As process conditions in the oil and gas industry become more demanding, the number of potential application areas requiring the use of high-performance superaustenitic stainless steels has increased. This has led to the reintroduction of the UNS S32654 grade (24Cr, 22Ni, 7.3Mo, 3Mn, 0.5N), which has a unique combination of high strength and outstanding resistance to corrosion, making it suitable for use in process streams as well as in seawater handling systems.

This paper presents results for UNS S32654 with regards to localized corrosion in chloride environments. This includes pitting, crevice corrosion and stress corrosion cracking in standardized laboratory tests, and also testing in natural seawater environments. Results are compared with other superaustenitic stainless steel grades such as UNS S31245 and UNS S34565, and to nickel-base alloys such as UNS N10276 and UNS S06625. The results show that UNS S32654 has higher resistance to the different forms of localized corrosion than the other superaustenitic grades. It is also shown that regarding resistance to crevice corrosion UNS S32654 can be on a par with or better than some nickel-base alloys.

UNS S32654 is qualified for use in H2S-containing environments in oil and gas production within NACE MR 0175/ISO 15156 and details of a number of qualification tests are described. Testing was carried out in accordance with NACE TM 0177 and also in autoclave environments up to 1.4 bar pH2S and no cracking was observed for UNS S32654.

Subject
Test methods, Marine environments, Materials, Stainless alloys, Nickel based alloys, Superaustenitic stainless steel, Seawater, Crevices, Crevice corrosion, Pitting, Corrosion resistance, Corrosion coupons, Stainless steel
Keywords:
Superaustenitic stainless steel, offshore, seawater, hydrogen sulfide, pitting corrosion, crevice corrosion, stress corrosion cracking, sulfide stress cracking
© 2012 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).
2012
Association for Materials Protection and Performance (AMPP)
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