The two-step potentiostatic anodizing process of a 1050 aluminum alloy (AA1050) in an oxalic electrolyte was studied. Special attention was paid to the effect of the applied anodic voltage on the dimensions, homogeneity, and order of the anodic alumina porous layer obtained after a second step. The experimental conditions for obtaining homogeneous and ordered anodic aluminum oxide layers were defined. The effect of symmetric (the same applied voltage in the two anodizing steps) and asymmetric signals (different applied voltages in the first and second anodizing step on the structure and geometry of the porous layer was studied. When the first anodizing voltage was higher than the second, the pore/cell ratio was greater than 1, meaning that the structure had more than one pore per cell. (c) 2007 The Electrochemical Society.