Reference

fSIBS Publications

N4T'L INST, OF STAND i TECH H.I.C.

AlllDM M331flfl

NBSIR 82-2553

Development of Interim

Performance Criteria for

Restoration Coatings for Porcelain

Enamel Surfaces

U S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Building Technology

Building Materials Division

Washington, DC 20234

June 1 982

Prepared for QQ

Division of Energy, Building Technology and Standards

Department of Housing and Urban Development

100 Washington, DC 20410

.056

82-2553

1982

ATIOHAX BUAAA*

or wrtAiroAMBm

UQUUUKX

2 1982

NBSIR 82-2553

DEVELOPMENT OF INTERIM . - PERFORMANCE CRITERIA FOR

RESTORATION COATINGS FOR PORCELAIN

ENAMEL SURFACES

James F. Seiler

Paul G. Campbell

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards

National Engineering Laboratory

Center for Building Technology

Building Materials Division

Washington, DC 20234

June 1 982

Prepared for Division of Energy, Building Technology and Standards

Department of Housing and Urban Development

Washington, DC 20410

U.S. DEPARTMENT OF COMMERCE, Malcolm Baldrige, Secretary

NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director
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ABSTRACT

A study was performed to develop interim performance criteria for restoration

coatings for porcelain enamel surfaces. The laboratory study consisted of

evaluating five restoration coatings which had been applied to porcelain enamel

test panels with various surface conditions. Performance characteristics of

the coatings examined included appearance, adhesion, impact resistance, stain

resistance and fungal resistance. Existing test methods were used in the

study if appropriate methods were available. However, the laboratory studies

led to the development of a new cyclic exposure test and the use of a newly

developed method for measuring adhesion. Adhesion of the coatings was the

performance characteristic most sensitive to change with time of exposure to

the newly developed cyclic exposure test. Interim performance criteria for

restoration coatings for porcelain enamel surfaces were developed, based upon

the results of the laboratory study.

Additional studies are being conducted to assess the performance and durability

of selected restoration coatings applied to bath tubs in public housing units.

Since the field studies are not yet completed, they are not addressed in this

report.

iii
TABLE OF CONTENTS

Page

ABSTRACT ill

LIST OF TABLES v LIST OF FIGURES vi

1. INTRODUCTION 1

1.1 Background 1 1.2 Objective 1

1 .3 Scope I

2. IDENTIFICATION OF COMMERCIALLY AVAILABLE RESTORATION COATINGS 2

3. PERFORMANCE REQUIREMENTS 3

4. LABORATORY EVALUATIONS 4

4.1 Materials 4

4.1.1 Treatment of Test Panels Prior to Restoration 4

4.1.2 Restoration Coatings 5

4.2 Test Methods 5

4.2.1 Accelerated Bathtub Exposure 5 4.2.2 Adhesion 7 4.2.3 Impact Resistance 8

4.2.4 Color 8

4.2.5 Gloss 8

4.2.6 Stain Resistance 8

4.2.7 Fungal Resistance 9

5. RESULTS AND DISCUSSION 10

5.1 Adhesion 10

5.2 Impact Resistance 11

5.3 Color 11

5.4 Gloss 11

5.5 Stain Resistance 12

5.6 Fungal Resistance 12

6. INTERIM PERFORMANCE CRITERIA 13

7. SUMMARY AND CONCLUSIONS 14

8. FUTURE RESEARCH 15

9. ACKNOV7LEDGEMENTS 16

10. REFERENCES 17

APPENDIX A - COMMERCIALLY AVAILABLE RESTORATION COATINGS A-1

APPENDIX B - INTERIM PERFORMANCE CRITERIA FOR RESTORATION COATINGS FOR

PORCELAIN ENAMEL SURFACES B-1

iv
LIST OF TABLES

Page

Table 1. Average Impact Resistance of Restoration Coatings, Surface

Condition 1, After ABECs 18

Table 2, Color Differences of Restoration Coatings, Surface

Condition 1, After ABECs 18

Table 3. Color Differences of Restoration Coatings, Surface Conditions

2, 3, and 4, After 25 ABECs 19

Table 4. 60° Gloss of Restoration Coatings, Surface Condition 1, After

ABECs 19

Table 5. 60° Gloss of Restoration Coatings, Surface Conditions 2, 3,

and 4, After 25 ABECs 20'

Table 6. Stain Resistance of Restoration Coatings Using Three

Removal Methods 21

V
LIST OF FIGURES

Page

Figure 1. Pattern for preconditioning test panels 22

Figure 2. Circuit diagram for recycling controls on modified

dishwasher 23

Figure 3. Recycling controls on modified dishwasher 24

Figure 4. Accelerated bath cycle apparatus - overall view 24

Figure 5. Accelerated bath cycle apparatus - machine unloaded 25

Figure 6. Accelerated bath cycle apparatus - panels loaded in rack .... 25

Figure 7. Modified abrasion procedure using P.E.I. abrasion tester

and alloy balls 26

Figure 8. Modified abrasion procedure - placing test panels on apparatus 26

Figure 9. Modified abrasion procedure - placing containers for

holding alloys balls and abrasive on test panels 27

Figure 10. Modified abrasion procedure - addition of alloy balls 27

Figure 11. Modified abrasion procedure - addition of abrasive 28

Figure 12. Modified abrasion procedure ~ addition of water 28

Figure 13. Modified abrasion procedure - abrasion test commences 29

Figure 14. Modified abrasion procedure - removal of test panels and

alloy balls after test 29

Figure 15. Modified abrasion procedure - rinsing alloy balls and

test panels 30

Figure 16. Adhesion procedure - yoke apparatus mounted in testing

machine 30

Figure 17. Adhesion procedure ~ insertion of test panel with

buttons attached 31

Figure 18. Adhesion procedure - joining upper aiid lower portions

of yoke apparatus 31

vi
LIST OF FIGUEIES - (CONTINUED)

Page

Figure 19. Adhesion procedure - joining upper and lower portions of

yoke apparatus 32

Figure 20. Adhesion procedure - after test, bottom of metallic

cylinder showing delaminated coating 32

Figure 21. Adhesion procedure - coated area pulled off after testing .... 33

Figure 22. Impact resistance procedure - apparatus with aluminum

impactor cylinder 33

Figure 23. Impact resistance procedure - apparatus with test panel

in place 34

Figure 24. Impact resistance procedure - raising impactor cylinder 34

Figure 25. Impact resistance procedure - test panel after impact 35

Figure 26. Stain resistance test procedure - chambers with

rubber seals 35

Figure 27. Stain resistance test procedure - chambers inserted in

upper section of holder 36

Figure 28. Stain resistance test procedure - upper holder prior to

clamping 36

Figure 29. Stain resistance test procedure - application of liquid

stain 37

Figure 30. Stain resistance test procedure - application of solid

stain 37

Figure 31. Stain resistance test procedure - test complete, removal

of rubber seals 38

Figure 32. Average stress at rupture for various accelerated bathtub

exposure cycles (Restoration Coating 1) 39

Figure 33. Average stress at rupture for various accelerated bathtub

exposure cycles (Restoration Coating 2) 40

Figure 34. Average stress at rupture for various accelerated bathtub

exposure cycles (Restoration Coating 3) 41

vii
LIST OF FIGURES - (CONTINUED)

