Absence Of Corrosion Research Articles

Preparation and properties of double-layer phenolic/polyurethane coated isophorone diisocyanate self-healing microcapsules

Single-layer isophorone diisocyanate (IPDI) are one of the most popular self-healing microcapsules but suffers from low shell strength, poor heat resistance, stability and aging properties. In this paper, IPDI microcapsules were encapsulated into double-layer phenolic (PF)/polyurethane (PU) by a two-step process involving interfacial polymerization and in-situ polymerization. The prepared microcapsule composites were comprehensively characterized for their physical and chemical properties using optical microanalysis, scanning electron microscope, Fourier transform infrared spectroscopy, thermal gravimetric analysis and depth-sensing indentation analysis. Compared with the single-layer PU-IPDI microcapsule counterpart, the mechanical performance, thermal resistance, aging property and environmental stability of double-layer PF/PU-IPDI microcapsules were significantly improved. The epoxy coating was enhanced with the incorporation of 10 wt.% PF/PU-IPDI microcapsules, whose self-healing performance was evaluated by scratch corrosion test. The results demonstrated successful repair of coating scratches, along with the absence of corrosion on the coated steel substrate soaked in a 10 wt.% NaCl solution for 7 days. By comparing the tensile strength of epoxy coating before and after crack formation, it could be found that the self-healing efficiency was 57.9% when loaded with 10 wt.% of PF/PU-IPDI microcapsules in coating. This study highlights that the rational design of double-layer microcapsules integrated into the epoxy coating matrix could provide excellent anti-corrosion and self-healing properties.

Evaluating the Relation of Cave Passage Formation to Stress-Field: Spatio-Temporal Correlation of Speleogenesis with Active Tectonics in Asprorema Cave (Mt. Pinovo, Greece)

Caves serve as time capsules, preserving significant markers of tectonic activity and offering insights into geological history. Fault geometries and past activations found in caves can be correlated with known deformational events in the broader area, temporally delimiting the speleogenesis. More specifically, cave passage formation is suggested to be affected by the regional stress-field. The Asprorema Cave in Northern Greece is a typical example of a fracture guided cave, with passage geometry influenced by relative sidewall movements, revealing these discontinuities as faults. This study constructs the timeframe and conceptual model of speleogenesis in relation to tectonic events, geomorphological evolution and hydrological zones, and verifies its relation to the stress-field. Active tectonics, mineralogy and cave geomorphology are investigated. Results suggest syntectonic speleogenesis under phreatic and epiphreatic conditions. The absence of corrosion on fault slip surfaces implies recent activations post cave’s shift to the vadose zone. Structural analysis identifies three main neotectonic phases: NNW-SSE striking faults (oldest group of structures), NE-SW striking faults with dextral strike-slip movement (post-middle Miocene), and NE-SW striking normal faults indicating extensional stress-regime (Quartenary). The last two phases affect cave passage shape causing wall displacement, highlighting passage formation along discontinuities perpendicular to the horizontal minimum stress axis.

EVALUATION OF THE MAGNETIC PROPERTIES OF Ag-Au-Pd-Cu DENTAL ALLOYS

The paper discusses four Ag-Au-Pd-Cu dental alloys, with different chemical compositions, which are used to produce fixed dental-prosthetic structures. These dental alloys must have a low level of biological risk after being implanted in the oral cavity, which means minimal release of ions from their surface, or the absence of corrosion, and, recently, the absence of ferromagnetism has been introduced as an additional requirement. The latter requirement is particularly important when magnetic resonance (MR) is used in the medical diagnosis of a patient who has an implanted fixed dental-prosthetic structure. With this technique, the internal structure of the human body is imaged using a strong magnetic field, radio waves and computer technology. Therefore, the absence of ferromagnetic, embedded biomaterials is necessary in the part of the body where medical diagnostics are performed. Microstructural investigations of four Ag-Au-Pd-Cu dental alloys (Auropal S, Auropal SE, Midor S and Midor SE) and measurements of their magnetic properties were carried out as part of the research. The results showed that Ag-Au-Pd-Cu dental alloys have a stable microstructure, which allows them to be processed later into fixed prosthetic constructions. The measurements of the magnetic properties showed that the Ag-Au-Pd-Cu dental alloys are diamagnetic.

