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The influence of co-regulating Mo and Sn on the corrosion resistance of low alloy steel in tropical marine atmospheric was investigated. The combined addition of Mo and Sn has been found to significantly improve the corrosion resistance of low alloy steel, augmenting the protective capabilities of the rust layer. This combined addition promotes the formation of protective compounds like α-FeOOH and FeCr2O4 within the alloy rust layer. Furthermore, it facilitates the conversion of Cr, Ni and Cu into corrosion-resistant oxides such as Cr2O3, NiFe2O4 and CuO, thereby enhancing the density of the rust layer. Additionally, as corrosion progresses over time, higher levels of Sn addition lead to increased Sn content within the inner rust layer, consequently bolstering the protective qualities of the rust layer. This comprehensive understanding sheds light on the synergistic effects of Mo and Sn in fortifying the corrosion resistance of low alloy steel, offering insights for the development of advanced corrosion-resistant materials in marine environments. [ABSTRACT FROM AUTHOR]

[Display omitted] • The self-healing and self-sensing coatings were developed based on pH stimuli. • The coating system shows excellent self-healing and self-sensing properties. • The cooperative effect of two inhibitors protects against steel corrosion. • The corrosion sensing ability is from the color change of Phen adsorbed on steel. Polyelectrolyte-encapsulated nanocontainers can effectively respond to changes of pH and thus control the on-demand release of corrosion inhibitors. A pH-responsive release system (Phen-Tpp@MTNs-PDDA) was developed based on the cationic polyelectrolyte poly dimethyl diallyl ammonium chloride (PDDA) encapsulated mesoporous TiO 2 nanocontainers (MTNs) loaded with 1,10-phenanthroline (Phen) and tripolyphosphate ions (Tpp) corrosion inhibitors. The epoxy coating (EP) embedded with Phen-Tpp@MTNs-PDDA (Phen-Tpp@MTNs-PDDA/EP) demonstrates superior self-healing properties and confers long-term protection on the metal substrate through the cooperative effect of Phen and Tpp. Simultaneously, this hybrid coating is endowed with corrosion sensing capability based on the color development originating from the interaction of Phen and carbon steel. This self-healing and corrosion-sensing multifunctional coating provides an effective strategy for the corrosion protection of metals. [ABSTRACT FROM AUTHOR]

Cold spraying is a promising technique for depositing wear-resistant coatings on components like hydroturbine steels. This paper highlights the feasibility of hard WC-17Co coating on 13Cr4Ni hydroturbine steel. The coating was deposited at 25, 30, and 40 bar at 800∘C and 50 bar at 900∘C. Further, different characterization techniques (SEM, XRD) were used to analyze the developed coatings. The Vicker hardness testing was employed to determine the hardness of the coated sample. It was observed that WC-17Co coatings deposited at 40 bar and 800∘C offered a maximum hardness of up to 275 Hv, which is an excellent quality for anti-wear applications in hydro turbine blades. [ABSTRACT FROM AUTHOR]

Corrosion of steel is an issue that cannot be ignored in contemporary society. Due to large-scale corrosion, it is urgent to develop a surface treatment process that enhances the corrosion resistance of steel, allowing for application in various scenarios as needed. This study aims to investigate a novel surface treatment process to extend the service life of corroded Q235 steel, reduce its sensitivity to corrosion, and enable its use in multiple environments. This study employs the sol-gel method, using manganese nitrate solutions of varying concentrations to treat the surface of Q235 steel after different electrolysis times. The optimal conditions for precursor preparation were found to be a Mn2+ concentration of 0.1 mol/L and an electrolysis time of 2 h. Electrochemical tests using NaCl solutions of different concentrations revealed a significant reduction in the corrosion current for the composite coating based on Q235 steel treated with this method in NaCl solutions with wt.% = 1, 2, 3, 4, 5. Furthermore, the resistance to corrosion was strongest in the NaCl solution with a concentration of 1 wt.% where the corrosion current decreased from 24.8 µA/cm2 to 6.79 µA/cm2. Additionally, the coating was found to be diffusion-controlled in the early stages of the corrosion process and charge transfer-controlled in the later stages. The MnFe2O4 spinel coating demonstrated the greatest enhancement in corrosion resistance in the wt.% = 1 NaCl solution. [ABSTRACT FROM AUTHOR]

Corrosion poses a significant challenge, causing severe damage to steel infrastructures across various industries, particularly those involved in delivering fossil fuel sources. The present study introduces an innovative approach to the development of corrosion inhibitors through the synthesis of a zinc nanoparticle (Zn NP) and polystyrene (PS) composite (ZnNPs@PS composite). The synthesized composite was characterized, revealing a surface area (SBET) of 33.62 m2 g−1 and an average pore diameter (Dp) of 9 nm. The analysis was conducted using several techniques including Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, and transmission electron microscopy (TEM). The successful immobilization of Zn NPs, with an average size range of 4–50 nm, within the PS matrix was confirmed. The composite's corrosion inhibition efficiency (CIE) was evaluated using the weight loss method. Treated steel samples, after immersion in formation water, diesel fuel, and sulfuric acid (H2SO4) for 10 days at 25 °C, demonstrated CIE percentages of 94.27%, 88.18%, and 85.05%, respectively. This novel composite thus shows promising potential as an effective corrosion inhibitor for steel in various corrosive environments. [ABSTRACT FROM AUTHOR]

Addressing the significant issues of sand burn-on defects and interfacial reaction in sand casted 13Cr9Mo1VNb steel castings, which notably compromise the quality of the steel castings, remains a persistent challenge. The interfacial behaviors between the novel mixed sands and the steel grade were investigated under various sands. The sintering behavior of the sands was also studied without liquid steel at various holding time. In the absence of the influence of molten steel, sintering of mixed chromite-MgO does not undergo solid-solid reaction, with no detected presence of liquid phase and 2MgO·SiO 2. The mixed sands undergo sintering reactions upon contact with molten steel, yet no liquid phase is detected. This is primarily attributed to the chemical reaction between MgO and the liquid phase, resulting in the formation of forsterite, leading to the near-complete liquid phase consumption. Magnesia grains can suppress the liquid phase sintering of chromite by 13Cr9Mo1VNb, thus weakening its sintering performance. The presence of 2MgO·SiO 2 , which exhibits excellent resistance to slag (liquid phase) and steel liquid corrosion, impedes the rising of the liquid phase. Consequently, this reduces the thickness of the adhesive layer and suppresses metal penetration. The production of 2MgO·SiO 2 diminishes with the escalation of MgO addition, which increases adhesive thickness and metal penetration as the magnesia content rises. Within the scope of this study, the incorporation of 20 % MgO is suggested to mitigate burn-on defects, which may represent an advantageous selection. [ABSTRACT FROM AUTHOR]

