Corrosion inhibitor tests typically evaluate performance with respect to general corrosion. However, pipeline failures in oil and gas production are predominantly caused by localised corrosion, not general corrosion. A novel evaluation technique, based on an artificial pit electrode, has been developed for inhibitor studies. Two examples of its application are presented. The first is a determination of the relative effectiveness of three generic inhibitors, a quaternary amine, a phosphate ester and oleic imidazoline, against localised corrosion in a slightly sour environment. The second is an assessment, using similar techniques, of three industrial inhibitors for use against existing localised corrosion on a north sea production platform subject to barium sulphate scaling of the topside pipework. In both cases the tests were able to discriminate between inhibitors which gave similar levels of protection against general corrosion. It was also found that prevention/mitigation of existing localised corrosion required far higher inhibitor concentrations than general corrosion, and inhibitor efficiency could not easily be increased beyond 75%.

Subject
Pits, Inhibitor performance, Corrosion rate, Sour environments, Scale inhibitors, Pipelines, Corrosion inhibitors, Pitting, Localized corrosion, Galvanic current, Electrodes, Types of corrosion, Anodic inhibitors
© 2002 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).
2002
Association for Materials Protection and Performance (AMPP)
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