Experimental and Computational Study of Trachyspermum Leaves Extract as a Green Inhibitor for Corrosion Inhibition of Mild Steel in HCl

The present study investigates the impacts of the extract of Trachyspermum leaves on mild steel corrosion in 0.1M hydrochloric acid (HCl) while highlighting its inhibitory mechanisms. The effects of mild steel corrosion in solutions of HCl were examined using gravimetric and galvanostatic polarization techniques, along with EIS analyses. The EIS data shows the highest coating undamaged index (83 %) after 100 hours of immersion. According to the results, the maximum inhibitory effectiveness corresponding to the minimum corrosion rate could be observed at the highest desirable level of inhibitor concentration equal to 100 ppm, while the corrosion rate decreases with an increase in the extract concentration. The adsorption study promotes that Langmuir isotherm with -31.85kJ/mol in room temperature with R2=0.95 best describes the metal surface interaction with the Trachyspermum leaves extract with the best exposure time for the Trachyspermum to adsorb to the metal surface at all concentrations. SEM, AFM, IR, and XRD showed good coverage of Trachyspermum on the surface of mild steel. Based on the polarization results, the inhibitors can play the role of a mixed inhibitor, which is confirmed by the computational data. The chemical potentials of thymol, cymene, and terpinene are -6.55, -6.91, and -6.49 eV respectively.