| 摘要 |
PURPOSE:To form a surface treated coat having high naked corrosion resistance and leaching out no Cr on the surface of zinc or zinc alloy by applying an acidic aqueous soln. contg. an aqueous Cr compound contg. traivalent Cr, SO4<2-> and a polycarboxylic acid resin as principal components to the zinc or zinc alloy surface and further coating the surface with an olefin resin. CONSTITUTION:A Cr-contg. aqueous soln. of <=3.5pH is applied to the surface of zinc or zinc alloy. The soln. contains 1-100g/l aqueous Cr compound having Cr<3+>/total Cr of <=50, especially 20-35wt% which is obtd. e.g. by the partial reduction of Cr2O3, 0.2-2.0g/l SO4<2-> and a 0.02-30g/l polycarboxylic acid resin such as polyacrylic acid as principal components. The resulting film is washed, and an aqueous soln. contg. an olefin resin contg. carboxyl groups as a principal component is applied to the film and dried to form a 0.2-1mum thick coat. Said olefin resin contains 5-30% carboxyl groups >=50% of which have been neutralized. |
