| 摘要 |
PURPOSE:To obtain a corrosion-resistant steel sheet for automobile with excellent corrosion resistance, weldability, processability, etc., by providing specified Zn-Co alloy plating layer, chromate-treated layer and protective resin film layer in this order on the surface of a steel sheet. CONSTITUTION:Both corrosion resistance, weldability and processability which are sufficiently satisfactory as a corrosion-resistant steel sheet for automobile are provided by placing 10-45g/m<2> Zn-Co alloy plating layer with a Co content of 3-15%, a chromate-treated layer with a Cr content of 30-300mg/m<2> and 0.3-25mum protective resin film layer in this order. In this case, the chromate- treated layer is formed by using either a chromate treating liq. contg. either or both a silane coupling agent with 0.01-fold or more unreduced chromic acid by molar ratio or/and one or more of a polyhydric alcohol, a polybasic carboxylic acid and an oxycarboxylic acid with 0.01-2.0-fold unreduced chromic acid by molar ratio or a chromate treating liq. contg. an insoluble chromic acid pigment with 0.1-1-fold of the whole chromic ions. |
