Inhibition of CO₂ corrosion of mild steel in a highly mineralized saline solution with a new synthesized α-aminophosphonate

• Yu.P. Khodyrev, E.N. Nikitin, G.G. Shumatbaev, K.O. Sinyshin, D.A. Terenzhev and A.M. Ermakova

A.E. Arbuzov Institute of Organic and Physical Chemistry, Subdivision of the Federal State Budgetary Institution of Science “Kazan Scientific Center of Russian Academy of Sciences”, Arbuzov Str. 8, 420088 Kazan, Russian Federation

Abstract: The inhibitory effect of new synthesized neonylethyldiethylaminomethylphosphonate (NEDMP) on the CO₂ corrosion of mild steel was studied the methods of linear polarization resistance (LPR), potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The results show that NEDMP is a good inhibitor with an inhibition efficiency of 60–98% at concentrations of 0.5–25 ppm. The adsorption of inhibitor molecules on the surface of the steel submits the Langmuir adsorption isotherm. The corrosion rate grows with increasing temperature from 30 to 70°C; however, inhibitor efficiency decreased very slightly. NEDMP can be considered as a mixed type inhibitor with a predominant effect on the metal dissolution reaction. NEDMP molecules are desorbed from the metal surface with anodic polarization. The desorption potential relatively to the open circuit potential does not depend from the concentration of the inhibitor in the solution; it decreases linearly with increasing temperature. Kinetic and thermodynamic parameters were calculated. Analysis of these parameters showed that adsorption mechanism of the molecules of NEDMP on mild steel may involve two types of interaction: chemisorption and physisorption. The inhibitor molecules block the surface of the metal during spontaneous electrostatic adsorption. The part of the molecules that was adsorbed on the active centres of metal dissolution forms a coordination bond, possibly through an oxygen atom. An increase in temperature or potential accelerates this process.

Keywords: steel, polarization, acid corrosion, inhibition

Int. J. Corros. Scale Inhib., 2019, 8, no. 2, 312-328 PDF (1 477 K)
doi: 10.17675/2305-6894-2019-8-2-13

Download PDF (Total downloads: 801)

Back to this issue content: 2019, Vol. 8, Issue 2 (pp. 150-436)