Corrosion of alloys and coatings for syngas coolers of entrained slagging gasifiers is accelerated by exposure to moist air during the start-up and shutdown periods of operation. Modes of attack include general corrosion, pitting, intergranular corrosion, and stress corrosion cracking. Corrosion is enhanced by chlorides that are absorbed by both the materials and the surface deposits from HCl in syngas produced by gasification of coal containing traces of chlorine. Attack appears to be electrochemical in nature and is accelerated greatly by slag deposits containing carbon. Laboratory tests have been devised to simulate shutdown corrosion conditions, and both the modes and degree of attack observed in pilot plants can be reproduced and studied. Materials with the best resistance to this form of attack include pitting resistance nickel alloys such as Hastelloy C-22 and high chromium stainless steels with 2-6% Mo. Corrosion of alloys also can be controlled by modification of the environment during start-up and shutdown.

Subject
Pits, Coatings, Materials, Salts, Corrosion rate, Mixtures, Corrosion attacks, Syngas, Steel, Pitting, Coal, Deposit corrosion, Chlorides
© 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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