Chloride-induced Corrosion Of Steel Research Articles

Chloride-induced corrosion of steel in concrete-insights from bimodal neutron and X-ray microtomography combined with ex-situ microscopy.

The online version contains supplementary material available at 10.1617/s11527-024-02337-7.

Interacting Action of Alkali-Silica Reaction and Chloride-Induced Steel Corrosion on The Reinforced Concrete Structures – A Critical Review

Interacting Action of Alkali-Silica Reaction and Chloride-Induced Steel Corrosion on The Reinforced Concrete Structures – A Critical Review

Evaluation of steel corrosion-induced concrete damage using electrical resistivity measurements

The main objective of this research study is to demonstrate the feasibility of Electrical Resistivity (ER) measurements as an in-situ, non-destructive evaluation method for monitoring progressive damage in concrete due to steel corrosion, particularly in a marine environment. To this end, a series of laboratory experiments is performed to investigate the variation of ER values in a total of 108 reinforced concrete cubes, each with a side dimension of 200 mm. The impressed current technique is utilized to accelerate the corrosion of steel reinforcement in the concrete cubes submerged in 3.0% NaCl solution, which simulates various degrees of concrete degradation. ER measurements are performed before and after the accelerated corrosion tests on the surface of concrete specimens. It is demonstrated that ER is an excellent NDE method for the monitoring of progressive concrete damage associated with chloride-induced steel corrosion.

3D mesoscale investigation of non-uniform steel corrosion in reinforced concrete under chloride environments

Chloride-induced corrosion of steel in reinforced concrete (RC) exhibits complicated mechanisms such as chloride diffusion, oxygen diffusion, electrochemical polarization, dissolution and deposition of steel. This work investigates the 3D non-uniform corrosion behavior of steel in RC by integrating all the possible mechanisms and mesoscale heterogeneities, for the first time. The anodic Tafel slope is used to describe the depassivation of steel induced by chloride, while the dynamic process of oxygen supply and consumption is considered as well as the inhibition of the cathodic reaction caused by oxygen concentration. The coupling of mass transfer and electrochemical corrosion in RC is developed and validated. Mesoscale RC models with realistic aggregate, mortar, steel and interface are generated through a physically-based approach similar to casting procedures. The simulation results show that the 3D mesoscale RC model can simultaneously capture the non-uniform corrosion patterns of steel along the circumferential and longitudinal directions, offering significant application value in accurately predicting steel corrosion morphology. The random distribution of aggregates affects the local non-uniform corrosion of steel, but has little influence on the overall cumulative corrosion level. The local non-uniform corrosion of steel gradually weakens with the increase in chloride erosion time. The non-uniform corrosion of side steel is enhanced with the increase of the steel diameter and the decrease of the protective layer thickness. Bi-directional erosion mainly enhances the uniform corrosion of corner steel.

Synergistic inhibition of molybdate and phytate on chloride-induced corrosion of carbon steel in simulated concrete pore solutions

Improving the corrosion resistance of reinforcing steel is particularly important to prolong the service life of reinforced concrete (RC) structures. This study proposes a novel mixed corrosion inhibitor of sodium molybdate and sodium phytate to enhance the corrosion resistance of Q235 carbon steel in concrete exposed to aggressive environments. Based on the synergistic inhibition of the mixed corrosion inhibitor with an optimal concentration ratio, the passivation and chloride-induced corrosion of steel in simulated concrete pore solutions were investigated using electrochemical measurements, XPS, AFM, SEM/EDS and ATR-FTIR. The results indicated that the mixed corrosion inhibitor could promote the passivation process of steel by increasing the passive film thickness, despite no significantly improved passivation ability was highlighted for steel. Furthermore, due to the formation of a protective and thick passive film with a specific three-layer structure, the mixed corrosion inhibitor markedly improved the pitting corrosion resistance of steel and exhibited a high inhibition efficiency after 30 days of chloride exposure. Accordingly, the corresponding synergistic inhibition mechanism of the mixed corrosion inhibitor was proposed.

