I
NATIONAL INSTITUTE OF STANDARDS &

TECIINOLOGY

Research Iriormation Center

Gaithersburg, MD 20899

AlllDO T^Qlbb

NATL INST OF STANDARDS a TECH R.I.C.

A1 11 009901 66

/Corrosion and protection ot steel piles QC100 .U556 Vr58;1977 C.I NBS-PUB-C 1977

NBS MONOGRAPH 158

U.S. DEPARTMENT OF COMMERCE / National Bureau of Standards

Corrosion and Protection

of Steel Piles in a

Natural Seawater Environment
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Corrosion and Protection of Steel Piles

in a Natural Seawater Environment

mR 8 1978

E. Escalante, W.P. Iverson,

W.F. Gerhold, B.T. Sanderson,

and R.L. Alumbaugh

Institute for Materials Research

National Bureau of Standards

Washington, D.C. 20234

(Supersedes NBSIR 76-1104)

U.S. DEPARTMENT OF COMMERCE, Juanita M. Kreps, Secretary

Dr. Sidney Harman, Under Secretary

Jordan J. Baruch, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Acting Director

Sponsored by:

American Iron and Steel Institute 1000 16th Street, N. W.

Washington, D. C. 20036

Issued June 1977
Library of Congress Cataloging in Publication Data Main entry under title: Corrosion and protection of steel piles in a natural seawater environment.

(National Bureau of Standards monograph ; 158) "Supersedes NBSIR 76-1104."

Includes bibliographical references and index. Supt. of Docs, no.: C13.44:158

I. Steel piling—Corrosion. 2. Sea-water—Corrosion.

I. Escalante, E. II. Series: United States. National Bureau of Standards. Monograph ; 158. QC100.U 5 56 no. 158 [TA786] 602Ms [624'. 154]

76-608410

National Bureau of Standards Monograph 158

Nat. Bur. Stand. (U.S.), Mongr. 158, 42 pages (June 1977) CODEN: NBSMA6

U.S. GOVERNMENT PRINTING OFFICE

WASHINGTON: 1977

For sale by the Superintendent of Documents, U.S. Govoriiment Printing Office Washington, D.C. 20402

Stock No. 003-003-01788-4
Contents

1. Introduction 1

2. Materials and Environment 1

3. Experimental Procedure 5

Specimen Preparation 5

Electrical Measurements 6

Physical Measurements 7

4. Results and Discussion 7

Bare Piles 8

Nonmetallic Coatings 8

Metal Pigmented Coatings 18

Nonmetallic Coatings on Metal Filled Coatings 20

Nonmetallic Coating on Metallic Coatings 24

Metallic Coatings 28

Cathodically Protected Piles 29

5. Summary 31

6. References 36

7. Index 37

iii

Corrosion and Protection of Steel Piles

in a Natural Seawater Environment

E. Escalante, W. P. Iverson, W. F. Gerhold, B. T. Sanderson,

and R. L. Alumbaugh *

This report describes the first eight years of a long term program in which

twenty-three coating systems and five cathodic protection systems are evaluated on

their ability to protect steel piles in offshore conditions. These systems are made up of nonmetallic coatings, metallic pigmented coatings, nonmetallic coatings on metal filled coatings, nonmetallic coatings on metallic coatings, metallic coatings, and cathodic protection on bare and coated piles.

It includes a description of the annual on site electrochemical coating evaluation

and a description of the final physical evaluation made on the piles after removal. The

results of these electrochemical and physical evaluations are presented graphically and

in tabular form.

Key words: Cathodic protection, coating systems; corrosion protection; offshore cor- rosion; sand erosion; seawater corrosion; splash zone corrosion.

1. Introduction

The corrosion of steel piles in seawater is presently being studied by several groups of in- vestigators. Some of these groups have channeled their activities toward laboratory studies

[1,2,3]\ These studies are of interest in that

insight into the corrosion problem can often be

obtained by testing under controlled conditions.

The very act of controlling conditions, however,

can bias the data in subtle and undesirable

ways. Other groups have used field tests that

expose materials to harbor or bay waters [4, 5,

6, 7]. Under this exposure, the effect of the tide on corrosion can be closely observed. Corrosion

studies in hydrospace are also reported in the

literature [8,9]. Such work involves the cor- rosion of materials in very deep water, often a

mile or more below the surface.

These studies by various groups produce

valuable information on the corrosion of materials under different types of exposure. However, very little work has been reported on the

corrosion of steel exposed to actual offshore

conditions [10, 11, 12]. Such work is of particular interest now because of the increased

need for offshore structures. These structures

must withstand all conditions of exposure, and

in particular the incessant action of the waves

found in open water. In addition, as structures

* Civil KntfinecriiiK Lalxiratory. XCHC, INirt Ilueneme,

( 'aliforiiia.

1 Figures in l)raekets indicate tlie literatvu-e references at the end of tliis paper.

are placed closer to the beach, their exposure

to surf action increases. Accompanying this

surf is a strong curi-ent of water returning to the ocean at the mud line. This under current

picks up sand and debris which impinges upon

any object in its path. This abrasive action ex- poses materials to their severest test. This paper describes some results of the first eight years of a fifteen year program in which

a variety of coating and cathodic protection sys- tems are evaluated on their ability to protect

steel piles in offshore conditions at Dam Neck,

Virginia. It includes a description of the methods used in the evaluation and the results found

on these systems.

2. Materials and Environment

To withstand the vigorous wave action ex- perienced at the offshore test site, 8 X 8 in

(0.20 m X 0.20 m) mild steel H-piles (ASTM

A36) weighing 48 lb per ft (71 kg m) were

chosen for exposure. Several 8-in (0.20 m)

diameter pile pipes (ASTM A252) were in- cluded to determine the effect of geometry on

the deterioration of the coating. Nine mariner

steel 8 X 8 in (0.20 m x 0.20 m) H-piles

(ASTM A690) were also exposed. All piles were

35 ft long (10.7 m).

There are twenty-three protective coating

systems used on the piles. Two of the twentythree are cathodically protected. In addition,

three systems of bare piles are protected

with anodes. The systems exposed are listed and

described in table 1.

1
Table 1 Description of Steel Pile Systems Exposed to the Atlantic Ocean at Dam Neck, Virginia'^'

Piling System

Number Description

Number

of

Coats

Average

Coating Thickness

on Each Pile'^'

(mils)

Coating Thickness

Range(^) Minimum-Maximum

(mils) Remarks

1 BARE CARBON STEEL

2 BARE CARBON STEEL WITH ZINC ANODES Protected beneath waterline

with two Zinc anodes^'^'

3 BARE CARBON STEEL WITH ALUMINUM

ANODES

Protected beneath waterline

with two Aluminum anodes(<^)

4 POLYAMIDE CURED COAL TAR EPOXY 2 A-16

B-16 C-15

A=ll-20

B=10-22 C=10-22

5 POLYAMIDE CURED COAL TAR EPOXY 2 A-20

B-20 C-19

A=13-30

B=12-30

C=ll-27

Protected beneath waterline

with two Zinc anodest*-)

6 POLYAMINE CURED COAL TAR EPOXY 2 A-15

B-15

C-13

A=12-20

B=10-28 C=7-20

7 POLYAMIDE CURED COAL TAR EPOXY

Coal Tar Epoxy and Aluminum Oxide

2

1

A-15(33)^'"

B-23(38)

C-2l(36)

A=7-32(20-40)^^'

B=17-30(40+) 0=16-30(25-40)

Third coat and Aluminum Oxide applied between 16' and 22' from bottom of piles only

8 ALUMINUM PIGMENTED COAL TAR EPOXY Amine Cured, Red-Lead Pigmented,

Coal Tar Epoxy Primer Amine Cured Coal Tar Epoxy Intermediate Amine Cured, Aluminum Pigmented,

Coal Tar Epoxy Finish

1

1

1

A-27

B-25 C-28

A=17-35

B=14-40

C=15-40

9 ALUMINUM PIGMENTED COAL TAR EPOXY Epoxy Primer Amine Cured Coal Tar Epoxy Intermediate Amine Cured, Aluminum Pigmented,

Coal Tar Epoxy Finish

1

1

1

A-19

B-18 C-18

A=12-35

B=12-25

C=13-27

10 HOT DIPPED ZINC (GALVANIZED) 1 A-9

B-8 C-8

A=5-13

B=5-15 C=5-14

11 HOT DIPPED ZINC (GALVANIZED) 1 A-7

B-9

C-7

A=4-12

B=5-15 C=3-18

Protected beneath waterline

with two Zinc anodes''-'

12 POLYVINYLIDENE CHLORIDE

Formula 113/54, Mil-L-18389

(Alternate Orange and White

Coats

)

7 A-7

B-5

C-7

A=5-13

B=3-12

C=3-ll

2
Table 1 (Con't)

Pil 1ng System

Number Description

Number

of Coats

Average

Coating Thickness

on Each Pile'o)

(mils)

Coating Thickness

Rangelo) Minimum-Maximum

(mils) Remarks

13 SEALED FLAMESPRAYED ALUMINUM

Flamesprayed Aluminum Wire

Wash Prime, Formula 117, Mil- P-15328B Clear Vinyl Sealcoat

1

1

2

A-10

B-9 C-9

A=4-15

B=6-14 C=5-15

Aluminum preceded with a flamesprayed steel wire

flash bonding coat one mil thick

14 FLAMESPRAYED ALUMINUM WIRE 1 A-9

B-9 C-9

A=6-16

B=5-15 C=6-18

Aluminum preceded with a flamesprayed steel wire

flash bonding coat one mil thick

15 COATED FLAMESPRAYED ZINC Flamesprayed Zinc Wire

Polyvinyl idene Chloride,

Formula 113/54, Mil-L-18389

(Alternate Orange and White

Coats)

17 A-12

B-12 C-13

A=7-20

B=5-18

C=9-25

16 COATED FLAMESPRAYED ZINC Flamesprayed Zinc Wire

Vinyl Red Lead Primer, Formula All 9 Mil-P-15929

15 A-8

B-6

C-6

A=4-l

5

B=2-15

C=2-14

17 PHENOLIC MASTIC Amine Cured, Red Lead Pigmented, Phenolic Mastic Primer (with Mica Filler) Amine Cured Phenolic Mastic

