NATIONAL BUREAU OF STANDARDS REPORT

8347

PROGRESS REPORT

January 8, 1964 through March 31, 1964

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 assuring

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 stand- ards 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 for incorporation in codes and specifications; advisory service to government agencies on scientific and technical problems; invention and development of devices to serve special needs of the Government; assistance

to industry, business, and consumers in the development and acceptance of commercial standards and

simplified trade practice recommendations; administration of programs in cooperation with United

States business groups and standards organizations for the development of international standards of

practice; and maintenance of a clearinghouse for the collection and dissemination of scientific, technical, and engineering information. The scope of the Bureau’s activities is suggested in the following

listing of its four Institutes and their organizational units. Institute for Basic Standards. Electricity. Metrology. Heat. Radiation Physics. Mechanics. Applied Mathematics. Atomic Physics. Physical Chemistry. Laboratory Astrophysics." Radio Standards Laboratory: Radio Standards Physics; Radio Standards Engineering.** Office of Standard Ref- erence Data. Institute for Materials Research. Analytical Chemistry. Polymers. Metallurgy. Inorganic Materials. Reactor Radiations. Cryogenics.** Office of Standard Reference Materials. Central Radio Propagation Laboratory.** Ionosphere Research and Propagation. Troposphere

and Space Telecommunications. Radio Systems. Upper Atmosphere and Space Physics.

Institute for Applied Technology. Textiles and Apparel Technology Center. Building Research.

Industrial Equipment. Information Technology. Performance Test Development. Instrumentation.

Transport Systems. Office of Technical Services. Office of Weights and Measures. Office of Engineering Standards. Office of Industrial Services.

* NBS Group, Joint Institute for Laboratory Astrophysics at the University of Colorado.

* * Located at Boulder, Colorado.
NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

1009-11-10190

PROGRESS REPORT

January 8, 1964 through March 31, 1964

8347

PORCELAIN ENAMEL INSTITUTE RESEARCH ASSOCIATESHIP

NATIONAL BUREAU OF STANDARDS

WASHINGTON, D. C.

IMPORTANT NOTICE NATIONAL BUREAU OF S'

for use within the Government,

and review. For this reason, tl whole or in part, is not authr Bureau of Standards, Washing!

the Report has been specif icall

ess accounting documents intended

, s subjected to additional evaluation Approved tor public release by the e |j Stj n g of this Report, either in Director Of the National Institute of ie Office of the Director, National Standards and Technology (NIST) '» ,hc >8C "C' wh,"‘

copies tor its own use. on October 9, 2015.

<JB§>

U.S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

PROGRESS REPORT

January 8, 1964 through March 31, 1964

PORCELAIN ENAMEL INSTITUTE RESEARCH ASSOCIATESHIP

NATIONAL BUREAU OF STANDARDS

WASHINGTON, D. C.

SUMMARY

This report describes the progress during the report period

on development of a standard alkali test, analysis of the five-and

six-year weathering data, and plans for initiation of a new porcelainenameled aluminum weathering test.

Several variables associated with alkali testing have been

investigated, and modifications to the earlier PEI-NBS test equipment have been incorporated. Experiments established that the ratio

of the solution volume to specimen area in the present equipment is

such that typical alkali-resistant porcelain enamels can be satisfactorily tested at 96°C for 6 hours without the necessity of renewing

the solution.

Specimens were tested in a heated and ultrasonical ly agitated

alkaline solution in an attempt to accelerate the rate of corrosion.

No significant effect was detected using a 40-watt ultrasonic generator, and no further ultrasonic tests are planned.
- 2 -

The PEI-Kirkpatrick alkali test apparatus was modified to

accommodate six specimens. Tests showed that rate of attack was

affected by position of the specimens. Additional equipment modifications intended to equalize rate of attack on specimens facing opposite directions will be checked. A low-cost commercial temperature

controller was tested, and results showed it to be adequate for the

intended use

.

The five- and six-year weathering data for enamels exposed at

Kure Beach and Washington were reduced and analyzed using new computer programs. On the basis of averages, good correlation existed

between acid resistance and change in color and gloss. As a group,

the acid-resistant glossy steel enamels showed the best resistance to

weathering after six years' exposure.

