| 1. |
- Anantha, Krishnan Hariramabadran, et al.
(författare)
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Experimental and modelling study of the effect of tempering on the susceptibility to environment-assisted cracking of AISI 420 martensitic stainless steel
- 2019
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Ingår i: Corrosion Science. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0010-938X .- 1879-0496. ; 148, s. 83-93
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Tidskriftsartikel (refereegranskat)abstract
- The resistance to environment-assisted cracking (EAC) of AISI 420 martensitic stainless steel (MSS) was investigated in 0.3 M NaCl solution (room temperature) at constant loads for 30 days. The steel tempered at 250 degrees C was superior to the 500 degrees C-temper, which showed corrosion pits favouring cracking. The fracture surface showed faceted grains, cleavage, striations, and inter- and transgranular cracks, suggesting a mixed stress corrosion cracking (SCC) and hydrogen embrittlement (HE) mechanism as the cause for EAC. Finite element modelling (FEM) indicated strain/stress localization at the mouth of deep pits and at the wall of shallow pits, displaying the favoured locations for pit-to-crack transition.
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| 2. |
- Anantha, Krishnan Hariramabadran, et al.
(författare)
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In situ AFM study of localized corrosion processes of tempered AISI 420 martensitic stainless steel : Effect of secondary hardening
- 2017
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Ingår i: Journal of the Electrochemical Society. - : Electrochemical Society. - 0013-4651 .- 1945-7111. ; 164:13, s. C810-C818
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Tidskriftsartikel (refereegranskat)abstract
- The effect of secondary hardening of tempered AISI 420 martensitic stainless steel on the corrosion behavior in aqueous 0.01 M NaCl has been studied, in-situ, using atomic force microscopy (AFM) to monitor real-time localized corrosion processes. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy, and X-ray diffraction analyses confirmed the presence of undissolved and secondary carbides (Cr23C6, Cr7C3, Cr3C2, Cr3C, Cr2C, and CrC) as well as retained austenite, all finely dispersed in the tempered martensitic matrix. Electrochemical measurements, consisted of monitoring of the open-circuit potential vs. time and cyclic polarization in 0.01 M NaCl solution, were performed to evaluate the passivity and its breakdown, and it was seen that initiation sites for localized corrosion were predominantly peripheral sites of carbides. In-situ AFM measurements revealed that there was a sequence for localized corrosion in which the neighboring matrix next to secondary carbides dissolved first, followed by corrosive attack on regions adjacent to undissolved carbides. Tempering at 500◦C reduced the corrosion resistance and the ability to passivate in comparison to tempering at 250◦C.
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| 3. |
- Cao, Yanhui, et al.
(författare)
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Insight into the Fabrication of ZnAl Layered Double Hydroxides Intercalated with Organic Anions and Their Corrosion Protection of Steel Reinforced Concrete
- 2019
-
Ingår i: Journal of the Electrochemical Society. - : Electrochemical Society. - 0013-4651 .- 1945-7111. ; 166:16, s. C617-C623
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Tidskriftsartikel (refereegranskat)abstract
- This work provides insight into the fabrication of ZnAl layered double hydroxides (LDHs) intercalated with organic phthalates (PTL) and their corrosion protection of steel reinforced concrete. The structure, composition and morphology of the LDH products prepared by various methods were systematically characterized to find out the relationship of preparation-structure-properties. The ZnAl-LDH-PTL prepared by co-precipitation method presented the best performance of corrosion protection due to its good crystallinity. The corrosion protection mechanism of LDH for steel in concrete system was also discussed.
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| 4. |
- Cao, Yanhui, et al.
(författare)
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Layered double hydroxide (LDH) for multi-functionalized corrosion protection of metals : A review
- 2022
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Ingår i: Journal of Materials Science & Technology. - : Elsevier BV. - 1005-0302. ; 102, s. 232-263
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Forskningsöversikt (refereegranskat)abstract
- Layered double hydroxide (LDH) has been widely developed in the field of corrosion and protection in recent years based on its unique characteristics including anion capacity, anion exchange ability, structure memory effect, and barrier resistance. This paper comprehensively reviews recent work on the preparations, properties of LDH in the forms of powder and film and their applications in different environments in corrosion and protection. Some novel perspectives are also proposed at the end of the review for future research in corrosion and protection field.
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| 5. |
- Chen, Dihao, et al.
(författare)
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Correlation between pitting susceptibility and surface acidity, point of zero charge of passive film on aluminum: Influence of alloying elements
- 2024
-
Ingår i: Corrosion Science. - : Elsevier BV. - 0010-938X .- 1879-0496. ; 227
-
Tidskriftsartikel (refereegranskat)abstract
- The pitting potential, intrinsic surface acidity, point of zero charge of passive film on Al are studied using first-principles calculations to establish their relationships. Influences of alloying elements Zn, Cr, Nb, Si, Mo and Sc on adsorption of NH3 and NaCl, pHpzc of Al2O3 and pitting susceptibility of Al are investigated. The efficiency for enhancing pitting resistance of Al is evaluated, yielding the ratios Si: Zn: Cr: Mo: Nb: Sc = 1.8: − 0.3: 1: 1.9: 1.4: 0.2. A model for the dependence of pitting potential on the concentration of alloying elements in Al alloy matrix is developed, based on effects of alloying elements on the surface charge of passive film. The effects of Sc on pitting potential and pHpzc of Al oxide are predicted based on the calculated results, which are supported by electrochemical measurement, XPS analysis and contact angle titration.
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| 6. |
- Chen, Dihao, et al.
(författare)
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Development of the General Methodology for Determining the Point of Zero Charge of Oxide Films by Contact Angle Titration
- 2023
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 170:8
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Tidskriftsartikel (refereegranskat)abstract
- The point of zero charge (pH(pzc)) is one of the most important properties in determining the nature of the surface charge on oxide films in contact with aqueous solutions. Contact angle titration is a simple, rapid and direct surface titration approach to determine the pH(pzc) of oxide films, compared with mass titration, potentiometric titration and batch equilibration method. Although contact angle titration has been an effective method to estimate the pH(pzc) in the past, there are some limitations in previous methodologies for the correlation between the contact angle and the surface charge density, due to the consideration of only the negative charged OH- at surface or the absence of a vital part of solution potential for the electrochemical potential of H+ in electrolyte. Based on the work of many previous contributors, two general thermodynamic methods for determining the pHpzc of oxide films by contact angle titration are developed here. The methods provide precise, fundamental understandings of the variation of the contact angle with surface charge density, which is of great significance for interfacial science.
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| 7. |
- Chen, Sulin, et al.
(författare)
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Mussel-Inspired Graphene Film with Enhanced Durability as a Macroscale Solid Lubricant
- 2019
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Ingår i: ACS Applied Materials and Interfaces. - : AMER CHEMICAL SOC. - 1944-8244 .- 1944-8252. ; 11:34, s. 31386-31392
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Tidskriftsartikel (refereegranskat)abstract
- Graphene has exhibited massive potential as a macroscale solid lubricant, but its durability is limited due to the weak adhesion between graphene sheets and the substrate. Here, inspired by mussel adhesive protein (MAP), effective reinforcement of the graphene-substrate interaction to attain remarkable enhancement on the durability of the graphene film is presented. The mussel-inspired graphene (mGr) film exhibits a coefficient of friction stabilizing at 0.16 up to 490000 sliding cycles in the friction testing against the silicon nitride ball; in the identical sliding condition, comparatively, the graphene (Gr) film without MAP only lasts 4300 sliding cycles. The analysis of Raman and ATR-FTIR demonstrates that, on the one hand, the MAP film firmly adsorbs onto the substrate via forming metal-catechol coordination bonds with metal atoms; on the other hand, it establishes strong interactions with graphene sheets by hydrogen bonding as well as the pi-pi overlap. As an interlayer, MAP retains graphene sheets within the contact interface in the form of a compact tribo-layer, which results in an over 2 orders of magnitude enhancement of durability for the mGr film. This strategy of improving the graphene-substrate adhesion via MAP offers an avenue for the development of effective and reliable graphene-based solid lubricants for engineering applications.
