The performance of magnesium sacrificial anodes was evaluated to improve the efficiency of anodes based on Mg-Mn, Mg-Al and Mg-Al-Zn alloys. Potentiodynamic polarization, galvanostatic-weight loss tests, EPMA and XRD analyses were used to investigate the corrosion rate, driving potential, efficiency, microstructure. Polarization results indicated that the alloying with Mn, Al, Zn reduced the corrosion rates of Mg anodes. Corrosion morphology was changed from localized to uniform attack by the alloying. Addition of Mn to the Mg anodes yielded increased driving potential and efficiency. The efficiency of Mg-Al anodes was improved up to the 6.37wt% Al addition. The addition of Zn had a little effect on the efficiency of Mg-Al-Zn anodes. Mg-Mn anodes produced higher efficiency in the T6 heat treatment than in the as-cast condition. The improvement of efficiency on Mg-Mn anodes by heat treatment was related to the redissolution of Mg₂Si and Fe-Mn particles.