Chloride-induced 3D non-uniform corrosion of steel in reinforced concrete considering mesoscale heterogeneities and early-age cracks

Considering that reinforced concrete structures typically work with cracks, this work aims to investigate the chloride-induced non-uniform corrosion of steel by proposing a five-phase cracked reinforced concrete model at mesoscale, including realistic aggregate, matrix, steel, early-age crack, and damage zone. A physically-based 3D mesoscale modeling approach is developed to accommodate all the phases by integrating gravity-driven compaction and vibration as in real casting procedures. This modeling approach is further developed to capture coupled mass transfer and electrochemical corrosion of steel, enabling simulations of non-uniform corrosion along both the circumferential and longitudinal directions of steel. The considerable variation in corrosion morphology due to aggregate distribution demonstrates the necessity of using 3D mesoscale models to predict steel corrosion. Early-age cracks accelerate the diffusion of corrosive agents, intensifying the corrosion of steel. Increasing the crack width, depth, and length all contribute to a higher dissolution thickness of the steel. With the same crack size, longitudinal cracks result in a larger average dissolution thickness of the steel. In addition, the maximum dissolution thickness of the steel is highly correlated with the degree of pitting corrosion, and in most instances, transverse cracks lead to a higher degree of pitting, causing a greater maximum dissolution thickness.

Inhibitive effect of sepiolite-supported MgAl-LDH on chloride-induced corrosion of steel in simulated concrete pore solution

This paper aims to evaluate the inhibitive effect of sepiolite-supported Mg-Al layered double hydroxides nanocomposite (SEP@LDH) on chloride-induced corrosion of steel in simulate concrete pore solution, which was synthesized by the in-situ coprecipitation method. The results show that the nanocomposite possesses a more superior corrosion protection performance than the pure LDH. The potential mechanism can be attributed to the reduction in agglomeration and increase in dispersion of LDH layers, leading to a stronger chloride binding capacity and simultaneous release of more nitrate ions.

Understanding the intrinsic effect of fly ash on passivity and chloride-induced corrosion of carbon steel and stainless steel in cement extract solutions

Compared with the ordinary Portland cement extract solution (OPC solution), the passivation capability and chloride-induced corrosion behavior of carbon steel (Q235) and 316 stainless steel (316ss) in fly ash modified cement extract solution (FA solution) were intensively investigated in this study. The composition and electrochemical properties of steel passive films were studied using XPS technique and a series of electrochemical measurements including M − S, EIS and CPP. Moreover, FT-IR, AFM and SEM/EDS were employed to analyze the corrosion products and morphology on the steel surface. After 10 d of passivation, the film resistance of Q235 in OPC solution was 1.42 times that in FA solution, but an opposite result was observed for 316ss, which is consistent with the subsequent chloride-induced corrosion behavior. Steel passive films of different thicknesses and protective characteristics for Q235 and 316ss formed in alkaline solutions were confirmed to be the dominating reason for the distinct passivity and corrosion resistance to chloride attack. Accordingly, the intrinsic impact mechanisms of fly ash on passivation capability and chloride-induced corrosion of Q235 and 316ss in extract solutions were proposed.

Electrochemical responses of carbon steel in ordinary Portland cement blended with calcium sulfoaluminate cement

This work investigated the passivation and chloride-induced corrosion of carbon steel exposed to an extract solution (PCSA) of ordinary Portland cement (OPC) blended with calcium sulfoaluminate (CSA) cement. As evaluated by EIS and XPS measurements, carbon steel gained inferior passivity by forming a thinner and less protective passive film in PCSA solution compared with that in the pure OPC solution. However, after chloride attack, comparable corrosion resistance was confirmed for steel exposed to both solutions. Furthermore, enhanced pitting corrosion resistance was identified for steel after 30 d of immersion in PCSA solution, which was mainly attributed to the formation of an Al-rich layer on the steel surface as well as the reduced chloride concentration in solution by the unreacted aluminum phase.

