Corrosion In Aggressive Environments Research Articles

Enhanced corrosion protection of copper in saline environments using bio-nanocomposite coatings based on chitosan and chitosan Schiff base

An in-depth study focuses on developing new environmentally friendly bio-nanocomposites, by incorporating SrTiO3 (STO) ceramic nanoparticles into matrices of chitosan and its derivatives, aiming to use them as protective coatings against corrosion. The various stages of this study include the cross-linking of chitosan, the synthesis of Schiff base chitosan, the cross-linking of Schiff base chitosan, and the preparation of nanocomposite coatings. The coatings' structure and composition were analyzed using different methods, including Fourier Transform Infrared Spectroscopy - Attenuated Total Reflectance (FTIR-ATR), X-ray Diffraction (XRD), Transmission Electron Microscopy coupled with Energy Dispersive X-ray Spectroscopy (TEM-EDX), and Scanning Electron Microscopy (SEM). In addition, Electrochemical Impedance Spectroscopy (EIS) and Potentiodynamic Polarization (PDP) measurements were carried out to assess the inhibitory efficacy of chitosan crosslinked with epichlorohydrin (Cs-Ep), epichlorohydrin-crosslinked chitosan-salicylaldehyde Schiff base (CS-S-Ep) and CS-Ep-STO and CS-S-Ep-STO nanocomposite coatings, as well as the long-term protection durability of CS-S-Ep-STO. These techniques revealed a significant reduction in corrosion current density after chemical modification of chitosan and incorporation of SrTiO3 (STO) nanoparticles into CS-Ep and CS-S-Ep matrices, confirming a notable improvement in the inhibitory efficiency of these coatings against copper corrosion in a saline environment. Computational modeling methods like Density Functional Theory (DFT), Molecular Dynamics (MD), and Monte Carlo (MC) simulations reinforced these results by demonstrating efficient adsorption of CS-S-Ep-STO nanocomposites on metal surfaces through the interaction with heteroatoms present in the functional groups (-C=N-, -C-O-, -OH) and STO nanoparticles. The present study's findings provide key information for developing innovative protective coatings, highlighting the potential of chitosan-based nanocomposites and derivatives, particularly with SrTiO3 incorporation, in mitigating metal surface corrosion in aggressive environments.

Impact of steel properties on the susceptibility to corrosion of weld mesh and mesh straps

Reinforcement and surface support are part of an integrated system that transfers and shares load until the excavation surface is stabilized or until the ground support system fails. Steel mesh is the most popular primary surface support element in underground hard rock mines in Canada. Mesh straps are a secondary surface support that provide additional containment as they distribute the load between and across the reinforcement elements. This investigation addresses the role of steel properties, and in particular steel chemistry, in the long-term performance of mesh and mesh straps when exposed to an aggressive corrosive environment. It reports on comparative accelerated corrosion studies to compare the resistance to corrosion of different surface support elements. This has significant implications on the choice of surface support and the anticipated rehabilitation requirements.

INNOVATIVE INSULATING MATERIAL IN THE ASPECT OF ENSURING THE SAFETY OF HYDROCARBON TRANSPORTATION

Ensuring continuous and safe operation of the main oil and gas pipelines is a critical aspect for preserving the environment and efficient use of hydrocarbon resources. More than half of accidents on trunk gas pipelines occur due to corrosion wear of the metal caused by insufficient protection of the insulation coating. The consequences of such incidents have a devastating impact on the environment and human lives: spilled oil and oil products pollute the soil, and leaking gas can lead to explosions and forest fires.Corrosion processes hiding under the coating due to poor adhesion and due to non-fulfillment of their functions by the coating lead to increased peeling of insulation and the formation of new corrosion foci, including stress-corrosion processes. Consequently, imperfect insulation coating and insufficient adhesion to metal are one of the main causes of accidents on main pipelines.The purpose of this work was to study and prove the chemical interaction of the functional groups of asmol insulation compositions with the metal surface. In the course of work, the following tasks were solved:- assessment of the ratio of initial adhesion parameters obtained in laboratory and route conditions and their values after 1.5 and 6 years of operation;- study of the IR spectrum in order to prove the presence of functional groups in the asmol material;- study of the protective capacity of the asmol coating structure in an aggressive corrosive environment at different temperatures.Methods were used to measure the quantitative adhesion of the anti-corrosion coating and the peel area during cathode polarization, in accordance with State Standard R 51164-98. The composition of the asmol material was studied by IR spectroscopy.It has been shown that functional groups, the presence of which has been confirmed by spectral analysis, of asmol material in the insulation coating make it possible to chemically adhere to steel. Indirect proof of this is the stability of the adhesion strength over time, the cohesive separation of the asmol coating in determining adhesion indicators under trace conditions and the relatively small area of coating detachment during cathode polarization.

