Facile synthesis and assessment of 2-alkoxy-4-(4-hydroxyphenyl)-6-arylnicotinonitrile derivatives as new inhibitors for C1018-steel corrosion in HCl: A combined theoretical and experiential investigations 

An effective and accessible synthesis of alkoxy arylnicotinonitriles was achieved  via  a four-component reaction of 4-hydroxybenzaldehyde, acetophenones, malononitrile in the presence of RONa. The synthesized alkoxy arylnicotinonitrile derivatives containing pyridine moiety were predestined as inhibitors for C1018-steel (CS) corrosion in 1.0 M HCl using potentiodynamic-polarization (PDP) and electrochemical impedance spectroscopy (EIS) methods. PDP plots were demonstrated that the arylnicotinonitriles behave as typical inhibitors of the mixed-type. They have also suppressed the CS corrosion at lower [inhibitor] and accomplished an inhibition capacity ranged from 87.6 to 98.2% in 0.7 mM. Their adsorption on the CS interface follows the isotherm model of Langmuir and they include both chemisorption and physisorption mechanisms, with a preference of chemisorption. The morphology of the CS surface was examined utilizing Fourier Transform Infrared Spectroscopy (FTIR) and field-emission scanning electron microscopy (FE-SEM). Moreover, Density Functional Theory (DFT) calculations confirm the empirical findings and the adsorption of arylnicotinonitrile derivatives   on the CS interface.