The use of sulfuric and oxalic acid mixtures to obtain AAO layers with different channel geometries

Abstract This study investigates the influence of electrolyte composition on the morphology and growth kinetics of anodic aluminum oxide (AAO) layers. Special attention was given to the role of individual components in H₂C₂O₄–H₂SO₄ mixtures used during two-step anodization processes. Experiments were carried out using aqueous and water–ethanol solutions under low-temperature conditions, with applied voltages ranging from 25 to 35 V. The results reveal that the presence of H 2 SO 4 significantly affects both the oxide growth rate and pore formation and reorganization. At higher potentials, H 2 SO 4 promotes the development of AAO layers with larger pore diameters and higher porosity, which is attributed to enhanced oxide etching. Furthermore, its presence was found to facilitate pore reorganization, contributing to improved structural order. Finally, the potential application of H₂C₂O₄–H₂SO₄ mixtures for the fabrication of AAO layers with highly ordered branched channels has been demonstrated. The results indicate that fine-tuning the composition of acid mixtures represents a promising strategy for engineering the morphological features of porous alumina layers.