This paper documents the measurement of the chloride diffusion coefficient through partially saturated porous materials. The method was electrochemical impedance spectroscopy, and it was validated by comparison to migration tests in fully saturated samples. A microstructure-based electrical equivalent circuit was developed to obtain the main features of the sample including the material electrical resistance for any water saturation degree. It is shown that the chloride diffusion coefficient varies over four orders of magnitude when the material is almost dry to fully saturated.