Abstract: An aqueous surface treatment composition for coated steel sheet securing sufficient working adhesion while causing the formation of a surface treatment layer imparting excellent overhang corrosion resistance even without containing chrome, that is, a surface treatment composition containing a specific organic silicon compound, hexafluorometallic acid, a urethane resin having specific cationic groups, a vanadium compound, and an aqueous medium and sufficiently securing working adhesion while imparting excellent overhang corrosion resistance by the urethane resin having cationic groups and a total amine value of specific values is provided.

Abstract: The aluminum-zinc plated steel sheet according to the present invention includes a plated steel sheet and a covering film that covers the plated steel sheet. The covering film contains a basic compound of transition metal other than cobalt and chromium, and metallic cobalt, or metallic cobalt and a cobalt compound. An amount of the covering film per one side is within a range of 0.01 to 0.8 g/m2. An amount in terms of mass of transition metal other than cobalt in the covering film per one side of the plated steel sheet is within a range of 4 to 400 mg/m2. An amount in terms of mass of cobalt in the covering film per one side of the plated steel sheet is within a range of 0.1 to 20 mg/m2.

Abstract: An aqueous surface treatment composition for coated steel sheet securing sufficient working adhesion while causing the formation of a surface treatment layer imparting excellent overhang corrosion resistance even without containing chrome, that is, a surface treatment composition containing a specific organic silicon compound, hexafluorometallic acid, a urethane resin having specific cationic groups, a vanadium compound, and an aqueous medium and sufficiently securing working adhesion while imparting excellent overhang corrosion resistance by the urethane resin having cationic groups and a total amine value of specific values is provided.

Abstract: The aluminum-zinc plated steel sheet according to the present invention includes a plated steel sheet and a covering film that covers the plated steel sheet. The covering film contains a basic compound of transition metal other than cobalt and chromium, and metallic cobalt, or metallic cobalt and a cobalt compound. An amount of the covering film per one side is within a range of 0.01 to 0.8 g/m2. An amount in terms of mass of transition metal other than cobalt in the covering film per one side of the plated steel sheet is within a range of 4 to 400 mg/m2. An amount in terms of mass of cobalt in the covering film per one side of the plated steel sheet is within a range of 0.1 to 20 mg/m2.

Abstract: A surface-coated aluminum and zinc plated steel sheet in accordance with the present invention includes: a plated steel sheet; a composite coating film formed by applying an aqueous surface treatment agent on the plated steel sheet and drying the aqueous surface treatment agent. The aqueous surface treatment agent contains a water dispersible resin (A), a cobalt compound (B), and water, and has a pH within a range of 7.5 to 10. The composite coating film contains the water dispersible resin (A) and the cobalt compound (B). A percentage by mass of the water dispersible resin (A) in the composite coating film is 90% or more. A mass of the composite coating film per one surface of the plated steel sheet falls within a range of 0.5 to 3.5 g/m2.

Abstract: A surface-coated aluminum and zinc plated steel sheet in accordance with the present invention includes: a plated steel sheet; a composite coating film formed by applying an aqueous surface treatment agent on the plated steel sheet and drying the aqueous surface treatment agent. The aqueous surface treatment agent contains a water dispersible resin (A), a cobalt compound (B), and water, and has a pH within a range of 7.5 to 10. The composite coating film contains the water dispersible resin (A) and the cobalt compound (B). A percentage by mass of the water dispersible resin (A) in the composite coating film is 90% or more. A mass of the composite coating film per one surface of the plated steel sheet falls within a range of 0.5 to 3.5 g/m2.

Abstract: Disclosed is a surface-treated precoated metal sheet of which resistance against contamination with a photocatalyst and a self-cleaning function can be retained for a long period. Also disclosed are a method and a surface-treating solution for producing the surface-treated precoated metal sheet properly.