Noise in electrochemical corrosion measurements is common, showing up in both the current and voltage signals. It originates from several different sources, including:
Noise is often a nuisance degrading the signals you are trying to measure, but in some situations it can be a benefit to the corrosion engineer. In pitting corrosion, noise measurements can detect the onset of pitting. There is a background noise in uniform corrosion processes caused by the first four mechanisms in the above list. At the onset of pitting, however, the noise from electrode surface reactions can increase dramatically. This noise can show up in either the current signal or voltage signal, or both.
There are several ways to measure current noise and voltage noise. You can apply a constant I signal and measure E noise, or vice versa. You can also measure both current and voltage simultaneously on an electrochemical cell under control of a ZRA (zero-resistance ammeter).
The Electrochemical Noise system measures noise using potentiostatic, galvanostatic, or ZRA control modes..
Galvanostatic tests are also three-electrode experiments where a constant current is applied to the cell, and the noise in the cell voltage is measured as a function of time.