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Eingeladener Vortrag
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With increasing demand and environmental concerns, researchers are exploring new materials that can perform as well or better than traditional materials while reducing environmental impact. X-ray absorption spectroscopy (XAS) enables unique atom-specific tool to probe the electronic structure of materials. The BAM plays a central role in this highly collaborative research. The BAMline, a real-life sample materials research beamline, at the Berlin Synchrotron BESSY-II, provides unique insights into materials’ electronic and chemical structure at different time and length scales. This enables real-time optimization of material properties and performance for various applications, such as energy storage and conversion, catalysis, and corrosion resistance. This talk provides an overview of the analytical methods and sample environments of the BAMline and addresses its potential for further advances in sustainable materials research.
Ziele der Jungen GfKORR
(2024)
Die Junge GfKORR soll ein attraktives Angebot für junge Leute sein, sich fachübergreifend zu vernetzen und einen Einstieg in Querschnittsthemen bieten. Sowohl der Korrosionsschutz zum Zwecke der Nachhaltigkeit und Sicherheit von Bauwerken als auch der Korrosionsschutz bei Energie- und Mobilitätssystemen soll in zukünftigen Veranstaltungen übergreifend betrachtet werden. Dabei wollen wir den fachlichen und informativen Input aus den Arbeitskreisen der GfKORR bei unseren Seminaren suchen. In diesem 1. Netzwerk- und Arbeitstreffen wurde die Fahrtrichtung der Jungen GfKORR genauer abgesteckt und es hat sich eine Leitungsebene gefunden. Weiter wollen wir ab 2024 interessante Präsenzveranstaltungen mit Exkursionen anbieten.
High‐temperature KCl‐induced corrosion of high Cr and Ni alloys investigated by in‐situ diffraction
(2024)
High‐temperature KCl‐induced corrosion in laboratory air was observed in situ utilizing X‐ray diffraction. High Cr‐containing model alloys (Fe‐13Cr, Fe‐18Cr‐12Ni, and Fe‐25Cr‐20Ni) were coated with KCl and exposed to dry air at 560°C. KCl‐free alloys were studied in the equivalent atmosphere as a reference. After exposure to KCl‐free environments, all alloys showed the formation of very thin oxide layers, indicating good corrosion resistance. In contrast, KCl‐bearing alloys showed distinct damage after exposure.
The corrosion behavior of galvanized steels and zinc components under atmospheric exposure depends mostly on the corrosion product‐based cover layer formation under the prevailing conditions. The use of agar‐based gel electrolytes makes it possible to use electrochemical methods to obtain a characteristic value from these cover layers that describe their current and future protective capacity. It is shown here that different states of galvanized steel can be distinguished very well under laboratory conditions and that this method is also suitable for use under practical conditions. Based on the characteristic values and assuming future time of wetness, it is very easy to draw up a forecast for the future corrosion rate, which provides plausible values.
Multi-principal element alloys (MPEAs) are gaining interest in corrosion and electrocatalysis research due to their electrochemical stability across a broad pH range and the design flexibility they offer. Using the equimolar CrCoNi alloy, we observe significant metal dissolution in a corrosive electrolyte (0.1 M NaCl, pH 2) concurrently with the oxygen evolution reaction (OER) in the transpassive region despite the absence of hysteresis in polarization curves or other obvious corrosion indicators. We present a characterization scheme to delineate the contribution of OER and alloy dissolution, using scanning electrochemical microscopy (SECM) for OER-onset detection, and quantitative chemical analysis with inductively coupled-mass spectrometry (ICP-MS) and ultraviolet visible light (UV-Vis) spectroscopy to elucidate metal dissolution processes. In-situ electrochemical atomic force microscopy (EC-AFM) revealed that the transpassive metal dissolution on CrCoNi is dominated by intergranular corrosion. These results have significant implications for the stability of MPEAs in corrosion systems, emphasizing the necessity of analytically determining metal ions released from MPEA electrodes into the electrolyte when evaluating Faradaic efficiencies of OER catalysts. The release of transition metal ions not only reduces the Faradaic efficiency of electrolyzers but may also cause poisoning and degradation of membranes in electrochemical reactors.
