A test parcel with three cylindrical copper electrodes in one bentonite block was emplaced at the Äspö Hard Rock Laboratory in October 1999. Real-time corrosion monitoring using these copper electrodes was initiated in May 2001. The test parcel will be retrieved for post test examination in February 2005. The copper electrodes, each of about 100 cm2 surface area, are exposed at a temperature of 24°C. The corrosion monitoring is performed with polarization resistance, harmonic distortion analysis and electrochemical noise techniques.

In December 2002 the instantaneous corrosion rate of the copper electrodes is 0.5 μm/y. This value is considerably lower than the average corrosion rate of about 3 μm/y estimated from retrieved copper coupons. The recorded localization factor (defined as the electrochemical current noise divided by the product between the surface area of the specimen and the corrosion current from the harmonic distortion analysis) falls in the range 0.12 to 0.15. For pure general corrosion, the localization factor tends to be in the region of 0.01 or less, and values close to 1 are expected for severe localized corrosion. Examination of already retrieved copper coupons has not revealed any obvious signs of pitting.

Subject
Materials, Corrosion rate, Rocks, Electrochemical noise, Metal coupons, Bentonite, Groundwater, Corrosion attacks, Copper, Localized corrosion, Corrosion monitoring, Polarization resistance, Electrodes
Keywords:
copper, bentonite, groundwater, general corrosion, localized corrosion, real-time corrosion monitoring
© 2004 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).
2004
Association for Materials Protection and Performance (AMPP)
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