Laminated alumina films, which resemble structures of shell nacre, have been fabricated via the ac oxidation of aluminum in different electrolytes. A variety of films composed of alumina layers of 50-200 nm thickness, were obtained by varying both the ac power supply and the type of electrolyte. The total film thicknesses were observed to increase with total charge. The thickness of each layer increased with ac voltage, but the anodizing time had little effect on the film thickness. The rate of formation of these layers was also affected by the type of electrolyte employed. These results suggested that the laminated structures were formed by the repeated cycles of formation of an alumina film via the anode reaction and generation of hydrogen gas via cathode reaction. (C) 2013 The Electrochemical Society. All rights reserved.