Formation, retention, and waste of products of the atmospheric corrosion of metals. 3. Corrosion losses and the weight of retained products

The dependence m/K = f(K) (m is the weight of retained products per the unit weight of corrosion losses) on the integral weight of corrosion losses K, which is observed for zinc, carbon steel, copper, brass, aluminum, as well as Д16 and AM_д alloys, in cold, temperate, and tropical cimates, is analyzed. Two groups of empirical equations are proposed to express the functional dependence m/K = f(K). The weight of retained products of outdoor corrosion on zinc, steel, aluminum, and copper, which was calculated from these equations, adequately agree with the experimental weights of products after 1-year outdoor tests of these metals carried out since the late 50s of the past century in Russia and China. Original Russian Text ? Yu.M. Panchenko, P.V. Strekalov, 2006, published in Zashchita Metallov, 2006, Vol. 42, No. 1, pp. 90–102.     

Formation, Retention, and Waste of Products of Atmospheric Corrosion of Metals. 2. Kinetics of Corrosion and Waste

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 Д16, AMц, 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. __________ Translated from Zashchita Metallov, Vol. 41, No. 6, 2005, pp. 602–613. Original Russian Text Copyright ? 2005 by Panchenko, Strekalov. The second, final part of paper. For the beginning see Zashch. Met., 2005, vol. 41, no. 4, p. 369.     

Diffusion mass transfer under the conditions of instability of products of electrochemical reaction

Theoretically considering the diffusion-migration mass transfer in binary z ₁–z ₂-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. Original Russian Text ? A.V. Noskov, S.A. Lilin, 2007, published in Zashchita Metallov, 2007, Vol. 43, No. 2, pp. 117–122.     

Effects of arylthio-and arylseleno(methoxy)methanes on acid corrosion of CT 3 steel

The effects of various arylthio-and arylseleno(methoxy)methanes on corrosion of CT3 steel in sulfuric and hydrochloric acid solutions were studied by gravimetric and voltammetric methods. Some compounds of theses classes were found to be effective inhibitors of the acid corrosion of CT3 steel. The presence of the-X-CH₂-O-CH₃ groups (X = S or Se) in aromatic amines and their derivatives enhanced their inhibitive properties. However, because these groups are highly hydrophobic, the molecules of inhibitors should contain other fragments that ensure sufficient solubility. Original Russian Text ? I.N. Chernyad’ev, A.B. Shein, A.N. Nedugov, 2007, published in Zashchita Metallov, 2007, Vol. 43, No. 3, pp. 285–289.     

Thermodynamics of chemical and electrochemical stability of corrosion active nonmetal inclusions

Diagrams potential-pH are plotted for different phase components of corrosive nonmetal inclusions in steels in sulfide-containing media at 25°C, 1 atm (air), and a _i = 10⁻³ mol/l. Thermodynamic peculiarities of their corrosion and electrochemical behavior are analyzed. Original Russian Text ? A.G. Tyurin, I.Yu. Pyshmintsev, I.V. Kostitsyna, I.M. Zubkova, 2007, published in Zashchita Metallov, 2007, Vol. 43, No. 1, pp. 39–49.     

Inhibition Effect of Thallium Cations on Aluminum Corrosion in Hydrochloride Solutions

The effect of contact thallium deposition on the corrosion rate of aluminum in hydrochloride solutions is studied. When a fraction of “metal” depolarization of aluminum corrosion is insignificant, the corrosion rate depends on the aluminum surface coverage with thallium deposit and the time. Partial inhibition coefficients, which are associated with the variations in the free-corrosion potential (K _ΔE ) and in the fraction of aluminum surface area occupied by thallium deposit (K _s ), are calculated. The variations of partial inhibition coefficients K _s and K _ΔE with the variations of thallium iodide concentration and the corrosion test time are analyzed. __________ Translated from Zashchita Metallov, Vol. 41, No. 5, 2005, pp. 467–472. Original Russian Text Copyright ? 2005 by Bartenev, Barteneva.     

Specifities of forming electrochemical dissolution zones at ferrite-cementite-structured alloys in sulfuric acid solutions

Specific features of the formation of electrochemical dissolution zones at steels C _T 20 and C _T 45 with a ferrite-cementite structure, were revealed by combining electrochemical and metallographic methods. A possibility of developing the self-dissolution process at the ferrite/cementite boundary is shown. A spontaneous sequence of the anodic dissolution of structural constituents of the alloys is found. Original Russian Text ? N.V. Tarasova, S.N. Saltykov, 2007, published in Zashchita Metallov, 2007, Vol. 43, No. 3, pp. 252–255.     

