The corrosion inhibition effect of aryl pyrazolo pyridines on copper in hydrochloric acid system: computational and electrochemical studies

Abstract

The inhibition effect of three aryl pyrazole pyridine derivatives, namely, 3-methyl-6-oxo-4,5,6,7-tetrahydro-2H-pyrazolo[3,4-b]pyridine-5-carbonitrile (APP I), 3-methyl-6-oxo-4-(3-phenoxyphenyl)-4,5,6,7-tetrahydro-2H-pyrazolo[3,4-b]pyridine-5-carbonitrile (APP II) and 3-methyl-6-oxo-4-(thiophen-2-yl)-4,5,6,7-tetrahydro-2H-pyrazolo[3,4-b]pyridine-5-carbonitrile (APP III), against the corrosion of copper in 0.5 M HCl solution has been systematically investigated by electrochemical impedance spectroscopy, potentiodynamic polarization measurements and quantum chemical methods. A good correlation between the computed energy gap (ΔE) data and the experimental inhibition efficiencies were found. Potentiodynamic polarization measurement results indicate that all three APP derivatives are cathodic type inhibitors. Among the studied compounds, APP I exhibited the best inhibition activity of 92.3% at 1.59 mmol L⁻¹. Scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) spectroscopy confirmed the presence of inhibitors on the copper surface.