The Effect of Melt Shearing Process and Addition of Bismuth, Lithium and Tin Elements on the Electrochemical Efficiency of Al-Zn-Mn-Fe Sacrificial Anodes

In the present work, it was tried to improve the electrochemical efficiency of aluminum base sacrificial anodes with Al-Zn-Mn-Fe alloy by two mechanical and chemical methods and to compare the effect of these methods. In this regard, the melt shearing process at 0, 2 and 4 minutes was used as a mechanical method and the addition of bismuth, lithium and tin elements was used as a chemical method. The results of the microstructure investigation using optical (OM) and transmission electron (SEM) microscopes revealed that the melt shearing process leads to grain refinement, increasing the number of equiaxed grains and reducing the size of intermetallic compounds. With increasing the melt shearing time, the effect of microstructure modification increased and therefore the electrochemical efficiency of the samples increased so that the 4 minute sample showed the most modification of structure and the highest electrochemical efficiency. Also, the results showed that among the additive elements, adding Bi caused the best electrochemical efficiency. The results of comparing the effect of mechanical modification and chemical modification demonstrated that the effect of chemical modification is far better than the mechanical modification. The electrochemical efficiency of the mentioned alloy without melt cutting and chemical additives was 11%, but by applying melt cutting in 4 minutes, the efficiency increased to 15%, while due to the addition of bismuth, the electrochemical efficiency increased from 15% to 68%.