The hot dip aluminized ASTM 1035 steels (Al‐coated steel) underwent anodic oxidization, and various thicknesses of Al2O3 coating were applied to the surface of the Al‐coated steels (Al–Al2O3‐coated steel). The corrosion resistance of the Al–Al2O3‐coated steel was investigated using potentiodynamic tests, electrochemical impedance spectroscopy tests and measurement of galvanic current density in a bimetallic cell. It was found that the anodic oxidation resulted in the formation of a porous Al2O3 coating on the surface of the Al‐coated steel, improving both its corrosion resistance and galvanic corrosion resistance when coupled with carbon fiber reinforced nylon 6 composite (Cf/PA6). Silane treatment effectively sealed the pores within the Al2O3 coating, resulting in improved corrosion protection for Al–Al2O3‐coated steel due to the exceptional insulation, impermeability and hydrophobic properties of silane coating. Compared to the Al‐coated steel/carbon fiber reinforced polymer (CFRP) couple and Al–Al2O3‐coated steel/CFRP couple, stable galvanic current density decreased by approximately 75% and 45%, respectively. [ABSTRACT FROM AUTHOR]

Prestressed spun high-strength concrete (PHC) piles are commonly used in various types of structures, including bridges, buildings and marine infrastructures. However, piles installed in aggressive environments are vulnerable to corrosion of the steel, which can lead to rapid degradation of the piles. As a corrosion-resistant material, carbon fiber-reinforced polymer (CFRP) is considered an alternative to steel tendons for durability enhancement. In this study, a new pile system with CFRP was proposed. Experimental tests of three full-scale piles and a numerical analysis of eight piles with various parameters were performed to investigate the flexural performance of CFRP prestressed spun high-strength concrete pile. The proposed piles were loaded under four-point bending after prestressing. The experimental and numerical results verified the feasibility of the proposed system, and the CFRP pile exhibited twice of flexural capacity of that of steel-reinforced piles. The flexural performance of the CFRP PHC pile was significantly affected by the reinforcement ratio, prestressing level and modulus of the CFRP. An analytical approach predicting the flexural capacity of the CFRP PHC pile was proposed based on the parametric study. Ninety percent accuracy was achieved for the proposed analytical approach. The presented study can significantly promote the application of CFRP in pile foundations and improve the durability of PHC piles. [ABSTRACT FROM AUTHOR]

High toxicity is the main reason for the limited application of traditional corrosion inhibitors. Herein, it is critical to find a green, efficient, and long-term stable alternative substitute for the hazardous and conventional corrosion inhibitor. Ambrosia trifida L is widely distributed in fields and riverside wetlands as an invasive plant in China. According to the concept of turning waste into treasure, the extract of Ambrosia trifida L leaves (ATL) has the potential to address this issue due to its natural origin and abundant presence of heterocyclic organics. Therefore, ATL, as a green corrosion inhibitor, is prepared for the first time via a simple water-based extraction method. FT-IR (Fourier transform infrared spectroscopy) and UV-Vis (UV-visible) indicate that ATL extract contains abundant heterocyclic organics with conjugated structures, which exhibit the potential to become a high-efficiency inhibitor. Notably, the active sites of ATL molecules and their interaction with Q235 steel at the molecular/atomic level are revealed via theoretical calculations. The highest Ebinding value observed for the major components in the ATL extract is 259.66 kcal/mol, implying a significant adsorption capacity. The electrochemical results verify that microdose ATL extract can prominently inhibit steel corrosion, and the highest inhibition efficiency (η) is 97.5% (1000 mg/L). Following immersion for 24 h, the η value is enhanced to 99.0%, indicating a reliable and long-term ATL extract protection film is formed on the steel surface in harsh acidic solutions. The results of the weight loss, SEM (scanning electron microscope), and LSCM (laser scanning confocal microscopy) are consistent with the above conclusions. Finally, this study anticipates providing theoretical support for developing novel green plant extract inhibitors and aiding in their application in industrial pickling environments. [ABSTRACT FROM AUTHOR]

In this study, CrNi alloyed coating was deposited on Q235 low carbon steel by arc-added glow plasma depositing technique in order to increase the corrosion resistance property. It was found that the CrNi alloyed coating was composed of face-centered cubic Cr0.7Ni2.9Fe0.36 phase. The EDS results indicated that 7.3 μ m coatings were prepared which was bonded metallurgically with the substrate. The salt spray corrosion test result showed that the corrosion product film of coating was dense while the corrosion film of carbon steel was multilayered in morphology. The corrosion product film of CrNi coating reduced the corrosion rate. However, the corrosion product of Q235 with loose multi-layer structure increased corrosion process. The erosion corrosion properties of carbon steel and coating were tested in NaCl solution with different flowing speed through electrochemical test methods. The erosion corrosion results showed that the corrosion rate of carbon steel was increased in flowing NaCl solution. The corrosion product of CrNi coating could protect inner material in NaCl solution at flowing speed of 2 m·s − 1 to 6 m·s − 1 . [ABSTRACT FROM AUTHOR]

