Experimental and Computational Study of Levocetirizine Drug as a Green Corrosion Inhibitor of Carbon Steel

The effect of levocetirizine (LCZ) on the corrosion rate of carbon steel (CS) in 1 M HCl medium was studied at different concentrations and at different temperatures. Polarization measurements indicate that LCZ functions as a mixed-type inhibitor, exhibiting inhibition efficiencies of 84.44% at 293 K for the optimum concentration of 100 ppm. Moreover, under the same conditions, electrochemical impedance spectroscopy (EIS) revealed an inhibition efficiency of approximately 87.2%. The adsorption of the inhibitor on the carbon steel surface follows the Langmuir adsorption isotherm. The standard adsorption free energy (ΔGº_ads) found is − 32.16 kJ mol⁻¹. Dissolution activation parameters were also calculated; it was found that the energy (Ea) increases from 43.723 to 74.615 kJ mol⁻¹, the enthalpy of activation (∆Ha) increases from 41.168 to 72.033 kJ mol⁻¹, and the entropy of activation (∆Sa) increases from − 98.44 to − 7.424 J mol⁻¹ K⁻¹ with presence of 100 ppm of LCZ. The experimental results are also confirmed by quantum chemical calculations using the density functional theory (DFT).