Corrosion characteristics of coated automotive parts subjected to field and proving ground tests

This project evaluated the corrosion damage over a five-year period of organic coated steels in automotive chassis parts during P/G and field tests using electrochemical impedance spectroscopy (EIS) in a 3.5 wt.% NaCl solution. EIS can provide both quantitative kinetic and mechanistic information about the performance of organic coating/metal systems. The difference in coating performance between the P/G and field test specimens was assessed in relation to the impedance parameters. In particular, it was found that the coating resistance and charge transfer resistance could be used to estimate the difference in corrosion damage between the P/G and field test specimens. The coating performance of the P/G and field test specimens was visually evaluated using SEM. The mechanism of corrosion occurring in the P/G test was similar to that taking place in the field test. The field test environment was about ten times as corrosive as the P/G environment in terms of the electrochemical impedance parameters and surface analysis.