NATIONAL BUREAU OF STANDARDS REPORT

9459

PROGRESS REPORT

July 1 through September 30 , 1966

Development of Methods of Test

For Quality Control of Porcelain Enamels

by

M. Do Burdick and M, A. Rushtner

Porcelain Enamel Institute Research Associateship

National Bureau of Standards

Washington, D. C.

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U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
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NATIONAL BUREAU OF STANDARDS REPORT

MBS PROJECT MBS REPORT

421 .04-= 12=4212270 94.59

PROGRESS REPORT

July 1 through September 30 s 1966

DEVELOPMENT OF METHODS OF TEST

FOR QUALITY CONTROL OF PORCELAIN ENAMELS

by

Mo Do Burdick and M. A. Rushmer

Porcelain Enamel. Institute Research Associateship

National Bureau of Standards

Washington j Do C,

IMPORTANT NOTICE NATIONAL BUREAU OF STAN

for use within the Government. Be

and review. For this reason, the pi whole or in part, is not authorize* Bureau of Standards, Washington ; the Report has been specifically p re

Approved for public release by the

Director of the National Institute of

Standards and Technology (NIST) on October 9, 2015

iccounting documents intended

ijected to additional evaluation

ting of this Report, either in

ffice of the Director, National

i Government agency for which

is for its own use.

0. S. DEPARTMENT 9F COMMERCE

NATIONAL BUREAU OF STANDARDS

SUMMARY

Research has been completed on a tentative method for the numerical

evaluation of the cleanability of porcelain enamel surfaces. The method,

based on the use of an oily soiling agent containing a fluorescent tracer,

measures the time required to restore a soiled surface to its original

appearance of cleanliness. The method is equally applicable to surfaces of

many materials regardless of gloss, color or texture, and has been shown to

be in essential agreement with less precise, non-numerical estimates of the

cleanability characteristic.

A method for calibrating the high-voltage continuity of coating test

equipment has been developed and a round robin test has been arranged to

determine whether this calibration procedure is applicable to all types of

high-voltage test equipment currently in use.

The one-year inspection of the enamels included in the 1965 Weathering

Test of Porcelain Enamels on Aluminum was completed with the examination of

the enamels exposed at Kure Beach and Los Angeles.

The last enamel to be included in the 1966 Weathering Test of Nature-Tone

enamels on Steel was received and the test specimens were installed at one of

the three exposure sites.

- 1 -
I. CLEANABILITY

INTRODUCTION

The ease with which porcelain, enamels can be cleaned is one of their

important performance characteristics. There is currently no satisfactory

test procedure by which to evaluate differences in cleanability among

various porcelain enamel types. It is felt that there is a need for a test

method which will permit a numerical determination of cleanability. Such a

test should assist in comparing various surface finishes for products intended

for the same service. A cleanability test would also be helpful in quality

control as well as in the development of porcelain enamels with increased

cleanability

.

This is a report of progress during a quarterly period. A background of

previous work may be obtained from previous reports in this series.

- 2 -
RESULTS AND PIS CUSS ION

A. The development of a Stable Soiling Agent.

The instrumental method for evaluating the cleanability of surfaces

requires a stable soil, the composition of which will not change with time,

as well as reproducible methods for soiling and cleaning and for the

extraction and determination of small residual amounts of soil.

Previous work had suggested that the solubility of the fluorescent compound of the soil in the oil base was of the order of 0.3 percent. A new

soil was compounded in which the fluorescent material was reduced from 3.3 to

0.3 percent. The fluorometer was calibrated with solutions of known concentration of the new soil in toluene. Extended trails of this soil gave

results that were consistent within a group of similar specimens and were

repeatable from day to day. Typical results of individual determinations on

polished plate glass, porcelain enamels, and a fiberglass-reinforced polyester

are given in Table 1. The scatter of results among six specimens of the same

material, as indicated by the standard deviations (0.03 to 0.07 pg/cm ), was

quite small when compared to the magnitude of the average values of the retained

soil

.

The present procedure is now considered satisfactory for the accurate

determination of small amounts of retained soil remaining on cleaned specimens.

B. The Effect of Surface Abrasion on the Cleanability of Porcelain Enamels.

Many domestic appliances which have been in service show a random pattern

of surface scratches. In many cases the appearance is not seriously affected

other than to reduce the glossiness of the surface. The ease with which these

- 3-
scratched or abraded surfaces may be cleaned would be expected to change in

such a way that cleaning would became more difficult. A limited experiment

was performed, using a matte and a high gloss porcelain enamel, to verify that

abrasion would result in an increase in the amount of soil retained after six

minutes of cleaning time. The results given in Table 2 shown a decrease in

gloss retained and an increase in the amount of retained soil as the abrasion

treatment was prolonged.

C. A Comparison of the Instrumental Procedure with Other Estimates of Cleanability.

Round-robin testing is often employed to determine whether different

operators in different laboratories, using the same method, can obtain the

same result. The purpose of this experiment, on the other hand, was to

determine whether individual operators using various methods of hand cleaning

could select the easier cleaning of two surfaces in a way that would agree

with an instrumental selection.

