| 1. |
- Fuertes, Nuria, et al.
(författare)
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Influence of mechanical stress on the potential distribution on a 301 LN stainless steel surface
- 2015
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 162:9, s. C465-C472
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the present work was to study the influence of the stress on the electrode potential of the austenitic stainless steel 301LN using Scanning Kelvin Probe (SKP). It was found that elastic deformation reversibly ennobles the potential whereas plastic deformation decreases the potential in both tensile and compressive deformation mode and this decrease is retained even 24 h after removal of the load. To interpret the stress effects, different surface preparations were used and the composition and thickness of the passive film were determined by GDOES. Slip steps formed due to plastic deformation were observed using AFM. The effect of plastic strain on the potential is explained by the formation of dislocations, which creates more a defective passive film.
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| 2. |
- Helbert, Varvara, et al.
(författare)
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Effect of cathodic polarisation switch-off on the passivity and stability to crevice corrosion of aisi 304l stainless steel
- 2021
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Ingår i: Materials. - : MDPI AG. - 1996-1944. ; 14:11
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Tidskriftsartikel (refereegranskat)abstract
- The effects of cathodic polarisation switch-off on the passivation of AISI 304L stainless steel in air and its crevice corrosion susceptibility in 3.5 wt.% NaCl aqueous electrolyte were investigated. Scanning Kelvin probe (SKP) data showed that the oxide film is significantly destabilised and the rate of steel passivation in air is slowed down. Thermal desorption analysis (TDA) highlighted that hydrogen absorption is proportional to the applied cathodic current density. A special crevice corrosion set-up was designed to realise simultaneous reproducible monitoring of potential and galvanic current to study the impact of prior cathodic polarisation on crevice corrosion onset. © 2021 by the authors.
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| 3. |
- Helbert, Varvara, et al.
(författare)
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Hydrogen effect on the passivation and crevice corrosion initiation of AISI 304L using Scanning Kelvin Probe
- 2021
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Ingår i: Corrosion Science. - : Elsevier Ltd. - 0010-938X .- 1879-0496. ; 182
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Tidskriftsartikel (refereegranskat)abstract
- Scanning Kelvin Probe was applied to study passivation of AISI 304L stainless steel after cathodic polarisation. The rate of passivation in air decreased as a function of duration and current density. X-ray Photoelectron Spectroscopy showed enrichment of the surface film by hydroxides of Fe (II) that was the result of hydrogen effusion from the bulk. SKP measured a decreased potential drop in the passive film. Pre-polarisation accelerates the crevice corrosion of steel in presence of chlorides. Using SKP mapping, increased hydrogen sub-surface concentration and lower level of passivity was observed in anodic zones of the crevice.
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| 4. |
- Helbert, Varvara, et al.
(författare)
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Kinetics of corrosion reactions on press hardened steel in atmospheric conditions under thin electrolyte films
- 2023
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Ingår i: Electrochimica Acta. - : Elsevier Ltd. - 0013-4686 .- 1873-3859. ; 458
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Tidskriftsartikel (refereegranskat)abstract
- Steels with high mechanical performance are prone to hydrogen embrittlement and environmental assisted cracking. Under atmospheric corrosion conditions, the source of hydrogen can be the steel corrosion process itself or galvanic coupling with a metallic coating. Electrochemical behaviour of Press Hardened Steel (PHS) under electrolyte films of different thicknesses using local electrochemical techniques was studied on a fundamental level. Scanning Vibrated Electrode Technique (SVET) was applied to study the evolution and localization of the corrosion process during PHS immersion in NaCl electrolyte. Kelvin Probe (KP) was used as a reference electrode to obtain cathodic and anodic polarization curves on PHS surfaces which were covered by thin electrolyte films (60 to 500 µm) of 0.1 M NaOH and 0.6 M NaCl. For both electrolytes, a strong increase in the oxygen reduction rate due to the decreasing of electrolyte thickness has been clearly demonstrated. Data are correlated well with a theoretical plot determined by Nernst-Fick equation. The influence of the rust layers on the kinetics of corrosion reactions under thin electrolyte films was investigated using KP. © 2023
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| 5. |
- Kim, Hye-Jin, et al.
