Electrochemical characterisation and modelling of passive films on Ni- and Fe-based alloys: Dissertation

Research output: ThesisDissertationCollection of Articles

2 Citations (Scopus)

Abstract

The behaviour of oxide films formed on Ni- and Fe-based alloys in different environments has been studied electrochemically. The aim was to study the effect of pH, temperature and Cr content of the alloy on the protectiveness of the oxide film using a wide combination of electrochemical techniques: conventional linear sweep cyclic voltammetry, rotating ring-disc voltammetry, electrochemical impedance spectroscopy (EIS), contact electric resistance technique (CER) and contact electric impedance technique (CEI). The other goal was to develop modelling tools to describe and predict the oxide film behaviour in different conditions. Increasing pH has been found to decrease oxidation rates in both the passive and transpassive regions. Increasing pH as well as increasing temperature shifts the passive region in the negative direction on the potential scale. A higher amount of Cr in the alloy leads to a more passive oxide film on the metal surface both at low and high temperatures. On the other hand, transpassive dissolution takes place at lower potentials and its rate increases with higher Cr content of the alloy. The potential region of transpassive oxidation and secondary passivation increases and the effect of Cr on the electrochemical behaviour especially on Ni-Cr alloys decreases at high temperatures. The behaviour of oxide films in the passive state in different environments was simulated using the Mixed Conduction Model (MCM). Using this model the diffusion coefficients of current carriers and reaction rate constants at room temperature and profiles of resistances against ionic transport in the oxide films at 200°C were estimated. Also the transpassive dissolution of Ni-Cr alloys at room temperature was studied and a kinetic model proposed to determine quantitatively the reaction rates in the transpassive region. The model describes the oxidation and dissolution reactions of metal cations at the film/solution interface. The proposed model can be used to estimate steady-state current densities as well as dependencies of surface fractions of dissolving species on potential.
Original languageEnglish
QualificationDoctor Degree
Awarding Institution
  • Aalto University
Supervisors/Advisors
  • Sundholm, Göran, Supervisor, External person
Award date30 Aug 2002
Place of PublicationEspoo
Publisher
Print ISBNs951-38-5997-5
Electronic ISBNs951-38-5998-3
Publication statusPublished - 2002
MoE publication typeG5 Doctoral dissertation (article)

Fingerprint

Oxide films
Electric contacts
Dissolution
Oxidation
Temperature
Reaction rates
Metals
Lead alloys
Voltammetry
Electrochemical impedance spectroscopy
Passivation
Cyclic voltammetry
Cations
Rate constants
Current density
Kinetics

Keywords

  • Ni-based alloys
  • Fe-based alloys
  • Ni-Cr alloys
  • Fe-Cr alloys
  • oxide films
  • passive films
  • electro-chemistry
  • kinetic models
  • pH
  • high temperature
  • dissertations

Cite this

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title = "Electrochemical characterisation and modelling of passive films on Ni- and Fe-based alloys: Dissertation",
abstract = "The behaviour of oxide films formed on Ni- and Fe-based alloys in different environments has been studied electrochemically. The aim was to study the effect of pH, temperature and Cr content of the alloy on the protectiveness of the oxide film using a wide combination of electrochemical techniques: conventional linear sweep cyclic voltammetry, rotating ring-disc voltammetry, electrochemical impedance spectroscopy (EIS), contact electric resistance technique (CER) and contact electric impedance technique (CEI). The other goal was to develop modelling tools to describe and predict the oxide film behaviour in different conditions. Increasing pH has been found to decrease oxidation rates in both the passive and transpassive regions. Increasing pH as well as increasing temperature shifts the passive region in the negative direction on the potential scale. A higher amount of Cr in the alloy leads to a more passive oxide film on the metal surface both at low and high temperatures. On the other hand, transpassive dissolution takes place at lower potentials and its rate increases with higher Cr content of the alloy. The potential region of transpassive oxidation and secondary passivation increases and the effect of Cr on the electrochemical behaviour especially on Ni-Cr alloys decreases at high temperatures. The behaviour of oxide films in the passive state in different environments was simulated using the Mixed Conduction Model (MCM). Using this model the diffusion coefficients of current carriers and reaction rate constants at room temperature and profiles of resistances against ionic transport in the oxide films at 200°C were estimated. Also the transpassive dissolution of Ni-Cr alloys at room temperature was studied and a kinetic model proposed to determine quantitatively the reaction rates in the transpassive region. The model describes the oxidation and dissolution reactions of metal cations at the film/solution interface. The proposed model can be used to estimate steady-state current densities as well as dependencies of surface fractions of dissolving species on potential.",
keywords = "Ni-based alloys, Fe-based alloys, Ni-Cr alloys, Fe-Cr alloys, oxide films, passive films, electro-chemistry, kinetic models, pH, high temperature, dissertations",
author = "Petri Kinnunen",
year = "2002",
language = "English",
isbn = "951-38-5997-5",
series = "VTT Publications",
publisher = "VTT Technical Research Centre of Finland",
number = "472",
address = "Finland",
school = "Aalto University",

}

Electrochemical characterisation and modelling of passive films on Ni- and Fe-based alloys : Dissertation. / Kinnunen, Petri.

