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The durability of reinforced concrete structures exposed to aggressive environments is affected by corrosion of carbon steel reinforcement. For this reason, it is of great practical interest to look for alternative solutions guaranteeing durability through the incorporation of corrosion‐resistant materials, such as stainless steel rebars. This type of steel is specially recommended for structures with a long lifespan, located in aggressive environments, with chlorides or de‐icing salts, and for structures where repair, inspection and rehabilitation is complicated. This solution presents a challenge from the point of view of the materials themselves, the mechanical design and their durability. This article presents the material properties of stainless steel and their influence on concrete structures. Furthermore, it is explained how these properties have been taken into account in the latest draft of the second‐generation Eurocode 2. [ABSTRACT FROM AUTHOR]

Gravimetric and electrochemical studies established that nitrogen-containing urotropin, urea, and cysteine of concentrations 1 g/L and the urea + cysteine composition exhibit satisfactory inhibitory properties in a chloride-acetate solution upon mixing. Cysteine and its compositions with urotropin and gum effectively inhibit the corrosion steel rate in stratal water. The studied compounds are inhibitors of mixed action since they retard electrode reactions. [ABSTRACT FROM AUTHOR]

Inhibitors for the prevention of corrosion in reinforced concrete are chemical substances able to reduce carbon steel reinforcements corrosion without altering the overall properties of concrete. Today, many commercially available substances have a negative impact on human safety during either the inhibitor synthesis, their handling or application in field. Green corrosion inhibitors are nontoxic, biodegradable and environmentally biocompatible substances. They are generally made of extracts from natural plants or waste, which are abundantly available in several countries. The majority of green inhibitor molecules usually contain multiple bonds, aromatic rings, polar functional groups and electronegative atoms as P, N, S or O; the latter are able to coordinate with metal cations to form protective layers on the metallic surface of the reinforcements, so as to inhibit the development (initiation and/or propagation) of the corrosion process. In this review, the most recent achievements on the study and investigation of green corrosion inhibitors for concrete structures are presented and discussed. Inhibitors are classified based on their nature and inhibition mechanism. The inhibition effectiveness of the substances is compared with the well-established effective nitrite-based inhibitor, distinguishing between accelerated and long-term tests. Based on the available data, a summary of corrosion inhibitors efficiency is reported. [ABSTRACT FROM AUTHOR]

Service failure of mild steel has been a challenge in many industries such as automotive, petrochemical and marine, thus, limiting the application of mild steel. This has prompted the use of several inhibitors as surface protectors against corrosion. In this work, the inhibiting action of the extract from leaves and peels of Chrysophyllum albidum on mild steel corrosion in 1 M H2SO4 solution was studied using weight loss, gasometric and polarization techniques. The results showed that the inhibiting action increased with the increasing concentration of the inhibitors. The highest efficiency of 94.39 and 99.96% were respectively obtained for leaves and peels extract for 18 days with a concentration of 1.5 g/L. More so, the leaves and peels extract inhibited mild steel exhibited a significant corrosion rate of 0.0616 and 0.0254 mm/year, respectively. There was a good agreement between weight loss, gasometric and electrochemical methods (potentiodynamic polarization). Chrysophyllum albidum adsorbed on the mild steel surface in accordance with a Langmuir isotherm adsorption model with R2 values of 0.9940 and 0.9937 for the leaves and peels extract, respectively. In this study, Chrysophyllumalbidum extract was shown to reduce corrosion of low carbon steel, and its use in acidic media is thus recommended. [ABSTRACT FROM AUTHOR]

Microbiologically influenced corrosion (MIC) is a serious threat to the integrity of crude oil pipelines. Sulphate-reducing bacteria (SRB) are the primary microorganisms responsible for MIC, and their aggressiveness is dependent on the energy source available to them. Acetate, a common energy source, has been shown to accelerate the corrosion of carbon steel in the presence of SRB. This study investigated the effect of acetate on the growth of SRB and the corrosion of carbon steel plates in simulated anaerobic conditions. The corrosion kinetics were studied using linear polarization resistance (LPR) and weight loss immersion tests for 42 days. The samples were characterized using Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDX). The results show that the addition of acetate to cultured media significantly increased the corrosion rate of carbon steel plates in both formation water and Postgate Medium B (PMB). This was due to increased growth of SRB in the presence of acetate, which led to the production of more corrosive hydrogen sulphide (H2S). The findings based on experimental data obtained from this study confirm that acetate can accelerate the corrosion of carbon steel in the presence of SRB. [ABSTRACT FROM AUTHOR]

The study investigated the corrosion-inhibitory properties of three synthetic triazole Mannich bases on C1018 carbon steel using various electrochemical techniques. The inhibitors, namely 4-amino-2-[(4-methylpiperazin-1-yl)methyl]-5-(pyridin-4-yl)-2,4-dihydro-3H-1,2,4-triazole-3-thione (4MPT), 4-amino-2-[(piperidin-1-yl)methyl]-5-(pyridin-4-yl)-2,4-dihydro-3H-1,2,4-triazole-3-thione (PPT) and 4-amino-2-[(morpholin-4-yl)methyl]-5-(pyridin-4-yl)-2,4-dihydro-3H-1,2,4-triazole-3-thione (MPT), demonstrated the high inhibition efficiencies of 92.8%, 93.3% and 92.6%, respectively, and adhered to the Langmuir adsorption isotherm. The inhibitors also functioned as mixed-type inhibitors and improved the protective layer on the metal surface. The study also utilized scanning electron microscopy - energy dispersive x-ray (SEM-EDX) analysis to examine the surface morphology of the uninhibited and inhibited carbon steel specimens. Furthermore, density functional theory (DFT) was utilized for theoretical calculations, which corroborated with experimental measurements. [ABSTRACT FROM AUTHOR]

