In this work the properties and structure of anodic bismuth oxide films or different thickness in phosphate solutions of different concentration, are studied. The Electrochemical Impedance Spectroscopy (EIS) response is strongly dependent of the total anionic concentration and was interpreted in terms of the passive pit model. Electric circuits taking into account the formation of porous films are formulated. Approximations performed as well as the response of the bilayer model obtained, are discussed. Electrical response is correlated with the surface morphology obtained by AFM.