GB412193A - Improvements in and relating the anodic coating of aluminium and aluminium alloys - Google Patents

Abstract

A sheet or other article of aluminium or an aluminium alloy having thereon an oxide film or coating produced by chemical or electro-chemical means is further treated to form thereon a semi-colloidal layer of the sulphide or arsenite of lead or antimony and is thereafter treated, for example, by agitation in a liquid, in such a way that the semi-colloidal layer is broken through in an irregular manner. In an example, the oxide-coated article is first dipped in a solution of an organic red dye. It is then washed and immersed in a 20 per cent. solution of lead acetate at 65-80 DEG F. It is then immersed in a 50 per cent. solution of ammonium sulphide at 65-85 DEG F. and oscillated therein. It is finally washed and gently brushed, leaving a pattern of dark brown on a red background. The dyeing may be effected after formation and local removal of the semi-colloidal film. The local removal of the film may be effected in several stages with intermediate treatment by different dyes. The lead sulphide finally remaining may be treated for modification of its colour, for example, by immersion in a 1 per cent. solution of chromic acid. The production of a variegated pattern in black, gold and red is described. The semi-colloidal films may be produced by successive immersion of the article in solutions of lead acetate and sodium arsenite, or in solutions of a salt of antimony and of a soluble sulphide or arsenite. Patterns of different scale may be produced by these means. Specifications 290,901, 290,903, [both in Class 41]; 378,521, 391,903; 395,390 and 396,743, [both in Group XXXVI], are referred to.