A NOVEL METHOD OF DECORATIVE CHROMIUM PLATING FROM TRIVALENT CHROMIUM

摘要

A NOVEL METHOD OF DECORATIVE CHROMIUM PLATING FROM TRIVALENT CHROMIUMThis invention provides a novel method to bind and to stabilise trivalent chromium ions inthe plating process by using two kinds of suitable complexants selected from carboxylicacids or their salts. Complexant I is selected from the group containing either amino-substituted carboxylic acids and their salts, or the unsubstituted carboxylic acids and theirsalts. Complexant II is selected from the group containing either hydroxy-substitutedcarboxylic acids and their salts, or the unsubstituted carboxylic acids and their salts. Thetrivalent chromium solutions contain chromium sulphate or chromium chloride as a sourceof chromium. Alkali metal salts are added to improve the conductivity of the solution andthe current distribution in the plating process. A buffering agent and wetting agent are alsoincorporated. The invention can be used to produce a bluish-white colour of trivalentchromium deposit, with high deposition rate and high current efficiency.