In this work, magnetic responses from artificial corrosion defects were investigated using a differential fluxgate probe. Different rates of corrosion defects were prepared based on the electrolytic corrosion process on the surface of a carbon steel plate by manipulating the corrosion period. Then, the differential fluxgate probe, consisting of two miniature fluxgates arranged in a planar configuration and a circular excitation coil, was used to measure the real and imaginary components of magnetic responses from the corrosion defects in the range of 5 to 510 Hz. The real differential magnetic response from the probe showed that the magnetic signal change was proportionally increased with the corrosion period, revealing the increased depth of the corroded region with the electrolytic corrosion period. The magnetic response induced by an excitation field from 10 to 110 Hz could be utilized to enable a sensitive depth estimation of a corrosion defect on high-permeability steel at a sub-millimeter resolution. [ABSTRACT FROM AUTHOR]

A thermodynamic model (U-Cal model) is proposed to predict the fugacity and water content in the CO2-rich phase (gas or supercritical fluid), and the CO2 solubility and pH in aqueous solutions in a CO2 capture and storage environment, i.e., a CO2 environment in a supercritical state. The values predicted by the U-Cal model agree well with measured values. The water content in the CO2-rich phase increases to 1-10 g/L as a result of the mutual dissolution of CO2 and H2O. The increase in the solubility of CO2 in aqueous solution and the decrease in the pH with increasing pressure are small. The CO2 corrosion behavior of carbon steel is discussed to use the U-Cal model. In iron dissolution-dominant CO2 corrosion in an aqueous solution with carbon steel, the corrosion rate can be understood as a function of the pH. In FeCO3 formation-dominant CO2 corrosion, it is considered that the corrosion progresses as FeCO3 dissolves to supersaturation and then FeCO3 precipitates on the surface of the material. The FeCO3 precipitation behavior is predicted from the crystal growth rate equation. Corrosion of carbon steel in the CO2-rich phase involves similar mechanisms to corrosion in an aqueous solution; however, the corrosion rate is lower. [ABSTRACT FROM AUTHOR]

The aim of this work is to develop new organic bio-sourced inhibitors that are ecofriendly and biodegradable. These natural inhibitors are organic, non-toxic molecules derived from plant extracts, containing numerous secondary metabolites, and are capable of being highly effective in protecting metals against corrosion. This study concerns the extraction, characterization and electrochemical study of natural organic compounds extracted from a species of Sargassum abundant on the coasts of Martinique, Sargassum fluitans III. The objective is to inhibit the corrosion of carbon steel. Electrochemical impedance spectroscopy (EIS) and linear polarization (LP) techniques have led to new experimental results showing inhibitor efficacy. The results obtained show that this plant extract could serve as an effective inhibitor for the C38 steel in acidic media. Studies on the phytochemicals of the crude extract were also carried out. Electrochemical studies, on each chemical families present, were also established to find the main constituents responsible for corrosion inhibition properties of the algae extract. The adsorption of Sargassum fluitans III extract on the C38 steel surface, obeys the Langmuir adsorption isotherm. [ABSTRACT FROM AUTHOR]

The TiO2-SiO2-Al2O3 composite coatings were fabricated on the surfaces of Q235 carbon steel via the sol-gel method to improve its corrosion resistance. The effects of the sintering temperature and the layer number on the corrosion performances were explored. The coating morphology, microstructure and phase composition were analyzed by scanning electron microscopy (SEM) and X-ray diffractometer (XRD). Friction wear experiment, immersion experiment, and electrochemical impedance spectroscopy techniques were used to investigate the corrosion properties of the coatings as well. The results show that the sample with the TiO2-SiO2-Al2O3 coatings sintered at 850 °C are more uniform and denser and have better corrosion resistance and wear resistance than the other coatings. The Rp value of the 3 L coating sintered at 850 °C was about 114 kΩ·cm2, and the average friction coefficient was about 0.36. [ABSTRACT FROM AUTHOR]

The effect of the benzimidazole-2-ylcarbamate methyl (Carbendazim) in corrosion inhibition for carbon steel has been studied using stationary and transient electrochemical techniques. The potentiodynamic curves show that Carbendazim acts as a mixed-type inhibitor. The electrochemical impedance diagrams show a capacitive response of carbon steel with and without inhibitors at different concentrations in 1M HCl. The polarization resistance increases with increasing inhibitor concentration. Consequently, the inhibition efficiency increases and reaches 84% at 10-2M and its adsorption follows the Langmuir isotherm. This shows that the protective effect of Carbendazim is significant in an acidic medium. The study of the synergistic effect with KI shows that an equimolar mixture of KI and Carbendazim compound enhances the inhibition efficiency. The theoretical investigation of the tested compound ability to inhibit corrosion using DFT shows that the HOMO, LUMO, and electrostatic potential maps surfaces can qualitatively identify the most nucleophilic and electrophilic centers, this will enable us to give an adsorption mechanism for the inhibitor studied on the metal surface. [ABSTRACT FROM AUTHOR]

Samples with two different binary blended concrete mixes were prepared, one containing cement replacement of 50% slag (referred here as SL mix) and the other containing cement replacement of 20% fly ash (termed here as FA mix). The water to cementitious ratio used to produce concrete specimens was 0.41. On the top surface of each specimen, various reservoir lengths that ranged from 2.5 cm to 17.5 cm were fitted, and these reservoirs were filled with a 10% NaCl solution. Electromigration was used to accelerate the transport of chlorides, with an applied potential of 9 V at first, and subsequently reduced to 3 V after about a week. The electromigration was applied for a short period (few weeks to a couple of months). For a period of about 1100 days, the corrosion related parameters such as concrete solution resistance, rebar potential, and corrosion current were monitored via the rebar potential measurements, linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS) measurements, the latter used only to obtain the solution resistance. The corrosion current values determined through experimental observations were then converted to mass loss using Faraday's law. The readings of corrosion current values (last 7 sets of readings) as well as the calculated mass loss values were found to be larger for the rebars embedded in specimens prepared with SL mix, followed by rebars embedded in specimens prepared with FA mix. Corrosion current and calculated mass loss values in general tended to increase with increasing solution reservoir lengths. No cracks or corrosion products that reached the surface of the concrete were observed on the specimens for the duration of the reported monitored propagation period. This study offers a framework for future studies on accelerated steel corrosion in concrete. [ABSTRACT FROM AUTHOR]

