CPC C25D 3/06 (2013.01) [C25D 3/10 (2013.01); C25D 17/002 (2013.01)] | 21 Claims |
1. An electroplating bath for depositing chromium metal coating on a substrate or chromium metal alloy coating on a substrate consisting essentially of:
(a) 50 to 400 g/L (0.164 M to 1.314 M) of at least one trivalent chromium salt,
(b) 100 to 400 g/L (2.17 M to 8.68 M) of at least one complexing agent,
(c) 5 to 50 g/L(0.0425 M to 0.425 M) of at least one halogen salt,
(d) 0.5 to 10 g/L of additives, wherein the additives comprise a quaternary ammonium compound,
(e) 70 to 110 g/L of ammonia, and
(f) optionally an alloy former,
wherein the electroplating bath has a pH from 4 to 7 and is substantially free of divalent sulphur compounds and boric acid, its salts and/or derivatives and wherein the molar ratio of the complexing agent to the trivalent chromium salt is from 10:1 to 15:1,
wherein the electroplating bath is substantially free of aluminium ions; and
wherein the at least one complexing agent is selected from the group consisting of carboxylic acids and carboxylate salts,
whereby, when the substrate is immersed in the electroplating bath and an electrical current is applied, the substrate is deposited with a chromium metal coating or a chromium metal alloy coating.
|