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Chloride ions are responsible for triggering severe corrosion in the marine environment. Hence, there is a need to deploy corrosion resistant materials such as hexagonal boron nitride (h-BN) sheet to protect mechanical components operating under such harsh conditions. In this work, a first-principles approach was employed to investigate the effect of fluorine modification on the thermodynamic and kinetic behaviors of oxygen on different kinds of vacancy-defective hexagonal boron nitride (h -BN) in a Cl-containing marine environment. Geometrical and electronic structures were systematically analyzed along with adsorption and diffusion behaviors. The existence of a low energy barrier implies that there is a relatively attenuated ability to inhibit O diffusion for double vacancy V BN - h -BN sheet compared to single vacancy V B - h -BN and V N - h -BN sheets. Interestingly, the fluorine functionalization for three defective h -BN sheet is found to cause an increased energy barrier of O diffusion. The F @ Cl @ V N - h -BN sheet possesses the highest diffusion energy barrier, indicating a superior anti-oxidation property in the marine environment. This study provides some fundamental guidelines for realizing high-performance h -BN sheets for protecting equipment and components used in marine applications. [ABSTRACT FROM AUTHOR]

In this paper, the reinforcement embedded in concrete is taken as the research object. By measuring the corrosion rate of the reinforcement in concrete, the open circuit potential of the primary battery composed of reinforcement and calomel electrode in concrete is measured. The chloride ion concentration on the surface of reinforced concrete was measured in situ by the nano-Ag/AgCl electrode. The chloride diffusion theory and corrosion electrochemistry theory were used to study the corrosion mechanism of reinforced concrete specimens. The corrosion rate of reinforced concrete increases with the increase of time in the initial stage of corrosion and reached maximum after 15 h. The pitting of concrete reinforcement is positively related to the concentration of chloride ion in the environment. [ABSTRACT FROM AUTHOR]

In this paper, the effects of chloride ions, oxygen, and carbon dioxide on the corrosion resistance of passive films formed on 316 L stainless steel were investigated in the aggressive oilfield environment using electrochemical testing and microscopic characterization techniques. The results showed that Cl− accelerated the anodic dissolution of the metal and compromised the structure and densification of the passive film, thus reducing its corrosion resistance. An increase in the partial pressure of carbon dioxide initially promotes pitting, but subsequently inhibited further corrosion development. The presence of oxygen enhanced the cathodic reaction and passive film formation, effectively preventing the invasion of aggressive chloride ions, thus inhibiting further corrosion. These findings provide a significant scientific basis for material selection and protection of oil extraction equipment in oilfield environments. [ABSTRACT FROM AUTHOR]

• Created an environment-specific model using historical environmental data and considering GBA-based exposure conditions. • The surrogate model surpasses alternative models with over 99% accuracy across all target variables and scenarios. • Physical and environmental factors' evolving impact on durability and mechanical measurements is disclosed over time. • Impact of global warming on coastal structures underscores non-linear and discrete effects of diverse factors. Long-term exposure to coastal and marine environments accelerates the aging of reinforced concrete (RC) structures, impacting their structural safety and society impact. Traditional assessments of long-term performance deterioration in RC structures involve complex, nonlinear, and time-intensive studies of physical mechanisms. While existing machine learning (ML) methods can assess the lifetime of these structures, they often prioritize data regression over mechanistic interpretation. To enhance the efficiency and interpretability of predicting the life-cycle performance of RC structures, this study introduces a generic framework based on interpretable ensemble learning (EL) methods. The framework predicts life-cycle performance efficiently and accurately, with optimal hyperparameters automatically tuned through Bayesian optimization. Interpretability algorithms clarify the influence of environmental, durability, and mechanical parameters on structural durability and mechanical predictions. Validation employs real-world cases of RC hollow beams in the coastal area of the Guangdong-Hong Kong-Macao Greater Bay Area (GBA). The comprehensive model for RC structures integrates actual data on temperature, humidity, and surface chloride content in the GBA, considering diffusion, convection, and binding effects of chloride ions, corrosion non-uniformity, and crack impact on durability estimation. Comparative analysis with existing ML methods underscores the effectiveness of the framework. The findings highlight the dynamic evolution of feature importance rankings throughout the service life, shedding light on the continuous changes in the significance of different factors when predicting mechanical resistance. [ABSTRACT FROM AUTHOR]

This study details the sonication-assisted synthesis and characterization of a cathodically deposited novel nickel-graphene oxide -zinc oxide (Ni-GO-ZnO) composite coating achieved through electrodeposition and its comparison with anodically deposited GO. This coating was comprehensively characterized using Fourier-transform infrared (FTIR), X-ray diffraction (XRD), Raman spectroscopy, Field emission scanning electron microscopy (FE-SEM) coupled with Energy-dispersive X-ray spectroscopy (EDAX). Subsequently, its corrosion resistance for MS1010 mild steel in 3.5 wt % (NaCl) was evaluated via weight loss, contact angle, electrochemical impedance spectroscopy (EIS), Potentiodynamic polarization, and surface analysis techniques. These observations suggest that graphene oxide-zinc oxide (GO-ZnO) adsorbs nickel onto the MS surface effectively and reduces defects, which helps in blocking active corrosion sites. Tafel plots and EIS revealed that the Ni-GO-ZnO coating exhibited the lowest current density (39.95 µAcm²) and the highest charge transfer resistance (1211 Ωcm²). This was further validated by long-term immersion testing, where the Ni-GO-ZnO coating exhibited significantly less weight loss (1.33 mils/Y) compared to the deposited GO coating (2.2 mils/Y). The mechanism of formation of deposited GO and Ni-GO-ZnO coating on the metallic surface is proposed. The enhanced corrosion resistance of the Ni-GO-ZnO coating is attributed to its ability to 1) form a more compact metallic layer and 2) Minimize the active surface area vulnerable to corrosion attack. 3) Diminishes the presence of holes and cracks for corrosive ion ingress.4) Functionally impedes the ingress of chloride ions, primarily liable for steel degradation. The synergistic effect of the GO-ZnO constituents within the nickel matrix significantly enhances the long-term durability and integrity of the protective layer, a phenomenon hitherto unexplored. The empirical outcomes advocate for the advanced application of GO-ZnO-nickel coatings in safeguarding infrastructural materials against corrosive degradation. [Display omitted] [ABSTRACT FROM AUTHOR]

• Chloride diffusion was investigated by a combination of experiments and simulations. • Sodium D-gluconate concentration affected the potential of wire beam electrodes. • A new non-destructive method obtained localized chloride concentrations in concrete. The effects of various concentrations of sodium D-gluconate (SD) on chloride ion diffusion in concrete were investigated using both the wire beam electrode (WBE) technique and the finite element method. WBEs were encapsulated within concrete and immersed in a 3.75 mol/L NaCl solution which contained either 0.0461 mol/L or 0.0152 mol/L SD. Observations indicated that the passive film on the part of WBEs was destroyed by chloride ions on the 14th day, with the surface potential falling below −0.47 V SCE. Furthermore, the number of active corrosion electrodes was less at 0.0461 mol/L SD than at 0.0152 mol/L SD. Simulated chloride ion concentrations on WBEs were in agreement with the experimentally obtained values, demonstrating the viability of WBEs as non-destructive tools for assessing chloride ion concentrations in concrete. [ABSTRACT FROM AUTHOR]

