The effect of heat treatment on element distribution and electrochemical properties of Al-Zn-In anodes

Purpose - The purpose of this paper is to consider the effect of heat treatment on alloying element distribution and the electrochemical properties of Al-5Zn-0.03In anodes. Design/methodology/approach - The Al-5Zn-0.03In alloy anodes are treated at 510 degrees C for 10 h, then cooled in water. Electron probe microanalysis of JXA-8800 and EDAX quantitative energy dispersive X-ray analysis is used to examine the microstructure of the anodes before and after heat treatment, and the electrochemical properties of the anodes are tested. Findings - By heat treatment, the solubility of Zn in aluminum is increased while the solubilities of Fe and Si are changed only slightly. The quantity of the AI-Zn intermetallic compounds is evidently decreased and the AI-Fe-Si intermetallic compound is preserved. Strip segregation along grain boundaries is changed to spherical particulates. The attack of aluminum anodes initiates and propagates in grain boundaries and interdendritic zones, which are enriched in In and Zn, so the current efficiency of the aluminum anodes is related to the degree of corrosion taking place at grain boundaries and the extent of exfoliation of grains. The greater the extent of AI-Zn metallic compounds that are present at grain boundaries, the more sensitive to grain boundary corrosion is the alloy and the greater the degree of desquamation of grains, the lower is the current efficiency of the aluminum anode. Originality/value - The results of this paper clarify the role of water-quenching affect on the microstructure and electrochemical properties of Al-Zn-In anodes.