In vitro corrosion-fatigue behaviour of rare-earth containing magnesium WE43 in sterile complex cell culture medium

Rare-earth containing magnesium alloys are promising biomedical materials for a new generation of biodegradable orthopaedic implant systems due to their excellent biocompatibility, mechanical and biodegradation properties. However, chemo-mechanical interactions in aggressive physiological corrosion environments result in rapid degradation and early loss of mechanical integrity, limiting its broader application for orthopaedic implants. To date, only few studies have assessed the corrosion-fatigue behaviour of medical-grade magnesium alloys in an organic physiological corrosion environment, especially under sterile test conditions. In the present work, the corrosion-fatigue behaviour of fine-grained medical-grade magnesium alloy WE43MEO was systematically analysed under in vitro conditions using an organic physiological fluid DMEM. The experimental results showed that the fatigue strength of the alloy is nearly unaffected by a 1-day precorrosion, while a 7-day precorrosion resulted in a significant deterioration of mechanical integrity. In corrosion-fatigue experiments, the fatigue life was considerably reduced by interactions between corrosion and fatigue damages. The SEM analysis revealed that the mixed mode of intergranular and transgranular fracture in the crack propagation zone transits to intergranular cracking dominant mode under the corrosion-fatigue conditions due to hydrogen embrittlement.

INVESTIGATION OF STRUCTURAL AND MECHANICAL PROPERTIES OF TUBING STEELS

The study of the structural and mechanical properties of tubing steels used in wells at oil and gas condensate fields is of particular interest due to the resource intensity of these systems and the high cost of their repair and restoration. Tubing is operated under conditions of increased loads under the influence of its own weight, internal pressure and constant contact with highly aggressive media. As a result of simultaneous exposure to corrosive media and operational loads, tubing is the most consumable downhole material. The destruction and, as a result, the breakage of the tubing suspension occurs as a result of mechanical abrasion and cracking of the pipe body, the development of fatigue cracks in the thread, etc. Contact with aggressive agents of the extracted fluid and reservoir waters leads to various types of corrosion damage: ulcerative, pitting, corrosion fatigue, corrosion cracking, meza corrosion, biocorrosion, etc. Corrosion foci are localized on the inner and outer surfaces of pipes. The problem is complicated by the increased content of carbon dioxide (CO2), hydrogen sulfide (H2S), as well as the presence of various bacteria in oil and gas fields.This article is devoted to the study of the mechanical characteristics and microstructure of tubing steels that were in operation under conditions of complicating factors and highly aggressive corrosive environment. Tubing pipes Ø73x5.5 of strength group E. were tested. The following research methods were carried out: visual inspection; determination of the chemical composition of steel; determination of hardness; uniaxial tensile test; optical microscopy.As a result of the tests, quantitative characteristics of the mechanical properties of the steels were obtained. A significant decrease in the hardness, tensile strength and yield strength of steel has been established under prolonged exposure to complicated operating conditions. Metallographic studies have established the contamination of steels with silicates of various shapes, amounting to 3 and 2 points according to GOST 1778. Microstructural studies have been carried out. The fine-grained ferrite-carbide structure of steels has been revealed. This structure corresponds to the heat treatment mode: quenching followed by tempering.

Mastering the complex time-scale interaction during Stress Corrosion Cracking phenomena through an advanced coupling scheme