In this paper, a new approach of bidirectional electro-migration rehabilitation (BIEM) using pulse currents was proposed. The effect of the duty cycle and frequency of the square wave pulse current on the BIEM was investigated. The results showed that the desalination efficiency was improved by 10 % with the decrease of duty ratio and frequency. Furthermore, With the increase of duty ratio and frequency, the hydrogen permeation of steel bars decreased by 28.5 %. More uniform desalination efficiency was obtained by using pulse current. The half-cell potential of the rebars was also measured and it was higher for the samples using pulse currents than for those using direct currents, indicating a lower risk of corrosion after pulse current treatment. The pH value of the concrete also increased during the BIEM process. • The amount of hydrogen permeation in the rebars of concrete repaired by pulse current is reduced. • Increasing frequency and decreasing duty cycle of pulse current make the desalination efficiency distributed more evenly. • Decreasing frequency and duty cycle of pulse current will increase the efficiency of chloride ions removal. [ABSTRACT FROM AUTHOR]

The electrochemical descaling treatment of circulating cooling water can effectively reduce the content of scaling ions, chloride ions and produce strong oxidizing substances with bactericidal properties in the water, which is beneficial for operation at high concentration ratio (N) of circulating water, meets the goal of clean production and has a good prospect. However, changes in ion concentration and type in water can have an impact on the corrosion behavior of metals. Currently, there is limited understanding of the impact of electrochemical treatment on the corrosion behavior of stainless steel, a commonly used material in cooling water systems, which increases the application risk of this technology. In this study, the effects of electrochemical treatment of simulated cooling water on the corrosion behavior and the passive film properties of Type 304 stainless steel with different N values were investigated by analysis of water composition, polarization curve and X-ray photoelectron spectroscopy. The results showed that the pitting potential of stainless steel decreased with the raise of N in untreated simulated water, while the pitting potential increased with the raise of N in electrochemically treated simulated water, and the highest pitting potential was observed when N was 10. The electrochemical treatment effectively reduced the Cl− content in the simulated water. With the increase of N, the concentration ratio of [Cl−]/[SO 4 2−] decreased, and the content of ClO− generated by Cl− oxidation in the water increased, which affected the corrosion behavior of stainless steel. Appropriate concentrations of the ClO− can effectively inhibit pitting corrosion of the stainless steel in simulated water, and the best inhibitory effect observed when ClO− concentration was 50 mg⋅L−1. The inhibition of pitting corrosion by ClO− was attributed to the effective improvement of the Cr/Fe ratio and the oxides/hydroxides ratio in the passive film on the surface of stainless steel, thus the compactness and the protection performance of the passive film was enhanced. The results can provide reference for the design of electrochemical treatment devices and processes. [ABSTRACT FROM AUTHOR]

The failure of pipelines during oil and gas exploitation is a pressing issue in the oil and gas industry. The high permeability of chloride ions (Cl−) alters the corrosion morphology of the N80 substrate and diminishes its ability to impede the penetration of corrosive substances. This study aims to deposit DLC films on the inner surface of N80 pipeline using plasma enhanced chemical vapor deposition (PECVD), and investigate the corrosion and friction behavior of DLC films in CO 2 saturated NaCl solutions with varying Cl− concentrations. The results indicate that the change in Cl− concentration possess minimal impact on the DLC film. The corrosion current density of DLC films in CO 2 saturated NaCl solution with three different Cl− concentrations is one order of magnitude lower than that of the N80 substrate. Moreover, a transfer film can still form in high-concentration CO 2 -saturated NaCl solutions, reducing wear. DLC film demonstrates exceptional stability, corrosion resistance, and wear resistance, making it an ideal material for safeguarding pipelines during oil and gas exploitation. [Display omitted] [ABSTRACT FROM AUTHOR]

The corrosion of archaeological bronzes is a complex process, and different corrosion phenomena can occur even within the same site, while previous studies paid little attention. Different corrosion phenomena can be observed on bronzes unearthed from Sujialong Cemetery, Hubei, China; in particular, some bronzes exhibit severe bronze disease, which is an uncommon phenomenon in Hubei bronzes. Multiple analysis methods were used to identify the corrosion products on the bronzes and to clarify the corrosion mechanisms. The results showed that the different corrosion phenomena were associated with the tomb microenvironment in different areas of the cemetery, which was confirmed by a spatial analysis of the whole cemetery; the outbreak of bronze disease was closely related to the presence of high chloride ion concentrations in the tomb environment and poor preservation conditions after excavation. The different corrosion phenomena are related to the archaeological contexts of the bronzes (especially microenvironments), which have been investigated only superficially in the past. [ABSTRACT FROM AUTHOR]

Electro-chemical Chloride Extraction (ECE) is considered one of the most effective techniques used to extract chloride ions from reinforced concrete structures. The effectiveness of using ECE depends on some important factors such as anode type, current intensity, extraction duration, type of rebar, and chemical properties of concrete. On the other hand, ECE may cause some detrimental effects on some mechanical properties of concrete and steel such as a reduction in bond and compressive strengths of concrete, and embrittlement (i.e. reduction in ductility) ductility of reinforcing steel. The major aim of this research work was to investigate the effectiveness of ECE using locally available un-galvanized steel mesh with conductive cement paste anode as a new type of anode on a reinforced concrete slab as a structural element. The slab behavior before and after ECE was studied by determining compressive strength, water absorption rate, concrete chloride content, and steel corrosion potential. The slab behavior was studied taking into consideration the established steel arrangement with spacing 20 cm between re-bars. The effect of initial chloride content on chloride extraction efficiency was investigated. Effectiveness of ECE with small initial chloride content 0.4% and 0.8% was compared with that of high initial chloride content 2.5% to know whether the initial chloride content is an important factor in ECE effectiveness or not. [ABSTRACT FROM AUTHOR]

The external beam-column connection in concrete structures is particularly important because it is necessary to secure the reinforcement bars of the beam that are embedded within the column, which are often formed as a 90° hook. The attack of chloride ions is also one of the most dangerous damages that affect constructions and reduce their service life. Hence, it was necessary to study the effect of corrosion resulting from chloride ion attack on the strength of hook bars. To achieve this purpose, 26 specimens were designed with various variables, including the corrosion level of the reinforcement bars, compressive strength of the concrete, specimen loading, and the spacing between the stirrups relative to their diameter (S/D). The specimens were subjected to accelerated corrosion in the laboratory using the current density method by applying 0.35 mA/cm2 for 21 and 58 days. The experimental results showed that corrosion of the reinforcing bar in the joint weakens the mechanical behavior of rebars by reducing their strength and the bond between them and the concrete. The effect of the compressive strength of the concrete, specimen loading, and S\D on the hook pulling force for corroded and non-corroded specimens has been observed, and they also affected the determination of the level of corrosion. Equations have been proposed to develop Faraday's law and determine the pulling force of a hook bar. The proposed equations yielded results that closely matched those from the experimental test. • The effect of corrosion on pullout force of hook in external joint was investigated. • Corrosion acceleration system was used by applying 0.35 mA/cm2 for 58 days. • The results showed effect of corrosion on reducing the bond strength of hook bars. • The results will lead to estimating the service life of corroded buildings. • Equations were derived to determine corrosion level and pulling force of hook bars. [ABSTRACT FROM AUTHOR]

