Plating and surface finishing vol:80 issue:7 pages:43-47
Silver alloy coatings with a germanium content up to 6 wt percent were electrodeposited from a cyanide solution without brighteners. Addition of GeO2 to silver cyanide solutions containing typically 40 g/L Ag, 140 g/L KCN, 7 g/L K2CO3, and 5 g/L KOH, results in bright deposits in a narrow zone on Hull Cell panels. By carefully selecting and controlling the current density and the hydrodynamics, partially bright 10-mum thick deposits can be obtained on flat cathodes. A commercial brightener appeared to be incompatible with the presence of germanium in the bath. In comparison with pure silver, codeposition of germanium with silver improves tarnish resistance in the thioacetamide test. The microhardness of the Ag-Ge alloy deposits was as much as 175 HV0.025, which is comparable to regular decorative hard silver coatings.