An Evaluation and Analysis of Commonly Used Accelerated Cosmetic Corrosion Tests Using Direct Comparisons with Actual Field Exposure

Direct comparisons of scribe creepage measurements were made between accelerated cosmetic corrosion tests and 2 year field exposure results from St. John's Newfoundland. Test acceleration rates were calculated for each of the ten AISI materials and their correlation with the field exposure was determined. Comparisons are made using twelve different cyclic corrosion tests, 3 laboratory environmental; 2 highway trailer and 3 proving grounds tests. All of the tests that were investigated accelerated the zinc-coated steels at a higher rate than cold rolled steel. The range of the higher acceleration was from 1.4 up to 110 times the field rate. The most favorable tests were the two outdoor scab tests at sea coastal sites, two proving grounds test cycles and a highway trailer test. The laboratory test with the most favorable response was the GM 9450 P, Method B cyclic corrosion test. Environmental conditions of the tests were analyzed for common features to understand the factors which have the most influence upon the acceleration rate of zinc-coated and cold rolled materials. Suggestions for modifying these cosmetic corrosion tests to obtain a more equal acceleration rate are given.