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Publications (10 of 124) Show all publications
Kharitonov, D. S., Sommertune, J., Örnek, C., Ryl, J., Kurilo, I. I., Claesson, P. M. & Pan, J. (2019). Corrosion inhibition of aluminium alloy AA6063-T5 by vanadates: Local surface chemical events elucidated by confocal Raman micro-spectroscopy. CORROSION SCIENCE, 148, 237-250
Open this publication in new window or tab >>Corrosion inhibition of aluminium alloy AA6063-T5 by vanadates: Local surface chemical events elucidated by confocal Raman micro-spectroscopy
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2019 (English)In: CORROSION SCIENCE, Vol. 148, p. 237-250Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2019
Keywords
Aluminium, Alloy, Raman spectroscopy, SEM, XPS, Vanadate inhibitor
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-244484 (URN)10.1016/j.corsci.2018.12.011 (DOI)000457950400023 ()2-s2.0-85059158841 (Scopus ID)
Note

QC 20190321

Available from: 2019-03-21 Created: 2019-03-21 Last updated: 2019-03-21Bibliographically approved
Anantha, K. H., Örnek, C., Ejnermark, S., Thuvander, A., Medvedeva, A., Sjostrom, J. & Pan, J. (2019). Experimental and modelling study of the effect of tempering on the susceptibility to environment-assisted cracking of AISI 420 martensitic stainless steel. Corrosion Science, 148, 83-93
Open this publication in new window or tab >>Experimental and modelling study of the effect of tempering on the susceptibility to environment-assisted cracking of AISI 420 martensitic stainless steel
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2019 (English)In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 148, p. 83-93Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2019
Keywords
Martensitic stainless steel, Residual stress, Tempering, Environment-assisted cracking, Pit-to-crack transition
National Category
Corrosion Engineering
Identifiers
urn:nbn:se:kth:diva-244485 (URN)10.1016/j.corsci.2018.12.010 (DOI)000457950400009 ()2-s2.0-85058373436 (Scopus ID)
Note

QC 20190321

Available from: 2019-03-21 Created: 2019-03-21 Last updated: 2019-03-21Bibliographically approved
Kharitonov, D. S., Örnek, C., Claesson, P. M., Sommertune, J., Zharskii, I. M., Kurilo, I. I. & Pan, J. (2018). Corrosion Inhibition of Aluminum Alloy AA6063-T5 by Vanadates: Microstructure Characterization and Corrosion Analysis. Journal of the Electrochemical Society, 165(3), C116-C126
Open this publication in new window or tab >>Corrosion Inhibition of Aluminum Alloy AA6063-T5 by Vanadates: Microstructure Characterization and Corrosion Analysis
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2018 (English)In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 165, no 3, p. C116-C126Article in journal (Refereed) Published
Abstract [en]

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 FeAl3 intermetallic 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.

Place, publisher, year, edition, pages
Electrochemical Society Inc, 2018
National Category
Corrosion Engineering
Identifiers
urn:nbn:se:kth:diva-230561 (URN)10.1149/2.0341803jes (DOI)000431790700049 ()2-s2.0-85044021625 (Scopus ID)
Note

QC 20180724

Available from: 2018-07-24 Created: 2018-07-24 Last updated: 2018-07-24Bibliographically approved
Örnek, C., Reccagni, P., Kivisakk, U., Bettini, E., Engelberg, D. L. & Pan, J. (2018). Hydrogen embrittlement of super duplex stainless steel - Towards understanding the effects of microstructure and strain. International journal of hydrogen energy, 43(27), 12543-12555
Open this publication in new window or tab >>Hydrogen embrittlement of super duplex stainless steel - Towards understanding the effects of microstructure and strain
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2018 (English)In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 43, no 27, p. 12543-12555Article in journal (Refereed) Published
Abstract [en]

