Chemical linkage in bifunctional chitosan-mercaptobenzothiazole (MBT) coatings for enhanced corrosion prevention and antifouling activities

Marine corrosion is a longstanding issue for underwater materials and structures, where the interlinked challenges of corrosion and biofouling require new approaches to source increasing needs of the marine resources. Herein we introduce environment-friendly chitosan coatings immobilized with corrosion inhibitor of 2-mercaptobenzothiazole (MBT) for active corrosion protection with antifouling properties against marine organisms. The molecular interaction between chitosan and MBT on corrosion resistance and antifouling performance was studied with the coatings where MBT was entrapped, physically associated, or chemically linked to chitosan. The physical association is achieved by the non-covalent π-π stacking between MBT and chitosan-benzophenone-3 (CS-BP-3) copolymer, which improved loading efficiency of MBT and formed a smoother coating. For the first time, MBT was chemically linked to chitosan confirmed by infrared spectroscopy. Electrochemical measurements revealed that both physical association and chemical linkage strategies can enhance the corrosion inhibition dramatically, where the chemical linked coating has a significantly higher corrosion resistance. The corrosion current of the physically associated coatings is a magnitude lower than that of MBT-entrapped coatings, while the coatings formed by chemical linking is even better, about one fifth compared to physically associated coatings. Antifouling activity of these coatings were evaluated against marine mussels (Mytilus coruscus), where chemically linked CS-MBT coating exhibits 10 % settlement after 48 h, compared to 20 % settlement on coatings prepared by physical association. The findings in this work provide a new route to construct coatings that are effective in corrosion inhibition and have long-term antifouling properties.