Paint delamination from electrocoated automotive steels during atmospheric corrosion. Part I. Hot-dip galvanized and electrogalvanized steel

—The mechanism of corrosion-induced paint delamination of electrocoated electrogalvanized and hot-dip galvanized automotive steels has been investigated. The materials were phosphated and electrocoated but not topcoated. The scribed panels were exposed to atmospheric conditions for 15 months. Two distinct regions were observed in cross-sectioned samples: a delamination zone without corrosion products which preceded a zone where the coating forms corrosion products, which consist largely of ZnO/Zn(OH)2. The mechanism of delamination is postulated to be mechanical in nature.