Abstract: The erosion-corrosion behavior of Ti80 alloy in simulated seawater under varying sand concentrations (3%, 5%, 7%, and 10%) was investigated. A combination of electrochemical techniques and mass loss measurements was employed to quantify the synergistic effects of mechanical erosion and electrochemical corrosion. Electrochemical impedance spec-troscopy and potentiodynamic polarization tests revealed that increasing the sand concentration significantly deteriorated the corrosion resistance of Ti80 alloy, shifting the mechanism from passive film-controlled to charge transfer-dominated. Morphological analysis indicated that edge regions experienced more severe erosion due to the enhanced shear stress. The decoupling analysis of erosion-corrosion components revealed that mechanical erosion was the dominant contributor to the total material loss, while corrosion-accelerated erosion accounted for major part of the synergistic damage, especially at higher sand concentrations. The repassivation capability of Ti80 alloy was effective at low sand contents but was over-whelmed at 10%, resulting in an active surface state and intensified material loss. Cathodic protection showed limited effectiveness at 7% sand concentration but became noticeably more effective at 10%, indicating its increasing benefit under more severe erosive-corrosive conditions.