Transfer properties and chloride-induced corrosion resistance of GGBS and metakaolin alkali-activated materials

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.

Effect of corrosion inhibitor on service life of cracked and non-cracked concrete

Corrosion of steel in reinforced concrete structures can cause damage and costs involved and attracts researchers to look for solutions that delay the onset of corrosion initiation or slow its development. The effectiveness of four corrosion inhibitors in cracked and non-cracked sections of reinforced concrete was studied: Migrating Corrosion Inhibitor (MCI-2005) based on amine carboxylate; CNCI 1.37 based on calcium nitrite Ca (NO)2 at a concentration of at least 30%; and two lab-made green corrosion inhibitors based on recycled materials – fluorosilicates obtained from fluorosilicic acid (H2SiF6), the by-product of the phosphate industry, and from LABS (Linear Alkyle Benzene Sulphonate), the by-product of the detergent industry. The study followed the guidelines of the ASTM G-109 standard which examines materials intended to inhibit chloride-induced corrosion of steel in concrete, and the ASTM C-876 standard which evaluates the electrical corrosion potential of uncoated reinforcing steel, for the purpose of determining the corrosion activity of the reinforcing steel. Controlled artificial cracks of different depth were created to speed up the corrosion process in the steel. Such cracks allowed a direct penetration of chlorides into the depth of concrete. As was expected, the cracked concrete samples exhibited a significantly higher level of corrosion than the non-cracked samples. In the non-cracked samples, the effectiveness of the CNCI 1.37 commercial corrosion inhibitor was the highest. However, in the cracked samples it appears that its efficiency has decreased, while the recycled corrosion inhibitor based on K2SiF6 has shown the best performance. This result can be explained by the fact that fluorosilicate reacts with calcium hydroxide present in concrete and creates a non-permeable protective layer that inhibits the movement of chlorides to the steel bar.

Evaluation of Early Concrete Damage Caused by Chloride-Induced Steel Corrosion Using a Deep Learning Approach Based on RNN for Ultrasonic Pulse Waves.

The objective of this study is to explore the feasibility of using ultrasonic pulse wave measurements as an early detection method for corrosion-induced concrete damages. A series of experiments are conducted using concrete cube specimens, at a size of 200 mm, with a reinforcing steel bar (rebar) embedded in the center. The main variables include the water-to-cement ratio of the concrete (0.4, 0.5, and 0.6), the diameter of the rebar (10 mm, 13 mm, 19 mm, and 22 mm), and the corrosion level (ranging from 0% to 20% depending on rebar diameter). The impressed current technique is used to accelerate corrosion of rebars in concrete immersed in a 3% NaCl solution. Ultrasonic pulse waves are collected from the concrete specimens using a pair of 50 kHz P-wave transducers in the through-transmission configuration before and after the accelerated corrosion test. Deep learning techniques, specifically three recurrent neural network (RNN) models (long short-term memory, gated recurrent unit, and bidirectional long short-term memory), are utilized to develop a classification model for early detection of concrete damage due to rebar corrosion. The performance of the RNN models is compared to conventional ultrasonic testing parameters, namely ultrasonic pulse velocity and signal consistency. The results demonstrate that the RNN method outperforms the other two methods. Among the RNN methods, the bidirectional long short-term memory RNN model had the best performance, achieving an accuracy of 74% and a Cohen's kappa coefficient of 0.48. This study establishes the potentiality of utilizing deep learning of ultrasonic pulse waves with RNN models for early detection of concrete damage associated with steel corrosion.