The efficient exploration of novel alloy compositions is crucial for advancing the development of new materials. One widely utilized approach for creating phase diagrams is the use of diffusion-controlled synthesis for gradient alloys. This method is also an effective means for rapidly identifying potential material combinations.
The present study focusses on the exploration of quaternary multi-principle-element alloys (MPEAs) using diffusion multiples. We established a diffusion system by combining an equimolar ternary alloy (FeNiCr) with single diffusing elements Mn and Mo. Using ThermoCalc simulations, we determined suitable temperature ranges where we can expect the formation of single-phase alloys. Depending on the diffusion constants of the selected metals, diffusion times were adjusted to obtain diffusion zones with a depth of greater than 50 μm. Microstructural and compositional information was gathered via scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) and correlated to local mechanical properties evaluated by means of nanoindentation. Local corrosion properties were examined using Atomic Force Microscopy (AFM) and Scanning Electrochemical Microscopy (SECM).
Our results indicate that the ThermoCalc simulations have a good predictive power for crystallographic phases. However, especially with the Mn-FeNiCr system, formation of Cr-rich secondary phases were observed, which led to Cr-depletion and thus to localized corrosion processes in the matrix at the vicinity of the secondary phases. Based on the results of the local electrochemical tests, we have selected single-phase compositions along the diffusion zone and synthesized these alloys in bulk for corrosion studies by means of potentiodynamic polarization and SECM.
The presentation will summarize our methodology using diffusion couples as an
efficient tool for exploring compositional spaces of MPEAs in the search for novel single-phase alloys and the results of our correlative study on the mechanical and corrosion properties of these materials.
The efficient exploration of novel alloy chemistries is crucial for advancing the development of new materials. Diffusion-controlled synthesis of gradient alloys is an intelligent approach for creating phase diagrams and to effectively identify potential material combinations with tailored properties.
This project focusses on the design of quaternary multi-principle-element alloys (MPEAs) using diffusion couples. Our diffusion system contains an equimolar ternary alloy (FeNiCr) and additional single diffusing elements e.g. Mn and Mo. We determined the optimal temperature ranges for the diffusion thermal treatment by means of ThermoCalc simulations with the aim to form single-phase MPEAs. Microstructure and chemical characterization of the diffusion couples were performed by means of scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). For most alloy couples, the diffusion zone contained a single-phase alloy matrix with diffusion-induced compositional gradient as well as precipitation phases. This heterogeneity makes the diffusion couples interesting materials to investigate local mechanical and corrosion properties. Thus, local corrosion properties were examined using Atomic Force Microscopy (AFM) and Scanning Electrochemical Microscopy (SECM). Nanoindentation was used for the analysis of local mechanical properties.
Based on the results of the local corrosion analysis, we have selected single-phase alloy chemistries along the diffusion zone and reproducibly synthesized these alloys in bulk for detailed corrosion studies by means of potentiodynamic polarization and SECM.
The presentation will briefly summarize our methodology and motivation for using diffusion couples as an efficient tool for exploring phase diagrams of MPEAs in the search for new alloy chemistries and the results of our correlative study on the mechanical and corrosion properties of these materials.
Old materials, new life: Using diffusion-controlled synthesis for discovery of novel alloy systems
(2023)
Multi principal element alloy (MPEAs) concept allows us to rethink how we develop application-tailored, sustainable materials. The vast composition space leads to nearly indefinite material combinations and will facilitate finding Pareto optimal materials with lower CO2 footprint and avoidance of critical minerals as design criteria. To probe this large compositional space efficiently, the use high-throughput screening methods is inevitable. Diffusion-controlled synthesis of gradient materials is the optimal technique for screening complex compositional materials that would otherwise require comprehensive modelling or experimental efforts.
