Electrochemical and immersion corrosion behaviour of TNZT-xSi-yMn/Fe/Zn composites for biomedical applications

The present study investigates the effects of low-cost alloying elements (Si, Mn, Fe, and Zn) on the corrosion behaviour, ion release, and surface characteristics of β-type Ti-35Nb-7Zr-4Ta (TNZT) composites for biomedical implant applications. TNZT-xSi-y (Mn/Fe/Zn) composites, where x = 0.5, 0.75, and 1.0 wt.% and y = 1.0, 1.5, and 2.0 wt.%, were successfully fabricated using powder metallurgy. The incorporation of Si and Mn/Fe/Zn alloying elements resulted in microstructural refinement, with the porosity ranging from 4.8 to 5.9%, compared with 5.82% for TNZT. Potentiodynamic polarization in 3.5 wt.% NaCl demonstrated improved corrosion resistance, with I _corr decreasing from 1.740 ± 0.072 µA/cm ² for TNZT to 0.125 ± 0.006 µA/cm ² for M4 and 0.120 ± 0.004 µA/cm ² for Z5. EIS further confirmed improved corrosion protection through increased polarization resistance (Rp), decreased CPE ₁ and CPE ₂ values, and increased n ₁ and n ₂ values, suggesting the formation of more compact and homogeneous passive films. XPS confirmed the formation of multicomponent passive films containing TiO ₂ , Nb ₂ O ₅ , ZrO ₂ , Ta ₂ O ₅ , and SiO ₂ , together with MnO _x , FeO _x , and ZnO. After 28 days of immersion in 0.9 wt.% NaCl, Ti ion release decreased from 0.0065 ± 0.0035 mg/L for TNZT to 0.0056 ± 0.0020 mg/L for M4 and 0.0031 ± 0.0001 mg/L for Z5, whereas F4 exhibited the highest Ti ion release of 0.0130 ± 0.0057 mg/L. The optimized M4 and Z5, exhibited improved microstructural refinement, passive-film stability, corrosion resistance, and reduced ion release, demonstrating their potential for biomedical implant applications.