EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Aluminum is an important metal because of its physical and mechanical properties, high strength-to-density ratio, and very good resistance to atmospheric corrosion. In atmospheric conditions, a passive layer of aluminum oxide forms on aluminum, which provides atmospheric corrosion resistance. However, this protective layer fails in harsh conditions, e.g. in presence of highly concentrated acids or bases. In order to prevent corrosion of aluminum, it is essential to understand the events occurring during acidic and alkaline aluminum corrosion.
In this work, the corrosion process of bare and oxide-covered aluminum in aqueous environment was investigated. The research was carried out using reactive molecular dynamics simulations (ReaxFF force field). Aluminum corrosion was studied in model acidic and basic solutions. Simulations of the system consisting of aluminum covered with a layer of aluminum oxide in an aqueous environment were also performed in order to check the protective properties of this layer. Two concentrations of H3O + or OH- ions (5% at. and 25% at.) and two temperatures (333K and 363K) have been considered. Simulated atom trajectories were used to analyze the charge distribution, structure and ion density distribution, which are used to understand the corrosion mechanism. Moreover, the thickness of the aluminum oxide or hydroxide layer was measured. Finally, topological analysis of the structures was performed using the Voronoi index method. The obtained results document the differences in aluminum corrosion mechanism under acidic and basic condition, which are discussed with available literature data.