Electrochemical characterization of chloride ion transport in rubber concrete

Chloride-induced corrosion of steel in concrete structures is a significant issue. As an environmentally-friendly building material, rubber concrete has been proven to have the potential to resist chloride-induced permeation. In this paper, the transport behavior of chloride ion in rubber concrete was investigated by electrochemical impedance spectroscopy (EIS) approach. A novel electrochemical equivalent circuit Rs(Q1(Rct1W1)) (Q2(Rct2W2)) was used to study the electrochemical properties of rubber concrete systems and compare with other equivalent circuits by evaluation indicator. The results demonstrate that Rs(Q1(Rct1W1)) (Q2(Rct2W2)) is more suitable for the study of rubber concrete system and the increase of rubber will enhance the resistance to chloride ion transmission. The equation was established by the relation between the equivalent circuit parameter (Rct1) and the migration depth of chloride ion. On this basis, the EIS method can be utilized to predict the depth of chloride ion penetration in rubber concrete.

Atomic scale insight into the mechanisms of chloride induced steel corrosion in concrete

Chloride (Cl) induced steel corrosion is a major cause of durability issues of reinforced concrete (RC) structures and causes a large economic loss every year. Understanding the mechanisms of Cl induced steel corrosion in concrete is of great importance to develop anti-corrosion methods and further lowers down the repair and strengthening frequency and cost. Hence, the nature of steel depassivation and corrosion induced by Cl at atomic scale was revealed through the density functional theory (DFT) calculations to better understand the Cl induced corrosion mechanism. The results indicated that Cl species weakened the bonding of oxygen (O) with outer iron (Fe) atoms while enhanced the hybridization of O with inner Fe atoms, thus induced the breakdown of passive films. Besides, Cl facilitated the charge loss of outer Fe atoms and improved the interactions of water molecular (H2O) with these Fe atoms. When co-adsorption with O atom, hydroxyl (OH) generated by dissociative adsorption of H2O enhanced the charge loss of outer Fe atoms. Then OH strongly bonded with the neighboring Fe atoms to form the initial corrosion products, iron hydroxides (Fe-OH). The above DFT calculations are consistent with the experimental results about the steel depassivation and corrosion processes in concrete and hopefully these results can guide the anti-corrosion design of RC structures.

Synergistic inhibition mechanism of phosphate and phytic acid on carbon steel in carbonated concrete pore solutions containing chlorides

Synergistic inhibition performance of trisodium phosphate (TSP) and phytic acid (PA) on chloride-induced corrosion of Q235 carbon steel in carbonated concrete pore solutions was investigated using electrochemical measurements, XPS, AFM and SEM/EDS. At the optimum concentration ratio of TSP and PA, the mixed inhibitor showed an inhibition efficiency of 89.8 % after long-term chloride exposure due to the progressive formation of a protective oxide film with specific bilayer structure on the steel surface, and the corresponding synergistic inhibition mechanism was proposed. However, the excessive content of PA could compete with TSP, thereby leading to an antagonistic effect with reduced inhibition efficiencies.

Durability characteristics and quantification of ultra-high strength alkali-activated concrete

Clinkerless ultra-high strength concrete formulated using alkali-activated binders (AAB-UHSC) emerges as a green high-performance construction material, but its durability characteristics have not been systematically investigated yet. In this work, the resistances of AAB-UHSC against water absorption, carbonation, chloride diffusion, and chloride-induced electrochemical corrosion of steel, are quantitatively evaluated and compared with those of ordinary Portland cement (OPC)-based UHSC and normal-strength AAB (AAB-NSC) counterparts. The results show that in comparison with OPC-UHSC of similar strength of ∼150 MPa, AAB-UHSC has lower water-permeable porosity and demonstrates superior performance against water absorption and chloride ingress, but a weaker carbonation resistance. However, despite lower CO2 uptake capacity, the carbonation resistance of AAB-UHSC is about six times stronger than that of AAB-NSC, owing to its highly densified microstructure. Under the same chloride level and relative humidity conditions, the corrosion rate of steel embedded in AAB-UHSC is higher than that in OPC-UHSC, likely due to its higher moisture content and [Cl−]/[OH−] ratio that expedite steel dissolution. Moreover, the incorporation of steel fibers has limited influence on the transport-related durability performance of AAB-UHSC, implying a densified interfacial zone between steel fibers and AAB-UHSC matrices.