Nine candidate materials were selected from the group on which instrumental determinations had previously been made. These were arranged in three

groups of three as indicated in Table 3. The code letter of the surfaces,

described in Table 6, is given together with the amount of soil in pg/cm retained after six minutes of cleaning time. It can be seen that if three

specimens. Nos 1, 2 and 3, are rated easy, medium or difficult to clean, with

respect to each other, the rating process provides information for comparing the

ease of cleaning of No 1 with No 2 ; No 2 with No 3, and No 1 with No 3. The

- 4 -
specimens for use in this test were selected in such a way that some specimenpairs had widely different amounts of soil retained after six minutes of

mechanical cleaning, and other pairs differed by intermediate and by small

amounts of retained soil under the same conditions.

The first three specimens (Part A) were soiled with the standard amount

of the soil used in the instrumental determination, and were presented to the

first operator. By the use of dry, cleaning tissues he was asked to select

the surface which was easiest to clean, which was hardest to clean, and if

possible which was intermediate. This procedure was repeated for the other

specimen groups. The results given in the lower part of Table 3 reflect the

judgements of eight operators each working with the same nine specimens.

When the difference in retained soil between the two specimens of a pair,

was over two pg/ crn^ , all of the operators were able to select, as easier

to clean, the specimen which retained the smaller amount of soil after 6 minute

of cleaning time. From those pairs with differences in retained soil between

one and two pg/crn^ the operators selected the same specimen that was instrumentally determined to be the more easily cleanable, 62 percent of the time.

When the difference in retained soil was 0.5 pg/cu/ or less there was only 55

percent agreement between the operators' ranking and that determined instrumentally

.

With eight operators ranking nine pairs of specimens there were 72 individ

ual comparisons of operator judgement with instrumental ranking. In 68 percent

of these comparisons there was agreement between the operators and the instrumental method. In 22 percent of the cases the operator was undecided and made

no selection. In only two specimen pairs was the operators' average ranking at

variance with the instrumental ranking. In both of these cases the difference

- 5

-
in retained soil was small and there was a marked color difference between

specimens which may have reduced the objectivity of the operators.

D. The Gleaning of Soiled Surfaces.

1. The Procedure Used in the Present Test.

In the preceding section of this report specimens which had been uniformly

soiled were subjected to a mechanical cleaning process. A brass disc, covered

with a wiping tissue was moved back and forth across the specimen which was

attached to a horizontally rotating, wheel. The tissues were changed at

specified intervals according to the following schedule: the first two tissues

were used for one-half minute each, the third was used for one minute and

additional tissues were used for two minutes each. The soil retained on the

specimen after six minutes was used as a preliminary index of cleanability

.

2. The Mechanisms Involved in the Procedure.

There appear to be two separate parts of the cleaning process. The first

is the removal of the gross excess soil by a combination of rubbing and

absorption on the tissue. It is believed that the removal of the excess in

normally completed during the first minute in the mechanical procedure described

above. Additional cleaning action appears to result in a continuous thinning of

the film of soil which is more or less firmly adherent to the surface by chemical

and/or physical forces.

3. Rate of Soil Removal.

The rates of soil removal were determined by two types of cleaning

experiments. Fluorometric analyses of small discs cut from the soiled tissues

allowed an estimation of the amount of soil removed as a function of time.

Another approach was to extract the soil remaining on a series of specimens

which had been cleaned for times between zero and ten minutes. The results of

- 6-
these experiments indicated a rapid and difficult to measure, rate of soil

removal during the first one or two minutes of cleaning. After two minutes,

however, the soil removal continued at a decreasing rate which could be

accurately measured. The logarithm of the soil retained was proportional to

the logarithm of the cleaning time for various surfaces for cleaning times

up to 60 minutes, as illustrated in Figure 1.

The slopes of the curves in Figure 1 are measures of the rate at which

soil is removed from various surfaces when subjected to a particular cleaning

action.

4. The Selection of an End-Point for the Test.

The cleaning rate curves described above can be used to estimate the

time required to reduce the soil to any desired level. It was desired to

select a suitable level of cleanliness for use as an end-point for the test.

Specimens of a glossy white porcelain enamel were soiled with the black soil

and then cleaned by the regular procedure for periods of time between one and

30 minutes. Before the soil remaining was extracted, a spot at the specimen

center was covered with 1-1/4 inch diameter mask. The entire surface of the

specimen, except under the mask, was cleaned by rubbing with tissues moistened

with toluene. This treatment removed all parts of the soil including the

graphite coloring agent. The visibility of the soil remaining within the masked

spot on a white specimen after a given cleaning treatment depended entirely on

the amount of coloring agent (colloidal graphite) present. The extraction

process dissolved and removed only the oil and fluorescent tracer but left the

graphite intact . The visual appearance of the spot remained unchanged after

the extraction of the oil and tracer. Following the extraction of the

fluorescent components of the soil, the group of specimens was examined by

eight individuals who were in unanimous agreement regarding which spots could

not be seen.

