Effect of addition of indium on corrosion resistance of AZ۶۳-۱.۵La anodefor seawater batteries

Developing anodes for seawater batteries need to control anodic reaction kinetics, cathodicreaction kinetics, and self-peeling discharge product films. Alloy AZ۶۳-۱.۵RE is a suitablechoice as anode in seawater batteries. In spite of its impressive corrosion resistance, AZ۶۳-۱.۵REalloys cannot satisfy the increasing demands for higher corrosion resistance, especially forsubmersion in seawater. The addition of indium can improve the properties of AZ۶۳-۱.۵REanode. In this study, corrosion resistance of AZ۶۳-۱.۵RE-۰.۵In is compared with the AZ۶۳-۱.۵RE alloy. The open circuit potential, potentiodynamic polarization, and electrochemicalimpedance spectroscopy tests were used to examine the corrosion resistance of alloys. As can beseen in Fig. ۱a, the corrosion potentials (Ecorr) of AZ۶۳-۱.۵RE alloy is ‒۱.۵۹۰ V vs. SCE, whichthe addition of In element causes a shift in the potential towards a more positive value (-۱.۶۳۲ Vvs SCE). The ۱.۵RE alloy has lower corrosion current (icorr) (۷.۵۸ × ۱۰-۵ mA cm-۲) and the loweranodic slope (βa) (۰.۱۱ mV dec‒۱), therefore it has higher corrosion resistance. The EIS plot (Fig.۱b) show that with an Rct of ۱۵۵۲ Ω cm۲, the AZ۶۳-۱.۵RE-۰.۵In alloy has the higher corrosionresistance than AZ۶۳-۱.۵RE alloy. There are two essential factors which determine the corrosionresistance, namely the β-Mg۱۷Al۱۲ phase continuity along the grain boundary, the number of β-Mg۱۷Al۱۲ phase and rod like Al-RE phase particles in the α-Mg grains (Fig. ۱c). The addition ofIn element helps in increasing the corrosion resistance of the alloy by reduction of contributionof β-Mg۱۷Al۱۲ phases.