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With the use of tracers, the separate effect of small nickel additions, as well as phosphorus and manganese impurities (including their combinations with sulfur) on the corrosion electrochemical behavior of active iron is studied. Nickel (2.2%) and phosphorus (only 0.07%), which are substantially more corrosion resistant than iron, are found to noticeably suppress the active dissolution of iron from its alloys, whereas the unstable manganese (0.43%) and its sulfides (in an alloy containing 0.43% Mn and 0.06% S) accelerate the dissolution. An effect similar to that of manganese is produced by a simple increase in the defectiveness of the iron crystalline structure. The largest deceleration is observed at a small surface coverage of the dissolving alloy with nickel or phosphorus, whereas the activating effect of manganese and its sulfides is accompanied by their selective transfer to the solution. With an increase in the potential, both effects decrease in magnitude. Generalizing these and other data on the effects of impurities and structural defects on the active dissolution of iron made us reveal the substantial effect of the metal purity and its surface defectiveness (including that induced by a potential increase) on the steady-state kinetics of the process. All the regularities of the effect theoretically follow from the crystal-chemistry concept of dissolution.

Section: Discussionmentioning

confidence: 99%

To the co-effect of impurity atoms and structure on the dissolution of iron and its low alloys

Plaskeev

2005

“…Atomic-topological kinetics is the branch of physical kinetics that deals with the self-consistency between the surface structures of a solid and the kinetics of material exchange between the solid and unordered (liquid or gas) phase [1]. The dissolution (corrosion) problem of a metal should be solved in terms of this approach, since the dissolution rate depends on the structure of the dissolving surface and, at the same time, determines it.…”

Section: Introductionmentioning

confidence: 99%

“…The dissolution (corrosion) problem of a metal should be solved in terms of this approach, since the dissolution rate depends on the structure of the dissolving surface and, at the same time, determines it. The degree of the mutual effect and, hence, the dissolution rate (and its inverse, the corrosion resistance) substantially depend on the defectiveness of the crystal lattice, and the most corrosion-resistant is the perfect defect-free crystal [2].…”

Section: Introductionmentioning

confidence: 99%

“…During the dissolution of the surface, the positions transform into each other because of the changes in the number of their neighbors. These mutual transformations are described as chemical reactions with a proper system of kinetic equations for the position concentrations [2].…”

Section: Introductionmentioning

confidence: 99%

“…In [2], a system of kinetic equations for the dissolution of a perfect crystal with a plain cubic lattice was constructed and investigated in the approximation of the nearest neighbors. It was found that solving this problem is accompanied by substantial difficulties caused by relatively strong correlations between the positions of the nearest neighbors, which result in the appearance of "averagely" ordered structures (atomic relief fragments) during the random dissolution process.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

2D Atomic-Topological Model of the Dissolution Kinetics of a Metallic Crystal: Typical Atomic Relief Positions and Fragments

Alekseev

Bityurin

2005

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The atomic-topological kinetics problem of the self-consistency between the dissolution kinetics and the atomic relief of the dissolving boundary is solved for an imaginary two-dimensional crystal in two ways: (i) in terms of the model of atomic positions determined by the number of the nearest neighbors and (ii) in terms of the typical atomic relief structures (steps, kinks, etc.). To a sufficient accuracy, the results provided by these two models coincide. The approaches developed are aimed at solving the problem of the dissolution of an actual three-dimensional crystal.

Thermodynamic Theory of “Irregular” Solutions and Kinetic Model of the Passive Alloy Dissolution

Alekseev

2005

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Developing a productive multivariate theory of corrosion, as well as anticorrosion alloying, is impossible unless the interactions between the alloy components are taken into account. These interactions may most substantially affect the qualitative regularities of the dissolution in passive state [1][2][3].The quantitative theoretical description of the dissolution kinetics is based on treating the passivating oxide as a solid solution of "component molecules", an interaction between which should necessarily be taken into account at least in the close-neighbors approximation. Considering thermodynamic "entities" as oxide "molecules" of the alloy components rather than metal cations in the oxide was based in [2] on the concept of the passive metal dissolution [4][5][6][7][8][9] as the transfer of metal cations to the electrolyte together with the stoichiometrically balanced amount of the oxide oxygen atoms. In other words, it is as if M particles ( z i is the charge of the i th alloy component ion) are actually transferred. Bearing in mind this idea, we proposed [1] a thermodynamic model of the interaction between the oxide "molecules," based on the theory of regular solutions, that is, assuming that the interaction between the solution components does not affect its structure ordering, so that the location of component molecules is chaotic as in an ideal solution where interactions between molecules of different kinds are the same or simply absent.Let us note that in a conventional classification of solutions, people use an ambiguous terminology. It may seem strange that a solution with a chaotic arrangement of molecules is named "regular," while a O Z i /2 partially structured (not chaotic) one is named irregular. However, the term "regular" primarily means customary, which reflects the historically conventional idea that a solution is similar to a gas mixture, in which a "uniformly" chaotic arrangement of molecules is typical, while an "irregular" solution is unusually ordered. ADVANTAGES AND DRAWBACKS OF THE MODEL [2, 3] OF PASSIVE OXIDE FILM AS A REGULAR SOLUTION OF THE ALLOY COMPONENT OXIDE "MOLECULES"In [2], we used a thermodynamic model [1] as a basis in constructing a model of the passive alloy dissolution.For that purpose, we utilized the ideas of the transition state theory [10], which enables one to relate the chemical potential of each solution component to its value in the individual state (that is, oxide "molecules" in the own phase). (For brevity, solution means solid solution, because electrolytes lie beyond the scope of this study.) This made it possible to take into account the change in the dissolution rate of each component due to mixing, i.e., as a result of the appearance of "molecules" of other kinds close to the "molecule" of a particular kind.Model [2] enabled us to estimate partial i i and summary i dissolution rates of the alloy as functions of its composition knowing the dissolution rates of the individual passive metals constituting the alloy. For partial dissolution rates of a binary...