Contact electric impedance and resistance studies of the conduction mechanism in passive films on ferrous alloys

Betova, Iva; Bojinov, Martin; Englund, Anders; Fabricius, Gunilla; Laitinen, Timo; Mäkelä, Kari; Saario, Timo; Sundholm, G.

doi:10.1016/s0013-4686(01)00641-7

Cited by 24 publications

(18 citation statements)

References 44 publications

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“…The increase in R fi lm as C fi lm decreases has also been observed during polarization experiments performed by Bojinov et al on Fe-Cr and Ni-Cr alloys. [13][14][15] …”

Section: Methodsmentioning

confidence: 99%

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The open-circuit ennoblement of alloy C-22 and other Ni-Cr-Mo alloys

Lloydis

Noël

Shoesmith

et al. 2005

JOM

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polarization, and electrochemical impedance spectroscopy were employed in the study. The composition of the fi lms formed was determined by x-ray photoelectron spectroscopy and time-of-fl ight secondary ion mass spectrometry. Passive oxide fi lm resistances increase and defect oxide fi lm concentrations decrease as fi lms thicken and chromium and molybdenum segregate to the alloy/oxide and oxide/solution interfaces, respectively. The high-chromium alloys exhibit higher fi lm resistances and lower fi lm defect concentrations consistent with the more positive potentials observed on these alloys. The results show that the observed ennoblement in corrosion potentials with time is coupled to the Cr/Mo segregation process and the suppression of defect injection at the alloy/oxide interface. By all measures, C-22 exhibited the best passive properties.

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“…The increase in R fi lm as C fi lm decreases has also been observed during polarization experiments performed by Bojinov et al on Fe-Cr and Ni-Cr alloys. [13][14][15] …”

Section: Methodsmentioning

confidence: 99%

“…12 Recently, Bojinov et al developed the mixed conduction model (MCM) for oxide growth on passive alloys. 10,[13][14][15] In this model, fi lm growth occurs by the transport of point defects that act as electron donors or acceptors. Each defect coexists with an electronic defect that contributes to the conductivity of the fi lm.…”

Section: Introductionmentioning

confidence: 99%

The open-circuit ennoblement of alloy C-22 and other Ni-Cr-Mo alloys

Lloydis

Noël

Shoesmith

et al. 2005

JOM

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“…A partir de la Tabla 4 se desprende que la mayor densidad de donores, para cada muestra C, F y A, lo presentan las capas pasivas formadas sobre estructuras de transición columnar -equiaxial, lo que indica una estructura más defectuosa. Los valores entre la muestra A y F son similares tanto para las estructuras columnares y exiaquiales, teniendo en cuenta que la composición entre ellas varían nada más en el contenido de Molibdeno, podemos concluir que la adición del mismo no conduce a una profundo cambio en las propiedades eléctricas y de transporte en las películas de óxido, es decir, no cambia la estructura electrónica de la misma [16]. La diferencia entre la densidad de donores de las estructuras equiaxial y columnar, está asociado a películas más o menos defectuosas, esto se puede relacionar con trabajos anteriores realizados en NaCl [17], donde las muestras A3 y F3 presentan valores de potencial de picado más bajos respectos a A1 y F1, así la estructura columnar (mayor densidad de donores) sufre picado antes que la estructura equiaxial.…”

Section: Probeta C Siunclassified

Pasividad en solución de fosfato de aceros inoxidables solidificados unidireccionalmente

et al. 2015

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RESUMENLa pasividad de los aceros inoxidables es atribuida a la formación de una película protectora, conformada por óxidos, sobre la superficie del metal. Esta película posee propiedades semiconductoras y está relacionada con múltiples factores que la hacen de importancia para la comprensión de los fenómenos de corrosión. En este trabajo se estudia la película pasiva formada en aceros inoxidables solidificados unidireccionalmente, Fe18Cr-10Ni-2Mo-0,08C (muestra A), Fe-18Cr-14Ni-8Mo-0,03C (muestra C) y Fe-18Cr-10Ni-8Mo-0,08C (muestra F), para determinar la influencia de la variación de la estructura (equiaxial, columnar y con transición de columnar a equiaxial-TCE) en la resistencia a la corrosión, así como investigar la relación entre la resistencia a la corrosión y el espaciamiento dendrítico secundario del material. Para ello se emplean técnicas potenciodinámicas y galvanostáticas, análisis de MottSchottky y espectroscopía de impedancia electroquímica que se realizaron en solución de Na 2 HPO 4 0,5 M (pH 9,2).Las curvas potenciodinámicas indican una región pasiva y un máximo de corriente en la región transpasiva. Las medidas galvanostáticas realizadas sobre películas pasivas formadas previamente indican dos amesetamientos de potencial, debido al óxido de Cr y óxido de Fe, del cual surgen dos tiempos de transición. El mayor espesor de óxido de hierro se encuentra en las estructuras equiaxial de la muestra F, que posee el menor espaciamiento dendrítico respecto de los otras dos muestras teniendo en cuenta la misma estructura. El análisis de Mott Schottky muestra que la película pasiva se comporta como un semiconductor tipo n en el rango de potenciales de -0,45 V a 0 V, con una densidad de donores que varía de acuerdo a la composición del acero inoxidable. También se observa que la densidad de donores varía de acuerdo al tipo de estructura para un mismo material.Palabras Clave: aceros inoxidables, película pasiva, Mott Schottky, resistencia a la corrosión. ABSTRACTPassivity of the stainless steel is attributed to the development of a protector film, formed by oxides on the metal surface. This film has semiconductor properties, and it is important for the understanding of corrosion phenomena.The objective of this work is to study the passive films formed in stainless steels samples solidified unidirectionally. The composition of the alloying elements in the samples are Fe-18Cr-10Ni-2Mo-0,08C (sample A), Fe-18Cr-14Ni-8Mo-0,03C (sample C) y Fe-18Cr-10Ni-8Mo-0,08C (sample F), and determine the influence of the structure (equiaxed, columnar and columnar-to-equiaxed transition, CET) in the corrosion resistance, as well as investigate the relationship between the corrosion resistance and the size of the secondary dendritic arm spacing. For this are used potentiodynamic and galvanostatic techniques, Mott Schottky analysis and electrochemical impedance spectroscopy.The measurements were performed in Na 2 HPO 4 0,5 M (pH = 9,2), at room temperature (25ºC).Potentiodynamic measurements indicate a passive region and a maximu...

