I suggest you to have a look at the following, interesting paper:
-Electrochemical Impedance Spectroscopy (EIS): A Review Study of Basic Aspects of the Corrosion Mechanism Applied to Steels
Héctor Herrera Hernández, Adriana M. Ruiz Reynoso, Juan C. Trinidad González, Carlos O. González Morán, José G. Miranda Hernández, Araceli Mandujano Ruiz, Jorge Morales Hernández and Ricardo Orozco Cruz
A chapter of book: Electrochemical Impedance Spectroscopy (2020), DOI: 10.5772/intechopen.94470
Available, as open access, at: https://www.intechopen.com/chapters/74147
That can result from corrosion products in your pores. That's depends of the coated system. Corrosion products can induce diffusion or inductive behaviour.