What Does Potentiostatic Mean?
Potentiostatic, like galvanostatic and potentiodynamic, is a polarization technique that allows for the controlled polarization of metal surfaces in electrolytes, in order to observe cathodic and anodic behaviors. Corrosion reactions are monitored on a sample of the desired metal. A number of characteristics of the metal/environment pairing can be determined through this technique.
Potentiostatic techniques can be used in:
- Corrosion product identification and analysis
- Industrial and chemical plant corrosion and chemical attack
- Alloy selection
- Crevice corrosion analysis
- Electronics corrosion
- Local corrosion analysis
Corrosionpedia Explains Potentiostatic
The potentiostatic technique is used to observe anodic and cathodic behaviors of a metal surface in electrolytes. Polarization experiments are performed with a computer-controlled potentiostat.
The metal sample is known as the working electrode (WE), which can be either bare metal or coated. The reference electrode (RE) should typically be a material that is very stable under the test conditions. The RE is used to monitor and maintain potential at the WE surface. A potentiostat monitors ionic current passing through the electrolyte between the counter electrode (CE) and the WE, and electron current passing between the CE and WE. Evaluation of behavior and reactions can help determine a material's:
- Open circuit or corrosion potential
- Instantaneous corrosion rate
- Passivation behavior
- Pitting potential and susceptibility
- Crevice corrosion susceptibility
- Sensitization of heat affected zones
- Galvanic corrosion behavior of dissimilar metal pairs
For determining critical pitting potentials, the most reliable approach is to use a potentiostatic technique in which a constant potential is applied, and the current is recorded as a function of time. At electrode potentials below the pitting potential, the current decays to a constant value. But at the pitting potential and above, the current increases with time as corrosion pits initiate and grow.