Development of an active/barrier bi-functional anti-corrosion system based on the epoxy nanocomposite loaded with highly-coordinated functionalized zirconium-based nanoporous metal-organic framework (Zr-MOF)

For the first time, the UIO-66, NH2-UIO, and NH2-UIO particles covalently functionalized by Glycidyl Methacrylate (GMA@NH2-UIO), were utilized as the novel functional anti-corrosive fillers. The functionality, high surface area, phase composition, excellent thermal properties as well as chemical stability of the Zr-MOFs were proved by FT-IR, BET, XRD, TGA, and water stability tests, respectively. The smart pH-sensitive controlled-release activity of the corrosion inhibitors (i.e., Zr ions and organic compounds) from the prepared Zr-MOFs was proved by the water stability test of the Zr-MOFs particles in the acidic (pH = 2), neutral (pH = 7.5), and alkaline (pH = 12) solutions containing 3.5 wt% sodium chloride. The active inhibition properties of the Zr-MOFs were obtained in saline solution by two methods of (i) the solution phase and (ii) scratched epoxy coated samples containing Zr-MOFs by Tafel polarization method and EIS analysis. According to the EIS data, the excellent barrier (passive) properties of the composite film filled with GMA@NH2-UIO particles (G-UIN/EP) were proved by the highest impedance level at the lowest f (frequency) (log (vertical bar Z vertical bar(10 mHz) = 9.86 Omega.cm(2)), the lowest value of the breakpoint frequency (log (f(b)) = -1.42 Hz) and the highest coating undamaged index (85.93%) after 120 h of immersion. The salt spray (accelerated corrosion test) test (SST), pull-off (testing the strength of adhesion), and cathodic disbonding test (CDT) experiments showed excellent interfacial-adhesion properties of the G-UIN/EP sample in two dry (unexposed) and wet conditions. The hardness test showed that through the incorporation of the UIO, UIN, and G-UIN particles into the epoxy coating, the hardness, and scratch-resistance of the coating were notably improved.