Role of Metastable Pitting in Crevices on Crevice Corrosion Stabilization in Alloys 625 and 22

Kehler, B. A.; Scully, John R.

doi:10.5006/1.3278202

Cited by 44 publications

(25 citation statements)

References 3 publications

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“…In order to demonstrate the validity of the model over a broad scope of micro-structural features, six sets of data (assigned as Set I-VI, with details listed in Table I) were collected from the literature on a variety of metallic materials, including stainless steel, 7,8 carbon steel, 35 pure iron, 4 pure aluminum, 36 and Alloy-22. 37 Note again that all the data selected in this work are on the nucleation of metastable pits, not stable pits, as emphasized above. Sets I-III are data of evolution of the nucleation rate of metastable pits, while Set IV-VI are data of evolution of cumulative number density of metastable pitting events.…”

Section: Results and Analysis By Numerical Optimizationmentioning

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: Results and Analysis By Numerical Optimizationmentioning

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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“…Metastable pitting is more easily stabilized in an occluded region like a crevice, giving rise to crevice corrosion (Szklarska-Smialowska, 2005). Stable crevice corrosion occurs at the sites where a row of metastable pits formed at a critical distance from the crevice mouth (Kehler & Scully, 2005).…”

Section: Stages Of Localized Corrosion and Critical Conditions To Promentioning

confidence: 99%

Inhibition of localized corrosion in chromium containing stainless alloys

Rodríguez

2012

Corrosion Reviews

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The application of stainless steels and chromium containing nickel-based alloys is limited by their susceptibility to localized corrosion in the forms of pitting and crevice corrosion or environmentally assisted cracking. Inhibitors may be normally found in service environments or added on purpose to mitigate or avoid the effects of aggressive agents such as chloride ions. The present study critically reviews the present knowledge on inhibition of chloride-induced pitting and crevice corrosion. Pioneering studies and recent fi ndings are analyzed in light of the present theories for describing the localized corrosion processes. This review particularly focuses on the inhibition of crevice corrosion of alloy 22, which has been thoroughly studied in the past decade.

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“…The crevice corrosion test results were in agreement with cyclic polarization test results in which the breakdown potentials of Ni-Cu alloys were lower than that of base metal, and the repassivation potentials were higher. Some researchers [32][33][34] proposed that crevice initiation could be related to the metastable pitting stage of an alloy. Pd addition increases the corrosion resistance of Ni-Cu alloys so that 308L/304L, with lower repassivation potential than Ni-Cu and Ni-Cu-Pd, is more susceptible to crevice attack.…”

Section: Generation Ii: Ni-cu and Ni-cu-pd Sma Weldsmentioning

confidence: 99%

A corrosion study of nickel–copper and nickel–copper–palladium welding filler metals

Liang¹,

Sowards²,

Frankel³

et al. 2010

Materials & Corrosion

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In an effort to reduce the release of fumes containing carcinogenic Cr 6þ during arc welding of stainless steel, Cr-free filler metals for welding of SS304 have been developed. Corrosion studies were carried out on 304L stainless steel samples welded with these Cr-free consumables. The corrosion properties of gas tungsten arc (GTA) and shielded metal arc (SMA) welds fabricated with Ni-Cu and Ni-Cu-Pd consumables were found to be comparable to those of welds fabricated with SS308L, the standard filler metal used with SS304. Although the breakdown potentials of the welds made using both welding processes were lower than that of the SS308L GTA weld, the repassivation potentials of these welds were much higher. Generally, the repassivation potential is a more conservative measure of susceptibility to localized corrosion. Accordingly, the Ni-Cu and Ni-Cu-Pd welds were more resistant to crevice corrosion than SS308L welds. The addition of a small amount of Pd improved the corrosion resistance relative to Ni-Cu welds, which is consistent with previous studies from specially-prepared button samples and bead-on-plate samples. Other corrosion studies such as creviced and uncreviced long time immersion, atmospheric exposure, and slow strain rate testing suggest that Ni-Cu-Pd filler metal can be a potential replacement for the conventional SS308L filler metal for joining SS304.

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Role of Metastable Pitting in Crevices on Crevice Corrosion Stabilization in Alloys 625 and 22

Cited by 44 publications

References 3 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

Inhibition of localized corrosion in chromium containing stainless alloys

A corrosion study of nickel–copper and nickel–copper–palladium welding filler metals

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