Acid corrosion of iron in the presence of mixtures of anionic additives and compounds of the reaction series of o-hydroxyazomethine derivatives with nucleophilic substituents

The effects of halide-and sulfur-containing additives on iron corrosion in 1 M H₂SO₄ in the presence of nucleophilic o-hydroxyazomethine derivatives are studied. Dependences of the inhibition factor (as well as its sensitivity to a change in the polarity of the substituents) and the effective activation energy on the nature and concentration of both the groups of additives are interpreted in terms of the Linear Gibbs Energy Relation (LGER) and the principle of Hard and Soft Acids and Bases (HSAB). Original Russian Text ? V.P. Grigor’ev, V.V. Boginskaya, 2006, published in Zashchita Metallov, 2006, Vol. 42, No. 6, pp. 627–631.     

Effect of some compounds on the sensitivity of the inhibitive properties of o-hydroxyazomethine derivatives to variation in the polarity of their electrophilic substituents

The sensitivity of the protective effect of an inhibitor from a reaction series to the variation of the polarities of electrophilic substituents in its molecule depends on the nature and concentrations of salt additives. The correlations obtained for iron corrosion were interpreted in terms of the Linear Gibbs Energy Relation (LGER) and the Principle of Hard and Soft Acids and Bases (HSAB). Original Russian Text ? V.P. Grigor’ev, V.V. Boginskaya, 2006, published in Zashchita Metallov, 2006, Vol. 42, No. 5, pp. 520–525.     

Comparison analysis of formation and some characteristics of microplasma coatings on aluminum and titanium alloys

The electrolyte and parameters of high-voltage anodic-cathodic process, which enable one to apply rather thick (to 340 μm) oxide coatings to titanium alloys, are selected. Characteristics of the coating formation on aluminum and titanium alloys are compared. It is found that, on the titanium alloys, the stage of microarc discharges occurs only at relatively high anodic and cathodic components of the current density. The voltage chronograms and oscillograms also have pronounced specific features. Original Russian Text ? O.P. Terleeva, V.I. Belevantsev, A.I. Slonova, D.L. Boguta, V.S. Rudnev, 2006, published in Zashchita Metallov, 2006, Vol. 42, No. 3, pp. 292–299.     

Peculiarities of electrochemical behavior of copper in alkaline solutions in the presence of alanine

Anodic oxidation of copper in alkaline solution in the presence of alanine is studied by electrochemical and ellipsometric methods. Thickness of films formed on the metal in the working solutions, are determined. Small additives of β-alanine (10⁻⁴–10⁻³ mol/l) cause additional stabilization of copper passivity due to an increase in the film thickness. The adsorption kinetics of α-and β-alanine is studied. It is shown experimentally that β-alanine adsorbs on copper according to the Frumkin isotherm. By contrast, no definite type isotherm can be obtained for α-alanine due to its higher activity and ability to form soluble complexes with copper ions. Original Russian Text ? E.V. Nikitchenko, S.A. Kaluzhina, N.P. Andreeva, 2006, published in Zashchita Metallov, 2006, Vol. 42, No. 3, pp. 279–284.     

Investigation of the oxidation kinetics of steel during its preliminary roasting before enameling

The oxidation kinetic peculiarities of traditional and prospective steels utilized in manufacturing hot-rolled enameled pipes are considered. The oxidation conditions, as well as its limiting stages, in a temperature range of 500–900°C, are determined. The x-ray diffraction analysis was applied to determine the composition of the scale formed. Ways of selecting the optimum temperature-time conditions of roasting the metal before its enameling are recommended. Original Russian Text ? O.R. Lazutkina, P.I. Buler, A.K. Kazak, N.B. Mullagalieva, 2006, published in Zashchita Metallov, 2006, Vol. 42, No. 4, pp. 437–440.     

