NATIONAL BUREAU OF STANDARDS REPORT

9301

PROGRESS REPORT

EXPOSURE TEST OF PORCELAIN ENAMELS ON ALUMINUM

Six Months Report

by

Margaret A. Rushmer

PORCELAIN ENAMEL INSTITUTE RESEARCH ASSOCIATESHIP

NATIONAL BUREAU OF STANDARDS

WASHINGTON, D. C.

U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
THE NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards is a principal focal point in the Federal Government for assur- ing maximum application of the physical and engineering sciences to the advancement of technology

in industry and commerce. Its responsibilities include development and maintenance of the national

standards of measurement, and the provisions of means for making measurements consistent with

those standards; determination of physical constants and properties of materials; development of methods for testing materials, mechanisms, and structures, and making such tests as may be necessary, particularly for government agencies; cooperation in the establishment of standard practices

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activities is suggested in the following listing of its three Institutes and their organizational units. Institute for Basic Standards. Applied Mathematics. Electricity. Metrology. Mechanics. Heat. Atomic Physics. Physical Chemistry. Laboratory Astrophysics.* Radiation Physics. Radio Standards

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NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

421 .04-12-4212270 9301

PROGRESS REPORT

Six Months Report

EXPOSURE TEST OF PORCELAIN ENAMELS ON ALUMINUM

by

Margaret A. Rushmer

PORCELAIN ENAMEL INSTITUTE RESEARCH ASSOC IATESHIP

NATIONAL BUREAU OF STANDARDS

WASHINGTON, D. C.

IMPORTANT NOTICE NATIONAL BUREAU OF STA

for use within the Government. I and review. For this reason, the whole or in part, is not authori; Bureau of Standards, Washingtoi

the Report has been specifically p

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST) on October 9, 2015.

> accounting documents intended

ubjected to additional evaluation

listing of this Report, either in Office of the Director, National he Government agency for which

Dies for its own use.

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

PROGRESS REPORT

EXPOSURE TEST OF PORCELAIN ENAMELS ON ALUMINUM

Six Months Report

PORCELAIN ENAMEL INSTITUTE RESEARCH ASSOCIATESHIP

NATIONAL BUREAU OF STANDARDS

WASHINGTON , D. C.

INTRODUCTION

Porcelain enamels for aluminum are one of the more recent innovations

in the porcelain enamel industry. These enamels offer the building industry

a versatile material that is not only light weight but it is also available

in a variety of colors, textures, and glosses. However, exposure data for

1 /

the early porcelain enamels on aluminum indicated that the accelerated

tests used with confidence to indicate the weatherability of porcelain

enamels on steel were not reliable indicators for these new, lower firing

enamels. Therefore, the Aluminum Council of the Porcelain Enamel Institute

authorized a new exposure test consisting solely of enamels on aluminum

to be conducted by the Porcelain Enamel Institute Research Associateship at

the National Bureau of Standards.

The first inspection of the enamels included in this test was scheduled

after six months' exposure. This report is a summary of the findings of

that inspection. There was a delay in the return of the specimens exposed

at Los Angeles so the data for these enamels is for eight months' exposure

as indicated in later tables.

- 2 -

MATERIALS AND PROCEDURES

1. Enamels

Sixteen enamel systems were included in this test. These enamel systems

are represented by nine colors, three gloss ranges, and both one and two coat

enamels as indicated in Table 1. The initial 45° specular gloss values and

the thicknesses of the enamels as well as their acid solubilities and acid

spot test ratings are also reported in Table 1.

The enamels in this test have been coded for easy identification. Each

enamel system can be identified by the first two code letters, while the

different fabricators for each enamel system are indicated by the third

code letter. The differences between the enamel systems are readily apparent

(see Table 1) for all systems except AA and AZ, These systems were planned

to be two coat enamels having significantly different thicknesses. However,

this difference did not materialize during manufacture of the specimens.

