C. Christodoulou, R. Kilgour – AECOM
Many reinforced concrete structures suffer from corrosion damage. Causes include salt ingress due to the application of de-icing salts during winter maintenance, exposure to marine environments and carbonation of the concrete. Corrosion is an electrochemical process and as such the use of electrochemical technology treatments has been very popular. Traditional treatments such as Impressed Current Cathodic Protection (ICCP) require the passage of a constant current through the concrete to arrest corrosion activity and hinder its future development. However, for prestressed reinforcement there are risks of hydrogen embrittlement of the steel if the applied polarisation is not strictly controlled.
Standards deal with such risks by limiting the induced change in the potential of the steel reinforcement by reducing the amount of hydrogen generated as a result of water hydrolysis during the application of an electrochemical treatment such as ICCP. However the risk to the asset owner remains throughout the long-term use of an ICCP system as monitoring and adjustments are usually undertaken at annual intervals only and this may not be sufficient. An alternative approach to reduce this risk would be to apply a brief impressed current treatment delivered using an external DC power supply to re-alkalise the corrosion sites and provide longterm corrosion prevention by means of galvanic corrosion protection. This combination of electrochemical treatments is more commonly known as hybrid corrosion protection.