• MATERIALS

    Effect of solanine on corrosion of steel 3 in lactic acid

    Machines. Technologies. Materials., Vol. 17 (2023), Issue 1, pg(s) 40-42

    The object of research – the natural glycoalkaloid solanine as a possible inhibitor of acid corrosion of steel St3. Modern data on the structure and physico-chemical properties of solanine, such as amphiphilicity, surface activity, basicity, characteristic of modern organic corrosion inhibitors, are presented. The basic concepts are defined: basic nitrogen, solanine amphiphilicity, mass and volume corrosion indicators, corrosion inhibitor, degree of protection, corrosion inhibition coefficient. The literature data on the corrosive activity of lactic acid (MC) are presented and characterized.

  • MATERIALS

    The Effect of Vanadium, Niobium and Boron on Microstructure, Mechanical and Corrosion Properties of High-Chromium White Cast Irons

    Machines. Technologies. Materials., Vol. 16 (2022), Issue 8, pg(s) 286-289

    The influence of the vanadium, niobium and boron addition on properties of high-chromium white cast iron alloys for grinding balls is investigated in this paper. These alloying elements were individually added to the high-chromium white cast iron alloys with monitoring of changes in microstructure, corrosion rate, and mechanical properties in the as-cast conditions. The microstructure in all tested alloys consists of primary austenite dendrites and eutectic colonies, which consist of M7C3 carbides and austenite. The addition of V, Nb or B affects, to a greater or lesser extent, the size, morphology and volume fraction of both primary austenite dendrites and eutectic colonies. Samples of iron alloyed with vanadium and boron have a much finer structure than unmodified (base) alloy and niobium alloyed iron sample. Vanadium affects the decrease in the volume fraction of the primary austenitic phase, and the increase in the volume fraction of eutectic colonies, and thus the eutectic carbide phase in hypoeutectic alloys of high-chromium iron. The tested alloys have a comparable values of average hardness in the cross section of cast balls, as well as compressive yield strength, noting that the addition of vanadium increases the hardness, while boron addition increases the compressive yield stress. The single addition of all of three tested alloying elements shifts the corrosion potentials (and Tafel curves) of modified high-chromium white irons toward less negative values. The most favorable values of mechanical and corrosion properties were measured for the iron modified with 0.021 % of boron.

  • MATERIALS

    Investigation of the causes of corrosion of galvanized steel pipes used for hot water supply

    Machines. Technologies. Materials., Vol. 15 (2021), Issue 7, pg(s) 283-286

    The object of the study is the part of the galvanized steel pipe (about 1-meter-long) supplied by the customers, which was used to supply hot water inside the residential building and which has corroded during exploitation of 5 years. To clarify the situation, quality of surface coating and microstructure of the obtained galvanized steel pipe was analysed. Electrical stray currents of the pipeline installed in the building were measured. The sample of the hot water was taken and analysed at the certificated laboratory.
    The aim of the investigation was to determine the possible causes of the hot water supply pipe corrosion during sufficiently short time of exploitation.

  • MACHINES

    Thin layer activation method. Potential applications and benefits for the food processing industry

    Machines. Technologies. Materials., Vol. 15 (2021), Issue 7, pg(s) 256-258

    Mechanical wear, corrosion and erosion of the structural materials in machines and apparatus are destructive processes which cause worsening of their basic operational characteristics throughout their life cycle. As a result, the technological equipment undergoes loss of efficiency and reliability. It becomes unsafe from hygienic point of view. The expenses needed for its maintenance in crease significantly as the time passes. Its economical efficiency decreases as well. Materials which are in direct contact with food products can also transmit metallic ions or low molecular compounds to the processed food products – a process which is known as “migration”. Thin Layer Activation (also known as Surface Layer Activation) is an unique, efficient and innovative radiation based method used for conducting of comprehensive studies on surface degradation of materials. It allows real-time measurements of wear intensities with exceptionally high sensitivity within the scope of several ηm/h (or μg/h). The article reviews the essential principles of the Thin Layer Activation Method (TLA Method), describes its applications, capabilities and advantages. Possible uses in food processing industry are assessed and potential benefits from its implementation are discussed. Technological equipment in food processing industry includes machines and apparatus for production and processing of food products and liquids, packaging equipment, sanitation equipment, equipment for refrigeration and maintaining of certain environmental conditions, transportation equipment and auxiliary tools and equipment.

