Steady‐State Passive Films: Interfacial Kinetic Effects and Diagnostic Criteria

Macdonald, Digby D.; Biaggio, Sonia R.; Song, Herking

doi:10.1149/1.2069165

Cited by 274 publications

(191 citation statements)

References 13 publications

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“…The PDM [26][27][28][29][30] proposes that the structure and properties of the barrier layer of the passive film are governed by a set of defect generation and annihilation reactions occurring at the metal/barrier layer (m/bl) interface and at the barrier layer/solution (bl/s) interface. Specifically, cation vacancies are generated at bl/s interface and annihilated at m/bl interface, with the latter process occurring via the reaction (Fig.…”

Section: Kinetics Of Metastable Pit Nucleation In Terms Of the Pdmmentioning

confidence: 99%

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: Kinetics Of Metastable Pit Nucleation In Terms Of the Pdmmentioning

confidence: 99%

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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“…According to Macdonald and co-workers, 6,30 the potential drop at the oxide/electrolyte interface reduces the activation energy 31 of the dissolution reaction, and the dissolution rate ͑mol s −1 ͒ of the oxide film is given by…”

mentioning

confidence: 99%

Breakdown Kinetics at Nanostructure Defects of Passive Films

Seyeux

Maurice

Marcus

2009

Electrochem. Solid-State Lett.

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Kinetics expressions for passivity breakdown have been determined based on a model taking into account the presence of intergranular defective sites in passive films. It is shown that depending on the interface at which the potential drop increase predominates, passivity breakdown can occur by enhanced dissolution ͑i.e., oxide thinning͒ at the oxide/electrolyte interface or by accelerated interfacial voiding at the metal/oxide interface. In all cases, the rate of the interfacial processes leading to passivity breakdown is increased at the intergranular defective sites of the passive film.

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“…In fact, before the voltage oscillations begin, the specimens are already passivated by an oxide film that is basically a non-porous, compact, and uniform barrier-type film 22,23 . The plasma discharges on the samples are observed to become more intense during the MAO treatment as the current density is increased.…”

Section: Surface Characterizationmentioning

confidence: 99%

Fatigue behavior and physical characterization of surface-modified Ti-6Al-4V ELI alloy by micro-arc oxidation

et al. 2012

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Anodizing has proven an effective method for preparing bioactive titanium and has been the subject of many studies regarding the performance and biological characterization of the layers obtained. However, the fatigue behavior of titanium alloys, after undergoing this process is still poorly studied. This study aims to investigate the influence of MAO (Micro-Arc Oxidation) process on the fatigue properties of titanium alloy Ti-6Al-4V. Therefore axial fatigue tests were performed to obtain SxN curves, of specimens in polished and anodized (MAO processed, phosphate salt solution, potential of 290 V) conditions. Roughness measurements, SEM, Raman spectra and X-ray photoelectron spectroscopy (XPS) analyses were used to characterize the features of the modified surface. SEM was also used to analyze the fatigue fractures of the tested specimens. The MAO process, with the parameters used in this investigation, had no influence on the fatigue behavior of the Ti-6Al-4V alloy, when compared to specimens without surface modification.

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Steady‐State Passive Films: Interfacial Kinetic Effects and Diagnostic Criteria

Cited by 274 publications

References 13 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

Breakdown Kinetics at Nanostructure Defects of Passive Films

Fatigue behavior and physical characterization of surface-modified Ti-6Al-4V ELI alloy by micro-arc oxidation

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