Stress corrosion cracking (SCC) failure is a multi-physics phenomena and is usually modelled at the microstructural level, which includes mechanical, chemical, and electrochemical contributions. In aggressive corrosive environments, materials prone to localized corrosion, can suffer heavy pitting corrosion. Subsequently, pit-to-crack transition events might be initiated. Respective mechanical assisted pitting corrosion propagation processes are determined by mechanical, chemical, and electrochemical properties as well as transport properties of ions at grain boundaries. Variations in the electrolyte exposure conditions (including the kinetics at the solid–liquid interface), different mechanical loading scenarios, grain-specific crystal anisotropies, and other local factors combine to produce a highly complex SCC-type interaction scenario at various time and length scales. Since corrosion is a slow process whereas brittle fracture is a rapid failure mechanism, the individual domain discretization-based solvers need to use distinct time steps and appropriate solver settings to become capable to accurately simulate such coupled events. In order to address the issues that arise while accounting for scaling effects in both time and space, and retaining coupled mechanistic interplay and including the aspects specified earlier, a sophisticated modelling method is necessary for the analysis of structural failure by SCC. In this work, a partitioned multi-physics computational approach is presented, using two separate single physics solvers coupled by the open-source coupling library preCICE. In the proposed computational setup, two separate software environments are used, with dedicated solver settings and different time steps, to simulate the mechanical fracture and dissolution-driven pitting corrosion for various loading and corrosion conditions, while also taking into account the effects of microstructural anisotropy. For a 2D polycrystalline model representing face-centered-cubic (fcc) material systems, selected numerical experiments are conducted that predict the evolution of fracture and crack path resulting from SCC. The framework has been further extended to simulate 3D problems as well. The corresponding results are evaluated to show the applicability of the proposed methodology.

Iodine–β-Cyclodextrin: An Effective Corrosion Inhibitor for Carbon Steel in Sulfuric Acid Solution - Experimental Design and Investigating Thermodynamic Parameters

Widely used across industries, carbon steel is vulnerable to corrosion in aggressive environments, especially acidic ones. Thus, effective methods to mitigate metal corrosion from acids are crucial. Inhibitors are extensively used to prevent corrosion in industries, with the potential for improved protective performance. The design of experiments was employed to determine the optimal conditions for enhancing the inhibitor efficiency of Iodine–β-Cyclodextrin (Iodine/β-CD) in a sulfuric acid solution at temperatures ranging from 20°C to 50°C. The relationship between the factors and responses was established using response surface methodology (RSM), employing regression statistical analysis and probabilistic analysis. A single response was recorded: inhibitor efficiency was determined by measuring weight loss before and after immersion in the inhibitor solution. Thermodynamic parameters were also computed to determine adsorption and activation processes. The statistical analysis revealed that the quadratic models for inhibition efficiencies (IE) were highly significant with a coefficient of multiple regressions R2= 0.997. Further validation of the model indicated a good fit (R2 Adj= 0.994), and the experimentally observed values aligned well with predicted ones, demonstrating a highly significant model with Q2= 0.978. The theoretical efficiency predicted by the RSM model was 88.41%, whereas the efficiency observed during the experimental test procedure with the best-evaluated variables was 82.45%. In conclusion, this paper aims to identify the optimal conditions for employing Iodine–β-Cyclodextrin as a new corrosion inhibitor for carbon steel, utilizing experimental design methods. The results indicate that iodine/β-CD exhibits remarkable corrosion inhibitory properties for carbon steel under specific conditions.

Laser peening induced mitigation of severe pitting corrosion in titanium stabilized 321 steel

Titanium stabilized 321 stainless steel, as a structural component in oil and petrochemical industries, often susceptible to severe pitting corrosion under aggressive corrosion environments (sulfuric acid and chloride ions). This study explores the applicability of laser peening without protective coating (at 6 GW cm−2 intensity and 75 % pulse overlap rate) to enhance the electrochemical stability of 321 steel against such severe pitting corrosion. Laser peening altered surface-mechanical and electrochemical properties were investigated by AFM, SEM and potentiodynamic polarization/impedance spectroscopy techniques. On the account of laser peening induced compressive residual stress (-408 MPa) hardness enhancement, a stable/dense and uniform oxide film was formed on 321 steel, subsequently mitigating the pitting corrosion. By contrast, unpeened surface exhibited more number of wider and deeper merged pits (maximum diameter of ∼ 2197 μm). Laser peening promoted oxidation has been confirmed via elemental composition analysis. A twentyfold enhancement in charge transfer resistance and improved oxide film resistance, attributed from the laser peening increased defect density as demonstrated by the improved hardness, evidenced a highly electrochemical stability on 321 steel.

