In-plant examinations along with laboratory evaluations of tube support plate intersections removed from operating plants have indicated that the tube denting phenomena, i.e., reduction of tube ID, is related to the corrosion of the carbon steel tube support plate.1  The corrosion of the carbon steel within the annular spacing between the Inconel Alloy 600* tubing and the carbon steel support plate produces a magnetite deposit (Fe3O4) that is more voluminous than the parent metal and contain chloride ions. The large volume increase resulting from the conversion of the parent metal to in situ magnetite within the tube/tube support plate annular gap cause large radial forces to be exerted on the Inconel Alloy 600 tubing. These large forces are responsible for the observed denting phenomena in some of the operating steam generators.

Subject
Oxides, Tubes, Chromium, Oxide layers, Iron, Metal oxides, Crevices, Chromium oxide, Weight loss, Carbon steel, Deposit corrosion, Stainless steel, Chlorides
© 1979 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).
1979
Association for Materials Protection and Performance (AMPP)
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