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1.
Hydrolysis of Interfacial Bonds in a Metal/Polymer Electrical Double Layer A. P. Nazarov and D. Thierry Korrosionsinstitutet, Kräftriket 23A, SE-10405, Stockholm, Sweden e-mail:
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Received October 13, 2003 Abstract — Effect of water on the electrical double layer structure at a metal/polymer interface is studied with the use of scanning vibrating capacitor and electrochemical impedance spectroscopy. In the initial stage, the Volta potential of the contact changes well reversibly and rapidly, being proportional to the water vapor pressure, following its diffusion in the polymer ( V = A + B log (time)1 /2). Water dipoles at the metal/polymer interface orientate counter the field and compensate it. Drying of the contact restores the initial potential drop. In the first stage of exposure, water somewhat enhances the interfacial interaction, which manifests itself in increasing the potential drop, as well as the charge transfer resistance, and in decreasing the capacitance of the electrical double layer. As time passes, the interface hydrolyzes, its capacitance grows and the time of subsequently restoring the electrical double layer by drying increases. Kinetic dependences of the potential and capacitance, exhibit two segments, we ascribe to easily removable and strongly bonded water molecules solvating the interface, respectively. It is shown that metal–polymer interfacial bonds passivate the metal; however, the passivation can be broken down because of the hydrolysis and the interfacial moisture film formation.
30/09/2008 | 1243 Hits | Print
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2.
On a Correlation between the Electronic Structure and Passivability of Fe Cr Alloys O. V. Kasparova*, Yu. V. Baldokhin**, and A. S. Solomatin** * State Scientific Center of the Russian Federation “Karpov Institute of Physical Chemistry”,
ul. Vorontsovo Pole 10, Moscow, 103064 Russia ** Semenov Institute of Chemical Physics, Russian Academy of Sciences,
ul. Kosygina 4, Moscow, 117977 Russia Received April 23, 2004 Abstract—The chromium (5.8 to 30.7 wt. %) effect on the superfine magnetic structure and surrounding electrons of the 57Fe nuclei in quenched and annealed Fe–Cr alloys is studied with the use of nuclear  -resonant (Mössbauer) spectroscopy. The following parameters of the Mössbauer spectra are calculated by using PC with a Normos software: the effective magnetic intensity Hef (in kOe), the isomeric (chemical) shift   (in mm/s), the quadrupole electric splitting eq (in mm/s), and the area fraction S (%) of the superfine-structure subspectrum. Significant changes in the superfine magnetic structure and the electron surrounding of the 57Fe nuclei are revealed as functions of the chromium content in the alloys. The conclusion on a correlation between the electronic structure of the alloys and their passivability is drawn.
30/09/2008 | 1155 Hits | Print
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3.
The Contact Electric Resistance of Copper, Silver, Gold, and Platinum in Ferrocyanide Solutions V. A. Marichev Institute of Physical Chemistry, Russian Academy of Sciences, Leninskii pr. 31, Moscow, 119991 Russia e-mail:
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Received January 29, 2003 Abstract - The contact electric resistance of copper, silver, gold, and platinum is studied in acid, neutral, and alkaline solutions containing 10–5 to 10–2 g-ion/l of ferrocyanide-ions. Their specific adsorption at the metals begins at rather negative potentials and is competitive. The data obtained do not prove an assumption on dissociative character of the ferrocyanide-ion adsorption at the 1st Group metals.
30/09/2008 | 1200 Hits | Print
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4.
To the Co-Effect of Impurity Atoms and Structure on the Dissolution of Iron and Its Low Alloys A. V. Plaskeev Karpov Institute of Physical Chemistry, ul. Vorontsovo Pole 10, Moscow, 103064 Russia Received April 9, 2003 Abstract — 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. Gener-alizing 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.
30/09/2008 | 1306 Hits | Print
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5.
To the Theory of Anticorrosion Alloying of Brasses V. Yu. Kondrashin Voronezh State University, Universitetskaya pl. 1, Voronezh, 394006 Russia e-mail:
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Received October 15, 2003 Abstract — The protective effect produced by alloying was interpreted in terms of the gradient energy of the near-surface diffusion zone formed as a result of the anodic dissolution or self-dissolution of ternary phases. The general reasons for a changed tendency of such phases toward selective anodic dissolution and selective corrosion compared to nonalloyed phases were revealed. The method for quantitative estimation of the protective effect produced by small amounts of arsenic added to  -brass was proposed. A number of alloying elements (As, P, Ni, and Au) to - and  -brasses were found to be similar in the nature of the protective effect.
30/09/2008 | 1199 Hits | Print
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6.
