Hem Flange Evaluation of Corrosion Performance

Field or service testing is the best procedure for evaluating the corrosion resistance of any material. However, in the development of a new product, complete service testing and long atmospheric exposure are impracticial due to the time required to develop data. Historically, the accepted method for accelerated testing has been the ASMT-B117 Salt Fog Test. Unfortunately, many investigators have found that salt fog test results do not correlate with field performance. For example; a light weight electro galvanized steel would be unacceptable based on only salt fog results, while field experience shows it to be marginally acceptable for a three to five year period. With a goal of approximating the conditions inside a car door, an investigation was undertaken to modify the current exterior paint scab cycle test to more closely match actual field conditions. This paper will cover how we developed our cycle test and correlation of our results with actual automotive performance.