Effect of SiC fillers on the microstructure, adhesive strength and corrosion resistance of polycarbosilane-derived coating on steel

Polycarbosilane-derived (PCS-derived) coating containing SiC fillers with enhanced adhesive strength and corrosion resistance were fabricated on Q235 steel by a simple method of dip coating. The effects of content and particle size of SiC fillers on the phase composition, surface morphology, adhesive strength and corrosion resistance of PCS-derived coatings were studied. Addition of SiC fillers could reduce the microcrack width on the coating surface. The microcrack width decreases with the decrease in particle size of SiC fillers. Addition of 2.5 wt% SiC fillers with particle size of 30 nm could make the coating surface crack-free. Different from particle size, the effect of filler content on the microcracks has a moderate value which is corresponding to lower microcrack width. In addition to the microcracks, SiC filler content and particle size have significant effects on the adhesive strength between coatings and substrates. The higher adhesive strength is 319.1 MPa for coatings fabricated with a particle size of 500 nm and a content of 10 wt%. SiC fillers can improve the corrosion resistance of the PCSderived coatings. In comparison with particle size of filler, filler content has a greater effect on the corrosion resistance of the coatings. The corrosion mechanism was analyzed. Appropriate content of fillers reduce the microcrack width and further improve the corrosion resistance of the coatings.