GB570287A - Improvements in or relating to the electrodeposition of lead - Google Patents

Abstract

570,287. Electroplating of lead. DU PONT DE NEMOURS & CO., E. I., and GRAY, A. G. Dec. 10, 1943, No. 20681. [Class 41] [Also in Group III] Baths suitable for electroplating lead at low current-densities, such as 0.1 amps. /ft.<2>, and particularly acid baths, contain an anthraquinone sulphonate, either as free acid, or as salt or partial salt, in amount preferably between 0.05 and 5 g.p.1. Specifically 1-, or 2-, anthraquinone sulphonic acid, or 1-8, or 2-7, anthraquine disulphonic acid, or the ammonium, potassium, or sodium bath-soluble salts of such acids are used, the pH value being less than 7 and preferably lying between 0.1 and 4.2. The plating bath may also contain sulphite cellulose waste or lignin sulphonic acid derived therefrom, in amount from 0.25 to 15, and preferably 1-5, g.p.1. Antimony may be co-deposited with the lead. The principal electrolyte may be the nitrate, oxalate, dithionate, or cyanide of lead, or sodium plumbite. Additionally, the anthraquinone sulphonate may be added to the acetate bath described in Metal Finishing, Vol. 38, p. 533 (1940), to the perchloride bath described in Transactions of the American Electrochemical Society, Vol. 23, p. 159 (1913), to the fluoborate bath set out in Vol. 36 of the latter journal at p. 243, the compositions of all of which are set out in the Specification. The preferred bath is a lead-sulphamate bath produced by mixing litharge, solid dry sulphamic acid, and ammonium sulphamate in the presence of traces of water (0.5 to 2.0% by weight) at 105-145‹ F.; the pH being between 0.1 and 4.2 and preferably between 1.0 and 3.0. The proportions used may vary within limits discussed in the Specification, but a preferred bath comprises, in g.p.1., litharge and sulphamic acid 150 each; ammonimn sulphamate 75, 1-anthraquinone sodium sulphamate 0.5, and sulphite cellulose waste 5, the solution having a pH of 1.5. Baths composed of sulphamic acid may have their pH adjusted by adding formic, acetic, or nitric acid.