The effects of austenite spacing, hydrogen charging, and applied tensile strain on the local Volta potential evolution and micro-deformation behaviour of grade 2507 (UNS 532750) super duplex stainless steel were studied. A novel in-situ methodological approach using Digital Image Correlation (DIC) and Scanning Kelvin Probe Force Microscopy (SKPFM) was employed. The microstructure with small austenite spacing showed load partitioning of tensile micro-strains to the austenite during elastic loading, with the ferrite then taking up most tensile strain at large plastic deformation. The opposite trend was seen when the microstructure was pre-charged with hydrogen, with more intense strain localisation formed due to local hydrogen hardening. The hydrogen-charged microstructure with large austenite spacing showed a contrasting micro-mechanical response, resulting in heterogeneous strain localisation with high strain intensities in both phases in the elastic regime. The austenite was hydrogen-hardened, whereas the ferrite became more strain-hardened. SKPFM measured Volta potentials revealed the development of local cathodic sites in the ferrite associated with hydrogen damage (blister), with anodic sites related to trapped hydrogen and/or micro voids in the microstructure with small austenite spacing. Discrete cathodic sites with large Volta potential variations across the ferrite were seen in the coarse-grained microstructure, indicating enhanced susceptibility to micro-galvanic activity. Microstructures with large austenite spacing were more susceptible to hydrogen embrittlement, related to the development of tensile strains in the ferrite.

Place, publisher, year, edition, pages
Elsevier, 2018
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-232907 (URN)10.1016/j.ijhydene.2018.05.028 (DOI)000438325200058 ()2-s2.0-85047740574 (Scopus ID)
Note

QC 20180808

Available from: 2018-08-08 Created: 2018-08-08 Last updated: 2018-10-19Bibliographically approved
Örnek, C., Långberg, M., Evertsson, J., Harlow, G., Linpe, W., Rullik, L., . . . Pan, J. (2018). In-situ synchrotron GIXRD study of passive film evolution on duplex stainless steel in corrosive environment. Corrosion Science, 141, 18-21
Open this publication in new window or tab >>In-situ synchrotron GIXRD study of passive film evolution on duplex stainless steel in corrosive environment
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2018 (English)In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 141, p. 18-21Article in journal (Refereed) Published
Abstract [en]

This paper presents new findings about the passive film formed on super duplex stainless steel in ambient air and corrosive environments, studied by synchrotron grazing-incidence X-ray diffraction (GIXRD). The passive film, formed in air, was seen to be a nano-crystalline mixed-oxide. Electrochemical polarisation to the passive region in aqueous 1 M NaCl at room temperature resulted in an increase of the passive film thickness, preferential dissolution of Fe, and partial loss of crystallinity. After termination of polarization to the transpassive regime, reformation of the mixed-oxides was observed, showing a thicker, semi-crystalline, and more defective nature (more vacancies) with further new oxides/hydroxides.

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2018
Keywords
Passivity, Oxide film, Duplex stainless steel, Grazing-incidence X-ray diffraction (GIXRD), Selective dissolution, De-alloying
National Category
Corrosion Engineering
Identifiers
urn:nbn:se:kth:diva-234174 (URN)10.1016/j.corsci.2018.06.040 (DOI)000441682000003 ()2-s2.0-85049421217 (Scopus ID)
Note

QC 20181009

Available from: 2018-10-09 Created: 2018-10-09 Last updated: 2018-10-30Bibliographically approved
He, Y., Dobryden, I., Pan, J., Ahniyaz, A., Deltin, T., Corkery, R. W. & Claesson, P. M. (2018). Nano-scale mechanical and wear properties of a waterborne hydroxyacrylic-melamine anti-corrosion coating. Applied Surface Science, 457, 548-558
Open this publication in new window or tab >>Nano-scale mechanical and wear properties of a waterborne hydroxyacrylic-melamine anti-corrosion coating
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2018 (English)In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 457, p. 548-558Article in journal (Refereed) Published
Abstract [en]

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 (approximate to 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.

