Two- and four-electrode electrochemical cells were designed for characterization studies of highly resistive non-aqueous automotive lubricant using electrochemical impedance spectroscopy (EIS). The influence of internal configuration of the impedance analyzer, the media’s temperature and properties, shielding of the cables, and the electrochemical cell geometry and arrangement on the impedance results were investigated. The most accurate EIS measurements can be made in the two-electrode configuration with active shields where a single arc at high frequencies and a complicated low frequency impedance feature were observed in complex impedance plots. When four-electrode cells were employed, the impedance load, geometry and positioning of voltage electrodes; finite resistance of the impedance analyzer; and capacitive coupling between the signal lines introduced two types of impedance measurement artifacts. A capacitive-resistive low frequency load was interpreted as a measurement artifact originating from geometry and positioning of voltage electrodes. The appearance of additional medium frequency load combining resistive, capacitive and inductive features is intrinsic to the measurement setup and is due to a combination of several instrumental and experimental factors resulting in a voltage divider effect.
