Nanoporous anodic aluminum oxide (AAO) films play an important role in nanotechnology due to their easily adjustable morphological properties and wide range of applications. Thus, a deep and systematic characterization of the morphological properties of these coatings is essential. The most important variables in the synthesis of nanoporous AAO films include the anodization voltage, nature, concentration and temperature of the electrolyte, which, combined, result in pores of different sizes and geometries. In the present work, AA 1050 alloy was used to synthesize AAO films, using 0.3 and 0.9 M oxalic acid as the electrolyte and combining different electrolyte temperatures (20, 30 and 40 °C) and anodizing voltages (30, 40 and 60 V), with the aim to correlate the morphological properties of the coatings with the synthesis parameters of a single anodization step. The coatings obtained were characterized by optical microscopy and scanning electron microscopy, determining pore diameter, interpore distance, pore density and coating thickness. The results showed that, by varying the anodic synthesis conditions, it is possible to obtain coatings with a pore diameter between 21 and 97 nm, an interpore distance between 59 and 138 nm, pore density between 2.8 × 1010 and 5.4 × 109 pores/cm2 and thicknesses between 15 and 145 µm. In this way, the right combination of synthesis variables allows synthesizing AAO coatings with morphological characteristics best suited to each particular application.

The anodic oxidation of aluminium is an electrochemical technique that allows obtaining nanostructures with easily adjustable morphology depending on the synthesis variables, for its application in medicine, engineering, biotechnology, electronics, etc. In this work, low-cost aluminium oxide nanostructured films were synthesized and morphologically characterized using two anodization steps in sulphuric acid, varying the concentration and temperature of the electrolyte and anodization voltage. The order of the porous matrix, pore diameter, interpore distance, pore density, thickness, and porosity were measured and statistically analyzed. The results showed that under the proposed conditions it is possible to synthesize low-cost nanoporous aluminium oxide films, with a short-range ordering, being the best ordering conditions 10 °C and 0.3 M sulphuric acid at 20 V and 5 °C and 2 M sulphuric acid at 15 V. Furthermore, it was determined that the pore diameter and the interpore distance vary proportionally with the voltage, that the pore density decreases with the voltage and increases with the concentration of the electrolyte, and that the thickness of the oxide film increases with electrolyte concentration, temperature, and anodization voltage.

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