The enamels exposed at the different sites lost gloss and

changed color at different rates, depending upon severity of weathering conditions at the sites and on acid resistance of the enamels.

The Kure Beach 80 site caused more severe changes in all specimens

than either the Kure Beach 800 or Washington sites. The seven-year

inspection will be completed and reported next quarter.

Detailed planning of the new weathering test of aluminum porcelain enamels consisted of (a) arrangements for new sites, (b) studying

methods of cutting specimens from large panels, (c) providing new racks,

and (d) making the necessary arrangements for procuring and labeling

specimens

.

Photomicrographs of sheared and sawed edges are presented showing the extent of coating damage for each type of cutting.
3

I. STANDARD ALKALI TEST

Intr oduct ion

The extensive use of automatic laundry and dishwashing equipment,

together with increasing water temperatures and more aggressive detergents, have intensified the need for greater alkali resistance in

1 - 12 / porcelain enameled products. Various testing procedures are being

used to evaluate alkali resistance. These employ different testing temperatures, testing times, alkaline solutions, and ratios of solution

volume to exposed specimen surface.

Many of these test methods are satisfactory for development of

improved porcelain enamel compositions. However, there is an urgent

need for a standard or referee method which permits all laboratories

to obtain equivalent test results for any given enamel. Such a method

must recognize and control the many test variables that influence results. While simulating service conditions insofar as possible, the

selected test method should also accelerate the rate of attack so

that appreciable attack can be obtained in relatively short time periods. Finally, the test must rank porcelain enamels in the same order

of merit as experienced in field performance.

One of the most important variables that affect the rate of attack

is the testing temperature, the higher the temperature, the greater

the rate. It has been shown that, for a titania-opacif ied sheet steel

enamel, a change from 90° to 91°C in solution temperature changes the

10 / weight loss by about 12%. This extreme temperature dependence
4

requires that ^ standard test be performed at a carefully controlled

temperature. The boiling temperature utilized by most present testing

methods, while roughly constant, is influenced by rate of boil, elevation above sea level and atmospheric pressure. Thus, temperature control associated with boiling is insufficient to achieve reproducible

results among different laboratories.

Several years ago an ad hoc committee headed by John T. Roberts

recommended a test procedure based largely on the work of Kirkpatrick,

et al. , at NBS . Five laboratories purchased the necessary equipment

and participated in a round-robin test. Analysis of the resulting

data showed that the recommended test procedure was reproducible to

within three percent. However, the equipment was not considered accept

able because of a design deficiency, relatively high cost, and low

capacity (three specimens per test).

Our current work on equipment modifications is an attempt to

overcome these objections.

Results and Discussion

1. Solution Renewal

There has been some question as to whether or not addition

of fresh alkali solution after each testing interval would affect the

weight loss. If the solution is not refreshed it may become sufficient

ly comtaminated or diluted by reaction products to give a lower rate of

attack

.
5

In order to seek a partial solution to this question, a

series of tests were made with specimens coated with the same alkaliresistant porcelain enamel. Results are given in Table 1. Under the

selected conditions, there was no statistically significant difference between the results for specimens tested in solutions that were

refreshed each two hours and those tested for the entire six hours in

a solution that was not refreshed. This type of result implies that

the testing of enamels with high alkali resistance cannot be accelerated with the present equipment through use of fresh alkali solution

at periodic intervals. However, for enamels of poor resistance, or

for longer testing times, refreshing of the solution might well cause

a significant effect.

2. Effect of Ultrasonic Agitation on Rate of Attack

The mechanism of corrosion of porcelain enamel by alkali

, 10 / solutions is not well understood. Kirkpatrick and co-workers

have discussed several possibilities. These involve preferential

adsorption of foreign ions at the glass -solut ion interface, the

rate-controlling effects of dissolved glass in the solution, and the

presence at the interface of a layer of hydrolized glass . If such a

layer does tend to form, then a strong ultrasonic agitation of the

solution should inhibit its growth and accelerate the rate of

attack
- 6 -

In order to explore this possibility, tests were made in which

a 40-watt ultrasonic generator was used to agitate a heated 57, sodium

pyrophosphate solution. The bath temperature was controlled at 78°C

(172°F), the maximum temperature at which the ultrasonic equipment

could be used. A constant level device was incorporated to replace

water that evaporated from the solution, and a motor driven stirrer

was used to inhibit thermal stratification and thus to improve temperature control.