The inhibiting efficiency of three newly synthesized organic compounds:5-((4'-(dimethylamino)-[1,1'-biphenyl]-4-yl)methylene)-1,3-diethyl-2-thioxodihydropyrimidine-4,6(1H,5H)-dione (HM-1228), 5-((4'-(dimethylamino)-[1,1'-biphenyl]-4-yl)methylene)-2-thioxodihydropyrimidine-4,6(1H,5H)-dione (HM-1227) and 5-((4'-(dimethylamino)-[1,1'-biphenyl]-4-yl)methylene)pyrimidine-2,4,6(1H,3H,5H)-trione (HM-1226) in oilfield produced water on the corrosion of carbon steel has been examined via electrochemical measurements; potentiodynamic polarization (PDP) and electrochemical impedance (EIS) techniques. The adsorption of these compounds on the surface of carbon steel followed Langmuir isotherm. In addition, the surface morphology of uninhibited and inhibited carbon steel was examined by Atomic Force Microscopy (AFM), observing surface improvement when carbon steel samples exposed to the inhibited corrosive solutions. The average surface roughness (Ra) in oilfield produced water solution in the presence of 0.5 mM of HM-1228 inhibitor was 138.28 nm compared to the uninhibited surface 571.62 nm. To explore the corrosion inhibition mechanism, quantum chemical calculations and Monte Carlo simulations were utilized. The HM-1228 inhibitor demonstrated the highest corrosion inhibition efficiency at 94.8% by PDP measurements. The higher corrosion inhibition of compound HM-1228 can be attributed to the presence of di-N-ethyl groups that enhance both electron donating ability and lipophilic properties. [ABSTRACT FROM AUTHOR]

The ethanolic extract of Lentinula Edodes, a fungal species, was evaluated as an ecological, green inhibitor to mitigate corrosion of carbon steel (CS) in acidic media. The Lentinula Edodes body fruit extract (LEBFE) was obtained using a well-established chemical method. Various electrochemical methods were employed to investigate the LEBFE's corrosion inhibition efficiency under different operating conditions. The results showed that LEBFE is an effective mixed-type corrosion inhibitor, with a maximum corrosion protection efficiency 88.5 ± 0.2%. The inhibitor demonstrated efficient corrosion inhibition of the carbon steel surface over extended immersion periods and at various electrolyte temperatures. The FTIR and UV/Vis results indicated that the LEBFE extract contains compounds containing oxygen and nitrogen heteroatoms, which are known to interact strongly with carbon steel. The adsorption mechanism of the inhibitor on the carbon steel surface was based on physisorption, following the Langmuir isotherm. The results support the conclusion that LEFBE can be considered an effective and eco-friendly green inhibitor to control low-carbon steel corrosion in acid media. [ABSTRACT FROM AUTHOR]

In this study, experiments were carried out to assess the microbially influenced corrosion (MIC) risk in the context of the French high‐level radioactive waste disposal. The exposures were carried out at 80°C in different repository relevant conditions, including the presence of different cement‐grout mixtures as filling material. Biotic conditions with nutrient and nonsterile conditions with indigenous microbes added from Callovo Oxfordian clayey rock and without nutrients were considered. For biotic conditions, specific preparations of microbial inoculum were carried out from samples collected at Andra's Underground Research Laboratory and microorganisms from microbial culture collection centers. Corrosion kinetics were determined using traditional coupons and completed with real‐time corrosion sensors. Microbiological characterizations consisted of cultural approach, quantitative polymerase chain reaction, and next‐generation sequencing. The obtained results show no significant MIC and a reduced risk with the use of more alkaline filling material. [ABSTRACT FROM AUTHOR]

The long‐term disposal of nuclear waste in deep geological repositories requires safe containment for up to one million years. To understand how the waste will respond to the gradually evolving environment, researchers can perform sensitive experiments in the laboratory to replicate the repository conditions at specific time points. In Belgium, spent nuclear fuel will be housed within a carbon steel overpack, which is encased within a cement buffer, which may include a stainless steel liner (the "envelope"). The range of corrosion behaviors for carbon steel, and to a lesser extent, stainless steel, has been studied through hydrogen evolution, an end‐product of oxidation under repository conditions. Considerable time may be required for metallic surfaces to approach a steady hydrogen evolution and this is dependent upon the starting condition of the specimen surfaces. The use of nominally‐similar materials can result in significant variation in the reported corrosion rates. The presence of cements, which generate their own hydrogen and influence water chemistry as a function of time, add complexity to even simple experimental configurations that requires careful interpretation. [ABSTRACT FROM AUTHOR]

In this paper, carbon steel corrosion rates from experiments performed in situ (performed in an underground rock laboratory) and ex situ (performed in a conventional laboratory) test methods in anaerobic saturated bentonite are compared. The results indicate that the long‐term corrosion rate follows a power law decay curve, with a higher initial rate and greater rate of decay at higher temperature. In compacted bentonite blocks, varying the density has no significant effect on the corrosion rate measured during in situ testing, whereas granular bentonite of an equal dry density leads to a higher corrosion rate. Precorrosion of test specimens in an aerated solution at room temperature has a negligible effect on the subsequent anaerobic corrosion rate when tested ex situ for durations up to 11.8 years. The main difference between in situ and ex situ tests is the formation of silicon‐rich corrosion products in the ex situ tests but not in the in situ tests. Despite these differences, the corrosion rates in both tests exhibit the same general temporal evolution and similar magnitudes, suggesting that the main steel degradation processes are maintained in both configurations. [ABSTRACT FROM AUTHOR]

