Buried or permanent reference electrodes are often installed close to pipelines and other buried or submerged structures with the idea that they will provide more accurate or more representative potential data, at that specific location, than a reference electrode on the ground surface.

Such potential data may be used to determine the local cathodic protection level, potential shifts, the presence or absence of interference or for control of automatic output rectifiers.

But what if proximity of pipeline and buried reference electrode is not a guarantee of accurate potential data at that point? If the buried reference electrode is installed adjacent to a pipeline with a high quality coating, what will it read?

Coating defects, away from the buried reference electrode location, can have a major impact on the measured potential. Compound this with the presence of foreign voltage gradients1,2 (at pipeline crossings), and it will be shown that the potential recorded using the permanent reference electrode may be far removed from reality.

Subject
Holidays, Coated pipes, Test methods, Pipe surfaces, Water, Piping, Voltage, Pipe to soil potential, Reference electrodes, Pipelines, Coating surveys, Coating defects, Electrode potential
Keywords:
permanent reference electrode, buried reference electrode, cathodic protection, coating defects, holidays, close interval potential survey (CIS), pipeline crossings, interference, voltage gradients, -0.85V criterion
© 2011 Association for Materials Protection and Performance (AMPP). All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means (electronic, mechanical, photocopying, recording, or otherwise) without the prior written permission of AMPP. Positions and opinions advanced in this work are those of the author(s) and not necessarily those of AMPP. Responsibility for the content of the work lies solely with the author(s).
2011
Association for Materials Protection and Performance (AMPP)
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