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| 8. |
- Cheng, Jie, et al.
(författare)
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Corrosion- and wear-resistant composite film of graphene and mussel adhesive proteins on carbon steel
- 2020
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Ingår i: Corrosion Science. - : Elsevier. - 0010-938X .- 1879-0496. ; 164
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Tidskriftsartikel (refereegranskat)abstract
- A new strategy was proposed to prepare a composite film using mussel adhesive protein Mefp-1 and graphene to achieve corrosion protection and surface lubrication on carbon steel. The dispersibility of graphene in Mefp-1 solution was firstly investigated and deposition methods of Mefp-1/graphene film were proposed. In-situ confocal Raman micro-spectroscopy and electrochemical impedance spectroscopy measurements were utilized to study the corrosion inhibition effect in NaCl solution. Friction tests were conducted to study the tribological properties. Results show that the Mefp-1/graphene film exhibits strong adhesion to carbon steel, provides improved corrosion- and wear-resistance, and a significantly increased lubricity on carbon steel.
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| 9. |
- Cheng, Jie, et al.
(författare)
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Interactions in Composite Film Formation of Mefp-1/graphene on Carbon Steel
- 2021
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Ingår i: Coatings. - : MDPI AG. - 2079-6412. ; 11:10
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Tidskriftsartikel (refereegranskat)abstract
- Mefp-1 adhesive protein derived from marine blue mussels, together with the 2D material graphene, was used to build the green composite film with enhanced anti-corrosion property and mechanical strength. The corrosion inhibition of the composite film, formed by different methods, was evaluated by using electrochemical impedance spectroscopy. The non-degraded adhesion of the composite film to the carbon steel substrate was proved by nano-scratch tests. Infrared spectroscopy was utilized to investigate the film formation process and "three-body interactions " between Mefp-1, graphene and carbon steel surface. The results show that the Mefp-1 adsorbs on the carbon steel surface mainly through the covalent bond between catechols and Fe(III). Meanwhile, Mefp-1 can bond to non-adhesive graphene by forming hydrogen bonds and pi-pi interaction non-covalent bonds, which facilitate the formation of a robust Mefp-1/graphene composite film on the carbon steel surface.
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| 10. |
- Eidhagen, Josefin, et al.
(författare)
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Synchrotron XPS and Electrochemical Study of Aging Effect on Passive Film of Ni Alloys
- 2023
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 170:2, s. 021506-
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Tidskriftsartikel (refereegranskat)abstract
- To investigate aging effect on the passive film of Ni23Cr15Mo and Ni22Cr9Mo3Nb, synchrotron-based X-ray photoelectron spectroscopy (XPS) was used to analyze the structure and composition of the air-formed passive film on the alloys. The corrosion resistance of the two Ni alloys in 1 M NaCl solution was evaluated with electrochemical cyclic polarization measurement. The synchrotron XPS measurement provided detailed information about chemical states of alloying elements in the passive film, showing that the passive film consists of an inner oxide layer and an outer hydroxide layer. The XPS data allowed precise determination of the chemical composition and the thickness of the outer hydroxide layer, the inner oxide layer, and the underlying subsurface alloy layer. The Cr-oxide in the inner layer grows thicker with aging time, leading to Cr-depletion in the subsurface region. Mo and Nb in the alloy form mixed oxides and hydroxides, and aging in air leads to transformation of the lower valence oxides into higher valence oxides. The freshly formed oxide film exhibits similar barrier properties as the aged oxide film. The stability of the passive film formed on Ni22Cr9Mo3Nb seems to be better than that on Ni23Cr15Mo.
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| 11. |
- Grespi, A., et al.
(författare)
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Probing the electrode-liquid interface using operando total-reflection X-ray absorption spectroscopy
- 2024
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Ingår i: Surface Science. - : Elsevier B.V.. - 0039-6028 .- 1879-2758. ; 748
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Tidskriftsartikel (refereegranskat)abstract
- Traditional methods to study electrochemical (EC) processes, although successful, are based on current/voltage measurements, providing information about performances rather than offering a direct observation of chemical and structural changes occurring at the electrode surface. These processes are localized at the electrode-electrolyte interface, the structure of which is the main determinant of their behavior, but most surface sensitive experimental techniques are limited to ex situ conditions, owing to the need for an ultra-high vacuum environment. In this contribution, we report operando X-ray absorption spectroscopy in total external reflection geometry (Refle-XAFS) at P64 beamline (DESY, Hamburg), using a simple and versatile EC flow cell designed for multimodal surface sensitive studies with hard X-ray scattering and spectroscopy techniques. We show that the Refle-XAFS method can be used to study chemical surface changes of industrial alloys and model electrodes in harsh electrochemical environments, without being limited to thin film samples. The surface passive film development and breakdown of a corrosion-resistant Ni-Cr-Mo alloy and the electro-oxidation of polycrystalline gold (poly-Au), relevant for fundamental studies on water electrolysis, were investigated. Despite the strong attenuation of the beam by the electrolyte and the PEEK walls of the EC cell, nanoscale surface oxide films were detected using beam energies down to 8 keV. The passivity breakdown region of Ni alloy 59 in 1 M NaCl at pH 7 and pH 12 was identified, showing differences in the composition of the surface oxides during anodic polarization. The electro-oxidation of poly-Au in 0.05 M H2SO4 was observed, showing a progression from two-dimensional Au1+/3+ to three-dimensional thick Au3+ surface oxide/hydroxide during OER.
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| 12. |
- He, Yunjuan, et al.
(författare)
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Comparative study of CNC and CNF as additives in waterborne acrylate-based anti-corrosion coatings
- 2020
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Ingår i: Journal of Dispersion Science and Technology. - : Taylor & Francis. - 0193-2691 .- 1532-2351. ; 41:13, s. 2037-2047
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Tidskriftsartikel (refereegranskat)abstract
- Nanocomposite coatings are of great interest as barrier coatings since synergy effects between matrix and additive properties can be achieved. This, however, requires favorable additive-matrix interactions to provide a strong interphase (interface region). In this work we elucidate the properties of two environmentally benign nanocomposite coatings based on a waterborne acrylate formulation with additives from renewable sources, i.e. either cellulose nanocrystals, CNC; or, alternatively, cellulose nanofibrils, CNF. We focus on the corrosion protective properties of these coatings and discuss the reason why the nanocomposite with CNC displays favorable corrosion protection properties whereas that with CNF does not. To this end we utilized scanning electron microscopy, water contact angle measurement, Fourier transform infrared spectroscopy and electrochemical impedance spectroscopy techniques to investigate the microstructure, surface wetting, interactions between cellulosic materials and matrix as well as corrosion protective properties of both composite coatings.
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| 13. |
- He, Yunjuan, 1987-, et al.
(författare)
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Corrosion protective properties of cellulose nanocrystals reinforced waterborne acrylate-based composite coating
- 2019
-
Ingår i: Corrosion Science. - : Elsevier Ltd. - 0010-938X .- 1879-0496. ; 155, s. 186-194
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Tidskriftsartikel (refereegranskat)abstract
- The present investigation highlights corrosion protection of carbon steel by a waterborne acrylate-based matrix coating, with and without reinforcement by cellulose nanocrystals, by using electrochemical impedance spectroscopy in 0.1 M NaCl solution over a period of 35 days. Interactions between cellulose nanocrystals and the matrix coating were demonstrated by Fourier transform infrared spectroscopy. The results show that both coatings have high barrier performance but different protective characteristics during long-term exposure. The differences can be attributed to the reinforcement effect of cellulose nanocrystals caused by hydrogen bonding interactions between cellulose nanocrystals and the matrix coating.
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| 14. |
- He, Yunjuan, et al.
