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1.
3D Visualization of the Dissolution Products of a Metal in the Near-Electrode Layer at the Metal Solution Interface V. A. Kotenev, M. A. Petrunin, L. B. Maksaeva, and A. Yu. Tsivadze Institute of Physical Chemistry, Russian Academy of Sciences,
Leninskii pr. 31, Moscow, 119991 Russia Received December 29, 2004 Abstract — A 3D profile of the layer of the metal dissolution products precipitated from a solution is reconstructed by means of reflectometry. Its nano-scale resolution in thickness enables one to investigate in situ the formation of micro- and nano-size adsorption islets, new phase nuclei, and steady-state localized superficial domains (with different rates of the metal dissolution and complex formation processes). In this way, the originally unseen structure of the metal surface defects is visualized. The digital optical images obtained with a scanner for a small probed surface spot were processed in order to clarify the pitting nature of the metal dissolution in distilled water and visualize the latent defective metal structure. Local dissolution centers (pits) appear mainly in the first 10 to 20 min and determine the corrosion rate. The technique is highly sensitive to thin layers and, consequently, to the ions in solution. All these peculiarities make the measurements of the tangential nonuniformity of the layer at the studied spot of the electrode surface highly informative. The secondary precipitated layer of dissolution products can be considered as a distributed sensor layer immobilized at defects of the metal surface. Minor changes in the solution chemistry (pH, oxygen content, etc.) lead to the change in the dissolution rate and, hence, in the thickness, structure, and composition of the secondary precipitated sensor layer.
20/09/2008 | 1358 Hits | Print
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2.
On the Coadsorption of Mephenaminate and Phenylundecanoate Anions at Passive Iron Yu. I. Kuznetsov and N. P. Andreeva Institute of Physical Chemistry, Russian Academy of Sciences, Leninskii pr. 31, Moscow, 119991 Russia e-mail:
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Received August 10, 2004 Abstract — Adsorption of sodium mephenaminate (SMEP), sodium phenylundecanoate (SPU), and their mixtures by oxidized iron from a borate buffer (pH 7.4) at the constant potential E = 0.2 V was studied by ellipsometry. Like the adsorption of the previously studied SMEP, that of SPU obeys the Frumkin equation with the higher Gibbs energy of adsorption (   = 33.1 kJ/mol). The Frumkin equation fails for the adsorption of an equimolar SPU + SMEP mixture (inhibitor IFKhAN-31), which is described by the Bockris equation. The calculations showed that   = 41.7  0.2 kJ/mol and the number of water molecules displaced by an adsorbed inhibitor species from the metal–solution interface is n = 4. It was found that SMEP anions preadsorbed at oxidized iron do not affect the shape of the SPU adsorption isotherm, yet altering its constants. In the case of preadsorbed SPU, the SMEP adsorption isotherm changes its shape and cannot be described by any known adsorption equation. In addition, SMEP begins to adsorb at the electrode in lower concentrations; i.e., PU anions stimulate the adsorption of SMEP.
20/09/2008 | 1422 Hits | Print
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3.
Initial Stages of Iron Chromium Alloys Passivation in Acid Sulfate Solutions A. N. Podobaev, I. I. Reformatskaya, and E. V. Trofimova 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 May 05, 2005 Abstract—Upon jumpwise applied “maximal critical passivation potential” (that is, the most positive potential at which Fe–Cr alloys still remain in the state of active–passive transition), chromium can continuously accumulate at the surface because of the selective dissolution of iron atoms. This probability can actualize at a chromium content in the alloy of up to 27.7% and pH < 1.2. Oxygen-containing compounds of bivalent chromium are the passivating agents at pH < 1.2 those of trivalent chromium, at pH  1.2.
20/09/2008 | 1399 Hits | Print
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4.
The Effect of Organic Mixtures of One and Two Reaction Series on the Electroplating of Fe Ni Alloys S. P. Shpan’ko*, V. P. Grigor’ev*, O. V. Dymnikova*, and A. S. Burlov** * Rostov State University, ul. Zorge, Rostov-na-Donu, 344090 Russia e-mail:
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** Research Institute of Physical and Organic Chemistry, Rostov State University,
pr. Stachki 194/2, Rostov-na-Donu, 344090 Russia Received May 26, 2004 Abstract — Characteristics of electroplating an iron–nickel alloy and its components in the presence of surfactant mixtures of one and two reaction series are described based on the linear Gibbs energy relations. The alloy composition depends on the number and polarity of substituents in the molecules of additives to electroplating baths.
20/09/2008 | 1438 Hits | Print
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5.
