GB236241A - Improvements in methods of treating and coating ferrous metal bodies, and the resulting products - Google Patents

Abstract

236,241. Madsenell Corporation, (Assignees of Knauss, F. V.). June 27, 1924. [Convention date]. Void [Published under Sect. 91 of the Act]. Pickling; tinning, galvanizing, and coating by dipping. - Ferrous metal objects such as steel sheets are treated to remove surface carbon or occluded hydrogen or other gas, preferably both carbon and gas being removed. The object is first treated with hot caustic soda or other alkali to remove grease, and after rinsing in hot or cold water is pickled in dilute hydrochloric or sulphuric acid. It is then rinsed, if an acid other than sulphuric has been used for pickling, and treated as anode in a bath of strong sulphuric acid, preferably above 84.5 per cent strength. The cathode may be of lead or of iron or steel covered with lead, or of iron or steel. A series resistance about five times that of the cell is employed. The current density is preferably 20 amps. per sq. ft. of anode surface, but 5 amps. per sq. ft. or less may be used. The treatment is continued until the current falls to a constant value about one-fifth or lees of the initial current. The temperature should be about 100‹ F. Hollow bodies are treated by filling with acid and inserting the cathode therein. The acid need not completely fill the body provided the body be rotated so that the whole of the interior surface receives treatment. The body should be rinsed after treatment. The properties of the treated articles are rendered more permanent by treatment with sodium carbonate or other alkaline solution. This may be allowed to dry on and then acts as a flux for coating metal such as lead, tin, or zinc, which may be applied by dipping, spraying, or flowing. Non-metallic coating materials such as paint, vitreous enamel, or baking enamel may alternatively be applied to the treated iron or steel.