| 摘要 |
PURPOSE:To obtain a steel material having high blackness, superior corrosion resistance, workability and weldability at a high line speed by cathodically electrolyzing a steel material at a proper current density in an electrolytic soln. contg. specified amounts of Zn<2+>, Ni<2+>, SCN<-> and NH4<+>. CONSTITUTION:A steel material is cathodically electrolyzed at 40-200A/dm<2> current density in an electrolytic soln. contg. 5-25g/l Zn<2+>, 5-63g/l Ni<2+>, 3-25g/l SCN<-> and <=100ppm NH4<+>. The steel material is then chromated as required to form a chromate film by 5-100mg/m<2> (expressed in terms of Cr) and/or it is coated with a water-dispersible or water-soluble resin and/or silica sol by 0.3-3g/m<2> on dry basis as required. Thus, a blackened and surface treated steel material having high blackness is obtd. The black layer of the steel material has superior adhesion. |
