Understanding Tribocorrosion of Aluminum at the Crystal Level

Aluminum (Al) and its alloys are excellent corrosion-resistant materials due to their sustained passivity in neutral aqueous solutions. However, tribocorrosion remains a major threat to the integrity of Al, during which corrosion and wear work synergistically to accelerate material degradation. In this work, a combined experimental and computational investigation was carried out using Al single crystals to develop a crystal-based tribocorrosion modeling framework that accounts for the effects of lattice reorientation and dislocations on surface corrosion. Specifically, the mechanical, corrosion, and tribocorrosion properties of Al (100), (110), and (111) single crystals were measured experimentally, followed by characterization of lattice rotation and dislocation density via electron backscattered diffraction (EBSD). Unlike the mechanical and corrosion properties that are orientation-dependent, the tribocorrosion rate was found to be insensitive to the initial orientations of the crystals. Using the experimental results as inputs and validations, a multiphysics finite element model was developed that successfully predicted the depassivation and repassivation currents during tribocorrosion by mapping the local corrosion kinetics as a function of passivation state, crystallographic orientation, and dislocation density. It was found that lattice rotation, rather than dislocations, dominates the overall tribocorrosion behavior. Finally, the decrease of orientation-dependence during tribocorrosion was explained in terms of the coupling between the un-rotated lattice in the unworn region and the rotated lattice from the worn region.