CHEMICAL CONVERSION COATED PLATED STEEL SHEET AND METHOD FOR PRODUCING SAME

摘要

Disclosed is a chemical conversion coated Zn-plated steel sheet which has excellent weather resistance, water resistance, blackening resistance and coating film adhesion. Specifically, a chemical conversion coating liquid is applied over and dried on the surface of an Al-containing Zn alloy-plated steel sheet, thereby forming a chemical conversion coating film that has a film thickness of 0.5-10 µm. The chemical conversion coating liquid contains: a fluorine-containing resin, which contains 7-20% by mass of F atoms and 0.05-5% by mass of hydrophilic functional groups that are selected from among a carboxyl group, a sulfonic acid group and salts of carboxyl group and sulfonic acid group and has a number average molecular weight within the range of 1,000-2,000,000; and an oxygen acid salt, fluoride, hydroxide, organic acid salt, carbonate or peroxygenated salt of a group 4A metal. The amount of the oxygen acid salt, fluoride, hydroxide, organic acid salt, carbonate or peroxygenated salt of a group 4A metal relative to the fluorine-containing resin in the chemical conversion coating liquid is within the range of 0.1-5% by mass in terms of the metal.