(författare)
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Nano-scale mechanical and wear properties of a waterborne hydroxyacrylic-melamine anti-corrosion coating
- 2018
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Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 457, s. 548-558
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Tidskriftsartikel (refereegranskat)abstract
- Corrosion protection is commonly achieved by applying a thin polymer coating on the metal surface. Many studies have been devoted to local events occurring at the metal surface leading to local or general corrosion. In contrast, changes occurring in the organic coating after exposure to corrosive conditions are much less studied. In this article we outline how changes in the coating itself due to curing conditions, environmental and erosion effects can be investigated at the nanometer scale, and discuss how such changes would affect its corrosion protection performance. We focus on a waterborne hydroxyacrylic-melamine coating, showing high corrosion protection performance for carbon steel during long-term (≈35 days) exposure to 0.1 M NaCl solution. The effect of curing time on the conversion of the crosslinking reaction within the coating was evaluated by fourier transform infrared spectroscopy (FTIR); the wetting properties of the cured films were investigated by contact angle measurement, and the corrosion resistance was studied by electrochemical impedance spectroscopy (EIS). In particular, coating nanomechanical and wear properties before and after exposure to 0.1 M NaCl, were evaluated by atomic force microscopy (AFM). Fiber-like surface features were observed after exposure, which are suggested to arise due to diffusion of monomers or low molecular weight polymers to the surface. This may give rise to local weakening of the coating, leading to local corrosion after even longer exposure times. We also find a direct correlation between the stick-slip spacing during shearing and plastic deformation induced in the surface layer, giving rise to topographical ripple structures on the nanometer length scale.
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| 15. |
- Hou, R. -Q, et al.
(författare)
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Corrosion inhibition of pre-formed mussel adhesive protein (Mefp-1) film to magnesium alloy
- 2020
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Ingår i: Corrosion Science. - : Elsevier Ltd. - 0010-938X .- 1879-0496. ; 164
-
Tidskriftsartikel (refereegranskat)abstract
- A range of ex situ and in situ analytical techniques were applied to gain insights into the formation and properties of the pre-formed Mefp-1 film on magnesium-1.0 wt.% calcium (Mg-1.0Ca) alloy. The results revealed that the Mefp-1 film pre-formed at pH 4.6 shows a net-like structure, whereas it is more packed at pH 8.5. in situ scanning micro-reference electrode technique results demonstrated the Mefp-1 films formed at both pH can effectively inhibit the localised corrosion of Mg-1.0Ca alloy. Moreover, the film pre-formed at pH 4.6 provides an increasing corrosion inhibition to Mg-1.0Ca alloy during 7 days of exposure.
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| 16. |
- Jin, Ying, et al.
(författare)
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First-Principle Calculation of Volta Potential of Intermetallic Particles in Aluminum Alloys and Practical Implications
- 2017
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Ingår i: Journal of the Electrochemical Society. - : Electrochemical Society. - 0013-4651 .- 1945-7111. ; 164:9, s. C465-C473
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Tidskriftsartikel (refereegranskat)abstract
- This work presents a theoretical assessment of galvanic (relative) nobility of four intermetallic particles (IMPs), Al2Cu, Al2CuMg, Mg2Si andMgZn(2), in aluminum alloys through work function calculation based on density functional theory (DFT). The concepts of work function, Volta potential and relative nobility are discussed with respect to the IMPs and aluminum matrix. The calculated Volta potentials are compared with reported experimental Volta potentials measured by scanning Kelvin probe forcemicroscopy (SKPFM). Various crystal faces and terminal types are examined in the DFT calculation, showing that these two factors have a significant effect on the work function value. Considering the large divergence in the reported experimental data, the comparison shows a general agreement between the calculated and experimental Volta potential data for the investigated IMPs. The DFT calculations provide theoretical explanations for several experimental phenomena. The results demonstrate that DFT calculation is a valuable theoretical approach for assessment of the relative nobility of different phases in the alloys, providing complementary information to experimental data from SKFPM. Moreover, the implications of the calculated Volta potentials are discussed with respect to the corrosion potentials.
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| 17. |
- Kharitonov, Dmitry S., et al.
(författare)
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Corrosion inhibition of aluminium alloy AA6063-T5 by vanadates : Local surface chemical events elucidated by confocal Raman micro-spectroscopy
- 2019
-
Ingår i: Corrosion Science. - : Elsevier BV. - 0010-938X .- 1879-0496. ; 148, s. 237-250
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Tidskriftsartikel (refereegranskat)abstract
- Chemical interactions between aqueous vanadium species and aluminium alloy AA6063-T5 were investigated in vanadate-containing NaCl solutions. Confocal Raman and X-ray photoelectron spectroscopy experiments were utilised to gain insight into the mechanism of corrosion inhibition by vanadates. A greenish-grey coloured surface layer, consisting of V+4 and V+5 polymerized species, was seen to form on the alloy surface, especially on top of cathodic micrometre-sized IMPs, whereby suppressing oxygen reduction kinetics. The results suggest a two-step mechanism of corrosion inhibition in which V+5 species are first reduced to V+4 or V+3 species above cathodic IMPs, and then oxidized to mixed-valence V+5/V+4 polymerized compounds.
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| 18. |
- Kharitonov, Dmitry S., et al.
(författare)
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Corrosion Inhibition of Aluminum Alloy AA6063-T5 by Vanadates: Microstructure Characterization and Corrosion Analysis
- 2018
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Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 5:3, s. C116-C126
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Tidskriftsartikel (refereegranskat)abstract
- Corrosion inhibition of aluminum alloy AA6063-T5 by vanadates (NaVO3) in 0.05 M NaCl solution has been investigated by electrochemical and weight loss measurements, and associated with microstructure and Volta potential data. X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy analyses confirmed the presence of micrometer-sized Fe-rich Al4.01MnSi0.74, Al1.69Mg4Zn2.31, and FeAl3intermetallic phases (IMPs) and nanometer-sized CuAl2, ZnAl2, and Mg2Si precipitates in the microstructure. Scanning Kelvin probe force microscopy measurements showed Volta potential differences of up to 600 mV between the microstructure constituents indicating a high susceptibility to micro-galvanic corrosion, with interphase boundary regions exhibiting the highest propensity to corrosion. Most IMPs had cathodic character whereas some nanometer-sized Mg-rich particles exhibited anodic nature, with large Volta potential gradients within interphase regions of large cathodic particles. Electrochemical potentiodynamic polarization measurements indicated that the vanadates provided mixed corrosion inhibition effects, mitigating both oxygen reduction, occurring on cathodic IMPs, and anodic metal dissolution reaction, occurring on anodic sites, such as Mg2Si and interphase boundary regions. Electrochemical measurements indicated that the sodium metavanadate inhibitor blocks active metal dissolution, giving high inhibition efficiency (>95%) during the initial exposure, whereas long-term weight loss measurements showed that the efficacy decreases after prolonged exposure.
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| 19. |
- Larsson, Alfred, et al.
(författare)
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Dynamics of early-stage oxide formation on a Ni-Cr-Mo alloy
- 2024
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Ingår i: NPJ MATERIALS DEGRADATION. - : Springer Nature. - 2397-2106. ; 8:1
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Tidskriftsartikel (refereegranskat)abstract
- Corrosion results in large costs and environmental impact but can be controlled by thin oxide films that passivate the metal surfaces and hinder further oxidation or dissolution in an aqueous environment. The structure, chemistry, and thickness of these oxide films play a significant role in determining their anti-corrosion properties and the early-stage oxidation dynamics affect the properties of the developed oxide. Here, we use in situ X-ray Photoelectron Spectroscopy (XPS) to study the early-stage oxidation of a Ni-Cr-Mo alloy at room temperature and up to 400 degrees C. Cr and Mo begin to oxidize immediately after exposure to O2, and Cr3+, Mo4+, and Mo6+ oxides are formed. In contrast, Ni does not contribute significantly to the oxide film. A self-limiting oxide thickness, which did not depend on temperature below 400 degrees C, is observed. This is attributed to the consumption of available Cr and Mo near the surface, which results in an enrichment of metallic Ni under the oxide. The self-limited oxide thickness is 6-8 angstrom, which corresponds to 3-4 atomic layers of cations in the oxide. At 400 degrees C, sublimation of Mo6+ oxide is observed, resulting in the formation of an almost pure layer of Cr2O3 on the alloy surface. Lastly, a mechanism is presented that explains the formation of the bi-layer oxide structure observed for Ni-Cr-Mo alloys, which involves the enhanced migration of hexavalent Mo ions in the electric field, which drives mass transport during oxidation according to both the Cabrera Mott model and the Point Defect Model.
