Self-Healing and Anti-Corrosion Nanocomposite Coatings Based on Polyurethane Nanocapsules containing Mercapto Benzimidazole

Self-healing and anti-corrosion nanocomposites were synthesized using polyurethane nanocapsules loading with 2-mercaptobenzimidazole (MBI) as an anti-corrosion agent. Polyurethane nanocapsules were synthesized using toluene diisocyanate and propanediol interfacial polymerization in an emulsion solution. The resulting nanocapsules were characterized using FTIR, SEM, and EDX. The polyurethane nanocapsules were added to a silane hybrid sol-gel coating, and the coating structure, anti-corrosion, and self-healing performance of the obtained coatings were evaluated using electrochemical and accelerated standard tests. SEM results indicate a uniform dispersion of PU nanocapsules and successful particle synthesis. The size of the nanoparticles was below 100 nm. The mechanical performance of the self-healing coating layer was analyzed by a pull-off adhesion test to determine compatibility with a commercially-available resin epoxy topcoat system. Meanwhile, a long-term 3000-hour salt spray and 4200-hour cyclic UV test were used to determine the self-healing coating’s durability under extreme environments. EIS results showed that polyurethane nanocapsules improve the coatings’ active corrosion protection. A pull-off test was also performed on the samples, indicating the coatings’ good surface adhesion.