| abstract |
Trivalent chromium is electrodeposited from an aqueous bath in which are dissolved very small proportions of compounds of classes (I) compounds containing ##STR1## group, preferably a thiocyanate or a compound of formula X--CSNR where X is R, S or, NR 2 or is --CSNR 2 joined by --S-- or --S--S-- and R is H, alkyl, alkenyl, alkynyl or aromatic: (II) compounds of formula (X)--SO 2 --(Y) in which X is (a) a saturated or unsaturated two or three carbon atom alpiphatic group terminating in a mercapto group or (b) the disulphide corresponding thereto, of formula Y--(SO 2 )--X--S--S--X(SO 2 )--Y or (c) single unsubstituted benzene ring; and Y is --ONa, --OH, --NH 2 or when X is a single unsubstituted benzene ring, a direct --NH-- linkage or indirect --NH--CO-linkage to the ortho position thereof, (III) compounds of formula HOOC --(CH 2 ) n --S m (CH 2 )COOH where n or m is 1 or 2; (IV) o-mercaptobenzoic acid and (V) sodium salts of sulphur, selenium and tellurium. |