| 摘要 |
PURPOSE:To obtain a uniform and fine brown color tone by pretreating a valve metal by pickling with a mixed aqueous soln. contg. hydrogen peroxide, hydrofluoric acid and nitric acid so as to prevent spot coloring. CONSTITUTION:A valve metal such as a titanium plate is pickled with a mixed aqueous soln. contg. 0.3-5wt% hydrofluoric acid, 0.1-13wt% nitric acid and >=5wt% hydrogen peroxide. The metal may be successively pickled with a dil. aqueous soln. contg. >=0.5wt% hydrofluoric acid and with a mixed aqueous soln. contg. 0.3-5wt% hydrofluoric acid, 0.1-13wt% nitric acid and >=5wt% hydrogen peroxide. The pickled metal is anodically oxidized to form a colored film. |
