In order to study the influence of cerium ion implantation on the aqueous corrosion behavior of zircaloy-4, specimens were implanted by cerium ions with a fluence range from 1 x 10(16) to 1 x 10(17) ions/cm(2) at maximum 150 degreesC, using MEVVA source at an extracted voltage of 40 kV. The valence of the surface layer was analyzed by X-ray photoemission spectroscopy (XPS) Three-sweep potentiodynamic polarization measurement was employed to value the aqueous corrosion resistance of zircaloy-4 in a IN H2SO4 solution. It was found that a significant improvement in the aqueous corrosion behavior of zircaloy-4 implanted with cerium ions compared with that of the as-received zircaloy-4. The improvement effect will decline with raising the implantation fluence. The bigger is the fluence, the less is the improvement. Finally, the mechanism of the corrosion behavior of the cerium-implanted zircaloy-4 is discussed. (C) 2003 Elsevier Science B.V. All rights reserved.