The large uncertainties of electrochemical input parameters, along with their variation with chemical environment and time, can significantly affect the accuracy of simulations and oversimplify the nonuniform corrosion distribution over time. To bridge the gap, this study investigated the effects of chloride ion concentration, humidity, and concrete mix on the electrochemical parameters through a long-term experiment of natural corrosion. The results revealed that the logarithmic anodic and cathodic exchange current density are almost constant values of −4.80 and −5.49 , respectively. The cathodic equilibrium potential slightly fluctuates around 253 mV versus the saturated calomel electrode. The increase in chloride ion concentration above 0% generally leads to a reduction in the anodic Tafel slope, while the absolute cathodic Tafel slope remains almost constant when chloride ion concentration exceeds 1.214%. Due to the distinct controlling mechanisms of corrosion, the effects of chloride and water-to-cement ratio on the electrochemical parameters are susceptible to the humidity level of concrete. Interestingly, at 90% humidity, the corrosion potential may shift negatively for a lower water-to-cement ratio, resulting in a decrease in the anodic Tafel slope. Nevertheless, a lower corrosion rate can still be anticipated. Employing the Butler–Volmer equation and Nernst equation, semiempirical models were constructed by representing the effects of humidity with piecewise functions. The accuracy has been validated through experimental data from both this work and previous studies. The results and empirical models of this study provide reasonable electrochemical input parameters for simulation of nonuniform corrosion and the evolution over time. [ABSTRACT FROM AUTHOR]

The chloride content is a critical factor influencing the corrosion of steel fibers in concrete. This study focused on the corrosion behaviors of steel fibers exposed to simulated concrete pore solutions with different chloride contents. The corrosion rates of the steel fibers were calculated based on the changes in the diameter and ultimate tensile load. The electrochemical parameters for the corrosion of the steel fibers were continuously monitored for 62 days. In addition, the surface micromorphologies of the corroded steel fibers were observed using scanning electron microscopy (SEM). The results showed that based on the change in the diameter, the corrosion rate of the steel fibers increased almost linearly when the NaCl content in the simulated solution increased from 2% to 5%. However, based on the variation of the ultimate tensile load, the corrosion ratio of the steel fibers increased linearly with the increase in the exposure time when the NaCl content was less than 3%, while it increased exponentially when the NaCl content exceeded 3%. According to the open circuit potential, Tafel polarization curves, and electrochemical impedance spectroscopy (EIS), the corrosion tendency and corrosion rates of the steel fibers exposed to the simulated solutions increased significantly when the NaCl content increased from 2% to 5%. Additionally, the corrosion damage on the surfaces of the steel fibers increased notably, and after 180 days of exposure to the simulated solution with 5% NaCl, the steel fiber was almost broken. These findings will help to understand the durability of SFRC in a chloride environment. [ABSTRACT FROM AUTHOR]

Durable and sustainable corrosion protection of reinforcing steel in waterway structures Corrosion damage due to hitherto widely unknown damage mechanisms, the critical review of previous design principles, but also new developments in building materials are leading to a reorientation in the design of measures to ensure the durability of hydraulic engineering structures with regard to reinforcing steel corrosion. [ABSTRACT FROM AUTHOR]

The corrosion behavior of Q345qNH steel and Q420qNH steel in simulated industrial atmospheric environment medium was studied by periodic immersion+infrared aging corrosion experiment. The results show that the corrosion type of both samples is uneven comprehensive corrosion, and the rust layer formed in the later stage of corrosion is relatively dense. But average corrosion rate of Q345qNH steel is always lower than that of Q420qNH steel, and the ratio of Iα‐FeOOH/Iγ‐FeOOH in rust layer is always higher. Compared with Q420qNH steel, Q345qNH steel has fewer surface pits but deeper local pits. The self‐corrosion potential of Q345qNH steel increases obviously, the resistance of the rust layer is larger, and protection to the matrix is stronger. This is because the formation of a large number of corrosion microcells induced by fine lamellar sorbite tissue that uneven distributed in Q420qNH steel, which increases the corrosion rate and makes corrosion uneven, while the larger pearlitic group in Q345qNH steel increases the local corrosion rate. However, the higher chromium/carbon ratio in Q345qNH steel promotes the conversion of lepidocrocite to goethite and inhibits the cathode reaction in the infrared drying stage, improving the density and stability of the rust layer. [ABSTRACT FROM AUTHOR]

The study investigates the practical application of cyclic wet/dry corrosion tests in simulated industrial atmospheres to assess the impact of chromium (Cr) on the protective properties of vanadium micro‐alloyed weathering steels. Two types of steels were examined: a V‐N steel and a V‐N‐Cr micro‐alloyed weathering steel. These steels were subjected to corrosion tests with 0.01 mol/L NaHSO3 at a pH range of 4.4–4.8 for varying durations. The findings indicate that the inclusion of Cr in the composition of vanadium micro‐alloyed weathering steel enhances corrosion resistance and leads to the accumulation of Cr in the inner rust layer. Furthermore, the distribution of corrosion‐resistant elements (Cr, Ni, Cu, P, and Mo) in V‐N and V‐N‐Cr steels is analyzed. The rust layer was observed to exhibit stratification in the corrosive environment, with the outer layers being dense and uniform, while the inner layers were porous and exhibited poor adhesion to the matrix. The study also delves into the anticorrosion mechanism of vanadium weathering steel using techniques such as X‐ray diffractometer, electron probe microanalysis, and potential‐phase diagram. [ABSTRACT FROM AUTHOR]

The use of simulated solutions is a common practice in corrosion studies to assess easily and quickly the corrosion behaviour of materials in real situations. In this context, it is frequent to substitute tests performed in concrete or mortar with tests performed in porous‐like solutions. Particularly, to simulate carbonated concrete, different carbonated porous‐like solutions (CPS) are found in the literature. However, it is not known whether the use of these solutions accurately predicts the behaviour of steel bars embedded in carbonated concrete. In the present work, a comparison between the corrosion behaviour of carbon steel in carbonated mortar and in different CPS was performed. It was found that none of the CPS studied in the present work adequately simulate the corrosion behaviour of the steel in carbonated mortar, but the CPS containing high concentrations of carbonates/bicarbonates is the only one that provides corrosion rates close to those obtained in carbonated concrete. [ABSTRACT FROM AUTHOR]

Acidizing is a vital oil well stimulation exercise but must be done with an effective corrosion inhibitor to reduce corrosion risk. It is, however becoming increasingly difficult to find a corrosion inhibitor that is ecologically compatible and effective in strong acids and high temperatures. In this scientific communication, aspartame (ASP), sodium dodecylsufate (SDS), and potassium iodide (KI) blend is presented as a highly efficient inhibitor for T95 steel in 28 wt.% HCl solution at 60–90 °C. The corrosion inhibition investigation was performed using weight loss and electrochemical (electrochemical impedance spectroscopy [EIS] and potentiodynamic polarization [PDP]) techniques complemented by surface analysis of the corroded steel without and with the inhibitor using scanning electron microscope (SEM)/energy dispersive x-ray spectrophotometer (EDX), and 3D optical profilometry (OP). ASP is an effective corrosion inhibitor for T95 steel in an acidizing environment. The inhibition efficiency (IE) increased with an increase in concentration and temperature. The additives (SDS and KI) enhanced the inhibitive performance of ASP due to synergistic effects, especially at 90 °C where an IE of 96% is tenable. Results from SEM/EDS and OP disclose apparent ASP-based inhibitor adsorption on the T95 surface and a high level of protection. [ABSTRACT FROM AUTHOR]