In this study, short‐term experiments were carried out to assess the microbially influenced corrosion (MIC) risk in the context of the French high‐level radioactive waste disposal CIGEO (Centre Industriel de Stockage Géologique). The exposures were carried out in different representative media, including the presence of different cement‐grout mixtures as filling material. Nonsterile and biotic conditions with nutrients were considered. For biotic conditions, specific preparations of microbial inoculum were carried out from samples collected at ANDRA's Underground Research Laboratory and microorganisms from the library. Corrosion kinetics were determined using both traditional coupons and completed with real‐time electrical resistance sensors. Microbiological characterizations consisted of cultural approach, quantitative polymerase chain reaction, and next‐generation sequencing. The obtained results show no significant MIC, but a reduced risk was observed using more alkaline filling materials. [ABSTRACT FROM AUTHOR]

For steel structures service in corrosive environments, corrosion reduces the mechanical properties and effective thickness of the structural steel, which has a significant effect on the durability of steel structures. Titanium–clad bimetallic steel (TCBS), a bimetallic material composed of titanium alloy and carbon steel with excellent corrosion resistance has been suggested to solve the corrosion issue. The TCBS consisting of the TA1 titanium cladding and Q235 carbon steel substrate was introduced in the plate girder as the web to improve durability in this study. The stress–strain properties and failure performance of TCBS and Q235 carbon steel were discussed. Notably, the separation between the cladding and the substrate in the TCBS was observed during the necking stage in the tensile coupon test. Welding method between TCBS web and Q235 carbon steel flange was suggested for processing the plate girder, which was validated to be appropriate according to the experimental results. No crack in welding and TCBS web of plate girder was observed during the patch loading test. A numerical parametric study on the ultimate resistance of TCBS plate girder subjected to patch loading was conducted using the finite element software ABAQUS, in which three different key parameters were included. A comparison between the numerical and predicted results indicated that the design equations suggested in EN 1993–1–5 were too conservative to be directly used for predicting the ultimate resistance of the TCBS plate girder under patch loading, which was caused by the strain–hardening effect and yield plateau of the structural steel. The current design equations were modified to effectively predict the resistance properties of TCBS plate girders. [ABSTRACT FROM AUTHOR]

In this work, the corrosion inhibition of carbon steel in 1 molar HCl solution was evaluated by experimental and modeling approaches using 2-mercaptobenzimidazole (2-MBI). To this end, an experimental design for the weight loss method using response surface methodology (RSM) was carried out and the corrosion rate (CR) and inhibition efficiency (IE) were determined. The study was completed at various values of temperature, exposure time, and inhibitor concentration to determine the optimal conditions for corrosion prevention. Using experimental data on the corrosion rate and inhibition efficiency of 2-MBI, new models were developed, the significance of which was tested using ANOVA-analysis of variance. The developed RSM-based CR and IE models were highly accurate and reliable, and their P-values were less than 0.0001. The novelty of this study lies in the newly developed model for the evaluation of 2-MBI inhibition performance and its application to high-temperature conditions in the petroleum industry. Besides, the R2-statistics (R2, adjusted-R2, and predicted-R2), adequate precision and diagnostic plots were used as main measures to verify the accuracy and adequacy of both CR and IE models. In addition, it was observed that inhibitor concentration had the most impact on both CR and IE models compared to other parameters due to its largest F-values (561.65 for CR and 535.56 for IE models). Moreover, the results indicated that adding 140–150 ppm of 2-MBI at low-level temperatures of 30–35 °C had the most interaction effect on the performance of the corrosion inhibition process. In this case, the CR was less than 0.9 mm/y and the IE more than 94%, even after a high exposure time of 105 h. Furthermore, numerical optimization of the corrosion inhibition process for 2-MBI showed that the optimum conditions for maximum IE and minimum CR were achieved at a concentration of 115 ppm, temperature of 30.7 °C, and exposure time of 60.4 h. Under these conditions, the efficiency and corrosion rate were 92.76% and 0.53 mm/y, respectively. Finally, the adsorption of 2-MBI on the sample surface was studied at various exposure times and temperatures. In all cases, the adsorption behavior obeyed the Langmuir isotherm. In this case, the Gibbs adsorption free energy varied from − 33 to − 37 kJ/mol, which reflects both physical and chemical adsorption of the corrosion inhibitor at all tested temperatures and test times. [ABSTRACT FROM AUTHOR]

The corrosion damage of carbon steel due to the breakdown of the coating becomes a major problem in causing the failure of the structure. Therefore, immediate and effective coating repair agents are particularly important. Cerium-based inorganic salts have been well-studied as corrosion-protective inhibitors but are less effective for carbon steels. To solve this problem, organic–inorganic hybrid methods can be applied. In this study, a rare earth element solvent extraction method was used to prepare a repair agent containing organic cerium phosphate complex (organo-cerium) in one step. A corrosion-protective hydrophobic film was formed after dropping it on the exposed substrate after scratch. The morphology, composition, and corrosion resistance of the formed film were investigated by scanning electron microscopy (SEM), Raman spectroscopy, and electrochemical impedance spectroscopy (EIS). The EIS results showed that the formed film has excellent corrosion protection for damaged coating. The quick repair agent prepared in this study has great application value in protecting the exposed steel substrate due to the coating damage in the marine environment. [ABSTRACT FROM AUTHOR]

