Influence of casting temperature on electrochemical behavior of Al-Zn-In sacrificial anodes

Aluminum anodes have been widely used in the cathodic protection of marine structures. However there are conditions in which these anodes become passivated or face some localized or unwanted corrosion, which influences their efficiency. Addition of alloying elements such as Zn and In not only have improved the efficiency of the anodes but also the effect of casting parameters such as ultra melt temperature T-m, mold temperature and grain refiners can adversely influence the capacity of aluminum anodes. In this work the effects of ultra melt temperature and mold temperature have been studied on the potential and current capacity of Al-Zn-In anodes. Electrochemical polarization and AACE standard methods were used to evaluate the anodic behavior, potential and current capacity of the anodes. It is shown that metallic molds having higher temperatures could provide better condition for obtaining homogenous structures with minor inclusions. The optimum condition of anode operation may be provided where mold and pouring temperatures equal to 400 degrees C and 710 degrees C respectively, in which a fine structure, phase distribution and lack of casting faults are obtained. The microstructures that can provide a homogenous anodic dissolution bring by itself optimum efficiency of the anodes.