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11.
Partial Electrode Processes at AC-Polarized Copper in Chloride and Nitrate Media O. Yu. Kuksina, V. Yu. Kondrashin, and I. K. Marshakov Voronezh State University, Universitetskaya pl. 1, Voronezh, 394006 Russia Received January 23, 2004 Abstract — The dissolution of a copper electrode by passing a rectangular alternating current of an infralow frequency (1/6 Hz) was studied by chronopotentiometric method. The near-electrode concentrations of copper oxidation products were calculated by the numerical solution of the boundary problem of transient diffusion. In concentrated chloride electrolytes, the shape of the E vs. t plot was found to be determined by transient mass transfer. The ratio of the copper reduced during the cathodic half-period to its amount dissolved in the anodic half-period was estimated experimentally. This ratio was used to determine the distribution of faradaic charges between different partial electrode processes. In nitrate electrolytes, cathodic process significantly affects the anodic dissolution of copper.
15/12/2008 | 864 Посещения | Печать
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12.
Fourier-Transform Diffuse Reflection IR-Spectroscopy in Studies of Thermal Oxidation of  18 10 Steel V. A. Kotenev, N. P. Sokolova, and A. M. Gorbunov Institute of Physical Chemistry, Russian Academy of Sciences,
Leninskii pr. 31, Moscow, 117915 Russia Received February 18, 2004 Abstract — Methodology potentialities of the Fourier-transform diffuse reflection IR-spectroscopy with sharply focused probing beam are discussed as applied to studies of  18 10 steel gaseous oxidation at 100–800°C. The method is shown to be promising as regards investigating thermodynamics of the process.
15/12/2008 | 840 Посещения | Печать
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13.
A Flow Line for Laser Diagnostics of Corrosion Damage V. A. Kotenev Institute of Physical Chemistry, Russian Academy of Sciences,
Leninskii pr. 31, Moscow, 117915 Russia Received February 18, 2004 Abstract — A method of laser ellipsometric diagnostics of corrosion layers on a great number of samples in laboratory and field conditions is presented. A procedure of laser monitoring is proposed and verified; it allows to remotely control the corrosion layer thickness. A highly sensitive return-path double-reflection optical-electrochemical cell is developed. Basic methodological aspects of using a remote-control laser-ellipsometric probe in a flow line for the laser corrosion monitoring in corrosion tests are illustrated by the example of continuous corrosion monitoring of copper–nickel alloy in saline water.
15/12/2008 | 879 Посещения | Печать
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14.
Electrocatalysis under Conditions of Ion Co-discharge with the Formation of an Alloy Yu. M. Polukarov, A. A. Edigaryan, and E. N. Lubnin Institute of Physical Chemistry, Russian Academy of Sciences,
Leninskii pr. 31, Moscow, 119991 Russia e-mail:
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Received April 1, 2004 Abstract — The distribution of elements in Ni–Cr alloy deposits is studied with the use of x-ray photoelectron spectroscopy and electron Auger spectroscopy. Nickel is shown to catalyze the deposition of chromium, while chromium catalyzes the reduction of oxalates to carbon. The alloys have nanocrystal fcc structures based on nickel lattice. At a high chromium content (88 at. %), a phase with hexagonal lattice forms.
15/12/2008 | 1218 Посещения | Печать
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15.
Information-Optical 3D-Techniques for Corrosion Monitoring V. A. Kotenev Institute of Physical Chemistry, Russian Academy of Sciences,
Leninskii pr. 31, Moscow, 119991 Russia Received December 20, 2003 Abstract — Methodical basis of using information-optical 3D-techniques and computer optical video microprobes in a high-performance monitoring of the thickness, topography, and statistical properties of thin corrosion layers on microscopic surface areas of a metal or semiconductor is considered. Forming a microscopic video image of such an area of an electrode and measuring the intensity distribution of the reflected optical signal in its field, one can obtain a 3D relief-map of the thickness and other properties of islets, new phase nuclei, and secondarily deposited layers on the electrode area in real time. The possibilities of combining the scanning and reflectometric 3D video microprobe techniques, diffuse-reflection infrared spectroscopy with a sharply focused probing beam, as well as photo-EMF technique, ellipsometry, and electrochemical methods when studying the corrosion behavior of metals and alloys, enable one to monitor the nonuniformity of the thickness and chemical composition of the corrosion layers. The information-optical 3D techniques of treating the images provides highly informative monitoring of the nonuniformity degree of the thickness, defectiveness, and chemical composition of the layer on the whole studied microscopic surface area of a corroded metal.
15/12/2008 | 1161 Посещения | Печать
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16.
Indirect Amperometry of Free Corrosion as a Method for Its Laboratory Investigation G. N. Markos’yan Russian Federation Scientific Center “Karpov Research Institute of Physical Chemistry,”
ul. Vorontsovo Pole 10, Moscow, 103064 Russia e-mail:
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Received December 18, 2003 Abstract — A formerly developed electrochemical cell able to continuously measure the oxygen corrosion rate of a metal through the absorbed oxygen quantity is described. By the example of various metals and alloys, the cell is shown to be applicable to clarifying the effect of various factors on their corrosion rate in acidic aqueous solutions. The rate constants are also determined for a series of homogeneous chemical reactions consuming oxygen. Peculiarities of hydrogenation and dehydrogenation processes under cathodic polarization conditions with access for air are investigated. It is shown that substituting chlorine for oxygen enables one to investigate chlorination of rubbers and chlorine corrosion of a great many metals and alloys.
