This paper deals with the evaluation of the subsea pipeline integrity through the combination of potential profile, electric field gradient and the modeling of the electric field originated by the bracelet galvanic anodes by Finite Element Method (FEM).

The potential profile as well as the electric field gradient measured during a survey provide the representation of the Cathodic Protection (CP) level and the location of anodes and coating defects. Nevertheless, by overlapping the electric field calculated by a dedicated FEM modeling, a more accurate interpretation is achieved in order to estimate the critical coating defect size and to evaluate the effect of the presence of multiple defects.

FEM modeling was based on a simplified 2D domain reproducing the main geometrical, physical and electrochemical parameters, such as sea depth, mud burial depth, seawater and mud resistivity, and current density and potential distribution. Boundary conditions were defined by assuming constant potential at galvanic anode, electrical insulation of the coating and by considering Butler-Volmer equation for steel surface at coating defects. Coating defect size, sea depth, mud burial depth were considered in a generalized parametric equation.

An example of the application of the model is shown on the basis of results obtained by an inspection campaign.

Subject
Water depth, Anode potential, Modeling, Ohmic drop, Probes, Reference electrodes, Pipelines, Drilling fluid, Coating surveys, Defects, Bracelet anodes, Coating defects, Electrode potential
Keywords:
cathodic protection, FEM, modeling, potential distribution, survey, subsea pipeline, coating defects, pipeline integrity
© 2013 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).
2013
Association for Materials Protection and Performance (AMPP)
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