Electrochemical techniques were used to study the characteristics of five zinc sacrificial anodes in 3.5wt% NaCl solution. The corrosion rate vs time was determined by linear polarization (or named polarization resistance). It was found that the anodes with high iron or low aluminum content exhibited lower corrosion rate, i.e., worse activity. From the potentiodynamic curves, it was also found that the less active anodes were much easier to be polarized anodically. Furthermore, the corresponding current for the less active anodes with 10 mV over-potential was only a quater of the normal ones. In addition, results of SEM image of the anodes, which had been immersed in 3.5wt%NaCl solution for 42 days, indicated that the corrosion products on the surface were influenced by aluminum element. The morphology of the corroded surface was divided into two types, i.e., particle-like and layer-like. The main product was Zn(OH)2.