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| 20. |
- Larsson, Alfred, et al.
(författare)
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In situ quantitative analysis of electrochemical oxide film development on metal surfaces using ambient pressure X-ray photoelectron spectroscopy : Industrial alloys
- 2023
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Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 611
-
Tidskriftsartikel (refereegranskat)abstract
- Ambient Pressure X-ray Photoelectron Spectroscopy combined with an electrochemical setup is used to study, in situ, the electrochemical oxide growth on an in-dustrial Ni-Cr-Mo alloy. The native oxide film was characterized in vacuum and in water vapor at 17 mbar, and was found to be 11.4 & ANGS; thick and rich in Cr3+. In 0.1 M NaCl electrolyte, anodic growth of the oxide film at potentials up to 700 mV vs Ag/AgCl nearly doubled the thickness of the oxide film. Moreover, a transformation of the oxide composition occurred, as the oxide became enriched in Mo6+ with a chemical fingerprint more like that of pure MoO3. Both thermodynamics and kinetics of the oxidation of the alloying elements dictate the oxide film growth and composition. Furthermore, we develop the quantitative analysis of oxide composition and thickness to take into account the attenuation through the liquid water and the water vapor atmosphere. Finally, we discuss the differences between ex situ, UHV, in situ, and operando measurements. Our approach is robust, fast, simple, and suitable for systematically probing metal surfaces after aqueous exposure and electro-chemical polarization, which promises wide applications for studies of solid-liquid interfaces in corrosion, batteries, fuel cells, and electrocatalysis.
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| 21. |
- Larsson, Alfred, et al.
(författare)
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Operando Surface Optical Reflectance Microscopy Study of Corrosion Film Growth on a Ni-Cr-Mo Alloy During Anodic Polarization
- 2023
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 127:44, s. 21871-21877
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Tidskriftsartikel (refereegranskat)abstract
- The solid-liquid interface, where corrosion reactions occur, is notoriously difficult to study in operando conditions. Few experimental techniques can provide surface sensitivity and spatial and temporal resolution and are compatible with liquid environments. 2-Dimensional surface optical reflectance (2D-SOR) is an emerging optical technique providing microscopic information with high temporal resolution. It complements methods such as ambient pressure X-ray photoelectron spectroscopy or inductively coupled plasma-mass spectrometry, which provides valuable chemical information from the surface and the dissolving species but lacks spatial resolution. Here, we show how 2D-SOR can be used to measure the formation and growth of corrosion products in operando through oscillations in the reflected signal caused by constructive and destructive interference of the light in the film of growing corrosion products. The total thickness of the corrosion product film obtained with 2D-SOR agrees well with that measured using scanning electron microscopy ex situ. 2D-SOR has proved to be an excellent and valuable tool for monitoring the corrosion process with spatial resolution in operating conditions.
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| 22. |
- Larsson, Alfred, et al.
(författare)
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The Oxygen Evolution Reaction Drives Passivity Breakdown for Ni–Cr–Mo Alloys
- 2023
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Ingår i: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 35:39
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Tidskriftsartikel (refereegranskat)abstract
- Corrosion is the main factor limiting the lifetime of metallic materials, and a fundamental understanding of the governing mechanism and surface processes is difficult to achieve since the thin oxide films at the metal–liquid interface governing passivity are notoriously challenging to study. In this work, a combination of synchrotron-based techniques and electrochemical methods is used to investigate the passive film breakdown of a Ni–Cr–Mo alloy, which is used in many industrial applications. This alloy is found to be active toward oxygen evolution reaction (OER), and the OER onset coincides with the loss of passivity and severe metal dissolution. The OER mechanism involves the oxidation of Mo4+ sites in the oxide film to Mo6+ that can be dissolved, which results in passivity breakdown. This is fundamentally different from typical transpassive breakdown of Cr-containing alloys where Cr6+ is postulated to be dissolved at high anodic potentials, which is not observed here. At high current densities, OER also leads to acidification of the solution near the surface, further triggering metal dissolution. The OER plays an important role in the mechanism of passivity breakdown of Ni–Cr–Mo alloys due to their catalytic activity, and this effect needs to be considered when studying the corrosion of catalytically active alloys.
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| 23. |
- Larsson, Alfred, et al.
(författare)
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Thickness and composition of native oxides and near-surface regions of Ni superalloys
- 2022
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Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 895
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Tidskriftsartikel (refereegranskat)abstract
- The surface chemistry and thickness of the native oxide, hydroxide, and modified sub-surface layer of three Ni superalloys (alloy 59, 625, and 718) were determined by synchrotron X-ray Photoelectron Spectroscopy (XPS) and X-ray Reflectivity (XRR). Taking advantage of the synchrotron radiation techniques, a procedure for normalizing the photoelectron intensity was employed, which allowed for accurate quantitative analysis revealing a total oxide thickness for all samples of 12-13 A, a hydroxide layer of 2-3 A, and a thickness of the sub-surface alloy layer of 20-35 A. The thickness results were compared to structural atomic models suggesting that the oxide thickness corresponds to four planes of metal cations in the oxide matrix. The XPS data revealed that the native oxides were enriched in Cr3+, Mo-(4,Mo-5,Mo-6)+, and Nb5+, while no Ni oxide was detected. The hydroxide layer mainly contained Ni2+ and Cr3+ hydroxide. The sub-surface layer was enriched in Ni and depleted in Cr, Fe, Mo, and Nb. The obtained oxide composition can be explained using thermodynamics, and it was found that the oxide composition correlates with the enthalpy of oxide formation for the metal elements in the alloys. Finally, the advantages of synchrotron radiation for composition and thickness determination are discussed.
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| 24. |
- Li, Jing, et al.
(författare)
-
Probing electrochemical mechanism of polyaniline and CeO 2 nanoparticles in alkyd coating with in-situ electrochemical-AFM and IRAS
- 2019
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Ingår i: Progress in organic coatings. - : Elsevier B.V.. - 0300-9440 .- 1873-331X. ; 132, s. 399-408
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Tidskriftsartikel (refereegranskat)abstract
- The corrosion protection and electrochemical mechanism of solvent-borne alkyd composite coating containing 1.0 wt.% polyaniline (PANI) and 1.0 wt.% CeO 2 nanoparticles (NPs) for carbon steel in 3.0 wt.% NaCl solution were investigated by means of scanning electron microscopy (SEM), ex-situ, in-situ and electrochemical controlled (EC) atomic force microscopy (AFM), open circuit potential (OCP) and electrochemical impedance spectroscopy (EIS) methods. The SEM and ex-situ AFM results revealed the micro- and nanostructure of the composite coating. The in-situ sequential AFM images and line profiling analysis indicated electrochemical activity of the NPs and a high stability of the composite coating in NaCl solution. The results of EC-AFM combined with cyclic voltammetry (CV) demonstrated volume change of the PANI NPs upon reduction and oxidation at certain applied potentials on the coating. The redox reactions between the different forms of PANI and the effect of the CeO 2 NPs on the polymerization of the composite polymer were further confirmed by infrared reflection absorption spectroscopy (IRAS). The OCP and EIS results revealed that the composite coating provided an improved corrosion protection for carbon steel within several days of exposure, which was attributed to the barrier protection of CeO 2 NPs and the passivation ability of PANI.
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| 25. |
- Li, Wenchao, et al.