- 7 -
The results of this experiment are given in Table 4 and the values up

to six minutes of cleaning time are plotted as curve C in Figure 1. These

results led to the selection of 0.5 jig/crn^ as a practical, end-point for the

test, which had for its basis, the threshold value, below which black soil

was not visible on a white specimen surface.

E. The "Soilability" of Surfaces.

1 / This property has been defined” as "the relative ease with which

extraneous matter attaches to or builds up on the surface of a material". For

the purpose of this discussion it will be considered that the y-intercept at

one minute cleaning time on the log- log plot of retained soil vs cleaning time,

is a parameter which is related to or is a measure of the "soilability" of a

surface. During the collection of the data which form the basis for Figure 1

it was observed that matte enamels such as M and H (Table 5) appeared very

dirty after one minute of cleaning when compared with glossy enamels such as

D and E after the same cleaning time. It may be rationalized that the y-intercept at one minute cleaing time represents the soil level at or near the time

at which the removal of the gross excess of soil has been completed. Reference

to Table 5 suggests that this measure of "soilability" depends, to some extent,

on the gloss level and/or the profilometer roughness height.

F. The Selection of an Index of Cleanability of Surfaces

Some of the factors that are involved in the determination of a cleanability

index are shown in hypothetical relationships in Figure 2. Various levels

of "soilability" are indicated along the ordinates as high (H) , medium (M) and

low (L) . The diagonal lines represent cleaning-rate curves. The dashed lines

in the lower portions of the plots represent the end-point value (0.5 Jig/cm^).

1 /

ASTM Defintions relating to Porcelain Enamel, C-286.

- 8 -
Figure 2A suggests that surfaces with different levels of "soilability" but

with the same rates of soil removal would require different cleaning times to

reach the end-point value of cleanliness. Figure 2B illustrates a condition

where a surface, I(, with a high degree of soilability and a rapid cleaning rate

is compared with surface J, having a lower soilability value but a less rapid

rate of soil removal. Although the cleaning rates of the surfaces J and K are

quite different, the cleaning time required to reach the end-point level of

cleanliness would be the same because of their different soilabilities . The

relationship shown in Figure 2C would result if curve K were translated to the

same soilability level as that of J. The use of times t, and t_ as indices of

1 z cleanability would emphasize the importance of the rapid cleaning rate of K

and avoid the influence of their differences in "soilability".

It is rationalized however, that the primary concern of the user of surfaces such as these, is the ability to clean an appliance in the minimum of

time (or effort). If the translation of curves such as in Figure 2C was

employed to avoid the effect of differing soilabilities, surface K would

receive a more desirable cleanability index than surface J. In reality, the

housewife might be equally satisfied with either surface J or K because the

cleaning time (or effort) is the same. Following this reasoning, the

translation of curves does not seem advisable and has not been suggested in

the proposed procedure outlined in paragraph G.

A preliminary index of cleanability has been used previously in this

report series: the soil retained after six minutes of cleaning time. Table 6

shows both of these indices for a series of surfaces. It can be seen that

either criterion places this group of surfaces in the same relative order. The

criterion expressed in units of time has several advantages:

1. Units of time required to clean a surface are more easily interpreted

than are units of weight retained per unit area.

9
2. This index is based on the time that would be required to get all

surfaces to the same degree of cleanliness, as compared to the preliminary

index in which the specimens are compared although some are clean and others

are not.

3. The use of a log-log plot of the cleaning rate permits the use of

the y- intercept as an estimation of the soilability of the surface.

G. A Proposed Procedure for Evaluating Cleanability

.

Details for the various operations will subsequently be prepared. In

essence the evaluation of the cleanability of a candidate surface involves

the use of 12 specimens as follows:

a) Determine the average amount of soil retained on six specimens after

six minutes of the cleaning treatment;

b) If the average soil retained is less than two micrograms per square

centimeter, repeat the operations on the remaining six specimens using a

cleaning time of two minutes for each specimen; or

c) If the average amount of soil retained on the initial group of six

second group of six specimens using a cleaning time of 12 minutes;

d) The average values of soil retained after the two cleaning periods

soil retained and time as the ordinate and abscissa respectively.

e) A straight line through these two points is extrapolated, if necessary,

f) The time, in minutes, corresponding to the above intersection is taken

as the index of cleanability.

determine the average retained soil on the

(2 and 6 minutes or 6 and 12 minutes) are plotted on log- log paper with the

to intersect the end-point soil level of 0.5 |ig/cm^;

- 10-
PLANS FOR THE NEXT REPORT PERIOD

One of the inadequacies of this procedure for determining cleanability

is that it can be applied only to those surfaces which resist the solvent

action of toluene. It is planned to substitute another fluorescent compound

in the soil composition so that a less agressive solvent can be employed in

the extraction.

