| This paper includes two parts. The first part was a study on a polyaspartic modified on aluminum zirconium-based conversion. The second part was about self-repairing tungstovanadate-zirconium conversion coating.(1) In this work, the composite conversion coating on aluminum alloys was performed by immersion in a solution containing polyaspartic. Spot test, electrochemical workstation, scanning electron microscopy, X-ray photoelectron spectroscopy (XPS) and other methods detected coating corrosion resistance, chemical composition and microstructure characterization, by adopt Stripping, water cook test, anti-Cupping test and conversion solution stability test discussed conversation coatings weight and adhesion, stability of conversion liquid composite. The results showed that:when polyaspartic added in the amount of 0.5?1.0g/L obtained the coating was of good corrosion resistance, corresponding electrochemical impedance fitting 64.26k?, polyaspartic acid by the addition may be changed coating's surface morphology, so that the content of the coating component of organic matter and oxygen compounds increases; in addition polyaspartic also makes the film more dense salt water soak longer, but the addition of organic matter will make the film weight increases, It is not conducive to lightweight equipment. By XPS data analysis, the main component of the composite conversion coating ZrO2, ZrOF2 and organic complexes, the composite conversion coating is friendly to environment.(2) In this work, self-repairing tungstovanadate-zirconium conversion coating (TZO) coating on alloy surfaces was performed by immersion in a solution containing tungstovanadate. The research also studied the influence of pH value, temperature and immersion time on the conversion of vanadium-zirconium composite coating corrosion resistance. By potassium dichromate spot test, electrochemical workstation, XPS, and field emission scanning spectroscopy (EDS) testing methods discussed the influence of different oxidizing on conversion coatings microstructure and corrosion mechanism. The results showed that:hydrogen peroxide and tungstovanadate-zirconium conversion coating can increase the corrosion resistance, among them tungstovanadate-zirconium demonstrated the obvious self-repairing performance, ammonium persulfate and potassium permanganate can reduce the corrosion resistance of vanadium-zirconium conversion coating and didn't show the desired self-healing properties. XPS results showed that when TZO is forming tungstovanadate particles can suspend in the coatings, when the coating was attacked by corrosive media, tungsten, inner tungstovanadate balance system will be undermined and when chloride penetrating pores occurred secondary protection, conversion coatings re-passivity delaying the occurrence of corrosion. Vanadium element reverted to the high state, heterophony acid aluminum body will produce secondary passivity, make conversion coating more compact, conversion coatings re-passivity delaying the occurrence of corrosion. |
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