Effect of polishing pretreatment on the fabrication of ordered nanopore arrays on aluminum foils by anodization

It is reported that a pretreatment step is required for the fabrication of ordered nanopore arrays on Al by anodization. In this study, one step anodization was carried out on the Al foils with different surface features that resulted from different polishing conditions. The effect of surface morphologies on their anodization characteristics was determined. When the nonelectropolished Al substrate was anodized, only limited-sized ordered domains could be obtained. Nearly perfect hexagonal close packed ordered pore arrays with domain size of about 2–4 μm could be obtained on the electropolished Al substrate even with different surface features due to different electropolishing conditions. In addition, the differences of current density for the electropolished and nonelectropolished substrates were affected by the distinct characteristics of the oxide. The increase of the oxidation current in the later stage of anodization was caused mainly by the breakdown of the oxide on the nonelectropolished substrates on which highly ordered pore arrays cannot be obtained.