Metal Finishing Guide Book

2012-2013

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trolyte). The fog is created by atomizing ASTM D1193 Type IV water without any salt whatsoever. This test method is used to gauge the life expectancy of coating systems by measuring their resistance to water penetration. ASTM D2247 ��� Standard Practice for Testing Water Resistance of Coatings in 100% Relative Humidity The ASTM D2247 Standard is used to investigate how a coating resists water, which can help predict its useful life. This is generally a pass/fail test; however, the time to failure and degree of failure can be measured. A coating system typically passes if there is either no sign of water-related failure after the specified test period or less than an established specified amount of failure. For the ASTM B2247 Standard the ASTM D1193 Type IV water is placed in the bottom of the exposure zone to a depth of 6 to 8 in. and then heated. The area of the exposure zone above the water is not heated directly in order to cause condensation on the test pieces. The water is introduced into the chamber before the test pieces and maintained at a temperature approximately 5 to 10��C (10���20��F) higher than the temperature of the vapor above it. The major variation in the chamber is the elimination of the fogging tower. The 100% humidity results from the vaporization of the heated water in the bottom of the chamber and/or having heatFig. 4. Humidity test chamber schematic drawing. ed humidified air pumped through the water. The humidifying tower is used when the option of having air pumped through the heated water is chosen. The exposure zone is maintained at 38�� �� 2��C (100�� ��4��F) and 100% relative humidity. This test method is performed in water-jacketed chambers (see Fig.2) with the 6 to 8 in. of water mentioned above in the bottom of the exposure zone and the water jacket filled to 12 in. above the bottom to ensure that the immersion heaters are submerged. It can also be run in larger chambers, such as walk-in or drive-in size units (see Fig. 3), equipped with heated water tanks in the exposure zone to generate the required humidity. A primary concern when conducting the ASTM D2247 test is that the chamber be sufficiently insulated. Figure 4 is a schematic of a typical ASTM D2247 humidity test chamber configuration. To ensure that the ASTM D2247 test is being performed consistently, it is recommended that a control test piece with known durability be included in each test run. ASTM B368 ��� Standard Test Method for Copper Accelerated Acetic AcidSalt Spray (Fog) Test (or CASS Test) The ASTM B368 Standard, originally developed by the National Association for Surface Finishing (NASF), is used primarily in the development of coated metal products, including decorative coatings, which will be exposed to severe service and more corrosive environments and also to evaluate the performance and protective properties of more durable coatings which would not be affected by 595

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