Chloride Ion Attack Research Articles

Deterministic and probabilistic approaches for corrosion in RC structures: A direct proposed model to total service life predictions

In this paper the negative effects of the chloride ions attack in reinforced concrete (RC) elements have been studied. For this the vertical and horizontal chloride diffusivity has been treated by several models to identify the more relevant factor affecting the chloride concentration. The pitting corrosion has been treated to define the resistance losses of the shear forces and bending moments. An alternative deterministic/probabilistic procedure, by a direct and systematic new model, has been proposed to estimate the total time of service life for RC elements at the design phase. Several detailing configurations of steel bars in a RC beam, water/cement ratio and level of aggressiveness have been analysed to compare the model predictions. In this sense, this paper should provide useful results for analysts in terms of probability of failure for resistance losses and time of corrosion initiation. The goal is not only to provide practical results but also to evaluate the issue in a more modern risk analysis throughout the proposed prediction model.

Thermal stability and corrosion behavior of a novel Zr22.5Ti22.5Hf22.5Ni22.5Ta10 high-entropy amorphous alloy

The present study reasonably designed and prepared a novel Zr22.5Ti22.5Hf22.5Ni22.5Ta10 high-entropy amorphous alloy with excellent thermal stability and corrosion resistance. The hysteresis diffusion effect caused by the high mixing entropy of the multi-principal system affects the formation of the crystalline phase and thus improves thermal stability. The alloy exhibits excellent corrosion resistance compared to 316 L in 3.5 wt% NaCl solution. The XPS results indicate that the passive film of Zr22.5Ti22.5Hf22.5Ni22.5Ta10 passive film is rich in oxides of Zr, Ti, Hf, and Ta, which has excellent resistance to chloride ion attack.

Corrosion Protection Evaluation of Copper Coated with a Block Copolymer and Block Coploymer/Carbon Black Nanoparticles in 3 wt% NaCl Solution

AbstractThis paper presents a successful preparation of SEBS (a copolymer polystyrene‐block‐poly (ethylene‐ran‐butylene)‐block‐polystyrene) and SEBS‐CB (SEBS‐Carbon Black nanoparticles) coatings on a copper surface following a well‐defined immersion protocol. Such coatings′ protection capacity was tested in a 3 wt% NaCl medium using potentiodynamic polarization, cyclic voltammetry (CV), and electrochemical impedance techniques (EIS). The electrochemical measurements indicate that SEBS and SEBS‐CB are cathodic‐type inhibitors mainly hindering the diffusion of oxygen molecules toward the copper substrate. It also indicates the decrease in chloride ion attack on the coated copper layer. Not only that, but it also affirms the decrease in ‘s transport to the bulk solution, resulting in our sample being further protected at more positive potential. Cu‐SEBS‐CB electrodes showed a slight improvement in corrosion protection compared to Cu‐SEBS electrodes. π‐π stacking was associated with improving the performance of these coatings. The keys functions of incorporating CB are improving the electrode conductivity and having a denser and more compact coating than that without CB. The order of inhibition efficiency obtained by potentiodynamic polarization is in good agreement with the results achieved by electrochemical impedance spectroscopy. Also, the inhibition efficiency of Cu‐SEBS and Cu‐SEBS‐CB increases with increasing the ratio of SEBS. Adsorption of SEBS and SEBS‐CB on copper surface follows the Langmuir isotherm.

Electroreduction of dissolved carbon dioxide on roughened molybdenum microelectrodes.

