The influence of different variables (stirring, degreasing, oxidant additions, pH, Ce concentration, anion type, time and temperature of immersion) on the optimization of Ce conversion and electrolysis coatings on both A3xx.x alloys and aluminium metal matrix composites A3xx.x/ SiCp was evaluated in 3.5 wt% NaCl at 22 degrees C using potentiodynamic polarization. Ce treated surfaces presented better corrosion behaviour in chloride media than original material surfaces without treatment. Both treatments preferentially covered the intermetallic compounds and SiCp. The electrolysis afforded a higher degree of protection than conversion treatment because the coating was more extensive. Coating microstructure was analysed by scanning electron microscopy (SEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). (c) 2006 Elsevier B.V. All rights reserved.