The high resistance to corrosion of 22 Cr, 25 Cr and super duplex stainless steels in chloride containing environments is well known. In sour service, resistance to stress corrosion cracking, pitting and crevice corrosion in the presence of CO2 and H2S is required. This paper presents the results of tests to determine the resistance of three duplex stainless steels to stress corrosion cracking, pitting and crevice corrosion at elevated temperature in a synthetic brine containing different concentrations of H2S. The three alloys were UNS S31803, UNS S32550 (low Cu) and UNS S32760.

All three materials were tested in the cold worked condition, and loaded to about the 0.2% proof stress. The tests were conducted with 93 bar (9.3 MPa) CO2 and either 0.125, 0.25 or 0.375 bar (12.5, 25 or 37.5 KPa) H2S. The results showed that only the super duplex alloy, UNS S32760, was resistant to SCC at 80°C at all of the H2S concentrations. Pitting and crevice corrosion occurred at 121°C only at the highest H2S concentration on all the alloys. The depth and severity of attack varied from alloy to alloy and indicated that super duplex UNS S32760 is more resistant than 25Cr, UNS S32550 (low Cu), which is more resistant than 22Cr UNS S31803.

Subject
Pits, Materials, Stainless alloys, Molybdenum alloys, Hydrogen attack, Copper alloys, Cracking resistance, C ring stress corrosion testing, Crevice corrosion, Pitting, Corrosion resistance, Duplex stainless steel, Stress corrosion cracking
Keywords:
Sour brines, Sulphide SCC, pitting corrosion, crevice corrosion, duplex stainless steels
© 1994 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).
1994
Association for Materials Protection and Performance (AMPP)
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