This study investigates localized CO2 corrosion on carbon steels in wet gas services both experimentally and theoretically. A 100 mm I.D., 40 meter long flow loop is employed to perform the corrosion studies along the top and the bottom of the pipe under stratified and annular flow conditions. Various corrosion monitoring techniques, including ER, LPR, and WL, and surface analysis techniques, including SEM/EDS, MM, and XRD are used during the experiments and for post-test analysis.

The parametric study involves the systematic investigation for the effect of temperature, CO2 partial pressure, Cl-, pH, and flow regimes on localized corrosion and formation of corrosion product films. Localized corrosion is found only at high temperature (90°C) in both Cl- containing and Cl- free solutions (with different pitting density). It also occurs at lower pH (4.5~6.0) while at pH 6.2 very protective films form and no localized corrosion is identified. CO2 partial pressure affects film formation and thus the localized corrosion when a partially protective film is formed. Corrosion behavior at the top approached that of the bottom when annular flow is maintained.

The theoretical study includes the development of a solution super saturation model and a scaling tendency model, which are good tools for predicting localized corrosion. Localized corrosion occurs when the solution is only slightly above the saturation point and when the scaling tendency is between 0.3 and 3.0.

Subject
Water, Piping, Corrosion rate, Protective films, Saturation, Partial pressures, Corrosion products, Corrosion attacks, Stratified flow, Film formation, Carbon dioxide, Localized corrosion, Scaling
Keywords:
localized CO2 corrosion, carbon steel, wet gas, stratified flow, annular flow, super saturation, scaling tendency, iron carbonate film, surface analysis
© 2004 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).
2004
Association for Materials Protection and Performance (AMPP)
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