Carbon dioxide (CO2) sweet corrosion was studied in a high pressure recirculating flow loop. The presence of hydrocarbon was found to have a large effect on the performance of corrosion inhibitors. The inhibitor performance was also found to vary with test method. Corrosion rate increases with CO2 partial pressure, and is independent of the total pressure. The solution pH is gradually increased by the cathodic reactions. The correlation of iron concentration with respect to metal loss suggests that corrosion progresses through three stages, representing different iron precipitation rates relative to soluble Fe2+ formation rate. Corrosion products on the surface were analyzed by various instrumental techniques. The results indicate that these products are mainly iron carbonate, which is rapidly oxidized to iron oxides upon exposure to the atmosphere, as well as a small amount of iron carbide. The surface corrosion film shows a morphology typical of mesa type attack. There are cracks present on the film, which account for the ineffectiveness of corrosion protection. Chloride ions were found to concentrate on certain raised areas thus facilitating pitting corrosion.

Subject
Carbides, Inhibitor performance, Flow loop, Corrosion rate, Iron carbonate, Steel coupons, Iron, Metal loss, Partial pressures, Corrosion products, Fluids, Film formation, Corrosion inhibitors
Keywords:
flow loop, CO2, sweet corrosion, SEM, EDS, oilfield, corrosion inhibitors, mesa 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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