| abstract |
A resin-chromate composition mainly comprising an emulsion of (a) an organic polymer composed of ethylenically unsaturated compounds in an aqueous medium, (b) a water-soluble chromium compound, and (c) a mineral acid, characterized in that the content of (a1) ethylenically unsaturated carboxylic acid components constituting the organic polymer (a) is more than 10 wt.% but below 30 wt.% based on the weight (in terms of solid matter) of the organic polymer (a), that of (a2) ethylenically unsaturated hydroxylated compound components constituting the polymer (a) is 0 wt.% or above but below 3 wt.% based thereon, and the balance is composed of (a3) ethylenically unsaturated compound components bearing neither carboxyl nor hydroxyl groups and that the content of components forming C 3 -C 7 monocarboxylic acids in an aqueous solution of chromic acid and/or a chromate coat is 20 wt.% or below based on the weight (in terms of solid matter) of the organic polymer; and a metal sheet surface-treated with this composition. The above chromate composition is excellent in bath stability and smelling characteristics and the metal sheet surface-treated with the composition does not produce any putrid smell and is excellent in corrosion resistance, prevention of leaching of chromium, resistance to alkali, adhesion of paint, and appearance and quality. |