Corrosion and corrosion test methods of zinc coated steel sheets on automobiles

The effect of zinc and zinc alloy coated steel sheets on perforation corrosion in actual automobiles and the relevant accelerated corrosion test methods were studied. The main factor affecting corrosion in the crevice of lapped panels was the coating weights of zinc and zinc alloys rather than the type of coating. Perforation corrosion process of galvanized steel in the crevice of lapped portion in automobiles was divided in four stages. Based on the analysis of corrosion in actual automobiles, a Perforation Corrosion Index, PCI for lapped steel panels was proposed. Assuming PCI for various accelerated corrosion test methods, the corrosion resistance of various types of coated steel sheets in actual environments was evaluated.