Synergistic effect of chloride assisted nanoporous anodic TiO2 and silver nanoparticle modification on the corrosion behavior of additively manufactured Ti-6Al-4V implant alloy

Titanium alloys are widely used as implant materials; however, their long-term performance in physiological environments is often limited by corrosion and surface instability. In this study, nanoporous TiO2 layers were formed on additively manufactured Ti-6Al-4V by anodization in H2SO4 and H2SO4 + NaCl electrolytes and subsequently functionalized with silver nanoparticles (Ag NPs) by cyclic voltammetry. The structural, morphological, topographical, and electrochemical properties of the modified surfaces were systematically investigated using XRD, SEM/EDS, 3D profilometry, and electrochemical tests in simulated body fluid (SBF). Anodization significantly improved the corrosion resistance of Ti-6Al-4V, increasing the coating resistance into the 103-104 MΩ·cm² range and reducing the corrosion rate by up to ∼84% compared with the untreated alloy. Samples anodized in H2SO4 + NaCl and further modified with Ag NPs exhibited the highest impedance values and the lowest corrosion current densities and retained high resistance after polarization, indicating superior electrochemical stability. Post-corrosion SEM/EDS analyses revealed reduced localized attack together with Ag- and Ca–P-containing surface layers on Ag NPs-modified samples. Overall, the results demonstrate that chloride-assisted anodization produces more compact and homogeneous nanoporous TiO2 layers, while Ag NPs modification enhances the stability of the oxide by sealing defects and promoting repassivation in SBF.