| 摘要 |
PURPOSE:To improve the corrosion and pitting resistances of a steel sheet for an automobile body at the worked part by preplating the steel sheet with Mn and plating it with a Zn-Ni alloy having superior corrosion resistance. CONSTITUTION:A steel sheet for an automobile body is preplated with Mn to form an Mn layer of 0.1-1mum thickness and it is plated with a Zn-Ni alloy contg. 9-16wt% Ni and having superior corrosion resistance. At this time, a very small amount of a metal nobler than Mn, e.g., Zn or Fe may be incorporated into the Mn layer or one or more kinds of metals such as Co, Cr and Fe may be added to the Zn-Ni alloy layer so as to further improve the corrosion and pitting resistances of the steel sheet at the worked part.
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