Development of localized corrosion damage on low pressure turbine disks and blades: II. Passivity breakdown

Yancheng, Zhang; Urquidi‐Macdonald, Mirna; Engelhardt, George R.; Macdonald, Digby D.

doi:10.1016/j.electacta.2012.01.023

Cited by 36 publications

(55 citation statements)

References 18 publications

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“…The approximation to an order of magnitude is used here, because different crystal planes in a unit cell of polycrystalline material have different atom densities. Alternatively, from the linear relationship between the potentiodynamically-determined pitting potential and the square root of the scan rate employed in the potentiodynamic scan, Zhang et al 21 found that, for Type 403 stainless steel in chloride containing borate buffer solutions (pH = 8.1), ξ is equal to 7 × 10 14 cm −2 , a value that agrees well with that obtained in the present work.…”

Section: Results and Analysis By Numerical Optimizationsupporting

confidence: 81%

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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 Optimizationsupporting

confidence: 81%

“…Numerous models have been proposed for passivity breakdown, 2,7,11,19 and the Point Defect Model (PDM) is one of the only a few that has been demonstrated [20][21][22] to be capable of yielding relationships between the dependent (e.g. pitting potential and induction time) and the common independent (e.g.…”

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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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“…Previous work reported by Shibata et al [55] and Zhang et al [9,22,56] suggests that the breakdown potential is near-normally distributed. The near-normal distribution in breakdown potential is attributed to a normal distribution of potential breakdown sites with respect to the cation vacancy diffusivity, D (the distribution is characterized by a mean value,Ē b , and a standard deviation, D ), noting that a large number of breakdown sites exist upon a barrier film per unit area [8].…”

Section: Resultsmentioning

confidence: 91%

Exploration of the effect of chloride ion concentration and temperature on pitting corrosion of carbon steel in saturated Ca(OH) 2 solution

et al. 2015

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“…The adsorption of chloride ions into a passive film may increase the cation vacancy concentration in two possible ways: (1) Chlorides may enhance the transfer of metal ions from the oxide to the electrolyte; 62 (2) Chlorides may fill anion vacancies according to the point defect model (PDM). 29,30,33 As a consequence of mechanism (1), the concentration of surface cation vacancies increases in solutions containing chloride. The catalytically-enhanced transfer of cations from the oxide to the electrolyte leads to a new passive layer steady state.…”

Section: Effects Of Ph On Mechanisms Of Sulfur-induced Passivity Degrmentioning

confidence: 99%

“…This information can be obtained by electrochemical methods such as Electrochemical Impedance Spectroscopy (EIS) and Electrochemical Noise (EN). EIS has been used to investigate thin passive films for many years to extract useful parameters to characterize the structure of the passive film, and several models such as the Electrochemical Equivalent Circuit (EEC), 14,[25][26][27][28] point defect model (PDM) [29][30][31][32][33][34] and kinetic model 35,36 were developed. The latter two models have been more widely used recently; however, the EEC method is limited because the elements of the EEC have no specific physical meaning in some cases.…”

mentioning

confidence: 99%

pH Effect on Sulfur-Induced Passivity Degradation of Alloy 800 in Simulated Crevice Chemistries

Xia

Zhu

Behnamian

et al. 2014

J. Electrochem. Soc.

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The effects of pH on sulfur-induced passivity degradation of Alloy 800 in simulated crevice chemistries were evaluated using electrochemical impedance spectroscopy (EIS), secondary ion mass spectroscopy (SIMS), and Mott-Schottky analysis methods. Experimental results reveal that the detrimental effect of impurities containing sulfur at the reduced or intermediate oxidation level (S x ) on the passivity of Alloy 800 depends significantly on the solution pH. In neutral crevice (NC) chemistry containing chloride ions, the S x obstructs the healing process during repassivation, retards the dehydration reaction and also incorporates H, -OH and S into the passive film. However, the detrimental effect of S x is insignificant in an alkaline crevice (AKC) solution due to a change in surface adsorption and surface charge. Impurities containing sulfur at the reduced or intermediate oxidation level would cause Alloy 800 to lose its passivity and become active in an acidic crevice (AC) chemistry. Experimental evidence also indicates that the solution pH alters the semiconductor type of the surface film -from n-type in NC solution to p-type in AKC solution.

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Development of localized corrosion damage on low pressure turbine disks and blades: II. Passivity breakdown

Cited by 36 publications

References 18 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

Exploration of the effect of chloride ion concentration and temperature on pitting corrosion of carbon steel in saturated Ca(OH) 2 solution

pH Effect on Sulfur-Induced Passivity Degradation of Alloy 800 in Simulated Crevice Chemistries

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