On the Evaluation of Corrosion Resistances of Amorphous Chromium-Carbon Thin-Films

Högström, Jonas; Andersson, Matilda; Jansson, Ulf; Björefors, Fredrik; Nyholm, Leif

doi:10.1016/j.electacta.2013.11.130

Cited by 35 publications

(17 citation statements)

References 37 publications

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“…This finding corresponds to a continuous oxidation process, which was particularly pronounced for the F 9 sample, containing the relatively small Ag NPs. The rapid increase in the current at potentials more positive than about +0.8 V (Figure a), which also was seen for sample A 0 , can mainly be ascribed to the oxidation of Cr 2 O 3 and CrC x yielding soluble Cr(VI) species, which is in good agreement with our previous findings for Cr−C films . Newly exposed Ag would also be oxidized in this potential region, but its contribution to the current should be relatively small, for two reasons.…”

Section: Resultssupporting

confidence: 90%

“…First, the Ag concentration was lower than that of Cr, and second, the oxidation of Ag only involves one electron. There may also be a small contribution from some oxidation of the a‐C phase …”

Section: Resultsmentioning

confidence: 99%

“…The second set of chronoamperometric experiments made use of separate regions on a D 6 sample and involved potential steps to +0.25 or +0.50 V, each with a duration of 5 or 15 minutes. Both potentials were sufficiently high to oxidize the NPs (see Figure ) and the results of these experiments should hence mainly reflect differences in the rate of the oxidation of the exposed Cr−C (which should take place at potentials above about 0 V) . In the evaluation of the results, the total oxidation charges were employed.…”

Section: Resultsmentioning

confidence: 99%

“…While carbide and nitride nanocomposites can exhibit a high corrosion resistance, primarily due to the high stability of the corresponding metal oxide, these properties may be affected by the inclusion of Ag in the coatings. Two‐phase nanocomposite Cr−C films, consisting of amorphous chromium carbide and amorphous carbon (a‐CrC x /a‐C), have been shown to have high oxidation resistances in acidic solutions due to the formation of a passive layer composed of Cr 2 O 3 and a‐C, which protects the material from further oxidation . Since Ag is a noble metal, it could be expected that a Cr−C/Ag film likewise would exhibit a high corrosion resistance.…”

Section: Introductionmentioning

confidence: 99%

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Influence of Nanoeffects on the Oxidation of Cr–C/Ag Thin Films Containing Silver Nanoparticles

et al. 2017

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Well‐controlled functionalization of carbide‐based nanocomposite films with noble‐metal surface nanoparticles of different sizes may lead to new materials with novel multifunctional properties. In this work, magnetron sputtering was used to deposit nanocomposite films comprising amorphous chromium carbide (a‐CrCx), amorphous carbon (a‐C), and a minority of silver in the form of embedded nanoclusters. Up to 5⋅1010 surface nanoparticles per cm2 with different size distributions were also found to be formed, owing to the diffusion of silver from the bulk of the film. The influences of these conductive nanoparticles on the electrochemical behavior of the films were investigated in dilute sulfuric acid. Although silver is a noble metal, the oxidation potential of the nanoparticles was about 0.4 V more negative than the Ag+/Ag standard potential, meaning that the nanoparticles were oxidized in the Cr passive potential region. While this effect can mainly be explained by a low concentration of Ag+ in the electrolyte, the sizes of the nanoparticles and interactions with the matrix were also found to be important. Scanning electron microscopy and X‐ray photoelectron spectroscopy were used to analyze the surface chemistries. As Ag can be replaced by other noble metals, the concept is of general interest for further studies.

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Section: Resultssupporting

confidence: 90%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Influence of Nanoeffects on the Oxidation of Cr–C/Ag Thin Films Containing Silver Nanoparticles

et al. 2017

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“…In aerated solution of pH ¼ 7.20, chromium undergoes oxidation to Cr 2 O 3 and partially to Cr(OH) 3 . When the pH of the solution in the cavity (pit) gradually decreases, due to reaction , amphoteric chromium (III) hydroxide reacts according to reaction , forming soluble Cr 3+ ions [23]. The highest chlorine and calcium concentrations were observed at the boundaries -between corrosion products layers and between the most outer corrosion products layer and a-C:H coating respectively (Fig.…”

Section: Micromechanical Properties Of Analyzed Coatingsmentioning

confidence: 97%

Microstructure characterization of localized corrosion wear of Cr/Cr2N+ a-C:H/a-C:H:Cr multilayer coatings on carbon fiber composites

Janusz¹,

Major²,

Lackner³

et al. 2017

Bulletin of the Polish Academy of Sciences Technical Sciences

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Abstract. The use of carbon fiber composites (CFC) for different applications is widespread. Carbon-based materials show, however, significant oxidative degradation in air. Modern materials are subjected to aggressive, corrosive environment. This type of environment may strongly reduce their mechanical properties. For the protection of CFC, it was necessary to apply coatings to the composite surface. In the presented paper, a chromium/chromium nitride (Cr/Cr2N) multilayer structure has been selected as the inner part. The outer part of the coating was a hydrogenated amorphous carbon (a-C:H), gradually implanted by Cr nanocrystals. The application of transmission electron microscopy (TEM) indicated that the proposed deposition method allowed the formation of a Cr/Cr2N multilayer of Λ = 150 nm, topped with a-C:H+ Cr23C6 composite of a varied carbides density. The micro-hardness of the deposited coatings was up to 14 GPa (at a load of 2 and 5 mN). The microstructure of the deposited coatings was described in detail by means of TEM in the authors' recently published paper [1]. This paper is a continuation thereof, aimed at describing microstructure changes after a localized corrosion process. In order to study localized corrosion in coatings, particularly in metallic (Cr) interlayers, the potential measurements and voltammetry experiments were performed in a Ringer solution. The open-circuit potential reaches stable values after a sufficient time period. The results indicated that the presence of a-C:H+Cr23C6, the outer part of the coating, speeds up the localized corrosion process in Cr interlayers in the inner part of a coating.

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Significance of Pourbaix Diagrams to Study the Corrosion Behaviour of Hardfacing Alloys Based on Chromium Carbides at 298 K (25 °C)

2016

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The Pourbaix diagrams also known as the E-pH diagrams were constructed for hardfacing alloys based on three chromium carbides: Cr 7 C 3 , Cr 23 C 6 and Cr 3 C 2 at 298 K (25°C). Using the thermodynamic data available for the main species at 298 K (25°C), Pourbaix diagrams for the chromium carbides are constructed at a concentration of 10-6 M of aqueous species. It was found that the diagrams are able to explain the results of experimental work performed on chromium carbides in NaOH. It was found that the stability of carbides is described only by the immune region of the Pourbaix diagram for carbides. Although passive region has been included in the study, it was unclear from the literature if there was a passive film or how protective it was.

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On the Evaluation of Corrosion Resistances of Amorphous Chromium-Carbon Thin-Films

Cited by 35 publications

References 37 publications

Influence of Nanoeffects on the Oxidation of Cr–C/Ag Thin Films Containing Silver Nanoparticles

Influence of Nanoeffects on the Oxidation of Cr–C/Ag Thin Films Containing Silver Nanoparticles

Microstructure characterization of localized corrosion wear of Cr/Cr2N+ a-C:H/a-C:H:Cr multilayer coatings on carbon fiber composites

Significance of Pourbaix Diagrams to Study the Corrosion Behaviour of Hardfacing Alloys Based on Chromium Carbides at 298 K (25 °C)

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