An Introduction to Sacrificial Anodes

What are anodes and how do they work?
Sacrificial anodes have been in common usage in a multitude of applications for many years. They protect all ships at sea, underground and above ground pipelines, boilers, hot water heaters and generally steel structures immersed in water or damp soil conditions where corrosion could 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 anode corrosion can vary substantially.

For fresh and groundwater applications our 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.

Steel hulls are all protected
by sacrificial anodes.

Anodes will protect a multitude of steel
structures in rural applications.

What about Metal Water Tanks (Squatter's Tanks)?
Many of the large rural water storage tanks today have plastic liners thus eliminating the problem of internal rust. In most cases however, they sit directly on the ground thus being exposed to potential external corrosion. Many tank manufacturers initially supply our bagged (ground bed) anodes with their products but for that very effective protection to be ongoing, the anodes need to be replaced generally on a 10 year cycle. The same anodes can be very effective in protecting metal pipelines, bore heads and casings etc..

For steel water tanks without an internal liner, very effective protection can be provided by the insertion of special tank anodes supplied complete with end mounting brackets suitable for either bolting or welding directly to the inside walls below the water level. Alternatively anodes are available which are designed to be suspended from the tank’s roof frame.