Simulated Aggressive Environment Research Articles

Experimental investigation on corrosion resistance and tribological properties of steel coated with glass-reinforced polymer

This work presents a comprehensive electrochemical corrosion analysis conducted on steel coated with glass-reinforced polymer (GRP), low alloy steel and stainless steel, focusing on their performance in a simulated aggressive environment (3 % NaCl). The corrosion rates were established and the corrosion mechanisms governing each material's behaviour were elucidated. By comparing the electrochemical behaviour of these materials, we aim to evaluate the efficacy of GRP coatings in preventing corrosion compared to conventional metallic materials used for pipeline systems. Furthermore, in addition to the corrosion analysis, the coefficient of friction determination between the GRP-coated steel and 25CrMo4 (EN 10083-3) steel was conducted to assess their tribological compatibility. Understanding the frictional behaviour between these materials is essential for optimising pipeline performance, minimising wear and ensuring operational efficiency in dynamic environments encountered in the petroleum and gas industry. The study includes, also, an evaluation of cumulative linear wear to quantify the material loss. This comprehensive approach provides a complete understanding of the interplay between corrosion resistance and mechanical durability.

EIS Study of Doped High-Entropy Alloy

The promising results obtained in the research of high-entropy alloys are increasingly encouraging new configurations of these alloys. Our research was conducted on the high-entropy CoCrFeMoNi alloy and the Ti-doped CoCrFeMoNi alloy. Electrochemical impedance spectroscopy (EIS) measurements were performed on samples with and without Ti-doped CoCrFeMoNi high-entropy alloys in order to evaluate the influence of voltage on their behavior in a simulated aggressive environment. The impedance spectra were measured between −1.0 and +0.8 V vs. SCE at various potential levels. Using an electrical equivalent circuit to match the experimental data, the impedance spectra were analyzed. The corresponding circuit that successfully fits the spectra has two time constants: the first one is for the attributes of the compact passive layer and the second one is for the features of the porous passive layer. The results show that doping CoCrFeMoNi alloy with 0.36 at.% Ti reduces the alloy’s ability to resist corrosion, as the alloy can react more quickly to the surrounding environment and cause a decrease in the corrosion resistance of the alloy.

Calcined clay process for durability performance of concrete pipe in simulated semi-arid area in Morocco

This study investigates the durability performance of local clay as a supplementary cementitious material (SCM) incorporated in the concrete pipe for drinking water distribution in the semi-arid region of Morocco. The service life of the buried pipeline is shorter in this environment because of aggressive corrosive soil, and fluctuation of temperature-humidity. The information on evaluating the durability of calcined clay in simulated semi-arid condition is limited. In this study, the effect of calcined clay on the performance of concrete pipe in simulated semi-arid environment has been investigated. Two mixes: a reference mix with Ordinary Portland Cement (OPC) and a mix with Limestone cement 17% calcined clay (LC3) buried in simulated aggressive exposure soils enriched with chloride and sulfate ions under drying wetting cycles were tested by electrochemical impedance spectroscopy. The results improve that the durability of concrete resistance (Rc) and polarization resistance (Rp) of the reinforcing steel embedded in concrete blinded by calcined clay was enhanced by approximately 86% and 96% respectively compared to the OPC reference concrete. Moreover, the compressive strength of the two mixes was approximately the same. Therefore, the concrete incorporated by LC3 as SCM improves sustainable performance in the simulated aggressive environments of semi-arid areas in Morocco. Our results are preliminary, further investigations on several samples are recommended.

Effect of Chemical Aggressive Media on the Flexural Properties of Cured-In-Place Pipes Supported by Microstructure Observation and Acoustic Emission.

The cured-in-place pipe (CIPP) method is currently the most frequently used approach for the renovation of piping without digging; this technology is suitable for pipes made from all types of material. The authors of this paper examined how chemical substances and increased temperature change samples of CIPP with vinyl-ester resin taken from a simulated installation. Changes were observed at several levels: visually via a digital optical microscope, through changes of short-term bending properties and by observation of the activity of the sample structure by means of acoustic emission (AE). Interdependencies among the observed parameters were examined, specifically, the cumulative number of hits (cnt)/deflection and flexural properties/mechanic wave velocity. The test results prove that after three weeks of immersion in a simulated aggressive environment that mirrors what may happen to CIPP in real conditions, short-term mechanical properties change. This is also proven by the results of the AE measurements. For clarity, the results include images from a digital optical microscope. In addition, this paper proves that CIPP samples have good resistance to the action of organic and inorganic acids and to increased temperatures. After three weeks of exposure to a temperature of 100 °C the CIPP flexural properties of the samples had even improved.

