Surface-treated steel sheet excellent in corrosion resistance, conductivity, and coating appearance

摘要

A surface-treated steel sheet includes a steel sheet; a plating layer containing at least one metal selected from zinc and aluminum; a first layer film containing (alpha) 1 to 2000 mg/m² of silica in terms of SiO₂, (beta) a total of 1 to 1000 mg/m² of phosphoric acid groups in terms of P, (gamma) a total of 0.5 to 800 mg/m² of at least one metal selected from Mg, Mn, and Al, and (delta) 0.1 to 50 mg/m² of a tetravalent vanadium compound; and a second layer film formed to a thickness of 0.1 to 5 mum on the first layer film and containing a resin (A) having at least one type of functional group selected from OH and COOH groups, and at least one rust-proofing additive (B) selected from (a) a phosphate, (b) Ca ion-exchanged silica, (c) a molybdate, (d) silicon oxide, and (e) at least one organic compound selected from triazoles, thiols, thiadiazoles, thiazoles, and thiurams.