Electrolytic brightening bath for silver - contg. alkali cyanide, alkali carbonate polyhydroxy carboxylic acid and polyvinyl pyrrolidone

摘要

An electrolyte polishing and brightening bath for silver (alloys) contg. 10-200 (20-150) g/l alkali cyanide and 10-150 (20-100) g/l alkali carbonate additionally contains 0.5-50 (1-30) g/l polyhydroxycarboxylic acid (I) and 0.1-40 (0.5-20) g/l polyvinylpyrrolidone (II). The bath has excellent throw (Streufahigbeit) and provides excellent gloss for silver alloys contg. large amts. of non-rare earth metals. It is esp. suitable for jewellery. In an example, silver was treated in a bath contg. KCN 90 g/l, KCO3 60 g/l, POC-OS 5060 (RTM)20g/l and (II) 5 g/l at 20-25V and 11A/dm2 for 1 minute. Current impulses of one second on and one second off were used.