Потенціал в області мікронерівностей поверхні металу, який працює в режимі катодного захисту

This effort presents the results of investigation of cathodic protection process of a section of the main pipeline, which has been operating in cathodic protection mode for a long time and which insulation has completely exfoliated from metal surface, and a cavity between is filled with water and salt impurities. In this case, a decisive factor is a fact that a metal surface is covered with microroughnesses in the form of protrusions with almost conical shape. The surface is immersed in electrolyte. At the electrolyte-metal interface, a potential difference is formed - a corrosion potential, which creates an unstable equilibrium among the potentials of metal and electrolyte. A mathematical model is designed and implemented into a numerical algorithm and computer program. A computational experiment has been carried out to calculate the potential around microroughness. The model describes a change in potential in this area at incomplete and complete cathodic protection of metal surface. The basis of computational model is a selection of one of metal protrusions of material microheterogeneity and placing it in a cylinder, which diameter coincides with that one of the lower base of this protrusion, and its upper part passes through the apex of the protrusion. Mathematical model equations with corresponding boundary conditions and their discrete implementation are presented. The solution of problems is obtained by iterative procedures based on reference values of protective potential taken from practice. The results of computational experiment are presented in the form of graphs: 1) potential distribution in the field of electrolytes; 2) changes in electrolyte potential at the border with protrusion at different values of polarization potential; 3) changes in polarization resistance in the area (calculated). The geometry of computational domain was also varied, and the values of protective potential were determined to ensure the absence of corrosion. Keywords: corrosion, microroughness, protective potential, plastic current density, electrolyte

The Device for Houseplants Caring

The article is devoted to the development of an automated device for plant care at home. The main factors influencing plant development are considered. A comparative analysis of existing devices was made. The growth of plants is influenced by many factors: the level of light, soil moisture, room temperature, carbon dioxide level. When plants are growing indoors, the most important thing is timely watering and access to light. The required amount of light for most plants is 12-18 hours per day. Our country is in the temperate climate zone, so we have 15 hours of light in summer, 13 hours in autumn and spring, and 9 hours in winter. The amount of light in summer is normal, in autumn and spring - within normal limits, but in winter there is a certain lack of light. The lack of natural insolation in winter leads to light starvation of houseplants and reduced intensity of photosynthesis. Therefore, the decrease of the amount of natural light is compensated by artificial light sources. Analysis of the devices on the market has shown that devices that can solve such problems exist, but there is no device with all functions simultaneously. Lighting devices illuminate on a timer, regardless of natural light. Irrigation devices are intended for industrial, not for domestic use. Existing technological solutions for home cultivation have only a warning function: sound or light, which can bring some inconvenience. Looking on these problems, a device is created to maintain the required soil moisture and the required amount of light. The control unit is based on a microcontroller that analyses the data obtained from the sensors and sends the appropriate signals to the climate control devices. The device is equipped with a soil moisture sensor, a light sensor, a real - time sensor, an LED lamp, a water pump, an LED lamp driver, and a control key of water pump. To control soil moisture, a capacitive humidity sensor is used, the advantages of it is the absence of corrosion of metal parts of the sensors that touch the ground. A light meter based on the BH1750 chip is used as a light sensor. This sensor has a wide measuring range, measuring accuracy - 1 lux, small dimensions and the ability to connect to a microcontroller via I2C interface. The DS3231 chip is used as a real-time clock that required to maintain a circadian rhythm close to the natural one for a given plant. An LED strip with red and blue LEDs is used for lighting. The ratio of blue / red LEDs depends on the stage of growth and the type of plant, but it is usually from 1/3 to 1/5. The key that controls the LED strip and the water pump are the MOS transistors. They are silent and allow you to adjust the brightness of the LED strip.

