| 摘要 |
PURPOSE:To obtain a surface-treated steel sheet having a uniformly stuck very thin chromate film by treating a steel sheet coated with a corrosion resistant metal in an acidic aqueous soln. having a proper concn. and by carrying out chromating. CONSTITUTION:A steel coated with one or more kinds of metals selected among Sn, Zn, Pb, Ni and Al is immersed in an acidic aqueous soln. of H2SO4, HCl or the like having 0.02-40% concn., or the sheet is electrolyzed in the soln. By the treatment, oxides on the surface of the metallic film are dissolved and removed to activate the surface of the coated steel sheet. The activated surface is then chromated by a conventional method. A chromate film can be uniformly stuck to the surface-treated steel sheet, and characteristics necessary for a steel sheet after surface treatment such as corrosion resistance, adhesive strength to paint and fine appearance are stably provided. |