(författare)
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Diffusible hydrogen behavior and delayed fracture of cold rolled martensitic steel in consideration of automotive manufacturing process and vehicle service environment
- 2020
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Ingår i: Journal of Materials Research and Technology. - : Elsevier Editora Ltda. - 2238-7854. ; 9:6, s. 13483-13501
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Tidskriftsartikel (refereegranskat)abstract
- This study aims to elucidate the behavior of diffusible hydrogen and delayed fracture in martensitic steel with 1500 MPa strength during automotive painting process and under vehicle service conditions. A sequential process of automotive pretreatment line and vehicle service environment is simulated to evaluate the hydrogen pick up in each process. In case of the automotive painting line, the absorption of hydrogen is within the common range in the process of phosphating treatment and electrodeposition. The baking process plays an effective role for desorbing the diffusible hydrogen absorbed during the automotive pre-treatment such as zinc-phosphating, and electrodeposition process. In case of the corrosion environment under the automotive driving conditions, hydrogen induced delayed fracture is accelerated as the exposure time increases. Further, it is clarified that severe plastic deformation are the significant factors for hydrogen induced delayed fracture under with low pH value and present of chloride ion in a chemical solution parameter. In summary, hydrogen is transported constantly during electrodeposition sequential line process of automobile manufacturing below the hydrogen content of 0.5 ppm, which is not critical value for leading to hydrogen delayed fracture based on results of slow strain rate tensile tests. However, exposure to extreme conditions under service environment of vehicle, such as acidic solution and chloride chemistry solution that result in high level of hydrogen absorption, severe plastic deformation in the sheared edge, and constantly applied internal or external stresses, can cause the hydrogen induced delayed fracture in the fully martensitic steels. © 2020 The Authors
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| 6. |
- Linder, Clara, et al.
(författare)
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Corrosion-Fatigue Performance of 3D-Printed (L-PBF) AlSi10Mg
- 2023
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Ingår i: MATERIALS. - : MDPI. ; 16:17
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Tidskriftsartikel (refereegranskat)abstract
- Additive manufacturing (AM) allows for optimized part design, reducing weight compared to conventional manufacturing. However, the microstructure, surface state, distribution, and size of internal defects (e.g., porosities) are very closely related to the AM fabrication process and post-treatment operations. All these parameters can have a strong impact on the corrosion and fatigue performance of the final component. Thus, the fatigue-corrosion behavior of the 3D-printed (L-PBF) AlSi10Mg aluminum alloy has been investigated. The influence of load sequence (sequential vs. combined) was explored using Wohler diagrams. Surface roughness and defects in AM materials were examined, and surface treatment was applied to improve surface quality. The machined specimens showed the highest fatigue properties regardless of load sequence by improving both the roughness and removing the contour layer containing the highest density of defect. The impact of corrosion was more pronounced for as-printed specimens as slightly deeper pits were formed, which lowered the fatigue-corrosion life. As discussed, the corrosion, fatigue and fatigue-corrosion mechanisms were strongly related to the local microstructure and existing defects in the AM sample.
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| 7. |
- Mendibide, Christophe, et al.
(författare)
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Effect of degraded environmental conditions on the service behavior of a X65 pipeline steel not designed for hydrogen transport
- 2024
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Ingår i: International journal of hydrogen energy. - : Elsevier Ltd. - 0360-3199 .- 1879-3487. ; 52, s. 1019-
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Tidskriftsartikel (refereegranskat)abstract
- With the international drive to deploy green energies and decarbonized intermediates in the place of fossil fuel sources, a large number of developed countries are actively preparing for a future where hydrogen plays a strategic role as an energy storage medium. Producing and using hydrogen requires the rapid expansion of a dedicated, economically viable industrial sector. Nevertheless, questions on how to safely store, transport and distribute hydrogen remain an important priority today. In countries with existing natural gas transport grids, the possibility to retrofit these networks to store and transport hydrogen-natural gas blends is being studied. A key challenge is to evaluate how pressurized H2 would interact with steel structures with regards structural embrittlement of the latter, with a view to exploiting existing transport infrastructures for storage and transport applications. In this work, we evaluate the H2-performance of a non-hydrogen service ×65 pipeline steel. The cracking susceptibility of this steel grade has been evaluated at 100 bar H2 using slow strain rate testing, Constant strain testing and fracture toughness measurements. Accompanying hydrogen permeation tests under pressure provide diffusion data and elucidate the discussion. Exposures were carried out in dry or wet H2 and with or without H2S contamination at levels representative of biogas. The results underline that the impact of dry or wet hydrogen on this grade are moderate. The presence of traces of H2S together with humidity could risk seriously degrading the mechanical performance of the ×65 steel grade. © 2023 The Authors
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| 8. |
- Nazarov, Andrej, et al.