The present procedure will be written for consideration as a tentative,

or interim Porcelain Enamel Institute method of test.

- 11 -
II. CONTINUITY OF COATING

INTRODUCTION

Porcelain enamel is often applied to a metal not only to add a pleasing

appearance, but also to protect the base metal from corrosion. A visual

. inspection of the older two and three coat glossy porcelain enameled products

was sufficient to determine whether the product had adequate enamel coverage to

protect the base metal from corrosion. However, visual inspection of the new

matte nature-tone enamels and the thinner direct-on enamels often pass enamels

that have extremely small, areas of poor coverage. These areas tend to permit

early corrosion of the base metal and the resultant iron oxide diffuses over

the enamel surface forming an unsightly irridescent or rust colored film. This

suggests the need for a test for continuity of porcelain enameled coatings.

The development of such a test method has been one of the goals of the PEI

Research Associateship

.
RESULTS AND DISCUSSION

The major effort toward the development of a test for continuity of

coating during this report period was focused on developing a method for

calibrating the test equipment. This was particularly necessary if both

ac and dc test equipment were to be used since the effects of maximum

voltage and charging currents in ac instruments could not be predicted by

simply checking the voltmeter on the test equipment with an independent

voltmeter

.

The method of calibration selected was a modified spark-gap measurement -

that is, measuring the voltage necessary to just arc across a gap of a

given thickness. However, instead of measuring the spark gap with a set of

fixed electrodes surrounded by air, it was decided to re-probe porcelain

enameled specimens ranging in thickness from 2-20 mils that had been previously

punctured with the high-voltage test equipment. While this method does not

give a uniform test geometry, it is indicative of the types of geometries, or

defects, that would be encountered when testing virgin specimens for continuity

of coating. The results of this calibration for both ac and dc test equipment

are illustrated in figures 3 and 4. The points in these figures are the

average thickness plotted against the average air-gap voltage for each enamel

tested. The curves are the least squares lines through these points. Although

there is some scatter in the data, it is believed to be caused mainly by the

different configurations of defects that the spark had to pass through on its

way to the base metal. The effect of test geometry is illustrated in Table 7

where handbook values for the dielectric strength of air tested with different

geometries are given.

- 13 -
The effects of the type of probe and relative humidity were investigated.

Figure 5 illustrates the shift in the curve caused by probing the specimens with

a wire brush probe instead of a 100 mesh wire gauze probe. Although there is

only a slight change in the calibration curve, the correlation coefficient is

slightly better when the gauze probe is used. For this reason a gauze probe

will be recommended in the test procedure.

A 48 percent change in relative humidity of the test atmosphere caused a

shift in the calibration curve of approximately 50 volts as illustrated in

figure 6. This is less than ten percent of the voltage required to puncture

the thinnest enamel with reputedly "bad" continuity. This indicates that

minor fluctuations (10-207.) in humidity that would occur in a laboratory are

not of major importance in this test procedure.

After developing calibration curves for both ac and dc instruments and

determining the effect of type of probe and relative humidity, it was desired

to determine whether replicate specimens of the same enamel tested with ac and

dc equipment would fail at similar voltages. To do this the replicate specimens

were probed with increasing voltage, both ac and dc , until failure occurred.

The thickness of the enamel was measured and the voltage necessary to arc

across the air gap was determined from the appropriate calibration curve (figure

7). The difference between the air-gap voltage and the puncture voltage was

calculated and is called the "overvoltage" required to puncture the enamel.

The overvoltage required to puncture replicate specimens of the same

enamel with both ac and dc test equipment is represented graphically in figure

8. It can be seen that a good linear correlation exists between the overvoltage

necessary to puncture an enamel with either ac or dc test equipment. If

the overvoltages were equal for both types of test equipment, the slope of the

least squares line in figure 8 would be 1.0. However, inherent differences

- 14 -
between the ac and dc test equipment have reduced the slope of this line

to 0.42.

The overvoltage, both ac and dc for the individual enamels probed is

given in table 8. The enamels in this table have been listed as having

’’good" or "bad" continuity based on either 1) the manufacturer's estimate of

continuity or 2) whether they rusted after 7-yrs of exposure at Kure Beach,

North Carolina” 80 feet from the ocean. The average overvoltage required to

puncture "good" enamels was 2.09 and 1.96 times that needed to puncture the

"bad" enamels for the ac and dc test equipment respectively. This indicates

that either type of test equipment would be on the average, equally sensitive

for separating the "good" and "bad" enamels. A further analysis of these

data are given in Table 9. Here pairs of "good" and "bad" enamels have been

arranged according to enamel type and thickness. The overvoltages required to

puncture the individual pairs of enamels using both ac and dc test equipment

are also given. If the overvoltage necessary to puncture the "good" enamels

was higher than that required to puncture the "bad" enamels, then the voltage

required to puncture the "good" enamels could be lowered slightly to pass them

but still puncture the "bad" ones, thus separating the good from the bad. The

data in table 9 indicate that 6 of the 8 pairs of enamels could be separated

with either type of test equipment, again indicating that similar results can

be obtained by using either type of test equipment.

