Rate Of Corrosion Process Research Articles

Влияние внутренних напряжений на интенсивность коррозионных процессов конструкционной стали

Introduction. The behavior of metal in a corrosive environment can be ambiguous, which is due to the peculiarities of the corrosion process. Both external and internal factors influence the corrosion process. External factors are determined by temperature, humidity, type of corrosive medium, etc., while internal factors depend on the parameters of the system (material): the presence of inclusions, phase composition, structure, and the magnitude of internal residual stresses. Internal factors ambiguously affect the behavior of the material in a certain aggressive medium, which ultimately affects the time of corrosion damage of the material and, as a consequence, the time of operation of objects made of this material. Therefore, differentiation of the influence of various internal factors on the rate of corrosion process in an aggressive environment is a priority area of research. The purpose of the present work is to consider the influence of the magnitude of internal residual stresses on the rate of corrosion process in an aggressive medium — 5% sulfuric acid solution. The object of research conducted in the work is sheet rolled steel St3 as received after different magnitude of plastic deformation, from which the specimens under study were made. The methods of investigation: microstructural study of deformed specimens was carried out on optical microscope Olympus GX53; software SIAMS 800 was used to compare the structure of the obtained material with the atlas of microstructures, determine the score of grain structure, determine the anisotropy of the structure after deformation of the material; X-ray diffractometer DRON-7 was used to register diffraction patterns and determine internal stresses; laboratory scales SHIMADZU UW620h was used to measure the mass of the specimens under study; tensile strength of the material’s specimens was measured. Results and Discussion. The obtained results show that the plastic deformation of the material in the rolling direction has an ambiguous effect on the structure anisotropy. When the degree of plastic deformation increases, there is an ambiguous change in the grain anisotropy value, which is associated with the internal effects of the processes occurring in the material structure during plastic deformation, such as: sliding of the crystal lattice in the {111} <110> directions; the occurrence of reverse residual internal stresses due to the presence of inclusions in the steel structure. However, the degree of plastic deformation correlates quite well with the magnitude of internal residual stresses. The increase in the magnitude of internal residual stresses leads to an increase in the corrosion rate of structural steel St3 in 5 % hydrochloric acid solution. The obtained dependence is described by a linear equation with a high coefficient of determination, which indicates that there is a strong relationship between the magnitude of internal residual stresses and the rate of corrosion of the material. At the same time, the coefficient of influence of internal stresses on the corrosion rate is equal to 0.72, which additionally proves the existence of interrelation between the considered parameters.

Contemporary approaches to reducing scale formation in heat-exchange equipment

Objectives. Scale formation and corrosion are serious problems for heat and power equipment. These processes, when intense, can completely block the operation of the system, accelerating corrosion and leading to clogging, local overheating, and burnouts and ruptures of boilers and pipes, which in turn can lead to major environmental problems. Therefore, protecting surfaces from scale formation and corrosion is an important task. Promising methods for preventing the development of undesirable consequences include changing the composition of polymer coatings, e.g., by introducing microencapsulated corrosion inhibitors, as well as surface modification approaches, such as hydrophobization of the polymer coating surface. The purpose of the present work is to analyze methods for reducing scale formation and the rate of corrosion processes, as well as to study the efficiency of modification of paints and coatings by introducing microencapsulated corrosion inhibitors.Methods. The study was based on the use of accelerated corrosion tests.Results. Existing methods for reducing scale formation and corrosion rate on the surfaces of heat and power equipment were analyzed. The efficiency of modifying protective polymer materials by introducing microcapsules containing an active phosphonate additive was compared with approaches involving the surface modification of such protective materials.Conclusions. It was determined that the modification of paints and coatings by introducing microencapsulated active additives can significantly reduce the rates of both scale formation and corrosion. By implementing stateof-the-art methods for modifying polymer coatings, a new generation of agents for efficiently preventing scale formation and corrosion processes can be developed for maintaining the high performance of heat-exchange equipment.

Study of inhibiting properties of multicomponent systems in aggressive media in the presence of surfactants

The article discusses the anticorrosive properties of inorganic orthophosphate compositions in relation to St-3 steel in an oil-water environment in the presence of surfactants, depending on the pH of the medium, the nature and concentration of phosphate, the nature of the modifier ion. The research was conducted using State Standard-based methods: gravimetry, potentiometry, photocolorimetry, infrared spectroscopy and scanning electron microscopy. On the basis of experimental data, quantitative indicators of corrosion process were determined: the rate of corrosion process, the degree of protection, the depth index, the coefficient of inhibition and the assessment of the stability of the formed film on the ball scale of corrosion resistance against steel. The analysis of experimental data allows to establish the influence of the above factors on the corrosion processes in the systems under study. The experimental data are supplemented by thermodynamic calculations of the corrosion process parameters, the results of which correlate well with the kinetic data of the process under study. In the course of the research work, the analysis of corrosion deposits was also carried out. The regularities established during the work contribute to the creation of effective orthophosphate inhibitors with the highest degrees of protection.

