| 摘要 |
PURPOSE:To obtain a plated steel sheet having superior suitability to chemical conversion treatment and superior pitting corrosion resistance by plating Zn-Ni alloy layers formed on both sides of a steel sheet, by plating with a Zn-Fe alloy having a specified composition, and by further plating one of the layers with a Zn-Fe alloy having a specified composition. CONSTITUTION:A three-layered film consisting of a Zn-Ni alloy layer as the 1st layer, a Zn-Fe alloy layer contg. 60-90wt% Fe as the 2nd layer and a Zn-Fe alloy layer contg. <60% Fe as the 3rd layer is formed on the outside of a steel sheet by electroplating. The amount of the 3rd layer deposited is 0.1-3g/m<2>. A two-layered film consisting of a Zn-Ni alloy layer as the 1st layer and a Zn-Fe alloy layer contg. >=60% Fe as the 2nd layer is formed on the rear side of the steel sheet by electroplating. Thus, a multiply electroplates steel sheet suitable for the outer plate of an automobile is obtd. The triply plated outside of the steel sheet has superior suitability to chemical conversion treatment and painting by electrodeposition, superior water resistance, adhesion and corrosion resistance after painting. The double plated rear side has superior pitting corrosion resistance.
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