15/12/2008 | 1210 Посещения | Печать
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17.
Peculiarities of Intergranular Corrosion of Silicon-Containing Austenitic Stainless Steels O. V. Kasparova Karpov Institute of Physical Chemistry, ul. Vorontsovo Pole 10, Moscow, 103064 Russia Received January 23, 2004 Abstract — Experimental data collected for the past two decades and a half are generalized, and the mechanism of intergranular corrosion (IGC) of austenitic silicon-containing (quenched and sensitized) steels in the envi-ronments with various redox characteristics is discussed. The synergistic intensification of IGC by the alloying silicon additives and carbon admixtures is experimentally revealed. The cause of the bivariant effect of silicon on the resistance of grain boundaries in sensitized steels at active–passive transition potentials is clarified. The effect of silicon on the electronic structure of a solid solution (including intergranular domains) is supposed to account for some peculiarities in the electrochemical behavior of the steels.
15/12/2008 | 1223 Посещения | Печать
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18.
Justifying the Model of Spatial Separation of Metal Dissolution and Passivation Processes R. M. Lazorenko-Manevich, A. N. Podobaev, and L. A. Sokolova FGUP State Scientific Center of the Russian Federation “Karpov Institute of Physical Chemistry,”
ul. Vorontsovo Pole 10, Moscow, 103064 Russia e-mail:
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Received February 18, 2004 Abstract — Results of studying the dissolution of fresh-formed iron surface and voltammetry of liquid and solid gallium are used to justify the concept of the direct participation of surface charge-transfer complexes, resulting from water adsorption, in the anodic dissolution of hydrophilic metals. The concept also implies both the effect of steady-state surface morphology on the kinetic parameters of the anodic dissolution and the effect of potential on the surface morphology. This concept underlies a model of spatial separation of processes of metal dissolution and passivation. Using this model, anodic voltammograms for iron in solutions with different concentration of chloride ion and pH were calculated. The calculated curves are in close agreement with experimental ones.
15/12/2008 | 1147 Посещения | Печать
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19.
Electrochemical Behavior of Nickel Hydride in Sodium Hydroxide Solutions D. S. Sirota and A. P. Pchel’nikov Karpov Institute of Physical Chemistry, ul. Vorontsovo Pole 10, Moscow, 103064 Russia e-mail:
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Received December 18, 2003 Abstract — Electrochemical behavior of nickel hydride Ni2H ( -phase) is studied in 0.01–1 N NaOH by using common (VA) and cyclic (CVA) voltammetry, chronocoulometry, amperometry, and potentiometry. The limiting anodic and cathodic currents in VA and CVA curves are caused by the hydride decomposition via the fol-lowing scheme Ni2H   '-phase  Ni + Habs, where the intermediate '-phase contains 0.003 at. % H, that is, one tenth that in the saturated -phase (0.03 at. %). At open circuit, the hydride maintains the equilibrium hydrogen potential. In the first 30 min, the hydrogen ionization from hydride is limited by solid-state diffusion and, later, the hydride decomposition. The anodic process involves ionization of sorbed hydrogen, while the cathodic process represents its electrochemical desorption: H2O + Hads + e  H2 + OH–. The hysteresis observed in the cathodic CVA and open-circuit chronograms of the hydride potential in the beginning of anodic dissolution reflect the changes in the surface coverage of hydride with adsorbed hydrogen. The rate constant of hydride decomposition k, the rate V itself, and the equilibrium constant K are as follows: k = k = 8  10–5 s–3, V= 3 10–5 C/cm2 , and K = 10. The kinetic parameters of hydrogen electrochemical ionization from the hydride are ba = 0.12 V and = 0.5.
15/12/2008 | 1184 Посещения | Печать
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20.
The Effect of Nonmetal Inclusions and Microstructure on Local Corrosion of Carbon and Low-alloyed Steels I. I. Reformatskaya*, I. G. Rodionova**, Yu. A. Beilin***, L. A. Nisel’son***, and A. N. Podobaev* * Karpov Institute of Physical Chemistry, ul. Vorontsovo Pole 10, Moscow, 103064 Russia e-mail:
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** Bardin Central Research Institute of Ferrous Metallurgy, Moscow, Russia *** Oil Company YuKOS, Moscow, Russia Received March 23, 2004 Abstract — The resistance of carbon and low-alloyed steels to local corrosion is shown to be directly determined by their phase-structure, rather than chemical, composition. A correlation between the presence of various nonmetal inclusions in steels and the local corrosion rate is revealed. Inclusions containing Ca and S are shown to be the most corrosive, manganese sulfide inclusions act less corrosively, and silicates are the least active. The formation of lamellar pearlite in the steel structure also impairs its resistance to local corrosion. By providing metal pure of corrosive nonmetallic inclusions at a melting stage and ensuring the pearlite spheroidizing during the stages of thermal treatment and processing, it is possible to enhance its resistance to total and local corrosion.
15/12/2008 | 1232 Посещения | Печать
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