GB700535A - Improvements relating to electro-plating, more particularly of ferrous-metal surfaces - Google Patents

Abstract

700,535. Electrodeposition of metals. PEACH, A. L. Aug. 14, 1951 [Aug. 21, 1950], No. 19138/51. Class 41. In electro-plating more particularly of ferrous metal surfaces a coat of lead or lead-alloy is deposited solely by electrolytic means, on to the article to be treated, prior to its being electroplated with nickel, or nickel and chromium. The lead alloy is preferably an alloy of lead and tin, but may be composed of lead and antimony. An article of ferrous metal is first smoothed and then treated as cathode in an electrolytic bath comprising 6 ozs. of trisodium phosphate per gallon of water. The article is then rinsed in fresh water and, if necessary, lightly scoured. It is then subjected to etching, either thermically in a bath of sulphuric acid or hydrochloric acid, or electrochemically, with the article as anode in a bath of sulphuric acid. A thin coating of nickel or copper may be applied, the article being next electro-plated in an aqueous bath containing lead as fluosilicate in hydrofluosilicic acid, lead as perchlorate in perchloric acid solution containing peptone, or lead carbonate in hydrofluoric solution containing boric acid and glue. The anodes may be of lead only, of lead and tin, or of lead-tin alloy. The plated article is polished and returned for cathodic treatment in the solution of trisodium phosphate. The article may be made anodic for 10 seconds before removal. It is then rinsed and immersed in nitric acid solution, rinsed again and is then suitable for nickel plating. A layer of copper may be applied to the lead or lead-alloy layer before nickel plating. For the plating of zinc or zincbearing alloys a suitable alkaline lead bath contains lead oxide and caustic soda or other alkali.