Finish

1

1

A-13

B-18

C-14

A=6-22

B=10-25 C=7-28

18 COATED ZINC RICH EPOXY

Zinc Rich Epoxy Primer Polyamide Cured

Coal Tar Epoxy Finish

12 A-19

B-21 C-22

A=10-35

B=13-30 C=15-40

19 COATED ZINC INORGANIC SILICATE

Zinc Inorganic Silicate Primer

High Build Vinyl Finish

1

1

A-12

B-10

C-12

A=8-25

B=6-20

C=7-18

20 COATED ZINC INORGANIC SILICATE

Zinc Inorganic Silicate Primer

(Self Cured) Polyamide Cured High Build

Epoxy Finish

1

2

A-10

B-14

C-12

A=8-15

B=6-35

C=6-18

21 COATED ZINC INORGANIC SILICATE

Zinc Inorganic Silicate Primer

(Self Cured) Amine Cured Coal Tar Epoxy

Finish

1

1

A-21 B-22 C-19

A=10-40

B=ll740 C=14-28

3
Table 1 (Con't)

Pil ing System

Number

Descri ption Number

of

Coats

Average

Coating Thickness

on Each Pilefb)

(mils)

Coating Thickness

Rangetb) Minimum-Maximum

(mils) Remarks

22 COATED ZINC INORGANIC SILICATE

Zinc Inorganic Silicate Primer

(Post Cured) Strontium-Chromate, Iron-Oxide

Vinyl Phenolic Primer

Vinyl Mastic Finish

1

1

1

A-10

B-8 C-13

A=7-16

B=4-17 C=7-38

23 BARE MARINER STEEL - - - Low Alloy Steel H-piles

24 BARE MARINER STEEL WITH ZINC ANODES Protected beneath water! ine with two Zinc anodest"^'

25 POLYAMIDE CURED COAL TAR EPOXY 2 A-17

B-16

C-17

A=6-40

B=8-28 C=10-30

Low Alloy Steel H-piles

26 BARE CARBON STEEL Carbon Steel Pipe Piles

11 POLYAMIDE CURED COAL TAR EPOXY 2 A-20

B-17 C-24

A=15-28

B=15-24 C=17-30

Carbon Steel Pipe Piles

28 POLYAMIDE CURED COAL TAR EPOXY

Coal Tar Epoxy and Aluminum

Oxide

2 A-21 (40+)*''' B-21(32) C-16(40+)

A=13-30(40)''^' 6=12-30(30-40)

C=16(40+)

Carbon Steel Pipe Piles

Third coat and aluminum oxid( applied between 16' and 22' from bottom of piles only

29 FLAKEGLASS FILLED POLYESTER 1 A-32

B-30

C-34

A=18-40

B=17-40 C=15-40

30 BARE CARBON STEEL

31 BARE CARBON STEEL

All piles were carbon steel "H" piles unless noted otherwise.

'piles in each system were coated as follows: A-Piles - Completely coated except for six 1" x 6" bare windows located at intervals along the outside face of the ocean flange of piles. B-Piles - Completely coated. C-Piles - Top'23 feet completely coated; bottom 12 feet left uncoated.

'Anodes on A and C-piles located in water below MLW; Anodes on B-piles located in the sand.

'values in parenthesis indicate total thickness after application of third coat of Coal Tar Epoxy

and Aluminum Oxide between 16 and 22 feet from bottom of piles.

4
Figure 1 illustrates the various zones en- countered by the pilings. The imbedded zone is the most stable area of exposure since conditions here remain fairly constant with time. It also is generally the least aggressive from the

standpoint of corrosion. Immediately above

the imbedded zone is the erosion zone which ex- poses the protective systems to their severest

test. Here, the continual motion of the water

due to surf and cross currents lifts the particles of sand from the floor which abrade the

surface of the pile. The rate of deterioration of

a pile in this zone is generally high. The fouling zone which includes the splash area develops a profusion of plant and animal life. The most

corrosive portion of this zone is the splash area. Above the waterline is the atmospheric zone. Wave action is so variable that this zone is not

clearly defined. In fact, in unusually heavy wave

action during high tide, the atmospheric zone

of the pile may momentarily be under water.

The corrosiveness of this zone is high.

Characterization data of the ocean water by

the U.S. Coast and Geodetic Survey Station at Virginia Beach, Virginia [13] show a mean

salinity of 26.8 parts per thousand and a mean

temperature of 57.9 °F (14.4 °C). The salinity

has ranged from 18.2 to 37.5 parts per thousand and the water temperature has varied

from 33.8 °F (1.0 °C) to 82.4 °F (28 °C) over

a seven year period.

ATMOSPH

'LASH 1 3ULING

a. 1

SEA WATER

u.

zo •

:ros|

^ N

IMBEDDED

MUD

LINE

FlGlKF, 1

Borings made near the low water line fronting the site indicate that the bottom material

consists primarily of fine sand. A thin strata

of blue-grey clay and silt, less than 3 ft thick

(0.9 m), exists near the surface. The median

diameter of sand particles on the bottom as sampled in 1967 was 0.15 mm (0.006 in). This

small particle size sand is easily carried into

suspension by the motion of the water. The

amount of suspended material in the immediate vicinity of a pile is even higher due to the

increased water velocity resulting from eddy

currents the pile generates. In addition to this

local sand action, winter storms, hurricanes,

and long summer-swells tend to move large

volumes of sand causing the bottom elevation

to change. Thus, the sand line and the erosion zone changed with time in a nonregular way

as illustrated in figure 2.

1969 1971 1973 1975 TIME

FlGliRK 2

3. Experimental Procedure

Specimen Preparation—A set of three pile

specimens, labeled A, B, and C, was prepared

for each system. The A-piles are completely

coated except for six windows located along the

length of the pile as illustrated in figure 3. A

window is a small area 1 X 6 in (2.5 cm by 15

cm) which is free of any coating material. Its purpose is to allow evaluation of the undercutting resistance of the protective coating. The

B-piles are completely coated. The bottom 12 ft

5
i

T

-a

a»

ro

1

1

1

r

ai i "cm

1

. t

Coated except ioo% Coated

for windows

FiClTRE 3. Frepanilioii oj coated piling specimeus.

(3.6 m) of the C-piles are uncoated. All coat- ings were applied in accordance to manufacturer's specifications which included sandblasting to a near white finish prior to coating application. Two Type 316 stainless steel bars were

welded between the flanges of each of the Hpiles. They are located in such a way that one

is approximately 2 ft (0.6 m) above mean high

water and the other 2 ft (0.6 m) below mean

high water. Stainless steel bars were buttwelded to the surface of the pipe piles. These

bars are contact points used during electrochemical measurements. The pipe piles had a cone-shaped tip welded to the bottom end to

facilitate installation. Each of the fifteen

cathodically protected piles has two anodes

located either in the water or below the mud

line.At the test site, the piles are positioned in three rows as indicated in figure 4. The dis- tance from shore to the piles is approximately

100 yards (90 m). In June of 1967 the piles were water-jetted into position with 19 ft (5.7

m) buried in the sand to ensure adequate

stability. Jetting reduces the likelihood of mechanical damage since the pile settles into

position from its own weight and the turbulent action of the sand caused by the water jet on the bottom end of the pile. Once in place the

jetting pipe is withdrawn.

Electrical Measurements—The steel piles are

inspected annually by electrochemical and vis- ual methods. The on-site electrochemical

evaluation of the coatings on the piles, is limited to that portion of the pile below the

waterline. Above the waterline, coating evaluation is in the form of visual inspection and

photography. This annual data is then correlated with the information obtained on the

evaluation after the piles are removed from the

site. The after removal data is in the form of

physical measurements and photographs. Extensive notes are kept on visual observations

made during this final inspection.

OCEAN

. Spacing between piles. 10ft ' %t>mi between piles. 5ft

C : Z Z Z Z Z ZZZZZZZZZZZ3 ZZZZZZZZZZOOO

B i z z X z z zzzzzzzzzzzzzzzzzzzz o o o

A

- Z Z Z Z X zzzzzzzzzzzzzzzzzzzzzzzOOO

System Mo 2 3 5 11 24 23 4 10 7 8 9 6 12 13 14 15 16 17 1 18 19 20 21 22 25 29 30 31 26 27 28

SHORE Z - H-piles- 8"«8". 48 lb/ft O - Pipe piles 8''scliedule 80

Figure 4. Test pile installation. Dam Neck, Virginia.

6
On-site electrical measurements are obtained

by having a steel cable suspended above the

water between a centrally located pile and a winch on a vehicle parked on the beach. On

this cable are hung two insulated 3 conductor

electrical cables with vise grips on the ends.

Electrical contact is made to the individual

piles by clamping a vise grip on the stainless

steel bar welded to the piling. The beach ends

of the electrical conductor are connected to

electronic instrumentation. The strong ocean

currents and surf action have made the over- water suspension of the cables necessary.

Two types of electrochemical measurements

are made in evaluating the condition of the

coatings. The first type, coating index, is primarily a coating resistance measurement for a given change in potential after a five minute

period. The potential of the piles with nonmetallic coatings is changed from open-circuit

potential (zero applied current) to — 0.850 V

versus Cu-CuSO,. In the case of metallic coat- ings a fixed overpotential is applied. For flame

sprayed aluminum the overpotential is —0.120

V and for flame sprayed zinc the overpotential

is -0.150 V. The coating index, AV AI, is calculated and compared from year to year giving a measure of the degree of coating deterioration. The coating resistance measurement

is also expressed in terms of relative coating

eff'ectiveness |12|. This approach compares the

coating resistance of each pile to an arbitrary

scale which has the bare piles at zero (0) rela- tive coating efl"ectiveness and the best coated

pile (7B in 1967) as 100. The value of relative

coating eft'ectiveness between 0 and 100 is based on the relation (not shown) between the

corrosion currents and the coating indices for

the piles. The second type of measurement is for determining the rate of corrosion of bare

piles and piles with metallic coatings. Both the

Stern-Geary approach 1 14] and the polarization

break method 1 15 | are used in this case. Since

the resistivity of seawater is so low, IR error compensation has been found to be unnecessary. Potential measurements of the cathodically

protected piles were made with a potentiometer

using both a Ag-AgCl half-cell and a Cu-CuSO,

half-cell. The Cu-CuSO, half-cell was the most

convenient to use. It was positioned in the

damp sand on the beach and covered to prevent

light and heat effects. The Ag-AgCl half-cell,

submerged in the water, served as a second

reference electrode. The protective current on

the cathodically protected piles is determined

from the cathodic polarization curve [16] as

well as the Stern-Geary technique.

