The hot corrosion of metallic chromium was studied in (Li0.62K0.38)2CO3 carbonate salt at 650°C under prototypical molten carbonate fuel cell environments. With the aid of phase stability diagrams of the Cr-Li-K-C-O system, the corrosion kinetics and scale morphologies were examined. The corrosion process in oxidizing atmospheres was divided into three distinct phases: (1) the formation of liquid corrosion product, chromate, from the reaction of carbonate and chromium; (2) the formation of nonprotective Cr2O3 scale under the liquid corrosion product; and (3) localized hot corrosion in the Cr2O3 scale due to the dry-out of the liquid corrosion product. The corrosion behavior in the oxidizing environment is primarily dependent on the oxygen concentration. Thus, the catastrophic corrosion of chromium with carbonate deposit can be alleviated by lowering the oxygen partial pressure in the gas phase. Very little corrosion was observed when chromium with a carbonate deposit was reacted under reducing gas environments. This low corrosion rate of chromium was the result of the scarcity of oxygen in the reducing gas atmosphere.

Subject
Scanning electron microscopy, Stability, Electrochemical cells, Corrosion rate, Chromium, Carbonate scales, Liquids, Corrosion products, Corrosion scales, Incubation period, Scale formation, Oxygen, Deposit corrosion
© 1986 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).
1986
Association for Materials Protection and Performance (AMPP)
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