Conventional anti-corrosion techniques provide short-term protection and are only suitable for low contaminate concrete. However, electrochemical techniques benefit highly contaminated concrete, but chlorides may reappear after some time. Developing on these techniques, Bidirectional Electromigration (BIEM) has recently received extensive interest. The present research injected an organic 2- Amino Pyridine Inhibitor into chloride-contaminated concrete under an electric field. The system's effectiveness was tested by measuring the chloride profile, inhibitor profile, change in corrosion rate and steel/concrete potentials. In addition, influence on various parameters such as initial admixed chloride content (1% and 3%), treatment duration (7 and 15 days), applied current density (1 A/m2 and 0.5 A/m2) and inhibitor concentration in the aqueous solution (0.3 M/L and 0.15 M/L) on treatment effectiveness was also investigated. The results indicated that after application of the BIEM, chlorides were extracted and inhibitors were migrated towards the steel bar. Further, chloride extraction and inhibitor migration efficiencies increased by increasing the treatment duration and current density. Additionally, results indicated that BIEM would be more effective for more severely chloride-contaminated structures. • An organic compound, 2 Amino pyridine has been employed in conjunction with ECE technique to protect RC under corrosion. • The technique effectively pushed the chloride ions away from the steel rebar. • The treatment can protect the corrosion with 99% inhibition efficiency. • The corrosion inhibitor forms a protective layer over rebar surface upon reaching its surface. [ABSTRACT FROM AUTHOR]

• Guiding principles to address deterioration due to corrosion are provided. • Available tests of determining the level of deterioration are culled from the literature. • A categorization of solution methods for protection, maintenance, and repair if offered. • A readily-available reference for practitioners and researchers on corrosion for coastal concrete structures. Deterioration due to corrosion is a key issue affecting the durability, safety, and sustainability of buildings and structures. Most cities are located in coastal areas and many reinforced concrete structures in these areas are exposed to aggressive marine environments. Therefore, it is important to provide protection and offer appropriate repair methods of buildings vulnerable to the degrading effects of corrosion. The first step of implementing recovery is determining the level of degradation undergone by exposed concrete structures. However, there is a lack of integrated guiding principles in this field. Thus, this review paper identifies the tests of determining the level of deterioration, with particular attention given to carbonation issues and chloride ion attacks. The paper also provides a categorization of solution methods for protection, maintenance, and repair, based on standards and codes culled from around the world. This research contributes to the field by providing a readily-available reference for practitioners and researchers, on the current state of knowledge on corrosion and repair strategies for coastal concrete structures. [ABSTRACT FROM AUTHOR]

• Steel fibers on surfaces of UHPC immersed in chloride solution were corroded after a year. • Flexural strength of thin UHPC panel (10 mm) was decreased by fiber corrosion. • Fiber corrosion on surface led no substantial strength decrease of thick UHPC panel. The results of experimental investigation of ultra-high performance concrete (UHPC) by evaluating the flexural response are presented in order to qualitatively evaluate the effects of chloride-induced corrosion. The third-point bending test is carried out using the hydraulic servo-controlled testing machine. The experimental variables are thickness of specimen (10, 25 and 50 mm), immersion duration, and mixture design of UHPC. The specimens are immersed in 10 wt% NaCl solution up to a year to induce corrosion. The effect of chloride-induced corrosion of steel fiber of UHPC is evaluated in terms of compressive strength, flexural strength and flexural toughness. The experimental results indicate that there is no significant loss in flexural strength and toughness for the specimens which were thicker than 25 mm over a period up to 365 days of immersion in chloride solution; whereas, the specimen with thickness of 10 mm showed about 10% decrease in maximum stress and corresponding toughness after 180 days of the immersion. Furthermore, it is revealed by comparing the compressive strength with and without fibers that the presence of steel fibers in UHPC under corrosive environments do not lead to substantial strength decrease. [ABSTRACT FROM AUTHOR]

Cavitation and corrosion on hydrodynamic components and systems reduces the operational efficiency. The use of wear resistant coatings has been studied as a solution to the problem of corrosion and cavitation in industrial environments. The high velocity oxy-fuel process (HVOF) can produce coatings with high density and bond strength. High velocity air-fuel (HVAF) is an alternative process, which can deposit coatings with higher velocity and lower temperatures, compared to the HVOF process, resulting in lower oxide content. This paper analyzes the HVOF and HVAF processes to deposit FeCrMnSiNi and FeCrMnSiB coatings, comparing their cavitation and corrosion resistance. HVAF coatings presented lower porosity and oxide levels, as well as higher hardness values. The HVAF process presented better cavitation and corrosion resistance, due to lower porosity and oxide contents of the coatings. The amount of oxides and pores in the coatings was crucial in their corrosive behavior, by facilitating the penetration of the chloride ions through the pores, leading to a higher corrosion rate and pitting formation. • The cavitation and corrosion resistance of different Fe-based coatings was examined. • Lower temperature of HVAF deposition led to lower oxide content compared to HVOF coatings. • The lower oxidation of HVAF coatings led to higher cavitation and corrosion resistance. • Higher Cr was effective to increase pitting potential, Ni addition reduced the passivation current. • Oxide layers were preferred sites for pitting growing and electrolyte penetration. [ABSTRACT FROM AUTHOR]

The corrosion behaviour of microporous nickel-chromium systems was studied by means of conventional electrochemical techniques and localized ones using two chloride based electrolytes with and without cupric ions in their composition. The conscious combination of different methodologies using these techniques has provided valuable information about the corrosion process. Open Circuit Potential (OCP) and Electrochemical Impedance Spectroscopy (EIS) measurements were performed in bulk solution, whilst Scanning Kelvin Probe (SKP) measurement were carried out using two methodologies: i) electrolyte droplets monitoring (measuring simultaneously potential and droplet height with time), and ii) potential maps of dried surfaces that previously were exposed to droplets. Further characterization was done based on the morphology of the attack and composition on the surface by Optical Microscopy (OM), Field Emission- Scanning Electron Microscope (FE-SEM) and X-ray Photoelectron Spectroscopy (XPS) together with the analysis of electrolyte composition with time by Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES). Results have shown the harmful effect of Cu2+ cations in the corrosion resistance and a different morphological impact on the surface. Such negative effect has revealed a new time constant at high frequency in the impedance diagrams as well as an abrupt potential decrease (due to a change in the cathodic reaction involved: Cu2+ + e− ↔ Cu+ takes place) using SKP droplet test. Apparently, Cu+ species were stabilized in bulk solution by the formation of chloride complexes, as was confirmed by the precipitation of a white CuCl compound during droplet evaporation, pointing out the key role of Cu+ in the corrosion process. [ABSTRACT FROM AUTHOR]

• Waste rubber aggregates in fiber and powder form were used in concrete. • Durability properties against aggressive environment were evaluated. • Improved resistance to acid and chloride attack was observed on inclusion of waste rubber aggregate. Waste rubber tyres in crumb aggregate form have been extensively studied (mechanical and durability performance) to produce reinforced structural elements. Rubber powder (incinerated tyres) and rubber fibers (shredded tyres) are two different forms of aggregate that require similar durability based evaluations for structural applications. Hence in this study, the durability of waste rubber powder and hybrid (rubber powder and rubber fibres) concrete against harmful environmental conditions was observed. The results showed that despite showing good resistance against acid attack and chloride ion diffusion, the rebar embedded in rubberised concrete was highly prone to corrosion as compared to the rebar in the control concrete. [ABSTRACT FROM AUTHOR]

