sensors

Linear Polarization Resistance (LPR)

Electrochemical sensor for real-time measurement of the instantaneous corrosion rate of rebar in concrete.

Model No
G94-900PR
Measurement Range
0.01 to 1000 µm/year
Electrodes
Ag/AgCl or MnO2 Reference Options

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Overview

Electrochemical sensor for real-time measurement of the instantaneous corrosion rate of rebar in concrete.

The Geolook G94-900PR LPR sensor is a sophisticated electrochemical tool used to quantify the speed at which steel reinforcement is corroding within a concrete structure. Unlike simple potential meters that only indicate the probability of corrosion, the LPR sensor provides a direct measurement of the corrosion current. By applying a very small electrical potential to the rebar and measuring the resulting current response, the sensor calculates the polarization resistance. This data allows engineers to determine the metal loss in micrometers per year, providing a definitive timeline for structural service life and maintenance requirements.

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Benefits & Features

  • Provides instantaneous corrosion rate (µm/year)
  • Non-destructive measurement technique
  • Multi-element probe (Reference, Auxiliary, and Working electrodes)
  • Integrated chloride ion and resistivity monitoring options
  • Stainless steel or Titanium housing for long-term embedment
  • Digital interface for high-resolution data acquisition
  • Essential for life-cycle cost analysis of infrastructure

Detailed Description

Measuring the Corrosion Current

LPR monitoring works on the principle that the relationship between a small externally applied potential and the resulting current is linear. The slope of this line is the 'Polarization Resistance' (Rp).

Using the Stern-Geary equation, the G94-900PR converts this resistance into a corrosion current density (Icorr). This is the most valuable metric in corrosion science because it tells you exactly how much steel is being 'eaten away' at that specific moment.

Probability vs. Rate

Standard sensors often just measure 'Potential' (the likelihood of corrosion). However, high potential doesn't always mean fast corrosion. The G94-900PR goes a step further by providing the 'Rate.'

For an asset manager, knowing that a bridge is corroding at 10µm/year versus 100µm/year is the difference between planning a repair in ten years or closing the bridge for immediate maintenance.

The Multi-Electrode Probe

The G94-900PR is an all-in-one probe embedded near the rebar. It contains a reference electrode to monitor stable voltage, an auxiliary electrode to apply the current, and connects to the rebar itself as the working electrode.

This configuration ensures that the measurement is localized. It measures the corrosion exactly where the sensor is placed, allowing for the creation of a 'corrosion map' when multiple sensors are installed across a structure.

Environmental Correlation

Corrosion is heavily influenced by humidity and temperature. The G94-900PR is typically used alongside our G89-series temperature sensors. By correlating the corrosion rate with internal concrete temperature and moisture levels, engineers can identify 'corrosion seasons' and predict how the structure will behave under changing climate conditions.

Available Models

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Specifications

Model No
G94-900PR
Measurement Range
0.01 to 1000 µm/year
Electrodes
Ag/AgCl or MnO2 Reference Options
Resolution
0.01 µA
Operating Temp
-10°C to +60°C
Probe Material
Stainless Steel / PVC / Epoxy
Cable
Multi-core shielded, chemical resistant