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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. • The effects of corrosion on the cavitation erosion of the aluminum alloy 7050 (AA7050) was studied. • Corrosion generated protective oxide film was the crucial factor in the cavitation erosion resistance of the AA7050. • Dislocation lines tended to concentrate at the grain boundaries and at the second phase boundaries during cavitation erosion. • Under a cavitation erosion condition, the stress on the surface of the AA7050 was mitigated by corrosion. [ABSTRACT FROM AUTHOR]