Catechol as a corrosion inhibitor of steel 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: There is information about the use of diatomic phenol C₆H₄(OH)₂ as a corrosion inhibitor of steel reinforcement in concrete. Catechol (ortho-dihydroxybenzene) has the greatest effectiveness among the three isomers for inhibiting corrosion of steel. However, the mechanism of its action has not been sufficiently studied. In this publication, a study of the corrosion behavior of unalloyed steel in a model solution of a pore liquid of concrete with a high chloride content has been performed. The electrochemical behavior of catechol under cathodic and anodic polarization on a platinum electrode is investigated. It has been found that in the cathode section of the polarization curve, in the presence of catechol, currents due to the reduction of dissolved oxygen are significantly reduced. With anodic polarization more positive than E = –170 mV (Ag/AgCl), an asymmetric peak is observed associated with the oxidation of catechol and the manifestation of unsteady diffusion of its oxidation products. From the polarization curves on steel it is evident, that the addition of catechol effectively reduces the oxygen recovery currents and affects the ratio of the oxidized iron forms (Fe(II)/Fe(III), but it does not affect the depassivation potential of steel at the same pH level of the solution with and without an inhibitor. By the method of linear polarization resistance, the dynamics of the corrosion rate from the concentration of catechol was studied. An increase in the inhibitory effect with an increase in the additive concentration to 1 g/L and its decrease at 5 g/L of catechol was found. The mechanism of the inhibitor effect is discussed.

Keywords: steel, model concrete pore fluid, inhibitor, catechol, corrosion

Int. J. Corros. Scale Inhib., 2023, 12, no. 3, 995-1012
doi: 10.17675/2305-6894-2023-12-3-12

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