PURPOSE: To improve the corrosion resistance of the fully joined part while the coating suitability is secured by interposing the upper Zn-Cr composite plated layer of a specific amount of content of Zn or Cr between the main Zn-Cr composite plating layer and the film of phosphate crystal.
CONSTITUTION: The Zn-Cr composite plated-steel sheet excellent in corrosion resistance is provided with the main Zn-Cr composite plated layer where the coating weight formed on the surface of the steel sheet is 5-40g/m2, and the Cr content is 1-30wt.%, the upper Zn-Cr composite plated layer which is formed on this Zn-Cr composite plated layer and where the coating weight is 0.5-3g/m2 and the content of Zn-Cr is ≤1wt.%, and the phosphate crystal film which is formed on the upper Zn-Cr composite plated layer, and where the coating weight is 0.5-3.0g/m2.
ABE MASAKI
URAKAWA TAKAYUKI
WATANABE TOYOFUMI
