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The research topic deals with one of the important problems that the oil and gas sector suffers from, which is represented by corrosion, as the corrosion of metals annually causes large losses in production as a result of stimulating oil wells using hot HCl solutions, which causes the occurrence of corrosion phenomenon in the well bottom tools, pipes and casing. In addition, a group of organic and inorganic acids and surfactants are used in well stimulation processes. In order to reduce the violent attack of the acid solution on the N80 mild steel casing materials and pipes, during the pickling process inhibitors are added to the acid medium, and to avoid the complexity of the inhibition process in the oil and gas fields, which requires organic inhibitors within the green chemistry depending on the nature of the work field such as pipelines and equipment, recovery wells, refineries, etc. Organic acids and acidic gases such as carbon dioxide and hydrogen sulfide complicate the well inhibition problem. Corrosion problems in the oil industry must be dealt with by considering various factors. Acids used in stimulation, the nature and type of reservoir rocks, and oil well equipment, whose operating conditions include casings and tubes, and these form part of the factors affecting corrosion. Thus, it needs to study each case as it is before determining the final opinion regarding the alternative materials. No suitable material can be found to survive the attack of corrosion. The designers and operators of the oil industry must take into account many serious economic and technical problems, the most important and most dangerous of which is the phenomenon of corrosion that is characteristic of the oil industry that deals with highly volatile and sometimes toxic materials and transported by pipelines over long distances and stored in huge warehouses in addition to because it requires a complex operational process that requires high heat and pressure, so if this equipment is so worn out that it is unable to withstand these harsh conditions, then there is no doubt that explosions may occur, which may be accompanied by fires, and sometimes their effect reaches the neighboring equipment and sometimes the entire production unit. [ABSTRACT FROM AUTHOR]

The effect of tempering temperature on the mechanical and corrosion properties of modified martensitic steel CA6NM is studied. Mechanical characteristics are determined in tensile and hardness tests, and corrosion properties are investigated using potentiodynamic and cyclic polarization in an artificial brine solution. The relationship between the microstructure and the mechanical and corrosion properties of the steel in the heat-treated state is revealed. It is shown that the best combination of mechanical and corrosion properties is achieved by tempering at a temperature of 600°C. [ABSTRACT FROM AUTHOR]

The usage of fossil fuels such as coal is now being reduced and shifted to bio-fuel in the boilers. It is because fossil fuels are exhaustible and generate CO2 emission during burning. Whereas, bio-fuels are abundantly available at low cost and also produce fewer greenhouse gases. However, burning of such fuels create a lot of corrosive species which can damage the components used for construction of boilers. Ferritic, austenitic, and martensitic steels are widely used to construct various parts of the boiler. Hence, in this study, four different grades of steels known as T91, SS304, SS316, and SS410 have been placed in the actual boiler environment for 493h. The boiler utilizes wood chips, rice husk, sawdust, bamboo base and leaf cuttings as burning fuel and operates at 850±50∘C. The results indicate that T91 steel showed a maximum rate of corrosion followed by SS304, SS316, and SS410. Martensitic steel 410 showed the minimum loss in weight among other steels. No intergranular corrosion was noticed in 410 steel, but the oxide so formed on the surface was fragile and porous although the chromium content is less in SS410 as compared to SS304 and SS316. [ABSTRACT FROM AUTHOR]

This study utilized a heat-moisture coupling model to characterize the internal microenvironment of concrete and establish the relationship between environmental temperature, humidity, external chloride ions, corrosion potential, corrosion current density, and rust layer thickness distribution on steel surface. The model enables dynamic characterization of steel depassivation, corrosion propagation, and rust layer expansion under natural climate environments. The development of temperature, humidity, chloride ions concentration, and corrosion current density in concrete under a time-varying environment was verified by experiment and the data obtained from literature. The research results show that taking heat-moisture coupling into account is necessary in steel corrosion modeling. Temperature and humidity are nonuniformly distributed in concrete leading to nonuniform distribution of chloride ions diffusivity. The growth rate of chloride ions concentration responds to environment temperature change more rapidly than humidity change. Under a time-varying environment, corrosion current density may increase briefly due to the increase of environment temperature and humidity. [ABSTRACT FROM AUTHOR]

Part II included using of calcined kaolinitic clay (CKC) prepared by a fluidized bed kiln as a supplementary cementing blend and assessing its effect on the OPC and the durability of concrete. The experimental protocol included optimization of the mixes of CKC/OPC containing 10 and 15% CKC for the production of hardened concrete as determined in part I, and in this work, the durability against chlorides, sulfate, seawater, and heating was studied. The effect on the reinforcement steel was also assessed. It was found that the partial replacement of cement with CKC (10 and 15%) caused slight expansion of concrete within the limits and there was no significant effect on the alkaline silica reaction or alkalinity of the concrete medium. The ratio of 15% CKC/OPC achieved a higher percentage of CSH that enhanced the compactness of the concrete matrix. When using CKC in plain concrete, the ratio of 10% CKC/OPC resulted in better resistance against the aggressiveness of salt solution attack and the highest compressive strength under the different conditions, whereas it reached 24.6 and 21.5% for 10 and 15% CKC/OPC respectively compared with the control concrete after aging of 180 days. The ratio of 10% CPDK/OPC achieved high resistance to heating. The porosity for the concrete modified with CKC was minimal resulting in low permeability of concrete for the salt solutions causing protection of the reinforcing steel against corrosion. [ABSTRACT FROM AUTHOR]