• Chloride ions in exposure solution significantly affected formation of compounds in concrete as indicated by XRD results. • OPC exhibited 4.82 and 2.02 times higher apparent chloride diffusion coefficient than PPC and OPC plus fly ash. • PPC exhibited better performance against corrosion as compared to OPC plus fly ash followed by OPC. • Developed empirical relations for OPC and PPC predicted the I corr with higher degree of accuracy for OPC plus fly ash. • Developed empirical relation between E 0 and I corr predicted well the I corr values reported in literature. This study aims to investigate and correlate durability parameters in concrete exposed to external chloride. Tests for corrosion, chloride diffusion, and X ray diffraction (XRD) analysis were performed. Based on results, ordinary Portland cement (OPC) exhibited 4.82 and 2.02 times higher apparent chloride diffusion coefficient than Portland pozzolana cement (PPC) and OPC plus fly ash. Reinforced concrete specimens made with PPC showed better performance against corrosion as compared to those made with OPC plus fly ash followed by OPC. Concentration of chloride ions in exposure solution significantly affected microstructure of concrete as indicated by formation of compounds from XRD results. Developed empirical relationships between durability parameters for OPC and PPC predicted well the corrosion current density for OPC plus fly ash that was independent of model development. [ABSTRACT FROM AUTHOR]

A chloride-induced accelerated corrosion test was conducted on steel bars embedded in mortar specimens prepared with thermally activated coal mining waste (ACMW). ACMW was observed to prompt two opposite effects: a delay in chloride ion penetration and a reduction in the critical chloride content needed to initiate corrosion. Service life predictions based on the findings revealed that adding 20% or 50% ACMW to cement improved reinforcement corrosion resistance. Optimal results were observed for 20% replacement, in which the mean reinforcement section loss was 21% lower than in OPC. [ABSTRACT FROM AUTHOR]

Abstract Understanding the kinetics of passive oxide formation and breakdown has been an ongoing problem for corrosion scientists for several decades. Here, we present a model for the formation of a passive oxide film on a metal that is an extension of the Point Defect Model (PDM) by Macdonald and coworkers. We replace the potential description of the PDM with a boundary value problem and ensure that Gauss's law is satisfied at the oxide-solution interface by considering the presence of the Helmholtz layer in solution. Our model predicts the observed linear variation of the steady-state film thickness with anode potential, and an increasing film thickness with increasing pH. We perform a linear stability analysis of the model and show that, depending on the parameters, the passive film may be unstable to morphological perturbations of the film interfaces, leading to nonplanar films and potentially the formation of a pit in the oxide. This also implies that one-dimensional models, which assume planar interfaces, can be inapplicable in broad classes of corrosion processes. The analysis shows that a morphological instability exists if the oxide dissolution mechanism is such that an increasing Helmholtz layer potential drop leads to an increasing dissolution rate. The instability behavior is consistent with the literature on breakdown of passivity in the presence of chloride ions. The theory provides insights on the initiation of passivity breakdown leading to pitting corrosion and the role that interfacial energy plays in determining stability. [ABSTRACT FROM AUTHOR]

This study compares the resistance against chloride-induced steel corrosion of two alkali-activated materials (AAMs) and a CEM III concrete. The AAMs studied are: a metakaolin activated with sodium silicate (AAMK), and a GGBS activated by sodium carbonate (AAS). In order to study the corrosion of the reinforcement due to chloride, electrochemical measurements were performed on reinforced samples kept in a humid room (passive conditions) and samples dried (40 °C) before their immersion in a 35 g/l chloride solution (active conditions). AAMK showed the highest transfer properties whereas AAS and CEM III showed similar performance. The highly interconnected porous network of AAMK concrete presented low resistance to the penetration of chloride ions and very low resistivity compared to CEM III and AAS concrete. AAS had a finer porosity and a high chloride fixation capacity, which led to better resistance to chloride penetration and high resistivity. However, in AAS, sulfide ions from the slag dissolution led to low corrosion potential compared to values measured in traditional concrete. The drying of these samples at 40 °C caused a drop in the resistivity and a sharp increase in the chloride migration coefficient, which was explained by damage of the material. No corrosion products were observed after 2 years on rebars embedded in AAMs (AAMK and AAS). However, in CEM III reference concretes, pits of corrosion were identified when the reinforced samples were split. AAMs seemed to provide good protection of the reinforcement regarding chloride corrosion in immersed samples. [ABSTRACT FROM AUTHOR]

• Barrier protection from galvanized steel in sulfate-rich grout can be compromised. • Sulfates in alkaline solution develop poor coverage of calcium hyroxyzincate. • Corrosion development of galvanized steel captured by EN technique. Corrosion mitigation strategies for structural steel bridge elements including post tensioned steel components include the use of galvanized steel. The zinc alloy layers and subsequent precipitation of a dense surface oxide in alkaline environments provide beneficial barrier protection to mitigate corrosion. However, severe corrosion of galvanized steel components in contact with sulfate-rich deficient cementitious grout was documented to occur in less than 8 years of bridge service. Electrochemical testing and material characterization showed that the presence of sulfates in alkaline solutions allow for prolonged zinc activity and hindered passivation by the incomplete surface coverage and the precipitation of large sized calcium hydroxy zincate. OCP, LPR, and electrochemical noise (EN) testing showed greater corrosion activity of galvanized steel in chloride and sulfate solutions. EN identified local corrosion activity of the zinc associated to the porous nature of the surface oxide layer. [ABSTRACT FROM AUTHOR]

There are several cases worldwide wherein sulfide-bearing aggregates in concrete elements/structures have undergone oxidation and caused extensive damage. Signs of observed deterioration include map cracking, pop-outs, and secondary products that were generated from swelling. Unfortunately, it takes years to detect these signs visibly. Thus, in this study, a new methodology is proposed to activate and accelerate the potential oxidation reaction of iron sulfide minerals in concrete aggregates using chloride ions as activators or catalysts for the oxidation reaction. To promote the rapid penetration of chloride ions through concrete specimens, an electrochemical treatment is proposed consisting of two main phases, namely chloride impregnation in the specimen and impressed voltage treatment. Concrete specimens each 100 mm in diameter and 200 mm in length were made using aggregates with or without iron sulfide minerals and a mix design resembling the one used for building house foundations in the Trois-Rivières case, Canada. The results showed that chloride ions could activate the reaction and act as catalysts for the oxidation reaction of sulfide-bearing aggregates under a constant current (impressed voltage). Finally, traces of iron oxides/hydroxides and the formation of secondary sulfates (i.e., gypsum and ettringite) were observed in the concrete made with sulfide-bearing aggregates. This new procedure is promising for evaluating the oxidation potential of concrete with sulfide-bearing aggregates over a reasonable testing period. [ABSTRACT FROM AUTHOR]

[Display omitted] • The atmospheric corrosion performance of structural steel bolts in a tropical marine environment was studied. • Degree of deterioration after 2 years was 40Cr steel > galvanized steel > 304SS. • 304SS bolt exhibited localized corrosion while the CS bolts showed uniform corrosion. • Metallurgy, environment, and surface conditions influenced the corrosion process. • Surface coatings applied to bolts made of carbon steel had limited efficacy. The atmospheric corrosion performance of three different grades of hexagonal head structural steel bolts with distinctive surface finishes (304 stainless steel (plain), galvanized steel (Zn coated), and 40Cr steel (black coated)) was examined in this study using surface analysis and characterization techniques. The bolts were exposed in the Wenchang marine environment for two years. Results showed that a combination of factors such as alloying content, microstructure, surface finishing, and environmental conditions impacted the corrosion performance of the examined bolts. The corrosion mechanisms and patterns varied between the different bolt materials; 304SS bolts exhibited localized corrosion, while galvanized steel and 40Cr steel bolts exhibited uniform corrosion. In terms of coating performance in the marine environment, the zinc coating provided minimal protection to the underlying steel substrate when compared to the black oxide coating which failed prematurely, rendering it unsuitable for use in the marine atmosphere. Furthermore, despite the formation of a dense rust layer on the galvanized and 40Cr steel substrates after 2 years of marine atmospheric exposure, the fastener degradation was critical, suggesting that the rust layer is not beneficial in the threaded fasteners due to the high susceptibility to exfoliation that may eventually lead to thread stripping. This poses a serious risk to bolted assemblies. [ABSTRACT FROM AUTHOR]

