Cathodic protection has been in use 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 origin of the ubiquitous −0.85 VCSE cathodic protection criterion and why does it work? Does cathodic protection really stop corrosion or simply reduce it to negligible levels? What does the instant off potential tell us and is it really the true polarised potential? Does hydrogen gas cause cathodic disbonding? 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.
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