Crevice corrosion kinetics of nickel alloys bearing chromium and molybdenum

Zadorozne, Natalia S.; Giordano, Cristina; Rodríguez, Martín A.; Carranza, Ricardo M.; Rebak, Raúl B.

doi:10.1016/j.electacta.2012.04.157

Cited by 70 publications

(61 citation statements)

References 18 publications

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“…This measure of the critical potential was therefore adopted as the repassivation potential (E rp ) because it provided a measurable, consistent, conservative lower bounding estimate. Rebak and coworkers 31,68,69 have extended these results to crevice corrosion in nickel alloys, attesting to this measurement as a consistent evaluation of a critical potential. A qualitative discussion on how this potential was related to surface concentration at repassivation based on arguments using ohmic drop 21,27,27 as well as mass transport restriction due to pit geometry was proposed in these studies.…”

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confidence: 92%

One-Dimensional Pit Experiments and Modeling to Determine Critical Factors for Pit Stability and Repassivation

Srinivasan

Kelly

2016

J. Electrochem. Soc.

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Experiments on stainless steel artificial pit electrodes in sodium chloride were used to inform a diffusion model developed based on the mass transport behavior within a one-dimensional corroding pit. Measurable estimates of the dissolution flux as well as the potential describing the conditions of interest were obtained from experiment as the one-dimensional pit stability product under a salt film (i · x) saltfilm and the repassivation potential E rp , respectively. These parameter estimates were acquired as a function of pit depth and were related to the concentration of the metal cation at the corroding surface at each depth via a one-dimensional mass transport model. These results allowed for the construction of a quantitative framework relating the various electrochemical parameters describing the transition from pit stability to repassivation. Such an analysis permitted the straightforward estimate of the critical surface concentration associated with this transition, which resulted in a single conservative lower bound of 50% of the saturation concentration for the minimum aggressive chemistry to sustain stable pitting and prevent repassivation. Along with published data, these results were utilized to advance the idea that the critical pit solution chemistry is independent of bulk chloride concentration up to 4 M, a range frequently encountered in atmospheric conditions. © The Author Many authors have separately reported the critical electrochemical conditions necessary for stable pitting and repassivation, focusing on dissolution flux, 1-8 pit solution chemistry, 9-16 or potential. 17-31The existence of these critical parameters is predicated upon the steady-state relationship that emerges between two competing processes. These processes are i) metal dissolution and hydrolysis that results in a local aggressive chemistry inside the pit, and ii) the dilution of this chemistry by diffusion out of the pit that contributes to repassivation. [32][33][34] The mathematical description of this relationship for a one-dimensional pit was framed by Galvele 1 in terms of the product of the current density and the pit depth, (i · x), which was termed the pit stability product in later studies. [35][36][37][38] Once this product decreased below a critical value, (i · x) crit , the conditions in the pit would no longer be able to sustain the local aggressive chemistry necessary for active dissolution. Galvele's formulation, originally intended to describe the conditions leading to pit initiation, has also been successfully extended to pit propagation. 4,7,[35][36][37] Experimental assessment of the Galvele pit model is typically performed using the artificial pit or lead-in-pencil electrode, 4,7,[39][40][41][42] which consists of a metal wire embedded in epoxy. The lead-in-pencil electrode is particularly useful because it closely represents Galvele's pit model configuration, i.e. a single activated surface and inert walls. 7,8 Additionally, the precipitation of a salt film 40,[43][44][45][46][47][48] at high anodic po...

