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Corrosion and Surface Studies of Stainless Steel and Chromium Carbide Thin-Films
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.ORCID iD: 0000-0003-2817-8209
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Although the passive films that form on stainless steels have been extensively studied, the concentration depth profiles are not fully understood. Their thinness makes passive films hard to study, but angle-resolved X-ray photoelectron spectroscopy (ARXPS) is a non-destructive technique that can be used to obtain depth information. An iterative approach to deconvolute ARXPS measurements into depth profiles is discussed, and the chemistry of passive films on a molybdenum-containing 316L stainless steel is investigated. Bipolar electrochemistry, in which the sample is placed along an electric field created by two driving electrodes in an electrolyte, is investigated as a screening tool. It is shown that the method is useful to create corrosion gradients on 304 stainless steel, both under pitting and non-pitting conditions. Chromium carbide thin films were deposited by magnetron sputtering with a variety of deposition parameters on stainless steel, and subsequently analyzed. It is shown that these films present a promising material system for protective coatings to improve the corrosion resistance of stainless steels while also maintaining other useful properties, such as low interfacial contact resistance. Particular attention is given to the electrochemical evaluation of the films, whose high carbon concentrations necessitates different interpretations of the electrochemical results compared to for stainless steels.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2013. , 66 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1082
Keyword [en]
corrosion, electrochemistry, thin film, stainless steel, passive film, chromium carbide, carbon oxidation, surface, depth profile, XPS, SEM, EQCM, sputtering
National Category
Materials Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-208410ISBN: 978-91-554-8766-9 (print)OAI: oai:DiVA.org:uu-208410DiVA: diva2:652266
Public defence
2013-11-08, Ångström 2001, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2013-10-18 Created: 2013-09-30 Last updated: 2017-01-20
List of papers
1. Cation profiling of passive films on stainless steel formed in sulphuric and acetic acid by deconvolution of angle-resolved X-ray photoelectron spectra
Open this publication in new window or tab >>Cation profiling of passive films on stainless steel formed in sulphuric and acetic acid by deconvolution of angle-resolved X-ray photoelectron spectra
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2013 (English)In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 284, 700-714 p.Article in journal (Refereed) Published
Abstract [en]

An approach for determining depth gradients of metal-ion concentrations in passive films on stainlesssteel using angle-resolved X-ray photoelectron spectroscopy (ARXPS) is described. The iterative method,which is based on analyses of the oxidised metal peaks, provides increased precision and hence allowsfaster ARXPS measurements to be carried out. The method was used to determine the concentrationdepth profiles for molybdenum, iron and chromium in passive films on 316L/EN 1.4432 stainless steelsamples oxidised in 0.5 M H2SO4 and acetic acid diluted with 0.02 M Na2B4O7 · 10H2O and 1 M H2O,respectively. The molybdenum concentration in the film is pin-pointed to the oxide/metal interface andthe films also contained an iron-ion-enriched surface layer and a chromium-ion-dominated middle layer.Although films of similar composition and thickness (i.e., about 2 nm) were formed in the two electrolytes,the corrosion currents were found to be three orders of magnitude larger in the acetic acid solution.The differences in the layer composition, found for the two electrolytes as well as different oxidationconditions, can be explained based on the oxidation potentials of the metals and the dissolution rates ofthe different metal ions.

Keyword
XPS, Stainless steel, Passive films, Deconvolution, Cation distribution, Ion solubility
National Category
Materials Chemistry
Research subject
Materials Science
Identifiers
urn:nbn:se:uu:diva-208400 (URN)10.1016/j.apsusc.2013.07.158 (DOI)000324248600099 ()
Available from: 2013-09-30 Created: 2013-09-30 Last updated: 2017-12-06Bibliographically approved
2. Bipolar electrochemistry for high-throughput corrosion screening
Open this publication in new window or tab >>Bipolar electrochemistry for high-throughput corrosion screening
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2013 (English)In: Electrochemistry communications, ISSN 1388-2481, E-ISSN 1873-1902, Vol. 34, 274-277 p.Article in journal (Refereed) Published
Abstract [en]

It is demonstrated that bipolar electrochemistry can be used for high-throughput corrosion testing covering a wide potential range in one single experiment and that this, combined with rapid image analysis, constitutes a simple and convenient way to screen the corrosion behaviour of conducting materials and corrosion protective coatings. Stainless steel samples (SS304), acting as bipolar electrodes, were immersed in sulphuric and hydrochloric acid and exposed to an electric field to establish a potential gradient along the surface. In this way, the same steel sample was exposed to a wide range of cathodic and anodic conditions, ranging from potentials yielding hydrogen evolution to potentials well into the transpassive region. This wireless approach enables rapid simultaneous comparison of numerous samples, and also provides the opportunity to perform experiments on samples that are of a complex shape, or which otherwise are difficult to employ in standard electrochemical corrosion tests.

