MOF-5@Phen@Chitosan/EP Coating: A Smart Dual-Functionality Self-Reporting and Corrosion-Inhibiting Coating for Identifying and Suppressing Early Steel Corrosion

Abstract

Steel corrosion beneath protective coatings remains a major threat to infrastructure safety, creating a need for coating that provide early warning and active inhibition. In this study, a multifunctional self-reporting and anti-corrosion coating system (MPC) is fabricated using MOF-5 loaded with 1,10-phenanthroline (Phen) and encapsulated within chitosan shells, enabling pH-responsive release. Physicochemical, spectroscopic, and electrochemical analyses confirm successful Phen loading (25.06–29.70 wt.%), controlled release behavior, and dual functions of visible self-reporting and corrosion inhibition. CLSM and Raman measurements further verify the formation of Fe(Phen)₃²⁺ at corrosion sites and the suppression of Fe ion. EIS shows that a 5 wt.% MPC coating achieves a 342% impedance increase compared with neat epoxy after 42 days in 3.5 wt.% NaCl solution. Salt-spray and immersion tests further demonstrate real-time visual corrosion indication and long-term protection. This work presents an effective strategy for integrating colorimetric reporting and active inhibition in MOF-based intelligent coatings for early-stage corrosion detection and suppression.