NATIONAL BUREAU OF STANDARDS REPORT

9004

PROGRESS REPORT

July 1 through September 30, 1965

Development of Methods of Test

For Quality Control of Porcelain Enamels

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

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problems: invention and development of devices to serve special needs of the Government; assistance

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NATIONAL BUREAU OF STANDARDS REPORT

NBS PROJECT NBS REPORT

42104-12-4212240 9004

PROGRESS REPORT

July 1 through September 30, 1965

Development of Methods of Test

For Quality Control of Porcelain Enamels

PORCELAIN ENAMEL INSTITUTE RESEARCH ASSOCIATESHIP

NATIONAL BUREAU OF STANDARDS

WASHINGTON, D.C.

IMPORTANT NOTICE NATIONAL BUREAU OF STANC

for use within the Government. Befc and review. For this reason, the pul whole or in part, is not authorized Bureau of Standards, Washington 2! the Report has been specifically prep

'.counting documents intended Atmroved for public release by the acted to additional evaluation re r ng Qf this RepQ,.^ either in Director of the National Institu e

j Ce Dj rectori National Standards and Technology (NIST) Government agency for which on October 9, 2015. for its own nee.

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

PROGRESS REPORT

July 1 through September 30, 1965

PORCELAIN ENAMEL INSTITUTE RESEARCH ASSOCIATESHIP

NATIONAL BUREAU OF STANDARDS

WASHINGTON, D.C.

SUMMARY

Work was continued on the development of a cleanability test for porcelain

enamel finishes* Because of its increased stability, BBOT was used instead of

anthracene as the fluorescent ingredient of the soil* The BBOT was combined

with powered graphite and mineral oil to give a composite soil that was

mechanically applied to specimens. These specimens were then subjected to

two slightly different cleaning treatments. After cleaning, the residual

fluorescent material was removed from the test surface with toluene.

Evaluation of the amount of soil extracted, which was done with a commercial

fluorometer, showed an improved reproducibility when the second cleaning

treatment was used (longer cleaning time).

The storage panels of porcelain enameled aluminum as well as those

exposed for six months' at Washington were washed and measured for changes

in both gloss and color. These data, however, have not been reduced into

percent gloss retained and color retention.

The Nature-Tone enimels exposed for six months' at Kure Beach-80 were

also washed and measured for changes in gloss and color* The reduced data

indicated that the Nature-Tone enamels have gloss and color retentions

comparable to the regular acid-resistant enamels on steel exposed for six

months' at this site in an earlier exposure test. However, 257, of these

Nature-Tone enamels showed rust stains at pinhole type defects in the

enamel coating.
2

Work on a continuity of coating test was continued with the major

emphasis on the development of direct current, high-voltage test procedures.

Test results indicated that 1) the high-voltage test equipment was capable

of indicating weak areas in the coating that were not detectable by an

electrolytic cell test, 2) a test voltage of either 1.5 and 2.5 KV could

be used for testing architectural enamels depending on the severity of

test desired, and 3) good reproducibility of results was obtained when

using the selected test procedure.

INTRODUCTION

I. CLEANABILITY

Previous reports in this series have pointed to the need for a cleanability test that would differentiate between different porcelain enamels as well as between porcelain enamels and the various

competetive finishes.

One approach to the evaluation of cleanability Us to measure

the effort required to completely remove a uniformly applied standard

soil. Either the energy or the time required for complete removal of

soil could then be used as a measure of the cleanability of the surface.

If this approach was used, considerable difficulty could be anticipated in determining when complete cleaning had been achieved, and in

addition, the precision of a well-defined visual end-point in the

cleaning operation would certainly depend strongly on the color of

the finish.
- 3

-

In order to circumvent these difficulties associated with complete

removal of soil, a second method is being investigated in which (a)

soil is applied to the specimen., (b) a standard cleaning treatment is

used., and (c) the amount of soil remaining on the surface after the

cleaning treatment is evaluated. Because measurements of a fluorescent

soiling agent,, in situ., were unsuccessful in earlier trials, emphasis

during this report period was placed on extracting the fluorescent

soil from the partially cleaned surface with a solvent and then determining the amount that was present by measuring the fluorescence of the

resulting solution.