If small variations in milling and firing of the enamels by the different

fabricators are taken into account there are, in effect, 51 different

enamels included in this test,

2. Test Specimens

Each enamel was applied to a 3 X 5 foot sheet of 0.064 inch aluminum

alloy. After the enamel was fired the sheet was cut, with a band saw, into

seventy-eight 4-7/16 inch square and nine 4X6 inch exposure specimens. This

was done to produce more uniform specimens than could be obtained by hand

spraying individual small metal blanks.

-3-

3. Exposure Sites

Three of the 4-7/16 inch square specimens of each enamel were exposed

on the roofs of Federal Government buildings in New York City, New York;

Los Angeles, California; and Washington, D. C.; as well as the roof of the

Stores Department Building in Montreal, Canada. Three of the 4X6 inch

specimens of each enamel were exposed at a ground site of the International

Nickel Company's Corrosion Laboratory at Kure Beach, North Carolina - 80

feet from the ocean.

The specimens were exposed at 45° and face south at all sites except

Kure Beach, where they are exposed at 30° and face the ocean at eastsoutheast

.

In addition to the exposed specimens, three specimens of each enamel

have been designated as "storage" enamels. These enamels were set aside in

a dark, dry place and allowed to age indoors.

After six months exposure, the exposed specimens were returned to the

laboratory for analysis. These specimens along with the storage specimens

were cleaned and measured to determine the changes resulting from exposure,

storage and cleaning.

The remaining 69 specimens of each enamel were kept for use in laboratory

tests and for the development of new tests as needed.

RESULTS

1. Cleaning of Specimens

In previous exposure testa^’^ the specimens exposed at one of the sites

required scouring before the enamel surface could be examined. These scouring

-4-

treatments tended to' increase the gloss readings of the enamels making them

incomparable with the enamels exposed at the other sites. Therefore, in

this test it, was decided that the enamels should be scoured both before and

after exposure. In order to determine a suitable cleaning procedure, enamels

in the three gloss ranges were scoured with a commercial cleanser (Bon Ami),

Potters 1’ Flint, and calcium carbonate. Gloss readings taken after scouring

for a predetermined number of strokes indicated that scouring with calcium

carbonate increased the gloss the least of the three scouring powders

tested (see Fig. 1 and 2). On the basis of this information, it was decided

to clean the specimens by 1) scouring 30 strokes with a sponge dampened with

a one percent, by weight, solution of trisodium phosphate and sprinkled with

calcium carbonate, 2) rinsing with tap water, 3) rinsing with distilled water,

and finally 4) rinsing with alcohol.

When the specimens were returned to the laboratory at the National Bureau

of Standards for inspection, it was noted that the specimens exposed at Kure

Beach appeared quite clean, while increasingly heavier dirt films were noted

on the specimens exposed at Washington, Los Angeles, Montreal, and New York

City. The cleaning treatment outlined above was satisfactory for cleaning

the specimens exposed for six months at all sites except New York City. The

dirt film on the specimens exposed at this site was approximately 0.03 mils

thick and was extremely difficult to remove. The cleaning procedure was

altered to scouring with calcium carbonate on a cheesecloth until the

specimens were clean. They were then rinsed as described above.

-5-

It was observed while cleaning the specimens exposed at New York City

that the high gloss enamels cleaned in less time (approximately two minutes)

than the low gloss enamels (approximately three minutes). However, these

values may be in error since the time required to clean all of the specimens

was not recorded.

Z. Gloss and Color

The 45° specular gloss of the enamels was measured at four orientations

near the center of the specimen, both before and after exposure. The gloss

is reported as the percentage gloss retained after exposure.

It should be mentioned that shortly after the gloss on the specimens

exposed for eight months at Los Angeles was measured, it was observed that

the gloss meter was out of adjustment. It is not certain whether it was in

perfect operating condition at the time the Los Angeles specimens were measured.

Therefore, these gloss values may be in error. If the gloss meter was not

in proper adjustment, it will probably be evident at the one-year inspection

of these enamels at which time the eight months® gloss data for Los Angeles

will either be kept or be discarded.