' The weight-loss data after 6 hours of treatment is given in

Table 2. Although the average weight loss was approximately 5% greater when the solution was agitated ultrasonically , this increase was

not statistically significant. While this test does not preclude the

possibility of a real effect of ultrasonic agitation on the rate of

attack, the results do suggest that the effect is not a large one. No

further work is planned on acceleration of corrosion with ultrasonic

generators

.

3. Increasing Specimen Capacity

The specimen holder boxes were altered by cutting an opening

in the back side of the box and inserting an "0" ring seal so as to

permit two specimens rather than one to be tested in each box.

With the stirring arrangement that is used in the present

apparatus, there is no assurance that attack on specimens facing toward the center of the container will be the same as that on specimens

facing the container wall. To determine if such a difference exists,
7

determinations were made with a series of specimens prepared from the

same white porcelain enamel. The tests were made at 96°C ± 0.15°C

for six hours in a 5°L sodium pyrophosphate solution.

The results are given in Table 3. The average weight loss

for specimens facing the center was approximately 127, greater than

those facing the container wall.

A "t" test based on differences between specimen pairs was

calculated as follows:

_ (d - 0) fn = d / n

S d

S d

where d = mean of the differences,

n = number of differences,

s^j = standard deviation of the difference, and is obtained from

(s d

) 2 = -L- (d! s + d2 2 + ...dn

2

- nd2

) n

The "t" value obtained was 8.41. Comparison with a critical value of

2.31 at the 957. confidence level indicates that the difference between

inside and outside positions is significant.

An analysis of variance of the data in Table 3 confirmed the

significance of this difference and also showed that the specimens did

not differ significantly one from another.

4. Temperature Controller

A commercially available temperature controller is under test

as a possible substitute for the more expensive controller previously

Used with the alkali test equipment. Tests were made to determine the
8

degree of control obtainable and its dependence on rate of stirring.

The data are given in Table 4. For the speeds so far explored, 1400

rpm provides ± 0.15°C control at a mean temperature of 96°C. Although

this is considered acceptable, there is good likelihood that it may be

further improved by use of more powerful heaters and/or higher stirrer

s peeds

.

Plans for Next Report Period

Additional equipment modifications will be investigated in an attempt to equalize the rate of attack on s pecimens facing the container

wall and those facing the center. These include:

(1) Changing the stirrer speed

(2) Inserting vanes or baffles to equalize the rate of flow

of solution past the two positions

(3) Raising the box height in the container to permit a greater

flow of solution under the boxes

(4) Reversing the specimen boxes at uniform intervals so as to

equalize the attack on the two specimens.

Of the four alternatives the latter, while easiest to incorporate,

is the least attractive because of the extra attention required of the

operator. Therefore, the greatest emphasis will be placed on the first

three possibilities.

The effect of higher stirrer speeds and more powerful heaters on

the degree and reliability of temperature control will also be determined.
9

It is expected that a decision on the suitability of the modified

version of- the alkali test equipment will be reached during the next

quarter .

II. PEI-NBS WEATHERING TEST

Introduction

The present weathering test was initiated in 1956, and included

94 different enamels which were divided into eight types:

1 . Regular glossy steel- acid-res isting

2 . Mat aluminum

3. 1300°F steel

4. Mat steel

5. Regular glossy steel - non-acid resisting

6. Glossy aluminum

7. 1000°F steel

8. Red and yellow screening pastes.

The weathering test has seven exposure sites: Kure Beach, North

Carolina - 80 feet from the ocean; Kure Beach, North Carolina - 800

feet from the ocean; New Orleans, Lousiana; Los Angeles, California;

