Experimental and theoretical investigation of pyrazinecarboxamide against mild steel corrosion

Abstract

Pyrazinecarboxamide was examined against mild steel corrosion in 0.5 M HCl solution. The electrochemical techniques like electrochemical impedance spectroscopy, linear polarization resistance and potentiodynamic polarization measurements were carried out in the presence of various concentrations of pyrazinecarboxamide ranging from 0.25 mM to 1.0 mM. The inhibition effect of pyrazinecarboxamide on the mild steel surface was studied by atomic force microscopy and scanning electron microscopy. The adsorption of this inhibitor was determined to fit Langmuir adsorption isotherm. The adsorption/desorption equilibrium constant was calculated as 2.985 × 104 M−1, indicating that high proportion of pyrazinecarboxamide takes place on mild steel surface. The inhibition efficiency was found as 93.5% from electrochemical impedance spectroscopy measurement in an acid solution containing 1.0 mM pyrazinecarboxamide. Quantum chemical parameters that were in good agreement with experimental results were determined by density functional theory.