Research on the Corrosion Resistance of an Epoxy Resin-Based Self-Healing Propylene Glycol-Loaded Ethyl Cellulose Microcapsule Coating

In this work, ethyl cellulose was used as a wall material, propanetriol as a core material, polyvinyl alcohol as a stabilizer and gelatin as an emulsifier. Self-healing microcapsules with a slow-release effect were prepared using the solvent evaporation method. Various analytical techniques, such as 3D confocal microscopy (LCSM), optical microscopy (OM), scanning electron microscopy (SEM), infrared spectroscopy (FT-IR), energy dispersive spectroscopy (EDS), thermal weight loss analysis (TGA), laser particle size tester and electrochemical impedance polarization, are utilized. The morphology, distribution, particle size, corrosion resistance and self-healing ability of the prepared microcapsules and resin-based coatings were characterized and analyzed. The results show that the cross-sectional core–shell structure is clearly seen in the LCSM, showing a smooth, hollow, spherical shape. OM and laser particle size testers have shown that the size of the microcapsules decreases over time. Also, in OM, the microcapsules are uniformly distributed in the emulsion with a smooth and non-adherent surface. In SEM, the microcapsule particle size is about 150 μm, the shell wall thickness is about 18 μm, and the hollow structure of ruptured microcapsules is obvious. FT-IR and TGA confirmed the successful encapsulation of the formulated microcapsules. The results show that when the core-wall mass ratio is 1.2:1 and the amount of microcapsule is 10% of the coating amount, the prepared microcapsule has high thermal stability and certain wear resistance. By electrochemical and immersion experiments, it was found that a 3.5 wt % NaCl solution has the best impedance, the lowest corrosion current density, and good adhesion and tensile toughness. The results showed that glycerol was successfully released from the broken microcapsules and self-healed, forming an anticorrosive coating with excellent corrosion resistance and self-healing ability.