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It is shown that the corrosion rates of aluminum and copper specimens in a 3% NaCl solution are 1.5-1.7 times higher than in a 0.1% NaCl solution. It is also discovered that the corrosion rate of copper in contact with aluminum placed in 3% NaCl is lower than for its individual specimens and, as the area of aluminum increases, decreases to zero. Thus, in particular, as the area of aluminum specimens (for a constant area of copper specimens) becomes 6.5 times larger, the corrosion rate of aluminum becomes 1.7 times higher. A discrepancy is discovered between the computed values of the rate of contact corrosion of aluminum for high values of the ratio of areas in the aluminum-copper couples and the experimental data. The polarization curves of aluminum in contact with copper placed in 0.1% NaCl are shifted to the region of less negative potentials and the ultimate diffusion and corrosion currents are greater by an order of magnitude than for the individual copper and aluminum specimens. It is established that the KORSOL inhibitor, which satisfactorily inhibits the rates of corrosion of copper and aluminum in tap water, practically fails to protects these metals, including the case of their contact, in 0.1% NaCl, whereas the TIS-4 inhibitor protects the metal by ~ 50-60%. [ABSTRACT FROM AUTHOR]

We study electric-arc coatings of the Fe-Cr-C and Fe-Cr-B systems. It is shown that chromium content of 12 wt.% is insufficient to guarantee higher corrosion resistance of the coatings in neutral aqueous solutions (as compared with steels) caused by the formation of chromium-based oxides, carbides, and borides. Therefore, the indicated chromium content of the compounds should be taken into account and compensated in finding the chemical composition of powder wires. Its unjustified increase is not reasonable because powder wires are characterized by filling coefficients restricting the possibility of their filling with alloying elements. Therefore, the content of each alloying element in the charge of powder wires should be well justified and determined. For this purpose, we propose to use the relations taking into account the nonlinear distribution of chromium in the lamellas of the coatings caused by their high microheterogeneity and the depletion of their solid solution of the indicated element as a result of the formation of oxides, carbides, and borides on its base. [ABSTRACT FROM AUTHOR]

We have determined the causes of depressurization of a pipeline of diameter 114.30 mm and wall thickness 6.02 mm (pipe steel of category X60), which transports natural gas from the gas field to the gathering point. We have performed spectral, electrochemical, and metallographic investigations of a metal fragment from the damaged pipe as well as chemical analysis of the corrosion products on the wall internal surface (X-ray microspectral analysis). Polarization measurements have been carried out in deaerated solutions and those aerated by air oxygen, having different salt content. It has been shown that, with increase in the salt content, the corrosion resistance of pipe steel decreases, and the corrosion rate increases from 0.06 to 0.89 A/cm under aerated conditions and from 0.16 to 1.48 A/cm under deaerated. [ABSTRACT FROM AUTHOR]

The equal-channel angular pressing (ECAP), as the most famous method of severe plastic deformation, has the potential for upscaling from the laboratory to industrial scale. Thus, it is important to examine the practice-relevant properties of large billets deformed by this process. Mechanical properties and corrosion resistance significantly affect the service life of the structural components. The mechanical properties of Al-6060 alloy after industrial-scale ECAP (the cross-sectional sizes of the billets were 50 × 50 mm) were analyzed by P. Frint. In the present work, we investigate the effect of one pass of the in-dustrial-scale ECAP on the electrochemical properties of Al-6060 alloy by means of potentiodynamic polarization tests in a 0.1 M NaCl solution. The corroded surfaces were analyzed by means of optical microscopy and scanning-electron microscopy. In order to characterize the homogeneity of the corrosion behavior of the ECAP-processed material, all analyses were taken in different zones perpendicular to the extrusion axis. The results indicate that one pass of ECAP does not deteriorate the electrochemical behavior of Al-6060 alloy. [ABSTRACT FROM AUTHOR]