Effect of cyclic benzo-12-crown-4 polyether on copper electrodepsosition from sulfate aqueous ethanol baths

It is found that the effectiveness of crown ether (with benzo-12-crown-4 as an example) is a function of the composition of the water-ethanol solvent and the bulk and surface concentration of sulfate anions. An increase in the adsorbability of sulfate anions at Cu in the presence of the crown ether (Ψ’-effect) enhances its inhibitive effect on copper electrodeposition. The electrode reaction is best inhibited, and electroplates with enhanced tribotechnical characteristics are obtained, in the zone of ethanol structure stabilization, in which the adsorption of SO₄ ²⁻ anions by copper is the highest because of the “desalting” effect. Original Russian Text ? V.V. Kuznetsov, L.M. Skibina, S.V. Geshel’, 2006, published in Zashchita Metallov, 2006, Vol. 42, No. 3, pp. 272–278.     

A correlation between the inhibition of acid corrosion of iron by a mixture of compounds of a reaction series and the polar properties of their substituents

The character of the adsorption isotherm of a mixture of o-hydroxyazomethine derivatives at an iron electrode is insensitive to the total polarity of the substituents in their molecules. The surface coverage of the electrode by adsorbed compounds of this reaction series (RS) does not depend on the number and concentrations of the components of the mixture, provided that their total concentration and the total polarity of the substituents in their molecules are constant. According to the Linear Gibbs Energy Relation, the overall and partial inhibition factors of the acid corrosion of iron in the presence of mixtures of compounds of this RS are determined by the total polarity of their substituents. Original Russian Text ? V.P. Grigor’ev, V.M. Kravchenko, V.V. Boginskaya, 2006, published in Zashchita Metallov, 2006, Vol. 42, No. 4, pp. 383–387.     

Anodic dissolution of ferrite phases from iron-carbon ferrite-cementite alloys with different forms of cementite

Methods of electrochemical analysis, metallography and mathematical statistics are applied to calculate the ferrite anodic dissolution rate from both the independent structural constituent and the subconstituent in lamellar or granular pearlite. The higher dissolution rate of the former compared to the latter is caused by the structure peculiarities. Original Russian Text ? S.N. Saltykov, N.V. Tarasova, 2006, published in Zashchita Metallov, 2006, Vol. 42, No. 5, pp. 542–547.     

The aftereffect of cyclic loading on the corrosion of aluminum-based alloys

Effects of bench loading and stresses on the corrosion resistance of д16AT alloy are studied. Complicated effect of the stress intensity and the cyclic loading on the surface morphology and pit concentration is demonstrated. Harmonic character of the loading dependence of the change of corrosion resistance is due to segregation effects. Original Russian Text ? V.Yu. Vasil’ev, V.S. Shapkin, N.V. Barulenkova, M.V. Antonova, and E.N. Antonova, 2006, published in Zashchita Metallov, 2006, Vol. 42, No. 3, pp. 227–232.     

Choice of effective corrosion inhibitors for acid treatment of wells

Protective effects of some commercial corrosion inhibitors (VNPP-2V, KI-1, and IKU) in fluids used for acid treatments of oil wells were studied by gravimetric and electrochemical measurements. The inhibitors were tested in the presence of Fe³⁺ ions and in “aged” inhibited fluids. Original Russian Text ? A.B. Shein, A.V. Denisova, 2006, published in Zashchita Metallov, 2006, Vol. 42, No. 1, pp. 39–42.     

Model concepts on the mechanism of microarc oxidation of metal materials and the control over this process

Based on a critical analysis of literature data, new model concepts on the mechanism of microarc oxidation (MAO) are developed. The correctness of these model concepts is confirmed by experimental results on the average growth rate of oxide-ceramic coatings for different duration of the MAO process on AД31, MA2-1, and MЛ-5 alloys, the morphology of the surface structure of coatings of different thickness, the comparative electrical strength of dielectric coatings, which is assessed during self-quenching of the MAO process and in air. Equivalent electric circuits developed describe this process and are experimentally shown to be the “tool” which allows controlling MAO of aluminum and magnesium alloys. Original Russian Text ? A.G. Rakoch, V.V. Khokhlov, V.A. Bautin, N.A. Lebedeva, Yu.V. Magurova, I.V. Bardin, 2006, published in Zashchita Metallov, 2006, Vol. 42, No. 2, pp. 173–184.     