1,4-Phenylenediamine-based Schiff bases as eco-friendly and efficient corrosion inhibitors for mild steel in HCl medium: Experimental and theoretical approaches

The application of Schiff bases as corrosion inhibitors is one of the economic, practical, and effective techniques to retard metal corrosion in aggressive environment. The continuous exploration of novel, lower-cost, more efficient, and eco-friendly corrosion inhibitors is an everlasting pursuit of excellence. In this study, two 1,4-phenylenediamine-based single Schiff base isomers, (E)-4-((pyridin-2-yl-methylene)amino)aniline (PMAA2) and (E)-4-((pyridin-3-ylmethylene)amino)aniline (PMAA3), were synthesized by one-step reaction. The corrosion inhibition mechanism and structure–activity relationship of PMAA2 and PMAA3 for mild steel in HCl solution were analyzed using electrochemical and weight loss experiments, morphology analysis, density functional theory (DFT) calculation, and molecular dynamic (MD) simulation. The results demonstrated that the corrosion inhibition efficiency of PMAA2 and PMAA3 exhibited an increasing trend with the elevation of inhibitor concentration while showing a slight decrease with the temperature rise. The optimal corrosion inhibition efficiency for 800 mg L−1 PMAA2 and PMAA3 in 1.0 mol L−1 HCl solution is 90.88 % and 91.78 % at 303 K respectively by using weight loss experiment. The electrochemical experiment results indicated that PMAA2 and PMAA3 are mixed-type corrosion inhibitors, with a preponderant control of anodic dissolution. Both the thermodynamics of adsorption and the kinetic of corrosion reaction were evaluated and discussed in detail. Their adsorption upon mild steel complies with Langmuir adsorption isotherm and is involved in phys- and chemisorption concurrently. The results from surfacemorphologyanalysis exhibited that a dense protective film on the surface of mild steel is formed through inhibitor adsorption, which results in changes in the hydrophilicity and hydrophobicity of the metal surface. The calculations of DFT and Fukui index also indicated that both the neutral and pronated species of PMAA2 and PMAA3 possess donor–acceptor interactions with the surface iron atoms through both forward and back-donations. Furthermore,MD simulations further revealed that the neutral molecules as neat-flat and parallel orientation are adsorbed strongly on the Fe (110) surface but the pronated species perform in bent fashion on the Fe (110) surface. Based on the experimental analysis and the theoretical calculation, a possible adsorption and corrosion inhibition mechanism was proposed rationally. These findings display good correlations between the experimental investigation and the theoretical computation and are of fundamental importance to understanding the adsorption and corrosion inhibition mechanisms of the inhibitors.

Efficient prediction of the load-carrying capacity of ECC-strengthened RC beams – An extra-gradient boosting machine learning method

As a result of the excellent crack width control capabilities of engineered cementitious composites (ECC), an ECC layer located in tension zones in reinforced concrete structures can transform wide harmful cracks into harmless dense microcracks. As a result, reinforced concrete structures are more durable and less prone to corrosion in aggressive environments. In the literature, there are equations that can predict the flexural capacity of ECC-strengthened RC beams. However, these equations are primarily regression-based and contain a limited number of parameters. With the help of the machine learning (ML) technique, a more comprehensive equation considering all the governing parameters can be proposed for ECC-strengthened RC beams. In the present study, a large database containing data from 217 ECC-strengthened beam specimens was collected from around two dozen publications. These data were then employed to develop an ML model using the XG boost algorithm. The model uses 20 input variables to predict the load-carrying capacity of the ECC-strengthened beam. The optimal model can produce a predicted-target dataset for the test dataset with an accuracy level of above 80%. Model parameters with the greatest significance according to Gini indexes were yield strength of the steel bars in the concrete substrate, beam depth, longitudinal reinforcement area, and ECC thickness. The analysis of SHAP (an acronym for SHapley Additive Explanations) values revealed a consistent pattern from the optimized model. Eventually, the study offers a free and easy-to-use graphical user interface to facilitate user interaction with the developed XG Boost model.

