The effect of calcium on corrosion behavior of biodegradable Mg-5Zn-1Y Alloy

Today, magnesium alloys as the new generation of biodegradable alloys, have attracted the attention of many researchers. In this research, the corrosion behavior of cast Mg-5Zn-1Y containing different amounts of calcium (0, 0.1, 0.5 and 1 weight percentage) was investigated. The microstructure of the alloys was analyzed using optical and scanning electron microscopes, and the corresponding phases were detected by X-ray diffraction. Corrosion behavior of cast alloys was measured using electrochemical polarization and immersion tests. Metallography analysis revealed that microstructure of the Mg-5Zn-1Y alloy includes α-Mg matrix and Mg3YZn6 lamellar phase formed at the grain boundary. The addition of calcium to the alloy refined the grains and resulted in the formation of continuous Ca2Mg6Zn3 at grain boundaries. No passive zone was detected in polarization curves, meaning domination of active polarization, indicating increased corrosion rate due to grain refinement which can be attributed to calcium addition in the alloy. The polarization and immersion tests results confirmed that the alloy Mg-5Zn-1Y-0.1Ca has the lowest corrosion rates among the investigated alloys, and the more the calcium content, the higher the corrosion rate due to the formation of cathodic Ca2Mg6Zn3 phase.