A statement previously published by NACE, ".… protective electric current must be applied to the structure in an amount sufficient to maintain its external surface, at every point, negative by at least -0.85 volt to a copper- saturated copper sulfate half cell in the immediate proximity thereof,”1  is based upon the following premises:

  • Brown and Mears proposed that complete cathodic protection is achieved when the cathode has been polarized to the open circuit potential of the anode.2 

  • In the absence of complexing agents, such as citrates, the protective potential for steel, as demonstrated by experience and computation, is close to -0.85 volt in reference to a copper- saturated copper sulfate half cell.

  • The magnitude of the IR drop, between the distant reference half cell position and the structure protected, included in the potential measurement, may have little significance in the control of the short lines of corrosion current flow related to local cell corrosion activity.3 

Subject
Underground structures, Pipe surfaces, Voltage drops, Piping, Cathodic protection, Structures, Soil resistivity, Potential measurements, Polarization, Polarized potential, Half cell potential, Half cells, Electrode potential
© 1968 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).
1968
Association for Materials Protection and Performance (AMPP)
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