GB491175A - Improvements in and relating to the coating of aluminium surfaces with metal - Google Patents

Abstract

To prepare an aluminium surface for spraying a coating or filling of metal thereon, the surface is cleaned by means of an abrasive, coated with silver, and then rubbed with a coating composition comprising mercury, mercury bichloride or borax, copper sulphate, zinc chloride, hydrochloric acid, and an abrasive. The silvering is preferably effected by brushing with a silver nitrate solution containing nitric acid in an amount less than 1 per cent by weight. The coating composition, which produces on the silvered surface a bright coating containing copper, mercury, and zinc, is prepared in two parts, one being a powder comprising the mercury, the bichloride of mercury or borax, and the abrasive, the latter preferably a mixture of quartz sand and the abrasive known under the Registered Trade Mark "Crystolon," and the other part being a solution of the copper sulphate, the zinc chloride, and the hydrochloric acid. The two parts are mixed together to form a thick paste and left for at least 12 hours before use, the paste being then applied with a wooden paddle and rubbed on with a felt pad. Any excess of the coating composition is removed and the prepared surface is then sprayed in the manner described in Specification 491,173, preferably by the use of the spray gun described in Specification 491,172, [Group XXIX]. The process is described with reference to the filling of dents or depressions in an aluminium motor-car body by spraying a filling of lead or lead alloy, the surface being first ground and then prepared and sprayed as described, the sprayed metal being deposited evenly over the depression and slightly beyond the edge thereof and then ground down. The sprayed surface and any surrounding parts with which the silvering solution or the coating composition has come in contact may then be cleaned, e.g. with caustic soda, and painted, for example by spraying.