RESULTS AND DISCUSSION

1. Fluorescent Tracer Selection.

Anthracene was used as the fluorescent material in the earlier

work. It was found, however, that this material was not stable when

dissolved in benzene, or other organic solvents. A photosensitive

reaction occured during aging of the solutions that transformed the

anthracene to dianthracene which is not fluorescent.

For this reason, another material was substituted for anthracene.

It is 2, 5“bis“ [5 ' "tert-butylbenz.oxazolyl (2 1 ) ] = thiophene which will be

referred to as BBQT. This material has a maximum fluorescence at a wave length (435 mu) that matches the optimum response of the commonly

used photo-multiplier detectors. BBOT is chemically stable and its

solutions are not altered by light exposure under nprmal conditions.

The solubility of BBOT in toluene is 53 g/1.
4

BBOT was used as a soiling agent both by itself, and in mixtures

with powdered graphite and mineral oil. A soil of the latter type which

was used with promising results consisted of:

The BBOT and powdered graphite were mixed by dry ball-milling for

five hours after which the mineral oil was added to form the composite soil.

To determine if uniform mixing was achieved by this ball-milling

treatment, weighed amounts of a nominal 10 percent by weight BBOT and 90

percent powdered graphite mixture were treated with known amounts of toluene.

The BBOT dissolved in the solvent and the graphite dropped out. After

sufficient dilution, the fluorescence of the solution was measured and its

BBOT content was calculated. Table 1 indicates that good mixing uniformity

was obtained. The average determined BBOT content of the dry powder mixture of 9.17 percent suggests that a disproportionate amount of the

fluorescent tracer adhered to the ball mill and balls, slightly changing

the intended BBOT content. The results for the samples analyzed was

used as a basis for the soil composition given above.

2. Soil Application and Cleaning Treatment.

The mechanical equipment used for soiling and cleaning porcelain

/ enameled specimens is shown in Figure 1. The main part of the equipment

is a conventional polishing lap. The specimen is attached to the lapping plate in a face-up position. A plastic covered brass head, one inch

in diameter then moves in a reciprocating motion across the rotating

Ingredient Amount in Percent

by weight

BBOT

Powdered graphite

Mineral oil

3.3

32.3

63.9
5

specimen. The combined action of the specimen rotation and the backand-forth motion of the head uniformly distributes a weighed amount of

soiling agent over a controlled circular area at the specimen center.

The cleaning treatment employed a heavier brass head of larger

diameter than was used for soil application. This 2 1/4-inch diameter

head was covered with four thicknesses of an industrial wiping tissue.

The extent of the back-and-forth stroke was increased for the cleaning

operation. This meant that the soil was first smeared over the entire

specimen surface and then partially absorbed by the tissue. The

degree of cleaning could be controlled both by varying the time of

operation and by varying the number of tissue renewals during the

course of the cleaning.

3. Extraction of Soil and Fluorescence Measurement.

Figure 2 shows the fluorometer used for measuring the extracted

solutions and also the device used for the extraction of the BBOT

from the soiled and cleaned surfaces. The extraction cell was a

150 ml reagent bottle from which the bottom had been removed and the

sawed edge ground smooth. The bottle and a fitted teflon gasket

were clamped against the specimen. In this way a reproducible test

area was defined when toluene was introduced into the reagent bottle.

Several rinse portions of toluene were introduced until a point was

reached where the last rinse portion showed a fluorescence that did

not exceed the fluorescence of the toluene blank.

The various extracts were combined in a flask, diluted if necessary,

to bring them onto the fluorometer scale, and a five ml portion used

for the fluoranetric intensity measurement.
6

4. Calibration of the Fluorometer.

The fluorometer was calibrated with solutions of known BBOT

content, prepared by careful dilution techniques. Table 2 and figure 3

give the results of the calibration.

