Electrochemical and metallographic evaluation of alloys C-22 and 625

Roy, Ajit K.; Fleming, D.L.; Lum, B.Y.

doi:10.2172/576007

Cited by 2 publications

(2 citation statements)

References 7 publications

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“…After 10,000 years at 80°C, the predicted penetration of Alloy C-22 does not exceed the thickness of the inner barrier wall (2 cm). [34][35][36]. M t s at 0,600,1200,1800,2400 and 3000 seconds are presented, though calculations were done at intervals of 1 second.…”

Section: Semi-empirical Modelsmentioning

confidence: 99%

CREVICE CORROSION & PITTING OF HIGH-LEVEL WASTE CONTAINERS: INTEGRATION OF DETERMINISTIC & PROBABILISTIC MODELS

Mccright¹

1997

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A key component of the Engineer& Barrier System (EBS) being designed for containment of spent-fuel and high-level waste at the proposed geological repository at Yucca Mountain, Nevada is a two-layer canister. In this particular design, the inner barrier is made of a corrosion resistant material (CRM) such as Alloy 625 or C-22, while the outer barrier is made of a corrosion-allowance material (CAM) such as carbon steel or Monel 400. An integrated predictive model is be'= developed to account for the effects of localized environmental conditions in the CM-CAM crevice on the initiation and propagation of pits through the CRM.

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Section: Semi-empirical Modelsmentioning

confidence: 99%

CREVICE CORROSION & PITTING OF HIGH-LEVEL WASTE CONTAINERS: INTEGRATION OF DETERMINISTIC & PROBABILISTIC MODELS

Mccright¹

1997

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“…[1] Previous studies have shown that the mechanical and corrosion properties of this alloy did not change when it was aged for up to 40,000 hours at 427 °C. [5,6,7] Microstructural changes that occur in the base material have been evaluated at temperatures from 427 °C to 760 °C. Tetrahedral close-packed (TCP) phases precipitate in the Alloy 22 at temperatures of 593 °C and higher.…”

mentioning

confidence: 99%

Influence of halide ions and alloy microstructure on the passive and localized corrosion behavior of alloy 22

Rodríguez

Carranza

Rebak

2005

Metall Mater Trans A

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Alloy 22 (N06022) is the current candidate alloy used to fabricate the external wall of the high-level nuclear waste containers for the Yucca Mountain repository. It was of interest to study and compare the general and localized corrosion susceptibility of Alloy 22 in fluoride and chloride solutions at 90°C. Standard electrochemical tests such as cyclic potentiodynamic polarization, amperometry, and electrochemical impedance spectroscopy were used. Studied variables included the solution pH and the alloy microstructure (thermal aging). Results show that Alloy 22 is highly resistant to general corrosion in all the solutions tested. Thermal aging is not detrimental and even seems to be slightly beneficial for general corrosion at the higher solution pHs. Pitting corrosion was never observed. Crevice corrosion was found only for high chloride-containing solutions after anodic polarization. The presence of fluoride ions together with chloride ions seems to increase the susceptibility of Alloy 22 to crevice corrosion compared to pure chloride solutions.The maximum allowed temperature by design specifications is 350 °C. [1] Previous studies have shown that the mechanical and corrosion properties of this alloy did not change when it was aged for up to 40,000 hours at 427 °C. [5,6,7] Microstructural changes that occur in the base material have been evaluated at temperatures from 427 °C to 760 °C. Tetrahedral close-packed (TCP) phases precipitate in the Alloy 22 at temperatures of 593 °C and higher. [8,9,10] These phases could have a detrimental effect upon corrosion resistance and cause loss of mechanical ductility. A long-range ordering (LRO) reaction can occur at lower temperatures and produce an ordered Ni 2 (Cr,Mo) phase. [7,8] This ordering reaction is thought to cause little or no effect on corrosion and causes only a slight loss in ductility.Alloys that rely on passive oxide films for protection against corrosion are susceptible to localized corrosion, especially in the presence of halide ions. [11,12] Different concentrations of fluorides and chlorides can be naturally found in ground waters. While the effects of chlorides on the passive state and localized corrosion have been extensively studied for austenitic alloys that form chromium oxide films, the effects of fluorides have not been fully characterized. [13][14][15][16] The aim of this study was to investigate the effects of pH and thermal aging on the susceptibility of Alloy 22 to general and localized corrosion in chloride, fluoride, and mixtures of chloride-fluoride solutions. The results presented in this study correspond to solutions containing a much larger amount of chloride and fluoride than in the ground water at Yucca Mountain, which are approximately 7 and 2 mg/L, respectively. One M fluoride represents 19,000 mg/L and one M chloride represents 35,000 mg/L; these values are 5000 to 10,000 times the concentration of halide in the ground water. [12] II. EXPERIMENTAL PROCEDURE Specimens of Alloy 22 were prepared from wrought mill annealed plate stoc...

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Electrochemical and metallographic evaluation of alloys C-22 and 625

Cited by 2 publications

References 7 publications

CREVICE CORROSION & PITTING OF HIGH-LEVEL WASTE CONTAINERS: INTEGRATION OF DETERMINISTIC & PROBABILISTIC MODELS

CREVICE CORROSION & PITTING OF HIGH-LEVEL WASTE CONTAINERS: INTEGRATION OF DETERMINISTIC & PROBABILISTIC MODELS

Influence of halide ions and alloy microstructure on the passive and localized corrosion behavior of alloy 22

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