- 15 -
PLANS FOR NEXT REPORT PERIOD

A tentative procedure for calibrating high-voltage continuity of coating

test equipment has been prepared. This procedure, together with the specimens

we used to calibrate our test equipment, will be sent to three companies that

have agreed to participate in a round-robin test. This test involves calibrating the high-voltage test equipment and then testing some enamels to

determine the overvoltage required to puncture them. Replicate specimens of

the tested enamels will then be sent to the other companies participating in

the round robin. This test should 1) determine whether all test instruments

give similar calibration curves and more important 2) whether the same enamel

will be punctured at the same overvoltage regardless of test equipment used.

- 16 -
III. WEATHERING TESTS OF PORCELAIN ENAMELS

INTRODUCTION

Weathering tests are one of the long-term projects of the research

associates. During this quarter the enamels exposed at Los Angeles and

Kure Beach in the 1965 Weathering Test of Porcelain Enamels on Aluminum were

returned for their one-year inspection. Specimens of the last enamel to be

included in the 1966 Weathering Test of Nature-Tone Enamels on Steel were

received; also, those enamels included in a preliminary exposure test of

Nature-Tone enamels on steel were returned for their final inspection after

one-year's exposure at Kure Beach-80.

- 17 -
INSPECTION PROCEDURE

1. Cleaning of Specimens

Before meaningful gloss and color measurements can be made on specimens

that have been exposed it is necessary to remove accumulated dirt, fingerprints etc. from the enamel surface. The procedure selected for cleaning the

enamels in the above tests was to 1) scour 30 strokes with a sponge that has

been moistened with a solution containing one weight percent trisodium phosphate and sprinkled with calcium carbonate, 2) rinse with tap water, 3) rinse

with distilled water and 4) rinse with alcohol.

2. Gloss and Color

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

near the center of the specimen. The gloss is reported as the percentage of

initial gloss retained after exposure.

The change in color was measured with a color difference meter. One of

the three storage specimens of each enamel 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 NBS

color standards to determine whether the enamels have changed color during

cleaning and storage. Since there were no extra specimens available in the

preliminary nature-tone test, these enamels were compared directly with the NBS

color standards. The color change after exposure is reported as color retention

which is 100 minus the color change in NBS units.

- 18-
RESULTS AND DISCUSSION

A. The 1965 Weathering Test of Porcelain Enamels on Aluminum

1. Cleaning of Specimens

The enamels exposed at Los Angeles and Kure Beach were returned to the

laboratory at the National Bureau of Standards for their one-year inspection.

The specimens exposed at Kure Beach appeared fairly clean while those exposed

at Los Angeles were covered with a loosely adhering dirt film. The enamels

exposed at both sites were easily cleaned by the above cleaning treatment.

2 . Gloss and Color

The gloss and color were measured as previously described. These data

have been reduced to percentage gloss retained and color retention and are

reported in Table 10.

The extreme color change of the black enamels exposed at Kure Beach was

unexpected. However, this large color change does correlate with the acid

solubility of the enamels.

3. Nature- Tone Enamels on Aluminum

Eight nature-tone enamels on aluminum were to be added to this test after

the one-year inspection. However, extreme delays in the production of one

enamel have cancelled its inclusion in this test program. The remaining seven

enamels will be added to the exposure racks when the original enamels are reexposed .

B. 1966 Weathering Test of Nature-Tone Enamels on Steel

The last enamel to be included in this test was received during this report

period. It was measured for gloss, color, acid resistance, thickness and

continuity of coating as described in previous reports.

The specimens have been installed in the exposure racks near Biscayne

Bay, Miami, Florida.

- 19-
C. 1965 Weathering Test of Nature-Tone Enamels on Steel

1. Final Inspection

The 1965 Preliminary Weathering Test terminated with the one-year inspection report. This preliminary test program will be superceded by the

expanded 1966 Weathering Test of Nature-Tone Enamels on Steel. The following

are the results of one-year S s exposure at Kure Beach for the Enamels included

in the preliminary test.

2. Gloss and Color

The color retention and percentage gloss retained for the Nature-Tone

enamels exposed for one-year in a preliminary test are given in table 11.

The blue enamels, as a group, appear to be less stable than the other colors

although there is one red-brown enamel, MC-9, which exhibited quite a large

color change.

It was also noted that the enamels with an initial gloss lower than

18 showed increased gloss retention between six months and one-year ®s exposure.

3.

Continuity of Coating

The main defect that was revelaed by this short-term exposure test was

the lack of continuity of coating. After six months’ exposure 25% of the

enamels showed rust on their surfaces. This rusting tendency has continued,

and following one-year's exposure 50% of these enamels have rust visible on

their surfaces

.

