l  Magnesium or aluminum anodes are called sacrificial anodes, they protect tank from corrosion by losing their mass in water.  

l  When a magnesium anode is used up, the tank is in danger of being corroded by water. 

l  So replacement of used-up magnesium anode is a must and this costs a lot during the work time of water heater.

l  Why to use powered anode systems