Abstract: The rare earth sealing procedure of the porous film of anodized aluminum alloy 2024 was studied with the field emission scanning electron microscope (SEM) and X-ray energy dispersive spectroscopy (EDS). The results show that RE solution can form cerium oxide/hydroxides precipitation in the pores of the anodized coating at the beginning of sealing. At the same time, the spherical deposits formed on the surface of the anodized coating created a barrier to the precipitation of RE solution in the pores. When the pore-structured anodizing film is covered all with the spherical deposits, RE conversion coating will form on the surface of the anodized coating. The reaction of the coating formation was investigated by employing cyclic voltammetry. The results indicate that accelerator H2O2acts as the source of O2 by carrying chemical reaction in course of coating formation. In the mean time, it maybe carries electrochemical reaction to generate alkaline condition to accelerate the coating formation. The porous structure of the film is beneficial to the precipitation of the cerium hydroxides.

Key words: Rare earth sealing, Anodized aluminum alloy, Scanning electron microscope...