Experimental and theoretical study on corrosion mechanism of aluminium alloy in different corrosive solutions

Abstract

A detailed comparison of the corrosion behaviour of Al–O (1 1 1) surfaces on 7A46 aluminium alloy in 1.0 M hydrochloric acid and sulfuric acid solutions was conducted using electrochemical, surface analysis, and density function theory calculations. The results show that the corrosion current density is around 80.62 μA.cm−2 in HCl solution and 104.21 μA.cm−2 in H2SO4 solution. Uncovered defects in the oxide film on the alloy surface can contribute to local erosion and degradation during the corrosion process. In addition, the amounts of charge transferred from the surface of the alloy to Cl− and O2− were 0.811 and 0.178e, respectively, suggesting the formation of an Al–O bond on the surface, which expedites the corrosion process in the HCl solution. In contrast to HCl, the O atoms on the surface of the aluminium alloy obtained 2.032 e and 1.611 e electrons from Al on the Al–O (1 1 1) surfaces and S atoms in H2SO4 solution, respectively, indicating a strong adsorption affinity for SO42−. Both Cl–Al and S–Al bonds form covalent bonds. It is worth mentioning that the resonance peaks in the HCl adsorption system was between −6 eV and 2 eV, whereas that in the H2SO4 adsorption system show a more pronounced shift to the right (−10 eV to 0 eV), suggesting heightened system activity and increased electronic interactions among the atoms in H2SO4 adsorption system. This research contributes to a comprehensive understanding of the surface corrosion behaviour of aluminium alloys, providing valuable insights for the design and application of aluminium alloys across diverse environmental contexts.