RESEARCH OF DYNAMICS OF HYDROGEN SULPHIC CORROSION OF METAL OF CASING UNDER THE LAYER OF MODIFIED CONCRETE

The issue of protection of problem areas of oil well casings, which are operated in aggressive environments of formation fluids of Iraq, containing hydrogen sulfide, carbon dioxide and chlorides, is considered. It is pro-posed to reduce the influence of aggressive factors by using modified cement compositions. The chemical composi-tion of Portland cements and modified compositions based on them was studied, experimental samples of cement stone were obtained and tested in a simulated aggressive environment (80% CO2 and 20% H2S) at a temperature of 105˚ C for 1200 hours. The dynamics of corrosion development in steel 45 under the cement layer is analyzed. It is shown that the rate of crevice corrosion of casing metal (steel 45), protected by modified concrete, obtained on the basis of Port-land cement grade G is much lower (5-6 times) relative to protection by unmodified concrete, and the protective effect of modified cement stone increases over time. It is concluded that the modification has a positive effect on the protective properties of cement stone. In the process of researching new grouting materials having improved anticorrosion properties, optimal for-mulations of the developed compositions were selected, the dependence of the strength characteristics, adhesion and gas permeability of the stone, as well as its anticorrosion properties on the ratio of components in grouting mixtures were studied. The use of new grouting materials with improved inhibitory properties will help to reduce the risks of prema-ture deformation of the deep sections of the casing string as a result of the corrosion destruction of its external surface, as well as improve the quality of formation demarcation in oil and gas wells with aggressive fluids con-taining hydrogen sulfide, carbon dioxide and a significant amount of dissolved in formation water of chloride ions, has practical value. The results of the work have the prospect of practical application for fastening deep wells, including direc-tional ones, in difficult mining and geological conditions on exploration areas and industrial oil fields of Iraq. Keywords: casing string, formation fluids, hydrogen sulfide, carbon dioxide, chlorides, corrosion, Portland cement, grouting materials, protective properties

Alkali-resistant glass fiber reinforced high strength concrete in simulated aggressive environment

The durability of the alkali-resistant (AR) glass fiber reinforced concrete (GFRC) in three simulated aggresive environments, namely tropical climate, cyclic air and seawater and seawater immersion was investigated. Durability examinations include chloride diffusion, gas permeability, X-ray diffraction (XRD) and scanning electron microscopy examination (SEM). The fiber content is in the range of 0.6 % to 2.4 %. Results reveal that the specimen containing highest AR glass fiber content suffered severe strength loss in seawater environment and relatively milder strength loss under cyclic conditions. The permeability property was found to be more inferior with the increase in the fiber content of the concrete. This suggests that the AR glass fiber is not suitable for use as the fiber reinforcement in concrete is exposed to seawater. However, in both the tropical climate and cyclic wetting and drying, the incorporation of AR glass fiber prevents a drastic increase in permeability.

Crack Analysis of Reinforced High Strength Concrete Elements in Simulated Aggressive Environments

Abstract In nowadays social and economic demands of rapid construction and durable behavior of building systems, high strength concrete is the material choice, with both rapid strength development and improved performance to aggressive environments. However, the performance of reinforced high concrete elements differs from that of ordinary concrete elements and the lack of design standards delays the implementation of the high strength concrete in private practice. Moreover, the service life performance, more specific, the durability of high strength concrete elements still remains difficult to assess, especially because of the inherent structural cracks that conduct the aggressive media to the embedded reinforcement, thus causing corrosion and possible failure of the element. The objective of the present study is to investigate the influence of the cracking pattern of reinforced high strength concrete elements exposed to accelerated corrosion on the structural behavior of the elements, with concrete cover of 25 and 50 mm. Witness specimens are used for comparison. The results of the study show that the influence of the reinforcement corrosion is more important on the 25 mm concrete covers, with the development of larger crack widths in lower stages of loading than for elements with 50 mm covers. However, the overall performance of the high strength concrete elements exposed to accelerated corrosion was above the theoretical, standard based, design capacity of structural members.