The corrosion rate of a pile can be determined by polarization which requires knowledge of the area of the pile. This area is determined by measuring the length of the pile

below the waterline at the time polarization

measurements are made. Two piles are polarized at a time ; one is anodically polarized while

the other is cathodically polarized. Electrochemical readings are taken on both piles simultaneously. Power is supplied by a 12 volt stor- age battery.

PJn/sical Measurements—The fii'.st removal

for inspection of the piles was made in April

1973, after six years of exposure. Almost one

third of the piles were extracted for final inspection. This extraction was done by a 100

ton floating crane that pulled the A-series

piles out one at a time. During initial trials an attempt was made at removing two piles at a

time, but this was abandoned because of the

damage that resulted to the coating and the

piles. The piles were then brought to shore for

initial cursory inspection and photography. An

extensive build-up of vegetable and animal life has developed on the piles. Wide steel spatulas were used to remove this build-up for preliminary inspection. Following this, the piles were

shipped to Bethlehem Steel Company where

the final intensive inspection took place. Here

the coatings on the piles were cleaned and

examined for extent of deterioration. The

"windows," or intentional interruptions in the

coatings described earlier, were examined for

development of undercutting (separation of

coating from substrate). During this entire

process of examination photographs were taken

to visually capture the appearance of the coatings. Upon completion of this process the piles were sandblasted to remove the coatings in preparation for the physical measurements

that followed. These measurements, consisting

of flange thicknesses, pit depth, and pit densities, were made in the following way. Each pile was marked with chalk at 1 ft (30 cm) intervals. Using an outside caliper micrometer,

flange thickness measurements were made at every foot mark 1 in (2.5 cm) in from the

flange's edge. Finally the deepest pit at every

foot of each face (there are eight faces) was

found and measured with a micrometer pit

depth gauge.

4. Results and Discussion

The results will be discussed in seven interrelated parts. First, the corrosion of the bare

steel piles will be described. This will be fol- lowed by a discussion of the five major coating

systems studied (i.e., nonmetallic coatings,

metal pigmented coatings, nonmetallic coatings on metal filled coatings, nonmetallic coatings on metallic coatings, and metallic coatings).

Finally, the results of the cathodically protected systems will be presented.

7
Bare Piles—After six years of exposure to the ocean, the corrosion of the bare piles has

been extensive compared to that observed on

the protected piles. These control specimens

serve as a reference against which all protected

piles are compared. Thus, they are important

not only in their own right, but as standards of

reference. The electrochemical measurements

(fig. 5) indicate that their rate of corrosion

has been fairly constant with time.

The last measurements of the A-piles were made in 1972 a few months before their re- moval for visual and physical inspection. Figure

5 shows that the corrosion rate of specimens

lA, 23A, and 30A was virtually identical in the

four years the measurements were made. Specimen 23A is of special interest because it is a low alloy mariner steel. Their corrosion rate ranges from 1 to 2 mils per year (5 to 10 mdd-)

for the entire area of the piles below the waterline. Electrochemical measurements were not

made on 26A (pipe pile), or 31A.

The actual observed corrosion as determined

from the flange thickness measurements made

after cleaning for pile lA is illustrated in

figure 6. The average flange thickness of the

pile is plotted for the entire length of the

pile. The dashed line indicates the location of

the original surface. This thickness measure- ment reflects the corrosion on both surfaces of

the flange. One can see from the diagram that

a large part of the corrosion occurs above

the high water line. The average corrosion

rate in this region is on the order of 8 to 12

mils per year (45 to 65 mdd) . The region below

the high water mark has a relatively low cor- rosion rate. However, the corrosion damage

increases as the erosion zone is approached.

The corrosion rate between the high water

mark and the mud line ranges from 4 to 8 mils

per year (20 to 45 mdd) on the average. Within

the erosion zone the observed corrosion is also

high. Note that the changing mud line has

caused deterioration between 14 and 21 ft (4.3 to 6.4 m) from the bottom of the pile. This

effect will be seen on all piles. In this narrow

band the average corrosion rate for pile lA

is approximately 9 mils per year (50 mdd).

Specimen 30A is practically identical in behavior to lA as illustrated in figure 7. This

figure also displays data on the deepest pits

found along the length of the pile. This data

indicates that a perforation of the pile developed at about the thirty-two foot level within

the six years of exposure. This perforation

occurred in the web which is the portion of the

pile between the two outer flanges. Pitting

- For iron ; mils in'V yvnv ~>AS — inillif,'i-;inis per s(iu;iro

(l^'C'imeiiter per dny.

tendency decreases markedly below the mu<-

line.Figure 8 illustrates the corrosion deterioration observed on Specimen 31A. The bare car- bon steel H-pile has developed more metal loss below the mud line than either lA or 30A, and

is of the order of 2 to 3 miles per year (10 to 15 mdd). Its pitting characteristics are very

similar to those of 30A even to the perforation.

All three of the uncoated carbon steel Hpiles developed at least one perforation

through the web in the splash zone. Specimen

23A, the low alloy steel H-pile, was not re- moved from the sice and, therefore, physical

measurements could not be made to verify the

electrochemical measurements which indicate

that its corrosion rate is essentially identical

to that of lA and 30A as shown in figure 5. The bare pipe pile, 26A, developed pitting

very similar to that found in the bare H-piles

with the exception that pitting did not develop

below the mud line (fig. 9). Electrochemical

measurements were not made on this pile.

However, measurements made on 26B indicate

that the corrosion rate on the bare pipe piles is slightly higher (25%) than that of the H-piles.

Because of the geometry of the pipe pile, thick- ness measurements could not be made.

A flange thickness measurement survey of

the bare piles revealed that the corrosion at any

given depth was not uniform. The greatest

corrosion observed was approximately 1 to 2

in (2.5 to 5 cm) from the edge of the flange.

Since the flange thickness measurements re- ported here were made in this region of higher

than average metal loss, the figures based on

these measurements reflect this. Fortunately

the survey also revealed that the bias was constant. Thus, all average flange thickness meas- urements reported for the four bare piles are high by 22 percent ± 5 percent. The corrosion

rates mentioned in the text take this into ac- count. Nonmetallic Coatings—The nonmetallic coat- ings will be discussed in two parts. First, the

coal tar epoxies will be described, and then

similar data on coatings of the same generic

type will be presented.

As a group, the coal tar epoxy paints have

not performed as well as anticipated in the en- vironment of this program. The electrochemical

measurements made on the A-piles in the first five years are presented in figure 10. In this

figure the coating index (electrical coating

resistance) versus time is plotted. Thus, as the

coating deteriorates more of the metallic substrate is exposed and the overall coating index

drops. Similarly the relative coating efi'ective- ness of the system drops. System 6, the poly-

.;^^amide-cured coal tar epoxy, appears to have deteriorated the most of the coal tar epoxies, but
30A BARE CARBON STEEL

H-PILES DADT DAric r^ADRrtM l^MriDUlM CTFPI OICCL

23A LOW ALLOY STEEL

- 30A BARE CARBON STEEL

30

1 J.

Figure 5

PERFORATION

AREA PITTED 100%

100% -100%

100% 100%

100%

100%

100%

100%

100%

100%

100%

100%

100%

100%

100%

100% 100%

0.5 0.6 0.7 AVERAGE FLANGE THICKNESS, in0 0.1 0.2 DEPTH OF DEEPEST PIT. in

1A BARE CARBON STEEL

P'lCllRE 7

31A BARE CARBON STEEL

PIT DEPTHS NOT MEASURED

% = AREA PITTED 100%

100%

- PERFORATION 100%

100% 100%

100%

100%

100% 100%

100%

100% 100%

100%

100%

100%

100% 100%

100%

0.5 0.6 0.7 AVERAGE FLANGE THICKNESS, in

0.5 0.6 0.7 AVERAGE FLANGE THICKNESS, in

0 0.1 0.2 DEPTH OF DEEPEST PIT, in

Figure 6 Figure 8

9
26A BARE CARBON STEEL (PIPE)

35

25

20

THICKNESS MEASUREMENTS

NOT MADE

i AREA PITTED — 100% — 100%

100%

100%

100%

100%

100%

100%

100%

100%

100% 100%

AVERAGE FLANGE THICKNESS, in

0 0.2 DEPTH OF DEEPEST PIT, in

Figure 9

6A COAL TAR EPOXY

35

30

25

:3 15

DASHED LINE IS ORIGINALSURFACE

MEAN HIGH WATER

MEAN LOW

WATER

• AREA PITTED 30%

0.6 0.7 AVERAGE FLANGE THICKNESS, in

0 0.1 DEPTH OF DEEPEST PIT, in

Figure 11 NONMETALLIC COATINGS

4A COAL TAR EPOXY

6A COAL TAR EPOXY

7A COAL TAR EPOXY PLUS ARMOR

25A COAL TAR EPOXY OVER MARINER

27A COAL TAR EPOXY (PIPE PILEI 28A COAL TAR EPOXY PLUS ARMOR (PIPE PILEI AVERAGE OF ALL BARE PILES

1967 1%9

TIME

Figure 10

1973

still has a coating effectiveness of 60 after five years of exposure. Figure 11 displays the aver- age flange thickness of pile 6A with accompanying pitting. Specimen 6A is typical of the coal tar epoxies in that the greatest attack occurred

above the high water line. The deepest pit in this region was less than 0.1 in (0.2 cm). Below

the waterline, sand impingment in the erosion zone caused severe damage to the coating. In

the atmospheric zone, undercutting of the windows in the coating system is difficult to appraise on this pile because of the extensive

general failure of the coating as shown in

figure 12. In the tidal zone, undercutting re- sistance is much improved, but general attack

is still apparent (fig. 13). Below the mud line undercutting of the coating is minor. Mechanical damage to the coating during installation

of the pile has caused most of the damage

seen in figure 14. The polyamide cured coal tar epoxy Systems

4, 7, and 25 are somewhat better than 6A and

have a relative coating effectiveness of 70 in the same period of time as shown in figure 10.

It is of interest to note that System 7, which

has the aluminum oxide armor in the erosion

zone, initially provided the highest degree of

protection to the steel as indicated by the elec10
Figure 12

Figure 13

Figure 14

P-olvamidc cured coal tar epoxy

trochemical measurements. The physical meas- urements of these three piles are illustrated in

figures 15, 16, and 17. The poor resistance of

the coal tar epoxy coatings in the atmospheric

and splash zones is well indicated in these

drawings. Below the waterline, however, they

have performed well. Pile 7A shown in figui'e

16 indicated that the armor coat did reduce

the rate of coating deterioration in the ei'osion zone. Figure 18 is a photograph of the window

in the atmospheric zone of pile 7A. Note the severe undercutting extending half the width

of the pile. The window in the tidal zone, that zone between mean high water and mean low

water, reveals only a slight amount of undercutting that extends 0.25 in (0.7 cm) as shown

in figure 19. Pitting due to coating failure is evident. Below the mud line undercutting re- sistance is even better as shown in figure 20. Generally the coal tar epoxy looks good in this

region.