Dallas, Texas; Pittsburgh, Pennsylvania; and Washington, D. C. The

enamels exposed at Washington and the two Kure Beach sites have been

inspected annually, those at Pittsburgh and Los Angeles have been inspected after 1, 2, 3 and 7 years' exposure , while those at Dallas and

New Orleans have been inspected after 1, 3, and 7 years' exposure. A

report entitled "Effect of Exposure Site on the Weather Resistance of

13/ Porcelain Enamels Exposed for Three Years" has been published.
10

Two quantitative measures of the effect of weathering on porcelain enamels are changes in gloss and color. The 45-degree specular

gloss is measured with a Hunter Precision Glossmeter, calibrated and

operated in accordance with the ASTM Designation C-346 "Standard Method

of Test for 45° Specular Gloss of Ceramic Materials." The measurements

are made at four fixed orientations at the center of each specimen and

are compared to similar measurements made before exposure. The results

are reported as the percent of the initial specular gloss retained.

The changes in color are measured with a Hunter Color Difference

Meter. Measurements are made at the beginning of the investigation and

after exposure. The color change is expressed as the color stability

index, which is equal to 100 minus the color difference in NBS units.

The weathering characteristics have also been correlated with the

spot-test acid resistance of the enamels. The acid resistance rating

was made in accordance with the "Test for Acid Resistance of Enamels,

14/

Part I, Flatware"—, except that the grading of Class A and Class B

enamels was modified to conform with the "Specification for Architectural Porcelain Enamel on Steel for Exterior Use."—

After three years' exposure three of the experimental screening

paste enamels had become so badly weathered that they were withdrawn

from the test. The 91 remaining enamels were evaluated after five and

six years' exposure.
11

Results and Discussion

1. Computer Programs for Data Reduction

The five- and six-year weathering data for three exposure

sites had been collected earlier but it had not been reduced. Before

the data could be processed on the Bureau's new 7094 computer, the

old 704 computer program needed to be converted to a Fortran program.

This conversion was completed during the quarter. The new program

computes the color stability index and the percent gloss retained for

each of the exposed specimens. It then calculates the average, sum of

the squares, and standard deviation for the three specimens of each

enamel at one site and for each enamel at all sites.

One of the features of the Fortran program is that it enables

the computer to punch cards with summary data including specimen number, average percent gloss retained, average color stability index,

acid rating, and type of enamel. An Omnitab program then instructs the

computer to sort the data on the cards by (1) type and (2) acid rating.

Once these data are sorted, the computer plots the color stability

index and the percent gloss retained against acid rating for each type

of enamel in the test. An example of the type of data the computer

plots is shown in Figure 1. After each plot the computer prints a

statistical summary which includes the number of specimens, sum, sum

of the squares, average, maximum, and minimum values of the data

plotted. When the data are sorted by acid rating, the statistical

summary is given for each acid rating and the plot is omitted.
12

Although these new programs cannot reduce the time necessary

to take the actual gloss and color measurements, they have greatly

reduced the time required to process and analyze the data, thus saving a large portion of the Research Associate’s time. Once the fiveand six-year data were collected, it took only fifteen minutes of

computer time to calculate, plot, and summarize the gloss retention

aid the color stability results.

2. Weather Resistance of Different Types of Enamel

Table 5 gives the average color stability index and percent

gloss retained for each type of enamel after five and six years' expos

ure . In all cases, the changes in gloss and color for the additional

year of exposure (from 5 to 6 years) are small and are not statistical

ly significant. Analysis of the data in Table 5 shows that, as a

group, the glossy acid-resistant steel porcelain enamels are the most

resistant to changes in color. This result is in agreement with the

13/

3 -yr analysis-—. It is important to point out, however, that individual enamels of any type deviate from the average.

3. Correlation Between Acid Resistance and Weather Resistance

As was expected, the weather resistance of enamels in this

test correlated with the citric acid spot test rating when averages

were considered. This is illustrated in Figures 2, 3, and 4. Many

individual specimens of low acid ratings have good gloss retention and

a high color stability, and some AA and A enamels have low gloss
13

retention and color stability. This scatter in the data for glossy

steel enamels is illustrated in Figure 1.

