Among these nano oxides, nano silicon dioxide (SiO2) is a kind of very high presence. It is a kind of inorganic nonmetallic material with excellent heat resistance and oxidation resistance, and its molecular state shows a three-dimensional network structure with [SiO4] tetrahedron as the basic structural unit. Among them, oxygen and silicon atoms are directly connected by covalent bonds, and the structure is firm, so it has stable chemical properties, excellent heat and weather resistance, etc.
Nano-SiO2 mainly plays the role of anti-corrosion filler in the epoxy coating. On the one hand, nano-SiO2 can effectively fill in the micro cracks and pores produced in the curing process of epoxy resin, and improve the permeability resistance of the coating. On the other hand, physical/chemical crosslinking points can be formed between nano-SiO2 and epoxy resin functional groups through adsorption or reaction, and Si -- O -- Si and Si -- O -- C bonds can be introduced into the molecular chain to form a three-dimensional network structure, which can improve the adhesion of the coating. In addition, the high hardness of nano-SiO2 can significantly enhance the wear resistance of the coating, so as to prolong the service life of the coating.


The simplest method is to add nano-SiO2 directly into the coating by blending. Palraj et al. synthesized nano-SiO2 powder by sol-gel method, and compared with micron-size SiO2, studied the effect of SiO2 with different particle sizes on the protective properties of epoxy coating. The results show that, compared with micron SiO2, nano-SiO2 can significantly enhance the resin-filler interface interaction, improve the density of epoxy coating, and thus improve the permeability resistance of epoxy coating.
Salt spray experiment shows that the salt spray resistance time of nano-SiO2 / epoxy composite coating can reach 720h. In addition, the dispersed nano-SiO2 particles in the composite coating can alleviate the impact load of the coating well and improve the mechanical properties of the coating. The experimental results show that the wear resistance of nano-SiO2 /EP composite coating is about 50% higher than that of pure epoxy coating. However, the silanols on the surface of nano-SiO2 easily agglomerate SiO2 itself, leading to the protective effect of the composite coating can not reach the expectation. Therefore, before this, the surface modification of nano-SiO2 is needed to improve its dispersion in the epoxy matrix.