Effects of SiO2 particle size on the corrosion resistance of fluoropolymer/SiO2 composite coatings

The surfaces of SiO2 ultra-fine particles with different sizes have been modified by γ-(2, 3-epoxypropoxy)propytrimethoxysilane (KH-560) silane coupling agent. Then the homogeneous fluoropolymer/SiO2 composite coatings have been successfully prepared on mild steel substrates. The surface grafting of KH-560 on SiO2 particles was detected by means of Fourier transform infrared spectroscopy, thermo gravimetric analysis and transmission electron microscopy. The surface morphologies and corrosion resistance of fluoropolymer/SiO2 composite coatings were characterised by field emission scanning electron microscopy, potentiodynamic polarisation as well as electrochemical impedance. The results showed that KH-560-modified SiO2 particles can decrease agglomeration effectively, and the particles play a beneficial role in improving the corrosion resistance of the coated steel significantly. There exists an obvious effect of SiO2 particles size on the corrosion resistance of fluoropolymer/SiO2 composite coatings. Also, the SiO2 particles with diameter of 150 nm are of the best effect among all particle sizes.