Corrosion protection of aluminum borate whisker reinforced AA6061 composite by cerium oxide-based conversion coating

Cerium oxide-based conversion coatings on Al18B4O33w/6061Al composite surface were obtained by immersing the composite into a cerium chloride (CeCl3) solution containing various concentrations of hydrogen peroxide (H2O2). Coating microstructures were observed by scanning electron microscopy (SEM). Coating composition and the cerium oxidation state were characterized using energy dispersive X-ray (EDX) analysis and X-ray photoelectron spectroscopy (XPS) respectively. Electrochemical methods were used to study the coatings corrosion resistance. Polarization experiments in 3.5% NaCl solution showed that the sensitivity to pitting corrosion for the conversion coated composites was much lower than that of the untreated samples. The results indicated that the uniformity of the coating had the biggest effect on corrosion behavior of the composite. The coating obtained from a Ce-solution containing 100 ml/L H2O2 (30 wt.%) produced better corrosion resistance due to the surface being covered by uniform conversion coating.