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1.
Diffusion Mass Transfer under the Conditions of Instability of Products of Electrochemical Reaction A. V. Noskov and S. A. Lilin Institute of Solutions Chemistry, Russian Academy of Sciences, ul. Akademicheskaya 1, Ivanovo, 153045 Russia Received May 12, 2006 Abstract — Theoretically considering the diffusion–migration mass transfer in binary z1 z2-electrolytes during anodic dissolution of metals is performed with due allowance for the decomposition of intermediates formed. The components’ concentration and electric potential distributions in the diffusion layer, as well as the system’s current–voltage characteristics are calculated. It is shown that under conditions of the cation slow removal the electrochemical process is slowed down with an increase in the products’ stability constant. PACS numbers: 66.30.Hs, 68.47.De, 73.40.-c, 82.45.Gj DOI: 10.1134/S0033173207020026
09/09/2008 | 1207 Hits | Print
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2.
Electrooxidation of Cr3+ Ions in Sulfuric Acid Solutions E. G. Vinokurova and V. V. Bondar’b a Mendeleev University of Chemical Technology, Miusskaya pl. 9, Moscow, 125190 Russia b All-Russian Institute of Scientific and Technical Information, Russian Academy of Sciences, Moscow, Russia Received March 2, 2006 Abstract — The effects the material nature of an anode, the cation radius and the metal–oxygen bond strength in the oxide anode on the rates of Cr3+ ion electrooxidation and the anode corrosion. A correlation between the rates of Cr3+ cation electrooxidation and corrosion of the anodes made of different metals is revealed. It is shown that the electrocatalytic activity of oxide anodes in the Cr3+ electrooxidation is caused by crystallographic and energy factors. The highest electrocatalytic activity is demonstrated by the oxides whose metal cat-ion radius exceeds that of dehydrated Cr3+ cation and the M–O bond energy is smaller than the bond energy in Cr2O3. The equation suggested takes simultaneously into account the effects of the oxide electrode cation radius and the mean energy of M–O bond on the relative rate of the Cr3+ ion electrooxidation. PACS numbers: 82.45.Mk, 82.45.Qr DOI: 10.1134/S0033173207020038
09/09/2008 | 1311 Hits | Print
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3.
Dissolution Mechanism and Partial Electrode Processes at Infralow Frequency AC Polarization of Brasses in Chloride Media. I.  -Brass Cu20Zn I. K. Marshakov, O. Yu. Kuksina, and V. Yu. Kondrashin Voronezh State University, Universitetskaya pl. 1, Voronezh, 394006 Russia Received May 14, 2006 Abstract—Being typical of a steady-state anodic polarization, the uniform dissolution of  -brass Cu20Zn is retained for the anodic half-period in the pulsed mode (f = 0.17 Hz). At such an ac polarization, the dissolution is alternated with the copper deposition in the cathodic half-periods to form a loose fine-grain deposit at the electrode. Under severe hydrodynamic conditions, no copper deposit is formed. With an increase in the current in the cathodic half-periods, the pH of a near-electrode solution layer increases, thus changing the anodic processes. Namely, the oxidation of brass components to soluble chloride complexes gives place to the formation of poorly soluble products. PACS numbers: 82.45.Bb DOI: 10.1134/S003317320702004X
09/09/2008 | 1346 Hits | Print
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4.