Page

Figure 35. Average stress at rupture for various accelerated bathtub

exposure cycles (Restoration Coating 4) 42

Figure 36. Average stress at rupture for various accelerated bathtub

exposure cycles (Restoration Coating 5) 43

Figure 37. Restoration coating 5 after adhesion tests; left panel

unexposed, center panel after two ABECs; right panel after

three ABECs 44

vlii
1 . INTRODUCTION

1.1 BACKGROUND

Within the last 15 years, processes have been developed for restoring in place

chipped or worn porcelain enamel fixtures, such as bathtubs and wash basins,

by application of an organic coating. Newer restoration techniques have been

developed which may cost only one-quarter as much as replacement of the

enamel-coated fixture. In the maintenance of public housing, a continuing

problem exists with regards to porcelain enamel coatings on steel and cast

iron fixtures which have been damaged by wear or abuse. The potential economic

savings could make these new restoration techniques attractive, provided that

they perform well. For example, one major problem has been that of adhesion

of the organic coating to the damaged or degraded porcelain enamel surfaces.

Performance criteria are needed to aid in ensuring the performance and durability of restoration coatings. Laboratory and field data, as well as accelerated test methods, are needed to serve as the technical bases for the

performance criteria.

1.2 OBJECTIVE

The objective of the research discussed in this report was to develop Interim

performance criteria for restoration coatings for porcelain enamel surfaces.

1.3 SCOPE

In order to meet the stated objective, tasks were performed to 1 ) identify the

available commercial restoration coatings for the repair of porcelain enamel

surfaces, 2) identify performance requirements and available test methods for

evaluating restoration coatings and, where appropriate existing tests were

not available, to develop new methods, 3) select and evaluate several commercial

coatings in the laboratory to identify factors which affect adhesion and

durability and 4) develop interim performance criteria based upon laboratory

studies. The results of the above tasks are given in this report.

Eield studies are currently being conducted to obtain performance and durability

data on selected coatings applied to bathtubs in public housing units. These

data will be used to assess the effectiveness of the interim performance

criteria. Since the field studies are not yet completed, they are not addressed

in this report.

1
2. IDENTIFICATION OF COMMERCIALLY AVAILABLE RESTORATION COATINGS

Thirty five renovation firms were identified throughout the country. Eleven

firms were contacted by telephone although contacts were sought with all firms.

It may be noted that many of these firms also franchised other firms or were

distributorships for other firms. Information sought was as follows; 1) the

type of enamelled metal renovated and whether spot repairs were also made to

porcelain enamel surfaces, 2) the type of surface preparation used, 3) generic

coatings used, and 4) costs for renovation/repair.

The list of identified companies and information obtained from the telephone

contacts are included in appendix A. To summarize the telephone responses, it was found that 1) bathtubs were the most frequently repaired units, 2) surface

preparation almost always included acid, solvent and sand treatment, 3) the

generic coatings most commonly used were urethanes and epoxies, and 4) the

renovation costs for a bathtub were $175 to $250 versus the replacement costs

estimated to be $600 to $1000.

2
3 . PERFORMANCE REQUIREMENTS

In order for the restoration coating to perform satisfactorily, the coating

must adhere to the substrate under elevated temperature exposure and wet/dry

cycling. Also, the coating should be resistant to color and gloss changes

(particularly after repeated scrubbing), resistant to impact, and resistant to

fungal attack and to stains when exposed to in-service use conditions.

Standard test methods were determined to be available for measuring impact

resistance, color, gloss, stain resistance and fungal resistance, A modified

standard method was used for measuring adhesion of coatings and a cyclic

exposure test was developed to accelerate the exposure conditions experienced

by a porcelain bathtub or wash basin finish. These methods are described in

section 4.2 of this report.

3
4 . LABORATORY EVALUATIONS

4 . 1 MATERIALS

The surfaces of porcelain enamel-coated steel panels, obtained through the

Porcelain Enamel Institute (PEI), were treated at the National Bureau of Standards to simulate four potential surface conditions that could be encountered by

a restoration coating company during a restoration operation. These conditions

included 1) glaze intact, 2) glaze eroded but no metal exposed, 3) glaze eroded

and metal exposed and 4)glaze chipped, metal exposed with damaged substrate.

Following the surface treatment, test panels were sent to five different restoration companies for restoration. The following paragraphs describe the surface

treatment performed at NBS and the restoration by the five companies.

4.1.1 Treatment of Test Panels Prior to Restoration

The porcelain enamel coated steel panels, obtained through the PEI, were

130xl50mm(4x6 in) in size. These panels were considered to be representative of a "typical" new porcelain enamelled steel bathtub or wash basin.

The surfaces of the test panels were subjected to one of the following four

pretreatments in order to simulate various surface conditions that could be

encountered prior to an actual field restoration:

Surface Condition 1. Porcelain enamel surface glaze retained intact, i.e., as received from PEI.

Surface Condition 2. Porcelain enamel surface lightly sandblasted to remove

surface glaze (but metal not exposed).

Surface Condition 3. Porcelain enamel surface lightly sandblasted and then

chipped with an impact tester in three locations (see

pattern* in figure 1) to expose, approximately, a 19 mm

(0.75 in) diameter area of the metal substrate. Prior

to shipping for restoration, these panels were placed

in distilled water until rust appeared.

Surface Condition 4. Porcelain enamel surface lightly sandblasted and then

sandblasted to white metal in three locations (see

figure 1) using a metal mask to expose 19 mm (0.75 in)

diameter areas. Prior to shipping for restoration.

* The three locations for chipping and sandblasting were within the circular

abrasion pattern created by the PEI abrasion tester^/ as described in ASTM

C 448 [1].

Certain commercial equipment, instruments or materials are Identified in

this paper in order to adequately specify the experimental procedure. Such

identification does not imply recommendation or endorsement by the National

Bureau of Standards, nor does it imply that the material or equipment

identified is necessarily Che best available for the purpose.

4
these panels were placed in distilled water until rust

appeared.

4.1.2 Restoration Coatings

Five restoration finish companies were selected for participation in this study

to provide a cross-section of the generic coatings typically used by restoration companies. The code for the companies and the generic types of restoration

coatings are as follows:

Each company received 77 test panels as described in 4.1.1 and was asked to

recoat or repair them in a manner consistent with procedures used in field

restorations. Thirty-five of the test panels sent to each company were pretreated using Surface Condition 1; 14 panels were sent for each of the Surface

Conditions 2, 3, and 4. The test panels were coated at the factory using the

companies' individual restoration techniques and then returned to the National

Bureau of Standards for laboratory testing.

4.2 TEST METHODS

Laboratory tests of the restored panels were performed to assess resistance to

degradation using an accelerated bathtub exposure and resistance to fungal

growth. Tests of adhesion, impact resistance, color, gloss, and stain resistance were performed at various exposure time increments to assess degradation.

