A review on smart self-healing anti-corrosion coatings for sustainable infrastructure

Smart self-healing anticorrosion coatings extend service life of metallic structures by coupling local sensing of corrosive environments with autonomous repair. Recent advances integrate electrochemistry and polymer engineering to target gradients in potential and pH that form around defects. Three design families dominate. Extrinsic systems embed microcapsules, mesoporous silica, layered double hydroxides, metal-organic frameworks, or halloysite nanotubes as reservoirs for inhibitors or reactive agents. Protection depends on high payload retention during storage, uniform dispersion, and gating or rupture that is triggered by damage or local chemistry rather than by processing shear. Intrinsic systems rely on dynamic covalent exchange, hydrogen bonding, ionic clustering, swelling microgels, or photothermal and shape memory activation to re-knit the network without consuming a finite stock. This approach requires a glass transition matched to service temperature, adequate segmental mobility for bond rearrangement, and resistance to water plasticization that can lower modulus and weaken adhesion. Hybrid architectures combine rapid defect sealing with delayed interfacial passivation, reducing electrolyte transport early while suppressing charge transfer during prolonged saline exposure and wet-dry cycling. Key gaps include limited quantification of inhibitor delivery to the metal interface, loss of gate function in alkaline environments, and inconsistent healing metrics across studies. Integrated workflows that link synthesis control, diffusion-based transport modelling, and electrochemical validation can improve comparability and accelerate translation to durable, manufacturable coatings for infrastructure under realistic multi-stress exposure.