Place, publisher, year, edition, pages
Elsevier, 2018
Keywords
Waterborne anti-corrosive coating, Electrochemical impedance spectroscopy, Nanomechanical property, Nanowear, Fast fourier transform analysis
National Category
Other Chemistry Topics
Identifiers
urn:nbn:se:kth:diva-235097 (URN)10.1016/j.apsusc.2018.06.284 (DOI)000441872300065 ()2-s2.0-85049824578 (Scopus ID)
Funder
Swedish Research Council, 2015-05080
Note

QC 20180917

Available from: 2018-09-17 Created: 2018-09-17 Last updated: 2018-09-17Bibliographically approved
Wang, Y., Yin, L., Jin, Y., Pan, J. & Leygraf, C. (2018). Numerical Simulation of Micro-Galvanic Corrosion in Al Alloys: Steric Hindrance Effect of Corrosion Product. Journal of the Electrochemical Society, 164(14), C1035-C1043
Open this publication in new window or tab >>Numerical Simulation of Micro-Galvanic Corrosion in Al Alloys: Steric Hindrance Effect of Corrosion Product
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2018 (English)In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 164, no 14, p. C1035-C1043Article in journal (Refereed) Published
Abstract [en]

An improved finite element model was established to demonstrate the steric hindrance effect of the precipitated corrosion product (Al(OH)(3)) on micro-galvanic corrosion triggered by intermetallic particles (IMPs) in an Al-matrix. In this model, the precipitation/ dissolution of the corrosion product could occur in the whole liquid field as the result of a reversible reaction. Simulation results show that the precipitated insulating Al(OH)(3) on the electrode surface can inhibit further corrosion by reducing the conductivity of the solution and the active electrode surface area. Meanwhile, the steric hindrance effect of the precipitated Al(OH)(3) also slows down the diffusion and migration of species in the solution. Moreover, considering the porous nature of precipitated Al(OH)(3), a porosity parameter epsilon was introduced to describe the degree of compactness of corrosion product, which reaches a certain minimum value epsilon(c) under a specific corrosion situation. Compared to the previous work in which a surface coverage parameter was used to describe the blocking effect of Al(OH)(3) on surface activity, the present model is more realistic in mimicking the micro-galvanic corrosion, and also useful for the simulation of the transition from metastable pit formation to pit propagation.

Place, publisher, year, edition, pages
The Electrochemical Society, 2018
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-221355 (URN)10.1149/2.0871714jes (DOI)000419187700079 ()2-s2.0-85040731911 (Scopus ID)
Funder
Swedish Foundation for Strategic Research , RMA11-0090
Note

QC 20180117

Available from: 2018-01-17 Created: 2018-01-17 Last updated: 2018-05-08Bibliographically approved
Anantha, K. H., Örnek, C., Ejnermark, S., Medvedeva, A., Sjöström, J. & Pan, J. (2017). In situ AFM study of localized corrosion processes of tempered AISI 420 martensitic stainless steel: Effect of secondary hardening. Journal of the Electrochemical Society, 164(13), C810-C818
Open this publication in new window or tab >>In situ AFM study of localized corrosion processes of tempered AISI 420 martensitic stainless steel: Effect of secondary hardening
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2017 (English)In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 164, no 13, p. C810-C818Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
Electrochemical Society, 2017
National Category
Corrosion Engineering
Identifiers
urn:nbn:se:kth:diva-218312 (URN)10.1149/2.1261713jes (DOI)000418409800096 ()2-s2.0-85033663829 (Scopus ID)
Note

QC 20171127

Available from: 2017-11-27 Created: 2017-11-27 Last updated: 2018-11-26Bibliographically approved
Yin, L., Jin, Y., Leygraf, C., Birbilis, N. & Pan, J. (2017). Numerical Simulation of Micro-Galvanic Corrosion in Al Alloys: Effect of Geometric Factors. Journal of the Electrochemical Society, 164(2), C75-C84
Open this publication in new window or tab >>Numerical Simulation of Micro-Galvanic Corrosion in Al Alloys: Effect of Geometric Factors
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2017 (English)In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 164, no 2, p. C75-C84Article in journal (Refereed) Published
Abstract [en]