Duplicate test panels for each coating and each surface condition were kept in

the laboratory as control specimens. The methods used in the laboratory tests

are described below.

4.2.1 Accelerated Bathtub Exposure

An accelerated bathtub exposure test was developed to simulate in-service

usage. It was designed to include the elements of wet and dry cycling, elevated

water temperatures and surface abrasion. One accelerated bathtub exposure cycle

(ABEC) included 28 bath cycles and one abrasion cycle (56 counts on the PEI

abrasion tester).

Company Code for Generic Description

Restoration Coatings of Coating Used

12

3

4

5

Phenolic

Epoxy

Urethane

Enamel

Urethane

5
The bath portion of the exposure test, which provided wet and dry cycling and

elevated water temperature exposure to the panels, utilized a modified Maytag^/

dishwasher (Model WC201). The control knob on the dishwasher was automated

to provide the desired bath cycle. The electrical circuit diagram is given

in figure 2 and shown in the photograph of figure 3. The bath cycle began at

the setpoint on the control knob where the rinse cycle started and stopped at

the drying period end point. The control knob automatically rotated from the

end point (completion of drying period) to the set point (start of rinse

period). During this 30 second interval, a solenoid operated valve automatically allowed liquid detergent to enter the machine. One complete bath cycle

required approximately 40 minutes and the conditions are illustrated in the

following table:

Time Period Dry Air Temp.

°C(°F)

Water Temp.^'

°C(°F)

Time

min.

End point^/ to set point^/ N.A. N.A. 0.5

Set point to end of wash N.A. 43 (110) 4.0

Start to end of first rinse N.A. 43 (110) 5.0

Start to end of second rinse N.A. 43 (110) 6.0

Start to end of drying period 77 (170) N.A. 23.5

Twenty-eight bath cycles were completed in each 24 hour period and the

procedure is illustrated in figures 4-6. Following each 28 cycles, the panels were cooled to room temperature and visually examined for any surface defects

.

The abrasion portion of the exposure test was carried out at the end of each

28 bath cycles using a modification of the ASTM procedure C 448 [1] and using

the PEI tester. The PEI abrasion tester was selected because it produces an

Certain commercial equipment, instruments or materials are identified in

this paper in order to adequately specify the experimental procedure. Such

identification does not imply recommendation or endorsement by the National

Bureau of Standards, nor does it imply that the material or equipment

identified is necessarily the best available for the purpose.

Internal timer stops, turning motor starts.

Turning motor stops, internal timer begins.

A previous study [2] of vitreous enamel and plastic sanitary fixtures used

tests for hot water resistance and thermal shock resistance at 93.3-100°C to

0°C (200-212°F to 32°F). Frechette, et al. [3] used a water temperature of

93.3°C (200°F) in studies of patch kits applied to poreclain enamel. A

water temperature of 43°C was selected for this study because the water

temperature from most residential water heaters currently is not believed to

exceed 43°C (110°F).

6
oscillating notion which simulates hand scrubbing of a porcelain fixture.

The ASTM C 448 procedure was modified so that the panels were abraded for 56

machine machine counts and the abrasive used was a mild cleanser containing

feldspar. The abrasion test procedure is illustrated in figures 7-15.

The panels were visually examined after 2, 5, 10, 15, 20, and 25 ARECs and

tested for changes in color, gloss, impact resistance and adhesion. The panels

were rinsed with dilute hydrochloric acid and water to remove traces of salt

deposits before testing. The stain and fungus tests were conducted after 25

ABECs.

4.2,2 Adhesion

Adhesion tests were performed to determine the level of adhesion of the

restoration coatings with increasing time of accelerated exposure. The test

method to determine the stress at rupture of the restoration coatings was a newly developed modification of the International Standards (ISO) method No.

4624 [4] which utilizes a pull-off technique. The adhesive used for bonding

the metallic button was an industrial strength epoxy and the yoke apparatus was

was especially designed for use with a testing machine. Figures 16-21 illustrate special apparatus and test procedure. Prior to bonding the metallic

buttons to the panels, the panels were allowed to stabilize at 21 °C (70°F) and

50 percent RH for at least 24 hours. A 19 mm (0.75 in) diameter, 19 mm (0.75 in)

high stainless steel cylinder was glued, plane face down, with the epoxy adhesive and cured at 70°C (158°F) for 40 minutes. Four small spacers were machined

on the outer edges of the planar surface of the stainless steel cylinder in

order to produce a bond line of 0.203 mm + 0.002 mm thickness. Three cylinders

were attached at uniform intervals to duplicate coated panels having porcelain

enamel Surface Condition 1. Thus, the reported stress at rupture values were

an average of 6 pull-off tests. Two cylinders were attached at uniform intervals on duplicate coated panels having Surface Conditions 2, 3, and 4. Thus,

stress at rupture values were an average of 4 pull-off tests for these surface

conditions. For Surface Conditions 3 and 4, the cylinders were attached

directly over the repaired areas that had been chipped or sandblasted. The

adhesion tests were conducted using the 300 kg (661 lb) range of the testing

machine with a chart drive of 50 mm/mln (2 in/min) and a console speed (movement rate of the screw drive) of 1 mm/min (0.04 in/min).

Preliminary studies with the PEI abrasion tester indicated that the alloy

balls did not affect the color or gloss of the restoration finishes, but that

the Pennsylvania glass sand abrasive used in the test was much too abrasive

on the organic coatings. Preliminarv studies indicated that the mild abrasive cleanser recommended by the restoration coating companies along with the

alloy balls would produce moderate abrasion on the organic coatings while

having little or no effect on porcelain enamel itself.

7
4.2.3 Impact Resistance

The test method to determine the impact resistance of the restoration coatings

after exposure to the accelerated exposure described in 4,2,1 was modified from

ASTM D 2794 [5], To provide improved sensitivity, a 0,45 kg (1 lb) aluminum

impactor cylinder was used Instead of the 0,9 kg (2 lb) steel cylinder of the

variable light duty impact tester. The aluminum cylinder was dropped in 25 mm

(1 in) height increments, starting at 25 mm (1 in), until a visible dent or chip occurred on the surface. The coated panels used for the test were those

having Surface Condition 1, (see 4,1,1), Figures 22-25 illustrate the impact

resistance procedure,

4.2.4 Color

ASTM test method D 2244 [6] was used to measure color differences (AE) on the

coated panels after exposure to the ABECs, Using a colorimeter, measurements

were made in both the abraded and unabraded areas,

4.2.5 Gloss

ASTM test method D 523 [7] was used to measure 60° gloss differences on the

coated panels after exposure to ABECs, Gloss measurements were made in both

the abraded and unabraded areas. Preliminary gloss measurements revealed the

necessity of removing traces of minerals or other deposits from the tap water

and detergents used in the bath cycle. Consequently, a dilute hydrochloric

acid wash And distilled water rinse was an essential part of panel preparation

before gloss measurements were made,

4.2.6 Stain Resistance

Test panels were rated visually for effectiveness of stain removal. The

measurement of stain resistance involved modification of the test method ASTM

D 1308 [8]

,

The test apparatus was the same as that used in a previous study

[2], In particular, the procedures were modified to ensure that the staining

materials would not evaporate during the 16 hour exposure. The staining

materials selected were those thought to be in common usage in bathroom areas

and those which had proved troublesome on other organic substrate such as fiber

glass reinforced polyester bathtubs [2] and plastic wall covering materials

[9], These staining materials were purple Tintex, black hair dye, black shoe

polish, lipstick and acetone. The test apparatus and its use is illustrated

in figures 26 to 31, The stains were removed after 16 hours exposure on the

restoration coating using the following three methods:

Method 1 - wipe with soft dry paper towel.

