Type 444 (18Cr-2Mo) (UNS S44400) ferritic stainless steel has been successfully used in hot water environments such as hot water tanks and solar collectors, where Type 304 (UNS S30400) austenitic stainless steel often suffered crevice attack which consequently led to stress corrosion cracking or pitting corrosion. These experiences show that in hot water environments, corrosion problems are related to crevice corrosion, and crevices are important factors for the application of stainless steels in waters.

In this work, electrochemical potentials, crevice corrosion potential and crevice repassivation potential, were measured by a cyclic polarization technique to predict actual performance, and the results are compared to actual experiences and laboratory immersion tests.

The results are summarized as follows;

  • Alloying elements, Cr and Mo, shifted V'crev significantly to the noble side, indicating improvement of crevice corrosion resistance.

  • Type 444 exhibited more noble V'crev than Type 304 at lower chloride level, indicating a superior crevice corrosion resistance of Type 444 in such media.

Subject
Noble potential, Seams, Immersion tests, Water, Repassivation potentials, Welding, Crevices, Crevice corrosion, Specimen preparation, Corrosion resistance, Stainless steel, Chlorides, Corrosion potential
© 1984 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).
1984
Association for Materials Protection and Performance (AMPP)
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