A finite element model for simulating the propagation of intermetallic particle driven micro-galvanic corrosion in an Al-matrix model system is presented. The model revealed dynamic changes related to localized corrosion, including the moving dissolution boundary, the deposition of reaction products (Al(OH)(3)), and their blocking effect. Modelling was focused on the effects of key geometric parameters, including the radius of cathodic particle (range 0.5 to 4 mu m) and the width of an assumed anodic ring surrounding the particle (range 0.1 to 2 mu m). Simulations revealed the dynamic flow of molecular and ionic species, along with influence of geometrical constraints. For ring widths below 0.5 mu m, deposition of Al(OH)(3) inside the dissolving volume was inhibited due to limited transport of OH- and O-2 into a constrained volume - resulting in local acidification. An increase in cathodic particle radius at given ring width resulted in a greater dissolution by providing a larger cathodic area for O-2 reduction, quantifying the effect of cathode/anode ratio. The model was also developed to include two cathodic particles to explore any interaction. The present study reveals a physicochemical model that contributes toward a framework for multi-process localized corrosion systems, which can be further adapted to commercial alloy systems.

Place, publisher, year, edition, pages
ELECTROCHEMICAL SOC INC, 2017
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-206310 (URN)10.1149/2.1221702jes (DOI)000397850800024 ()
Note

QC 20170505

Available from: 2017-05-05 Created: 2017-05-05 Last updated: 2018-05-08Bibliographically approved
Yin, L., Jin, Y., Leygraf, C. & Pan, J. (2017). Numerical Simulation of Micro-Galvanic Corrosion of Al Alloys: Effect of Chemical Factors. Journal of the Electrochemical Society, 164(13), C768-C778
Open this publication in new window or tab >>Numerical Simulation of Micro-Galvanic Corrosion of Al Alloys: Effect of Chemical Factors
2017 (English)In: Journal of the Electrochemical Society, ISSN 0013-4651, E-ISSN 1945-7111, Vol. 164, no 13, p. C768-C778Article in journal (Refereed) Published
Abstract [en]

A finite element model for simulating the propagation of micro-galvanic corrosion of Al alloys induced by intermetallic particle was established to reveal the dynamic changes including a moving dissolution boundary, deposition of reaction products and their blocking effect. This model has previously been used to study the influence of geometrical factors such as the particle size and width of the anodic ring. In this work, we explore effects of chemical factors including pH and bulk concentration of O-2 by using chemical-dependent electrochemical kinetics as input parameters. The simulations reveal that the micro-galvanic corrosion rate is slowest at pH = 6. For pH > 6, the rise of pH increases the dissolution rate of Al and also the deposition rate of Al(OH)(3), leading to a faster but more short localized Al dissolution. For pH < 6, the decline of pH accelerates Al dissolution and inhibits Al(OH)(3) deposition, leading to a faster and more long lasting Al dissolution. At pH <= 4, deposition of Al(OH)(3) becomes negligible, and localized corrosion will propagate continuously. Within the O-2 concentration range relevant for atmospheric conditions, a lower O-2 concentration in the solution leads to a slower rate of micro-galvanic corrosion.

Place, publisher, year, edition, pages
Electrochemical Society Inc, 2017
National Category
Corrosion Engineering
Identifiers
urn:nbn:se:kth:diva-220868 (URN)10.1149/2.0691713jes (DOI)000418409800091 ()2-s2.0-85033671822 (Scopus ID)
Funder
Swedish Foundation for Strategic Research , RMA11-0090
Note

QC 20180108

Available from: 2018-01-08 Created: 2018-01-08 Last updated: 2018-05-08Bibliographically approved
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