Method 2 - scrub gently with warm soapy water and brush, and

Method 3 - scrub on PEI abrasion tester for 28 cycles.

The panels used for this test were Surface Conditions 1 and 2, (see 4,1,1) which

had been exposed to the ABECs, Surface Conditions 3 and 4 panels were not used

8
for this test because staining is a surface related phenomena and the restoration coating surfaces of Surface Condition 3 and 4 panels were comparable to

those of Surface Condition 1 and 2 panels.

4.2.7 Fungal Resistance

Measurement of fungal resistance was by test method ASTM D 3273 [10]. The

coated test panels were examined in accordance with test method ASTM D 3274

[11] after 30 days exposure in the incubation chamber.

9
5. RESULTS AND DISCUSSION

5.1 ADHESION

The change in measured stress at rupture of the test panels with ABECs is given

in figures 32-36 for Restoration Coatings 1, 2, 3, 4, and 5. Prior to exposure,

to range of measured stress at rupture values for all surface conditions of each

Restoration Coating were as follows: Restoration Coating 1: 3.0 MPa

(430 psi) the 1.7 MPa (250 psi); Restoration Coating 2: 2.6 MPa (375 psi) to

1.4 MPa (200 psi); Restoration Coating 3: 2.8 MPa (400 psi) to 1.8 MPa

(260 psi); Restoration Coating 4: 5.2 MPa (750 psi) to 1.7 MPa (250 psi); and

Restoration Coating 5: 4.3 MPa (630 psi) to 1.9 MPa (275 psi). The surface

condition of the panels prior to restoration/repair had an Influence on the

stress at rupture of the restored/repaired panels. The stress at rupture of

panels of Surface Conditions 1 and 2 would have been expected to have been

nearly equal. The lower stress at rupture values of Surface Condition 2 panels

may have been the result of the sandblasting treatment treatment causing microcracking which weakened the cohesive bonding of the porcelain enamel. The

stress at rupture values of Surface Condition 3 and 4 panels were usually lower

than the others. Also, the values were more erratic for Surface Conditions 3

and 4 than for Surface Conditions 1 and 2, which may reflect the influences of

the epoxy fillers used for the repair and the stresses imposed on the panels

during impact and sandblasting treatment. The stress at rupture of all the

restoration coatings decreased with increasing number of exposure cycles.

However, the rate of decreasing stress at rupture with ABECs was noticeably

different for the different restoration coatings. As examples, 1) the stress

at rupture of Restoration Coating 5, Surface Condition 1, decreased rapidly

from 4.3 MPa (630 psi) to 1.9 MPa (275 psi) after 2 ABECs before stabilization,

and 2) the stress at rupture of Restoration Coating 4, Surface Condition 1,

decreased from 5.2 MPa (750 psi) initially to 3.7 MPa (537 psi) after 25 ABECs.

For each of the coatings, the general shape of the ABEC curve for Surface

Conditions 2, 3, and 4 was similar to that of the Surface Condition 1 curve. This implies that the properties of each of the restoration coatings were a more important factor in the degradation process than the individual surface

condition treatments.

When the average stress at rupture was greater than 4.1 MPa (600 psi),

failures occurred in the porcelain enamel-metal interface. For example, all

of the panels of Restoration Coating 4, Surface Condition 1, delaminated in the

porcelain enamel for up to 20 ABECs, while none of the panels of Restoration

Coating 1, Surface Condition 1, delaminated in the porcelain enamel following

accelerated exposure. Also of interest, the mode of adhesion failure changed

with a decrease in average stress at rupture as exposure cycles increased.

This is illustrated in figure 37 for Restoration Coating 5, Surface Condition 1;

the initial failure was in the porcelain enamel substrate; after two ABECs,

failure was observed at the primer to organic top coat interface; and after

three ABECs, cohesive failure occurred within the organic top coat. The mode

1 / MPa = mega pascal.

10
of failure in order of decreasing frequency was 1) failure in the enamel,

2) primer-to-top coat failure, and 3) cohesive failure in the top coat. The

latter failure mode was primarily observed as the stress at rupture values

decreased with increasing exposures. In general, stress at rupture values of

the restoration coatings over repaired areas (Surface Conditions 3 and 4) were

not as high as those for Surface Conditions 1 and 2. Influences other than the

test exposure on the adhesion of the restoration coatings may have been the

thickness of coating and/or filler surface treatment, stress concentrations from

bonding to the relatively thin steel substrate, and the air and water temperatures used in the bath cycles which may have accelerated polymer degradation.

5.2 IMPACT RESISTANCE

The average impact resistance of the restoration coatings was determined by a modification of ASTM D 2794 [5] after exposure to ABECs. The results are shown

in table 1. For comparison purposes, the impact resistance test was also

performed on unrestored porcelain enamel panels. Surface Condition 1. The

average impact resistance of six of these panels was 0.53 Nm.

All the restoration coatings had better initial impact resistance than the

unrestored porcelain enamel panel. The change in impact resistance of the

restoration coatings after exposure was small and considered insignificant.

5.3 COLOR

Color difference measurements were made on both the abraded and unabraded areas

of the restoration coatings after exposure to ABECs. The results of coatings.

Surface Condition 1, are illustrated in table 2. For comparison purposes,

color measurements were performed on unrestored porcelain enamel panels. Surface

Condition 1. These data are Included at the bottom of table 2. The color

differences of Restoration Coatings, Surfaces Conditions 2, 3 and 4, are illustrated in table 3 after 25 ABECs.

The color changes for the restoration coatings after accelerated exposures were

generally 2 NBS color difference units or less and thus, color changes are considered insignificant. Restoration Coating 2 (table 3), was an exception

in that color changes were visible. Varying panel surface conditions did not

affect the color changes after accelerated exposures except for possible minor

effects due to surface differences (defects).

5.4 GLOSS

The 60° gloss measurements were made on both the abraded and unabraded areas of

the restoration coatings after exposures. The test results of coatings. Surface

Condition 1, are illustrated in table 4. For comparison purposes, gloss measurement was also performed on unrestored porcelain enamel panels, Surface

Condition 1. These data are shown at the bottom of table 4. The gloss measurements of restoration coatings, for Surface Conditions 2, 3, and 4, after

25 ABECs are illustrated in table 5.

11
Gloss changes for the restoration coatings after accelerated exposures, i.e.,

25 ABECs, in the unabraded areas were minor. However, large gloss changes were

found in the abraded areas for all restoration coatings. The unrestored porcelain enamel panel. Surface Condition 1, had a 21 percent loss in gloss in the

abraded area after 25 ABECs. While the abrasive used in the tests is of a type

recommended for restoration coating and fiber glass reinforced polyester bathtubs, its use in this study proved to be devastating on the gloss of the finishes. The abrasive medium for organic coatings should be a softer inorganic

material or an organic fibrous material, e.g.. Nylon mats, in order to retain

gloss

.

