ELECTROCHEMICAL CORROSION AND WATER ELECTROLYSIS TESTING
Researchers find electrochemical corrosion testing useful for studying and investigating green hydrogen production during water electrolysis, as well as for predicting metal corrosion behavior. The investigation of corrosion and electrolysis entails subjecting a test specimen or two electrodes to a liquid medium. This is done while monitoring their electrochemical activity.
An electrolyzer is composed of a metal-electrode assembly in which the water-splitting reaction takes place. Letomec team can perform several tests to characterize and search for improvements in water electrolysis.
Moreover, electrochemical tests provide the means for predicting metal corrosion behaviour and protection properties of coatings exposed to the electrolyte.
For more details please see the dedicated section:
Linear scan voltammetry
Letomec Researchers commonly use potentiodynamic Linear scan voltammetry, also known as Linear Sweep Voltammetry (LSV), to investigate the electrochemical behavior of metals (Working Electrode).
In this technique, we record the current while linearly increasing or decreasing the potential of the sample. This variation occurs within a defined window relative to a fixed reference potential (e.g., Ag/AgCl or other references). Moreover, during the test, we measure and plot the current passing through the electrode. It is possible to adjust the scan rate to better suit the process under analysis, focusing on a potential window around the open circuit potential (OCP). This elucidates the system’s behavior in the Tafel region and enables the identification of the corrosion potential and the corrosion current of the metal in a specified medium.
Furthermore, we can investigate the oxygen or hydrogen evolution reaction, typically occurring on the electrode surface during water electrolysis, by deviating the potential far from equilibrium.
Multi-step potentiometry/amperometry for a single-cell electrolyzer
With the use of a lab-scale electrolyzer cell, we can evaluate the quality and quantity of low and high-power hydrogen generators’ performance. The setup includes a single experimental electrolyzer cell onto which various electrode samples and ion exchange membranes can be assembled.
By employing multi-step potentiometry and amperometry, we can obtain the voltage-current behavior of the system. Additionally, the system is equipped to measure the generated gas flow. Furthermore, analysis of this lab-scale system enables assessment of the coulombic and thermodynamic efficiency of the electrode-membrane assembly.
Moreover, the stability of a system can also be investigated with intermittent or long-term tests.
Electrochemical Impedance Spettroscopy (EIS)
EIS is an electrochemical test technique that analyzes the response of a system under an alternating current or potential signal. EIS data is generated by applying an AC potential to a system, measuring the AC current response, and recording phase shift and amplitude changes over a range of applied frequencies. Resistance and capacitance values are obtained from each frequency, and these quantities can provide information on corrosion behavior and rates, diffusion, and coating properties. Finally, fitting the results with an equivalent electrical circuit model allows identification and separation of processes that occur on different timescales.
Cyclic Voltammetry (CV)
CV consists of imposing on an electrode a linear ascending/descending potential between two values and measuring the resulting current. Peaks on the current plot correspond to the redox reaction taking place on the electrode-surface interface. The potential of this working electrode is controlled versus a reference silver/silver chloride electrode (Ag|AgCl).
We typically use CV to obtain the electrochemical double-layer capacitance of a metal. In fact, this property can be measured to investigate the electrochemical active surface area. In this case, we perform CV in a potential window where no faradaic processes take place. The coefficient of the linear relationship between the scan rate and current density variation gives the value of the double-layer capacitance.
Electrochemical measure of elements dissolved in a solution
The electrochemical measure of elements dissolved in a solution can be obtained through cyclic voltammetry and potentiometric titration.
We also conduct cyclic voltammetry to investigate the presence of an element in a conductive solution. This test consists of evaluating the oxidation and reduction reaction potentials, by comparing them with a standard solution prepared in the laboratory.
Potentiometric titration is an analytical method that allows the concentration of an element to be obtained indirectly by measuring the variation of the electrochemical potential of the cell following the addition of a titrant.
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