Magnesium anodes are a type of sacrificial anode used in cathodic protection systems. Cathodic protection systems are used to protect metal structures such as pipelines, tanks and ships against corrosion. The magnesium anode is composed of a magnesium alloy, which is more active than the metal structure it is protecting. When connected to the structure, the anode corrodes preferentially over the structure, providing cathodic protection by diverting the corrosion reactions to the anode.

Magnesium anodes are suitable for use in a variety of environments, including saltwater, freshwater, and soil. They are also relatively inexpensive and easy to install. However, they have a relatively short lifespan compared to other types of anodes, typically about 2-3 years. They also require regular inspection and replacement, as the magnesium alloy will be consumed over time. They are also more commonly used in freshwater applications, as they have a lower driving voltage than zinc or aluminum anodes which are more suitable for salt water applications.