The high weather resistance of Class AA and Class A glossy

steel porcelain enamels is illustrated in Figure 2. These two classes

of enamel drop to between 78 and 80 percent gloss retention after two

years' exposure at Washington;, after which they decrease only very

slowly with additional exposure time. The average gloss retention

of these two classes of enamels differ from each other by not more

than five percent during the six-year weathering period.

The Class B enamels have a slightly larger gloss loss, retaining only 73 percent of their initial gloss after two years’ exposure. They also show only a slight change in gloss between two and

six years' exposure.

The change in gloss is much greater for the Class C and D

enamels. They retain only 62 and 59 percent of their initial gloss

at two years and 61 and 53 percent gloss at the end of six years' exposure .

The differences in the color stability index (see Figure 3)

of the Class AA and A and the Class C and D glossy steel enamels is

noted by the decrease in the rate of color change of the AA and A

enamels after two years' exposure while the C and D enamels continue

to change color at about the same rate from two to six years as they

did during the first two.
14

As there were no colored glossy steel enamels with a B acid

rating in the test, the color retention of this class of enamels cannot be evaluated.

The averages for all enamels of the different acid ratings

after five years' exposure are given in Fig. 4 and after five and six

years in Table 6. It can be seen that there is not much difference

in the weathering behavior of the Class AA, A and B enamels at the

moderate site (Washington) but that the differences between these

same enamels are significant at the severe site (Kure Beach, 80 feet).

4. Comparison of Exposure Sites

The gloss data for the enamels exposed at Kure Beach - 80 feet,

Kure Beach - 800 feet, and Washington indicate a significant difference

(95 percent confidence level) between Kure Beach - 80 feet and Kure

Beach - 800 feet, and Kure Beach - 80 feet and Washington, while there

is no significant difference between Kure Beach - 800 feet and

Washington. The Kure Beach - 80 feet site was ranked as severe, and

13/ the other two as moderate at the end of three years 1 exposure — .

After three additional years of exposure Kure Beach - 80 feet remains

a severe site, while Washington and Kure Beach - 800 feet remain as

moderate sites.
15

5. The Effect of Exposure Time

The changes in gloss and color of the glossy steel acid resistant enamels (AA, A, and B) are illustrated in Figure 5. The

enamels exposed at Washington lose gloss rapidly during the first two

years' exposure with little further loss during the next four years.

These same enamels lose about two NBS units of color during the first

year's exposure. The color loss remains near this level with exposure up to six years. The enamels exposed at Kure Beach - 80 feet

did not follow this type of curve inasmuch as the specimens at this

site continued to change gloss and color throughout the six years'

exposure

Plans for Next Report Period

The seven-year exposure data have been collected for all sites

except the two at Kure Beach. These data will be reduced. Also,

measurements will be made on the Kure Beach specimens. It is hoped

that the preparation of the 7-yr report can be started during the

next quarter with a view to publication late in 1964 or early 1965.

Boiling acid solubility tests have been made on storage specimens

of the aluminum enamels. In the next quarter the test will be made on

some of the storage specimens of glossy steel enamels to determine if

the resulting weight loss correlates better with the weathering characteristics of the enamels than does the spot test rating.
- 16 -

III NEW ALUMINUM WEATHERING PROGRAM

Introduction

On January 9, 1964 the Porcelain Enameled Aluminum Council's

Weathering Test Committee voted to initiate a weathering test of porce

lain enameled aluminum.

The tentative plans are to include the following colors in the

test

:

White

:

semi gloss and full gloss, one and two coats

Black

:

mat, semi gloss and full gloss, one coat

Red

:

full gloss, one coat

Green

:

full gloss, one coat

Pastel Green: mat and semi gloss, two coats

Pastel Blue: semi gloss, two coats

Pastel Grey: semi gloss, two coats

Pastel Brown: semi gloss, two coats

Pastel Yellow: semi gloss, two coats .

In addition to studying the effect of weathering on coloring

oxides with the frit commonly used to produce that color, it was decided to use five different production frits with the same color.

Light and dark green were chosen for this part of the investigation.