The color change of the specimens was measured with a color difference

meter. One of the three storage panels was used as the standard in measuring the color difference. This was done to obtain maximum efficiency with

this type of instrument. The storage specimens were, in turn, measured

against calibrated NBS color standards to determine whether the enamels

changed color during storage. The color change is reported as color re37 tention, which is 100 minus the color difference in NBS units—' .
.

.
- 6

-

The average percentage gloss retained and color retention for the

three specimens of each enamel exposed at each site as well as the storage

enamels are given in Table 2.

3. Comparison of Exposure Sites

The average values for color retention and percentage gloss retained

for all enamels exposed at each site are given in Table 3„ A two-sided sign

4 / test- performed on the data in Table 2 indicated a significant difference

between Kure Beach and all other sites for both gloss and color . A significant difference was also noted for one of the two parameters when Washington

was compared with New York, Montreal, and Los Angeles and when Los Angeles

and New York were compared. However, since the significant difference

occurred for only one of the parameters, the difference in site severity

was not considered to be significant at this time. However, this may

change with increased exposure times.

4. Comparison of Enamel Colors

The average color retention and percentage gloss retained for each

of the nine colors included in the test are presented in Table 4. It is

obvious that the red enamels showed the poorest color retention at all

sites. However, all the red enamels failed the 15-second nitric acid spot

test included in the Specification for Porcelain Enamel on Aluminum for

Weather Exposure; PEI: ALS-105 , In addition, all the red enamels failed

the cupric sulfate test for color retention which is included in the Specification for Architectural Porcelain Enamel on Steel for Exterior Use;

PEI: S-100.

-7-

There was very little difference between the color stability of the

remaining eight colors. The slight differences that did occur were not

considered to be significant at this time. Again this may change with

longer exposure time.

5. Comparison of Enamels in the Different Gloss Ranges

The enamels were divided into three gloss ranges as indicated previously. The low gloss enamels had an initial 45° specular gloss value of 35

or less 5 the medium between 36 and 69 and the high 70 or over. Table 5

shows the average gloss and color data for these enamels. The data in this

table are based on the actual initial gloss values given in Table 1, not the

nominal values. The color retention data are considered to be a better

criteria for comparing the enamels because small changes in gloss result in

increasingly larger percentage losses as the initial gloss of the enamel is

lowered 5 also small changes in color are much more noticable than large

changes in gloss. When comparing the color retention data for these three

groups of enamels, it is easily seen that there are no significant differences

among these three gloss ranges at this time.

6. Comparison of Coating Thicknesses

The enamels included in this test were applied in either one or two

coat systems. This was to determine whether the one coat systems, which are

less expensive to produce, are as durable as the two coat systems. The data

in Table 6 indicate a slight difference between these two systems. Again this

difference is not significant after this short exposure time.

- 8

-

7. Comparison with Enamels in Previous Exposure Tests

Data comparing three sets of porcelain enamels exposed for six months

at Kure Beach-80 are presented in Table 7. Two sets of data are for enamels

on aluminum, one from this test and one from a* test initiated in 1956-i^ . The

third set of data is for the acid-resistant enamels on steel included in the

1956 test. There are only minor differences among these three sets of

enamels at six months. However, longer exposure times were found to produce

marked differences between the two sets of enamels included in the 1956 test.

8. Spall Resistance

Triplicate specimens of each enamel were tested for 96 hours in

ammonium chloride for spall resistance. A slight tendency to spall was

noted for eight enamels. However, the spalled areas were so small that they

did not constitute failure. Likewise, some enamels exposed at all sites

except Washington exhibited a few very small spalled or corroded ureas on one

of the tru'ee specimens exposed. These very small areas are not considered

failures at this time.

SUMMARY

In summary it can be said that after six months’ exposure at Kure

Beach, Washington, Montreal, New York City, and Los Angeles, triplicate

specimens of 51 different percelain enamels on aluminum:

1. were easily cleaned except those exposed at New York City,

2. appeared to have good color stability except for the red enamels,

3. showed no significant difference between different gloss or thickness ranges of enamel, and

-9-

4. showed greater changes in gloss and color at Kure Beach than at

any of the other exposure sites.

