The electrochemistry of stress corrosion cracking — from theory to damage prediction in practical systems

Macdonald, Digby D.; Engelhardt, George R.; Balachov, Iouri

doi:10.1016/b978-008044635-6.50049-2

Cited by 4 publications

(8 citation statements)

References 37 publications

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“…The CGR vs. temperature data plotted in Figure 28 have important implications for operating BWRs that undergo start-up and shutdown of the reactor [73,74]. Thus, for the stated conditions, the CGR at 288 • C is 2 × 10 −8 cm/s, corresponding to a crack extension of 0.63 cm/a, but during start-up and shut-down the CGR is about 2 × 10 −7 cm/s (6.…”

Section: Effect Of Temperaturementioning

confidence: 96%

The Role of Determinism in the Prediction of Corrosion Damage

Macdonald

2023

CMD

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This paper explores the roles of empiricism and determinism in science and concludes that the intellectual exercise that we call “science” is best described as the transition from empiricism (i.e., observation) to determinism, which is the philosophy that the future can be predicted from the past based on the natural laws that are condensations of all previous scientific knowledge. This transition (i.e., “science”) is accomplished by formulating theories to explain the observations and models that are based on those theories to predict new phenomena. Thus, models are the computational arms of theories, and all models must possess a theoretical basis, but not all theories need to predict. The structure of a deterministic model is reviewed, and it is emphasized that all models must contain an input, a model engine, and an output, together with a feedback loop that permits the continual updating of the model parameters and a means of assessing predictions against new observations. This latter feature facilitates the application of the “scientific method” of cyclical prediction/assessment that continues until the model can no longer account for new observations. At that point, the model (and possibly the theory, too) has been “falsified” and must be discarded and a new theory/model constructed. In this regard, it is important to stress that no amount of successful prediction can prove a theory/model to be “correct”, because theories and models are merely the figments of our imagination as developed through imperfect senses and imperfect intellect and, hence, are invariably wrong at some level of detail. Contrariwise, a single failure of a model to predict an observation invalidates (“falsifies”) the theory/model. The impediment to model building is complexity and its impact on model building is discussed. Thus, we employ instruments such as microscopes and telescopes to extend our senses to examining smaller and larger objects, respectively, just as we now employ computers to extend our intellects as reflected in our computational prowess. The process of model building is illustrated with reference to the deterministic Coupled Environment Fracture Model (CEFM) that has proven to be highly successful in predicting crack growth rate in metals and alloys in contact with high-temperature aqueous environments of the type that exist in water-cooled nuclear power reactor primary coolant circuits.

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Section: Effect Of Temperaturementioning

confidence: 96%

The Role of Determinism in the Prediction of Corrosion Damage

Macdonald

2023

CMD

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“…Based on the theory of differential aeration set forth by UR Evans, Macdonald and coworkers posited that a Coupling Current (CC), which is a current that flows from within a localized corrosion event (e.g., crevice, crack, pit, etc…) to the external surface as a result of the coupling between the internal and external environments, must exist during SCC of 304 SS alloy in a boiling water reactor primary coolant environment [1][2][3][4][5][6]. The seminal research performed by Macdonald, et al showed that a time-based measurement of the Coupling Current (CC) could be made by mounting external cathodes within a few hundreds of microns of an electrically insulated fracture mechanics test specimen [1][2][3][4][5][6]. Once the load was applied to the specimen exceeding the critical stress intensity for crack growth under Mode I loading (KISCC), they observed that current flowed from the freshly exposed alloy in the crack-tip to the external cathode.…”

Section: Introductionmentioning

confidence: 99%

“…Once the load was applied to the specimen exceeding the critical stress intensity for crack growth under Mode I loading (KISCC), they observed that current flowed from the freshly exposed alloy in the crack-tip to the external cathode. Macdonald and coworkers [1][2][3][4][5][6] expected the CC to flow from the crack tip to the nearest external surface to the growing crack. Alternatively, other researchers suggested that if this CC exists, some or all of it can be extinguished within the confines of the crack mouth [7,8].…”

Section: Introductionmentioning

confidence: 99%

Observation of the Coupling Current During Stress Corrosion Cracking of Aluminum Alloy 5083

Macdonald¹

2023

J Miner Sci Materials

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A unique fracture mechanics device was created to allow for simultaneously measuring the load and localized electrochemical potential gradients in AA5083 bend bars. For the first time, periodic Scanning Vibrating Probe (SVP) maps were collected in order to obtain a full view of the coupling current, (which can be deduced from measured potential gradients) that emanates from an anodic crack tip. As a result of mapping the current density over a wide surface area compared to the area of the notch and crack tip, clarification is given on whether or not the external surfaces of an alloy or any other metal that experiences Stress Corrosion Cracking (SCC) play a role in crack growth. The SVP maps clearly show the anodic and cathodic potential gradients of a growing crack (resulting from SCC) in an AA5083 fracture mechanics specimen while the stress intensity increases. The notch and crack-tip remained anodic throughout most of the obtained scans for sensitized and as-received specimens. Furthermore, a coupling effect is observed on sensitized specimens even at low fracture toughness values in sensitized specimens under load for longer periods of time (> 1 week). These higher resolution maps captured during the crack growth process give more insight to the SCC phenomenon and the electrochemical mechanisms of crack growth in AA5083 and other alloys.

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“…Some of the component models of these codes are routinely used to calculate radiolytic species concentrations, electrochemical corrosion potential (ECP), crack growth rate, and accumulated damage over the full range of operating conditions experienced in this type of reactor [9][10][11][12][13][14]. The impetus for developing the models was to prevent, or at least minimize, intergranular stress corrosion cracking (IGSCC) and irradiation assisted stress corrosion cracking (IASCC) of stainless steels components in the reactor primary coolant circuits.…”

Section: Introductionmentioning

confidence: 99%

“…Sophisticated radiolysis/chemical/electrochemical codes have been developed for describing the electrochemistry and corrosion properties of the primary coolant circuits of boiling water reactors (BWRs) [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Some of the component models of these codes are routinely used to calculate radiolytic species concentrations, electrochemical corrosion potential (ECP), crack growth rate, and accumulated damage over the full range of operating conditions experienced in this type of reactor [9][10][11][12][13][14].…”

Section: Introductionmentioning

confidence: 99%