Multiscale modeling of a mechanochemical degradation path in aluminum surface coatings

Protective surface coatings inhibit aluminum corrosion pathways by replacing the highly reactive metal surface with one that is more chemically stable. Processes which erode these protective films render aluminum more susceptible to corrosion. We use ab initio molecular dynamics to model the erosion of γ-alumina surfaces and calculate associated reaction barriers while subjecting the oxide surface to environmental stressors, including vacuum, pooled water, and mechanical stress. We find that the presence of water reduces erosion reaction barriers by over 60% with respect to vacuum. Connections with microstructure-aware micromechanics models show that localized shear stresses can develop, which are predicted to couple with an aqueous environment resulting in further barrier reductions. These findings highlight the relevance of solvent and surface strain on aluminum corrosion and serve as a basis for predictive multiscale lifetime models.