Developing wide pH-responsive, self-healing, and anti-corrosion epoxy composite coatings based on encapsulating oleic acid/2-mercaptobenzimidazole corrosion inhibitors in chitosan/poly(vinyl alcohol) core-shell nanofibers

In this research, the oleic acid (OA) and 2-mercaptobenzimidazole (MBI) encapsulated in the chitosan/poly(vinyl alcohol) (CS/PVA) core-shell nanofibers are synthesized and used for developing core-shell/epoxy composite coatings on Q235 steel substrate to enhance the service-life of coating systems. The results indicate the successful preparation of the CS/PVA core-shell nanofibers loaded with corrosion inhibitors. The corrosion protection performance of the composite coatings are evaluated by electrochemical impedance spectroscopy, revealing that the maximum inhibition efficiency of OA and MBI is 96.66% and 99.36% after 10 and 20 days immersion in alkaline and acidic electrolyte, respectively. Furthermore, the formation of a self-healing film over the metallic substrate after immersion in corrosive electrolyte is confirmed. The synergistic effect of chitosan protonation and MBI corrosion inhibitor makes the composite coating have high corrosion inhibition efficiency in acidic electrolyte. This pH-responsive self-healing approach is potentially useful for designing next-generation of self-healing coatings with high healing efficiency. • We designed the self-healing core-shell nanofibers and added them to the epoxy coating. • The coating's highest heal rates in acidic and alkaline solution were 96.66% and 99.36%, respectively. • The corrosion inhibitors released by the nanofibers form protective film to cover the crack. • The structure of nanofibers allows the heal agents to be released effectively.