Study on the rare earth sealing procedure of the porous film of anodized Al6061/SiCp

The rare earth (RE) sealing procedure of the porous film of anodized aluminum based metal matrix composites (MMC) Al6061/SiCp was studied with the field emission scanning electron microscope (SEM) and X-ray energy dispersive spectroscopy (EDS). The results show that RE solution gets into the pores of the anodized coating to form cerium oxide/hydroxides precipitation at the beginning of sealing. At the same time, the spherical deposits formed on the surface of the anodized coating create a barrier to the permeation of RE solution getting into 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 H2O2 acts as the source of O2 by carrying chemical reaction in course of coating formation. In the mean time, it may carry 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 film.