Browsing by Author "Fachikova D.I."

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    APPLICATION OF ORGANIC COATINGS ON AMORPHOUS PHOSPHATED ZINC SURFACES
    (2023-01-01) Liubenova T.L.; Fachikova D.I.
    The phosphating of zinc surfaces, increasing their roughness and surface tension, provides high adhesion and a significant increase in the protective ability of subsequently applied organic coatings. This paper presents the results obtained in a study of combined coatings, including the formation of amorphous phosphate films on galvanized steel surfaces, followed by the application of layers of three type paints and varnishes. By means of gravimetric and physical-analytical methods, the influence of various factors such as concentration and temperature on the formation, composition and properties of the coatings obtained on zinc surfaces in phosphating solutions have been investigated. Coatings obtained at pH 4.0 are distinguished with best homogeneity and color density. The thickness of the coatings grows with increasing of temperature, at other conditions being equal. Тhe composition, structure, roughness and probable compounds of the obtained phosphate coatings have been determined by physical analytical methods. The phosphate coatings contain such elements as oxygen, phosphorus, zinc, molybdenum, nickel, which are probably combined as phosphate and oxide compounds.The phosphate films are X-ray amorphous, with indefinite habit and very well expressive relief. Using physico-mechanical methods, the adhesion, elasticity and impact strength of paint and varnish coatings on phosphated and non-phosphated zinc surfaces were measured.
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    CORROSION BEHAVIOR OF MILD AND LOW ALLOYED CARBON STEELS IN MINING CONDITIONS
    (2022-01-01) Fachikova D.I.; Ilieva G.P.; Fachikov L.B.
    This communication addresses corrosion behaviors of two steels employed as construction elements in underground mining, precisely mild steel st.25 (0.23 % C) and low alloyed carbon steel KP-355 (0.19 % C, 0.96 % Cr, 0.36 % Cu). Tests were carried out in representative synthetic media containing chlorides and sulphates in different ratios and various pH. The concentration of the chloride and sulphate ions, as well the values of pH were relevant to the ranges of variations observed in real mining waters. The studies were performed by physical (optical microscopy) and electrochemical (potentiodynamic polarization) methods. The microstructures of both steels are almost identical, that is, they are ferrite-perlite in nature. The mechanical characteristics, the yield strength limit, Re, 0.2, MPa and tensile strength, Rm, MPa are higher to the alloyed steel respectively with about 30 % and 20 %. The polarization relationships allow obtaining the main parameters characterizing the corrosion process - the corrosion potential, Еcorr, V (SCE) and the corrosion current density, icorr, A сm-2. The latter are processed by the methods of mathematical statistics.
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    ELECTROCHEMICAL EXTRACTION AND CHARACTERIZATION OF A RECOVERY TIN
    (2023-01-01) Fachikova D.I.; Fachikov L.B.
    Statistics on the production of а secondary tin show that its use in many countries reaches a significant amount. One of the most important sources of secondary tin is a scrap of white sheet metal formed by stamping various products, waste from used cans, and other obsolete tin products. In the present work, using chemical, electrochemical and physical methods, a technology for dissolving tin from used cans in alkaline solutions with the addition of p-nitroaniline and its electroextraction from solutions is proposed. The optimal conditions of dissolution and extraction (concentration and temperature of the medium, current density, current yield), as well as the chemical composition of the obtained metal tin, are determined.