Fluorinated Porous CeO₂ with Enriched Oxygen Vacancies as Dual-Functional Fillers for Durable Corrosion Protection

A dual-interface engineering strategy is proposed to exploit the anticorrosion potential of cerium oxide fillers by combining an oxygen-vacancy-rich porous core with a fluorinated superhydrophobic shell. Porous CeO 2 (P-CeO 2 ) is synthesized via a P123-templated hydrothermal process and then functionalized with perfluoroalkyl silane to form fluorinated porous CeO 2 (F-CeO 2 ). Conventional CeO 2 , P-CeO 2 , and F-CeO 2 are dispersed into a fluorocarbon resin to prepare composite coatings at different filler loadings. Characterization confirms that fluorination preserves the mesoporous fluorite framework while converting the surface from hydrophilic to superhydrophobic (water contact angle 164°) and promoting an oxygen‑vacancy-enriched surface character. The fluorinated porous particles also show improved colloidal stability in xylene, enabling homogeneous dispersion in the coating matrix. Electrochemical tests in 3.5 wt.% NaCl identify 1.0 wt.% F-CeO 2 as the optimal formulation: The corrosion current density decreases from 5.226 μA·cm −2 for the neat resin to 0.00353 μA·cm −2 , corresponding to 99.93% inhibition efficiency and exceeding coatings with conventional CeO 2 (91.50%) or P-CeO 2 (94.03%). Electrochemical impedance spectroscopy shows that this coating maintains near-ideal capacitive behavior over 21 days of immersion, with coating and double-layer constant-phase exponents remaining ~ 0.92-1.00; a diffusion-controlled Warburg element emerges only after prolonged exposure, indicating delayed electrolyte access to the metal/coating interface. AFM and XRD support a synergistic mechanism in which the fluorinated shell suppresses wetting and ion ingress, while the oxygen-vacancy-rich porous core promotes active passivation. Here, the “dual-functional” design refers to the integration of a superhydrophobic physical barrier provided by the fluorinated shell and a chemical passivation effect induced by oxygen vacancies in the CeO 2 core, which operate synergistically to enhance corrosion resistance. This dual-interface design makes F-CeO 2 an efficient bifunctional filler for durable anticorrosion fluorocarbon coatings. Overall, the approach improves barrier integrity, durability under chloride attack.