The process of preparing and evaluation of silica-alumina composite coating properties with different proportion

Silica-alumina composite coatings have been applied on metals, alloys and special steels to increase the wear resistance, corrosion resistance, and resistance to oxidation. In this regard, silica-alumina ceramic coating by sol-gel method was applied on Carbon Steel. Alumina sol was prepared by using Aluminum-isopropoxide as a precursor and Silica sol was prepared by using Tetraehyl Orthosilicate as a precursor. Then the sols with the different weight ratios of SiO2:Al2O3 were mixed together and steel samples after polishing and degreasing were coated by dipping method. Microstructure and Phase analysis of coated samples evaluated by using scanning electron microscopy and X-ray diffraction techniques. Corrosion resistance and adhesion strength evaluated by using electrochemical testing and pull off method. The results show that with increasing silica content in the silica-alumina composite coatings corrosion resistance and adhesion strength of the coating to the substrate increases .