An Introduction to Sacrificial Anodes

What are Anodes and how do they work?

Simply it is the use of a very pure metal to attract the destructive electrolysis that causes rust, away from the metal surface and onto itself.

Sacrificial anodes have been in common and constant use in a multitude of applications for many years. They protect all ships at sea, underground and above ground pipelines, boilers, water heaters and generally steel structures immersed in water or damp soil conditions where corrosion could be expected to be a problem.

The corrosion (rust) is the result of electrolytic action travelling through moisture or fluid to home in on the metal surface at risk. Depending upon the existing conditions such as amount and quality of the fluid (water?) and the effective presence of any other protective coating on the metal surface, the rate of corrosion can vary substantially.

For this application the anodes are of a particular grade of magnesium which is “electro-negative relative to steel” which means that they will attract the destructive electrolytic action on to themselves. This type of galvanic protection is called sacrificial and the principle of electrolytic corrosion control is called cathodic protection. Because cathodic surfaces cannot rust, the steel surface is protected while an active anode is in place.