Abstract
The use of a cyclic corrosion tests, consisted of the salt spraying, wet and dry conditions, is desirable in the evaluation of the corrosion of automotive body panels in an accelerated manner.
Defining a wet % as a percentage of a wet period in a total test time, it is required to use the wet % of below 40 for the evaluation of the cosmetic corrosion resistance. This is a reasonable requirement when the corrosion of actual automotive bodies is considered.
In this experiment it was found that zinc coated sheets showed less blisters than cold rolled steel sheets and exhibited good cosmetic corrosion resistance at 40 wet %. When the wet % was above 70, significant blister occurred on the Zn coated sheets with the anodic Zn dissolution.
For the perforation corrosion the percentage of the wet period should be above 50 % since the corrosion proceeds in a wet condition. It was found that the high frequencies of a wet-dry cycle was effective to accelerate the corrosion and that zinc coated steels showed good perforation corrosion resistance.
