What Does Electrochemical Corrosion Test Mean?
Electrochemical corrosion tests assess the state of corrosion in a concrete or metal element. Based on electrochemical theory, electrochemical corrosion testing characterizes corrosion damage and, where possible, estimates corrosion rates.
Electrochemical corrosion tests are used to determine:
- Corrosion rates (Tafel plot)
- Active/passive characteristics for a specific sample/solution system
- Passivation rates
- Anodic and cathodic protection
- Analysis of finished medical devices for pitting and crevice corrosion susceptibility
- Comparison of raw materials (screening) for corrosion characteristics
- Evaluating effects of passivation or surface modifications on corrosive behavior
- Evaluating/comparing processing effects on corrosion properties
- Evaluating bimetal combinations for galvanic corrosion behavior
Corrosionpedia Explains Electrochemical Corrosion Test
Electrochemical corrosion testing measures and/or controls the potential and current of oxidation/reduction reactions. Several types of experiments are possible by manipulating and measuring these two variables. Most experiments impose a potential on the working electrode and measure the resulting current.
For example, corrosion of steel embedded in concrete is an electrochemical process that involves the formation of an electrical circuit between areas of active corrosion (anodes) and passive areas (cathodes). Information about the extent of corrosion activity can be developed from electrochemical testing of the concrete and reinforcing steel. Corrosion testing typically includes measurements on both the reinforcing steel and concrete and is most commonly used to assess uncoated, bonded reinforcing steel.
Electrochemical tests can directly amplify the impact of corrosion processes. This is because all electrochemical tests use some fundamental model of the electrode kinetics associated with corrosion processes to quantify corrosion rates. The amplification of the electrical signals generated during these tests permits very precise and sensitive measurements to be carried out.
There are two basic methods of electrochemical measurement:
- Applying external current to generate electrochemical data away from the free corrosion potential. These tests generally explore the relationship between electrochemical potential and current.
- Electrochemical measurements at the free corrosion potential, without the application of an external current.
Electrochemical corrosion tests include the following techniques:
- Linear polarization resistance (LPR) measurements
- Potentiodynamic polarization curves
- Electrochemical potentiokinetic reactivation (EPR) measurements for intergranular corrosion
- Current vs time curves (at a given potential)
- Electrochemical impedance spectroscopy (EIS)
- Harmonic analysis
- Electrochemical noise (EN) measurements
Samples for electrochemical corrosion testing must utilize electrical conductors and must be small enough to fit in the polarization cell. Components can be tested as a whole or as a smaller section. Metal coupons are specially prepared for some tests.