Effect of Erbium on Microstructure, Hardness and Electrochemical Properties of Al-5Zn-0.03In Alloy

Abstract

Al-5Zn-0.03In series alloys have been widely studied and used as sacrificial anode materials. Adding rare-earth (RE) element to Al-5Zn-0.03In sacrificial anode is the important way to improve its microstructure and properties. This paper focused on the effect of Er addition on the microstructure and properties of the Al-5Zn-0.03In-xEr alloy. Thermal analysis showed that the presence of Er in the series alloys reduced the solidification ranges and made their liquidus and solidus move to lower temperature. The microstructural analysis and hardness testing reveal that Er existed in the form of precipitation, refined the dendrites of the series alloys and improved the hardness of the series alloys. Investigation of the potentiodynamic polarization and the electrochemical impedance measurements were performed in 3.5 wt. % NaCl solution. The potentiodynamic polarization results indicated that the corrosion potential increased and the corrosion current density reduced with the increase of the Er addition. The Al-5Zn-0.03In alloy shows higher corrosion resistance with the increase of Er content. The EIS electrochemical impedance results showed that Al-5Zn-0.03In anode presented relatively uniform dissolution due to the refined microstructure by the addition of Er.