Perforation Corrosion Resistance of Several Coated Steels in Two Simulated Model Tests

Perforation corrosion resistance of several precoated steel sheets developed for automotive panels, have been evaluated in a hemmed portion model test and a lapped portion model test. Corrosion behavior at hemmed sections can be simulated by a simple hem model with thin electropaint film. Ni-Zn alloy electroplated steel sheet (30g/m²) and an organic composite coated steel sheet showed excellent perforation resistance than galvannealed steel sheet (60g/m²) and hot-dip galvanized steel sheet (135g/m²). In a lapped portion model test, there was not a large difference in perforation resistance between cold rolled steel sheet and zinc alloy plated steel sheets. Organic composite coated steel sheets showed excellent perforation corrosion behavior in this test too. The ranking of precoated steels in two tests was different from that in conventional flat panel test.