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Schlagworte
Sensors for the detection of general corrosion are well established. However, the detection of early phases of localized corrosion still remains a challenging task since the initiation steps can proceed without showing significant contribution to the electrochemical signal of a macroscopic surface. Along with electrochemical noise based methods, utilization of multielectrode arrays can be used to address this problem.
The aim of this study is to develop and test multielectrode arrays for early detection of corrosion processes. By means of a multielectrode analyser the current flow, potential and impedance spectra on each single electrode can be measured as a function of time. Thus, maps of the probe can be generated with real time information for instance showing individual electrodes persistent anodic or cathodic signals. This approach has been utilized in combination with scanning electrochemical techniques such as scanning electrochemical microscope or scanning vibrating electrode to select active electrodes for detailed investigation.
As the sensitivity is strongly dependent on the wire diameter and array configuration, a systematical investigation has been performed to optimize the preparation procedures and probe geometry. Stainless steel X5CrNi18-10 (1.4301) wires of different diameters have been embedded in a carrier material made of epoxy resin providing electrical insulation. The multielectrode probes consisting of at least 3 x 3 and a maximum of 10 x 10 single electrodes have been tested in corrosive media, with different chloride concentrations, as well as in the presence of metal reducing bacteria to assess their applicability in the detection of the onset of corrosion. This contribution will summarize our optimization study and the evaluation of the sensor performance.
Multielectrodes are arrays of single electrodes arranged in a particular geometry. In our work, all the single electrodes are identical stainless steel X5CrNi18-10 (1.4301) wire electrodes. Using a multielectrode analyser all single electrodes are connected via zero resistance ammeters, simulating a galvanically coupled single electrode surface. The advantage of the multielectrode analyser (MMA) is that the currents flowing between single electrodes can be measured. Thus, real-time maps can be generated indicating where anodic and cathodic areas lie on the surface of the multielectrode and how they behave.
The combination of the multielectrode analyser with the scanning electrochemical microscopy (SECM) enables the identification of corrosion sites and the detailed electrochemical analysis.