Metal object with roughened surface and method of production

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 bio-effective material, the method comprising the following steps:

• (a) contacting the metal object with an anodising electrolyte, and applying an anodising voltage to the metal object to passivate the metal by forming an anodised oxide layer on the metal object;
• (b) continuing the application of an anodising voltage to produce regions in the oxide layer having a higher O/M ratio, where O is the number of oxygen atoms and M is the number of valve metal atoms;
• (c) producing a hydrous metal oxide in said regions in the oxide layer by electrochemical or chemical reduction in contact with an electrolyte or a solution, so the oxide layer and the hydrous metal oxide in said regions together constitute the surface layer;
• (d) removing or separating the anodised metal object resulting from step (c) from the electrolyte or the solution of step (c);
• and
• (e) contacting the anodised metal object with a solution containing a bio-effective material so as to incorporate said bio-effective material into the surface layer;
• wherein during step (b) the anodising voltage is repeatedly subjected to voltage cycles, each voltage cycle comprising ramping the voltage between a lower threshold voltage and an upper threshold voltage, and then returning the voltage to the lower threshold voltage, both the lower threshold voltage and the upper threshold voltage being less than the maximum voltage applied during the passivating step (a).