Stimuli-Responsive Epoxy Coatings with pH-Triggered Self-Healing for Long-Term Marine Corrosion Protection

Abstract

Marine steel structures suffer severe corrosion from continuous seawater exposure, chloride ions, and mechanicaldamage, while conventional epoxy coatings provide limited protection after coating failure. This research develops three pH-triggered self-healing epoxy coatings using a zinc-rich epoxy primer on American Society for Testing and Materials (ASTM A36) marine steel and a bisphenol-A epoxy matrix containing pH-responsive Polyurethane-Formaldehyde (PUF) microcapsules loaded with dicyclopentadiene (DCPD) healing agent and benzotriazole (BTA) corrosion inhibitor. Coating performance was evaluated using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), adhesion strength, scratch self-healing, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS). Among the developed coatings, the 10 wt% microcapsule formulation exhibited optimum performance with 69.8% healing efficiency, 0.6 μA/cm2 corrosion current density, 0.007 mm/year corrosion rate, and 9.1×106 Ω·cm2 impedance modulus. SEM confirmed crack closure, while FTIR verified successful healing component incorporation, providing durable corrosion protection for marine steel structures.