| 摘要 |
PURPOSE:To form an oxide film with regulated color tone and improved strength by alternately applying anodic electrolysis and cathodic electrolysis to a chromium alloy under specified conditions in an aq. soln. consisting essentially of a chromium compd., and further applying cathodic electrolysis with higher current density. CONSTITUTION:The chromium alloy 20 and a counter electrode 22 are dipped in an aq. soln. 26 contg. a chromium compd. as the essential agent and sulfuric acid and opposed to each other. A current having 0.05-2A/dm<2> current density is passed from a constant-current power source 12 for >=1sec through a polarity changing switch 14, and anodic electrolysis and cathodic electrolysis are alternately applied to the chromium alloy 20 two or more times to form an oxide film on the surface of the chromium alloy 20. The color tone of the oxide film is regulated by changing the current density, processing time, and number of repetitions of the respective anodic and cathodic electrolysis. Cathodic electrolysis is further applied to the chromium alloy 20 with a current having 0.5-5A/dm<2> current density which is higher than the current density of the above-mentioned cathodic electrolysis to harden the oxide film.
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