Development of a Test Method for the Durability of Carbon Textiles Under Anodic Polarisation

Abstract

Cathodic protection (CP) is a widely used method to protect steel reinforcements against corrosion. In the course of the last half century, it has been established as a proven method for repairing corrosion-affected reinforced concrete structures, exposed mainly to chlorides. The impressed current anode system for the protection of steel in concrete is already known and applied in practice for more than 30 year. The CP anodes can be embedded in mortar, applied as coating or distinct anode on the repair structure surface. Using CP, the potential of the steel reinforcement is shifted in cathodic direction towards more negative values and consequently the anodic dissolution of iron is suppressed. The current densities on the surface of the reinforcement play a key role in shifting of the potential in cathodic direction. For the anode material nowadays Mixed Metal Oxide coated Titanium (MMO) is often used due to its high durability under anodic polarization. As an alternative anode material, Carbon Textiles embedded in mortar, which provide extraordinary mechanical properties and are also conductive, have already been studied. The results demonstrate that Carbon Textiles are generally suitable as an anode material for CP on reinforced concrete. Deterioration of Carbon is likely to occur in CP systems using carbon as anode material, when critical current densities are exceeded. Therefore the durability of Carbon Textiles at typical CP current densities of less than 20 mA/m2 with respect to concrete surface is considered of special interest.