5. Effect of Cleaning Time.

It is obvious that the amount of soil that remains on a surface

will be dependent not only on the cleaning method that is used tyut also

on the time of cleaning. In an attempt to arrive at a value for the

reproducibility of one possible cleaning method and also to determine

the effect of cleaning time, the following experiment was performed:

First a glossy, buff colored enamel with a reflectance of about 50

percent was selected for test. A total of 16 specimens of this enamel

were then tested, eight by Method No. 1 and the remainder by Method No. 2.

In Method No. 1, 0.097 grams of the graphite-BBOT-mineral oil soil,

described in section 1 was placed on a specimen. The specimen was then

placed on the lap and the one-inch diameter head was operated for one

minute with the stroke set at 1.5 inches. This served to distribute

the soil over the test surface. Next, the small head was removed and

replaced with the 2 1/4-inch head that had been covered with four

thicknesses of a commercial wiping tissue. After 15 seconds, with a stroke of 3.0 inches, the equipment was stopped and the soiled tissues

replaced with clean ones. After three cycles of this treatment (total

time 45 seconds) the specimen was removed and the BBOT remaining on the

surface was extracted with toluene, and the fluorescence of the resulting solution evaluated.
7

The soil application, cleaning procedure, and measurement technique

were the same for Method No. 2 as for Method No. 1 except that the

final cleaning treatment was continued for 60 seconds rather than for

15 seconds.

Table 3 gives the results of the measurements. The calculation

of the total soil retained on the specimen is based on the BBOT

content of the soil, the BBOT found, and the area from which the

extraction was made:

BBOT = 3.3 percent of soil

2

Total soil retained, yg/cm = BBOT, yg found

BBOT content x Extraction Area

= BBOT, yg found

0.033 x 14.3 cm

= BBOT, yg found x 2.12

As would be expected the amount of soil retained on the

treated specimens was less with the second method than with the

first. This was true whether the indicator of retained soil was bychange in reflectance or by measurement of fluorescence.

The variability of Method No. 2 was smaller than that of Method

No. 1 by a factor of three when the fluorometric determinations were

considered, and by a factor of two for the reflectance measurements.

Separate analyses of variance were made on the fluorometric

and on the reflectance data. These indicated a statistically significant difference existed between the two methods with respect to the

fluorometric measurements but no significant difference was indicated

for the reflectance data. The results of the tests showed that Method

No. 2 with its longer cleaning treatment was superior to Method No. 1
8

in that much more reproducible and precise measurements were obtained.

The results also indicated that the fluorescence measurements gave

better precision than the reflectance approach.

PLANS FOR NEXT REPORT PERIOD

Work during the next report period will be concerned with (a)

development of a cleanability testing procedure, (b) testing of

various porcelain enamels to determine if small differences in

cleanability can be detected and (c) testing of other types of

finishes for which values of cleanability might be of interest.

Brief progress reports on the development of a cleanability

test method will be presented at the PEI Shop Practice Forum and at

the November meeting of the Eastern Enamelers Club in Philadelphia.

II. EXPOSURE TEST OF PORCELAIN ENAMELS ON ALUMINUM

INTRODUCTION

Early in 1964, the Aluminum Council of the Porcelain Enamel

Institute authorized an exposure test of Porcelain Enamels on aluminum to be conducted jointly by the Porcelain Enamel Institute and the

National Bureau of Standards. The 53 enamels included in the test were

applied by nine fabricators to a single lot of 6061 aluminum alloy.

The first specimens were Installed in March of 1965 and have been

exposed for six months.

RESULTS AND DISCUSSION

The aluminum specimens that had been exposed for six months at

Washington were removed from the racks at the National Bureau of

Standards at Washington. Similar specimens have been removed from the

exposure racks in Montreal and Kure Beach. However, these specimens

I
9

did not arrive at the laboratory in time for inspection during this

report period.

