PURPOSE:To obtain a surface treated steel sheet for a car with superior corrosion resistance before and after coating and superior press workability by electroplating a steel sheet with a Zn-Fe or Zn-Fe-P alloy having a specified composition and an electrochemically single phase. CONSTITUTION:A steel sheet is electroplated with a Zn-Fe alloy contg. 7- 35wt% Fe and having an electrochemically single phase or a Zn-Fe-P alloy prepd. by adding 0.0003-0.5wt% P to the Zn-Fe alloy to obtain a surface treated steel sheet. Since the resulting alloy layer has said specified Fe content and an electrochemically single phase, the surface treated steel sheet has superior corrosion resistance before and after coating as well as superior suitability to welding, working, chemical conversion treatment and coating, and it also has superior pitting resistance especially at joined part.
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