1, You analyse the polarization curve with the Stern and Geary formula which corresponds to an anodic and a cathodic reaction following a Tafel law. In presence of a coating the dc current is not following a Tafel law.
2，The presentation of the impedance data in Nyquist plot is not correct. The Z\' and Z" axes of the Nyquist plot should have exactly the same scales; it is also necessary to add some characteristics frequencies on the diagrams.
3，The Warburg impedance is a part of the faradaic impedance, then W must be in series with the charge transfer resistance, W+Rct must be in parallel with the double layer capacitance.
4，In the second equivalent circuit I do not understand how CPE2 could be in direct contact with the metal. It will be clearer if the equivalent circuit and the different layers are on the same scheme.
5，In order to evaluate the value of the double layer capacitance represented by a CPE, I suggest to use the Brug’s formula (G.J. Brug, A.L.G. van den Eeden, M. Sluyters-Rehbach, and J. H. Sluyters, J. Electroanal. Chem. 176(1984) 275).
6，In table 3 you gave the results with 5 figures, what is the accuracy of your measurements.