The next inspection of these enamels is planned after they have been

exposed for one year.

GLOSSY

ENAMELS

140

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Table 1 Summary of Initial Data for Porcelain Enamels on Aluminum

Enamel Visual Color Nominal

Gloss

45°

Specular

Gloss

Number

of Coats

Thickness

mils

Acid

Solubility

mg/in^

Acid Spot

Test Rating

AA-A White High 70.1 Two 4.5 5.5 A AA-B White High 74.2 Two 4.3 5.9 A AA-C Whi te High 71.5 Two 3.4 5.0 AA AA-D White High 71.9 Two 6.5 12.7 AA AB-A White Medium 56.8 Two 4.0 7.2 B AB-C White Medium 55.6 Two 4.0 4.9 A AB-D White Medium 28.9 Two 6.2 7.9 A

AC -A White High 74.5 One 3.5 6.4 A AC-B White High 71.8 One 2.8 11.3 AA AC-C White High 70.5 One 3.3 9.9 AA AD-A White Medium 55.0 One 2.8 6.2 AA AD-3 White Medium 68.3 One 4.3 6.7 B AD-C White Medium 42.4 One 3.2 7.1 B AD-D White Medium 34.9 One 2.7 12.4 A AE-A Black High 75.6 One 2.4 6.5 A AE-B Black High 78.0 0 ne 1.6 10.1 A AE-C Black High 78.

1

One 2.0 12.

1

A AE-D Black High 75.0 One 3.4 15.5 B AF-A Black Medium 78.4 One 1.5 14.2 B AF-B Black Medium 58.5 One 2.7 9.0 B AF-C Black Medium 76.8 One 3.1 10.1 C AG-B Black Low 26.0 One 3.0 12.5 B AG-C Black Low 12.6 One 2.0 7. 5 A AH -A Red High 46.9 One 2.8 8.1 A AH-B Red High 85.3 One 3.1 8.8 B AH-C Red High 85.6 One 3.1 6.5 B AH-D Red High 82.0 One 1.9 10.5 B

AO -A Dark Green High 78.8 One 3.2 19.9 A AO-B Dark Green High 79.8 One 1.6 10.

1

A AO-D Dark Green High 78.3 One 2.1 17.0 A AP-A Light Green Medium 42.4 Two 6.4 12.3 B AP-B Light Green Medium 38.5 Two 4.

1

6.4 A AP-C Light Green Medium 30.2 Two 4.0 6.2 A AP-D Light Green Medium 45-3 Two 6.4 10.0 A AR-A Light Green Low 9.6 Two 3.2 4.4 A AR-B Light Green Low 7.3 Two 2.7 5.5 A AR-C Light Green Low 5.7 Two 4.3 8.1 A

AS -A Gray Medium 64 .

9

Two 5.0 13.4 A AS-B Gray Medium 61.6 Two 5.5 7.4 AA AS-C Gray Medium 62.2 Two 3.9 5.4 A AT-A Blue Medium 32.9 Two 4.4 6.2 A AT-B Blue Medium 54.8 Two 3.6 7.0 A AT-C B lue Medium 62.4 Two 2.9 6.1 AA AU-A Brown Medium 50.0 Two 7.2 5.3 A AU-B Brown Medium 35-4 Two 6.4 7. 5 A AU-C Brown Medium 46.6 Two 4.4 7.6 A

AW -A Yellow Medium 62.4 Two 5.8 7.8 A AW-B Yellow Medium 63.1 Two 4.1 8.7 A AW-C Yellow Medium 80.9 Two 5.0 18.6 A AZ-A White High 72.0 Two 4.2 9.5 A AZ-B White High 71.2 Two 2.7 5.2 A

Table 2 Summary of Six Months' Exposure Data for Porcelain Enamels on Aluminum

Enamel Kure :Beach Washington Montreal New York Los Angeles* S torage

Glos s Color Gloss Color Gloss Color Glos 8 Color Gloss Color G lo 6 8 Color Visual Color

AA-A 85.5 99.4 93.2 99.5 93.8 99.5 98.3 99.4 95.6 99.5 98.8 99. 9 White

AA-B 94.0 99.3 92.7 99.5 98.6 99.4 94.5 99.7 103.0 99.3 99.2 99-7 White

AA-C 90.7 99.0 90.7 98.8 92.0 98.9 92.3 99.2 96.0 99.0 99.1 99.9 White

AA-D 76.0 98.3 94.6 97.8 100.0 97.8 101.1 91.9 101.0 98.2 99.2 99.8 White

AB-A 81.2 98.8 82.8 98.8 83.9 98.7 95.9 98.

