Furnace wall corrosion has been a problem in coal fired boilers for many decades. This paper presents a study of several examples of ash corrosion failures of furnace tubes. Common to all samples was the presence of carbon and sulfide corrosion products. EDAX scans show only sulfur. However, a low melting point, 650-800°F, constituent of the ash was detected by a differential scanning calorimeter but was present in insufficient quantity to be identified by x-ray diffraction. A possible corrosion mechanism is presented that suggests tube wastage occurs by the formation of iron sulfide. A liquid phase, probably the pyrosulfates of sodium and potassium, is necessary to transport sulfur trioxide to the tube surface and carbon is necessary to reduce sulfur trioxide.

Subject
Sulfur, Metal surfaces, Tubes, Walls, Carbon monoxide, Melting point, Liquids, Furnaces, Ash, Coal, Carbon, Sulfides, Deposit corrosion
© 1982 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).
1982
Association for Materials Protection and Performance (AMPP)
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