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In this work, the corrosion performance of stainless steel materials for application in the automotive industry has been evaluated by means of on-vehicle testing and laboratory cyclic corrosion tests. Additional laboratory measurements have also been performed in well defined exposure conditions. The results indicate that no cosmetic corrosion was observed upon on-vehicle exposures after 2 years exposure in Sweden and Germany and 5 years exposure in France. Cyclic corrosion tests were also performed in order to assess the corrosion resistance of different stainless steel grades. The results indicate large discrepancies in corrosion resistance when comparing the different cycles. This is explained by differences in chloride deposition, wet/dry cycle condition and way of deposition of the pollution on the samples.

The use of cyclic corrosion tests which consist of salt spraying, humidifying, and drying phases is desirable in the evaluation of the corrosion performance of automotive body panels. In this work, coupons of zinc-coated steel and of cold rolled steel were exposed to a defined cyclic corrosion test (CCT) which has shown to be suitable for simulating diverse outdoor conditions for evaluating the cosmetic corrosion of precoated steel. Micro-environment data in the gap of lapped panel specimens, such as wetness, corrosion rate of test materials, pH value, chloride content, have been obtained during the CCT test. The galvanic current flowing between a gold electrode and the test materials was measured to monitor the degree of wetness inside the crevice. The results show that the surface of the test materials never became really dry even during the dry period of the CCT cycle. Furthermore, the wetness during wet and dry periods in the crevice increased with increasing number of CCT cycle.