Corrosion behavior of new ternary zirconium alloys as alternative materials for biomedical applications

The in vitro corrosion behavior of four Zr‐based alloys (Zr97.5Nb1.5VM1.0; VM = valve metal: Ti, Mo, W, Ta; at%) to be used as implant materials has been assessed and compared with that of Grade 2 Ti, which is known to be a highly compatible metal standard. Corrosion resistance was investigated by open circuit potential and electrochemical impedance spectroscopy (EIS) measurements, as a function of exposure time to an artificial physiological environment (Ringer's solution). Open circuit potential values indicated that Zr‐based alloys and Grade 2 Ti undergo spontaneous passivation due to spontaneously formed oxide film passivating the metallic surface, in the simulated aggressive environment. It also indicated that the tendency for the formation of a spontaneous oxide is greater for the Zr97.5Nb1.5Ta1.0 alloy and that this oxide has better corrosion protection characteristics than the ones formed on Grade 2 Ti or on Zr97.5Nb1.5Ti1.0, Zr97.5Nb1.5Mo1.0, and Zr97.5Nb1.5W1.0 alloys. EIS study showed high impedance values for all samples, increasing with exposure time, indicating an improvement in corrosion resistance of the spontaneous oxide film. The fit obtained suggests a single passive film present on the metals surface, improving their resistance with exposure time, presenting the highest values to the Zr97.5Nb1.5Ta1.0 alloy. All these electrochemical results suggest that Zr97.5Nb1.5VM1.0 alloys are promising materials for osteo‐synthesis prosthetic devices, since corrosion stability is directly associated with biocompatibility and is a necessary condition for applying a material as biomaterial.

Colmenar Limestone, Madrid, Spain: considerations for its nomination as a Global Heritage Stone Resource due to its long term durability

Abstract Colmenar Limestone is one of the traditional materials most commonly used in monuments in Madrid, Spain. The petrophysical properties of this stone determine its high resistance to decay. Its low water absorption and pore size distribution favour good hydraulic behaviour, which is likewise furthered by its high ultrasound velocity and low anisotropy. The durability findings pursuant to the 280 freeze–thaw, 42 thermal shock, 30 salt crystallization and 120 salt mist cycles conducted confirmed the stone's resistance to decay in these simulated aggressive environments. The mass loss recorded in the samples and the variation in petrophysical parameters were generally very low after all except the salt crystallization trials, which induced loss of cohesion on the stone surface, increased roughness and the formation of concentric microcracks, sub-parallel to the more exposed surface, that also affected the arris and vertices of the specimens tested.

Flexural strength and impact resistance study of fibre reinforced concrete in simulated aggressive environment

In addition to being exposed to chloride and sulphate attacks, marine structures are subject to seismic and impact loads resulting from waves, impact with solid objects, and water transports. Therefore, the flexural behaviour and impact resistance of Fibre-Reinforced Concrete (FRC) in marine environment must be elucidated. However, such information is scarcely reported. Therefore, this study aims to explore the effects of simulated aggressive environments on flexural strength and impact resistance of FRC and to identify the relationship between the two parameters. Three types of fibres, namely, coconut fibre, Barchip fibre (BF), and alkali-resistant glass fibre, were used in this study. The fibre dosage ranged from 0.6% to 2.4% of the binder volume. All mixes have constant water/binder ratio of 0.37 and their compressive strengths were all exceeding 60MPa. The specimens were prepared and exposed to three different aggressive exposure environments, namely, tropical climate, cyclic air and seawater conditions, and seawater environment for up to 180days. Results indicate that flexural strength and impact resistance of FRC have a direct relationship with fibre content. Nonetheless, change in fibre type is more significant than increasing fibre dosage in enhancing flexural strength but alteration in both matters would significantly impact the impact resistance. Tensile strength of an individual BF (640MPa) is much higher than the flexural strength of the BFRC composite. Thus, failure of concrete matrix was observed to occur prior to the rupture of the fibre which in turn resulted in fibre pull out from the concrete matrix. Among the various FRC examined, FRC containing the highest BF content (2.4%) demonstrated the best flexural strength performance. The flexural strength of the Barchip FRC was observed to be increased by 11–13% in all exposure environments after 180days. The pre-crack energy absorptions, which were determined through impact load test were found to increase by 60–63% as compared to the control concrete, which exhibited no post-crack energy absorption. Meanwhile, the post-crack energy absorptions of the 2.4BF were found to range between 3.67J and 3.71J for various environmental exposure conditions. Analysis of variance (ANOVA) results showed that flexural strengths were significantly increased after six months of exposure to the various aggressive environment conditions, especially in seawater. This could be due to formation of salt crystals which contributed towards enhancing the fibre/matrix frictional bond. However, the exposure environments have no significant effect on impact resistance performance. A logarithmic relationship was found between flexural strength and total impact energy absorption.

