AA6063 Chromium-Free Zirconium ( Titanium ) Coloring Film Forming And Its Mechanism

The corrosion resistance of aluminum natural oxide film is limited, and the binding of the film coated with paint is low. So aluminum is easy to corrosion, and aluminum must be an effective anticorrosion treatment. The best anti corrosion treatment of aluminum is pre prepared surface conversion coating, and then spraying. The recognized treatment is chromate treatment, but the Cr（Ⅵ） is carcinogenic toxicity. The U.S. and EU have specific limit, toxic elements chromium must be replaced.The chromium free treatment is in situ growth chemistry chromium free anti corrosion film on aluminum alloy surface. Many manufacturers claim that they already have the method to alternatives the Cr（Ⅵ）. However, analysis of test results from the public, without any kind of technology can completely replace the chromate conversion technology. In this article, AA6063 as the base material, use the zirconium and titanium to replace chromium. Chemical methods used in the aluminum surface of the growth color conversion film.The color is useful in aluminum anti corrosion treatment. It can quickly and easily by the color conversion film to determine the formation, to determine the film thickness. The titanium zirconium conversion film is difficult to replace the traditional chromate technology. The important reason is the colorless.The first chapter reviews the chromium free conversion coating of aluminum. The second chapter introduced zirconium as the main elements for preparation the conversion coating. According to different pre treatment, the film’s color is dark and gray or white. The third chapter analyzes the growth of film and coloring mechanism. The fourth chapter introduced adding nickel as a coloring agent. The nickel can deepen the color of conversion film. The chapter five introduced adding titanium element as film forming accelerator. The chapter six introduced the performance of Ti Ni film. The chapter seven is the summary of this article.We use an optical camera to take pictures of the sample, and compare the color different between aluminum alloy and film. And use the color scanner to scan the sample, compare the color change. Observation of aluminum alloy sample by microscope, compare the different of AA6063 and coating sample. Compare the hydrophobic properties of the sample by wetting phenomena. Compare the electrochemical properties of the sample by VMP3 electrochemical workstation. And simulation the electrochemical structure of the film, analysis of the corrosion mechanism of conversion coating. Compare morphology of coating by SEM, TEM and FIB SEM. Using XRD, EDS, XPS analysis the composition of conversion coating. Use Color Icontrol analysis the color of conversion film.In this paper, the main film forming agent is potassium zirconium fluoride, the solution concentration is 0.0762 0.0381 mol L^-1, pH value is 4.3, reaction temperature is 23 30℃, reaction time is 6 13min. The morphology of AA6063 and its coating is significant different, the conversion coating has good corrosion resistance, and analysis the structure and performance of the coating by SEM, EDS, TEM, FIB SEM, XRD, XPS and DSC. The surface of film is roughness, help to improve the combination of aluminum and polymer coating. The structure of the coating are Al、Al₂O₃、AlF₃、KZrF₃（OH）2 H2O and KZrF₃O·₂H₂O. The film also has some hydrophobic properties.Use Color Icontrol analysis the color of coating. If the surface of AA6063 is rough, the small units of film extending in different directions, showed irregular structure. About 77% of visible light is absorbed, then showing a black and gray. If the surface of AA6063 is smooth, the small units perpendicular to the aluminum surface, show more regular structure. Just about 35% of visible light is absorbed, then showing a white.Use Ni₂SO₄ 6H₂O as the coloring agent. The Zr Ni coating is black. The conversion coating is uniform, some short structure on the surface. The structure of the coating are ZrO_0.44F_3.12、AlNi、Zr（F,O）_3.6、NiZrF₆、KAlF₄、Al and AlF₃. The Zr Ni coating has good corrosion resistance. Simulated film structure is C₁/R₁/（L₂+R₂）/（L₃+R₃）.Use Ni2SO4 6H2O as the coloring agent, and K2TiF6 as accelerator. The Zr Ti Ni coating is light green. The structure of the coating are Al、Ni、NiZr、Ti and NiZr3. The Zr Ti Ni coating has good corrosion resistance. Simulated film structure is C₁/R₁/（L₂+R₂）/（L₃+R₃）/（L₄+R₄）.Use titanium as the film forming agent, nickel as the coloring agent. The Ti Ni coating is rainbow colors. Simulated film structure is C₁/R₁/（L₂+R₂）.