Copyright of Baghdad Science Journal is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The current paper revolves around the conduct of newly synthesized eco-friendly pyrazole derivative, N-((3,5 dimethyl-1H-pyrazol-1-yl)methyl)-4-nitroaniline (L5), as corrosion inhibitor for carbon steel (CS) in molar hydrochloric acid (1M HCl) solution. Both chemical and electrochemical techniques, namely weight loss measurements (WL), potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) were used to evaluate the efficiency of L5 molecule, as well as quantum-chemical methods. The organic compound was confirmed to be a good anti-corrosion compound with a maximum inhibition efficiency (IE%) of 95.1% at 10-3 M. In accordance to PDP outcomes, the inhibitor L5 acts as a mixed-type inhibitor. Assessment of the temperature influence evinces that L5 is chemisorbed on CS. The adsorption of L5 on CS surface appears to follow the Langmuir model. Scanning Electron Microscopy (SEM-EDX) and UV-visible disclose the constitution of a barrier film limiting the accessibility of corrosive ions into CS surface. Theoretical studies were executed to support the results deriving from experimental techniques (WL, PDP and EIS). Furthermore, theoretical studies were carried out utilizing density functional theory (DFT) and molecular dynamics simulation (MDS) to investigate the most reactive locations of the L5 molecule and its adsorption process. [ABSTRACT FROM AUTHOR]

Copyright of Corrosion & Protection in Petrochemical Industry is the property of Corrosion & Protection in Petrochemical Industry Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study provides two case studies involving carbon steel and 3%-Cr steel exposed to a CO2–H2S environment with a moderate scaling index. The carbon steel tubing show shows pitting and severe corrosion, whereas the 3% chromium steel tubes are undamaged. XRD results showed that the chromium-rich layer did not alter scaling on both tubes. Investigations using SEM and EDS reveal the formation of a dense and compact layer in the 3%-Cr steel, which serves to resist corrosion. In contrast, carbon steel has a porous structure and is easily detachable due to wall shear stress caused by slug movement. In 3%-Cr steel, the EDS analysis reveals a compact layer with a significant number of chromium, which is an indication of a Cr-rich iron oxide layer. Potentiodynamic polarization shows that the anodic curve is shifting, which means that the rate of corrosion is slowing down. This study shows that 3% Cr steel is a good choice for a mixed CO2–H2S environment with a high total dissolved solid (TDS). [ABSTRACT FROM AUTHOR]

Corrosion constitutes a significant issue in industries that handle metals. Corrosion inhibitors with a low impact on the environment provide a significant economic benefit in various engineering applications. In this work, the effectiveness of olive leaves extract is evaluated as a cost-effective and environmentally-friendly corrosion inhibitor. The corrosion of carbon steel in different concentrations of hydrochloric acid (0.1, 1.0, and 2.0 M) when protected by an aqueous solution of olive leaf extract of concentrations ranging from 10 to 60 ppm is investigated. A green extraction process based upon water extraction is used to ensure minimum impact on the environment. Results show that the corrosion inhibition efficiency increased as the concentration of the olive leaf extract increased. An analysis of variance showed a significant effect of acidic molarity, temperature, and inhibitor concentration on the corrosion rate. A significant statistical model indicates that the inhibitor exhibits higher efficiencies at higher acidic molarity. Results of SEM and EDX also demonstrated that a protective film of the inhibitor on the specimen surface plays a role in corrosion inhibition, suggesting that the inhibitor molecules are adsorbed at the interface between the carbon steel and the acid solution. The study provides an insight on the corrosion mechanism and highlights the potential of olive oil extract as an eco-friendly alternative to traditional corrosion inhibitors. [ABSTRACT FROM AUTHOR]

Using gravimetric and electrochemical research methods, the corrosion-electrochemical behavior of carbon steel grade St3 in Kura river water has been. Gravimetric measurements were carried out under operating conditions of the Shemkir and Yenikend hydroelectric power stations for one year. Along with this, the ionic and bacteriological composition, as well as some physicochemical parameters of these waters were established. It revealed that St3 in the Kura water corrodes at a rate of (0.04÷0.05) g/m2•hour, which is characteristic of steel corrosion in fresh waters. In the atmosphere of hydraulic structures, steel corrodes at rather a low rate, i.e. (5÷6)10-3 g/m² hour. As a result of biochemical analysis, sulfate-reducing bacteria (SRB) were discovered in these waters, which are a dangerous organism that releases the corrosive substance of H2S. By taking the anodic and cathodic polarization curves, a quasi-stationary steel corrosion rate was established to be 0.06g/m² h [ABSTRACT FROM AUTHOR]

Potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) were applied to study the inhibitory effect of N-acetylcysteine (NAC) on corrosion inhibition of carbon steel in hydrochloric acid solution. N-acetylcysteine influenced the iron dissolution to a greater extent than the hydrogen evolution reaction acting as a mixed inhibitor, predominantly anodic. The charge transfer resistance (Rct) gradually increased with the inhibitor concentration. From both methods, the inhibition efficiency (IE) reached a value of 89 ± 1% and NAC adsorption followed the Temkin isotherm. The value of adsorption Gibbs energy (Δ G ads o ), around −35 kJ mol−1, indicated a spontaneous adsorption and mixed action mechanism, with NAC chemical adsorption prevailing over physical one. New data will be reported by the computational study, that was performed using the density functional theory (DFT) method in aqueous phase. Quantum chemical descriptors were determined by B3LYP theory level with 6–31G+(d) basis set. Metropolis Monte Carlo atomistic simulation was used to reveal the adsorption configuration and interactions between acetylcysteine molecules and the carbon steel surface. Theoretical results were consistent with the experimental data, showing that the inhibitor action mechanism consisted of mainly chemisorption of its molecules on the carbon steel surface accompanied by van der Waals forces and electrostatic interactions. [ABSTRACT FROM AUTHOR]

