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

Highlights: • Corrosion damage evolution in AA 7075-T651 under potentiodynamic polarization was studied by correlative microscopy. • Concentric Corrosion Patterns were observed before the second breakdown potential due to induced magnetic field and a Lorentz force. • Exfoliation Corrosion led to a combination of intergranular and transgranular corrosion leading to extensive grain dissolution. • Al₇Cu₂Fe particle dissolution was observed due to selective dissolution of Fe, Al, leaving behind Cu-rich clusters within the particle. 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.