The storage specimens and the Washington specimens were cleaned by

(1) scouring 30 strokes with a sponge that had calcium carbonate sprinkled

on it and was moistened with a one percent solution of trisodium phosphate, (2) rinsing with tap water, (3) rinsing with distilled water, and

(4) rinsing with alcohol. The 45° specular gloss and the change in color

were measured on a Hunter Precision Glossmeter and a Gardner Automatic

Color Difference Meter, respectively. The data for the storage specimens

were reduced with a desk calculator. These calculations showed that the

average percentage gloss retained was 99.0, and that the average color

change was 0.3 NBS units.

The specimens exposed at Washington had a slight dirt film on them

which was easy to remove by the aforementioned cleaning procedure.

However, tan stains were present on two of the white enamels (AA-D and

AD-D) and these stains were still present after the cleaning treatment.

Microscopic examination of the surfaces did not reveal any difference

between the stained and unstained areas. At the present time the cause

of the staining is not known. However, two additional specimens of

enamel AD-D, which showed the worst stains, have been installed on the

Washington, D.C. racks. After six months' these two specimens will be

removed and studied in considerable detail, including sectioning, in an

attempt to arrive at a logical explanation.

The only enamels that showed a visually detectable color change

after six months at the Washington, D.C. site were the red enamels.

The worst of these, AH-D showed a measured change of 11.1 NBS units.
10

It should be mentioned in this connection that all four of these red

enamels failed the 15-second nitric acid spot test that is currently

included in the aluminum architectural specification (PEI Specification

No. ALS-105). In addition, they also failed the cupric sulfate test

which is a part of the architectural specification for steel enamels

(PEI Specification No. S-100)

.

A second observation of interest was that no spalling on any of

the enamels at Washington after six months' exposure.

PLANS FOR NEXT REPORT PERIOD

The specimens from Kure Beach, Montreal, New York and Los Angeles

will be returned to the National Bureau of Standards in Washington for

measurement early in the next report period. The changes in both gloss

and color will be measured, these data will be reduced and presented at

a meeting of the Aluminum Council on November 9. All specimens will be

returned to the exposure racks after examination.

III. NATURE TONE ENAMELS

INTRODUCTION

Nature-Tone enamels were introduced recently as a new concept

for architectural porcelain enamels. These particular enamels, which

have been well received by architects, are characterized by both (1)

very low gloss and (2) neutral or "earthy" colors. However, data is

needed on their weather resistance. To fill this need, duplicate

specimens of thirty of the new Nature-Tone enamels on steel were

exposed at Kure Beach-80, a site known from previpus testing to cause

fairly rapid deterioration of some porcelain enamels. Late in September,
11

the specimens were removed from the racks and returned to the laboratory

at the National Bureau of Standards for evaluation of changes that occurred

after the first six months of exposure.

RESULTS AND DISCUSSION

Upon arrival at the laboratory the specimens were cleaned by: (1)

scouring for 30 strokes with a sponge that had been dampened with a onepercent solution of trisodium phosphate and then sprinkled with calcium

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

and finally, (4) rinsing with alcohol. The cleaned specimens were then

measured for changes in both gloss and color.

The results of the measurements are listed in Table 4. Since all

of the Nature Tone enamels have either satin or mat finishes, thqlr

initial gloss readings were quite low. These low values mean that small

changes in gloss from exposure to weathering will be reflected by small

values for percentage gloss retained. For this reason the gloss retained

values in Table 4 are of only limited usefulness in gaging the weather

resistance of the enamels.

Color change, on the other hand, is a very good criterion. Table 4

shows that the average f color change of the 30 enamels was 0.80 NBS unit

with the individual values varying from a low of 0.17 (brown enamel, ME11 and Light gray enamel, MC-5) to a high of 2.02 (blue enamel, MC-4),.