The surfaces of 5083 aluminum alloy were coated with chromate conversion coatings. Then epoxy paints were applied to the chromate and nonchromate treatment surfaces. The adhesion, hardness, and corrosion resistance of the coated samples were evaluated by using adhesion tape tests, pencil hardness tests, salt spray, and electrochemical technique. The results indicated that the adhesion of coating systems (including chromate treatment) was better than the adhesion of nonchromate conversion coatings, whereas the hardness of the coating systems was identical. The salt-spray results showed that the corrosion propagation from the scratched area in the painted samples with chromate treatment was lower than for the nonchromate coated surfaces. In addition, the electrochemical corrosion measurements indicated that the coating system including chromate treatment presented lower corrosion current densities, higher polarization resistance, and less negative corrosion potential than the corresponding values obtained for the nonchromate conversion coated surfaces. [ABSTRACT FROM AUTHOR]

Nickel- and titanium-based alloys are promising materials for dental orthodontic wires due to their superior mechanical properties and corrosion resistance. The studies of the corrosion resistance of these materials according to their surface characterization in artificial salivas are limited. We study the changes of the surfaces of NiTi-alloy-based orthodontic wires in artificial salivas with (or without) additions of F and $ {\text{PO}}_4^{{3 - }} $ after a period of time by the SEM and EDS methods. [ABSTRACT FROM AUTHOR]

Zn-Ni coatings were deposited under galvanostatic conditions at current densities varying within the range 20- 60 mA ⋅ cm. The influence of the current density of deposition on the surface morphology, chemical and phase compositions, and corrosion resistance was investigated. Structural investigations were performed by the X-ray diffraction (XRD) method. The surface morphology and chemical composition of deposited coatings were studied by using a JEOL JSM-6480 scanning electron microscope. The studies of general electrochemical corrosion resistance were carried out in a 5% NaCl solution by using potentiodynamic and electrochemical impedance spectroscopy (EIS) methods. The local corrosion resistance was determined by the Scanning Kelvin Probe (SKP) method. On the basis of the research, the possibility of deposition of Zn-Ni coatings containing 14-18 at.% Ni was demonstrated. It was stated that the surface morphology, as well as the chemical and phase compositions of these coatings depend, to a small extent, on the current density of deposition. However, current density of deposition determines the quantity of zinc which is codeposited with nickel and is bounded in the form of an inter-metallic compound or a solid solution. Small differences between the chemical composition and the uneven distribution of the Zn(Ni) and NiZn phases on the surfaces of the coatings may cause differences in the local Kelvin potential. As a result, the Zn-Ni coatings exhibit corrosion resistances varying depending on the current density of deposition. The optimal values of the current density from the viewpoint of corrosion resistance were found to be j = 30-40 mA ⋅ cm. [ABSTRACT FROM AUTHOR]

We have established that the preliminary plastic deformation of 12Kh18N12T austenitic steel causes cold-work hardening, which depends on the strain rate. With increase in the strain rate of specimens from 8∙10 to 417∙10 sec, both strength (ultimate strength) and plasticity (percentage elongation) characteristics of 12Kh18N12T steel decrease. After holding of the preliminarily work-hardened steel at a temperature of 650°C, its strength increases, and its plasticity decreases. At the same time, the isothermal influence for 1 and 10 h does not facilitate intercrystalline corrosion of the steel during its holding in a corrosive medium for 24 h. [ABSTRACT FROM AUTHOR]

We compare 20Kh13 steel in the intact state and after 3∙10 h of operation in blades of the low-pressure cylinders of steam turbines by the mechanisms of fracture, structural, mechanical, corrosion, and stress corrosion properties. It is shown that, as a result of operation, steel hardens and becomes less plastic, its corrosion characteristics, and the parameters of fatigue and cyclic crack-growth resistance significantly deteriorate. [ABSTRACT FROM AUTHOR]

