Cathodic protection studies on steel in concrete.

Cathodic protection of steel reinforcement is an economic method of corrosion control which is being increasingly used to extend the life of selected control which is being increasingly used to extend the life of selected structures already at risk. Many of the practical engineering details have, or are, being pragmatically solved but there is, however, a lack of scientific data on reinforcement corrosion rates under cathodic protection. Note that even small rates of corrosion would ultimately give rise to concrete cracking and spalling. The criterion typically used to assess whether an installed cathodic protection system is operating satisfactorily is based on the change of measured potential when the current is temporarily switched off. The paper reports on laboratory experiments designed to assess this practice and also addresses the problem of obtaining corrosion rates. In particular, the use of harmonic analysis, an extension of electrochemical impedance measurements, is described and data from electrode arrays presented show that corrosion kinetics can be assessed even under cathodic protection conditions. Comparison of cathodic protection efficiency with control samples are also included. (A)