Theoretical prediction and experimental study of 5- methyl- 1H -pyrazole-3- carbohydrazide as a novel corrosion inhibitor for m ild steel in 1.0 M HCl

摘要

This work is devoted to examine the effectivenes of 5-methyl-1H-pyrazole-3-carbohydrazide(MPC) on corr osion of mild steel in 1 M HCl solution using the weight los s measurement at various temperature and concentrat ion effects. Polarization curves and electrochemical impedance s pectroscopy (EIS) methods were employed to evaluate corrosion rate and inhibition efficiency. Inhibitio n efficiency of 95% is reached with 10 -3 M of ( MPC ) at 308 K. Potentiodynamic polarization showed that the MPC be haves as mixed-type inhibitor. The Nyquist plots sh owed that increasing MPC concentration, charge-transfer resis tance increased and double-layer capacitance decrea sed, involving increased inhibition efficiency. Adsorpti on of the inhibitor molecules corresponds to Langmu ir adsorption isotherm. Quantum chemical calculations showed that the inhibitor has the tendency to be protonated in the acid and the results agree with experimental observation s.