Settling Peculiarities of Silver Sulfide Potential in Acetate Media

G. V. Makarov and I. G. Soboleva

Lipetsk State Technical University, ul. Moskovskaya 30, Lipetsk, 398600 Russia

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Received May 26, 2003

Abstract — Peculiarities of the argentite (-g₂S) electrode potential settling in acetic acid–acetate solutions are revealed by electroless chronopotentiometry, voltammetry at low polarization, and measuring the rim (wetting) angle. The process rate and the rate constant for the chalcogenide dissolution in a pre-equilibrium state are calculated from the self-dissolution current and the potential transient, respectively. The zero charge potential is found; the pH effect on the above parameters is revealed. It is shown that the potential-determining reaction involves the metal, rather than sulfide, ions.

Electroplating of Chromium-Cobalt Alloy Coatings from Sulfate Solutions

B. A. Spiridonov

Voronezh State Technical University, Voronezh, Russia

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Received March 20, 2003

A Computer System Measuring the Electrical Parameters of Microplasma Processes in Solutions

A. I. Mamaev* , V. N. Borikov** , V. A. Mamaeva* , and T. I. Dorofeeva*

* Institute of Strength Physics and Material Science, Siberian Division, Russian Academy of Sciences,
Akademicheskii pr. 8/2, Tomsk, 634070 Russia

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** Tomsk Polytechnical University, Tomsk, 634006 Russia

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Received January 12, 2004

Corrosion Resistance of Hastelloy-B in the Ozonized Medium

G. O. Tatarchenko¹ and K. V. Cherkas²

¹ North-Donetsk Technological Institute of the East Ukrainian State University,
Sovetskii pr. 59a, North-Donetsk, Lugansk oblast, 93400 Ukraine

² North-Donetsk State Industrial Enterprise “Nitrogen Company”,
ul. Pivovarova 5, North-Donetsk, Lugansk oblast, 93403 Ukraine

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Received September 25, 2003

Corrosion of Highly Dispersed Systems Based on Iron and FeSi Alloys in Neutral Electrolytes. II. Iron-Based Systems Obtained by Grinding in Heptane with an Organosilicon Additive

A. V. Syugaev*, S. F. Lomayeva*, and S. M. Reshetnikov**

* Physicotechnical Institute, Ural Division, Russian Academy of Sciences,
ul. Kirova 132, Izhevsk, 426000 Russia

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** Udmurt State University, ul. Universitetskaya 1, Izhevsk, 426034 Russia

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Received November 18, 2003

Protective Effects of 2-Thioquinazolin-4-One Derivatives on Steel 20 in Various Corrosive Media

O. I. Sizaya, O. L. Gumenyuk, and L. Yu. Chumakova

Chernigov State Technological University, ul. Shevchenko 95, Chernigov, 14027 Ukraine

e-mail: verv@ mail.cn.ua

Received May 20, 2004

Simulation of Outdoor Atmospheric Corrosion of Carbon Steel in Wet Tropics from Three-Month and One-Year Tests

P. V. Strekalov* and Do Thanh Binh**

* Institute of Physical Chemistry, Russian Academy of Sciences,
Leninskii pr. 31, Moscow, 119991 Russia

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** Institute of Tropical Technology, Vietnamese Academy of Sciences and Technology,
Hoang Quoc Viet, Hanoi, Vietnam

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Received September 16, 2004

Abstract — Mathematical models of the kinetics of outdoor atmospheric corrosion of metals were approved for a plain 3 carbon steel in the wet tropics of Vietnam and periods from 0.5 to 10 years by the results of 3-month and one-year outdoor atmospheric tests. The least deviation of the predicted from actually observed corrosion rate were observed for the time periods ranging from 1.5 to 2 years (the minimum error = 0.05%; the maximum = 12.7%). The average error of the predicted estimates, for all the models employed, falls into a rangefrom 10.9 to 41.4% for 3–5 years. However, for 10 years, it ranges either from 39.9 to 62.5% or from 4.8 to 38.9% depending on whether the results of 3-month or one-year outdoor tests were used, respectively. Past century data on the corrosion resistance of a 3 steel were also used as the initial, whereas the calculated corrosion rates were compared to the most recent results of testing the steel in the rural atmosphere of North Vietnam (suburban district of Hanoi). The maximum prediction error ( = 23–139%) corresponds to calculations based on the tests for three winter months; the minimum (= 8–54%), to those for three months in summer.

Kinetic Parameters and Mechanism of Gold Electrooxidation in Thiocarbamide Solutions

L. F. Kozin*, S. A. Kozina**, and A. K. Bogdanova*

* Vernadsky Institute of General and Inorganic Chemistry, National Academy of Sciences of Ukraine,
pr. Akademika Palladina 32/34, Kiev-142, 03680 Ukraine

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** Dumanskii Institute of Colloid and Water Chemistry, National Academy of Sciences of Ukraine,
bulv. Vernadskogo 42, Kiev-142, 03680 Ukraine

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Received January 23, 2003

Abstract — Kinetics and mechanism of gold electrooxidation in sulfuric acid solutions of thiocarbamide (TCA) are studied by measuring voltammograms (VA) of gold and glassy carbon (GC) electrodes. In a potential (E) range from –0.2 to 1.2 V (SCE), VA of a gold electrode demonstrate three peaks. The first and the second peaks correspond to gold electrooxidation to [AuTCA_ads]⁺ and [Au(TCA_ads)₃]³⁺ ions at E of 0.152 and 0.554 V, while the third one corresponds to TCA electrooxidation. The electrooxidation of TCA on GC electrodes is characterized by two VA peaks at 0.983 and 1.437 V. The first peak corresponds to the formation of formamidine dis-ulfide (FADS) (k_a1 = 6.4010⁴ cm/s), while the second peak corresponds to TCA oxidation to sulfides and hydrosulfides (k_a2 = 7.7810⁵ cm/s). The composition of adsorption layers formed at the Au electrode is ana-lyzed by Auger spectroscopy. The introduction of sodium sulfide into TCA solutions eliminates the formation of adsorption layers and accelerates Au oxidation in such solutions. The rate constants of gold electrooxidation k_a = 6.31 10^–3 cm/s and Au(I) electroreduction k_c = 5.46 10^–4 cm/s in TCA solutions are estimated. Kinetic parameters (charge transfer coefficients, reactions orders in carbamide) are determined and the mechanisms of Au and TCA oxidation in sulfuric acid solutions are proposed.

Kinetics of Galvanostatic Chloride Pitting of Stainless Steels in Chloride Solutions

I. I. Zamaletdinov

Perm State Technical University, Komsomol’skii pr. 29a, Perm, 614600 Russia

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Received March 12, 2001; in final form, July 15, 2003

Abstract — To check the theory, the corrosion of steels 121810 and 1017132 is studied during galvanostatic polarization at different , current densities, and temperatures. The morphology and size distribution of pits are discussed. In E vs. log curves are shown to demonstrate a single linear segment for steel 121810 and two linear segments for 1017132 (as for pure Fe, according to the literature data [12]), namely, the initial segment with a steep slope and the later one with more gentle slope. The single slope E/of steel 121810 and the later (gentle) slope, which is observed for both steel 1017132 and Fe, correspond to those predicted in [3, 4, 7], while the earlier steep slope corresponds to crevice-type pitting.

Hydrolysis of Interfacial Bonds in a Metal/Polymer Electrical Double Layer

A. P. Nazarov and D. Thierry

Korrosionsinstitutet, Kräftriket 23A, SE-10405, Stockholm, Sweden

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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.