(författare)
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Numerical simulation of carbon steel atmospheric corrosion under varying electrolyte-film thickness and corrosion product porosity
- 2023
-
Ingår i: NPJ MATERIALS DEGRADATION. - : Springer Nature. - 2397-2106. ; 7:1
-
Tidskriftsartikel (refereegranskat)abstract
- A finite element model is developed to study dynamics of atmospheric corrosion of carbon steel, focusing on the influence of thin electrolyte film thickness under varying corrosion product porosity. Calculations have been done to evaluate the impact of electrolyte film thickness and corrosion product porosity on oxygen diffusion path, and the hindrance effect of corrosion products on the metal surface activity. The time evolution of corrosion current density and controlling steps in the corrosion process are explored. When the corrosion products are loose, oxygen diffusion is the dominant controlling step, and the thicker the electrolyte film, the lower the corrosion rate. When they are dense, the corrosion process is controlled by the mixture of oxygen diffusion and the surface discharge. The oxygen diffusion path is determined only by the corrosion product porosity, and therefore the corrosion rate is not affected by the electrolyte film thickness.
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| 26. |
- Li, Yuchen, et al.
(författare)
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Fabricating an anti-corrosion carbonate coating on Mg-Li alloy by low-temperature plasma
- 2022
-
Ingår i: Surface & Coatings Technology. - : Elsevier BV. - 0257-8972 .- 1879-3347. ; 439
-
Tidskriftsartikel (refereegranskat)abstract
- Despite the huge demand for ultra-light magnesium-lithium (Mg-Li) alloys, practical applications of Mg-Li alloys are still severely restricted due to their poor corrosion resistance. Here, we report a new method utilizing low-temperature plasma to grow an oxide layer on the Mg-Li alloys in atmospheric condition, which reacts with CO2 and water in the air and consequently transform into a protective coating. The prepared coating has a layered structure consisting of a Mg(OH)(2) inner layer and a Li2CO3 outer layer. The composition distribution can be attributed to the different migration rates between Li+ and Mg2+ during coating formation. The Li2CO3 outer layer is sufficiently compact and very stable, with an ultra-low solubility in water, explaining the superior corrosion resistance of the coating in 3.5% NaCl solution. This simple and eco-friendly surface treatment provides a novel way of fabricating protective coatings on Mg-Li alloys.
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| 27. |
- Liew, YanHam, et al.
(författare)
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In-situ time-lapse SKPFM investigation of sensitized AA5083 aluminum alloy to understand localized corrosion
- 2020
-
Ingår i: Journal of the Electrochemical Society. - : IOP Publishing Ltd. - 0013-4651 .- 1945-7111. ; 167:14
-
Tidskriftsartikel (refereegranskat)abstract
- Sensitized AA5083-H2 aluminum alloy was exposed to chloride-laden thin-film electrolyte at ambient temperature (20%–85% relative humidity) and the local Volta potential measured, in-situ and in real-time, using the Scanning Kelvin Probe Force Microscopy, with the intention to elucidate the earliest stage of localized corrosion. Positive Volta potentials vs alloy matrix were measured for magnesium silicides in ambient air, which, however, underwent a severe nobility loss during corrosion, causing their nobility to invert to active potentials (negative) relative to the alloy matrix. The reason for the nobility inversion was explained by the preferential dissolution of Mg2+, which resulted in an electropositive surface. Aluminides, both with and without silicon, were seen to form the main cathodes at all exposure conditions. The local alloy matrix next to closely-separated aluminides were seen to adopt the Volta potential of the neighbor aluminides, which, hence, resulted in local corrosion protection. The phenomenon of nobility adoption introduced in this work raises questions regarding the anode-to-cathode ratio, which was observed to change during corrosion, and the resulting impact to localized micro-galvanic corrosion. This work further demonstrates that it is necessary to measure the Volta potential during corrosion to reflect the true relationship between the Volta potential and corrosion potential or breakdown potential. © 2020 The Author(s).
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| 28. |
- Liew, YanHan, et al.
(författare)
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Towards understanding micro-galvanic activities in localised corrosion of AA2099 aluminium alloy
- 2021
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Ingår i: Electrochimica Acta. - : Elsevier Ltd. - 0013-4686 .- 1873-3859. ; 392
-
Tidskriftsartikel (refereegranskat)abstract
- The micro-galvanic interactions between Cu-Fe-Mn-Li-containing aluminides and the alloy matrix of aluminium alloy AA2099 during chloride-induced corrosion were investigated in-situ with real-time monitoring of the local contact potential difference (VCPD) using the scanning Kelvin probe force microscopy (SKPFM) at controlled relative humidities. The aluminides showed noble potentials and were able to ennoble their neighbouring matrix sites when a cluster of aluminides surrounded the matrix. The matrix, hence, adopted a more positive VCPD, towards that of the aluminides. The anode-to-cathode ratio changed throughout the corrosion exposure and was seen to show a dynamic character. Much higher local VCPD activities were recorded during the earliest stages of corrosion, when the Al-Li AA2099 surface was first exposed to high humidities, than in later RH cycles; a phenomenon not seen in other aluminium alloys.
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| 29. |
- Liu, Min, et al.
(författare)
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A DFT-Study of Cl Ingress into α-Al2O3(0001) and Al(111) and Its Possible Influence on Localized Corrosion of Al
- 2019
-
Ingår i: Journal of the Electrochemical Society. - : Electrochemical Society. - 0013-4651 .- 1945-7111. ; 166:11, s. C3124-C3130
-
Tidskriftsartikel (refereegranskat)abstract
- Ingress of chloride into alpha-Al2O3(0001) and Al(111) was calculated by first-principles theory calculations by considering Cl insertion into Al or O vacancies within alpha-Al2O3(0001) or into vacancy or interstitial sites within Al(111). For alpha-Al2O3, the formation of an O vacancy is energetically more favorable than of an Al vacancy. The insertion of Cl into an O vacancy is also more favorable than into an Al vacancy. A high energy-barrier has been derived for Cl transport within the neighboring O vacancies. In addition, the work function decreases with Cl ingress into the interior of the oxide. For Al(111), Cl insertion into either an Al vacancy or an interstitial site is less favorable compared to the insertion into alpha-Al2O3. The work function only changes slightly with Cl insertion into an Al vacancy. Moreover, the pre-inserted Cl reduces the energy-barrier for further Cl ingress into alpha-Al2O3, whereas Cl tends to stay in the sub-surface layer of Al(111), suggesting Cl accumulation at the Al2O3/Al.
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| 30. |
- Liu, Min, et al.
(författare)
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Co-adsorption of H2O, OH, and Cl on aluminum and intermetallic surfaces and its effects on the work function studied by DFT calculations
- 2019
-
Ingår i: Molecules. - : MDPI. - 1431-5157 .- 1420-3049. ; 24:23
-
Tidskriftsartikel (refereegranskat)abstract
- The energetics of adsorption of H2O layers and H2O layers partially replaced with OH or Cl on an Al(111) surface and on selected surfaces of intermetallic phases, Mg2Si and Al2Cu, was studied by first-principle calculations using the density function theory (DFT). The results show that H2O molecules tended to bind to all investigated surfaces with an adsorption energy in a relatively narrow range, between -0.8 eV and -0.5 eV, at increased water coverage. This can be explained by the dominant role of networks of hydrogen bonds at higher H2O coverage. On the basis of the work function, the calculated Volta potential data suggest that both intermetallic phases became less noble than Al(111); also, the Volta potential difference was larger than 1 V when the coverage of the Cl-containing ad-layer reached one monolayer. The energetics of H2O dissociation and substitution by Cl as well as the corresponding work function of each surface were also calculated. The increase in the work function of the Al(111) surface was attributed to the oxidation effect during H2O adsorption, whereas the decrease of the work function for the Mg2Si(111)-Si surface upon H2O adsorption was explained by atomic and electronic rearrangements in the presence of H2O and Cl.
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| 31. |
- Liu, Min, et al.
