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41.
Formation, Retention, and Loss of the Metals Atmospheric Corrosion Products. 1. The Integral Weight Modelof the Products Formed Yu. M. Panchenko and P. V. Strekalov Institute of Physical Chemistry, Russian Academy of Sciences,
Leninskii pr. 31, Moscow, 119991 Russia e-mail:
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Received May 20, 2004 Abstract — Changes of the total weight of tested samples, as well as changes in the weight of the retained atmospheric corrosion products, are studied as functions of corrosion losses in different climate zones and different test duration, for carbon steel, zinc, copper, magnesium, aluminum,  16 and   alloys, and brass. An experimen-tal mathematical model for integral weight of formed corrosion products is suggested. Climate effects on the change in the weight of corrosion products retained by metals are studied during long-term exposure of plates and wire spirals recommended by the ISO 9226-92 Standard for the monitoring of atmospheric corrosivity.
23/09/2008 | 1431 Hits | Print
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42.
Biocorrosion of Oil and Gas Field Equipment and Chemical Methods for Its Suppression. I L. S. Moiseeva* and O. V. Kondrova** * Scientific and Engineering Center, LUKOIL Oil Company, ul. Usacheva 11, Moscow, 119048 Russia e-mail:
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** Dneprodzerzhinsk State Technical University, ul. Dneprostroevskaya 2, Dneprodzerzhinsk, Russia Received in final form, October 14, 2004 Abstract — Main groups of corrosive microorganisms are considered. The parameters of the medium that intensify biocorrosion and the conditions for the formation of biofilms are described. The mechanisms of biocorrosion induced by the main groups of unicellular microorganisms are proposed, and the characteristic types of biodamage, specified.
23/09/2008 | 1531 Hits | Print
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43.
Theoretical Foundations and Practical Development of Few-Component Anticorrosive Oil-Based Conservation Materials V. I. Vigdorovich and N. V. Shel’ Derzhavin Tambov State University, ul. Internatsional’naya 33, Tambov, 392662 Russia e-mail:
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Received July 3, 2004 Abstract — The concept of creating few-component anticorrosive oil-based conservation materials and the functional properties of industrially used formulations from waste motor oil and still bottoms in the production of synthetic fatty acids (SFAs) were considered. Corrosion, electrochemical, and rheological properties, as well as water permeability of films of such formulations, were determined. Mixtures of SFAs with individual n-alkanes C8 C15 were tested.
23/09/2008 | 1461 Hits | Print
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44.
On the Physical Sense of Chemical Potential R. R. Salem Higher Chemical College, Russian Academy of Sciences, Moscow, Russia e-mail:
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Received August 20, 2004 Abstract — The polarization effects of intermolecular and intramolecular interactions are the most universal basis to formulate the physical meaning of chemical potential.
23/09/2008 | 1415 Hits | Print
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45.
On Unacceptable Use of Austenitic Sleeves and Surfacing Alloys for Repair of Carbon-Steel Equipment M. L. Medvedeva, L. A. Efimenko, and A. V. Sidorenko Gubkin State University of Oil and Gas, Leninskii pr. 65, Moscow, 119991 Russia Received September 10, 2004 Abstract — Substantial part of equipment in gas-treating plants for removal of acidic impurities in oil and gas refineries needs repair, for which purpose austenitic sleeves are often used. Austenitic surfacing nickel alloys recommended for restoring the damaged surface by overlaying welding was found to be unsuitable because both the deposited material and the fusion line with the base metal are electrochemically heterogeneous, which makes repaired apparatuses insufficiently reliable. Use of sleeves is also inexpedient.
23/09/2008 | 1389 Hits | Print
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46.
A  Geometric Model of Glass-Enamel Coating. Part 2. Contact Area with Metal, the Gas-Phase Volume Fraction, and the Minimum Coating s Cross-Section N. T. Shardakov and V. Ya. Kudyakov Institute of High-Temperature Electrochemistry, Ural Division, Russian Academy of Sciences,
ul. S. Kovalevskoi 20, Yekaterinburg, 620219 Russia Received June 12, 2004 Abstract — In terms of a geometric model, an equation of the minimum cross-section area of a glass-enamel coating, as well as its particular form to calculate the contact area between the coating and the metal substrate, is derived. The expressions to assess the gas-phase volume fraction in the coating and its density are also obtained. It is shown that tearing the coating off occurs most probably in the plane of the minimum coating’s cross-section rather than the metal/coating interface.
