| abstract |
An object of the present invention is to provide a surface-coated aluminum-containing zinc-plated steel sheet which is excellent in corrosion resistance, alkali resistance, blackening resistance, slip resistance and weather resistance and has good outgassing properties due to its appearance hardly deteriorated by forming or the like. A water-based metal surface treatment agent is applied to the surface of an aluminum-containing zinc-based plated steel sheet and then dried to coat a composite film formed by drying. The water-based metal surface treatment agent comprises a polyester polyurethane resin (a) having a structural unit derived from a polyester polyol in the molecule, and a polymer unit derived from a (meth) acrylic acid ester having an alicyclic structure in the molecule, α, β A water-dispersible acrylic resin (b) comprising a polymer containing a polymerized unit derived from an ethylenically unsaturated carboxylic acid and a polymerized unit derived from another (meth) acrylic acid ester, a zirconium compound (c), and hindered amines (D), plasticizer (e) and water. In the composite coating, (a) / (b) is 69/31 to 40/60. [Selection figure] None |