Link to glossary of corrosion and materials maintenance terms

Corrosion engineering consultant

Corrosion Doctors site map

Alphabetical index of the Corrosion Doctors Web site

Linear Polarization Resistance (LPR)

... and the Stern-Geary Equation

With this widely used technique in corrosion monitoring, the polarization resistance of a material is defined as the slope of the potential-current density (DE/Di) curve at the free corrosion potential, yielding the polarization resistance Rp that can be related (for reactions under activation control) to the corrosion current by the Stern-Geary equation: (reference)


The Tafel slopes themselves can be evaluated experimentally using real polarization plots. The corrosion currents estimated using these techniques can be converted into penetration rates using Faraday's law or a generic conversion chart.

The study of uniform corrosion or studies assuming corrosion uniformity are probably the most widespread application of electrochemical measurements both in the laboratory and in the field. The widespread use of these electrochemical techniques does not mean that they are without complications. Both linear polarization and Tafel extrapolation need special precautions for their results to be valid. The main complications or obstacles in performing polarization measurements can be summarized in the following categories: