About a critical thickness of the passive layer on iron at the flade potential

Abstract

An analysis of capacitance potential data of passive iron on the basis of the theory of critical states yields a critical point near the Flade potential EF. The critical point is characterized by a minimal critical thickness of the passive layer of about 1.3 nm at EF, yielding a field strength within the passive film of 4.6 . 106 Vcm-'. The Flade potential can be interpreted within the framework of the PIN model of the iron passive layer (91 as the minimal external "force", necessary for the formation of stoichiometric y-Fez03. The system behavior near the critical point can be appropriate described by the short range order or lattice gas model.Eine Analyse von Kapazitats-Potential-Messungen an passivem Eisen auf der Grundlage der Theorie der kritischen Zustande ergibt einen kritischen Punkt in der Nahe des Flade-Potentials EF. Der kritische Punkt ist charakterisiert durch eine minimale kritixhe Schichtdicke von etwa 1,3 nm bei EF, entsprechend einer Feldstarke innerhalb der Passivschicht von 4,6 . 106 Vcm-'. Im Rahmen des PIN-Modells der Eisenpassivschicht f9] kann das made-Potential als die minimale adere ,,Kraft" gedeutet werden, die erforderlich ist, um stochiometrisches y-Fe,03 zu erzeugen. Das Verhalten des Systems in der Nahe des kritischen Punktes kann am besten durch das Gitter-Gas-Modell beschrieben werden.

Reconstruction in Air of an Iron Passive Film Formed at −0.4 V in a Borate Buffer Solution

“…It is found that a critical thickness of 0.71 nm at t = t c is required before passivity with more protection is established. Similar results were observed in conferring the stability of air-formed oxide film 41 and passive film ,, against open-circuit breakdown in borate buffer solutions. The critical thickness presented here is much less than those reported for air-formed oxide film (1.7 nm) 41 and passive film (1.3 nm) .…”

“…Similar results were observed in conferring the stability of air-formed oxide film 41 and passive film ,, against open-circuit breakdown in borate buffer solutions. The critical thickness presented here is much less than those reported for air-formed oxide film (1.7 nm) 41 and passive film (1.3 nm) . Therefore it is inferred that crystal structures, especially surface crystal structures, play an important role in the resistance of passive films against open-circuit breakdown after a necessary oxide thickness is reached.…”

Χωροχρονικές Συμμετρίες Και Χάος Σε Ηλεκτροχημικά Δυναμικά Συστήματα

“…Από τις εξισώσεις (1.82) προκύπτει: από μεταλλικό Fe [Franck, 1958]: Για να ερμηνευτεί η ασυμφωνία αυτή, οι Göhr και Lang, Cohen, 1962, Cohen & Hashimoto, 1974. Οι Hickling και Ives [Hickling & Ives, 1975] Θεωρώντας ότι η μετάβαση από την παθητική στην ενεργή κατάσταση του ηλεκτροδίου Fe καθορίζεται κυρίως από τις ηλεκτρονικές ιδιότητες του παθητικού οξειδίου ο Pinkowski [Pinkowski, 1986]…”