We have seen several examples where a customer has recorded an open circuit voltage of 3, 4, or even 5 volts when running EIS on a coated sample. The Eoc values that were recorded in these experiments are probably not real Eoc readings. For very, very good coatings, such as the ones that these researchers were studying, we recommended that the potentiostatic EIS measurement be done at a potential vs. Eref, not vs. Eoc. The Eoc values are often not related to the coating or to the substrate: They are a function of the length of time the potentiostat has been connected to the cell.