Contact Electric Resistance (CER) Technique for In-Situ Characterisation of Surface Films

Saario, Timo; Laitinen, Timo; Piippo, Juha

doi:10.4028/www.scientific.net/msf.289-292.193

Cited by 15 publications

(8 citation statements)

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“…31 As indicated above, when contacting mechanically two rough surfaces, the real contact area is always less than the nominal contact area. 34 The real contact area can be estimated by measuring the resistance of a metal rod and comparing the result with the CER response of the same rod cut into two pieces and inserted in the sample holders of the CER equipment.…”

Section: Methodsmentioning

confidence: 97%

Conduction Mechanism of the Passive Film on Iron Based on Contact Electric Impedance and Resistance Measurements

Bojinov¹,

Laitinen²,

Mäkelä³

et al. 2001

J. Electrochem. Soc.

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The application of a mixed conduction model and a new contact electric impedance ͑CEI͒ technique to predict quantitatively the electronic and ionic transport properties of oxide films on iron in a nearly neutral tetraborate solution is discussed. The mixedconduction model emphasizes the coupling between the ionic defect structure and the electronic conductivity in an anodic film. Conventional electrochemical techniques have not been sufficient to characterize properly the electronic and ionic properties of anodic films on metals. The CEI technique makes it possible to distinguish between processes taking place at different rates within oxide films. Using this technique together with the contact electric resistance technique, we have found that the diffusion coefficient for the electronic conduction in the anodic film on iron is several orders of magnitude higher than that for the ionic transport. This shows that the passive film on iron is predominantly an electronic conductor. The fitting of the experimental results to the mixed conduction model gives a good agreement and thus supports the validity of this model in the present case.The objective of this paper is to predict quantitatively the electronic and ionic transport properties of oxide films on iron from the ionic defect structure in the film. This prediction is based on a newly proposed mixed conduction model ͑MCM͒ for anodic passive films and experimental determination of the required parameters using a new contact electric impedance ͑CEI͒ technique.We believe that the transport properties of the film are closely related with the corrosion behavior of metals and alloys. Thus the results of this work serve to assess the resistance of metals and alloys to both general and localized corrosion.We have chosen iron in a nearly neutral environment to be the model system in our work. A considerable amount of work on iron has already been carried out to clarify the film growth and dissolution kinetics, 1-3 the electronic properties of the oxide film, 4-14 and the mechanism of ionic transport through it. [1][2][3]15,16 The close correlation between the dissolution kinetics and the electronic properties of the passive film on iron and synthetic iron oxides has been established in recent work. [17][18][19][20][21][22] The application of spectroscopic techniques based on synchrotron radiation and scanning probe microscopy 23,24 has revealed that anodic layers on iron have a spinel-like nanocrystalline structure. Consequently, the concepts based on point defects in crystalline materials 25-29 can with justice be applied to model the electronic and transport properties of thin passive films on iron. Quantitative correlations between the electronic and ionic transport properties of passive films, film composition, and film structure have not been established so far.Because of the need to combine the understanding of passive film structure and transport in the film, we have proposed a model for the coupling between ionic defect structure and electronic conduction in stea...

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Section: Methodsmentioning

confidence: 97%

Conduction Mechanism of the Passive Film on Iron Based on Contact Electric Impedance and Resistance Measurements

Bojinov¹,

Laitinen²,

Mäkelä³

et al. 2001

J. Electrochem. Soc.

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“…After pretreatment, the working and the Ir electrodes were brought in contact by the step motor driven system used in CER measurements [23,29]. The contact was opened only when the desired conditions (temperature and pressure) have been established in the autoclave.…”

Section: Apparatus and Proceduresmentioning

confidence: 99%

“…Briefly, in order to consider an impedance spectrum measured in the contact situation valid, its low-frequency limit should be independent on the contact pressure applied to the electrodes and it should be equal to the value measured by a four-point dc method to exclude the influence of the spreading resistance of the contact on the frequency response [43]. Both criteria were checked by measuring impedance spectra at pressures ranging from 0.3 to 7 MPa together with the resistance by the CER technique which is a four-point measurement method [28,29]. It has been found that the low-frequency limit of the impedance decreases with increasing contact pressure and reaches a constant value for a pressure of 3.5-4 MPa, which is still ca.…”

Section: Impedance Spectra In the Symmetrical Configuration And Theirmentioning

confidence: 99%

“…Such a configuration has been applied for the study of electroactive polymers by some of us [23] and also by others [24,25]. Recently, a combination between impedance measurements in an asymmetrical and a symmetrical configuration has been employed to characterise the conduction mechanism of the passive film on pure Fe [26], Fe-Cr and Fe-Cr-Mo alloys [27] in a borate so- [28,29] to the frequency domain [23,26,27]. The present paper focuses on the characterisation of the electrical and electrochemical properties of oxide films formed on Fe-Cr and Fe-Cr-Mo alloys in a borate electrolyte at 200 and 300°C using impedance spectroscopy in asymmetrical and symmetrical configurations.…”

Section: Introductionmentioning

confidence: 99%

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Conduction mechanism in oxide films on ferrous alloys studied by impedance spectroscopy in symmetrical and asymmetrical configurations

Betova

Bojinov

Kinnunen

et al. 2004

Journal of Electroanalytical Chemistry

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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%

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 Resistance (CER) Technique for In-Situ Characterisation of Surface Films

Cited by 15 publications

References 0 publications

Conduction Mechanism of the Passive Film on Iron Based on Contact Electric Impedance and Resistance Measurements

Conduction Mechanism of the Passive Film on Iron Based on Contact Electric Impedance and Resistance Measurements

Conduction mechanism in oxide films on ferrous alloys studied by impedance spectroscopy in symmetrical and asymmetrical configurations

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

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