In presence of stray current interference due to DC transit systems, CP is operated at so-called “constant potential” condition. This technique consists of a continuous measurement of the pipeline potential by a fixed reference electrode, and the use of such measured potential to pilot the feeder dynamically, in order to maintain that potential constant. An accurate analysis of this technique reveals that what is maintained constant is IR drop in soil rather than the true potential of the structure. On the basis of this evidence, a new approach was investigated, consisting on two steps: the first was the measurement of the true potential by means of a corrosion coupon with an embedded reference electrode, to check protection conditions, and the second was the measurement of the coupon current. The innovation consists of the use of such current to pilot the feeder on the basis of an effective range of the current the coupon should receive. Laboratory tests confirmed the feasibility of such new approach. Modeling and test results are presented and discussed.

Subject
Electric current, Ohmic drop, Probes, Stray current interference, Reference electrodes, Structures, Potential measurements, Constants, Stray current, Corrosion coupons, Soil, Electrode potential, Luggin-Haber probes
© 2007 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).
2007
Association for Materials Protection and Performance (AMPP)
You do not currently have access to this content.