Influence Of Aggressive Media Research Articles

Ultrasonic diagnostics of concrete destruction under the influence of corrosion environment

Introduction. Modern methods of studying the corrosion damage of concrete are quite lengthy and time-consuming, which makes their use difficult. This necessitates the search for new approaches to study the destruction of concrete under the influence of aggressive media. Currently, the ultrasound diagnostic method is effectively used to identify various structural defects, but the possibility of its use for concrete corrosion studies is poorly understood. This work is devoted to filling this gap.The methods of research. Concrete samples of 2.5x2.5x10 cm and 2.5x2.5x16 cm of various composition (cement: placeholder = 1:9, 1:7, 1:5). The control samples hardened under normal conditions, the test samples were stored in various aggressive environments. The samples of all storage media were subjected to periodic tests on the Pulsar-2.2 ultrasound diagnostic device. In parallel, the strength parameters obtained by the destructive method on the PGM-100MG4 hydraulic press, as well as the resistance coefficient, were determined.Results. The relationship between the growth periods, extremes and abrupt changes in the velocity of passage of ultrasonic waves and the stages of strength gain, the conditions of hardening of samples, and time factors has been established. It is shown that ultrasound diagnostics is quite sensitive to the processes caused by the corrosion destruction of concrete and allows us to obtain reliable data, while the strength and coefficient of resistance do not always adequately reflect the development of corrosion processes. It has been established that the use of ultrasound diagnostics makes it possible to increase the reliability of the results of concrete corrosion studies.Conclusion. The use of the ultrasound diagnostic method enables to obtain new data on the processes of concrete destruction under the influence of aggressive media, which makes it possible to increase the reliability of the results of concrete corrosion studies.

SYNTHESIS OF COPOLYMERS FOR PROTECTIVE COATINGS

Copolymers were obtained in this work and the methodology for their synthesis was worked out. Various fillers were selected for the polymer coating. Resulting copolymers have good adhesion required for composite protective coatings. An experiment was conducted to determine the corrosion resistance of metals coated with copolymers when exposed to aggressive environments, as well as to determine the hardness and thickness of the polymer coatings obtained. It was found that the polymer coating filled with bronze powder, despite the small thickness of 43.4 μm, hasthe best adhesion and corrosion properties, as well as having the highest hardness values of 80.5 HB. Such physical and mechanical properties of polymer coatings allow them to be used as protective coatings for metal products working under the influence of aggressive media.

ИДЕНТИФИКАЦИЯ ФАКТОРОВ КОРРОЗИОННОГО ИЗНОСА

The identification of corrosion wear factors at the site of the corrosion process is proposed by the initial and actual dimensions, by type, depth, intensity and danger of destructive changes in structural elements under the influence of aggressive media. Identification has a relatively simple implementation scheme, since an experimental and theoretical approach is used, which increases the accuracy of assessing the corrosion wear of structural material for both individual elements and the technical device as a whole

THE CHROMIUM AND COBALT DISTRIBUTION IN THE DIFFUSION LAYER OF STEEL X35CrNi2-3 DURING THERMОDIFFUSION SATURATION

For parts of machines and equipment operating under the influence of aggressive media, abrasive, high temperatures, the creation of a hard, wear-resistant surface is an urgent task. Cobalt is used as a binder to create hard alloy materials that work under these conditions. It was of interest to evaluate the possibility of using cobalt as an additive in complex thermal diffusion chromium plating of structural steel. The article describes the features of thermal diffusion saturation of steel X35CrNi2-3 with chromium and cobalt at a temperature of 1000°C. A technique for analyzing the obtained coating is presented, based on the possibilities of X-ray spectral microanalysis of the diffusion layer on transverse microsections of the obtained samples. The elemental composition of the diffusion layer was monitored using the JEOL JSM-6460 LV universal scanning (scanning) electron microscope. The microstructure was studied using the optical metallographic microscope Axio Observer D1.m. The X-ray phase analysis was carried out with the Rigaku Ultima IV diffractometer. The hardness measurement was carried out with the FM-800 microhardness tester at a load of 50 g. Data were obtained on the distribution of chromium and cobalt in the surface layer of steel. It is shown that the resulting thermal diffusion coating consists mainly of a substitutional solid solution based on Cr‒Fe‒Co with bcc lattice and chromium carbides. The average diffusion coefficients of chromium in the α-phase of chromium were determined to be DCr = 3,22·10‒15 м2/с; in the γ-phase of iron DCr = 9,41·10‒15 м2/с. The diffusion coefficient of cobalt in the γ-phase of iron DCo = 7,89·10‒15 м2/с. The depth of the outer coating on the sample was about 15–20 µm, the depth of the diffusion layer of chromium in the base metal was about 70 µm, and that of cobalt was about 40 µm. The maximum hardness of the outer surface layer was 1740 HV, the diffusion layer in the base metal was 900–560 HV, and the base metal was about 510 HV.

