Enhancing the Corrosion Resistance and Antibacterial Performance of Titanium Alloys via Neodymium Addition in Natural Seawater

Microbiologically influenced corrosion (MIC) and chloride‐driven corrosion remain critical challenges for titanium alloys in marine service, while effective alloying strategies to simultaneously suppress interfacial degradation and biofouling are limited. Herein, we investigate Nd microalloying effects on corrosion and MIC behaviors of three typical titanium alloys (Ti–6Al–4V, Ti–3Al–2Mo–2Zr, Ti–4Al–0.005B) using microstructural, electrochemical, surface/interfacial and biological characterizations. In chloride‐containing seawater, Nd microalloying refines the grains by approximately 50%–60%, which stabilizes the interface, mitigates surface degradation, and reduces the susceptibility to severe localized corrosion. Meanwhile, the surface roughness is improved by approximately 14%–49% at the macroscopic scale, and the impedance response of the alloys increases to the order of 10 ⁵  Ω·cm ² at the microscopic/interfacial scale.In anaerobic static SRB systems, Nd‐modified alloys exhibit sparser viable cells and weaker corrosion‐product accumulation, indicating suppressed bioadhesion, biofilm stability and under‐film corrosion. The alloy‐dependent benefits arise from regulated microstructure and interfacial active sites, which reduce electrochemical heterogeneity and enhance interfacial protection. A unified mechanism is proposed to rationalize the coupled anticorrosion and antifouling effects, providing guidance for designing rare‐earth microalloyed titanium alloys for marine applications.