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An attempt has been made to increase the corrosion resistance properties of medium steel substrate by using silica sol.The results show that: sol-gel method can increase corrosion resistance of phosphating coating. PS(silicon sol coated after phosphating )’s corrosion potential reduced more than P(phosphating sample)’s and its corrosion density also reduced.Polarizationg resistance of PS can improved many times.R2 of PS more reduced than P,but R3 improved more than ten times and R4 improved over sixty times by using equivalent circuit to fit EIS measurement. Corrosion resistance of PS was higher than that of P.

The properties of nano Al2O3modified electrolytic phosphating film have been studied through using the accelerated corrosion test, electrochemical testing techniques, scanning electron microscope (SEM) and X-ray diffraction (XRD) .The results show that, after adding nano- Al2O3 in electrolytic phosphating bath , morphology of phosphating film surface turned dense flake crystallization from needle crystal morphology of free-adding nano- Al2O3powder, and the value of impedance of the Al2O3incorporated phosphate coating was increased obviously.When the nano- Al2O3concentration was 15mg / L in electrolytic phosphating bath, the value of impedance of the coating is approximately two times larger than the phosphating coating directly formed on the low carbon steel.The corrosion resisting time of the coating was more than 420 s by CuSO4dripping test, and the corrosion current density of the phosphating sample was 1.164μA/cm2，in 3.5% NaCl solution, the corrosion inhibition efficiency reached 96.7%.

Ni-TiO2 nanocomposite coatings have been successfully fabricated via a route electrodeposition from nickel Watts bath containing nano-TiO2 particles, and characterized by scanning electron microscopy (SEM),X-ray diffraction(XRD), energy dispersive X-ray spectroscopy (EDS)and electrochemical techniques. The influence of preparation parameters on the properties of the coatings were investigated. The obtained results indicated that nano-TiO2 particles were distributed uniformly in the Ni matrix. It was found that the Ni-TiO2 nanocomposite coatings exhibited more excellent corrosion resistance and microhardness in comparison with pure nickel coating.