A Comparative Evaluation between New Ternary Zirconium Alloys as Alternative Metals for Orthopedic and Dental Prosthetic Devices

We assessed in vitro the corrosion behavior and biocompatibility of four Zr-based alloys (Zr97.5 Nb1.5VM1.0 ; VM, valve metal: Ti, Mo, W, Ta; at%) to be used as implant materials, comparing the results with grade-2 titanium, a biocompatible metal standard. Corrosion resistance was investigated by open circuit potential and electrochemical impedance spectroscopy measurements as a function of exposure time to an artificial physiological environment (Ringer's solution). Human bone marrow stromal cells were used to evaluate biocompatibility of the alloys and their influence on growth kinetics and cell osteogenic differentiation through histochemical and gene expression analyses. Open circuit potential values indicated that Zr-based alloys and grade-2 Ti undergo spontaneous passivation in the simulated aggressive environment. High impedance values for all samples demonstrated improved corrosion resistance of the oxide film, with the best protection characteristics displayed by Zr97.5 Nb1.5Ta1.0. Cells seeded on all surfaces showed the same growth kinetics, although matrix mineralization and alkaline phosphatase activity were maximal on Zr97.5 Nb1.5Mo1.0 and Zr97.5 Nb1.5Ta1.0. Markers of ongoing proliferation, however, such as podocalyxin and CD49f, were still overexpressed on Zr97.5 Nb1.5 Mo1.0 even upon osteoinduction. No relevant effects were noted for the CD146-expressing population of bone progenitors. Nonetheless, the presence of a more differentiated cell population on Zr97.5Nb1.5Ta1.0 samples was inferable by comparing mineralization data and transcript levels of osteogenic markers (osteocalcin, osteopontin, bone sialoprotein, and RUNX2). The combination of passivation, corrosion resistance and satisfactory biotolerance to bone progenitors make the Zr-based alloys promising implant materials. Among those we tested, Zr97.5Nb1.5Ta1.0 seems to be the most appealing.

The anticorrosive performance of zinc-free non-toxic pigment for paints

The objective of this research was to study the efficiency of calcium aluminium phosphosilicate hydrate (PSh), as anticorrosive pigment for paints in simulated aggressive environments. This compound is zinc-free and the phosphate content is less than 30% by weight. Alkyd and epoxy paints, of the solvent-borne type, containing 30% by volume (v/v) of the pigment, were formulated. The pigment volume concentration was fixed at 42.3%. Standardised accelerated salt spray exposure and electrochemical tests were used to assess the protective performance of the coatings. Analysis and interpretation of the experimental data showed that PSh inhibits corrosion of painted steel panels exposed to aggressive environments. Zinc phosphate (ZP), a traditional anticorrosive pigment, was used as reference in all the essays.

Galvanic Corrosion of Carbon and Steel in Aggressive Environments

The demand for the use of carbon-fiber-reinforced plastics (CFRP) in rehabilitation of deteriorating infrastructure is increasing worldwide. The design characteristics of reinforced concrete or steel members can be enhanced significantly by epoxy bonding CFRP laminates to the critically stressed tension areas. There is, however, a concern regarding possible galvanic corrosion when carbon and steel are bonded together. This paper presents the result of a study on the galvanic corrosion between CFRP laminates and steel. A total of 38 specimens made of steel and carbon fibers were prepared and tested. Two simulated aggressive environments and three different amounts of epoxy coating were used in addition to samples with no coating at all. Furthermore, the effect of the sizing agent on the galvanic corrosion rate was investigated, and three different solvents were used to remove the sizing agents from the surface of the carbon fibers. Potentiodynamic polarization and galvanic corrosion tests were conducted. T...