- 20-
PLANS FOR NEXT REPORT PERIOD

A. 1965 Weathering Test of Porcelain Enamels on Aluminum

The specimens in this test are to be returned to the exposure racks

during the next report period. The next inspection is tentatively planned

after 2 years' exposure.

B. 1966 Weathering Test of Nature-Tone Enamels on Steel

The enamels in this test are to be put on the exposure racks at Gaithersburg,

Maryland and Kure Beach. The first inspection of these enamels will be made

after six months' exposure.

- 21 -

Table 1. Individual Determinations on Polished Plate Glass Specimnes

Showing the Amount of Soil Retained after Six Minutes of

Cleaning

Spec

No.

Retained

Soil

Spec

No.*

Retained

Soil

Spec

No.

Retained

Soil

Spec

No.*

Retained

Soil

Mg/ cm

2 Mg/cm2 M-g/ cm

2

M-g/ cm

2

1 0.71 1 0.74 10 0.74 10 0.77

2 0.73 2 0.74 11 0.68 11 0.65

6 0.75 6 0.85 12 0.71 12 0.72

8 0.65 8 0.65 13 0.66 13 0.72

5 0.65 5 0.72 14 0.65 14 0 . 66

7 0.61 7 0.64 16 0.66 16 0.62

17 0.66 17 0.61

Ave

0.68 0.72 0.68 0.68

S. D. .056 .076 .034 .059

*Repeat determinations made on previously used specimens.

Individual Determinations on Four Porcelain Enamels and a Gel Coat Showing the Amount of Soil Retained after' Six

Minutes of Cleaning Time

Specimen Enamel "G" Enamel MG" Enamel "F" Enamel "A" Gel Coat "P"

Mg/cnf3 Mg/crtf3 Mg/cm2 Mg/ cnf

2 Mg/ cm

2

1 0.33 0.46 0.39 0.15 2.1

2 .26 .42 .41 o 00 « 2.5

3 .42 .44 .32 .11 2.4

4 .28 .34 .47 .24 2.5

5 .29 .29 .46 .07 2.7

6 .33 .49 .38 .14 2.3

Ave 0.32 0.41 0.40 0.13 2.4

Std. Dev .057 .076 .055 .062 .041
Table 2 Effect of Abrasion on Cleanability

of Porcelain Enamels

Porcelain Initial Abrasion Retained Retained Soil After

Enamel Gloss Time If Gloss 6 Minutes Gleaning 2/

min. percent |ig/ cm2

C 63 0 100 0.32

2 82 1.9

6 55 7.8

10 34 13.6

N 9 0 100 4.7

2 81 174.

1/ Using the PEI Abrader

2/ This value used as an index of Cleanability ; small amounts of

retained soil are associated with good cleanability.
Table 3. A Round-Robin Test Comparing Two Methods for

Determining the Cleanability of Surfaces.

Specimens Used

Part A D-BUFF J-GLASS N-LAVENDER

0.32 0.69 4.7

Part B I -PINK K-WHITE P -WHITE FRPE a/

0.55 0.84 2.4

Park C A- BLUE F -WHITE O-LAVENDER

0.13 0.40 0.59

Analysis of Results

Difference in the Agreement Between

Instrumental Deter- Individual Operators

mination of the Total and the Instrumental

Soil Retained After

6 Minutes Cleaning

Determination b/

Specimen Pairs Time

|J.g/ cnf3 percent

D-N BUFF- LAVENDER 4.4 100

J-N GLASS -LAVENDER 4.0 100

I-P PINK-FRPE* 1.8 62

K-P WHITE-FRPE* 1.5 62

A-0 BLUE -LAVENDER 0.5 100

D-J BUFF-GLASS 0.4 0

I-K PINK-WHITE 0.3 62

A-F BLUE -WHITE 0.3 12

F-0 WHITE -LAVENDER 0.2 100

a/ Fiberglass Reinforced Polyester

b/ 100 percent agreement was considered to be attained when each

of the operators selected as the more cleanable of a pair,

the same surface that retained the lesser soil after six minutes

of mechanical cleaning time.
Table 4

The Det ermi na t i on of a Practical Level of

Visual Cleanliness

Specimen Cleaning Retained Visual. Inspection

No. Time Soil Results

min. / 2

(j, g/ cm t

5

!| 1 1.8 visible

9 6 2 o.97 »» 53 3 . 62 tf 78 li . ^9 not visible

101 6 .23 ry 99 8 . 19 T V *» 100 17 . 10 yy »y 118 39 . 98 *f »y

l/ Eight individuals examined this series of soiled

specimens in a random arrangement and unamimously . reported the r e s u 1 1 s shown. All specimens were a glossy white p o r c o ] a i n e; a me 1 (C) soiled with the

1 1 a c k , oily, soiling agent developed in this research,
Table 5. The Relationship of 45° Specular Gloss, Soilability

and the Roughness Height of Several Surfaces.

