When blisters are formed underneath organic coatings the anodic and cathodic areas will become separated, which further stimulates the growth of the anodic and cathodic areas. In the case of a blister with a defect in the coating the contribution of these areas theoretically becomes visible in the impedance spectrum. Due to the lack of knowledge on the processes and especially the geometry of the anodic and cathodic regions it is not known whether these contributions can be quantitatively analysed. From experiments it became clear that the corrosion products in the defect are dominating the impedance characteristics, thus masking other contributions. In order to control the geometry we designed several types of artificial blisters. In one type the anodes and cathodes were fixed by using substrates that were partially covered with gold. With two other types we produced the film of corrosion products that normally is present in blisters in an artificial way without a coating. The impedance measurements on these artificial blisters led to an extension of the mechanistic model for cathodic delamination. From the experiments the conclusion can be drawn that characterisation of the anodic and cathodic regions in blisters is not possible with EIS. However, the impedance characteristics of the corrosion product in the defect can be investigated.