer surfaces as 

a physical defence against fouling, but evidence was virtually non-existent. A 

subsequent study found two gorgonian corals to have surfaces with surface energies in 

the range previously correlated with minimal bioadhesiveness (Vrolijk et al., 1990). 

Surface qualities and chemistries were considered to be important evolutionary 

strategies for antifouling defence as they were not as metabolically demanding as 

constant production of secondary metabolites or mucus, and antifouling compounds do 

not always elicit an inhibitory or toxic response across the full spectrum of potential 

colonists. However, with biofouling such a complex phenomenon, it is considered 

improbable that a single strategy could inhibit the full range of potential fouling 

organisms, nor are mechanisms likely to be mutually exclusive (Vrolijk et al., 1990; 

McKenzie & Grigolava, 1996). Several antifouling strategies may operate 

synergistically, with minimally adhesive surfaces based on low energy outermost layers 
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a primary, passive, antifouling defence, at least in gorgonian corals. In echinoderms, 

antifouling capabilities have also been attributed to a physical primary defence system, 

consisting of steric repulsion and low adherence (McKenzie & Grigolava, 1996). 

Microorganisms that breach this defence and do attach are possibly attacked by 

chemical mechanisms integral to the cuticular surface and/or shed by localised 

sloughing.

Becker (1995) investigated the natural antifouling mechanisms of the green mussel 

Perna viridis, which appeared to be less densely colonised by epibionts than other 

artificial and natural hard substrata. The filtration activity of aggregated mussels was 

found to be a major factor in reducing fouling settlement. Grazing gastropods also 

reduced numbers of protozoa and macroorganisms. Shell extracts showed some toxicity 

to bacteria and fungi, but the effect was not strong.

3.5.2 Natural Antifouling Products

More than 2000 natural products have been described from marine organisms 

(Faulkner, 1991; Pawlik, 1992). Many algae and soft-bodied invertebrates are 

conspicuously free of foulers, and chemical defence, through the creation of 

unfavourable or toxic conditions at or above an organism’s surface by surface bound or 

exuded secondary metabolites, is often suggested as a widespread antifouling 

adaptation (Bakus et al., 1986; Davis et al., 1989). Natural antifouling products have 

therefore received considerable attention in the search for novel antifouling biocides 

(Wahl, 1989; Clare, 1995, 1996; Abarzua & Jakubowski, 1995; Abarzua et al., 1999). 

The prime candidates for screening of natural antifoulant activity have been plants and 

animals able to maintain fouling free surfaces. Using this approach, natural antifouling 

products have been isolated from sponges (Targett et al., 1983; Rittschoff et al., 1985; 

Porter & Targett, 1988; Sears et al., 1990; Sarma et al., 1991; Goto et al., 1992; Willemsen & 

Ferrari, 1993; Bakus et al., 1994; Tsukamoto et al., 1997; Henrikson & Pawlik, 1998; Geraci 

et al., 2001), octocorals (Keifer et al., 1986; Rittschoff et al.,, 1986; Gerhart et al., 1988; 

Avelin Mary et al., 1991; Avelin Mary et al., 1994), bryozoa (Kon-ya et al., 1994), ascidians 

(Stoecker, 1978; Young & Chia, 1981; Davis & Wright, 1990; Wahl & Lafargue, 1990; Teo 

& Ryland, 1995; Davis & Bremner, 1999), algae (Bakus & Kawaguchi, 1984; Katsuoka et 

al., 1990; de Nys et al., 1995; Lau & Qian, 2000; Geraci et al., 2001; Hellio et al., 2001) and 

seagrasses (Todd et al., 1993; Callow & Callow, 1998). Active antifouling products have 

also been extracted from terrestrial plants (Sawant et al., 1992; 1994). Identification of 

antifouling activity has generally been by solvent extraction of the organisms’ tissues 

then use of a bioassay to assess the antifouling potential of the extract. 

Of the large number of studies have been undertaken to identify natural antifoulants, 

few have involved the isolation and chemical characterisation of the active agent. 

Where they have been identified, a range of structures has been elucidated. For 

example, homarine (Targett et al., 1983), furanogermacrene (Izac et al.,, 1982), muricins 

(Bandurruga & Fenical, 1985) and the diterpenes, renillafoulin (Rittschoff et al.,, 1986), 

pukalide and epoxypukalide (Gerhart et al., 1988), have been identified from different 

octocorals. The antifouling substances can also have varying and quite specific effects. 

Renillafoulins and pukalides inhibit barnacle settlement but have no effect on the 

settlement of larvae of the bryozoan Bugula neritina (Rittschoff et al., 1988). A different 

fraction inhibited bryozoan settlement, but had no effect on barnacle larvae. Isolated 

substances with the most potent antifouling activity are fatty acids, terpenes, 
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terpenoids, lipoproteins, glycolipids, phenols, lactons, peptides and steroids (Abarzua 

& Jakubowski, 1995). A number of furan analogs of octocoral metabolites have been 

found to reduce diatom numbers in bioassays more effectively than copper (Targett & 

Stochaj, 1994). 

A U.S. Navy sponsored research program has focussed on the terpenoids renillafoulin, 

pukalide and juncellin, and zosteric acid in an attempt to further understand and 

possibly exploit such natural agents and their analogs (Sundberg et al., 1997). Synthetic 

pathways for producing these compounds and/or their derivative was considered an 

important part of the program because their isolation from organisms would represent 

prohibitive production costs and unacceptable impacts on natural populations.

Zosteric acid, a sulphated phenolic acid isolated from the marine angiosperm Zostera 

marina, appears to prevent fouling attachment by non-toxic means (Sundberg et al., 

1997). The specific mechanism is thought to involve changes in cell surface 

hydrophobicity that prevent cells such as bacteria from interacting with filmed surfaces 

that may themselves possess cues for settlement, interaction with specific receptor 

molecules on the surfaces of bacteria and algal spores that prevent binding to molecules 

present on the target surfaces, or blocking the polymerisation or curing of 

proteinaceous adhesives secreted by invertebrates. 

Compounds without acute toxicity are frequently considered to be non-toxic, but most 

compounds that prevent settlement or metamorphosis increase the probability of death 

of the target organism (Rittschof, 2000). Non-toxic mechanisms include disruption of 

attachment and metamorphosis, reversible anaesthesia and repulsion. Complex natural 

products often display multiple activities.

Compounds with antifouling activity have also been isolated from microorganisms and, 

in the case of bryozoans and sponges, some of the antifouling activity exhibited by these 

animals may originate from epiphytic or symbiotic microorganisms (Clare, 1996). 

Several bacteria have been isolated from surfaces in marine waters that inhibit or are 

toxic to fouling bacteria or settling larvae (Avelin Mary et al., 1993; Holmström et al.,

1992; Holmström & Kjelleberg, 1994; Armstrong et al., 2000; Peppiatt et al., 2000). One 

isolate, from an adult tunicate, secreted substances that inhibited both settlement of 

barnacles and a range of marine bacterial species. In reviewing bacterial effects on larval 

settlement, Holmström & Kjelleberg (1994) found that inhibitory strains were quite 

common in marine waters. In one study, twelve of 16 isolates from biofilms associated 

with the barnacle Balanus amphitrite were found to be inhibitory to larvae of that species 

(Avelin Mary et al., 1993), and in a second study seven of 18 isolated strains inhibited 

barnacle settlement (Maki et al., 1988). Bacterial films have also been found to affect the 

attachment of both diatoms and algal spores (Holmström et al., 1996). Bacterial strains 

isolated from living surfaces such as marine plants and animals seem to be more active 

in preventing the settlement of fouling organisms when compared to bacterial strains 

from inanimate surfaces (Holmström et al., 1996). This habitat-specific mechanism may 

be due to the bacteria requiring specific exudate metabolites from the host organism. 

The use of bacteria as a source of naturally-produced antifoulants clearly has a number 

of advantages in that bacteria are easy to culture and maintain and it is easy to collect 

large amounts of the inhibitory component (Holmström & Kjelleberg, 1994). 
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Methods for immobilising antifouling bacteria in gels have been investigated 

(Holmström et al., 2000). The life span of ‘‘biological active’’ gels was extended to more 

than 2 months, which was considered a period of time consistent with the needs of 

some antifouling and antibacterial applications. 

After reviewing the available literature on chemical inhibition of settlement, Pawlik 

(1992) concluded that, although many natural extracts could be demonstrated to have a 

toxic effect on competent larvae, there was little evidence that these putative fouling 

inhibitors are released at concentrations that would influence settling larvae. Clare 

(1996) concluded that research aimed at discovering natural product antifoulants was in 

its infancy with few chemical structures elucidated and little testing in the field. As with 

synthetic biocides, the challenge remains to find natural products that were both broad 

spectrum and environmentally benign. Procurement or synthesis of commercial 

quantities of product would also be necessary, as would investigation of chemical and 

toxicological properties to ensure compliance with the requirements of regulatory 

authorities. Clare did however take an optimistic view that the potential for 

discovering marine natural product antifoulants is great. To fully determine this 

potential, he called for fundamental research on the ecological role of these compounds, 

their relation to other natural antifouling defences and their mechanism of action, 

coupled to applied research on coatings compatibility, controlled delivery, minimum 

effective release rates and field testing.

In a subsequent paper, Clare (1996) commented that although general statements about 

the mechanism of action of ‘‘natural product antifoulings’’ could be made, in no 

instance had precise mechanisms been established. In this context, he considered that a 

paucity of information on the molecular basis of chemical cue perception by fouling 

larvae during settlement was apparent, and an understanding of this offered potential 

in identify ways of interfering with the process. Calcium had been identified as 

important in settlement of several invertebrate larvae, including the barnacle Balanus 

amphitrite, and also to adhesion and motility in the fouling diatom Amphora coffeaeformis

(Wigglesworth-Cooksey & Cooksey, 1992; Cooksey & Wigglesworth-Cooksey, 1995; 

Holmström et al., 1996). Clare considers this to be encouraging from the viewpoint of 

antifouling development, since it offered the prospect of broad-spectrum activity. 

Further studies on how natural products inhibit larval settlement might enable 

components of the processes to be identified, which could then be used in screening for 

candidate antifoulings (Clare, 1996; Morse, 1994). 

Natural antifouling products are easily degraded chemically, photochemically and 

biologically and, when incorporated in paint formulations, antifouling effectiveness of 

the surface diminishes within a short period of time. Marine organisms are able to 

continually synthesise new compound to maintain the antifouling effect, but such an 

option is not available to the paint formulator. One novel approach to overcome this 

deficiency was microencapsulation and controlled release (Price et al., 1992, 1994). 

Microcylinders of copper or iron metal formed on a substrate of phospholipid have 

been utilised to deliver tetracycline, isothiazolone antifouling agents and crude extracts 

of the sea pansy Renilla. The latter study found microencapsulation to enhance the 

activity of the natural antifoulants, with metallic tubules providing heat and solvent 

stability and a barrier to light.
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Lanolin and ti-tree oil have both been claimed to have antifouling activity and products 

containing these substances have been promoted in Australia. Long-term efficacy of 

these products has not been substantiated. Capsaicin, a chilli extract, has also been 

claimed to be effective as an antifouling agent. In the U.S., the Center for 

Biotechnological Research in Pennsylvania has produced a product called Hot Bottom 

Paint (Kettlewell, 1999). The product contains 33% copper and a ‘‘secret formula based 

on capsaicin’’.

3.6 PAINT ADDITIVES

An antifouling paint additive marketed in the U.S. under the name Compound-X is 

claimed to increase the effectiveness of antifouling paints by stopping barnacles, slime, 

and grassy growth when added to other bottom paints and to ‘‘double the life of most 

antifouling paints’’ (Kettlewell, 1999). Starbrite Compound-X ® is an antibiotic 

compound, with the active ingredient is listed as oxytetracycline hydrochloride. The 

additive is reported to be non-toxic, EPA approved, and not to affect paint adhesion, 

workability or appearance. A 10 gram bottle treats one gallon of antifouling paint 

(www.boatingreview.com). University of Florida tests are claimed to show reductions 

in fouling during two-year tests. 

Peterson et al. (1993) investigated the impact of tetracycline following the publication of 

an article in a yachting magazine advocating the addition of tetracycline capsules to 

cheap copper-based antifouling paints to boost their effectiveness (Palley, 1988). 

Preparation of antifouling paints using tetracycline powder was found to produce an 

unstable product that leached rapidly into seawater. Concentrations toxic to bacterial 

and algal fouling were considered unlikely to be reached at the paint surface, and on 

release into seawater the tetracycline would be rapidly inactivated through complexing 

with calcium and magnesium. The authors concluded that tetracycline would not pose 

an environmental threat to marine ecosystems, nor would it be likely to produce an 

effective antifoulant.

Verbal accounts have been given of small boat owners adding herbicides, such as 

Round-Up ®, to antifouling paints in southern Australia. Users claim that the herbicide 

improves the antifouling effectiveness and life of the paint. The addition of any 

substance to an antifouling paint is illegal in Australia (L. Cahill, pers. comm.).
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4. FOULING RELEASE COATINGS

4.1 FLUORINATED POLYMER COATINGS

Poly(tetrafluorethylene) (PTFE) was initially considered to offer promise as a fouling 

release or non-stick coating because of its low surface energy. However PTFE is not 

easily processed because it is not dissolved, softened or wetted by commercial solvent. 

In their liquid state, conventional epoxy and polyurethane resins, which produce the 

toughest marine coatings, also do not wet PTFE (Brady et al., 1987).

Fluorinated epoxy and polyol resins were subsequently synthesized with low surface 

energies similar to PTFE and these enabled powdered PTFE to be used as commercial 

paint pigment. However, the usefulness of PTFE coatings was still found to be limited. 

PTFE surfaces rapidly accumulated fouling because irregularities in the surface enabled 

adhesives to invade and cure in microcavities and create a secure mechanical interlock 

(Brady, 1994, 1997; Davis, 1996). The ability of barnacles to adhere securely to 

fluorinated surfaces, despite their low critical surface tensions, was considered to 

possibly relate to a highly localised polarity to the carbon-fluoride bond which allowed 

very polar groups in barnacle cement to develop a close association over time (Griffith 

& Bultman, 1997). 

An alternative approach was to polymerise perfluorooctyl acrylate or perfluorooctyl 

methacrylate esters with monomers containing ionising functional groups to create a 

fluorinated polymeric surfactant (Brady, 1994; Schmidt et al., 1994). The polymer was 

reacted with a water-reactive cross-linking polymer to form a sturdy cross-linked film 

when applied to a surface and cured. The coating has a surface energy of 111-16 mJ m

-2

, 

synthetic adhesive did not stick to the film, and it was not wetted or attacked by 

common solvents. The performance of this surface as a fouling release coating has yet to 

be assessed.

Adsorbed monolayers of perfluorinated surfactants are considered to have the lowest 

known surface free energies (Lindner, 1992, 1994). Monolayers were simulated by 

mixing compounds into an epoxy coating and by synthesizing acrylate, methacrylate 

and siloxane polymers with long perfluorinated sidechains. These polymers showed 

much lower surface free energies than Teflon-type perfluorinated polymers with no 

side chains, and showed excellent antifouling properties. Fluorinated diols have also 

been considered to have potential for creating minimally adhesive surfaces (Ho & 

Wynne, 1992).

To achieve effective fouling release from a fluorinated coating, initial bonding of marine 

organisms must be discouraged (Brady, 2000a-c). The requires construction of a 

well-organised surface of closely-packed fluorinated groups, to achieve as low a surface 

energy as possible, and cross-linking or otherwise stabilising the surface so that it resists 

rearrangement and penetration of marine adhesives. To minimise fouling, fluorinated 

coatings must meet five conditions:

• The surface must be very smooth;

• The surface must be composed exclusively of fluorinated groups;
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• There must be sufficient fluorine in the bulk of the coating to ensure the presence of 

a sufficient amount of fluorine at the surface;

• Fluorinated groups must be large enough to cover polar groups and dipoles; and 

• The surface must be cross-linked in order to hold fluorine in place, resist 

rearrangement and infiltration of marine adhesives, and maintain stability in the 

marine environment.

A fluorinated coating considered to have achieved these goals contains an array of 

closely packed, oriented CF3-terminated perfluoroalkyl groups on the surface (Brady, 

2000b). In a recent study, the coating was found to resist the attachment of fouling more 

effectively than any other fluorinated coating (Brady et al., 1999; Brady, 2000a-c).

Reduced settlement of bacteria, algal spores and barnacle larvae has been observed on 

fluoropolymer films (Graham et al., 2000). Bacteria attached more weakly to the films 

than to control surfaces, algal zoospores tended to settle at surface faults and cracks and 

showed some sensitivity to fluorine content, and barnacle cyprids could find only 

occasional sites for attachment on the films. The overall conclusion from this study was 

that, due to their low surface energies, smooth films of perfluoropolymers showed 

considerable promise as fouling resistant coatings. However, further work was seen as 

necessary to achieve adequate smoothness over large areas of film, freedom from cracks 

and surface blemishes, and strong attachment to underlying substrates. 

4.2 SILICONE COATINGS

The most successful fouling release coatings to date have been formulated using 

silicone polymers, confirming the hypothesis proposed by Baier (1973) and Meyer et al. 

(1988) that, from physico-chemical surface analyses, silicone based coatings should 

behave as fouling release coatings (Callow & Fletcher, 1994). Silicone polymers are 

based on a backbone of repeating (- Si - O -) units with the non-backbone valencies of 

the silicone attached to saturated organic radicals (Milne & Callow, 1984). The potential 

of silicone rubbers as materials for fouling control on underwater surfaces was 

essentially happened upon by accident (Milne & Callow, 1984). Rubber sheeting 

containing organotin compounds had been found to potentially have an effective life of 

five or more years but the application method was considered inconvenient, requiring a 

wallpapering or tiling process. Efforts were therefore directed toward reproducing the 

systems but for application in liquid form. The possibilities were limited to a small 

number of ambient-temperature-curing liquid elastomers including urethane 

elastomers and room-temperature vulcanised (RTV) silicone rubbers. In initial trials it 

was found that the biocide-free controls showed better antifouling characteristics than 

the experimental antifouling materials containing biocides, and even biofilms were 

remarkably non-adherent. Initially this effect was suspected to be due to the release of 

a toxin, such as the diorganotin compounds used as curing agents, but bioassays using 

Enteromorpha spores discounted this possibility. The inhibitory effect was therefore 

attributed to surface effects and studies were initiated in 1970 to find the optimal 

silicone fouling release elastomer.

A problem faced in the development of silicone coatings was that the coatings were 

non-stick on both sides, and were therefore difficult to apply to surfaces (Griffith & 

Bultman, 1997; Brady, 2000a). It was necessary to develop a coating system that coupled 
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the soft elastomeric silicone coating to the hard metal substrate, which became known 

as the ‘‘duplex’’ approach. . This has been achieved by using a three coat system: an 

epoxy-polyamide anticorrosive primer, a tiecoat consisting, for example, of an 

interpenetrating polymer network of butyl acrylate styrene and silicone polymers, and 

the polydimethylsiloxane top coat. The styrene butyl acrylate copolymer is not a good 

anti-adhesive topcoat, but is a near perfect transition layer because of the strength of the 

bonding that can be developed with epoxy substrates and with silicone topcoats. This 

tie coat also imparts ‘‘pseudo toughness’’ to the entire system because only the topcoat 

is susceptible to damage.

Griffith & Bultman (1997) listed other difficulties in converting silicone moulding 

compounds to practical marine paints such as flow and drip control, spray ability, gel 

and cure times, VOC restrictions, and repair and recoat. The cost of silicones was also 

an issue as silicones were among the most expensive synthetic materials on the general 

market for caulks, sealants, adhesives etc. 

In 1973, Baier proposed that the application of controlled surface energy coatings could 

be used to combat biological fouling (Baier, 1973). Subsequent studies demonstrated 

that the optimum range for the free energy of a surface designed to shed biofouling is 

recommended to be between 20 and 30 mJ m

-2 (Baier & Meyer, 1992). Efforts to reduce 

the surface energy below this range are considered to be counterproductive. The 

effectiveness of fouling release coatings appears to be based, not only on a combination 

of surface energy, surface structure and surface roughness (Watermann et al., 1997), but 

also on the low glass transition temperatures and low modulus of elasticity (Swain, 

1999). These properties minimise mechanical locking of biological glues, thereby 

increasing slippage and fouling release. Brady (1999b) examined the influence of bulk 

and surface properties apart from critical surface tension and, from this, developed 

requirements for polymers which refuse or resist strong bonding to other materials. The 

influence of properties apart from surface energy is supported by studies on the fouling 

of glass rods silanized with different reagents to produce coatings with different surface 

energy (Holm et al., 1997). The effect of surface energy on the development of fouling 

communities in the long term appeared indirect at best, and was complicated by 

temporal variation.

