ES368263A1 - Bright silver electroplating - Google Patents

Abstract

Glossy Ag is electro-deposited from a cyanidic Ag electrolyte comprising at least one S-containing compound of the formula R1-CX-NH-CS-SH or R1-CX-NR11-NH-CS-SH, and/or salt thereof with an inorganic or organic base (e.g. as Ag, Na, K, NH 4 or NH(C 2 H 5 ) 3 salt), in which R11 is H or a C 1-4 alkyl (preferably methyl) group, X is S or O or imino group, and R1 is an aliphatic hydrocarbon group (preferably containing C 1-5 ) or a C 1-3 alkoxy (preferably methoxy), a C 1-4 mono alkylamino (preferably methylamino) or phenylamino group or a group of the formula: in which R111 is a halogen, a C 1-5 alkyl, alkoxy, alkylamino or acylamino group. When X is O or imino group, R1 may be an -NH 2 group. Many examples of such glossing agents are specified such as hydrazine-N-(methyl- or phenyl-thio) carboxylic acid amide (-N-methyl)-N1 -dithiocarboxylic acid, or hydrazine-N-(methyl or ethyl) guanyl-N1 -dithiocarboxylic acid. The electrolyte may also contain one or more other glossing agents such as thicarbonates (e.g. Na or ethylenetrithiocarbonate), xanthatis (e.g. of K), thiocarbamates (e.g. of ammonium), organic Se compounds (e.g. a piaselenole) or inorganic Se compounds (e.g. K selenocyanate or sodium selenite) or Group V metal (e.g. Sb) compounds wetting agents and/or colloids may be added. The C.D. may range from 0À05 to 3 amp/dm2 . The electrolyte may contain 20-50 g/l Ag as AgCN, K or Na dicyanoargentate, 50-200 g/l free KCN (or NaCN) and 0-100 g/l K 2 CO 3 . 2, 5 dimercaptothiodiazole-(1, 3, 4) and thiosemicarbazide-dithiocarboxylic acid are specified as comparative glossing agents.