Using the methods of chronopotentiometry and electrochemical impedance spectroscopy, we investigate the influence of the procedure of deposition and thermal fixation of oligomeric films (which serve as protective corrosion-resistant coatings) on the surface of Fe(Me)SiB magnetic amorphous alloys (where Me is Ni, Mo, Cu, or Nb). [ABSTRACT FROM AUTHOR]

Results of investigations of main physicomechanical and tribological properties of hot-forged layered powder composites based on Kh18N15 corrosion-resistant steel are presented. We use a powder composite of Kh18N15 steel with 25 mass % of CrC and 5 mass % of MoS as a working layer and the same steel with 0.6 mass % of carbon as a base material. It is established that the bending strength of the obtained materials depends substantially on the thickness of the working layer, whereas the hardness of the working layer barely depends on it. [ABSTRACT FROM AUTHOR]

Based on the results of voltammetric investigations, we have shown that the partial replacement of nickel by 4 at. % Fe in AlGdNi amorphous alloy leads to a decrease in the corrosion currents and an increase in the polarization resistance, which demonstrates the higher corrosion resistance of AlGdNiFe alloy. Using the method of electrochemical impedance spectroscopy, we have studied the durability and protective capacity of passivation oxide layers at electrodes made of this alloy in 0.1 M NaCl aqueous solution. We have also selected an impedance model of the formation of interfaces oxide-0.1 M NaCl and amorphous metal alloy-0.1 M NaCl. We have established that active diffusion redox reactions, described by the Warburg element, take place at the interface oxide film-0.1 M NaCl. The diffusivities of anions from the solution into the surface oxide layer have been calculated. Finally, we show that, with increase in the time of electrochemical reaction in 0.1 M NaCl aqueous solution, diffusion decreases due to the compaction of the surface oxygen-containing layers. [ABSTRACT FROM AUTHOR]

We study the possibilities of increasing the corrosion resistance of MA5 magnesium alloy by applying aluminum electric-arc coatings from D16 and AMg6 solid wires, a mixture of wires of different kinds (D16 + AMg6), and a powder wire in an aluminum sheath with B4 C + Ni Cr B Si mixture. The electrochemical characteristics of these coatings are studied in a 3% NaCl aqueous solution. It is shown that aluminum electric-arc coatings strongly increase the corrosion resistance of the alloy. The best characteristics are exhibited by the AMg6 coatings. [ABSTRACT FROM AUTHOR]

It is shown that the structure-selective corrosion observed in sulfuric media, in cyclohexane-oxidation media, and in the process of carbamide production may serve as a source of initiation of corrosion cracking. In this case, fracture occurs under relatively low loads. We analyze possible scenarios of the development of this process depending on the rate of structure-selective corrosion. It is shown that corrosion cracking is especially dangerous for the devices made of bimetallic materials and operating at elevated temperatures. This can be explained by additional loading caused by the strong difference between the coefficients of linear thermal expansion of the base metal and the cladding layer. [ABSTRACT FROM AUTHOR]

We have studied the effect of laser alloying of 20Kh13 and 12Kh18N10T steels with niobium on their physicochemical properties. Microalloyed surface layers of thickness more than 350 μm, enriched with niobium, carbon, and oxygen in the solid solution and separate oxycarbide inclusions, were formed by means of laser treatment. The microhardness of the external layers of steels becomes 2–3 times higher (up to 7.1–7.7 GPa). Laser alloying reduces the wear of 20Kh13 steel by a factor of 5–6 under a contact pressure of 0.29 MPa and cuts it in half under 0.42 MPa. The wear of 12Kh18N10T steel is reduced by a factor of 2–3. We have also proposed a scheme of the wear of steels, according to which their wear resistance increases owing to the formation of hardened surface layers, where the oxycarbide inclusions exert a reinforcing action on the more plastic solid solution of niobium, carbon, and oxygen in iron. [ABSTRACT FROM AUTHOR]