Keyword
Bipolar electrochemistry, Corrosion, Stainless steel, Screening, Image analysis
National Category
Materials Chemistry Inorganic Chemistry
Research subject
Materials Science
Identifiers
urn:nbn:se:uu:diva-205921 (URN)10.1016/j.elecom.2013.07.011 (DOI)000324963900070 ()
Note

Highlights

• Bipolar electrochemistry for high-throughput corrosion screening

• Simultaneous evaluation of anodic and cathodic conditions on single samples

• Wireless production of corrosion gradients on stainless steel and image analysis

• Comparison of the bipolar approach with conventional three-electrode experiments

Available from: 2013-08-25 Created: 2013-08-25 Last updated: 2017-12-06Bibliographically approved
3. Deposition and characterization of magnetron sputtered amorphous Cr-C films
Open this publication in new window or tab >>Deposition and characterization of magnetron sputtered amorphous Cr-C films
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2012 (English)In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 86, no 9, 1408-1416 p.Article in journal (Refereed) Published
Abstract [en]

Thin films in the Cr-C system with carbon content of 25-85 at.% have been deposited using non-reactive DC magnetron sputtering from elemental targets. Analyses with X-ray diffraction and transmission electron microscopy confirm that the films are completely amorphous. Also, annealing experiment show that the films had not crystallized at 500 degrees C. Furthermore, X-ray spectroscopy and Raman spectroscopy show that the films consist of two phases, an amorphous CrCx phase and an amorphous carbon (a-C) phase. The presence of two amorphous phases is also supported by the electrochemical analysis, which shows that oxidation of both chromium and carbon contributes to the total current in the passive region. The relative amounts of these amorphous phases influence the film properties. Typically, lower carbon content with less a-C phase leads to harder films with higher Young's modulus and lower resistivity. The results also show that both films have lower currents in the passive region compared to the uncoated 316L steel substrate. Finally, our results were compared with literature data from both reactively and non-reactively sputtered chromium carbide films. The comparison reveals that non-reactive sputtering tend to favour the formation of amorphous films and also influence e.g. the sp(2)/sp(3) ratio of the a-C phase. 

Keyword
Amorphous, Chromium carbide, Magnetron sputtering, Electrochemical, Nanoindentation
National Category
Inorganic Chemistry
Research subject
Chemistry with specialization in Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-174582 (URN)10.1016/j.vacuum.2012.01.021 (DOI)000302839400037 ()
Available from: 2012-05-29 Created: 2012-05-22 Last updated: 2017-12-07Bibliographically approved
4. On the evaluation of corrosion resistances of amorphous chromium carbide thin-films
Open this publication in new window or tab >>On the evaluation of corrosion resistances of amorphous chromium carbide thin-films
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2014 (English)In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 122, no SI, 224-233 p.Article in journal (Refereed) Published
Abstract [en]

The possibilities of evaluating the corrosion resistance of amorphous chromium carbide (Cr-C) films containing nanometre-sized carbide grains embedded in an amorphous carbon matrix on the basis of polarization curves, voltammograms and the oxidation charge have been studied for Cr-C films with different carbon concentrations. The films, which were manufactured by non-reactive directcurrent magnetron sputtering, were studied in 1.0 mM H2SO4 at both 22 °C and 80 °C, and with scanning electron microscopy and X-ray photoelectron spectroscopy prior to and after the electrochemical experiments. It is demonstrated that the oxidation of these Cr-C films gives rise to a surface composed of Cr2O3 and partially oxidized carbon and that the non-corroding oxidation current due to the carbon oxidation increases with increasing carbon concentration in the films as well as with the electrolyte temperature. Since the oxidation current is composed of contributions from both Cr-C and carbon oxidation it is not straightforward to evaluate the corrosion resistances of these films based on the current in the passive region, the mixed potential (i.e., the corrosion potential) or the open circuit potential. The present results in fact indicate that Cr-C films with high carbon concentrations may have better corrosion resistances than the corresponding films with lower carbon concentrations although larger currents in the passive region can be seen in polarization curves.

Keyword
chromium carbide, corrosion
National Category
Inorganic Chemistry
Research subject
Chemistry with specialization in Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-212777 (URN)10.1016/j.electacta.2013.11.130 (DOI)000334007900029 ()
Funder
Swedish Foundation for Strategic Research
Available from: 2013-12-13 Created: 2013-12-13 Last updated: 2017-12-06
5. Corrosion resistance of amorphous, nanocomposite, and crystalline Cr-C films deposited by magnetron sputtering
Open this publication in new window or tab >>Corrosion resistance of amorphous, nanocomposite, and crystalline Cr-C films deposited by magnetron sputtering
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(English)Manuscript (preprint) (Other academic)
Keyword
Chromium carbide, Amorphous, Nano-composite, Deposition temperature, Carbon oxidation
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-208409 (URN)
Available from: 2013-09-30 Created: 2013-09-30 Last updated: 2017-01-20

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