(författare)
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Density Functional Theory Study of Influence of Oxide Thickness and Surface Alloying on Cl Migration within alpha-Al2O3
- 2021
-
Ingår i: Journal of the Electrochemical Society. - : The Electrochemical Society. - 0013-4651 .- 1945-7111. ; 168:8
-
Tidskriftsartikel (refereegranskat)abstract
- Insertion and migration of chlorine atoms (Cl) in alpha-Al2O3 were studied by density functional theory calculations focusing on the influence of oxide thickness and doping by Mg, Cu and Si. Work function, electronic band gap, and insertion energy were calculated to explore thermodynamics of Cl migration. Partial density of state (PDOS) calculations revealed the role of dopants in the electronic character of metal-O and Al-Cl bonds. Work function data showed the effect of Cl insertion into the oxide film on the corrosion resistance. Cl can locate at an O vacancy (V-O) with a large exothermic insertion energy, independent of oxide thickness, but can only locate at superficial Al vacancy (V-Al) exothermically. The energy barrier for Cl migration via neighboring V-O increases with oxide thickness, and is 2 similar to 2.5 eV for thicker oxides. Cl insertion causes a work function reduction exceeding 2 eV, implying a decreased corrosion resistance. The inhibition of Cl migration by Si-doping can be explained by a more intense hybridization peak of Si-O over Al-O in the PDOS profile, while the reduction of energy barrier by Mg-/Cu-doping probably is due to the deviation of metal-s state from the Fermi energy, thus facilitating Cl movement within the oxide.
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| 32. |
- Liu, Min, et al.
(författare)
-
Density-functional theory study of point defect formation and diffusion in alpha-alumina and effects of applied strain and alloy doping
- 2023
-
Ingår i: Materials Today Communications. - : Elsevier BV. - 2352-4928. ; 34
-
Tidskriftsartikel (refereegranskat)abstract
- Oxidation of alumina-forming alloys and breakdown of a-Al2O3 are important processes for alloys used in hightemperature environments. By using density-functional theory simulations, we investigate the formation and diffusion of three common point defects. Influences of diffusion pathway, axial strain and alloy doping on defect energetics during its formation and diffusion are systematically investigated. Results indicate a positive correlation between the diffusion energy barrier and the pathway length. We highlighted that diffusion barrier of vacancy defects can be reduced to that of interstitial defects by applying tensile strain, indicating that the strain state can transform the diffusion mechanism within a-Al2O3 . Moreover, the alloying dopants (Cr, Mo, Cu, Si, Y, Zr) investigated here can be categorized as: inhibitive, promotive, and inert, depending on their roles in determining the diffusion barrier of oxygen vacancy, which is analyzed by the element-dependent substitution energies, atomic radius, electronegativity, volumetric change, and electronic transition.
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| 33. |
- Liu, Min
(författare)
-
DFT calculations of initial localized corrosion of aluminum : Influence of aqueous ad-layer, chloride ions, and intermetallic particles
- 2019
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Localized corrosion of aluminum (Al, here including Al alloys) involves a series of physico-chemical processes at the interface between the metal and the aqueous ad-layer or the aqueous solution. The mechanisms that govern localized corrosion are quite complex and have been the subject of many experimental studies. Efforts to improve our understanding through computational studies have so far been much more limited. The primary aim of this Doctoral Thesis was to apply Density Functional Theory (DFT), together with some Molecular Dynamics calculations (limited effort), to gain a deeper mechanistic understanding of some of the most influential factors for the initiation of localized corrosion of Al: chloride ions, intermetallic particles (IMPs) and the presence of an aqueous ad-layer on the solid phase.In the scientific literature three scenarios have been proposed for the interaction of chloride ions with an aluminum and/or passive aluminum surface: through adsorption onto the passive layer, through breakdown of the same layer or through migration of chloride ions into the layer. DFT-calculations have been able to explore these scenarios in more detail, and provide evidence that chloride ions induce partial de-passivation in several ways. On the bare Al surface, chloride ions may inhibit the re-passivation through competitive adsorption with oxygen molecules, as suggested by density of state calculations. Chloride ions are also found to migrate via oxygen vacancies into the inner part of the investigated aluminum oxide films (α- and γ-Al2O3), where a critical amount of accumulated chloride can promote meta-stable pitting propagation. γ-Al2O3 exhibits a more open structure than α-Al2O3, resulting in a lower energy barrier for chloride migration.Micro-galvanic effects induced by Volta potential differences between representative intermetallic particles (Mg2Si and Al2Cu) and the surrounding Al matrix were predicted by calculating the work function of the bare surfaces of these phases with DFT. These values vary with crystalline face orientation and with terminal atomic configuration in the outmost surface layer. Calculated Volta potential differences between IMPs and Al show a reasonable agreement with reported experimental data, and suggest the possibility of predicting the nobility of specific IMPs relative to Al. Moreover, both DFT and scanning Kelvin probe force microscopy show evidence of electrochemical nobility inversion of Mg2Si versus Al upon adsorption of pure water ad-layers. This implies that an originally- 2 -cathodic Mg2Si phase becomes anodic compared to Al upon water adsorption, and is attributed to surface relaxation according to DFT calculations. With subsequent introduction of chloride ions into the water ad-layer, the nobility inversion of both Mg2Si and Al2Cu retains. This is due to a strong oxidizing effect of water on Al, while the effect of chloride seems less pronounced.In all, these and other examples presented show that DFT-calculations can provide more detailed atomistic and molecular information on physico-chemical processes governing localized corrosion of Al than experiments alone can do.
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| 34. |
- Liu, Min, et al.
(författare)
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Relevance of implicit and explicit solvent in density-functional theory study of adsorption at electrochemical NaCl/Al interface
- 2022
-
Ingår i: Materials Today Communications. - : Elsevier BV. - 2352-4928. ; 31, s. 103425-
-
Tidskriftsartikel (refereegranskat)abstract
- The adsorption behavior of NaCl on Al(111) surface was studied by density functional theory (DFT) using implicit or explicit solvation models. Charge and total energy of adsorption systems indicate that the inclusion of an implicit solvent is necessary to construct a situation relevant to corrosion. Only certain configurations containing explicit water molecules with a direct NaCl interaction with Al are relevant to corrosion scenarios, attributed to a more predominant interaction of H2O-Al over NaCl-Al. Implicit and explicit solvent models yield consistent results, confirming that both solvent models can be used to study Cl- adsorption on Al within a corrosion regime.
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| 35. |
- Långberg, Marie, et al.
(författare)
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Characterization of Native Oxide and Passive Film on Austenite/Ferrite Phases of Duplex Stainless Steel Using Synchrotron HAXPEEM
- 2019
-
Ingår i: Journal of the Electrochemical Society. - : Electrochemical Society. - 0013-4651 .- 1945-7111. ; 166:11, s. C3336-C3340
-
Tidskriftsartikel (refereegranskat)abstract
- A new measurement protocol was used for microscopic chemical analysis of surface oxide films with lateral resolution of 1 mu m. The native air-formed oxide and an anodic passive film on austenite and ferrite phases of a 25Cr-7Ni super duplex stainless steel were investigated using synchrotron hard X-ray photoemission electron microscopy (HAXPEEM). Pre-deposited Pt-markers, in combination with electron backscattering diffraction mapping (EBSD), allowed analysis of the native oxide on individual grains of the two phases and the passive film formed on the same area after electrochemical polarization of the sample. The results showed a certain difference in the composition of the surface films between the two phases. For the grains with (001) crystallographic face // sample surface, the native oxide film on the ferrite contained more Cr oxide than the austenite. Anodic polarization up to 1000 mV/(Ag/AgCl) in 1M NaCl solution at room temperature resulted in a growth of the Cr- and Fe-oxides, diminish of Cr-hydroxide, and an increased proportion of Fe3+ species. by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited.
