Patent ID: 9096943
Filing Date: 2015-08-04
Classification: A61L,C23C,C25D

Abstract:
1. A method of treating a metal object so as to form thereon a surface layer which is integral with the metal object, and which includes a biocidal metal, the method comprising: (a) contacting the metal object, which is to provide a substrate for the surface layer, with an anodising electrolyte comprising phosphoric acid, and applying an anodising voltage of between 30 V and 150 V to the metal object to passivate the metal by forming an anodised integral surface layer on the metal object, wherein the metal object comprises titanium, niobium, tantalum or zirconium, or an alloy comprising such a metal; (b) continuing, in the same electrolyte, the application of an anodising voltage to produce pits through the integral surface layer and into the substrate; (c) producing a hydrous metal oxide in the surface layer by electrochemical reduction in contact with an electrolyte or a solution; (d) removing or separating the anodised metal object resulting from the electrochemical reduction of step (c) from the electrolyte or the solution of step (c); and (e) contacting the anodised metal object with a solution containing a biocidal metal so as to incorporate said biocidal metal by ion exchange into the surface layer; wherein the voltage in the pit-forming step (b) is less than the maximum voltage applied during the passivating step (a) and is between 20 V and 60 V; and wherein the anodising steps (a) and (b) are performed in a total time of no more than 60 minutes.