Corrosion inhibition performance and computational studies of pyridine and pyran derivatives for API X-65 steel in 6 M H2SO4

Abstract The present investigation aims to synthesize and explore the influence of pyridine and pyran derivatives on the API X-65 steel corrosion in a 6 M H2SO4 solution. The compound was examined at different concentrations to optimized the best concentration for the corrosion inhibition effect. weight loss measurements, potentiodynamic polarization measurement (PDP), electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and theoretical methods were used to evaluating the inhibition efficiency. The obtained adsorption data achieved the model of Langmuir isotherm. The pyridine derivatives showed higher inhibition than pyran derivatives. The PDP tests proposed that pyridine and pyran derivatives are mixed-type inhibitors. The EIS parameters demonstrate that the double-layer capacitance (Cdl) decreases with the increase of inhibitor concentration, which implies a reduces dielectric constant. It was observed from experimental data that the inhibition efficiency reached 92.7%, 89.1, 94.7, and 85.2% for concentration 2.66 × 10−3 M of I, II, III and IV, respectively indicating the inhibition order is III > I > II > IV. The parameters derived from the theoretical quantum chemical calculations were found adequately correlated with the obtained experimental results.