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| 36. |
- Långberg, Marie
(författare)
-
Passivity & Breakdown of Super Duplex Stainless Steel : Studied with Electrochemical & Synchrotron Techniques
- 2020
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Super duplex stainless steel consists of two phases: austenite and ferrite, and is a highly corrosion resistant material, with a wide range of applications. The corrosion resistance of stainless steels is determined by the performance of a spontaneously formed thin Cr oxide rich film with a thickness of 1-3 nm. This film makes the stainless steel passive towards further oxidation processes, corrosion. The passive film is a dynamic system where degradation and formation reactions occur simultaneously. Super duplex stainless steel is a multi-phase, multielement material which has a high corrosion resistance and the question is whether its microstructure and alloying elements are affecting its passive film properties. This thesis contains two parts: real time synchrotron measurements to study the degradation mechanism during anodic polarization which pushes the material toward oxidation processes; and ex-situ measurements to map the lateral thickness and microscopic elemental distribution in the passive film. The in-situ/operando synchrotron experiments combined several experimental techniques, including X-ray reflectivity (XRR), X-ray diffraction (XRD), X-ray fluorescence (XRF) and electrochemical impedance spectroscopy (EIS), to simultaneously characterize the structure and chemical/electrochemical properties, as well as their changes of the surface region of the samples. It was found that the oxide film became more defective with increasing potential, leading to a decreased density of the passive film. On the other hand, the Ni rich alloy surface layer below the oxide film showed an increasing density, indicating an increased concentration of heavy elements (Mo and Ni). The XRD data showed evidence of nanocrystalline passive film whereas the amorphousness of the passive film increased with increasing potential. The ex-situ investigations employed by hard X-ray photoelectron emission microscopy (HAXPEEM), providing chemical data from individual grains with different crystallographic orientations parallel to the sample plane. The Cr content was higher on the ferrite than the austenite, whereas the thickness was rather uniform. The grain orientation has a small but detectable influence on the thickness and Cr content of the native passive film.
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| 37. |
- Ni, Y., et al.
(författare)
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Corrosion mechanism of CuAl-NiC abradable seal coating system—The influence of porosity, multiphase, and multilayer structure on the corrosion failure
- 2021
-
Ingår i: Journal of Materials Science & Technology. - : Elsevier BV. - 1005-0302. ; 88, s. 258-269
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, the corrosion behavior of the CuAl-NiC abradable seal coating system in chloride solution was investigated to systematically research the effect of porosity, multiphase, and multilayer structure on the corrosion failure. Through the composition and structure analysis, the corrosion process of the system was predicted and then verified with mercury intrusion porosimetry, cross-section SEM/EDS analysis, and electrochemical measurements. The results demonstrated that the interphase selective corrosion caused the porosity of the top layer to decrease first and then increase during the corrosion development. The interlayer galvanic corrosion, determined by the pore connectivity, is crucial for corrosion failure.
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| 38. |
- Norlin, Anna, et al.
(författare)
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Fabrication of Porous Nb2O5 by Plasma Electrolysis Anodization and Electrochemical Characterization of the Oxide
- 2006
-
Ingår i: Journal of the Electrochemical Society. - : Electrochemical Society. - 0013-4651 .- 1945-7111. ; 153:7, s. B225-B230
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Tidskriftsartikel (refereegranskat)abstract
- Porous Nb2O5 electrodes were fabricated by applying anodic pulses of 700 V and 10 ms duration to pure Nb in phosphate bufferedsaline solution (PBS), aiming at biomaterial applications. The porosity of the oxide could be controlled by the number of pulses. X-ray photoelectron spectroscopy analysis confirmed the oxide to be Nb2O5. The electrochemical behavior and interfacial propertiesof the porous Nb2O5 were characterized in PBS by using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). EIS measurements indicate that the oxide film has a two-layer structure with a compact inner layer and a porousouter layer, and the pores were sealed by precipitates during long-time aging in PBS. The two-layer structure of the oxide film wasobserved by examination of the cross section using scanning electron microscopy in backscatter mode. The CV measurementsreveal that the oxide exhibits an electrochemical “rectifying” property. It is stable over a wide potential range but shows hydrogenuptake upon cathodic polarization below −1 V vs Ag/AgCl.
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| 39. |
- Oernek, Cem, et al.
(författare)
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Understanding passive film degradation and its effect on hydrogen embrittlement of super duplex stainless steel-Synchrotron X-ray and electrochemical measurements combined with CalPhaD and ab-initio computational studies
- 2023
-
Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 628
-
Tidskriftsartikel (refereegranskat)abstract
- The passive film stability on stainless steel can be affected by hydrogen absorption and lead to microstructure embrittlement. This work shows that the absorption of hydrogen results in surface degradation due to oxide reduction and ionic defect generation within the passive film, which decomposes and eventually vanishes. The passive film provides a barrier to entering hydrogen, but when hydrogen is formed, atomic hydrogen infuses into the lattices of the austenite and ferrite phases, causing strain evolution, as shown by synchrotron x-ray diffraction data. The vacancy concentration and hence the strains increase with increasing electrochemical cathodic po-larization. Under cathodic polarization, the surface oxides are thermodynamically unstable, but the complete reduction is kinetically restrained. As a result, surface oxides remain present under excessive cathodic polari-zation, contesting the classical assumption that oxides are easily removed. Density-functional theory calculations have shown that the degradation of the passive film is a reduction sequence of iron and chromium oxide, which causes thinning and change of the semiconductor properties of the passive film from n-type to p-type. As a result, the surface loses its passivity after long cathodic polarization and becomes only a weak barrier to hydrogen absorption and hence hydrogen embrittlement.
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| 40. |
- Ornek, Cem, et al.
(författare)
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Hydrogen-Induced Micro-Strain Evolution in Super Duplex Stainless Steel-Correlative High-Energy X-Ray Diffraction, Electron Backscattered Diffraction, and Digital Image Correlation
- 2022
-
Ingår i: FRONTIERS IN MATERIALS. - : Frontiers Media SA. - 2296-8016. ; 8
-
Tidskriftsartikel (refereegranskat)abstract
- The local lattice strain evolution during electrochemical hydrogen charging and mechanical loading in 25Cr-7Ni super duplex stainless steel were measured in-situ using synchrotron high-energy x-ray diffraction. Post-mortem electron backscattered diffraction analysis showed that the austenite phase underwent plastic deformation in the near-surface due to hydrogen-enhanced localized plasticity, where the ferrite phase experienced hardening. In bulk regions, the ferrite was the softer phase, and the austenite remained stiff. Digital image correlation of micrographs recorded, in-situ, during mechanical tensile testing revealed intensified plastic strain localization in the austenite phase, which eventually led to crack initiation. The absorption of hydrogen caused strain localization to occur primarily in austenite grains.
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| 41. |
- Ornek, Cem, et al.
(författare)
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The causation of hydrogen embrittlement of duplex stainless steel : Phase instability of the austenite phase and ductile-to-brittle transition of the ferrite phase-Synergy between experiments and modelling
- 2023
-
Ingår i: Corrosion Science. - : Elsevier BV. - 0010-938X .- 1879-0496. ; 217, s. 111140-
-
Tidskriftsartikel (refereegranskat)abstract
- Various mechanisms have been proposed for hydrogen embrittlement of duplex stainless steel, but the causation of hydrogen-induced material degradation has remained unclear. This work shows that phase instability (decomposition) of the austenite phase and ductile-to-brittle transition of the ferrite phase precedes hydrogen embrittlement. In-situ diffraction measurements revealed that Ni-rich sites of the austenite phase decompose into metastable hydrides. Hydride formation is possible by increasing the hydrogen chemical potential during electrochemical charging and low defect formation energy of hydrogen interstitials. Our findings demonstrate that hydrogen embrittlement can only be understood if measured in situ and in real-time during the embrittlement process.
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| 42. |
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| 43. |
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| 44. |
- Pan, Jinshan, 1962-
(författare)
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Studying the Passivity and Breakdown of Duplex Stainless Steels at Micrometer and Nanometer Scales - The Influence of Microstructure
- 2020
-
Ingår i: FRONTIERS IN MATERIALS. - : FRONTIERS MEDIA SA. - 2296-8016. ; 7
-
Forskningsöversikt (refereegranskat)abstract
- Duplex stainless steels (DSSs) consist of ferrite and austenite phases with approximately equal volume fraction. They exhibit combined superior mechanical strength and corrosion resistance, therefore are increasingly used in various applications. However, under certain conditions, passivity breakdown may occur, leading to corrosion initiation, which is often related to weak points in the heterogeneous microstructure. To understand the influence of microstructure on the passivity and breakdown of DSSs requires local probing techniques that can be used in situ, so that corrosion initiation process can be correlated to the microstructure. Recent studies employing advanced scanning probe microscopy and synchrotron-based techniques, in combination with electrochemical measurements, have contributed to a deep understanding of the passive film, passivity breakdown, and corrosion initiation of DSSs, as well as the influence of microstructural and environmental factors. This mini review presents a short summary of recent literature focusing on the studies utilizing local probing techniques and synchrotron-based analyses.
