Humidity tests, cyclic ASTM

ASTM G 60, Test Method for Conducting Cyclic Humidity Tests... 

Alternative atmospheric cabinet simulation tests are available, including ASTM G 87, Practice for Conducting Moist SO2 Tests and ASTM G 85, Practice for Modified Salt Spray Testing. Service in environments where humidity or moisture varies may be simulated by cyclic humidity or alternate immersion tests. See ASTM G 60, Test Method for Conducting Cyclic Humidity Tests and ASTM G 44, Practice for Exposure of Metals and Alloys by Alternate Immersion in Neutral 3.5 % Sodium Chloride Solution. 

Organic coatings are commonly evaluated using salt water immersion, salt fog or spray, modified salt exposure tests (e.g., salt fog with added SO2), and various cyclic exposure tests. Humidity exposure and water immersion, and, for many applications, physical resistance tests (adhesion, impact resistance, etc.) are widely used preliminary tests. Standard methods for most of these tests are given in compilations of standard tests such as the Annual Book of ASTM Standards (16). Test methods have been extensively reviewed (e.g., 17-23). 

Applicable test methods include [28] Continuous Salt Spray Tests (ASTM B 117), Neutral Salt Spray Test (ASTM B 117), Acetic Acid Salt Spray Test, Copper-Accelerated Salt Spray Test (CASS) (ASTM B 368), Cyclic Salt Spray Tests, the Copper Development Association (CDA) Test, the Hitachi Salt Spray Test, Climate Tests, The Humidity Test, The International Electrotechnical Commission/Intemational Organization for Standardization (lEC/ISO) Test and Mud Test. 

Lab exposure—cyclic corrosion test (CCT-IV) This is a cyclic test method, consisting of three environments salt spray (per ASTM B 117), diyoff (60 °C, or 140 °F, ambient relative humidity), and high-humidity (60 °C, 95% relative humidity). Salt spray was tqtplied for 10 min, followed by 155 min at d off, followed by 75 min of humidity. Five repetitive cycles of 160 min dryoff and 80 min humidity complete the 24 h cycle. Exposure time was 50 cycles (5 cycles per week, weekends at ainbient). Results are shown in Fig. 3(f). 

Another variation of the immersion test is the cyclic test procedure where a test specimen is immersed for a period of time in the test environment, then removed and dried (either air diy or use of heat lamps), then re-immersed to continue the cycle. Normally hundreds of these cycles are completed during the course of the test program. In ASTM G 60, test specimens are dipped in a test solution before being exposed to atmospheres varying in relative humidity. The intent of the test is to develop a layered corrosion product similar to that found on sheltered outdoor exposure test specimens. These tests can be either manually performed or conducted in apparatus equipped for automatic cycling. 

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