Corrosion inhibition potentials of Cucurbita polyesteramide urethane on mild steel in hydrochloric acid medium: Experimental and computational studies

Polyesteramide urethane was synthesized from Cucurbita maxima seed oil and characterized via Thermogravimetric analysis, Fourier Transformed Infrared spectroscopy, and Differential Scanning Calorimetry. The inhibiting effect of the synthesized polyesteramide urethane (CPEAU) on mild steel in 1.0 Molar concentrations of HCl was investigated through electrochemical and weight loss measurements. The temperature effect on the corrosion performance of the mild steel with or without CPEAU was studied in the range of 303–333 K. It was found that an increase in temperature led to a decrease in inhibition efficiency. The adsorption of CPEAU molecules on mild steel was spontaneous and the isotherm model which the adsorption obeyed was Langmuir's. It was observed that, the value of activation energy for the uninhibited test solution (35.82 kJ/mol) was discovered to be less than those obtained for the inhibited test solutions at different temperatures (49.91 kJ/mol, 50.49 kJ/mol, 53.78 kJ/mol, 62.78 kJ/mol and 69.89 kJ/mol), that signifying electrostatic interaction (physisorption mechanism) of CPEAU on mild steel. Potentiodynamic polarization investigation signified a mixed-type inhibition mechanism of CPEAU at a lower concentration with predominant cathodic effects at a higher concentration. Quantum chemical descriptors revealed the carboxylic group on CPEAU molecule as the active adsorptive sites through which adsorption occurred on the mild steel surface, and a molecular dynamics simulation showed the adsorption and binding energies of the inhibitor. The experimental and computational results were in good agreement