Only limited work has been completed to characterize and quantify the chloride ion (Cl) maximum phenomenon and its impact on service-life prediction. In addition, there is limited long-term experiment to examine the evolution of the maximum phenomenon. The present study investigates the maximum phenomenon in concrete samples with sixteen varying combinations of water-to-binder ratios (w/b) and silica fume (SF) contents which have been exposed to tidal zone of marine environment for five years. Results show that the presence of maximum phenomenon is time-dependent, and both the maximum phenomenon thickness and the maximum Cl concentration are evolving with time. In addition, concrete matrix plays an important role in occurrence of the maximum phenomenon. Neglecting the maximum phenomenon results in a large discrepancy between the simulated and measured Cl profiles and can cause a significant overestimation in predicted service-life of concrete structures. [ABSTRACT FROM AUTHOR]

This study aims to investigate the efficiency of active and passive protection of the pre-corroded steel reinforcement in reinforced concrete (RC) columns using an externally bonded carbon fibre reinforced polymer (CFRP) wrap. Active protection is a novel technique used to impede corrosion achieved by employing the CFRP wrap as the anode of the impressed current cathodic protection (ICCP). Passive protection denotes the anti-corrosion behaviour of the CFRP fabric. Nine reinforced concrete columns with different degrees of corrosion (theoretical mass losses of 1%, 3%, and 6%) were prepared and then treated with different protection methods (non-protection, passive protection, and active protection) by exposing them to wet–dry cycles. By measuring the steel potential, linear polarization, and electrochemical impedance spectroscopy (EIS) of all investigated specimens, the efficiency of active protection was found to be closely related to the degree of the pre-corrosion of the protected specimens. Furthermore, the efficiency of active protection decreased with time, which may be attributed to the deterioration of the CFRP anode and CFRP/concrete interface. Passive protection was proven to be effective in every case, however, it can only slow down the corrosion process but cannot stop the elicited corrosion response. [ABSTRACT FROM AUTHOR]

This work aimed at studying the depassivation mechanism of the passive film on galvanized steel bar in concrete pore solution with different concentrations of chloride ion. The results showed that in a saturated Ca(OH) 2 solution, the critical chloride values for the depassivation of the passive films formed on galvanized steel bars and zinc metal specimens were 0.2 M and 0.3 M respectively. When the Cl − concentration was lower than the critical value, the donor density of the passive film increased and thus the protective property reduced with increasing the concentration of chloride ion, which could be interpreted by the point defect model (PDM). The corrosion products formed on the galvanized steel surface could inhibit the further ingress of the chloride ions and enhance the protective property, while such effect was not obvious for the zinc metal. [ABSTRACT FROM AUTHOR]

In reinforced concrete (RC) structures, reinforcement corrosion, concrete carbonization, and chloride ion erosion occur during service life, which deteriorate the seismic structural capacity of the structures. Most researchers have focused on the effect of the reinforcement corrosion on the seismic behavior of RC columns showing flexural behavior. On the other hand, research on the influence of the combined reinforcement corrosion and concrete carbonization on the seismic behavior of in-service RC columns showing shear-flexural behavior has not been performed. The present study evaluates the seismic performance of low-corroded in-service RC columns showing shear failure under cyclic load. Four RC columns with shear-span ratio 2.3 and light transverse reinforcement were obtained from an in-service RC moment frame building constructed in 1987, and quasi-static cyclic tests were conducted to investigate the seismic behavior of these columns. For the test parameters, axial compression force ratios and longitudinal bars arrangements were considered. The test results showed that as the compression force ratio increased, the failure modes of the in-service RC columns shifted from shear-bond failure to shear-compression failure, and the ductility and energy dissipation capacity decreased. The shear strength of the column specimens was evaluated by five existing shear strength models, considering the effect of reinforcement corrosion. Finally, seismic performance of RC short columns with corroded bars was discussed. [ABSTRACT FROM AUTHOR]

This investigation aimed to study the passivation and corrosion performance of sandblasted steel in a concrete environment. The surfaces of the steel specimens were modified using sandblasting method for three durations: 5, 10, and 15 min. The specimens were immersed in the chloride-free concrete pore solution for 14 days and then 3% by weight of chloride ions were added to the solution. The specimens were then kept in the chloride-contaminated pore solution for 60 days. Results from the electrochemical tests indicated that the passive layer formed on the surface on all specimens exposed to a simulated concrete pore solution were highly disordered n-type semi-conductors. In all specimens, except the 15 min sandblasted ones, the presence of chloride ions decreased the slope of the Mott-Schottky plots and increased the donor density which indicated formation of a thinner passive layer and corrosion. The results of electrochemical experiments on steel rebar exposed to chloride-contaminated pore solution showed significant improvement in corrosion resistance of the sandblasted specimens. This improvement was proportional to the increase in the sandblasting time. Microscopic analysis of the steel specimens at the end of the experiment showed the formation of a dense calcium-rich crystalline structure on the surface of sandblasted specimens. The density and the uniformity of the calcium-rich layer increased by increasing the sandblasting time. It was hypothesized that the formation of this layer combined with the enhanced passive layer in sandblasted specimens were the reasons for the improvement in corrosion resistance of the sandblasted steel specimens. [ABSTRACT FROM AUTHOR]

In this paper, an embedded ultrathin-film iron (Fe) corrosion sensor passivated with an anion-exchange membrane is developed to reveal the extent of corrosion tendency in reinforced concrete. Rebar in reinforced concrete is mainly corroded due to penetration of chloride ions which are one of the most dominant degradation factor for reinforced concrete. An effective method to monitor the extent of corrosion is to determine the positions where the chloride ions are present beyond the chloride threshold level (CTL). The sensors consist of ultrathin-film iron (Fe) layers deposited on the PET substrate, Au lines as electrode connection lines, and anion exchange membrane encasing the sensor. As the chloride ions exist near Fe layer of sensors, as if rebar has been corroded in reinforced concrete, the macro cells which occur relatively low anode and high cathode with somehow distance between them are made up and pitting corrosion accelerates. The pitting corrosion on the Fe layer of sensor induces the variation of electrical properties, which indicates the corrosion level using variations of resistance ( R ) and electrical response ( R / R 0 ). To protect the sensor from mechanical and chemical stimuli in a concrete, sensors are encapsulated with an anion exchange membrane that functions not only as a protector, but also as a selector of anions including chloride ions among degradation factors. Therefore, by embedding sensors at every 10 mm depth from the surface of reinforced concrete, we can monitor the corrosion tendency causing penetration of chloride ions with respect to depth. Through the variation of electrical properties in sensors, the velocity of corrosion ( Δ R · R 0 - 1 · t - 1 ) is suggested as a new parameter, which shows the tendency for corrosion under the surrounding conditions. To confirm the relationship between corrosion velocity as determined by the sensor and the concentration of diffused chloride ions, the chloride concentration in mortar is measured. The developed sensors in this paper are effective to sensitively and accurately monitor the corrosion level of concrete. [ABSTRACT FROM AUTHOR]

