Abstract
The anodic dissolution and passivation processes of zinc and zinc-indium alloys were investigated in an alkaline solution of 6 M KOH using galvanostatic, electrochemical impedance, and charge–discharge measurements. Galvanostatic measurements exhibit anodic potential/time transient of the zinc anode and its alloys in the concentrated alkaline solution at different current densities. The data reveal that the passivation time (tpass.) diminishes with increasing the content of indium in the alloy under investigation. This means that the alloying of minor indium with zinc retards its dissolution at the active region. The high oscillations in potential, which are observed in the case of zinc, disappeared with the addition of a minor indium content to zinc (Zn-In alloy). The data acquired from impedance (EIS) exhibited that the values of polarization resistance (Rp) and Warburg impedance increase, while the double-layer capacitance (Cdl) diminishes with increasing a minor indium content at both two investigated potentials (−500 and + 500 mV vs. SCE). It is interesting to show that the inductive loop for alloys I and II at −500 mV is observed at intermediate frequencies, in addition to the capacitive loop and Warburg tail. The results of charge–discharge measurements show that the average charge discharge separation voltages of alloys I and II are 0.8 and 0.9 V, respectively, which are higher than that of pure zinc (0.7 V) at constant time. This indicates that indium alloying with zinc leads to improvement in both energy and charge efficiency.
Keywords Zn-in alloys · Galvanostatic measurements · Impedance · Charge–discharge properties · Charge efficiency · Specific capacitance