| 摘要 |
A process is applied for the production of colored, protective coatings on articles of aluminum or aluminum alloys by passing an alternating current between a previously anodically oxidized aluminum article and a counter-electrode immersed in an acid aqueous bath containing salts of metals capable of coloring the aluminum oxide layer, the alternating voltage supplied being modulated as to its amplitude and/or frequency so as to make it asymmetrical thereby to control the color tone on the aluminum article. The asymmetrical voltage may be produced, for example, by supplying two or more alternating voltages of different amplitude, frequency and/or phase, or by using a direct voltage superimposed on the alternating voltage.
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