The corrosion of carbon steel is always a very serious issue, and the addition of corrosion inhibitors is an effective approach to prohibiting the corrosion of carbon steel. Because expired drugs are environmentally friendly, green, and non‐toxic; thus, this work provides a new idea for the treatment of expired drugs. The expired flunarizine hydrochloride (FH) is used as corrosion inhibitors for Q235 steel, investigating the corrosion inhibition efficiency of expired FH with different concentrations for carbon steel and illustrating the corrosion inhibition mechanism. Electrochemical impedance and Tafel curves are used to investigate the corrosion inhibition of carbon steel under 1 M HCl solution with different concentrations of the expired FH, and the corrosion efficiency is calculated according to the immersion tests, and the corrosion inhibition efficiency is more than 88.5%. Scanning electron microscopy (SEM), Fourier transform infrared spectrometer (FTIR), and Raman spectroscopy strongly support the results of the electrochemical experiment. Besides, the simulation results also provide the strong supports for the experimental results. [ABSTRACT FROM AUTHOR]

To explore the potential of new ecological corrosion inhibitors, we investigated the mechanism of corrosion inhibition in carbon steel using Halopitys incurvus, an algal extract available in both crude and chromatographic fractions, in a 0.5 M H2SO4 medium. Various methods were employed, including gravimetry, electrochemical impedance spectroscopy, polarization curves, scanning electron microscopy (SEM) techniques, and molecular dynamics. The crude extract exhibited a high corrosion‐inhibiting potential, with a maximum inhibitory efficiency of 85.30% at 600 mg/L. The electrochemical results indicated mixed behavior of the crude extract. Furthermore, we found that the adsorption of the crude extract onto the metal surface followed the Langmuir isotherm pattern. The SEM study confirmed our proposition that extract molecules were adsorbed onto the carbon steel surface. Using the chromatographic fractionation protocol, we were able to distinguish four main fractions, and the most effective fractions reached an inhibitory efficiency value of 96.00% at 100 mg/L. The molecular dynamics simulation confirmed the experimental results. [ABSTRACT FROM AUTHOR]

A novel alanine ternary complex (ALA-T) is prepared by the reaction of alanine (ALA), phosphoric acid, and dibutylamine. FTIR technique is used to characterise its structure. The weight-loss experiments in the closed space study the volatility of the alanine ternary complex. The ultrathin coating is formed on the surface of carbon steel by vapour phase assembly of the alanine ternary complex. The thickness of the coatings is measured using spectroscopic ellipsometry. The inhibition effect of ultrathin coatings on the corrosion of carbon steel is studied by the volatile-inhibiting ability (VIA) and the electrochemical tests. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) are utilised to examine the morphology and composition of the carbon steel surface. It shows that the complex ultrathin coating has good corrosion inhibition for carbon steel. The protection mechanism of the ultrathin coating is discussed and analysed. [ABSTRACT FROM AUTHOR]

The performance of Bromhexine syrup has been investigated as a corrosion inhibitor for carbon steel (C-steel) in acid medium using the weight loss method and response surface methodology (RSM) of the design experiment. The effect of the concentration of the inhibitor, temperature and exposure time on inhibition efficiency and corrosion rate was studied. The experimental results revealed that expired drug is an effective inhibitor and its inhibition efficiency increases with the increasing concentration to attain a maximum of 97.23 % at 1.0 (v/v %) at 293 K. The thermodynamic parameters show that adsorption reaction on the C-steel surface is spontaneous and exothermic. Moreover, the energy barrier for the corrosion reaction increases in presence of the inhibitor. The individual and interactive effects of these three parameters were optimized for maximum response of inhibition efficiency using response surface methodology (RSM) within the experimental design. Second-order polynomial model was suggested to predict the inhibition efficiency as a function of three variables. The results from RSM gave a best second order polynomial model for the inhibition efficiencies (IE) with high R²= 0.998 and R² Adj= 0.997. Moreover, the value of Q² greater than 0.9 indicating that the model used is excellent. This confirms a good agreement between experimental observed data and the predicted ones. The optimal inhibition efficiency (IE) obtained by RSM is 101.65 % for a concentration of 0.282 %, temperature of 20.87 °C and immersion time of 4 h. [ABSTRACT FROM AUTHOR]

The corrosion rate of carbon steel under the attack of electrolytic mediums saturated by CO2 at a working temperature of 65 °C under dynamic conditions is studied in this paper. The effect of Ca2+ ions on corrosion rates and their dependency on the associated anion (Cl− or CO32−) with respect to the Ca2+ cation and Na+ are also assessed. A potentiostat/galvanostat associated with a rotor stator in an AISI 1040 steel-ring configuration, rotating at 600 rpm, was used. A linear polarization-resistance technique was applied to calculate the corrosion rate. It is found that the corrosion rate depends not only on the presence of Ca2+, but also on the salt anion added to the electrolytic medium. There was a strong inhibitory effect of the corrosion in the presence of Ca2+ in chloride-free mediums because of an ankerite deposition with a lower solubility compared to siderite. Moreover, it was observed that, even if the corrosion rate increased together with the Cl− concentration, its value depended on the cation introducing the anion. It was higher when Cl− was associated with Na+ compared to when it was associated with Ca2+. We found the following decreasing order in the carbon steel corrosion rate: 2% NaCl + 1380 ppm CaCl2 > 2% NaCl > 2% NaCl + 1360 ppm Na2CO3 > 2% NaCl + 1.25 g/L CaCO3 > 1450 ppm of NaCl > 1380 ppm CaCl2 > 1360 ppm Na2CO3 > 500 ppm CaCl2 > 424 ppm Na2CO3 >> 1.250 g/L CaCO3. [ABSTRACT FROM AUTHOR]

