The Anodic Dissolution of a Ni-Base Superalloy

Cavanaugh, Margaret A.; Kargol, J.A.; Nickerson, Jessica L.; Fiore, N.F.

doi:10.5006/1.3580829

Cited by 21 publications

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“…This was consistent with the observations of others that Mo-containing alloys exhibit lower crevice pH. 16,25 The dissolution and hydrolysis of Mo containing species is quite complex, depending upon the potential and acidity of the solution. For example, at high applied potentials, dissolution of Mo to form Mo(VI) results in the formation of molybdate (MoO 4 2-) and generation of H + by the following reaction: …”

Section: Effect Of Alloy Composition On Ph Changessupporting

confidence: 90%

“…However, when Mo content in the alloy was very high, such as in alloy C-276 (UNS N10276, [1] 16% Mo), Mo concentration in the solution decreased, and the resulting pH in the pit was higher than a lower Mo-containing alloy, such as type 316L SS (UNS S31603). 25 The total Clconcentration increased to values as high as 12 N. However, there was a maximum in Clconcentration inside pits at intermediate values of pit volumes, corresponding to a pit diameter of ~ 0.4 mm. [16][17] The Clconcentration inside crevices, which usually can be regarded as large pits, has not been found to attain such large values.…”

Section: Corrosion-november 1994mentioning

confidence: 91%

“…25 MoO 4 2has been identified in pits by Cavanaugh, et al, for alloy C-276 that was polarized anodically to ~ 0.95 V SCE . 25 Suzuki, et al, determined that Mo 3+ was present in pits of type 316L SS polarized to ~ -0.2 V SCE . 16 Hydrolysis of Mo 3+ can occur by the reaction:…”

Section: Effect Of Alloy Composition On Ph Changesmentioning

confidence: 95%

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Effect of Applied Potential on Changes in Solution Chemistry Inside Crevices on Type 304L Stainless Steel and Alloy 825

Sridhar

Dunn

1994

CORROSION

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Section: Effect Of Alloy Composition On Ph Changessupporting

confidence: 90%

Section: Corrosion-november 1994mentioning

confidence: 91%

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Effect of Applied Potential on Changes in Solution Chemistry Inside Crevices on Type 304L Stainless Steel and Alloy 825

Sridhar

Dunn

1994

CORROSION

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“…i HCl = 3 × 10 −6 e 1.3·m HCl [12] where i HCl is the peak current density, and m is the HCl concentration in molal. Equating the HCl and metal salts relationships, i salt = i HCl , the following relationship is obtained …”

Section: Discussionmentioning

confidence: 99%

“…Cavanaugh et al 12 studied the composition of an alloy C-276 solution produced by a high anodic polarization (10 mA/cm 2 ). Analysis of the dissolved metal cations in solution indicated that the relative dissolution rates of the alloy elements were Fe≥Ni>Mo>Cr.…”

mentioning

confidence: 99%

Metal Salt Solutions as a Simulant for the Chemistry in Crevices of Nickel Alloy 625