Although the surface energies of silicones lie within the optimum range for good 

fouling release of 20-30 mN m

-1 (Meyer et al., 1988), not all work effectively (Nevell et 

al., 1996). Surface energies of various silicone elastomers have also been observed to 

increase with increasing immersion time in seawater and, although this takes years for 

some materials, ultimately the material became susceptible to fouling. The changes are 

considered to be due to rearrangement of polymer chains close to the surface, driven by 

the formation of hydrogen bonds between the solvent and oxygen atoms in the 

backbone (Nevell et al., 1996). 

Silicone elastomers used in commercial fouling release coatings are mainly based on 

polydimethylsiloxane (PDMS), which consists of siloxane subunits in the form of chains 

and rings (Watermann et al., 1997). Silicone coatings used for antifouling purposes are 

rubbers and elastomers (Watermann et al., 2001). Curing (vulcanisation) converts the 

silicone compounds into silicone rubbers or elastomers but, as unfilled silicone rubbers 

have low mechanical strength, reinforcing fillers such as high surface area silicas, quartz 

powders, chalk, talcs and calcium silicates are incorporated. Condensation-curing 

compounds are used, which cure (vulcanise) at room temperature (RTV), and metal 
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catalysts including dibutyltin or titanium compounds are added to achieve complete 

curing. 

Yonehara and Momiyama (1993) compared the fouling release performance of a 

number of silixane-based formulations. They concluded that surface energy was not 

important in improving antifouling performance of the silicon polymers, but the surface 

structure played a significant role. Microphase separation was found to improve 

antifouling performance, with the minimum amount of adsorbed proteins occurring on 

the most clearly phase-separated surface.

Mera et al. (1997) compared properties and performance of alkoxysilane and 

platinum-cured PDMS. The former was found to be unstable when immersed in water 

for three months, with mass lost and the contact angle hysteresis changing 

substantially. This was attributed to the presence of CaCO3, filler and cross-linking 

chemistry. In contrast, the surface of Pt-cured PDMS was found to be chemically stable 

in water, and this was reflected in better fouling release performance. 

Fouling release from an unfilled hydrosilation cured PDMS network was compared to 

an RTV, filled ethoxysiloxane cured PDMS elastomer (RTV11) (Wynne et al., 2000). 

Barnacle adhesion strength was significantly less on the former, and this was attributed 

to differences in bulk and surface properties. Preliminary results suggested that bulk 

modulus may be the most important parameter in determining barnacle adhesion 

strength. Thickness of coatings was also important, with thin coatings favouring 

adhesion.

The performance of fouling release coatings is determined by three properties (Brady, 

2000c; Brady & Singer, 2000). The first is surface energy, which governs the ability of a 

surface to bond to another surface. Low surface energy will minimise the strength of 

adhesion of the fouling. The second, the elastic modulus of the coating, influences the 

mechanism by which the joint between the surface and the fouling organism will fail. 

Minimum adhesion has been found to correlate with the lowest value of elastic 

modulus tested, although this did not correspond to the lowest surface energy tested 

(Kohl & Singer, 1999). Thirdly, the thickness of the coating can influence whether the 

separation of an organism from the surface will be a peel fracture or a shear fracture. 

Elastomeric coatings, such as silicone fouling release coatings, deform readily and 

fouling is released by a peeling mechanism, unlike fluoropolymers which release 

fouling by shear. A peeling mechanism requires less energy than a shearing 

mechanism. Studies on the release of mechanism of barnacles from silicone elastomers 

have confirmed the separation to be a peeling process and that release forces decrease 

with increasing coating thickness (Singer et al., 2000).

The most effective route to fouling-free performance of silicone coatings is to promote 

quick and easy peeling at the adhesive joint of the fouling and the surface by judicious 

control of thickness and elastic modulus (Brady, 1999; 2000c). This is best enabled by:

• The silicone resin having a linear, highly flexible silicone-oxygen backbone that 

bears a sufficient number of groups to diminish surface energy while preserving 

backbone mobility;

• The silicone resin being stable in the marine environment and resistant to 

hydrolysis, which causes loss of mass and development of surface roughness;
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• The coating being applied at a thickness that favours release by peeling rather than 

sheer; and

• The coating being very smooth.

Various materials have been added to silicone coatings in order to enhance the foul 

release properties or to impart an antifouling capability to the foul release layer (Griffith 

& Bultman, 1997). The addition of oil that slowly exudes to the surface provides a thin, 

liquid layer to enhance foul release properties. Some silicone coatings are designed as 

microcellular sponges filled with hydrophobic fluids to exude from the surface. For 

example, the addition of polydimethyldiphenylsilicone (PDMDPS) oil to a PDMS 

coating decreased the addition of barnacles and certain species of oyster (Truby et al., 

2000). Fluids incorporated have included mineral oils, polyolefines, silicone fluids and 

paraffin. These additives may create weak surface layers and macromosaic surfaces that 

further promote fouling release (Swain, 1999). The addition of silicone oil that migrates 

from the bulk of the coating to the surface can initially improve fouling release, due to 

the fouling attachment to the oil being very weak and failing readily (Brady, 2000b). 

One of the first reported experimental applications of a non-toxic fouling release coating 

was on offshore platforms (Miller et al., 1984). These systems were manufactured from 

silicone-rubber-based materials to which an exuding fluid was added. 200 μm thick 

coatings applied to test panels on a raft remained free of fouling for over four years, and 

applications on pipe sections on offshore rigs showed similar success. The performance of these 

coatings was improved by the addition of hydrophobic fluids and the life expectancy of the 

coatings was expected to be a function of the reservoir of fluid within the coating. 

However, despite promising performance from commercial coatings containing free 

silicone oil, depletion of the oil within several years causes the coating to loss physical 

integrity, become brittle and crack. Fouling can then attach tenaciously. The coatings 

also release silicone oil into the environment which, although not considered toxic, does 

not readily degrade. 

In some studies, the addition of silicone fluids to elastomers has appeared to enhance 

long-term antifouling performance (Milne & Callow, 1984), but in others it appeared to 

have no influence (Callow et al., 1986). Studies sponsored by the UK Defence Research 

Agency (DRA) found that the addition of a silicone oil to a silicone elastomer was only 

beneficial if a dissimilar oil and polymer were used and that addition of small quantities 

of oil could reduce performance in contrast to the enhancement from greater quantities 

(Davis, 1996). 

In barnacles, experiments to determine the force required to remove cyprids from a 

variety of surfaces show that, in general, low surface energy surfaces promote a weak 

bond between the attachment disc and the surface (Callow & Fletcher, 1994; Yule & 

Walker, 1987). On effective silicone coatings, the basic adhesion mechanism of adult 

barnacles seems to be fundamentally disrupted (Watermann et al., 1997). Those that did 

not fall off immediately after metamorphosis produced an excess amount of cement, 

probably to compensate for reduced adhesion. Adhesion can also involve deformation 

of the basal plates to enable sucker-like attachment. Watermann et al. (1997) observed a 

discrepancy in that the more effective coatings did not inhibit barnacle settlement in the 

laboratory but did so to a high extent in the field. This was attributed, at least in part, to 

different hydrodynamic forces under field conditions.
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The failure mechanism of barnacle bioadhesive bonding to PDMS coatings was 

determined to be a cohesive failure (Berglin & Gatenholm, 1999). Good fouling release 

from these surfaces was considered to result from a combination of low surface free 

energy, resulting in few chemical interactions, low glass transition temperature, and 

possibly the amount of uncross-linked molecular chains present on the surface. These 

polymer chains are removed when a barnacle is dislodged as a result of the low 

intramolecular forces between the PDMS chains. 

On low surface energy surfaces, the byssal pad of mussels has been found to cover a 

greater surface area and force of adhesion is a function of the surface energy of the 

surface (Crisp et al., 1985; Walker, 1987). The break load for the byssus pad was 50 

times less from PTFE than from slate (Young & Crisp, 1981). Blue mussels have been 

found to be unable to attach their byssal pads to effective silicone coatings (Callow & 

Fletcher, 1994), and attachment of the freshwater mussel Limnoperna fortunei was 

considerably reduced on substrates with low surface energy (Ohkawa et al., 1999). In the 

latter study, only 1 of 50 mussels tested (2%) attached to silicone, compared to 4/50 

(8%) to Teflon and 22/40 (55%) to slate.

The adhesive of fouling organisms varies between organism types and influences the 

release mechanism from a coating. Bryozoans secrete a hydrophilic collagen-containing 

adhesive, whereas barnacle adhesive is a hydrophobic protein (Brady, 1997). The 

adaptability of proteins is evident when their adhesion to polymers is tested; barnacles 

prefer surface energies in the range from 30 to 35 mJ m

-2

, but bryozoans adhere best to 

surfaces with energies of between 10 and 30 mJ m

-2

, which encompasses the critical 

value of 22 mJ m

-2 at which adhesion is considered to be minimised. In field studies, 

dominant fouling organisms showed three common patterns in response to surface 

energy (Rittschof et al., 1998). Bryozoans settled on surfaces with low energy, barnacles 

settled on surfaces with high energy, and hydroids settled in equal proportion on 

surfaces of all energies. Successful fouling release coatings would therefore not be 

produced by determining surface energy alone (Brady, 1997). A detailed consideration 

of the fracture mechanics at the interface of the fouling and the coating suggests that 

thick coatings having low elastic modulus and low surface energies should provide the 

least resistance to removal of fouling and therefore be the best fouling release surfaces 

(Brady & Singer, 2000).

Test programs have shown that silicone based coatings performed better than other 

surfaces due to a slower rate of fouling accumulation, a tendency to slough, and ease of 

cleaning (Mussalli, 1989; Meyer & Baier, 1992; Fletcher & Callow, 1992; Watermann et 

al., 1997). It was initially considered that the poor abrasion resistance and tear strength 

of the silicone elastomers would inhibit their general use as marine antifoulings, but 

that they had potential for use in coastal power stations, offshore and in aquaculture 

(Milne & Callow, 1984). However, silicone paints have since shown potential in ship 

trials (Brady et al., 1987; Matsushita & Ogawi, 1993), as well as in controlling fouling on 

salmon-cage netting (Hodson & Burke, 1994) and for resisting the invasive zebra 

mussel in power station cooling water conduits in the Great Lakes (Leitch & Puzzuoli, 

1992). The Electric Power Research Institute (EPRI) in the U.S. evaluated 30 non-toxic 

fouling release coatings for control of fouling on steel and concrete surfaces and found 

silicone coatings performed best with predicted field lives of two to four years. 

(Mussalli, 1989, cited in Baier & Meyer, 1994). 
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Conventional procedures for assessing the performance of antifouling paints on test 

panels, in which the composition and abundance of fouling attachment was quantified, 

are not suitable for foul release coatings because these frequently foul under static 

conditions. The effectiveness of the coating is indicated by the strength of adhesion of 

this fouling. Two test methods have been developed to quantify fouling adhesion 

strength on fouling release coatings (Swain et al., 1994; Swain & Schultz, 1996; Swain, 

1997): a barnacle shear test, and a water jet test. The barnacle adhesion test was 

approved as an American Society for Testing and Materials (ASTM) standard in 1994 

(ASTM, 1994). A brush abrasion test to sequentially evaluate fouling release coatings 

after increasing numbers of wet brushing cycles has also been developed because 

standard abrasion tests were not applicable to elastomeric coatings (Baier et al., 1997).

Two-year exposure tests were undertaken in Italy on sets of panels coated with 

silicone-based coatings, with and without additives, and results compared both to sets 

of panels coated with ablative copper and non-toxic epoxy paints (Terlizzi et al., 2000). 

The best performing coatings were silicone foul release coatings without additives, and 

these substantially influenced community composition, shifting it to the earliest stages 

of colonisation and proving to be unsuitable for colonisation typical of mature 

communities due to their low surface energy. The study led to the conclusion that 

silicone coating technology represented an alternative to the use of biocidal antifouling 

paints. However, the need for improvements in aspects such as delamination and 

abrasion were noted.

Reduced macrofouling abundance on silicone fouling release coatings may be due, at 

least in part, to biotic factors. Caging experiments have demonstrated that fouling 

development on caged panels was much higher than on uncaged and partially caged 

panels, suggesting that grazing and predation influences community development 

(Swain et al., 1998). The implications of these findings were that silicone coatings 

exposed in environments with high biotic disturbance would perform well but, in 

environments where predators were absent, heavy fouling may occur. 

The commercial availability of silicone-based fouling release coatings has been 

increasing but, within the shipping sector, applications of silicone coatings were 

initially largely restricted to naval vessels, fast patrol boats, high speed catamarans and 

fast ferries (Hunter & Cain, 1996). Widespread research has continued, however, in 

attempts to improve both the durability and the fouling release properties of fouling 

release coatings (Clarkson & Evans, 1995a; Adkins et al., 1996). The fouling release life of 

silicone elastomers varies according to the formulation from a few, to up to 12 years 

(Callow, 1996).

Research on the adhesion of organisms to fouling release coatings undertaken at the 

Florida Institute of Technology led to the development of a model to predict the ship 

speed required for self-cleaning of individual barnacles (Schultz et al., 1999; Swain, 

1999). This predicted that, assuming free stream velocity and no boundary layer, the 

best-performing silicones would self-clean at about 10 knots. However, Swain 

considered that there was insufficient information available at present to predict the 

water velocities required to remove other fouling types and communities. This was due 

to differences in the adhesion strengths and the drag and lift coefficients for different 

fouling types as well as the variable hydrodynamic characteristics of boundary layer 

thickness and flow characteristics along a ship hull. Data suggested that hydrodynamic 
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lift and drag forces would be insufficient to remove all the fouling on the best 

present-day formulations.

Heavy slime films and macroalgal attachment has been observed on silicone elastomers 

cured with dibutyltin dilaurate (DBTDL) (Callow et al., 1987). Laboratory studies 

confirmed that Enteromorpha zoospore settlement was enhanced on silicone elastomers 

cured by DBTDL (Callow & Callow, 1998). Residual DBTDL in the coating would 

hydrolyse to dibutyltin hydroxide and lauric acid, or calcium laurate in seawater, and 

experiments with fatty acids suggested that it was the lauric acid component of DBTDL 

that was responsible for enhanced zoospore adhesion. However, early colonisation by 

algae was considered unlikely to adversely affect the long-term performance of 

commercial silicone coatings with this curing agent, since the combined effects of 

minimal adhesion and grazing were likely to ensure the surfaces remain relatively free 

of algal fouling (Callow & Callow, 1998).

Organic booster biocides can be used effectively in silicones to provide a temporary 

antifouling capability that is backed by the fouling release properties (Griffith & 

Bultman, 1997). Griffith & Bultman report favourable results from U.S. Naval Research 

Laboratory (NRL) trials of a broad spectrum, rapidly degrading biocide used in this 

way. Test panels immersed in Chesapeake Bay for a year were effectively antifouling 

while retaining a strong fouling release nature as the active ingredients became 

depleted. Vincent & Bausch (1997) suggested that to improve performance of silicone 

foul release coatings in the short term, it might be necessary to utilise coatings with a 

non-toxic fluid additive, or low release rates of biodegradable antifouling agents. 

Additional development was considered necessary to identify commercially viable 

means of combing the antifouling agents and PDMS based coatings. 

Experiments have been conducted in which non-leaching biocides have been added to 

silicone elastomer polymers (Clarkson & Evans, 1995b). The addition of 

(3-(trimethoxysilyl) propyloctadecyldimethyl ammonium chloride (DC5700) caused a 

reduction of fouling in the short term (23 d), but in the longer term (13 wk) both 

controls and experimental materials were fouled by a similar biomass of slime, barnacle 

and hydroids. 

Anderson (1998) summarised the key features and benefits of fouling release coatings 

for shipping as:

• Non-biocidal

o No release of biocides into the sea

o No toxic waste in dry-dock

o Not affected by biocide legislation

• Smooth, glossy surface

o Maximum speed

o Minimal fuel consumption
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• Extended fouling control

o Long-in-service periods (5 years)

o Reduced maintenance costs

• Chemically durable

o Surface stays smooth

o Only touch-up to damage needed at maintenance docking

• Copper-free

o Lower weight than standard antifoulings

o Safe to use on aluminium

• High solids

o Low solvent content

o 2 coat system (for 5 years)

Disadvantages of silicone systems were that they are expensive and more difficult to 

apply than biocidal antifouling paints (Anon., 1999b). An additional problem is that 

these systems cannot be applied on single component products and therefore cannot be 

used on top of existing antifouling systems. Griffith & Bultman (1997) warn that, if there 

is a defect in a silicone coating that can allow an immature barnacle to achieve a solid 

attachment, the coating will be undermined at that spot.

Silicones used in fouling release coatings are persistent, and their degradability is likely 

to be zero (Watermann et al., 1998). Several silicone coatings extrude oils that act on the 

surface to enhance effectiveness and, if the oils are silicone-based, such a mechanism is 

of concern because of environmental contamination. However, not all silicone fouling 

release coatings exude oil in this manner.
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5. NOVEL COATINGS

5.1 FIBRE COATINGS

Flocking is a process for making smooth surface into fibrous ones using an adhesive 

and electrostatically-charged fibres (Phillippi et al., 2001). The fibres are attached 

vertically and create a three-dimensional surface. Forsberg (1994) reported that larvae of 

mussels did not grow on fibre-flocked surfaces and barnacles appeared to be deterred 

from settling. Gyllenhammer (1997) found that flocked surfaces had a lower abundance 

of barnacles and green algae than untreated surfaces.

Fibre characteristics were also found to be important in determining the effectiveness of 

flocking. Gyllenhammer (1997) found that fibres longer than 1 mm were more effective 

at controlling hydroid and barnacle fouling, while shorter fibres were more effective 

against mussels, tunicates, and brown and red algae. 

Flocking can be done to most surfaces and with a variety of adhesives (Müller, 1995; 

Phillippi et al., 2001). PVC and nylon nets have been flocked for study and antifouling 

paint has been used as an adhesive for the flock fibres (Phillippi, 1999). 

5.2 ELECTROMAGNETIC COATINGS

A different approach to fouling control has been achieved through the use of an 

electrically conductive paint that is insulated from the substrate by non-conductive 

coatings (Hare, 2000). Minor differences in potential are electrically introduced between 

the hull and the coating. This leads to the electrolytical generation of either chlorine or 

hypochlorous ions. The conductive paint alternates as either the cathode or the anode of 

a cell on the hull, depending on the polarity of the current. Marine growth is inhibited 

when the hypochlorous ion concentration in the lamella zone next to the coating is 

above 0.1 ppm (Nishi et al., 1992).
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6. CURRENT AND PROSPECTIVE LEGISLATION ON ANTIFOULING PAINT USAGE

6.1 STATE CONTROLS

In Australia, the authority to control antifouling products initially rested with the 

States, and controls on the use of TBT antifoulings were introduced through State 

legislation and regulation. The general approach to TBT regulation by the States was to 

ban their application to vessels less than 25 m in length. For larger vessels, only paints 

with a TBT release rate of less than 5 μg cm-2 day-1 (as measured by the U.S. EPA 

Method) could be applied, and only under permit in some States. A number of States 

also imposed regulations on vessel repair facilities to ensure TBT contaminated hull 

wash-down water and grit-blasting waste was contained for disposal on land as toxic 

waste and not released into the adjacent waterway.

Authority for the registration of antifouling products passed to the Commonwealth in 

1994, when the National Registration Authority, an organisation established to approve 

agricultural and veterinary chemicals, was assigned this role. Regulation of waste 

discharges and practices within vessel repair facilities remains with the States.

6.2 NATIONAL REGULATIONS

6.2.1 NRA Registration

The National Registration Authority for Agricultural and Veterinary Chemicals (NRA) 

was established by the Commonwealth in 1993 as the responsible authority for the 

registration of agricultural and veterinary chemicals up to the point of retail sale (NRA, 

1999). Following an application to register a product, the NRA undertakes a detailed, 

independent assessment of all data on the chemical to ensure that high standards of 

quality, safety and efficacy are met, and that the product will have no unacceptable 

adverse impact on public health, occupational health and safety, trade or the 

environment. 

For specialist advice during the assessment process, the NRA receives input from three 

Commonwealth agencies:

• The Chemicals and Non-prescription Drugs Branch of the Department of Health 

and Aged Care, which undertakes detailed assessment of toxicology and human 

health data;

• The Risk Assessment and Policy Section of Environment Australia, which assesses 

the product’s environmental implications; and

• The National Occupational Health and Safety Commission, which assesses the data 

relating to occupational health and safety to ensure that risk to chemical users is 

avoided.

Registration may take up to 15 months (or more if there are major deficiencies in 

applications) to complete in the case of new products with new active constituents 

(NRA, 2000).
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Antifouling substances are defined as agricultural chemicals by the relevant 

Commonwealth legislation as they are ‘‘designed to destroy, stupefy, repel, inhibit the 

feeding of, or prevent pests on plants or other things’’ (C. Byrnes, NRA Antifouling 

Seminar/Workshop, Melbourne, September 2000). Antifouling paints which fit the 

definition are interpreted to be those which contain biocides, including products 

produced from ‘‘natural’’ antifouling agents. Operationally, the NRA has determined 

that the following antifouling products do not require registration:

• Paints that do not involve any biocidal action, such as:

• Silicone coatings

• Fibrelock coatings

• Products which are ‘‘foulant release’, i.e. modify surface tension

• Construction materials such as copper cladding.