5.5 STAIN RESISTANCE

The stain test results are given in table 6 for the restoration coatings.

Surface Condition 2, which had been exposed to 25 ABECs. In preliminary experiments, unrestored porcelain enamel coatings were completely resistant to all of

the stain materials. With the exceptions of the effects of the black hair dye on Restoration Coatings 2 and 3, and the effects of acetone in dissolving

Restoration Coatings 1, 3, and 5, the stains were readily removed from the

coatings

.

5.6 FUNGAL RESISTANCE

Since restoration coatings would often be exposed to fungi growth in a hot,

humid bathroom environment, the procedure in test method ASTM D 3273 was used

to examine’ the fungi resistance of these materials. After 30 days test exposure

of the five restoration coatings, and an unrestored porcelain enamel panel,

which had previously been exposed to 25 ABECs, no fungal growth was observed on any of the panels.

12
6. INTERIM PERFORMANCE CRITERIA

Interim performance criteria for restoration coatings for porcelain enamel

surfaces are presented in appendix B and are based upon the laboratory test

results described in chapter 5 of this report. These performance criteria are termed "interim" because they may be modified after the completion of the field

studies

.

The key to the development of the performance criteria was exposure of the test

panels to accelerated bathtub exposure cycling (ABEC) which included wet and

dry cycling, elevated water temperatures and surface abrasion. All panels were

exposed to 25 ABECs (each cycle included 28 bath cycles with detergent injection

at each bath cycle, then cooling and abrading the panels on the PEI abrasion

tester for 56 machine counts using feldspar-containing cleanser and the alloy

balls as abrasive before evaluation). The criteria selected were chosen to

reflect performance charadteristics which these materials would be expected to

exhibit in service; they included appearance, abrasion resistance, adhesion,

impact resistance, stain resistance and fungal resistance.

Based upon the laboratory test results, all of the five restoration coatings

had good performance with regard to appearance, impact resistance, stain resistance, and fungal resistance which is reflected in the respective proposed test

requirements. The proposed test requirements are as follows:

° Appearance: 60° gloss: Before exposure - > 75

After 25 ABECs - > 70

45° reflectance: Before exposure - > 85

color change: After 25 ABECs - < 2 NBS units

° Impact resistance: 0,53 Nm (4,7 inch pounds) after exposure to

25 ABECs

° Stain resistance: very light stain residue after scrubbing with warm

soapy water on specimens exposed to 25 ABECs

° Fungal resistance: no fungus after 30 days exposure to conditions of

ASTM D 3273 (i,e,, rating 10, ASTM D 3274),

Test data indicated differences in stress at rupture for adhesion tests in both

the initial and exposed restoration coatings. The adhesion test requirement is

proposed of a 3,1 MPa (450 psi), initial, and 1,4 MPa (200 psi), after exposure

to 25 ABECs, This is thought to represent the criteria for heavy use areas,

e,g,, children, transient tenants, whereas the adhesion criteria may well be

modified for use in light use areas, e,g,, elderly occupants. At this time, the

interim performance criteria do not differentiate between various use conditions, The additional field test study should aid in the validation of the

interim criteria and provide guidance in differentiating criteria for different

use areas.

13
7. SUMMARY AND CONCLUSIONS

An accelerated bathtub exposure cycle (ABEC) was developed to study the

performance of restoration coatings for porcelain enamel surfaces. The exposure

test contained the elements of elevated water tempertures, wet and dry cycling

and surface abrasion. Five companies applied restoration coatings to porcelain

enamel panels which had been treated to simulate various conditions of surfaces

in need of repair. The restored panels were exposed to the accelerated exposures for selected time periods prior to evaluation. Performance characteristics of the restoration coatings examined Included appearance, adhesion. Impact

resistance, stain resistance and fungal resistance. Interim performance criteria were developed based upon these characteristics of the five restoration

coatings.

General conclusions based upon the laboratory results are as follows:

1. Adhesion was the performance characteristic most sensitive to change with

the length of time of accelerated exposure. Damage to the porcelain enamel

surface during sandblast surface preparation and prior to restoration coating application appeared to have had a noticeable deleterious effect on

stress at rupture. This could be of concern in future restoration

procedures

.

2. The restoration coatings examined had good performance with regards to

appearance, impact resistance, stain resistance, and fungal resistance.

3. The use of the feldspar-containing cleanser in the PEI abrasion tester was judged to be too severe for the restoration coatings tested. This conclusion is based upon the large changes in gloss in abraded areas of test

specimens. While a housewife cleaning a bathtub with a feldspar-containing

cleanser ordinarily would not abrade a bathtub under the severe conditions

used in the PEI abrasion test, consideration should be given to the development of an even milder abrasive for use with restoration coatings. Also,

modification of test procedures for measuring abrasion resistance and

resultant gloss changes will require milder abrasives for more sensitive

detection of changes.

14
8. FUTURE RESEARCH

The interim performance criteria presented in appendix B for restoration

coatings for porcelain enamel are based only upon accelerated exposure tests

and require field testing to validate the interim criteria. As pointed out in

previous sections of the report, field tests are currently underway. The

effectiveness of the adhesion test in assessing changes in coatings performance

necessitates the use of adhesion tests in the field test study. The development of a portable pneumatic adhesion tester is needed to permit these tests to

be carried out; research is currently underway to develop a portable tester.

Research is also needed to determine the effects of surface preparation treatments prior to restoration coating application. The development of non-abrasive

cleansers for use with restoration coatings is needed.

15
9 . ACKNOWLEDGMENTS

The authors thank Mr. Larry Masters, Dr. Mary McKnight and Mr. Harvey Berger

of NBS for their helpful guidance and assistance in preparing this report,

Mr. Jack Lee of NBS for his dedicated laboratory work and collation of data

and Mr. Ronald Morony and Ms. Dorothy Allen of HUD and Mr. Richard Moss, PEI,

for their helpful guidance and assistance. Also, we wish to thank the Department of Housing and Urban Development for supporting this research and the

manufacturers and suppliers who provided materials and assistance in this

project

.

16
10. REFERENCES

[1] "Tests for Abrasion Resistance of Porcelain Enamels," C 448, ASTM Book

of Standards, Part 17, American Society for Testing and Materials,

Philadelphia, PA 19103, 1980.

[2] Building Research Division, Institute of Applied Technology, "Investigation of Performance Characteristics for Sanitary Plumbing Fixtures,"

NBS Report 8975, National Bureau of Standards, Washington, D.C.,

September 1965.