A simplified index to quantify the irritation/corrosion potential of chemicals – Part II: Eye

Eye irritation is a key human health endpoint assessed by in vitro and in vivo methods. One of the commonly used scoring methods to quantify the eye irritation potential of chemicals is the Modified Maximum Average Score (MMAS). It is dependent on the eye irritation effects (e.g. corneal opacity) originally proposed by Draize and then partially adopted by the OECD TG 405. These scores are not always fully reported in regulatory dossiers and lead to several drawbacks, 1) the difficulty to translate MMAS into a classification within the existing EU CLP/UN GHS criteria, 2) the absence of corrosion (serious eye damage), and 3) the dependency on input parameters which are usually not required under the OECD TGs (e.g. eye surface area). This study determined if classification can be driven by a maximum of two observed effects thereby simplifying the scoring calculation. The Simplified Irritation Index (SIIEYE), based only on corneal opacity and conjunctival redness, was developed using validated studies representing multiple chemical groups. A correlation was observed between the MMAS and the SIIEYE allowing harmonisation of the classification for the existing data. This index proved to be useful in the development of in silico model.

Wear-Corrosion Synergy on Din-16MnCr5 Steel Under Nitriding and Post-Oxidizing Treatments

New results about the wear-corrosion synergy behavior of nitrided DIN-16MnCr5 steel immersed in a saline solution were obtained in this work. Tribocorrosion tests were performed on three different samples under ball-on-flat configuration: nitriding, nitriding plus post-oxidation, and untreated material using electrochemical polarization with an open-circuit potential in a 5% NaCl solution. The sliding wear tests in the presence and absence of corrosion were developed under 20 N of normal load, 2.5 mm of stroke length, 10 mm/s of speed, 100 m of total sliding distance, and Al2O3 balls of O = 4.8 mm that were used as a counterpart according to the ASTM G119 standard procedure. The results showed that the presence of a magnetite phase (Fe3O4) at the surface of the nitrided plus post-oxidation on DIN-16MnCr5 steel increased the wear-corrosion synergy around ~ 5 times with respect to the untreated samples, which provides a potential solution to reduce the degradation impact in mechanical components for navy military industry applications. However, the wear-corrosion synergy (T) contribution to volume removal is higher than wear-corrosion (∆WC) by itself and also than the contribution of corrosion due to wear (∆CW).

SERVICE BEHAVIOUR OF THE SELF-STRESSED MEMBERS REINFORCED WITH FRP BARS

Fiber reinforced polymer (FRP) bars, as a structural reinforcement, are characterized by the number of advantages, such as: high strength-to-density ratio; absence of corrosion; resistance to the negative influence of the different aggressive mediums. Nevertheless, a wide practical application of such a bars finds an embarrassment because of the law modulus of elasticity (it varies from 30 GPa to 60 GPa), that leads to the development of the excessive crack opening as well as deflections under the loading. To enhance structural performance of the FRP reinforced concrete members, pretensioning of FRP bars can be considered as a good option. Opposite to the concrete members mechanical pretensioning, physico-chemical method of bars pretensioning based on the self-stressing concrete utilizing is considered. Influence of the controlled initial stress-strain state obtained during early age concrete expansion on the mechanical resistance of the self-stressed concrete members reinforced with both steel and FRP bars was studied.

Tribocorrosion of DIN 16MnCr5 Steel Modified by Carburization and Manganese Phosphate Coating

In this study, the wear–corrosion synergy of DIN 16MnCr5 steel on samples treated by carburization coating, carburized with manganese phosphate coating, and untreated material were evaluated to select the coating with better mechanical and chemical properties for navy military applications. Initially, thermochemical treatments were carried out to obtain thickness coatings of ~ 50 and ~ 70 microns, respectively. The tribocorrosion test for treated and untreated samples was performed in a 5% NaCl solution, and then open circuit potential and wear loss were calculated using a ball-on-flat configuration according to the ASTM G119-09 standard procedure. The sliding wear test, in the presence or absence of corrosion, was performed with a normal force of 20 N, a distance of 100 m and a sliding speed of 10 mm/s; a counterpart of alumina (ball 4.8 mm of diameter) was used for this purpose. The results showed that the coating carburized with manganese phosphate increased ~ 3.8 times the synergistic effect than that of the untreated material, with the presence of a wear–corrosion regime and degradation mechanism in contrast to a wear-dominated regime for the untreated material.

