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True or False? Facts and Fallacies in Cathodic Protection

Paper Number: 17
Author/s: B Ackland1 & K Dylejko2
Organisation: Bruce Ackland & Associates1, Melbourne, Australia, DST Group2, Melbourne, Australia


Cathodic protection has been used for almost two hundred years, yet there still exist a number of misunderstandings surrounding its application. In this paper we question some common statements and beliefs to determine whether they are based on fact or fiction. Our questions include: What is the true basis of the ubiquitous -850 mVCSE cathodic protection criterion? Does cathodic protection really stop corrosion or simply reduce it to negligible levels? Does hydrogen gas cause cathodic disbonding? Can cathodic current pass through and underneath some coatings sufficiently to provide cathodic protection? Do the potential shifts measured during interference testing indicate real interference? The answers to these questions are important because they allow the correct interpretation of field and experimental data, based on a true understanding of the electrochemical and thermodynamic basis of cathodic protection.