The Influence of Aggressive Media on the Weight and Surface Hardness of Epoxy-Glass Waste Composite

The world is evolving toward a circular economy, which focuses on decreasing waste and extending the life of commodities. This work suggests using waste of glass to prepare composite. Epoxy was reinforced 50% by weight using waste glass. At room temperature were prepared samples reinforced and unreinforced and immersed in five solutions (HCl, Water, NaOH, Kerosene and Benzene) for four weeks, to find out the resistance of the epoxy after reinforcing. It is found that reinforced samples have resistance of increased after immersion in corrosive media comparison pure epoxy and it was obvious that the hardness were modified by 57% and remain constant during the immersion period in solutions. After immersing specimens in HCl the weight of the specimens decreases by 3.6%, unlike other solutions the weight of the specimens’ increase. Indicating that epoxy gains resistance after being reinforced with glass waste, allowing it to be used in a variety of applications.

DEGRADATION OF INCLUSION − MATRIX BOUNDARIES IN ACTIVE ENVIRONMENTS

Purpose. The aim of the work was to analyze the features of the destruction of the inclusion − matrix interphase boundaries under aggressive influences and in the process of wear as a result of the degradation of their structure. Methods. The samples of steels 08, R7, ShKh15 were tested for low-cycle fatigue in air and in corrosive environments (1…5 % aqueous solution of NaCl and 2…1 % aqueous solution of H2SO4). A test method was used to test the tendency of steels to stress corrosion cracking on an IM-12 installation. Fatigue strength tests were carried out on an NU machine. Samples of steels 08kp, 08Yu, 08GSYuTF, ShKh15, R7, M74 were exposed to holding in an atmosphere of hydrogen for 2 h at of 650 and 1 100 °C, the pressure 5 and 10 MPa. The features of the wear of the rolling surface of railway wheels (steel R7), which have worked for 5 years under a passenger train, have been investigated. Research methods: metallographic ("Neophot-21"), electron microscopic ("JSM-35"), petrographic. Results. The features of the fracture of the interphase inclusion − matrix boundaries under various thermal-deformation and aggressive actions are investigated. The role of inclusion − matrix boundaries in the formation of cracks of fatigue, fatigue-corrosion and hydrogen origin is considered. Scientific novelty. It is shown that under the influence of aggressive media and cyclic stresses, the structure of the inclusion − matrix interphase boundaries degrades, which is associated not only with the accumulation of interfacial stresses, but also with the facilitation of the penetration of surfactant atoms from the environment along these boundaries. As a result, fatigue-corrosion destruction of the inclusion − matrix boundaries occurs, and the effect of an adsorptive decrease in their strength is manifested. Practical significance. The research results can be useful in the development of methods of targeted influence on non-metallic inclusions and inclusion − matrix boundaries in various types of steel processing and the operation of steel products.

The role of inclusion-matrix boundaries in steels fracture processes

The features of the fracture of the interphase inclusion-matrix boundaries under various thermal-deformation and aggressive actions are investigated. The reasons and conditions for the formation of cracks as a result of decohesion of the inclusion-matrix boundaries associated with the concentration of interfacial thermal and deformation stresses are discussed. It was found that the character of decohesion of the inclusion-matrix boundaries (rupture of interatomic bonds of a nonmetallic inclusion and a steel matrix) caused by interphase thermal stresses is due to the conditions of heating and cooling, depending on the type of processing (conventional heating, laser or electromagnetic treatment), which determines the possibility of passing relaxation processes associated with the redistribution of interfacial defects within the specified boundaries. The mechanisms and features of decohesion of the interphase inclusion-matrix boundaries at different methods and temperatures of deformation are discussed. It is shown that the decomposition of the inclusion-matrix boundaries upon deformation occurs in cases of certain types of nonmetallic inclusions (oxides, spinels, some sulfides). For different types of inclusions and steels, parameters have been determined that characterize the cohesive strength of the inclusion-matrix interface depending on the loading conditions. It is shown that decohesion (fracture) of the inclusion-matrix boundary into two free surfaces can be considered as the transformation of interphase misfit dislocations into surface steps as a result of loss of conjugation. The role of inclusion-matrix boundaries in the formation of cracks of fatigue and fatigue-corrosion origin is considered. It is shown that under the influence of aggressive media and cyclic stresses, the structure of the inclusion-matrix interphase boundaries degrades, which is associated not only with the accumulation of interfacial stresses, but also with the facilitation of the penetration of surfactant atoms from the environment along these boundaries. As a result, fatigue-corrosion destruction of the inclusion-matrix boundaries occurs, and the effect of an adsorptive decrease in their strength is manifested.

