Study On The Green Sealing Methods For Alumnium Alloy Anodic Oxide Film

A green sealing process for aluminum alloy anodic oxide film was studied in this paper, that kept the Ce salt solution at a certain temperature, then put the alloy oxide film into the solution for a certain time. The sealing quality and corrosion resistant performance of the alloy film after the green sealing were compared with that after the traditional sealing. And the optimal process was obtained by the study of the factors, that the temperature is 80℃, the concentration of sealing solution is 70 g/L, and the sealing time is one hour.The sealing quality was researched by mass loss test immersing in phosphoric-chromic acid solution. The result showed that the performance of the film sealed by Ce salt was as well as that sealed by traditional method and better than that sealed by nickel fluonide.The corrosion resistant performance of the sealing films was studied by neutral spray test metallic coatings-copper accelerated acetic acid salt spray test (CASS test). The result showed that the corrosion resistant performance of the film sealed by Ce salt was better than that sealed by nickel fluonide. The corrosion behavior of LY12 aluminium alloy with the sealed oxide film was researched by the potentiodynamic polarization and the electrochemical impedance spectroscopy (EIS) in NaCl solution at different pH value. The EIS result showed that the corrosion resistant performance of the Ce salt sealing film was the best of the testing methods including Ce salt, nickel fluonide, potassium dichromate and boiling water.The surface of the andic oxide film sealed by Ce salt was observed by scanning electron microscope and the surface composition was analyzed by X-ray photoelectron spectroscopy and X-ray diffraction. The oxide film was still even after Ce salt sealing, the Ce3+ was present, and the form of the Ce salt is amorphous. It showed that the sealing process didn't affect the phase composition of the oxide film.As a result, the Ce salt sealing method tested has good performance of sealing quality and corrosion resistant, that is a green sealing method instead of the traditional sealing methods.