GB845527A - Antimony electroplating solutions and processes - Google Patents

Abstract

845,527. Electroplating with antimony. HARSHAW CHEMICAL CO. Oct. 30, 1956 [Nov. 7, 1955], No. 33128/56. Class 41. Antimony is electrodeposited from an aqueous solution comprising antimony wholly or mainly as the soluble fluoride and at least two co-operating brighteners, one of which is a N-heteroaromatic compound having a benzenoid structure and the other is an aromatic compound containing a sulphonyl group linked to a nuclear carbon atom, typically a sulphonamide containing an -SO 2 NH 2 or an -SO 2 .NH.SO 2 - group, a sulphonate, or a sulphinate. Typical N-heteroaromatic compounds are pyridine, α-α<SP>1</SP>-bipyridyl, 5:6- benzoquinoline, 2 :6-dimethyl quinoline, and salts thereof and quinolinium methosulphates such as the N-methyl-, N-methyl-2-carboxy-,and2:N- dimethyl derivatives and N:N<SP>1</SP>-( oxydiethylene)- bis-isoquinoliniumsulphate. The preferred aromatic sulphonyl compounds are benzene and toluene sulphon-amide, di-benzene sulphonamide (C 6 H 5 SO 2 NH.SO 2 C 6 H 5 ), bi-(di-benzene sulphonamide) ether, and bi-(di-benzene sulphonamide) but saccharin may also be used although it is less satisfactory than the sulphonamides. To further increase the brightness small quantities of a soluble zinc or copper salt e.g. the fluoride, chloride or sulphate, and/or coumarin or a derivative thereof may be added to the bath. To avoid deposition of antimony fluoride, an α-hydroxy acid such as tartaric, citric, gluconic, glycolic, or lactic acid or an ammonium, sodium, potassium, or amine salt thereof or excess of halogen ion may be included in the bath. Preferably sulphate ion is included in the bath to avoid chemical plating. A typical bath to which the addition agents are added comprises antimonyoxide, ammonium bifluoride glycolic acid, ammonium sulphate adjusted to pH 4 with ammonium hydroxide and used at a temperature of 145‹F. with a current density of 40 amps./sq. ft. to plate on lead panels. Plating may also be effected on tin, silver, or alloys thereof with each other or with lead which may be coated on steel bases, or on roughened steel.