Linear Polarization Resistance (LPR)

Linear polarization resistance (LPR) is used to rapidly identify corrosion upsets and initiate remedial action, thereby prolonging plant life and minimizing unscheduled downtime. LPR is used to maximum effect when installed as a continuous monitoring system in almost all types of water-based, corrosive environments. The measurement of linear polarization resistance (LPR) has very similar requirements to the measurement of full polarization curves.

Linear polarization resistance (LPR) Tuses a series of electrodes, a voltmeter, an ammeter and a current source. The direction of current flow is reversed in the test, causing the test electrode to become the anode with an accelerated corrosion rate. The current level is increased to maintain a constant polarization potential voltage. The corrosion rate is directly proportional to the current level [Corrosion rate = ((K)(I)]; however, the corrosion rate information is not as accurate as corrosion coupon data. There are essentially four different methods of making the measurement according to whether the current or the potential is controlled and whether the current (or potential) is swept smoothly from one value to another, or simply switched between two values. In addition, the measurement may be made between two nominally identical electrodes (a two-electrode system), or a conventional three-electrode system (working, reference and counter) may be used.