Under the NRA process, 10 chemicals are presently registered for use as active 

constituents in antifouling products (Table 1). Only two of these, Sea-Nine 211 and 

zinc pyrithione have been fully assessed, with the remainder either ‘‘grandfathered’’ 

into the present system or registered for agricultural use. Actives that have not been 

fully assessed are likely to be at some time in the future. Irgarol 1052 was not 

grandfathered into the system, was submitted for approval a number of years back, but 

has not been registered. The antifouling biocides dichlofluanid, TCMTB and TCMS 

pyridine, which are approved for use in the UK, have never been considered by the 

NRA for use in Australia (L. Cahill, pers. comm.). 

Table 1 The registration status of antifouling biocides in Australia (L. Cahill, pers. 

comm.)

Active Registration Status

Metallic copper Registered for agricultural use

Cuprous oxide Registered for antifouling − not yet fully assessed

Cuprous thiocyanate Registered for antifouling − not yet fully assessed

Chlorothalonil Registered for antifouling − not yet fully assessed

Diuron Grandfathered: registered for agricultural use 

Seanine 211 Registered for antifouling − properly assessed

Thiram Registered for antifouling

Zinc oxide Registered for antifouling − not yet fully assessed

Zinc pyrithione Registered as antifouling - properly assessed

Zineb Grandfathered: registered for agricultural use
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Applications for registration of antifouling products must also provide evidence of 

efficacy of the product. Applicants are expected to be able to show that when their 

antifouling coating is used according to label directions, it is effective for the purpose 

claimed. In most cases, this requires applicants to submit the results of properly 

designed and conducted laboratory, simulated field trial and field trials that prove the 

efficacy of the product. Data produced under Australian conditions are required in 

most cases, but relevant data from overseas is also considered. 

6.2.2 ANZECC Code of Practice

The Australian and New Zealand Environment and Conservation Council (ANZECC) 

released a Code of Practice that sets out best practice in the application, use, removal 

and disposal of antifouling paints to minimise adverse environmental effects 

(ANZECC, 1997; Australian Marine Conservation Society, 1998). Major issues 

addressed by the code include:

• Human occupational health and safety considerations;

• The need to limit application, maintenance and removal of antifouling coatings to 

approved, licensed facilities;

• The need for uniform licensing of such facilities;

• The need for more restrictions on the use of tributyltin based antifoulants on craft 

>25m in length, where these operate in confined waters;

• The need to ensure that new facilities be designed to enable eventual safe disposal 

of treated waste waters; and

• The need to ensure that existing facilities plan for upgrading to safe disposal of 

waste waters and to sewer if waste water plants will accept these wastes.

The pamphlet promoting the ANZECC Code of Practice (Australian Marine 

Conservation Society, 1998) promotes a number of alternatives to TBT paints: 

foulant-release coatings, ceramic-epoxy coatings, epoxy-copper flake paints, electrical 

current systems, and biological compounds. Alternative biocidal systems are essentially 

dismissed with the statement: ‘‘Toxic alternatives to TBT, such as copper oxide paints 

and triazine herbicides, accumulate in marine systems and damage marine biota.’’ 

An ANZECC Code of Practice for In-water Hull Cleaning and Maintenance was also 

established in consultation with the Australian Quarantine Inspection Service (AQIS) 

and published along with the Code of Practice on Antifouling (ANZECC, 1997). 

6.2.3 Australian Government Policy

The Australian Government’s current policy on TBT was set in late 1998 with the 

release of ‘‘Australia’s Oceans Policy’’ (Anon., 1998). The policy is that the Government 

will:
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• Ban the use of tributyltin (TBT) antifouling paint by 2006 on vessels being repainted 

in Australian docks, unless the International Maritime Organisation sets an earlier 

date for such ban, in which case Australia will ensure that it complies with any such 

arrangements noting Defence’s operational requirements; and 

• Continue to promote the introduction of a global ban on TBT through the 

International Maritime Organization.

With the IMO adopting the International Convention on the Control of Harmful 

Anti-Fouling Systems on Ships, 2001, Australia is committed under the Oceans Policy to 

a ban on the application of TBT paints in Australian docks from 1 January 2003. The 

process has now commenced to enable Australia to formally ratify the International 

Convention (E. Kleverlaan, pers. comm.).

To support its position on banning TBT, the Australian Government allocated $650,000 

over 1999-2002 to an Antifouling Program to support the development of suitable 

alternatives to TBT, and to facilitate the implementation of the Government’s proposed 

ban. One major project initiated through this process is the Antifouling Patch Trial 

Project which aims to test the effectiveness of a range of ‘‘new technology’’ antifouling 

paints (see Section 7.3.2). 

6.2.4 International Regulation

At its Diplomatic Conference in October 2001, the International Maritime Organisation 

adopted the ‘‘International Convention on the Control of Harmful Anti-Fouling 

Systems on Ships, 2001’’ (International Maritime Organization, 2001). The purpose of 

this convention was to provide for the reduction or elimination of adverse effects on the 

marine environment and human health caused by anti-fouling systems. The prime 

intent was to ban the use of organotin antifouling biocides and, to fulfil this, Annex 1 to 

the Convention specifies that, for organotin compounds which act as biocides in 

antifouling systems, ships shall not apply or re-apply such compounds from 1 January 

2003. Further, from 1 January 2008, ships either: (1) shall not bear such compounds on 

their hulls or external parts or surfaces; or (2) shall bear a coating that forms a barrier to 

such compounds leaching from the underlying non-compliant anti-fouling system.

The Convention was framed, not only to eliminate the use of organotins, but to also 

enable action on other antifouling biocides perceived to cause harm at some time in the 

future. Under Article 6 of the Convention, any Party may propose and amendment to 

Annex 1. If considered warranted, the Committee can then proceed with an in-depth 

review which may lead to the introduction of international controls on the biocide of 

concern by means of an amendment to Annex 1. 

6.3 ANTIFOULING REGULATION & REGISTRATION IN OTHER COUNTRIES

6.3.1 United Kingdom

In the UK antifouling products are regulated as pesticides under ‘‘The Control of 

Pesticides Regulations 1986’’ and ‘‘The Plant Protection Products Regulations 1995’’. A 

list of approved products is published annually by the Pesticides Safety Directorate in 

conjunction with the Health and Safety Executive (e.g., Health & Safety Executive, 

2001). Products are listed by product name and marketing company under the active 
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biocide(s), and approved use (amateur and/or professional) designated. Details of 

listed biocides and products for 2001 are discussed in Section 7.2.

In 1997, following reviews of the triorganotin and copper compounds in antifouling 

products, UK’s independent Advisory Committee on Pesticides (ACP) agreed that 

reviews of all booster biocides should be considered in the year 2000 to allow a 

concerted environmental risk assessment (Advisory Committee on Pesticides, 2000). 

The ACP considered all available physico-chemical, toxicological, environmental fate 

and behaviour, ecotoxicological and efficacy data relating to the use of the eight booster 

biocides approved at that time for use in antifouling products: Kathon 5287, Irgarol 

1051, chlorothalonil, dichlofluanid, diuron, TCMTB, zinc pyrithione and zineb. The 

recommendations of the ACP were subsequently accepted by government and, as a 

consequence, in addition to specifying maximum permissible w/w concentrations for 

all biocides, the following actions were taken:

• Amateur use of Kathon 5287, chlorothalonil and TCMTB was revoked, due to 

concerns over the skin sensitisation potential of the compound;

• Amateur use of Irgarol 1051 was revoked, and its professional use restricted to 

vessels over 25 m in length, in view of adverse environmental monitoring data 

collected in 1998; and 

• Amateur and professional use of diuron was revoked, in view of both adverse 

monitoring data collected in 1998 and human health concerns.

At least one paint company has already acted to reformulate a number of major 

antifouling products on sale in the UK by replacing Irgarol 1052 and diuron with more 

environmentally preferred booster biocides (Nash, 2001b).

6.3.2 Europe

In the European Union, Council Directive 98/8/EC concerning biocidal products 

obligates the member states to implement national laws installing an approval 

procedure for biocides in antifouling coatings based on extensive data requirements 

(Ranke & Jastorff, 2000). The Biocide Products Directive (BPD) entered into force in May 

2000. The Directive had little immediate impact on the supply of existing active 

substances and their biocidal products, but this was expected to change over the 

subsequent three years (Watermann et al., 2001). The intent of the directive is to remove 

barriers to trade in biocides across the EU by harmonising controls for their marketing 

and use while ensuring high levels of health and environmental protection (Chapman, 

1998). Antifoulings are exempt from certain criteria in the directive during a 10-year 

transition period. 

The BPD process is described by Watermann et al. (2001). A first review regulation 

establishes the processes and the timetable that the companies must follow if the active 

substances currently supplied or included in products are to be included in the review 

programme. It requires that companies identify existing active substances and notify 

those they wish to have evaluated. A subsequent review regulation will list all 

identified and notified active substances. This will also give the deadline for final 

withdrawal from the EU market of all active substances, for use in biocidal products 

that are not on the list.
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Under the directive, biocides approved for use anywhere in the EU before 2000 can be 

approved for use in national states until 2010 under existing directive national rules 

(Denn, 2000). However, all new biocides proposed for market authorization cannot be 

approved unless the active ingredient is listed in the directive as one that is safe for use. 

Companies developing novel active ingredients have to compile a dossier proving they 

are eligible for inclusion. Products authorized by one member state and approved by a 

member state committee of experts can then be marketed freely in the rest of the EU. If 

a new compound is developed, which is not based on an existing active substance, the 

company must provide human and environmental toxicity data to get the new active 

substance on the list of active substances.

Watermann et al. (2001) considered that the BPD process would reduce the number of 

biocides on the EU market. In addition, they saw the BPD increasing the manufacturing 

costs , thus cutting the number of manufacturers and biocidal products. Some estimates 

put the costs at more than EUR 5 million for each biocide. Small and medium sized 

companies would not have the money to generate the data required by the BPD. 

Many European countries presently have domestic regulation of antifouling products. 

All antifouling coatings sold and applied in Belgium, the Netherlands, Ireland and 

Sweden within the EU, and Austria, Malta, and Switzerland outside of the EU, require 

registration, while other States have no restrictions.

In 2000, Denmark prohibited the import, sale and use of antifouling paints containing 

diuron and Irgarol for ships less than 25m in length. They also banned the use of 

antifouling paints on pleasure craft used predominantly in freshwater, and on boats of 

less than 200 kg.

6.3.3 United States/Canada

In the United States, antifouling biocides and formulations containing these biocides 

must be approved by the Environmental Protection Agency (Anon., 1999b). 

Registration of a new active ingredient requires the development of an expensive 

technical data package. The EPA, as mandated under the Federal Insecticide, Fungicide 

and Rodenticide Act (FIFRA), must determine that the benefits of the new pesticide 

outweigh the risks prior to granting approval for the new product (Bingaman & 

Willingham, 1995). This review and approval process can typically take at least 3-5 

years, given submission of a complete database and no evidence that the active 

ingredient will pose a significant risk to human health or to the environment. US EPA 

registration is not only important for the US, but is also viewed globally as a measure of 

environmental acceptability.

Alternative biocides are subject to a comprehensive risk assessment of data submitted 

by the manufacturer (Wood-Thomas, 1998, 1999). Requirements include data on 

product chemistry, residue chemistry, toxicology, ecological effects, environmental fate, 

and human exposure. The system is a two-tiered system: Tier 1 tests and data are 

required in all applications (although specific test may be exempted if specified 

conditions are met); Tier 2 tests and data may be required depending on the results 

obtained through Tier 1 testing. 
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With respect to toxicology data requirements, Tier 1 requirements are (Wood-Thomas, 

1998): acute and 90-day oral, dermal and inhalation toxicity, acute and 90-day 

neurotoxicity, primary eye and dermal irritation, dermal sensitisation, developmental 

toxicity, reverse mutation and mammalian cell assays, in vivo cytogenetics and 

immunotoxicity. Tier 2 requirements are: developmental toxicity, dermal penetration, 

chronic feeding, carcinogenicity and reproduction. For ecological effects, Tier 1 

requirements are: avian oral LD50, freshwater fish LD50, acute EC50 freshwater 

invertebrates, acute LC50/EC50 estuarine and marine organisms, fish early life stage 

aquatic invertebrate life cycle, fish life cycle, whole sediment acute invertebrates 

freshwater and marine, seedling emergence and aquatic plant growth. Tier 2 

requirements are: aquatic organism bioavailability/biomagnification, simulated or field 

testing aquatic organisms, and whole sediment acute invertebrates freshwater and 

marine. Environmental fate testing requirements are: Tier 1, hydrolysis and leaching 

studies; Tier 2, photodegradation in water, aerobic and anaerobic aquatic metabolism, 

adsorption/desorption, bioaccumulation studies in aquatic non-target organisms, and 

monitoring of selected U.S. waters. Data required on human exposure includes product 

use information, dermal and inhalation exposure outdoor during application and 

biological monitoring. Similarly, post application data on dermal and inhalation 

exposure and biological monitoring is required to evaluate human exposure during the 

removal of antifouling coatings from boat hulls.

To then get approval of coatings containing approved biocides, formulators must 

accumulate data studies on the performance of their formulations, generally over a 60 

month period. Formulations for application in U.S. shipyards must also meet Volatile 

Organic Compound (VOC) emission standards and products available for use in Japan 

and Europe may not be permissable (Wood-Thomas, 1998). To comply with air quality 

legislation a maximum of 400g of Volatile Organic Hazardous Air Pollutants (VOHAPs) 

per litre of wet paint is allowed.

All antifouling products applied in Canada must be Government registered, and 

registered antifoulings containing copper must have a release rate of less than 40 μg 

cm-2 day-1. Registration is not required for non-biocidal systems such as silicone fouling 

release coatings.

6.3.4 Asia/ New Zealand/South Africa

In Singapore, Malaysia, Korea, Taiwan and China there are no restrictions on the use of 

antifouling products. In Japan and Hong Kong China, all antifouling products must be 

registered. Registration is not required for non-biocidal systems such as silicone fouling 

release coatings.

All antifouling products for application in New Zealand, except non-biocidal fouling 

release systems, must be registered and registration of antifouling paints is also 

required in South Africa.
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6.4 PROSPECTIVE RESTRICTIONS AND REGULATIONS ON ANTIFOULING 

COATINGS

As Ranke & Jastorff (2000) comment, despite the environmentally motivated wish to 

generally dispense with the use of biocides in fouling protection, in the short term this 

seems unrealistic. There is therefore a need for better understanding of advantages and 

risks of using alternative biocides to ensure that those used cause no environmental 

harm.

A number of antifouling biocides apart from TBT have now come under scrutiny. As 

discussed above (Section 6.3.1) approval of diuron as an antifouling biocide has been 

revoked in the UK, the use of Irgarol 1051 restricted to vessels longer than 25 m, and 

amateur use of Kathon 5287 (Sea-Nine 211), chlorothalonil and TCMTB revoked. Both 

Irgarol and diuron have also been banned on pleasure boats in Scandinavian countries 

(Watermann et al., 2001).

Although Irgarol has never been approved for use in antifouling products in Australia, 

diuron is a predominant booster biocide and is present in nearly half of the antifouling 

products registered by the NRA in Australia.

With respect to copper, a traditional view of antifouling paints for small boat owners 

was ‘‘the heavier the can, the better the antifouling properties and the higher the cost’’ 

(Kettlewell, 2000). This was a consequence of the copper content, with paint 

effectiveness considered proportional to copper content, and copper content 

proportional to cost. Kettlewell commented that consumer publications frequently told 

consumers to weigh paint cans to find best value. Paints with lower copper content, 

boosted with organic biocides are now being promoted as a more effective and 

environmentally preferable approach.

Watermann et al., (2001) observed that the use of copper as an antifouling biocide is 

becoming increasingly restricted. Sweden has a ban on copper-containing antifoulings 

on recreational craft operating on its east coast, and a ban on the west coast will take 

effect in 2002. Scandinavian countries have banned the use of copper in freshwater 

areas and, from the beginning of 2001, the Netherlands will no longer approve 

copper-based antifouling paints for pleasure boats. Recent investigations in San Diego 

Bay, California, have found dissolved copper levels in the yacht basin to exceed the 

federal and state standard of 3.1 mg l

-1

. This may lead to the Regional Water Quality 

Control Board in San Diego requiring that copper levels be reduced, possibly by 

introducing non-toxic antifouling strategies. More widespread US restrictions on the 

use of copper antifouling paints within 5 years have also been predicted (Kettlewell, 

2000).

A number of countries have indicated a desire to reduce the input of copper from 

antifouling paints by imposing limits on the permissible copper release rate. However, 

the standard test method developed for measuring TBT release rates from antifouling 

coatings was unsuitable for copper (Lewis & Baran, 1993). Research was undertaken to 

develop such a method and, in 2000, both an ISO Method (ISO, 2000a, 2000b) and an 

ASTM method (ASTM, 2000) were released. Canada appears to be the first country to 

restrict copper-based antifouling paints by imposing a release rate restriction.
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The threat of a ban on copper as an antifouling has prompted five European and North 

American biocide manufacturers to form a pressure group to fight any such move 

(Nash, 2001c). The group, the Copper Antifouling Environmental Program (CAEP) was 

established to undertake research in an effort to ensure legislating authorities have the 

full scientific facts at their disposal before making decisions that are considered possibly 

to have wide-ranging, long-lasting and highly expensive consequences. CAEP is 

concerned that the bans in Sweden and the Netherlands will be used by radical 

environmentalists to persuade other governments to institute a ban on copper.
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7. ALTERNATIVES TO TBT ANTIFOULING COATINGS

7.1 REQUIREMENTS OF THE BOATING & SHIPPING INDUSTRY

Boat and ship owners would, ideally, prefer never to have to dock or slip their boats for 

underwater hull maintenance. However, fouling aside, mechanical damage and damage 

to anticorrosive coating systems necessitates dockings to avoid hull structural damage 

due to corrosion. Maritime safety regulations mandate ship owners to dock their 

vessels at a maximum interval of 5 years, and for older vessels the mandatory docking 

cycle can be shorter. TBT copolymer antifouling systems were the first to provide 5 year 

fouling protection for ship hulls, and this facilitated the implementation of 5 year 

docking cycles. Five years has therefore been the target longevity for premium TBT 

alternatives.

However, despite the efficiency of TBT, not all ships owners extended docking cycles to 

the permissible 5 years. Anderson (1998) analysed data on dry dock intervals of vessels 

greater than 4,000 dwt recorded in the International Paints database and compared data 

from the 1980s with data from the 1990s. The two most frequent dry-dock intervals for 

ships were at 24 and 30 months (Figure 4). Overall there were more ships dry-docking 

at these intervals in the 1990s than in the 1980s, which Anderson attributed to the 

increased use of TBT antifoulings in the 1990s. However, a greater percentage of ships 

dry-docked at less than 40 months interval in the 1990s compared to the 1980s; i.e. there 

was a trend to shorter, not longer, dry-dock intervals. Overall, the number of ships that 

docked at 60 month (5 year) intervals was small, representing less than 10% of the total.

Figure 4 DWT and dry-dock interval for the 1980’s vs. 1990’s (from Anderson, 

1998)

Damodaran et al. (1999) surveyed shipowners for drydocking information. Their survey 

found that nine of eleven shipping companies that used TBT paints operated on a 

five-year dry-docking interval, whereas eight of eight that used tin-free paints 

dry-docked on a 30-month cycle. The TBT painted ships operating on less than a 

five-year dry-docking interval generally did so because other maintenance needs 

necessitated more frequent dry-docking. U.S. ships, for example, are required by law to 

dry-dock every 30 months.

Watermann et al. (2001) made a similar observation on docking intervals. They 

comment that although TBT SPCs could provide performance of 60 months, only 
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15-20% of the world fleet need actual docking intervals of 60 months. However, this 

percentage was mostly composed of container ships, which are of increasing 

importance in world trade. Shipowners operating in the Baltic and North Sea also 

commented that the average vessel goes three years between drydocking and only 

about 10% need a five year system (MER, 1998a). Liberia, in a submission to IMO 

(MEPC 46/5/10, 16 February 2001), estimated that 20% of ships, representing a majority 

of tankers, bulkers and container ships, operate on a dry-dock schedule of 60 months.

7.2 TBT-FREE ANTIFOULING COATINGS

There are presently 43 tributyltin-free antifouling products registered by the NRA for 

use in Australia (Appendix 1). These contain 10 different active ingredients (Table 2). 

The registration of these actives was discussed in Section 6.2.1. Almost all contain 

copper as the primary biocide, with 74% containing cuprous oxide. Those without 

cuprous oxide, including those containing cuprous thiocyanate, are marketed primarily 

for application to aluminium hulls, stern drives and other submerged aluminium 

components, although yacht owners desiring white or other light coloured paint 

systems would also need to use cuprous oxide free products. The most commonly used 

booster biocide is the herbicide diuron.

