In a petrochemical plant, two reinforced concrete seawater structures were constructed with built in cathodic prevention (CP) systems to prevent corrosion of the steel reinforcement from day one. The anode system consisted of mixed metal oxide coated titanium mesh ribbon and titanium conductor bar. The CP system was split into multiple anode zones exposed to different environments. The CP systems were commissioned in June 2000 and now have a service life of about 5 years. The performance of the CP systems and their compliance to the specified criteria is described and discussed. The specified criteria was met at most of the monitoring locations. The current requirement for sufficient protection was different in different zones and varied between 2-8 mA/m2 of steel current density. Long-term application of CP have resulted in shifting free corrosion potentials towards less negative values by some 100 to 300 mV, this provides evidence that CP is effectively controlling or preventing corrosion of the reinforcing steel and also maintaining its passivity.

Subject
Depolarization, Electric current, Environmental zones, Steel structures, Corrosion prevention, Compliance, Rebar, Free corrosion potential, Negative potentials, Current densities, Steel, Potassium chloride, Instant off potential
Keywords:
cathodic prevention, Instant-off -720mV criterion, 100 mV decay criterion, Ag/AgCl/0.5M KCl reference electrodes, steel current density
© 2006 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).
2006
Association for Materials Protection and Performance (AMPP)
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