Commercial polymer films as calibration standards for EIS measurements

The current protocol regarding calibration and troubleshooting of potentiostats used to conduct electrochemical impedance spectroscopy (EIS) measurements on coated metals involves dummy cells made of simple electrical components. This concept has two major limitations: first, the instrument is used at an impedance range it has not been calibrated for—the instrument is calibrated for impedances in the order of ohms, but corrosion protective coatings usually have impedance values in the range of GΩ cm2 or higher; second, commercial coating systems do rarely behave like ideal equivalent circuits of electronic components. In view of these limitations, we propose the use of thin polymer films such as PVF or poly ethylene terephthalate (PET) as new calibration standards for EIS measurements. These films are well defined in thickness and composition and give a highly reproducible response when subjected to EIS measurements. In addition, they closely mimic commercial coating systems with regard to target impedance range and electrical characteristics.