This is comparable to the color changes observed in the currently operating PEI-NBS test for the acid resisting enamels at the end of the first

six months of exposure. Thus, from the standpoint of color stability,

the Nature-Tone enamels appear to have a stability equal to the earlier
12

enamel types. The only exception is the blue enamel MC-4 which changed

2.02 NBS units in only six months. This particular enamel will be carefully monitored in future inspections. If it continues to change at this

high rate, either its composition should be modified or it should be

eliminated from consideration as one of the Nature-Tone series of enamels.

The next to the last column in Table 4 lists the measured coating

thicknesses of the Nature-Tone specimens. Good coverage of the steel

would normally be expected at this thickness of application; yet the

last column shows that rust spots were observed on the face surfaces

of 15 of the 60 specimens (25%). Admittedly, the Kure Beach-80 site

greatly accellerates corrosive attack over that which would occur if the

enamels were exposed in commercial or industrual locations. At the

same time, however, past experience has shown that those enamels that

permit rusting of the metal in six months at Kure Beach-80 will also

permit rusting to occur after longer periods at the other exposure sites.

Therefore, the appearance of the rust spots at Kure Beach-80 in such

a short time is a cause of serious concern.

Examination of the specimens indicated that the observed rusting

occured at very small pinholes of a type that would not normally be

detected by a visual inspection of the enamel surface. The rusting was

evidenced by iron stains on the enamel surface which would be removed

by scouring.

The tentative conclusion that might be made from this first inspection is that the Nature-Tone enamels are susceptible to pinhole defects
13

and that careful inspection by a coating continuity test would be highly

desirable on all architectural parts to which the Nature-Tone enamels a

are applied. The continuity test discussed in the next section would

probably be satisfactory for this purpose.

PLANS FOR NEXT REPORT PERIOD

The 60 specimens will be returned to the exposure racks at Kure

B each-80 during the next quarter. The next inspection of these enamels

is tentatively scheduled after one years’ exposure.

IV. CONTINUITY OF COATING

INTRODUCTION

Since porcelain enamels are applied to many products to prevent

corrosion of the base metal, it follows that a method of test to evaluate

the protection offered to the base metal or the degree of continuity of

would prove useful in avoiding defective ware. The development of such

a test is one of the current goals of the Research Associates.

Previous reports have outlined the various defects that should be

detected with a continuity of coating test. A review of the literature

showed that a number of different tests had been used for this purpose.

Preliminary work indicated that the direct current, high-voltage test

showed considerable promise, although a low-voltage electrolytic cell

test also might have merit.

RESULTS AND DISCUSSION

1. Comparison of Electrolytic Cell Test with D.C. HighVoltage Test

The electrolytic cell test was outlined in the previous report.
14 -

Briefly, it consists of first forming a reservoir on the enameled surface

with any good calking compound, and then filling the reservoir with an

aqueous solution consisting of 1% by weight sodium chloride and 1/2%

sodium carbonate. Next, a DC potential of nine volts is applied for 15

minutes between the solution and the metal backing of the specimen after

which the enameled surface is washed and the number of rust spots counted.

This test was performed on duplicate specimens of several enamels that

had rusted badly after only short-time exposure at Kure Beach-80. No

rust spots were indicated after the 15-minute treatment. The same

specimens were then probed with the direct current, high-voltage tester

after which they were again subjected to the electrolytic cell treatment.

Rust spots appeared during this second treatment at the points where

the high voltage punctures had occurred. These results indicate that

the electrolytic cell test detects only those defects that are open to

both the surface of the enamel and the base metal. On the other hand,

the high-voltage discharge method, operated at properly selected voltages,

will also detect weak areas in the coating of a type that permit rusting

to occur during actual weathering.

2. Comparison of High-Voltage Test Results with Service Data for

Architectural Enamels.

