By connecting AC corrosivity probes to AC interfered pipelines the accumulated as well as instant corrosion rate can be assessed. Simultaneously adjusting and monitoring of the electrical (AC/DC) conditions of the pipeline, the corrosion rate can be measured as a function of these parameters. Measurements performed in the field confirm a mechanism of AC induced corrosion which involves local alkalization of the local soil environment close to a coating defect. An intelligent switch devise (ISD) has been presented which controls earthing of the pipeline via capacitors. When a timer is connected to the CP rectifier in connection with CP surveys (ON/OFF potential measurements) the ISD detects the regularly pulsed (ON/OFF) CP and disconnects the earthing system thus allowing for instant OFF measurements of the CP potential. In combination with the AC corrosivity probes, a concept is provided similar to management of internal corrosion by controlled inhibitor dosage carefully adjusted and optimized by use of on-line and real time intrusive corrosivity probes.

Subject
Piping, Voltage, Corrosion rate, Probes, Corrosivity, Thickness measurement, Capacitors, Pipelines, Resistors, Corrosion probes, Coating defects, Corrosion resistance, Elements
Keywords:
AC corrosivity probe, on line - real time monitoring, AC corrosion mechanisms, corrosion rate vs. AC voltage, AC mitigation by intelligent switch device
© 2004 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).
2004
Association for Materials Protection and Performance (AMPP)
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