Patent ID: 8858775

Claim:
A method treating a metal object so as to form thereon a surface layer which is integral with the metal object, and which includes a biocidal material, the method comprising: (a) immersing the metal object, which is to provide a substrate for the surface layer, in an anodising electrolyte containing a solvent, and anodising the metal object to passivate it by forming an anodised integral surface layer on the metal object by applying a positive voltage between 15 and 200 V; (b) continuing the anodising of the metal object by the application of a positive voltage, to produce pits through the integral surface layer and into the substrate; (c) then, after anodising the metal object during steps (a) and (b), producing a hydrous metal oxide or phosphate by: (i) applying a negative voltage which is insufficient to cause electrolysis of the solvent to the metal object, while in contact with the anodising electrolyte, or (ii) contacting the metal object with an electrolyte solution containing a reducible soluble salt of titanium or the substrate metal and an other solvent and applying a negative voltage which is insufficient to cause electrolysis of the other solvent; (d) removing or separating the anodised metal object resulting from step (c) from the anodising electrolyte or the electrolyte solution; and (e) then contacting the anodised metal object with a solution containing a biocidal material so as to incorporate said biocidal material into the surface layer.