Influence of aggressive media on the relaxation properties of wood-polymer composites

Measurements of stress relaxation of two samples of decking boards after exposure in rain and chlorinated water, in ice, and in a mixture of gasoline and water in different concentrations from 1 to 7% were carried out. Samples consisting of 60% wood flour, 30% polyvinyl chloride and 10% additives were used for measurements. Additives are flame retardants, stabilizers, modifiers and dyes. The mineral filler CaCO3 was used as modifier. In sample No.1, the CaCO3 content was 42% and the wood content was 18%. For sample No.2, the CaCO3 content was 24% and the wood content was 36%. As a result of measurements after exposure for 200 days, it was found that the relative drop in mechanical stress decreases when the mineral filler is added to the composition. The nonlinear mechanical behavior for the initial sample No.1 is observed at 2% strain, and for the sample No.2 – at 3% strain. When aged in chlorinated water and in ice, the nonlinear mechanical behavior is observed for all deformations. The generalized relaxation curves indicate that decking boards can be used with confidence for a long time.

Investigation of a Steel Local Corrosion in Chloride-Containing Media

Aspects of the development of local corrosion on the metal surface under the influence of aggressive media containing chloride ions are presented. The main mechanisms leading to the formation and development of local damage of the surface of metals are described. The process of electrochemical corrosion of steel under the influence of chloride-containing medium is experimentally investigated. By constructing corrosion diagrams, the main indicators of steel corrosion in a 10% sodium chloride solution were determined, which allows one to judge the rate of development of corrosion processes with local damage to the protective coating and the degree of steel resistance depending on the aggressiveness of the medium. It is shown that protective coatings, such as modified phosphate and oxide-phosphate films, prevent the penetration of an aggressive medium to the surface of the protected metal and, accordingly, the anodic dissolution of the metal.

Influence of aggressive media on mechanical properties of wood-polymer composites

Mechanical properties of two samples of decking boards were measured after exposure in rain and chlorinated water, in ice, and in a mixture of gasoline and water in different concentrations from 1 to 7%. Samples consisting of 60% wood flour, 30% polyvinyl chloride and 10% additives were used for measurements. Additives are flame retardants, stabilizers, modifiers and dyes. The mineral filler CaCO3 was used as modifiers. For sample №1, the CaCO3 content was 42% and the wood content was 18%. For sample №2, the CaCO3 content was 24% and the wood content was 36%. As a result of measurements after exposure for 150 days, it was found that the specific impact strength increases by 120%, the bending strength decreases by 60%, and the Shore D hardness decreases by a maximum of 10%. Consequently, decking boards can be confidently used for a long time, since a number of properties almost do not change, but even increase, and some decrease in strength remains within acceptable values.

Corrosion resistance of epoxy composite coatings for the transport industry in aggressive environments

Epoxy diane oligomer ED-20, 2,4-diaminoazobenzene-4'-carboxylic acid modifier, polyethylene polyamine hardener,microdispersed particles of synthesized powder charge and a mixture of discrete fibers were used to form composite materials and protective coatings for the transport industry. The influence of aggressive media: oil, gasoline, sea water, acetone, NaOH (50 %), HCl (10 %) and H2SO4 (10 %) on the corrosion resistance of the developed composite materials with different content of ingredients was studied. The results of experimental studies suggest that the least swelling was observed for samples of composite containing components in the following ratio – modified binder: microdisperse filler in the form of a synthesized powder charge (Fe (70 %) + Ti (10 %) + TiC ) + Fe3C (5 %)) (d = 10–12 mm) : mixture of discrete fibers (modal (42 %), polyacrylic (38 %), polyamide (38 %)) – 100 : 0.05 : 0.10. The use of such a composite in the form of protective coatings of vehicles will ensure (if compared to the modified epoxy matrix) reduction of the permeability of aggressive media in: 1.5–1.7 times (when being used in oil and gasoline); 1.6–1.8 times (when being used in seawater, acetone and NaOH solution (50 %)); 3.0 and 2.5 times (when being used in solutions (10 %) of hydrochloric and sulfuric acids, respectively. Increased corrosion resistance compared to the matrix is caused by a decrease of the amount of polymer in the developed material and its increased cohesion strength, which increases the path of penetration of molecules of corrosive agents during their diffusion into the composite due to additives.

