| abstract |
A water-based coating composition for the surface treatment of metallic materials which contains a cationic water-compatible urethane resin excellent in chemical resistance, non-corrosive properties, solvent resistance, and adhesion. The cationic water-compatible urethane resin (F) is obtained by subjecting a cationic urethane prepolymer (D) to chain extension with water or a polyamine compound (E), the prepolymer (D) being one obtained by neutralizing with an acid or quaternizing with a quaternizing agent the tertiary amino groups contained in a urethane prepolymer obtained from constituent elements comprising a compound (A) having two or more active hydrogen atoms, an organic polyisocyanate (B), and a chain extender (C) having a tertiary amino group. |