| 摘要 |
PURPOSE:To obtain a surface-treated steel plate with superior adhesive strength to paint after degreasing by treating a Zn plated steel plate with chromating soln. contg. specified amounts of chromic acid having a specified ratio between Cr<3+> and Cr<6+>, water-soluble acrylic resin and a mineral acid, washing the treated plate in water, and treating it with an org. resin soln. CONSTITUTION:A steel plate plated with Zn, a Zn alloy or Al is degreased and treated with a chromating soln. contg. 3-30g/l chromic acid having 1/1- 1/5 ratio of Cr<3+>/Cr<6+>, 0.1-5g/l water-soluble acrylic resin and a mineral acid. The treated plate is washed in water and subjected to sealing treatment with an org. resin soln. Polyacrylic acid or the like is used as the water-soluble acrylic resin, and acrylic resin as the org. resin. Sulfuric acid, nitric acid, phosphoric acid or hydrofluoric acid is used as the mineral acid, and the concns. of the acids are about 0.5-3g/l, 1-30g/l, 0.3-3.0g/l and 0.1-1.0g/l expressed in terms of SO4, NO3, PO3 and F, respectively. |
