| 摘要 |
PURPOSE:To reduce the cost by forming under plating and surface plating each having a specified composition and a specified amount of deposition while interposing intermediate plating which is nobler than the surface plating and has a specified amount of deposition to improve the corrosion resistance of a steel material. CONSTITUTION:A film having a three-layered structure consisting of under plating 1, intermediate plating 3 and surface plating 2 having different functions, is formed on a steel material S. The under plating 1 is made of a Zn-Fe alloy contg. 5-30wt% Fe, and the amount of deposition is 5-100g/m<2>. The surface plating 2 is made of an Fe-Zn alloy contg. 5-40wt% Zn, and the amount of deposition is 0.2-6g/m<2>. The intermediate plating 3 is made of Ni which is electrochemically nobler than the plating 2, and the amount of deposition is 0.05- 5g/m<2>. |
