Interfacial effect of Camellia oleifera fruit shell extract in enhancing the corrosion resistance of steel in dichloroacetic acid solution

• A novel green inhibitor based on Camellia oleifera fruit shell extract (CFSE) is developed. • The corrosion inhibition efficiency of CFSE on cold-rolled steel (CRS) is determined to be 98.1% in 0.50 M dichloroacetic acid (DCA) solution at 40 °C. • The corrosion is effectively reduced by CFSE through the blocking of active corrosion sites on CRS surface. • The appearance of Fe-N, FeOCH 2 -, and FeCNO 2 - complexes confirms the film-forming mechanism of CFSE. • The self-diffusion of corrosive ions is effectively retarded by the CFSE film. Dichloroacetic acid (DCA) is an aggressive organic acid whose industrial application is hampered by a lack of effective, eco-friendly corrosion inhibitors. This study pioneers a novel solution by valorizing agricultural waste, introducing an extract from Camellia oleifera fruit shell (CFSE) as a high-performance green inhibitor for cold-rolled steel (CRS) in concentrated (0.50 M) DCA. A multidisciplinary approach combining molecular dynamics (MD) simulations and experimental validation elucidated the inhibition mechanism. MD simulations revealed that the seven active components in CFSE (e.g., rutin, naringin) strongly adsorb onto the Fe (110) surface via heteroatoms, with binding energies up to 1559.53 kJ mol -1 , significantly hindering the diffusion of corrosive ions (Cl 2 CHCOO - , H 3 O + ). Experimentally, CFSE achieved an exceptional inhibition efficiency of 98.1% at 200 mg L -1 and 40 °C, maintaining robust performance (> 93%) across a 20-50 °C range. Electrochemical and surface analyses confirmed its mixed-type inhibition mechanism and the formation of a protective film via coordination bonding between CFSE's polar atoms and Fe sites, as unequivocally evidenced by XPS and TOF-SIMS. Owing to synergistic multi-component effects, CFSE outperforms existing plant-derived inhibitors (e.g., Mikania micrantha ) by achieving superior efficiency in a more aggressive medium at a comparable concentration. Beyond providing a sustainable and highly effective corrosion inhibitor for industrial applications, this work establishes a comprehensive mechanistic framework that successfully bridges molecular-level simulation with experimental analysis, offering a blueprint for the rational design of next-generation green inhibitors.