Espoo : VTT Technical Research Centre of Finland, 2002. 77 p.

Research output: ThesisDissertationCollection of Articles

TY - THES

T1 - Electrochemical characterisation and modelling of passive films on Ni- and Fe-based alloys

T2 - Dissertation

AU - Kinnunen, Petri

PY - 2002

Y1 - 2002

N2 - The behaviour of oxide films formed on Ni- and Fe-based alloys in different environments has been studied electrochemically. The aim was to study the effect of pH, temperature and Cr content of the alloy on the protectiveness of the oxide film using a wide combination of electrochemical techniques: conventional linear sweep cyclic voltammetry, rotating ring-disc voltammetry, electrochemical impedance spectroscopy (EIS), contact electric resistance technique (CER) and contact electric impedance technique (CEI). The other goal was to develop modelling tools to describe and predict the oxide film behaviour in different conditions. Increasing pH has been found to decrease oxidation rates in both the passive and transpassive regions. Increasing pH as well as increasing temperature shifts the passive region in the negative direction on the potential scale. A higher amount of Cr in the alloy leads to a more passive oxide film on the metal surface both at low and high temperatures. On the other hand, transpassive dissolution takes place at lower potentials and its rate increases with higher Cr content of the alloy. The potential region of transpassive oxidation and secondary passivation increases and the effect of Cr on the electrochemical behaviour especially on Ni-Cr alloys decreases at high temperatures. The behaviour of oxide films in the passive state in different environments was simulated using the Mixed Conduction Model (MCM). Using this model the diffusion coefficients of current carriers and reaction rate constants at room temperature and profiles of resistances against ionic transport in the oxide films at 200°C were estimated. Also the transpassive dissolution of Ni-Cr alloys at room temperature was studied and a kinetic model proposed to determine quantitatively the reaction rates in the transpassive region. The model describes the oxidation and dissolution reactions of metal cations at the film/solution interface. The proposed model can be used to estimate steady-state current densities as well as dependencies of surface fractions of dissolving species on potential.

AB - The behaviour of oxide films formed on Ni- and Fe-based alloys in different environments has been studied electrochemically. The aim was to study the effect of pH, temperature and Cr content of the alloy on the protectiveness of the oxide film using a wide combination of electrochemical techniques: conventional linear sweep cyclic voltammetry, rotating ring-disc voltammetry, electrochemical impedance spectroscopy (EIS), contact electric resistance technique (CER) and contact electric impedance technique (CEI). The other goal was to develop modelling tools to describe and predict the oxide film behaviour in different conditions. Increasing pH has been found to decrease oxidation rates in both the passive and transpassive regions. Increasing pH as well as increasing temperature shifts the passive region in the negative direction on the potential scale. A higher amount of Cr in the alloy leads to a more passive oxide film on the metal surface both at low and high temperatures. On the other hand, transpassive dissolution takes place at lower potentials and its rate increases with higher Cr content of the alloy. The potential region of transpassive oxidation and secondary passivation increases and the effect of Cr on the electrochemical behaviour especially on Ni-Cr alloys decreases at high temperatures. The behaviour of oxide films in the passive state in different environments was simulated using the Mixed Conduction Model (MCM). Using this model the diffusion coefficients of current carriers and reaction rate constants at room temperature and profiles of resistances against ionic transport in the oxide films at 200°C were estimated. Also the transpassive dissolution of Ni-Cr alloys at room temperature was studied and a kinetic model proposed to determine quantitatively the reaction rates in the transpassive region. The model describes the oxidation and dissolution reactions of metal cations at the film/solution interface. The proposed model can be used to estimate steady-state current densities as well as dependencies of surface fractions of dissolving species on potential.

KW - Ni-based alloys

KW - Fe-based alloys

KW - Ni-Cr alloys

KW - Fe-Cr alloys

KW - oxide films

KW - passive films

KW - electro-chemistry

KW - kinetic models

KW - pH

KW - high temperature

KW - dissertations

M3 - Dissertation

SN - 951-38-5997-5

T3 - VTT Publications

PB - VTT Technical Research Centre of Finland

CY - Espoo

ER -