  • MATERIALS

    Advantages and disadvantages of fiberglass casing in oil and gas wells

    Machines. Technologies. Materials., Vol. 15 (2021), Issue 5, pg(s) 209-211

    Casing is an extremely important element in the process of drilling a well borehole, as they define the diameter of the well and, among many other tasks, protect it from collapsing. In order to ensure long-term successful performance of all tasks, it is necessary to appropriately dimension casing, which means that the appropriate inner and outer diameter should be selected with the appropriate material and its quality, with proper installation depth for each set of casing. Conventional casing made of steel is most often used and this is still an ideal material for most wells. However, this material is prone to corrosion, which is a major problem on certain locations du ring the
    production life of the well. Reduction and possibly elimination of corrosion on casing led the industry to explore financially viable composite materials, such as fiberglass, that could withstand expected stresses in well conditions with better corrosion resistance th an steel.

  • The influence of Zn on the corrosion behaviour of amorphous and nanosized rapidly solidified (Al75Cu17Mg8)100-хZnx alloys and their crystalline analogues

    Materials Science. Non-Equilibrium Phase Transformations., Vol. 6 (2020), Issue 3, pg(s) 73-76

    The influence of Zn on the corrosion behavior of amorphous and nanosized rapidly solidified aluminum alloys (Al75Cu17Mg8)100-xZnx (x = 0; 1; 3) at. % and their crystalline analogues was studied. Data were obtained for resistance of basic and rapidly solidified aluminum alloys (Al75Cu17Mg8)100-xZnx (x = 0; 1; 3) at. % to uniform corrosion. It has been found that increasing the percentage of zinc increases the corrosion rate of both base alloys and rapidly solidified ribbons with similar composition. Pitting and intergranular corrosion tests have been performed. The parameters affected area, pitting density and pitting size were evaluated. An XRD analysis of the separated corrosion products was performed. It was found that the chemical composition, and not the amorphous microstructure of the ribbons, was of leading importance for the course of the corrosion process in the studied rapidly solidified ribbons (Al75Cu17Mg8)100-xZnx and base alloys.

  • MATERIALS

    Corrosion of high purity magnesia refractories from iron-rich slags of ferronickel enrichment in OBM converters

    Machines. Technologies. Materials., Vol. 14 (2020), Issue 4, pg(s) 177-180

    The corrosion of high purity MgO refractories from molten iron-rich OBM converter slag has been investigated by performing experiments in an electric laboratory furnace. Corrosion tests were conducted at 1600 – 1650oC for 1, 2 or 4 hours. Following lab experiments, the mineralogical phases of MgO refractories, slags and the intermediate infiltration zone were identified by SEM/EDS. It has been shown that Fe infiltrates and replaces Mg in MgO refractories, thus forming magnesiowustite ((Mg,Fe)O). The maximum depth of the slag infiltration zone was estimated to 1.31 mm in the laboratory test where slag was in contact with the refractory for 4 h, at 1650⁰ C Thermodynamic modeling of the slag and refractories equilibrium conducted with FactSage 7.0, confirmed the formation of magnesiowustite in the intermediate zone, with progressively higher substitution rate of Mg by Fe. This increasing substitution results in a decrease of the melting point of magnesiowustite, thus causing the collapse of the refractories even at temperatures lower than the operational temperature.

  • TECHNOLOGIES

    An innovative approach for repairing of corroded reinforced concrete industrial structures in aggressive environment by high-tech hybrid reinforced sprayed concrete with capillary crystalline admixture

    Machines. Technologies. Materials., Vol. 13 (2019), Issue 6, pg(s) 259-262

    Solvay Sodi JSC, Devnya, Bulgaria, is the biggest calcite soda production plant in Europe. It is built in 1974 and it works in three-shift production regime up to present days. The exploitation environment is highly influenced by numerous factors, acting corrosively on main reinforced concrete structures – active atmospheric processes (in continental type moderate climate), sea water born chloride-aerosols, as well chemical attack caused by carbon dioxide and nitric acid, presented in the air in form of evaporation. The most reinforced concrete structures need urgent remedial measures to restore the load-bearing capacity of its components.
    The “light soda” silos are reinforced concrete facilities (cylindrical shells) which repair has to be executed during continuous production process. The options for repair of these structures and restoration of their load bearing ability by specially designed innovative high-tech hybrid reinforced sprayed concrete, containing capillary crystalline admixture, are discussed in the report.
    The in-situ tests and wide-range comparative studies are carried out, covering basic physical and mechanical structural characteristics of the proposed sprayed concrete for wet spraying and another one – based on proportioned dry ready mix.
    The original scientific results concerning strength-deformation properties, phase composition and structure of hardened sprayed concrete, directly related to the durability in aggressive environment, are obtained by X-ray diffraction (XRD), differential thermal analysis (DTA), mercury porosimetry, low temperature gas adsorption (BET-method) and computer X-ray tomography.
    The static and dynamic analysis of the structure is performed using the test results obtained and the fully specified engineering solution has been presented to restore the load-bearing capacity of the structures with a guaranteed service life of at least 50 years.