The concrete cover is an important factor that influences the corrosion of rebar in concrete. When the specified cover depth is not achieved due to improper placement of formwork or sagging of rebars at the construction stage of RC structures, it results in a partial cover thickness. This partial cover thickness would create an electrochemical imbalance enhancing the macrocell current. This study investigated the influence of partial cover thickness, water-cement (W/C) ratio, and chloride ions on the corrosion of rebar in mortar. A special divided bar was used to make cylindrical specimens with a full cover thickness of 20 mm and partial cover thickness (20 mm and 7.5 mm) with W/C ratios of 0.30 and 0.70. Electrochemical methods such as macrocell, microcell, electric resistivity, and polarization curves were used for measurement. The corrosion current density for a partial cover thickness of 7.5 mm with a W/C of 0.30 was 3.46 µA/cm², and for 20 mm, it was 1.85 µA/cm². This study concludes that for a low W/C of 0.30; decreasing the cover thickness partially by 62.5% (7.5 mm) will increase the magnitude of total corrosion current density by 47%. However, for a W/C of 0.70, a partial cover thickness had no influence on the corrosion rate. [ABSTRACT FROM AUTHOR]

In this study, the leaf extract of the plant Daphne gnidium L. (Thymemeacea) was used as a corrosion inhibitor for mild steel in 0.1 M NaCl. The content of total polyphenols was evaluated by UV visible spectrophotometry and with cyclic voltammetry. The results show that the extract contains a high content of total phenols estimated at 90.26 (mg GAE/g). Besides this, the plant extract was characterized via Fourier transform infrared spectroscopy. Electrochemical impedance spectroscopy and polarization techniques were used to investigate the extract's anticorrosive performance. The results indicated that the addition of 3% of the extract increased the inhibition efficiency to 90.8% after 4 h of immersion. In addition, the results of the polarization tests showed that the extract acted as a mixed‐type inhibitor, mainly affecting the anodic reaction. Scanning electron microscopy was used to study the morphology of the metal surface. The results revealed a less corrosion impact on mild steel in an inhibited solution. [ABSTRACT FROM AUTHOR]

The corrosion behavior of C20 pipeline steel was studied under Fe oxide and sand deposits in oilfield produced water containing sulfate‐reducing bacteria (SRB) via electrochemical techniques and surface analyses. A galvanic current of about 2 μAcm−2 was detected when the Fe oxide deposited sample and the bare steel were coupled in zero resistance ammeter (ZRA) mode, with the former being the anodic member of the couple. The Fe oxide deposited steel recorded severe localized corrosion after 14 days of testing in the SRB inoculated oilfield produced water. Corrosion severity decreased on the sand‐deposited steel, with general corrosion as the dominant morphology of surface attack. The development of product film was a vital factor in steel corrosion under the Fe oxide deposit. [ABSTRACT FROM AUTHOR]

A fundamental approach is used to better understand the influence of Cr on the resistance of low alloy steel to marine corrosion. It focuses on the formation and transformation of corrosion products of steel in seawater-like electrolytes. Fe(OH)2 precipitates are then prepared by mixing a solution of NaCl, Na2SO4·10H2O, FeCl2·4H2O or FeCl2·4H2O + CrCl3·6H2O (so that Cr = 8% and Fe = 92%), with a solution of NaOH. The initial concentration ratio of reactants, Q = 2 [ Fe 2 + ] + 3 [ Cr 3 + ] [ OH − ] , is set at Q = 0.88, 1, and 1.136. In a first approach, the obtained aqueous suspension is stirred, at a controlled temperature of 25 ± 0.5 °C, to be oxidized by air. The resulting oxidation product is characterized by XRD and Raman spectroscopy. In a second approach, the Fe(OH)2 precipitates are aged one week in suspension in anoxic conditions, filtered, mixed as a wet paste with glycerol and set as a thin compact layer on the sample holder of a X-ray diffraction system. The oxidation process of Fe(OH)2 is then monitored in situ during the acquisition of the X-ray diffractogram. The obtained results demonstrate that Cr(III) hinders the formation of green rust compounds, hence hindering the formation of γ-FeOOH, i.e., the main oxidation product of green rust compounds. The other oxidation pathways of Fe(OH)2, which lead to Fe3O4 or α-FeOOH, are thus favored. Nevertheless, Cr(III) favors mainly the solid state transformation pathway of Fe(OH)2, thus promoting α-FeOOH via the formation of poorly ordered Fe(III) oxyhydroxides, namely feroxyhyte and ferrihydrite. [ABSTRACT FROM AUTHOR]

One of the common causes of damage to the concrete structures close to the sea line is corrosion on the steel reinforcement in the concrete, which may cause spalling on the concrete cover. This paper presents the results of the simulation of the corroded reinforced concrete beams, which were repaired using the grouting method and FRP strengthening. The concrete cover of the beam specimens on the tensile side was filled with grouted concrete instead of filled with normal concrete to simulate the repair of concrete spalling. Three types of beam specimens were prepared and tested under a monotonic loading. BG and BPF were the specimens for beams with grouting only and beams with grouting and flexural strengthening using FRP sheets, respectively. Flexural strengthening using FRP sheets was carried out to restore the flexural capacity. As a comparison, control beams were also prepared in the form of normal reinforced concrete (BN). The results showed that the BG beam had a capacity of only about 50% compared to the control beam (BN). However, applying flexural strengthening using FRP sheet as on the type BGF beams showed that it had approximately the same capacity as BN specimens. This indicated that the repair method using grouting on damaged concrete covers and strengthening using FRP sheets was an effective alternative to repairing the corroded reinforced concrete beams. [ABSTRACT FROM AUTHOR]

