The effect of zinc phosphate over the barrier properties of different paints was studied using EIS and gravimetric techniques. Previously, X-ray diffraction measurements were performed to determine the hydration rate of the pigment. This analysis revealed that the commercial powder zinc phosphate was a mixture of the dihydrate and tetrahydrate species, nevertheless, when it is blended to the resin, just the tetrahydrate form was detected.The incorporation of this pigment to the paint led to a clear improvement on the barrier properties. The same conclusion was obtained using both techniques. That improvement was stronger for chlorinated rubber resin, which suggested that the nature of binder-pigment interactions was an important point to take account.