Table 2 List of NRA approved antifouling actives and their usage in registered 

antifouling products.

Active No of Products % of Products

Metallic copper 1 2.0

Cuprous oxide 38 77.6

Cuprous thiocyanate 8 16.3

Chlorothalonil 1 2.0

Diuron 23 46.9

SeaNine 211 1 2.0

Thiram 2 4.1

Zinc oxide 11 22.4

Zinc pyrithione 0 0

Zineb 4 8.2

Total 49

For comparison, in the UK there are 355 approved TBT-free antifouling products 

containing 17 different actives (Table 2). A comparison of the actives shows a similar 

proportion of copper-based products to Australia. Major differences are in the use of 

booster biocides. Diuron is used less widely, seemingly substituted by the use of the 

actives Irgarol and dichlofluanid which are not permitted in Australia. However, in 

1998, diruon was estimated to be present in ~50%, Irgarol 1051 ~30%, ZPT ~3% and 

dichlofluanid ~2% of the paints used in the UK (Thomas et al., 2001). The incorporation 

and registration in the UK of the ‘‘newer’’ biocides, Kathon 5287 (=Sea-Nine 211) and 

zinc pyrithione is also significant, these now found in 8.7% and 7.9% of products 

respectively. Zinc oxide is not considered an active constituent in the UK.
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Table 3 List of UK approved antifouling actives and their usage in registered 

antifouling products. (* approval of products containing diuron has since 

been revoked)

Active No of Products % of Products

Metallic copper 15 4.2

Cuprous oxide 269 75.8

Cuprous thiocyanate 56 15.8

Copper napthenate 1 0.3

Copper resinate 3 0.8

Cuprous sulphide 1 0.3

Copper sulphate 1 0.3

Chlorothalonil 11 3.1

Dichlofluanid 26 7.3

Diuron* 90 25.4

Irgarol 99 27.9

Kathon 5287 31 8.7

TCMS Pyridine 8 2.3

TCMTB 5 1.4

Zinc napthenate 3 0.8

Zinc pyrithione 28 7.9

Zineb 8 2.3

Total 355

203 antifouling products (TBT-containing and tin-free) are registered for use in the US 

but, in contrast to the UK, fewer antifouling actives are approved for use (Table 3) (J. 

Bloom, pers. comm.). Apart from copper compounds, only three booster biocides 

(Irgarol, Sea-Nine 211 & zinc pyrithione) are approved and all are relatively new 

products. Significant exclusions are diuron and the dithiocarbamates such as zineb. The 

lower usage of cuprous thiocyanate is considered to be due to US legislation allowing 

the continued use of TBT paints on aluminium hulls and other underwater components 

on small craft. 
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Table 4 List of US approved antifouling actives and their usage in registered 

antifouling products.

Active No of Products % of Products

Metallic copper 13 6.4

Copper hydroxide 4 2.0

Cuprous oxide 176 86.7

Cupric oxide 2 1.0

Cuprous thiocyanate 6 3.0

Irgarol 7 3.4

Seanine 211 3 1.5

TBT methacrylate 15 7.4

Zinc oxide 1 0.5

Zinc pyrithione 5 2.5

Total 203

The majority of the products registered for use in Australia, the UK and the US are 

mostly conventional coatings directed at the recreational and small boat markets and 

the expected effective antifouling life of these would range between 12 and 36 months. 

7.2.1 Conventional TBT-Free Antifouling Coatings

Anderson (1998) compared the performance of TBT and TBT-Free antifouling paints 

using data extracted from the International Paints database known as Dataplan (see 

AMOG Consulting, 2001). For this comparison, a fouling rating of less than 10, which 

represents only microfouling (slime) presence, was deemed as satisfactory.

The graphical representation of results (Fig 5) show that of 966 ships painted with TBT, 

more than 80% were deemed satisfactory after 37-42 months. In contrast, of 399 ships 

painted with soluble matrix paints and 299 ships painted with contact leaching paints, 

less than 75% were deemed satisfactory after only 13-18 months and, at 37-42 months, 

around 60% of those with soluble matrix paints and under 45% of those with contact 

leaching paints remained satisfactory.

 

Figure 5 Percentage of ships satisfactory vs. in-service period (from Anderson, 

1998)
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This performance is reflected by Bennett (1996) in describing the experience of 

shipowners who evaluated ‘‘new’ formulations introduced in response to TBT 

regulations in the late 1980s and early 1990s. Paints performed well for the first two or 

three years, but then problems including poor structural integrity, premature fouling, 

and the need for more frequent dry-docking were reported. British Petroleum (BP), 

which switched to tin-free systems in the early 1990s, found their performance was not 

equal to TBT systems (MER, 1999).

Conventional soluble matrix and contact leaching systems, as discussed in Section 2.1.2, 

have limited effectiveness due to the rapid leach layer build up, deposition of basic 

cupric carbonate, and consequent exponential decay in biocide release rates, ultimately 

restricting effectiveness to 12-18 months. Though considered obsolete technology, with 

little technical advance over the last 30 years, these remain and are likely to continue to 

remain at the ‘‘cheap and cheerful’’ end of the market (Royston, 1999). 

Ablative/eroding systems, such as CDP types, are essentially better formulated 

versions of conventional systems, which erode by a combination of dissolution and 

mechanical removal, and can have effective life of up to 36 months.

Damodaran et al. (1999) conducted a comparative analysis of the costs of using TBT SPC 

antifouling coatings and their alternatives to determine the nature and sources of 

economic impact on the operators of deep-sea vessels. The analysis included the costs of 

antifouling paint, dry-docking rates, clean hull fuel consumption, and fuel consumption 

penalties as a result of hull fouling. An assumption of this analysis was that tin-free 

products could not match the five-year dry-docking interval of TBT painted ships, and 

that a 30-month dry-docking interval would be required. Copper ablatives were 

estimated to be one-and-a-half to four times more expensive than TBT SPCs, due to fuel 

penalties, higher dry-docking costs, revenue lost, and paint costs. Based on information 

supplied by three paint companies, paints costs for copper ablative paints were quoted 

as varying from 68% to 290% of the cost of TBT SPCs. 

7.2.2 ‘‘New Technology’’ Antifouling Coatings

As discussed in Section 2.1.5, ‘‘new technology’’ tin-free antifouling coatings are based 

on new resin systems, which are claimed to polish consistently in service and to provide 

antifouling performance comparable to TBT copolymer systems, i.e. 5 or more years. 

Products considered to be ‘‘new technology’’ products are listed in Table 4 and 

Appendix 2.
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Table 5 List of ‘‘new technology’’ copper-based antifouling coatings.

Manufacturer Product Series Name Resin System Actives

Akzo Nobel Intermooth Ecoloflex Copper acrylate Cuprous oxide

ZPT

Chugoku Sea Grandprix 1000, 2000 Silyl polymer Cuprous oxide

?

Sea Grandprix 500, 700 Metallic acrylate Cuprous oxide

?

Hempels Globic SP-ECO Zinc carboxylate Cuprous oxide

SeaNine 211

Jotun Sea Quantum Silyl polymer Cuprous oxide

CPT

Kansai Exion Zinc acrylate Cuprous oxide

ZPT

Sigma Alphagen ? Cuprous oxide

SeaNine 211

A common characteristic of these systems is the use of one of three of the ‘‘new’’ 

biocides as booster biocides, Sea-Nine 211, zinc pyrithione and copper pyrithione, to 

complement the performance of the copper.

 Some manufacturers’ claims for these products are as follows:

Jotun Seaquantum:

‘‘These new products will be the most effective non-tin self-polishing products to date. 

The technology will be equal to the performance of the previous tin-containing 

formulations and will be capable of providing dry dock intervals of five years or more. 

Jotun’s products have been applied to more than 194 test vessels since 1995’’ (C. Rosler 

in Anon., 1999b).

SeaQuantum was developed by Jotun in conjunction with Nippon Oils and Fats (NOF 

Corporation) in Japan. The base is a silyl polymer which is claimed to hydrolyse in a 

similar manner to TBT copolymers and smooth in service (MER, 2001). Jotun have cited 

a 15% reduction in the fuel consumption of a SeaQuantum-coated VLCC which equated 

to over NOK 2.5 M in the first two years alone. Jotun also claim that the performance of 

the product has been proven over seven years of testing. The product is quoted as being 

three or four times the cost per litre of tin-based products (MER, 2001).

Three SeaQuantum products have been formulated to suit different antifouling needs 

(Anon., 2000a):

• SeaQuantum Plus, for vessels with speeds above18 knots;

• SeaQuantum Classic for speeds of 12 − 20 knots; and
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• SeaQuantum FB for use on flat bottoms.

The benefits of SeaQuantum are stated to be (Anon., 2000a):

• Constant linear polilshing rate giving total protection for up to 60 months;

• Environmentally acceptable while giving TBT-containing performance;

• Hard paint film making it suitable for high speed vessels;

• High dry film thickness allowing long-term system design;

• Good recoatability, giving virtually no limit to overcoating; and 

• Well suited to newbuildings.

International Intersmooth Ecoloflex:

‘‘Developed in conjunction with International’s technology partner in Japan, Nippon 

Paint Marine Coatings, the patented, self-polishing copolymer technology of 

Intersmooth Ecoloflex SPC ensures continual biocide release and inherent self 

smoothing for extending in-service periods.......

Intersmooth 460 Ecoloflex SPC has a number of major features and benefits in deepsea, 

as well. The medium polishing rate with controlled biocide release allows tailored 

specification design with optimum dry-film thickness. Its self-smoothing controls 

average hull roughness for maximum fuel efficiency.

Just like its deepsea counterpart, Intersmooth 360 Ecoloflex SPC assists operating 

efficiency with freedom from current or future restrictions on the use of tin and 

associated waste disposal costs........’’ (J. Kelly in Anon., 1999b).

The Intersmooth Ecoloflex SPC system is claimed to be have been proven through 

experience in more than 5000 ship applications over 9 years (Anon., 2000c). Intersmooth 

460 and 465 Ecoloflex are for use on deepsea ships, while Intersmooth 360 and 365 

Ecoloflex are for coastal vessels, with both providing an equivalent performance level to 

premium-grade TBT SPC antifoulings. They are considered suitable for in-service 

periods of up to 60 months, and to offer controlled biocide release, even at slow vessel 

speed, and self-smoothing characteristics that reduce hull roughness and therefore 

generate fuel savings.

Hempel: Globic SP-ECO

‘‘Globic SP-ECO is Hempel’s new generation of tin-free antifouling. The hydrolysable 

zinc carboxylate polymer salt binder technology makes use of a composite 

reinforcement with micro fibres (patent pending) for improved polishing and 

mechanical properties, compared to conventional tin-free antifoulings.......
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In Globic SP-ECO there is a controlled buildup of the leaching layer, thus the release of 

bio-active material is constant through the system’s lifetime. Its controlled polishing 

rate results in a better self-smoothing effect, with fuel-saving benefits’’ (Hempel in 

Anon., 1999b).

Globic SP-ECO is marketed as a fast and slow polishing type and targeted towards 

coastal operating and world-wide deepsea vessels respectively. The fibres incorporated 

in the paint are claimed to yield exceptional mechanical strength and optimal polishing 

control, virtually eliminating cracking, peeling and impact damage (MER, 2001). A high 

solids content minimises the use of solvents and VOC emissions, and the controlled 

leach layer enables recoating at dockings with only a high pressure freshwater 

washdown.

Chugoku Sea Grandprix

Chugoku Marine Paints claims a holding of around 50% market share in Japan, and 

15% worldwide, in the supply of paints and coatings to the shipping and shipbuilding 

markets (Anon., 2000b). With respect to tin-free coatings, they claim full-ship 

applications of their Sea Grandprix to more than 1000 large deepsea vessels. Three types 

of tin-free technology are utilised by Chugoku, silyl resin, acrylate resin, and hydration 

resin, with the silyl based systems claimed to provide 5 year protection.

To quote from a recent report (Anon., 2001a):

‘‘Chugoku offers four different mainstream systems, the newest of which is Sea 

Grandprix 1000 for ships with a high fouling risk such as LNG tankers and VLCCs 

trading to the Arabian Gulf, also cruise liners, short-sea and coastal ships sailing in the 

Mediterranean and Caribbean regions. An associated version − Sea Grandprix 2000 − is 

particularly formulated for vessels generally sailing on coastal voyages. Both these 

systems are based on organo-silyl acrylate resins and offer owners up to five-year 

periods between drydockings. An equivalent performance to paints containing 

high-strength tributyl-tin (TBT) is claimed.

The company’s second-generation concept (Sea Grandprix 500, or Sea Grandprix 700 for 

coastal ships) is based on metallic acrylate resin and is suitable for most deep-sea and 

coastal vessels. Drydocking intervals between three and five years are possible, and 

perfomance is said to be equivalent to a medium-strength TBT system. It can be applied 

over other antifoulings. Typical uses are on bulk carriers and tankers, ferries and ro-ro 

ships, and car carriers.......’’ .

Sigma AlphaGen 

The AlphaGen series of coatings released by Sigma Coatings are based on ‘‘newlypatented European technology and [are] believed to be the first to utilise a pure organic 

molecular system to control the polishing action’’ (Anon., 2000d). The AlphaGen series 

comprises Sigma AlphaGen 20, for general deepsea tankers and bulker service, Sigma 

AlphGen 50, for ships with lower and more intermittent operational rates, and Sigma 

AlphaGen 10 for the flat bottom areas of all ship types. The AlphaGen series is claimed 
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to use co-biocides with superior resistance to UV degradation, to have low VOC levels, 

and to enable specifications for 24, 36 or 60 month performance.

A comparison of the performance of the International paints copper acrylate system, 

using data extracted from the International Paints Dataplan, showed 90% of 302 ships 

painted with this system to have satisfactory performance after 37-42 months; better 

than the 80% performance from 966 ships painted with TBT SPC (Fig. 7.2.2) (Anderson, 

1998).

Figure 6 Percentage of ships satisfactory for copper acrylate SPC vs. TBT SPC 

(from Anderson, 1998).

A comparison of the performance of new technology products (Ecoloflex) against a TBT 

copolymer antifouling (Intersmooth 210) and a conventional types of tin-free 

antifouling (Interspeed 642), extracted from the International Paints Dataplan database 

(Tables 5, 6), shows better performance overall of the new technology product with 

respect to weed fouling. The Dataplan ‘‘Satisfactory Performance Ratings’’ for these 

products were: Intersmooth 210 − Weed: 75%; Interspeed 642 − Weed: 79%, Animal: 

95%; Ecoloflex SPC 200 − Weed: 85%, Animal: 99%; Ecoloflex SPC 600 − Weed: 87%, 

Animal: 100% (J. Millett, pers. comm.).

Table 6 Percentage of all vessels with respective antifouling ratings.

Fouling 

Rating

Interspeed 642 

(256 vessels)

Intersmooth 210 

(555 vessels)

Ecoloflex SPC 200

(363 vessels)

Ecoloflex SPC 600 

(66 vessels)

Weed Animal Weed Animal Weed Animal Weed Animal

0- <1 44.1 74.6 43.1 n/a 66.7 87.3 66.7 89.4

01-04 14.8 12.5 18.4 n/a 11.6 8.8 9.1 7.6

05-09 12.5 4.3 10.5 n/a 5.0 2.2 4.5 3.0

10-19 11.3 3.5 10.3 n/a 6.3 0.8 6.1 -

20-29 5.1 0.8 5.9 n/a 3.6 0.6 3.0 -

30-49 3.1 2.0 4.3 n/a 1.7 0.3 6.1 -

50-74 5.1 1.6 4.0 n/a 2.5 - 3.0 -

75-100 3.9 0.8 3.6 n/a 2.8 - 1.5 -
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Table 7 Percentage of vessels within scheme life with respective antifouling 

ratings.

Fouling 

Rating

Interspeed 642 

(129 vessels)

Intersmooth 210 

(296 vessels)

Ecoloflex SPC 200

(141 vessels)

Ecoloflex SPC 600 

(39 vessels)

Weed Animal Weed Animal Weed Animal Weed Animal

0- <1 51.2 79.1 47.8 n/a 67.4 93.6 76.9 92.3

01-04 12.4 14.0 19.7 n/a 12.8 4.3 5.1 5.1

05-09 15.5 2.3 8.1 n/a 5.0 1.4 5.1 2.6

10-19 8.5 2.3 8.8 n/a 4.3 0.7 - -

20-29 3.9 1.6 6.1 n/a 1.4 - - -

30-49 2.3 0.8 2.7 n/a 2.8 - 7.7 -

50-74 1.6 - 4.4 n/a 5.7 - 2.6 -

75-100 4.7 - 2.4 n/a 0.7 - 2.6 -

Five year Intersmooth Ecoloflex SPC systems have now been applied to entire 

underwater hulls, and International Paints recently reported on its performance on one 

ship after 61 months in service (www.international-marine.com). To quote:

‘‘The M/V Ramiah, a 300,361 DWT Double Hull Tanker was built in Japan, and 

delivered to the owners, National Shipping Company of Saudi Arabia, in January 

1996. The antifouling system applied at Newbuilding was Intersmooth Ecoloflex 

SPC.

Mideast Ship Management Co Ltd, who manage the M/V Mariah for the owners, 

drydocked the vessel in Dubai during February 2001. The Intersmooth Ecoloflex 

SPC antifouling on a total underwater are of 20,050 sq metres was found to be in 

excellent condition, with slime only after 61 months in-service.

The attending Superintendents were very impressed with the performance of the 

antifouling system and commented that they had never seen a vessel in such good 

condition after such a long in-service period.

A sister vessel M/V Safaniyah also dry-docked in Dubai during April 2001 and the 

antifouling system was again in excellent condition after 51 months in-service.’’

Patch trials of tin-free antifouling systems were undertaken by DSTO and the RAN on 

operational vessels based in Cairns, Sydney and Western Australia over the period 

1993-1999 (Lewis 2001). In these trials, six different tin-free antifouling coatings were 

applied to each side of each vessel in strips extending from above the waterline to the 

keel. International Ecoloflex was the only ‘‘new technology’’ tin-free system available 

when the trials were initiated; the other five coatings were soluble matrix/CDP 

technology systems. International Ecoloflex was clearly the best-performing tin-free 

product on all three vessels, and remained macrofouling free and physically sound after 

4 years on the Cairns-based vessel and for over 5 years on the Sydney based vessel. Full 

hull applications have since been applied to two RAN ships: the patrol boat HMAS 

Geraldton, and the ANZAC frigate HMAS Warramunga. To date, the coating has 
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demonstrated excellent antifouling performance and physical durability on these ships, 

and dynamic flow experiments by DSTO have demonstrated polishing performance 

similar to TBT SPC (Lewis, 2001). Lewis (2001) saw the immediate future without 

tributyltin as a return to copper-based products for most shipowners. However, use of 

the new technology products would come at a price, as these were more expensive than 

TBT systems. 

International Ecoloflex has recently been registered by the NRA (NRA, 2001, 2002) and is 

now the first and only ‘‘new technology’’ tin-free coating available for application in 

Australia.

Under the Coasts and Clean Seas program, Environment Australia are currently 

funding an antifouling patch trial project to evaluate ‘‘new technology’’ tin-free coatings 

on Australian commercial shipping. The Australian Shipowners Association is 

managing the project, and the Technical Committee also includes representatives from 

the National Registration Authority, The Australian Paint Manufacturers Federation, 

and the Defence Science and Technology Organisation. Seven paint companies are 

represented, Ameron, Chogoku, Hempels, International, Jotun, Kansai, and Sigma, and 

patches will be applied on up to 24 vessels. To date patches have been applied to three 

vessels, BHP’s Iron Monarch and Iron Chieftain, and the Altrans. 

Some concerns have been raised about the performance of Ecoloflex on Liquid Natural 

Gas (LNG) and Liquid Petroleum Gas (LPG) ships operating between Australia’s north 

west shelf region and Japan. A company analysis of International Dataplan data 

indicated that fouling levels were much higher on LNG/LPG ships painted with both 

Ecoloflex and TBT coatings than on other ship types with the same systems. 

Approximately 50% of LNG/LPG tank ships had fouling ratings greater than 10, 

irrespective of which system they were painted with, whereas for bulk carriers, only 

17% painted with TBT and 6% painted with Ecoloflex has fouling ratings greater than 10. 

The fouling levels are attributed to the LNG/LPG ships operating in one of the toughest 

fouling environments on a global basis (Akzo Nobel, 1999). 

One of the LNG ship operators, ALSOC, now uses the new technology systems Jotun 

Sea Quantum, Chugoku Sea Grandprix, and International Intersmooth Ecoloflex on 

their fleet (D. Amble, pers. comm.). Vessels are on a 24-month docking cycle and the 

operators are finding little reduction in ship performance over this time. Minimal 

maintenance is required at the scheduled dockings of these vessels. These vessels, built 

in Japan, were compelled to use TBT-free paints under Japanese regulations.