In order to clarify the difference in corrosion performance between low Cr-containing (3Cr, 5Cr, and 9Cr) tubing material and carbon steel N80 in the Carbon dioxide (CO2) flooding injection and production environment and the range of adaptation, corrosion tests and analysis were carried out in simulated working conditions. In this paper, the electrochemical potentiodynamic testing technology and the weight loss method were used to comparatively analyze the corrosion performance and variation law of three types of tubing materials with different Cr contents in a simulated CO2 flooding-produced water environment under different partial pressure conditions. Additionally, scanning electron microscopy and Energy Dispersive Spectrometer (EDS) analysis were conducted to examine the surface corrosion morphology characteristics and elemental composition of material films under various conditions. The results indicate that the open circuit potentials of 3Cr, 5Cr, and carbon steel N80 were similar under the same experimental conditions. However, the open circuit potentials of 9Cr were relatively high and there was an obvious passivation zone in anodic polarization. Nevertheless, compared to that of 13Cr, the passivation state was unstable, and pitting corrosion continued to expand once it formed. This demonstrates that the corrosion resistance of the material can be effectively enhanced and a stable passivation state can be achieved in the anodic polarization region when the Cr content of the material reaches at least 13%. The service life of materials can be predicted based on their corrosion rate under high temperature and pressure simulation environments. We found that 9Cr materials exhibited good adaptability while 3Cr and 5Cr materials showed poor adaptability. Therefore, it was not recommended to use 3Cr and 5Cr materials. Therefore, 3Cr, 5Cr, and N80 materials will be used at lower partial pressure levels of CO2 (<0.2 MPa). [ABSTRACT FROM AUTHOR]

Graphene oxide (EGO) was prepared via an electrochemical exfoliation method and modified with dopamine and tannic acid, and it was then incorporated into epoxy resins to enhance their barrier, self-healing and anticorrosion performances. The morphologies, structures and compositions of the HGO (GO prepared via Hummers' method), EGO and MGO (modified EGO) were characterized via SEM, TEM, AFM, Raman spectroscopy and XPS. The protective performances of the epoxy varnish coatings, EGO/epoxy coatings and MGO/epoxy coatings with different contents of MGO were evaluated via EIS measurements, and the role played by MGO on the coating defects was determined via LEIS and salt spray tests on the scratched coatings in a 3.5% NaCl solution. The results show that the dopamine and tannic were successfully grafted onto the EGO surface via π–π interactions and chemical bonding, and that the dispersibility of the MGO in the epoxy resins was facilitated. The epoxy coatings with a 0.1% addition of MGO possessed the best anticorrosion properties (|Z|0.01Hz > 1010 Ω cm2 after 70 days immersion in 3.5% NaCl solution) in comparison to the other coatings due to the "labyrinth effect" formed by the uniformly dispersed MGO. Meanwhile, the grafted tannic acid was released at the coating defects and provided inhibition functionalities for the substrate. As a result, the corrosion of the carbon steel was significantly decreased. This work provides a new perspective on the efficient modification of electrochemically exfoliated GO epoxy coatings for metals by combining the advantages of dopamine and corrosion inhibitors. [ABSTRACT FROM AUTHOR]

We present an ultrasonic research technique that can carry out in situ, direct monitoring of the 3D morphologies of corrosion substrates. The technique has a customizable lateral resolution, an ultra-high axial resolution of 100 nm, and an experimentally proven measurement accuracy. In using the technique to monitor the localized corrosion processes of carbon steel under constant DCs, it was observed that during each of the experiments conducted in alkaline environments, iron dissolution accelerated for a certain period of time and then slowed down. Based on the various features of the ultrasonic signals acquired and the XRD spectra of the corrosion products obtained, it was deduced that an increase in iron dissolution rate as such was accompanied by the depositing of solid corrosion products onto the substrate used and driven by the formation of Fe3O4, which consumed electrons. After a while, the corrosion product layer collapsed and the formation of Fe3O4 was halted. [ABSTRACT FROM AUTHOR]

While carbon steel cross‐sections are traditionally categorized as Class 1, 2, 3 or 4, depending on when local instability occurs relative to the key stages of yielding, for stainless steel the lack of a well‐defined yield point and the presence of continual strain‐hardening render this approach artificial and superfluous. A new design methodology is therefore needed, which accounts for the effects of both strain‐hardening and local buckling. The proposed method is based on a modified finite strip method, which accounts for the effects of gradual loss of stiffness due to yielding on the stability of thin‐walled members. Extensive verification of the new method against experimental data showed that cross‐sectional capacities are generally well predicted, with average ratios of the measured to the predicted capacity of 1.18 and 1.19 in compression and bending, respectively, and a standard deviation of 0.10 in both cases. This is a significant improvement over the EN 1993‐1‐4 design rules, where the averages over the same dataset were 1.27 and 1.40, respectively, with standard deviations of 0.14 and 0.17. The rotational capacity of stainless steel cross‐sections in bending was also reasonably well predicted, with an average ratio of measured to predicted curvature of 1.79. [ABSTRACT FROM AUTHOR]

The transformation kinetics, microstructure, and mechanical properties of medium-carbon bainitic steel with and without niobium (Nb) were investigated by dilatometric measurements, microstructural characterization, and mechanical testing. It was found that the addition of 0.018 wt.% of Nb can accelerate the bainite transformation kinetics (incubation time, completion time, transformation velocity, bainite volume fraction) of the medium-carbon steel. The completion time of isothermal bainite transformation was reduced from 813.6 to 424.8 s. Furthermore, Nb addition also refined bainitic ferrite plates from 140 ± 0.5 to 116 ± 0.6 nm. The higher volume fraction of finer bainitic ferrite resulted in higher steel strength and toughness. Due to bainitic ferrite refinement, more carbon atoms were discharged into film-like retained austenite. Hence, the Nb-containing medium-carbon steel had higher work hardening capability than the steel without Nb due to the presence of finer retained austenite with a high carbon concentration. [ABSTRACT FROM AUTHOR]

The influence of polyvinylpyrrolidone (PVP) with molecular mass of 12 600 and 28 000 at concentrations of 0.2; 0.5 and 1.0 g/dm3 on the corrosion rate of 20 steel in the chloride-acetate solution and in the model stratal water was investigated by gravimetric and electrochemical methods. Under dynamic conditions maximum inhibition of the steel corrosion rate was observed at a PVP concentration of 0.5 g/dm3 in both environments. A further increase in inhibitor concentration to 1.0 g/dm3 reduces the degree of protection more significantly in chloride-acetate solution than in the stratal water. The PVP with a higher molecular mass reveals higher protective properties, which is typical of polymers capable of adsorbing both linearly and in a ball. [ABSTRACT FROM AUTHOR]

