GB592443A - Improvements in or relating to electro-plating - Google Patents

Abstract

592,443. Electro-deposition of alloys. SHEPHERD, G. R. (Westinghouse Electric International Co.). Sept. 14, 1944, No. 17595. [Class 41] An alloy of copper zinc and tin is deposited from a bath containing cyanides of the metals using an anode composed of- 50-75 per cent copper, 15-30 per cent tin and 5-20 per cent zinc. Preferred anode proportions are 55-65 per cent copper, 20-30 per cent tin and 8-20 per cent zinc. The bath may contain per U.S.A. gallon free cyanide 0.5-5.0 oz., copper 0.2-0.5 oz., tin 0.05-0.20 oz., zinc 0.1-0.5 oz., sodium carbonate 2-12 oz. and may be made up by dissolving appropriate proportions of copper, zinc and sodium cyanides, sodium stannate and sodium carbonate. The bath is maintained at pH 11-13. Alkali metal thiocyanate in amount 0.5-2 oz. per U.S.A. gallon may be added as a brightener. A complexing agent such as Rochelle salts or citric acid may also be added. As an anti-pitting and brightening agent there may be added 0.01-1 oz. per U.S.A. gallon of a betaine having at least one non-cyclic hydrocarbon radical which contains 10-20 carbon atoms. Examples of such betaines are : trimethyl-C-decyl alpha betaine, trimethyl-C-cetyl alpha betaine, trimethyl-C- cetyl gamma betaine, dimethyl beta-hydroxyethyl-C-cetyl alpha betaine, methyl di-(betahydroxyethyl)-C-cetyl alpha betaine, trimethyl- C - lauryl alpha betaine, trimethyl - C - lauryl gamma betaine, trimethyl - C - stearyl alpha betaine, dimethyl-N-stenyl alpha betaine, dimethyl - N - stenyl - C - methyl alpha betaine, methyl-N-distenyl alpha betaine, dimethyl-N- stenyl-C-cetyl beta betaine, dimethyl-N-decyl beta - hydroxy gamma betaine, dimethyl - N - heptadecyl alpha betaine, dimethyl - N - octa - decyl - C - methyl alpha betaine, dimethyl - N - octadecyl beta betaine, dimethyl - N - octadecyl beta-hydroxy gamma betaine. Alternatively, there may be added 0.01-5 oz. per U.S.A. gallon of a water-soluble surface active agent having a minimum of 15 carbon atoms connected in a long chain selected from the group consisting of oleates, palmitates, stearates, sulphonated oils, ricinoleates, polyoxyalkylene ethers, and quaternary ammonium compounds. Satisfactory quaternary ammonium compounds are those having either of the formulas where X is a halogen, n is 12 or greater and m is 14 or greater. Sodium thiocyanate, sodium disulphate, tri-sodium phosphate and sodium sulphate may be present in addition to the organic agents. A voltage of 3-5 may be employed with the electrodes 4-6 inches apart. Insoluble anodes of steel or carbon may be employed in addition to the alloy anode, the latter constituting 15 per cent of the total anode area. Supporting hooks of steel may be cast into the anodes or the anodes may be cast into balls for insertion in a supporting frame. The .bath has high throwing power. The plating applied to copper may be readily soldered. It is non-magnetic and has high corrosion resistance. The plating may be applied to steel directly or with an intermediate copper coating. Objects 24 to be plated may be mounted on hooks 26 on a support 22 coated with insulation except at contact surfaces.