The high cost of corrosion can be substantially reduced by installing a cathodic protection system to transfer the corrosion from the structure being attacked to an anode system. Corrosion takes place when an anode and cathode are electrically connected and are surrounded by an electrically conductive electrolyte, such as moisture in the soil. When these conditions occur, an electrical current will flow, and the anode will be consumed.
Because magnesium is one of the least noble elements, it makes a superior sacrificial anode for the protection of underground steel pipelines and structures, and water heaters. By connecting a magnesium anode to a structure of a different metal, electrical current is generated that polarizes the structure, making the entire surface cathodic and protection complete.
Often times the importance of current efficiency is overlooked when evaluating magnesium anodes. Current efficiency is the percent of metal consumed in producing useful cathodic protection to the total metal consumed. Because anodes must be installed in a corrosive environment to produce useful amount of current, the environment also promotes self‐corrosion of the anode material. Electrical currents produced by self‐ corrosion cannot be used to advantage; the higher the percent of current efficiency, the better the anode, which also translates into longer life. A quality high potential magnesium anode should have a minimum current efficiency of 50%.