4A COAL TAR EPOXY

35

30

25

u. 20 O

X

H

C3Z

HIJ 15

10 DASHED LINE IS ORIGINALSURFACE

MEAN HIGH WATER

MEAN LOW

WATER

AREA PITTED

18%

17% 32% 7%

6%

1%

19%

14% 22%

10%1%

1%

1%

1%

0.6 0.7 AVERAGE FLANGE THICKNESS, in

Figure 15

0 0.1 DEPTH OF DEEPEST PIT, in

Pile 4A shown in figure 21 lacks the armor

protection and has developed greater deterioration of the coating in the erosion zone as compared to pile 7A. The appearance of the window

11
25A COAL TAR EPOXY ON MARINER STEEL Figukk 19

0.6 0.7 0 0.1 AVERAGE FLANGE THICKNESS, in DEPTH OF DEEPEST PIT, in

FlClKE 17

12
FiGliHK 21 Figure 24
27A COAL TAR EPOXY (PIPE)

28A COAL TAR EPOXY WITH ARMOR (PIPE)

35 -

30

25

20

15

10

MEAN HIGH WATER

THICKNESS MEASUREMENTS NOT MADE

% = AREA PITTED — 16% 7%

4%

2%

1% — 3%

5% — 4%

2%

4%

2%

1%

5%

5%

5%

5%

4%

5%

35

30

u- 20 O

I

I-o

z

_i 15

10 THICKNESS MEASUREMENTS

NOT MADE

% = AREA PITTED 20%

10% 5%

1%

10%

10% 5%

1%5%

1%5%

1%

5%

20%5%

1%5%

AVERAGE FLANGE THICKNESS, in

0 0.2 DEPTH OF DEEPEST PIT, in AVERAGE FLANGE THICKNESS, in

0 0.2 DEPTH OF DEEPEST PIT, in

Figure 27 Figure 28

in the atmospheric zone of pile 4A is similar

to that of 7A after six years of exposure as

figure 21 shows. In the tidal zone, however, the

window on 4A has undergone considerable damage not readily seen in figure 22. Undercutting

in this area extends almost 1 in (2.5 cm) beneath the coating. General damage to the coat- ing in the surrounding area is also apparent.

Below the mud line the coating is in excellent

condition with practically no undercutting as shown in figure 23. In the erosion zone, the coal tar epoxy on mariner steel. System 25, has not fared as well as the same coating on carbon steel (System

4A). Figure 17 indicates loss of metal at the

flange in this area. Its pitting resistance below

the mud line, however, is far better than any

of the other similarly coated piles. Undercutting of the coating in the atmospheric zone is severe as illustrated in figure 24. Coating damage in the tidal zone is also very extensive

(fig. 25). Below the mud line, however, figure

26 illustrates that the coal tar epoxy on mariner steel has not been undercut.

In general, the coal tar epoxies on the H-piles

have deteriorated considerably in the atmospheric zone with resulting metal losses averaging 2.3 mils per year (13 mdd). Below the water

line metal loss has been minimal and on the

order of 0.25 mils per year (1.4 mdd). Undercutting at windows ranged from severe in the

atmospheric zone to insignificant below the

mudline. From an electromechanical standpoint, the coal tar epoxy coated pipe piles look

very good as illustrated in figure 10. Their

rate of deterioration has been low, and after

five years they have a coating effectiveness

above 85. The physical measurements on the pipe piles

consists only of pit depth measurements (figs.

27 and 28) as meaningful wall thickness meas- urements were not practical. These observations indicate that though there were fewer

coating failures on the pipe piles, (% area

pitted) as compared to the H-piles, the resulting pits were deeper on the pipe piles. The

deepest pit in the erosion zone of 27A was al- most 0.2 in (0.5 cm) deep. Undercutting of the

coating on pile 27A extends about 2 in (5 cm)

beyond the edge of the window as shown in

figure 29, and is considered severe. In the tidal zone undercutting resistance is improved.

Undercutting extends 0.5 in (1 cm) at the most

(fig. 30). Figure 31 illustrates that below the

14
Figure 29 FlGUKK 32
NONMETALLIC COATINGS 17A PHENOLIC MASTIC

10| ,

time average flange thickness, in depth of deepest pit. in

Figure 35 Figure 36

mud line, undercutting of the coating has progressed almost 1 in (2.5 cm) from the edge of

the window. Coating delamination is also visible

in this photograph. The windows in the coat- ing on pile 28A are almost identical in appear- ance to those on 27A. In the atmospheric zone

deterioration is extensive (fig. 32). In the tidal zone undercutting of the coating is moderate

(fig. 33) with some mechanical damage visible. Below the mud line undercutting has progressed at least 1 in (2.5 cm) from the edge of

the window (fig. 34).

The second group of nonmetallic coatings in the program are Systems 12 (Polyvinylidene

Chloride), 17 (Phenolic Mastic), and 29 (Polyester Glass Flake). The electrochemical meas- urements on these piles are given in figure 35. This data reveals the good resistance to deterioration of Specimen 17A. Specimen 29A is almost as good, and both have a coating eff'ec- tiveness above 80. The physical measurements

for pile 17A are illustrated in figure 36. The

resistance to deterioration of the phenolic

mastic has been very good over the entire

surface of the pile in the six years of exposure.

Even in the erosion zone the amount of pitting was low with maximum pit depths less than

0.1 in (0.2 cm). The maximum degree of corrosion observed on this system was just below

the mean high water line with a rate of 0.15

mils per year (0.8 mdd). In the atmospheric

zone, the window in the coating suffered only

moderate undercutting as shown in figure 37

with a maximum penetration of 1 in (2.5 cm)

or less. The same figure shows that the coating

in the vicinity of the window is still in excellent

condition. Most of the rusty color is surface

staining of the coating. In the tidal zone (fig.

38) undercutting extends less than 0.25 in

(0.6 cm) beyond the window. Some coating

failure at the edge of the flange is visible in this photograph. Below the mud line undercutting was practically nonexistent as shown

in figure 39. The dark globular material on the

window is an adhering mud and sand mixture

that apparently does not affect the phenolic

mastic.

The polyester glass flake. System 29, has an

average coating thickness of 32 mils (0.8 mm).

This system has displayed very good resistance

to deterioration. Figure 40 is a plot of the

physical measurements made on this coating.

It is apparent from this data that the degree

of pitting is minor. Flange thickness measure- ments were not made for two reasons. First,

coating breakdown was so minimal that little

16
would be gained by removing the coating for

examination. Secondly, and equally important,

it was very difficult to remove the polyester

glass flake by sandblasting. The severest deterioration of the coating, which was minor,

occurred at the edges of the flange in the ero- sion zone. Beyond that there was little deterioration of the coating. Even in the atmospheric or the splash zones little damage developed. The tendency to undercut as indicated

at a window in the atmospheric zone is shown

in figure 41. Undercutting extends at most 1 in (2.5 cm) from the original edge of the window. The coating was chipped away from the

edge of the damaged area to reveal the degree

of undercutting. In the tidal zone the degree

of undercutting was minor as seen in figure

42. Not visible in this photography is damage

at the edge of the flange. The coating was also

removed from around the window below the

mud line. The photograph of this window,

figure 43, indicates that undercutting extends

0.5 in (1.2 cm) under the coating. In general,

the polyester glass flake coating, System 29,

performed exceptionally well, developing only a few scattered pits over its surface. Though

physical measurements were not complete,

from its appearance one can estimate the total corrosion rate to be less than 0.1 mil per year

(0.5 mdd) over the six years of exposure.

Figure 35 illustrates the degree of deterioration of polyvinylidene chloride, System 12, as measured by electrochemical means. Without

question, this system has given the least

amount of protection to the steel. Initially it had a coating effectiveness of slightly more

than 80. After five years the effectiveness of

the coating dropped to 40. Figure 44 illustrates

the data taken from the physical measurements. It is apparent from this figure that

while the resulting corrosion of the pile is no where near that observed on the bare piles, it is considerably more than that seen on any of

the piles protected by other types of nonmetallic coatings. The worst area of attack is in the erosion zone with a corrosion rate of 5

mils per year (27 mdd) in this narrow region.

The average corrosion rate over the entire pile

surface is calculated to be 2.4 mils per year

(13 mdd). The deepest pits developed between

mean low water and the mud line as shown in the same figure. Photographs taken of the

window in the atmospheric zone show considerable deterioration of the polyvinylidene chloride not only in the area immediately adjacent

to the window, but also in other surrounding

areas. Figure 45 is an example of this observation. The least amount of undercutting is observed in the tidal zone where damage ex- tends 0.3 in (0.8 cm) beyond the window as shown in figure 46. Below the mud line, the

17
29A POLYESTER GLASS FLAKE

35

30

25

LL 20 O

X

I-a

I 15

10

5

-

MEAN HIGH WATER

MEAN LOW

WATER

THICKNESS MEASUREMENTS NOT MADE

% = AREA PITTED5%

1%

1%

5%

5%

1%

0 0.1 AVERAGE FLANGE THICKNESS, in DEPTH OF DEEPEST PIT, in

Figure 40

coating has been undercut almost two inches

(5 cm) beyond the original edge of the window

as shown in figure 47.

Metal Pigmented Coatings—Two alummum

pigmented coal tar epoxy coating systems

(Systems 8 and 9) were included in the investigation. The electrochemical measurements on

these two piles are illustrated in figure 48. From this figure one can see that the coating

svstem on 8A has a relative coating effective- ness of over 70 while system 9A has slightly more than 60. The electrical resistivity of these

two metal filled coatings is so high, that for all practical purposes they are nonconducting in the voltage ranges of our experiments. This is an important consideration as any conductivity

through the film will affect the electrochemical

measurements as will be pointed out later. The

flange thickness measurements for pile 8A are

illustrated in figure 49. This figure reveals that

very little deterioration of the coating has

taken place in the six years of exposure Most

of the damage to the coating has occurred in the erosion zone. The corrosion rate in this

region has averaged less than 0.1 mil per year

(0.5 mdd). The degree of pitting damage is

f 4!