[3] Frechette, V.D., Holleran, L.M. , Pasto, A., and Quackenbush, C.L.W.,

"Commercial Patch Test Kits - Tests and Evaluation," Proceedings of

the Porcelain Enamel Institute Technical Forum, Porcelain Enamel

Institute, Inc., Washington, D.C., Volume 30, 1968.

[4] "Paints and Varnishes - Pull-off Test for Adhesion," International

Standard ISO 4624, 1978.

[5] "Test for Resistance of Organic Coatings to the Effects of Rapid

Deformation (Impact)", D 2794, ASTM Book of Standards, Part 27,

American Society for Testing and Materials, Philadelphia, PA 19103,

1980.

[6] "Instrumental Evaluation Color Differences of Opaque Materials,"

D 2244, ASTM Book of Standards, Part 27, American Society for Testing

and Materials, Philadelphia, PA 19103, 1980.

[7] "Test for Specular Gloss," D 523, ASTM Book of Standards, Part 27,

American Society for Testing and Materials, Philadelphia, PA 19103,

1980.

[8] "Tests for Effect of Household Chemicals on Clear and Pigmented Organic

Finishes," D 1308, ASTM Book of Standards, Part 27, American Society

for Testing and Materials, Philadelphia, PA 19103, 1980.

[9] Clark, Elizabeth J. and Campbell, Paul G. , "Evaluation of Plastic

Wallcovering Materials," NBS Technical Note 984, National Bureau of

Standards, October 1978.

[10] "Test for Resistance to Growth of Mold on the Surface of Interior

Coatings in an Environmental Chamber," D 3273, ASTM Book of Standards,

Part 27, American Society for Testing and Materials, Philadelphia, PA

19103, 1980.

[11] "Evaluating Degree of Surface Disfigurement of Paint Films by Fungal

Growth on Soil and Dirt Accumulation," D 3274, ASTM Book of Standards,

Part 27, American Society for Testing and Materials, Philadelphia, PA

19103, 1980.

17
Table 1. Average Impact Resistance of Restoration Coatings,

Surface Condition 1, After ABECs

Impact Resistance (Nm)*

Company Code for

Restoration

Coating

ABECs

0 2 5 10 15 20 25

1 0.87 0.82 0.84 0.84 0.79 0.82 0.84

2 0.59 0.62 0.56 0.67 0.56 0.67

3 0.82 0.79 0.67 0.79 0.84

4 0.87 0.79 0.82 0.79 0.81 0.73 0.80

5 0.79 0.65 0.76 0.67 0.67 0.67 0.64

* Each value is an average in Newton meters of four measurements.

Table 2. Color Differences of Restoration Coatings, Surface

Condition 1, After ABECs

Color Difference

Company Code for ABECs

Restoration 2 5 10 15 20 25

Coating A* u* A U A U A U A U A U

0.93 0.41 1.28 0.59 1.33 0.48 1.70 0.80 1.64 0.98 1.77 1.00

4 1.37 0.40 1.58 0.50 1.39 0.34 1.16 0.54 1.4 0.70 1.37 0.74

5 2.43 0.34 1.87 0.24 2.42 0.49 2.47 0.33 2.51 0.47 2.54 0.32

Unrestored

Porcelain

Enamel***

0.35 0.59 0.52 0.56 0.71 0.74 0.50 0.53 0.95 1.22 0.55 0.36

*A = abraded area, i.e., PEI abrasion test area; *U = unabraded area

** Restoration coatings 2 and 3 were not included because of insufficient

specimens

*** The unrestored porcelain enamel specimens. Surface Condition 1, were

included as a basis for comparison of restoration coatings with

porcelain enamel.

18
Table 3. Color Differences of Restoration Coatings, Surface

Conditions 2, 3, and 4, After 25 ABECs

Company Code

for

Restoration

Coating

Surface

Condition

Color Difference

A* U*

1

2 1.16 0.34

3 0.75 0.74

4 0.63 0.62

2

2 3.01 3.24

3 5.52 3.17

4 4.51 3.23

3

2 1.10 1.44

3 0.69 0.98

4 0.88 0.92

4

2 1.77 1.16

3 1.87 1.25

4 1.83 1.33

5

2 0.94 0.59

3 1.05 0.52

4 1.40 0.80

*A = abraded area, i.e., PEI abrasion test; *U = unabraded area

Table 4, 60° Gloss of Restoration Coatings, Surface Condition 1,

After ABECs

Gloss

Company Code for ABECs

Restoration

Coating

0

A*

> U*

c A U A

LO U A

L5 U A

10 U

21 A U

1 53 47 67 36 58 22 63 16 65 12 54 9 50

2 94 59 93 45 92 29 91 - - - - 18 78

3 92 - - 55 92 28 88 18 88 - - 7 81

4 92 42 92 32 78 15 87 9 92 7 84 5 90

5 76 66 79 45 71 23 81 16 82 11 70 11 70

Unrestored porcelain enamel 98 99 99 100 100 93 96 89 97 82 96 75 95

19
Table 5. 60° Gloss of Restoration Coatings, Surface Conditions

2, 3, and 4, After 25 ABECs

Company code

for

Restoration

Coating

Surface

Condition

60° Gloss

A* U*

1

2 7 79

3 13 74

4 11 72

2

2 42 89

3 36 89

4 34 89

3

2 10 83

3 10 87

4 8 82

4

2 6 91

3 6 93

4 5 89

5

2 25 84

3 24 76

4 28 81

*A = abraded area, i.e., PEI abrasion test area; *U = unabraded area

20
Table 6. Stain Resistance of Restoration Coatings Using Three

Removal Methods^/

Method 1 Company Code

Restoration

Coating

Purple

Tintex

Black

Hair Dye Acetone

Black Shoe

Polish Lipstick

1 VL L DS VL L

VL L DS VL L

2 L D NE VL VL

L D NE VL VL

3 L D DS L L

L D DS L L

4 L L NE L L

L L NE L L

5 VL L DS VL L

VL L DS VL L

Method 2 Method 3

Company Code

Restoration

Coating

Purple

Tintex

Black

Hair Dye

Black Shoe

Polish Lipstick

Purple

Tintex

Black

Hair Dye

Black Shoe

Polish Lipstick

1 VL L VL VL VL L VL R

'VL L VL VL VL L R R

2 VL D VL R VL D VL - VL D VL R VL D R

-

3 VL D VL VL VL D VL VL

VL D VL VL VL D VL VL

4 R L VL VL - L VL VL

R L VL VL - L VL VL

5 R VL R R - L

- - R VL R R L

•

Method 1 - Wipe with soft dry paper towel

2 - Scrub gently with warm soapy water and brush

3 - Scrub on PEI tester 28 cycles

Description of Abbreviations

R - Stain removed

NR - Stain not removed

VL - Very light strain remained

L - Light stain remained

D - Dark stain remained

DC - Discolored surface

DS - Dissolved surface

SDC - Slightly discolored surface

SDS - Slightly dissolved surface

ME - No effect

21
10.2 cm

Figure 1. Pattern for preconditioning test panels

8.3cm

22
Figure 2

WHITE WIRE EXCEPT BLACK WIRE EXCEPT

23

110

VAC
Figure 3. Recycling controls on modified dishwasher

Figure 4. Accelerated bath cycle apparatus - overall view

24
)

