Effects of environmental factors such as H2S partial pressure, pH, Cl− concentration and temperature on SSC property of modified 13Cr steels were systematically investigated. Critical H2S partial pressure for SSC is affected mainly by temperature and chloride concentration, while pH effect was quite small. In mild conditions such as chloride free solution at 25 °C , the steels presented the passive state inhibiting hydrogen entry into steel so that no SSC susceptibility was observed. With increase in Cl− concentration, corrosion morphology changed from passive state into either pitting or general corrosion allowing hydrogen entry into steel so that SSC susceptibility was observed. In higher temperature condition, passive film also became unstable to cause general corrosion, however, cracking susceptibility was decreased. Based on the test results, a principal SSC mechanism of modified 13Cr steels is considered to be hydrogen embrittlement in condition that some breakdown of passive film undergoes beforehand.

Subject
Hydrogen embrittlement, Materials, Hydrogen concentration, Passive films, Sodium chloride, Partial pressures, Acidity, Sodium chloride solution, Corrosion morphology, Steel, Pitting, Sulfide stress cracking, Corrosion potential
Keywords:
SSC, pH, H2S, Cl−, Temperature, Yield strength, Modified 13Cr steel
© 1997 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).
1997
Association for Materials Protection and Performance (AMPP)
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