Influence of Mo equivalent in the corrosion resistance of Ti-10Mo-xNb alloys

β-Ti alloys are gaining space in biomedical applications due their favorable combination of mechanical properties including their low elastic modulus and corrosion resistance. In this context, β titanium Ti-10Mo-xNb (x = 0, 6, 9, 20 and 30wt%) alloys were designed and produced. The relationship among the alloy composition, microstructure, and corrosion properties was investigated. The results were compared with those of the commercial Ti-6Al-4V and Ti(cp) alloys. Results showed that with increasing Mo equivalent, the contents of the α’’ and ω phases decreased, while the content of the β phase increased accordingly. The produced Ti-10Mo-xNb alloys exhibited hardness values higher than commercially pure Ti (cp). Among them the Ti-10Mo, Ti-10Mo-6Nb and Ti-10Mo-9Nb alloys showed hardness values comparable to Ti-6Al-4V alloy. Furthermore, each alloy exhibited a lower elastic modulus than Ti-6Al-4V, with Ti-10Mo-20Nb (74 GPa) and Ti-10Mo-30Nb (94 GPa) showing significantly reduced values. All the Ti-10Mo-xNb alloys exhibited high corrosion resistance, attributed to the formation of a passive film after exposure to the physiological saline solution. The corrosion properties were evaluated using potentiodynamic polarization curves and chronoamperometry. Alloys with lower Nb contents (0 and 6%) exhibited relatively higher corrosion resistance, whereas those with higher Nb content showed reduced effectiveness of the protective film. This behavior can be related to the presence of fine α″-phase precipitates distributed within the matrix of the Ti-10Mo and Ti-10Mo-6Nb alloys. The Ti-10Mo-20Nb alloy, however, exhibits the most favorable overall balance, combining the lowest elastic modulus with high corrosion resistance.