FlClRE 4]

Figure 42

FiGI RE 43

Fhihc^ldss filled polyester

18
12A POLYVINYLIDENE CHLORIDE

% = AREA PITTED

2%

14%

0.6 0.7 0 0.1 0.2 AVERAGE FLANGE THICKNESS, in DEPTH OF DEEPEST PIT, in

FlGUKE 44

minor over most of the pile. In the atmospheric

zone, undercutting of the coating extends less than 1.2 in (3 cm) beyond the original edge of

the window as shown in figure 50. The same

figure shows the otherwise excellent condition

of the coating in the surrounding area. Most

of the apparent damage is rust staining. In the tidal zone the coating at the edge of the

window is in fairly good condition with only

0.1 in (0.2 cm) of undercutting as seen in figure 51. Some coating damage is visible in

the surrounding area. Figure 52 is a similar

window below the mud line which displays

essentially no undercutting and no coating deterioration in the visible area. The second system of aluminum pigmented

coal tar epoxy, System 9, has a film thickness

that is 30 percent thinner than System 8. Specimen 9A has undergone more damage as the physical measurements illustrate in figure

53. Incomplete sandblasting of the surface during the cleaning process has caused the flange

of specimen 9A in figure 53 to appear thicker

in the erosion zone than it really is. The coat- ing ] in (2.5 cm) from the edge where the

flange thickness measurements are made is in

Figure 47

/'o/i (//! y//f/f-;ic chloride

19
8A Al PIGMENTED COAL TAR EPOXY

METAL PIGMENTED COATING

8A Al PIGMENTED COAL TAR EPOXY

9A Al PIGMENTED COAL TAR EPOXY A AVERAGE OF ALL BARE PILES

1967 1969TIME

1971

90

80 >

I-U

60 a

z

40 <

20 8

m>

1973

35

30 -

25

u. 20 - O

X

I-(S§ 15 1-

10 DASHED LINE IS ORIGINALSURFACE

MEAN HIGH WATER

AREA PITTED - 1%

0.6 0.7 AVERAGE FLANGE THICKNESS, in

0 0.1 DEPTH OF DEEPEST PIT, in

Figure 48 Figure 49

good condition, but two or three inches (5 to 7

cm) from the edge, the coating had deteriorated as indicated by the pitting data in the same figure. The average corrosion rate over

the entire surface of the pile is calculated to be sligthly less than 0.2 mils per year (1 mdd).

In the atmospheric zone, the coating window

has produced undercutting extending about 1.5 inches (4 cm) under the coat as seen in figure

54. In the tidal zone, coating damage at the

window is minor as can be seen in figure 55. Below the mud line undercutting has extended

as much as 2 in (5 cm) under the paint system

as shown in figure 56. Coating breakdown at the

edge of the flange is also visible in this photograph. In general, both aluminum pigmented

coal tar epoxy substrates have performed

fairly well, although the thicker film. System

8A, has performed somewhat better in the six

years of exposure.

Nonnu'tallic Coatings on Metal Filled Coatings—Metallic Zinc powder has been used in

the metal filled undercoats of the five 2-coat

systems discussed here. Whereas all of the top- coats are electrically isulating, three of the five metal filled undercoatings are electrically con- ducting. These three, Systems 18, 20, and 21

will be considered separately from the rest Figure 57 is a plot of the electrochemical data

of these coatings. System 18, coal tar epoxy

over zinc rich organic primer, is maintaining a

relative coating efi'ectiveness of 85. At the same

time System 20, epoxy polyamide over zinc

rich inorganic primer, has a relative coating

eff'ectiveness of 80. The coal tar epoxy over

zinc rich inorganic primer. System 21, also has

a relative coating effectiveness of 85. The rela- tive coating effectiveness of these three sys- tems may actually be slightly better than indicated by the electrochemical data. The reason being that as the overcoat erodes away or fails

from some other cause, the electrically conducting metal filled undercoat is exposed. This un- dercoat may be protecting the steel very well,

but because of its low electrical resistance it displays a lower coating effectiveness (coating

index) than it really has.

The physical measurements on System 18A

are illustrated in figure 58. The deterioration

of the steel pile has been slight. The coating

system has performed well in all of the zones

of exposure. Average corrosion rate for the pile

has been less than 0.2 mils per year (1 mdd).

In the atmospheric zone, damage of the coating

at the window has been severe as shown in

figure 59. Undercutting of the coating extends

almost 2 in (5 cm) beyond the window. Undercutting of the coating in the tidal zone has been

20
minor as shown in figure 60. Below the mud

line the eflect is negligible as seen in figure

61. Some of the coating damage visible in this

photograph is mechanical abrasion due to re- moval and shipping.

System 20A has also shown good resistance

to the ocean exposure as illustrated by the

physical measurements of figure 62. In this case some deterioration has occurred at the

erosion zone, but with insignificant attack

below the mud line. The coating was not completely removed in some areas which accounts

for the flange appearing thicker than it was

originally. This certainly indicates that the

coat was still protecting in these areas. The

average corrosion rate for this pile was con- siderably less than 0.1 mil per year (0.5 mdd).

Undercutting resistance has been very good in

all zones. The window located in the atmospheric zone developed less than 0.5 inches (1.2

cm) of undercutting as shown in figure 63. General pitting can be seen in the surrounding

coating. Figure 64 illustrates the excellent appearance of the coating in the tidal zone. Below

the mud line undercutting resistance is also

very good, however, some blistering is visible

in the coating in the adjacent areas (fig. 65).

System 21 has displayed unusually good re- sistance to deterioration in the offshore ex- posure as shown in the physical measurements

of figure 66. Incomplete sandblasting has led to the data showing the flange to be thicker than

it was originally. As mentioned before, this

clearly indicates that there was no metal loss

in these areas. Thus, pile 21A is in excellent

condition after six years of exposure. The

amount of pitting is minor as the same figure

shows. Undercutting of the coating in the at- mospheric zone has been moderate with damage

extending about 0.6 in (1.5 cm) beyond the

window as seen in figure 67. The coating in

the surrounding area is in excellent condition.

In the tidal zone undercutting is of minor con- sequence and extends less than 0.1 in (0.2

cm) as illustrated in figure 68. Below the mud

line there was no measurable undercutting of

the coating as shown in figure 69. Mechanical

damage to the edge has removed some of the

coating.

Attention is again directed to figure 57 which

illustrates the electrochemical data for the

nonmetallic coatings on metal filled coatings.

Systems 18, 20, and 21 have been described.

The remaining systems in this category are

piles 19A (vinyl over zinc rich inorganic

primer), and 22A (vinyl mastic over zinc rich

inorganic primer).

The electrochemical data indicate that Systems 19 and 22 are very similar in their deterioration and degree of protection as figure

57 illustrates. The relative coating effectiveness

21
9A Al PIGMENTED COAL TAR EPOXY

35

30

25

li. 20 O

I

KO

z

!fi 15

10

MEAN HIGH WATER

MEAN LOW

WATER

DASHED LINE IS ORIGINAL SURFACE

% = AREA PITTED 1%

1%

1%

1%

10% 5%

25%5%

1%

1%

0.6 0.7 AVERAGE FLANGE THICKNESS, in

Fk.I UK .'jH

0 0.1 DEPTH OF DEEPEST PIT, in

of both is slightly over 60. The physical meas- urement data for pile 19A is plotted in figure

70. Attack of the pile has been general over its length. However, there was more attack in the

erosion zone than this data, taken 1 in (2.5

cm) from the edge, indicates. The corrosion

extended from the 15-ft mark to the 20-ft

mark on the inner surface of the flanges and 2

to 3 in from the elge. This attack is indicated

by the pit depth measurements of figure 70. Its average corrosion rate is about 0.2 mils per year

(1 mdd). Undercutting in the atmospheric

zone shown in figure 71 extends less than 0.5

in (1.2 cm) beyond the window with some edge

deterioration evident. General deterioration

has been extensive in the tidal zone. Figure 72

is a photograph of the window in this region

that reveals less than 0.1 in (0.2 cm) undercutting. Below the mud line undercutting was

also less than 0.1 inches (0.2 cm) as shown in figure 73. The coating was damaged mechanically, but no undercutting was found under the

surrounding encrustation.

Pile 22A, vinyl mastic over inorganic zinc

rich, has a relative coating effectiveness slightly above 60 after six years. The flange thick- ness measurements are illustrated in figure 74.

KiGiJUE 54

FlGUKE 55

Fi(;iiiiE 5(1

Alinniiiiini piiimrntcil coal tar cpoxy

22
10 NONMETALLIC COATING/

METAL FILLED COATING

ISA COAL TAR EPOXY / ORGANIC ZN RICH

19A VINYL/INORGANIC ZN RICH

20A EPOXY POLYAMIDE/ INORGANIC ZN RICH

21A EPOXY TAB/INORGANIC ZN RICH

22A VINYL MASTIC/INORGANIC ZN RICH AVERAGE OF ALL BARE PILES

90

1967 1969 1971 1973 TIME

Figure 57

18A COAL TAR EPOXY / Zn RICH ORGANIC

35

30

25

20

15

10 DASHED LINE IS ORIGINAL SURFACE

MEAN LOW

WATER

% = AREA PITTED 5%

1%

1%

1%

1%

1%1%

1%

Figure 59

Figure 60

Figure 61

(oated zinc rich epoxy

0.6 0.7 AVERAGE FLANGE THICKNESS, in

0 0.1 DEPTH OF DEEPEST PIT, in

Figure 58

23
20A EPOXY POLYAMIDE / ZN RICH INORGANIC

DASHED LINE IS ORIGINAL SURFACE

MEAN HIGH WATER

MEAN LOW

WATER

% = AREA PITTED 1%1%

1%

1%

1%

1%

10% 25%5%

1%

0.6 0.7 AVERAGE FLANGE THICKNESS, in

Figure 62

1%

0 0.1 DEPTH OF DEEPEST PIT, in

There is very little attack in the atmospheric

zone. Undercutting in this area is less than 0.1

in (0.2 cm) as shown in figure 75. In the tidal zone general deterioration of the coating has

taken place, but with very little actual metal

loss. This is illustrated in figure 76. Undercutting here is also less than 0.1 in (0.2 cm).

Below the mud line undercutting extends about

0.2 in (0.5 cm) beyond the window as figure

77 shows. Notice the blistering of the coating

in the surrounding area. The overall avei-age

corrosion rate for pile 22A is less than 0.25

mils per year (1.4 mdd).

