Zinc is a more active metal and is electronegative compared to steel and common metal structural materials. However, the electrode potential of zinc is only less negative than that of magnesium electrode, and its protective potential relative to steel is only 0.25V potentiodynamic potential %. Therefore, zinc anodes are not suitable for high resistivity soil or fresh water, and are usually used for seawater, some chemical media and low resistivity soil or beaches. However, the current efficiency of zinc and zinc alloys as sacrificial anodes is only very high.