Interfacial modification of clay nanotubes for the sustained release of corrosion inhibitors

Long-lasting anticorrosive coatings for steel have been developed on the basis of halloysite nanotubes loaded with three corrosion inhibitors: benzotriazole, mercaptobenzothiazole, and mercaptobenzimidazole. The inhibitors' loaded tubes were admixed at 5-10 wt % to oil-based alkyd paint providing sustained agent release and corrosion healing in the coating defects. The slow 20-30 h release of the inhibitors at defect points caused a remarkable improvement in the anticorrosion efficiency of the coatings. Further time expansion of anticorrosion agent release has been achieved by the formation of release stoppers at nanotube ends with urea-formaldehyde copolymer and copper-inhibitor complexation. The corrosion protection efficiency was tested on ASTM A366 steel plates in a 0.5 M NaCl solution with the microscanning of corrosion current development by microscopy inspection and studying paint adhesion. The best protection was found using halloysite/mercaptobenzimidazole and benzotriazole inhibitors. Stopper formation with urea-formaldehyde copolymer provided an additional increase in corrosion efficiency as a result of the longer release of inhibitors.