Multiscale investigation of corrosion damage initiation and propagation in AA7075-T651 alloy using correlative microscopy

Abstract

The evolution of the overall microstructure and contribution of constituent second phase particles during the accelerated corrosion of AA 7075-T651 warrants further scrutiny. A correlative microscopy-based approach was employed to study corrosion damage evolution in the microstructure of AA 7075-T651 subjected to potentiodynamic polarization. X-ray Computed Tomography (XCT) and scanning electron microscopy were used to track corrosion damage initiation and propagation globally and at specific regions of the microstructure starting from the first breakdown potential. Additionally, Focused Ion Beam and Electron Backscattered Diffraction were used to investigate local corrosion processes such as pitting and intergranular corrosion. Interesting concentric corrosion patterns, Fe-rich intermetallic particle dissolution and exfoliation corrosion were observed and mechanisms for the same have been proposed.