Corrosion inhibitors for protecting oil and gas pipelines exhibit surface active behavior, and this surface activity affects not only their inhibition efficiency but also their ability to form and stabilize emulsions. Even though interfacial phenomena play a vital role, the interfacial properties of corrosion inhibitors have not been extensively examined with respect to their effect on corrosion inhibition and water quality. The work presented here has been designed to address some of these issues.

Corrosion inhibitors are known to partition between oil and water phases. The amount of inhibitor partitioning into the aqueous phase has been shown to be highly dependent upon the volume fraction of oil in the system. A significant quantity of inhibitor also adsorbs at the oil-water interface which results in a lowering of the interfacial tension. For certain highly surface active inhibitors the tension can be reduced by a factor of 105. Some commercial inhibitors have been shown to exhibit a break point in their interfacial tension versus log concentration plots. The concentration at which the interfacial tension levels off is the critical micelle concentration (CMC).

It has been shown that inhibitors exhibiting low interfacial tensions promote the formation and stabilization of emulsions. This is critical to the understanding of the impact of inhibitors on produced water quality. It has also been shown that the additional surface area generated during emulsion formation can consume a significant quantity of inhibitor. Adsorption onto these unwanted surfaces can dramatically reduce the overall availability of chemical for corrosion inhibition.

From the determination of the corrosion inhibition efficiency of a series of inhibitor actives, it appears that for those inhibitors that exhibit a CMC, this value is also seen to be similar to the minimum effective concentration required for inhibition.

Subject
Water, Materials, Inhibitor performance, Salts, Emulsions, Interfacial tension, Partitioning, Interfaces, Salt concentration, Inhibition efficiency, Corrosion inhibitors, Brines, Oil
Keywords:
corrosion inhibitor, surface activity, partitioning, interfacial tension, emulsification tendency, inhibition performance
© 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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