Carbonization is the main cause of corrosion and decrease in bearing capacity of internal steel bars in concrete structures. Conducting durability assessment and remaining life prediction for existing railway bridges is of great significance for their subsequent maintenance and reinforcement. This paper evaluated the durability of several prestressed concrete beams in experimental railway super large bridges, and tested their concrete strength, carbonization depth, and protective layer thickness. Combined with measured data and durability models, the remaining durability life of the bridge was predicted. The results show that the average strength of prestressed concrete with a service life of 32 years is around 38.5 MPa, and the average carbonization depth is around 10 mm. Compared to the flange and web plates, the actual thickness of the protective layer at the bottom of the beam is relatively small, and the probability of corrosion of the internal steel bars here is higher. The durability model based on in-situ testing and carbonation depth correction indicates that the bottom of the prestressed beam began to experience steel corrosion after 29.5 years of service. Finally, based on the durability criterion of 7% critical steel corrosion rate, the service life of different parts of the prestressed bridge was predicted. [ABSTRACT FROM AUTHOR]

Alkali-activated slag (AAS) materials are one of the most promising alternatives to ordinary Portland cement (PC), as the AAS curing process does not require thermal activation, unlike the activation of other wastes. In addition, AAS exhibit lower porosity than PC, but experience shrinkage problems that can negatively affect their in-service implementation and durability. Shrinkage can directly impact the mechanical properties of AAS as well as the corrosion protection of steel reinforced structures in environments with chlorides, and be a factor affecting durability. The length change during the curing of these mortars can generate high stresses that are released through the formation of microcracks or cracks in their structure. Cracks can act as preferential diffusion paths for aggressive chloride ions and favor the corrosion of the reinforcement. The aim of the present work is to study the reduction in shrinkage that can be achieved for AAS using five different activators: NaOH 4 M, waterglass (WG) with two different SiO2/Na2O molar ratios (MR) and Na2CO3 solution without and with 10% MgO additions. The results reveal that AAS activated with Na2CO3 shows very reduced microcracking. The addition of expansive MgO completely eliminates microcracking but makes the mortar more porous. In the latter case, the pits become much smaller and potentially less dangerous than the ones appearing in the other studied mortars. Alkali-activated slag mortars manufactured in five different ways (Na2O fixed ratio) are tested. Shrinkage behavior of mortars is related to the corrosion of the embedded steel. Cyclic immersions in NaCl favour chloride diffusion and precipitation in reinforced mortars. Pit morphologies are related to Cl- transport through cracks, microcracks or/and porosity. WG (0.8 SiO2/Na2O MR) or Na2CO3 are promising options to activate slag for carbon steel-reinforced mortars. [ABSTRACT FROM AUTHOR]

This paper aims to perform a comparative investigation on the corrosion protection of steel in the simulated pore solutions of alkali-activated slag (SH) by NO3− and NO2− intercalated Mg-Al layered double hydroxides (MAL) which were fabricated by the calcination rehydration method. The corrosion potential, electrochemical impedance spectroscopy, potentiodynamic polarization and corrosion condition of steel were measured. Furthermore, changes in the microstructures of NO3− intercalated MAL (MAL-N3) and NO2− intercalated MAL (MAL-N2) before and after the adsorption of chloride ion were observed by X-ray diffraction and Fourier transform infrared spectroscopy. The results show that compared to the simulated concrete pore solution (OPCH), MAL-N3 and MAL-N2 exhibit lower chloride adsorption capacities and better corrosion inhibition effects in SH. The chloride adsorption capacity of MAL-N2 is lower compared with that of MAL-N3 due to the different volumes of intercalated anions. In contrast, MAL-N2 presents superior corrosion inhibition than MAL-N3. Furthermore, the decreases in [OH−] in SH due to the additions of MAL-N3 and MAL-N2 are more prominent than those in OPCH. The different synergistic effects due to the competitive anion-exchanges in the interlayers of NO3− and NO2− intercalated MAL in the two solutions contribute to the above effects. [ABSTRACT FROM AUTHOR]

In the petroleum industry, the casing steel is fixed with a cement sheath to ensure reliable service in demanding conditions characterized by high temperature, high pressure, and exposure to multiple types of media. After the hydration of the cement, a porous material is produced with a highly alkaline solution filling the pores, commonly referred to as the pore solution. The casing will form a protective passive film when in contact with a highly alkaline pore solution. Nevertheless, once the cement sheath cracks, chloride ions in the stratum will pass through the cement sheath to the surface of the casing. When chloride ions accumulate to a certain concentration, the passive film will be destroyed, without exerting a protective influence on the substrate. After chloride ions come into direct contact with the casing, the casing is prone to severe failure due to corrosion perforation. The casing failure can cause a blowout outside the casing and even scrapping of the oil well. Controlling casing corrosion and ensuring casing integrity relies on understanding the critical chloride ion concentration that can cause the degradation of the passive film. Therefore, to assess the electrochemical properties and analyze the damage process of the passive film under varying chloride ion concentrations, several characterization techniques were employed. These included potential–time curves (E-t), polarization curves, electrochemical impedance spectroscopy (EIS), and Mott–Schottky curves. In addition, the composition of the passive film on the surface of the P110 casing steel was qualitatively analyzed using X-ray photoelectron spectroscopy (XPS). To further understand the surface morphology of the P110 casing steel, scanning electron microscopy (SEM) was used. [ABSTRACT FROM AUTHOR]

