GB710375A - Improvements in or relating to electroplating - Google Patents

Abstract

710,375. Electro-plating. WESTING- HOUSE ELECTRIC INTERNATIONAL CO. Oct. 26, 1951, No. 25078/51. Drawings to Specification. Class 41. A process of electro-plating on a base member a metal from the group consisting of copper, silver, zinc, cadmium, tin, gold and alloys in which these metals predominate, utilizes a plurality of cycles of periodically-reversed current, each cycle comprising a plating electrical current for at least 45 seconds to plate metal on the base members, and a de-plating electrical current for a period of time at least 30 per cent of the plating period, the average de-plating current density on the member being less than the average plating current density, and the coulombs delivered by the deplating current being between 30 per cent and 95 per cent of the coulombs delivered during the plating portion of the cycle, whereby a substantial portion of the previously-plated metal is de-plated, the plurality of cycles producing a smooth level deposit of plated metal. In the plating of copper an alkaline cyanide electrolyte containing from .0038 to .57 ozs. per gallon of zinc and from i to 10 ozs. per gallon of thiocyanate as addition agents may be used. The electrolyte and base member may have a relative movement of at least one foot a minute. Examples are given of aqueous cyanide baths for the plating of copper, brass, cadmium, silver and gold, and an acid bath for the plating of copper. Electrotypes and electroforming base members consisting of wax or resinous patterns plated or coated with powdered graphite or precipitated silver may be electroplated by the process claimed, and the electrodeposited metal stripped off. Plating in accordance with the invention may be followed by plating of nickel and chromium by direct current, without need for buffing. Specification 630,165 is referred to.