This paper reports the performance of HVOF-sprayed corrosion resistant alloy (CRA) coatings in an aqueous solution pressurized with 50 MPa supercritical CO2.

UNS N10276, UNS N06625 and UNS S31603 were procured in power form and sprayed onto carbon steel with a HVOF system and holidays were drilled in the coating to expose the steel substrate. These were then exposed to 3.5 wt.% NaCl solution for 70 days, bubbled with 50 MPa CO2. Tests were conducted at 40°C. Post-test microstructural characterization revealed that the coatings protected the steel substrate from CO2 corrosion where intact. The bare steel in the exposed region formed a siderite scale, while no such scale was seen in the undamaged regions. The substrate close to the coating showed accelerated corrosion due to galvanic effects.

It was concluded that thermally sprayed CRA coatings are candidates to provide cost-effective corrosion mitigation in wet supercritical CO2. However, care must be taken to ensure that the thermally sprayed CRA layer does not have any through-porosity or damage; else, such coatings may accelerate corrosion of the underlying steel due to galvanic interactions.

Subject
Holidays, Test methods, Steel surfaces, Coatings, Substrates, Corrosion scales, Interfaces, Iron carbonate scale, Scale formation, Steel, Carbon steel, Risk reduction, Thermal spray coatings
Keywords:
Supercritical CO2, Corrosion resistant coatings, Thermal spray coatings, HVOF Coatings, High pressure CO2, Dense Phase CO2
© 2017 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).
2017
Association for Materials Protection and Performance (AMPP)
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