In the present study, a complete evaluation was performed to assess the effect of blasting steel with various grit materials during surface preparation on the surface characteristics and corrosion protection behavior of FBE coatings. Blasting was executed with different constituents such as steel, sand, granite and glass beads to pretreat the hot-rolled steel, and the subsequent surface microstructure, interfacial adhesion bonding and surface protective performance against corrosion were analyzed using different techniques. Surface characterization studies revealed that the different blasting materials highly influenced surface roughness, and the highest roughness of about 40 µm was gained using sandblasting. Adhesion test results for the coatings with steel blasted specimens confirmed the improved adhesion strength by showing the highest adhesion strength of 44% compared to the coating on untreated specimens. Corrosion test results corroborated that scratched FBE coatings with blasted specimens exhibited the highest corrosion protection performance compared to that of FBE coatings with the bare surface by displaying higher impedance values (4.44 × 105 Ω cm2), a nobler shift in corrosion potential (− 0.4134 V versus SCE) and lowest corrosion current density (1.97 × 10−8 A/cm2) after immersion of 15 days in NaCl solution. [ABSTRACT FROM AUTHOR]

Inconsistencies in standards and codes result in confusion, increased costs, and do not promote the efficient use of concrete. In addition to inconsistencies, the lack of science-based approaches and data used for defining criteria in these standards and codes can limit the reliability and trust of these requirements. A review of industry documents indicates that inconsistencies and lack of science-based approaches exist across many documents, both throughout the industry and within ACI, relating to the corrosion of steel reinforcement embedded in concrete. This paper proposes to address five key issues to promote science-based standardization of requirements necessary for reinforced concrete systems exposed to corrosive conditions. These five issues include the need for: 1) standardization of chloride testing methods and requirements; 2) standardization of chloride reporting units; 3) standardization of terminology for specifying chlorides in cementitious systems; 4) standardization of exposure classifications for corrosive conditions; and 5) standardization of allowable chloride limits. This paper presents current inconsistencies in guide documents and codes for each of the items listed previously and then proposes an approach to standardize each using either available data and/ or a scientifically based approach. Recommendations for testing, reporting, definition of exposure classifications, and allowable chloride limits are then proposed. It is hoped that the systematic approach used herein will lead to standardization and consistency, less confusion, and will promote the efficient use of durable and economical concrete. [ABSTRACT FROM AUTHOR]

The application of deep learning (DL) algorithms has become of great interest in recent years due to their superior performance in structural damage identification, including the detection of corrosion. There has been growing interest in the application of convolutional neural networks (CNNs) for corrosion detection and classification. However, current approaches primarily involve detecting corrosion within bounding boxes, lacking the segmentation of corrosion with irregular boundary shapes. As a result, it becomes challenging to quantify corrosion areas and severity, which is crucial for engineers to rate the condition of structural elements and assess the performance of infrastructures. Furthermore, training an efficient deep learning model requires a large number of corrosion images and the manual labeling of every single image. This process can be tedious and labor-intensive. In this project, an open-source steel bridge corrosion dataset along with corresponding annotations was generated. This database contains 514 images with various corrosion severity levels, gathered from a variety of steel bridges. A pixel-level annotation was performed according to the Bridge Inspectors Reference Manual (BIRM) and the American Association of State Highway and Transportation Officials (AASHTO) regulations for corrosion condition rating (defect #1000). Two state-of-the-art semantic segmentation algorithms, Mask RCNN and YOLOv8, were trained and validated on the dataset. These trained models were then tested on a set of test images and the results were compared. The trained Mask RCNN and YOLOv8 models demonstrated satisfactory performance in segmenting and rating corrosion, making them suitable for practical applications. [ABSTRACT FROM AUTHOR]

The corrosion of mild steel in HCl solution remains a critical issue in various industrial applications. In the quest for effective corrosion inhibitors, 4‐(2‐Hydroxy‐3‐Methoxybenzylideneamino) antipyrine (HMBA) has emerged as a promising candidate. This study investigates the inhibitory properties of HMBA on mild steel corrosion in HCl solution through weight loss measurements, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PDP) techniques. The experiments spanned over various time periods, including 1, 5, 10, 24, and 48 h. The results reveal that HMBA exhibits exceptional inhibition efficiency (IE), with an impressive 94.7% inhibition rate. This outstanding performance underscores its potential as a corrosion inhibitor for mild steel in aggressive HCl environments. To elucidate the adsorption behavior of HMBA on the mild steel surface, Langmuir isotherm modeling was employed, demonstrating a strong correlation between the experimental data and the Langmuir adsorption isotherm model. Furthermore, the study employs density functional theory (DFT) to gain insight into the mechanism of HMBA inhibition. DFT calculations suggest that both physisorption and chemisorption mechanisms are involved in the interaction between HMBA and the mild steel surface. The calculated Gibbs free energy of adsorption (ΔGadso $\Delta {G}_{\mathrm{ads}}^{o}$) is found to be approximately −33.8kJmol−1 $-33.8\mathrm{kJ}\mathrm{mo}{\text{l}}^{-1}$, indicating a spontaneous and energetically favorable adsorption process. In conclusion, HMBA emerges as a highly effective corrosion inhibitor for mild steel in HCl solution, offering impressive IE over various time intervals. The combination of experimental techniques, such as WL, EIS, and PDP, along with computational insights from DFT calculations, provides an understanding of the inhibitory properties of HMBA. These findings hold great promise for the development of environmentally friendly corrosion inhibitors in industrial applications. [ABSTRACT FROM AUTHOR]

