Salt-Gated Releasing Effect to Open Visual Self-Reporting/Self- Repairing Function of Coatings toward Corrosion Protection

Detecting and repairing coating damages at nanoscale or microscale are essential for metal corrosion protection. Here, we develop a smart anticorrosion coating with autonomous self-reporting and self-healing abilities by saline-responsive triggered polyaniline (PANi) nanocapsules containing a fluorescein isothiocyanate (FITC) fluorescent indicator and benzotriazidazole (BTA) corrosion inhibitor. Once the damaged coating is wet with the salt solution, the sodium ions penetrate the crack and react with PANi, causing a gating effect of PANi nanocapsules to be triggered and opened. This leads to the diffusion of molecules and expelling of the guest payload from the capsule mesopores. Therefore, the scratched FITC@PANi/Epoxy coatings express pronounced green fluorescence signals under UV light irradiation within only 30 min, highlighting the coating failure. Meanwhile, the microcracks can be promptly repaired with the BTA@ PANi/Epoxy coatings, and their long-term anticorrosion properties are further extended under a NaCl solution, indicating the prolonged service lives of the coatings. Therefore, the salt-responsive release strategy with self-reporting and self-healing functions allows for timely corrosion warning, fast crack repair, and effective extension of barrier performance, which is appealing and of great importance in practical applications.