Self-healing materials offer tremendous potential for providing long-lived structural materials. In this study, isophorone diisocyanate (IPDI) microcapsules as self-healing materials were synthesized via in situ polymerization. Thermogravimetric analysis characterized the thermal ability of IPDI, microcapsules and microcapsule shells. The morphology of microcapsules and microcapsule shells were characterized by FE-SEM. Scanning micro-reference electrode technique demonstrated that epoxy resin coatings with IPDI microcapsules on the surface of reinforcing steel Q235 could cure the scratched crevice by immersion in 0.01 M NaCl solution after the coating was scratched. The self-healing epoxy resin coating could protect Q235 from corrosion.