Corrosion Mechanisms in Bright Stainless Steel Trim Systems

Exterior automotive trim materials are exposed to aggressive environments and therefore must have satisfactory corrosion resistance. Stainless steel materials such as bimetal (stainless steel clad aluminum) are therefore used extensively in this application. This paper addresses the effect of surface contamination on the corrosion behavior of stainless steels which have been fabricated with the application of a PVC polyfilm protector. The effect of residual deposits on the stainless steel has been investigated using CASS and cyclic immersion corrosion tests, Auger analysis, and gas chromatography coupled with Fourier Transform Infrared Analysis (FTIR). The mechanism of reduced corrosion resistance attributed to these residual deposits is described.