| 摘要 |
PURPOSE:To form a black chemical conversion coating suitable for use as an underlayer for painting on the surface of Al by bringing the surface into contact with an aqueous soln. contg. specified amounts of a chromate, Na2CO3, NaOH and triethanolamine, drying the treated surface, and bringing it into contact with the soln. again. CONSTITUTION:The surface of Al or an Al alloy is brought into contact with an aqueous soln. contg. essentially 5-25g/l chromate such as Na2Cr2O7, 20-70g/l Na2CO3, 3-10g/l NaOH and 2-5g/l triethanolamine at 90-95 deg.C for about 1-2min to form a film of about 0.5-1.0mum thickness. The treated surface is well dried with hot air or the like and brought into contact with the soln. again at 80-95 deg.C for about 3-10min. Thus, a black chemical conversion coating of about 3-5mum thickness having a prescribed color tone is formed continuously and uniformly. The film has high adhesion to the metallic base and is suitable for use as an underlayer for painting. |