Effect of Chloride Ions on the Rate of Iron Dissolution in Weakly Acid Sulfate Solution A. N. Podobaev 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 November 23, 2004 Abstract — In acid (pH 0 or lower) and weakly acid (pH 1.72) sulfate solutions, chloride ions either decelerate or accelerate iron dissolution, depending on whether the chloride concentration is low or high, respectively. The acceleration effect in a weakly acid solution occurs at a chloride concentration approximately two orders lower than in acid solution. The difference is due to an increase in the surface concentration of chemisorbed water molecules with an increase in the solution pH. The deceleration is mainly caused by the chloride-ion adsorption at the metal; the acceleration, by its incorporation into metal–water surface complexes.
20/09/2008 | 1443 Hits | Print
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6.
The Electrochemical Behavior of  -Phase in the Cu30Ni H System in Sodium Hydroxide Solutions D. S. Sirota and A. P. Pchel’nikov 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 July 21, 2004 Abstract — The electrochemical behavior of Cu30Ni alloy hydride in 1 N NaOH solution was studied. One-shot and cyclic voltammograms, chronocoulometric, amperometric, and potentiometric curves, as well as time variation of the open-circuit (free-corrosion) potential Ecor, were measured. Both types of voltammograms show a limiting current plateau, which can be explained by a preceding chemical reaction of the hydride decomposi-tion. It is concluded (from the character of Ecor vs. t curves) that the hydride decomposition involves the alloy’s copper component activation through the copper oxide reduction with hydrogen. The alloy hydride decomposition rate was determined by using chronocoulometry: V = 4.6  10–4 A/cm2 . No potential arrest was observed in the Ecor vs. t and E vs. t curves, which is due to concurrent reactions of electrochemical and chemical recom-bination involving hydrogen atoms adsorbed at the alloy surface.
20/09/2008 | 1336 Hits | Print
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7.
Formation, Retention, and Waste of Products of Atmospheric Corrosion of Metals. 2. Kinetics of Corrosion and Waste* 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 — This publication is the second, final part of the paper (see Zashch. Met., 2005, vol. 41, no. 4, p. 369), in which the empiric mathematical model of the integral weight of corrosion products formed was considered. In this part, the kinetics of changes in the weight of formed and wasted corrosion products of carbon steel, zinc, copper, magnesium, aluminum, and alloys  16,   , and brass is considered. Moreover, the proposed model is used in estimating the amounts of copper and zinc in the environment-contaminating products of atmospheric corrosion accumulated during their 1-, 2-, and 4-year exposure. The conclusions (drawn based on the experimental data) correspond to both parts of the paper.
20/09/2008 | 1451 Hits | Print
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8.
The Effect of Inorganic Pollutants on the Biocorrosivity of Marine Environment to a Low-Carbon Steel A. P. Suponina, M. D. Koryakova, and U. V. Kharchenko Institute of Chemistry, Far East Division, Russian Academy of Sciences,
pr. Stoletiya Vladivostoka 159, Vladivostok, 690022 Russia e-mail:
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Received June 21, 2004 Abstract — The effect of heavy metals such as Fe, Zn, Pb, Cd, and Cu in quantities simulating economical pollution of natural sea water on its biological pollution and corrosivity to a low-carbon   3 steel is investigated under laboratory conditions. It is shown that under the experimental conditions, the steel corrosion is controlled by biological factor of the medium.
20/09/2008 | 1346 Hits | Print
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9.
Use of Modified Mustard Oil in Steel Corrosion Protection O. N. Savchenko, O. I. Sizaya, and O. L. Gumenyuk Chernigov State Technological University, ul. Shevchenko 95, Chernigov, 14027 Ukraine e-mail:
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Received June 3, 2004 Abstract — The inhibitive properties of sulfated mustard oil in neutral and alkaline media (3% NaCl and 0.25M CH3COONa) in the presence of alkyl- and arylbenzoimidazole derivatives were studied. Mixtures of diethylammonium salts of sulfated mustard oil with benzoimidazole derivatives were found to be promising combined inhibitors of metal corrosion.
20/09/2008 | 1358 Hits | Print
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10.
Inhibition Effect of Rhodanine for Corrosion of Mild Steel in Hydrochloric Acid Solution1 R. Solmaz, G. Karda , B. Ya i i, and M. Erbil Department of Chemistry, Faculty of Art and Science,
Cukurova University, 01330, Balcali, Adana, Turkey e-mail:
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Received July 5, 2004 Abstract — The inhibition effect of Rhodanine on the corrosion performance of mild steel (MS) was studied in 0.5 M HCl solution. For this purpose, potentiodynamic polarization, electrochemical impedance spectroscopy, and long-term corrosion tests including hydrogen evolution and change in open-cirquit potential during immer-sion time were used. To determine activation energy of corrosion process, potentiodynamic polarization curves were also obtained in a temperature range from 298 to 328 K. The results show that Rhodanine effectively inhibits the MS corrosion in hydrochloric acid solution.
20/09/2008 | 1341 Hits | Print
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