Corrosion mechanism of austenitic Fe-Cr-Ni alloys containing 0.06-3.76%Si in Highly oxidizing HNO3 solutions have been studied by exposure testing, electorochemical polarization, high resolution analytical electron microscopy (HRAEM), and Auger electron spectroscopy (AES) techniques. Results of these studies indicate that intergranular corrosion of ~1%Si alloy is caused by galvanic coupling effect between Si-rich grain boundaries and normal grain faces. Lower Si-content alloys have high corrosion resistance by an absence of the effect and forming Cr-rich oxide films. Corrosion tests using laser surface melted alloy and coupons simulating a galvanic couple support the identified mechanism.

Subject
Stainless alloys, Corrosion rate, Metal surfaces, Nickel based alloys, Oxide formation, Oxide films, Oxide surfaces, Film formation, Stainless steel, Elements, Grain boundary, Alloys, Intergranular corrosion
Keywords:
silicon, austenitic stainless steel, intergranular corrosion, general corrosion, nitric acid solution, dichromate, segregation, galvanic corrosion, laser surface melting, electrochemical measurement
© 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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