Synergetic Inhibition and Corrosion-Sensing Abilities Based on pH-Sensitive ZIF-8@CeO ₂ Core–Shell Nanocontainers toward Intelligent Coating

In this work, we designed a core-shell structure by modifying hollow mesoporous CeO₂ microspheres with a zeolitic imidazolate framework (ZIF-8). The prepared ZIF-8@HMCM can be loaded with the corrosion indicator/inhibitor 1,10-phenanthroline (Phen). ZIF-8 functionalization markedly increases the specific surface area of the nanocontainers, thereby enhancing their Phen loading capacity. More importantly, due to the stimuli-responsive nature of ZIF-8, the nanocontainers can rapidly release Phen at corrosion sites. The released Phen complexes with metal ions at coating defects, producing a distinct red coloration that enables real-time visualization of corrosion initiation. Based on these nanocontainers (ZIF-8@HMCM-Phen), we developed a multifunctional coating that combines durable corrosion resistance, self-healing ability, and early corrosion detection. Electrochemical impedance spectroscopy further confirmed its superior corrosion resistance: after 80 days of immersion in 3.50 wt % NaCl solution, the |<i>Z</i>|_{0.01 Hz} of the ZIF-8@HMCM-Phen/WEP coating remained at 1.02 × 10⁹ Ω·cm², more than 1 order of magnitude higher than that of pure WEP. The immersion test of the scratched coating provided a rapid visual response within 15 min, enabling early identification of corrosion initiation at damaged regions. Overall, incorporating ZIF-8@HMCM-based nanocontainers into WEP coatings enables the concurrent functions of corrosion monitoring, active inhibition, and self-healing, offering a practical strategy toward durable smart anticorrosion coatings.