Electrochemically obtained Al2O3 nanoporous layers with increased anticorrosive properties of aluminum alloy

Abstract

The nanoporous layers of aluminum oxide obtained by means of the anodic oxidation process, in 1 M H2SO4 in which 1 g/L Al2(SO4)3 × 18H2O was added, at constant potential and three oxidation times, are subjected to corrosion tests in 3.5% NaCl solution, pH = 5.75, to evaluate their anticorrosive properties compared to the unmodified surface of the Al1050 aluminum alloy. Electron microscopy and EDX compare the morphology of nanostructured aluminum oxide surfaces with their composition and layer thicknesses. Also, by analyzing the X-ray diffraction, the aluminum oxide is highlighted by the specific diffraction peaks. The evaluation of the corrosion resistance is performed by the electrochemical methods like evolution of the free potential depending on the immersion time and electrochemical impedance spectroscopy. From the analysis of the obtained results, a uniform and size distribution of the nanopores is observed, between 17.8 nm and 47 nm, depending on the anodic oxidation time. All nanoporous layers of aluminum oxide obtained have improved anticorrosive properties compared to untreated aluminum alloy.