Effect of aggressive media on working capacity of composite elements in mechanical engineering

Composite elements can improve not only the strength but also the protective properties of engineering products, thus reducing corrosion losses. At present, there is no sufficient study of the environment influence on the working capacity of composite elements, in particular on the decrease of their crack resistance. The article discusses the calculation and experimental methodology, which allows increasing the accuracy and reliability of the assessment of crack resistance of composite elements under the influence of aggressive media. The presented methodology can be implemented without a test facility by testing directly experimental specimens. To determine the magnitude of the crack propagation energy, a mathematical model is proposed that includes only one independent parameter (radius of curvature). The authors investigated qualitative and quantitative characteristics of the effect on the fracture toughness of such aggressive media as machine oil and water. It is shown that the effect of air and machine oil on the crack resistance is approximately the same. A decrease in crack resistance by 1.56-11.1 times is observed under the influence of water. The composite elements based on the VAK-A adhesive composition have the highest crack resistance in aggressive media.

Modified Composition for Fixing Sandy Soils

The possibility of using a modified composition based on slag Portland cement with the addition of stabilized finely dispersed slag in geotechnical construction and in landscape design is considered. The physical, mechanical and structural characteristics of samples hardening in normal conditions and under the influence of aggressive media were studied. It is established that the compressive and flexural strength of the modified samples is higher than that of the control sample. When hardening in normal conditions, on the first day, the flexural strength of modified specimens increased by 59%, at the grade age by 51%, compressive strength - 2.3 times and by 83%, respectively. When hardening in aggressive media, an increase in the strength of the modified specimens is also observed (flexural by 35–58%, compressive by 7–15%). This is explained by the fact that stabilized slag particles in a hardening system perform two functions: they are centers of directional crystallization for nucleation and growth of newgrowths, and full participants in the hydration process, binding calcium hydroxide to crystallohydrate compounds, thereby preventing the formation of ettringite when the concrete structure is exposed to aggressive media.

Influence of Aggressive Media and Its Effect on Student Behaviour

Influence of Aggressive Media and Its Effect on Student Behaviour

ОЦЕНКА ВОЗДЕЙСТВИЙ КЛИМАТИЧЕСКИХ ФАКТОРОВ НА ЭКСПЛУАТАЦИОННЫЕ СВОЙСТВА СТЕКЛОПЛАСТИКА МАРКИ ВПС-42П/Т-64

The study of the operational properties of fiberglass, developed for use in the air conditioning system of aircraft, after exposure to accelerated climatic factors. The results of studies of the properties of fiberglass based on phenol-formaldehyde binder grade VSF-16M after exposure to thermal and heat-moisture aging, the influence of aggressive media, as well as mycological tests are considered. The microhardness of a polymer matrix in plastic is investigated depending on the influence of operating factors. The assessment of the properties of fiberglass for compliance with the norms of AP-25 (p. 831 «Ventilation» – the content of toxic impurities in the air).

Joint Work of Cement Concrete and Composite Reinforcement with Periodic Profile Winding

A study of the joint work of cement concrete and material winding fiberglass composite reinforcement with different types of coatings and types of windings was conducted. The type of periodic profile winding is presented, which increases the adhesion of the material of glass fiber reinforcement winding with cement concrete. It has been established that the winding of the periodic profile improves the strength properties of the composite reinforcement material. The influence of aggressive media on the adhesion of fiberglass rods with different types of surface preparation from cement concrete is estimated.

Impact of Aggressive Media on the Properties of Polymeric Coatings with Solidification Products as Fillers

Dealing with waste materials, particularly hazardous waste, is a serious problem. Disposal areas keep growing, and the costs incurred are high. Disposing of such waste reduces negative environmental impacts and offers considerable financial savings. This paper focuses on the possibilities of incorporating pollutants found in hazardous wastes as fillers in coatings based on polymers (epoxide and polyurethane). These coatings are intended mainly for concrete and metal bases and offer secondary protection against adverse weather conditions. Important physical and mechanical properties of the newly developed materials were determined; they include surface hardness, impact resistance, tensile properties, and chemical resistance. These properties were also compared to those of the reference filler. At the same time, the influence of aggressive media on the properties of these materials was observed, in particular on flexural characteristics. The microstructures of the developed coatings were tested using a high-resolution optical microscope, before and after exposure to the chemicals. The positive effect of using progressive fillers, such as solidified hazardous waste (a solidification product (SF)), was witnessed by their constructive contribution to the materials’ physical and mechanical properties. The use of solidification products is unambiguously advantageous from technical, ecological, and economical stand points (utilization of hazardous waste as a progressive filler instead of landfilling, improvement of tensile properties, reduction in the price of coating system, and incorporation of the pollutants into the polymer matrix).

