Adsorption-induced surface potential shifts governing electrochemical passivation on the Zr50–Ti40–Nb5–Ta5 (1 0 0) surface in chloride-containing physiological media: DFT and experimental evidence

Metallic bioimplants frequently experience corrosion in physiological environments, resulting in chronic inflammation and failure. A combined DFT and experimental study is proposed for the newly synthesized Zr50–Ti40–Nb5–Ta5 multicomponent alloy (MCA) and a comparison is made with the existing Ti MCA to benchmark corrosion behavior. Adsorption studies involving physiologically relevant corrosive species reveal preferential binding at (1 0 0) surface hollow sites on both alloy surfaces. While Ti MCA exhibits stronger adsorption energies, Zr MCA displays a positive electrochemical potential shift upon O₂ and –OH adsorption, indicative of enhanced surface passivation and corrosion resistance. In contrast, Cl^- adsorption induces negative shift which leads to surface destabilization with less pronounced effect in Zr MCA. Potentiodynamic polarization in Phosphate Buffer Solution (PBS) shows that Zr MCA achieves an extremely low corrosion current density and corrosion rate with a wide passive window. A stable transpassive region followed by rapid repassivation is observed indicating strong self-healing behavior of the passive film even at high anodic potentials. Electrochemical Impedance Spectroscopy shows a compact passive layer with high charge transfer resistance (314.03 ± 2.35 kΩ) and thickness of 5.94 ± 0.54 nm. SEM-EDS indicates a dense multicomponent oxide layer without any localized breakdown, supporting electrochemical evidence of chloride-resistant passivation.