In this study, we have used a series of diffusion couples of pure metals and alloys with the aim to create a materials library with correlated data on composition and microstructure. With future recycling prospects in mind, and possible applications of Cu containing alloys in electrocatalytic carbon dioxide reduction and antimicrobial alloys we have generated diffusion couples of brass (Cu63Zn37) and bronze (Cu89Sn11) with either pure metals (Fe, Ni, etc.) or with binary or ternary alloys (FeNi, FeNiCr etc.). For different diffusion times and temperatures, we calculated diffusion constants for the material combinations. Following a detailed characterisation of the gradient materials, we have investigated general and local corrosion properties, electrocatalytic activity for oxygen evolution reaction (OER) and carbon dioxide reduction reaction (CRR) as well as mechanical properties (hardness, elastic modulus) on single-phase alloys synthesized in bulk by means of vacuum arc-melting based on the selected local compositions.
In most cases, due to the short diffusion times, the contact between the diffusion couples lead to two separate diffusion zones and thus, different alloy families on both sides. Especially with ternary alloys, interesting selective diffusion processes and unexpected repulsion effects were observed. The presentation will provide an overview of the gradient materials with a focus on the functional properties of single-phase alloy families derived from them.
Due to their favorable mechanical and anti-corrosion properties, medium entropy alloys (MEA) are of high academic and industrial interest as novel materials for engineering and catalytic applications. Previous studies on general corrosion behavior indicate high current densities at high anodic potentials for MEAs. Further investigations of the underlying transpassive dissolution and local corrosion behavior remain scarce.
To understand the passivation behavior of MEAs CrCoNi and FeCrNi at high anodic potentials, the mechanisms of transpassive dissolution and the oxygen evolution reaction were investigated in this project. Scanning electrochemical microscopy (SECM) was applied in the interrogative mode for the detection of evolving metal species and oxygen. By means of ICP-MS analysis, dissolved metal species were quantified to provide a fundamental understanding on the transpassive dissolution. As the oxygen evolution reaction (OER) may contribute a large percentile to the observed current at high anodic potentials, SECM measurements were employed to analyze the onset of the OER. Potentiodynamic, potentiostatic and chronoamperometric techniques as well as different electrolytes were used to induce precisely controlled corrosion loads during the SECM experiments and for the ICP-MS analysis. Macroscopic corrosion properties of the alloys, electrical and chemical properties of the passive films were studied by means of potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and X-Ray Photoelectron Spectroscopy (XPS), respectively.
Finally, the analysis of the corrosion morphology and the potential of the surface before, during and after passivity breakdown was carried out by means of in-situ atomic force microscopy (AFM) and scanning Kelvin probe force microscopy (SKPFM). The presentation will summarize our results on the interplay of anodic passivation and oxygen evolution of MEAs in aqueous NaCl electrolytes.
It is well known that cement manufacture, including CaCO3 calcination and clinker formation, is associated with substantial energy consumption and significant greenhouse gas emissions. Alkali-activated binders (AAB) and concretes made from them can significantly contribute to reducing CO2 emissions caused by the construction industry. However, to what extent and for how long concretes made from AAB can protect the steel in reinforced concrete components from corrosion is still unclear. Unlike PC-based binders, AABs are made by reacting alkaline solutions with solid precursors such as fly ash and ground granulated blast furnace slag (GGBFS). Therefore, steel reinforcement corrosion mechanisms in AAMs differ from PC-based binders. The present study aims to evaluate the corrosion behavior of steel rebar in alkali-activated materials (AAMs) synthetic pore solution with different chemical concentrations representing different GGBFS and Flay Ash based binders by performing electrochemical tests to measure the corrosion rate and corrosion potential of steel rebar. This information can be used to improve the design of AAMs in order to ensure a longer service life for these materials.
