Two groups of corrosion pits were examined using scanning electron and optical microscopes: (1) MIC pits in Type 304/304L stainless steels and E308 stainless steel welds and (2) non-MIC chloride induced corrosion pits in the same materials. A faceted appearance is common to MIC and non-MIC pitting/crevice corrosion of Type 304/304L stainless steel base metal. Facets were found even in dendritic skeletons in MIC and non-MIC cavities of E308 stainless steel welds. Dendritic skeletons are common to MIC and non-MIC pits in E308 stainless steel welds. Thus, no unique morphological characteristics exist for MIC pits. Scanning electron and optical micrographs are presented to support the findings.

Subject
Pits, Pipe surfaces, Steel surfaces, Water, Piping, Magnification, Micrography, Base metals, Pitting, Tunnels, Stainless steel, Chlorides, Microbiologically influenced corrosion
Keywords:
corrosion pits, stainless steel, preferential corrosion, ferrite, austenite, faceted appearance, MIC, chloride, dendritic skeletons, dendritic corrosion
© 1999 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).
1999
Association for Materials Protection and Performance (AMPP)
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