Effects of alloying elements on the corrosion behavior and discharge performance of Al-Zn-Mg-In-Ti-Sn sacrificial anode

A range of Al-Zn-Mg-In-Ti-Sn sacrificial anode alloys were designed and prepared, and the effects of In, Sn and Ti elements on the microstructure, self-corrosion and discharge properties of the alloys were investigated by orthogonal experiments. The experimental results indicate that In and Ti are solidly dissolved in the matrix, and Sn exists as Mg9Sn5 phases at the grain boundaries. Ti refines the grain size. The order of alloying elements affecting the corrosion rate and current efficiency of Al-Zn-Mg-In-Ti-Sn alloy is In>Sn>Ti. In promotes the activated dissolution of the anode due to dissolution-redeposition mechanism, but excessive addition of In inhibits the shedding of discharge products, leading to deteriorative discharge activation. Addition of Sn in Al anode increases the amount of anodic Mg9Sn5 phases and promotes the discharge activation of the substrate due to the galvanic corrosion. Al-5.5Zn-1.0Mg-0.02In-0.04Sn sacrificial anode has a current efficiency of 98.6 % and an actual capacity of 2816.9 Ah/kg, demonstrating an excellent discharge performance. During the discharge process, anodic dissolution mainly occurs along grain boundaries and the second phases, forming corrosion pits and then expanding over time. The accumulation of discharge products and excessive second phases leading to grain detachment significantly decrease the current efficiency of the Al-Zn-Mg-In-Ti-Sn alloy.