Based on BP neural network and higher-order moment method, combined with measured data, a time-varying reliability analysis method for the bending resistance of reinforced concrete aqueduct side walls is proposed. In order to evaluate the bending time-varying reliability of aqueduct side walls under the influence of steel corrosion, this paper considers the effective cross-sectional area loss effect of steel bars in concrete structures, and derives the bending time-varying performance function under the limit state of bearing capacity of the aqueduct side wall. Then, combined with the measured data of steel corrosion and the principle of BP neural network, the prediction model of steel corrosion rate is designed, and the calculation formula of effective cross-sectional area of steel bars in concrete structures is established through the hemispherical pitting model. On this basis, the point estimation and high-order moment reliability theory is introduced to develop the time-varying reliability analysis method of aqueduct structure, and finally the proposed method is applied to the bending time-varying reliability analysis of the side wall of an actual aqueduct. The results show that compared with the previous eight practical empirical models, the prediction model of BP neural network built in this paper can predict the corrosion rate of rebar in concrete structures more accurately, comprehensively, easily and quickly. By comparing with Monte Carlo simulation method, the time-varying reliability index of this method is efficient and accurate, which can provide an effective way for the evaluation and prediction of time-varying reliability of aqueducts. [ABSTRACT FROM AUTHOR]

The corrosion of carbon steel infrastructure in acidic environments poses significant economic and safety challenges. Traditional inhibitors such as chromates are being phased out due to toxicity concerns. Thus, there is a need to develop effective and sustainable green alternatives. In this work, we evaluated an epoxy-based inhibitor, bisphenol A tetrabromo dipropoxy dianiline tetraglycidyl ether (TGEDADPTBBA), for protecting carbon steel against corrosion in 1 M hydrochloric acid. An integrated experiment-computation approach was employed. Polarization curves and electrochemical impedance spectroscopy were used to assess the inhibition efficiency and mechanism of TGEDADPTBBA. Quantum chemical calculations and molecular dynamics simulations provided atomic-level insights into adsorption behavior. Scanning electron microscopy with energy-dispersive X-ray spectroscopy characterized the surface morphology. The results showed that TGEDADPTBBA acted as a highly effective mixed-type inhibitor, achieving over 95% inhibition efficiency at a 10−3 M concentration. It suppressed corrosion currents while increasing the charge transfer resistance. Theoretical studies revealed that TGEDADPTBBA adsorbed onto steel surfaces via both electrostatic and van der Waals interactions. This stable adsorption facilitated the formation of a protective barrier layer, as observed experimentally. Notably, our work demonstrated the synergistic potential of combining experimental corrosion testing with computational modeling to develop structure–property relationships for innovative inhibitor design. This integrated approach offers insight into inhibition mechanisms and presents TGEDADPTBBA as an attractive green corrosion inhibitor alternative for industrial applications. [ABSTRACT FROM AUTHOR]

This study investigates the efficacy of ZnCl2 as a corrosion inhibitor for mild steel across varied pH environments (3.5, 7, and 10). Findings highlight a significant reduction in corrosion rates with increasing ZnCl2 concentrations, pinpointing optimal levels at 350 ppm (pH 3.5), 575 ppm (pH 7), and 325 ppm (pH 10). Through comprehensive experimental analyses, the study robustly validates the protective capacity of the inhibitor, shedding light on its practical application in safeguarding metallic materials amidst varying pH conditions. ZnCl2 will be applied as a solution, forming a protective layer on the surface of mild steel, thereby acting as a barrier against corrosive agents. The study's originality lies in its specific exploration of ZnCl2 efficiency under varied pH conditions, emphasizing its substantial contribution to corrosion protection in different environmental settings. [ABSTRACT FROM AUTHOR]

The present paper reports on four-year field investigations aimed at ascertaining internal corrosion rates for offshore wind-power generation monopiles, despite these being designed to obviate internal corrosion through oxygen exclusion. Results for mild steel strips within the enclosed, quiescent, uPVC simulated seawater environments are presented as a function of relative to mean tide level, period of exposure and localised pollution of seawater. Detailed pit depth measurements are also reported for various exposure periods, with the magnitude of such corrosion displaying a bi-modal behaviour as a function of exposure time, consistent with much other data. No evidence was found of the classical corrosion profile for vertical steel structures (e.g. piles) or of accelerated low water corrosion usually associated with microbiologically influenced corrosion caused by elevated seawater nutrient concentrations. It is proposed that the observed corrosion behaviours primarily are the result of the shielded quiescent environment. The practical implications are briefly discussed. [ABSTRACT FROM AUTHOR]

Calcium hexaaluminate (CA6) materials have garnered attention for their potential use as lining materials in metallurgical furnaces during the steel-making process. The present work explored the effects of M2O5 (M = Nb, Ta) on the steel corrosion behaviour of calcium hexaaluminate combined with the evolution of physical properties. The introduction of M2O5 (M = Nb, Ta) was proved to be advantageous in mitigating the emulsification of CA6 material in the molten steel, and the increase in the densification of emulsion layer could prevent CA6 materials from further steel corrosion and penetration. The improved steel corrosion resistance of CA6 materials was attributed to the optimization of the physical properties facilitated by the formation of defects and the in situ phase. In addition, the reduction in the wettability between the CA6 materials and molten steel served to diminish the reactivity of the interface reaction. This work determined the corrosion behaviour and corrosion mechanism of the CA6 materials in molten steel and provided a new research route for designing CA6 materials with improved corrosion resistance to molten steel.

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.

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.