23/09/2008 | 1382 Hits | Print
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47.
Corrosion Resistance and Dezincing of Brasses I. K. Marshakov Voronezh State University, Universitetskaya pl. 1, Voronezh, 394006 Russia e-mail:
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Received March 23, 2004 Abstract — The corrosion behavior of brasses in aerated electrolyte solutions (where dezincing is frequently observed) is studied. In this case, a layer of fine-grained copper forms on the brass surface. Ignoring this copper as the corrosion product, that is, calculating corrosion loss by the sample weight loss, one underestimates actual corrosion rate by 1.5–2 times. However, in closed systems, in the absence of dezincing, oxidized copper accumulates in solution and acts as a catalyst of cathodic process increasing significantly the corrosion rate. The following methods of reducing the corrosion rate and brass dezincing are considered: deoxygenation of medium, the use of zinc anodes, and the alloying of brasses with the third component. The conditions, under which these methods are the most efficient, are determined.
30/09/2008 | 1184 Hits | Print
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48.
Chronoammetry and Chronopotentiometry on Electrodes with a Microrough Surface: Theoretical Consideration O. A. Kozaderov and A. V. Vvedenskii Voronezh State University, Universitetskaya pl. 1, Voronezh, 394006 Russia e-mail:
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Received August 17, 2004 Abstract — The problem of transient two-dimensional diffusion to a microrough electrode under galvano- and potentiostatic polarization conditions is solved. The effect of the scale and morphology of roughness, as well as the diffusivity on the time dependences of I current and   overpotential is analyzed. Both of them are found to be practically independent of the type of the roughness, while its degree (the microroughness factor fr) decisively affects the shape of the current- and overpotential-decay curves. At a relatively short polarization when the diffusion front profile repeats the electrode surface relief, the parameters of transient electrochemical methods (the I current in the potentiostatic measurements and the  1/2 rooted transient time in the galvanostatic ones) linearly depend on the microroughness factor. Upon a relatively long polarization when the diffusion front is noticeably distant from the surface and almost planar, the current and overpotential values fit in with classical equations of chronoammetry and chronopotentiometry, being independent of fr . At a thickness of the diffusion layer comparable to the height of surface irregularities, the current (as well as the rooted transient time) ratio of the microrough to perfectly smooth electrode surface looses its linear dependence on the surface parameters. The time location of this range is chiefly determined by the diffusivity and the mean distance between the microscopic surface irregularities.
30/09/2008 | 1208 Hits | Print
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49.
2D Atomic-Topological Model of the Dissolution Kinetics of a Metallic Crystal: Typical Atomic Relief Positions and Fragments G. Yu. Alekseev*, Yu. V. Alekseev*, **, and V. A. Bityurin* * Institute of High Temperatures, Russian Academy of Sciences, Moscow, Russia ** Karpov Institute of Physical Chemistry, ul. Vorontsovo Pole 10, Moscow, 103064 Russia e-mail:
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Received November 11, 2003; in final form November 15, 2004 Abstract — 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.
30/09/2008 | 1138 Hits | Print
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50.
Electrochemical Behavior of Manganese Silicides in Sulfuric Acid Solution A. B. Shein and E. N. Zubova Perm State University, ul. Bukireva 15, Perm, GSP, 614990 Russia e-mail:
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Received December 23, 2002 Abstract — The corrosion-electrochemical behavior of Mn5Si3 and MnSi silicides in the sulfuric acid electrolyte is studied by using the steady-state and cyclic voltammetry in combination with atomic absorption analysis. The following main regularities of the anodic dissolution of silicides are revealed: Mn dissolves selectively from the sublattice in silicide and, then, the process is controlled by diffusion of Mn in the compound and oxidized Mn through a layer of hydrated SiO2 oxide formed at the surface.
30/09/2008 | 1166 Hits | Print
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