The increasing levels of carbon dioxide (CO2) in the atmosphere may dissolve into the ocean and affect the marine ecosystem. It is crucial to determine the level of dissolved CO2 in the ocean to enable suitable mitigation actions to be carried out. The conventional electrode materials are expensive and susceptible to chloride ion attack. Therefore, there is a need to find suitable alternative materials. This novel study investigates the electrochemical behaviour of dissolved CO2 on roughened molybdenum (Mo) microdisk electrodes, which were mechanically polished using silicon carbide paper. Pits and dents can be seen on the electrode surface as observed using scanning electron microscopy. X-ray diffraction spectra confirm the absence of abrasive materials and the presence of defects on the electrode surface. The electrochemical surface for the roughened electrodes is higher than that for the smoothened electrodes. Our findings show that the roughened electrodes exhibit a significantly higher electrocatalytic activity than the smoothened electrodes for the reduction of dissolved CO2. Our results reveal a linear relationship between the current and square root of scan rate. Furthermore, we demonstrate that saturating the electrolyte solution with CO2 using a bubbling time of just 20 minutes at a flow rate of 5 L min-1 for a 50 mL solution is sufficient. This study provides new insights into the electrochemical behaviour of dissolved CO2 on roughened Mo microdisk electrodes and highlights their potential as a promising material for CO2 reduction and other electrochemical applications. Ultimately, our work contributes to the ongoing efforts to mitigate the effects of climate change and move towards a sustainable future.

Investigation of the reverse-seepage technique to enhance the chloride ion invasion resistance of rectangular section concrete: Experiments and numerical analysis

This paper looks at the application of the reverse-seepage technique in reinforced concrete (RC) structures with rectangular cross-sectional forms under chloride ion attack. Experiments and numerical analyses of the chloride invasion within rectangular section concrete which applied the reverse-seepage technique are performed. A two-dimensional convection–diffusion model of chloride is developed, which can be used to further investigate the effect of the shape of permeable tube arrangement and ratio of water permeable area. The results indicate that the reverse-seepage technique can greatly inhibit the chlorine accumulation effect in the corner of the rectangular cross-section under the effect of wetting–drying cycles. In addition, it is recommended that the water permeable area ratio should be set at about 0.6, and the permeable tubes should be arranged in a rectangular shape to improve the chloride ion intrusion resistance efficiency. These results have important implications for the further application of the new anti-chloride erosion technique in engineering.

Synthesis and performance of two ecofriendly epoxy resins as a highly efficient corrosion inhibition for carbon steel in 1 M HCl solution: DFT, RDF, FFV and MD approaches

An ecofriendly epoxy resins derivatives namely tetraglycidyl methyl -β-D-glucopyranoside (GlP) and tetraglycidyl methyl -β-D-galactopyranoside (GaP) were synthesized and characterized. The corrosion protection of GlP and GaP on carbon steel in a corrosive electrolyte (1 M HCl medium) was investigated using Fourier transform infrared (FTIR), electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), temperature effect (TE), scanning electron microscopy (SEM), atomic force microscopy (AFM), density function theory (DFT), molecular dynamics (MD) simulations, fractional free volume (FFV) and radial distribution function (RDF). The EIS results show that the two GlP and GaP have excellent inhibitory efficiency and GlP (93.65%) higher than GaP (93.08%) at 10−3 M. SEM and AFM analysis illustrated that the protective layer formed on CS surface in the presence of GlP and GaP could be stopped the chloride ions attack. FFV value of GlP films (34.20%) is lower than compared to GaP (34.31%), due to the most condensed film by the GlP epoxy resin on CS surface.

Empirical assessment and refinement of corrosion distribution models in the perimeter of corroded steel rebar subjected to chloride ions attack

Predicting the volume of corrosion products (CP) and their distribution in the steel rebar periphery will play an essential role in estimating the expansion stresses and, consequently, the behaviour of concrete in extreme environmental circumstances. In this respect, using the outcomes of performed laboratory studies, an attempt has been made to evaluate and compare the accuracy of the existing models for forecasting the thickness of CP. To this end, by applying the statistical analysis to predicted values, the error margin of the intended models in comparison to empirical observation has been computed. In addition, given that the studied models are mainly focused on estimating the corrosion product distribution (CPD) on the concrete cover, a research effort has been made to upgrade the models to estimate the corrosion distribution in the concrete core side. Based on the results obtained, it can be concluded that the modified Zhao model is the best-fitted model among the reviewed models, and performed refinement on this model could estimate the results more accurately. Furthermore, an empirical relationship for estimating the coefficient of CP expansion was introduced.

