This paper reports the use of thermal spray corrosion resistant alloy (CRA) coatings to mitigate corrosion of carbon steel in an environment containing high pressure, supercritical CO2 and an aqueous phase.

CRA coatings were sprayed using high velocity oxy-fuel (HVOF) onto carbon steel substrates. 8 mm holidays were drilled in the coatings to expose the steel substrate and they were tested in de-aerated 3.5 wt.% NaCl solution for 30 days, bubbled with 10MPa CO2. Tests were conducted at two different temperatures, 40°C and 80°C. Microstructural characterization revealed that the coatings protected the steel substrate from CO2 corrosion when undamaged. The bare steel in the exposed region formed a siderite scale, while no such scale was seen in the case of undamaged CRA-coated steel. The substrate close to the coating showed accelerated corrosion due to galvanic effects.

It was concluded that thermally sprayed CRA coatings can provide a cost-effective corrosion mitigation method for infrastructure likely to be in contact with wet supercritical CO2. The same coatings can potentially be used as inner lining of pipes for transport of impure CO2. However, care must be taken to ensure that the thermally sprayed layer does not have any through porosity; else, such coatings may accelerate corrosion of the underlying steel due to galvanic interactions.

Subject
Holidays, Test methods, Steel surfaces, Coatings, Substrates, Corrosion products, Corrosion scales, Interfaces, Iron carbonate scale, Scale formation, Steel, Carbon steel, Thermal spray coatings
Keywords:
Supercritical CO2, Corrosion resistant coatings, Thermal spray coatings, HVOF Coatings, High pressure CO2, Dense Phase CO2
© 2016 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).
2016
Association for Materials Protection and Performance (AMPP)
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