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Comparing Impressed Current Rods and Magnesium Anodes

by Donald Woods

When water, electricity and metal surfaces come into contact, they result in chain reactions that can lead to significant damage. Take the case of a water tank with a heater in your home. Using electric current to heat the water corrodes the surface of the metal tank. Therefore, you need a reliable method to help you take care of the metal walls of your tank. Anodic protection using sacrificial metals is the way to go these days. Particularly, using impressed current rods and magnesium anodes has proven effective over the years. Even though they produce similar results, both types of anodes work in different ways. Here is a thorough look at both forms of anodic protection to help you gain more insight:

Impressed Current Rods    

Impressed current rods are a mix of both cathodic and anodic protection systems. Essentially, a cathodic system is unique because it has two anodes. One is the impressed current anode while the other is a sacrificial anode. They rely on direct electric current (DC) to initiate and sustain the protection.

The purpose of the impressed current anode is to use a rectifier or external source of power to create an electrical potential difference between the surface you are protecting and the sacrificial anode. In doing this, the impressed current rod and the sacrificial anode both lose mass in the process, although the erosion is a lot slower than that experienced by ordinary anodic protection techniques. Impressed current rods are therefore ideal for large tanks and water heaters in both domestic and commercial settings. This is because you will need few anodes despite the size of the tank and you will enjoy a low set up cost.

Magnesium Anodes     

Magnesium anodes have also found widespread applications in anodic protection systems. Magnesium is actually preferred to zinc and aluminium anodes because of its highly negative electron chemical potential. It is thus suitable for use in areas where the surface you are protecting is in an area with high electrical resistivity such as in fresh water or in the soil.

During the process, magnesium anodes are involved in a chemical reaction where oxidation and reduction occurs. The anode plays the role of a reducing agent. Electrons leave the surface of the magnesium and result in an actual loss of mass. In doing this, the anode protects the surface of your metal tank, which would have otherwise been eroded by the electrochemical reaction. Magnesium is ideal for domestic settings to save on cost.