Electrochemical experiments have been carried out in Ca(OH)2 solutions, in mortar slabs with and without chloride additions and on reinforcement bars at a large bridge at the coast. The study is mainly focused on galvanostatic pulse experiments with monitoring of potential as a function of time. Only in an initial period the electrodes behaved in agreement with an equivalent circuit with a resistor and a capacitor in parallel. Modelling with two RC-links in series gave good fit with the observations. However, this type of modelling leads to uncertainty about which of the RC-links are related to the corrosion rate. It is concluded that changes at the metal surface and in the environment induced by polarisation occur with a delay with respect to the impressed current. In the modelling with equivalent circuits these effects cause capacitance and resistance not connected with the Faraday current and the polarisation resistance. Therefore, different electrochemical methods for determination of the polarisation resistance give unacceptable divergence. How to determine the corrosion rate from electrochemical measurements for steel in concrete is finally discussed.

Subject
Electric current, Circuits, Corrosion rate, Capacitors, Mortar, Capacitance, Steel, Corrosion resistance, Chlorides, Polarization resistance, Corrosion potential, Concrete, Electrode potential
Keywords:
Corrosion measurements, concrete, steel, electrochemistry, polarisation resistance
© 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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