In order to study the effect of yttrium (Y) and chromium (Cr) ion implantation on the crevice corrosion behavior of carbon steel, the carbon steel was implanted with Y and Cr ion using MEVVA source at an energy of 40 keV. Electrochemical measurement was employed to evaluate the crevice corrosion of implanted carbon steel in NaCl solution. The results indicated that, after Y and Cr ion implantation, the carbon steel's crevice corrosion resistance and electrochemical characteristic were significantly improved in NaCl solution when the implantation dose of Y increased. Auger electron spectroscopy (AES) analysis of the implanted carbon steel manifested that the surface layer was mainly composed of elements Fe, Cr, O, and Y. Most of element Y was located near the outside region of the surface layer/solution interface, whereas Cr was enriched in the transition area between surface layer and matrix. By Xray photoelectron spectroscopy (XPS) analysis, the implanted Y was in the form of Y2O3, whereas Cr in the form of Cr2O3 in the surface layer. The mechanism of the crevice corrosion resistance and electrochemical characteristic improvement was that, after Y and Cr ion implantation, the surface layer seemed to be constituted by Y2O3 and Cr2O3. The surface layer acted as a barrier to reduce the metal matrix to contact with the corrosion medium such as inhibiting Cl ions from corroding the layer. (C) 2008 Elsevier B.V. All rights reserved.