Recent advances in structural fibre-reinforced concrete focused on polyolefin-based macro-synthetic fibres

Fibre-reinforced concrete (FRC) allows reduction in, or substitution of, steel-bars to reinforce concrete and led to the commonly named structural FRC, with steel fibres being the most widespread. Macro-polymer fibres are an alternative to steel fibres, being the main benefits: chemical stability and lower weight for analogous residual strengths of polyolefin-fibre-reinforced concrete (PFRC). Furthermore, polyolefin fibres offer additional advantages such as safe-handling, low pump-wear, light weight in transport and storage, and an absence of corrosion. Other studies have also revealed environmental benefits. After 30 years of research and practice, there remains a need to review the opportunities that such a type of fibre may provide for structural FRC. This study seeks to show the advances and future challenges of use of these polyolefin fibres and summarise the main properties obtained in both fresh and hardened states of PFRC, focussing on the residual strengths obtained from flexural tensile tests.

New material for anti-wear corrosion-resistant coating of agro industrial complex machinery parts

The article presents the results of an experimental study of the corrosion resistance of the ta-C double coating of parts by PVD method with intermediate and final surface polishing with a discrete tool. The influence of regime factors on the results of polishing the ta-C coating with a discrete tool is shown, and optimal processing modes are proposed. Tests of samples in a salt bath showed that the double ta-C coating by PVD method with intermediate and final polishing ensures the absence of corrosion and coating peeling

Influence of the initial prestressing on the crack resistance of the self-stressed members reinforced with steel and FRP bars

Fiber reinforced polymer(FRP) bars are widely utilized in the civil engineering practice and characterized by the number of advantages, among them are the following: high strength-to-density ratio; absence of corrosion; resistance to the negative influence of the different aggressive mediums. Nevertheless, a wide practical application of such a bars finds an embarrassment because of the law modulus of elasticity (in the diapason from 30 GPa to 60 GPa), that in its turn lead to the development of the excessive crack opening as well as deflections under the loading. To enhance structural performance of the FRP reinforced concrete members, pretensioning of FRP bars can be considered as a good option. Opposite to the concrete members mechanical pretensioning, physico-chemical method of bars pretensioning based on the self-stressing concrete utilizing is considered. Influence of the controlled initial stress-strain state obtained during early age concrete expansion on the mechanical resistance of the self-stressed concrete members reinforced with both steel and FRP bars was studied. Comparison of the prestressing effectiveness of the self-stressing concrete members with steel and FRP bars was performed. Proposition for effective utilizing of the FRP bars in the self-stressed concrete members was formulated based on results of the presented investigation.

Tribocorrosion and cytotoxicity of FeB-Fe2B layers on AISI 316 L steel

New results about the tribocorrosion resistance and cytotoxicity of FeB-Fe2B layer developed by the powder-pack boriding process on the surface of AISI 316 L steel are presented in this work. Initially, the tribocorrosion tests in the borided AISI 316 L steel and the untreated material (AISI 316 L steel) were performed in Hank's solution, using a ball-on-flat configuration, which was connected with a three electrode-chemical cell. The sliding tests, in the presence or absence of corrosion, were performed under 20N normal force using an alumina ball as a counter body. For the overall experimental conditions, the material loss for each material was estimated according to the ASTM G119 procedure. Further, the in vitro cytocompatibility of FeB-Fe2B layer on AISI 316 L steel and the untreated material was evaluated by the indirect contact method, in which cell lines of immortalized human fibroblast (CHON-002) and normal renal epithelium of Cercopithecus aethiops (Vero) were used.The results showed that the presence of FeB-Fe2B layer on the AISI 316 L steel improves the tribocorrosion resistance 1.5 times than that of the untreated material, with a presence of a wear-corrosion degradation mechanism in contrast with a wear-dominated regime for the untreated material. Finally, the cytotoxicity tests revealed satisfactory properties in terms of effects on survival and proliferative activity of human fibroblasts and Vero cells on the surface of the borided AISI 316 L steel.