The previous report indicated that storage specimens of many of the

architectural enamel specimens in the PEI-NBS Exposure Test~^ that corroded

after 7-years exposure had defects that could be located at a probe voltage of 2.5 KV. During the present report period, additional test were

made. Triplicate specimens of 59 of the storage enamels were probed.
15

When making the tests, the voltage was increased from 1 to 5 KV in increments of 0.5 KV. As an aid in analysing the data, the enamels were arbitrarily separated into two classes: good and fair. Exposed specimens

of the enamels designated good, showed no rusting at any of the seven

exposure sites after 7-years exposure, while the fair enamels showed

rusting at Kure Beach-80 after this same time interval. The results of

the high-voltage tests made on storage specimens of these same enamels

are illustrated in Figure 4. Examination of this figure shows that when

the storage specimens were probed at 2.5 KV approximately 90% of the

enamels that rusted at Kure Beach-80 in 7-years would have failed the

test as compared to only 30% for the enamels that did not rust under

this same exposure. Kure Beach-80 is, of course, a very severe site

with respect to corrosion. Therefore, the fair enamels were further subdivided. Those enamels that rusted at the less severe sites, either

Kure Beach-800 orNew Orleans, in addition to Kure Beach-80 were separated

from the fair enamels and reclassified as poor enamels. Figure 4 shows

that a test voltage as low as 1.5 KV would eliminate 90% of the enamels

that fell into the poor catagory.

3. Reproducibility of High-Voltage Test Results

Triplicate specimens of two hot water tank enamels as well as 59

architectural enamel were probed with the high-voltage test equipment.

The test results were then analyzed to determine the reproducibility of

test procedure. Results that are typical of the scatter are plotted in

Figure 5. In each case the points represent the average values and

horizontal lines the maximum spread. It can be seen that the good enamels
-16

gave fairly reproducible responses from specimen to specimen. However,

the enamels that were designated poor showed fairly high scatter between

specimens. In many cases, one of the three specimens would show only a very few defects or none at all while the remaining specimens a large

number of defects would be detected. This trend of large variability

was also noted in the specimens that were exposed to weathering.

4. Results of Questionnaire on Testing for Coating Continuity

It was mentioned in the preceding report that a questionnaire had

been prepared and sent to porcelain enamel fabricators, who are members

of the PEI. To date 12 replies have been received. The following is

a summary of the findings:

1 . Approximately 90% of the fabricators agree that a "discontinuity is any defect which leads to early corrosion of the base metal."

2. While all fabricators inspect the ware for discontinuities,

most of the inspections are visual.

3. The defects looked for are primarily: pinholes, blisters,

cracks

,

fishscale, and copperheads. (It is significant that the highvoltage test equipment is capable of locating all five of these defects.)

4. Most of the fabricators thought of a test for continuity of

coating as a Quality Control test.

5. Everyone who answered the questionnaire thinks that continuity

of coating is important for at least one of the products he produced.

PLANS FOR NEXT REPORT PERIOD

During the next report period it is planned to test current production enamels that are used for specific applications with a goal of
17

selecting probe voltages that will differentiate between satisfactory

and unsatisfactory enamel application. The actual performance of this

task is of course dependent on receiving suitable specimens from the

fabricators. Also, a paper will be prepared for presentation at the PEI

Fprum at Ohio State.
18 -

STANDARD REFERENCE MATERIALS

The following stock of standards was on hand October 1, 1965:

Corundum abrasive, March 1960 issue,

for subsurface abrasion 261 lbs., 65 jars

Standard Pennsylvania Glass Sand, July 1963 issue,

for surface abrasion 285 lbs., 94 jars

Distinctness of image gloss standards 20 sets.

Calibrated glass paltes for abrasion testing 27.5 doz.

Respectfully submitted,

y?i /Si"

M. D. Burdick

M. A. Rushmer

Research Associates, PEI
19

REFERENCE

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

Enamels Exposed for Seven Years at Various Sites, Proceedings of

of the Porcelain Enamel Institute Forum, Vol. 26, 1964.

