In order to prevent high temperature corrosion of waterwall tubes in waste incineration boilers, fireside corrosion factors were investigated. Important factors accelerating corrosion were considered to be heavy metal (Zn, Pb) chlorides, unburned carbon included in deposits, and reducing gas atmosphere formed by increasing of unburned gas components and decreasing of O2. It is confirmed by laboratory corrosion test that increasing these factors mentioned above increased the corrosion rate of carbon steel. These tendencies were in good agreement with those in actual furnaces.

Furthermore, as a corrosion prevention method, a gas spray coating of two-layer Al/80Ni20Cr, selected by laboratory corrosion test, was applied on waterwall tubes on site. The Al/80Ni20Cr spray coating maintained excellent durability for more than three years, and the effectiveness as a corrosion prevention method was confirmed. This coating system has now been applied at five plants. In this case, main deterioration factors of the coating layer were considered to be the formation of corrosion scale and the decreasing of bonding strength at the boundary surface between coating layer and base metal due to penetration of corrosive gas components through blow holes in the coating layer.

Subject
Waste incineration, Coatings, Materials, Tubes, Spray coating, Heavy metals, Corrosion testing, Waterwalls, Surface layers, Ash, Boilers, High temperature corrosion, Corrosion resistance
Keywords:
municipal waste, fireside corrosion, incineration, waterwall tubes, metal spray coating, corrosion test, corrosion factors, corrosion prevention, heavy metal chloride, coating layer
© 1995 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).
1995
Association for Materials Protection and Performance (AMPP)
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