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The polarization resistance technique is a non-destructive technique used to obtain a rapid estimate of the corrosion rate of a metal in a solution. Cell current readings are taken during a very short, slow sweep of the potential. The sweep typically is from –10 mV to +10 mV relative to Eoc. Over this range, the current-vs.-voltage curve is roughly linear. A linear fit of the data to a standard model yields an estimate of the Polarization Resistance Rp. Rp is then used to calculate Icorr and corrosion rate.
Disadvantages:
•The corrosion-rate calculation requires that you provide kinetic parameters (βs) which you must estimate or obtain from another type of experiment.
•The result of a polarization-resistance calculation is typically less accurate than the corrosion rate calculated from Tafel data.
Advantages:
•Polarization Resistance experiments run very quickly.
• The scan in a polarization-resistance experiment does not appreciably polarize the sample. This minimizes changes in the surface of your sample caused by the test itself. This is especially important for long-term monitoring.
Analysis of the curve can yield the following types of information:
•Corrosion current and corrosion rate
ASTM Standard G59, "Practice for Conducting Potentiodynamic Polarization Resistance Measurements" contains useful information about polarization resistance measurements.