Characterization of Ti-Se Conversion Coatings on Aluminum Alloy.

In this work, a new type of Ti-Se conversion coating was formed on the surface of an aluminum alloy using titanium and selenide as the main salts. An examination of the surface morphology, composition and microstructure of the conversion coating was done using scanning electron microscopy, energy-dispersive spectrometry and x-ray photoelectron spectroscopy. The results showed that the surface of the conversion coating possessed a reticular structure with uniform cracks and a dense coating with a thickness of 0.4 μm. The elements in the conversion coating were C, O, Ti, Al and Se. The corrosion resistances of both the Ti-Se conversion coatings and the bare substrate were evaluated by an immersion test, polarization curves and electrochemical impedance spectroscopy. The results showed that the corrosion current of the conversion coating improved the corrosion resistance of the aluminum alloy and effectively protected the aluminum alloy in the immersion test. Furthermore, the corrosion current obtained from the polarization curves and electrochemical impedance spectroscopy decreased by one order of magnitude after the formation of the Ti-Se conversion coating, suggesting an improvement in polarization resistance. [ABSTRACT FROM AUTHOR]