GB712238A - Improvements in methods of gas shielded arc welding of aluminium and aluminium alloys - Google Patents

Abstract

A bare aluminium or aluminium alloy wire substantially free of any hydrogen containing compound is employed as an electrode when aluminium or aluminium alloy is welded by the gas shielded arc welding process. All moisture, hydrocarbons such as oil and grease and hydrated oxide film are removed from the wire before welding. An alkaline bath containing sodium carbonate, trisodium phosphate and sodium hydroxide may be used to remove oil, grease and hydrated acid film. The wire is then immersed in an acid, e.g. nitric, nitric-hydrofluoric or chromic based to brighten it, and it is rinsed and dried. An alkaline bath, e.g. 3 per cent. sodium carbonate and 3 per cent. sodium phosphate with an inhibitor, e.g. pyridine or aniline or a vapour degreaser, e.g. trichlorethylene, perchlorethylene carbon tetrachloride or benzol may be used to remove oil and grease and an acid bath, e.g. of nitric, phosphoric and acetic to remove the oxide film. The acid bath may be replaced by a solution of caustic soda, zinc oxide and water in which the oxide film is dissolved to expose the aluminium which on dissolving is replaced by zinc. The zinc is removed in a nitric acid bath. Stainless steel brushes may be used to mechanically remove the oxide film. After removing oxide, moisture and hydrocarbons the wire may be packaged in a moisture-proof container. Specifications 687,666, [Group XXII], and 712,271 are referred to. Reference has been directed by the Comptroller to Specification 659,015, [Group XXII].