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Understanding the effectiveness of cathodic protection under disbonded coatings

journal contribution
posted on 20.12.2015, 00:00 authored by Bob Varela, Mike Yongjun TanMike Yongjun Tan, Maria ForsythMaria Forsyth
© 2015 Elsevier Ltd. All rights reserved. Factors affecting the effectiveness of cathodic protection under disbonded coatings were studied using a partially covered two dimensional electrode array that simulates a crevice under a disbonded coating and allows for the mapping of electrochemical currents under the influence of cathodic protection (CP). This technique enabled the study of the effects of major factors, including crevice gap size, solution conductivity and applied CP potential on the distribution and evolution of CP currents over the electrode array surface. The effect of each of these factors on the overall current distribution profile has been explained using a new electrochemical model. This model suggests that, despite the detrimental effect of cathodic shielding, the steel under disbonded areas could still be protected, independent of the crevice geometry and solution resistivity, by means of concentration polarization instead of direct electrochemical polarization. A set of conditions for maintaining CP potentials more negative than -850 mVCSE along disbonded coating areas was deduced from the proposed model and validated against potential profiles available in the literature. The possible practical implications of the current mapping technique used in this study for developing in-situ CP monitoring sensors has also been discussed.

History

Journal

Electrochimica acta

Volume

186

Pagination

377 - 390

Publisher

Elsevier

Location

Amsterdam, The Netherlands

ISSN

0013-4686

Language

eng

Publication classification

C Journal article; C1 Refereed article in a scholarly journal

Copyright notice

2015, Elsevier