)

Figure 5, Accelerated bath cycle apparatus - machine unloaded

Figure 6, Accelerated bath cycle apparatus - panels loaded in rack

25
Figure 8. Modified abrasion procedure - placing test panels on apparatus

26
Figure 9. Modified abrasion procedure - placing containers for holding

alloy balls and abrasive on test panels

Figure 10. Modified abrasion procedure - addition of alloy balls

27
Figure 11. Modified abrasion procedure - addition of abrasive

Figure 12. Modified abrasion procedure - addition of water

28
Figure 13. Modified abrasion procedure - abrasion test commences

Figure 14. Modified abrasion procedure - removal of test panels and alloy

balls after test

29
Figure 15. Modified abrasion procedure - rinsing alloy balls and test panels

Figure 16. Adhesion procedure - yoke apparatus rnounted in testing machine

30
Figure 17, Adhesion procedure - insertion of test panel with buttons

attached

Figure 18, Adliesion procedure - joining upper and lower portions of yoke

apparatus

31
Figure 19. Adhesion procedure - joining upper and lower portions of yoke

apparatus

Figure 20. Adhesion procedure - after test, bottom of button showing

delaminated coating

32
Figure 21. Adhesion procedure - coated area pulled off after testing

Figure 22, Impact resistance procedure - apparatus with aluminum impactor

cylinder

33
Figure 23. Impact resistance procedure - apparatus with test panel in place

Figure 24. Impact resistance procedure - raising impactor cylinder

34
Figure 25, Impact resistance procedure - test panel after impact

Figure 26. Stain resistance test procedure - chambers with rubber seals

L

35
Figure 27, Stain resistance test procedure - chambers inserted in upper

section of holder

Figure 28. Stain resistance test procedure - upper holder prior to clamping

36
Figure 29. Stain resistance test procedure - application of liquid stain

37
Figure 31. Stain resistance test procedure - test complete, removal of

rubber seals

38
MAXIMUM

BOND

STRESS

AT

RUPTURE,

MPa

5.6

Condition 1 Condition 2

Condition 3

Condition 4

4.2 -

0 2 5 10 15 20 25

ACCELERATED BATHTUB EXPOSURE CYCLES

Figure 32. Average stress at rupture for various accelerated bathtub

exposure cycles (Restoration Coating 1)
MAXIMUM

BOND

STRESS

AT

RUPTURE,

MPa

Figure 33. Average stress at rupture for various accelerated bathtub

exposure cycles (Restoration Coating 2)

40
MAXIMUM

BOND

STRESS

AT

RUPTURE,

MPa

ACCELERATED BATHTUB EXPOSURE CYCLES

Figure 34. Average stress at rupture for various accelerated bathtub

exposure cycles (Restoration Coating 3)

41
MAXIMUM

BOND

STRESS

AT

RUPTURE,

MPa

ACCELERATED BATHTUB EXPOSURE CYCLES

Figure 35. Average stress at rupture for various accelerated bathtub

exposure cycles (Restoration Coating 4)

42
MAXIMUM

BOND

STRESS

AT

RUPTURE,

MPa

re 36. Average stress at rupture for various accelerated bathtub

exposare cycles (Restoration Coating 5)

43
Figure 37. Restoration coating 5 after adhesion tests; left panel unexposed,

center panel after two ABECs; right panel after three ABECs

44
Appendix A. Commercially Available Restoration Coatings 1 /

Company Name Types of Repairs

Surface

Preparation

Generic

Finishes

Cost of

Reflnlshing^/

($)

Nu-Glaze __ Perma-Patch Inc. — — — —

Lik-Nu Porcelain Inc. — — — —

Dyna-Glaze Co. — — — —

Authorized SPR

Tub Reglazing Tubs , Commodes

,

sinks

A.S.S. 2/ Polyurethane 225

Porcellte Tubs, sinks A.S.S. Polyurethane —

Enterprises, Inc. City Porcelain Tubs only A.S.S. Polyurethane 175

Reflnlshing Co. Inc. Porcelain Repair Tubs, some sinks A.S.S. Epoxy urethane 200

Company, Inc. New Life Electro Glaze Tubs, sinks A.S.S. Ester 175

Process

Regal House Tubs, sinks A.S.S. Phenolic 250

(Bathmasters Inti.)

Uni-Tub Co. — — — —

ACME Porcelain — — — —

Resurfacing Co.

JEVCO Co. — — — —

Thermo Bond, Inc. — — — —

New Gloss, Inc. — — — —

Dura Glaze Porcelain Tubs only A.S.S. Enamel 225

Reflnlshing Service

Perraa-Brite of Northern

Illinois, Inc. Tubs, sinks,

commodes outside

Acid,

solvent

Epoxy 225

Ark Porcelain — — — —

Ref tnishers

Lectro Glaze

of Chicago

Tubs, sinks,

commodes

A.S.S. 215

K.R.T. Porcelain Tubs — Epoxy 175

Ref inishing

Active Porcelain

Reflnlshing — — — —

Custom Coating — — — —

California Bathtub Tubs only A.S.S. Polyurethane 200

Reflnlshing

J.C. Blending Serv. — — — —

V.C.S. Vinyl — — — --- Repair

Perraaceram of South — — —

California

Valley Porcelain Reflnlshing — — “ —

Seismore 's — — — —

Fiberglass

Cerraa Glaze — — — ’

ACME Perfect Patch Co. -- — — —

RM Bathtub Reflnlshing — — — —

Bathtubs and Sinks — — — —

Reflnlshing, Inc Dokan Plerrl — — — —

Kott Koa tings — — — —

Gnu-Services Corp. — — — —

The Information presented in this table was provided by the restoration

companies

.

A.S.S. = Acid, solvent, sand.

Cost of reflnlshing one bathtub
'" - ' '"'^'

"®,cn C.

.zaJ

t- -;i*

. ,j»0a'O Vo^ .W:%- .' afw "

, ssictt I'f*^’'^'*^ w* iC'

»yi'gA

-p- riiipH y

. ihn^; x^tfcawoSTi

'qi ’,'f/

,.'i;

|?r RA)|tl#

;• *oJ J1

;fc'?,M<f»i''itv<»'l|.-/:

ib

fwtfv ftlrtl<J!SH#3 s^

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..|,'^»i«yw^

%li|^iuaI, T-9 H d a .1 -: !«ft ^

. ' tt^f) If: •

.•'aiitAA*!', <.g I

' 'i»'»'''r,SEii^'

. ia»Wf^ ;3 f -< ‘ : , •’ .-*’' "

I.,, it ... (^4,„

. - Wl

-

.;.;V-%i3^E;:. ,a.w, .

r

ilK.pp ,Mi>A . •' If

•

.

