Potential distribution in a corroding pit

Newman, John; Hanson, Donald N.; Vetter, K.

doi:10.1016/0013-4686(77)80005-4

Cited by 41 publications

(24 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…9 is now compared to the expected ohmic potential drop in pits. The magnitude of the ohmic potential drop for small cubic etch pits is estimated using a solution of Laplace's equation for a hemispherical pit with uniform current density, on an insulating plane (18). This calculation includes the resistance of the solution outside the pit.…”

Section: Potential Transients--a Potential Transient For Current Stementioning

confidence: 99%

Passivation of Surfaces within Aluminum Etch Tunnels

Wiersma

Tak

Hebert

1991

J. Electrochem. Soc.

View full text Add to dashboard Cite

Transient events accompanying passivation of active surfaces in aluminum etch tunnels are investigated. Passivation is induced by pulsed reductions of the anodic etching current, of several milliseconds duration. Scanning electron microscopy is used to measure the area passivated. Potential transients are analyzed to identify a possible potential driving force for passivation. For the experimental conditions of this work, at 0.13 ms after the current step, there is a temporary reduction in the metal dissolution current in tunnels. The change in dissolution current is proportional to the cathodic surface overpotential, relative to the critical repassivation potential. The transient reduction in dissolution current is associated with passivation, since no variation in dissolution current with potential is observed during steady tunnel growth. Surface changes resulting in permanent passivation occur later, at times between 3 and 12 ms after the current step.

show abstract

Section: Potential Transients--a Potential Transient For Current Stementioning

confidence: 99%

Passivation of Surfaces within Aluminum Etch Tunnels

Wiersma

Tak

Hebert

1991

J. Electrochem. Soc.

View full text Add to dashboard Cite

show abstract

“…e.g., [67][68][69]). Newman et al [70] and Harb and Alkire [71] have carried out numerical calculations of the potential distribution in the solution. It is important to emphasize that formation of a pit, i.e., the flow of local current, which causes in the solution an ohmic potential drop and decreases the interfacial potential (i.e., makes it less anodic) in the vicinity of the first pit, prevents the formation of other pits around it.…”

Section: The Pitting Corrosion Of Steel As a Cooperative Processmentioning

confidence: 99%

Cooperative Dynamics of Coupled and Forced Oscillators

Orlik

2012

Self-Organization in Electrochemical Systems II

View full text Add to dashboard Cite

The formation of dissipative patterns on electrode surfaces is related to various kinds of spatial couplings that interact with the electrochemical process in a way dependent, among others, on the geometrical arrangement of the electrodes and the operational mode of the electrochemical experiments. A natural development of the concept of individual reaction sites engaged into such couplings is the case of coupled oscillators. It is thus not surprising that the treatment of coupling of the individual oscillators and spatiotemporal phenomena in a single oscillator may have common points. The analysis of such complex systems allows to understand better the general mechanisms underlying the spatiotemporal phenomena, including the coupling that exist between oscillators in living systems, e.g., in the biological cell membranes.The coupling of chemical or electrochemical oscillators can lead to either more complex or simpler oscillatory regimes, in the latter case including even ceasing of the oscillations. A special variant of such coupling can be realized through the external perturbation of a single oscillator or of a set of them.Karantonis and Nakabayashi [1] have analyzed the case of coupling of two limit cycle electrochemical oscillators, described by only two dynamical variables. In this work the diffusive coupling in one dynamical variable is considered which, under appropriate conditions, can lead to dephasing of the oscillators. This particular problem is related to the suggestion by Kuramoto [2] that chemical spatiotemporal chaos might arise where diffusive coupling leads to dephasing. The problem is important since it was shown, in terms of the model approach, that the diffusive coupling of the transmembrane voltage, in the presence of a strong deformation of the phase flow in the vicinity of the limit cycle, can cause the dephasing of oscillators and bursting oscillations [3]. The model of electrochemical M. Orlik, Self-Organization in Electrochemical Systems II, Monographs in Electrochemistry,

show abstract

“…19. Figure 8 shows the centerline profiles for the product of the second hydrolysis reaction, Al(OH) 2 ϩ . As with the other aluminum species, the profiles showed that the transition region between migration-controlled dissolution and diffusion-controlled dissolution occurred around a dimensionless Cl Ϫ concentration of Ϫ0.1 and demonstrated the approach to a limiting concentration profile as the bulk Cl Ϫ concentration increased.…”

