With the better localize corrosion resistance than carbon steel, the low Cr (1%-5%) alloy steels are amongst the most promising candidates as pipeline steel to transport oil and gas. An increase in Cr content leads to a lower susceptibility to localized corrosion. The improved CO2 corrosion resistance of 3-5%Cr steel stems from the better protectiveness of corrosion product film. To understand the formation of corrosion protective film on 3%Cr steel, a large number of autoclave experiments simulating the oilfield environment had been carried out at various corrosion times.

The morphology and the composition of the corrosion product film were analyzed using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), potentiodynamic polarization curve and electrochemical impedance spectrum (EIS), respectively. The results showed that, the higher Cr/Fe ratio of the corrosion product film, the better corrosion resistance. And the changes of the EIS plot clearly reflect the emergance and evolvement of the pit observed by SEM.

Subject
Pits, Scale morphologies, Films, Electrochemical impedance spectroscopy, Energy dispersive X-ray spectroscopy, Steel surfaces, Corrosion products, Corrosion scales, Film formation, Steel, Pitting, Immersion, Corrosion resistance
Keywords:
CO2 corrosion, low Cr alloy steels, EIS, pitting
© 2012 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).
2012
Association for Materials Protection and Performance (AMPP)
You do not currently have access to this content.