Features of operation of sewage pumping stations of heat and power stations in in conditions the Far North

Introduction. The subject of the study is the study of technologies to ensure the reliability of sewage pumping stations (SPS), exploited in the Far North. One of the most important problems is the freezing of water in the SPS tanks, associated with the incorrect selection of the insulation of the SPS of new TPPs, as well as the deterioration of the insulation of the SPS under the influence of aggressive media on the old TPPs. As a solution, the article considers two main methods of internal heating: liquid and electric. Both methods were analyzed using the example of the Yakutsk State District Power Plant-2, where the disruption of the drainage system may lead to a station shutdown. Materials and methods. The purpose of the study was a comparative analysis and selection on the basis of a feasibility study of the most reliable method of heating the pumping unit of the Yakutsk State District Power Plant-2, exposed to low temperatures and, as a consequence, the freezing of wastewater in tanks. On the basis of field surveys and the processing of their results using mathematical statistics, the causes of the problem of water freezing in the SPS units at Yakutsk State District Power Plant-2 were studied and analyzed. Technological characteristics of the installed SPS were also analyzed, heat engineering calculations were performed, economic indicators were calculated, and further solutions to the problem under consideration were determined. Results. Analysis of the technical parameters and configuration of the SPS showed that the installed insulation and the heating system do not correspond to the territorial conditions in which this equipment is installed. To bring the SPS into working condition, two solutions for internal heating of tanks were developed and their comparative analysis was performed. Selected heating option with heating cable. This system has been successfully implemented and is operating normally. Conclusions. The results of the work can be used to repair thermal insulation and install a heating system for industrial pumping stations without using earthworks in the conditions of the Far North and on the territory of permafrost soils.

Comparison of the Strength of Normal Sections of Rubber Concrete Rectangular and T-beams

Polymer concretes permit to solve the problems associated with the influence of aggressive environment of various natures. Aggressive media, penetrating through the cracks in the body of the structure, in addition to corrosion of concrete, lead to corrosion of the reinforcement and, consequently, the load-bearing capacity of the element significantly reduced. The different types of polymer concrete are furan, epoxy, polyester and others. At the Department of Building Constructions, Bases and Foundations of the Voronezh State Technical University (VSTU), rubber concrete (rub-con) was developed, which is one of the types of polymer concrete based on liquid rubbers. This liquid rubber is produced at the Voronezh Synthetic Rubber Plant (SK-2). Rubcon has favorable physi-co-mechanical properties, high strength and high chemical resistance (almost universal). Thus, rub-con allows solving the problems of corrosion of various structures functioning under the influence of aggressive media.

Different aggressive media influence related to selected characteristics of concrete composites investigation

The loss of mass of concrete matrix and sub- sequent corrosion of concrete has been reported very often. Aggressive liquids such acids, bases, solutions of salts or aggressive gases as well as microorganisms penetrate the concrete and cause deterioration and biodeterioration, respectively. Presented paper is aimed at investigation of concrete corrosion (chemical as well as biologically induced) activated by influence of different aggressive media. Concrete cylinder samples of a 32 mm diameter and 15 mm height were formed as a drilled core from prepared concrete cubes. Concrete samples were exposed to different aggressive media under laboratory conditions (acid mine drainage, cultivation media for different bac- teria species, sulphuric acid, aluminium sulphate) as well as in situ (waste water of sewage system in Kosice city) for 3 months. Influence of aggressive media and sulphur-oxi- dising and sulphate-reducing bacteria on concrete samples has been determined in terms of weight and surface changes of investigated concrete samples and leaching of the selected ions. The weight changes varied in the range 0.04-3.7 %. The visual changes of samples surface were observed. Content of Ca, Si and Fe ions in leachates were measured by X-ray fluorescence methods. Higher per- centage of calcium ions released has been measured com- paring to silicon ions in all media except for distilled water. The results of elements releasing correspond to results of weight changes of investigated concrete samples.