Inhibiting action of amino-heterocyclic compounds under conditions of iron corrosion in sulfuric acid solutions

• V.P. Grigor’ev¹, E.V. Plekhanova², E.G. Drogan², L.D. Popov¹ and T.G. Plekhanova³

¹ Southern Federal University, ul. Zorge 7, 344090 Rostov-on-Don, Russian Federation
² Don State Technical University, Gagarin sq. 1, 344000 Rostov-on-Don, Russian Federation
³ Shakhty Automobile and Road Institute (branch), South Russian State Polytechnic University (NPI) named after M.I. Platova, Lenin sq. 1, 346500 Shakhty, Russian Federation

Abstract: Amino-heterocyclic compounds were studied as acid corrosion inhibitors. The gravimetric method was used to determine the degree of protection of the studied compounds during iron corrosion in 1 M H₂SO₄ solution at various concentrations of compounds over a wide temperature range. The values of the corrosion inhibition coefficients K of iron under the conditions studied depend on the inhibitor concentration in the solution. Based on the data of gravimetric and temperature-kinetic measurements, the effective activation energy of the corrosion process was determined. Potentiostatic measurements were carried out in a three-electrode cell with a platinum auxiliary electrode and a silver–silver chloride reference electrode. Suppression of metal dissolution occurs both in the cathodic and anodic regions, but these substances inhibit the cathodic rather than anodic reaction. Partial inhibition coefficients were calculated from polarization measurements. It was found that the test substances are mixed-type inhibitors with a predominant blocking effect. With an increase in concentration, the contribution of the blocking factor to the protective effect of the inhibitor decreases, while the contribution of the activation component increases. An explanation of these facts is given based on the structure of the compounds studied. The AFM method was used to determine the efficiency of the additives as inhibitors. The surfaces of metals treated with both pure acid and inhibited solutions were studied. AFM images of the samples after the corrosion tests in the presence of inhibitors demonstrate the absence of damage, smoothing and levelling of the metal surfaces.

Keywords: inhibitor, corrosion, corrosion inhibition coefficient, adsorption

Int. J. Corros. Scale Inhib., 2020, 9, no. 2, 584-594 PDF (617 K)
doi: 10.17675/2305-6894-2020-9-2-13

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