Carbon steel is thermodynamically unstable in water with dissolved CO2 and the only reason that carbon steel is so attractive and can be so widely used in oil and gas production is that the steel surface becomes covered by a protective layer of corrosion products, oil, mineral scale or inhibitors. It is relatively easy to predict and explain the high corrosion rates on bare steel. The real challenge is to reduce the corrosion and that requires knowledge about the performance of the protective layers, means to predict the breakdown of the layers and methods and techniques to ensure that robust layers form on the surface.

The paper discusses how CO2 affects the water chemistry, the electrochemical reactions on the bare steel surface, and the initiation and growth of protective corrosion product films. As many sweet systems contain organic acids that affect the solution chemistry and the formation and stability of the FeCO3 corrosion product films, organic acids need also to be considered when the effect of CO2 is discussed.

Subject
Steel surfaces, Water, Precipitation (solids), Corrosion rate, Iron carbonate films, Solubility, Partial pressures, Acidity, Supersaturation, Corrosion products, Anodic reactions, Film formation, Brines
Keywords:
CO2 corrosion, carbon steel, internal corrosion, mechanisms, corrosion films
© 2006 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).
2006
Association for Materials Protection and Performance (AMPP)
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