A methodology for CO2 corrosion rate prediction is presented which is based on mechanistic modelling. The effect of fluid flow is included, which hitherto often has been ignored. Examples of corrosion models shown are a simple Limiting Corrosion Rate (LCR) model and a more advanced numerical model. The former is based on mass transport considerations, whereas the latter also includes reaction chemistry and electro-chemistry. Linking of corrosion rate predictive models with models for gas/liquid multi-phase flow is dealt with.

The (LCR) model provides a theoretical upper limit for the corrosion rate based on the assumption that the rate-determining steps are the transport and production of protons and carbonic acid in the diffusion and reaction boundary layers. Comparison with experimental data confirms the LCR model to provide an upper limit indeed. For flow velocities below 3 m/s and non-scaling conditions, there is reasonable agreement with single-phase flow experimental data with pH’s controlled by the CO2 partial pressure. Including charge transfer kinetics provides a way to get agreement also at higher flow velocities. For flow velocities around 1 m/s, corrosion rates do not deviate too far from the "deWaard-Milliams" nomogram values. Comparisons for multi-phase flow conditions reveal that both further modelling and more and better experimental data are needed.

Subject
Mechanistic models, Fluxes, Diffusion layers, Corrosion rate, Diffusion, Flow velocity, Carbonic acid, Experimental data, Corrosion modeling, Hydration, Corrosion data, De Waard corrosion model, Risk reduction
Keywords:
carbon dioxide corrosion, corrosion prediction, mass transport, reaction chemistry, electro-chemistry, multi-phase flow
© 1995 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).
1995
Association for Materials Protection and Performance (AMPP)
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