The Effect of Chloride and Sulfate Anions on the Iron Dissolution Rate in Neutral and Nearly Neutral Media A. Yu. Aleksanyan, I. I. Reformatskaya, and A. N. Podobaev Federal State Unitary Enterprise “Karpov Research Institute of Physical Chemistry,”
Vorontsovo Pole 10, Moscow, 103064 Russia
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) Received June 5, 2006 Abstract — Analysis of results of steady-state potentiostatic measurements on iron in the neutral and nearly neutral borate solutions is complicated by the fact that the metal is in the state of active–passive transition near the free-corrosion potential. This difficulty is overcome using the method of neural network simulation. The study of the behavior of neural-network model shows that chloride and sulfate ions can promote or inhibit iron dissolution depending on their concentration and the pH value of solution. The ambiguous effect of anions is explained by the fact that, when they are adsorbed at the metal, they prevent its cations from passing to the solution, and, entering into the metal–water adsorption complexes, they assist the decomposition of complexes thus promoting the dissolution. Sulfate ions, compared with chloride ions, are, probably more adsorption-active with respect both to iron and to water adsorbed on it. PACS numbers: 82.45.Bb, 82.45.Fk, 82.45.Qr DOI: 10.1134/S0033173207020051
09/09/2008 | 1226 Hits | Print
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5.
Electron Hydration Energy: Nonempirical Estimate Yu. V. Novakovskaya Laboratory of Quantum Mechanics and Molecular Structure, Chair of Physical Chemistry, Department of Chemistry,
Moscow State University, Leninskie Gory, Moscow, 119992 Russia E-mail:
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Received September 1, 2006 Abstract — Based on the results of quantum chemical calculations, the energies of vertical (photoionization) electron removal from superficial and bulk water layers are estimated as 2.9 and 4.4 eV respectively. For the first time, a nonempirical estimate of the electron hydration energy is obtained, 2.6 eV, which characterizes the electron state both at the superficial and bulk hydration. To find these value, molecular cluster systems modeling the Bjerrum defects of the hydrogen-bond network of water localizing the additional electron were calculated. Typical ways of the reorganization of defects upon the electron removal are identified. Conditions under which the relaxation of defects is reversible upon the re-addition of the charge are determined. The pre-existence of defects is shown not to be an indispensable condition of the effective localization of excess electrons by water. Small distortions, as well as breakage, of the continuity of the hydrogen-bond network are sufficient. PACS numbers: 33.15.Ry; 36.40.Wa; 31.25.Qm DOI: 10.1134/S0033173207020063
09/09/2008 | 1305 Hits | Print
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6.
Thermodynamic Calculation of the Critical Potentials of the Selective Dissolution of Ag Au and Cu Au Alloys A. E. Kutyrev and Yu. Ya. Andreev Moscow State Institute of Steel and Alloys, Leninskii pr. 4, Moscow, 119049 Russia E-mail:
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Received August 11, 2006 Abstract — A thermodynamic approach to estimating the critical potential of the selective alloy dissolution Ec at a vacancy concentration N (s) in the superficial layer is considered. The N (s) dependence on the potential and the concentration of gold NAu in the alloy is calculated. The Ec potential corresponds to the critical concentra-tion of vacancies N (s)  10 2, and the Ec value itself is determined chiefly by the zero-point potential of the alloy, which is a pronounced function of the surface enrichment in gold. The calculated Ec NAu functions for Ag–Au and Cu–Au alloys satisfactorily coincide with the experimental dependences. PACS numbers: 68.35.Md DOI: 10.1134/S0033173207020075
09/09/2008 | 1277 Hits | Print
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7.
On the Protection of Carbon Steels from Hydrogen-Sulfide Corrosion with Mixtures of Volatile and Contact Inhibitors Yu. I. Kuznetsov, L. V. Frolova, and E. V. Tomina Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences,
Leninskii pr. 31, Moscow, 119991 Russia Received February 18, 2006 Abstract — The effects of volatile (IFKhAN-118) and contact inhibitors (aliphatic primary amine, diphenylguanidine (DPG), and a quaternary ammonium salt (QAS)) and their 1 : 1 and 2 : 1 mixtures on the corrosion and electrochemical behavior of carbon steels in an aqueous electrolyte (0.5% NaCl + CH3COOH (0.25 g/l) + H2S (2 g/l); pH 3.6) were studied. It was found that QAS is most effective among the individual inhibitors. As regards mixed inhibitors, steels were best protected by IFKhAN-118 + QAS (2 : 1) and slightly worse by IFKhAN-118 + Amine (2 : 1). The mixture DPG + VCI was less effective. The protective films of IFKhAN-118 + Amine (2 : 1) exhibited the aftereffect on steel in an atmosphere of moist H2S for 10 days (Z = 97 to 98%); however, a relatively long period of time (about 5 days) was required for the formation of stable adsorbed films in the vapor phase of the inhibitor. PACS numbers: 81.65.Kn DOI: 10.1134/S0033173207020087
09/09/2008 | 1304 Hits | Print
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8.