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| 45. |
- Pan, Jinshan, 1962-, et al.
(författare)
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Tafel slopes used in monitoring of copper corrosion in a bentonite/groundwater environment
- 2005
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Ingår i: Corrosion Science. - : Elsevier. - 0010-938X .- 1879-0496. ; 47:12, s. 3267-3279
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Tidskriftsartikel (refereegranskat)abstract
- The harmonic analysis, the polarization resistance, and the noise resistance methods have been applied in an effort to monitor corrosion of pure copper in a bentonite/groundwater environment with commercially available equipment. Without the need to use a reference electrode, the first method supplies not only an estimate of the corrosion rate, but also estimates of Tafel slopes required by the other methods. The recorded corrosion rate is overestimated but to a varying degree. While the recorded corrosion rates for the first two methods give quite similar values far below 3 lm/year, the electrochemical noise resistance method gives considerably higher values.
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| 46. |
- Ratia-Hanby, V., et al.
(författare)
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Characterization of surface films that develop on pre-oxidized copper in anoxic simulated groundwater with sulphide
- 2023
-
Ingår i: Colloids and Surfaces A. - : Elsevier BV. - 0927-7757 .- 1873-4359. ; 676
-
Tidskriftsartikel (refereegranskat)abstract
- Surface films formed on pre-oxidized copper in anoxic simulated groundwater with sulphide were characterized by field emission gun scanning electron microscopy (FEG-SEM), Fourier transform infrared spectroscopy (FT-IR), open circuit potential (OCP) measurements, and via analysing the water chemistry and weight changes in the specimens. Additionally, films developed under identical conditions on pre-oxidized and ground copper specimens were characterized by glow discharge optical emission spectroscopy (GDOES). The results revealed that the sulphide content in the groundwater significantly influences the morphology, composition and thickness of the surface film. The build-up of Cu2S was evidenced at the sulphide contents of 32 mg/L and 320 mg/L. GDOES depth profiling revealed that sulphur and oxygen coexisted in the film all through its thickness, yet the surface was essentially rich in sulphur. The results from characterization are presented in detail in this paper and discussed from the perspective of capabilities of the used methods.
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| 47. |
- Tang, Huajie, et al.
(författare)
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Electrochemical and localized corrosion behavior of 316 L SS/copper/316 L SS sandwich composite in chloride-containing environment
- 2022
-
Ingår i: Corrosion Science. - : Elsevier BV. - 0010-938X .- 1879-0496. ; 209, s. 110719-
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Tidskriftsartikel (refereegranskat)abstract
- Electrochemical and localized corrosion behavior of a 316 L SS/copper/316 L SS composite in 0.5 wt. % NaCl solution was investigated from cross-sectional and plane directions by electrochemical measurements and high -resolution microscopic examination. The galvanic coupling accelerated the dissolution at the internal surface and pitting attack at the external surface of the 316 L layer. Polarization up to 1 V/SCE resulted in formation of a corrosion product layer (ca. 992 nm) composed of metal oxides/hydroxides on top of the passive film, which consisted of a Fe2O3-rich outer layer (3.3 nm) and a Cr2O3-rich inner layer (4.1 nm). The copper corrosion was quite uniform.Data availability statement: The raw/processed data required to reproduce these findings cannot be shared at this time as the data also forms part of an ongoing study.
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| 48. |
- Wang, Di, et al.
(författare)
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A strong enhancement of corrosion and wear resistance of polyurethane-based coating by chemically grafting of organosolv lignin
- 2024
-
Ingår i: Materials Today Chemistry. - : Elsevier. - 2468-5194. ; 35
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Tidskriftsartikel (refereegranskat)abstract
- Corrosion and wear pose significant challenges to equipment operating in harsh environments. Thus, protective coatings are needed. Anti-corrosion and anti-wear coatings are traditionally fossil-based and often contain environmentally harmful additives. Achieving anti-corrosion and anti-wear coatings based on environmentally benign and sustainable materials is important and a significant challenge. This work focused on the development of organosolv lignin-based polyurethane (OS_lignin-PU) coatings. The coatings were synthesised and evaluated for corrosion protection using electrochemical impedance spectroscopy (EIS) and for wear properties using nanoindentation and nano scratch measurements. EIS revealed that the optimal lignin content for corrosion protection purposes in the OS_lignin-PU coatings was 15Â wt%. Moreover, addition of 15Â wt% lignin to the OS_lignin-PU coatings also enhanced their wear resistance, as evidenced by reduced thickness loss during tribometer tests. The nano scratch measurements revealed that OS_lignin-PU coatings containing 15Â wt% lignin exhibited the lowest scratch depth and friction coefficient. It is found that the developed lignin-containing coating exhibits remarkable corrosion and wear resistance, making it a promising sustainable material in various applications for pursuing sustainable development.
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| 49. |
- Wang, Di, et al.
(författare)
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Green synergy: Eco-friendly, high-performance anti-corrosion and wear-resistant coatings utilizing organosolv lignin and polydimethylsiloxane
- 2024
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Ingår i: Progress in organic coatings. - : Elsevier B.V.. - 0300-9440 .- 1873-331X. ; 190
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Tidskriftsartikel (refereegranskat)abstract
- Anti-corrosion and anti-wear coatings provide an effective solution. However, traditional coatings are often fossil-based and contain heavy metals, posing environmental concerns. The drive for eco-friendly coatings has led to the exploration of green materials. This study combined lignin, an abundant organic material, and polydimethylsiloxane (PDMS), a known hydrophobic material, to address the challenges. Organosolv lignin was functionalised with (3-Aminopropyl)triethoxysilane (APTES), then chemically grafted on PDMS for the final coating synthesis. The optimised coating achieved through an eco-friendly process, exhibiting enhanced hydrophobicity and barrier properties, showing excellent long-term corrosion resistance in NaCl solution. The optimal coating formulation contained 15 wt% lignin and 40 wt% PDMS, demonstrating a high corrosion resistance (measured impedance of 1010 Ω·cm2), which remains effective even after 3 weeks of immersion in 1 M NaCl solution. This coating also showed good wear resistance, with a low friction coefficient evident from nano scratch tests.
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| 50. |
- Wang, Di, et al.
(författare)
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In-situ coating wear condition monitoring based on solid-liquid triboelectric nanogenerator and its mechanism study
- 2023
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Ingår i: Nano Energy. - : Elsevier Ltd. - 2211-2855 .- 2211-3282. ; 112
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Tidskriftsartikel (refereegranskat)abstract
- Various more or less wear-resistant coatings have been developed and used to protect metal substrates. However, the damage caused by wear is still a problem for most coatings. It is of great importance to monitor the wear of coatings in real-time during the applications. Recently reported wear monitoring methods (image processing, luminescent layers and the use of a sensing underlayer) require complex external equipment or additional coating preparation process steps, which limit their applications. As an emerging technology, a triboelectric nanogenerator (TENG) can convert mechanical energy into electricity, and it has been applied as a self-powered sensor. In this study, a new coating wear monitoring method is developed based on a solid-liquid TENG. The developed TENG generates electric signals corresponding to different wear states, which facilitates easy monitoring of the coating’s wear conditions. The results show that the surface composition change caused by wear is the main reason affecting the TENG signal output. The coating-liquid contact-separation motion generates real-time output signals that directly reflect the coating wear states without the need of any additional equipment. This study provides a promising new technology for in-situ coating wear monitoring.
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