In Sweden, where the use of TBT was subject to greater restriction than the rest of 

Europe, a survey found that the majority of shipyards and shipowners who used the 

latest non-TBT paints have observed insignificant problems − economic or otherwise 

(MER, 1998a).

A cost analysis of TBT SPC coatings and tin-free alternatives for deep-sea vessels 

(Damodaran et al., 1999), compared costs of both copper ablatives and tin-free SPCs. 

Tin-free SPCs were estimated to be one to one-and-a-half times more expensive than 

TBT SPCs due to higher dry-docking costs, revenues lost, and paint costs. It was 

assumed in this analysis that use of tin-free SPCs would necessitate increasing the 

frequency of dockings because the authors ‘‘found no data indicating that tin-free 

paints can, at present, match the 60-month dry-docking interval TBT SPC paints can 

offer shipowners and operators’’. The overall cost analysis therefore factored in the 
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costs of additional dockings for vessels using tin-free SPCs. Based on information 

supplied by three paint companies, paints costs for copper SPC paints were quoted as 

varying from 160% to 295% of the cost of TBT SPCs. 

ORTEPA, the association of organotin producers, circulated a similar analysis by e-mail 

ahead of the IMO Diplomatic Conference in October 2001. The data was extracted from 

a report prepared by Princeton Economic Research and claims that the cost of using 

TBT-free paints on tankers, bulkers and containers is between two and two-and-a-half 

times more expensive. The set of figures presented for tankers is given in Table 7.

Table 8 Comparative costs per tanker of TBT-based paints and TBT-free 

alternatives (Source: ORTEPA))

TBT (60 mos.) Copper Ablative (60 

mos.)

Copper SPC (60 mos.)

Dry Dock Rate $196,000 $392,000 $392,000

Paint Cost 24,884 (est.) 45,786 (est.) 70,670 (est.)

Lost Revenue 322,000 644,000 644,000

Diversion Cost 138,000 276,000 276,000

Total ($) US $ 680,884 US $ 1,357,786 US $1,382,670

The underlying assumption in this analysis, which seems to be based on the 

Damodaran et al. (1999) study, is that ships using TBT-free coatings will need to dock 

for repainting twice as often as when painted with TBT coatings. While this may be true 

for copper ablative systems, results now suggest that TBT-free SPCs are able to provide 

60-month performance. If this is so, all costs in Table 7, apart from the paint cost would 

be equivalent for the TBT SPC and the Copper SPC. The paint cost for Copper SPC 

would also be halved, as only one application would be required for the 60-month 

period, so the comparative paint cost would be $24,884 for TBT SPC, and $35,355 for 

Copper SPC. This represents an increase of less than one half in paint costs, and an 

increase in costs of less than one tenth overall.

Evans et al. (2000) reported on a survey of ship operators on their experiences using 

non-TBT paints conducted by the International Chamber of Shipping. Satisfaction with 

performance was expressed by many of the 37 respondents (from eight countries), 

although 10 respondents claimed that fouling rates of alternatives were higher than 

those of TBT paints. No indication was given as to the type of tin-free paints used by 

these operators: ‘‘new’’ or conventional technology.

Trials of experimental surface-fragmenting, self-polishing, tin-free antifouling coatings 

showed promising results (Kuo et al., 1999). As expected, polishing rates were faster 

than in other self-polishing tin-free paints and varied with the resin used in the 

formulation. Paints containing cupric oxide and chlorothalonil were determined in raft 

tests to be 80-90% as effective as the conventional tin-containing antifouling paints and, 

in tests on two fishing vessels, were free of macrofouling after 26 months. 
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7.3 BIOCIDE-FREE ALTERNATIVES

7.3.1 Fouling-Release Coatings

Many of the major international marine paint companies market silicone-type fouling 

release coatings and these include the systems listed in Table 9 and Appendix 3. 

Watermann et al. (1997) reported that since the 1970s there had been roughly forty 

patents for silicones as fouling release coatings on ships and underwater constructions. 

These included pure poly(dimethylsiloxane) (PDMS) elastomers (e.g. Intersleek, 

Everclean) and silicone coatings containing hydrophobic liquids (e.g. Biox, Bioclean). A 

fluorinated coating has also been marketed, but this is based on early fluoropolymer 

coating technology (R. Brady, pers. comm.). 

Table 9 Fouling release coatings available on the world market

Manufacturer Product Name

Chugoku Marine Paints Bioclean / Eco-Speed

Hempels Hempasil SP-EED

International Intersleek / Veridian

Kansai Biox

Sigma Sigmaglide

NOF Corporation Everclean

Silicone-based fouling release coatings have been considered ideal for high speed, high 

activity craft, particularly ‘‘Fast Ferries’’ which operate at speeds in excess of 30 knots 

(Anderson, 1998). Ferry operators to have applied the International Paints system 

Intersleek in 1998 included Buquebus (Argentina), Stena (UK), Ceres (Greece), 

CTS-Parkview (Hong Kong), Condor (UK), CMNN (France), ACTV (Italy), FBSF 

(Norway), Fuller Cruises (New Zealand), Trasmediterranea (Spain), Deniz Otobusleri 

(Turkey), Crew Boats Inc (USA), and Mashantucket Pequot (USA). Fuel consumption 

on one vessel was measured to drop by between 20,000 and over 30,000 l mo-1 when it 

switched from a conventional antifouling coating to Intersleek.

Observations on the performance of silicone FR coatings on fast ferries have noted that 

slime fouling can remain adhered to the coatings, even at speeds greater than 30 knots 

(Anderson, 1998). This was attributed to the slime-forming organisms having a low 

profile, which enabled them to exist within the laminar layer next to the hull. This 

protected them from turbulent flow, irrespective of vessel speed.

The price of silicone-based FR coatings is much higher than that of other types of 

antifouling paints (Anderson, 1998). It was therefore only considered by Anderson to be 

economically tenable as a replacement for TBT SPC systems on vessels able to fully 

exploit its particular characteristics (see Section 4.2). However, Anderson commented 

further that the original TBT SPC systems were considerably more expensive (x3) than 

the products they replaced, and that as the technology matured, and economies of scale 

were realised, the price dropped significantly. He predicted that the same would 
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happen with fouling release coatings and that the technology would become 

increasingly important for control of fouling in the 21st century.

Clarkson (1999) reviewed the status and antifouling potential of silicone elastomers. She 

concluded that non-toxic silicone elastomers seemed to be a successful alternative to 

toxic systems and, with continued research and development, could fulfil their foul 

release potential. They were considered a high cost alternative to conventional paints, 

but lower overall costs were anticipated from the potential effects of increased sales on 

production and raw material costs, simplification of the composition and ease of 

application, and improvement and extension of coating life. 

The accumulation of fouling on three silicone fouling release coatings, GE RTV11, Dow 

Corning RTV 3140 and International Intersleek, was examined on test panels immersed 

in Pearl Harbor, Hawaii, and compared to an epoxy anticorrosive paint as the control 

(Holm et al., 2000). The control coating failed rapidly (180-220 d); fouling of the GE 

coating and Dow Corning coatings was slower, but eventually reached a similar 

community structure and coverage as the control (~300 d); the Intersleek coating 

remained lightly fouled throughout the experiment (743 d). Changes in the surface 

properties of GE silicone elastomers on prolonged immersion in water were 

investigated (Estarlich et al., 2000). Considerable increases in hydrophilicity and surface 

rugosity were measured, which were attributed mainly to surface structural 

rearrangements accompanying adsorption of water. Although fouling settlement was 

least on GE RTV11 and greatest on fluorosilicones, the range of variation was small 

compared to the long term fouling resistance of the materials.

The Royal Australian Navy and the Defence Science and Technology Organisation have 

undertaken panel trials of a range of fouling release coatings and vessel trials of the 

International Intersleek system (Lewis, 2001). The first Defence vessel application of 

Intersleek was to an aluminium-hulled workboat based in Western Port in 1993. This 

boat has a maximum speed of 8 knots and low activity. Fouling has been easily 

removed by water jetting at pressures of about 1500 psi. No recoating or repainting has 

been undertaken since the coating was first applied. The bow section of a patrol boat 

based in Cairns was coated with Intersleek in 1995. The system performed effectively, 

with no significant macrofouling, through a 4 year docking cycle. However, significant 

fouling growth did establish on submarines painted with the Intersleek system. This 

was attributed to their shape, operating profile and speed. Fouling could be easily 

removes by water jetting when the boats were out of the water, but improved cleaning 

methods were seen as necessary for in-water hull husbandry.

The U.S. Navy have also undertaken patch trials of Intersleek and other fouling release 

coating systems. The U.S. Organotin Anti-fouling Paint Control Act of 1998 required that 

the Environmental Protection Agency (EPA) and the Navy conduct research on 

chemical and non-chemical alternatives to organotin paints (Pilgrim et al., 1995). 

Concerns were also held that increasing regulatory pressure on cuprous oxide 

antifouling paints could leave the Navy with no compliant alternatives. Accordingly, 

the Naval Sea Systems Command (NAVSEA) established a 

Non-polluting/Biodegradable Antifouling Coatings program. Under this program test 

patches were applied to the U.S.S. Spruance and U.S.S. Paul F. Foster in 1995. Six fouling 

release coatings were applied as patches to the U.S.S. Spruance, and six fouling release 

and five cobiocide systems to the U.S.S. Paul F. Foster (Pilgrim et al., 1995). The fouling 

release coating systems applied are listed in Table 10.
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Table 10 Fouling release systems applied as test patches to USN 

ships

U.S.S. Spruance U.S.S. Paul F. Foster

International Intersleek International Intersleek

Dow Corning/Hempel 8730 Dow Corning/Hempel 8730

Dow Corning/Hempel 8740 Dow Corning/Hempel 8740

Chugoku Marine Bioclean Chugoku Bioclean DX

General Electric Exsil 2200 General Electric Exsil 2200

Naval Research Laboratory Duplex system Devoe Devclear

The test systems were to be inspected by divers at three-month intervals, but reports 

from these inspections or other reports on system performance have not been seen. 

In a subsequent trial under the NAVSEA program, International Intersleek was applied 

to the entire underwater hull of the U.S.S. Scott in 1996 (Di Giovanni et al., 1996). This 

was the first full ship application of an easy-release coating system on a U.S. Naval 

surface combatant. As with the patch tests on the U.S.S. Spruance and U.S.S. Paul F. 

Foster, no subsequent reports on the trial have been seen.

A cooperative project between Defence research laboratories in Australia, Canada and 

the United States compared the performance of fluorinated urethane and silicone 

fouling release coatings on elastomeric surfaces (Lewis et al., 1997). The silicone 

elastomer coating (=Intersleek) was found to be both flexible and durable on the flexible 

substrates and to retain effective fouling release properties through long-term 

immersion.

In early 1998, LimnoMar in Germany undertook a trial of biocide free coatings on two 

ferries operating in the Wadden Sea (Watermann et al., 1998). Four coatings were 

silicone fouling release coatings, a fifth a biocide-free self-polishing coating. Test 

patches 1 or 2 m wide were applied to the ships’ sides between the water line and chine. 

Patches were inspected at two-month intervals by allowing the vessels to ground and 

dry on low tides.

The silicone coatings performed reasonably well. The patches fouled to a certain degree, 

but the adhesion of the organisms was reduced. On one vessel, macrofouling cover was 

estimated to be 10, 35 and 10% at the three inspection times. The composition was 

predominantly macroalgal, with some barnacles. At the third inspection, 

biocide-containing control coatings were 20% fouled by macroalgae. On the second 

vessel, barnacle abundance dropped between the second and third inspections, 

indicating that fouling had been sloughed during vessel operation. All fouling could be 

easily cleaned from the silicone coatings by light brushing or sponging, and/or water 

pressure of 1 bar. The majority of fouling was removed during the exposure time prior 

to inspection, and fouling removal was positively related to the speed of the vessel. 
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Later in 1998, WWF Germany extended the ferry trials by initiating a collaborative 

project to test environmentally sound biocide-free alternatives on vessels >25m in 

length in coastal and brackish waters (Cameron, 2000). The project involved a wide 

range of interest groups, including three Ministries, eight shipping companies (both 

federal and private), eleven paint manufacturers, the German Paint Manufacture 

Association, LimnoMar, and WWF Germany. Four types of coating were tested: 

non-toxic, non-stick coatings (smooth silicone, Teflon or hydrostatic coatings), 

self-polishing, biocide-free coatings, fibre-flock coatings, and hard, non-abrasive 

coatings in combination with special cleaning procedures (e.g. hydro-jetting, rotating 

brushes). In total 23 biocide-free formulations were tested and compared with paints 

based on TBT, copper and organic biocides. Test conditions encompassed ships which 

did and did not contact the sea bottom, high to low fouling pressures, and a range of 

ship speeds from slow (5 knots) to fast (19 knots). Tests ran for 1 or 2 years.

All silicone-based coatings were ‘‘fairly’’ effective (Cameron, 2000). Although some 

fouling developed, most of the organisms did not adhere securely. On all silicone 

coatings the adhesion force of barnacles was substantially less in comparison to surfaces 

such as epoxy resins, and algal growth was also reduced. The silicone coatings could be 

easily cleaned with a water pressure of 1-10 bars. On fast moving vessels the coatings 

were more effective than on slow moving vessels and those with longer periods in port. 

All silicone coatings remained intact through the trials and still performed well in the 

second year. 

The hydroviscosic and Teflon-based coatings did not perform well in marine waters, 

but could be cleaned on ships operating in brackish water. However, higher water 

pressures were required to clean these coatings than the silicone coatings. The hard, 

non-abrasive coating did not perform well and cleaning was ineffective.

A more detailed report on this project is provided by Watermann et al. (2001), and an 

overview of the project also appears in the coatings journal JPCL (PCE-JPCL Staff, 2001). 

Nineteen vessels were selected for the trials: two container ships, two bulkers, one 

chemical tanker, one frigate, two cruisers, two passenger ferries, five research vessels, 

three patrol boats and one fishery vessel. The two cruisers and the frigate travel world 

wide, the two container ships operate in the South and North Atlantic, the bulkers and 

the chemical tanker operate in the Baltic Sea, North Sea, N-E Atlantic and the 

Mediterranean Sea, and the remaining vessels are coastal traders. Three of the vessels 

had test patches applied in 1998, one in 1999, and the remainder in 2000. Thirteen 

‘‘non-stick’’ fouling release coatings, mainly based on silicone, are included in the 

evaluation, and these are applied as patches, hull sections, or full hull applications. Two 

fibre coatings, nine biocide-free self-polishing coatings, and three anticorrosive coatings 

are also being evaluated in this program. The trials are intended to continue for 60 

months.

Until the end of 2000, six ships had been inspected. Of the test patches applied in 1998 

and inspected after 28-31 months, only silicone fouling release coatings remained in 

fairly good condition. Four of the silicone coatings were considered to be highly 

effective over this period of time, while the effectiveness of two others decreased with 

time. On vessels with low activity levels and a low average speed only one 

silicone-based coating showed good performance over 6-11 months. On the coast guard 

patrol boat, which had low activity level (20%) but high average speed (18 knots) , three 

silicone coatings showed consistent performance over three years with fouling cover of 

about 20%. The performance of a fourth silicone coating on this vessel diminished after 
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one year, with fouling coverage increasing to 80%. Similar results were seen on a more 

active (50%), but slower (11 knots) passenger ferry. Over three years two silicone 

coatings maintained fouling levels at around 20% while, on a third, fouling levels 

increased to 70% in the second and third year of the trial. On the fishing vessel, which 

operated in coastal waters subject to high fouling pressures, three silicone-based 

non-stick coatings maintained fouling levels at 20-30% on one side, and 10% on the 

other over a 28 month period. 

Scammell (2000) reports on trials of a silicone fouling release coating, Aquoxsil, he has 

developed in Australia. The coating was applied to six small craft in three marinas in 

the Sydney region and performance monitored over subsequent months. Results were 

indicative of results seen with other silicone fouling coatings: the coating deterred some 

fouling, boat speed increased when the hull was clean, and any established fouling was 

easily removed. The coating was estimated to cost 20% more than traditional 

antifouling paints, but concurrent savings were expected in pollution control practices 

during application and maintenance.

Swain (1999) concluded, from full-scale ship and boat trials, that under optimum 

operating conditions the present generation of silicone fouling release coatings were 

able to provide satisfactory biofouling control. The major advantage of these systems 

was considered to be that they were non-toxic and, in addition, that they provide a 

smoother surface, reducing skin friction drag and therefore improved performance. The 

disadvantages were that they were expensive, could exhibit poor adhesion to the 

substrate, were easily damaged, and required some form of hull cleaning. These 

drawbacks was thought possibly overcome by improved coating application and dock 

yard practice, improved fendering and hull care, and new technology for in-water 

cleaning.

A decision to use a non-toxic coating is also seen as a decision to accept responsibility 

for routine hull maintenance by Brady (2000b). The interval between cleanings would 

depend on the waters in which the ship was operating and the length of time the ship 

spends at berth. Brady quoted 22 knots as the effective water velocity for removal of 

attached fouling and considered that high-performance, high-activity craft may never 

need cleaning. For those that did, Brady saw a need for a new generation of hull 

cleaning equipment to remove marine fouling from complex hull shapes without 

excessive damage to the coating. For non-toxic coatings, the new equipment should be 

designed to take advantage of the unique ways in which fouling is released from these 

coatings. Hard, tough fluoropolymers that release fouling by shear fracture at the 

coating-fouling joint should be cleaned by devices that apply shear force parallel to the 

coating surface at high speed. In contrast, softer, lower modulus silicone coatings are 

much more susceptible to cuts, tears and other mechanical damage and release fouling 

by letting it peel from the surface. These need to be cleaned by a machine that applies a 

weak force to the fouling at low frequency and maintains the force on the fouling until 

the joint with the coating peels apart.

Brady (2000b) also commented that although the cost of the silicone coating materials is 

high, application and removal costs are less than other systems. This was because no 

toxic materials were present, and costs for containment, environmental monitoring, and 

waste disposal would therefore be less than for other coatings. Silicone coatings were 

more susceptible to tearing and puncturing than other coatings, but were readily 

repaired by removing the damaged coating completely down to bare steel and 
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rebuilding the primer, tie coat, and topcoat, giving close attention to the adhesion 

between the old coating and the patch. 

Lewis (2001) concluded that non-toxic, fouling release coatings do show promise for 

some sectors of the shipping industry. The systems were found to foul on low activity 

vessels, and the ideal platform was therefore considered to be a fast vessel with rapid 

port turnaround times. Attached fouling could be easily removed, but development of 

more efficient methods for cleaning surfaces in-water without causing damage to the 

coatings was seen as necessary.

Towing tank experiments have shown that silicone fouling release coating systems have 

less drag than a typical SPC antifouling when initially applied, and the reduction in 

drag could be correlated with the surface roughness (Candries et al., 2001). In a second 

series of tests, although the roughness of the foul release system was higher than the 

SPC due to poor surface conditions at the time of application, the foul release system 

still exhibited lower drag. Data from full ship applications of foul release coatings in 

service have shown that the ubiquitous presence of slime fouling appears to offset the 

initial reduced drag. However, even with the slime present, foul release coatings give 

speed and fuel performance equivalent to that of TBT SPC antifoulings. Recent 

applications of foul release systems to propellers of LNG tankers have resulted in 

reports of reduced vibration and an increase in ship speed of up to 1 knot (C. Anderson, 

pers. comm.).

International Marine Coatings have now extended applications of Intersleek beyond 

fast ferries (MER, 2001). Test patches of Intersleek applied to the Agawam, a 35,000 dwt 

tanker with a maximum speed of 15 knots, and the Tampa, a 44,000 dwt Ro-Ro vessel, 

were found to be in excellent condition and to have only a light to moderate slime 

covering after 69 an 59 months in service respectively (www.international-marine 

.com). Intersleek 700 is now marketed for deepsea, high activity vessels with speeds 

between 15 and 30 knots. ‘‘Outstanding’ potential durability and longevity are 

promised, with no deterioration seen in long-term tests. A single application is 

recommended to provide up to 5 years service. International Marine Coatings recently 

applied Intersmooth Ecoloflex to the sides, and Intersleek 700 to the underwater flats of 

the P&O cruise ship Oriana.

Sea Grandprix Eco-Speed, the copper and biocide-free fouling release coating system 

offered by Chugoku Marine Paints, is considered primarily of interest to high-profile 

operators, such as navies and environmental agencies (Anon., 2001b). However, 

container and cruise ship companies can also benefit from potential fuel savings over 

five-year drydocking cycles. The base coating, Sea Grandprix Eco-Speed, is suitable for 

deepsea and fast coastal vessels, while a second-generation version, Sea Grandprix 

Eco-Speed C, is designed for slow coastal and low activity vessels. 

7.3.2 Fibre Coatings

Fibre-flock coatings (see Section 5.1) have been developed into a commercial product. 