The increasing use of crushed concrete aggregates (CCA), formerly referred to as recycled concrete aggregates (RCA), has led to research into the effects of coarse CCA in higher value structural applications. Concerns exist regarding the effect on chloride ion ingress which ultimately can cause deterioration of reinforced concrete. This concern is reflected in existing European and British concrete design standards as limitations prevent their use in environments where chlorides may be present. The rapid chloride migration coefficient and rate of accelerated corrosion of structural CEM I and CEM III/A CCA concretes was measured to determine the effect on chloride ion ingress. Three sources of coarse CCA were evaluated; results show that coarse CCA generally had a detrimental effect on the chloride ion ingress of structural concrete. However, these effects can be mitigated by the inclusion of GGBS to produce structural CEM III/A concretes, thus allowing higher proportions of coarse CCA. It is recommended that the GGBS and coarse CCA content be limited to 50% and 60% respectively as this reduces the risk of a significant detrimental effect on chloride ion ingress. The results also suggest that the limitations in existing European and British standards are conservative and sustainable structural CEM III/A concrete with the inclusion of coarse CCA could be a viable option for future responsibly sourced projects, provided that a reliable and consistent source of CCA can be obtained. This is a positive outcome for the wider implementation of coarse CCA into structural concrete applications. [ABSTRACT FROM AUTHOR]

Experimental results on the effects of chloride content of ultra high performance concrete (UHPC) are presented. The experimental variables are the amount of sodium chloride, ranging from zero to 3.0% per cement weight, and matrix strength, including normal mortar and high strength mortar. Sodium chloride is directly mixed with cement matrix in order to simulate harsh environments by promoting the corrosions of fibers and matrix. The effects of chloride content are evaluated in terms of visual observation, electrical resistivity change, compressive strength, bending strength, and dynamic Young's modulus. The experimental results show that UHPC has the superior capability to resist chloride ions due to its dense microstructures, which prevent the growth of rust crystals. Furthermore, the experimental findings suggest that the potentials for corrosion of steel fibers and for corrosion-induced matrix cracking are inconsequential in UHPC even if chloride ions penetrate into UHPC. [ABSTRACT FROM AUTHOR]

In humid continental climate areas, brine rejection results in the metal being exposed to higher and changing concentrations of chloride ions derived from precipitation. In this study, the corrosion behavior of carbon steel in different conditions especially in high chloride ions concentrations and at low temperature were investigated via electrochemical methods Liner Sweep voltammetry (LSV), Electrochemical Impedance Spectroscopy (EIS), and surface analysis. The results indicate that the dominant factor in affecting current in the temperature range from 20 ºC to 0 ºC is different from that in the range from 0 ºC to −20 ºC. It was found that the charge transfer reactions were inhibited in high concentrated NaCl solutions, and corrosion morphology changed from pitting corrosion to general corrosion due to the frequent occurrence of passive film destruction induced by chloride ions. Furthermore, in addition to the common corrosion products found at both 0 ºC and 20 ºC, Fe 3 O 4 / γ-Fe 2 O 3 was detected only at 20 ºC. [ABSTRACT FROM AUTHOR]

Sodium chloride (SC) is by far the most cost-effective deicing agent in winter road maintenance and therefore is used by road authorities worldwide. However, chloride ions foster high corrosivity, which significantly reduces the service lifetime of metals and reinforced concrete of transport infrastructures. Hence, a holistic evaluation with the main criteria of deicing performance and corrosion is demanded and, if possible, alternatives should be considered. This paper focuses on the deicing performance of sodium chloride and other common acetate-, carbonate-, chloride- and formate-based deicing agents. A newly developed test method is presented, enabling high volume testing at good repeatability. From its results a nonlinear model is derived to predict deicing performance up to five hours after application. Subsequently, this model is compared with both existing empirical and theoretical approaches for evaluating the deicing performance. In addition, the impact of added corrosion-inhibiting substances like sugars on deicing performance is investigated. Finally, a comparison of all tested substances in terms of corrosivity and deicing performance is presented, with corrosion being investigated in detail in another paper. • A new method for evaluation of deicing performance is presented (called CEDA). • CEDA is compared to other theoretical and empirical evaluation methods, showing the possible limit of the theoretical approach. • CEDA is a more reliable and more efficient testing method compared to the common SHRP method. • Statistical analysis shows the variation of the time-dependent deicing performance of different deicing agents. • Deicing performance is compared to mass loss due to corrosion, showing advantages of certain deicing agents and inhibitors. [ABSTRACT FROM AUTHOR]

Concerning the Fukushima Daiichi nuclear power plant accident, we investigated the effect of chloride ion on the corrosion behavior of SUS316L stainless steel, which is a typical material for the equipment used in reprocessing, in HNO 3 solution containing seawater components, including under γ-ray irradiation condition. Electrochemical and immersion tests were carried out using a mixture of HNO 3 and artificial seawater (ASW). In the HNO 3 solution containing high amounts of ASW, the cathodic current densities increased and uniform corrosion progressed. This might be caused by strong oxidants, such as Cl 2 and NOCl, generated in the reaction between HNO 3 and Cl − ions. The corrosion rate decreased with the immersion time at low concentrations of HNO 3 , while it increased at high concentrations. Under γ-ray irradiation condition, the corrosion rate decreased due to the suppression of the cathodic reactions by the reaction between the above oxidants and HNO 2 generated by radiolysis. [ABSTRACT FROM AUTHOR]

Self compacting concretes (SCCs) modified by different volumes of granulated imperial smelting process (ISP) slag were tested during the research program. Granulated ISP slag was used as a replacement for natural sand. Mechanical properties of such SCCs are already known, but their durability and possible life span of structures made out of them need to be studied further. The conducted tests were focused on chloride ions infiltration into SCCs. The tests were planned in such a way that the achieved results would allow to use a theoretical diffusion model proposed by Szweda and Zybura. The model was verified by a comparison with the results acquired in a real diffusion. Finally, the forecast durability of concrete structures made out of tested SCCs was calculated. The foreseen life span of the structures was differentiated due to thickness of concrete coating of rebars. The proposed approach to SCC with ISP enables reliable prediction of its durability over time and precise technical life span of the structure made out of it. The study proved that replacing sand by ISP slag, even for small ratios, is counterproductive from the durability point of view. It can become feasible, only if an environmental impact study demonstrates it as a very good solution from that point of view. [ABSTRACT FROM AUTHOR]

This work studies the corrosion characteristics of reinforcement in a 4-year naturally corroded concrete beam after accelerated chloride penetration. The results show that the presence of transverse cracks in the tension surface of reinforced concrete beam can globally exacerbate the loss of cross-sectional area of rebar. However, there is no strong correlation between the width of transverse cracks, with the width of longitudinal cracks and loss of cross-sectional area of corroded rebar at a specific location. The self-healing of cracks and sacrificing roles of stirrups at crack tips seem to reduce the impacts of cracks on the corrosion propagation. [ABSTRACT FROM AUTHOR]

