Study on properties of porous SiO2/GO modified polyurethane coatings loaded with corrosion inhibitor

Abstract

Polyurethane (PU) coating can provide physical barrier for metal surface, but the penetration of corrosive ions will affect the long-term corrosion resistance of the coating. In order to improve the corrosion resistance of the coating, it is necessary to modify the coating to reduce the internal defects of the coating and improve the corrosion resistance of the coating. Using mesoporous silica (SiO2) as the carrier to support the corrosion inhibitor 2-mercaptobenzimidazole (MBI), and using the silane coupling agent GPTS as the bridging agent to compound with graphene oxide (GO) to prepare f-GO-MBI @SiO2 composite nano-materials, f-GO-MBI @SiO2 composite nano-materials are added to the polyurethane varnish in different proportions, and the f-GO-MBI @SiO2 modified PU coating is obtained on the surface of carbon steel by spraying method to improve the carbon corrosion resistance of steel substrate. The composition and loading conditions of drug-loaded composite nanomaterials were characterized by fourier infrared spectroscopy (FTIR) and laser particle size analyzer; electrochemical impedance spectroscopy (EIS) and neutral salt spray test were used to study the properties of different coatings corrosion resistance. The results shows that the addition of f-GO-MBI @SiO2 composite nano-materials significantly improves the corrosion resistance of the coating, the low addition amount will reduce the anti-corrosion effect, and the addition of too high can easily lead to agglomeration of composite nano-materials and produce paint film defects. When the addition amount of f-GO-MBI @SiO2 is 5 wt%, the low-frequency impedance of the coating is two orders of magnitude higher than that of the pure polyurethane coating, the corrosion spread width at the neutral salt spray scratches is reduced to 1.5 mm, and the coating has the best corrosion resistance.