Cathodic protection for historic properties

The structural condition of the Oldehove, the pride of the people of Leeuwarden, is in good shape for the time being. The metal ring anchors in the national monument have been preventively treated against corrosion and cannot cause any damage to floors or walls for the next fifty years. A safe future for the Oldehove and for much more monumental heritage.

In the Netherlands, we know better than anyone else the effects of water on metals. The chemical reaction between metal (iron) and oxygen causes corrosion, resulting in loss of material and the deterioration of ships, pipes, installations, systems and structures. Increasingly, this degradation process is stopped with cathodic protection. A highly efficient approach, also for the preservation of historic buildings.

One company highly skilled in the application of cathodic protection is Van der Heide. "Too often for building preservation, the choice is made to replace the metal," kicks off Leo van Kuijl, expert in cathodic protection. "But that requires a lot of demolition work, especially if the corrosion occurs in the anchors of walls that are sometimes more than a meter thick. That is precisely what you don't want in a monument. After all, there are other effective methods to stop the corrosion. Both with the active protective current and with sacrificial anodes, we can halt corrosion processes."

The sacrificial principle is based on the fact that base metals "sacrifice" themselves for the precious metals. Van Kuijl explains: "In ships where zinc anodes are applied to steel, the zinc will corrode, reducing the corrosion potential of the ship's steel. The same principle takes place when we apply zinc anodes on steel anchors in masonry. Wherever this principle is applied, the anchors are cathodically protected and last longer." 

Another form of cathodic protection is the application of an active protective current or "impressed current" system. This system uses a continuous direct current of only five to 10 volts, similar to the voltage required for an LED light. Anodes are used to conduct the tiny current to the steel elements to be protected. Van Kuijl: "This cathodic protection lasts up to fifty years and is therefore also sustainable. The power box - the rectifier - has a lifetime of more than twenty years and can be replaced very easily."

At the Oldehove in Leeuwarden, the impressed current system has been successfully applied. Anchors with cross sections of up to three centimeters are now permanently protected and will keep the monument's thick walls standing for at least another fifty years. In the same way, Van der Heide has already secured several church towers and a water tower for the future. "For historic buildings, cathodic protection is the solution of choice. The conductive elements are simply cut into the joints, causing minimal damage to the monument. In fact, there is no question of demolition at all. Not for nothing do the clients of renovation projects increasingly know how to find us."