[Display omitted] • Amino acid derivative is first time reported as corrosion inhibitor. • High efficiency for N80 steel in in 20% formic acid was recorded. • Synergism with KI resulted in 99.4% efficiency at high temperature of 90 0C. • Mixed type inhibition behaviour was observed. • Inhibitor adsorption was in accordance with Langmuir isotherm. Organic acids are employed as scale dissolvers in the oil & gas industry during production to stimulate oil recovery by pumping in the formations. Corrosion of metallic surfaces in organic acid solutions poses a significant issue in the oil and gas sector. In recent years, considering the stringent environmental regulations, there has been a growing research interest in environmentally safe inhibitors. This paper explores the synthesis of 2-(3-(carboxymethyl)-1H-imidazol-3-ium-1-yl) acetate (IZ) and its first-time application for corrosion mitigation of N80 steel in 20% formic acid. A detailed experimental study involving gravimetric, electrochemical, and surface analytical techniques is reported herein. The electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) analyses suggest a rise of impedance with IZ and a mixed-type inhibition behavior, respectively. The inhibition efficiency (IE) is 99.54% at 200 mg/L at 308 K, reaching 99.4% at 363 K with the introduction of KI as a synergistic agent. Computational studies revealed that the inhibitor IZ gets protonated in the experimental environment. The protonated form shows a tendency to receive electrons from the metal surface and shows a greater energy of adsorption compared to that of the neutral form. [ABSTRACT FROM AUTHOR]

Nowadays, choosing a corrosion inhibitor is not only based on efficiency, but must also consider the toxicity of the compound, the impact on the environment, and, obviously, the regulations in the field. In the last two decades, a special class of substances has begun to be studied, namely polyoxometalates (POMs). Their electronic properties and redox characteristics make the polyoxometalates potential candidates to be used in many electrochemical processes, and as potential corrosion inhibitors. Electrochemical methods such as a Tafel extrapolation plot, chronopotentiometry, or gravimetry have been used to establish the capacity of corrosion inhibition of S235 and SS304 steels in the presence of phosphovanadomolibdate acid (@PMoV) and phosphovanadotungstate acid (@PWV) in 0.5 M sulphuric acid solution. The inhibition efficiency for S235 steel is about 90.6% for @PMoV, and 69.5% for @PWV after 24 h of immersion. In the case of SS304 steel, polyoxometalates have similar effects: the inhibition degree, as a function of Flade potential, is 4.66 for @PMoV; better than 3.26 for @PWV, with both proving the passivant effect. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate Diplotaxis simplex (DS) extract as an eco‐friendly corrosion inhibitor in a harsh 1 M H2SO4 solution, focusing on its effectiveness against both general and localized concrete corrosion. Electrochemical methods, including linear polarization, were employed to assess the DS extract's corrosion inhibition capabilities. The results demonstrate DS extract's exceptional inhibitory properties, with inhibition efficiency increasing with higher concentrations. This enhanced performance is attributed to the extract's phenolic compounds, containing nitrogen and oxygen heteroatoms with π‐electrons. Notably, sinapic acid, a known corrosion inhibitor for steel in acidic environments, was found in DS extract. Electrochemical Impedance Spectroscopy (EIS) further validated the findings, showing an 84.22 % inhibition efficiency at a DS extract concentration of 300 ppm. Scanning Electron Microscopy (SEM) analysis of the electrode surface confirmed the formation of a protective layer, supporting DS extract's potential as a concrete corrosion inhibitor in aggressive environments. In summary, this study highlights DS extract's potent corrosion inhibition properties, making it a promising candidate for safeguarding concrete structures against corrosion. These findings offer exciting prospects for sustainable corrosion protection strategies in challenging settings. [ABSTRACT FROM AUTHOR]

Two distinct binary blended concrete mixes were prepared for the study. The first mix involved a cement replacement of 50% slag, denoted as SL. The second mix incorporated a cement replacement of 20% fly ash, referred to as FA. No chlorides were added during the preparation of these concrete specimens. To accelerate chloride transport, electromigration was employed by placing specimens with varying reservoir lengths (ranging from 2.5 cm to 17.5 cm) on their top surfaces. These reservoirs were subsequently filled with a 10% NaCl solution. In this paper, corrosion propagation was monitored over a period of approximately 650 days using electrochemical measurements such as open circuit potential, linear polarization resistance (LPR), and electrochemical impedance spectroscopy (EIS). The evolution of rebar potential, polarization resistance, solution resistance, and corrosion current were analyzed to understand the corrosion behavior. This paper focuses on how the length of the solution reservoirs influences the corrosion-related parameters such as polarization resistance, solution resistance, rebar potential, and corrosion current. During the monitored propagation period, the corrosion current values (last 7 sets of readings) exhibited higher magnitudes for the embedded rebars in specimens made with SL mix in comparison to those made with FA mix. Corrosion current measurements likewise showed an increasing trend as the reservoir lengths increased. None of the specimens had any visible cracks or corroded products that could reach the concrete surface throughout the monitored period. The experimental results provide insights into the corrosion mechanisms and the effectiveness of accelerated corrosion techniques in simulating real-life conditions. [ABSTRACT FROM AUTHOR]

This study investigates the impact of high-temperature, high-pressure carbon dioxide on the steel-cement interface, crucial in engineering structures and carbon capture storage systems. Experiments conducted on N80 steel and ordinary portland cement in synthetic aquifer brine revealed that CO2 exposure significantly exacerbates steel corrosion and cement degradation. The corrosion current density of steel increased to 1.2 μA/cm2 after six months in CO2, compared to 0.3 μA/cm2 in unexposed samples. Cement samples showed a marked decline in mechanical properties, with hardness reducing from 1.25 GPa (giga-Pascal) in control samples to 0.65 GPa after six months. The steel—cement interface integrity also diminished, as evidenced by a decrease in acoustic impedance from 45.0 M-Rayl to 34.0 M-Rayl over six months. These results emphasize the need for advanced materials and strategies to enhance the durability and safety of structures in CO2-rich environments. [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]

