Hydrophobic modification of CeO2@ZIF-7 composite structure for enhanced long-term anti-corrosion performance of epoxy coatings

Metal-organic framework (MOF) materials have significant advantages in corrosion protection due to their remarkable specific surface area and exceptional porosity. This work combined cerium dioxide (CeO₂) nanoparticles and zeolitic imidazolate framework-7 (ZIF-7) with the long-chain hydrophobic agent hexadecyltrimethoxysilane (HDTMS) to create a composite nanostructure (CeO₂@ZIF-7@HDTMS) with a multistage barrier function. The structure takes CeO₂ nanoparticles as the core to achieve chemical corrosion inhibition by using its oxygen-deficient property; ZIF-7 is induced to form an ordered microporous adsorption layer at its periphery by surface carboxylic acid molecules; and ultimately, the outer repulsive barrier is constructed with the help of hydrophobic modification of HDTMS, thus forming a synergistic anticorrosion mechanism in three dimensions, namely physical barrier, chemical passivation, and hydrophobic protection, and constructing a ‘Physical barrier + double synergistic corrosion inhibition’ three-level protection system. The successful preparation of CeO₂@ZIF-7@HDTMS nanoparticles was confirmed by a number of characterization tools, such as field emission scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). Subsequently, they were well characterized by electrodynamic polarization curves, electrochemical impedance spectroscopy (EIS), and salt spray test aspects, which indicated that CeO₂@ZIF-7@HDTMS epoxy composite coatings have good corrosion protection and hydrophobic properties. After 60 days of immersion, EIS analysis showed that the impedance of the 1.0 % EP/CeO₂@ZIF-7@HDTMS coating was still as high as 4.636 × 10⁸ Ω·cm² and its low-frequency impedance was about two orders of magnitude higher than that of the pure epoxy coating, which further indicated that the composite coating could provide excellent corrosion resistance and durability. In conclusion, CeO₂@ZIF-7@HDTMS nanoparticles as fillers offer an innovative idea for the development of multifunctional and long-life anticorrosive coatings, broaden the application of metal oxide@MOF composites, and open up a new direction for the design and preparation of nanostructured materials.