In general, these two-coat systems, nonmetallic coatings over metal filled coatings, have

performed very well with overall corrosion

rates averaging less than 0.2 mil per year (1

mdd). The coal tar epoxy over inorganic zinc

rich, 21A, has shown above average resistance

to the ocean environment in the six years of

exposure.

Nonmetallic Coating on Metallic Coativgs—

This group of coatings is made up of three

systems: 13A, Vinyl sealer over flame sprayed

aluminum, 15A, Polyvinylidene Chloride over

flame sprayed zinc, and 16A, Vinyl-red lead over flame sprayed zinc. With these systems, as

24
21A EPOXYTAR/ ZN RICH INORGANIC

35

30

25

i 20 O

z

IS 15

10 DASHED LINE IS ORIGINALSURFACE

MEAN HIGH WATER

MEAN LOW

WATER

% = AREA PITTED

1%

1%

1%

10%

10%

1%

0.6 0.7 AVERAGE FLANGE THICKNESS, in

FicuKE 66

0 0.1 DEPTH OF DEEPEST PIT, In

with some of the electrically conducting metal

filled coatings, the coating index (relative coat- ing effectiveness) measurements are more complex. The electrochemical data still gives an

excellent indication of the protective ability of

the nonconducting top coat. Furthermore, as the top coat deteriorates the same data reflects the changes occurring on the metallic

base coat. Figure 78 illustrates the electrochemical data gathered for the systems indicated. The vinyl sealer over flame sprayed

aluminum system, pile 13A, now has a rela- tive coating effectiveness above 60. It is imporant to point out that the vinyl seals

the pores of the flame sprayed aluminum and is not intended to form a continuous film over

the surface of the aluminum. The flame

sprayed aluminum coating, however, is still providing mechanical and electrochemical protection to the steel piling with the relative

coating effectiveness being much better than

that indicated by figure 78. Figure 79 illus- trates the data on the physical measurements

of this piling. Only a small amount of metal

has been lost in the area of the erosion zone. The amount of pitting is practically insignifi- cant. The average corrosion rate of 13A has

Fi(;iHK 67

FlGliKK 68

Fu.t UK 69

( nnlfd zinc liiori:<inic silirnte

25
19A VINYL/ ZN RICH INORGANIC

35

30 -

25

20

15

10

MEAN HIGH WATER

DASHED LINE IS ORIGINALSURFACE

% = AREA PITTED 5%

1%

1%

1%

10% 1%

5%

40%

20%1%

1%

1%

0.6 0.7 AVERAGE FLANGE THICKNESS, in

0 0.1 DEPTH OF DEEPEST PIT, in

Figure 70

been less than 0.05 mils per year (0.3 mdd)

for the six years of exposure.. In the atmospheric zone, the coating is in excellent condition. Corrosion damage extends slightly less than 0.5 in (1.2 cm) from the edge of the

window as shown in Figure 80. Undercutting

of the coating at the window in the tidal zone

is too slight to be measurable, however, general

coating failure is visible as figure 81 shows.

Though the coating has obviously deteriorated

below the mud line (fig. 82), there has been

little subsequent attack to the steel pile. Damage to the coating at the window extends about

0.1 in (0.2 cm).

Pile 15A, polyvinylidene chloride over zinc

flame spray, is unusual in that the electrochemical readings indicate that initially its coating effectiveness decreased as the nonmetallic coating failed, but then the metallic

zinc coating proceeded to provide protection.

Consequently, the coating efl'ectiveness of the

system improved as illustrated in figure 78. Total coating eff'ectiveness below the water line

is well above 85. In general, the zinc seems to have developed some nonconducting film, probably an oxide, that has brought this improvement about. The average flange thickness meas- urements are plotted in figure 83. Total metal

Fir.ijRE 71

Figure 72

Figure 73

( oati-d zinr inorganir silicate

26
22A VINYL MASTIC/ ZiVI RICH INORGANIC

35

30

25 -

20 -

15

10

MEAN HIGH WATER

DASHED LINE IS ORIGINAL SURFACE

AREA PITTED

15% 5%

30%

65% 80% 20%

1%

1%

1%

0.6 0.7 AVERAGE FLANGE THICKNESS, in

Figure 74

0 0.1 DEPTH OF DEEPEST PIT, in

loss is small and uniform over the sui^face of

the pile. Similarly, pitting is scattered and of

minor consequence. The average corrosion rate

for the entire pile is about 0.1 mil per year

(0.5 mdd). There were no v^indows in the coat- ing of this pile. The following photographs are

included to display its appearance in areas

similar to those seen for the other pilings. The

coating in the atmosphere is in very good

condition with only minor damage in a few

areas. Unfortunately the photograph of this area is of such poor quality that it will not be

shown. In the tidal zone the nonmetallic coat- ing is badly blistered as figure 84 shows, but

the piling is still being protected by the zinc. Top coat blistering extends into the area below

the mud line as figure 85 illustrates, but cor- rosion damage to the pile is minor.

The vinyl over zinc flame spray system, pile

16A, has undergone the most deterioration of

the topcoated metallic coating systems. The

relative coating effectiveness of 16A is about

50 percent as figure 78 illustrates. After the

top coat began to fail during the first year of

exposure, the flame sprayed zinc protected the

piling for a short period. Soon after, however,

the system started to deteriorate steadily. It is of interest to note that the total coating thickFiGiiiiE 75

Figure 76

Fk.i'rk 77

(.anted zinr inorganic silicate

27
NONMETALLIC COATING/

METALLIC COATING

13A VINYL /Al FLAME SPRAY

15A POLYVINYLIDENE CHLORIDE /ZN FLAME SPRAY

16A vinyl; ZN FLAME SPRAY

A AVERAGE OF ALL BARE PILES

- 90 a

80

0.1

0.01

60 <

40 8

1969 1973 TIME

13A VINYL/ Al FLAME SPRAY

35

30

25

20

10 DASHED LINE IS ORIGINALSURFACE

% = AREA PITTED

1%

1%

1%

1%

0.6 0.7 AVERAGE FLANGE THICKNESS, In

0 0.1 DEPTH OF DEEPEST PIT, In

Figure 78 Figure 79

ness of this system is about 50 percent less than that of pile 15A. Corrosion damage to the

steel pile in the form of general corrosion and

pitting has been extensive as the plot of the

physical measurements in Figure 86 illustrate.

The average corrosion rate for the entire pile

is about 1.5 mils per year (8 mdd). In the at- mospheric zone coating failure was severe as

figure 87 shows. The window in the coating is barely visible. In the tidal zone failure was also

entensive as shown in figure 88. Figure 89

illustrates the condition of the piling below the

mud line where it has fared somewhat better

than in other zones. With such complete failure

of the coating, evaluation of the undercutting

is of no consequence and, therefore, is not

attempted.

The nonmetallic coating on metallic coating

systems have displayed a broad spectrum of

coating response to the offshore exposure. With

the exception of 16A, they have protected the

steel piles well. Metallic Coatings—Two metallic coating

systems will be discussed. The first one, lOA,

is a hot dipped galvanized steel piling. Pile 14A,

the second one, was coated with a flame sprayed

aluminum coating.

Corrosion rates for the nonferrous coatings

cannot be calculated easily from the electrochemical data because it is not known with

any degree of certainty what fraction of the

total corrosion current measured is due to the

corrosion of the steel substrate and what fraction is due to the nonferrous coating. Therefore, the corrosion current density shown in figure 90 is reported for these highly conducting coatings rather than the coating index

used for the nonconducting coatings.

The results on the bare carbon steel piles are shown for reference as was done in all illustrations of electrochemical data. The cor- rosion current indicates that the bare steel corroded at a relatively uniform rate with time

while the corrosion of the galvanized pile, lOA,

has changed considerably in the same period.

During the first three years, the corrosion

current decreases by a factor of ten. Thereafter it increased steadily until now, eight

years later, it is approaching the corrosion of

the bare carbon steel pile. This data on the galvanized steel is made up of information from

piles A, B, and C, two of which are still at the

off"shore site. Figure 91 illustrates the physical

measurements on pile lOA. The pile shows some

28
FicntK 82

Flame.sprayefl aluminum wire

corrosion in the atmospheric zone and con- siderable corrosion in the abrasion zone. The

average corrosion rate for the pile is less than

0.15 mils per year (0.8 mdd). There are no windows in this system, but photographs are

included for information. Above the high water

line, coating failure is in the form of pits as

figure 92 illustrates. In the tidal zone pitting

continues along with some undercutting of the

coating. A small section of coating was easily

separated from the substrate as figure 93

shows. Below the mud line the coating was very

thin or altogether missing in some areas as figure 94 illustrates.

The flame sprayed aluminum system, pile

14A, is similar to pile lOA in its electrochemical

behavior as indicated in figure 90. It too shows

an increase in corrosion which is approaching

that of bare steel as the aluminum deteriorates.

The flange thickness measurements, figure 95,

reveal some metal loss in the erosion zone, and

practically no pitting anywhere. In the atmospheric zone the aluminum flame spray coating

appears in excellent condition with the exception of the corrosion damage extending almost

1 in (2.5 cm) from the window shown in figure

96. In the tidal zone the coating is also in

excellent condition (fig. 97) with minor damage

extending from the window. From the mud line

down, however, damage is more extensive.

Figure 98 illustrates the window in this region

with coating damage over most of the visible

surface.

The metallic coatings began to show signs

of deterioration after approximately five years

of exposure. The steel piles that they protected

are in excellent condition with minor damage in

the abrasion zone. CathodicaUy Protected Piles—The potentials

of the cathodically protected piles over an eight

year period are presented in table 2. Although

the potentials of the steel piles versus a AgAgCl half -cell and a Cu-CuSO, half-cell were

both measured, only the potentials versus Cu-CuSO, half -cell are indicated. In general,

the potentials of the piles with anodes in the

sand were less negative (more noble) during

the eight year period than those piles with

their anodes in the water. After one year, the

potentials of the bare steel piles with aluminum

and zinc anodes in the sand^rogs to more negative values which then remained rather con- stant during the eight year period.

The average corrosion current densities of

several bare steel piles and the average protective current densities of steel piles with zinc

anodes are plotted in figure 99. The protective

current density of the protected piles represent both the galvanic current as well as local action current on the anodes. The local action

current was not directly determined but it has

29
35

30

25

20 X

I-o

z

_i 15

10

15A POLYVINYLIDENE CHLORIDE/

ZINC FLAME SPRAY

% = AREA PITTED 1%2%

1%

1%2%

1%

1%

I MEAN HIGH WATER

DASHED LINE IS ORIGINAL SURFACE

2%

2%

2%

1%

2%

0 0.1 DEPTH OF DEEPEST PIT, in

0.6 0.7 AVERAGE FLANGE THICKNESS, in

Figure 83

been estimated to be about 10 percent of the

total corrosion current density [12]. The cur- rent density calculations were based upon the

total submerged area of the pile. The areas of

the anodes (originally 5-10% of the total

submerged pile area) were not included in the

calculations. Their consideration would have

made the total protection current densities for

the piles with anodes slightly less. These con- siderations apply to all of the systems to be

discussed.

