In order to study the effects of the lanthanum ion implantation on the aqueous corrosion behavior of zircaloy, specimens were implanted with lanthanum ions using a MEVVA source at an energy of 40 keV, with a dose range from 5 x 10(16) to 2 x 10(17) ions/cm(2) at about 150degreesC. The surface structure was investigated by X-ray Diffraction (XRD) and the valence of the lanthanum ions in the surface layer was analyzed by X-ray Photoemission Spectroscopy (XPS). Three-sweep potentiodynamic polarization measurement was employed to evaluate the aqueous corrosion behavior of zircaloy in a 0.5 M H2SO4 Solution. It was found that a significant improvement was achieved in the aqueous corrosion resistance of zircaloy compared with that of the as-received zircaloy. The mechanism of the corrosion resistance improvement of the lanthanum-implanted zircaloy is probably due to the addition of the lanthanum oxide dispersoid into the zircaloy matrix. (C) 2005 Springer Science + Business Media.