| 摘要 |
Trivalent chromium is electrodeposited from an aqueous bath in which are dissolved very small proportions of compounds of classes (I) compounds containing <IMAGE> group, preferably a thiocyanate or a compound of formula X-CSNR where X is R, S or, NR2 or is -CSNR2 joined by -S- or -S-S- and R is H, alkyl, alkenyl, alkynyl or aromatic: (II) compounds of formula (X)-SO2-(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-(SO2)-X-S-S-X(SO2)-Y or (c) single unsubstituted benzene ring; and Y is -ONa, -OH, -NH2 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 -(CH2)n-Sm(CH2)COOH where n or m is 1 or 2; (IV) o-mercaptobenzoic acid and (V) sodium salts of sulphur, selenium and tellurium. |
