Multi-scale study on the electrochemical behavior and corrosion mechanism of 5083 aluminum alloy with different microstructures in a NaCl environment

We conducted electrochemical experiments on 5083 aluminum alloy with different microstructures and measured the samples before and after corrosion by SEM and EBSD. At the same time, density functional theory was used to calculate the chloride ion adsorption behavior of the Mg₂Al₃ phase, which explained the corrosion mechanism on a multi-scale. The results indicated that edge and heart specimens with varying grain sizes exhibited different trends post heat treatment. Specifically, increasing temperature led to larger grain sizes in the heart region, while smaller grain sizes were observed at the edge. Furthermore, the quantity of the second phase was higher after heat treatment at 550 °C compared to 520 °C. The grain size affects the densification of the passivation film and the potential difference between the second phase and the substrate, leading to variations in corrosivity. Density functional theory calculation demonstrates that the Mg₂Al₃ (001)MgAl and (001)Al surfaces exhibit higher susceptibility to Cl⁻ adsorption, showing the lowest adsorption energies of Cl⁻ at the Mg-top of (001)MgAl and Al-top sites of (001)Al. A stronger bond between Cl⁻ and Mg atoms leads to intergranular corrosion in different directions.