This study delves into the atmospheric corrosion behavior of chromium-free complex-phase (CP) steel, specifically investigating the influence of wet/dry frequency and ratio in cyclic corrosion tests (CCT). The study employs a modified ISO 14993 standard CCT method, which involves salt spray, dry, and wet stages. After 15 and 30 CCT cycles, mass loss, maximum corrosion depth, and corrosion products were analyzed to gain insights into corrosion mechanisms. In general, increasing the frequency and wet/dry stage ratio in CCT extends the time for autocatalytic reactions to occur, leading to accelerated localized CP steel corrosion and increased pitting factors. However, as the rust layer thickens, uniform corrosion may also intensify, so careful considerations are necessary. This study underscores the importance of controlling the frequency and ratio of wet/dry stages in CCT for effectively analyzing localized corrosion behavior in specimens. [ABSTRACT FROM AUTHOR]

To explore the formation of corrosion products of steel bars in coral aggregate seawater concrete (CASC), this study used X-ray powder diffraction (XRD) to examine the ingredients of corrosion products of CASC steel bar, and scanning electron microscopy (SEM) to scan the surface structure of the steel rust layer to understand the difference between the steel corrosion products under different test environments. In addition, this paper analyzes the steel corrosion in CASC and seawater sea-sand concrete (SSC) at the micro level. The results demonstrate that the CASC in the marine environment undergoes electrochemical reactions to produce insoluble Fe(OH)2. Under the immersion environment, the large amount of α-FeO(OH) contained in the rust layer of the steel bars can accelerate the corrosion process. There are more free chloride ions (Cl−) in the dry and wet cycle environment, which leads to the corrosion products of the steel bar containing more β-FeO(OH). Furthermore, it was noticed that the presence of small openings in the needle-shaped crystals can cause water molecules to become trapped, making the pitting corrosion of the steel bar worse. This situation provides an ideal setting for the occurrence of severe corrosion. The corrosion process in a dry–wet cycle environment is less than the corrosion products of the steel bar under the full immersion environment; the structure of steel corrosion products of CASC are less than that of SSC. [ABSTRACT FROM AUTHOR]

In this work, the influence of the area ratio of the low corrosion probability area (prone to becoming cathode) and high corrosion probability area (prone to becoming anode) on the initiation of macrocell corrosion of a steel bar in a simulated pore solution was investigated, along with the depassivation mechanism under the macrocell effect. Meanwhile, the set cathode-to-anode area ratio (SC/A) and the actual cathode-to-anode (pitted) area ratio (SC/A′) after corrosion initiation were compared. The results reveal that the increase in SC/A not only increases the corrosion current density but also promotes corrosion initiation drastically. A pronounced positive shift was observed at high SC/A in the initiation phase due to intensified chloride adsorption and the double-layer effect on the passive film of the anodic steel bar. The chloride threshold value (CTV) could be reduced to 42% of the original time in the simulated concrete pore solution, and the pit depth was increased by up to 124% due to the macrocell effect. In addition, the actual corrosion area (Sact) is much smaller than the set anode area (SA) because the corrosion area created by chloride ions is tiny, resulting in SC/A′ being higher than SC/A. [ABSTRACT FROM AUTHOR]

The ingress of carbon dioxide CO2 into concrete is an issue that, unfortunately, does not have sufficient precedents at the national level for the execution of the Residual Service Life analysis of concrete structures. As a precursor element of steel corrosion, it is necessary to count on information on the behavior that concrete could have in Chile, according to the levels of aggressiveness expected for specific project locations. It was only in 2016 that the NCh170 Concrete Standard included this type of Exposure with Grade C1 as Mild Aggressiveness. This work presents a review of background information collected from various third-party and own works, along with measurements of Carbonation Rates in 20-year-old concretes made in the city of Santiago, relating them to Air Permeability measured in a non-destructive way, which allowed generating a proposal for the Classification of the Degree of Exposure to Carbonation. [ABSTRACT FROM AUTHOR]

Image based-corrosion detection has become a widespread practice for steel structures, but fine-tuning their model parameters is time-consuming. Alternatively, convolutional neural networks (CNNs) can also be trained fast and automatically, but they demand a huge training dataset. In this paper, a corrosion detection approach based on an artificial neural network (ANN) whose training dataset size is less than 0.1% of that of typical CNNs is introduced. The input layer of the proposed ANN consists of textural and color properties. In the present work, different color spaces and textural properties are examined for their impact on the robustness of the ANN. Results reveal that the best color channels can be achieved by combining CIE L*u*v* and YUV color spaces. Moreover, energy is selected as the best texture feature with respect to the ANN robustness. The proposed ANN outperforms an available image processing algorithm from the perspective of both speed and accuracy. In conclusion, this ANN can be used for actual applications after a fast and straightforward training step. [ABSTRACT FROM AUTHOR]

The inhibitory effects of extracts from Phaseolus vulgaris and Vicia faba beans, obtained from boiled beans, on the corrosion of EN Fe37-3FN mild steel in a 0.5 M hydrochloric acid medium were meticulously investigated utilizing electrochemical techniques and Electrochemical Impedance Spectroscopy (EIS). The corrosion rate was observed to decrease by 40% upon the introduction of 20 mg/L of the Phaseolus vulgaris extract, with a notable reduction of 70% when the concentration was increased to 2 g/L and beyond. The Vicia faba extract, however, displayed a slightly inferior inhibitory performance, with corrosion rates diminishing by 20% at 20 mg/L and 60% at concentrations of 2 g/L and above. The adsorption of extract constituents onto the steel surface was found to conform to the Langmuir adsorption isotherm model, thereby facilitating the calculation of the sorption equilibrium constant and revealing that the adsorption was primarily physical in nature. These extracts, which are typically discarded by-products of bean cooking, have emerged as cost-effective, readily accessible, and environmentally benign alternatives for mitigating steel corrosion in acidic environments. [ABSTRACT FROM AUTHOR]