Forsberg (1994) reported that a company in Sweden, Seal-Flock AB, was established to 

develop a Swedish patent for a fibre-flock coating. The coating is now available under 

the name SealCoat AF and marketed by the company Sealcoat Scancoat, based in Greece 
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but operating in 20 countries around the world (www.sealscoat.com). The product is 

claimed to be a poison free method of preventing the build up of hard fouling growth. 

Alm & Gyllenhammer (1999) report that the Sealcoat fibre-flock surface gives good 

protection against hard fouling organisms like barnacles, mussels and tubeworms. 

There was slight attachment of soft fouling organisms, such as hydroids, tunicates and 

seaweed, on static vessels, but this growth was claimed to be loosely attached and 

would be washed off a vessel underway.

Gyllenhammer (1997) found that although flocked surfaces reduced the recruitment of 

barnacles and green algae, red and brown algae were more abundant on the flocked 

surfaces. Larsson (1997) similarly found that barnacle recruitment was reduced on 

flocked surfaces, but recruitment of mussels, green algae and the solitary ascidian Ciona 

were increased.

Phillippi et al. (2001) reported the results of a further investigation into the effects of 

flocking on the recruitment of fouling organisms. They found that flocking surfaces 

resulted in lower recruitment of green (Enteromorpha spp.) and brown (Feldmannia sp., 

Petroderma sp.) algae, but had no effect on red algae (Polysiphonia spp.). For 

invertebrates, flocking was effective at inhibiting the recruitment of encrusting animals 

(encrusting bryozoans, encrusting ascidians, spirobid tubeworms), had no effect on 

stoloniferous animals (hydroids, stoloniferous bryozoa), and increased the abundance 

of tube-building polychaetes (Polydora ligni) and solitary ascidians. An exception was 

the encrusting sponge, Halichondria sp., which recruited equally to flocked and 

unflocked surfaces. The settlement processes of the various organism groups were 

examined in an attempt to explain the variable settlement. For example, the motile 

spores of green and brown algae were considered more likely to respond to the stimuli 

of the fibres than those of red algae, which settle passively. Alternatively, flocked 

surfaces were considered to possibly provide a favourable habitat for small grazers such 

as copepods, amphipods and nudibranchs, which could graze on settled spores. 

Phillippi et al. (2001) concluded that flocking could be a cost-effective strategy for 

aquaculturists if the organisms causing problems were those inhibited by flocking, i.e. 

green and brown algae or encrusting invertebrates including barnacles. The major 

disadvantage of flocking was considered to be wet weight gain in areas where solitary 

ascidians were abundant because of their high water content and affinity for flocked 

surfaces. Flocked surfaces also gained mass from the detritus and sediment they 

trapped. 

The fibre-flock coating tested in the WWF-Germany coastal vessel trials performed well, 

with selective effectiveness against barnacles even on slow vessels with long periods in 

harbour (Cameron, 2000). Algal growth was also negligible. However, the system was 

only tested over one year.

Two fibre coatings are being evaluated as part of the German trial of biocide-free 

antifouling paints on deep-sea vessels (Watermann et al., 2001; see Section 7.3.1). The 

two coatings differed in the length of the fibres: one had fibres 1.1 mm long, the other 

1.3 mm long. To date four vessels painted with these coatings have been inspected. On 

one vessel, a research vessel with an average speed of 8 knots, fouling levels were 

around or less than 20% after 12 months, but increased to 50-70% after two years with 

most of this animal fouling. In general, after 12 months, the fibre coatings showed 

‘‘fairly good’’ performance in preventing barnacle settlement, but poor performance in 
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preventing macroalgal growth. The coating with longer fibres seemed marginally more 

effective than that with the shorter coatings.

In 2001, Sealcoat patches 350 and 200 m2 in area were applied to the VLCC Libra Star in 

Dubai (K. Alm, pers. comm.). The vessel travels between North America and the 

Arabian Gulf. At a recent inspection the patches were largely free of macrofouling and 

physically sound apart form pigment loss near the water line. A full hull application to 

a ULCC is planned for April/June 2002 .

7.3.3 Biocide-Free Self-Polishing Coatings

The biocide-free self-polishing coating included in the patch trials on German ferries 

showed variable performance (Watermann et al., 1998). On one vessel the coating was 

completely fouled by macroalgae after 4 months, and on the second fouling levels were 

higher than the silicone coatings. Some fouling loss between inspections was noted, and 

this correlated with ship speed.

In the two-year German trials of biocide-free antifouling systems on coastal vessels, one 

of the two self-polishing coatings performed well, especially on fast moving vessels 

(Cameron, 2000). Adhesion of barnacles and total length of algae were reduced and, 

when green weed developed, it was easily removed.

Nine biocide-free self-coatings were included in the German trial of biocide-free 

coatings on deep-sea vessels (Watermann et al., 2001). From observations to date, best 

performance was seen on a slow-moving (11 knots) research vessel where, after 12 

months, animal fouling was limited to less than 20% coverage, which was better than 

for the silicone coatings on the same vessel. On a second vessel, with average speed of 

only 8 knots, animal fouling coverage was between 20 and 60%, but this was still less 

than on the silicone coatings. 

A Swedish company Lotréc AB was reported early in 2001 to be releasing what it 

claimed to by the world’s only biocide and metal-free, non-toxic antifouling coating 

under the LeFANT brand name (Nash, 2001a). Testing over more on more than 5000 

yachts in Holland, Germany, Austria and Sweden over the 2000 season is claimed to 

have yielded outstanding results. Some scepticism has however been expressed on the 

likely performance of the product under high fouling conditions. 

7.3.4 Scrubbable and Inert Coatings

Watermann (1999) discusses the option, proposed by David Jones (UMC International, 

UK), of not applying an antifouling coating at all, but instead applying a hard, smooth 

anticorrosive system and to maintain it in this condition by regular underwater cleaning 

for several years. Watermann and his colleagues determined that special coatings were 

needed to extend cleaning intervals up to several months. For such a system to be 

economic, Watermann (1999) considered that sophisticated, possibly robotic, cleaning 

systems were necessary to support this approach. A network of hull cleaning stations 

on all important trade routes would also be required, and cleaning should be automatic, 

either by means of a car wash system or remotely operated vehicle. Even then, 

awkward areas such as bilge keels, rudders and stern arches would still require manual 

cleaning.
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This approach extends the in-water cleaning practices commonly used in recent years to 

extend the time between an antifouling losing effectiveness and dry-docking. Diver 

operated machines with rotating brushes were utilised for this purpose, and vessels 

cleaned while loading or unloading in port. Such practices have become increasingly 

restricted because of concerns about the pulse release of antifouling biocides during the 

scrubbing of the paint. In Australia, ANZECC have recommended that in-water 

cleaning be banned by ports because of a perceived risk that the practice could facilitate 

spread of marine pests (ANZECC, 1997; Parliament of Victoria, 1997). 

The U.S. Naval Surface Warfare Center (NSWC) is developing an Automated Hull 

Maintenance Vehicle (AHMV) capable of cleaning hulls and of removing the debris the 

process creates (Anon., 1999a). Hull cleaning has been widely used by the USN to 

extend the dry-docking intervals and maintain propulsive efficiency of major vessels, 

but the methods used release fouling and copper into the environment. The AHMV is 

designed to contain both chemical and biological debris and remove it to the quayside. 

A prototype has been constructed and tested successfully on a model hull.

Swain (1999) observed that many, particularly larger, marine creatures frequently adopt 

behavioural activities which prevent biofouling. These can include spending extended 

periods of time out of the water (seals, sea lions, sea otters etc.), migrating into fresh 

water or, as is seen on coral reefs, attending cleaning stations where fish or shrimp pick 

off attached fouling organisms. Such practices are mirrored by boat owners using dry 

boat storage, freshwater soaks, and hull cleaning.

7.4 METALLIC COATINGS

Between 1970 and 1994, 17 vessels are known to have been constructed with solid 

copper-nickel or with copper-nickel clad steel hulls (Powell, 1994). Copper-nickel 

sheathing has also been used on oil and gas platforms, and in the form of mesh for fish 

cages and power station intake screens. Copper and copper alloy sheet and mesh have 

proven to be highly effective in preventing fouling by zebra mussels in the Great Lakes 

(Dorman et al., 1996). The cost of initial application of copper-nickel cladding or 

sheathing may seem prohibitive in comparison to the costs of an antifouling coating. 

However, it has been estimated that the cost can be recouped in 4-7 years through 

decreased hull roughness, fuel savings, and reduced docking costs (Powell, 1994). A 

detailed economic analysis of copper-nickel sheathing in comparison to a conventional 

and SPC antifouling paint similarly concluded that copper-nickel sheathing had 

economic potential (Czimmek & Sandor, 1985). Swain (1999) notes that a 1 millimetre 

thick copper foil, corroding uniformly at a rate of 20 μg cm-2 day-1, would theoretically 

last about 120 years.

The yacht Pretty Penny was designed and built with the aim of creating a maintenance 

free sailing yacht and the frame, hull and structural topside were fabricated in 90-10 

copper nickel (Powell, 1995). Launched in 1979, the vessel was docked and inspected in 

detail for the first time in 1995. During this time the yacht had been afloat continuously 

and moored for the greater part of the time in the River Swale off the Thames estuary. 

The owner reported that the vessel had remained free of fouling for the first three years 

but, after that, the vessel needed to be scrubbed at least once a year to remove fouling. 

The fouling consisted mostly of weed and barnacles within about 12 inches of the water 

line. These were quite easily removed. The degree of fouling was attributed to the low 

activity of the vessel, and sailing speeds insufficient to remove fouling once it had 
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occurred. When the hull was inspected in 1995 the hull plating was considered to be in 

‘‘almost new condition’’. 

Copper nickel sheathing has also been evaluated on two commercial passenger ferries 

operating in Auckland Harbour, New Zealand (Boulton et al., 2001). One ferry was a 

monohull, slow ferry (10 knots) which is kept mostly in reserve, the other a fast 

catamaran ferry (22 knots) which has been in service for about 30,000 nm since 

construction. Both had fibreglass reinforced polymer (FRP) hulls, with the former 

retrofitted with adhesive-backed 90-10 copper-nickel foil in 1993, the latter sheathed 

with the same foil during construction in 1994. The sheathing was found to have good 

resistance to macrofouling, but green algal slimes did form during service. When 

macrofouling did colonise, it was loosely attached and could be easily removed. An 

annual low-pressure water blast easily removed fouling, but this docking was not 

considered necessary with periodic hull cleaning using brushing.

Swain (1999) thought it somewhat surprising that cupro-nickel sheathing had not been 

more widely used. He cited higher capital costs compared to antifouling paints, the 

possibility of galvanic interaction with other metal components and cathodic protection 

systems, and unpredictable performance in polluted waters as possible reasons. 

Metallic copper can also be applied in a metallising process where molten metal is 

sprayed on to the surface (MER, 1998b). The U.S. based company International 

Metalising Corporation promotes such a product called Copperclad 888, which is 

claimed suitable for application to steel, aluminium, wood, plastic and fibreglass 

structures. The product is promoted as a permanent antifouling for various marine 

structures including ships. 

Though not truly metallic sheathing, copper containing epoxy coatings are considered 

to be a similar approach to fouling control, with the epoxy serving as a binder for the 

copper metal. A number of these products have been available over the past twenty 

years, but none have seemingly achieved market penetration.

7.5 PROSPECTS FOR OTHER ANTIFOULING TECHNOLOGIES

7.5.1 New Biocides

Bingaman and Willingham (1995) highlight the rigour and expense required to obtain 

the environmental and toxicological data necessary to gain approval of new antifouling 

biocides. Registration in the U.S. already takes at least 3-5 years, and the cost to obtain 

required data estimated at US$10 million. Registration requirements are also likely to 

become more rigorous as regulators increase the scope of their data needs. We now see 

that one biocide, Irgarol 1051, approved in comparatively recent time by the U.S. EPA is 

now being restricted or banned elsewhere because of concerns about its environmental 

fate and effects. 

The prospects for the discovery of new antifouling biocides do not seem high. Not only 

have few effective products been found in over 150 years of antifouling research, but 

the added necessity of environmental safety makes the task even more daunting. 

Added to this, the costs of assembling regulatory data sets puts development and 

commercialisation beyond the reach of all by the major pesticide companies.
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However, research does continue in efforts to identify new, environmentally acceptable 

antifouling biocides (e.g. Finlay & Callow, 1996, 1997).

7.5.2 Minimally Adhesive Surfaces and Surface Micro-topography

Griffith & Bultman (1997) commented that very few classes of synthetic polymers hold 

any promise for being sufficiently anti-adhesive minimise adhesion of all marine 

organisms. They observed that barnacles bond securely to epoxies, polyurethanes, 

alkyds, polyesters, polysulphides, and practically all other common coating types. They 

saw only fluoropolymers and silicones as offering possibilities for practical coatings. 

Polymeric hydrocarbons, such as polyethylene and polypropylene, were considered to 

have some promise, but to lack the necessary ‘‘convenience-of-use’’ to be seriously 

considered. 

Considerable research is continuing to more generally understand the critical features 

of fouling release coatings, including silicones, in an effort to improve their 

performance (Bonafede et al., 1999; Brady, 1999b; Brady & Singer, 2000). Approaches 

suggested include, for alkoxysilane cured PDMS, modification of the crosslinking 

chemistry and improved reinforcement materials for improved stability (Mera et al., 

1997). Similarly, for platinum-cured silicone coatings, more robust catalysts for 

hydrosilation and investigation of novel reinforcement methods to improve toughness 

are seen as necessary.

Advances in fluoropolymer technology may also lead to new commercial products 

superior to those already commercialised (see Section 4.1). Silicone coatings are 

considered to presently have the edge over fluoropolymer coatings, but in the longer 

term both are likely to find sustained use in hull coatings (Brady, 2000a, b). 

As well as silicones and fluoropolymers, other chemistries are being investigated to 

minimise the strength of attachment of fouling organisms. ADSIL, a U.S. company is 

undertaking research on silicate coatings as potential antifouling products (Kettlewell, 

1999). The company describe the products as utilizing ‘‘SiO or SiO2 structures 

chemically grown without firing’’. These inorganic, advanced silicates chemically bond 

to the surface at room temperature to form a thin, durable pre-ceramic layer. The coated 

surface has similar characteristics to a sheet of glass, and fouling organisms are claimed 

to have difficulty adhering to the surface. 

The potential of ‘smart polymers’ as biofouling-release agents has been investigated by 

initial experiments using thin films of poly(N-isopropylacrylamide) (PNIPAAM) (Ista & 

Lopez, 1998). Results demonstrated the potential of this and similar polymers for 

antifouling applications, and suggested that tethered PNIPAAM might be useful as 

regenerable fouling-release surfaces. 

In Sweden, MASTEC, an interdisciplinary program at Göteborg University and 

Chalmers University of Technology, aims to increase the understanding of interfacial 

phenomena at the polymeric surface (Gatenholm et al., 2000). The long-term goal of this 

research program is to develop a non-toxic coating that will control biofouling by 

synergism between directed biological response and low bioadhesion. Studies have 

been undertaken on the effect of microtexture on biofouling resistance of low surface 

energy RTV silicones. Microtextured surfaces were found to be less fouled by barnacles 

than smooth control surfaces (Andersson et al., 1999). Surface texture with profile heights 

within a topographic range of 30-45 μm reduced settlement and recruitment by 92% as 
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compared to smooth surfaces (Berntsson et al., 2000a). This reduction in settlement is 

attributed to a behavioural response by the settling larvae which show a preference for 

smooth over microtextured surfaces. Further investigations have determined that 

optimum reduction of barnacle settlement was achieved with riblets in the range of 50 

to 100 μm with low angle of inclination, and that such surface geometry also reduced 

drag (Gatenholm et al., 2000). The orientation of the microstructures was found to be 

important, with minimum friction when the grooves were parallel to the flow 

(Berntsson et al., 2000b). For one surface, the skin friction was ~ 10% lower compared to 

a hydraulically smooth surface. Various techniques are now being investigated for 

preparing surfaces with tailor-made architecture.

Microtextured silicone surfaces are considered to have potential use in Scandinavian 

countries where barnacles are serious fouling organisms and where the use of toxic 

antifouling coatings on pleasure boats is becoming increasingly restricted (Berntsson et 

al., 2000a). However, it is recognised that surface textures that reduce barnacle 

settlement may be preferred by other fouling organisms such as mussels and hydroids. 

The success of including one or several scales of surface texture is considered a difficult 

optimisation problem, which would differ among applications and for different 

geographical areas (Berntsson et al., 2000b). 

Hydrophobic surfaces have been found to favour the formation of biofilms, and 

hydrophilic surfaces have therefore been investigated for their antifouling potential. 

Hydrogels are a special class of hydrophilic material that absorb large amounts of water 

into their structure (see Cowling et al., 2000). They are used in biomedical applications 

and generally show minimal protein interaction. On this basis, the antifouling 

behaviour of PHEMA hydrogels, based on 2-hydroxyethyl methacrylate (HEMA), with 

and without the incorporation of active substances was investigated (Cowling et al., 

2000). The research was primarily directed at finding a method of keeping 

oceanographic sensors free of fouling and PHEMA hydrogel containing benzalkonium 

chloride (BCL) was successful in keeping surfaces visually clean for a period of twelve 

weeks, longer than the requirement for the sensors. One sample remained free of 

fouling for five months. 

As a potential antifouling agent, toxicity studies assessed BCL as being, at worst, two 

orders of magnitude less toxic to oysters than TBT and one order of magnitude less 

toxic than copper (Cowling et al., 2000). At laboratory scale production, the costs of the 

PHEMA/BCL combination was of the order of three times the cost per square metre of 

premium quality proprietary copper-based antifouling paints, purchased in volumes 

typically required for family-sized boats. However, this cost differential was 

considered likely to be eliminated if the hydrogel was produced in a commercial 

production process.

The creation on hydrophilic non-stick coatings by the ‘‘tethering’’ of drag-reducing 

molecules such as polyox (polyoxyethylene) to surface was proposed by Gucinski et al. 

(1984). This has not been developed further in the marine area. However, hydrophilic 

polymers and zwitterionic polymers are used in the biomedical area to prevent or 

reduce the adhesion of microbial cells, some of which may have antifouling applications 

(Milne, 1991).

The surface characteristics and hydrodynamics of the skin of cetaceans, teleosts and 

elasmobranchs have attracted interest in relation to fouling performance (Swain, 1999). 

The no-foul condition of porpoise and killer whale skin has been attributed to the 
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outermost surface being composed of a glycoproteinaceous material with low surface 

energy (Gucinski & Baier, 1983). 

In Germany, researchers at the Hanover School of Veterinary Medicine found that the 

surface of pilot whale skin is made up of tiny pores, 0.1 micron across, surrounded by 

raised ‘‘nanobridges’’ (Randerson, 2001). A rubber-like gel, containing enzymes that 

denature proteins and carbohydrates, is found between the ridges, and this gel is 

replenished as the whale sheds its skin. The fouling bacteria and diatoms are thought to 

be unable to attach to the ridges, and to be attacked by enzymes in the gel. 

Macrofouling settlement is in turn inhibited by the absence of a biofilm. The German 

researchers are proposing to create a similar surface using a hard polymer matrix with 

silica crystals embedded in the surface to provide the nanoridges. 

7.5.3 Natural Antifoulants

Wahl (2000) summarised the outcomes of studies (e.g. Wahl et al., 1998) on how marine 

species maintain fouling-free body surfaces over periods equivalent to those sought for 

antifouling protection of artificial structures. Studies of many species indicated that 

defences could fall into four categories: mechanical (microtopography, mucous 

secretion, sloughing, grooming, burrowing), physical (‘‘biocompatible’’ surface 

tension), chemical (extreme pH values, repellents) and associational (commensal 

grazing, cumulative filtration, defended epibionts or neighbours). Several case studies 

were presented to show that, typically, natural antifouling defence relies on a multiple 

system where several mechanisms act together and where each potential coloniser is 

inhibited by more than one mechanism. The selective advantage of such a system is 

that the defender does not rely on one highly toxic broad-spectrum poison, with the risk 

of autotoxicity, and that the multiple defence barrier blocks co-evolution of epibionts. 

Research by Davis (1998) led to a similar conclusion, that the suite of sessile 

invertebrates examined utilised a suite of antifouling defences, and did not depend on 

chemical defences alone.

Wahl also presented a case study to illustrate the sometime doubtful ecological 

relevance of antifouling bioactivity as determined by classical toxicity screening. 

Although many species of colonial tunicates exhibited antibacterial activity when 

screened, their defence levels did not correlate with the degree of epibioses. In contrast, 

non-toxic repellent activities did. Further investigation suggested that the defensive 

activity varied with time, and stochastic alternation of different repellents at the body 

surface would effectively reduce fouling while maintaining chemical crypsis.

Despite this general pessimism in regard to natural antifouling solutions, some positive 

results have been achieved using substances derived from natural product chemistry. 