1

84.9 98.7 99.6 99. 9 White

AB-C 79.6 99.6 81.0 99-5 82.7 99.4 83.9 99.2 83.6 99.4 98.

1

99.8 White

AB-D 75-3 98.5 93.3 98.9 80.0 98.9 100.5 98.3 79.6 98.4 99.2 99.9 White

AC -A 90.2 99.4 93.0 99.3 98.6 98.6 96.3 99.3 102.6 99.1 99.0 99.4 White

AC-B 85.8 98.7 •92.8 99.1 101.3 99.0 103.4 99.0 102.1 98.6 99.3 99.8 White

AC-C 90.6 98.3 93.7 98.6 98.3 98.9 99.0 98.7 98.2 98.9 99.8 99-7 White

AD-A 87.6 98.9 91.7 99.4 90.3 99.5 100.9 99.2 90.3 99.4 99-6 99.7 White

AD-B 89.O 99.4 89.8 99.6 90.5 99.5 97.4 99.1 92.4 99.4 99.6 99-8 White

AD-C 82.8 98.1 90.9 99.0 88.6 99.1 105.3 98.1 87.5 98.5 98.8 99. 7 White

AD-D 87.5 98.1 98.0 96.9 87.7 98.8 104.7 98.1 88.6 98.4 99.6 99.1 White

AE-A 76.4 99.1 81.3 98.6 82.1 99.8 82.1 99.8 80.5 99.8 97.8 99.6 Black

AE-B 65.I 98.

6

86.

5

99.8 88.8 99.5 84.6 99.6 87.9 99.1 98.8 99.8 Black

AE-C 72.6 98.9 89.4 99.6 91.9 99.5 86.7 99.6 91.1 99.4 98.4 100.0 Black

AE-D 71. 1 98.6 82.2 98.0 87. 4 99-7 83.3 98.9 85.5 99.4 98.6 99 . 5 Black

AF-A 65.6 98.4 85.7 99.2 90 .

4

99.3 82.1 98.5 85.7 99.6 99.0 99.1 Black

AF-B 69.7 99.

1

93.2 98.8 95.6 99.4 88. 3 99.4 96.1 99.3 98.5 99.8 Black

AF-C 72.2 98.4 84.

5

98.8 88.2 99.8 84.4 99.3 87.5 99.6 98.8 99.6 Black

AG-B 82.0 97.6 100.

5

98.6 81.3 98.9 76.2 98.4 79.5 99.3 98.6 99.7 Black

AG-C 46.9 98.2 105.7 99.4 31.8 99. 5 35.9 98.3 33.2 99.4 96.2 99.4 Black

AH-A 90.8 97.5 95.8 98.

1

97.8 97.5 118.3 97.6 103.7 97.4 100.3 99.3 Red AH-B 64.3 93.0 72.3 94.6 75.4 95.2 81.7 96.6 76.8 ‘ 95.5 100.1 99.1 Red

AH-C 73.

9

90.

1

70.8 91.9 77.3 92.8 75.5 91.5 77.6 91.9 100.1 99.4 Red

AH-D 59.7 83.6 74.7 88.9 82.8 89.7 79.0 95.2 83.2 91.0 99.6 99.6 Red

AO -A 76.6 95.4 82.1 99.1 83.8 99.3 80.2 99.7 83.3 99.9 99-5 99.7 Dark Green

AO-B 72.5 99.5 84.0 99.5 83.4 99.7 83.0 99.7 84.6 99.8 99.2 99.7 Dark Green

AO-D 74. l 97.8 83.8 98.5 87.8 99.4 81.0 99.4 87.0 98.9 98.9 99.7 Dark Green

AP-A 82.2 98.7 95-5 99.4 92.

