Multiplexed Rp/Ec Trend Purpose

This experiment measures changes in the polarization resistance, Rp, and corrosion potential, Ec, of up to eight samples. The samples are connected to the Framework™ system via an ECM8 Electrochemical Multiplexer. A polarization resistance measurement is made on each sample in turn. The result is a plot of Rp and Ec versus time for each cell. This plot is very useful in metal- or inhibitor-screening studies and on-line monitoring.

The polarization resistance technique obtains a rapid estimate of the corrosion rate of a metal in a solution. The polarization resistance technique is particularly applicable to long-term monitoring because it involves non-destructive (<15 mV) excursions relative to Eoc. Such small excursions are less likely to change the sample than the larger voltages applied in other techniques. Polarization resistance data yield an estimate of Icorr, which, in turn, can be used to calculate a corrosion rate. Estimation of Icorr requires kinetic parameters, e.g., β constants, which must be calculated or estimated from other data, such as a Tafel scan.