Anodic Behavior of Alloy 22 in Calcium Chloride and in Calcium Chloride Plus Calcium Nitrate Brines

Evans, K. F.; Day, S D; Ilevbare, G. O.; Whalen, Michael T.; King, Kenneth J.; Hust, Gary A.; Estill, John C.; Rebak, Raúl B.

doi:10.1115/pvp2003-2140

Cited by 14 publications

(24 citation statements)

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“…13 Before mounting them onto the metallic specimens, the CF were covered with PTFE tape to ensure a tight crevicing gap. [14][15][16] The specimens had a ground finish of 600grit paper. There are two types of specimens mentioned in this work: (1) The as-received wrought mill annealed (MA) and (2) the solution heat-treated (MA + SHT) which were annealed in air for 20 min at 1121°C and then water quenched.…”

Section: Methodsmentioning

confidence: 99%

Influence of Black Annealing Oxide Scale on the Anodic Behavior of Alloy 22

et al. 2006

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The resistance of Alloy 22 (N06022) to localized corrosion, mainly crevice corrosion, has been extensively investigated in the last few years. The effect of influencing variables such as temperature, applied potential, chloride concentration and nitrate inhibitor concentration have been addressed previously. At this time, it was important to address the effect an oxide film or scale that forms during the high temperature annealing process or solution heat treatment (SHT) and its subsequent water quenching. Electrochemical tests such as cyclic potentiodynamic polarization (CPP) have been carried out to determine the repassivation potential for localized corrosion and to assess the mode of attack on the specimens. Tests have been carried out in parallel using mill annealed (MA) specimens free from oxide on the surface. The comparative testing was carried out in six different electrolyte solutions at temperatures ranging from 60°C to 100°. Results show that the repassivation potential of the specimens containing the black anneal oxide film on the surface was practically the same as the repassivation potential for oxide-free specimens.

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Section: Methodsmentioning

confidence: 99%

Influence of Black Annealing Oxide Scale on the Anodic Behavior of Alloy 22

et al. 2006

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“…al. found that in potentiodynamic testing of Alloy 22 in 5 M calcium chloride (CaC12) solutions, the onset of localized corrosion could be shifted from 7S°C to 105OC by adding 0.5 M calcium nitrate (~a(N03)2).~ AS the ratio of nitrate to chloride is increased, an increase in both breakdown potentials and repassivation potentials occurs, and the difference between these potentials and open circuit values increases. 2,3,7,11 In this study the effect of nitrate on localized corrosion of welded Alloy 22 specimens at extremes of chloride concentration and temperature in CaCI2 + Ca(N03)2 solutions was examined.…”

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confidence: 99%

The Electrochemical Behavior of Alloy in Extreme Chloride and Bitrate Environments

Etien

Gordon²,

Ilevbare

2006

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Alloy 22 specimens were tested in high temperature (100 to 160°C), high concentration chloride and nitrate environments. Results of this study indicate that increasing nitrate to chloride ratio to 0.5 in these electrolytes increases resistance to localized breakdown and enhances repassivation. In these extreme environments, localized corrosion occurred by pitting even though specimens were tested using artificial crevice formers. Open circuit (E,,,), breakdown and repassivation potentials all increase, and pitting morphology changes as nitrate to chloride ratio increases from 0.05 and 0.15 to 0.5. Results also indicate that increasing the temperature from 100 to 160°C increases E,,, values, while breakdown potentials and repassivation potentials peak at 130°C for the 0.5 nitrate to chloride ratio electrolytes. Keywords:Alloy 22, localized corrosion, nitrate, chloride, welds, deliquescence INTRODUCTION ' Alloy 22 is a nickel-based alloy that is highly corrosion resistant. It falls into the general category of nickel-chromium-molybdenum alloys known for their high corrosion resistance. Like other alloys in this family, Alloy 22 exhibits both low general corrosion rates and high resistance to localized corrosion in a wide range of environment^.'-^ Alloy 22 is the corrosion barrier material for the waste packages intended for the underground disposal of radioactive waste at Yucca Mountain. One of the most probable exposure mechanisms of the waste packages to aqueous solutions will be through the process of deliquescence. Deliquescence is the process by which a crystalline solid absorbs moisture and subsequently dissolves. As the waste packages cool and the relative humidity rises, the likelihood of deliquescence occurring on the package surface increases. The initial solutions that form through this process are predicted to exist at high temperatures (probably above 100°C) and contain high salt concentration^.^' lo Solutions containing high amounts of chloride and nitrate have been identified as one type of deliquescence solution that can forrn,in the repository.10 Nitrate has been shown to have an inhibitive Knolls Atomic Power Laboratory, Schenectady, NY + Integrated Science Solutions Inc., Walnut Creek, CA effect on the localized corrosion behavior of Alloy 22 in chloride solutions at lower concentrations and temperatures than those used in this study.2$ 3' 79 I ' Dunn and Brossia found that for welded Alloy 22 specimens tested in 0.5 M NaCl solutions at 95OC, there was no crevice corrosion initiated in potentiodynamic tests for nitrate to chloride ratios of 0.2 or greater but crevice corrosion did occur at ratios of 0.1 and below.3 Evans et. al. found that in potentiodynamic testing of Alloy 22 in 5 M calcium chloride (CaC12) solutions, the onset of localized corrosion could be shifted from 7S°C to 105OC by adding 0.5 M calcium nitrate (~a(N03)2).~ AS the ratio of nitrate to chloride is increased, an increase in both breakdown potentials and repassivation potentials occurs, and the difference between the...

