Preparation and Corrosion Resistance of Microcapsule-based Self-reporting and Self-healing Epoxy Coating
Organic barrier coatings fail prematurely under synergistic marine corrosion factors, necessitating autonomous damage reporting and repair. This study synthesizes DT@PU/UF microcapsules via one-step in-situ polymerization, encapsulating 2′,7′-dichlorofluorescein (DCF) as a reporting agent and tung oil (TO) as a healing agent within a polyurethane/urea-formaldehyde hybrid shell. Single-variable experiments established optimal processing parameters: stirring speed 400 r/min, reaction time 3 h, and emulsifier (EMA) dosage 0.5 wt.%. The resulting microcapsules achieved DCF and TO loading capacities of 1.3% and 35.82%, respectively. Incorporating these microcapsules into an epoxy matrix yielded DP coatings. Electrochemical impedance spectroscopy, adhesion testing, and optical microscopy revealed that a 9 wt.% microcapsule loading (DP9wt.%) delivered optimal performance. After 240 h of seawater immersion, DP9wt.% exhibited an impedance modulus of 2.88×10^5 Ω·cm^2, one order of magnitude higher than the neat epoxy (EP) coating, and a wet adhesion loss of only 37.7%. Scratch tests confirmed that microcapsule rupture releases DCF, which reacts with residual amine groups to form a red precipitate under natural light and yellow fluorescence under UV, enabling dual-mode damage reporting. Simultaneously, TO fills cracks and crosslinks with oxygen to restore barrier integrity. This dual-action mechanism offers a viable route for extending the service life of epoxy coatings in marine environments.