Performance Comparison of a Vapor-Adsorption Cycle-Based Gas Turbine Inlet Air Cooling System for Different Refrigerants

Presently, to enhance the thermal efficiency of a gas turbine power plant, turbine inlet air cooling (TIAC) is the widely used technique. The conventional refrigeration methods like vapor compression refrigeration and evaporative cooling need electric power, hence absorption and adsorption refrigeration systems are attractive options as they can be powered using the waste heat energy of the exhaust gases. Adsorption system has advantages over absorption system like scalability, requirement of lower heat source temperature, absence of corrosion and crystallization. This paper focuses on the thermodynamic analysis of waste heat powered adsorption chiller used for the cooling of intake air to enhance the net power output of the gas turbine power plant. This paper also presents a comparative analysis of the vapor-adsorption cycle-based TIAC system for four different refrigerants viz. HFC-134a, carbon dioxide, ethanol and ammonia with the motive of finding a substitute refrigerant for HFC-134a which has a high global warming potential (GWP). The adsorption chiller is mathematically modeled in MATLAB with activated carbon as the adsorbent and each one of carbon dioxide, ethanol and ammonia as the adsorbate. The variation of the coefficient of performance (COP) and specific cooling effect (SCE) with varying adsorption temperatures is presented for each pair. The net power output and primary energy rate (PER) improvement of the gas turbine power plant at different ambient temperatures are also discussed. It is observed that ammonia can improve the power plant performance significantly better compared to the other three refrigerants at ambient temperatures less than 40[Formula: see text]C.

Stub resonators for online monitoring early stages of corrosion

Here we demonstrate the proof-of-principle of a new type of sensor to assess effects due to corrosion of metal surfaces. The method can be applied to all situations where metals are exposed to a corrosive (fluidic) environment, including, for instance, the interior of pipes and tubes. The sensing device is based on the operating principle of a quarter wave length open-ended stub resonator. In the absence of corrosion, inner and outer conductors of the resonator are separated by a single dielectric, i.e., a fluid. Oxidation of the metal surface of inner and/or outer conductor changes the properties of the dielectric between inner and outer conductor because it introduces a dielectric permittivity that differs from that of the fluid. Additionally, corrosion affects the skin effect and the effective resistance of the corroding inner and outer conductors of the stub resonator. As a result the recorded amplitude-frequency (AF) plot shows a shift of the resonance frequency and/or a change of shape of the resonance peak(s). The two types of transmission line designs explored are coaxial and coplanar stripline (CPS). Irrespective the design, the method outlined here offers an equipment-undemanding, low maintenance and cost-efficient in-line early warning system to detect (the onset of) corrosion. The additional advantage of the system is the freedom of design as for its geometry, from coax to one embedded in printed circuit boards, both designs with hardly any constraints on the particular dimensions. Depending on the precise geometry, the sensor may be able to detect corrosion in tap water after just 1h. Experimental data (recorded after four days) are in close agreement with simulation data representing a 17μm homogeneous oxide layer.

On an Inverse Problem that Models the Detection of Corrosion in Metallic Plate whose Lower Part is Embedded

Abstract In this work, we will study an inverse problem to determine the corrosion in an inaccessible location of a metallic plate. Our study area is inside a metallic plate whose lower part is embedded, therefore inaccessible. We will perform measurements on the upper part of the plate, which is not in contact with the ground. For this, we will send an electric field on this part, and take measurements. This problem is modeled by a mixed Laplace problem with presence of an unknown term in the boundary conditions; this term is an unknown function which can take several forms. This function detects the presence or absence of corrosion inside the plate. For this, we make electrical measurements on different parts of the plate on different time intervals, this gives us information about detection and evolution of the corrosion on this part of the plate. We will first formulate our problem which is an inverse problem, and we will make a theoretical study. We will show that this problem has a unique solution, also this solution is stable. After, we will solve this problem by constructing an iterative algorithm which gives a series of cross problems which give the approximate values of impedance functions, which determine the rate of corrosion. Finally we study the convergence and make a numerical application.

