Considerable controversy persists among cathodic protection (CP) practitioners concerning the science involved with the pipe-soil (P/S) interface and the -0.85 Volt (V), co per/copper sulphate electrode, CP criterion on buried steel pipelines. !?
Much of the controversy stems from differences in past and present electrical models of the P/s interface and the past and present definitions of the word polarization and the term polarized potential.
Laboratory data, field data and information from past and present CP literature references are presented and discussed in this article in an endeavor to resolve some of the more divisive controversy that persists.
The early CP practitioners represented, (modeled) the 1 From the P/s interface as purely resistive. -0.85 V CP criterion (with the CP applied) standpoint this is technically sound; because this criterion can be achieved in the absence of the counter electromotive force of cathodic polarization since it always includes the protective voltage shift across the P/S interface that is always synchronous with the application or removal of the CP.2
The proponents of the -0.85 V Polarized Potential CP criterion model the P/s interface as a resistor in parallel with a capacitor (R-C Circuit-) .1?5 This -0.85 V CP criterion can not be achieved in the absence of the counter electromotive force of cathodic polarization; because, it ignores and does not include the protective voltage shift across the P/s interface that always occujs and i.s always synchronous with the application or removal of the CP. This article offers information that clarifies the differences in the two (2) ?0.85 V CP criteria.