Аналитический расчет потенциала при контактной коррозии металлов в морской среде

One of the most common types of ship corrosion is contact corrosion, which occurs at the interface of dissimilar metals being washed. It poses a serious danger to the ship's hull and ship metal structures, as it leads to a sharp increase in the rate of corrosion damage to one of the contacting metals. Therefore, the fight against contact corrosion is one of the most urgent tasks in the field of anti-corrosion protection of ships. Protection of ships from contact corrosion requires solving a set of interrelated engineering problems that require a quantitative assessment of the rate of corrosion processes on ship structures and the effectiveness of anti-corrosion protection means used on ships [1, 2]. The article discusses an analytical approach in assessing the local rate of electrochemical corrosion processes of ship hull structures based on the phenomenon of polarization using polarization curves and approximation methods.

Increasing of Corrosion Resistance for Metal Products of Livestock Premises

The purpose of the work was to identify and analyze the causes of corrosion destruction of metal products, used in conditions of animal keeping on farms of the agro-industrial complex, and to find effective methods of combating it. In order to increase corrosion resistance of metal products of livestock farms and complexes, it is proposed to use the developed preparation, which has fungicidal and anticorrosive properties simultaneously. The rate of metal products corrosion during the experiment was evaluated by the museum strain of Aspergillus niger fungi. The article describes the causes of fungal corrosion, the principle of its effect on metals; proposes an inhibitor of complex action for the control of electrochemical and bio-corrosion. The protection efficiency of metal products by the inhibitor was evaluated by the corrosion braking coefficient and the degree of protection. The effect of inhibitor concentration on the rate of low carbon steel bio-corrosion has been studied. It has been proven that the rate of corrosion processes decreased by 50 times, when exposed to a medium, contaminated with fungus spores, on metal samples treated with an inhibitor.

Study of the inhibitory ability of inorganic di- and polyphosphate compositions

The article considers the anticorrosive properties of inorganic di-and polyphosphate compositions in relation to St-3 steel, depending on the pH of the medium, the nature and concentration of phosphate, and the nature of the modifier ion. The research was conducted using GOST-based methods: gravimetry, potentiometry, photocolorimetry, infrared spectroscopy and scanning electron microscopy. On the basis of experimental data, quantitative indicators of corrosion process were determined: the rate of corrosion process, the degree of protection, the depth index, the coefficient of inhibition and the assessment of the stability of the formed film on the ball scale of corrosion resistance against steel. The analysis of experimental data allows to establish the influence of the above factors on the corrosion processes in the systems under study. The experimental data are supplemented by thermodynamic calculations of the corrosion process parameters, the results of which correlate well with the kinetic data of the process under study. In the course of the research work, the analysis of corrosion deposits was also carried out. The regularities established during the work contribute to the creation of effective di-and polyphosphate inhibitors with the highest degrees of protection.

Analysis of the process of corrosion destruction of settling tanks for preparation of high-viscosity oil to transport through main oil pipelines

Most of accidents and failures of vertical steel tanks are related to metal corrosion of their shells and equipment. The choice of optimal corrosion protection to extend the life of such tanks is impossible without an understanding of the mechanisms of its origin and development, as well as the degree of influence of operational factors on these mechanisms.Of particular interest is the study of corrosion processes taking place in tanks to prepare for the transport of high-viscosity oils operating in the specific conditions of the Far North. The complex effect of factors such as temperature, total salt content of bottom water, the concentration of corrosion inhibitors, demulsifiers, and mechanical impurities on the rate of corrosion processes is not fully understood to date.This article analyzes the process of corrosion destruction of settling tanks for the preparation of high-viscosity oil to transport through main oil pipelines using the example of the RVS-5000 of the park of input tanks of the Yareganeft oil and gas department. Analysis of operating conditions made it possible to identify factors affecting corrosion processes and to identify potentially the most dangerous zones of contact between media entering the reservoir and the shell metal, the bottom and roof of the tank. The study have showed that the greatest interest is the study of the effect of the presence of mechanical impurities in the fluid supplied to the settling tank on the intensity of corrosion processes on the internal surfaces of the tank in potentially dangerous areas.

Effect of fruit juices and chloride ions on the corrosion behavior of orthodontic archwire

ABSTRACTElectrochemical and surface analytical study on the corrosion behavior of AISI 316L stainless steel orthodontic archwire in different fruit juices was carried out. The electrochemical parameters were measured after immersing the wires for approx. 24 h in artificial saliva (AS) containing different fruit juices and separately in fruit juices with 1% NaCl in AS. All the fruit juices used in this study increased the rate of corrosion process in AS in the presence or absence of salt. Addition of 1% NaCl to the AS, all experiments exhibited pitting. Solanum lycopersicum (Tomato) and Durio zibethinus (Amra) are rated as most detrimental to the surface followed by Prunus domestica Linn. (Plum) juice. SEM Micrographs of the specimens show formation of blisters onto the steel surface which are remnants of passive film.

