Method for forming a multi-layer anodic coating

A method for producing a multi-layer anodic coating on a metal which comprises the steps of:

• (i) placing the metal in a first electrolytic solution and applying a current as a steady state current to form a first anodic layer having a barrier region;
• (ii) reducing the applied current to cause a reduction in thickness of the barrier region;
• and
• (iii) placing the electrolytically modified metal in a second electrolytic solution and applying a current to form a second anodic layer, wherein the multi-layer anodic coating comprises the first anodic layer and the second anodic layer, and wherein the first anodic layer comprises pores having relatively large pore diameter size and the second anodic layer comprises pores having relatively small pore diameter size, and wherein step (i) comprises a first anodizing process having a final forming voltage and step (iii) comprises a second anodizing process having an initial forming voltage;
• wherein following step (ii), the final forming voltage of the first anodizing process is less than the initial forming voltage of the second anodizing process and wherein the final forming voltage after step (ii) is in the range of 2V to 10V.