| 摘要 |
<p>Electrodeposition of a hard, bright, ductile gold alloy having a white coloration, useful for decorative purposes, is effected using an aqueous cyanide-free electroplating bath essentially comprising:… (a) from 4 to 20 g/l of gold,… (b) from 0.2 to 5.0 g/l of palladium,… (c) from 0.1 to 3.0 g/l of copper,… (d) from 5 to 200 g/l of free sulphite ion,… (e) from 0 to 150 g/l of one or more buffering agents and/or conducting salts, and… (f) water. The bath has a pH in the range from 7 to 10.5, preferably about 9.5 and electrodeposition of the white alloy can be carried out at a cathode current density of from 0.25 to 1.25 amp/dm<2> and a temperature of 50 to 65 DEG C., preferably with moderate agitation of the cathode during the electroplating process The white alloy will normally contain, on a parts by weight basis, 85-95 gold, 3-10 palladium and 2-5 copper, the palladium always being present in a larger amount than the copper. …<??>Such a bath is not as susceptible to colour stability problems as conventional cyanide-based electroplating baths for producing white gold electrodeposits.</p> |