  • An innovative approach for repairing of corroded reinforced concrete industrial structures in aggressive environment by high-tech hybrid reinforced sprayed concrete with capillary crystalline admixture

    Innovations, Vol. 7 (2019), Issue 2, pg(s) 66-69

    Solvay Sodi JSC, Devnya, Bulgaria, is the biggest calcite soda production plant in Europe. It is built in 1974 and it works in three-shift production regime up to present days. The exploitation environment is highly influenced by numerous factors, acting corrosively on main reinforced concrete structures – active atmospheric processes (in continental type moderate climate), sea water born chloride-aerosols, as well chemical attack caused by carbon dioxide and nitric acid, presented in the air in form of evaporation. The most reinforced concrete structures need urgent remedial measures to restore the load-bearing capacity of its components.
    The “light soda” silos are reinforced concrete facilities (cylindrical shells) which repair has to be executed during continuous production process. The options for repair of these structures and restoration of their load bearing ability by specially designed innovative high-tech hybrid reinforced sprayed concrete, containing capillary crystalline admixture, are discussed in the report.
    The in-situ tests and wide-range comparative studies are carried out, covering basic physical and mechanical structural characteristics of the proposed sprayed concrete for wet spraying and another one – based on proportioned dry ready mix.
    The original scientific results concerning strength-deformation properties, phase composition and structure of hardened sprayed concrete, directly related to the durability in aggressive environment, are obtained by X-ray diffraction (XRD), differential thermal analysis (DTA), mercury porosimetry, low temperature gas adsorption (BET-method) and computer X-ray tomography.
    The static and dynamic analysis of the structure is performed using the test results obtained and the fully specified engineering solution
    has been presented to restore the load-bearing capacity of the structures with a guaranteed service life of at least 50 years.

  • BUSINESS

    PAINT COATINGS FOR CORROSION PROTECTION OF LIVESTOCK MACHINERY

    Science. Business. Society., Vol. 3 (2018), Issue 2, pg(s) 69-70

    The machinery in livestock farming works in a highly aggressive environment, increased ammonia content and high humidity. Anticorrosive protection of machines and equipment is widely used on the basis of lacquer materials. Their effectiveness is mainly determined by the selection of the varnish materials according to the type and degree of corrosion hazard.

    Modern lacquer-based materials based on melamine, pentaftal, nitrocellulose, butyl methacrylate, chlorovinyl, epoxide and other resins are characterized by high protective properties and the possibility of renewal.

  • MATERIALS

    ENVIRONMENTALLY FRIENDLY CONVERSION FILMS ON Zn AND TERNARY ZINC BASED ALLOYS – OBTAINING AND PROTECTIVE PROPERTIES

    Machines. Technologies. Materials., Vol. 10 (2016), Issue 9, pg(s) 44-47

    The objects of this study are galvanically deposited Zn and Zn-Ni-P coatings additionally treated (passivated) in environmentally friendly Cr(III)-based composition for obtaining of conversion films (CF). The aim of this treatment is to improve the corrosion-resistant properties of the coatings.

    The elemental composition and surface morphology of the newly obtained systems “galvanic coating/conversion film” are investigated with EDS and SEM analyses.

    Protective properties of the conversion films are defined with potentiodynamic polarization curves and polarization resistance measurements in a model medium containing chloride ions (5% NaCl) which leads to appearance of local corrosion.

  • MATERIALS

    CORROSION PROPERTIES OF COMMERCIALLY PURE TITANIUM DEPENDING ON THE MICROSTRUCTURE AND SURFACE TREATMENT METHOD

    Machines. Technologies. Materials., Vol. 10 (2016), Issue 9, pg(s) 33-35

    This paper presents the results of preliminary corrosion tests of samples from commercially pure titanium Grade 4 with a coarse- grained (annealed) and ultrafine-grained structure after severe plastic deformation, as well as of samples processed by microarc oxidation and with an ion-plasma coating. The effect of microstructure on the corrosion of the material under study is shown. A comparative evaluation of the corrosion rate is performed.