• face 45° Specular Soilability Roughness Height

Gloss M-g/ cm2 a/ micro-inches

Matte Surfaces

M 8 11 52

H 6 10.5 36

High Gloss Surfaces

F 67 5.5

K 58 4.0 12

L 56 3.4 -- B 60 3.0 11

G 64 2.7 --

E 60 2.5

I 61 2.3 9 D 55 2.2 8

C 63 1.8 12

J 55 1.4 -- A 56 0.8 --

a/ Relative numbers which are related to the soilability of these

surfaces. They were experimentally determined as the y-intercept at one minute cleaning time, from the log-log plot of re- tained soil as a function of cleaning time.

b/ Arithmetic average height as indicated by a Talysurf Profilometer

.
Table 6. Experimental Values for Cleanability and Soilability

of a Series of Sur faces

Surface Soil Retained Time Required Soilability a/

Code After 6 Minutes To Reduce Soil

Cleaning Time To 0.5 i^g/ctd

3

|ig/ cm

2 minutes M-g/cn?

A 0.13 2 0.8

B .26 4 3.0

C .32 4 1.8

B .32 4 2.2

E .35 4 2.5

F .40 5 5.5

G .41 5 2.7

H .47 6 10.5

I .55 9 2.3

J .69 11 1.4

K .84 11 4.0

L 2.0 800 3.4

M 5.6 3000 11.0

Characterization of Surfaces

Surface Specular Acid Roughness

Code Material Color Gloss Resistance Height

micro-inches

A P/E Blue 56 C „ * B P/E Brown 60 AA 11

C P/E White 63 A 12

D P/E Buff 55 A 8

E P/E Blue 60 B --

F P/E White 67 AA - G P/E White 64 -- H P/E Lavender 6 C 36

I P/E Pink 61 B 9 J Plate Glass Clear 55 -- --

K P/E White 58 AA 12

L FRPE b/ White 56 -- M P/E Lavender 8 A 52

b/ Fiberglass Reinforced Polyster

a_/ Relative numbers which are related to the soilability. They were experimentally determined as the y-intercept at one minute cleaning

time, from the log-log plot of retained soil as a function of

cleaning time.
Table 7. Dielectric Strength of Air, volts/mil

From Handbook of Chemistry and Physics

Test Voltage Test Geometry

kV 2.5 cm 5 cm 10 cm 25 cm Spheres Spheres Spheres Spheres Points

25 84.6 82.6 81.5 78.5 29.0

20 87.6 84.6 82.0 79.5 29.0

15 90.7 86.

6

82.8 79.5 29.2

10 94.0 87.6 84.6 79.5 30.2

5 97.8 84.6 84.6 79.5 30.2
Table 8.

Comparison

of

"Good"

and

"Bad"

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Ename

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Table

9.

Comparison

of

"Good"

and

"Bad"

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Enamels

of

the

Same

Type

and

Thickness

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Ename

1

10. Summary of Data for Porcelain Enamels on Aluminum Exposed for One Year at Beach and Los Angeles

Kure Beach Los Angdes Visual

Gloss Color Gloss Color Color

6 mo. 1 yr. 6 mo. 1 yr. 8 mo. 1 yr. 8 mo. 1 yr.

Kure

Acid

S 0 lub i 1

mg/ in

AA-A 85.5 95.2 99.4 98 . 1 95.6 97.8 99. 5 99. 3 White 5.5

AA-B 94.0 87. 5 99. 3 98.7 103.0 100.

9

99. 3 99.0 White 5.9

AA-C 90.7 107.

4

98. 3 97.6 96.0 96.8 99.0 98.5 White 5.0

AA-D 76.0 33.0 98. 3 97.0 101.0 100.4 98.2 98.8 White 12.7

AB-A 81.2 88 . 4 98.8 97.8 84.9 88. 3 98.7 98.6 White 7.2

AB-C 79.6 86.4 99.6 99. 1 83.6 87.9 99.4 99. 3 White 4.9

AB-D 75.1 80.2 98.5 97-6 79.6 98.

1

98. 4 99. 1 White 7.9

AC -A 90.2 90.7 99 . 4 90.

7

102.6 101.0 99.

1

98.7 White 6.4

AC-B 85.8 37.3 98. 7 98.1 102.1 101.3 98.6 99.2 White 11.3

AC -C 90.6 65.3 98 . 3 96.9 98.2 98.

1

98.9 98.8 White 9.9

AD-A 87.6 96. 9 08 . 9 97.6 90.3 95.7 99. 4 99. 3 White 6.2

AD -B 89.0 93.8 99. 4 98. 3 92.4 94.9 99. 4 99. 3 White 6.7

AD-C 82.8 91.3 98.

1

96.

9

87.5 95.

4

98. 5 98.4 White 7.1

AD-D 87 . 5 58.0 98 . 1 97. 3 88.6 103.1 98 . 4 98. 9 White 12.4

AE-A 76.4 68.4 99- 1 94 . 3 80 . 5 80.

5

99.8 97.2 Black 6.5

AE-B 65.1 55.8 98.6 89 . 1 87.