As seen in figure 99, the pi^-eetiw- current

densities of the zinc anode protected systems

are less than those of the unprotected piles. It appears that there is not very much difference

in the protective current densities provided by

the anodes in the water and buried in the sand

over the 6 year period (1970 to 1975). More

time will be required to determine any real

differences.

Aluminum anodes in the sand appear to be

less effective than the anodes in water in protecting the steel (fig. 100). In the case of mariner steel, however, the

protection current density of the zinc anodes

buried in the sand, over the 6 year period, is definitely less than the current density of the

zinc anodes exposed to the water (fig. 101).

Figure 84

Figure 85

Coated flamesprayed zinc

The coal tar epoxy coated piles, with zinc

anodes in the sand appear to be more effective

(from a galvanic current standpoint) than the

coated piles without cathodic protection except

for one year (1971). For the piles with windows

(5A and 25A), there was little discernible

differences for two years (1971, 1972) between

the piles with anodes in the water and the piles

without anodes (fig. 102).

A comparison of the galvanized pile, with

zinc anodes (System 11) and without zinc

anodes (System 10), is shown in figure 103.

Only a portion of the curve for the protective

current density of the galvanized pile is shown.

From 1973 to 1975 the curve represents the

averages on piles B and C. Initially (1967) the

average corrosion current density on piles A,

B, and C was quite high and then decreased to very low values for 1967-1971 (fig. 90). The

protective current density is very low for the

zinc anodes buried in the sand and appears to be steadily decreasing with the passage of

time. The protective current density for the

zinc anodes in the water is about 3 times higher

and appears to be increasing with time.

30
16A VINYL/ZN FLAME SPRAY

25

o

I 20

MEAN HIGH WATER

MEAN LOW

WATER

% = AREA PITTED 10%

15%

15% 20%

40%

45%

80%

90%

70% 65%

1%5%

5%

0 0.1 DEPTH OF DEEPEST PIT, in

0.6 0.7 AVERAGE FLANGE THICKNESS, in

FiGUKE 86

5. Summary

Every coating system reduced the corrosion

of the steel piHng in seawater. In this respect

they differed only in the degree of protection

they afforded the steel. In the first six years of

exposure some coatings reduced corrosion by a

factor of 200 while others reduced corrosion

by a factor of 2 as compared to the bare piles. In table 3, the coatings are listed in order of

increasing degree of corrosion of the piling. It

is apparent from this table that there is no group of coatings (i.e., nonmetallic, metal pigmented, etc.) that is entirely satisfactory.

An average corrosion rate of 0.1 mpy (0.5

mdd) or less was measured for six systems.

Four of these six are two-coat systems. Generally the two-coat systems performed very well

in this program. The other two systems with

average corrosion rates <0.5 mpy (0.5 mdd)

are an aluminum pigmented coating, and a glass

flake filled coating. Both performed very well

with the glass flake filled coating being particularly resistant to the abrasive action of the

erosion zone.

b'lCDKE 87

Figure

)I6IAI-13

FiGrRE 89

( odled ftdinesprayed zinc

31
32
14AAI FLAME SPRAY

35

30

25

20

15

MEAN HIGH WATER

MEAN LOW

WATER

DASHED LINE IS ORIGINAL SURFACE

, = AREA PITTED

1%

0 0.1 DEPTH OF DEEPEST PIT, in

0.6 0.7 AVERAGE FLANGE THICKNESS, in

Figure 95

Seven systems exhibited corrosion rates in

the range of 0.14 mpy (0.8 mdd) to 0.24 mpy

(1.3 mdd) as table 3 reveals. All seven of these

coatings performed well. Two are metallic

coatings that were distinctive in their ability

to protect the piling uniformly including the

corners of the flange. Most coatings first failed

at the corners. System 22 suffered extensive

breakdown in the erosion zone but unusually

good resistance to attack in the atmosphericsplash zone. The remaining six systems were the least protective with average corrosion rates on the

.steel greater than 0.53 mpy (3 mdd). Four of

the six systems are coal tar epoxy coatings

which were particularly poor in the atmospheric-splash zone leading to relatively high aver- age corrosion for the steel. Of all the coatings.

System 12 provided the least protection to the

steel, even though it has been reported to per- form well by other laboratories | 7 1

.

As expected, the electrochemical measure- ments of the cathodically protected systems

clearly indicate that their corrosion rates are much lower than similar piles without protection. Furthermore, it is of interest to note that,

FiGL KE 97

FiGLRE 98

Sealed flamesprriyed aluminum

33
Table 2 - Potentials of Cathodically Protected Steel Piles Over a Period of

8 Years of Exposure (Offshore) in the Atlantic Ocean at Dam Neck, Virginia.

Potential of Pile, V-Ref-Cu-CuSO,, Positioned Remote - On the Beach

Pile Pilel^ Anode^'' 1 967—^ 1 968 1 969 1 970 1 971 1 972 1 1 Dsscn ption System High High High High Hi gh High High

iate Tide Tide Tide Tide Tide Tide Tide Tide Tide

2A Znin water _1 Q4 -1 .03 -1 08 -1 07 -1 08 -1 04 -1 06 -1 07 -1 03

2B Zn, in sand -0. 70 -0.73 -0. 91 -0. 83 -0 96 -0 93 -0 89 -0 97 -0 88

2C Bare Steel Zn, in water -K05 -l!05 -K05 -l!04 -1 !07 -l!06 -l!o6 -l!06 -I.'OB

3A Al, in water -1 04 -1 03 -1 04 -1 04 -1 05 -1 03 -1 06 -1 04 -1 03

38 Al, in sand -0.71 -0. 73 -0. 92 -0.82 -0.94 -0.87 -0.96 -0.85 -0.92

3C Bars Stefil Al, in water -1 . 04 -1 .04 -1 .04 -1 .03 -1 .05 -1 .04 -1 .06 -1 .03 -0.99

5A -^Coated Steel Zn, in water -1.10 -1 .07 -1.12 -1.09 -1.05 -1.07 -1.10 -1.12 -1.08

• 58 Coated Steel Zn, in sand -1.09 -1 .07 -1.10 -1 .08 -1.03 -1.09 -1.09 -1.08 -1.07

5C Coated Steel Zn, in water -1.09 -1.08 -1.11 -1.09 -1.04 -1 .00 -1.08 -1.06 -1.04

llA Galv. Steel Zn, in water -1.08 -1.06 -1.08 -1.08 -1 .02 -1 .03 -1 .08 -1.07 -1.05

IIB Hot-Dipped Zn, in sand -1.05 -0.99 -1.01 -0.98 -0.98 -0.98 -1.03 -0.98 -0.96

lie 3 oz Coat Zn, in water -1.08 -1.06 -1.08 -1.07 -1 .02 -1.06 -1.04 -1.06 -1.04

24A Bare Zn, in water -1.07 -1.05 -1.07 -1.07 -1 .01 -1.03 -1.06 -1.08 -1.04

24B Low Alloy Zn, in sand -0.86 -0.93 -1.00 -0.92 -0.94 -1 .00 -1.00 -0.96 -0.97

24C Steel Zn, in water -1 .05 -1.05 -1.07 -1.07 -1.01 -1 .05 -1.04 -1.06 -1.03

1/aii piles, except system 24, are mild carbon steelall are H-piles, 8 in. X 8 in. X 48 lbs/ft. -35 ft. long . In al cases, the sand line was from 19 to 21 ft. measured from the bottom of the pile, in general the row of C piles having

the more sand. The length of a pile exposed to sand and water varied between 24 ft. and 28 ft., depending on the normal tide.

2/— Zinc anodes are 4 in. x 4 in. x 35 in. weighing 150 lbs. Aluminum anodes are 4 in. x 4 in. x 38 in. weighing 60

lbs. Each pile is protected by two anodes permanently mounted on opposite flanges at the same elevation. On the

A and C piles, the anodes are mounted in the water zone between the sand line and the mean low water line. On the

B piles, the anodes are mounted in the sand zone, the tops of the anodes being about 6 ft. below the sand line.

3/—'Piles are coated with coal tar epoxy. Pile A has 5 windows (bare area, 1 in. x 6 in.). Pile B was completely

coated, and pile C was completely coated except for the lower 12 ft. in the mud zone.

4/— Initial measurements - made in 1967, 4 months after installation.

Table 3. Corrosion Rates of H-Piles Based on Flange Thickness Measurements

COATING DESCRIPTION

Overall Average

Corrosion

Rate

!!Ey!

Imbedded

Zone

to 15 ft.

Average Corrosion Rate Within Zone,

Erosion

Zone Immersed

Zone . 15 to 29 ft.°

Atmospheric

Zone K

21 Coal Tar Epoxy/Zinc Rich Inorganic <0 01 '0.01 '0.01 '0.01 '0.01

13 Vinyl /Flame Sprayed Aluminum 0 03 0.01 0.17 0.07 0 20 Epoxy Polyamide/Zinc Rich Inorganic 0 05 0.02 0.22 0.10 0

8 Aluminum Pigmented Coal Tar Epoxy 0 07 0.07 0.06 0.08 0.03

29 Polyester Glass Flake <0 10 <0.10 <0.10 '0.10 '0.10

15 Polyvinylidene Chloride/Flame Sprayed Zinc 0 10 0 0.14 0.12 0.29

10 Galvanized 0 14 0 0.67 0.32 0.06

17 Phenolic Mastic 0 14 0.11 0.11 0.15 0.21

14 Flame Sprayed Aluminum 0 16 0.19 0.39 0.19 0.03

9 Aluminum Pigmented Coal Tar Epoxy 0 18 0.18 0.08 0.21 0.04

18 Coal Tar Epoxy/Zinc Rich Organic 0 19 0.17 0.15 0.21 0.24

19 Vinyl/Zinc Rich Inorganic 0 20 0.19 0.22 0.18 0.31 22 Vinyl Mastic/Zinc Rich Inorganic 0 24 0.02 1.4 0.61 0 4 Coal Tar Epoxy 0 53 0.17 0.21 0.27 2.1 25 Coal Tar Epoxy on Mariner Steel 0 53 0.18 0.44 0.45 1.6

7 Coal Tar Epoxy plus Armor 0 55 0.13 0.07 0.07 2.7

6 Coal Tar Epoxy 0 80 0.27 0.72 0.46 2.9

16 Vinyl-Red Lead/Flame Sprayed Zinc 1 4 0.08 3.2 1.8 2.3

12 Polyvinylidene Chloride 2 4 0.81 4.9 3.6 3.5

30 Bare Carbon Steel 4 9 0.9 8.9 6.7 10.5

1 Bare Carbon Steel 6 0 1.8 9.7 7.9 12.2

31 Bare Carbon Steel 7 3 2.8 10.5 9.0 13.9

26 Bare Carbon Steel Pipe"- 27 Coal Tar Epoxy Pipe"" 28 Coal Tar Epoxy plus Armor Pipe*"

^For Iron; mils per year x 5.48 = milligrams per square decimeter per day.