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“…[8][9][10][13][14][15] The presence of nitrate (NO 3 -) and other oxyanions in the solution minimizes or eliminates the susceptibility of Alloy 22 to crevice corrosion. [8][9][10][16][17][18][19][20][21][22][23] The value of the ratio R (R = [NO 3 -]/([Cl -]) has a strong effect of the susceptibility of Alloy 22 to crevice corrosion. [16][17][18][19][20][21][22][23] The higher the nitrate to chloride ratio the stronger the inhibition by nitrate.…”

Section: Introductionmentioning

confidence: 99%

“…[2][3][4][5][6] The combined presence of Cr, Mo and W imparts Alloy 22 with high resistance to localized corrosion such as pitting corrosion and stress corrosion cracking even in hot high chloride (Cl -) solutions. [7][8][9][10][11][12] Alloy 22 may suffer localized corrosion such as crevice corrosion when it is anodically polarized in chloride containing solutions. [8][9][10][13][14][15] The presence of nitrate (NO 3 -) and other oxyanions in the solution minimizes or eliminates the susceptibility of Alloy 22 to crevice corrosion.…”

Section: Introductionmentioning

confidence: 99%

“…[7][8][9][10][11][12] Alloy 22 may suffer localized corrosion such as crevice corrosion when it is anodically polarized in chloride containing solutions. [8][9][10][13][14][15] The presence of nitrate (NO 3 -) and other oxyanions in the solution minimizes or eliminates the susceptibility of Alloy 22 to crevice corrosion. [8][9][10][16][17][18][19][20][21][22][23] The value of the ratio R (R = [NO 3 -]/([Cl -]) has a strong effect of the susceptibility of Alloy 22 to crevice corrosion.…”

Section: Introductionmentioning

confidence: 99%

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Crevice Repassivation Potential of Alloy 22 in High-Nitrate Dust Deliquescence Type Environments

Lian

Gdowski

Hailey

et al. 2007

Volume 7: Operations, Applications and Components

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The nitrate ion (NO 3 -) is an inhibitor for crevice corrosion of Alloy 22 (N06022) in chloride (Cl -) aqueous solutions. Naturally formed electrolytes may contain both chloride and nitrate ions. The higher the ratio R = [NO 3 -]/[Cl -] in the solution the stronger the inhibition of crevice corrosion. Atmospheric desert dust contains both chloride and nitrate salts, generally based on sodium (Na + ) and potassium (K + ). Some of these salts may deliquescence at relatively low humidity at temperatures on the order of 150°C and higher. The resulting deliquescent brines are highly concentrated and especially rich in nitrate. Electrochemical tests have been performed to explore the anodic behavior of Alloy 22 in high chloride high nitrate electrolytes at temperatures as high as 150°C at ambient atmospheres. Naturally formed brines at temperatures higher than 120°C do not induce crevice corrosion in Alloy 22 because they contain high levels of nitrate. The inhibitive effect of nitrate on crevice corrosion is still active for temperatures higher than 100°C.

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Anodic Behavior of Alloy 22 in Calcium Chloride and in Calcium Chloride Plus Calcium Nitrate Brines

Cited by 14 publications

References 0 publications

Influence of Black Annealing Oxide Scale on the Anodic Behavior of Alloy 22

Influence of Black Annealing Oxide Scale on the Anodic Behavior of Alloy 22

The Electrochemical Behavior of Alloy in Extreme Chloride and Bitrate Environments

Crevice Repassivation Potential of Alloy 22 in High-Nitrate Dust Deliquescence Type Environments

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