The synergistic effect and synergistic mechanism of quinoline quaternary ammonium salt (QQAS) and L-methionine (L-Met) as Q235 carbon steel corrosion inhibitors in 1.0 M HCl solution were studied by weight-loss and electrochemistry and theoretical methods at 60°C. Both the weight-loss and the electrochemistry experiment results show that there is obvious synergistic effect with a synergistic index of 8.81 between QQAS and L-Met. The results of the electrochemical experiments show that the inhibition efficiency of the mixture corrosion inhibitor reaches 98.46% when the concentration of the mixture inhibitor is 50 mg/L with the molar ratio of QQAS and L-Met of 3 to 1. The quantum chemical parameters calculated at B3LYP/6-311++G** level indicate that QQAS can be preferentially adsorbed for its stronger offer electron ability. The results of molecular dynamics studies show that QQAS is preferentially adsorbed onto the surface of carbon steel forming the framework of the corrosion inhibitor film. And L-Met molecules fills the gap to make the film more condensed. The adsorption energy and the density distribution of the inhibitor and water molecules indicate that the corrosion inhibition performance is the best when the molar ratio of QQAS and L-Met is 3:1. And the synergistic inhibition mechanism is the monolayer adsorption mechanism. These results can provide useful guidance for further study on the synergistic corrosion inhibition effects of QQAS and other compounds. [ABSTRACT FROM AUTHOR]

One of the main corrosive environments in gas processing is the moisture condensation condition in the vapor phase and variable wetting on the inner surface of equipment. In this case, steel microstructure and non-metallic inclusion content affect formation and development of corrosion defects of carbon and low alloy steels. It is shown that localization of carbon dioxide corrosion within a welded seam of X65 steel proceeds more intensively than within basic metal. Tests conducted in a specially designed stand under variable wetting conditions show that at the surface of 09Mn2Si steel local defects in the form of corrosion pitting occur in places where corrosion products are carried away. The morphology (density, continuity, etc.) of corrosion products (FeCO3) formed affects their potential barrier properties with respect to carbon dioxide corrosion of steel. Use of corrosion inhibitors prevents generation of local damage on steel under the action of media containing CO2. [ABSTRACT FROM AUTHOR]

Carbon steel suffers from serious corrosion in NaCl solution, the development of effective inhibitor has become a hot issue. The corrosion inhibition performance of sodium lauryl ether sulfate (AES) and lauryl betaine (BS‐12) and the mixture of the two inhibitors were studied using electrochemical and weight‐loss methods. Results showed the corrosion inhibition efficiency order is AES + BS‐12 > BS‐12 > AES, the inhibition efficiency of the inhibitor increases with the increasing of concentration and the maximum inhibition efficiency is 95.9% in the solution with 200 mg L−1 AES + BS‐12. Inhibitor can adsorb on Q235 surface through physical and chemical interactions and the adsorption obeys Langmuir isotherm. The migration of the corrosive ions to the metal is hindered and the metal is protected. [ABSTRACT FROM AUTHOR]

The inherent defective morphology of the physical vapor deposition (PVD) hard coatings limits their corrosion protective ability. We examined the impact of nitride‐based PVD coatings, including TiN, TiAlN, and CrN deposited on inert substrates by cathodic arc PVD method (CA‐PVD), on the galvanic corrosion of carbon steel. Their contribution was evaluated by zero‐resistance ammeter (ZRA) and electrochemical impedance spectroscopy (EIS) in 3.5 wt.% NaCl at pH 2 and 6, with and without aeration. The results indicated the prominent role of the coating type and the coupling environment on the generated galvanic currents. Immersion tests for the TiN‐, TiAlN‐, and CrN‐coated steel cross‐sections visually verified these results. The galvanic current contribution was distinct in environments where oxygen reduction is the dominant cathodic reaction. However, the layers' contribution to galvanic corrosion was minimal in deaerated acidic solutions, which is attributed to the high bonding strength of adsorbed intermediates to the coating surfaces. [ABSTRACT FROM AUTHOR]

Metal surfaces can become damaged by corrosion when they interact with their surroundings, leading to huge financial losses. The use of corrosion inhibitors is one of the most crucial ways to combat the risky and hazardous effects of corrosion. In the present research, electrochemical techniques and surface analysis have been used to characterize the inhibition properties of (3-hydroxy-4-((4-nitrophenyl)diazenyl)-5-(phenylamino)thiophen-2-yl)(phenyl)methanone for the corrosion of carbon steel in an aerated 1.0 M HCl solution. Steel's corrosion resistance was discovered to be improved by the presence of the examined inhibitor in 1.0 M HCl medium through the adsorption of the inhibitor species to create a barrier layer. The findings showed that when inhibitor concentrations increased and solution temperatures decreased, the inhibition performance (%IE) of the compound under study enhanced. In the light of inhibitor probe's chemical makeup and theoretical analysis, the mechanism of the inhibition process was addressed. In a 1.0 M HCl solution containing 5 × 10−5 M of the inhibitor, the inhibition performance, at room temperature, was found to be almost 97%. The electrochemical results revealed that the examined compound successfully prevented carbon steel corrosion as a mixed-type inhibitor. The Langmuir and Freundlich isotherms are pursued by the adsorption of the examined inhibitor. Additionally, using Arrhenius and transition state equations, the activation thermodynamic parameters ΔEa, ΔH*, and ΔS* were determined and explained. The adsorption process was illustrated using DFT computation and MC simulations. The experimental findings and theoretical simulations concurred surprisingly well. Finally, the paper presents a discussion of the inhibitory mechanism. [ABSTRACT FROM AUTHOR]