Hi Ross, thank you for your very thought provoking question. Corrosion protection systems using DC rectifiers are used quite often to protect buried pipes and other metallic object, and we have not ever run across a situation where a high-resistance ground has been generated due to a protective anode. However, that’s not to say it can’t occur or that it might be occurring on a regular basis without general knowledge of it.
This question has really sparked some interest over here in our engineering department. It is quite possible that we could model this scenario for you in our computer simulation software. We would of course need some more information from you, such as a detailed schematic, soil resistivity data, and the electrical data information on the DC Rectifier (volts and amperage).
Have you tested the ground to see if it is indeed resistive?
The E&S Grounding Solutions Engineering Team