Wednesday, July 8, 2009

Electroplating of Alloys

Electroplating of alloys sometime difficult to plate because its composed from different other metals. By using two or more metals can, with some difficulty, be electroplated simultaneously to give a mixed metal coating. The properties and appearance of such a mixture are, however, often different from that of the metallurgical alloy, which, having been melted, has come into metallurgical equilibrium.

Brass is electroplated from a mixed copper and zinc cyanide solution, and gold alloys from mixed cyanide solution of gold with copper, silver, zinc or nickel. The objective is usually to obtain a tin plating of a particular color for purely decorative purposes.

Bronze (copper-tin), speculum alloy (copper-tin) and tin-zinc alloys can be electroplated to achieve some of the advantages of each constituent, chiefly good corrosion protection with maintenance of appearance; control is difficult however. A true inter-metallic compound of tin and nickel can be electroplated. This has unique properties although rather dark, it is relatively untarnishable and gives good metal protection.

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