The objective of this research work is the study of the inhibitory effect of Warionia saharea essential oil (WSEO) on the corrosion of mild steel (MS) in molar HCl solution, employing both experimental and theoretical methods. This inhibitory effect (IE) has been evaluated by using a combination of weight loss measurements (LW) and various electrochemical methods, such as open circuit potential (OCP), potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) experiments. The LW results indicated that IE increased with inhibitor concentration, reaching 83.34% at 3.00 g/L. The PDP analysis suggested that WSEO functions as a mixed inhibitor, while in the EIS results the R_ct values increased with inhibitor concentration to reach 165.8 Ω cm² at 2.00 g/L, suggesting a defensive film formation by WSEO molecules over the metallic surface. The thermodynamic study demonstrated that the WSEO molecules adsorption on the MS surface followed a Langmuir isotherm, involving mixed physical and chemical (physicochemical) adsorption on the MS surface. Theoretical methods, including density functional theory (DFT) and molecular dynamics (MD) simulations, were employed to elucidate the inhibition mechanisms of the three main components of WSEO. The quantum chemical analysis, using density functional theory (DFT) and molecular dynamics (MD) simulations, showed a low ΔE_gap value of 6.30 eV and a low adsorption energy (E_ads) value on an Fe (110) substrate of −258 Kcal/mol for (E)-Nerolidol, indicating the significant contribution of this molecule to the overall corrosion inhibition effect of WSEO. The scanning electron microscope (SEM) analysis verified the presence of a protective film formed by the inhibitor on the MS surface. This study highlights the potential of WSEO as a sustainable and green corrosion inhibitor in acidic environments.

In the present work, the economical synthesis strategy of the compound in high yield was reported through the reaction between fluorescein and benzoyl chloride under different operating conditions. The synthesized compound: 3-oxo-3H-spiro[isobenzofuran-1,9′-xanthene]-3′,6′-diyldibenzoate was characterized by IR, ¹H NMR, ¹³C-NMR and mass spectral. This reaction has been studied also theoretically using Gaussian 09 based on the DFT method at B3LYP/6-311G (d, p). The results revealed that the theoretical study is in good correlation with the experimental one. The analysis of the absorption spectrum shows that the prepared product which has optical properties is a colored pigment.