Pre-painted steel sheet goes through forming processes after painting. Therefore, the paint adhesion at deformed parts and the corrosion from the edges are serious problems. To avoid these problems, the conventional pre-painted steel sheet is treated including the six-valent chrome. However, the demands for the chromate free pre-painted steel sheet are increasing recently from the viewpoint of environmental issues. Therefore, we have developed the chromate free pre-painted steel sheet exhibiting high corrosion resistance. This product has good paint adhesion in the various forming ways such as bending, drawing and press forming. Furthermore, it has high corrosion resistance in the outdoor exposure test. It is concluded that the newly developed product can replace the conventional product.
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