Influence of Nano-SiO₂ on Phosphate Coating on Mild Steel at Common Temperature

At common temperature,the phosphate coating on mild steel surface was prepared by adding nano-SiO2 into phosphating solution.The influence of nano-SiO2 on structure and performance of the phosphate coating was studied by electrochemical testing.The results showed that the coating thickness increased with increasing the nano-SiO2 concentration.When the nano-SiO2 concentration was 1 g/L,the thickness of phosphate coating was 7.81 μm,the corrosion resisting time of the coating evaluated by CuSO4 dripping test was more than 115 s,and the corrosion current density of the phosphating sample was 0.931 μA/cm2 in 3.5% NaCl solution,the corrosion inhibition efficiency reached 97.9%.