Growth of Anodized Layer and Cerium Sealing on Al7xxx/SiC Composite

Abstract

Anodizing process conducted in Al7xxx/SiC produced non-uniform thickness of porous anodic film with cavities, micro-pores and micro-cracks. Cerium sealing was chosen as a post treatment to remedy the poor anodic film by providing a composite layer in order to further enhance the corrosion resistance in aggressive environment. In this study, anodizing process was conducted in H2SO4 solution at current density values of 15, 20, and 25 mA/cm2 at room temperature, 0°C and-25°C for 30 minutes. Subsequently, electroless sealing was conducted in CeCl3.6H2O + H2O2 solution at room temperature and pH 9 for 30 minutes. Integrated protection composed of anodizing at 0°C and cerium sealing process in Al7xxx/SiC produced cerium rich deposits in the diameter of 64 nm (± 3nm) on the surface of anodic oxide layer. These spherical deposits covered the entire surface of anodic oxide layer in accordance with the morphology of the oxide layer. Otherwise, almost no cerium deposit formed on the surface of the oxide layer by conducted integrated protection at room temperature and-25°C. The integrated process conducted at anodizing temperature of 0°C presented a highest protection degree. The cerium protective layer which leads to the decreasing of corrosion rate and current density up to 99,99% or four orders magnifications than that of bare composite.