BETA-CHROMIUM PLATING FROM A CHROMIC-ACID ELECTROLYTE CONTAINING FORMIC-ACID

β-chromium has been deposited from a cold (20°C) chromic acid electrolyte containing formic acid. The film remains stable for more than two months. The lattice type is found to be that of ZnS of wurtzite type with lattice constants of a = 0.2724 nm and c = 0.4422 nm. The chemical composition is CrH0.53C0.04O0.013. The film exhibits strong texture; its microstructure is very different from that of conventional hard chromium. The film starts to decompose at about 120°C to become a-chromium in a nitrogen atmosphere and, concurrently, the microhardness drops from Hv 880 to Hv 600. © 1990, The Electrochemical Society, Inc. All rights reserved.