On the Mechanism of Cathodic Protection and Its Implications on Criteria Including AC and DC Interference Conditions

In recent years, a wide agreement with respect to the processes associated with cathodic protection (CP) has been reached within the CP industry. The increase of the pH value at the steel surface and the generation of passivating conditions as a result of the CP current are widely accepted as the relevant underlying mechanism. Based on this understanding it was possible to identify the relevant processes with respect to AC and DC interference and explain the empirical observations. This led to the development of ISO 18086 and has significantly influenced the work on ISO/DIS 21857. This paper summarizes present state of knowledge, the more recent developments, and their implications with respect to the CP criteria. It summarizes the relevant aspects in association with interference conditions and highlights possible future approaches with respect to the assessment of the effectiveness of CP.