Alcan Research and Development Limited

Tarun K Gupta

Peter G Sheasby

Graham Cheetham

Rainer W Stuckart

Edward P Short

The invention provides aluminium articles having porous anodic oxide films colored by means of an optical interference effect. In FIG. 4, the article 10 carries a first anodic oxide film 12 with pores 14 enlarged at their inner ends 20 and containing deposits 22. The products may be made by growing a second anodic oxide film 26 underneath the deposits 22 which are preferably of acid-resistant material. X is at least 26 nm, Y is preferably at least 60 nm, Z is preferably 15 nm to 200 nm, (Y+Z) is preferably 75 nm to 600 nm, and W is preferably at least 15 nm.

Aluminium articles having anodic oxide coatings and methods of coloring

In a process for the electrocoloring of anodized aluminium in which colors are obtained by interference effects the pores of an anodic oxide film, produced by D.C. anodizing in sulphuric acid, are enlarged by electrolytic treatment in an acid electrolyte having a high dissolving power for aluminium oxide under alternating current conditions.

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Maharahstra, India

Tarun K Gupta