Electrochemical and electrophysical nondestructive testing methods for protective polymer coatings

• V.A. Golovin and S.A. Dobriyan

A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences, Leninsky pr. 31, 119071 Moscow, Russian Federation

Abstract: Based on own and literature data, the possibility of using various electrochemical and electrophysical nondestructive testing methods, including their use for monitoring the state of the coating film and corrosion of the metal being protected, was analyzed for protective polymer coatings in various corrosive environments. Primary attention is paid to the evaluation of the capabilities of the electrochemical impedance method (EIS). The methodological aspects are considered and the validity of the choice of equivalent circuits for various types of polymer protective coatings on various substrates is analyzed. The results of evaluating the sorption of a corrosive medium based on changes in the coating capacitance on inert and corrosive substrates are considered. Models describing the defects of thin-layer paint and thick-layer protective polymer coatings were estimated. It was shown that there is a relationship between the resistance and the inverse capacitance of the Faraday process for thin-layer paint coatings. However, this relationship is more complicated than that predicted by the model in the works by Mansfeld–Titz and is non-linear over the entire time range. More promising are the results of testing the model of sub-film corrosion under thick-layer and multilayer protective coatings, for which the through porosity is insignificant, which allows one to uniquely associate the variation in the integral resistance of the Faraday process, R_dl, with the fraction of sub-film corrosion. It seems that the results of this work may be useful for devices for the nondestructive EIS analysis of the health of operating protective coatings that are currently being developed.

Keywords: corrosion protection, polymer protective coatings, sorption, under-film corrosion, EIS

Int. J. Corros. Scale Inhib., 2020, 9, no. 3, 1059-1083 PDF (843 K)
doi: 10.17675/2305-6894-2020-9-3-18

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