9

86.6 99. 7 99.1 Black. 10.1

AE-C 72.6 68.2 98.9 92.9 91.

1

89 . 9 99.4 99.2 Black 12.

1

AE-D 71.1 37.8 98.6 76.6 85.5 83.2 99. 4 97.2 Black 15.5

AF-A 65.6 67. 9 98.4 88.8 85.7 84.3 99.6 97.

9

Black 14.2

AF-B 69. 7 58. 5 99. 1 88 . 7 96.1 96. 5 99.6 99. 4 Black 9.0

AF-C 72.

2

76.8 98.4 93.1 87 . 5 86.6 99.6 98.3 Black 10.

1

AC-B 82.0 83.7 97.6 88.2 79. 5 103.1 99. 3 98.1 Black 12.5

AG-C 46.9 112.8 98.2 97. 1 33.2 103.8 99. 4 99.0 Bla ck 7. 5 AH-A 90.8 79. 3 97. 5 93.5 103.7 H3.2 97.4 96.9 Red 8.1

AH-B 64 .

3

44.8 93.0 83.1 76.

8

77.6 95.5 94 .

4

Red 8.8

AH-C 73.9 59.2 90.

1

86.3 77.6 77.4 91. 9 91. 4. Red 6.5

AH-D 59.7 37.8 83.6 70.2 83.2 81.8 91.0 88.4 Red 10 . 5

AO -A 76.6 60.

9

95 .

4

91. 7 83.3 83.3 99. 9 99.2 Dk. Green 19. 9 AO -B 72.

5

67.0 99. 5 97. 3 84.6 86.0 99. 8 99.4 Dk. Green 10.

1

AO-D 74 .

1

50.8 97.8 92 .

0

87.0 84.2 98. 9 98.6 Dk. Green 17.0

AP-A 82.2 80.4 98.7 95.2 90.2 97.4 99- 3 99. 3 Lt. Green 12.

3

AP-B 75.

5

87.

1

99.4 98 . 7 77.0 89.6 99.6 99.6 Lt. Green 6.4

AP-C 73-9 84.1 99. 5 98. 9 72.5 91.3 99-2 99.6 Lt. Green 6.2

AP-D 87 . 5 88. 9 99- 1 97. 1 88.0 95.2 99.2 99. 3 Lt . Green 10.0

AP-A 4 7.0 128.2 99.6 99.6 25.5 122.2 99.6 99.6 Lt. Green 4 . 4 AR-B 0.

0

96.

1

99. 4 98.8 0.0 81.7 99.6 99.6 Lt. Green 5. 5 AB-C C ; 0 105.9 99. 4 98 . 3 0.0 81.6 99. 5 99.4 L t . Green 8 . 1

AS -A 78 . 2

’ 59.9 98. 7 96.2 92.

1

93.0 99. 5 99.6 Gray 13.4

AS -B 83.7 86.4 98. 9 97. 3 82 .

5

84.6 99. 3 99.3 Bray 7.4

AS -C 92.5 97. 7 99.8 99 .

6

93.3 95.5 99. 8 99.6 Gray 5.4'

AT -A 75 .

2

93.8 99.0 97 . 4 71.

4

91.0 99-

1

99.3 Blue 6.2

A'T-B 79 .

8

93.4 98.6 94.9 90.9 95.

5

97. 9

' 97.8 Blue 7-0

AT-C 81 . 5 82.0 98. 7 96.2 82 .

0

84.o 99.0 98.

9

Blue 6.

1

AU -A P9.

1

89.

8

95- 3 99.

4

87.7 92.5 95.

7

95.7 Brown 5.3

AU-B 75.7 93.4 99.2 99.4 80.3 94.9 99.8 99. 7 Brown 7. 5 AU-C 87.4 94.7 99.8 99.6 91.4 97. 9 99.8 99.8 Brown 7.6

AW -A 81.4 80.

1

99.2 98.7 85.3 85.8 99.6 99. 5 Yellow 7.8

AW-B 78.8 79.2 99.3 97. 3 93.7 95.2 99.3 99. 3 Yellow 8.7

AW-C 72. 1 47.6 98; 9 95.9 91.

7

90. 3 99.4 99. 5 Yellow 18.6

AZ-A 100 .

9

50.

1

97.7 98.9 104. l 102.

1

98.9 99.

1

White 9. 5 AZ-B 94.2 110.

7

99.

1

97.8 99.

1

98.0 _ 98.8 98.8 White 5.2

Average 75.8 77.9 98.2 95.1 82.9 92.9 98.9 98.7
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Figure
Figure

4

.

Calibration

Curve

for

Hypot,

AC

Test

Equipment
asq.9W
Figure

6.

Effect

of

Humidity

on

the

Air

Gap

Voltage

-

AC

equipment

used
•X93-SW oa JCO o
Overvoltage

kV,

-

AC

Meter

I

Overvoltage, kV - DC Meter

Figure 8. Comparison of Overvoltages Necessary to

Puncture Virgin Enameled Specimens.