A study was carried out to investigate the effect of various hydrodynamic parameters on the corrosion rate of low carbon steel in CO2 environments. Two different flow geometries: rotating cylinder and pipe flow were studied simultaneously in the same electrolyte within a glass loop. The comparisons were carried out over a wide range of parameters: T=20-80°C, pH 4-6, PCO2=0−1bar⁠, v=0-13 m/s. The hydrodynamic conditions studied cover the range from static to highly turbulent flow. The corrosion process was monitored with the following electrochemical measuring techniques: polarisation resistance, potentiodynamic sweep and electrochemical impedance. The comparison of the two flow geometries was carried out in terms of hydrodynamics, mass transfer and CO2 corrosion.

The measured mass transfer rates were found to agree well with previously published correlations for the rotating cylinder and straight pipe flow. In case of CO2 corrosion it was possible to achieve good agreement between corrosion rates in the two flow geometries at low temperatures by having the same water chemistry and mass transfer conditions. This conclusion is valid for the case when no protective corrosion product, scale or inhibitor films are present. However, at higher temperatures films with a certain degree of protectiveness were observed. In that case lower corrosion rates were obtained on the straight pipe specimen due to more dense and protective films.

Subject
Electric current, Films, Water, Piping, Cylinders, Geometry, Corrosion rate, Metal surfaces, Sodium chloride, Mass transfer, Film formation, Risk reduction, Chemical reactions
Keywords:
CO2 corrosion, rotating cylinder, pipe flow, mass transfer, carbon steel
© 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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