In situ wetting of aluminium during the growth of porous alumina by anodic oxidation

The growth of nanoporous alumina at an aluminium surface which is not completely covered by an electrolyte has been investigated. At one point the electrolyte forms three interfaces: oxide/electrolyte, metal/electrolyte, electrolyte/air. At this three-interfaces-point a self-wetting induced oxide growth occurs. The wetting increases up to 7 mm from the electrolyte contact edge. At this final stage of wetting an equilibrium between the wetting induced flow (bottom-up) and the gravity-driven flow (top-down) is reached. The thickness of the nonporous layer decreases with the distance from the starting point.