Nowadays, application of 100mV criterion is more desirable than other criteria especially for buried structure in high resistivity soils where corrosion potentials may be low. Also, since this criterion can be readily evaluated by comparison of two potentials (Normally, Instant-off potential and free corroding potential), some errors by monitoring equipments include half cell and potentiometer can be avoidable.

According to all relevant NACE standards, for assessment of 100mV formation or decay criterion, measuring and recording of instant-off potential is a necessity. For new structure immediately after synchronized energizing an "instant-on" potential can be read. Reasonably the difference between this potential and free corrosion potential refers to IR drop, as well as, the difference between "instant-on" and steady on potential is the "net polarization". This paper compares the results by Instant-off method and Instant-on method for buried piping in a big plant. At the same time, evaluation of laboratory results is another major subject of this paper.

Subject
Electric current, Steel structures, Underground structures, Voltage drops, Cathodic protection, Cathodic potential, Free corrosion potential, Potential measurements, Electrical resistivity, Polarization, Instant off potential, Half cell potential, Electrode potential
Keywords:
Instant on potential, Buried piping, Cathodic Protection criteria
© 2012 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).
2012
Association for Materials Protection and Performance (AMPP)
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