The capacitance of passivated iron electrodes under simulated erosion-corrosion conditions

Pinkowski, A.; Thiessen, Karsten Peter

doi:10.1016/0040-6090(86)90315-9

Cited by 4 publications

(4 citation statements)

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“…The authors justify it by the fact that the particles are brought in the diffusion layer only through particle-particle collisions, that become sufficiently frequent only above the threshold. However, not only this last point is questionable (4)(5)(6)(7), but the experimental results of this model are not satisfactory enough to allow a clear separation of the role of the velocity perturbation from that of the diffusion layer. Such a separation was achieved in the case of fiber suspensions (6) using microelectrodes inserted into an active or inactive RDE.…”

mentioning

confidence: 86%

“…D~pp can be given (11) by Cv ] 2/3 Dapp = DM + DM l/a [(9/2)~]1/aa 4/3 (b:/) 2/3 k 1--~-~3j [5] where b is a numerical coefficient lower than 1/2. Taking into account the q value at the wail in the supernatant Dap p can be expressed as follows Dapp = DM(1 + Ar 213) [6] where A is a coefficient equal to…”

Section: W I T H R E S P E C T To Diffusion Prov I D E D T H a T T H ...mentioning

confidence: 99%

“…However, not only this last point is questionable (4-7), but the experimental results of this model are not satisfactory enough to allow a clear separation of the role of the velocity perturbation from that of the diffusion layer. Such a separation was achieved in the case of fiber suspensions (6) using microelectrodes inserted into an active or inactive RDE. It has thus been established that the shear rate at the wall remains unaffected while the diffusion layer is perturbed (8).…”

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confidence: 99%

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Mass Transfer in Laminar Flow at a Rotating Disk Electrode in Suspensions of Inert Particles: II . Theoretical Evaluation of Experimental Results

Caprani

Ficquelmont‐Loïzos

Tamisier

et al. 1988

J. Electrochem. Soc.

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In a previous publication, we studied mass transfer at a rotating disk electrode in "inert" particle suspensions. We now account for the variations of the limiting diffusion current with numerous parameters by different phenomena. These involved either the topography of the interface through adhesion of the particles to the electrode or the mass exchanges in the diffusion layer through changes in the velocity field and/or diffusion coefficient. Each phenomenon, considered separately, gives rise to one or more linear segments for the variations of current with the rotation speed ft, in logarithmic coordinates. Considering all the invoked phenomena, we would expect more segments than the four observed in experimental log I vs. log gt plots. Analyzing the consequences of each phenomenon in the whole f~ range allows one to disregard some of them for certain ft values and to account for most of the experimental results. At low ft values, two predominant phenomena, with antagonistic effects, explain the deviations from the one-phase media behavior: the reduction of the exchange area and the increase of the apparent diffusion coefficient through changes in the size of aggregates along the streamlines. Moreover. for small-size particles or for particle concentrations sufficiently high, deviations from newtonian behavior are also observed. At intermediate and high ~ values, the predominant phenomenon is the variation of the diffusion coefficient with the shear rate. Depending on the ratio of the diffusion layer thickness over the particle size (g/a), two different laws can describe this variation.In the first paper of this series (1), we determined, using an electrochemical method, the influence of several parameters on mass transfer in two-phase media. These parameters are inherent in the particle, the medium, and the rotating disk electrode (RDE). The fact that the influence of each of them is closely dependent on the influence of the others suggests that various phenomena must take place at the interface, with shear rate dependent relative weights.We present here a general model in order to take into account most of our experimental results and to interpret the "particle-wall-flow" interactions which control the mass transfer to the wall.The particles are known to induce discrepancies on mass transfer with respect to the supernatant. Three different approaches have been used in the literature to account for these discrepancies: a hydrodynamic approach, a diffusional approach, and a third approach in which blocking of the exchange area is invoked. The two first approaches disregard the role of the electrode surface, and lead to an increase of mass transfer. The third approach only takes into account the phenomena at the interface and leads to a decrease of mass transfer. This last approach ignores the particle-induced perturbations of the volume-related phenomena.The first and most microscopic approach was employed in the case of the rotating disk electrode (2, 3). It consists in solving with important approximations th...

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Section: W I T H R E S P E C T To Diffusion Prov I D E D T H a T T H ...mentioning

confidence: 99%

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confidence: 99%

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Mass Transfer in Laminar Flow at a Rotating Disk Electrode in Suspensions of Inert Particles: II . Theoretical Evaluation of Experimental Results

Caprani

Ficquelmont‐Loïzos

Tamisier

et al. 1988

J. Electrochem. Soc.

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“…39 This shows that the deposition of Sn was monolayer-level, taking into account the roughness factor of 2-3 for a polished steel surface. 40,41 The difference in thickness between polarization potentials of −0.40 and −0.35 V (SSE) implies that the surface coverage of Sn was dependent on the polarization potential. If the Sn species were fully oxidized to SnO 2 by air after polarization to −0.40 and −0.35 V (SSE), the thickness would be equivalent to 1.19 and 0.83 nm, respectively (the density of SnO 2 is 6.95 g cm −3 ), 39 and this is much less than that found using XPS depth analysis.…”

Section: Xps Analysis-figurementioning

confidence: 99%

Inhibition of Anodic Dissolution of Steel by Sn²⁺ in Perchloric Acid Solution

Takabatake

Sugae

Ito

et al. 2019

J. Electrochem. Soc.

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The inhibition effect of Sn 2+ on the anodic dissolution of Fe-0.05C steel was investigated electrochemically in a solution of 0.2 M HClO 4 . Anodic currents were suppressed in the presence of Sn 2+ , and the suppression behavior depended on the concentration of Sn 2+ and the electrode potentials. The experimental condition for the current suppression is explained by the theory of underpotential deposition (UPD). X-ray photoelectron spectroscopy (XPS) depth analysis revealed the deposition of metallic Sn on the steel, while inductively coupled plasma-mass spectrometry (ICP-MS) analysis demonstrated that the Sn layer thickness was monolayer-level. This strongly suggests that the anodic dissolution of iron was suppressed by the UPD of Sn. The proposed mechanism for corrosion inhibition by Sn-UPD also explains the superior corrosion resistance of Sn-bearing steel under atmospheric environments.

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Erosion-corrosion of nickel

Tomlinson

Ayerst

1988

Wear

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The capacitance of passivated iron electrodes under simulated erosion-corrosion conditions

Cited by 4 publications

References 49 publications

Mass Transfer in Laminar Flow at a Rotating Disk Electrode in Suspensions of Inert Particles: II . Theoretical Evaluation of Experimental Results

Mass Transfer in Laminar Flow at a Rotating Disk Electrode in Suspensions of Inert Particles: II . Theoretical Evaluation of Experimental Results

Inhibition of Anodic Dissolution of Steel by Sn²⁺ in Perchloric Acid Solution

Erosion-corrosion of nickel

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The capacitance of passivated iron electrodes under simulated erosion-corrosion conditions

Cited by 4 publications

References 49 publications

Mass Transfer in Laminar Flow at a Rotating Disk Electrode in Suspensions of Inert Particles: II . Theoretical Evaluation of Experimental Results

Mass Transfer in Laminar Flow at a Rotating Disk Electrode in Suspensions of Inert Particles: II . Theoretical Evaluation of Experimental Results

Inhibition of Anodic Dissolution of Steel by Sn2+ in Perchloric Acid Solution

Erosion-corrosion of nickel

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Product

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Inhibition of Anodic Dissolution of Steel by Sn²⁺ in Perchloric Acid Solution