The corrosive potential of quench system water of an entrained slagging gasifier plant was studied in laboratory autoclave tests. Five tests (one 200-h and four 1000-h) were conducted using ferritic steel 1 1/4Cr-1/2Mo (T-11), austenitic stainless steels 304L and 321, and Incoloy 825.(1) In the vapor phase with autoclave solution pH in the 4.5-4.8 range, 304L SS, 321 SS, and Incoloy 825 double U-bends suffered significant intergranular stress-corrosion cracking (SCC). Some crevice-assisted cracking is suspected. Pitting corrosion, as measured by maximum pit depth, may become serious since the rate of growth is not known. At the pit base, preferential dissolution was identified similar to grain- and twin-boundary preferential corrosion. General corrosion chloride levels of the stainless steels was low, but T-11 cannot be used unprotected. Low acidic pH (6.2 and 6.4) and lower total chloride levels eliminated SCC problems and reduced pitting and corrosion. Of the two phases in a quench system, the vapor phase poses more danger to the materials of construction, particularly to the internal attachments and extensions where welding is required.

Subject
Pits, External stress corrosion cracking, Intergranular stress corrosion cracking, Autoclaves, Ammonia, Vapors, Acidity, Liquids, U bends, Pitting, Chlorides, Stress corrosion cracking, Chloride stress corrosion cracking
© 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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