GB629603A - Improvements in method of polishing metal surfaces - Google Patents

Abstract

629,603. Electropolishing metals. LITTLE, Inc., A. D. July 19, 1946, No. 21656. Convention date, Feb. 2, 1943. Drawings to Specification. [Class 41] A metal surface composed of silver, copper, cadmium and alloys thereof, including alloys of these metals with nickel and/or zinc, is electropolished by subjecting as anode in an electrolytic bath containing in solution a soluble simple cyanide of alkaline reaction capable of forming complex cyanides with the metal to be polished, there being an amount of the free simple cyanide in excess of any complex cyanide equivalent to at least .01 mol per litre, employing a potential difference, above the polarizing potential, between the electrodes, which is below the point at which periodic flashing or permanent film formation occurs, and applying these conditions for a period of time to effect the dissolution of superficial protuberances from the surface and to leave the surface polished. The potential difference is preferably maintained substantially constant and the anode is freely spaced from the cathode and other solid surfaces sufficiently to prevent the effects thereof which are found to promote periodicity or flashing, and also to avoid turbulence, when the electrolyte is agitated, preferably in stream-line relationship to the metal surface, e.g. by moving the anode with continuous forward movement. The soluble cyanide may consist of alkali metal cyanide, e.g. sodium or potassium cyanide and conductivity of the electrolyte may be increased by the addition of an inert electrolyte such as potassium carbonate or sodium sulphate.