Homogeneous corrosion of high pressure torsion treated Mg–Zn–Ca alloy in simulated body fluid

Magnesium alloys have got extensive attention as biodegradable implant materials due to their biodegradability in the physiological environment and similar elastic modulus to natural bone. But their poor corrosion resistance is a dominant problem that limits their clinical application due to the inhomogeneous distribution of the second phase. Nevertheless, after high pressure torsion (HPT) treatment, the second phase became nano-sized particles and distributed uniformly in grain interiors instead of along grain boundaries. The immersion tests indicated that the HPT-treated sample exhibited homogeneous corrosion resulting from the uniform distribution of the second phase. The results of the potentiodynamic polarization experiments showed that, compared with the as-cast alloy, the corrosion current density of the HPT-treated alloy decreased from 5.3 × 10 − 4 A/cm 2 to 3.3 × 10 − 6 A/cm 2. ► The second phase exhibited uniform distribution as nano-sized particle after HPT. ► The HPT-treated sample showed uniform corrosion in immersion tests. ► The corrosion current density decreased by two magnitudes after HPT treatment.