In this paper, the microstructure, microhardness and adhesive strength of Al-12Si coating produced by cold spraying were investigated. It is found that a thick, dense and well bonded Al-12Si coating could be produced by cold spraying with a relatively large powder through the control of spray conditions. The critical velocity for large Al-12Si particles was lower than that of small Al-12Si particles. The as-deposited Al-12Si coating had the same crystal structure as Al-12Si powder. The localized interfaco melting occurred resulting from both the adiabatic shearing upon impact and the thermal effect of hot gas. Some fine Si particles precipitated in alpha-Al matrix because of the thermal effect of hot gas during coating deposition. The dispersed Si particles in Al-12Si coating improved the coating microhardness. (c) 2007 Elsevier B.V. All rights reserved.