Coupled multielectrode arrays sensors (CMAS) have been used for real-time monitoring of corrosion, particularly localized corrosion. The internal anodic current on the most anodic electrode in a CMAS was evaluated for aluminum and carbon steel in simulated seawater and dilute HCl solutions. The Tafel extrapolation method was used to derive the internal currents on the most anodic electrode and the average corrosion current. In the simulated seawater, aluminum corroded dominantly in the form of localized corrosion and carbon steel corroded dominantly in the form of nonuniform general corrosion. In these cases, the externally measured nonuniform corrosion current on the most anodic electrode from the CMAS probe accounted for more than 90% of the total corrosion current. In the dilute HCl solution, both aluminum and carbon steel corroded dominantly in the form of uniform corrosion and the externally measured localized corrosion current on the most anodic electrode from the CMAS probe accounted for less than 56% of the total corrosion current.

It was concluded that if the externally measured nonuniform corrosion current from a CMAS probe is larger than the Tafel extrapolated currents, non-uniform corrosion is dominant and the effect of the internal current is not significant. In this case the CMAS probe reasonably measures the corrosion currents. However, if the externally measured nonuniform corrosion current from a CMAS probe is less than the Tafel extrapolated currents, uniform corrosion is dominant and the effect of the internal current may be significant. In this case, the CMAS probe only measures the nonuniform portion of the corrosion currents (which is not significant).

Therefore, CMAS probes are effective tools for corrosion monitoring in localized corrosion and nonuniform type of general corrosion. The unpolarized CMAS probes cannot be used to measure purely uniform type of general corrosion.

Subject
Corrosion currents, Probes, Anodic electrodes, Aluminum, Current measurements, Extrapolation, Silicate deposits, Anodic current, Corrosion probes, Carbon steel, Localized corrosion, Electrodes, Corrosion potential
Keywords:
Multielectrode sensor, corrosion monitoring, corrosion sensor, localized corrosion sensor, multielectrode array, nonuniform corrosion, coupled multielectrode
© 2009 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).
2009
Association for Materials Protection and Performance (AMPP)
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