To achieve better uniformity among specimens of the same enamel,

it was decided to cut the 4% by 4%-inch test specimens from a 3 by 5-

foot sheet of enameled aluminum rather than to fabricate each specimen
17

individually. To determine how the large sheet could best be prepared

into specimens with minimum damage to the enamel, cuts were made with

a band saw, a radial saw, and a shear. The band saw used had a ^-inch

wide blade with a 12-8 broach tooth set. The radial saw had a 16-inch

diameter, carbide tip blade which was revolving at 3524 rpm, and the

shear was a hand shear. The specimen edges , after cutting, were examined

with a metal lographic microscope. Photomicrographs are shown in Figures

6, 7 and 8. It can be seen that the band saw cuts with minimum chipping

damage to the enameled surface. The radial saw gives a smoother edge but

the chipped enamel surface is much wider and in some places the bare

metal is visible. The shear not only chips a wide area of the enamel

from the metal, but it also causes cracks which extend into the unchipped

enamel surface. On the basis of this information, it has been decided

to cut the enameled sheets with a band saw.

The specimens are to be exposed at Kure Beach, Los Angeles, New York

City, and Washington. Permission has been obtained to put exposure racks

on a government building in New York City, and arrangements are being

made to place exposure racks on roof tops in Washington and Los Angeles,

as well as at the International Nickel Company's exposure site at Kure

Beach, North Carolina. There is also an excellent possibility of

establishing a fifth exposure site in Canada.
18 -

Plans for Next Report Period

Procurement of the 36 by 60 by 0.064-inch sheets of porcelain

enameling grade 6061 aluminum alloy with an H-12 temper has been

arranged. These will be sent to the Research Associate who will

divide the sheets into small lots for shipment to the fabricators.

Current planning calls for the sheets, coated with the selected enamels, to be in the hands of the Research Associate by the end of the

next quarter

.

IV. STANDARD REFERENCE MATERIALS

The following stock of standards was on hand April 1 , 1964 :

Corundum abrasive, March 1960 issue, for subsurface

abrasion test - 249 lbs . , 83 jars

Standard Pennsylvania Glass Sand for surface abrasion

test, July 1963 issue, -342 lbs., 114 jars

Dist inctness -of -Image Gloss Standards - 20 sets

Calibrated Glass Plates for Abrasion Testing - 5 dozen.

A new supply of glass plates has been ordered and will be calibrated next quarter .

Respectfully submitted,

M. D. Burdick

M. A. Rushmer

Research Associates
TABLE 1. Effect

Test

Per iod

of Refreshment of Alkali Solution on Weight

REFRESHED SOLUTION—^ SOL. NOT REFRESHED—

Loss .

Difference

in Wt .Loss

Specimen

Number

Weight , Loss—Specimen

Number

Weight , Loss—

fag • ) (ffig •

)

fag • )

First two hours B-12 0.0281 B-ll 0.0367 + 0.0086

B-24 .0145 B-31 .0155 + .0010

B-36 .0154 B-42 .0169 + .0015

Average 0.0193 0.0230

Second two hours B-12 0.0377 B-ll 0.0417 + 0.0040

B-24 .0180 B-31 .0191 + .0011

B-36 .0188 B-42 .0224 + .0036

Average 0.0248 0.0277

Third two hours B-12 0.0560 B-ll 0.0469 - 0.0091

B-24 .0218 B-31 .02 06 - .0012

B-36 .0233 B-42 .02 35 + .0002

Average 0.0337 0.0303

Average difference in wt . loss after 6 hrs V

r-~ II o o o

1—1 o

a/ Fresh solution added after each 2-hr test period,

b/ Same solution used for the entire 6-hr test period

c/ Total wt . loss for 3 5/16 in. diam. test area.
TABLE 2. Comparison of Corrosion Rates of Porcelain Enamel

With and Without Ultrasonic Agitation

(A) With Ultrasonic Agitation

of Alkali Solution

Specimen

No.

