GB586250A - Electrolytic cleaning of metals - Google Patents

Abstract

586,250. Electrolytic removal of oxide from metal surfaces. DU PONT DE NEMOURS & CO., E. I., and GILBERT, H. N. Dec. 11, 1944, No. 24772. [Class 41] Surface oxide is removed from a metal article by treatment as cathode in a molten alkali metal hydroxide bath containing alkali metal hydride in solution. The proportion of hydride may be 0.5-10 per cent. by weight, preferably 1-2 per cent. The temperature may be 250‹-600‹C., preferably 350‹-500‹C. The hydride is preferably confined to the vicinity of the cathode. It may be prepared in situ by passing hydrogen into the bath in the vicinity of the cathode, the amount of hydrogen being preferably molecularly equivalent to at least a major proportion of the alkali metal liberated at the cathode. Sodium compounds are preferred, but one or more other alkali metal hydroxides and hydrides may also be used. Treatment may be carried out in the apparatus shown in which the anode is separated from the cathode by a steel wire gauze diaphragm A and from the adjacent wall by a baffle B whereby circulation of the electrolyte is effected by oxygen rising at the anode. Hydrogen is introduced below the cathode by a tube C. Sodium monoxide may be introduced into the anode compartment to react with the water liberated, preferably into the descending stream of the circulating electrolyte. Iron, steel, nickel, silver, copper or other metal articles may be treated. Specifications 442,859 and 557,530, [Group II], are referred to.