Chloride-induced depassivation and corrosion of mild steel in magnesium potassium phosphate cement

This study investigated the chloride-induced depassivation and corrosion of mild steel in the magnesium potassium phosphate cement (MKPC) pore solutions at different magnesia-to-phosphate (M/P) ratios via several electrochemical methods and surface characterisations. Results showed that although the pH of MKPC is much lower than that of PC, the corrosion resistance of mild steel is significantly higher, with critical chloride values in MKPC being several orders higher than that in PC. Chloride-induced corrosion resistance increases with increasing M/P ratios. Whilst both pH and HPO42-/PO43- ions influence the formation of corrosion products, the pH plays a dominant role in the corrosion resistance.

Influence of Partial Rust Layer on the Passivation and Chloride-Induced Corrosion of Q235b Steel in the Carbonated Simulated Concrete Pore Solution

A partial pre-rusted wire beam electrode (WBE) was designed to study the influence of the rust layer on rebar corrosion in the carbonated simulated concrete pore solution (SCPS). The results show that the passive film generated on the pre-rusted steel area is more fragile than that formed on the fine polished steel area in carbonaceous media. Nevertheless, the pitting corrosion resulting from the presence of chloride ions still tends to occur on the fine polished steel surface due to the local acidification process being hindered by the rust layer. The rust layer could play a more important role than the passive film in inhibiting the initiation of chloride-induced corrosion on rebar. The expansion path of the corrosion product would be blocked by the rust layer, leading to the pit propagating in the fine polished region. Furthermore, the growth of pitting corrosion is greatly accelerated due to the catalytic cathodic reaction of the rust layer.

Passive film alteration of reinforcing steel through [MoO42−]/[RCOO−] interfacial co-interaction for enhanced corrosion resistance in chloride contaminated concrete pore solution

Chloride-induced corrosion of carbon steel could be inhibited by molybdate (MO), while the MO/chloride ratio plays a vital role. This ratio has been reduced in constant chloride concentration using acetate (AC) as an organic corrosion inhibitor. Results showed that the MO-AC mixture, regardless of the concentration, possessed remarkable inhibition capability at the low concentration of MO. Electrochemical evaluations and surface analyses demonstrated the excellent behaviour of MO-AC, which promoted the formation of Fe2(MoO4)3, resulting in enhancing the properties of the passive-adsorbed layers. Based on the XPS results, more MO contributed to the formation of Fe2O3 in MO-AC as the Mo6+/Mo4+ ratio decreased and the value of Fe3+/Fe0 increased. Also, the low MO concentration assisted AC adsorption.

Studying the effect of two isomer forms thiazole and thiadiazine on the inhibition of acidic chloride-induced steel corrosion: Empirical and Computer simulation explorations

Two isomeric forms thiadiazines (AZIN) and thiazoles (AZOL) are produced through a simple reaction of monohydrazone with α-haloketohydrazonoyl derivatives in the alkaline medium. The prepared materials were characterized through spectral information. The corrosion inhibition performance of AZIN and AZOL for the C-steel corrosion in a 15% hydrochloric acid solution was evaluated via Open circuit potential (EOCP) vs. time, electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PDP) techniques. The inhibition efficiencies of AZIN and AZOL at an optimum concentration (2.0 × 10-3 M) are 96.4% and 98.3% at 50 °C, respectively. The assessed values of the standard adsorption free energy (ΔGads0) revealed the typical behavior of physisorption and chemisorption of AZIN and AZOL on C-steel and followed the Langmuir isotherm model. Surface morphology studies by FTIR and FESEM analyses confirmed the adsorption of the AZIN and AZOL molecules on the C-steel interface. Density functional theory (DFT) calculations and Monte Carlo (MC) simulations exhibited that the efficiency of the AZIN and AZOL associates well with their structures and this protection was due to their adsorption on metal surfaces.