Cerium-rich conversion coatings were deposited on porous film of anodized aluminum by cathodic polarization in a solution containing 2.68 mol/m(3)CeCl(3).7H(2)O and 10 dm(3)/m(3) H2O2. X-ray photoelectron spectroscopy, scanning electron microscopy and X-ray diffraction have been used to study these cerium-containing conversion coatings. It was revealed that the deposition took place at the top of each pore wall of porous film and gradually resulted in sealing of original pores of anodized film. The coatings predominately consisted of 3-valent-state cerium compound, was up to about 140 nm thick after one-hour cathodic polarization. Formation mechanisms of the cerium conversion coatings were discussed.