Outdoor Exposure Test on Prepainted 55 percent Al-Zn Coated Steel Sheet Subjected in 15-year

摘要

We carried out a 15-year outdoor exposure test to investigate the corrosion behavior of prepainted 55 percent Al-Zn coated steel sheet in comparison with prepainted galvanized steel sheet. The edge creep of prepainted 55 percent Al-Zn coated steel sheet is larger than that of prepainted galvanized steel sheet in the early stages of the exposure test. However, the progress of edge creep of prepainted 55 percent Al-Zn coated steel sheet slows down year after year then stopps, while that of prepainted galvanized steel sheet remains almost constant. The edge creep widths of both sheets were almost the same at 6 to 8 years. After that point, the edge creep width of prepainted 55 percent Al-Zn coated steel sheet was smaller than that of prepainted galvanized steel sheet. Also, the scribed part and T-bend part of prepainted 55 percent Al-Zn coated steel sheet shows better corrosion resistance than those of prepainted galvanized steel sheet. The effect of pretreatment and primer on the corrosion of prepainted 55 percent Al-Zn coated steel sheet was not clearly noticed.