Structural characteristics and chloride intrusion mechanism of passive film

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.

Insight of development of two cured epoxy polymer composite coatings as highly protective efficiency for carbon steel in sodium chloride solution: DFT, RDF, FFV and MD approaches

• EP/AlA and EP/ArA present higher protective efficiency compared with 3.5% NaCl only. • 3D, AFM and SEM analysis showed that EP/AlA and EP/ArA act by chemisorption on the CS surface. • DFT, MDs, RDF, FFV and experimental data lead to investigate EP/AlA and EP/ArA as potential anticorrosive coating for CS in 3.5% NaCl medium. Cured epoxy polymers namely 3.3′-(phenylazanediyl) bis(1-((6-aminohexyl)amino)propan-2-ol) (EP/AlA) and 3.3′-(phenylazanediyl) bis(1-((4-(4-aminobenzyl)phenyl)amino)propan-2-ol) (EP/ArA) were used as potential protection coatings for carbon steel (CS) in 3.5% NaCl solution. The protection coatings of EP/AlA and EP/ArA on CS were investigated through, electrochemical impedance spectroscopy (EIS), potentiodynamic polarization curves (PC), atomic force microscope (AFM), scaning electron microscopy (SEM), contact angle (CA), natural bond orbitals (NBO), frontier molecular orbitals (FMO), fractional free volume (FFV), radial distribution function (RDF) and molecular dynamics (MD) simulations. PC and EIS data indicated that the two cured epoxy polymers investigated have excellent protective efficiencies. Further, protective efficiencies of EP/ArA (92 and 94.6% for EIS and PC, respectively) are higher than that of EP/AlA (86.3 and 88.7% for EIS and PC, respectively) in 3.5 %NaCl solution. SEM and AFM results displayed the protective layer formed on CS coated through EP/AlA and EP/ArA could be stopped the chloride ions attack. Also, the quantum chemical analyzes of cured epoxy polymers EP/A1A and EP/ArA were employed at DFT/B3LYP/6-31G(d,p) level to appraise the reactivity behaviors and possible regions via using the FMO and NBO methods. The results disclosed that the dominant interactions for both molecules were determined as the resonance (n → Π* and Π → Π*) interactions. FFV value of EP/ArA film (20.22%) is lower than compared to EP/AlA (28.02%), due to the most condensed film by the EP/ArA on CS surface. Experimental results combined with theoretical approaches were used to investigate the proction coatings.

Degradation of concrete in marine environment under coupled chloride and sulfate attack: A numerical and experimental study

The corrosion of offshore reinforced concrete structures under combined chloride and sulfate ions attack is a complex corrosion phenomenon. The purpose of this study is to develop numerical models in conjunction with experimental studies for long-term durability assessment of offshore concrete structures. A numerical model was developed to describe the simultaneously transport of chloride and sulfate ions considering the competitive binding by hardened cement pastes effect. The model was validated by a series of experimental studies. The validated model was implemented to predict the service life of the offshore RC structures under various chloride and sulfate solutions. The results show that chloride ions induced corrosion of steel bars in offshore RC structures is highly influenced by the concentration of sulfate ions. The sulfate ions induced concrete expansion and cracking from ettringite formation could potentially accelerate chloride ions induced corrosion of steel bars in concrete, ultimately the premature failure of the offshore RC structures.

An innovative location-dependent stochastic model for prediction steel bars area under chloride ion attack in the presence of transverse rebars

A novel location-dependent stochastic model is introduced for predicting the area of the corroded steel bars in the presence of transverse reinforcement. A 3D optical scanning technique was used to investigate the morphology and corrosion distribution patterns of different longitudinal steel rebars under various accelerated corrosion conditions. The result indicated that the existence of transverse bars significantly affects the corrosion pattern, which was not considered previously. Furthermore, it is shown that the Dagum probability function fits better to the scatter of areas. Utilizing zone-based lognormal function, a location-dependent stochastic model was developed to estimate the probable reduced rebars cross-section.

