Electrochemical and Theoretical Study of Pyrazole 4-(4,5-dihydro-1H-pyrazol-5-yl)-N,N-dimethylaniline (D) as a Corrosion Inhibitor for Mild Steel in 1 M HCl

This work is devoted to examine the effectiveness o f pyrazoles 4-(4,5-dihydro-1Hpyrazol-5-yl)-N,N-dimethylaniline (D) on corrosion of mild steel in a 1 M HCl solution, using weight loss measurement at concentration effe cts. The inhibitor (D) was synthesized in our laboratory. The formation of thi s pyrazole was carried out with hydrazine and α-unsaturated aldehydes, and the structure was check ed by spectroscopic means, such as FT-IR, 1H NMR and 13C NMR. Polarizat ion curves and electrochemical impedance spectroscopy (EIS) method s were used to assess both the corrosion rate and inhibition efficiency. Potentio dynamic polarization showed that D behaved as a mixed-type inhibitor. The Nyquist plot s showed that, while D concentrations increased, charge-transfer resistanc e i creased and double-layer capacitance decreased, involving increased inhibiti on efficiency. Adsorption of the inhibitor molecules corresponds to Langmuir adsorpt i n isotherm. Quantum chemical calculations showed that the inhibitor was prone to be protonated in the acid, and the results were in full agreement with experimental ob servations.