Car body corrosion in North America and Canada caused by de-icing salt is classified into cosmetic corrosion and perforation. The cosmetic corrosion starts from paint defects or damages of the outer panel, and brings about rust formation and paint exfoliation. It can well be simulated by a cyclic corrosion test (CCT), which is a combination of salt spray, drying, humidifying and freezing. Zinc plated sheet exhibits much better performance in CCT than cold sheet, although it gives a poor paint adhesion in salt spray test (SST). There is a difference of the underfilm corrosion mechanism between CCT and SST. Nowadays several types of zinc coated steel are widely used for car body.