• Lower compressive strength was observed for GGBS based RAC mixes at early ages and at later ages comparable CS was obtained. • Resistivity increased almost two times with the inclusion of GGBS. • As expected, GGBS based RAC showed greater carbonation depths. • Inclusion of GGBS increased the resistance to chloride ion migration. • The corrosion rates for GGBS based RAC were almost half that of the OPC based RAC. By understanding the importance of recycled aggregates in the development of sustainable environment, the present study investigated the corrosion performance of recycled aggregate concrete. Since the water to binder ratio has a substantial impact on the performance of concrete, corrosion studies was conducted on a wide spectrum of water to binder ratio varying from 0.25 to 0.75 at 0.1 intervals. In addition, the impact of 50 % ground granulated blast furnace slag on corrosion performance was investigated for the same range of water to binder ratio. For all these developed concretes, coarse natural aggregates were totally replaced with coarse recycled aggregates and their corrosion performance was explored through surface resistivity test, accelerated carbonation test, rapid chloride migration test, half-cell potential, and corrosion rate test. From the results it can be concluded that the inclusion of ground granulated blast furnace slag into the recycled aggregate concrete mix 1) achieved 70 MPa compressive strength in 90 days of curing 2) increased the surface resistivity to 88 kΩcm and 3) decreased the carbonation resistance. By accessing the real time corrosion resistance of steel inside the concrete, an increase in potential and decrease in corrosion rate was observed for ground granulated blast furnace slag based concrete. Hence, it can be concluded that the inclusion of ground granulated blast furnace slag in the recycled aggregate concrete mixes increased the corrosion resistance. [ABSTRACT FROM AUTHOR]

Iron plays a vital role in natural processes such as water, mineral, iron, and nutrient cycles. Iron undergoes reduction-oxidation and catalytic reactions to produce various corrosion films depending on its chemical environment. Near ambient pressure X-ray photoelectron spectroscopy, polarized modulated infrared reflection absorption spectroscopy, and Auger electron spectroscopy were used to study the key reactants, from O 2 (g), H 2 O vapor, Na+ and Cl− on the initial stages of iron surface corrosion. With increasing the ratio of O 2 and H 2 O, surface hydrocarbons were shown to oxidize into carbonates, while the Cl− was found to migrate into the interface. The effect of each individual reactant was measured separately and water was shown to have a first order rate dependence on the carbonate growth at low pressures, with little dependence for O 2. Near ambient pressures, both H 2 O and O 2 were found to increase the carbonate growth, which was estimated using the Langmuir isotherm model, yielding Gibbs energies between −9.8 to −8.5 kJ/mol. A mechanism is suggested to explain the oxidation is catalyzed by NaCl on iron surfaces and the adventitious hydrocarbons served as the source for surface carbonation. These findings have implications for understanding other surface catalytic and redox interface chemistry in complex environments. [Display omitted] • Synergistic effect of H 2 O and O 2 facilitated by Cl and Na ions on iron surfaces leads to surface oxidation and corrosion. • Exposure to both H 2 O and O 2 oxidize surface hydrocarbons to produce surface carbonates by NAP-XPS. • Chloride ions are found to move away from the surface. • Water was found to have a 1st order kinetics dependence on the growth of carbonates. [ABSTRACT FROM AUTHOR]

• The corrosion inhibition of 3003 AA alloy in carbonate medium in presence of chloride ions was studied. • AAT shows an inhibition efficiency of 92% at 10−3 M against 3003 AA corrosion. • The drawn-in-silico conclusions are in good agreement with experimental findings. This present work focuses on investigating of efficiency of Acetaldehyde Ammonia Trimer (AAT) in the corrosion inhibition of 3003 aluminum alloy (3003AA) in carbonate medium in presence of chloride ions using electrochemical measurements, quantum chemical calculations based on DFT/B3LYP and Monte Carlo simulation methods for understanding the mechanism of corrosion inhibition. The results showed excellent inhibition corrosion of aluminum alloy with an efficiency reaching 92% for an optimum concentration of 10−3M at 298K. The adsorption results of the tested molecule obeyed Langmuir adsorption isotherm. The thermodynamic and kinetic parameters were determined and discussed. Furthermore, the capacity of AAT to act as an effective anti-corrosion agent was justified using these computational tools. Overall, the drawn-in-silico conclusions are in good agreement with experimental findings. [Display omitted] [ABSTRACT FROM AUTHOR]

• PO 4 3− and Cl− ions exhibit combined effect on mechanical and corrosion properties. • The formation of FePO 4 and γ-Fe 2 O 3 impart corrosion resistance. • Ca 3 (PO 4) 2 and Ca 5 (PO 4) 3 Cl crystals fill the cement mortar pores. • PO 4 3− ions should be greater than Cl− ions for excellent corrosion resistance. The present work focuses on the role of different amounts i.e. 0.295 and 2.95 kg/m3 ammonium phosphate monobasic (NH 4 H 2 PO 4 : APM) inhibitor and 1.2 kg/m3 NaCl as admixtures in cement mortar under wetting–drying accelerated condition to mitigate the corrosion of steel rebar. The results show that phosphate ions (from APM) react with NaCl and ordinary Portland cement (OPC) constituents to form Ca 3 (PO 4) 2 and Ca 5 (PO 4) 3 Cl as hydration products, which led to make the cement mortar matrix dense and compact, and thus, improved the compressive strength after 28 days of water curing. Consequently, the phosphate ions in the cement mortar initiate the oxidation of embedded steel rebars immersed in 3.5 wt. % NaCl solution due to the formation of Fe(H 2 PO 4) 2 , and FeHPO 4 as intermediate. These could be transformed into stable and protective tertiary iron phosphate (FePO 4) if optimum amount of phosphate ions is present but in the case of 0.295 kg/m3 APM, mostly phosphate ions consumed in the formation of Ca 3 (PO 4) 2 and Ca 5 (PO 4) 3 Cl. Therefore, this sample became vulnerable to corrosion. On the other hand, 2.95 kg/m3 APM, the phosphate ions are significant and, thus, it helps to properly form the Ca 3 (PO 4) 2 , Ca 5 (PO 4) 3 Cl, FePO 4 and maghemite (γ-Fe 2 O 3). [ABSTRACT FROM AUTHOR]

[Display omitted] • A quantitative simulation approach for corrosion reaction in steel–concrete composite structures. • Electrochemical reaction occurred on Ferrum with presence of oxygen and water. • Corrosion pattern of shear stud related to the configuration of boundary condition. • Pull-out performance of shear stud regarding corrosion pattern. Geometric shape of shear stud connector plays an important role on its connecting capacity in steel-composite structures. Recent application of steel–concrete structures showed the degradation of structural performance due to aggressive medium from environment. Available research indicated that the presence of chloride ions in concrete induced depassivation on the surface of steel shear stud connector and resulted in its corrosion accordingly. Thus, it is essential to obtain the corroded shape of shear stud connector for further accurate assessing structural performance of steel–concrete composite structure. As the focus of this paper, based on Fick's second law and Butler-Volmer equation, a quantitative simulation method for reaction of corrosion in steel–concrete composite structures was introduced and discussed. Wherein, two steps of this approach were listed. Firstly, mass transportations of chloride ion, oxygen and hydroxide were simulated for their concentration for preparation of electrochemical reaction. Secondly, electrochemical reaction of Ferrum with presence of oxygen and water, catalyzed by chloride ion, was numerically simulated. Furthermore, two cases of ingression of chloride ion into concrete were discussed for the influence of boundary condition on structural characteristics of steel–concrete composite structure. Random distribution of aggregate in concrete was considered. Result of numerical simulation indicated that, corrode shape of shear stud connector was related to configuration of boundary condition and different pull-out performance were obtained by finite element analysis. Moreover, degradation of mechanical properties of shear stud during its service life were provided. [ABSTRACT FROM AUTHOR]

