GB483776A - Improvements in or relating to the production of coloured effects on aluminium and aluminium alloys - Google Patents

Abstract

483,776. Colouring aluminium; printing processes. SHEPPARD, S. R. March 12, 1937, No. 7322. [Class 93] [Also in Group XVI] Multi - coloured designs are produced on aluminium or aluminium alloys provided with an oxide film, e.g. by anodic treatment, by colouring the whole or a part of the oxidecoated article, coating that part of the coloured surface which is to retain the colour with a resist, e.g. by means of a brush, by offset printing, or by means of a stencil screen, removing the colour from the unprotected surface, and recolouring the unprotected surface in another colour. The exposed colour may be destroyed by immersing the article in sulphuric acid or in a reducing-agent such as titanous chloride or sulphate. The resist may be (1) a solution of an acid-resisting varnish of melting point above 100‹ C., such as solutions of celluloid or "Bakelite" (Registered Trade Mark) in non-greasy volatile solvents such as amyl or butyl acetates ; (2) a dispersion of inert oxides in drying oil, with driers; or (3) a dispersion of pigments insoluble in aqueous solutions, such as carbon, in heavy oils of high viscosity at temperatures up to 100‹ C., thinners such as benzole or toluol being added. After applying the resist, the oxide film may be revitalized by treatment with sulphuric or nitric acid. Parts of the original surface may be protected from oxidation, and, after colouring the unprotected parts, the resist may be removed and the aluminium surface matted by a scratch brush or by scouring, the coloured part then protected, and the metal oxidized and coloured or left uncoloured. The resist in this case may be a dispersion of an oil-soluble pigment, such as Brunswick black, in a drying oil and turpentine. In a particular example for producing effects in silver, pink, gold, green, and crimson on a black background, an aluminium plate is buffed and cleaned in boiling caustic soda solution, an anodic film is produced in a bath of glycerine and sulphuric acid as described in Specification 359,494, [Group XXXVI], the parts to remain silver are coated with a resist such as a cellulose varnish or lithographic ink, the whole unprotected part is dyed pink in a solution of Alizarine Red SW, the parts to remain pink are protected and the remaining pink is removed, and the process is repeated using, in succession, Benzo Fast Orange 2RL; Acid Blue 7218 and Quinoline Yellow; Chlorazol Fast Pink BKS; and Eriochrome Black ST with Gallazol Green Bluish FD powder. Specifications 439,403 and 445,242, [both in Group XVI], also are referred to.