A model for the transpassivity of molybdenum in acidic sulphate solutions based on ac impedance measurements

Bojinov, Martin; Betova, Iva; Raicheff, R.

doi:10.1016/0013-4686(95)00468-8

Cited by 39 publications

(25 citation statements)

References 10 publications

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“…[34][35][36][37][38][39][40][41][42][43][44][45][46][47] In other systems the transition is rather sharp, particularly if measured potentiostatically under steady-state conditions, rather than being measured potentiodynamically ͑which is normally the case͒. [34][35][36][37][38][39][40][41][42][43][44][45][46][47] In other systems the transition is rather sharp, particularly if measured potentiostatically under steady-state conditions, rather than being measured potentiodynamically ͑which is normally the case͒.…”

Section: E a I V E B I L E C I Ph For The Interfacial Defect Generatimentioning

confidence: 99%

On the Existence of Our Metals-Based Civilization

Macdonald

2006

J. Electrochem. Soc.

201

165

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The stability of the barrier layers of bilayer passive films that form on metal and alloy surfaces, when in contact with oxidizing aqueous environments, is explored within the framework of the point defect model using phase-space analysis, in which the rate of growth of the barrier layer into the metal ͑dL + /dt͒, and the barrier layer dissolution rate ͑dL − /dt͒, are plotted simultaneously against the barrier layer thickness. A point of intersection of dL − /dt with dL + /dt indicates the existence of a metastable barrier layer having a steady-state thickness greater than zero. If ͑dL − /dt͒ L=L ss Ͼ ͑dL + /dt͒ L=0 , the barrier layer cannot exist, even as a metastable phase, as the resulting thickness would be negative. Under these conditions, the surface is depassivated and the metal may corrode at a rapid rate. Depassivation due to potential-enhanced dissolution ͑transition to the transpassive state͒ and to acid attack on the barrier layer ͑"acid depassivation"͒ are explored. The boundaries for depassivation may be plotted in potential-pH space to develop kinetic stability diagrams as alternatives to the classical Pourbaix diagrams for describing the conditions under which metals or alloys exist in the passive state.

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Section: E a I V E B I L E C I Ph For The Interfacial Defect Generatimentioning

confidence: 99%

On the Existence of Our Metals-Based Civilization

Macdonald

2006

J. Electrochem. Soc.

201

165

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“…Based on the hypothesis of selective dissolution of Fe through the passive film on Fe-Cr alloys, it is assumed that the dissolution of Cr as Cr(III) at the film-solution interface is negligible compared with the dissolution of Fe as Fe(III) [4]. According to the surface charge approach proposed by Bojinov and coworkers [4,14,[27][28][29][30][31], the passive film was represented as a doped ntype semiconductor-insulator-p-type semiconductor (n-i-p) structure with an injection of oxygen vacancies (donors) from the metal substrate during film growth and metal vacancies (acceptors) from the electrolyte during film dissolution. The cation vacancies accumulate at the film-solution interface if the transport rate of these vacancies is slower than the rate of their annihilation at the metal-film interface.…”

Section: Discussionmentioning

confidence: 99%

Transpassivity characterization of the alloy UNS N08367 in a chloride-containing solution

Karayan

Maya-Visuet

Castaneda

2014

J Solid State Electrochem

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We investigate the transpassivity of superaustenitic stainless steel UNS N08367 in 2.5 M LiCl solution by using cyclic potentiodynamic polarization (CPP), electrochemical impedance spectroscopy (EIS), and X-ray photoelectron spectroscopy (XPS). The CPP curve exhibits negative hysteresis, which indicates a transpassive dissolution process instead of pitting corrosion. The transition from the passive region to the transpassive region is characterized by EIS and equivalent circuit analysis. During the transpassive dissolution of the N08367 alloy, two reactions of adsorbed intermediates are dominant, as indicated by the two inductive loops at the transpassive region. The first inductive loop is associated with the faster reaction, i.e., the adsorption of Fe intermediates. This fast reaction is significantly influenced by the preferential dissolution of Fe during the transpassive dissolution. The second inductive loop is correlated with the adsorption of the Cr intermediate. In contrast to Fe, the Cr content on the surface increases in the transpassive region compared with the content in the passive region. The XPS spectra support the time and frequency domain approach for the preferential dissolution, and the dominant species resulted from the interfacial processes at the transpassive region.

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“…Molybdenum [10][11][12][13][14][15][16] is used as alloying element for titanium because it has a good thermodynamic stability. The passivity domain of molybdenum coincides with its immunity domain, so, the dissolution process is controlled by the passive surface oxides with a mean composition of molybdenum pentoxide (Mo 2 O 5 ) [11,[17][18][19].…”

Section: Introductionmentioning

confidence: 99%

“…The passivity domain of molybdenum coincides with its immunity domain, so, the dissolution process is controlled by the passive surface oxides with a mean composition of molybdenum pentoxide (Mo 2 O 5 ) [11,[17][18][19]. At superior anodic potentials (higher than þ0.45 V), molybdenum dissolves transpassive as molybdate ions (MoO 2À 4 ), the transpassive domain being until þ0.75 V. At more electropositive potentials of þ0.75 V, the molybdenum pentoxide is transformed into molybdenum trioxide (MoO 3 ) with electronic conductivity and reduced solubility, producing some limit currents of dissolution.…”

Section: Introductionmentioning

confidence: 99%

Electrochemical and SEM studies of a new implant bioalloy in physiological electrolytes

Popa

Vasilescu

Drob

et al. 2009

Materials & Corrosion

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A new implant Ti-7Al-3V-2Mo-2Fe alloy was elaborated and its behaviour in Ringer-Brown and Ringer solutions (of different pH values) was studied using cyclic potentiodynamic and linear polarisation, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM) with its link energy dispersive X-ray system (EDX). Cyclic potentiodynamic polarisation curves revealed that the Ti-7Al-3V-2Mo-2Fe alloy is self-passivated in Ringer solutions. Pitting corrosion appeared in alkaline Ringer solution but at very electropositive values of the breakdown and pitting protection potentials and it is not possible to develop local corrosion on this alloy, even in extreme functional conditions. EIS spectra at open circuit potential exhibited two phase angles characterising a resistant passive film and some charge transfer reactions. SEM-EDX analysis shows the presence of some aggregates containing complex compounds of calcium, magnesium, phosphor, silicon deposited on the alloy surface.

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A model for the transpassivity of molybdenum in acidic sulphate solutions based on ac impedance measurements

Cited by 39 publications

References 10 publications

On the Existence of Our Metals-Based Civilization

On the Existence of Our Metals-Based Civilization

Transpassivity characterization of the alloy UNS N08367 in a chloride-containing solution

Electrochemical and SEM studies of a new implant bioalloy in physiological electrolytes

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