A laboratory inhibitor selection study for a newly developed sweet gas field was conducted. Six inhibitors were screened using static autoclave tests at simulated worst case field conditions of 3.4 bar (50 psi) CO2 partial pressure at 77° C (170° F) in 10% and 33% methanol/water solutions. Three inhibitors exhibited an inhibition efficiency of over 85% and were selected for further testing in a flow loop capable of producing two phase flow. The performance of the inhibitors revealed that static tests are not sufficient to qualify inhibitors. While static tests showed excellent inhibition efficiency, flow loop tests revealed less than optimum performance. Two experimental cautions are noted: solution saturation or sample passivation may affect weight loss measurements and produce incorrect data and methanol/NaCl environments induce pitting. Pitting only occurred under dynamic flow in tests longer than 120 hours. Only two inhibitors were effective in preventing pitting with one showing optimum persistency behavior. Electrochemical monitoring of corrosion tests is essential to the understanding of corrosion variation with time and performance of inhibitors. This paper focuses on inhibitor evaluation techniques and not on inhibitor selection.

Subject
Field performance, Test methods, Water, Inhibitor performance, Flow loop, Corrosion rate, Autoclaves, Sodium chloride, Pipelines, Inhibition efficiency, Corrosion inhibitors, Pitting, Methanol
Keywords:
corrosion, corrosion testing, inhibitors, CO2, pipelines, wet gas pipeline, methanol, flow effect, flow loop, pitting corrosion
© 1994 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).
1994
Association for Materials Protection and Performance (AMPP)
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