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“…Recently, a combination of impedance measurements in an asymmetrical and a symmetrical configuration has been employed to characterize the conduction mechanism of the passive film on pure Fe [36], Fe-Cr and Fe-Cr-Mo alloys [37] in a borate solution at room temperature. The CEI measurements in the symmetrical configuration are an extension of the CER technique [38,39] to the frequency domain [33,36,37]. TLEC is used to measure the asymmetric configuration.…”

Section: Symmetrical and Asymmetrical Configurations For In Situ Studmentioning

confidence: 99%

“…It has been previously demonstrated [36,37,43] that the potential drop at the M/F interface is independent of the external applied potential in the steady state. In other words, only the rate constant of consumption of the ionic current carrier at the F/S interface depends on the applied potential: …”

Section: Kinetic Models For the Asymmetrical Configurationmentioning

confidence: 99%

Fundamental Understanding of Crack Growth in Structural Components of Generation IV Supercritical Light Water Reactors

Balachov¹,

Kobayashi²,

Tanzella³

et al. 2004

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REPORT DOCUMENTATION PAGEForm Approved OMB NO. Public Reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comment regarding this burden estimates or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302, and This work contributes to the design of safe and economical Generation-IV Super-Critical Water Reactors (SCWRs) by providing a basis for selecting structural materials to ensure the functionality of in-vessel components during the entire service life. During the second year of the project, we completed electrochemical characterization of the oxide film properties and investigation of crack initiation and propagation for candidate structural materials steels under supercritical conditions. We ranked candidate alloys against their susceptibility to environmentally assisted degradation based on the in situ data measured with an SRI-designed controlled distance electrochemistry (CDE) arrangement. A correlation between measurable oxide film properties and susceptibility of austenitic steels to environmentally assisted degradation was observed experimentally. One of the major practical results of the present work is the experimentally proven ability of the economical CDE technique to supply in situ data for ranking candidate structural materials for Generation-IV SCWRs. A potential use of the CDE arrangement developed at SRI for building in situ sensors for monitoring water chemistry in the heat transport circuit of Generation-IV SCWRs was evaluated and proved to be feasible. Understanding basic phenomena. Kinetic parameters of the charge and mass transport processes in the metal/oxide film/supercritical water system are derived from in situ oxide film studies to understand and quantify the rate-controlling processes and, eventually, the fundamentals of the metal oxidation phenomenon at supercritical temperatures. Providing a basis for the development of new alloys. Integration of the in situexperimental information on oxide film resistance to charge and mass transport for alloys of various compositions, along with fracture surface analysis and current theoretical understanding of the relationship between properties of the oxide films and stability of materials, is expected to aid in material selection and the development process. It will do so by providing recommendations for chemical compositions of the alloys in regard to their expected locations in the reactor (or more specifically, in regard to local temperature and oxidizing conditions). 1 WORK PERFORMED AND PRELIMINARY RESULTSDuring this project, SRI completed the electrochemical characterization of the oxide film prop...

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Contact electric impedance and resistance studies of the conduction mechanism in passive films on ferrous alloys

Cited by 24 publications

References 44 publications

The open-circuit ennoblement of alloy C-22 and other Ni-Cr-Mo alloys

The open-circuit ennoblement of alloy C-22 and other Ni-Cr-Mo alloys

Pasividad en solución de fosfato de aceros inoxidables solidificados unidireccionalmente

Fundamental Understanding of Crack Growth in Structural Components of Generation IV Supercritical Light Water Reactors

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