Occurrence of sulphate reducing bacteria (SRB) associated with biocorrosion on metallic surfaces in a hydroelectric power station in Ibirama (SC) - Brazil

The aim of this study was evaluate, two methods for the detection and identification of sulphate reducing bacteria (SRB): ML medium and PCR with specific primers for SRB groups. SRB were detected through the selective medium only on carbon steel, which showed corrosion. Employing specific PCR primer, SBR were detected from all the metallic components assayed, even those that did not present visible corrosion spots, such stainless steel and copper alloys. Despite the presence or absence of corrosion at the later stages effectively by using the selective medium,, the initial stages of the corrosion could only be detected by the amplification of total DNA with SRB specific primers. The early detection of SRB could be employed for preventing the damages on metal surfaces before the installation of corrosion processes. Strategies for reducing the time spent on SRB isolation and identification could be auxiliary tools for controlling the corrosion of materials.

Reinforcement corrosion in alkaline chloride media with reduced oxygen concentrations

It is commonly considered that the corrosion of steel in concrete is controlled by the oxygen content of the pore solution and there are service life models that relate the corrosion rate to the amount of oxygen. It is also commonly believed that in water saturated conditions the oxygen content in the pores is negligible and that underwater there is no risk of depassivation and the corrosion rate is very low. However, the available data on corrosion rates in immersed conditions do not indicate such performance; on the contrary corrosion develops when sufficient chloride reaches the reinforcement. In the present paper, results are presented for tests performed in alkaline chloride solutions that were purged with nitrogen to reduce the oxygen content. The results indicate that at very low oxygen concentrations, corrosion may develop in the presence of chlorides. The presence or absence of corrosion is influenced by the amount of chloride, the corrosion potential and the steel surface condition.

Wear-Corrosion Synergism in a CoCrMo Hip Bearing Alloy Is Influenced by Proteins

Although numerous in vitro studies report on the tribological performance of and, separately, on the corrosion properties of cobalt-based alloys in metal-on-metal (MoM) bearings, the few studies that take into account the synergistic interaction of wear and corrosion (tribocorrosion) have used canonical tribo-test methods. We therefore developed synergistic study using a test method that more closely simulates hip bearing conditions. (1) Is the total material loss during tribocorrosion larger than the sum of its components generated during isolated mechanical wear and isolated corrosion? (2) How is the tribocorrosive process affected by the presence of protein? High carbon CoCrMo alloy discs (18) were subjected to corrosion and tribocorrosion tests under potentiostatic conditions in an apparatus simulating hip contact conditions. The input variables were the applied potential and the protein content of the electrolyte (NaCl solution versus bovine serum, 30 g/L protein). The output variables were mass loss resulting from wear in the absence of corrosion, mass loss resulting from corrosion in the absence of wear, and the total mass loss under tribocorrosion, from which the additional mass loss resulting from the combined action of wear and corrosion, or synergism, was determined in the presence and absence of protein. The degradation mechanisms were sensitive to the interaction of wear and corrosion. The synergistic component (64 μg) in the presence of protein amounted to 34% of total material loss (187 μg). The presence of protein led to a 23% decrease in the total mass loss and to a considerable reduction in the mean current (4 μA to 0.05 μA) under tribocorrosion. Synergistic effects during tribocorrosion may account for a considerable portion of MoM degradation and are affected by proteins. The in vivo performance of some large-diameter MoM joints is unsatisfactory. The synergistic component resulting from tribocorrosion may have been missed in conventional preclinical wear tests.

Failure analysis of the fractured wires in sternal perichronal loops

We report failure analysis of sternal wires in two cases in which a perichronal fixation technique was used to close the sternotomy. Various characteristics of the retrieved wires were compared to those of unused wires of the same grade and same manufacturer and with surgical wire specifications. In both cases, wire fracture was un-branched and transgranular and proceeded by a high cycle fatigue process, apparently in the absence of corrosion. However, stress anlysis indicates that the effective stress produced during strong coughing is lower than the yield strength. Our findings suggest that in order to reduce the risk for sternal dehiscence, the diameter of the wire used should be increased.