Das elektrische Feld innerhalb der Passivschicht des Eisens

Vetter, K.

doi:10.1002/bbpc.19540580406

Cited by 21 publications

(3 citation statements)

References 25 publications

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Section: Kinetics Of the Fe+++/fe ++ Reaction On Fe-cr Alloysmentioning

confidence: 99%

“…The kinetics of the Fe + + +/Fe + + couple on superficially oxidized electrodes present a number of interesting features (1)(2)(3)(4). In general, the exchange currents are low (N10 -6 amp/cm2), the transfer coefficients have unusual values and sums less than unity, and the anodic and cathodic curves are generally asymmetrical (1)(2)(3)(4). These features appear to be basic to an electrode covered with a thin oxide (i.e., a passive electrode) and not to be related to the specific nature of the redox couple.…”

Section: Kinetics Of the Fe+++/fe ++ Reaction On Fe-cr Alloysmentioning

confidence: 99%

“…In general, a superficial oxide is expected to change the specific interaction of oxygen (or of reaction intermediates) with the electrode, to alter the potential distribution between metal and electrolyte, and to modify the dissolution kinetics of the metal. The change in the kinetics of dissolution has been studied in detail, since it is the characteristic phenomenon in passivity (2)(3)(4)(5)(6). However, relatively little work has been done on the effects of oxide films on electrochemical reactions other than corrosion reactions.…”

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Kinetics of Redox Reactions on Passive Electrodes

Makrides¹

1964

J. Electrochem. Soc.

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Overpotential measurements for the Fe + + +/Fe + + couple on passive Ni, Fe, and Ti, were carried out in solutions of fixed ionic strength but of varying pH. Tafel lines were generally obtained with exchange currents between 10 -7 and 10 -5 amp/cm 2 and cathodic transfer coefficients of about 0.45. The anodic transfer coefficients were less, particularly with Ti and Fe electrodes. A limiting anodic current, which was unrelated to diffusion of Fe + + ion in solution, was observed under certain conditions on Fe and Ti. The contribution of ionic current to the total current through the film is negligible in most cases. In general, the passive film has rectifying properties, the easy direction of electron flow being from metal to solution. This rectification is additional to the usual Faradaic rectification observed with most electrochemical reactions. The apparent transfer coefficients, calculated from the anodic and cathodic polarization curves, yield sums significantly less than unity. The results demonstrate the existence of a potential drop across the passive film, the magnitude of which depends on the thickness and composition of the film.The electrochemical cell was described previously (9). Potentials were measured through a Luggin-Haber capillary probe 0.05 cm OD placed 0.10 cm

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Section: Kinetics Of the Fe+++/fe ++ Reaction On Fe-cr Alloysmentioning

confidence: 99%

Section: Kinetics Of the Fe+++/fe ++ Reaction On Fe-cr Alloysmentioning

confidence: 99%

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Kinetics of Redox Reactions on Passive Electrodes

Makrides¹

1964

J. Electrochem. Soc.

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Über die Passivität der Metalle

Schwabe

1966

Angewandte Chemie

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Nach einer Ubersicht uber die Vielzahl der sowohl vom Metall als auch vom angreifenden Medium abhangenden Faktoren, welche die anodische Metallauflosug beeinflussen konnen, wird die Natur der Passiv-Schichten auf Grund elektrochemischer und optischer Untersuchungen behandelt. Die fur die Passivierung charakteristische steile Abnahme der anodischen Stromdichte bei wachsender Galvanispannung wird schon durch eine monomolekulare, den Durchtritt der Metallionen durch die Phasengrenze hemmenden Schicht hervorgerufen. Das Wachstum dieser Schicht wird majgeblich durch Transportvorgange vor allem in ihr selbst beeinfkrjt. Die Kinetik der Passivierungs-und Aktivierungsvorgange la& sich durch p~tentialabhang~ge, Jconkurrierende S~mu~tanreaJ~fionen deuten, wobei die Austawchadsorption im Passiv-Verhalten eines Metalls gegeniiber verschiedenen Sauren eine Rolle zu spielen scheint.

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The Passivity of Metals

Schwabe

1966

Angew. Chem. Int. Ed. Engl.

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After a survey of the various factors, depending both on the metal and on the attacking substance, that can influence the anodic dissolution of metals, the nature of the passive layer is discussed on the basis of electrochemical and optical studies. Passivation is characterized by a rapid decrease in the anodic current density as the Galvani tension is increased; this is due to the presence of a monomolecular layer, which prevents the metal ions from passing across the phase boundary. The growth of this layer is strongly influenced by transport processes, particularly within the layer itseIf. The kinetics of the passivation and activation processes can be explained by the simultaneous occurrence of competing reactions which depend on the potential; exchange adsorption appears to play some part in the passive behavior of metals towards various acids.

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Das elektrische Feld innerhalb der Passivschicht des Eisens

Cited by 21 publications

References 25 publications

Kinetics of Redox Reactions on Passive Electrodes

Kinetics of Redox Reactions on Passive Electrodes

Über die Passivität der Metalle

The Passivity of Metals

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