Experiments were performed whereby steel cathodes were cathodically polarized in natural sea water by galvanic coupling to an aluminum anode through an external resistor. The change in potential versus current density data with time was found to be linear with a slope equal to the product of the total circuit resistance and cathode surface area and with the vertical intercept corresponding to the anode corrosion potential. Based upon the data from these experiments and comparison with survey results from an instrumented offshore structure, it is projected that the potential-current density behavior of galvanic cathodic protection (cp) systems of vastly different geometries can be quantitatively interrelated through this slope parameter. It is proposed also that this same slope parameter can serve as the basis for cp system design and that this approach offers advantages compared to present and historical design practice. Lastly, it is proposed that by calculation of the elope parameter and knowledge of the anode corrosion potential the current density at local regions of an existing structure can be projected based upon potential survey data alone.

Subject
Cathodes, Water, Anode potential, Cathodic potential, Slopes, Anode resistance, Experimental data, Current densities, Cathodic current density, Steel, Polarization, Corrosion potential, Anodes
© 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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