Formation, Retention, and Discharge of Products of Atmospheric Corrosion of Metals. 4. Model: Corrosion Discharge of Products Yu. M. Panchenkoa, P. V. Strekalova, and T. V. Nikulinab a Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy of Sciences,
Leninskii pr. 31, Moscow, 119991 Russia
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b Institute of Biology and Soil Sciences, Far East Division, Russian Academy of Sciences, pr. Stoletiya Vladivostoka 159,
Vladivostok, 690022 Russia Received November 10, 2005 Abstract - An empirical mathematical model K = K0 + kmlos (relating atmospheric corrosion to the weight loss of its products) for incubation + transient and steady-state stages of the process, is considered. To develop the model, we used the results of long-term (from 3 month to 1–17 years) field tests of metals according to the Russian, International ISOCORRAG, and Russia–Vietnam–Cuba programs. The K0 and k factors in the model were determined according to the corrosion of   3, copper, brass, zinc, aluminum,  16 alloy, and   alloy in the zones of cold, moderate, subtropical, and tropical climates. The model quantitatively relates the corrosion losses of a metal to those of the products discharged to the environment. It may be useful when it is necessary to estimating the amount of detrimental metals, e.g., unprotected copper and zinc dispersed to the environment, but there is no data on the weight of products that had been retained by the metal in the air. PACS numbers: 82.45.Bb DOI: 10.1134/S0033173207020099
09/09/2008 | 1360 Hits | Print
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9.
Inhibition of the Early Depassivation of  -Brass in Neutral Chloride Electrolytes M. V. Rylkina and M. V. Didik Udmurt State University, ul. Universitetskaya 1, Izhevsk, 426034 Russia E-mail:
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Received July, 14, 2005; in final form, April 13, 2006 Abstract — Sodium anthranilate (SA), sodium phenyl anthranilate (SPA), and benzotriazole (BTA) were tested as inhibitors of the early depassivation stages of  70 -brass in neutral chloride electrolytes. Although SA and SPA were found to initiate pitting corrosion at -brass, the antagonism between SA (or SPA) and Cl ions can result, at a certain ratio of their concentrations, in the inhibition of the pitting corrosion of -brass. -Brass wasbest protected from pitting by BTA. PACS numbers: 81.65.Kn; 82.45.Pb DOI: 10.1134/S0033173207020105
09/09/2008 | 1296 Hits | Print
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10.
Chromium Electroplating from Sulfate Oxalate Solutions Containing Nanoparticles of Alumina and Silicon Carbide E. N. Lubnin, N. A. Polyakov, and Yu. M. Polukarov Frumkin Institute of Physical Chemistry and Electrochemistry, Russian Academy
of Sciences, Leninskii pr. 31, Moscow, 119991 Russia Received January 27, 2006 Abstract — The effect of the introduction of Al2O3 and SiC particles into the base chrome-plating sulfateoxalate Cr (III) bath on the electrochemical characteristics of chromium deposition, as well as the structure and mechanical properties of deposits, is studied. It is shown that Al2O3 particles are incorporated only into the surface film and are not detected in the bulk of the coating. Particles SiC are incorporated into both the surface film and the deposit. Introducing the particles into the bath makes the cathode polarization at a fixed current density, as well as the current efficiency and the bath throwing power, increase. PACS numbers: 81.15.Pq, 82.30. 6, 82.45.Qr DOI: 10.1134/S0033173207020117
09/09/2008 | 1546 Hits | Print
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