LAUSR

Abstract The effects of the hydrous oxide film obtained from the hydrothermal treatment of the electropolished aluminum sheet on the porous anodic alumina produced by the first step of anodization in oxalic acid were investigated. It is indicated that the dense barrier layer within the hydrous oxide film can bring about a nearly exponential decrease of the current as a function of time. As to the porous layer of the hydrous oxide film, namely the ‘cornflake’ structure onto the barrier layer, it can optimize the initially nucleated site of the nanoporous during the anodization, which is beneficial to the self-ordered array of the nanoporous generated on the PAA film. It is concluded that the hydrous oxide film produced by the hydrothermal treatment can facilitate the self-assembly of the porous anodic alumina even if the applied potential is 60 V in oxalic acid.