Experimental and theoretical studies of isonitrosoacetanilides derivatives as corrosion inhibitors for mild steel in 1 mol L−1 HCl

Abstract

The isonitrosoacetanilide, 2-bromoisonitrosoacetanilide and 2-methoxyisonitrosoacetanilide were synthesized and investigated as mild steel corrosion inhibitors in 1 mol L−1 HCl solution by potentiodynamic polarization curves, electrochemical impedance, weight loss measurements, scanning electron microscopy analysis and theoretical calculations. The weight loss measurements varying temperature show that the isonitrosoacetanilides are adsorbed on the mild steel surface by physisorption. The adsorption of inhibitor obeys the Langmuir's adsorption isotherm and the adsorption is an exothermic process with a decrease in entropy. The Tafel polarization method reveals that the inhibitors act as mixed type inhibitor. The obtained experimental results suggested that the maximum inhibition efficiency of isonitrosoacetanilide derivatives were over 90% at 5 × 10−3 mol L−1 at 25 °C. The weight loss measurements and electrochemical results were confirmed with scanning electron microscopy (SEM). Quantum chemical calculation was applied to correlate electronic structure parameters of isonitrosoacetanilides molecules with their corrosion inhibition performances and showed that possibly the adsorption process is of the physical type. The 2-bromoisonitrosoacetanilide and 2-methoxyisonitrosoacetanilide results were slightly superior to those obtained in the presence of isonitrosoacetanilide, showing that the bromo atom and methoxy group enhances the inhibitory properties.