An adsorption strength model is developed to describe the mechanism of codeposition of alpha-alumina and Fe-P alloy. Based on hypotheses concerning the effective adsorption and the distribution of the adsorption strength of particles on the cathode, a general expression relating the content of embedded particles to the suspension concentration and the current density is deduced. This relationship is in good agreement with the experimental results. The variation of the content of particles in deposits with current density is an overall balance of two opposing effects which leads to a maximum in the particle content against current density curve.