The durability of reinforced concrete structures is significantly influenced by the effectiveness of small molecular inhibitors in preventing the corrosion of steel reinforcements. In a concrete environment, the passive film on steel bars serves as a critical protective component. In this study, a molecular dynamics (MD) simulation is used to study the inhibition mechanism of chloride ions by common corrosion inhibitors (2-Amino-2-thiazoline) in concrete in an excess chloride solution. The results reveal that inhibitors adsorb onto the steel surface primarily through van der Waals forces, with more than 90% of the adsorption occurring vertically. Despite this strong adsorption, inhibitors alone do not form a protective film. In the presence of chloride ions, which frequently penetrate concrete, the coverage rate of inhibitors on the steel surface decreases from 74% to 64%. Nevertheless, inhibitor molecules still provide substantial protection in chloride-rich concrete environments. Further analysis indicates that inhibitor molecules inhibit chloride ions in two ways. Corrosion inhibitor molecules actively desorb from the steel surface to capture chloride ions and prevent them from approaching. Additionally, inhibitors form a multi-electron layer on the steel surface to enhance passive film protection and hinder chloride ion diffusion through Coulombic interactions. [ABSTRACT FROM AUTHOR]

In saline environments, it is difficult for reinforced concrete structures to meet normal durability requirements, which in turn affects the mechanical properties of the members. In this context, this paper proposes a reinforcement method that involves wrapping corroded reinforced concrete columns with CFRP (carbon fiber reinforced polymer) cloth. By conducting axial compression tests on four specimens, key mechanical performance indicators such as failure mode, ductility, and bearing capacity during the entire stress process of the specimens were analyzed, revealing the failure mechanism of CFRP-confined corroded reinforced concrete columns. A refined finite element model of CFRP-confined corroded reinforced concrete columns was established using ABAQUS software. The influence of key parameters such as the number of CFRP wrapping layers, longitudinal reinforcement corrosion rate, and axial compression ratio on the mechanical properties of the specimens was studied, and the influence of each parameter was determined. Furthermore, a formula for the axial compression bearing capacity of CFRP-confined corroded reinforced concrete columns was proposed. The results indicate that in the presence of corroded steel reinforcement, specimens confined with CFRP undergo substantial lateral constraints during the mid to late stages of loading. This approach effectively alleviates the transverse deformation of the concrete. The specimen demonstrated yield bearing capacities and peak loads of 1441 KN and 1934 KN, respectively, representing a 2.2-fold and 2.5-fold increase compared to the non-reinforced specimen. With the increase in the transverse strain of concrete, CFRP begins to play a restraint role, and a more obvious restraint role in the failure stage of members. It is recommended to apply 1–3 layers of CFRP wrapping for a longitudinal reinforcement corrosion rate of 5%, 3–5 layers for a rate of 10%, and 6–8 layers for an overall corrosion rate of 15%. This paper establishes a theoretical framework for investigating the performance characteristics of such columns and offers technical assistance for practical engineering purposes. [ABSTRACT FROM AUTHOR]

Steel monopile support structures for offshore wind turbines require protection from corrosion and consideration with respect to biofouling on their external and internal surfaces. Cathodic protection (CP) works effectively to protect the external surfaces of monopiles, but internally, byproducts from aluminum sacrificial anode CP (SACP) and impressed current CP (ICCP) induce acidification that accelerates steel corrosion. Through an 8-week sea water deployment of four steel pipes, this project investigated the effect of perforations on internal CP systems. Additionally, marine growth on the internal and external surfaces of the pipes was assessed. SACP and ICCP systems inside perforated pipes performed similarly to external systems at a lower current demand relative to internal systems in sealed pipes. The organisms that grew inside of the perforated SACP and ICCP pipes were similar, suggesting that the CP systems did not affect organism recruitment. The results of this study demonstrate the potential benefits of designing perforated monopiles to enable corrosion control while providing an artificial reef structure for marine organisms to develop healthy ecosystems. [ABSTRACT FROM AUTHOR]

The study was designed to explore the corrosion prevention capabilities of Citrullus colocynthis seeds alkaloid-rich extract (CSEA) on MS in a 1 M HCl environment by use of electrochemical and theoretical methods. Notably, Electrochemical Impedance Spectroscopy (EIS) and potentiodynamic polarization were used to probe the impact of immersion time and temperature. Energy-dispersive X-ray spectroscopy (EDX) and spanning electron microscopy (SEM) were used to confirm the presence of a protective layer on the substrate surface. Density functional theory (DFT) method was used to optimize the investigated species by use of B3LYP/6–31 + G(d, p) level of theory. The global and local quantum chemical reactivity descriptors were calculated to explore the inhibition corrosion efficiency and to identify the most favorable sites for electrophilic and nucleophilic attacks. Monte Carlo (MC) and molecular dynamics simulation (MDS) methods were used to study the interactions between corrosion inhibitor and metal surface. Noteworthy, results showed that CSEA exhibited an impressive inhibition efficiency, which reached 94.3% with a concentration of 2 g/L at 298 K. Potentiodynamic polarization revealed that the extract acted as a mixed-type inhibitor. Nyquist graphs showed that charge-transfer resistance and dæouble-layer capacitance both rised with increasing CSEA concentration, suggesting better inhibition efficiency. Notably, the Langmuir adsorption isotherm is well-aligned with the adsorption of inhibitor compounds. Importantly, all aforementioned theoretical methods were in agreement with the experimental findings. The outcome of the present work supported using Citrullus colocynthis seeds alkaloid-rich extract as ecofriendly agents to prevent corrosion. [ABSTRACT FROM AUTHOR]