Evaluation of the Prediction and Durability on the Chloride Penetration in Cementitious Materials with Blast Furnace Slag as Cement Addition

Blast furnace slag (BFS) is a mortar additive in which the utilization of varied curing conditions and the basicity of BFS determine the fineness of the resulting mortar and, thereby, its salt prevention properties. This study evaluates and compares the salt-prevention properties of mortar prepared by either steam curing or water curing. The physical properties, for example, the BFS fineness, revealed the factors significantly affected by basicity that influence the salt-preventive properties of mortar in the specimens examined, such as the lead time and diffusion coefficient. Furthermore, these factors were also significantly affected by differences in curing conditions and other physical properties. However, few studies have examined its use in reducing chloride ion permeability as the main factor of corrosion reactions. Thus, this study evaluates specific surface, water/binder ratio (W/B), and curing conditions on the chloride penetration in cementitious materials with blast furnace slag as cement addition in terms of delaying chloride ion penetration, which affects corrosion reactions. Results of the study are intended to guide development of products for use in the precast concrete industry, toward extending the life of concrete structures, especially reinforced concrete structures in marine environments. In addition, the resulting durability measurements from the experiment conducted are illustrated. This study indicates that differences in Blaine size properties significantly influence water curing. Furthermore, results reveal the effects of combining BFS with various Blaine values and ratio-affecting properties on mortar. In conclusion, concrete materials that decrease durability against chloride attack and improve mechanical properties for precast manufacturer industrial applications are successfully developed in this study. In addition, the use of water-curing conditions, high Blaine value, high cement replacement ratio, and W/B tend to improve the general mechanical property performance and durability against chloride ion attack.

Toward superior fatigue and corrosion fatigue crack initiation resistance of Sanicro 28 pipe super austenitic stainless steel

The present work deals with the fatigue and corrosion-fatigue crack initiation in cold-pilgered Sanicro 28 super austenitic stainless steel. Toward this end, the stress-controlled symmetric reverse bending fatigue tests were conducted in air and mixed acid aqueous solution under the stress amplitude of 200–570 MPa with the stress ratio of −1 and frequencies of 1 and 15 Hz at ambient temperature. The fatigue study was supplemented with electrochemical experiments and advanced microstructural analyses to explore the damage characteristics in detail. The planar character of dislocation substructure owing to the low stacking fault energy of the material, and formation of parallel slip bands led to a more homogenous distribution of the imposed strain which retarded the progress of damage accumulation. According to the X-ray photoelectron spectrometer results, the formation of the insoluble and stable MoO3 oxide increased the rate of repassivation. This sticky oxide resisted against breakdown rendered by the attack of aggressive chloride ions. The corrosion fatigue behavior of the experimented alloy under the various test frequencies was discussed relying on the synergistic effects of mechanical and environmental damages.

Multifactorial Chloride Ingress Model for Reinforced Concrete Structures Subjected to Unsaturated Conditions

The attack of chloride ions is one of the most important factors affecting reinforced concrete (RC) durability. Chloride ingress into concrete is usually studied by assuming constant diffusivity and constant surface chloride concentration. However, these two approximations could badly estimate the chloride concentration in RC structures and then the lifetime assessment. Several factors influence the chloride concentration and ingress mechanisms in the convection area. In this paper, a new multifactorial and multiphase model to account for some effects on chloride surface concentrations in the convection zone is proposed. 136 values have been collected to identify the position and the chloride concentration in the border between the diffusion and convection zones. In addition, a time-dependent multifactorial diffusivity is considered. Diffusivity, which is the key parameter of the mechanical diffusion accounts in this paper for the water/cement ratio, chloride binding, temperature, concrete age, internal humidity, concrete deformation, and damage. The surface chloride model considers environment humidity, temperature, superficial concrete irregularities, and convection area of concrete. Advanced numerical solutions have been carried out to consider space and time dependencies in the model. Results show that the error function-based solutions could underestimate the chloride concentration C for periods < 10 years and for concrete depths > 4.0 cm in comparison with the proposed model.

