Disbonded, shielding coatings over pipeline steel can often lead to serious corrosion problems that cannot be readily controlled by conventional cathodic protection system. Cathodic protection effectiveness in these cases is limited by the high resistance electrical path in the crevice formed between the steel surface and disbonded coating. This study investigates the hypothesis that application of pulsed cathodic protection may improve the penetration of protective cathodic protection beneath disbondments to provide more effective corrosion control. Polarization experiments beneath a simulated disbondment were conducted using conventional and pulsed cathodic protection. Current demand, potential profiles, polarization, pH differences and effectiveness of each system were calculated. Results indicate that certain pulsed waveforms increase the distance in a crevice at which protective potentials can be achieved.

Subject
Holidays, Electric current, Openings, Cathodic protection, Pipelines, Disbondment, Crevices, Rectifiers, Steel, Electric potential, Polarization, Conductivity, Electrode potential
Keywords:
cathodic protection, pulse, potential, current, polarization, disbonded, coatings, corrosion, pipeline
© 1997 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).
1997
Association for Materials Protection and Performance (AMPP)
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