(författare)
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Effect of mechanical stress on the properties of steel surfaces : Scanning Kelvin probe and local electrochemical impedance study
- 2017
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Ingår i: Journal of the Electrochemical Society. - : Electrochemical Society Inc.. - 0013-4651 .- 1945-7111. ; 164:2, s. C66-C74
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Tidskriftsartikel (refereegranskat)abstract
- The influence of mechanical stress on the electrochemical properties of ferritic steel SAE 1008 and austenitic stainless steel 301LN was studied using Scanning Kelvin Probe and Localized Electrochemical Impedance Spectroscopy (LEIS) techniques. The probe-working electrode Volta potential difference was mapped in situ under load. It was found that the influence of elastic deformation on the potential was small. Plastic deformation decreased the potential of steel by 150–300 mV, whereas the relaxation of the load from the plastic domain increased the Volta potential. However, some locations, which can contain residual stress, remained at low potential. The pre-strained surfaces were characterized by X-ray Photo Electronic Spectroscopy and by Atomic Force Microscopy. Distribution of the capacitance across strained and strain-free surfaces was studied by LEIS in boric/borate electrolyte. The plastic stress increases the capacitance and decreases the ability of the steels to passivate the surface indicating that emerging of pile-ups of dislocations create defective oxide films. © The Author(s) 2017.
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| 9. |
- Nazarov, Andrej, et al.
(författare)
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Hydrogen entry and distribution in steel : Assessments by different local electrochemical techniques
- 2018
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Ingår i: High-Strength Steels: New Trends in Production and Applications. - : Nova Science Publishers, Inc.. - 9781536139075 - 9781536139068 ; , s. 35-59
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- The sensitivity of high strength steels (HSS) to hydrogen embrittlement is well established. Cracking is likely to occur even at very low hydrogen content. Hence, it is important to develop new and very sensitive methods (e.g., with high lateral resolution) to study the sources of hydrogen, the distribution of hydrogen in the metal and the mechanisms of hydrogen interaction with microstructural defects and with the surface oxide. This report reviews the application of the localized electrochemical techniques such as Scanning Kelvin Probe (SKP), Scanning Vibration Electrode Technique (SVET), Local Electrochemical Impedance Spectroscopy (LEIS), and Scanning Electrochemical Microscopies (SECM) to study the hydrogenation of austenitic stainless steel, HSS and galvanized HSS under different experimental conditions. For example, SKP can detect 0.01 ppm of atomic hydrogen. This low detection limit is based on the nanoscale interaction of emerged hydrogen with the surface oxide film. Hydrogen diffuses and decreases the Volta potential of the surface at the locations of the emerging due to the reduction of Fe3+ species in the oxide film. It enables real time monitoring of the reduction of oxide film that is related to the failure of the steel passivity. SKP measurements are carried out in air and provide information on the relative hydrogenation due to atmospheric corrosion. In the case of LEIS, hydrogen interacts with surface oxide increasing the capacitance and decreasing the resistance of the film that can be monitored in a water electrolyte. SECM is able to map hydrogen distribution in the electrolyte in the vicinity of the steel surface. Advantages and disadvantages of the different techniques are discussed. The combined effect of mechanical stress and the hydrogen on the steel passivity is also under the scope of this review.
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| 10. |
- Nazarov, Andrei, et al.
(författare)
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Scanning Kelvin Probe for Detection in Steel of Locations Enriched by Hydrogen and Prone to Cracking
- 2023
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Ingår i: Corrosion and Materials Degradation. - : Multidisciplinary Digital Publishing Institute (MDPI). - 2624-5558. ; 4:1, s. 158-173
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Tidskriftsartikel (refereegranskat)abstract
- Hydrogen, due to corrosion processes, can degrade high strength steels (HSS) through embrittlement and stress corrosion cracking mechanisms. Scanning Kelvin probe (SKP) mapping of surface potential was applied, to visualize the locations with an increased subsurface concentration of hydrogen in mild steel and martensitic HSS. This work can help to determine the reasons behind hydrogen localization in a steel microstructure, leading to embrittlement and hydrogen-assisted cracking. Cathodic charging was used to insert hydrogen, which decreased the steel potential. Hydrogen effusion in air passivates steel, increasing the potential of HSS and mild steel. The passivation of steels was monitored depending on different conditions of cathodic pre-charging and the amount of absorbed hydrogen. The SKP could determine the area of diffusible hydrogen and the area of cracks. In addition, low potential locations linked to the hydrogen trapped in the deformed HSS microstructure were also determined, which delayed the steel passivation. Mild steel showed a uniform potential distribution related to interstitial hydrogen, without potential extremes attributed to locally accumulated hydrogen. Thus, SKP sensing can detect locations containing increased concentrations of hydrogen and sensitive to steel cracking.
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