Development of seismic resistant steel with high strength and corrosion resistance

Corrosion of reinforced steel inside concrete structures poses threat on designed life span of the buildings. This is more dangerous when used in seismic prone zones. Rebars with high strength and ductility can only provide better seismic resistance. Both strength and ductility can be obtained in steels produced through Quenched and Tempered (Q&T) process. Steels produced in this process acquire dual phases with tempered martensite at the case and ferrite plus pearlite at core. While, martensite is responsible for providing strength to the rebar and Ferrite plus pearlite provides the requisite ductility. Generally, corrosion starts from the surface of the steel bar in contact with concrete, because of the carbonation and chloride ion attack of the concrete. As the corrosion continues, both strength and ductility gets reduced substantially and ultimately results in failure of the structure during seismic activity. In view of this, a special steel was developed in this study and named as Earthquake, Corrosion Resistance, Fire Resistance (EQCRFR) steel. Corrosion studies were performed on 3 grades of steel such as Fe500D, DHSCRM and EQCRFR in carbonated and non-carbonated concrete pore solutions with varied chloride concentrations. Further, salt immersion tests were also carried out to supplement the results. This paper analyses the results to establish the corrosion characteristics of EQCRFR steel vis-à-vis two conventional steel grades Fe500D and DHSCRM. On the basis of experimental results, it is understood that EQCRFR grade steel possess improved corrosion resistance in comparison to other two grades considered in this study. In case of EQCRFR, the critical corrosion current density (icorr) did not exceed the limit of 0.1 µA/cm2 up to Chloride strength of 1.5 M in non-carbonated and carbonated solutions. However, the critical chloride concentration was very low at 0.05 M and 0.5 M for Fe500D and DHSCRM grades respectively.

Chloride Transport Behaviour and Service Performance of Cracked Concrete Linings in Coastal Subway Tunnels.

The concrete lining in subway tunnels often undergoes cracking damage in coastal cities. The combination of cracked tunnel lining structures and high concentrations of corrosive ions in the groundwater (e.g., chlorine) can accelerate concrete erosion, reduce the mechanical performance of the lining structures and shorten the tunnel service life. This paper investigates the chloride ion concentration in the groundwater of several subway tunnels in the coastal city of Qingdao, China. Indoor experiments and numerical simulations are conducted to investigate the chloride ion transport behaviour and service performance of cracked concrete linings. The results are applied to predict the service life of lining structures. The crack depth in concrete linings is found to have the most significant effect on the transport rate of chloride ions, followed by the crack width. The numerical simulations are carried out using COMSOL software to study the chloride transport behaviour in cracked specimens and predict the service lifetimes of lining structures of different thicknesses, and the results correspond well with the experimental data. The durability of a concrete lining can be enhanced by increasing the thickness of the protective concrete layer. Additional measures are proposed for treating cracked concrete linings to resist chloride ion attack in subway tunnels.

Time-dependent chloride transport models for predicting service life of bridge decks under chloride attack

This study aims to propose a set of time-dependent chloride transport models based on the measured data of 16 locations of monolithic concrete bridge decks under the attack of chloride ions in form of de-icing salts. This is carried out due to the shortcomings in the previous study which developed time-independent models containing two regression parameters. In this study, there are four regression parameters to be determined. They are simultaneously calculated using the finite difference formulation embedded with regression analysis. From the study, it is observed that the developed chloride transport model can predict the chloride content in most bridge decks. Although the prediction in some cases falls outside 50% margin of difference, they are on the conservative side. The regression parameters in the surface chloride function calculated here is higher than those in the previous study by two times. Seemingly, the diffusion coefficient in this study is comparable with that in Life-365 program. On the measurement or field survey date, if using the critical chloride value of 0.6 and 1.2 kg/m3, most and 5 of 16 bridge decks, respectively, would have rebar corrosion. However, there would be no concrete cracking if using the critical chloride value of 2.0 kg/m3.

