Effect of melting method on the bio-corrosion resistance of Mg67Zn28Ca5 cast magnesium alloy in simulated body fluid

Abstract

In recent years, biodegradable magnesium alloys have attracted considerable attention in medical devices, such as permanent implants and stents. However, poor corrosion resistance is a major problem limiting the practical application of magnesium alloys. In this study, Mg67Zn28Ca5 alloys were prepared via two different methods, namely, vacuum induction melting and ulfur hexafluoride shielded melting. The effect of melting method on the bio-corrosion resistance of MgZnCa cast magnesium alloy was also studied. The microstructure and phase composition of Mg67Zn28Ca5 alloys were investigated by optical microscopy and X-ray diffraction. The element distribution and surface morphology of Mg67Zn28Ca5 alloys were examined by scanning electron microscopy and energy-dispersive spectroscopy. The corrosion resistance of Mg67Zn28Ca5 alloys was measured via electrochemical and immersion tests. Results showed uniform composition of the Mg67Zn28Ca5 alloy melted by vacuum induction. Immersed in the simulated body fluid, the corrosion rate of Mg67Zn28Ca5 by vacuum induction melting (0.2618 mm/a) was lower than that by ulfur hexafluoride shielded melting (0.9686 mm/a); the corrosion potential of Mg67Zn28Ca5 melted by vacuum induction (−1313 mV) was nobler than that by ulfur hexafluoride shielded melting (−1483 mV); the corrosion current of Mg67Zn28Ca5 by vacuum induction melting (1.202 × 10−5 A) was lower than that by ulfur hexafluoride shielded melting (4.332 × 10−5 A). The Mg67Zn28Ca5 by vacuum induction melting showed uniform corrosion behavior.