CO2 corrosion in a wet gas pipeline is influenced by pH, temperature, partial pressure of CO2, oxygen content, H2S level, flow rate of the solution, solid particles content, surface condition, water chemistry and oil condensate drop out. The microstructure of steel has also been found to affect the corrosion rate because of its impact on the corrosion scale characteristics. The mechanism and characteristics of iron carbonate scale formation on API X-52 grade of steel and the pertinent factors that affect the corrosion rate under different heat treatment conditions in a CO2 - brine solution has been studied and discussed as a function of temperature and pressure of carbon dioxide. An interface controlled corrosion mechanism has been suggested for temperatures up to 60°C. A transport controlled corrosion rate is supported by the measurements above 60°C. Conditions that promote tight and adherent scale result in lower corrosion rate than conditions that promote the formation of porous and less tenacious scale. The volume and thicknesses of the primary and secondary layers of the carbonate scale are found to be a strong function of the microstructural feature of the steel, particularly those involving ferrite-pearlite type of microstructure. A predictive model is being developed which relates the composition and steel microstructure with the corrosion rate.

Subject
Corrosion rate, Microstructure, Linepipe, Partial pressures, Corrosion scales, Pearlite, Iron carbonate scale, Scale formation, Steel, Carbon dioxide, Corrosion mechanisms, Ferrite, Quenching and tempering
Keywords:
Steel, heat-treatment, microstructure, carbon dioxide, linepipe, iron carbonate, aqueous corrosion, scale formation, activation energy, pH
© 1993 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).
1993
Association for Materials Protection and Performance (AMPP)
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