Fifteen-year exposure test of porcelain enamels

Abstract

Changes in gloss and color were taken as criteria of weather resistance. A direct relation existed between acid resistance and weather resistance, except that a few of the red enamels of good acid resistance showed a pronounced fading after exposure. A modified acid-resistance test w r as devised that separated red enamels that showed pronounced fading from those that were highly resistant to color change. The ease of cleaning was related to the weather resistance, the enamels that lost most of their initial gloss on weathering being more difficult to clean than those that showed high gloss retention. All of the enamels protected the steel from corrosion when initial coverage was complete. Except for a relatively few enamels, variations in climate at the four exposure sites had only a minor effect on their weathering behavior.

Weather resistance of porcelain enamels

“…The regular enamels include all the enamels on steel, except the 1000°enamels, while the low-temperature enamels include the enamels on aluminum, both mat and glossy, and the 1000°enamels on steel. The regular enamels were found to follow the same pattern, with respect to weathering, as those reported by Moore and Harrison [3] . The weatherability of these enamels can be predicted reasonably well by two relatively simple laboratory tests: The 7-year results confirm the 3-year findings that acidic pollutants and moisture in the atmosphere affect the rate at which an enamel weathers.…”

“…With Those Produced Before World War II Table 7 compares the gloss retention values of the regular mat and glossy enamels on steel exposed 7 years at Washington, in both the present test and in a test initiated in 1939 [3] . This comparison shows that there is only a two-percent difference in the average gloss retained between the enamels in the two tests.…”

“…The weather resistance of porcelain enamels is important to architects and engineers who have the responsibility of selecting exterior finishes for various types of buildings, as well as to owners who are interested in obtaining a long, mainte- An investigation started at that time resulted in a series of reports issued after exposure periods of 1 [1],** 7 [2], and 15 [3] years. The principle finding of that investigation of porcelain enamels on steel, was that the best enamels showed no objectionable changes in either gloss or color at any of Junior and Senior Research Associate, respectively, for the Porcelain Enamel Institute at the National Bureau of Standards.…”

Effect of exposure site on weather resistance of porcelain enamels exposed for three years

“…It cannot be stated with certainty that those enamels that show good resistance to weathering at 3 yr will also be good at 20. However, from the results of the 15-yr study [2], it seems probable thai (here will be very few deviations from the observed pattern with continued testing.…”

“…[10] Tables 5 and 6 show that the sea spray conditions at the Kure Beach-80 ft site are especially severe on the aluminum enamels, the screeningpaste steel enamels, and the class B 1,000°F steel enamels and it is mostly because of this severity that the averages given in The mat aluminum enamels, as a group, show the second best color retention of all of the enamel types (table 8), and some of the glossy aluminum enamels showed good stability at some sites. A recent paper by Sopp, Wallace, and Picker [12] gives the color change of three glossy green aluminum enamels after about 3 [2,12,13,14] Thus, on the basis of short -time tests only, these two enamels might be considered as suitable for architectural use even though they fail the citric acid spot-test requirement of the architectural specification [10]. However, because there is usually a lack of exact knowledge as to severity of conditions at a proposed building site, and also because the producer does not always know where his product will be used, the safest approach might be to consider as architectural enamels only those compositions that give the best resistance to all types of weather conditions.…”