Measurements of double layer capacity as a criterion of efficiency of corrosion inhibition on light metals in sea-water and salt solutions with and without cathodic protection

The differential capacity of AlMg-, AlMn- and AlZn-alloys during corrosion in sea-water, with and without addition of inhibitors, was determined by means of a specially made corrosion cell using an impedance bridge. Observations were made on the surfaces of alloys, with and without protective cathodic polarization immediately after immersion and after being allowed to stand in aerated sea-water, for 1, 10, 100, 300 and 1000 d. The values obtained for the differential capacity are compared to those obtained for the corrosion rate. It was found that decreasing differential capacity, also causes the decrease of the corrosion rate. This effect can be produced either by the addition of the inhibitor or by cathodic protection. The correlation between double layer capacity and the efficiency of inhibitors and cathodic polarization is interpreted as due to the formation of passive layers with adsorbed inhibitors and oxide hydrates. Thus, it has been shown that by measuring differential capacity it is possible to determine the inhibitor efficiency and cathodic prepolarization, as well as the rate of corrosion processes.

Reaction Between Sulfer Compounds and Metal Surfaces at High Temperatures

From the viewpoint that the action of EP additives is a kind of controlled corrosion, the high temperature corrosion of metals in hydrocarbon oils containing sulfur compounds was studied by using the Barcroft method.The corrosion rate of iron was observed to keep the parabolic law, and the reaction between sulfur compounds and metal surfaces could conceivably be controlled by the diffusion of reactants through the formed films on the metal wire surface. With the white oil solutions of dibenzyldisulfide, the rate of corrosion process was made to deviate from the parabolic law and the intensive corrosion was observed. The action of dibenzyldisulfide apparently depends on the characteristics with which the corrosion was associated with the cracking of surface resultant layers.It should be noted that the amount of corrosion observed in white oil alone was almost equivalent to that obtained in the case where the solution containing didodecyldisulfide or diphenyldisulfide was used. According to the data obtained by X-ray analysis of the sulfurized products, the formation of iron oxide and iron sulfide was fairly well detected. The sulfurization reaction, therefore, seems to be accompanied with oxidation reaction at high temperatures.With the corrosion of stainless steel, the corrosion rate was observed to be very slow compared to that of iron, and in the scope of this experiment, there was no promoting action during corrosion, even when dibenzyldisulfide was used.

Processes of Electrochemical Corrosion★

Abstract Theoretical considerations involved in determining the potential of hydrogen and oxygen electrodes are reviewed briefly. Overvoltage is discussed in detail. The various connected stages involved in the process of the passage of ions into solution are outlined. Use is made of the Evans diagram for real processes. In making the study of processes with hydrogen depolarization it was found convenient to use a model of a microelement. A comparison of experimental data obtained with models and from deductions from the Evans diagrams indicates that there was a complete agreement between the theory and experiment for processes with hydrogen depolarization. Considerable attention was given to the factors affecting the rate of oxygen diffusion to the metal in view of the fact that the rate of corrosion processes with oxygen depolarization is determined mostly by the rate of oxygen diffusion toward the metal surface. A model was used to examine the part played by the electrical resistance of a cell with oxygen depolarization. It was found that it was only when the resistance became very large and the potential difference was close to the initial value that the current started to decrease. Experiments showed also that changing the anodic material did not influence the rate of the cathodic process when it was controlled by the rate of oxygen diffusion to the cathode. The theory of microcells is examined in detail and a review made of some of the experimental data for processes with hydrogen depolarization. The influence of alloying elements on corrosion rates of metals in various media is discussed. A number of explanations are offered to show why the regularities observed on models are not applicable to corrosion of microelements. The “difference effect” is discussed in connection with corrosion processes having hydrogen depolarization. Other topics considered include electrochemical cells with differential aeration, corrosion processes in a moisture film, and atmospheric corrosion. Extensive data are reported in 54 figures and 6 tables. 3.6.8

Effect of the temperature factor on the rate of corrosion of metals in electrolytes

1. The effect of temperature on the rate of corrosion processes having different kinds of limitation was studied for model corrosion couples and for a real microcouple-an alloy of zinc with 0.92% of iron. 2. It was shown that the variation of the rare of the corrosion process with change of temperature is determined primarily by the 3. The effect of temperature on the rate of corrosion was studied for different kinds of cathodic controls the rate of discharge of hydrogen ions, the rate of diffusion of oxidizing agent (hydrogen peroxide), and the rate of ionization of oxygen. It was shown that the rate of a corrosion process that is limited by the rate of ionization of oxygen shows the greatest increase with rise in temperature, and the rate of the process limited by the rate of transport of the oxidizing agent shows the least increase.