| 摘要 |
PROBLEM TO BE SOLVED: To provide a chromium-free surface-treated galvanized steel sheet superior in corrosion resistance, chemical resistance, thermal yellowing resistance, or the like in a planar section and also a section processed after alkali-degreasing treatment.SOLUTION: The galvanized steel sheet includes two-layered films consisting of: a chemical conversion undercoat film layer containing Zr and F by bringing a surface of the galvanized steel sheet in contact with a chemical conversion treatment agent (X) containing at least one kind of inorganic acid (Xb) selected from among hexafluorozirconate (Xa), hydrofluoric acid, and nitric acid, thereafter washing the surface thereof by water; and a finish coating film layer formed thereon, which is a water-dispersible polyurethane resin having glass-transition temperature 80°C or more and minimum film forming temperature of 40°C or less, and having a carboxyl group as a functional group, and is formed by bringing the undercoat layer in contact with a coating type treatment agent (Y) containing at least one kind (Ya) selected from polyether series and polyester series, water-soluble carbodiimide resin (Yb), an organic titanium compound (Yc), colloidal silica (Yd), and polyethylene wax (Ye) in a specified proportion. |