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confidence: 92%

One-Dimensional Pit Experiments and Modeling to Determine Critical Factors for Pit Stability and Repassivation

Srinivasan

Kelly

2016

J. Electrochem. Soc.

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“…As mentioned in the introduction, although E rp is defined as the potential below which no pitting proceeded, the actual measurement of the value depends on a user-specified current density -a value that has ranged from 1 μA/cm 2 to 100 μA/cm 2 . 19,57,59,60,[75][76][77] The value used in the studies by Srinivasan et al [26][27][28]37 (and referred to in this work) was 30 μA/cm 2 , based on current densities similar to those employed by Tsujikawa et al 57,75,76 and Sridhar and coworkers, 19,78 as well as the ASTM G-192 standard. 79 The validity of this specification and its sensitivity to the individual anodic and cathodic kinetics can be examined using Mixed Potential Theory under the constraints of the critical pH condition as shown in the next section.…”

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confidence: 99%

Evaluating the Critical Chemistry for Repassivation at the Corroding Surface Using Mass Transport Model-Based Artificial Pit Experiments

Srinivasan

Kelly

2016

J. Electrochem. Soc.

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One-dimensional mass transport model calculations were utilized to design experiments with stainless steel artificial pit electrodes to determine the critical concentration of cations at the corroding surface representing the transition between stable pitting and repassivation. Rapid polarization scans following salt film precipitation and consequent open circuit dilution to different surface concentrations permitted the evaluation of kinetics at various degrees of saturation. These experiments showed a distinct change in kinetics as the surface concentration decreased, thus identifying the critical pit chemistry for the onset of repassivation. Chemical modeling of oxide precipitation from solution permitted the investigation of oxide nucleation across varying surface concentration as a function of pH as the cause of repassivation. This analysis enabled the estimation of the pH at which the first oxide would precipitate in the critical pit solution chemistry, which when combined with cation hydrolysis calculations, resulted in the evaluation of the critical pH at the transition between pit stability and repassivation. A mixed potential theory-based analysis of these results was utilized to provide mechanistic support to the quantitative framework describing critical factors for pitting stability and repassivation.

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“…6 Other studied nickel-based CRAs include the recently developed alloys C-22HS (UNS N07022), HYBRID-BC1 (UNS N10362), 59 (UNS N06059), C-2000 (UNS N06200), etc. [16][17][18][19] Selection of a nickel-based alloy as the material for the corrosion-resistant layer of waste containers for saturated and unsaturated repositories has distinct advantages relative to other metals/alloys: 20,21 • The expected containment is very long, synonymous with low corrosion rates.…”

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Crevice corrosion of nickel-based alloys considered as engineering barriers of geological repositories

Carranza

Rodríguez

2017

npj Mater Degrad

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Nickel-based alloys are considered among other candidate materials as engineering barriers of geological repositories due to their excellent corrosion resistance. These alloys possess unique advantages: they may be used in saturated and unsaturated repositories, hosted by practically any rock type, while also compatible with any (or no) backfill, and have minimal impact in other barriers. Alloy-22 (UNS N06022) has been the most studied of this class of alloys for its potential application in the proposed repositories (namely Yucca Mountain, USA). Crevice corrosion is however an important and often unintended degradation process that may limit the waste container lifetime if a nickel-based alloy is selected. Alloy susceptibility to crevice corrosion is influenced by environmental and metallurgical variables. This review gives an account of the current knowledge regarding crevice corrosion of nickel-based alloys as candidate materials for the corrosion-resistant layer of high-level nuclear waste containers. Although there is a significant amount of research supporting the use of nickel-based alloys for this application, the effect of the different variables on crevice corrosion resistance is described. Special focus is given to the current criterion for crevice corrosion occurrence in repository environments, recent works and criticisms. The presently established criterion appears robust for ruling out crevice corrosion in saturated repositories; however, the development of a less conservative criterion for crevice corrosion occurrence is necessary to use these alloys in unsaturated repositories.

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Crevice corrosion kinetics of nickel alloys bearing chromium and molybdenum

Cited by 70 publications

References 18 publications

One-Dimensional Pit Experiments and Modeling to Determine Critical Factors for Pit Stability and Repassivation

One-Dimensional Pit Experiments and Modeling to Determine Critical Factors for Pit Stability and Repassivation

Evaluating the Critical Chemistry for Repassivation at the Corroding Surface Using Mass Transport Model-Based Artificial Pit Experiments

Crevice corrosion of nickel-based alloys considered as engineering barriers of geological repositories

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