Corrosion Protection of In Situ Al-Based Composite by Cerium Conversion Treatment

Cerium conversion films were deposited on the surface of in situ aluminum-based composite in solutions containing different cerium chloride (CeCl₃) and hydrogen peroxide (H₂O₂) concentrations at 30 °C. The morphology and composition of conversion films deposited in various solutions were investigated using scanning electron microscopy, energy dispersive x-ray analysis, and x-ray photoelectron spectroscopy (XPS). SEM observations revealed that only patches of film can be deposited on the composite surface when immersed in solutions with low CeCl₃ and H₂O₂ concentrations. However, entire composite surface was covered with a compact film when immersed in a solution containing 10 g/L CeCl₃ and 100 mL/L H₂O₂. XPS results indicated that cerium was incorporated as Ce⁴⁺ species in the hydrated oxide film. The formation of such hydrated conversion film on the composite resulted in low anodic current density and more noble pitting potential when exposed to 3.5% NaCl solution.