This paper describes the effect of extended sensitization heat treatment (650°C) and applied potential on the corrosion behaviour and the stress corrosion cracking of low-carbon AISI 316L stainless steel (0.02%C) in a concentrated lithium hydroxide solution at 95°C. The results are compared to the behaviour of solution annealed material under the same conditions.

In general, their is a fairly clear effect of prolonged heat treatment times on the material, and its susceptibility to intergranular attack (IGA) and stress corrosion cracking (SCC) - as determined in slow strain rate tests - increases with increasing times of sensitization heat treatment.

When the heat treatment extends to 100 hours or more, the potential range in which IGA is observed extends to lower potentials (-300 mV SCE, open circuit conditions) compared to the solution annealed material. SCC, on the other hand, is observed on both materials in approximately the same potential ranges (i.e., above about -100 mV SCE). However, not only intergranular but also transgranular cracking occurs with the heat treated specimens. Moreover, transgranular SCC - and not intergranular SCC - even tends to be the predominant fracture mode when the heat treatment time is increased to 200 hours if the applied potential is sufficiently high (+ 100 mV SCE). No such phenomenon has been observed with the solution annealed material.

A possible explanation for these different results and for the effects of sensitization treatment is provided based on the electrochemical and the surface-chemical behaviour of the alloy.

Subject
Materials, Intergranular stress corrosion cracking, Hydroxides, Circuit potentials, Transgranular stress corrosion cracking, Open circuits, Lithium, Steel, Sensitization, Stainless steel, Heat treatment, Primary passive potential, Stress corrosion cracking
Keywords:
AISI 316L stainless steel, lithium hydroxide, cyclic polarization, electrochemical potential, slow strain rate technique (SSRT), heat treatment, sensitization, intergranular attack (IGA), intergranular stress corrosion cracking (IGSCC), transgranular stress corrosion cracking (TGSCC)
© 1992 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).
1992
Association for Materials Protection and Performance (AMPP)
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