TY - CONF A1 - Dimper, Matthias A1 - Hampel, Marco A1 - Schenderlein, Matthias A1 - Özcan Sandikcioglu, Özlem T1 - Multielectrode array probes for early detection of corrosion processes N2 - 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. T2 - EUROCORR 2017 & 20thICC CY - Praha, Czech Republic DA - 04.09.2017 KW - Corrosion KW - Multielectrode array sensors KW - Stainless steel KW - Corrosion monitoring PY - 2017 AN - OPUS4-43420 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hampel, Marco A1 - Dimper, Matthias A1 - Schenderlein, Matthias A1 - Özcan Sandikcioglu, Özlem T1 - Combination of SECM with a multi-electrode analyzer for resolving local processes during microbiologically influenced corrosion N2 - Electrochemically active bacteria such as iron oxidizing bacteria (IOB) or iron reducing bacteria (IRB) accelerate the corrosion of stainless steel via the oxidation and reduction of iron oxides in the passive layer. The exposure to medium containing IOB and IRB leads to pitting corrosion with deep pits on stainless steel surfaces. Improving corrosion control via a better understanding of localized corrosion processes is highly relevant especially for reasons of safety or environmental protection since advancing pitting corrosion can easily lead to unpredictable material failure. Classic electrochemical methods however, provide insufficient information about the spatial heterogeneity of a corroding sample and fall short in detecting localized corrosion. The aim of this work is to develop methods for the analysis of localized corrosion, on stainless steel surfaces induced by IRB and IOB biofilms. It is quite challenging to address the complexity of the variations in the passive layer composition and microstructure as well as the biofilm’s complexity with its local differential aeration cells and electrochemical parameters both at the same time. Thus in this study, agarose artificial biofilms mimicking the physical properties of a natural biofilm have been used as model systems to be able to differentiate between individual effects. This artificial biofilm is applied on a multi-electrode stainless steel sample to identify local anodic sites during exposure experiments. For more detailed analysis of active sites, a scanning electrochemical microscopy (SECM) has been applied. Using the SECM as an amperometric sensor, we have investigated concentration gradients of iron ions or oxygen within the biofilm and its immediate vicinity on actively corroding electrodes. The presented analytical approach delivers promising results in clarifying how localized corrosion of stainless steels develops chronologically and spatially in the presence of IRBs and IOBs. Our results on model systems do also provide the basis for the investigation of natural biofilms in the future. T2 - EUROCORR 2017 & 20thICC CY - Prague, Czech Republic DA - 04.09.2017 KW - Scanning electrochemical microscope (SECM) KW - Stainless steel KW - Microbiologically influenced corrosion (MIC) KW - Local electrochemistry KW - Corrosion PY - 2017 AN - OPUS4-43406 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -