An electrochemical impedance study of Alloy 22 in NaCl brine at elevated temperature. I. Corrosion behavior

Priyantha, Namal; Jayaweera, Palitha; Macdonald, Digby D.; Sun, Adan

doi:10.1016/j.jelechem.2004.06.031

Cited by 79 publications

(84 citation statements)

References 12 publications

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“…It has been demonstrated previously [41][42][43] that the PDM can readily explain the observations of the passive state on Alloy-22. Characterization work 41,[44][45][46] has demonstrated that the passive film on Alloy-22 has a distinct layered structure with the inner layer primarily comprising Cr(III) oxide, so it is assumed in the optimization that point defective Cr 2 O 3 is the principal composition of the barrier layer.…”

Section: Results and Analysis By Numerical Optimizationmentioning

confidence: 79%

The Kinetics of Nucleation of Metastable Pits on Metal Surfaces: The Point Defect Model and Its Optimization on Data Obtained on Stainless Steel, Carbon Steel, Iron, Aluminum and Alloy-22

Lü

Engelhardt

Kursten

et al. 2016

J. Electrochem. Soc.

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The theory of the kinetics of metastable pit nucleation in terms of the Point Defect Model (PDM) has been applied the first time to describing the evolution of the nucleation rate of metastable pits on a variety of metallic substrates. The PDM successfully accounts for the experimental data that have been reported in the literature on stainless steel, carbon steel, iron, aluminum, and Alloy-22, and which are judged to be reliable and reproducible. Important fundamental parameters related to metastable pitting such as total number density of pitting nucleation sites, dissolution time of the cap over the pit, energy related to absorption of the aggressive ions into oxygen vacancies in the surface of the barrier layer, vacancy condensation rate, and the time at which the nucleation rate of metastable pits is maximum were obtained from the optimization of the PDM on the experimental data, as reported in the present paper. The values obtained for those parameters are in good agreement with values and observations reported elsewhere. The present work successfully demonstrates the capacity of the PDM in accounting for experimental observations of metastable pitting and that the PDM can be applied as an underlying theory for studying and understanding metastable pitting on metal surfaces. The passive state is not perfectly protective and passivity breakdown occurs for various reasons, giving rise to enhanced general corrosion rate or to localized corrosion. Localized passivity breakdown is especially of great concern, because it results in the nucleation and propagation of pits and the subsequent nucleation and growth of cracks provided that there is sufficient tensile stress in the system to initiate crack nucleation at the stress raiser represented by the pit. Metastable pitting, in which passivity breakdown occurs followed immediately by repassivation, is now well-accepted as being an integral part of the process of pitting corrosion on a metal or alloy, culminating in the accumulation of damage via the development of stable pits. It is also well-recognized that repassivation reflects the failure on the part of the pit nucleus to establish a spatial separation between the local cathode and the local anode with the former occurring on the external surfaces and the latter taking place in the nucleus, which is necessary for the buildup and maintenance of the aggressive conditions of high [Cl − ] and high [H + ] (low pH) that cause the pits to grow as stable pits, until they, too, die via delayed repassivation (due to the inability of the pit to maintain separation of the local cathode and the local anode, because of the limited availability of resources of the cathodic depolarizer on the external surfaces).Numerous authors have reported metastable pit nucleation rate data measured under more-or-less well-defined conditions. Williams et al.1-3 reported a good proportional correspondence for Type 304L SS between the nucleation frequency of metastable pits and the frequency of occurrence of propagating (stable) pits, that ...

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Section: Results and Analysis By Numerical Optimizationmentioning

confidence: 79%

The Kinetics of Nucleation of Metastable Pits on Metal Surfaces: The Point Defect Model and Its Optimization on Data Obtained on Stainless Steel, Carbon Steel, Iron, Aluminum and Alloy-22

Lü

Engelhardt

Kursten

et al. 2016

J. Electrochem. Soc.

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“…Other studies have used this circuit to fit the impedance data obtained with conductive metallic oxides [14][15][16]. Another electrical circuit, Rs L (R 1 Q 1 ) (R 2 Q 2 ) (R 3 Q 3 ) has also been reported, where (R 1 Q 1 ), (R 2 Q 2 ) and (R 3 Q 3 ) correspond to the capacitive and resistive contributions of the barrier layer/metal interface, the bulk barrier layer and the electrolyte/barrier layer interface, respectively [17,18].…”

Section: Introductionmentioning

confidence: 94%

Electrochemical impedance spectroscopy investigation of spinel type cobalt oxide thin film electrodes in alkaline medium

et al. 2008

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Spinel type Co 3 O 4 thin films, for the oxygen evolution reaction (OER) in 1 M KOH, have been prepared, on stainless steel supports, using the thermal decomposition method at 400°C. The electrochemical behaviour of the oxide film/1 M KOH interface was investigated by cyclic voltammetry and impedance techniques. The impedance measurements were carried out at different positive potentials, from the open circuit potential to a potential in the OER region and the electrical equivalent circuit, L (R 1 Q 1 ) (R 2 Q 2 ) (R 3 Q 3 ) was used to fit the experimental results. At each potential, a good correlation between experimental and simulated data is found, thereby validating the proposed equivalent circuit model. The roughness factor value determined in the potential region where the charge transfer reaction is negligible is similar to that obtained by cyclic voltammetry, with a value of 70 ± 2.

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“…Point defect model (PDM) [19][20][21] has been used to provide an excellent description of the passive film growth and breakdown. Using this model it can be obtained quantitative analysis of the passive film as well as an analytical expression for the flux and concentration of vacancies within the passive film.…”

Section: Mott-schottky Analysismentioning

confidence: 99%

Electrochemical Behavior of the Passive Films Formed on Alloy 22 (UNS N06022) in Acidic Solutions

2015

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Passive behavior and semiconducting properties of alloy 22 in sulfuric and nitric acidic solutions were studied. Corrosion current density was measured from potentiodynamic polarization plots, defect density was drawn from Mott-Schottky analysis, and finally polarization resistance and passive film thickness were estimated by electrochemical impedance spectroscopy. Potentiodynamic polarization curves suggested that alloy 22 showed excellent passive behavior in both nitric and sulfuric solutions. Mott-Schottky analysis revealed that the passive films formed on alloy 22 in both acidic solutions behave as n-type and p-type semiconductors. Also, this analysis indicated that the donor and acceptor densities are in the range 10 21 cm −3 and increased with solution concentration. In conclusion, electrochemical impedance spectroscopy and Mott-Schottky analysis revealed that dilute nitric and sulfuric acidic solutions offer better conditions of the passive film formation on alloy 22 with higher protection behavior than concentrated nitric and sulfuric solutions, due to the growth of a much thicker and less defective films.

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An electrochemical impedance study of Alloy 22 in NaCl brine at elevated temperature. I. Corrosion behavior

Cited by 79 publications

References 12 publications

The Kinetics of Nucleation of Metastable Pits on Metal Surfaces: The Point Defect Model and Its Optimization on Data Obtained on Stainless Steel, Carbon Steel, Iron, Aluminum and Alloy-22

The Kinetics of Nucleation of Metastable Pits on Metal Surfaces: The Point Defect Model and Its Optimization on Data Obtained on Stainless Steel, Carbon Steel, Iron, Aluminum and Alloy-22

Electrochemical impedance spectroscopy investigation of spinel type cobalt oxide thin film electrodes in alkaline medium

Electrochemical Behavior of the Passive Films Formed on Alloy 22 (UNS N06022) in Acidic Solutions

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