GB771314A - Improvements in and relating to the electrolytic cleaning of articles of metal - Google Patents

Abstract

771,314. Cleaning metal electrolytically. WALTON, H. D. March 11, 1954 [March 18, 1953; March 3, 1954], No. 7171/54. Class 41. A method of cleaning a metal article comprises connecting it as cathode in an electrolyte of a solution of hydrochloric acid of 1 to 10 per cent concentration by weight at a temperature not exceeding 120‹ F. at a steady voltage of 5 to 25 and at a cathodic current density of 12 to 120, e.g. 18, amps. per square foot. Substances having wetting and detergent properties, e.g. sulphonated oils and sulphated fatty alcohols, sequestering and ion-exchanging properties, e.g. ethylene diamine, and chelating properties, e.g. polybasic amino acids, may be added to the electrolyte in amounts of <SP>1</SP>/ 30 oz. to 4 oz. per gallon. Corrosion inhibitors may likewise be added, and a peptizing agent, e.g. sodium chloride or metasilicate. One or more iron or steel anodes may be used, and may be fixed along the sides and bottom of the bath, and, where the articles to be cleaned are pipes, may be inserted therein. Articles may be passed on a conveyer through the bath, or be drawn therethrough in continuous lengths, or immersed therein in batches, the current being automatically controlled as the articles leave and enter. The cleaned articles may be washed, e.g. by brushing, in water containing 0.05 to 3 per cent phosphoric acid, and may be subjected to preliminary vapour or solvent degreasing operation. The electrolyte may be agitated.