^ Distance from bottom of pile.

''Flange thickness measurements not made on pipe

pil es.

34
BARE CARBON STEEL • WITH AND WITHOUT 2n ANODES

NO ANODES

IIA.B.C, 30A.E

31A,B)

Zn ANODES

IN SAND

(2BI

Zn ANODES

IN WATER

(2A,CI

1973 TIUP1975

Figure 99

bare carbon steel protected with al anodes

Al ANODES

IN SAND

I3B)

Al ANODES

IN WATER

I3A,CI

1973 TIME

BARE MARINER STEEL - WITH AND WITHOUT Zn ANODES

NO ANODES

I23A,B.CI

2n ANODES

IN SANO

(24 B|

2n ANODES

IN WATER

(24A,C)

1971 1973 1976 TIME Figure 101 carbon steel - coal tar epoxy coating

with and without zn anodes

Zn ANODES

IN SANO

(5BI NO ANODES

(2581

Zn ANODES

IN WATER

(5AI NO ANODES

I25A)

Figure 100 Figure 102

GALVANIZED STEEL - WITH AND WITHOUT Zn ANODES

NO ANODES

(10A,B,C) Zn ANODES

IN SAND

(118) Zn ANODES

IN WATER

(IIA.CI

1973 TIME Figure 103

35
with only one exception, the anodes located

below the mud line are providing more protection than similar anodes above the mud line. These preliminary results on the cathodically

protected systems must await verification

pending their removal for physical examination.

The authors are grateful for the continuing

cooperation and financial support of the American Iron and Steel Institute, and the funding

aid from the U.S. Army Corp of Engineers at the initial phase of the program. In our own

laboratory we wish to thank J. L. Fink and

J. T. Hill for their valuable assistance in vari- ous phases of the work, and W. J. Schwerdtfeger (retired) for his many helpful discussions, suggestions, and participation at the

start of the investigation. Appreciation is ex- tended to the coating manufacturers who provided technical and material assistance, and

the U.S. Navy Amphibious Construction Battalion No. 2 for installation and removal of the

piles ; to the U.S. Navy Fleet Combat Directions Systems Training Center for providing

the site, and to the divers from the U.S. Navy

Underwater Demolition Units for their aid in

making electrical connections. This work is dedicated to the memory of Melvin Romanoff

without whom the program would not have

existed.

6. References

HI Schwerdtfeg-er, W. J., J.Res. Nat. Bur. Stand. 60, No. 3, 153-159 (1958) RP2833.

|2| Burgbacher, J. A., Materials Protection, 6, No. 1, p. 56 (1967).

[3J Cleary, H. J., J. of Metals, 22, No. 3, p. 39 (1970).

[41 Brouillette, C. V., Corrosion, 14, No. 8, p. 352

(1958).

(5 1 Peterson, M. H., and Waldron, L. J., Corrosion,

17, No. 4, p. 188t. (1961).

[6] Balala, B., Materials Protection and Performance,

11, No. 9, p. 30 (1972).

171 Alumbaugh, R. L., Materials Protection, 3, No. 7, p. 34 (1964).

181 Reinhart, F. M., Corrosion of Materials in Hydrospace, TR-504, U.S. Naval Civil Engineering

Laboratory, Port Hueneme, California, Dec.

(1966).

[91 Monney, N. T., Materials Protection and Performance, 12, No. 1, p. 10 (1973).

[101 Larabee, C. P., Materials Protection, 1, No. 12, p. 95 (1962).

I ll I Watkins, L. L., J. Waterways, Harbors and Coastal

Engr. Div., ASCE, 97, Proc. Paper 8292, 549

(1971).

1121 Romanoff, M., Gerhold, W. F., Schwerdtfeger,

W. J., Iverson, W. P., Sanderson, B. T., Escalante, E., Watkins, L. L., Alumbaugh, R. L., Protection of Steel Piles in a Natural Seawater

Enviionment—Part I Proceedings, 3rd Inter- national Congress on Marine Corrosion and

Fouling, 1973.

[131 U.S. Dept. of Commerce ESSA, Coast and Geodetic

Surv., Pub. 31-1, 4th ed. (1972).

[141 Stern, M., and Geary, A. L., J. Electrochem. Soc.

104, No. 1, p. 56 (1957).

[151 Schwardtfeger, W. J. and McDorman, 0. N., J. Electrochem. Soc, 99, No. 10, p. 407 (1952).

[161 Schwerdtfeger, W. J., ASTM Mat. Res. and Stand.

10, No. 3, p. 22 (1970).

36
7. Index

Piling

System Text Number Coating- or Protection System Page Figures Tabl

1 Bare Carbon Steel 8

2, 5, 6, 90, 99 1, 3 2 Bare Carbon Steel (Zn anodes) 29 99 1, 2

3 Bare Carbon Steel (Al anodes) 30 10, 100 1, 2

4 Coal Tar Epoxy 8

10, 15, 21, 22, 23 1, 3

5 Coal Tar Epoxy (Zn anodes) 30 2, 102 1, 2

6 Coal Tar Epoxy 8 10, 11, 12, 13, 14 1, 3

7 Coal Tar Epoxy plus Armor 30 10, 16, 18, 19, 20 1, 3 8 Aluminum Pigmented Coal Tar Epoxy 18 48, 49, 50, 51, 52 1, 3

9 Aluminum Pigmented Coal Tar Epoxy 18 48, 53, 54, 55, 56 1, 3 10 Galvanized 28 90, 91, 92, 93, 94, 103 1, 3 11 Galvanized (Zn anodes) 30 103 1, 2 12 Polyvinylidene Chloride 16 35, 44, 45, 46, 47 1, 3

13 Vinyl/ Aluminum Flame Spray 24 78, 79, 80, 81, 82 1, 3 14 Aluminum Flame Spray 28 90, 95, 96, 97, 98 1, 3 15 Polyvinlyidene Chloride/ Zinc Flame Spray 24 78, 83, 84, 85 1, 3 16 Vinyl/ Flame Spray Zinc 24 78, 86, 87, 88, 89 1, 3 17 Phenolic Mastic 16 35, 36, 37, 38, 39 1, 3 18 Coal Tar Epoxy/ Organic Zinc Rich 20 57, 58, 59, 60, 61 1, 3 19 Vinyl/Inorganic Zinc Rich 21 57, 70, 71, 72, 73 1, 3 20 Epoxy Polyamide/ Inorganic Zinc Rich 20 57, 62, 63, 64, 65 1, 3 21 Coal Tar Epoxy/ Inorganic Zinc Rich 20 57, 66, 67, 68, 69 1, 3 22 Vinyl Mastic/ Inorganic Zinc Rich 21 57, 74, 75, 76, 77 1, 3 23 Bare Mariner Steel 8 5, 101 1 24 Bare Mariner Steel (Zn anodes) 30 101 1, 2 25 Coal Tar Epoxy on Mariner Steel 10 10, 17, 24, 25, 26, 102 1, 3 26 Bare Carbon Steel 8 9 1, 3 27 Coal Tar Epoxy 14 10, 27, 29, 30, 31 1, 3 28 Coal Tar Epoxy plus Armor 14 10, 28, 32, 33, 34 1, 3 29 Polyester Glass Flake 16 35, 40, 41, 42, 43 1, 3 30 Bare Carbon Steel 8 5, 99 1, 3 31 Bare Carbon Steel 8 8, 99 1

* U. S. GOVERNMENT PRINTING OFFICE : 1977 —240-848/184

37
NBS-1 14A (REV. 7-73)

U.S. DEPT. OF COMM. BIBLIOGRAPHIC DATA

SHEET

1. puhlk:ation or report no. NBS MN-158

2. Gov't Accession

No.

3. Recipient's Accession No.

4. TITLE AND SUBTITLE Corrosion and Protection of Steel Piles

in a Natural Seawater Environment

5. Publication Date June 1977

6. Performing Organization Code

7. AUTHOR(S) E. Escalante, W.P. iverson, W.l'". Gerhoid,

Bo T. Sanderson, R.L. Alumbaugh

8» Perfor mi n g 0 rgan. Report No

9. PERFORMING ORGANIZATION NAME AND ADDRESS

NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

10. Project/Task/Work Unit No. _Pro^^g^s^^,^e^ort

1 1. Contract/Grant No.

12. Sponsoring Organization Name and Complete Address (Street, City, State, ZIP)

American Iron and Steel Institute

1000 16th St. N. W,

Washington, D.C. 20036

13. Type of Report & Period Covered Final

14. Sponsoring Agency Code

15. SUPPLEMENTARY NOTES O riginally p rinted for limited distribution to sponsor as NBSIR 76-1104. This document has gone through the editorial review.

Library of Congress Catalog Card Number: 76-608410

16. ABSTRACT (A 200-word or less [actual summary of most significant information. If document includes a significant

bibliography or literature survey, mention it here.)

This report describes the first eight years of a long term program in

which twenty-three coating systems and five cathodic protection systems are

evaluated on their ability to protect steel piles in offshore conditions. These

systems are made up of nonmetallic coatings, metallic pigmented coatings,

nonmetallic coatings on metal filled coatings, nonmetallic coatings on metallic

coatings, metallic coatings, and cathodic protection on bare and coated piles.

It includes a description of the annual on site electrochemical coating

evaluation and a description of the final physical evaluation made on the piles

after removal. The results of these electrochemical and physical evaluations are presented graphically and in tabular form.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons

)

Cathodic protection; coating systems; corrosion protection; offshore corrosion;

sand corrosion; seawater corrosion; splash zone corrosion.

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