Character of the dissolution and partial electrode processes at the alternating-current infralow-frequency polarization of brasses in chloride media. II. Cu44Zn β-brass

The dissolution of β-brasses in a chloride medium at a pulse anodic polarization proceeds at first (up to ∼1 min) nearly uniformly, but when the charge of anodic pulse is carried out partly on the ionization of zinc and partly on the ionization of copper, it becomes selective. In this case the most part of the copper component does not oxidize, but rearranges to form the individual phase, which causes a substantial destruction of the brass electrode. When the cathodic alternating-current component is also switched on and hydrogen evolution begins, pH of the layer near electrode increases preventing the formation of soluble oxidation products in the subsequent anodic half-period. Thus, on a β-brass electrode, the partial cathodic processes affect the anodic oxidation of copper and zinc. Original Russian Text ? I.K. Marshakov, O.Yu. Kuksina, V.Yu. Kondrashin, 2007, published in Zashchita Metallov, 2007, Vol. 43, No. 4, pp. 360–366.     

Zinc-and aluminum-based protective coatings obtained in a fluidized bed

Sherardizing and zinc-aluminizing Ct3 steel in a fluidized bed are considered. Microhardness, microbrittleness, porosity, and corrosion resistance of zinc coatings are analyzed. Original Russian Text ? Yu.A. Balandin, A.S. Kolpakov, E.V. Zharkov, 2006, published in Zashchita Metallov, 2006, Vol. 42, No. 4, pp. 379–382.     

Dissolution mechanism and partial electrode processes at infralow frequency AC polarization of brasses in chloride media. I. α-brass Cu20Zn

Being typical of a steady-state anodic polarization, the uniform dissolution of α-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. Original Russian Text ? I.K. Marshakov, O.Yu. Kuksina, V.Yu. Kondrashin, 2007, published in Zashchita Metallov, 2007, Vol. 43, No. 2, pp. 128–134.     

Corrosion inhibitors of the SNPKh brand. 2. The P,N-Containing corrosion inhibitor for protection of oil-field equipment

Series of functionalized pyridinium alkyl[poly(oxyethylene)] phosphites, isoquinolinium alkyl[poly(oxyethylene)] phosphites, pyridinium aryl[poly(oxyethylene)] phosphites, and isoquinolinium aryl[poly(oxyethylene)] phosphites were obtained and their properties were studied systematically. Some of them were found to be effective corrosion inhibitors in aqueous CO₂-and H₂S-containing media. Isoquinolinium dodecyl-and dodecylphenyl[dodeca(oxyethylene)] phosphites proved to be the best inhibitors. The isoquinolinium aryl[poly(oxyethylene)] phosphites obtained were used to create a new corrosion inhibitor. Original Russian Text ? O.V. Ugryamov, O.A. Varnavskaya, V.N. Khlebnikov,V.A. Ivanov, S.I. Vasyukov, G.V. Romanov, Ya.V. Ivshin, R.A. Kaidrikov, Kh.E. Kharlampidi, F.Sh. Shakirov, 2007, published in Zashchita Metallov, 2007, Vol. 43, No. 1, pp. 94–102.     

Inhibition of cooper and zinc dissolution with 5(6)-nitrobenzoimidazoles in phosphate electrolytes

Effects of the concentration and chemical structures of 2-substituted 5(6)-nitrobenzoimidazoles (5(6)-NO₂-2-R-BIs) on the dissolution of copper and zinc in phosphate electrolytes were studied. Introduction of the nitro group into benzoimidazole derivatives was found to make them more effective for copper but less effective for zinc; this is due to an increased degree of dissociation of the nitro derivatives and the possibility of ionic bonding in their complexes. The protective effects of 5(6)-NO₂-2-R-BIs on copper and zinc depend on their chemical structures and are accurately described by the equation log γ = α ± ρσ₁. The sign and magnitude of ρ indicate that electron-withdrawing substituents in 5(6)-NO₂-2-R-BIs enhance the protection of copper, while electron-donating ones enhance the protection of zinc; this is due to different abilities of these metals to form σ-and π-bonds in their complexes. Original Russian Text ? Yu.I. Kuznetsov, L.P. Podgornova, 2006, published in Zashchita Metallov, 2006, Vol. 42, No. 1, pp. 76–82.     

Microbiological corrosion and measures to protect against such corrosion part VI. Corrosion of copper in the marine atmosphere: A technique

A technique is developed to enable one to study in a sufficiently objective way the processes of the microbiological corrosion of copper and its alloys in the marine atmosphere. This technique is recommended for diagnosing and forecasting corrosion processes in real conditions for the storage and transportation of products. Original Russian Text ? A.A. Gerasimenko, G.V. Matyusha, L.M. Petrova, 2007, published in Korroziya: Materialy, Zashchita, 2007, No. 3, pp. 33–37. Part V. see Corrosion: Materials and Protection, 2005, no. 8, pp. 45–47.     

Formation, Retention, and Loss of the Metals Atmospheric Corrosion Products. 1. The Integral Weight Model of the Products Formed

Changes of the total weight of tested samples, as well as changes in the weight of the retained atmospheric corrosion products, are studied as functions of corrosion losses in different climate zones and different test duration, for carbon steel, zinc, copper, magnesium, aluminum, Д16 and AMЦ alloys, and brass. An experimental mathematical model for integral weight of formed corrosion products is suggested. Climate effects on the change in the weight of corrosion products retained by metals are studied during long-term exposure of plates and wire spirals recommended by the ISO 9226-92 Standard for the monitoring of atmospheric corrosivity.__________Translated from Zashchita Metallov, Vol. 41, No. 4, 2005, pp. 402–416.Original Russian Text Copyright © 2005 by Panchenko, Strekalov.     

