Two birds with one stone: Nanocontainers with synergetic inhibition and corrosion sensing abilities towards intelligent self-healing and self-reporting coating

A smart coating integrating high-performance self-healing and sensitive self-reporting abilities was developed based on mesoporous SiO2 nanoparticles (MSN) containing both 1,10-phenanthroline-5-amine (Phen-NH2) and cetyltrimethylammonium bromide (CTAB). In the obtained MSN-PC nanocontainers, Phen-NH2 functioned as both the corrosion inhibitor and the coloration species, while CTAB acted as not only the template agent but also the corrosion inhibitor. The synthesis of MSN-PC was achieved in a facile one-step process with high encapsulation degree, and both Phen-NH2 and CTAB exhibited the accelerated release behaviors from MSN-PC triggered by pH variation. Electrochemical impedance spectroscopy (EIS) measurement and quantum chemical calculation results confirmed the synergistic inhibition effect of Phen-NH2 and CTAB against the corrosion of steel substrate and thus a self-healing effect of the damaged coating. Compared with the blank epoxy coating, the healed epoxy coating containing 4 wt% of MSN-PC could increase the low frequency impedance modulus by more than 20 times after 120 h of immersion in 3.5 wt% NaCl solution, hence suppressing the corrosion activity on the exposed metal surface. In addition to the self-healing property, the generated Fe2+ ions from the anodic site of exposed steel surface could quickly react with the released Phen-NH2 from MSN-PC nanocontainers to produce a prominent red color, achieving the timely indication of coating damage within 20 min of salt spray test. The smart coating realized sensitive corrosion visualization while significantly delaying the corrosion degradation, which holds great potential for long-term corrosion protection.