Corrosion of carbon steel boiler tubes in municipal solid waste (MSW) combustors is a serious problem for the industry and is often controlled by applying Alloy 625 weld overlay to the tubes. While this has given good service, corrosion resistant thermal spray coatings offer significant cost savings compared to the weld overlay.

Thermal spray coatings of nickel alloys including Ni-Cr-Co-Si, Ni-Cr-Fe-Al-Y, and Ni-Cr-Mo-W (N06022) were applied to an air-cooled corrosion probe and tested in a MSW boiler for 76 days. The spray coatings were applied by a relatively new inert-gas electric arc process which produces high quality coatings with minimal porosity and oxide inclusions. Coating performance was compared to Alloy 625 weld overlay, monolithic alloys 304L and 825, and bare carbon steel. The coatings provided significant protection for the carbon steel showing thickness loss rates comparable to weld overlay. Some electric arc sprayed coatings suffered disbonding at the steel interface and delamination within the coating demonstrating that the thickness, as well as the composition, are crucial to coating performance.

Subject
Coatings, Materials, Corrosion rate, Nickel based alloys, Tubes, Spray coating, Steel, Boilers, Corrosion probes, Carbon steel, Deposit corrosion, Alloys, Thermal spray coatings
Keywords:
MSW incineration, corrosion, thermal spray coatings, weld overlay, corrosion probe, nickel alloys, carbon steel, stainless steel
© 1993 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).
1993
Association for Materials Protection and Performance (AMPP)
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