Standard Aluminum Zinc-Anode Rod

A sacrificial galvanic anode rod is used to prevent corrosion to a more noble metal. When attached to the noble metal, the anode will corrode before the noble metal will corrode. In the case of a water heater application, the sacrificial anode rod is inserted into the tank and the metal it is protecting, the inside of the tank, will not corrode unless the anode rod corrodes away first.

The type of anode rod chosen for a water heater depends on water quality. Magnesium rods are intended for soft water or not-so-hard water applications. As it corrodes, magnesium will dissolve into the water, making a healthy water for drinking. Aluminum rods are used for hard water or even salt water applications. Aluminum rods mixed with zinc will help remove sulfur dioxide smells from water, which will be present when there is heavy amounts of Iron in the water.

Sacrificial anode rods should be checked periodically for excessive corrosion. Once the rod has been spent, it should be replaced with a new rod. The time in which it takes for the rod to corrode depends entirely on the quality of the water. In good water conditions, the rod may only need servicing every 5 years. In bad water conditions, it may need to be serviced as early as 1 year.