Application of the EIS method to study the mechanism of the inhibitory effect of catechol on steel corrosion in an alkaline medium containing chlorides

• V.E. Kasatkin, I.V. Kasatkina, L.P. Kornienko, I.G. Korosteleva, V.N. Dorofeeva and N.N. Andreev

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

Abstract: Various classes of compounds, including those from the phenol group, are used to inhibit steel corrosion. These include catechol, the structure of which is a benzene ring containing two hydroxyl groups in the ortho position. This compound has high antioxidant activity and reacts easily with reactive oxygen species present in electrolytes under conditions of natural aeration. In this case, catechol is oxidized, forming a brown resinous compound oxanthrene-2,3-dione. The latter is deposited on the solid phase of the system, including on the protected metal in the form of a viscous resinous mass. On the other hand, catechol can form adsorption chelate layers on steel, causing blocking of active centers. In previous publications in this journal, we presented the results of a study of catechol as an inhibitor of steel corrosion in alkaline, chloride-containing media. Its protective effect was found in concentrations from 1 to 5 g/L. Continuing this cycle of work, this publication is devoted to a comparative assessment of the effect of two possible mechanisms of catechol inhibition of steel corrosion: due to the formation of thin chelate films and due to the accumulation of a resinous precipitate on the surface, which can limit the diffusion of oxygen from the volume of the solution. Analysis of the results of 28-day experiments using the EIS method showed that the inhibitory effect of catechol is mainly determined by the formation of strong adsorption films on the surface of steel, which protect the metal even when it is transferred to a solution without an inhibitor. The optimal concentration according to the results of these experiments was 5 g/L of catechol.

Keywords: catechol, inhibitor, corrosion, electrochemical impedance spectra

Int. J. Corros. Scale Inhib., 2024, 13, no. 1, 526-541
doi: 10.17675/2305-6894-2024-13-1-26

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