TiO2/Nb5+ film was prepared and deposited on 304 steel and preventive its potential for corrosion was evaluated. The film was obtained by the sol–gel method, and its deposition by the dip-coating process has been followed by thermal treatment. XRD results with Rietveld refinement revealed the occurrence of isomorphic substitution and predominance of anatase phase. Scanning electron microscopy confirmed the deposition of film on substrate. Corrosion properties of the TiO2/Nb5+ layer was determined by open-circuit potential, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). Polarization curves showed a corrosion current of 129.72 μA for 304 steel without coating, which was larger than that observed for the samples recovered with TiO2/Nb5+ films (9.00 μA). EIS revealed high charge transfer resistance in the molar ratio of 1 to 5% compared to the uncoated 304 steel, highlighting the protective effect of TiO2/Nb5+ films against corrosion. [ABSTRACT FROM AUTHOR]

New trifunctional polybenzoxazines were developed and utilized as a high-potent coating material for superhydrophobic cotton fabrics and mild steel corrosion protection applications. New trifunctional benzoxazines resin have been synthesized using trihydroxytriphenylmethane (TTM) with dimethylaminopropylamine (dmapa), 1-(3-aminopropyl)imidazole (ipa) and aminoethoxyethanol (aee) as amine sources with paraformaldehyde through Mannich condensation. The structural confirmation of synthesized benzoxazines was ascertained by spectral studies. The ring opening polymerization of TTM-Bzs was studied using DSC analysis. All the three TTM-Bz monomers show curing temperature lower than 210°C. The thermo-stability and water contact angle (WCA) of polybenzoxazines were studied using thermogravimetric analysis and goniometer, respectively. Among the TTM-PBz studied, the poly(dmapa) exhibit better thermo-stability and hydrophobic behavior when compared to rest of the synthesized polybenzoxazines. Poly(TTM-dmapa)-coated cotton fabric exhibits the superhydrophobic behavior and mild steel (MS)-coated specimen possesses the higher charge transfer resistance value of 3.47 × 107 Ω cm². It was also inferred that all the TTM-PBz-coated MS specimens exhibit higher corrosion protection behavior as well as good thermo-stability and hydrophobic nature. Further, the obtained results suggested that these materials can be suitably exploited for hydrophobic anticorrosion applications with improved performance and enhanced longevity. [ABSTRACT FROM AUTHOR]

The assumptions of contemporary energy policies are increasing the share of renewable energy sources. Biomass combustion is developing as an alternative to fossil fuels. However, it faces challenges such as limited corrosion resistance of steel boiler components due to chloride compounds in flue gases and fly ash. This paper provides a comprehensive thermodynamic analysis of chloride-induced corrosion in steel in the Fe-O-Cl-Na environment, focusing on the influence of steam concentration in the gas phase. The study was performed by using the general thermodynamic rules, the thermodynamic properties of the pure components involved in the reaction, and the properties of the solutions formed in the liquid and gas phases. The study also examined the impact of alkali metal chlorides, particularly NaCl, on the formation of NaFeO2 in the passive oxide scale layer Fe3O4/Fe2O3. Furthermore, it investigated the condensation of NaCl vapour formation of low-melting eutectic mixtures in deposits and the resulting consequences on the corrosion process. The role of HCl in the chlorination and oxidation process of steel in melted ash deposits was also discussed. The presented thermodynamic analysis was compared with assumptions of an "active oxidation" model. This study can be a valuable resource for experimental research planning and a guide for preventing corrosion in industrial settings. [ABSTRACT FROM AUTHOR]

The performance of corrosion-induced cracking of reinforced concrete members under transverse constraints was studied. Based on the theory of elastic-plastic mechanics and the hypothesis of uniform corrosion of a steel bar, a three-layer hollow cylinder model was established to predict the critical corrosion of the steel bar at the time of the cracking of the concrete cover. Taking the constraint of stirrups on surrounding concrete into consideration, it can be used to predict the corrosion rate of members with stirrups at the time of the cracking of the concrete cover, which further expands the application range of the corrosion-induced cracking models of concrete. On this basis, the critical corrosion rate of concrete under different stirrup ratios at the time of cracking was measured. The calculated results of the model are in accordance with experimental data. For corner steel bars, when the stirrup spacing is less than 100 mm, the existence of stirrups can effectively delay the occurrence of rust expansion cracks and enhance the durability of the structure. On the basis of this study, the problem of corrosion expansion and cracking of the concrete cover caused by non-uniform corrosion of steel bars along longitudinal and radial directions needs to be further studied in the future. [ABSTRACT FROM AUTHOR]

Among the alloy systems for the fabrication of metallic components using additive manufacturing (AM), steels as a broad family of alloys attract significant attention owing to their established mechanical and corrosion properties under various loading and environmental conditions. In an erosive/corrosive environment, the possible failure mechanisms necessitate consideration in materials selection and design. Although functional alloying elements are deliberately added to steels to improve corrosion resistance, the crucial role of initial microstructure and post-process heat treatments are equally critical and cannot be neglected. Specifically, the proper selection and optimization of AM process parameters are essential steps in minimizing microstructural defects. This comprehensive review provides a consolidated treatise of powder atomization techniques, AM process parameter control, rapid solidification principles, their roles on the as-built microstructure. The role of different phases and microstructures formed during post-process heat treatments, and corrosion behavior of various grades of AM steels are also presented. The review presents the interplay between process-microstructure-corrosion properties of the AM steels through the entire fabrication process - from powder feedstock to final AM product exposed to harsh environments. In the first section of this review paper, the authors comprehensively explain the important factors, which affect the processability and quality of AM steel components. In the second section, the authors focus on the microstructure of both as-printed and heat-treated AM steel products, the parameters which determine variations of the microstructure, the effect of microstructural features such as the grain size and the dendrite arm spacing on the mechanical properties, and the detrimental effect of inclusions embedded into the matrix. Finally, the third part of the paper is a comprehensive review of the corrosion of different types of stainless steels (316 L austenitic stainless steel, 420 martensitic stainless steel, martensitic precipitation-hardened stainless steels of 15-5 PH, 17-4 PH, and Corrax) fabricated by AM techniques. [ABSTRACT FROM AUTHOR]