Electrodeposition and physico-mechanical properties of chromium coatings modified with disperse particles

Chromium electroplates from Cr(III)-baths modified with disperse phases of CeO₂, Cr₂O₃, graphite, and ultradisperse diamond are studied. Mechanical properties of the composite coatings are investigated. The Cr₂O₃-particles present in the bath are found to cause the destruction of the coatings already during the plating. When modifying with CeO₂-particles, good coatings with enhanced microhardness can be obtained at their concentration in the bath of no more than 15 g/l. The deposition rate in such cases exceeds that in the blank baths. The optimum range of the CeO₂-particle concentration, allowing to obtain the maximal microhardness, is 5–8 g/l. The self-lubricating chromium-graphite composite coatings can be deposited at a graphite concentration in the bath of up to 4 g/l. The microhardness of the chromium coatings is most strongly affected by ultradisperse diamond particles that increase the microhardness by a factor of 1.4; they also decrease the coatings’ brittleness. When the ultradisperse diamond concentration in the solution is as high as 30 g/l, the diamond content in the composite coating reaches its limiting value of 12–14 vol % (or 6.4–7.2 wt %). The optimum ultradisperse diamond concentration was found to be 17 g/l in the baths and 10.5 vol % (or 5.6 wt %) in the composite coating. At these concentrations, the coatings with the maximum microhardness and lowest brittleness are obtained. Original Russian Text ? E.G. Vinokurov, A.M. Arsenkin, K.V. Grigorovich, V.V. Bondar’, 2006, published in Zashchita Metallov, 2006, Vol. 42, No. 3, pp. 312–316.     

Tunnel scanning microscopy and spectroscopy in studying Fe-Cr stainless steels

Scanning tunnel microscopy (STM) and scanning tunnel spectroscopy (STS) are used in studying highly pure iron and chromium and Fe-x%Cr (2.4 ≤ x ≤ 60 wt %) alloys at the air boundary, as well as some of the alloys in 0.01 N H₂SO₄. The obtained probability coefficients (α) of the electron tunnel transfer from a specimen to the needle and the slopes (β) of the logarithmic U _t /log (I _t ) dependences as functions of the chromium content in Fe-Cr alloys confirm the critical compositions of the alloys containing ∼6.5 and 10–13% chromium, which is in accord with the results of the steady-state and transient electrochemical measurements. A correlation between these critical compositions of the alloys and sharp changes in the histograms of α and β values is observed. Pronounced extreme properties of the Fe-25.2% Cr alloy surface, which corresponds to the inclusion of Cr atoms in tetrahedral voids of the alloy crystal lattice, are noticed. Original Russian Text ? E.V. Trofimova, E.V. Kasatkin, I.I. Reformatskaya, 2006, published in Zashchita Metallov, 2006, Vol. 42, No. 3, pp. 245–255. The work was financially supported by the Russian Foundation for Basic Research, project no. 04-03-32337.     

New corrosion-resistant electrodes: Synthetic diamond and diamond-based materials. The semiconductor and structure aspects—a review

Specific features of electrode behavior of synthetic diamond and diamond-based materials (in particular, diamond-nondiamond carbon nanocomposites, nanocrystalline diamond, and diamond-like carbon) are reviewed. Effects of the crystal structure and semiconductor nature of diamond on its electrochemical properties are discussed. Original Russian Text ? Yu.V. Pleskov, 2006, published in Zashchita Metallov, 2006, Vol. 42, No. 2, pp. 115–131.     

Long-term inside corrosion attack of an oil main operation

X-ray diffraction and metallographic analyses were applied when investigating the corrosion type and products of the cut-offs from an oil main with welded joints after its 33-year operation. Such a long-term effect of the transported medium and varying dynamic loading led to a considerable corrosion-mechanical damage to the inner surface of the pipe. The highest was the knife-line type of damage to the filler-parent boundaries of welded joints. The main corrosion products were Fe₂O₃ and Fe₃O₄ oxides that formed layers 300 to 350 μm thick. Beside the oxides, the deposits of hydrocarbon products (asphaltenes, resins, and paraffins), as well as calcium salts (CaCO₃ and CaSO₄), were present. Original Russian Text ? V.A. Andriashin, A.A. Kostyuchenko, A.I. Komarov, V.V. Vorobs’ev, 2006, published in Zashchita Metallov, 2006, Vol. 42, No. 1, pp. 52–56.     

