| 摘要 |
PURPOSE:To provide a zinc surface treated steel sheet having excellent corrosion resistance after painting by forming a specific Zn alloy plating layer on the surface of the steel sheet then forming further a specific Ni-Zn plating layer thereon. CONSTITUTION:The Zn or Zn alloy plating layer contg. >=80% Zn is formed as the 1st layer on at least one surface of the steel sheet. Zn-Ni plating, Zn-Fe alloy plating, etc. are preferable for such plating layer in which Fe, Ni, etc., are required to be incorporated at >=20% in total. Ni-Zn alloy plating contg. 16wt% or above and <=80% in total Ni and Co and/or Mn is formed at 0.5-5g/m<2> as the 2nd layer on the 1st layer. The Ni, Co or Mn is thereby eluted in a zinc phosphate treatment which is a treatment before painting. A zinc phosphate film taking the Ni, Co or Mn therein is thus formed in the stage of forming a zinc phosphate film and the corrosion resistance after painting is improved.
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