GB190500A - Process for the deposition of metals by electrolysis - Google Patents

Abstract

190,500. Govaerts, P. A., and Wenmaekers, P. M. Dec. 19, 1921, [Convention date]. Metals and alloys, depositing; electrodes; preparing surfaces ; treating after electrolysis.- Thiosulphate baths for use particularly in depositing other metals upon aluminium, are prepared in the following way. For depositing iron, nickel, zinc and like metals, a solution of sodium thiosulphate is acidified with an organic acid such as acetic acid until decomposition of the thiosulphate just begins, and a small quantity of the sulphate of the metal to be deposited is added; the solution is cooled and filtered. Alloys e.g. of iron and zinc and nickel may be produced by using a mixture of sulphates. For depositing copper, silver, lead and like metals, a concentrated solution of the sulphate slightly acidified with sulphuric acid is treated with sodium thiosulphate solution. A precipitate is formed which is washed with cold water and dried rapidly in the cold e.g. by anhydrous sulphuric acid in a vacuum, while protected from the action of light. The dried precipitate is dissolved to saturation ,in warm sodium thiosulphate solution and diluted to double the volume by further thiosulphate solution. An alloy e.g. of copper and silver may be produced from a bath prepared by dissolving a mixture of the precipitates. The colour of the alloy is determined by varying the E.M.F. which should not exceed 1 volt. For depositing brass, a small quantity of the copper solution prepared as above is added to a solution of sodium thiosulphate and zinc sulphate. This is warmed until the liquid becomes opalescent and then cooled, depositing a small quantity of copper sulphide, and filtered. An anode of the metal or alloy to be deposited is used in all cases; during electrolysis it may become coated with a non-adherent coating of sulphide. The cathode is cleaned before electrolysis first mechanically and afterwards with caustic soda or potash. After plating, it may be annealed, polished, hammered or burnished. Objects of aluminium coated with copper may be gilded by applying gold amalgam and heating.