This study reports the fabrication of porous anodic aluminum oxide (AAO) on a 6xxx series aluminum alloy by a two-step anodization route and systematically examines how anodization parameters govern the resulting morphology and wetting behavior. AAO samples were prepared in two groups: in Group 1, the anodization voltage was varied between 20 and 60 V at a fixed time of 60 min; in Group 2, the anodization time was varied between 30 and 120 min at a fixed voltage of 30 V. All anodizations were carried out in 0.3 M oxalic acid at room temperature. The AAO structures were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and contact angle measurements. The pore diameters and interpore distances were found to be 13.3–40.6 nm and 45.3–86.7 nm, respectively, in Group 1, and 19.1–23.6 nm and 41.0–44.4 nm in Group 2. Analysis of SEM images reveals that increasing the anodization voltage results in larger pore diameters, interpore spacings, and porosity, but a reduced pore density. In contrast, changes in anodization time at a fixed voltage have a more modest effect on pore geometry. The anodized surfaces exhibit a marked change in wettability, with the water contact angle increasing from ~45° for the non-anodized alloy to ~123° for the best-performing AAO surface, without any additional chemical modification. These results demonstrate that, even under simple room-temperature conditions, AAO morphology and hydrophobic behavior can be tuned in a predictable manner by appropriate choice of anodization parameters, which is relevant for the design of membranes, sensors, and functional surface coatings.
Balkan et al. (2026) studied this question.