The corrosion behavior of metal-matrix composites (MMCs) is closely associated with the presence of heterogeneities such as reinforcement phase(s), microcrevices, porosity, secondary phase precipitates, and interaction products [1, 2]. Among the various possible corrosion mechanisms, microgalvanic coupling between the matrix alloy and the reinforcement phase(s), which is commonly associated with intermetallic precipitates, is generally recognized to be responsible for causing pitting corrosion in some silicon carbide reinforced aluminum MMCs [3±5]. Paciej [6] demonstrated that solution heat treatment combined with a high extrusion ratio could affect the precipitation behavior and enhance the corrosion resistance of an Al7091=SiCp composite. Ahmad [7] also denoted that a natural age-hardening process after solution heat treatment (T4) could reduce the corrosion rate of an Al-6013=SiCp composite by re®ning and homogenizing its secondary phases. However, using bulk heat-treating processes to improve the corrosion properties of MMCs can sometimes reduce the mechanical properties of the material. To solve this problem, surface treatment techniques are recommended. It is well known that laser surface melting can produce a rapidly solidi®ed surface layer, in which both the microstructure and the distribution of alloying elements can be greatly modi®ed. Our previous studies [8±10] have demonstrated that excimer laser surface treatment was an ef®cient way to improve the corrosion resistance of both aluminumand magnesium-based composites. However, the relatively low energy output of excimer lasers and their high running costs have so far restricted them from being extensively used for surface treatment. Unlike excimer lasers, Nd:YAG lasers can now be operated in continuous mode and in kilowatts range. With these new facilities, highpower YAG lasers could be effectively used for surface modi®cation of metals and composites alike. Preliminary results reported in this paper formed part of a wider study of the laser surface treatment of MMCs. The material used in this study was a 15 vol % SiC whisker, reinforced aluminum AA2009(Al3.8Cu-1.3 Mg) composite, which was produced by using a powder metallurgy route, and was supplied in 2.5 mm-thick annealed sheets. The diameter of the SiC whisker was between 0.4 im±0.65 im. Prior to laser treatment, all the specimens were polished with a 1 im diamond suspension. A laser surface treatment was conducted using a 2 kW continuous wave (CW) YAG laser. In the experiment, the laser beam size was ®xed at 3 mm, and the laser power and the scanning velocity were ®xed at 500 W and 35 mm sy1, respectively. During laser treatment, argon gas was blown over the molten pool to minimize any oxidation problem. Anodic polarization tests were carried out in a 3.5 wt % NaCl solution, which was prepared by using analytical grade reagents. The initial pH value of the solution was 7.8. The specimen was driven from y0.250 V below the steady open circuit potential at a scanning rate of 0.333 mV sy1 to produce potentiodynamic polarization plots. All potentials were measured with reference to a standard calomel electrode (SCE). Fig. 1(a,b) shows the surface morphology of the untreated and the laser-treated specimens, respec-