Study of Modified Properties on Electrolytic Phosphate Coatings with Nano-Al2O3
The properties of nano Al2O3 modified 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- Al2O3 powder, and the value of impedance of the Al2O3 incorporated phosphate coating was increased obviously.When the nano- Al2O3 concentration 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 CuSO4 dripping 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%.
Jianzhong Wang and Jingang Qi
J. J. Hao et al., "Study of Modified Properties on Electrolytic Phosphate Coatings with Nano-Al2O3", Advanced Materials Research, Vols. 299-300, pp. 616-620, 2011