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<< Click to Display Table of Contents >> Navigation: Experiments > H - Electrochemical Noise > Techniques > Multiplexed Potentiostatic Mode ECN |
The multiplexed potentiostatic-mode ECN test is a high-throughput version of the single-cell Potentiostatic Mode ECN test. An Electrochemical Noise test in potentiostatic mode measures current noise at a fixed electrode-potential. A corrosion specimen is immersed in a solution and its potential (versus a reference electrode) is controlled by a three-electrode potentiostat.
Potentiostatic Mode ECN (single-cell or multiplexed) is useful when the system that you are modeling is not at its open-circuit potential. One example is a system under cathodic protection. ZRA Mode ECN cannot test this type of system.
Potentiostatic Mode ECN may also be superior to ZRA Mode ECN for coated samples. In ZRA mode, the assumption is that anodic current on one specimen flows as cathodic current from the other specimen. If two coated specimens are tested in ZRA mode, both coatings have to fail for current to flow. In potentiostatic mode, every failure results in increased current noise.
A multiplexed ECN test can run on up to eight cells concurrently. Cells are switched using Gamry Instruments' Electrochemical Multiplexer. We use the following terms to describe the channel and cell status:
Cell status |
Description |
|---|---|
Active Cell |
The cell (if any) currently connected to the system potentiostat. Any measurements are made on that cell. |
Standby Cell |
Standby cells are attached to the multiplexer but not presently connected to the system potentiostat. Depending on the standby mode, they may be shorted (working electrode to counter electrode or working electrode #2 ), open circuit, or connected to a local potentiostat in the Multiplexer . |
Selected Cell |
Cells may be either selected or not. If selected, the Explain™ script assumes a cell is connected to that multiplexer channel and tests that cell. If not selected, that channel is skipped. |
The terms channel and cell are often used interchangeably when discussing multiplexed tests.
The script connects the potentiostat or ZRA to each selected cell. In the period that a cell is connected, an entire block of data is acquired. This block is then treated to extract its noise parameters. The script then switches to the next selected cell and repeats the process.
Separate noise-trend curves are maintained for each cell. Using the curve-list control, you can review the last data block or the accumulating noise-trend curve for any selected cell.
The data treatments are identical to those in the single-cell tests.
Potentiostatic Mode Electrochemical Noise