One type of cathodic protection system is the sacrificial anode. The anode is made from a metal alloy with a more "active" voltage (more negative electrochemical potential) than the metal of the structure it is protecting (the cathode). Sacrificial anodes generally come in three metals: magnesium, aluminum, and zinc.
Regarding this, how often should you replace the anode rod in a water heater?
When the rod itself becomes so corroded that it can no longer do its job, the tank soon rusts out, leaks and needs replacement. However, if you replace your anode rod before it fails, about every five years, you can double the life of your water heater.
Do powered anode rods work?
The electrode is made of titanium. Interestingly, while sacrificial anodes are consumed more rapidly in softened water, powered anodes actually work less hard because higher conductivity makes it easier for electricity to flow between anode and cathode (tank steel).