Electrodeposition and corrosion behavior of Sn and Sn-reduced graphene oxide coatings on mild steel from the non-cyanide acid chloride bath solution

Reduced graphene oxide (rGO) derived from graphite has received attention among researchers because of its special unique characteristic properties. Based on the studies, rGO-based coatings on stainless steel (SS) act as an anti-corrosive protective coating on stainless steel. Herein, we prepared a few layered rGO via graphite oxide by a simple thermal exfoliation of graphite oxide. Tin and Sn-rGO coatings have been electrodeposited on SS using an optimized acid chloride bath composition in the absence and presence of rGO respectively. The prepared specimens were subjected to an aggressive corrosive environment (aqueous 5% NaCl). The corrosion behavior of Sn and Sn-rGO composite coating has been examined by potentiodynamic polarization and electrochemical impedance spectroscopic (EIS) techniques. The potential shifted towards the negative region after polarization for Sn-rGO composite coating compared to pure Sn coating. Also, Sn-rGO composite coating exhibits more resistance when subjected to EIS measurements in 5% NaCl. The change in the surface morphology of coatings before and after exposure to corrosive environments has been observed by Scanning electron microscopy. After exposure to aqueous 5% NaCl, Sn coated specimen exhibited pores on the SS surface whereas fewer pore structures were observed on the SS surface for Sn-rGO coating. The results reveal a significant increase in anti-corrosion properties of Sn-rGO on SS compared to that of pure Sn coating.

Effect of a 3.5% NaCl-10% HCl Corrosive Environment on the Fatigue Behavior of Hot Rolled Aluminum 5083-H111.

This study deals with the microstructure of rolled Al5083-H111 materials, their hardness, corrosion in different solutions, and rotary bending fatigue properties of non-corroded and corroded samples in different solutions. This study is the first to report the fatigue behavior of corroded samples in different aggressive corrosion environments of Al5083. The microstructure of the Al5083-H111 material is in the form of grains oriented towards the rolling direction and it consists of binary Al-Mg, Al-Mn, and Mg-Si; ternary Al-Mg-Si; and quaternary Al-Mn-Fe-Si and Al-Cr-Mn precipitated randomly at the grain boundary. The Brinell hardness of the Al5083-H111 material is 68.67 HB. According to the results of the immersion corrosion, while the sample was more resistant to corrosion in a 3.5% NaCl environment, it showed a less resistant behavior in a 3.5% NaCl + 10% HCl environment. As a result of the fatigue test, it was observed that the sample that did not undergo corrosion showed a higher fatigue life than the samples that were exposed to corrosion. The fatigue rate of the 3.5% NaCl corrosion sample was 3.5 times lower than the fatigue rate of the 3.5% NaCl + 10% HCl corrosion sample.

Структура и свойства покрытий WC-10Co4Cr, полученных высокоскоростным плазменным напылением

Introduction. Carbon steel is often used for the manufacture of various machine parts, but its operation in aggressive conditions (operation of steel parts under conditions of wear, high temperatures and aggressive corrosive environments) contributes to an extreme decline in properties, up to failure. To solve this problem the modification of the working surfaces of steel parts can be used. It increases its wear resistance, corrosion resistance, and service life. Metal-ceramic coatings based on WC are often used to improve the hardness, wear resistance and corrosion resistance of steel parts. The work purpose is to study the effect of high velocity atmospheric plasma spraying (HV-APS) modes on the structure, phase composition and properties of WC-Co coatings. Materials and methods. 86% WC-10% Co-4% Cr coatings were deposited on a mild steel substrate with help of the HV-APS method. The structure and phase composition of the coatings were analyzed using optical microscopy, scanning electron microscopy, and X-ray phase analysis. In addition, the results of measurements of porosity, microhardness, wear resistance, as well as a qualitative assessment of the adhesion are shown in this paper. Results and discussion. It is shown that all coatings are characterized by high density, absence of cracks and oxide films. Using the SEM and XRD methods, it is found that the coatings contain WC and W2C particles uniformly distributed in the metal matrix. The matrix is an amorphous or nanocrystalline supersaturated Co(W,C) solid solution. The maximum amount of carbides (49%) is observed in coatings obtained by deposition from a distance of 170 mm, arc current — 140 A; the minimum (25%) is observed in coatings obtained by deposition from a distance of 250 mm, arc current — 200 A. The coatings with the maximum amount of carbides have the maximum values of microhardness (1,284 HV0.1) and wear resistance. It is established that all coatings are characterized by high adhesion.

Evaluation of Protective Properties of Lacquer Coatings on Copper Products Operating in a Low Aggressive Corrosive Environment

Lacquered copper membranes are sometimes used in operate equipment containing low aggressive corrosive water-based fluids. In some cases, the lacquer coating does not prevent the occurrence of corrosive processes leading to through damage to the product and equipment failure. In this work, a review of the most common copper corrosion mechanisms is carried out. During a visual inspection of the products, the peculiarities of the state of the membrane surfaces and corrosive damage were noted. On the basis of metallographic, X-ray structural and electrochemical studies, the assumptions put forward at the stage of visual inspection were confirmed. The conclusions contain assumptions about the reasons for the formation of pitting corrosion on copper membranes.

