This paper discusses the basic operating principles of the Surface Second Harmonic Generation (SSHG) technique and its application to the remote in-situ detection of low levels of surface corrosion. SSHG is a nonlinear-optical technique which is surface sensitive. As an optical technique, SSHG is nonintrusive, noninvasive and nondestructive. In comparison, the vast majority of surface sensitive techniques which could detect corrosion onset require an ultra-high vacuum environment. SSHG technique has spectroscopic capability. Formation of an iron oxide or other species due to corrosion will lead to a change in the spectral signature produced at the surface. This provides a means to monitor the onset of corrosion. Since the SSHG technique is surface specific, it can examine any optically accessible interface. For example, in examining the corrosion-induced chemical changes at a water-metal interface, the chemical changes at the interface between the two could be probed with this technique as the corrosion occurs while in contact with the water, since the water is transparent. In this way, the technique can be used in an in-situ fashion.

Subject
Materials, Metal surfaces, Metal coupons, Roughness, Corrosion detection, Surfaces, Lead, Substrate surfaces, Oxide surfaces, Interfaces, Lasers, Copper, Polarization
Keywords:
corrosion, optical, second-harmonic, corrosion on-set
© 1994 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).
1994
Association for Materials Protection and Performance (AMPP)
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