Metal Finishing Guide Book


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(ASTM B 368) solution as an electrolyte. The cell is placed onto the test specimen with a gasket to prevent leakage. A potential is applied between a platinum anode and the test specimen (cathode). As hydrogen is discharged from the cathodic sites (pores), alkalinity is developed, attacking the coating and decreasing the cell voltage. The decreasing cell voltage is integrated over time, yielding a comparative result. Weatherometer (ASTM G 23) This test is utilized to evaluate the performance of paint and lacquer systems under simulated outdoor exposure. The test yields data on the resistance of the coating system to condensation effects (rain) and the stability of the pigment in the paint (colorfastness) when exposed to sunlight. Intense ultraviolet radiation from twin carbon arc lamps and variant humidity levels (cycling from approximately 70 to 100% relative humidity) provide long-range test results in a short time frame (100-2,000 hr). Lactic Acid Lacquered brass- and copper-based alloys are tested for porosity and resistance to tarnishing by everyday handling (perspiration), using this test. Although not ASTM standardized, the procedure is gaining industrial acceptance. The principal mechanism is chemical attack. The procedure is as follows: 1. The item is dipped in a room-temperature solution of lactic acid (85%) saturated with sodium chloride. We Now Provide Contract Corrosion Testing Services 511

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