Anodes Explained

Unless you are in the heating and air, pipe-fitting, or boating industries, you probably do not know about anodes and how they protect metals that spend their lives in constant contact with water. Water heaters for example cannot resist corrosion for years on end without a little help, the same goes for boat hull made of aluminum. Eventually the corrosion will eat away at the housing metal, causing a leak that is essentially the end of life for these products. In order to prolong this inevitable death, another metal has to enter the scene and sacrifice itself to save the heater walls or hull. This martyr is the sacrificial anode and its duty is a bit complex.

The Science of Corrosion
Metal corrodes in a watery environment and some metals corrode faster than others. The corrosion is inevitable, caused by electrochemical reactions between the metal and the liquid it is immersed in. it is a natural phenomenon. The anode reroutes the electrochemical currents away from the metal casing or container to another piece of metal that is basically more reactive. The current flows to and through the anode, giving the heater or hull cathodic protection, or protection from the corrosion. The anode is called sacrificial because it corrodes to disintegration so that the other metal can be safe. The metal used to make the product submerged in water is called a noble metal. Steel is an example of a noble metal. Multiple anodes are used to extend the life of a water heater.

Why They Are Called "Zincs"
Anodes are often called zincs because they are usually made of zinc. Zinc is chosen to place the role of sacrificial anode because it has a higher galvanic voltage than iron, aluminum and other metals that are used in the industries. Zinc is more likely to attract the electrochemical current that leads to corrosion. Some anodes are made of aluminum, magnesium and other metals. The choice depends on the metal used in creating the pipe, heater, hull, etc.

How Magnesium Fits In
Magnesium has been found to be highly reactive to salt and is often used on boats that travel in salt water. Magnesium is also preferred because it is not reactive as the zinc is. When the boat is out of the water, the corrosion on a zinc alloy will accelerate. Magnesium anodes are also more reactive than aluminum anodes.

Magnesium anodes play an important role in the corrosion prevention process. Call it yet another advantage of being magnesium. Anodes are die-cast magnesium alloy, usually comprised of both zinc and aluminum. The combination brings the best of all three metals to sacrifice for the greater good of your water heater.