Smartvessel: A New Extinguisher Prototype Based on New Materials and IoT Sensors

Smartvessel is an innovative fire extinguisher prototype supported by new materials and IoT technology that seeks to improve the functionality and efficiency of conventional fire extinguishers. Storage containers for gases and liquids are essential for industrial activity as they enable higher energy density. The main contributions of this new prototype are (i) innovation in the use of new materials that provide lighter and more resistant extinguishers, both mechanically and against corrosion in aggressive environments. For this purpose, these characteristics are directly compared in vessels made of steel, aramid fiber and carbon fiber with the filament winding technique. (ii) The integration of sensors that allow its monitoring and provide the possibility of predictive maintenance. The prototype is tested and validated on a ship, where accessibility is complicated and critical. For this purpose, different data transmission parameters are defined, verifying that no data are lost. Finally, a noise study of these measurements is carried out to verify the quality of each data. Acceptable coverage values are achieved with very low read noise, on average less than 1%, and a weight reduction of 30% is obtained.

The Structure and Properties of Laser-Cladded Inconel 625/TiC Composite Coatings.

This article presents production results concerning metal matrix composite-coatings made using the laser-cladding technology. The enhancement of the wear resistance of the material surface is the one of the main goals accompanying the manufacturing of composite coatings. Nickel-based superalloys are used in several industries because they are characterized by a number of desirable properties including high tensile and fatigue strength as well as resistance to high-temperature corrosion in aggressive environments. One of the most interesting materials from the group of superalloys is Inconel 625, used as a matrix material in tests discussed in this article. However, nickel-based superalloys are also characterized by an insufficient wear resistance of the surface, therefore, in relation to the tests discussed in this article, Inconel 625-based composite coatings were reinforced by adding 10%, 20% and 40% of titanium carbide particles. The addition of hard phases, i.e., TiC, WC or SiC particles can have a positive effect on the erosion resistance of cladded specimens. The aim of the experiment was to determine the impact of the titanium carbide content on the structure of the alloy and its resistance to corrosive wear, enabling the extension of the service life of Inconel 625/TiC composite coatings. The investigation included microhardness tests, corrosion resistance analysis, penetrant tests, macrostructure and microstructure analyses and X-ray diffraction (XRD) tests. The TiC particles increased the hardness of the coatings and, in general, had a negative impact on the corrosion resistance of pure Inconel 625 coatings. However, the increased homogeneity of composite coatings translated into the improvement of corrosion resistance.

Study of the corrosion properties of structural steels using magnetic characteristics

Heterogeneities of the crystal structure and chemical composition, as well as the impurity elements forming inclusions cause deviations of the properties of test object from the required physical and mechanical parameters which significantly affects the reliability and service life of the product. We present the results of studying the susceptibility of structural steels to corrosion in aggressive environment using their magnetic characteristics. Structural-phase transformations occurred in steels under the effect of heat treatment change their properties, including magnetic and corrosion ones. Heat-treated 09G2S, St3, 15XSND steel samples were studied. In addition to the main magnetic parameter — coercive force, we also used spectral characteristics of the samples obtained using a remagnetization curve, magnetic hysteresis loop. The multi-parameter approach with harmonic components was used to identify the corrosion rate and coercive force correlation. Determination of the corrosion rate in this case can be reduced to classical problems of technical diagnostics. It is shown that a complex parameter based on harmonic components obtained using a magnetic hysteresis loop and the corrosion rate exhibit a pronounced correlation which provide developing a non-destructive method for predicting the corrosion resistance of structural steels. The results obtained can be used to improve the rapid method for determining the corrosion-hazardous zones of steels using the magnetic parameters.

