We calculate interdiffusion coefficients in a two component, weakly or strongly coupled ion plasma (gas or liquid, composed of two ion species immersed into neutralizing electron background). We use an effective potential method proposed recently by Baalrud and Daligaut (PRL, 110, 235001, 2013). It allows us to extend the standard Chapman-Enskog procedure of calculating the interdiffusion coefficients to the case of strong Coulomb coupling. We compute binary diffusion coefficients for several ionic mixtures and fit them by convenient expressions in terms of the effective Coulomb logarithm. These fits cover a wide range of plasma parameters spanning from weak to strong Coulomb couplings. They can be used to simulate diffusion of ions in ordinary stars as well as in white dwarfs and neutron stars.

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