An Active Protective Waterborne Epoxy Coating with Mesoporous Silica-1,10-Phenanthroline Microcontainers on Carbon Steel

This study reported highly dispersible mesoporous silica (MSP) with a uniform particle size, which was used as host to load 1,10-Phenanthroline (Phen) to prepare Phen@MSP microcontainer. Improving the dispersion of microcontainers prevents performance degradation caused by their agglomeration. Phen can form a red-colored complex with Fe2+ ions generated during corrosion of steel substrate, enabling early corrosion warning while also acting as a corrosion inhibitor to suppress further corrosion of the substrate. Phen@MSP microcontainers were incorporated into a waterborne epoxy (EP) resin to construct a coating with dual functionality of corrosion self-diagnosing and self-healing. As a key component, the average diameter of Phen@MSP microcontainers is approximately 1 μm, with a Phen loading rate of 18.45 wt.% in the microcontainers. Surface observation shows that substrate corrosion can be detected within 10 min by the appearance of red color. After 30 d of immersion in 3.5 wt.% NaCl solution, the impedance modulus value (|Z|0.01Hz) of the 5 wt.% Phen@MSP coating (2.27 × 109 Ω·cm2) on Q235 carbon steel substrate is five orders of magnitude higher than that of the blank coating (8.79 × 103 Ω·cm2). Salt spray tests demonstrate that the 5 wt.% Phen@MSP coating effectively suppressed corrosion propagation on the substrate.