Surface Activity and Adsorption Mechanism of Castor Oil‐Derived Biosurfactants for Steel Corrosion Protection

ABSTRACT In this study, the potential of castor oil‐derived heterocyclic compounds as green surfactants for mitigating the corrosion of XC48 carbon steel in 1 M HCl was explored. In addition, the surface activity and micellization behavior were studied using gravimetric techniques, showing that the compounds exhibited increased inhibition efficiency with increasing concentration, reaching an optimum near the CMC. Among the compounds tested, the heterocyclic compound 5‐(ricinoyl)‐1,3,4‐oxadiazole‐2‐thione (OXA) was found to be the most potent inhibitor of corrosion. Thermodynamic parameters, density functional theory calculations, and molecular docking studies also indicated efficient interfacial adsorption and a strong electron‐donating ability, making the compound an effective inhibitor of biologically induced corrosion processes. In addition, the results obtained using the Box–Behnken design were consistent with the experimental results. Monte Carlo simulations further revealed pronounced adsorption of the compound on the Fe (110) surface.