Effect of Alloying Elements on Electrochemical Properties of Magnesium-Based Sacrificial Anodes Available to Purchase

Effects of alloying elements on electrochemical properties of magnesium-based sacrificial anodes were evaluated. Potentiodynamic, galvanostatic, potentiostatic, scanning electron microscopy (SEM), and x-ray diffraction (XRD) analyses were used to investigate the corrosion rate, efficiency, and surface characteristics of anodes. Polarization data indicated that alloying with manganese, aluminum, and zinc reduced the corrosion rates of magnesium anodes. All anodes did not undergo passivation but demonstrated only active behavior. Corrosion morphology was changed from localized to uniform attack by the alloying. Addition of manganese to magnesium anodes yielded increased driving potential and efficiency. The efficiency of Mg-Al anodes was improved up to ~ 6% Al addition. The addition of zinc increased the efficiency of Mg-Al-Zn anodes compared to the efficiency of Mg-Al anodes, but the reversal of this behavior happened as the zinc content exceeded ~ 3%. The increase in the efficiency of Mg-Al and Mg-Al-Zn anodes was accompanied by a decrease in the driving potential. The decrease of driving potential might have resulted from a somewhat resistive film on the surface, which hindered the transport of ions. The increased corrosion resistance generally improved anode efficiency.