WATER-BASED RESIN COMPOSITION FOR METAL COATING USE, METHOD FOR TREATING METAL SURFACE AND SURFACE-TREATED STEEL PLATE

摘要

PROBLEM TO BE SOLVED: To provide a water-based resin composition for metal-coating use, suitable for the coating of metals, especially steel plate plated with aluminum- zinc alloy and having excellent fabricaility, corrosion resistance, weatherability and storage stability. SOLUTION: The water-based resin composition for metal-coating use contains hexa-valent chromium compound and a resin emulsion produced by the emulsion polymerization ofα,β-ethylenic unsaturated monomers. The monomers are composed of (1-a) an unsaturated monomer containing a cyclic hydrocarbon group and expressed by CH2=CR1R2 or CH2CR1COOR3, (1-b) a hydroxyl-containing unsaturated monomer and (1-c) otherα,β-ethylenic unsaturated monomer. The content of the monomer (1-a) in the above monomer mixture is 10-40 wt.% and the value obtained by dividing he hydroxyl value of the monomer mixture by the percentage of the monomer (1-a) is 0.5-2.