Long-term corrosion behaviour of an ω-resistant, β-type Ti-12Cr-3Sn alloy: Effect of Sn addition on surface passivation and metal ion release in simulated physiological environment

β-Ti alloys are considered to be the next generation of biomaterials, mainly due to their improved biomechanical compatibility for load-bearing applications. Control of the ω phase formation kinetics by ternary additions of Sn is expected to open up opportunities for tailored biomedical implants, particularly in the context of advancing additive manufacturing techniques. However, excellent corrosion resistance in the human body environment is an essential requirement to be considered in alloy design. In this study, the effect of Sn addition (3 at.%) on the corrosion and passivation behaviour of a β-Ti-12Cr alloy in PBS is evaluated by potentiodynamic polarisation and long-term electrochemical impedance spectroscopy. Furthermore, the composition of the formed passive layer and the concentration of released ions are analysed by X-ray photoelectron spectroscopy and inductively coupled plasma optical emission spectrometry. The TiCr(Sn) alloys exhibit low corrosion rates (i _corr≈42 to 52 nA cm ⁻²) and a stable anodic passivity, especially in the body potential region. In contrast to the clinically used Ti-6Al-4V, the TiCr(Sn) alloys retain their high corrosion resistance up to 168 h of immersion with no signs of dissolution of the protective layer formed. Their passivation behaviour is governed by a Ti- and Cr-oxide layer, while the less stable Sn-oxide seems to reduce the corrosion resistance and slightly increases the passive dissolution rate. Nevertheless, the concentration of metal ions released during long-term immersion remained below the detection limit. The observed corrosion performance of the Ti-12Cr-3Sn alloy suggests that the proposed design strategy is suitable for implant applications.