Contact person
Karin Törne
Forskare
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EIS for determination of corrosion mechanisms
Electrochemical impedance spectroscopy (EIS) is a non-destructive experimental technique used to characterise electrochemical processes such as corrosion. Typical investigation made with EIS are for instance deterioration of protective paints on metals or coatings in batteries, but also precipitation of corrosion products.
Purpose
The purpose of the technique is to measure and characterize the interface between an exposed surface and the surrounding environment. From the measurement the polarization resistance and double layer capacitance can be obtained. These parameters can then be used to calculate corrosion rates and to describe a corrosion process; initiation of pitting corrosion, the degradation of a protective coating or the precipitation of corrosion products. As opposed to many other electrochemical techniques the measurement is performed in-situ and is non-destructive. This allows for repeated measurements on the same sample to evaluate how the surface changes with time
Method
EIS can be described as measuring the alternating current as a response to an applied alternating potential. By applying the potential over a range of frequencies (usually 100 000 - 0.1 Hz) different electrochemical processes can be separated depending on their time dependence. For example, the charge transfer from a metal atom to an ion, which is a fast process (at high frequencies), and diffusion of ions through a coating, which is a relatively slow process (at low frequencies). The test is usually performed with the sample immersed in a conductive liquid, an electrolyte. We have the possibility to analyze EIS data using the common electrical equivalent circuit (EEC) approach but also with physics-based/mechanistic models.
Deliveries
A report with the data summarized in diagram and analysis of the results