We propose a new method of fractal analysis of the phase images obtained by the atomic-force microscopy (AFM) to study the properties of molecular adsorption films of corrosion inhibitors on the coarse polycrystalline surface, which can hardly be distinguished by using AFM height images due to the roughness of the surface. The system of polycrystalline aluminum and SDS (Sodium Dodecyl Sulfate) inhibitor is chosen as the research object. The electrochemical measurements of aluminum electrodes precoated with SDS films are carried out in HCl solutions, and the results show that the inhibition efficiency increases with the concentration of SDS in the prefilming solution and then remains nearly constant as the CMC (critical micelle concentration) of SDS is exceeded. The fractal analysis of the AFM images of prefilmed aluminum surfaces obtained in SDS solutions is performed and demonstrates that, as the SDS concentration increases, no obvious changes are observed for the fractal dimensions of height images, whereas the phase images present regular changes in the values of fractal dimensions, thus displaying the consistent alteration rule as revealed by electrochemical tests. The results prove the feasibility of the fractal analysis of AFM phase images in characterizing the adsorption behavior of the corrosion inhibitor on polycrystalline coarse surfaces. [ABSTRACT FROM AUTHOR]

The article discusses the study on corrosion resistance of the zones of welded joints in neutral media. It notes that corrosion resistance can be improved through surface modification using special corrosion inhibitors. It mentions the use of welded joint whose surface heterogeneity was quantitatively investigated according to its reaction with ferroxyl indicator. It concludes that the combination of mechanical hardening with carburizing can improve its resistance to corrosion fracture.

The article discusses the research of the efficiency of corrosion inhibitors for pipe steels in hydrogen sulfide-containing media. It notes that gas fields in Ukraine have high rates of corrosion, causing unreasonable costs and this can be reduced using inhibitors. It mentions that Naftokim-8, Naftokim-3 and DODICOR inhibitors were investigated for their protective ability. It concludes that Naftokim-8 and DODICOR have mixed action and Naftokim-8 exhibits the best protective properties.

The corrosion properties of ferritic stainless steel with admixtures of 0.5, 1.0, and 3.0 wt.% Nb are studied in 0.1M H2SO4 and 0.3M HCl solutions. The results obtained by the impedance and mass-loss methods demonstrate that the procedure of alloying with niobium and diffusion treatment positively affect the corrosion resistance of steel in these solutions. [ABSTRACT FROM AUTHOR]

We study the corrosion resistance and tribological characteristics of composite materials based on an aluminum-silicon alloy with dispersed metallized graphite particles. Graphite decreases the friction coefficient and makes the wear resistance of materials 3–5 times higher as compared with the matrix alloy without decreasing its corrosion resistance. [ABSTRACT FROM AUTHOR]

Using the method of mathematical design of experiments, we have studied the influence of ethylene glycol concentration and temperature over a wide range of their variation on the corrosion of AMg3 aluminum alloy. We have established that, irrespective of the ethylene glycol concentration, the maximum corrosion losses are observed at temperatures of 60–70°C. The inhibiting action of ethylene glycol at concentrations exceeding 40% is caused by an increase in the viscosity of the solutions and by the formation of slightly soluble surface complexes of aluminum with ethylene glycol and the products of its oxidation. [ABSTRACT FROM AUTHOR]

We have established correlations between the effect of hydrogen under a pressure of 35 MPa on the low-cycle fatigue of 15 corrosion-resistant steels, on the one hand, and their initial mechanical characteristics and the parameter of austenite stability A γ on the other. Materials with A γ<1 are subjected to catastrophic degradation in hydrogen. We have proposed relations that enable one to range adequately steels with different structures according to their hydrogen resistance and to regulate this property of steels by means of alloying. [ABSTRACT FROM AUTHOR]

We study the influence of the principal parameters of pulsed electrolysis (amplitude of the current density, frequency and on-off time ratio of the pulses, and the durations of the pulse and pause) on the deposition of cobalt-tungsten alloys. The extreme character of the dependences of current yield and the tungsten content of the alloy on the indicated factors requires the optimization of technological processes for the production of coatings with prescribed compositions. The corrosion and electrochemical behavior of the coatings is determined by the content of alloy-forming elements and lies within the framework of the kinetic regularities confirmed by the results of impedance measurements. [ABSTRACT FROM AUTHOR]

