The concept of controlled current output of ICCP anodes

Vector Corrosion Technologies Ltd, St Luke’s House, 27a Upper High Street, Cradley Heath, West Midlands B64 5HX, UK

Abstract

A common issue with Impressed Current Cathodic Protection (ICCP) anodes is the lack of control of the current that each individual anode can deliver to the steel. Currently, the problem is faced by separating the structure into several individual zones of grouped anodes or anode sections, according to the localised environment and steel density and ensuring that a depolarisation of over 100 mV is achieved at the high-risk regions of the structure. This arrangement cannot avoid localised current dumping on sections of the reinforcement lying in low resistance paths or in cases of circuit shorting. The work described in this paper involves the fundamental work carried out using controlled current output diodes (CCD’s) attached to embeddable anodes in a concrete slab, followed by controlling current flow through circuitry simulating variable concrete resistances. The results were very encouraging, suggesting that such anodes can distribute the current around the steel reinforcement much more evenly and avoid short-circuiting by not exceeding the preselected current output. Extensive zoning could also be avoided by using a combination of anodes of different maximum current output per zone fed by the same feeder wire or conductor bar. An example of an ICCP field design is described and discussed.