Effects of grain size and secondary phase on corrosion behavior and electrochemical performance of Mg-3Al-5Pb-1Ga-Y sacrificial anode

Abstract

Abstract Grains with size of 4.5–20.5\xa0μm were studied for their corrosion behavior and electrochemical performance in a Mg-3Al-5Pb-1Ga-Y sacrificial anode using immersion testing, electrochemical measurements and microstructure analysis. The results show that fine-grained microstructure has higher chemical activity and more negative discharge potentials than coarse-grained samples. The sample with the smallest average grain size of 4.5\xa0μm exhibits corrosion current density of 7.473\xa0×\xa010−5 A/cm2, and work potentials of\xa0−1.721\xa0V at current density of 10\xa0mA/cm2. The density of grain boundaries and LAGBs increases with grain refinement, which leads to higher rates of dissolution and diffusion for the atoms. The secondary phases promote the occurrence of corrosion and improve the chemical activity of alloy due to their higher potential than the substrate. Higher corrosion rate and discharge activity are directly attributed to the higher density of grain boundaries and LAGBs, as well as the secondary phase.