U-bend, C-ring, and slow strain-rate tests have been performed to evaluate the effects of texture, stress, surface condition, heat treatment, electrochemical potential, and strain rate on stress corrosion cracking (SCC) of zirconium in 90% nitric acid at room temperatures. It has been shown that careful control of texture, surface condition (scratching, cleaning and oxide coating), and/or applied stress can effectively lead to the prevention of SCC of zirconium in 90% HNO3. Heat treating at 760°C, 880°C, or 1000°C does not seem to improve the SCC resistance. However, if the potential of zirconium is maintained at 500 mVSCE or lower, or 200 ppm of HF is added, zirconium's SCC susceptibility in 90% HNO3 is eliminated. In the case of adding HF, zirconium sponge must also be added in order to avoid high corrosion rates.

The mechanism for SCC of zirconium in 90% HNO3 appears to be stress assisted local anodic dissolution, since the highest susceptibility is observed at strain rate = 7.5 x 10−7/sec, and, at a higher or lower strain rate the susceptibility decreases. There is additional evidence to support this mechanism.

Subject
Strain rate, Materials, Corrosion rate, Zirconium, Sponges, Thermal stress, Stress, Metals, Zirconium alloys, Corrosion potential, Weld metal, Stress corrosion cracking, Electrode potential
© 1987 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).
1987
Association for Materials Protection and Performance (AMPP)
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