A Review of Recent Patents on Trivalent Chromium Plating
Zhixiang Zeng, Aiming Liang and Junyan Zhang
Affiliation: State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, PR China.
Conventional Cr-matrix coatings electrodeposited from hexavalent Cr baths have been widely used for decoration and anti-wear. Electrodeposition of Cr from hexavalent Cr needs to be replaced by another material system due to the intense toxicity and carcinogenicity of hexavalent Cr. Trivalent Cr plating is considered to be a promising ‘environmental acceptable’ replacement technology for hexavalent Cr plating. This paper gives a review of patents and publications in the field of trivalent Cr plating. We primarily introduce the discharge mechanism of trivalent Cr, development of trivalent Cr electrolytes, anodic materials for the trivalent Cr plating, elimination of hexavalent Cr produced on the anode as a result of trivalent Cr oxidation and the electrodeposition of functional thick Cr coatings and black Cr coatings from trivalent Cr baths.
Keywords: Trivalent Cr plating, Anodic materials, Brightener, Ligand
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