Preparation And Characterization Of Potassion Fluotitanateconversion Coating On Aluminium Alloy LY12

LY12 aluminium alloy is a high-strength alloys, and it is is widely used in aerospace, machinery manufacturing, automobile and many other fields. However, because of the effect of CuAl2 and Al2 CuMg in aluminium alloy, LY12 aluminium alloy is easily corroded so that its industrial application is limited. Traditional chromate conversion coating is a economically efficient method to prevent corrosion, but due to high toxicity and carcinogenicity of Cr(?), the use of this technology is strictly prohibited. Therefore, an alternative to chromate conversion coating is urgently needed.In this study, the environment-friendly titanium-salt conversion coating was prepared on LY12 aluminium alloy. The treatment solution was made up with potassium hexafluorotitanate 10.0g/L and film forming promoter 0.125g/L, under the condition of pH 12.0, 14.4 ? and 20 minutes. The color of titanium conversion coating formed on the surface of aluminium alloy is milk-white, and the neutral salt spray time of the prepared conversion coating could reach 72 hours.The test results from scanning electron microscope(SEM), energy dispersive spectrometer(EDS), X-ray diffraction(XRD), X Ray photo electron spectroscopy(XPS) and electrochemical showed that the milk-white conversion coating is closely packed particles with similar sizes; it consisted of O 6.19%?F 36.19%?Na 3.69%?Al 27.91%?K 14.77% and Ti 11.25%; the crystal structures of conversion coating are croylite compounds;the composition of the conversion coating consists of Na3AlF6 and TiO2; the surface corrosive potential turns negative by 0.25 V and the corrosion current density of pretreated and transformed LY12 aluminium alloy is 1.08×10-5A/cm2 and 5.17×10-6 A/cm2,separately,current density deceases by 52.17%, and the corrosion resistance of aluminium alloy was improved.