Recent Technical Developments Applying Metal Protective Coatings by the Spray Method—Light Aeroplane Wireless—Aluminium Castings

Abstract

Spraying on Coatings A NEW method of applying a protective coating to materials, metallic or non‐metallic, as an alternative to the electrolytic, is being introduced into England. The system, which has for some time been in use in Germany and America, is being marketed here by Metals Coating Co., Ltd., It consists in spraying the coating on to the surface to be protected by means of a special form of pistol, known as “Metalayer.” This pistol, as can be seen from the illustration, is connected by rubber hose to oxygen and acetylene cylinders and to a compressed air tank. The metal to bo deposited is used in the form of ordinary commercial wire, and any metal that can be drawn into wire can be applied. The wire enters the pistol at the back, and is fed automatically from a reel through the nozzle, where it meets the oxyacetylene flame in combination with compressed air, and the atomised metal is blown on to the surface at a velocity of some 3,000 ft. per second. In this way, a zinc coating can be applied to aluminium, as has been done to “Jaguar” engine parts experimentally. In the same way, aluminium itself, which is largely used in America as a primary coating for aluminium alloys prior to a final covering with zinc, can be sprayed on to duralumin. Aluminium does not, of course, lend itself to application by the usual electro‐deposition methods and, therefore, this system offers a way of surmounting the difficulty and giving a coating to Duralumin which is, in itself, more capable of resisting corrosion.