Oil and gas pipelines are often threatened by mechanical degradation and corrosion damage. This mechanical degradation is attributable to the aging of the carbon steel, and corrosion damage results from the level of environmental aggressiveness combined with the material's metallurgical characteristics. Unfortunately, studying the natural aging of steel in in-service pipelines is difficult because many tests are destructive. For this reason, the present study used isothermal artificial aging to simulate the mechanical degradation of pipeline steel. Charpy energy tests were carried out to assess the changes in the material's ductility. It was found that this energy exhibited random behavior. Our findings indicate that, on average, the aged material exhibited lower Charpy fracture energy and a much higher variance. This evidence will help experts select the correct material properties while considering its degradation over time. In addition, according to the fractographic study, it was confirmed that the aged pipeline steel tended to be more brittle than the unaged material. Moreover, the dominant corrosion mechanism observed during electrochemical tests for aged and unaged steel was analyzed. We concluded that a moderate chloride ion content is insufficient to stimulate pitting corrosion. Corrosion rates with three different electrochemical techniques (LPR, EIS, and ENA) were obtained, showing that the unaged material tended to be more vulnerable to corrosion effects. [ABSTRACT FROM AUTHOR]

Coating is a popular technique for the corrosion protection of mild steel (MS) in its various service environments. This work investigated the effectiveness of protecting mild steel from corrosion in sulphuric acid (H2SO4) solutions using calcined cattle bone waste powder coating. A cattle bone (CB) femur was obtained from an abattoir, washed, dried, pulverized, and sieved to obtain powder of 75-micron size. The powder was calcined at 600°C, 750°C, and 900°C using a constant holding time of 3 hrs. The functional groups present in uncalcined and calcined samples were identified using FTIR spectroscopy. The calcined CB powder was dissolved in HNO3 to obtain a 0.5 g/ml concentration that was deposited on the mild steel substrates using the spray deposition method at a set deposition time of 5 minutes. The thickness of the deposits was determined using a thickness gauge, while the surface of coated samples was viewed with a scanning electron microscope (SEM). The corrosion protection of the coating on mild steel samples was ascertained in 1M H2SO4 using the potentiodynamic polarization technique. The results indicated that the corrosion protection efficiency increased with an increase in calcination temperature to attain a maximum value of 91% for the sample coated with CB powder heated to 900°C. The corrosion rate of the uncoated sample, which was 0.02063 g/hr., decreased to 0.000178 g/hr. The FTIR result showed that uncalcined and calcined samples contained OH−, CO32−, and PO43− ions, which impacted their corrosion behaviours. This study proved that CB waste powder coating reduced the corrosion rate of mild steel in H2SO4 solution significantly and added value to this waste material. [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]

The partial cover thickness of reinforced concrete structures near the coastline enhances the early corrosion onset, which reduces the service life. As a countermeasure under the preventive maintenance approach, to delay early corrosion onset in structures with partial cover thickness and increase durability throughout the service life, this study used silane and silicate-based surface penetrants. Mortar specimens with a partial cover thickness and embedded, specially segmented bars were prepared. Both penetrants were applied to specimens with partial cover thicknesses (20 and 7.5 mm). Further, electrochemical methods such as macrocell current, microcell current, electric resistivity, and potentiodynamic polarization curves were used to assess the corrosion resistance before and after coating. The penetration depth of silane was measured visually, and the Vickers hardness test was used for the silicate penetrant. The "equivalent cover approach" was adopted to evaluate the performance of penetrants throughout their service lives. Results revealed that the total corrosion current density decreased by 79% for specimens coated with silane and 52% for silicate penetrant, whereas no change was observed in the uncoated specimens. Based on the equivalent cover approach, the silane penetrant was determined to be most effective in delaying the corrosion onset and propagation time for cover thicknesses of 60 and 50 mm at 100 m distance against 70 mm, and for 40 and 30 mm against 50 mm at 250 m from the coastline. Further, the silicate-based penetrant was only effective for a deficient cover thickness of 5 mm against the specified cover thicknesses at a distance of 100 and 250 m from the sea coast. [ABSTRACT FROM AUTHOR]

The performance of quenched and self-tempered (QST) steel bars embedded in concretes with Limestone calcined clay cement (LC3), fly ash (70% OPC and 30%fly ash – PFA), and traditional OPC was assessed in severe chloride environments. Additionally, the performance of commercially available, calcium nitrite-based inhibitors in the three binder systems was also evaluated. The specimens were subjected to an alternate wet-dry cycle using the ASTM G109 test method. The findings show that LC3 concrete performs better than the OPC and PFA systems with and without inhibitors. Furthermore, when the surface resistivity, ρ, is more than 37 kΩ.cm, the concrete has high ionic resistance and the macrocell current across the two rebars could not be established as described in ASTM G109 test method. This highlights the limitations of the ASTM G109 test method and the need for more sophisticated testing methods for assessing steel corrosion in highly resistive cementitious systems. [ABSTRACT FROM AUTHOR]

The effect of calcium silicate hydrate (C-S-H) on chloride (Cl−) binding and steel corrosion in simulated concrete pore solution (SCPS) was evaluated. The results showed that Cl− absorbed by C-S-H conformed to Freundlich isotherm for 0.1–1.0 M of Cl−. When C-S-H reached equilibrium in saturated Ca(OH)2 solution, its degree of polymerization increased. The high pH is unfavorable for the absorption of Cl− by C-S-H, but favorable for the passivation of steel. The synthetic C-S-H powder contains NO3−, which prolongs the passivation time of steel, but the presence of silicate is favorable for the formation of a passivation film with good corrosion resistance. The addition of C-S-H promoted the chloride threshold value of steel corrosion and delayed the corrosion development process. [ABSTRACT FROM AUTHOR]