Effects of SiO 2 particle size on the corrosion resistance of fluoropolymer/SiO 2 composite coatings

Abstract

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.