Very low tolerable partial pressures H2S have been reported for duplex stainless steels in sour environments. However, it is shown in the paper that such steels resist SCC in sour environments even at substantial PH2S values.

To assess the applicability limits it is necessary to perform SCC-tests including an environment of reasonably accelerated severity. It is also very important to take practical experience into account.

SSRT (slow strain rate testing) is considered to put unrealistic mechanical demands on the material, since the stress can reach the UTS and the strain rate is controlled to give maximum SCC- sensitivity. Constant-strain and constant-stress tests are more relevant to practical conditions.

The actual environment is always more complex than the plain H2S/Cl- - or H2S/CO2/Cl- -environments used in the majority of laboratory tests. Bicarbonate ions are most often present, and by increasing the pH-value they reduce the aggressivity of the environment.

Duplex stainless steels have been used for many years in applications with significantly higher p„7C. than many laboratory tests have indicated to be possible.

Subject
Hydrogen sulfide, Test methods, Strain rate, Materials, Sour environments, Bicarbonates, Acidity, Stress, Constants, Fluids, Duplex stainless steel, Chlorides, Stress corrosion cracking
Keywords:
High alloy steel, Stress corrosion cracking, Stress, Test methods, Accelerated tests, Hydrogen sulfide, pH, Gas wells
© 1990 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).
1990
Association for Materials Protection and Performance (AMPP)
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