Chemical modification of the surface of a carbonyl iron powder

The surface of a carbonyl iron powder was chemically modified with functional triethoxysilanes and ethyl n-alkylphosphonates. The grafted layers were examined by x-ray photoelectron spectroscopy and conductivity measurements. Original Russian Text ? S.G. Belyavskii, P.G. Mingalyov, F. Giulieri, R. Combarrieau, G.V. Lisichkin, 2006, published in Zashchita Metallov, 2006, Vol. 42, No. 3, pp. 262–271.     

Electroplating kinetics of a nickel-tungsten alloy

Electroplating a nickel-tungsten alloy under various electrolysis conditions (direct and alternating current) is studied. A radical-film mechanism of the alloy formation by the cathodic deposition is experimentally proved. The effect of sorption processes at the film-electrolyte boundary on the alloy formation, as well as the possibility of controlling the film composition and structure by changing the electric field intensity, is studied. Deposits with a content of the high-melting component of up to 61% are obtained. Original Russian Text ? V.L. Kotov, M.V. Shmukler, 2006, published in Zashchita Metallov, 2006, Vol. 42, No. 2, pp. 168–172.     

Steel protection inhibitors in electrochemical machining in concentrated sodium chloride solutions

Optimal inhibitors for the protection of #38KhN3MFA and #30KhN2MFA steels in concentrated sodium chloride solutions during electrochemical machining (EM) are revealed. Compositions of solutions used in washing of the surface of samples subjected to EM are selected. Corrosion and electrochemical methods are used. The most effective corrosion inhibitors are found and their optimal concentrations are determined, which allows one to reduce the corrosion rate of studied steels by a factor of 5–7. Original Russian Text ? V.G. Revenko, V.V. Parshutin, G.P. Chernova, N.L. Bogdashkina, 2008, published in Zashchita Metallov, 2008, Vol. 44, No. 2, pp. 153–161.     

On the passivation of iron in aqueous solutions of zinc 1-hydroxyethane-1,1-diphosphonate

This work is devoted to studying the passivating ability of the zinc complex of the 1-hydroxyethane-1,1-diphosphonic acid (HEDP) in a borate buffer solution. For the first time, we used the in situ ellipsometric method to study the mechanism of formation of a protective film on iron in the presence of HEDP, HEDPZn, and ZnSO₄ in the course of the cathodic polarization of the electrode. The investigations of adsorption of HEDPZn on iron (at E = −0.65 V) in combination with X-ray photoelectron spectroscopy (XPS) have shown that on the metal surface there is formed a multilayer protective film consisting of an internal layer of Zn(OH)₂ and an outer layer consisting of HEDP complexes with Fe²⁺ and/or Zn²⁺. It has been found that the thickness of the passivating film does not exceed 60 ?, of which 7–10 ? correspond to the low-soluble zinc hydroxide. Original Russian Text ? Yu.I. Kuznetsov, G.V. Zinchenko, L.P. Kazanskii, N.P. Andreeva, Yu.B. Makarychev, 2007, published in Korroziya: Materialy, Zashchita, 2006, No. 9, pp. 19–26.     

Electrodeposition of metal molybdenum from electrolytes containing hydrofluoric acid

The effect of hydrofluoric acid on the cathodic reduction of molybdate ions is studied. It is shown that the mechanism of this process is determined by the acid concentration: in a concentration range below 25 g/l the intermediate products of molybdate-ion reduction, namely, black or colored deposits containing molybdenum with the average valence of 3.6–4 are formed on the cathode. For the concentration above 50 g/l, molybdate ions are completely reduced and form at the cathode dense light metallic coatings with a thickness of 3–5 μm and good adhesion to the substrate. The addition of hydrofluoric acid prevents polymerization of molybdate ions. Original Russian Text ? N.D. Ivanova, S.V. Ivanov, E.I. Boldyrev, O.A. Stadnik, 2006, published in Zashchita Metallov, 2006, Vol. 42, No. 4, pp. 388–392.