Analysis of adsorption of a carbon steel corrosion inhibitor in model stratum waters by means of a polylogarithmic isotherm

• L.E. Tsygankova¹, N. Alshikha¹, M. Vigdorowitsch² and I.V. Zarapina³

¹ Derzhavin State University, Internatsyonalnaya str., 33, 392000 Tambov, Russian Federation
² Angara GmbH, In der Steele 2, D-40599, Düsseldorf, Germany
³ Tambov State Technical University, Sovetskaya str., 106, 392000 Tambov, Russian Federation

Abstract: Using the methods of gravimetry, potentiodynamic polarization, and impedance spectroscopy, the protective ability of inhibitory composition INCORGAZ-111 with respect to hydrogen sulfide corrosion of carbon steel St3 in NACE and Samotlor oil field (М1) model stratum waters is studied. The concentration of hydrogen sulfide was 50–400 mg/L. The inhibitory composition INCORGAZ-111 is a condensation product of tall oil fatty acids and polyamines in the salt form in a water-alcohol solvent (Developed by “INCORGAZ” LLC). The INCORGAZ-111 inhibitor exhibits a relatively high protective effect in NACE and M1 media reaching 80–90% at a concentration of 200 mg/L. Analysis of the polarization curves in the solutions studied indicates that the INCORGAZ-111 inhibitor slows down the anodic process in both media. According to impedance data, the charge transfer resistance in the anodic reaction increases with increasing concentration of INCORGAZ-111 inhibitor. The surface coverage was determined on the basis of the electric double layer capacitance in the presence of the inhibitor. Its adsorption was interpreted using the polylogarithmic isotherm with a big energy gradient of adsorption centers, that indicates a linear energy heterogeneity of the surface. The constants of adsorption equilibrium, energy gradient and energy dispersion of adsorption centers as well as adsorption free energy were calculated.

Keywords: corrosion, stratum water, hydrogen sulfide, inhibitor, capacitance, adsorption, surface coverage, polylogarithmic isotherm

Int. J. Corros. Scale Inhib., 2021, 10, no. 1, 120-131 PDF (559 K)
doi: 10.17675/2305-6894-2021-10-1-7

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