Synchrotron X-ray radiography studies of pitting corrosion of stainless steel: Extraction of pit propagation parameters

Ghahari, Majid; Krouse, Donal; Laycock, N.J.; Rayment, Trevor; Padovani, Cristiano; Stampanoni, Marco; Marone, Federica; Davenport, Alison J.

doi:10.1016/j.corsci.2015.06.023

Cited by 88 publications

(74 citation statements)

References 54 publications

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“…A number of factors were suggested to influence the gradient of pit growth, such as the area of perforation of the metal lacy covers, chloride concentration, applied potential, type of electrolyte and temperature, as well as pit growth direction, with respect to the sample position. 7,9,14,21,[35][36][37][38] For example, a difference of 15% was reported between pit growth with the sample facing upwards versus downwards in 2-D. 7 In our study, all pits grew vertical at the wire, and minor differences in diffusivity parameters estimated for pits 2 and 3 may even be a result of the difference in perforated area of both pit covers. 9 If the diffusion coefficient (D) is assumed to be constant at 0.85 × 10 −5 cm 2 .s −1 , 9,19 the mean metal salt concentration inside the pits can be estimated from the diffusivity parameters given above.…”

Section: 22mentioning

confidence: 84%

“…4 An undercutting mechanism was suggested for pit growth at high electrochemical potentials, leading to the development of dish shaped pits covered by metal lacy covers. [5][6][7][8][9][10] Pit propagation is controlled by diffusion of species through the salt film at the inner surface of pits. A high anodic dissolution rate, which facilitate critical ion concentrations inside a pit, is the criterion for pits to propagate.…”

mentioning

confidence: 99%

“…The study also showed that pit growth under potentiostatic control in 3.5% wt NaCl and seawater was similar to pits grown under open circuit conditions in 1 M FeCl 3 solution, both indicating an exponential relation of pit growth with time. 17 One dimensional (1-D) pit growth investigations using pencil electrodes 18 and two-dimensional (2-D) pit geometry estimated using thin foils and in-situ recording or radiography images 9 have been used to allow estimation of pit stability product. These methods allow pits underneath the metal surface to be observed, but the developed pit shape does not necessarily represent pit growth in 3-D.…”

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confidence: 99%

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Application of a Quasi In Situ Experimental Approach to Estimate 3-D Pitting Corrosion Kinetics in Stainless Steel

Al-Muaili

McDonald

Withers

et al. 2016

J. Electrochem. Soc.

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Pitting corrosion kinetics of type 304L stainless steel have been obtained using a quasi in-situ X-ray computed tomography (X-ray CT) approach. A miniature electro-chemical cell was constructed to allow imaging during potentio-dynamic polarization of a wire specimen in chloride solution. The formation of three discrete pits was observed, allowing comparison between real pit geometry and different geometrical assumptions to estimate pit growth kinetics. The pit volumes obtained by X-ray CT showed a good fit with the volume of metal dissolution calculated using Faraday's law. Large fluctuations of the mean current density were observed during the pit nucleation stage, followed by pit growth with mean current densities of 1-3 A.cm −2 . Stability products associated with these pits were on the order of 0.3-0.6 A.m −1 , with a diffusivity parameter (D . C) of 1. Pitting or crevice corrosion can occur on stainless steels exposed to halide containing environments. The breakdown of the passive surface film results in the nucleation of local attack, which is followed by pit growth, with a number of mechanisms proposed for each stage. 1,2Electrochemical polarization above the critical pitting potential leads to formation of pits, in the form of localized metal dissolution, with corrosive electrolyte developing inside the nucleated pit due to hydrolysis of dissolved metal ions, and chloride ions being attracted from bulk solution to maintain charge neutrality.3 At high applied electrochemical potentials, pits grow with a polished inner surface morphology, associated with salt film formation, whereas pits grown at lower applied potentials display more irregular etch morphologies of the internal pit surface. 4 An undercutting mechanism was suggested for pit growth at high electrochemical potentials, leading to the development of dish shaped pits covered by metal lacy covers. 5-10Pit propagation is controlled by diffusion of species through the salt film at the inner surface of pits. A high anodic dissolution rate, which facilitate critical ion concentrations inside a pit, is the criterion for pits to propagate. 11 The anolyte concentration inside a pit influences pit growth kinetics and the pit shape. For example, a 3 M concentration of dissolved metal ions was proposed as the minimum concentration to turn an open hemispherical meta-stable pit into a stable pit. However, pits developed with lacy metal covers grow at far lower metal ion concentrations, since these covers are believed to provide an effective diffusion barrier 12 and an increased ohmic resistance between pit interior and the bulk electrolyte.1 Based on these observations for the transition between meta-stable and stable pits, the "pit stability product" (0.3 A. m −1 ≤ i.r ≤ 0.6 A. m −1 ) was proposed, with the latter based on the evolution of pit current density (i) and pit depth (r). 12To sustain stable pit growth under anodic polarization, a minimum current density is required, with typical values for stainless steel in the region of 1-5 A.cm −2 . 13,14 For ...