Purpose: This study aims to investigate the corrosion inhibitor effect of migrating corrosion inhibitor (MCI) on Q235 steel in high alkaline environment under cathodic polarization. Design/methodology/approach: This study investigated the electrochemical characteristics of Q235 steel with and without MCI by polarization curve and electrochemical impedance spectroscopy. Besides, the surface composition of Q235 steel under different environments was analyzed by X-ray photoelectron spectroscopy. In addition, the migration characteristic of MCI and the adsorption behavior of MCI under cathodic polarization were studied using Raman spectroscopy. Findings: Diethanolamine (DEA) and N, N-dimethylethanolamine (DMEA) can inhibit the increase of Fe(II) in the oxide film of Q235 steel under cathodic polarization. The adsorption stability of DMEA film was higher under cathodic polarization potential, showing a higher corrosion inhibition ability. The corrosion inhibition mechanism of DEA and DMEA under cathodic polarization potential was proposed. Originality/value: The MCI has a broad application prospect in the repair of damaged reinforced concrete due to its unique migratory characteristics. The interaction between MCIs, rebar and concrete with different compositions has been studied, but the passivation behavior of the steel interface in the presence of both the migrating electric field and corrosion inhibitors has been neglected. And it was investigated in this paper. [ABSTRACT FROM AUTHOR]

The quality of construction projects is related to the safety of people's lives and property, and also has a greater impact on the stability of the entire society; factory structure is one of the most common productive buildings, and some factory buildings have been partially lost its using function due to a long service history; in order to ensure the safety, applicability and durability of these factory buildings and continue to utilize or strengthen these factory structures, it is necessary to perform safety testing and identification for factory buildings at the first time. Structural safety assessment is the process of inspecting, measuring, analyzing and evaluating the structural effects, structural resistance and their interrelationships and finally obtaining structural safety grade of buildings that have been built or in service for many years. On the basis of summarizing and analyzing previous research works, this article expounded the research background, current status and future challenges of building safety grade identification, elaborated material testing methods, specifications, frameworks and processes of security grade identification for factory structure buildings, analyzed the concrete strength and steel corrosion detection, structural seismic identification and bearing capacity calculation of factory building, and proposed corresponding reinforcement measures and discussed its reinforcement effect. The final identification results of an engineering case are in good agreement with its actual construction conditions and on-site inspections and basically satisfactory the results of the factory building structure. The study results of this paper provide a reference for the further researches on the safety grade identification and reinforcement effect of the factory structure building. [ABSTRACT FROM AUTHOR]

In recent years, numerous innovative approaches have emerged to enhance the corrosion resistance of materials. This study investigates the effect of enhancing mild steel corrosion through the incorporation of unzipped multiwalled carbon nanotube oxides (UMCNO) into epoxy resin. Additionally, the effect of various operating parameters, such as temperature, UMCNO concentration, salt concentration, duration of exposure, and coating thickness, have also been considered in the study. The Box–Behnken method was used for experimental design and correlation of corrosion rate with various operating parameters, followed by analysis of variance of both five‐ and three‐parameter models. Notably, despite variations in temperature and salt concentration, the corrosion rate remained negligible, confirming its suitability in various marine conditions. Furthermore, it was observed that the corrosion rate of mild steel coated with epoxy decreased with the addition of UMCNO. A corrosion rate of 0.182 mpy was observed for epoxy resin incorporated with 0.5 % UMCNO over a 14‐day period, which is lower compared to other conditions. Electrochemical impedance spectroscopy and potentiodynamic polarization analysis showed higher corrosion‐resistant properties in epoxy coating incorporated with UMCNO. In addition, it was evident from the contact angle measurement that the corrosion rate of mild steel was highly dependent on the concentration of UMCNO. [ABSTRACT FROM AUTHOR]

Early CO2 curing acting as a new curing technique is an effective way to cut down on carbon footprint in cement industry. It also improves the strength development and long-term durability of concrete without reinforcement. Given the fact that reinforcement concrete is most widely used in construction and building fields, the carbon sequestration potential will be enhanced remarkably if this curing technology can be used in reinforced concrete. However, the impacts of early CO2 curing on the corrosion behavior of steels, which is the major concern for reinforced concrete exposure to chloride, is unclear yet. In this work, the permeability of chloride, threshold chloride value and corrosion behaviors of steels in cement mortar were determined to comprehensively study the effect of early CO2 curing on the chloride induced corrosion of steels. Early CO2 curing lowers the chloride ions permeability of mortars, in particular for the mortars with 28 day curing ages. Steels take longer time to form stable passive films in early CO2-cured mortar than in conventional moist-cured ones. Early CO2 curing reduces the chloride threshold concentration of mortar, in particular for the mortars that the whole cross section is carbonated, the reduction reaches ∼50%. However, it exerts few effects on corrosion induction phase of steel rebar. Moreover, early CO2 curing decreases the corrosion rate of steel bars in corrosion propagation phase and thus the overall corrosion rate of steels during the whole testing process due to slower chloride ingress rate. Thus, early CO2 curing can act as an alternative curing technique in the production of pre-cast reinforced concrete exposed to chloride. [ABSTRACT FROM AUTHOR]

In the present study, 104 sets of flexural tests on corroded prestressed concrete (CPC) beams were gathered from different publications. A flexural strength database for CPC beams was created by incorporating standardized concrete strength and the corrosion rate of prestressed steel. This database enables the analysis of the impact of different factors on the flexural capacity, such as the beam's width and effective depth, concrete compressive strength, shear span ratio, the prestressed steel's corrosion level, prestressing ratio (PPR), and the effective prestress. The findings show that the flexural strength of the CPC beams is notably influenced by variations in beam width, shear span ratio, and the prestressed steel's corrosion level and prestressing ratio compared to other parameters. Furthermore, a comparison was conducted of the Chinese code, Eurocode and ACI standard for evaluating the flexural strength of CPC beams using the established database. It shows that the three design codes overestimate the flexural strength of CPC beams, and it is unsafe to predict flexural strength using these three codes without taking into account the impact of corrosion. Finally, a practical model based on the ACI standard is suggested to provide precise and reliable predictions across a diverse set of test data. [ABSTRACT FROM AUTHOR]

