Cavitation erosion of the AA7050 aluminum alloy in 3.5 wt% NaCl solution-Part 1: mitigating effect by corrosion

The corrosion in 3.5 wt% NaCl solution caused a mitigated weight loss of the aluminum alloy 7050 (AA7050) under cavitation erosion condition. The mechanism was observed using high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), electro back-scattered diffraction (EBSD), and potentiodynamic polarization. Both in deionized water and in 3.5 wt% NaCl solution, the cavitation erosion degradation of the AA7050 was mainly attributed to fatigue fracture like peeling off of surface layer materials. The corrosion significantly mitigated the weight loss of AA7050 under cavitation erosion condition because the loose surface oxide film (generated by corrosion) dissipated the cavitation impact energy and therefore alleviated the stress concentration on the alloy surface.