Cyanoacetamide derivatives as corrosion inhibitors; Synthesis, Characterization, DFT and Monte Carlo simulation

Corrosion behavior of X65-type carbon steel exposed to 1M HCl aqueous solution was studied in the absence and presence of various concentrations of new synthesized 3-(4-chlorophenyl)-2-cyano-N-(4-hydroxyphenyl) acrylamide, abbreviated as (P2), and 6-amino-4-(4-chlorophenyl)-1-(4-hydroxyphenyl)-2-oxo-1,2-dihydropyridine-3,5-dicarbonitrile, abbreviated as (P3), at 25oC. Potentiodynamic polarization data indicated that the synthesized Cyanoacetamide derivatives suppress both anodic and cathodic reactions via adsorption on the carbon steel surface and blocking the active sites. The adsorption of the inhibitor molecules forms a protective film which decreases the surface heterogeneity. Electrochemical impedance spectroscopy (EIS) measurements reveal that as the inhibitor concentration is increased, both the inhibition efficiency (η%) and the charge transfer resistance (Rt) are increased while the electrochemical double layer capacity (Cdl) is decreased. The experimental impedance data were analyzed according to a proposed equivalent circuit model for the electrode/electrolyte interface. Chemical descriptors are calculated through the density functional theory (DFT), also adsorption of inhibitors on the metal surface investigated through Monte Carlo simulation. The mechanism of corrosion inhibition was discussed given the obtained results of surface analysis and the molecular structure of the additive obtained from quantum chemical calculations. Keywords: Corrosion inhibition; Polarization; Electrochemical impedance spectroscopy (EIS); Surface analysis; Quantum chemical calculations