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AssigneeAlcan Research and Development Limited
InventorsPeter Geoffrey Sheasby, Graham Cheetham
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Anodized aluminium having an anodic oxide film of at least 3 microns thickness is colored by electrolytically depositing inorganic pigment from metallic salt solutions, particularly nickel, cobalt, tin and copper salts and mixtures. The pigment deposits are characterized by outer ends of an average size in excess of 260 A lying at a distance of 500 - 3000 A from the aluminium/aluminium oxide interface. In a preferred method of production the anodic oxide coating is formed under conventional anodizing conditions in a sulphuric acid-based electrolyte. The anodized aluminium is then treated in phosphoric acid at a voltage of 8 - 50 volts to enlarge the pores to above 260 A in a region at the base of the pores adjacent the barrier layer. The pigment is then deposited in the pores to the specified depth and interesting new color shades are obtained as a result of optical interference due to the presence of the large size shallow inorganic pigment deposits.
An aluminium article having a porous anodic oxide film on its surface, said porous anodic film having a thickness of at least 3 microns, the pores of said coating having inorganic pigmentary material deposited therein, characterized in that the average size of said deposits at their outer ends is at least 260 A and the separation between the outer ends of said deposits and the aluminium/aluminium oxide interface being in the range of 500 - 3000 A.
An aluminum article having a porous anodic oxide coating on its surface, said porous anodic coating having a thickness of at least 3 microns and including a thin aluminum oxide barrier layer which is immediately adjacent to the aluminum surface, said coating having pores which extend from said barrier layer outward to the surface of the coating, said pores having an average width, at least at their base regions to a distance of 500 - 3000 A from the aluminum/aluminum oxide interface, which is at least 260 A, and said pores having inorganic pigmentary material deposited therein, the average size of said deposits at their outer ends being at least 260 A, and the separation between the outer ends of said deposits and the aluminum/aluminum oxide interface being in the range of 500 - 3000 A.
Dependencies are inferred from the claim text.