Pyrazole carbohydrazide as corrosion inhibitor for mild steel in HCl medium: Experimental and theoretical investigations

The inhibitory effect of 1,5-dimethyl-1H-pyrazole-3-carbohydrazide (PyHz) on the corrosion of mild steel in 1 M HCl medium has been examined and characterized using electrochemical impedance spectroscopy (EIS), polarization curves plot (PDP), gravimetrical and SEM/EDX methods. The obtained results indicate that PyHz has a good inhibitory and its inhibition efficiency reaches 96% at 10(-3) M. Weight loss and electrochemical techniques results were in reasonable agreement. The inhibitory effect increased with the concentration rise of PyHz but decreased with the increase in temperature. PDP technique suggested that the PyHz acted as a mixed type inhibitor. The adsorption process obeyed the Langmuir isotherm model. Thermodynamic parameters and the scanning electron microscopy analysis were discussed for mild steel in 1 M HCl medium and revealed the adsorption mechanism of PyHz. An electrical equivalent circuit was utilized to analyze EIS data in order to give an adequate model for adsorption process. Surface topography analysis strongly confirmed the electrochemical findings. The adsorption behavior of PyHz on steel surface was also inspected using Density Functional Theory (DFT) method and simulations of Monte Carlo. Quantum chemical calculations and Monte Carlo simulations have confirmed the experimental findings.