1

99.5 102.3 99.4 90.2 99.3 99.2 99.8 Light Green AP-B 75.5 99.4 82.9 99.4 78.6 99.6 86.3 99.6 77.0 99.6 98.7 99.8 Light Green

AP-C 73.9 99.5 85.7 99.0 76.4 99.5 85.8 99.6 72.5 99.2 98.2 99.8 Light Green

AP-D 87.5 99.

1

93.9 99.0 91.7 99.3 95.4 99.5 88.0 99.2 98.1 99.8 Light Green

AR-A 47.0 99.6 111.8 99.5 62.4 99.6 54.2 99.3 25.5 99.6 94.5 99.7 Light Green AR-B 0.0 99.4 82.5 99.6 4.4 99-7 0.0 98.8 0.0 99.6 100.0 99.8 Light Green

AR-C 0.0 99.4 85.7 99.6 0.0 99.7 0.0 98.8 0.0 99.5 100.5 99.7 Light Green

AS -A 78.2 98.7 90.2 99.4 91.2 99.5 91.7 99.4 92.1 99. 5 98.7 99.9 Gray

AS-B 83.7 98.9 83.0 99.3 83.0 99.4 85.0 99.2 82.5 99.3 99.1 99.6 Gray

AS-C 92.5 99.8 91.8 99.6 91.7 99.8 90.4 99.6 93.3 99.8 99.0 99.7 Gray

AT-A 75.2 99.0 83.8 98.9 68.3 99.1 80.4 98.9 71.4 99.1 98.8 99.8 Blue

AT-B 79.8 98.6 93.8 98.9 91.0 99-3 91.5 98.6 90.9 97.9 99.4 99.9 Blue

AT-C 81.5 98.7 78.8 97.1 80.9 99.3 83.3 99.7 82.0 99.0 98.8 99.8 Blue

AU-A 89.

1

99. 3 84.3 99.7 81.2 99.8 88.3 99.7 87.7 99.7 99.1 99.6 Brown

AU-B 75.7 99.2 92.4 99.6 79.9 99.8 98.0 99.5 80.3 99.8 98.2 99.8 Brown

AU-C 87.4 99.8 94.5 99. 5 91.5 99.8 95.1 99.6 91.4 99.8 98.6 99.9 Brown

AW -A 81.4 99.2 82.7 99.4 85.7 99.6 86.2 99.5 85.3 99.6 98.8 99.9 Yellow

AW-B 78.8 99.3 93.3 99.2 94.2 99.2 95.6 99.3 93.7 99.3 98. 5 99.8 Yellow

AW-C 72.1 98.9 84.6 99.4 90.3 99.4 91.4 99.4 91.7 99.4 99.7 99.9 Yellow

AZ-A 100.9 97.7 93.5 99.3 102.4 99.1 103.4 99.2 104.1 98.9 100.7 99.9 White

AZ-B 94.2 99.

1

90.6 99.0 93.9 99.3 90.9 99.2 99.1 98.8 100.0 99.7 White

Average 75.8 98.2 88.8 98.6 81.7 98.9 85.7 98.8 82.9 98.9 99.0 99.7

* The data for Los Angeles are after eight monghs ' exposure.

Table 3. Average Percentage Gloss Retained and Color

Retention of Porcelain Enameled Aluminum at

the Different Exposure Sites

Exposure Site Coloi R e t e ; tion Percentage

Gloss Retained

Kure Beach-8o 98.2 75.8

Washington 98.6 88.8

Montreal 98.9 81.7

New York 98.8 85.7

Los Angeles 98.9 82.9

Storage 99.7 99.0

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tb- OA o 1—1

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VO OA no OA no 1 1 P

CM OA no VO CO 1—1 o OA co CO CO CO OA Oa

OA 1 1 -4 -4* CO on i—1 • • 0 • • • c VD a\ -4 -4 CM -4

CO VO D- CO Lf\ CO

co P p OA P CO t— • • • • « , OA OA OA OA CA OA OA

OA OA OA OA GA OA OA

OA LTV LTV -4 LTV -4 CO • • • • • • ' co OV On On OV On OA OA On On OV OV OV OA

Oa i—!

VO -4 -4 on vo • • « • • • . CO Oa OA OV Ov ov OA OA OA OA OV OV OV OA

CM LTN LTA -4 VO vo CO • • • • • • « OA ON Oa OV OA Oa Oa OA OV OA OV OA OA Oa

oa o O on -4 -4 vo • • • • • • • 00 OA Oa Ov OV Ov Oa OA OA Oa Ov OV OV Oa

CO LTV vo (—1 1—1

no -4 9 • • • • • • CO CO t

OV OV Oa OV

OA OV Oa ov Ov OA OV

12 £ X £ O -P £ £

-p o 44 £ 1 1 X £ >

•H £ £ £ 1 1 £ bO £ O

j£ i—1 £ £ (V £ •H £ £

IS PQ

Q

O

O P O PQ

Table 5. Average Color Retention and Percentage Gloss Retained

for the Different Gloss Ranges of Porcelain Enameled Aluminum Exposed for Six Months.

Color Retention

Gloss

Range

Kure

Beach

Washington Montreal New

York

Lo s Angeles*

Storage

Low 98.8 99.2 99-4 98.7 99.2 99-7

Medium** 99.0 99.0 99.5 99.2 99.3 99.8

High** 98.6 99.1 99.2 99.2 99.3 99.8

Percentage Gloss Retained

Gloss

Range

Kure

Beach

Washington Montreal New

York

Lo s Angeles*

Storage

Low- 46.6 94.7 46.9 49.6 50.0 98.3

Medium** 82.

1

88.9 87.1 92.9 87.8 98.9

High** 78.4 86.3 90.4 88.8 93.0 99.6

* The data for Los Angeles are after eight months' exposure.

** The averages for the medium and high gloss enamels were calculated

omitting the red enamels since they showed such great color

changes

.

Table 6. Average Color Retention and Percentage Gloss Retained

for One and Two Coat Systems of Porcelain Enameled

Aluminum Exposed for Six Months.

Color Retention

Number

of Coats

Kure

Beach

Washington Montreal N ew

York

Lo s Angeles*

S to rage

0 ne** 98.5 98.9 99.3 99.1 99.3 99.7

Two 99.1 99.2 99. b 99.2 99.2 99.8

Percentage Gloss Retained

Number

of Coats

Kure

Beach Washington Montreal

New

York

Los

Angeles* Storage

One** 76.8 90.0 86.7 87.

1

86.5 98.9

Two 75-7 88.7 80.8 81.3 80.

1

98.9

* The data for Los Angeles are after eight months* exposure.

** The red enamels were omitted when the average values for the

one coat systems were calculated because they showed such

great color changes.

Table 7* Comparison of Porcelain Enamels on Aluminum with

Other Porcelain Enamels Exposed for Six Months at

Kure Beach-8o

Exposure Test Gloss Color N umber

Present Aluminum

Test 75.8 98.2 51

Aluminum Enamels

in 1956 Test 80.5 98.5 10

Acid-Resistant

Enamels on Steel,

1956 Test 77.8 98.4 25

REFERENCES

1. M. A. Rushmer and M. D. Burdick, Weather Resistance of

Porcelain Enamels, Effect of Exposure Site and Other

Variables after Seven Years, NBS Building Science Serie

No. 4. To be published in 1966.

2. D. G. Moore and W. N. Harrison, Fifteen-Year Exposure

Test of Porcelain Enamels, National Bureau of Standards

Building Materials and Structures Report 148, June 1957

3. R. S. Hunter, Photoelectric Color-Difference Meter, J.

Optical Society of America. 38 * 66l (1948).

4. M. G. Natrella, Experimental Statistics, NBS Handbook

91 (1963).
'