Metal Finishing Guide Book


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hours and remains at this level for the duration of the test cycle. One test cycle is 24 hours. A test can be run for as many cycles as are agreed upon between the purchaser and seller; however, the SO2 and water must be changed for each 24-hr cycle. The 24-hr test cycles are executed in one of the following ways: 1. Continuous — change of water and SO2 with as little disturbance as possible 2. Alternating Exposure — 8-hr exposure; drying in ambient for 16 hours with 20–30°C (68–86°F) and 75% relative humidity The variations differing from the B117 practice are that for this test method all test pieces be placed on the same horizontal plane and all test pieces in a given test run be of similar reactivity. NOTE: While adding corrosive gases may expedite degradation of the protective properties of the coating on the steel substrate, the purpose of the test must be 544

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