The homogeneous acid etching of conventional acid in porous heterogeneous carbonate reservoirs leads to a large amount of consumption in the near-wellbore area, which makes the acidification effect often not ideal. In order to improve the acidizing effect of porous heterogeneous carbonate reservoirs, viscous acid is used to increase the stimulation of the target block in this paper. Through systematic experiments, the adaptability of the viscous acid in the four layers of the M reservoir in the target block was evaluated, and the MD and ME layers suitable for acidizing stimulation were determined in combination with physical property analysis. Finally, based on the geological characteristics and experimental data of the preferred layers, a two-scale acid wormhole growth radial model was established, and the construction parameters of acidizing stimulation were optimized. The results show that (1) The preferred viscous acid system has a dissolution rate of more than 95% for the rock powder in the four layers. When the matrix permeability is high, the effect of the acid wormhole is obvious and the permeability increase is higher. (2) The steel sheet corrosion and residual acid damage experiments showed that the acid system was not corrosive to the wellbore, and the reservoir damage rate of the residual acid after the reaction was low. (3) Based on the relationship between reservoir porosity and permeability and the position of edge and bottom water, the MD and ME layers with more potential for acidizing stimulation are selected. (4) The results of the numerical simulation show that the optimal acid pump rate of the MD and ME layers is 1.4 bpm and 1.0 bpm, and the acidizing fluid volume is 255 bbl, which can form effective acid wormholes, and the range of reservoir permeability transformation is the largest. The field application results show that the optimization scheme effectively improves the production of oil wells, verifies the practicability of the scheme, and provides a reference for the process optimization of viscous acid in the same type of porous heterogeneous carbonate reservoir stimulation. [ABSTRACT FROM AUTHOR]

In this study, the properties of steel strand-reinforced reactive powder concrete (RPC) with mixed steel fibers and basalt fibers were investigated. The volume ratios of steel fibers and basalt fibers ranged from 0% to 2%. The reinforcement ratio of steel strands was 1%. The flexural strength and toughness were measured. Moreover, the impact toughness was determined. The studies were carried out under an erosion environment with chlorides and sulfates. The electrical resistance and the ultrasonic velocity were obtained to assess the salt corrosion resistance performance of steel strand-reinforced RPC. The results show that the addition of basalt fibers and steel fibers can improve the mechanical strength, ultrasonic velocity, flexural toughness, and impact toughness and decrease the performance degradation of the steel strand-reinforced RPC under the conditions of dry–wet alternations of NaCl and Na2SO4 solutions. Basalt fibers and steel fibers can improve the steel strand-reinforced RPC's flexural strength by rates of up to 13.1% and 28.7%, respectively. Moreover, the corresponding compressive strength increases by 10.3% and 18.3%. The flexural strength decreases by 11.2%~33.6% and 7.3%~22.7% after exposure to the NaCl and Na2SO4 dry–wet alternations. Meanwhile, the corresponding compressive strength decreases by 22.1%~38.9% and 14.6%~41.3%. The electrical resistance increases with the addition of basalt fibers and decreases with the increasing dosages of steel fibers. The steel strand-reinforced RPC with the assembly units of 1% steel fibers and 1% basalt fibers shows the optimal mechanical properties and salt resistance considering its wet–dry alternation performance. The properties of steel strand-reinforced RPC decrease more rapidly after undergoing NaCl erosion than Na2SO4 erosion. [ABSTRACT FROM AUTHOR]

Diagnostics of existing buildings includes, among others research to assess their durability. In the case of reinforced concrete structures, such tests include semi-destructive electrochemical tests to forecast the corrosion risk of steel bars in concrete, and one of the methods used is the electrochemical, polarizing galvanostatic pulse method. The aim of the article was to recognise the influence of element effort on the measurement results obtained with this method. For the tests, a reinforced concrete cantilever slab loaded monotonically was used. During the tests, the stationary potential and corrosion current density of the main reinforcement bars, as well as the resistivity of the concrete cover, were measured. On the basis of the results obtained, it was found that the level of effort on the element affects the values of the measurements performed. Differences in the values of measured parameters at different levels of element effort are sometimes so large that they may significantly affect the conclusions about the corrosion risk of the tested reinforcement, and thus incorrectly estimate the durability of the tested element. [ABSTRACT FROM AUTHOR]

Abstract Predicting the corrosion rate for soil-buried steel is significant for assessing the service-life performance of structures in soil environments. However, due to the large amount of variables involved, existing corrosion prediction models have limited accuracy for complex soil environment. The present study employs three machine learning (ML) algorithms, i.e., random forest, support vector regression, and multilayer perception, to predict the corrosion current density of soil-buried steel. Steel specimens were embedded in soil samples collected from different regions of the Wisconsin state. Variables including exposure time, moisture content, pH, electrical resistivity, chloride, sulfate content, and mean total organic carbon were measured through laboratory tests and were used as input variables for the model. The current density of steel was measured through polarization technique, and was employed as the output of the model. Of the various ML algorithms, the random forest (RF) model demonstrates the highest predictability (with an RMSE value of 0.01095 A/m2 and an R 2 value of 0.987). In light of the feature selection method, the electrical resistivity is identified as the most significant feature. The combination of three features (resistivity, exposure time, and mean total organic carbon) is the optimal scenario for predicting the corrosion current density of soil-buried steel.

Steel corrosion is one of the main factors limiting the durability of existing reinforced concrete components. Based on the corrosive circumstances, different prevention and repair methods can be applied. In the case of carbonation-initiated corrosion, chemical re-alkalisation (CRA) is one of the standard measures to counteract alteration processes in the concrete that lead to reinforcement corrosion. The current state of research on the CRA of carbonated concrete and the various materials that have been investigated in terms of their applicability for this repair measure are summarised. The review summarises current research results in the field of carbonated concrete and the proven pozzolanic reactivity of the carbonation products in contact with portlandite, which suggests an inhibitory effect on CRA, although this has not yet been investigated. There are also initial attempts that deviate from the application of classic Portland cement as a repair material, but their applicability in practice must be questioned. The use of alternative binders and the associated different compositions of pore solutions and varying alkalinity of these binders (e.g. composite cements with a high substitution rate or alkali-activated binders), have not yet been investigated for repair processes such as CRA, although the chemical composition of binders is of the greatest importance for successful application of the repair measure. [ABSTRACT FROM AUTHOR]

