Potentiostat

Cormetrics has 3 high-sensitivity potentiostats for performing electrochemical measurements in our autoclave and RCE experiments. The potentiostat has a potential range of ±12 Volts and maximum current of ±1 Amps. It takes high-precision current readings across 9 ranges, with a minimum resolution of 3.3 x 10^-15 amps. In combination with the attached multiplexer we can perform these measurements over multiple cells.

Depending on the test requirements, the following DC electrochemical methods can be used to monitor corrosion during the exposure period:

Linear Polarization Resistance (LPR)

Test design is to measure the resulting current across a small applied potential range. The resulting Polarization Resistance is used to calculate an electrochemical corrosion rate. This short measurement is taken at 15 or 30-minute intervals and allows the tracking of corrosion rates over the course of testing. The standard experiment is run over a four-day period in the pressurized autoclaves (AC), or over a two-day period at atmospheric pressure in the rotating cylinder electrode (RCE) apparatus.
In the case of RCE testing, this allows for visualization of LPR corrosion rates in response to changes in test parameters, such as changes in rotation rate or the effects of chemical additions, such as a higher dosage of corrosion inhibitor.

Cyclic Potentiodynamic Polarization (CPP)

Test design is to investigate the pitting and repassivation of materials. Also used to indicate inhibitor influence on pitting potentials. Standard test is run in the autoclaves over a two day period. Reporting includes discussion on the open circuit, pitting and repassivation potentials.

Zero Resistance Ammeter (ZRA)

Test design is to measure potential differences and current flow between different alloys or metals and report on corrosion rate, identifying the extent to which one material is anodic to the other. Weight loss corrosion rate is also recorded. The standard experiment is completed over a four-day period in the pressurized autoclaves, or over a two-day period at atmospheric pressure in the rotating cylinder electrode apparatus.

Potentiostatic Polarization

Test design is to apply a small anodic potential to the electrode to induce corrosion activity and determine the current response. This technique is used to evaluate materials and can be informative for corrosion inhibitor testing. The technique is combined with the CPP scan to determine the applied potential for the test and is typically run over a three-day period.