Transfer time of the MDP and its effect on the time-dependent lateral deformation capacity of coastal bridge piers

In the maritime environment, the persistent attack of chloride ions will induce degradations of structural performance. Because of the surrounding exposure conditions, coastal bridge piers usually undergo discrepant deteriorations along the height, causing the maximum damaged position (MDP) to transfer from the conventional pier bottom to the zone that corroded most seriously. This study presents an analytical method to forecast the transfer time of the MDP for coastal bridge piers. The relationship between the structural capacity and seismic demand of the bottom section in each zone is monitored synchronously, aiming to capture the time and place that the structural capacity is first exceeded by the seismic demand. Next, an illustrative example of coastal bridge piers is adopted to demonstrate the proposed approach. The time-dependent lateral deformation capacity of the coastal bridge pier is investigated by considering the effect of the transfer time of the MDP. The analytical results show that the ultimate drift ratio of coastal bridge piers increases firstly and then, decreases significantly when the discrepant corrosion damages along the pier height is considered. As for the conventional simplified corrosion mode, i.e., using an equivalent mean corrosion level to describe the corrosion level for the global bridge pier, it cannot be adopted to estimate the actual time-dependent seismic performance of coastal bridge piers corroded non-uniformly along the height.

Performance of curing epoxy resin as potential anticorrosive coating for carbon steel in 3.5% NaCl medium: Combining experimental and computational approaches

Triglycidyl ether triethoxy triazine (TGETET) epoxy resin cured by 1.6-diaminohexane (TGETET/DAH) and 4.4-diaminodiphenyl methane (TGETET/DDM) was investigated as potential anticorrosive coating for carbon steel in sodium chloride medium. Polarization curves (PC) and electrochemical impedance spectroscopy (EIS) results displayed the protective efficiency of TGETET/DDM is higher than that of TGETET/DAH in 3.5 %NaCl medium. SEM data showed that both TGETET/DAH and TGETET/DDM could be significantly stopped the chloride ions attack due to adhesion between the protective layer formed on CS coated. Chemical reactivity tendency of TGETET/DAH and TGETET/DDM compounds were evaluated using global quantum chemical descriptors (GQCDs) and molecular dynamics simulation (MDs).

Investigating the potential of low-grade calcined clays to produce durable LC3 binders against chloride ions attack

Utilization of limestone calcined clay cements (LC3) as a recently developed ternary blends could be a promising economic approach to reduce the environmental impacts of Portland cement production. This study presents a comparative experimental investigation between LC3 mortars and binary blends, prepared with kaolinitic calcined clays as prominent sustainable resources of supplementary cementitious materials (SCMs). In this regard, four different low to high-grade kaolinitic clays, provided from various resources, were calcined and incorporated in both binary and LC3 blends. Furthermore, the pure Portland cement and limestone Portland cement blends were also prepared to compare the results with calcined clay containing mixtures. Thermogravimetric analysis (TGA) was performed on paste samples to study the phase assemblage of systems. Besides, compressive strength, water absorption and sorptivity, total and free chloride ions penetration profiles, and chloride ions diffusion coefficients of mortar mixtures have been investigated. According to experimental results, the pozzolanic reactivity of calcined clays is not only influenced by the metakaolin content and thermal activation process, but also by the crystallinity of these materials. Besides, although the compressive strength of binary and LC3 mortars may be lower than the control mixture, but the permeability and resistance against chloride ions ingress have been significantly enhanced. Ultimately, low-grade calcined clays have been recognized as a promising resource to produce LC3 blends with adequate durability against chloride ions ingress.