USCOMM-NBS-DC

TABLE 1. Results of Measurements to Test

Uniformity of Mixing of a Graphite-BBOT Soil

Specimen No.

a / BBOT Contentpercent

1

2

3

4

5

6

78

9.14

9.26

9.04

9.41

9.06

9.07

9.16

9.20

Average

Coef. Variation

9.17

1.3

a / Applied soil consisted of 10% by wt. BBOT and

90% powdered graphite.
TABLE 2. The Fluorescence of Solutions of Known Concentration

of BBOT^ in Toluene.

Solution Concentration Fluorescence Reading»s yg/ml No Filter Filter

b/

FilterFilter A B C

CC 0.0699 — 100+ 100+ 79.0

DD 0.0599 -- 100+ 100+ 69.0

EE .0498 — 100+ 100+ 57.0

FF .0399 — 100+ 79.0 46.0

GG .0299 — 90.5 60.0 35.0

HH .0200 — 60.5 41.0 24.0

II .0100 100+ 31.0 22.0 12.5

C .0042 47.0 16.0 10.0 6.5

E .00312 36.0 — — —

F .00259 31.5 — — —

G .00207 24.0 — — —

H .00155 18.0 — — —

I .00104 11.0 — — —

J .00052 5.0 — — —

BLANK .00000 0.0 0.0 0.0 0.0

a/ 2 , 5-bis [ 2- (5-tert-Butylbenzoxazolyl) ]

•Thiophene

("Scintillation Grade) : M.W. 430.58, M. P. 201-202° C,

Fluor. Max 4350 A, and Solubility in Toluene: 53 g/1.

b/ The neutral density filters used had the following

percentage transmission:

Filter Neutral Transmissipn

Designation Density percent

Designation

A 0.5 31.6

B 0.7 20.0

C 0.9 12.5
TABLE 3. Comparison of Two Soiling and Cleaning Methods

in a Cleanability Test

Fluorometric Determination

of Total Soil Retained

a/

Method 1 —

yg/cm2

Method 2^

2

V*g/ cm

1.97 1.46

3.09 1.63

1.82 1.40

1.25 1.61

3.69 1.31

2.80 1.72

2.37 1.65

1.78 1.80

Average 2.35+0.67—/ 1.57+0.14

Coef. of

Variation 34% 11. %

a./ Pressure applied for application

Pressure applied for cleaning was

b/ 95 percent confidence limits.

Reflectance Change

Method 1 Method 2

percent percent

3.9 5.5

5.1 4.5

2.8 2.2

2.2 5.7

10.4 4.0

5.6 5.6

7.6 4.6

5.0 6.3

5.32+2.2 4.80+1.08

50. % 27. %

1.1 psi (79. g/cm2

) 0.5 psi (32 g/cm2

)
COg 3 CD X

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1.

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Equipment

Used

for

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and

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Specimens.

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2

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FIG.

3

CALIBRATION

OF

FLUOROMETER

WITH

BBOT

IN

TOLUENE.

PERCENTAGE

OF

ENAMELS

WITH

HIGH-VOLTAGE

DISCHARGES

Figure h. High-Voltage test results for storage specimens

of enamels in PII-NBS exposure test. The good

enamels did not rust at any site after 7-yrs

exposure, the fair enamels rusted at Kure Beach80 in 7-yrs, while the poor enamels rusted at

both lure Beach-80 and either Kure Beach-800 or

New Orleans.

NUMBER

OF

DEFECTS

LOCATED

22

20

18

16

14

12

IQ

8

6

4

2

0

w

GOOD ENAMELS

n

T

HOT WATER TANK ENAMEL

POOR ENAMELS

. . n £ n 1

1

8 E-4,PA-2,B-!l,C-4,L-2,L-3 —r—

“T" nn —i

i— OF - E-2 , L-4 K

W

PQ£

8 _i i i £5 —r——p 1— I 1 2 — A-4 —

0 tiii_

1 1 J i t

VOLTAGE, KV

Figure 5. Reproducibility of testing good and poor hot water tank

and architectural enamels. The architectural enamels are

designated by their code letters ._!/
.