Anti-corrosive properties of Catha Edulis leaves extract on C38 steel in 1 M HCl media. Experimental and theoretical study

The anti-corrosive properties of Catha Edulis extract have been investigated for its protective action as a green inhibitor in 1 M HCl media. An ethanolic extract of Catha Edulis leaves (CELE) was used to inhibit corrosion of C38 steel. Electrochemical Impedance Spectroscopy (EIS) and Potentiodynamic Polarization methods were applied to investigate the inhibitory efficacy of this extract. Polarization measurements revealed that the inhibitor behavior is of a mixed nature. The inhibitory efficiency values (IE) produced by the two approaches were nearly identical, with the maximum value (92%) obtained at 2 (g.L-1) of CELE. A study on the impact of immersion time was also carried out, which demonstrated that CELE was a stable inhibitor throughout all trials, independent of immersion duration. The adsorption isotherm was also examined, revealing that CELE adsorbs on the C38 steel surface according to the Langmuir isotherm, with a Delta G(ads)(0) of about -10.27 (kJ.mol(-1)), suggesting that the current inhibitor limits the corrosion process by physical adsorption. The study of surface morphology by Scanning Electron Microscopy coupled with X-ray energy dispersive spectroscopy (SEM-EDX) confirmed that the extracted molecules adsorb on the metal's surface, forming a protective layer responsible for inhibiting the corrosion of C38 steel. The computational results show that CELE in its protonated forms (Cathinone-H, Amphetamine-H, and Cathine-H) has a propensity to adsorb onto the C38 surface, resulting in the creation of a protective film, these results supported experimental findings.