Graph Theory and the Passivity of Binary Alloys

McCafferty, E.

doi:10.1149/1.1637899

Cited by 13 publications

(9 citation statements)

References 26 publications

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“…The implication for Cu-9.7Sn-0.1Zn (Figure 8c) is that there is sufficient Sn oxidized near the surface to form a continuous or nearly continuous SnO 2 layer which is semi-passivating in that it does not restrict direct release of ionic Cu into solution (Figure 20). Graph theory [46] considers the 'connectivity' (a mathematical abstraction) of the passivating solute oxide (SnO 2 ) interrupted by solvent cations (Cu + in this case), and the critical solute (Sn) content to produce a continuous 'connected' or passive layer is 10.3 wt% Sn. Cu-9.7Sn-0.1Zn closely approaches this value, and hence its semi-passive behavior may be explained by a nearly continuous or 'connected' layer of SnO 2 while permitting cuprous ion transmission through this layer.…”

Section: Summary Of Findings -Corrosion Behavior and Ion Releasementioning

confidence: 99%

Enhanced Electrochemical Cu Release from Commercial Cu-Sn Alloys: Fate of the Alloying Elements in Artificial Perspiration

Hutchison

Zhou

Ogle

et al. 2017

Electrochimica Acta

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Commercially pure Cu (Cu), Cu-4.5Sn-0.1Zn, and Cu-9.7Sn-0.1Zn (wt%) were evaluated for corrosion and cation release in modified artificial human perspiration solution. Open circuit corrosion exposures were conducted for up to 130 hours to determine corrosion rate and the fate of Cu and Sn. Released aqueous ion concentrations were monitored via inductively-coupled plasmaoptical emission spectroscopy (ICP-OES). Operando atomic emission spectroelectrochemistry (AESEC) analysis was utilized to elucidate the fate of Cu, whether in oxides or solution and deduce the dominant valence states, Cu(I)/Cu(II), of soluble Cu in artificial perspiration. Sn was not observed as a soluble ionic species within ICP-OES or AESEC limits of detection (LOD). Corrosion products were characterized using grazing incidence X-ray diffraction (GIXRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS), and quantified with coulometric reduction (CR). Cu-4.5Sn-0.1Zn displayed the highest corrosion rates in artificial perspiration, followed by Cu-9.7Sn-0.1Zn, and then Cu. Primary corrosion products were Cu 2 O, with CuCl as an outer solid product, and an inner layer of SnO 2 for Sn-containing alloys. Cu was dissolved as cuprous (Cu +) ions. Minor Sn alloying in solid solution catalyzed Cu dissolution which is counteracted at higher Sn contents by a passivating layer of SnO 2 , achieving complete passivity at 10.3 wt% Sn according to graph theory. Cu-9.7Sn-0.1Zn indicated semi-passive behavior, speculated to be due a SnO 2 layer and close proximity (9.7 wt%) to this critical value for passivation (10.3 wt%). The effect of alloyed Sn as a dissolution promoter for electrochemical Cu ion release, critical Sn contents for passivity, and subsequent implications of antimicrobial function are discussed. Oxidized Zn was not detected above LOD nor demonstrated any measurable effect on corrosion in artificial perspiration.

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Section: Summary Of Findings -Corrosion Behavior and Ion Releasementioning

confidence: 99%

Enhanced Electrochemical Cu Release from Commercial Cu-Sn Alloys: Fate of the Alloying Elements in Artificial Perspiration

Hutchison

Zhou

Ogle

et al. 2017

Electrochimica Acta

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“…In addition, one would expect a much higher Ta concentration to be necessary to form a coherent oxide passivation layer. No data for a critical Ta threshold concentration in Mo is available, however for a similar TiCr alloy the graph theory predicts a critical alloying element concentration of 39 at.-% Cr to render Ti passive [4]. However, the concentration in the present alloy film was much lower (4.7 at.-% Ta).…”

Section: Discussionmentioning

confidence: 71%

“…For every alloy system, there exists a critical threshold concentration of the alloying element in order to passivate the alloy. This critical concentration can be predicted using the "graph theory" of McCafferty [4]. The passivity of a binary alloy is attributed to the formation of a passivation oxide film, protecting the underlying metal from further oxidation.…”

Section: Theoretical Considerationsmentioning

confidence: 99%

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56.3: High Corrosion Resistance Mo Alloy for TFT‐LCD and Touch Screen Panel Metallization

Winkler

Reinfried

Knabl

2009

Symp Digest of Tech Papers

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“…Previous models of the passivity of Fe-Cr alloys have been based on the idea that a static network of Cr conveys stability [27,23,16,17]. In this section we will investigate the possibility that the migration of Cr can also play a role.…”

Section: Chapter 2 Motivationmentioning

confidence: 99%

Kinetic Monte Carlo Modelling of Dissolution and Passive Film Formation in Fe-Cr Alloys

Parker¹

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<p>Stainless steels differ from iron in that chromium content allows for the formation of a passive iron-chromium oxide film which is only nanometres in thickness, offering protection from the environment. While the composition of this oxide layer has been established, the mechanism of its formation is not well understood. In particular, the threshold level of chromium for oxide formation is significantly lower then the chromium content of the alloy itself. We present a Cahn Hilliard type analytical model that relates the onset of passivation to an instability which leads to a phase segregating current above 17% Cr in a bulk alloy. Proposing that this current could lead to Cr enrichment at a surface, we compare atomistic simulations with and without a surface driven Cr current. We implemented a kinetic Monte Carlo algorithm with extensions to allow for vacancy assisted nearest neighbour migration in a body centered cubic alloy, tracking a surface, dissolution and surface passivation. We compare the time evolution of Fe dissolution rates, Cr surface enrichment and the threshold for passive film formation and find that the Cr current has a significant impact on each of these properties.</p>

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Graph Theory and the Passivity of Binary Alloys

Cited by 13 publications

References 26 publications

Enhanced Electrochemical Cu Release from Commercial Cu-Sn Alloys: Fate of the Alloying Elements in Artificial Perspiration

Enhanced Electrochemical Cu Release from Commercial Cu-Sn Alloys: Fate of the Alloying Elements in Artificial Perspiration

56.3: High Corrosion Resistance Mo Alloy for TFT‐LCD and Touch Screen Panel Metallization

Kinetic Monte Carlo Modelling of Dissolution and Passive Film Formation in Fe-Cr Alloys

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