• Raman mapping was employed to investigate the carbonation depth in a microscale. • The redistribution of the chloride due to carbonation was detected, and a chloride accumulation zone was found before the carbonation front, which directly caused the corrosion. • The corrosion mechanism of reinforcing steel in cement paste containing chloride under a CO 2 diffusion scenario was discussed and demonstrated in a schematic. Desalinated sea sand concrete (DSSC) is increasingly used to mitigate the shortage of natural river sand. However, one major concern lies in the corrosion risks of steel reinforcement embedded in DSSC under combined chloride and carbon dioxide attacks. To understand the corrosion mechanism, the corrosion process of steel reinforcement embedded in the cement paste containing chloride ions (Cl−) was monitored by electrochemical measurements, during which pH, Cl− profile and corrosion products were examined simultaneously. Raman spectroscopy was employed to evaluate the carbonation depth in microscale. Tests results showed that corrosion was initiated before the carbonation front reached the steel reinforcement. Interestingly, it was the carbonation-induced Cl− redistribution rather than the decrease of pH that dominated the corrosion initiation. Before the carbonation front, a Cl− accumulation zone was identified, and the corrosion mechanism was revealed. This study shall advance the understanding of the corrosion of steel reinforcement in DSSC for durability design of reinforced concrete structures. [ABSTRACT FROM AUTHOR]

In this work, the effect of chloride ions on copper corrosion behavior in an acidic sulfate solution, in the presence of binary inhibitor system of azoles and potassium sorbate was studied. Electrochemical measurements, weight loss measurements and surface analysis (SEM/EDS) were used in this investigation. Results of potentiodynamic polarization experiments indicate that azoles and potassium sorbate, in appropriate concentration, act as mixed-type inhibitors. Surface analysis (SEM/EDS) of copper confirmed that the rate of copper dissolution in aggressive medium is reduced as a result of formation of the protective layer on its surface. [ABSTRACT FROM AUTHOR]

• Graphene improves the resistance of concrete to chloride attacks by densering microstructures of concrete. • Graphene reduces the brittleness of concrete during chloride corrosion. • Graphene retards the deformation of concrete during chloride attacks. • Graphene enhances the compressive performance of concrete. In a marine environment, chloride ingress has the most prominent effect on the durability of concrete. The effect of graphene on the microstructure and compressive properties of concrete subjected to long-term chloride ion corrosion was investigated in this study. The results showed that an increase of up to 20.92 %, 21.97 %, 19.13 %, 19.43 % and 17.81 % is achieved in compressive strength respectively due to the addition of 0.05 wt% graphene nanoplatelets (GNPs) after 0, 40, 80, 120 and 240 days of immersion in sodium chloride solution, compared with ordinary concrete. With an increase in chloride ion deterioration time, the dynamic elastic modulus of graphene concrete gradually increased. The SEM, XRD, compressive performance and chloride ion content test results of the two concretes show that graphene concrete has better and more stable chloride ion resistance than ordinary concrete. [ABSTRACT FROM AUTHOR]

[Display omitted] • Revealing the effects of structural strain on the deterioration of passivation film in chloride attack. • Clarifying that the brittle fracture in the high strain and the plastic fracture in the low strain of passivation film. • Suggesting that the chloride ions deteriorate passivation film in high strain through penetrating the γ-FeOOH structure. Structural strain of steel is a general phenomenon in reinforced concrete, which significantly affects the performance of the passivation film but is still unclearly due to its nanoscale characteristics. In this work, the process of the chloride attack on γ-FeOOH is revealed by the molecular dynamics simulation with different structural strains. It is found that the properties of the γ-FeOOH structure changed significantly with the increase of strain. In the low strain status, the γ-FeOOH structure exhibit typical ductility. However, it exhibits obvious brittleness in the high strain state. The analyses of molecular interaction indicate that the chloride is easier to penetrate the layer structure of γ-FeOOH in high strain status, thus resulting in a huge shift in the γ-FeOOH properties. The generation of iron hydroxyl induces the penetration of chloride ions and is regarded as the origin of the γ-FeOOH deterioration. [ABSTRACT FROM AUTHOR]

In this work, electrochemical measurements are applied with the aim to obtain detailed information about diethylene triamine (DETA) influence on corrosion of carbon steel in Ethanol-Gasoline Blends (EGB). High corrosion inhibition efficiency of DETA in both E60 and E85 fuels is documented. Significant increase of the inhibitive effect with exposure time suggests steel passivation effect triggered by DETA in EGB. Main factors which facilitate passivation are alkalization resulting from DETA protonation, DETA+ cations bonding of chloride ions in ion pairs and high concentration of dissolved oxygen in EGB. Electrochemical tests show that alkalization has only negligible effect on cathodic process and main cathodic reaction is dissolved oxygen reduction. It is also illustrated that electrochemical measurements can help assess chemical changes in EGB environment due to polarization. [ABSTRACT FROM AUTHOR]

Passive film is a natural barrier against corrosion, which forms spontaneously in alkaline solution. But as a key problem for corrosion resistance, the growth and failure process of passive film has not been clearly confirmed. In this paper, the fine structure of passive film is explored on the atomic scale, and the growth mode of crystals is demonstrated; ion channels are found in inner passive film, which explains the appearance of defect zones and concentrated attack of chloride ions in corrosion. This study will help to judge the corrosion initiation from the perspective of micro damage of passive film. • A fine 5-layer structure of passive film in the growth process was found. • Crystal growth and amorphous aggregation is promoted by chloride ions in short term. • Putting forward special ion channel is the way that chloride invade the passive film. [ABSTRACT FROM AUTHOR]

The present work focuses on the corrosion behaviour of scratched epoxy coated carbon steel in simulated pore solution (SPS) containing varying % of chloride ions (added as NaCl) by localized electrochemical impedance spectroscopy (LEIS). LEIS results indicate that the |Z| at the scratch is decreased significantly with an increase in % of Cl − ions in SPS, which is evidenced by the formation of a depressed semicircle in the LEIS Nyquist plots. The intermediate corrosion products involved in the local corrosion process appears to be a function of the % of Cl − ions present in SPS. The competition between the aggressive Cl − ions and the inhibitive OH − ions and the extent of decrease in pH at interface determines the rate of corrosion. The LEIS maps acquired at 10 Hz provides a better understanding of the involvement of the anodic and cathodic areas on the local corrosion process of scratched epoxy coated carbon steel. The continuous decrease in |Z| at the scratch is due to the higher extent of dissolution of Fe at the scratch while the change in |Z| over the coating is determined by the extent of dissolution of Fe and accumulation of corrosion products over the coating due to the high bulk pH of SPS. No significant decrease in |Z| at the scratch is observed when the % of Cl − ions in SPS is 0.05. However, when the % of Cl − ions in SPS is increased beyond 0.05%, a significant increase in the corrosion rate of scratched epoxy coated carbon steel is observed. Hence, 0.05% NaCl can be considered as a threshold level of chloride ions in SPS. A pictorial model is proposed to explain the local corrosion process and mechanism of scratched epoxy coated carbon steel in chloride containing SPS. [ABSTRACT FROM AUTHOR]