'

'

I

%& vj ^
APPENDIX B. INTERIM PERFORMANCE CRITERIA FOR RESTORATION COATINGS FOR

PORCELAIN ENAMEL SURFACES

B.l INTRODUCTION

These interim performance criteria are based upon the results of laboratory

tests conducted on five restoration coatings and on specimens of unrestored

porcelain enamel test panels. The tests and criteria are Intended to be used

in evaluating the performance of restoration coatings and they may be more

severe than In-service situations. The criteria selected were chosen to reflect

performance characteristics which these materials would be expected to show inservice; they include appearance, adhesion, impact resistance, stain resistance,

and fungal resistance. Abrasion resistance is included as part of the cyclic

exposure test.

The key to the development of performance criteria was exposure of the panels to accelerated bathtub exposure cycling (ABEC) which includes wet and dry cycling,

elevated water temperatures and surface abrasion. An automatic dishwasher was modified for continuous cycling using water temperatures of 43°C (110°F), air

drying temperatures of 77°C (170°F) and detergent injection at each bath cycle.

At the end of 28 bath cycles (24 hours), the cooled panels were abraded on a P.E.I. abrasion tester for 56 machine counts where the abrasive used is

feldspar-containing cleanser (modified ASTM C 448 test) before repeating the

cycle. Thus, one accelerated bathtub exposure cycle (ABEC) included 28 bath

cycles and one abrasion cycle.

B.2 PERFORMANCE CRITERIA

B.2.1 Appearance

Requirement

When applied at the restoration coating company's designated rate and method,

the restoration coating shall provide a smooth, uniform gloss appearance under

ordinary conditions of illumination and viewing, both initially and after

in-service exposure.

Criterion

When applied to a porcelain enamel test panel using the designated rate and

method, the initial (before exposure) 60° gloss measurements shall be 75 or greater as described in ASTM D 523. The initial apparent reflectivity (white

only) [Directional Reflectance, 45°, 0°] shall be at least 85 as described in

ASTM D 2244. After exposure to 25 ABECs , the 60° gloss in the unabraded area

shall be 70 or greater, and the color difference ( E) shall be less than two NBS units (ASTM D 2244).

Commentary

Materials for the restoration of porcelain enamel substrates should have initial

gloss and reflectance characteristics similar to those of porcelain enamel.

B-1
After exposure to accelerated bathtub exposure cycling, the restoration coatings

should retain both color and gloss.

B.2.2 Adhesion

Requirement

The restoration coating shall adhere to a porcelain enamel substrate both

initially and after in-service exposure.

Criterion

The restoration coating shall have a stress at rupture value of at least 3.1 MPa

(450 psl) before exposure, and of at least 1.4 MPa (200 psi) after exposure to

25 ABECs when the adhesion is measured by a pull-off technique, as described in

section 4.2.2 of this report.

Commentary

The degree to which restoration coatings adhere to porcelain enamel substrates

is very Important, especially after exposure to in-use conditions such as wet

and dry cycling, elevated water temperatures and abrasion.

B.2.3 Impact Resistance

Requirement

The restoration coating shall have an impact resistance equal to or greater than

that of the porcelain enamel substrate.

Criterion

The restoration coating shall have an impact resistance of at least 0.53 Nm

(4.7 in pounds) after exposure to 25 ABECs, when using a modified ASTM D 2794

procedure with a one pound aluminum cylinder.

Commentary

The minimum impact resistance of 0.53 Nm stated above is the mean value obtained

during testing of unrestored porcelain enamel test panels. All of the restoration coatings had impact resistance values higher than that of the unrestored

porcelain because they were elastomeric.

B.2.4 Stain Resistance

Requirement

The restoration coatings shall be resistant to household stains common to bathroom areas.

B-2
Criterion

When Tintex, black hair dye, black shoe polish and lipstick are applied for a 16 hour period to restoration coating panels which had been exposed for 25

ABF.Cs , only a very light stain residue shall remain after scrubbing gently with warn soapy water (modified ASTM D 1308).

Commentary

These staining materials are among those which would likely be used in a bathroom area. In order to maintain an attractive appearance, the restoration

coating should be easily cleaned if staining materials are spilled on the

coating's surface.

B.2.5 Fungal Resistance

Requirement

The restoration finishes shall be resistant to fungal attack when exposed to in-use conditions.

Criterion

No fungus growth shall appear on the restoration finish after the 30 day

exposure to the conditions of test method ASTM D 3273 (l.e., a rating of 10

according to ASTM D 3274).

Commentary

It is important that an organic coating used in warm, moist environments be

resistant to fungal growth.

B-3
NBS-114A (REV. 2-80

U.S. DEPT. OF COMM. 1. PUBLICATION OR 2. Performing Organ. Report No. 3. Publication Date BIBLIOGRAPHIC DATA

REPORT NO.

July 1982 SHEET (See instructions) NBSIR 82-2553

4. TITLE AND SUBTITLE

Development of Interim Performance Criteria for Restoration Coatings for

Porcelain Enamel Surfaces

5. AUTHOR(S)

James F. Seiler and Paul G. Campbell

6. PERFORMING ORGANIZATION (If joint or other than MBS, see instructions} 7. Contract/Grant No. NATIONAL BUREAU OF STANDARDS

DEPARTMENT OF COMMERCE 8. Type of Report 8< Period Covered

WASHINGTON, D.C. 20234

9. SPONSORING ORGANIZATION NAME AND COMPLETE ADDRESS (Street, City. State, ZIP)

Department of Housing and Urban Development

Washington, DC

10.

SUPPLEMENTARY NOTES

Document describes a computer program; SF-185, FIPS Software Summary, is attached.

11.

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

bibliography or literature survey, mention it here)

A study was performed to develop interim performance criteria for restoration coatings

for porcelain enamel surfaces. The laboratory study consisted of evaluating five

restoration coatings which had been applied to porcelain enamel test panels with

various surface conditions. Performance characteristics of the coatings examined

included appearance, adhesion, impact resistance, stain resistance and fungal resistance.

Existing test methods were used in the study if appropriate methods were available.

However, the laboratory studies led to the development of a new cyclic exposure test and

the use of a newly developed method for measuring adhesion. Adhesion of the coatings was the performance characteristic most sensitive to change with time of exposure to

the newly developed cyclic exposure test. Interim performance criteria for restoration

coatings for porcelain enamel surfaces were developed, based upon the results of the

laboratory study.

Additional studies are being conducted to assess the performance and durability of

selected restoration coatings applied to bath tubs in public housing units. Since

the field studies are not yet completed, they are not addressed in this report.

12.

KEY WORDS (S/x to twelve entries; alphabetical order; capitalize only proper names; and separate key words by semicolon s) Accelerated bathtub exposure cycle; performance criteria for restoration coatings;

porcelain enamel restoration; restoration coatings

13. AVAILABILITY

Unlimited

I I For Official Distribution. Do Not Release to NTIS

Order From Superintendent of Documents, U.S. Government Printing Office, Washington, D.C.

20402.

Order From National Technical Information Service (NTIS), Springfield, VA. 22161

14. NO. OF

PRINTED PAGES

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15. Price

$9.00

USCOMM-DC 8043-P80

II