The structure and properties of laser-cladded Inconel 625/TiC composite coatings

Abstract The article presents the research in the field of production of metal–matrix composite coatings using laser cladding technology. The general purpose of producing composite coatings is the improvement of wear resistance of the material surface. In this research, Inconel 625 was used as a matrix material. Nickel-based superalloys are used in several industries for unique applications because they possess a number of beneficial properties including high tensile and fatigue strengths and resistance to high-temperature corrosion in aggressive environments. However, for some applications, this alloy shows insufficient wear resistance of the surface; therefore, for the tests, Inconel 625-based composite coatings were produced with the addition of 10 vol.%, 20 vol.%, and 40 vol.% of titanium carbide (TiC) particles as reinforcement. In general, the addition of TiC particles had a positive effect on the erosion resistance of the surface. The aim of the current research was to test the influence of TiC particle reinforcement of Inconel 625 laser-cladded coatings on corrosion resistance of the surface. For the tests, the laser-cladded composite coatings with uniform phase distribution were produced. The proceeded tests included penetrant tests, macrostructure and microstructure analysis, X-ray diffraction (XRD), and microhardness and corrosion resistance tests. The results showed that using laser cladding, TiC-reinforced Inconel 625 uniform composite coatings may be produced. The addition of TiC particles caused microstructure changes in the Inconel 625 matrix and an increase in hardness. The addition of TiC particles had a negative influence on Inconel 625 corrosion resistance, but with the increased composite coating homogeneity, the corrosion resistance improved.

Promising WC-30WB-10Co Cemented Carbide Coating with Improved Density and Hardness Deposited by High Velocity Oxy-Fuel Spraying: Microstructure and Mechanical Properties

WC-Co coatings sprayed by HVOF attracted much attentions, benefiting from the satisfactory wear resistance and high bonding strength to the steel substrates. Nevertheless, high density of conventional coatings required excessive Co binder, which decreased the hardness and operation life. Based on this, a strengthened WC-30WB-10Co coating was developed with both high density and improved hardness, using high-qualified thermal sprayed composite powders. Comparison between the phase composition, microstructure, interfacial bonding strength and properties of the newly developed coatings and WC-12Co conventional coatings was clarified in detail. Compared to WC-12Co powders, spherical WC-30WB-10Co powders showed higher apparent density and flowability, due to the in situ formed CoWB and CoW2B2 phases during the accelerated metallurgy reaction. Oxidation and decarburization were confirmed during HVOF spraying with the formation of W2C, Co3W3C and Co6W6C phases in both coatings. Attracting WC-30WB-10Co coating with microhardness of 1639HV0.3 and relative density of 99.44% was achieved, higher than those of 1222 HV0.3 and 99.27% of WC-12Co. This was attributed to the formation of the ternary compounds and the consumption of the ductile Co binder in the WC-30WB-10Co coatings. The hard alloy coatings are expected to be well applied in aggressive wear and corrosion environments due to the high hardness and low metal phase content.

Bond performance of basalt FRP bar against aggressive environment in high-strength concrete with varying bar diameter and bond length

• Bond Performance of Basalt FRP Bars with high strength concrete is investigated. • The bond strength of FRP bars was found to be higher than that of steel bars. • FRP bars provide a cost-effective solution for corrosion mitigation of steel reinforcement bars in RC structures. • Higher Bond Strength retention was observed in alkaline environment in comparison to sea water. Concrete is a porous material and prone to attacks by aggressive media such as sulphates, carbonates, and alkali-silica reactions. These aggressive media penetrate the reinforced concrete members and not only damage the concrete but also the steel reinforcement. It has been observed that the bond between the ordinary steel rebars and concrete degrades significantly over time besides reducing the mechanical properties of the rebar. As a result, the service life of concrete structures reduces significantly and adversely impacts their overall structural behavior, hence, raising safety issues that are expensive to repair. Recently, Basalt Fiber Reinforced Polymer (BFRP) bars are found to be an emerging solution that could alleviate the issue of steel reinforcement corrosion in aggressive environments. This research comprises a detailed investigation of bond strength reduction between concrete and BFRP bars through pull-out testing. Since FRP rebar’s bond behavior is expected to differ from that of steel, therefore, to evaluate the bond performance of BFRP bars, the concrete specimens reinforced with BFRP bars having varying parameters, i.e., different bar diameters and development lengths, were exposed to the alkaline solution and sea water for three months. The results showed that both aggressive media triggered the bond strength reduction between the concrete and BFRP bars, however, a slightly higher bond strength retention was observed in comparison to steel rebars, i.e., 86% and 82% of bond strength retention was observed in the case of alkaline and seawater exposure, for three months respectively. The future bond strength retention for BFRP bars was lastly evaluated using the Fib bulletin model.