Thermal behavior of an oxide layer on aluminum

Films 16 to 17 μm thick were obtained on the ^#AMg5 alloy by plasma electrolytic oxidation (PEO) in an orthophosphate-borate electrolyte. Air annealing at 250, 300, 400, and 500°C for 4 h did not affect the thickness, weight, and the elemental composition of the resulting films. The contact angle for water changed from 75° to zero. In a temperature range from 250 to 300°C, the content of the crystalline γ-Al₂O₃ phase jumped. Above 300°C, the film surface cracked and became less resistant to corrosion. Original Russian Text ? V.S. Rudnev, A. E. Lysenko, P. M. Nedozorov, T. P. Yarovay, A.N. Minaev, 2007, published in Zashchita Metallov, 2007, Vol. 43, No. 5, pp. 510–514.     

Scanner-assisted quantitative reflectometry in the checking of corrosion-electrochemical systems

The described method for the study of the metal-electrolyte interface combines videoreflectometric and electrochemical measurements. Scanned digital optical images of a surface area in an electrolyte solution made it possible to examine a 3D structure of spatially heterogeneous surface layers composed of dissolution products of metals and alloys in liquids. Parallel electrochemical measurements allowed one to monitor the anodic and cathodic processes during the dissolution of specimens. The combined method was found to be highly sensitive to thin heterogeneous near-electrode layers, provide highly efficient corrosion checking of long specimens, and allow parallel studies of a large number of specimens. The method was tested in the in situ checking of the microtopography of a layer of products formed in the dissolution of a Cu-Ni alloy in a solution of NaCl. Original Russian Text ? V.A. Kotenev, 2007, published in Zashchita Metallov, 2007, Vol. 43, No. 5, pp. 534–539.     

Peculiarities of electroplating tantalum coatings from fluoride melts

Electroplating tantalum coatings on molybdenum, copper, and steel is studied. The effects of various factors (the composition of a fluoride bath, its temperature, current density, and the electric charge spent) on the electrocrystallization of the deposit, its roughness, the degree of dendrite formation, current efficiency, and a possibility to plate multilayer coatings and produce tantalum wares by electrotyping are investigated. To compare the characteristics of the coatings, the studies in a standard chloride-fluoride salt system containing potassium fluorotantalate (K₂TaF₇) were also carried out under similar conditions. Original Russian Text ? V.A. Pavlovskii, 2007, published in Zashchita Metallov, 2007, Vol. 43, No. 3, pp. 303–306.     

On the nature of anomalously high plasticity of high-strength titanium nickelide alloys with shape-memory effects: II. Mechanisms of plastic deformation upon isothermal loading

Mechanisms of plastic deformation have been studied in detail in the process of isothermal loading at room temperature in a high-purity shape-memory alloy of composition Ti_49.4Ni_50.6. The alloy was studied in two initial states: usual coarse-grained (with an average grain size of 20–30 μm) and submicrocrystalline (with an average grain size of 0.2–0.3 μm). It has been shown that during tensile tests there occurs a mechanically induced martensitic transformation in the alloy at stresses corresponding to stages I, II, and III in the tensile curve and then elastic and plastic deformation of B19′ martensite is observed at stages IV, V, and VI, respectively. Optical metallography in situ and electron microscopy have been used to study microstructural features and mechanisms of plastic deformation of the alloy up to its failure. Original Russian Text ? E.F. Dudarev, R.Z. Valiev, Yu.R. Kolobov, A.I. Lotkov, V.G. Pushin, G.P. Bakach, D.V. Gunderov, A.P. Dyupin, N.N. Kuranova, 2009, published in Fizika Metallov i Metallovedenie, 2009, Vol. 107, No. 3, pp. 316–330.     

Contact corrosion of metals in aqueous media. Part I

The corrosion behavior of aluminum, steel, and cast iron in aqueous solutions is studied both for individual metal specimens and short-circuited systems (aluminum-steel, aluminum-cast iron, steel-cast iron, and aluminum-steel-cast iron). It is shown that aluminum behaves as a cathode with respect to steel and cast iron. The high corrosion rates of ferrous metals are caused by the specificity of iron surface state in aqueous solutions of electrolytes. Original Russian Text ? V.N. Esenin, L.I. Denisovich, 2007, published in Zashchita Metallov, 2007, Vol. 43, No. 4, pp. 390–395.     

Electrooxidation of Cr3+ ions in sulfuric acid solutions

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 cation 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. Original Russian Text ? E.G. Vinokurov, V.V. Bondar’, 2007, published in Zashchita Metallov, 2007, Vol. 43, No. 2, pp. 123–127.