In the present paper, characteristics of the AC corrosion problem are demonstrated using laboratory results and field measurements as examples.

Evidence has been given that the AC corrosion mechanisms involve alkalization of the environment nearby the coating defect, and in combination with AC, corrosion may be induced.

Accordingly, besides the level of induced AC voltage, the CP level has a dramatic influence on the AC corrosion process. Excessive CP increases the AC corrosion rate and should therefore be avoided. Increasing the CP seems definitely to be the wrong solution to a potential AC corrosion problem.

Subject
Electric current, CP coupons, Ions, Voltage, Cathodic protection, Corrosion rate, Pipelines, Polarization curves, Current densities, Alternating current corrosion, Coating defects, Soil, Conductivity
Keywords:
AC corrosion mechanisms, alkalization, cathodic protection requirements
© 2005 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).
2005
Association for Materials Protection and Performance (AMPP)
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