Supercritical water is recognized as a promising medium for various chemical processes. However, one of the major problems to industrial application of the processes is thought to be corrosion of structural materials. In this paper, dependencies of corrosion resistance on alloying elements were investigated on twelve kinds of nickel base alloys in 400°C30MPa and 400°C60MPa supercritical water containing 0.01mol/kg sulfuric acid. The investigations reveals that Cr controls the corrosion resistance of the alloys in the test conditions and thresholds of changes in improvement rate in corrosion resistance with increasing Cr content are observed for the testing pressures.

Properties of oxide on the specimens are examined by X-ray diffraction technique (XRD) to investigate correlation between the corrosion resistance of the Ni base alloys and crystallinity of the oxides on the Ni base alloys. The investigation suggests that corrosion resistance of the alloys improve with higher oxide crystallinity. The reasons for the effect of crystallinity on corrosion resistance are discussed.

Subject
X-ray diffraction, Grain size, Supercritical water, Corrosion resistant alloys, Corrosion rate, Nickel based alloys, Autoclaves, Metal oxides, Alloying elements, Oxide scales, Weight loss, Scale thickness, Corrosion resistance
Keywords:
supercritical water, corrosion, Ni base alloy, chromium, crystallinity of oxide, X-ray diffraction, sulfuric acid
© 2007 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).
2007
Association for Materials Protection and Performance (AMPP)
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