This note assumes that you have read and understand the material covered in the Application Note “Basics of Electrochemical Impedance Spectroscopy.”
The purpose of this Technical Note is to show that you can do EIS using Gamry Instruments’ potentiostats not only on flat samples in electrochemical cells, but also on curved parts not immersed in a liquid medium.
Curved, machined pieces of steel (the samples) were tested under the following conditions:
In a two-electrode EIS experiment, the sample acted as the Working Electrode and Working Sense Electrode. A graphite rod was used as Counter Electrode and Reference Electrode. (See Fig. 1.)
To provide an ionic path for the measurements, a moist paper towel was placed between the sample and the graphite rod. The paper towel was wrapped around the rod and secured in place using a polymer O-ring. The paper towel was thick enough to prevent a short circuit between the sample and rod. The aqueous solution in the towel was 1% weight/weight KNO3 dissolved in de-ionized water. (See Fig. 2.)
Various samples, including passivated and non-passivated surfaces, were tested. Each passivated sample was passivated via a different method. All data were recorded using a Gamry Instruments 600+™ potentiostat and Framework™ software, in potentiostatic mode. DC potential was set to open-circuit potential.
Read the complete Technical Note and download in PDF at Gamry.com.