Section: Figure 6 Influence Of Parameter |Y ϱmentioning

confidence: 99%

“…They derived the expression for the flux (reaction rate) of a species present on the surface of a sphere at constant concentration into a medium of lower concentration [2] In order to determine an expression for the variation of current density and radius with time, Eq. 2 was combined with Faraday's law r ϭ [r o 2 ϩ (2Dc s M r t/) 1/2 [3] [4]…”

mentioning

confidence: 99%

Experimental and Modeling Studies of Single Pits on Pure Aluminum in pH 11 NaCl Solutions I. Laser Initiated Single Pits

Verhoff

Alkire

2000

J. Electrochem. Soc.

View full text Add to dashboard Cite

During localized corrosion, a large number of phenomena exert themselves over wide ranges of length scale. During the growth of a corrosion pit, for example, surface and homogeneous reactions, equilibration among many species, transport by migration, diffusion and convection, and three-dimensional interactions among adjacent pits are all important simultaneously. The large number of phenomena as well as the large range of length scales over which they occur places stringent demands on the design of experimental techniques for measuring localized phenomena. For example, the chemical environment in a corrosion pit is much different than the chemical environment in which the metal is initially immersed. Measurements of the various critical chemical species in the pit micro environment represents an extreme challenge for experimentalists. Mathematical models therefore prove useful because they allow for the testing of hypothesis and, in addition, can direct experimental efforts to complex regions of operation that can easily confound one's intuition.In the present investigation (Part I), experimental measurements were carried out with use of an in situ laser initiation technique that allowed for the precise control of the location of the initiation site as well as electrochemical control of single-pit dissolution rate. These data were compared with several mathematical models in order to determine the transport mechanism that best described controlled dissolution in the experimental conditions. Several chemistries were considered in mathematical models, although all were related to the hypothesis of Wong and Alkire 1 that for Al pits grown in basis NaCl solutions, the pit contains aluminum oxychloride species. The testing of several chemistries was important for two reasons: (i) to investigate the effect of chemistry on the mechanisms that control dissolution and (ii) to determine which chemistry was to be used in Part II of this series. In Part II, one of the mathematical models of Part I was selected for further refinement to consider transient behavior, and to test hypotheses of the local chemical conditions required to keep a corrosion pit growing.Newman et al. 2 solved Laplace's equation for the potential field in the concave hemisphere geometry subject to the boundary condition that the surface dissolved at constant current density which is obviously a good assumption for conditions that yield smooth, hemispherical pits. 3 Using the results of the model, Newman 3 derived the following equation to describe the variation of current density with radiusEquation 1 predicts that the current density varies as r Ϫ1 .Beck and Alkire 4 developed a simple mathematical model to describe the relationship between current density and radius, and current density and time for a convex hemisphere. They derived the expression for the flux (reaction rate) of a species present on the surface of a sphere at constant concentration into a medium of lower concentration [2] In order to determine an expression for the variation of curren...

show abstract

Potential distribution in a corroding pit

Cited by 41 publications

References 0 publications

Passivation of Surfaces within Aluminum Etch Tunnels

Passivation of Surfaces within Aluminum Etch Tunnels

Cooperative Dynamics of Coupled and Forced Oscillators

Experimental and Modeling Studies of Single Pits on Pure Aluminum in pH 11 NaCl Solutions I. Laser Initiated Single Pits

Contact Info

Product

Resources

About