The formation of protective iron carbonate (FeCO3) corrosion product layers on X65 carbon steel has been investigated experimentally in high-temperature, high-pressure autoclave corrosion tests. Corrosion testing was performed in carbon dioxide (CO2)-saturated, 3 wt.% sodium chloride (NaCl) brine at an operating temperature of 80 °C and pressure of 5 bar. The evolution in corrosion rate and mass transfer processes during the formation of an FeCO3 layer were monitored using in-situ linear polarization resistance and electrochemical impedance spectroscopy. Over time, the precipitation of FeCO3 resulted in the formation of a high-density layer that formed an effective diffusion barrier and reduced the corrosion rate of the underlying carbon steel by over an order of magnitude. The restricted corrosion rate in the presence of a porous FeCO3 layer is subsequently represented in a one-dimensional mechanistic CO2 corrosion model. A parametric study was conducted to investigate the effects of surface coverage from FeCO3 and the effective diffusion coefficient through the layer on the predicted corrosion rate of the underlying carbon steel surface.

Subject
Electrochemical impedance spectroscopy, Steel surfaces, Ions, Corrosion rate, Diffusion, Corrosion testing, Porosity, Corrosion modeling, Surface layers, Carbon steel, Corrosion protection, Corrosion mechanisms, Risk reduction
© 2025 Association for Materials Protection and Performance (AMPP). All rights reserved. This work is protected by both domestic and international copyright laws. 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).
2025
Association for Materials Protection and Performance (AMPP)
You do not currently have access to this content.