We ight Loss

©iTTn2

F-19 0.0179 0.0005594

F-20 .0177 .0005531

F-2 1 .0176 .0005530

F-22 .0205 .0006046

F-23 .0197 .0006156

F-24 .0188 .0005875

Average .0187 .000585

Std .Dev

.00119

Coef.of var . 6.47>

(B) Without Ultrasonic Agitation

of Alkali Solution

Specimen

No. Weight Loss

•*g- *»g/inA

F-25 0.0169 0.0005281

F-2 6 .0157 .0004906

F-2 7 .0173 .0005406

F-28 .0182 .0005687

F-29 .0193 .0006031

F-30 .0190 .0005938

Average .0177 .000554

Std .Dev

.00136

Coef.of var. 7 . 7%
TABLE 3. Effect of Specimen Position in Holder on Weight Loss

Ins ide Outside

Specimen

No.

Weight Loss Spec imen

No. Weight Loss

•»g • / in" <*g. *9g/in"

F-2 0.0282 0.003272 F-l 0.0294 0.003411

F-3 .02 88 .003342 F-4 .0251 .002912

F-5 .0259 .003005 F-6 .0241 .002796

F-7 .0286 .003318 F-8 .0249 .002889

F-10 .0290 .003365 F-9 .0248 .002878

F-ll .02 79 .003237 F-12 .0238 .002762

F-32 .0265 .003075 F-31 .0237 .002750

F-33 .02 77 .003214 F-34 .0230 .002669

F -36 .0260 .003017 F -35 .0230 .002669

Average .02 76 .003256 Average .0246 .002941

Std .Dev

,

. .0012 .0001317 S td .Dev

, .0019436 .0002373

Coef . of var . 4.35% 4 . 34% Coef . of var. 7.87% 7.88%

Weight Loss

Difference

£ng/ in°

0.000139

.000430

.000209

.000429

.000487

.000475

.000325

.000545

.000348

.000376

.0001342

7.88%
TABLE 4. Effect of Stirrer Speed on Temperature Control

Total

Length

of

Speed of

Stirrer

Heat ing

Time

Cooling

Time

Solution

Maximum

Temperature

Minimum

Control

Cycle

Control

Range

R.P.M. Min

.

Min

.

°C °C Min

.

°C

800 4.73 0.80 97.3 96.9 5.52 0.40

1000 4.60 .83 96.5 96.1 5.44 .40

1200 7.00 1.12 96.2 95.7 8.25 .50

1400 3.07 0.60 96.2 95.9 3.67 .30
Table

5.

Average

Gloss

and

Color

Stability

Index

for

the

Types

of

Enamels

Tested

44

cd COu nO o m T—

ON CN NO t-H o CO CNJ ON o NO ON LTi r—

uO CN 00 r—

CO ON

x >N • Q) m 00 oo m NO CO NO in cO CO CN NO NO r—

NO CN| r—

CNJ TOC

nD ON ON on ON O' ON ON ON ON ON ON ON O' ON ON 00 OO NO oo 00 oo ON ON

w

4=>3

44 CO

4io

rHo

COU CO CNJ 00

m CO o r—

OO NO oo

m no CO CN NO CN

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REFERENCES

1. Ralph L. Cook and Andrew I. Andrews, "Chemical Durability of Porce

lain Enamels", J. Am. Cer . Soc . 28 [9] 229-56 (1945).

2. George B. Hughes, "The Determination of Alkali Resistance of Porce

lain Enamel by the Total Immersion Method", Proc. P.E.I. Forum

87-95 (1952).

3. Charles H. Fuchs, "A Test Method for Measuring Alkali Resistance

of Vitreous Enamel", Proc. P.E.I. Forum 96-100 (1952).

4. G. V. Stanley and J. T. Roberts, "Two Methods for Testing the Resistance of Porcelain Enamels to Alkali by Alkaline Solutions",

Proc. P.E.I. Forum 102-107 (1952).

5. H. R. Toler & J. T. Roberts, "Relative Action of Various Alkaline

Solutions on Enamels", Bull. Am. Cer. Soc. 32 r 5 ] 92-95 (1953).