While a lage amount of research on high entropy alloys is oriented towards mechanical properties and the microstructural improvement it is also necessary to keep an eye on the environment that potential application materials will be submitted to. The Co-Cr-Fe-Ni based high entropy family has shown great potential over the years of high entropy research and some candidate alloys are chosen for an insight into their corrosion behaviour. Several atmospheres are studied, i.e. O2, H2O, SO2 and a mix thereof in argon as well as synthetic air. Just as for classic alloys, the chromium is the most important element in terms of protection agains further corrosion. The addition of manganese, as in case of the “Cantor alloy” CrMnFeCoNi, overpasses Cr when it comes to oxygen affinity and thus counteracts the layer formation of Cr2O3. Even without Mn, a temperature chosen too high will also affect the formation of the chromium oxide layer and spall it off, annulling its protective potential. We can also observe how trace elements influence the layer formation. These effects and their mechanisms will be discussed for the alloys CrFeNi, CoCrNi, CrMnFeCoNi and variations of Al10Co25Cr8Fe15Ni36Ti6 using a combination of electron microscopy, thermodynamic calculations and x-ray diffraction.
In the late 1980s, a new type of corrosion appeared in drinking water installations where galvanized steel pipes failed forming a deep groove with no corrosion at the other surfaces. The reason was discussed quite fiercely between failure analysts and material suppliers. In the end the discussion lead to the solution: inductive welded pipes of a certain sulphur content were prone to selective corrosion. The history of the arguments is discussed using old communications between Wilhelm Schwenk and Wolfgang Stichel, who later published the results in a paper unfortunately only I german.
Thus the knowledge got lost and new cases based on the same material problems are observed in application of so-called C-Steel piping systems. Failure cases are shown.
In the late 1980s, a new type of corrosion appeared in drinking water installations where galvanized steel pipes failed forming a deep groove with no corrosion at the other surfaces. The reason was discussed quite fiercely between failure analysts and material suppliers. In the end the discussion lead to the solution: inductive welded pipes of a certain sulphur content were prone to selective corrosion. The history of the arguments is discussed using old communications between Wilhelm Schwenk and Wolfgang Stichel, who later published the results in a paper unfortunately only I german.
Thus the knowledge got lost and new cases based on the same material problems are observed in application of so-called C-Steel piping systems. Failure cases are shown.
With increasing demand and environmental concerns, researchers are exploring new materials that can perform as well or better than traditional materials while reducing environmental impact. The BAMline, a real-life sample materials research beamline, provides unique insights into materials’ electronic and chemical structure at different time and length scales. The beamline specializes in x-ray absorption spectroscopy, x-ray fluorescence spectroscopy, and tomography experiments. This enables real-time optimization of material properties and performance for various applications, such as energy transfer, energy storage, catalysis, and corrosion resistance. This paper gives an overview of the analytical methods and sample environments of the BAMline, which cover non-destructive testing experiments in materials science, chemistry, biology, medicine, and cultural heritage. We also present our own synthesis methods, processes, and equipment developed specifically for the BAMline, and we give examples of synthesized materials and their potential applications. Finally, this article discusses the future perspectives of the BAMline and its potential for further advances in sustainable materials research.
In this study, we propose the use of nondestructive, depth-resolved, element-specific characterization using grazing exit X-ray absorption near-edge structure spectroscopy (GE-XANES) to investigate the corrosion process in compositionally complex alloys (CCAs). By combining grazing exit X-ray fluorescence spectroscopy (GE-XRF) geometry and a pnCCD detector, we provide a scanning-free, nondestructive, depth-resolved analysis in a sub-micrometer depth range, which is especially relevant for layered materials, such as corroded CCAs. Our setup allows for spatial and energy-resolved measurements and directly extracts the desired fluorescence line, free from scattering events and other overlapping lines. We demonstrate the potential of our approach on a compositionally complex CrCoNi alloy and a layered reference sample with known composition and specific layer thickness. Our findings indicate that this new GE-XANES approach has exciting opportunities for studying surface catalysis and corrosion processes in real-world materials.
