Effect of multipass thermomechanical processing on the corrosion behaviour of biomedical Co–Cr–Mo alloys

•Co–28Cr–6Mo–0.14N–0.04C (mass %) alloy is prepared by multipass hot rolling.•The process leads to significant grain refinement and accumulation of dislocations.•Influence of this microstructural evolution on the corrosion behaviour is studied.•The structural change had limited detrimental effect on the corrosion behaviour.•Finer grains and a high dislocation density likely contributed to enhanced passivity. We prepare a high-strength Co–28Cr–6Mo–0.14N–0.04C (mass%) alloy by multipass hot rolling and clarify the influence of the associated microstructural evolution on the corrosion behaviour. Potentiodynamic polarisation, static immersion tests, and electrochemical impedance spectroscopy indicate that the corrosion behaviour and passive film characteristics do not vary significantly between the annealed and hot-rolled samples. However, hot rolling was found to weaken the active-to-passive transition during anodic polarisation. These results suggest that significant grain refinement and accumulation of dislocations, which occurred simultaneously during multipass hot rolling, enhance the passivity.