| 摘要 |
A process for electrolytically colouring an anodized piece of aluminium or aluminium alloy, comprising the co-deposition of at least a metal salt.
<??>The process is characterized in that it comprises the following steps:
a) electrolitically treating the piece, in absence of the metal salts, in an electrolyte of low dissolution capacity and exhibiting a chemical activity inferior to the activity equivalent to a concentration of 4 g:l of H2SO4, by applying an alternating current having a peak voltage preferably of 55 to 85 volts and a current density of less than 0,3 Amp/dm<2>, which alternating current is derived from a polyphase network or from the secondaries of a transformer of a polyphase network; in such a manner that that the positive and negative half-cycles are made to conduct with the same angle of conduction and both being variable according to the necessities, and a cycle of the first phase is followed by the second consecutive cycle of the second phase and by the third consecutive cycle of the third phase and soon until the number of phases is completed, thus balancing the distribution of the charges between the phases of the polyphase supply system; and
b) electrolitically colouring the treated piece in an acid electrolyte containing the metal salt(s), using alternating current with a peak voltage preferably from 55 to 85 volts derived from the same source as the corresponding alternating currente applied in the preceding step. |
