N-[Morpholin-4-yl(phenyl)methyl]acetamide as corrosion inhibitor for mild steel in hydrochloric acid medium

The inhibiting effect and adsorption behavior of N-[morpholin-4-yl(phenyl)methyl]acetamide (MPA) on mild steel in hydrochloric acid solution were studied by weight loss measurements, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and scanning electron microscopy techniques. The inhibitor showed greater than 90% inhibition efficiency at 0.01 M. Potentiodynamic polarization studies showed that the inhibition action is concentration dependent, at low concentration anodic, higher concentration cathodic, inhibition predominant. Electrochemical impedance spectroscopy (EIS) confirmed that changes in the impedance parameters (Rt and Cdl) are due to surface adsorption. The inhibition efficiencies obtained from weight loss measurements and electrochemical tests were in good agreement. The adsorption process of MPA at the mild steel/hydrochloric acid solution interface is described by Langmuir adsorption isotherm model. The negative value of standard free energy of adsorption in the presence of inhibitor suggests spontaneous adsorption of MPA molecule on the mild steel surface. The activation energy of corrosion and other thermodynamic parameters were calculated to elaborate the mechanism of corrosion inhibition.