Evaluation of the microstructural, mechanical and anti-corrosive properties of a new ternary Ti-15Zr-5Nb alloy in simulated oral environment

A new ternary Ti-15Zr-5Nb alloy was elaborated with the aim to satisfy the most stringent requirements of a good implant material. The alloy has alpha + beta bi-phase microstructure (by XRD and optical microscopy) and presents a proper combination between Young's modulus, elasticity and good ultimate tensile strength and 0.2% yield strength (from stress-strain tensile curve), indicating a good suitability as implant material. Electrochemical behaviour in artificial Carter-Brugirard saliva of different pH values (3.96, 7.84, and 9.11) and composition (un-doped and doped with 0.05 M NaF) that simulate the severe functional conditions in the oral cavity was evaluated. All electrochemical parameters of the new alloy revealed more favourable values than those of the CP Ti and Ti-6Al-4V ELI alloy, showing a more compact, resistant passive film formed on the new alloy surface. The corrosion rates and corresponding ion release rates for the new Ti-15Zr-5Nb alloy exhibited very low values (hundreds of times smaller) in comparison with similar commercial biomaterials. Electrochemical impedance spectra distinguished bi-layered passive film formed by inner, barrier layer and outer, porous layer. X-ray photoelectron spectra and scanning electron microscopy (SEM) observations proved that in time, protective compounds were deposited from saliva on the alloy surface, enhancing its corrosion resistance.