Corrosion of steel bars embedded in reinforced concrete structures considerably reduces the service life and even causes early failure of the structure. This paper investigates the early corrosion behavior of an alloy corrosion-resistant steel bar in seawater–sea sand concrete (SWSSC) using various electrochemical measurements [electrochemical impedance spectroscopy (EIS) linear polarization resistance (LPR)] and surface characterization techniques [scanning electron microscope-energy dispersive spectroscopy (SEM-EDS), atomic force microscope (AFM), and X-ray photoelectron spectroscopy (XPS)], in comparison to low carbon steel bar (LC) and stainless steel bar (SS). The results reveal that the Cr10Mo1 alloy corrosion-resistant steel bar (CR) in SWSSC shows significant increase in the radius of the capacitive arc in later stages, particularly in the low frequency region. This increase in CR can be attributed to the enhanced corrosion resistance of the passivation film, as well as the rise of impedance at the interface between the passivation film and the concrete matrix. These improvements have effectively inhibited the penetration of free chloride ions into the concrete, thereby impeding the initiation and propagation of corrosion in CR In addition, the mechanical properties, pore structure and the hydration production of SWSSC were investigated. Based on the interactions between steel substrate and concrete matrix, the possible resistance mechanism of CR was proposed. This study innovatively provides a comprehensive evaluation of the effectiveness of CR in SWSSC. [ABSTRACT FROM AUTHOR]

The mechanism of steel corrosion in recycled brick powder (RBP)–incorporated concrete remains unclear considering the potential utilization of active RBP for low-carbon design in engineering structures. This study aimed to point the influence of RBP on the corrosion behavior of reinforced concrete under the action of chloride or carbonation. Mortar containing RBP (RBPM) was used in this study to concentrate on the effect of RBP and limit the effect of coarse aggregate. The mechanical, chloride penetration, and carbonation properties of RBPM were first investigated. Then the steel corrosion in reinforced RBPM under the action of chloride or carbonation was evaluated by different electrochemical tests. The underlying mechanisms were elucidated by the chemical composition, pH value, and pore structures of RBPM. The results showed that the compressive strength of mortar decreased 21.7% when 30% RBP was used. The addition of RBP reduced the chloride ion permeability but increased the carbonation depth of RBPM. The corrosion caused by chloride penetration in reinforced RBPM was reduced with a higher corrosion potential and lower corrosion current density, which resulted in an approximately 20% lower mass loss with 30% RBP. However, compared with normal concrete, RBPM suffered an increase in corrosion after carbonation. The corrosion current density and mass loss were greatly increased with increasing the RBP content. When the replacement ratio of RBP was 20%, the mortar was in low corrosion state after carbonation curing for 56 days. This was because a combination of the pozzolanic, filling, and nucleation effect of RBP contributed to a 16.28% lower cumulative pore volume and lower pH of RBPM. Considering the effect of RBP on the mechanical properties and corrosion of reinforce mortar, this study suggested a utilization ratio of 20% for RBP in the practical project. [ABSTRACT FROM AUTHOR]

The current study investigates the influence of immersion time (7, 14, 21, and 28 days) on the corrosion behaviour of American Petroleum Institute (API) X70 and X80 steel grades in freely aerated simulated concrete pore solution (pH ~ 12 to 13.8) utilizing electrochemical techniques such as electrochemical impedance spectroscopy, linear polarization, and cyclic polarization. The electrochemical results suggest that the corrosion resistance of X70 line pipe steel increases as immersion time increases (from 7 to 28 days) due to the formation of a stable protective oxide layer on the surface. In the case of X80 line pipe steel, however, the corrosion resistance increases as immersion time increases from 7 to 14 days due to the preferential dissolution of bainite as a result of its higher activity, which initiates the formation of passive film. Furthermore, after 21 days of immersion of X80 line pipe steel in simulated pore solution, a considerable decline in corrosion resistance was observed, which indicates de-passivation, as a result of an increase in oxide film thickness and subsequent spalling off. Intriguingly, as compared to X80 line pipe steel, X70 line pipe steel has a greater potential for producing a stable protective oxide layer without the appearance of minor cracks after a 28-day immersion period, thereby preventing further corrosion and enhancing corrosion resistance. [ABSTRACT FROM AUTHOR]

Abstract Chloride-induced steel corrosion is known to be a very common kind of deterioration of reinforced concrete. It is beneficial to bind free chloride ions to reduce the corrosion probability of the reinforcement embedded in the concrete. The binding capacity of the concrete varies according to its cementitious system. This paper investigates the chloride binding capacity of different kinds of supplementary cementitious materials (SCMs): Ground granulated blast furnace slag (GGBFS), Fly ash, and Metakaolin as a partial replacement of Ordinary Portland Cement (OPC). Different properties of concrete after chloride binding are assessed by carrying out the following tests: half-cell potential, accelerated corrosion test, compressive strength, rapid chloride penetration test, sorptivity test, measuring pH value of concrete, and XRD. The results showed that utilizing the SCMs in concrete can enhance the chloride binding capacity, especially those materials that have high quantities of aluminate and calcium in their chemical composition like GGBFS. Based on testing results, it’s recommended that the limit of the chloride content in the different codes should be revised regarding the binding capacity according to the type and quantity of the cementitious materials used.

An atmospheric plasma spray deposition process was adopted for coating regular-shaped, Stellite 6 powder directly on a rolled 3mm size AISI 304 austenitic grade stainless steel substrate without any intermediate bond layers. Coating thickness as measured in a scanning electron microscope was obtained as 74 μm, 128 μm, and 215 μm. An experimental investigation of the functional behavior such as corrosion, microhardness, and erosion of the coated steel at different operating temperatures was undertaken to determine the suitability of its application in the industry. Erosion tests were conducted in an air jet tribo-tester utilizing alumina as an erodent with normal impingement angle at room temperature, 300∘C, and 600∘C. It was difficult to identify a single coating thickness that can be satisfactorily used for superior erosive wear properties with corrosion resistance. So modern management tools such as tri-vector and technology sieve analysis procedures as identification techniques were adopted for the selection of the best coating thickness by complying with the mechanical, erosion, and corrosion resistance properties. Steel coated with 128-μm coating thickness provides the best result for a combination of functional characteristics. [ABSTRACT FROM AUTHOR]