Effect of the chloride on passivity breakdown of Al-Zn-Mg alloy

•The corrosion behavior of Al-Zn-Mg alloy was explained using point defect model (PDM).•As the chloride concentration increases, the number of corrosion pits on the surface of the Al-Zn-Mg alloy increases.•The polarizability of the passive film/solution interface (α) is calculated to equal to 0.3654 for Al-Zn-Mg alloy.•The critical metal cation vacancy concentration required for breakdown of the passive film is about 8.85×1014 cm−2. The influence of chloride on the corrosion behavior of Al-Zn-Mg alloy was explored, and the results are explained using the Point Defect Model (PDM). Cyclic potentiodynamic polarization was utilized to study the breakdown behavior, and the corrosion morphologies for different chloride concentrations were observed using scanning electron microscopy, and the depth of the corrosion pit was measured using laser confocal microscopy. Furthermore, SPM and XPS were used to further analyze the behavior of pitting corrosion of Al-Zn-Mg alloy. The findings provide strong evidence that the PDM correctly simulates passivity breakdown of aluminum alloys in chloride-bearing coastal environments.