# Linear Polarization Resistance (LPR)

Last updated: January 8, 2019

## What Does Linear Polarization Resistance (LPR) Mean?

Linear polarization resistance (LPR) is a broadly used electrochemical method of monitoring corrosion as well as other processes such as material polarization resistance. LPR involves the monitoring of the existing relationship between the current from charged electrons and the electrochemical potential, allowing the measurement of corrosion rates.

This method is widely employed in liquid solutions, where it is most effective. The measurement of the corrosion rate lets operators generate immediate feedback. It has been in use for more than five decades due to its efficiency.

## Corrosionpedia Explains Linear Polarization Resistance (LPR)

A fluid’s electrical conductivity is associated with its ability to cause corrosion. In this test, two to three electrode probes are included in the process system where the electrodes are isolated electronically. Typically, 20mV is put into the elements to produce current. With this, the linear polarization resistance refers to the applied potential ratio with the current level resulting from the process. The output or resistance is inversely proportional to the rate of corrosion.

The following equation shows conductor electrical resistance:

R= V/I

Where:

R is the instantaneous resistance

V is the applied voltage

I is the instantaneous current that exists in between the electrodes

If the electrodes are corroding at elevated rates while metal ions easily pass within the solution, this results in low levels of linear polarization resistance and high current, which is equivalent to high levels of corrosion.

Monitoring of LPR is a rapid method of measuring corrosion rate. Since the rate of corrosion can be identified in minutes using this method, an immediate measuring system can be implemented. This also allows for instant feedback, which leads to more effective monitoring and evaluation of corrosion in various operations. 