6. J. T. Roberts, "Progress Report of a Test Method", Proc. P.E.I.

Forum 16 152-160 (1954)

7. J. H. Giles, Jr., "Practical Tests For The Porcelain Enameling

Industry", Proc. P.E.I. Forum _1_7 99-109 (1955).

8. R. J. Brown and R. L. Cook, "A Method of Measuring the Alkali Resistance of Glazes and Overglaze Decorations", Bull. Am. Cer. Soc.

35 [12] 472-475 (1956).

9. J. T. Roberts, "Alkali Test - A Progress Report", Proc. P.E.I.

Forum 18 49-55 (1956)

10. H. B. Kirkpatrick, E. L. McGandy and J. C. Richmond, "Resistance

of Enamels to Corrosion by Alkaline Solutions", J. Am. Cer. Soc.

40 [11] 389-395 (1957).

11. J. T. Roberts, "Report on Status of P.E.I. Alkali Test", Proc.

P.E.I. Forum 19 98-103 (1957).

12. John E. Cox, "Reproducibility of Alkali Resistance Testing",

Proc. P.E.I. Forum 19_ 103-110 (1957).

13. Dwight G. Moore and Alan Potter, "Effect of Exposure Site on Weather Resistance of Porcelain Enamels Exposed for Three Years",

N.B.S. Monograph 44 (1962) U. S. Government Printing Office,

Washington, D. C. 20402.
14 Test for Acid Resistance of Porcelain Enamels

Issued by the Porcelain Enamel Institute, Inc

Washington, D. C. 20036.

Pt 1, Flatware.

1145 - 19th St . N . W.

15. Specifications for Architectural

terior Use, P.E.I. S-100 (1959).

Institute, Inc., 1145 19th St. N

Porcelain Enamel on Steel for ExIssued by the Porcelain Enamel

W. , Washington, D. C. 20036.
1 10

100

90

80

70

60

50

40

30

20

A

&

A A

• A

“ o

& • —

_ 8 § A

§ o

°

° B

o - o o o 8 9 —

o o O

o

O

- A-INDIVIDUAL COLOR VALUES —

•-AVERAGE COLOR VALUE

- O-INDIVIDUAL GLOSS VALUES

o —

-AVERAGE GLOSS VALUE o

o

0 —

o

1 1 1

I L

AA A B C D

ACID RATING

Figure 1. Five-year weathering data for glossy steel enamels with

different citric acid spot test ratings, exposed at

'Washington. Gloss data for all enamels; color data for

non-white enamels only.

90

80

70

60

50

40

-B ACID RATING

“C ACID RATING

O” D ACID RATING

J12I I I I L

3 4 5 6

TIME IN YEARS

figure 2 The effect of time on the gloss retention of all

glossy steel enamels exposed at 'Jashington.

COLOR

RETENTION

Figure 3. The effect of time on the color retention of all

non-white gloss steel enamels exposed at Washington.

100

90

80

70

60

50

40

30

20

ACID RATING

Five-year weathering data for all enamels tested

with different spot test ratings. Gloss data for

all enamels, color data for non-white enamels

only

e 4

100

90

80

TO

60

50

I 2 3 4 5 6

TIME IN YEARS

igure 5. The effect of time on gloss and color retention of

glossy steel enamels - acid-resisting type, exposed

at Washington, and Kure Beach-80 ft. Gloss data for

all enamels, color data for non-white enamels only.

I

Edge of

Specimen

Chipped

Enamel

Surface

Original

Enamel

Surface

Fig. 6

Photomicrograph Illustrating Chipping of

Porcelain Enameled Aluminum Surface After

Cutting Specimen with a Band Saw

Edge of

Specimen

Chipped

Enamel

Surface

Original

Enamel

Surface

Fig. 7

Ehotomicrogra^h Illustrating Chipping of

Porcelain Enameled Aluminum Surface after

Cutting Specimen with a 16 inch Hadial Saw

Edge of

Specimen

Chipped

Enamel

Surface

Cracks Extending

into Original

Enamel Surface

Fig. 8

Photomicrograph Illustrating Chipping and

Cracking of Porcelain Enameled Aluminum

Surface after Cutting Specimen with a Shear


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