Salgado

Lillard

2017

J. Electrochem. Soc.

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The development of a critical crevice solution plays an important role in crevice corrosion propagation in nickel alloy 625. In this investigation, the polarization response of alloy 625 in a set of simulated crevice chemistries using metal chloride salts has been studied. Specifically, solutions were made from NiCl 2 , CrCl 3 , FeCl 2 , MoCl 3, and NbCl 5 in the same stoichiometric ratio as they appear in the alloy and ranging in concentration from 3.0 to 5.0 molal (m). It was found that Mo and Nb contributed to lower open circuit potentials (OCP) and increased critical peak current densities (i.e. activation). Solutions that substituted NiCl 2 for MoCl 3 and NbCl 5 , such that the chloride content was equivalent to that of the NiCrFeMoNb solution, presented high OCP values and passive behavior. To better understand the polarization data, solution speciation and pH were calculated using a commercially available software package. It was found that for concentrations ranging from 3.0 to 5.0 m, the pH values were on the order of −1.0. In addition, the active to passive transition appeared to correlate with an increase of Mo 3+ concentration in solution. For comparison, the polarization response of alloy 625 in HCl-based solutions was investigated. Over the range of HCl concentrations studied, the critical peak current densities were typically lower than the metal salt solutions at equivalent calculated pH. In addition, an equation for preparing HCl solutions at the needed pH to obtain an equivalent critical peak current density as observed in the NiCrFeMoNb solutions is presented. Oldfield and Sutton's model 1,2 has been widely used for explaining crevice corrosion initiation and propagation based on the solution chemistry change within crevices. According to Oldfield's and Sutton's model, the initiation stage of crevice corrosion is divided into three processes occurring inside the crevice: 1) depletion of oxygen, 2) metal hydrolysis resulting in lower pH and chloride-migration, and ultimately 3) formation of a critical crevice solution (CCS). Once crevice corrosion initiates, the propagation stage immediately follows (stage 4). The passive current density (i pass ) and the crevice geometry (depth-to-gap ratio) are the key parameters that aid the development of a CCS. The model predicts that for a constant i pass , larger crevice gaps required deeper crevices to initiate crevice corrosion. Thus, occluded regions with large depth-to-gap ratios have increased susceptibility to crevice corrosion damage. The Oldfield-Sutton-model does not, however, consider the effect of the IR-drop within the crevice (i.e. the electrode-potential variation between the cavity and the outer surface), nor does it predict the location and rate of the crevice damage that occurs within the crevice.A model based solely on IR-drop as the cause for initiating and propagating crevice corrosion was proposed by Pickering.3,4 Early versions of the Pickering model did not separate the initiation and propagation stages. Instead, the critical requi...

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Korrosionsverhalten von Plasma‐ Heißdraht‐Auftrag‐Schweißungen. Teil I: Beständigkeit von auftraggeschweißten Nickelbasislegierungen gegen Loch‐ und interkristalline Korrosion

Garz

Schultze

Göllner

et al. 1995

Materials & Corrosion

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den in zunehmendem MaBe Duplexstahle sowie Nickelbasislegierungen der Hastelloy-C-Reihe fur den Einsatz in aggressiven Medien, wie z.B. chlorid-und fluoridhaltigen Sauren, genutzt [l]. Zur Herstellung derartiger Schichtverbunde steht eine Vielzahl von Technologien zur Verfiigung, bei denen dem Walzplattieren, dem Sprengplattieren und dem Hochleistungsauftragschweifien eine besondere Bedeutung zukommt. Von diesen Verfahren wird besonders das Auftragschweifien mit gro-Bern Erfolg bei Bauteilen eingesetzt, die auf Grund ihrer Gro-Be und komplizierten Geometrie nicht walz-und sprengplattiert werden konnen. Eine wirtschaftlich gunstige Moglichkeit, dunne aufmischungsarme Schichten mit einer geringen Lagendicke aufzutragen, stellt das Plasma-Heil3draht-Auftrag-Schweifien (PHA) dar [2-51. Gegenstand der vorliegenden Arbeit sind PHA-SchweiBungen der Nickel basislegierungen C 276 (NiMo16CrlSW), C 4 (NiMol6Crl6Ti) und C 22 (NiCr2lMo14W) auf St 52-3. In einer weiteren Arbeit (Teil 11) 0947-5 1 1 7/95/0808-0460$5.00+.25/~ 0 VCH Verlagsgesellschaft mbH, D-69451 Weinheim, I995 Materials and Corrosion 46, 460-467 (1995) Korrosionsverhalten von Plasma-Heil3draht-Auftrag-SchweiRungen

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The Anodic Dissolution of a Ni-Base Superalloy

Cited by 21 publications

References 0 publications

Effect of Applied Potential on Changes in Solution Chemistry Inside Crevices on Type 304L Stainless Steel and Alloy 825

Effect of Applied Potential on Changes in Solution Chemistry Inside Crevices on Type 304L Stainless Steel and Alloy 825

Metal Salt Solutions as a Simulant for the Chemistry in Crevices of Nickel Alloy 625

Korrosionsverhalten von Plasma‐ Heißdraht‐Auftrag‐Schweißungen. Teil I: Beständigkeit von auftraggeschweißten Nickelbasislegierungen gegen Loch‐ und interkristalline Korrosion

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