The high-temperature corrosion behaviors of the equimolar CrCoNi medium- and CrMnFeCoNi high-entropy alloy were studied in a gas atmosphere consisting of a volumetric mixture of 10% H2O, 2% O2, 0.5% SO2, and 87.5% Ar at 800 °C for up to 96 h. Both alloys were initially single-phase fcc structured and showed a mean grain size of ~50 µm and a homogeneous chemical composition. The oxide layer thickness of the Cantor alloy CrMnFeCoNi increased linearly with exposure time while it remained constant at ~1 µm for CrCoNi. A Cr2O3 layer and minor amounts of (Co,Ni)Cr2O4 developed on CrCoNi while three layers were detected on the Cantor alloy. These layers were a thin and continuous chromium rich oxide layer at the oxide/alloy interface, a dense (Mn,Cr)3O4 layer in the center and a thick and porous layer of Mn3O4 and MnSO4 at the gas/oxide interface. Additionally, a few metal sulfides were observed in the CrMnFeCoNi matrix. These results were found to be in reasonable agreement with thermodynamic calculations.
Since geothermal wells are a feasible energy source to replace fossil fuel supply, many technologies have been developed to take advantage of geothermal energy. Nevertheless, service conditions in geothermal facilities are in many cases extreme in terms of corrosion due to the chemical composition of hydrothermal fluids and temperatures. Therefore, materials selection based on preliminary material qualification is essential to guarantee a secure and reliable operation of the facilities. During operation of a geothermal research facility in Groß Schönebeck copper and lead effects have been found downhole. Occurring mechanisms and measures to prevent precipitation or scaling needed to be investigated as well as potential influences of such precipitates on corrosion resistance of metallic materials used for equipment.
This contribution deals with the evaluation of the corrosion behavior of carbon steel and corrosion resistant alloys in copper and/or lead containing artificial geothermal water, simulating the conditions in the Northern German Basin.
The behavior of these materials in an artificial geothermal water obtained by electrochemical measurements and exposure tests are presented. While carbon steel exhibits precipitation and deposition, higher alloyed material shows different response to such species and a higher resistance in saline geothermal water.
Basing on these results the suitability of the investigated corrosion resistant alloy is given for use in such conditions, whereas carbon steel creates difficulties due to its susceptibility to Cu- and Pb-precipitation.
Significant Cu-deposition and precipitation only occurred in combination with carbon steel. High-alloyed materials prevent the disturbing Cu-agglomeration. Pb-deposition and precipitation only occurred in combination with carbon steel. No negative Pb-effect could be observed in combination with high-alloyed steels. High alloyed corrosion resistant alloys are suitable and shall be chosen for future design of the piping system, either in massive or in cladded form, to prevent unwanted interactions with brine components.
Industries transporting CO2 gas-saturated fluids have infrastructures made of carbon steel. This is a good material with great mechanical properties but prone to corrosion and potential failure. Corrosion in sweet environments involves the formation of FeCO3 as a corrosion film, which is recognized to play a protective role under certain conditions. This work on the dissolution of corrosion films in sweet environments, under acidic and undersaturated conditions, demonstrates that the effects on the integrity of steel are far more significant than the damage observed on the surface of the corrosion film. Our results prove that dissolution of FeCO3 involved the presence of an amorphous phase, the intermediate formation of FeCl2 or FeCl+, and the presence of a phase with short distance atom–atom correlations. The amorphous phase was identified as a mixture of retained γ-Fe and Fe3C. Partially broken α-Fe and Fe3C structures were identified to prove the damage on the material, confirming the interface zone without evident damage on the corrosion film. Dissolution affected both the α-Fe and FeCO3, with the lattice [102̅] from the FeCO3 crystalline structure being the fastest to dissolve. The damage of steel at the molecular scale was evident at the macroscale with pit depths of up to 250 μm. The impact on the integrity of steel can be, therefore, more drastic than frequently reported in industrial operations of CO2 transport industries that use cleaning procedures (e.g., acid treatment, pigging) as part of their operational activities.