Stainless steel panels with various surface finishes were exposed to winter salt and ash conditions on trucks and automobiles, salt atmosphere, industrial atmosphere, and rural atmosphere for periods of one to four years. They were also evaluated by six accelerated tests either presently used by, or proposed by, the automobile industry.
Comparisons of the average results of the multiple specimens were made in an attempt to determine the relative superiority among the grades of stainless and among the surface finishes in each exposure environment. Statistical correlation coefficients were calculated to determine the degree of corrosion resistance correlation among the sites and to determine the correlation between “in-service” corrosion and the accelerated tests.
No clear superiority of any grade in all environments could be determined. With the exception of chromium flash plating, no surface finish tested was significantly superior to any other. The automobile and truck exposures showed that the varying weather conditions from one winter to another could cause unpredictable, conflicting results. The correlation between corrosion resistance and temperature, snow-fall, and de-icing agents was not clear. The statistical correlation analysis conducted showed that very limited or no correlation exists between in-service corrosion and and accelerated tests. Even among the tests, the correlation was poor or not existent. This study indicates that none of the accelerated tests evaluated can be expected to predict stainless steel corrosion performance in service.