ABSTRACT
Cathodic protection (CP) has been successfully used for more than a 150 years on ships, where the high conductivity of sea water made it easy to pass the current. CP came ashore over a 100 years ago to protect steel in the ground, and this was found to be achievable despite the lower conductance of the soil electrolyte compared to sea water. Robert Kuhn has become known as the ‘Father of Cathodic Protection’ in America, and he installed the first impressed current installation in 1928 (Baeckmann et al., 1997) on a long-distance gas pipeline in New Orleans. By experimentation, Kuhn found that a protective potential of −850 mV with respect to a copper/copper sulphate electrode provided sufficient protection against any form of corrosion. He found that this level of protection was being obtained at a current density of 10–20 mA/m2 for the steel of uncoated pipe. An early way of measuring effectiveness of CP was the incidence of pipe bursts. This was because electrochemical corrosion was responsible for the pipe failures in aggressive soils. The incidence of these failures 88could be easily recorded. After CP was applied (Peabody, 2001), the number of pipe bursts was shown to reduce to zero incidences.