We studied the effect of laser treatment of electric arc coatings produced of powder wires of the Fe-Cr-B system on the changes in their structure, electrolytic potential, and polarization currents. We additionally introduced aluminum, nickel, and copper to the charge of these coatings. Laser treatment was realized by means of Nd: YAG laser radiation. We have shown that the addition of a small amount of these elements to the coating under study in different ways affects the character of formation, structure, and electrochemical characteristics of the fused layer. In particular, copper and nickel additions increase the fluidity of the coating. The parameters of laser treatment affect strongly the uniformity of the distribution of elements in the fused zone. In the case of alloying with copper, the nonuniformity of their distribution is more pronounced, which can exert a slight negative influence on the corrosion characteristics of the coating. Aluminum addition improves the corrosion resistance of laser-modified coatings. [ABSTRACT FROM AUTHOR]

We demonstrate the possibility of application of the polarization-current method to the corrosion monitoring of the operating equipment and present the numerical results showing that the indicated method enables one to estimate the degree of damage to the equipment at distances from the electrochemical probe not smaller than 5 m. The sensitivity of the method depends on the resistance of the electrolyte and the sizes of the tested object. [ABSTRACT FROM AUTHOR]

We study the influence of texture on the propagation of short cracks on the basis of the evolution of a family of microcracks in 316L austenitic stainless steel under the conditions of symmetric tension-compression. It is shown that the process of crack initiation is concentrated on grain boundaries and strongly depends on the mesostructure. In the process of fatigue fracture, the transcrystalline propagation of the largest crack (affected mainly by the global texture) is predominant. We discuss two approaches to the prediction of the influence of texture on the fatigue life. According to the concept of equivalent crack, this influence can be estimated depending on the size of the largest crack. On the contrary, the Zhurkov criterion deals with the state of the defect characterized by the presence of a family of microcracks. [ABSTRACT FROM AUTHOR]

We consider the possibilities of surface hardening of zirconium and titanium alloys with conversion oxide-ceramic coatings. These coatings have been produced by the method of plasma-electrolytic treatment in alkaline solutions. We have established that the plasma temperature in discharge spark channels reaches (6–9) · 103 K. The thickness of the coatings is 100 to 120 and 30 to 40 µm, and their microhardness is ∼ 800 and ∼ 1000 MPa for zirconium and titanium alloys, respectively. The functional properties of the coatings depend on the synthesis conditions, including the electrolyte composition, the cathode and anode current densities, and also the treatment time. We have evaluated the thickness, microhardness, and wear resistance of the coatings under conditions of dry friction and cavitation as well as their fatigue strength and corrosion resistance. We have established that this treatment provides a high wear and corrosion resistance of the alloys under study with insignificant decrease in their fatigue strength. [ABSTRACT FROM AUTHOR]

Using the results of electrochemical and impedance investigations, we have established that the introduction of modified zinc phosphate to the composition of silicon-organic prime coat, commonly applied for the painting of steel main pipelines at the outlet of gas-compressor stations, improves its protective properties and increases the corrosion resistance of the metal. We also have shown that the introduction of a mixture of modified zinc phosphate with fine filler (omiacarb) to the composition of silicon-organic coatings enables one to improve their protective properties. [ABSTRACT FROM AUTHOR]

We study two-phase cast steels in aggressive media most extensively encountered in industry and nature, namely, chloride, alkali, and hydrogen-sulfide media. Unlike austenitic cast steels, two-phase cast steels prove to be promising structural materials for the operation in hot concentrated alkali media and chloride solutions of low concentrations. In the case where the concentration of chlorides may increase, working stresses can be found according to their threshold values. The two-phase cast steels are unsuitable for operation in hydrogenating media. [ABSTRACT FROM AUTHOR]

