Electrochemical potentiokinetic reactivation (EPR) testing provides quantitative detection of small degrees of sensitization. We have used double-loop (DL-EPR) testing, a method which has been characterized for use on austenitic stainless steels, to measure sensitization resulting from aging or from welding of PH 13-8 Mo martensitic stainless steel. Aging at either 500°C or 620°C results in an increase of the reactivation current density. The 500°C treatment promotes preferential susceptibility to corrosion along prior austenite grain boundaries, and the 620°C treatment promotes preferential susceptibility along martensite interlath boundaries. A narrow band in the heat-affected zone of autogenous weldments also undergoes localized corrosion during the reactivation scan. Increased reactivation current density is likely caused by classic Cr-depletion resulting from carbide precipitation.

Subject
Test methods, Materials, Precipitation (solids), Thermocouples, Thermal cycle, Welding, Corrosion morphology, Sensitization, Stainless steel, Grain boundary, Intergranular corrosion, Austenite, Martensite
© 1987 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).
1987
Association for Materials Protection and Performance (AMPP)
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