Kinetics of the Anodic Oxidation of Metals in the Presence of Unstable Products of the Electrochemical Reactions A. V. Noskov and E. P. Grishina Institute of Chemistry of Solutions, Russian Academy of Sciences,
ul. Akademicheskaya 1, Ivanovo, 153045 Russia e-mail:
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Received January 26, 2004 Abstract — The resistance-controlled potentiodynamic passivation of metals is theoretically discussed with consideration of the chemical decomposition of the passive surface layer. The developed concepts were tested in the anodic oxidation of silver in sulfuric acid solutions. The rate constants of the chemical decomposition of the passive film material were calculated for different temperatures.
30/09/2008 | 1308 Hits | Print
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7.
 Anionic Effect in Copper Plating from Sulfate Aqueous-Ethanolic Electrolyte Containing Cyclic Polyester V. V. Kuznetsov, L. M. Skibina, S. V. Geshel’, I. N. Loskutnikova, and E. F. Kuznetsova Rostov State University, Rostov-na-Donu, ul. Zorge 7, 344090 Russia e-mail:
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Received February 20, 2004 Abstract — It is shown that, in contrast to aqueous electrolytes, where the electrode process is promoted by the electroreduction of activated surface complexes of Cu2+ with S anions, in aqueous-ethanolic electrolytes, it is promoted by sulfate complexes of copper(II) formed in the solution bulk and needing dissociation prior to the discharge. In the presence of cyclic polyester, the discharging complex species have to permeate through the barrier layer at the cathode surface. The layer consists of ethanol molecules and electroneutral associates of sulfate ions with Cu2+ cations containing crown-ester molecules in the coordination sphere. As a result, the electrode reaction is considerably inhibited with an increase in the concentration of S anions (“anionic effect”), and tribotechnical characteristics of copper coatings are significantly improved.
30/09/2008 | 1216 Hits | Print
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8.
Performance of Lubricants in the Rolling Friction Zone and Kinetics of Their Tribochemical Transformations V. G. Mel’nikov All-Rusian Research Institute of Oil Processing, ul. Aviamotornaya 6, Moscow, 111116 Russia e-mail:
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Received September 16, 2004 Abstract — There are two viewpoints on tribology: (1) an independent science that occupies a certain niche in physical chemistry, thermodynamics, and mechanics of interacting bodies and (2) a technology aimed to enhance the reliability and service life of machine elements in contact during relative motion. In any case, this requires the knowledge of physicochemical processes within the real contact zone of interacting bodies, i.e., in the lubricant itself and at its phase boundaries. This predetermines the importance of studying not only tribol-ogy, which is recognized for a long time, but also the tribochemistry of lubricant materials. In this study, we systematically analyze the mechanism and kinetics of tribochemical transformations of lubricant materials (oils and greases) in the rolling friction zone and the main directions of their consumption, which determine the break of metal bonds in the structural material of bearings. Based on the proposed kinetic mechanism, one can predict the depth of tribochemical processes and the service life of friction units with accuracy tolerable for practice.
30/09/2008 | 1265 Hits | Print
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9.
Effect of Oxidants on Protection of Mild Steel by Zinc Hydroxyethylidenediphosphonate G. V. Zinchenko and Yu. I. Kuznetsov 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 — The corrosion and electrochemical behavior of   3 steel and Armco iron in soft corrosive water at 20 and 80°C in the presence of a zinc complex with hydroxyethylidenediphosphonic acid (HEDPZn) and sodium nitrite and m-nitrobenzoate was studied. It was found that a mixture of this nontoxic phosphonate with oxidants inhibits steel (iron) corrosion or, at least, can be used in lower protective concentrations. The mixed inhibitor is effective because of its protective film (mainly composed of HEDPZn) that impedes both the electrode reactions. The components of such a mixture showed synergism of their inhibitive effects only when the concentration of HEDPZn was above a certain critical value and a certain [HEDPZn]/[oxidant] ratio was used.
30/09/2008 | 1183 Hits | Print
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10.
Effect of a Diphilic Corrosion Inhibitor on the Iron Passivity in Oil-Field Electrolytes A. A. Gonik Association for Protection from Corrosion in Oil and Gas Industry,
pr. Oktyabrya 144/3, Ufa, 450055 Russia e-mail: IPTER@SOROS BASHEDU.RU Received February 15, 2003 Abstract — The diphilic corrosion inhibitor IKB-4, which is widely used in oil industry, was studied by the chemical passivation method. This micelle-forming inhibitor was found to impede, via oxide-free passivation, iron dissolution in neutral mineralized waters of oil fields.
30/09/2008 | 1255 Hits | Print
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