Effect of Lamellae Modification in Eutectic Al<sub>82.70</sub>Cu<sub>17.30</sub> Alloy on its Electrochemical Performance as Anode Using Symmetric Cell Electrochemical Impedance Spectroscopy

The purpose of this research is investigating the effect of eutectic lamellae modification through heat-treatments on the electrochemical performance of Eutectic aluminum-copper (E-Al 82.70 Cu 17.30 at%) alloy. The alloy works as anode in less expensive aluminum chloride (AlCl 3 ) aqueous electrolyte using Symmetric Cell Electrochemical Impedance Spectroscopy (SCEIS). The alloy was produced using an arc furnace followed by heat-treatments at different conditions. X-ray diffraction (XRD), optical microscope (OM), were used to characterize the alloys followed by SCEIS testing. The as-cast E-Al 82.70 Cu 17.30 showed some inhomogeneities in the lamellae microstructure, while heat-treating the as-cast E-Al 82.70 Cu 17.30 produced homogenized sponge-like eutectic microstructure. Two heat-treatment conditions were employed, that is 1. Heating the as cast alloy at 535 °C and soaking for one hour, and 2. Heating at 535 °C and soaking for five hours. Electrochemical Impedance spectroscopy measurements were performed on these three (3) samples. The Nyquist plot of as-cast E-Al 82.70 Cu 17.30 , 1 and 5 hours annealling heat-treated (1HT and 5HT respectively) displayed characteristic diameters in high, medium, and also low frequency range. After fitting using complex non-linear least squares method, 1HT condition has bulk resistance (R I ) and charge transfer resistance (R CT ) of ~9 Ω and ~566 Ω respectively, as compared to As-cast condition, which has R I of ~ 14 Ω and R CT of ~ 695 Ω, whiles 5HT condition has R I of ~26 Ω and R CT of ~724 Ω.