SURFACE-TREATED STEEL SHEET

摘要

PURPOSE:To improve the adhesion of a surface-treated steel sheet to paint and the corrosion resistance in the naked state by successively forming a reactive chromate film and an electrolytic chromate film each contg. a specified amt. of Cr stuck on the surface of a Zn or Zn alloy plated steel sheet. CONSTITUTION:A reactive chromate film contg. 3-200mg/m<2> Cr as an underlayer is formed on the surface of a Zn or Zn alloy plates steel sheet to render satisfactory corrosion resistance. An electrolytic chromate film contg. 10-200mg/m<2> Cr is further formed to render superior adhesion to paint as well as to improve the corrosion resistance in the naked state.