The effect of surface vacancies on the interactions of Cl with a α-Fe2O3 (0001) surface and the role of Cl in depassivation

Pang, Qin; DorMohammadi, H.; Isgor, O. Burkan; Árnadóttir, Líney

doi:10.1016/j.corsci.2019.03.052

Cited by 38 publications

(25 citation statements)

References 52 publications

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“…The iron vacancy, resulting from iron complex dissolution, is represented using dashed circle. Previous studies 7,8 show that these vacancies diffuse through the oxide film toward the film/metal interface to create discontinuities eventually leading to detachment/ breakdown of the film, similar to the mechanism proposed by the point defect model. These stages are not shown in this figure since they were not studied herein.…”

Section: The Structural Changes Caused By Adsorbatessupporting

confidence: 58%

“…Therefore, in the third and fourth stages, only one or none of the adsorbed chloride is replaced, forming Fe(OH)Cl 2 and FeCl 3 respectively. These surface species can dissolve into the solution, releasing chlorides back to the solution, while creating iron vacancies that diffuse toward the oxide-film/metal interface as suggested in previous studies 7,8 . This indicates that chloride can act as catalyst in the depassivation process consistent with previous density functional theory (DFT) studies 8,9 , while also providing support for the point defect model [10][11][12][13] .…”

Section: Introductionmentioning

confidence: 73%

“…These surface species can dissolve into the solution, releasing chlorides back to the solution, while creating iron vacancies that diffuse toward the oxide-film/metal interface as suggested in previous studies 7,8 . This indicates that chloride can act as catalyst in the depassivation process consistent with previous density functional theory (DFT) studies 8,9 , while also providing support for the point defect model [10][11][12][13] . The four-step process for the initiation of the passive film breakdown also explains the concept of the critical chloride threshold, which requires the concentration of chlorides in the electrolyte to exceed certain threshold to initiate the depassivation process.…”

Section: Introductionmentioning

confidence: 73%

“…The magnetic state for of α-Fe 2 O 3 is applied as antiferromagnetic (+ + − −) based on our previous study 29 . More information regarding properties of α-Fe 2 O 3 and surface structure can be found elsewhere 8,9,29 .…”

Section: Methodsmentioning

confidence: 99%

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Thermodynamic feasibility of the four-stage chloride-induced depassivation mechanism of iron

et al. 2020

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The atomistic mechanism of chloride-induced depassivation of iron is still debated. A recent study suggests a four-stage depassivation mechanism, in general agreement with the point defect model. The proposed four-stage mechanism is based on reactive force field molecular dynamics simulations and is rather complex but here we use density functional theory to confirm the thermodynamic feasibility of the proposed mechanism. We find that the four surface species, formed in the four stages, have decreasing surface stability, which is consistent with the order of species formed in the depassivation process proposed in the reactive force field molecular dynamics study. The Fe vacancy formation energy, that is the energy needed to form a surface Fe vacancy by removing different surface species, indicates that surface species with more chlorides dissolve more easily from the surface, suggesting that chloride acts as catalyst in the iron dissolution process. The results are consistent with the suggested fourstage reaction mechanism and the point defect model.

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Section: The Structural Changes Caused By Adsorbatessupporting

confidence: 58%

Section: Introductionmentioning

confidence: 73%

Section: Introductionmentioning

confidence: 73%

Section: Methodsmentioning

confidence: 99%

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Thermodynamic feasibility of the four-stage chloride-induced depassivation mechanism of iron

et al. 2020

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“…. The Cl ¹ has strong penetrating power and the ability to assist the formation of Fe vacancies, 22 which can directly reach the substrate and corrode the metal surface; the HCO 3 ¹ is that easily produces a FeCO 3 film on the electrode surface. At the high flow rate, the high mass transfer rate, would enhance the transportation of Cl ¹ and HCO 3 ¹ towards the electrode surface, which provides favorable conditions for the formation of initial pits on the surface, thus, at 0.5 m/s, fewer corrosion points will be formed on the surface of the steel, as shown in Fig.…”

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confidence: 99%

Flow Corrosion Behavior of X100 Pipeline Steel in Simulated Formation Water

Tian³

et al. 2021

Electrochemistry

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The self-designed flow system was used to study the flow corrosion of X100 pipeline steel in simulated formation water environment by electrochemical measurements as well as computational fluid dynamics (CFD) simulation. The effects of fluid flow velocity and fluid impact angle on X100 steel were determined. When the fluid flow velocity changes between 0.5-2.0 m/s, X100 steel is controlled by activation, and as the flow velocity increases, the self-corrosion current I corr increases, the corrosion rate increases; when the impact angle increases from 30°to 90°, the self-corrosion current I corr decreases and the corrosion rate decreases. CFD simulations show that at different flow velocities and impact angles, the velocity field distribution on electrode surface is different. At the minimum impact angle of 30°, the electrode area has the largest flow velocity and shear stress, therefore the corrosion damage is the most serious.

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Improved Corrosion and Long‐Term Immersion Behavior in 3.5 wt% NaCl Solution of Laser Powder Bed Fusion Produced Ti5Cu After Heat Treatment

et al. 2023

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This work investigates the corrosion behavior and mechanism of laser powder bed fusion produced (LPBFed) Ti5Cu and its heat‐treated counterparts in 3.5 wt% NaCl solution. The results indicate that heat treatment can enhance the corrosion resistance of LPBFed Ti5Cu by generating Ti2Cu phase, and heat treatment at higher temperature enhances corrosion resistance by forming a stable oxide film with a lower electron diffusion rate. The existence of Ti2Cu phase in the heat‐treated sample acts as the microanode that decelerates the corrosion on α‐Ti phase (prior dissolution of Ti2Cu phase). The long‐term immersion test results also confirm that the Ti2Cu phase present in HT900 (at higher heat‐treatment temperature) provides a better protective effect against corrosion compared to the one in HT740 and as‐LPBFed samples. Compared with the heat‐treated counterparts, the worst corrosion resistance of the as‐LPBFed Ti5Cu is attributed to that the acidic environment (e.g., Cl−) increases the electron diffusion rate in the film/solution interface, which makes the thermodynamically unstable α'‐Ti phase be preferentially corroded.

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The effect of surface vacancies on the interactions of Cl with a α-Fe2O3 (0001) surface and the role of Cl in depassivation

Cited by 38 publications

References 52 publications

Thermodynamic feasibility of the four-stage chloride-induced depassivation mechanism of iron

Thermodynamic feasibility of the four-stage chloride-induced depassivation mechanism of iron

Flow Corrosion Behavior of X100 Pipeline Steel in Simulated Formation Water

Improved Corrosion and Long‐Term Immersion Behavior in 3.5 wt% NaCl Solution of Laser Powder Bed Fusion Produced Ti5Cu After Heat Treatment

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