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Section: 22mentioning

confidence: 84%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Application of a Quasi In Situ Experimental Approach to Estimate 3-D Pitting Corrosion Kinetics in Stainless Steel

Al-Muaili

McDonald

Withers

et al. 2016

J. Electrochem. Soc.

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“…From pit depth measurements, it has already been shown that the current density at the pit bottom can be calculated [29]. Indeed, there is a constant current density at the bottom of the pit as it was recently found by quantifying the variation of local current density around the perimeter of the pit using X-Ray radiography [19]. Fig.…”

Section: Discrimination Between Diffusion and Ohmic Control For The Pmentioning

confidence: 99%

On the Propagation of Open and Covered Pit in 316l Stainless Steel

Heurtault

Robin

Rouillard

et al. 2016

Electrochimica Acta

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Pitting corrosion on stainless steel has been widely studied during the last decades, but since it is a stochastic process, it remains difficult to analyze experimentally such a phenomenon. In this work, reproducible single pits were performed on 316L steel by using an experimental setup based on the use of a glass microcapillary to locally supply chloride ions on the steel surface in order to characterize the pit propagation. This original approach allowed obtaining new results about pit propagation. Indeed, it was possible to control the presence of a metallic cap recovering the pit by adjusting the experimental parameters (potential -chloride to sulfate ratio -temperature). The presence of this cover was shown to be an important issue concerning the propagation mechanism.It was also possible to study the evolution of both the pit depth and the pit diameter as a function of various parameters. Then, based on the simulation of the current densities at the pit bottom and at the pit aperture, a special attention has been paid for the investigation of the local propagation mechanism.

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“…42 Pits on stainless steel grow by undercutting of the passive metal surface. The upward growth of lateral lobes perforates the metal surface and produces metal particles leaving a porous cover known as a 'lacy cover'.…”

Section: Discussionmentioning

confidence: 99%

In-Situ Synchrotron X-ray Characterization of Corrosion Products in Zr Artificial Pits in Simulated Physiological Solutions

Zhang

Addison

Gostin

et al. 2017

J. Electrochem. Soc.

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Corrosion products generated in artificial pits of zirconium were characterized in-situ by synchrotron X-ray diffraction and X-ray absorption near edge structure (XANES) in physiological saline, with and without addition of 4% albumin and/or 0.1% H 2 O 2 . Zr metal fragments and tetragonal ZrO 2 particles were detected in aggregated black corrosion products away from the corrosion front. At the corrosion front, a ZrOCl 2 ·8H 2 O salt layer of a few hundreds of microns thickness was formed. Coarsened ZrOCl 2 ·8H 2 O crystallites were found farther out into the solution. The Zr solution species were confirmed to be in a tetravalent state by XANES. TEM imaging of the corrosion products revealed heterogeneity of the morphology of the Zr metal fragments and confirmed their size to be less than a few microns. The formation and speciation of Zr corrosion products were found not affected by the presence of H 2 O 2 and/or albumin in physiological saline. Furthermore, bulk Zr electrochemistry identified that the presence of H 2 O 2 and/or albumin did not affect passive current densities and pitting potentials of the bulk Zr surface. Therefore, it is concluded that the pitting susceptibility and pit chemistry of Zr in physiological saline were unaffected by the presence of H 2 O 2 , albumin or their combinations.

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Synchrotron X-ray radiography studies of pitting corrosion of stainless steel: Extraction of pit propagation parameters

Cited by 88 publications

References 54 publications

Application of a Quasi In Situ Experimental Approach to Estimate 3-D Pitting Corrosion Kinetics in Stainless Steel

Application of a Quasi In Situ Experimental Approach to Estimate 3-D Pitting Corrosion Kinetics in Stainless Steel

On the Propagation of Open and Covered Pit in 316l Stainless Steel

In-Situ Synchrotron X-ray Characterization of Corrosion Products in Zr Artificial Pits in Simulated Physiological Solutions

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