Solution: Corrosion protection for reinforced concrete

Repairing damage to reinforced concrete structures caused by reinforcement corrosion is generally very labor-intensive and costly. Chloride-induced corrosion, in particular, leads to significant damage that compromises the structural integrity of the reinforcement and, in the worst case, can even cause buildings to collapse. Conventional renovation and repair methods often prove ineffective. In such cases, cathodic corrosion protection offers a gentle and cost-effective alternative.

The application of cathodic corrosion protection is regulated by EN 12696 and has been recognized in Europe for approximately 25 years as a repair method for reinforced concrete structures. In our region, it is primarily transportation structures such as bridges and parking garages, but also tunnels, seawater structures, or buildings under monument protection, such as churches, that are renovated using cathodic corrosion protection.

By applying an electrical voltage between the metal and the ground, the corrosion process can be actively influenced. Cathodic corrosion protection causes a potential reduction, thereby reducing the corrosion rate to a technically negligible value (approx. 0.01 mm per year).

Normally, the reinforcing steel in alkaline concrete is protected from corrosion by a very thin passive layer. However, the penetration of chlorides and carbonation leads to local destruction of this protective layer and, subsequently, to corrosion (Fig. 1).

The principle of cathodic corrosion protection is based on the fact that the anodic partial reaction—i.e., metal dissolution—is stopped by a direct current flowing in the opposite direction. To achieve this, an anode system is applied to the concrete surface, and the exposed reinforcement is connected to the negative terminal while the anode is connected to the positive terminal of a rectifier serving as the power source (see Fig. 2). After switching on the rectifier, a current flow opposite to the anodic metal dissolution is generated, which prevents further corrosion of the reinforcing steel. The corrosion process is stopped.