We study the corrosion resistance of St3S steel under loading and its susceptibility to corrosion and hydrogen-induced cracking in bottom water. Sections of a tank are distinguished according to the character of the media interacting with the metal of the inner surface in the process of operation. It is shown that bottom water is characterized by high levels of corrosion activity and that the degrees of in-service degradation of different sections of the tank are different. The worst corrosion and stress-corrosion resistance are exhibited by steel operating in contact with bottom water. Significant levels of plastic strains intensify the process of corrosion in steel and make the rates of corrosion in different sections of the tank closer to each other. The in-service degradation of steel can not only intensify the process of corrosion of the inner surface of the tank but also promote the brittle fracture of the material characterized by the elevated susceptibility to hydrogen-induced cracking. [ABSTRACT FROM AUTHOR]

We deduce the dependences of low-cycle durability of 11 corrosion-resistant steels from basic structural classes on the pressure of gaseous hydrogen within the range 0.1–35 MPa at 293°K. It is discovered that the highest serviceability in hydrogen is exhibited by homogeneous austenitic steels and steels with intermetallic hardening. The durability of Ni–Al–Ti steels treated for maximum heat resistance in hydrogen is proportional to the content of Ti and Ti//Al ratio and depends on the conditions of treatment. Steels in the state of substitutional solution are not affected by the medium. The materials from the transient class and steels with unstable austenite are characterized by medium sensitivities to hydrogen. High-strength martensite-aging and ferritic steels exhibit catastrophic embrittlement in hydrogen. [ABSTRACT FROM AUTHOR]

It is shown that the corrosion resistance of titanium increases as a result of deposition of molybdenum-carbide coatings from melts. The cathode passivating titanium with molybdenum-carbide coatings is much more active than the cathode made of molybdenum carbide. In solutions of sulfuric acid (9.5 mol. parts) at 70–80°C, the molybdenum-carbide coatings passivate titanium and, as a result, its corrosion resistance becomes 2000–4000 times higher. [ABSTRACT FROM AUTHOR]

We present the results of investigation of the technology of application of coatings in zinc baths at temperatures different from the standard temperatures of the process of galvanization. The corrosion resistance of the coatings is determined under the action of neutral salt mist and sulfur dioxide in the case of condensation of moisture. With the help of galvanization at elevated temperatures of 540–560°C, it is possible to obtain coatings of constant thickness with improved structure and higher corrosion resistance as compared with the coatings obtained at standard temperatures. [ABSTRACT FROM AUTHOR]

We studied the corrosion inhibition of galvanized steel in artificial acid rain solution by chromate-free pigments containing phosphate and calcium ions. We used the methods of electro- chemical impedance spectroscopy, potentiodynamic polarization, electron microscopy, and X- ray microspectrum analysis. It was established that the combination of modified zinc phosphate and ion-exchange-type calcium-containing pigment provides a significant synergistic anticorrosion effect on galvanized steel as compared with the same inhibiting pigments used separately. The charge-transfer resistance of the metal in acid rain solution saturated with this pigment composition approaches that in the same solution with a chromate inhibitor and is significantly higher as compared with the solutions of separate pigments. Owing to the combination of non- chromate pigments, a protective film is formed on galvanized steel, which represents a complex mixture of calcium and zinc phosphates and guarantees the corrosion inhibition of galvanized steel under mixed cathodic-anodic control. [ABSTRACT FROM AUTHOR]

We study the influence of tannin extracts obtained from natural raw materials on the corrosion resistance of 20 steel. [ABSTRACT FROM AUTHOR]

Investigates the corrosion resistance of cans for beverages to establish reasons for their depressurization. Cans made of aluminum strips 0.28 millimeters thick of the Rochinery Phenalu firm; Metallographic macro- and microsections of depressurized cans from which a beverage flowed out; External examination with magnification from 20 to 120.