Microstructural and Electrochemical Analyses of Al-Zn-In Sacrificial Anode Produced Using Semisolid Slope Casting Process Under Various Casting Conditions

The effect of superheat temperature, slope angle, and the length of the cooling surface on the microstructure and electrochemical behavior of the Al-Zn-In sacrificial anode were investigated. The optimal microstructure, as measured by the highest sphericity (0.72) and the smallest grain size (32 μm), was obtained by the melt at a temperature of 680°C, the slope angle of 45°, and the cooling surface length of 500 mm. Increasing the superheat temperature and the length of the cooling surface had the greatest influence on the sacrificial anode’s microstructural characteristics and electrochemical performance. The corrosion rate for the optimal and primary as-cast Al-Zn-In (blank) samples was 0.14 mm/y and 0.034 mm/y, respectively, indicating that implementing a semisolid process had a positive effect on the corrosion rate of the sacrificial anode. Furthermore, the reduction in corrosion resistance for the optimal sample compared to the blank sample, as well as the continuous corrosion process occurring without significant changes in corrosion resistance over time as measured by the electrochemical impedance spectroscopy (EIS) test, indicates that corrosion data and EIS results were in agreement. In addition, the electrical current that the optimal anode sample can provide has increased from 0.006 A to 0.012 A when compared to the blank sample, according to the results of the chronoamperometry test.