Furanones from the red alga Delisea pulchra, appear to be non-toxic inhibitors of 

colonisation, inhibiting bacterial colonisation by interfering with genetic regulatory 

processes (Steinberg et al., 1998). UNSW trials in Norway comparing the performance 

of various furanone/coating combinations against Sea-Nine 211 have given some 

positive results (R. De Nys, pers. comm.). This research is primarily directed toward the 

aquaculture industry, where an effective life of six months would be a successful 

achievement, but the technology could also be developed for the boating and yachting 

market. Long life coatings, suitable for shipping, would require development of 

coatings able to provide controlled release of the furanones over the required life of the 

coating. 
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Elsewhere paints containing other natural antifouling products are under trial. Japan’s 

Marine Biotechnology Institute is evaluating paints containing synthetic compounds 

similar in characteristics to tribrogramine (TBG), a compound produced by the 

bryozoan Zoobotryon pellucidum (Hadfield, 1998). TBG is claimed to be a repellent rather 

than a toxin, as it acts by interfering with the neurotransmitter serotonin in the larvae of 

barnacles and mussels by blocking its receptors. This prevents the larvae from settling. 

A mixture of the enzyme hexose oxidase, an extract of the red alga Chondrus crispus, and 

paint has been patented by Danisco of Copenhagan as a non-polluting antifoulant (Fox, 

2001). The patent claims that, in the presence of oxygen, the enzyme breaks down any 

glucose and maltose nutrients nearby, which stops marine growth. 

Rittschof (1999) reviewed the prospects for natural products as antifoulants. He 

considered that the concept of non-toxic antifouling, using natural products or their 

analogues, is a theoretical impossibility. This was despite more than 20 years of research 

into non-toxic antifouling compounds, and increasing popularity of the concept. 

Rittschof’s pessimism was summarised in four points:

• Fouling is a result of a large number of different mechanisms, and a surface can only 

be protected if the entire spectrum of mechanisms is inhibited;

• An effective approach would require the delivery at the correct concentrations to an 

impractical number of molecules that interfered with specific kinds of fouling, and 

delivery of large numbers of molecules in a single coating with correct physical and 

mechanical properties is unlikely;

• Organic molecules contain energy and those energy-containing molecules serve as 

food for some kinds of fouling organisms. Organisms that colonize the surface and 

consume the available food source would neutralise the antifouling activity; and

• Many fouling mechanisms are physical chemical interactions that cannot be 

chemically inhibited.

Rittschof did consider the possibility of application of non-toxic natural antifouling 

products in situations with reduced numbers of foulers, or against pernicious fouling 

groups such as barnacles or tubeworms. However, he observed that these approaches 

had had limited experimental success.

Although non-toxic antifouling action was considered near impossible, Rittschof 

thought reduced toxicity antifouling approaches using degradable organic compounds 

possible. However, this possibility was tempered by the view that, non-toxic 

antifoulants are vulnerable to consumption by non-target species, natural products are 

often not compatible with existing coatings and require new technology for 

compatibility and delivery, and toxic natural products must meet all the standards 

required of other registered biocides and have similar technical issues as the non-toxic 

alternatives. Some biological compounds are among the most toxic known; bufalin, for 

example, is over 100 times more toxic than TBT and over 6000-fold more potent with 

respect to anti-settlement activity (Rittschof, 2000).

Rittschof (1999) considered that the development of natural products was influenced by 

political reality that economics are more important than the environment, and a 

political balance would exist between economically viable alternatives and 

environmental degradation. Until there was a political incentive to develop non 
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metal-based technology, the actual possibilities would not be explored. Political climate 

notwithstanding, the timing and economics associated with registering, licensing, and 

developing the necessary technology was very unfavourable. He quoted, as an example, 

the U.S. EPA registration of the Rohm & Haas biocide Sea-Nine 211, which was 

reported to have taken 11 years and cost approximately US$11,000,000. Combining this 

time and expenditure with an equally sluggish testing approach for new antifouling 

coatings led to a time interval for commercialisation of an already developed coating to 

approximately 15 years in the United States. This commitment was considered 

prohibitive for most businesses.

Rittschof (2000) considered that the practical challenge to be met for successful 

introduction of antifouling solutions with reduced environmental impact was to find 

ways to promote industry/academic interactions, accelerate testing and reduce the 

expense of essential environmental fate and effects assessment. Unless these issues were 

resolved, he felt there would be no substantial progress with novel approaches. Such an 

approach was not presently achieved because academia has often frowned on industry 

collaboration and industry does research in-house. Also, because of the cost of potential 

failures, the antifouling coatings industry and consumers were very conservative. 

7.5.4 Physical, Electronic & Chemical Deterrents

Electrochemical systems have been investigated for the control of fouling on submersed 

panels, in pipe systems, and on ship hulls (Smith & Kretschmer, 1984; Fears & Mackie, 

1997; Ryan, 1998; Smythe et al., 1998; cited in Leya et al., 2001). In recent studies, 

electrochemical prevention of bacteria and diatom fouling was demonstrated in 

laboratory experiments (Nakayama et al., 2001; Okochi et al., 2001). The effect here was 

attributed to direct electrochemical oxidation of intracellular substances rather than 

electrochemically generated toxic substances. High frequency alternating current has 

also been investigated as a potential means for keeping immersed sensor surfaces free 

of fouling for periods of at least 30 days (Leya et al., 2001). The control mechanism was 

attributed to interference with the fouling organisms’ cell membrane potential. In Italy, 

continuous anodic polarization has been proposed as a method to prevent fouling of an 

offshore buoy system (Salvago et al., 2001). In small-scale field experiments, no 

macrofouling developed on a small buoy over a period in excess of two years. 

The electro-conductive coating developed by Mitsubishi and discussed in Section 5.2 

was tested on the hull of a small ship with an underwater area of approximately 100 m2 

(Nishi et al., 1992). No fouling growth was present after 3 months. However, before the 

system could be considered for application to larger vessels, it was considered 

necessary to improve the performance of the coating with respect to durability and 

electro-conductivity, optimise the relationship between current supply and seawater 

properties, establish effective application systems, verify long-term antifouling 

performance and durability, and confirm practicality and reliability on actual ships. 

More recent reports on the performance of this system, named the Marine Growth 

Prevention System by Electrolysis Technology (MAGPET), indicate effective antifouling 

activity over several months on a tug and similar success in trials on ferries and cargo 

vessels (Watermann, 1999). An advantage of this system is that the systems can be 

switched on and off as required, as for example when the vessel is in harbour or 

travelling at low speed. One concern has been raised, the potential generation of 

halogenated by-products. 
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Another electroconductive system is the Alternating Current Anti Fouling (ACAF), 

which is claimed, to prevent barnacle attachment by ‘‘capacitance technology’’ 

(Watermann, 1999). The system consists of a conductive coating sandwiched between 

two non-conductive coatings. A bare electrode exposed to the seawater forms the other 

side of the capacitor. 

Swain (1999) commented that neither systems that function by creating anodic (chlorine 

evolution) nor cathodic (high pH) conditions at the paint surface have been made to 

work for extended periods of time due to voltage drop across the surface, cathodic 

chalk formation, and possible corrosion of the underlying steel. Chapman (1998) 

considered that widespread use of these technologies was limited by cost, lack of 

industry experience, and application difficulties.

Barnacle settlement can be inhibited by low frequency (30 Hz) sound waves 

(Branscomb & Rittschof, 1984) with less than 1% of very young cyprids settling in the 

presence of the sound. Frequency was considered to be critical, with 30 Hz found to be 

significantly more effective than either 15 or 45 Hz. In the laboratory, per cent 

settlement did increase in older larvae as they became less discriminating, but this may 

not be as critical a factor in the field if alternative settlement sites are available. The low 

frequency sound caused no harm to the barnacle larvae, unlike ultrasonic frequencies, 

which are known to be lethal to barnacles and mussels. The method was considered to 

have potential for fouling control in situations where other methods are ineffective, 

such as inside pipes and cooling systems. 

More recent studies have added additional information on the response of fouling 

larvae to sound (Rittschof et al., 1998). Particular findings were that:

• The vibration from ocean waves on a sand beach deterred barnacle settlement; this 

vibration contained 27 Hz harmonics;

• The vibration pattern generated by point source sound transducers on a rigid 

surface was complex, and structure such as ribs greatly altered the vibration 

signature;

• There was a clear relation between inhibition of barnacle settlement, the amplitude 

of the vibration, and the surface energy of the settlement substrate; and

• Sound did not deter the settlement of the bryozoan Bugula neritina.

Several sound generation units claimed to prevent fouling have been marketed. These 

include the Barnakil ® vibration anti-fouling system (Sciencetech Inc.), and the Clean 

Machine

sonic anti-fouling system (Rodadd Ltd, UK). Magnetic fields have also 

recently been reported to reduce seaweed fouling (Ainsworth, 2001). Although not 

preventing fouling completely, the research at the Glasgow Marine Technology Centre 

and the University of Newcastle in the UK suggested that incorporating magnets in 

steel structures would be beneficial. 

None of the above methods show either the broad spectrum or long-term antifouling 

performance needed by shipping. 
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8. THE IMPACT OF THE BAN ON TBT COATINGS AND ITS IMPACT ON THE 

INTRODUCTION OF EXOTIC MARINE SPECIES

The risk of transfer of exotic marine species as hull fouling relates directly to the 

effectiveness of the antifouling coating system. Up until the introduction of TBT 

self-polishing copolymer antifouling paints in the 1970s, the effective performance of 

antifouling paints rarely extended beyond two years, and invariably ships were 

significantly fouled within this time. TBT copolymer paints enabled ships to maintain 

fouling-free hulls for periods in excess of 5 years. Banning TBT paints has created fears 

of a return to the pre-TBT days, with a consequent increase in the translocation of 

fouling species and of exotic and potentially invasive marine pests. 

As recently as last year, concerns were still being expressed that efficient and 

cost-effective alternatives to TBT were not available for large vessels. Strandenes (2000), 

for example, considered that the ban on TBT would not only have first order effects on 

ship operators by reducing ship speed and fuel consumption as a consequence of 

increased fouling levels, but would also have second order effects, such as shifting trade 

from seaborne to other transport modes as a consequence of increased shipping costs, 

and adding to global environmental problems such as global warming and acid rain as 

a consequence of increased fuel consumption. Abel (2000) claimed that not only was 

there no effective substitute for TBT currently available, but there were disincentives to 

the paint manufacturers to developing one. Manufacturers were considered likely to 

benefit from the shipping industry reverting to less effective substitutes as more paint 

would be sold. If such a situation did exist and continue, the risks of increased 

transport of exotic species as fouling would similarly be expected to increase.

However the competitiveness of the major companies in marketing new alternatives to 

TBT paints appears to belie such claims. In the past five years, most of the major marine 

paint companies have releases ‘‘new technology’’ coatings that are claimed to provide 

performance comparable with TBT SPC copolymer coatings. Many of these 

developments originated in Japan, which was the first country to introduce a ban on the 

use of TBT paints on all shipping built or maintained in that country. Increasing 

evidence from trials and commercial applications of these coatings supports the 

optimism that they will provide efficacy and longevity comparable to TBT systems.

Concerted arguments have also been put forward that the ban on TBT will lead to other, 

possibly greater environmental impacts from alternative biocides (e.g. Evans et al., 

2000). Increasing concerns regarding the persistence of Irgarol 1052 were commonly put 

forward to support this argument, but various countries have already acted to ban or 

restrict this biocide, and it was never approved for use in Australia. New antifouling 

booster biocides, Sea-Nine 211, ZPT and CPT, have had to progress through a much 

more rigorous toxicological and environmental risk assessment to gain approval for use 

in countries such as the U.S. and Australia, and evidence suggests they are much safer 

products than those they are replacing and furthermore, when incorporated in a coating 

as a booster biocide to copper, indications are that they provide antifouling 

effectiveness equivalent to organotins.

Two major constraints are faced by the shipping industry in adopting the ‘‘new 

technology’’ products. The first is registration status, the second the higher costs of the 

coating. In light of the consequences of the introduction of TBT antifoulings, there is 

justifiable caution applied to the acceptance and approval of new antifouling products 

in the U.S., Australia and a number of other countries. As a consequence, registration of 
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a new product can take many years, particularly if the product contains an active that 

has not previously been assessed. However, with most international deepsea vessels 

constructed, maintained and repaired outside of Australia, the benefits of new 

technology systems are likely to be seen in Australian ports and inshore waters long 

before products are registered for use in Australian ship repair facilities. 

Increased product costs are also, at least in part, attributable to the increased scrutiny of 

new products. The cost to biocide manufacturers of acquiring data required for 

toxicological and environmental assessment by regulatory authorities has been 

estimated at US$10 million or EUR5.5 million (Denn, 2000), and this cost is 

subsequently reflected in material supply costs. Similarly the cost of developments in 

resin technology would add to coating costs. However, it is anticipated that costs will 

come down as the technologies mature and volume sales increase. 

Another predicted consequence of the reduced number of approved biocides is that 

antifouling formulas will become more universal and standardised among 

manufacturers, eliminating marketing differences between companies (Denn, 2000). The 

increasing costs of development and long development cycles will make it more 

difficult for small companies to compete against the big companies. If a manufacturer is 

not prepared to invest the money, time and resources to obtain antifouling product, 

whether in the EU, Australia, or the U.S., they will not be able to sell their products. 

Three major alternatives are commercially available as alternatives to TBT copolymer 

paints for large vessels: conventional tin-free, copper-based coatings, ‘‘new technology’’ 

tin-free, copper based coatings, and non-toxic silicone fouling release coatings.

Failure and consequent fouling of an antifouling system is a result of either ineffective 

biocides or inadequate release of the biocides at the coating surface. In conventional 

coatings, in theory, failure would occur when the biocide reservoir within the coating 

was completely exhausted. However this rarely occurred. More often the failure was a 

result of impervious layers of spent paint, insoluble copper precipitates, or biofilms or 

detritus developing on the surface and preventing further biocide release. In effective 

self-polishing copolymer coatings, failure would not occur until the coating had 

completely polished away. However, premature failure can occur if the surface of the 

coating is chemically transformed to obstruct the polishing action, or if the polishing 

rate is not matched to the operating speed and activity of the vessel. 

The challenge to paint researchers and formulators has been to develop tin-free coatings 

with performance and polishing actions comparable to that achievable with tributyltin 

acrylate coatings, and to find environmentally benign biocide packages to match the 

broad spectrum performance achieved in TBT copolymer paints. The development of 

copper and zinc acrylate and silyl polymer resin systems, combined with new biocides 

such as Sea-Nine 211, zinc pyrithione and copper pyrithione to boost the performance 

of cuprous oxide, appears to have achieved this aim. Further refinement of these 

systems would also be expected as more experience is gained in ship applications. 

However, an additional constraint on the development of effective antifouling systems 

is the rarity of biocides which meet the stringent requirements of broad spectrum 

effectiveness, rapid degradation, solubility, stability, and limited ecotoxicity needed for 

formulating safe yet effective antifouling systems.
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Conventional coatings do not provide the long-term performance achieved with TBT. 

Even the most advanced of the soluble matrix paints, the Controlled Depletion Polymer 

systems, can only offer effective performance for up to 3 years, and polishing is not as 

consistent as in TBT copolymer systems. Many of the biocides used to boost the 

antifouling performance of these systems, such as diuron and Irgarol, are also now 

under scrutiny and have been banned or use restricted in some countries. However, the 

‘‘new technology’’ copper-based systems offer both consistent polishing rates, effective 

performance for up to 5 years, and more environmentally acceptable booster biocides. 

In considering current alternatives to TBT copolymer paints, Chapman (1998) tabulated 

the pros and cons of the various systems. This comparison is reproduced in Table 11 

and highlights the general availability of products for the shipping industry and the 

cost and performance considerations inherent in product choice. Chapman 

recommended that ship operators should consider the following in choosing an 

antifouling:

• The risk of fouling is higher when an antifouling that does not meet a vessel’s 

performance criteria is selected;

• The costs of fouling − both in terms of trading time lost due to reduced speed as 

well as extra fuel consumption − should be weighed against the costs of a product 

that meets a vessel’s antifouling needs in terms of film thickness and biocide 

strength;

• By looking at a vessel’s typical trading pattern and speed, a ship owner can select 

an antifouling that balances cost with performance. In some ways, paying for 

higher performance is similar to buying insurance. The cost of the premium 

reduces the risk of failure; and

• Any environmental restrictions on the product selected should be considered.

The above considerations also relate directly to product choice to minimise risk of 

carriage of marine pests. They highlight the fact that adopting best products to 

minimise marine pest translocation also confers economic and operational benefits to 

the ship operator, a corollary which should be exploited in promoting best practice.

Table 11 Pros and cons of different antifouling types (from Chapman, 1998)

PROs CONs

Tin-Based Self-Polishing Antifouling

■ Relatively low cost/m2; economical through 

life costs

■ Polishes with time, reducing coating 

build-up

■ Polishing leads to smoothing, which reduces 

fuel consumption

■ High performance and reliability

■ No problems recoating at next dry docking

■ Can withstand constant immersion and 

drying

■ Long life (5+ years)

■ Environmental effects/restriction

■ Large range of performance levels 

available, leading to possibility of 

selecting an inappropriate product for 

the needs of the ship
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Table 11 Pros and cons of different antifouling types (from Chapman, 1998)

PROs CONs

Tin-Free Self-Polishing (‘‘New Technology’’) Antifouling

■ High antifouling performance

■ No problems recoating at next dry-docking

■ Long life (predicted 5 years)

■ Polishes with time, reducing coating 

build-up

■ Polishing leads to smoothing, which reduces 

fuel consumption

■ Relatively high cost/m2

■ New in market, so not yet fully proven

Tin-Free Erodible Antifouling

■ Relatively low cost/m2

■ Dry-docking intervals of up to 3 years

■ Polishes over time, reducing coating 

thickness

■ Provides only moderate antifouling 

performance

■ Problems recoating at next 

dry-docking due to skeletal film left at 

surface

■ Deterioration of film properties over 

time, leading to reduced performance 

on boottops

■ Slow drying

Tin-Free Conventional Antifouling

■ Low cost/m2 ■ Life of up to 12-24 months only

■ Hard, non-polishing, which leads to 

coating build-up

■ Increased hull roughness leads to 

higher fuel consumption

■ Performance only suitable for low 

fouling areas

Non-Biocidal Antifouling

■ Environmentally friendly

■ High performance in specialist applications

■ Can last 5 years or more

■ High cost/m2

■ Limited to specific applications, not yet 

a mainstream product

■ Application technique is critical for 

successful results

The performance of ‘‘new technology’’ tin-free products is considered comparable to 

that of TBT paints. This risk of transport of exotic species on ships using these products 

as replacements to TBT is therefore not expected to significantly increase. However, 

vessels painted with conventional tin-free coatings would not be expected to achieve 5 

year docking intervals without some fouling. As hull fouling also equates to loss of 

performance, an increase in fuel costs, and economic losses to due prolonged voyage 

time, a judicious ship owner would elect to apply the more expensive ‘‘new 

technology’’ systems on vessels with five year docking cycles.

Aluminium hulled vessels are a special case as most tin-free coatings cannot be applied 

to these hulls due to corrosion problems. The only long-life option for these vessels are 

silicone fouling release coatings. While these systems can remain fouling free on high 

speed, active vessels, slower and less active vessels will foul. In-water cleaning 
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procedures must be carried out on these hulls to both prevent the translocation of hull 

fouling species and to maintain operational efficiency.

As discussed in the Phase 1 report (AMOG Consulting, 2001), hull fouling has 

continued to pose a risk on recreational craft. ‘‘New technology’’ coatings have the 

potential, not only to provide an effective alternative to TBT paints for large vessels, but 

to also better protect small craft if the technology can be transferred to this sector of the 

industry. Similarly, the possibility of greater reliability over shorter time frames could 

provide positive benefits if new technology products are used on ships with docking 

cycles of 36 months or less.

The regulation and registration process for antifouling paints impacts significantly on 

the availability of products. While essential to ensure the safety of products used, the 

time needed to approve new products can be seen to be counterproductive if the 

introduction of new and safer products is delayed. The inertia of the system proved 

beneficial in the case of Irgarol, which proved to be environmentally hazardous during 

the period it was under review, but similar delays in the registration of ‘‘new 

technology’’ coatings could increase the risks of pest transfer if not approved by the 

time of the TBT phase-out. A case could be put that, for products showing superior 

performance in overseas applications, and where other countries with comprehensive 

regulatory controls have considered the actives as safe, then either fast-tracking of 

registration or the issuing of interim approvals could be justified. This option may be 

environmentally more responsible than allowing the continued use of actives such as 

diuron, now banned in some overseas countries, and not yet fully assessed as it was 

grandfathered into the present system. The possibility exists of more environmentally 

acceptable and better performing products only being applied in countries with no, or 

limited regulation on antifouling use. 

From the viewpoint of marine pest transfers, the structure of the present Australian 

regulatory controls has another limitation in that it only requires registration of 

products with an ‘‘active’’ constituent. While manufacturers have to demonstrate 

efficacy, as well as environmental safety, for coatings with actives, for a coating with no 

defined active, such as a fouling release coating, to be sold no guarantee of efficacy is 

required. This poses a risk that such coatings could be ineffective, foul, and therefore act 

as vectors for invasive pest species.

