Synthesis and Characterization of Thymol Derivatives as Corrosion Inhibitors for Carbon Steel in Acidic Environments: Experimental and Computational Approaches

Corrosion in acidic media, particularly for E24 steel, remains a critical issue in various industries due to the high aggressiveness of hydrogen ions. The present study reports the synthesis of two new organic inhibitors, 3‐(3,4‐dimethoxyphenyl)‐5‐((2‐isopropyl‐5‐methylphenoxy)methyl)‐4,5‐dihydroisoxazole (TVM) and 3‐(4‐ethoxy‐3‐methoxyphenyl)‐5‐((2‐isopropyl‐5‐methylphenoxy)methyl)‐4,5‐dihydroisoxazole (TVE), derived from a vanillin‐thymol platform. Electrochemical investigations, including potentiodynamic polarization and electrochemical impedance spectroscopy, along with surface analysis (SEM/EDS), demonstrate that both compounds act as efficient corrosion inhibitors for E24 steel in 1 M HCl over a wide concentration range. The inhibition efficiencies reached 88.25% for TVM and 91.98% for TVE. Based on its superior performance, TVE was selected for further investigation. The effects of temperature (298–328 K) and immersion time (up to 24 h) were also examined. The results indicate that TVE behaves as a mixed‐type inhibitor with a predominant cathodic effect, while maintaining high efficiency under aggressive conditions. Thermodynamic analysis revealed that the adsorption process is spontaneous and follows the Langmuir isotherm. Furthermore, DFT, DFTB, and molecular dynamics simulations confirmed the strong adsorption affinity of TVE on the metal surface through electronic and steric interactions. Overall, both TVM and TVE exhibit promising potential as corrosion inhibitors in acidic media, with TVE showing superior efficiency, stability, and durability.