| 摘要 |
PROBLEM TO BE SOLVED: To improve the pitting corrosion resistance after electrodeposition coating of a galvanized steel sheet used for an automotive body in particular. SOLUTION: On the surface of a steel sheet, a galvanized layer of 20 to 60 g/m2 coasting weight per surface and a zinc phosphate film of 0.5 to 3.0 g/m2 coating weight per surface are successively formed in layers, in the zinc phosphate film, Mg is contained by 0.5 to 10.0 mass %, Ni by 0.1 to 2.0 mass %, and Mn by 0.5 to 8.0 mass %, and also, the contents of Mn and Ni sastisfy the inequality of [Ni]×7.6-10.9<=[Mn]<=[Ni]×11.4, where [Mn] denotes Mn mass %, and [Ni] denotes Ni mass %.
|