Although trials of new technology tin-free products to date are very positive, the 

reliability of long term (i.e. 5 year) effectiveness is yet to be proven. However, the first 

vessels painted with these systems are now approaching five-year dockings. 

Independent trials, such as the Environment Australia patch trial project, and the WWF 

Germany project, will be invaluable in the evaluation of these systems. However, it 

should be noted that these trials will not be completed until well after the ban on TBT is 

introduced. The approval of zinc pyrithione and registration of the first new 

technology coatings in Australia benefited substantially from the DSTO/RAN trials in 

which this new product was included on the basis of promising results in Japan, and 

ahead of it being commercialised for the global market.

The down side of the new technology products is their higher cost relative to TBT SPC 

systems. Although economies of scale and competitiveness may bring prices down with 

time, it has been noted that new biocides are always likely to cost more to compensate 

for the costs incurred in obtaining all the necessary data now requires for regulatory 

approval. There is an expectation in the coatings industry that many shipowners will 
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shorten docking cycles rather than pay additional costs for high performance coatings 

(J. Millett, pers. comm.). However, the benefits to shipowners of new products over 

cheaper, less reliable products, in terms of both ship performance and reduced 

maintenance and dockings should substantiate their use, or at least warrant a detailed 

cost benefit analysis. Such benefits, if promoted through the industry, would 

secondarily minimise the risks of hull fouling and consequent pest translocation.

A second deficiency of the new technology systems is that, because they contain 

cuprous oxide as the primary biocide, they cannot be used safely on aluminium hulled 

vessels or other underwater aluminium fittings. The major maritime sector likely to be 

impacted by this is the high speed catamaran, fast ferry industry. For long-term 

effectiveness, silicone fouling release coatings may be the most effective option. 

This leads to another difficulty with current regulations relating to hull maintenance in 

Australia; the ban on in-water cleaning. Vessels painted with even the most effective 

fouling release coatings will foul if inactive for extended periods of time. While the bulk 

of this growth may be subsequently dislodged when the vessel leaves port, it is likely 

that some growth, particularly low profile growth, will persist. To manage this, and 

ensure that organisms are not translocated, in-water cleaning would be the most 

effective way of ensuring that what grows in the port stays in the port. A vessel leaving 

port with a clean hull will also benefit from the smooth hull and perform more 

efficiently due to reduced skin friction.

Looking to the future, in the short to medium term, it is unlikely that any new material 

able to provide the long-term antifouling effectiveness needed on large shipping will 

become available. Despite optimism expressed with respect to natural antifouling 

products, none are yet commercially available or proven effective in coatings, even for 

less demanding applications, and no registration applications are known to have been 

submitted for natural compounds. Other novel approaches, such as the use of fibre 

flock coatings, or physical or electrochemical have not yet shown the broad-spectrum 

effect necessary for effective antifouling control.
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9. CONCLUSIONS

The withdrawal of TBT antifouling products will leave shipowners with a limited set of 

options for antifouling control: 

• Conventional copper-based (copper metal, cuprous oxide or cuprous thiocyanate) 

antifouling paints, often containing a secondary biocide such as diuron, 

chlorothalonil, thiram or zineb;

• ‘‘New technology’’ self-polishing copper-based antifouling paints, likely to contain 

a ‘‘new’’ secondary biocide such as ZPT, CPT or Sea-Nine 211;

• Silicone-based, ‘‘non-toxic’’ fouling-release coatings;

• Novel coatings based on new ‘‘natural’’ biocides, or having fibrous surfaces; or 

• Physical, electronic and chemical deterrents. 

Of these, only the first three are considered to be commercial options for ship owners at 

this time. While numerous ‘‘natural’’ antifouling biocides have been identified and 

some formulated into experimental coatings, no commercial coatings based on this 

technology are seen to become available in the foreseeable future. Other technologies 

are yet to be proven as viable antifouling solutions for shipping.

Conventional copper-based coatings have not been found to match the performance of 

TBT-based antifouling paints, and expected effective life rarely exceeds 36 months. 

However, ‘‘new technology’’ copper-based paints have been demonstrated to remain 

effective for 5 or more years. Silicone-based fouling-release coatings show the 

necessary durability and can remain macrofouling free on faster, active vessels, but do 

require hull cleaning on slower, less active vessels.

The conclusion to be drawn from this review is that the impending ban on TBT is 

unlikely to greatly compound the problem of transfer of marine pest species as new 

products are available which approach, if not match, the performance of TBT-based 

antifouling systems. Application of these products on vessels currently using 

conventional TBT-free systems may actually offer benefits by reducing the risk of 

fouling. In particular, the transfer of new technology systems and biocides to the 

recreational and small boat marker would improve overall antifouling control and act to 

minimise the risk of transfer of hull fouling organisms.

The Phase 1 report (AMOG Consulting, 2001) listed the following vessels as posing the 

greatest risk in relation to fouling and pest translocation:

• Platforms, barges, pontoons, and derelict and laid-up vessels which have been 

moored for extended periods of time;

• Recreational and small craft which spend significant periods at moorings or in 

marinas, and which also do not, or could not use high performance antifouling 

coatings; 

• Poorly maintained merchant vessels;
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• Vessels nearing the end of their docking cycles; and 

• Vessels with long docking cycles which do not undertake in-water cleaning of 

unprotected or poorly protected areas, such as propellers, and around rudders and 

seawater intake grates between dockings.

The TBT ban is likely to impact significantly only on one of these categories, vessels 

nearing the end of their docking cycles, if less effective coatings are used. Admittedly 

this could be highly significant if a system failed well short to the scheduled docking. 

Promotion of the use of high performance, new technology coatings is therefore 

important to minimise these risks. The bottom line is to promote best practice in hull 

maintenance and use of ‘‘best available’’ antifouling technology. 

One limitation in the adoption of ‘‘new technology’’ copper-based is that only one, of 17 

or more such products commercially available elsewhere in the world, is registered by 

the NRA for application to vessels docking in Australian shipyards. While this impacts 

on only a small proportion of the ships visiting Australia, as most international 

shipping docks for maintenance in overseas ports, there are several potential negative 

effects for those ship operators who generally choose to have maintenance undertaken 

in Australia:

• One paint company has a clear advantage over its competitors in provided an 

effective alternative to TBT;

• Shipowners not electing to use this paint company will be forced to either use a less 

effective product, with consequent hull fouling risks, or take their maintenance 

work offshore; and 

• Australia’s strong political stance in promoting the global TBT ban could be 

compromised by Australia not facilitating use of the full range of best performing 

alternatives.

Looking to the future, there are indications that the use of copper in antifouling coatings 

may also come under scrutiny. In terms of marine pollution, fouling release coatings 

offer the most environmentally benign approach to fouling control. These coatings are 

of immediate relevance for aluminium-hulled craft, such as high-speed catamarans, 

which cannot use cuprous oxide based systems due to their potential corrosive effect. 

However, close attention needs to be directed to developing hull management practices 

for fouling release coatings for this to be a safe option with respect to marine species 

translocation. 
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10. RESEARCH GAPS

In researching for this review, the most significant deficiency in information relates to 

the limited number of independent, comparative studies of antifouling coating 

performance on any scale. The exceptions are the international program of panel trials 

of extensive ship patch trials of non-toxic coatings in the WWF-LimnoMar program in 

Germany (Watermann et al., 1998, 2001), and the Environment Australia funded 

antifouling patch trial project and DSTO/RAN projects in Australia. Most other 

information on performance and efficacy of products comes from trials conducted by 

the paint manufacturers themselves and, understandably, only positive outcomes are 

publicised.

Also, despite the considerable number of research programs underway worldwide 

directed at finding new methods of fouling prevention and control, the limited number 

of commercially-available alternatives to TBT products highlights the continuing need 

for research in this area. Few active agents or processes identified in research programs 

have been transitioned through to commercial products and research to facilitate this 

process is warranted. Such research would include both the development of 

technologies into usable products, and determination of environmental and 

ecotoxicological characteristics necessary for the approval and registration of any new 

bioactive substance or process. Ways of facilitating technology transfer and linkages 

between research organisations and paint manufacturers also warrant investigation. 
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11. RECOMMENDATIONS

11.1 REGISTRATION AND APPROVAL OF ANTIFOULING PRODUCTS

The NRA process for registration of antifouling products in Australia is essential to 

ensure the environmental and occupational safety of these products. However, the data 

needs, costs and time currently required to process a new antifouling product are all 

high which means that registration of a new products, particularly if it contains a 

previously unregistered active, can take a number of years. While designed to protect 

the environment, the process could be interpreted as counter productive if the 

introduction of new, more effective and more environmentally sound products is 

prolonged. The use of less effective products can heighten the risks of translocation of 

marine organisms as hull fouling.

A second aspect of the current registration process of relevance to hull fouling is the 

requirement that only antifouling products containing an ‘‘active’’ agent must be 

registered and therefore have demonstrated efficacy. Any ‘‘non-toxic’’ product can be 

commercially distributed regardless of its effectiveness.

With respect to registration, the following recommendations are made to further 

minimise the incidence of hull fouling on shipping:

• That the registration process be reviewed with respect to allowing new commercial 

products to be granted interim approval, or use under permit, until the full 

registration process can be completed. Such approval or use would be subject to 

availability of certain data, most likely from overseas, that indicates the product is 

both safe and effective, or on the basis of approval overseas; and

• The need to register ‘‘active’’-free antifouling products be investigated to provide 

some warranty of efficacy

11.2 EVALUATION AND VALIDATION OF ANTIFOULING PRODUCT PERFORMANCE

The benefits of effective antifouling technology in regard to reduced risk of marine 

organism translocation equates to benefits to the shipowner in improved vessel 

performance and reduced operating and maintenance costs. The dearth of independent, 

comparative studies of antifouling effectiveness leaves most ship and boat owners with 

only personal experience, or in the hands of the paint supplier, in the decision on what 

antifouling system to use.

The few independent comparative studies of antifouling performance have 

demonstrated the variability in both antifouling efficacy and coating durability that can 

occur between products claimed to be equally effective. Independent studies are also of 

considerable value in meeting NRA registration requirements for data on efficacy in 

Australian conditions, as seen in the value of DSTO/RAN trials in providing data for 

recent registration processes. 

The Environment Australia funded antifouling patch trial project, in which patches of 

‘‘new technology’’ antifouling products from a number of paint manufacturers have 

been applied to commercial vessels, was established in recognition of the need for this 

type of study. However, such a project is not without difficulties, largely because of 
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competitive, commercial issues from within the paint companies. To be successful, 

considerable cooperation between ship and/or boat owners, government agencies, 

research organisations, paint companies and other involved parties is essential. An 

alternative to the conduct of such trials on commercial vessels may be to utilise 

Government owned vessels, such as research, customs and defence vessels, for such 

trial programs

Education is a major component in improving fouling control measures, and a wider 

understanding of antifouling product performance in all maritime sectors, to hopefully 

lead to more effective antifouling practices would not only minimise marine organism 

transfer risks but also generate operational and economic benefits to ship and boat 

owners.

It is therefore recommended that:

• The current antifouling patch trial project be reviewed to determine how future, 

similar programs can be introduced to ensure best available antifouling products 

are available and promoted for use by all ship and boat owners; and

• An education program be established to ensure boat and ship owners are cognisant 

of the options, performance and efficacy of different antifouling products to ensure 

optimum fouling control. 

11.3 HULL MAINTENANCE PRACTICES FOR FOULING RELEASE COATINGS

The current and future prospects for use of non-toxic fouling release coatings require 

the development of hull fouling management and maintenance practices to ensure 

vessels do carry fouling between ports. 

It is therefore recommended that research be undertaken to enable:

• Development of mechanised, non-abrasive cleaning technology for in-water hull 

cleaning;

• A clearer understanding of performance with respect to vessel speeds, surface 

degradation; and 

• Development of cleaning regimes to ensure vessels hulls are maintained fouling 

free- both to optimise ship performance and to prevent pest transfer 

11.4 RESEARCH AND DEVELOPMENT OF NEW ANTIFOULING TECHNOLOGIES

The limited number of environmentally-acceptable options presently available as 

alternatives to the TBT coatings highlights the continuing need for research into new 

methods of fouling control. The apparent wealth and diversity of research programs 

underway world-wide, into both the biofouling process and means of its control, 

should not be seen to negate the need for continued and increased support of research 

within Australia. The significance and economic importance of marine pest issues in 

Australia, the recognition that hull fouling is a significant vector for the introduction of 

marine organisms to Australia, and the international position taken by Australia in 
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advocating a global ban on TBT antifouling paints, all support the need for Australia to 

foster research in the area of biofouling control.

Also, recognising the need to ensure the environmental safety of any new products in 

the Australian environment, support for related research on the environmental fate and 

ecotoxicology of antifouling agents is also warranted. Such information would support 

the NRA in assessing the safety of new antifouling products.

It is therefore recommended that active support be provided to:

• Australian research on biofouling processes and new methods of fouling control; 

and 

• Studies on the environmental fate and ecotoxicology of antifouling agents relevant 

to the Australian marine environment.

11.5 COOPERATIVE RESEARCH ON FOULING PREVENTION

A recommendation of the Phase 1 Report (AMOG Consulting 2001) was the concept of 

a cooperative research program or centre, which would bring together universities, 

paint companies, shipping companies, boating organisations and other research 

organisations with a specific interest in hull fouling and its prevention, should be 

considered. This would facilitate research with outcomes offering economic benefits to 

the maritime industry, while at the same time reducing the risks of marine pest 

introductions and translocations in Australia. A number of the programs 

recommended above could be facilitated within such a facility.
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13. PERSONAL CONTACTS

Alm, K., SealCoat Corp., Greece

Amble, D., Australian LNG Ship Operating Co Pty Ltd, Perth

Bloom, J., U.S. EPA, Washington DC

Burghaty, E., Wattyl Paints, Brisbane 

Byrnes, C., National Registration Authority, Canberra

Cahill, L., National Registration Authority, Canberra

de Witt, E., The Netherlands

Elliott, D., Hempels Marine Paints, Melbourne

Kleverlaan, E., Environment Australia, Canberra

McCullough, K., Canada

Millett, J., Akzo Nobel, Sydney

Otto, S., WWF, Germany

Riding, E., Jotun Paints, Melbourne

Vyse, J., Chugoku Marine Paints, Perth

Watermann, B., LimnoMar, Germany
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APPENDICES
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APPENDIX 1

Antifouling Products Registered by the National Registration Authority in Australia

Source: PUBCRIS Database on NRA Website (www.nra.gov.au)

Company Product Name

Copper Metal

Cuprous Oxide

Cuprous Thiocyanate

Chlorothalonil

Diuron

Sea-Nine 211

Thiram

Zinc Oxide

Zinc Pyrithione

Zineb

NRA Code

Resene Paints (Aust) Ltd ABC-3 X X X 42420

Hempel’s Olympic 76600 (7154) X X 42603

Nautic 7190 X X 46920

Mille Dynamic 71700 X X 46919

Mille Dynamic ALU 71600 X X 46918

Seatech X X 49687

Pacific 7609 X 46921

International (Akzo 

Nobel)

Intersmooth 360 Ecoloflex X X

51971

Interspeed Super Topcoat X X 47588

Interviron Super Basecoat X X 47587

(Epiglass) VC Offshore Extra X X 49609

(Epiglass) Longlife High Strength X X 49606

(Epiglass) Interspeed 2000 X X 49607

(Epiglass) Cruiser Superior X X 49608

(Epiglass) Bottomkote X 49610

(Epiglass) Micron CSC X X 49611

(Epiglass) Coppercoat X X 49612

(Epiglass) Coppercoat Extra Trade X X 49992

Biolux Micron Extra X X 53398

Jotun Sea Guardian X 40163

Supertropic X 40164

Seasafe X X X 46487

SeaVictor 50 X X 46488

SeaVictor 40 X X X 46489

Kansai1 Rabamarine AF100 X 48675

Norglass Topflight X 54048

Wattyl Marine Coatings Ecol IV Black X 52864

Ecol IV Red/Brown X 52961

Newport 77 X X 52243

Newport 88 Hard Racing X 52241

Newport 99 X 52240

Seapro X 40185

Sigmaplane Ecol X X 40186

Sigmaplane Ecol HA 120 X X 52242

Trawler X X 54009
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Company Product Name

Copper Metal

Cuprous Oxide

Cuprous Thiocyanate

Chlorothalonil

Diuron

Sea-Nine 211

Thiram

Zinc Oxide

Zinc Pyrithione

Zineb

NRA Code

Tasmanian Paints Coppertox Longlife X X 42439

Membrane CR95 X X 42708

Fishermans X X 42709

CR97 CTC X X X 42710

Atlantic Controlled 

Solubility

X X X

48843

Asian Paints (Qld)) Transocean Cleanship 2.95 X X 48969

Transocean Longlife 2.77 X 48970

Rextel Pty Ltd, for U.S. 

Paint Corporation 

AWLSTAR Gold Label X

49377
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APPENDIX 2

List of ‘‘New Technology’’ Copper-based Antifouling Coatings

Company Product Name Matrix Biocides Life Vessel type

Akzo Nobel 

(International) 

(Nippon Paint)

Intersmooth Ecoloflex 

460/465

Copper acrylate Cuprous oxide 

Zinc pyrithione

5 yrs Deepsea

(Nippon Paint) Intersmooth Ecoloflex 

360/365

Copper acrylate Cuprous oxide 

Zinc pyrithione

5 yrs Coastal

Chugoku Sea Grandprix 1000 Organo-silyl 

acrylate polymer

Cuprous oxide 5+ 

yrs

Deepsea

Sea Grandprix 2000 Organo-silyl 

acrylate polymer

Cuprous oxide 5+ 

yrs

Coastal

Sea Grandprix 500 Zinc acrylate 3 yrs Deepsea

Sea Grandprix 700 Zinc acrylate 3 yrs Coastal

Hempel’s Globic SP-ECO 81900 Zinc carboxylate 

polymer/ 

inorganic fibre

Cuprous oxide 

Sea-Nine 211

Coastal

Globic SP-ECO 81950 Zinc carboxylate 

polymer/ 

inorganic fibre

Cuprous oxide 

Sea-Nine 211

Deepsea

Globic SP-ECO 81920 Zinc carboxylate 

polymer/ 

inorganic fibre

Cuprous oxide 

Sea-Nine 211

Deepsea

Jotun (Henry Clark) 

(NOF)

SeaQuantum Plus Organosilyl 

polymer

Cuprous oxide 

Copper pyrithione

< 5 

yrs

>18 knots

(NOF) SeaQuantum Classic Organosilyl 

polymer

Cuprous oxide 

Copper pyrithione

< 5 

yrs

12-20 knots

(NOF) SeaQuantum FB Organosilyl 

polymer

Cuprous oxide

 Copper pyrithione

< 5 

yrs

Flat 

bottoms

SeaQuantum Ultra Organosilyl 

polymer

Cuprous oxide 

Copper pyrithione

Extended 

port time, 

laid up, 

stationary 

vessels/

structures

Kansai1 Exion Zinc acrylate 

polymer

3+ 

yrs

Deepsea

Captain Exion Zinc acrylate 

polymer

3+ 

yrs

Coastal

Colour Exion Zinc acrylate 

polymer

Fishing 

vessels, 

pleasure 

craft
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Company Product Name Matrix Biocides Life Vessel type

Sigma Coatings Pty Ltd 

(Wattyl)

Alphagen 50 Cuprous oxide 5 yrs Coastal

Alphagen 20 Cuprous oxide 5 yrs Deepsea

Alphagen 10 Cuprous oxide 5 yrs Flat 

bottoms

Notes: 

1 Kansai products distributed in Australia by Corrosion Control Management, Melbourne
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APPENDIX 3

List of Commercial, Biocide-Free, Fouling Release Coatings

Company Product Name Matrix Type Life Vessel type

Advanced Silicone 

Products (US)

Sea Thru PDMS

Aegus Seapoxy Polysiloxane Single pack Slow- or fast-moving

Chugoku Seajet 2000 Silicone Fast ferries, Navy

Bioclean DX Silicone

Eco-Speed Silicone 5 yrs Deepsea & fast coastal

Eco-Speed C Silicone 5 yrs Slow coastal & 

low-activity

Hempel’s Hempasil SP-EED 

77100

Silicone Moisture cure Medium- high speed

International Intersleek 425 Silicone Three pack 5+ yrs >30 knots

Intersleek 700 Silicone Three pack 5+ yrs 15-30 knots

Kansai1 Captain Biox Silicone Coastal, low speed

Lehmann Pacific 

Industries (Aus)

Teqmar Single pack

Leigh’s Biogard = Captain 

Biox

Sealcoat Sealcoat Epoxy Fibre-flock 3-5 yrs

Sigma Sigmaglide Silicone

Sound Speciality Coatings 

(US)

Aquaply M

Transocean Ultima Silicone

Futureline 95.60 Surface 

repellents