Simulated Concrete Pore Solution Research Articles

Passivity and Pitting Corrosion of 316L in Simulated Concrete Pore Solutions under Marine Environment

Passivity and Pitting Corrosion of 316L in Simulated Concrete Pore Solutions under Marine Environment

Electrochemical investigation of the influence of a durable exterior emulsion coating on the corrosion resistance of mild steel in simulated concrete pore solution

Electrochemical investigation of the influence of a durable exterior emulsion coating on the corrosion resistance of mild steel in simulated concrete pore solution

Corrosion Resistance of CeO2-GO/Epoxy Nanocomposite Coating in Simulated Seawater and Concrete Pore Solutions.

Reinforced concrete structures in the marine environment face serious corrosion risks. Coating protection and adding corrosion inhibitors are the most economical and effective methods. In this study, a nano-composite anti-corrosion filler with a mass ratio of CeO2:GO = 4:1 was prepared by hydrothermally growing cerium oxide on the surface of graphene oxide. The filler was mixed with pure epoxy resin at a mass fraction of 0.5% to prepare a nano-composite epoxy coating. The basic properties of the prepared coating were evaluated from the aspects of surface hardness, adhesion grade, and anti-corrosion performance on Q235 low carbon steel subjected to simulated seawater and simulated concrete pore solutions. Results showed that after 90 days of service, the corrosion current density of the nanocomposite coating mixed with corrosion inhibitor was the lowest (Icorr = 1.001 × 10-9 A/cm2), and the protection efficiency was up to 99.92%. This study provides a theoretical foundation for solving the corrosion problem of Q235 low carbon steel in the marine environment.

Enhancing corrosion resistance of the CaCO3/MgO coating via ultrasound-assisted chemical conversion with addition of ethylenediamine tetra-acetic acid (EDTA) on AZ41 Mg alloy

In order to enhance the corrosion resistance of the AZ41 Mg alloy used as concrete formwork, a bilayer CaCO3/MgO coating was fabricated on the surface of AZ41 Mg alloy with addition of Ca-EDTA in the chemical conversion solutions. Effect of different Ca-EDTA concentrations on the surface morphology of as-prepared CaCO3/MgO coating and corrosion resistance in simulated concrete pore solutions with 3.5 wt% NaCl were investigated. SEM, XPS and XRD were combined to investigate the morphology and composition of the coatings. Electrochemical methods and immersion tests were used to assess the anticorrosion performance of the as-prepared coatings. Results show that an integrated bilayer CaCO3/MgO coating can be prepared on AZ41 Mg alloy by the addition of Ca-EDTA. Electrochemical tests reveal that the CaCO3/MgO coating prepared at 0.01 M Ca-EDTA possesses the best corrosion resistance at varying concentrations of Ca-EDTA. Ca-EDTA accelerates the release of Mg2+ and further affects both nucleation and growth of CaCO3 particles. Appropriate addition of Ca-EDTA can simultaneously preserve the stability of CaCO3 and enhance coating density.

Pomegranate peel extract as a sustainable corrosion inhibitor on steel in a simulated concrete pore solution and mortar: Experimental and theoretical studies

Various techniques, such as electrochemical impedance spectroscopy, potentiodynamic polarization, linear polarization resistance, and scanning electron microscopy, were used to investigate the inhibitory effect of pomegranate peel extract (PGPE) on the corrosion of carbon steel in a simulated concrete pore solution containing 0.5 M NaCl and in mortar exposed to chlorides. The results obtained revealed that the corrosion resistance of steel, in the presence of the PGPE, was greater than that of the inhibitor-free system, validating the ability of the pomegranate peel extract to produce a protective layer on the steel surface.The optimal concentration of pomegranate peel extract found is around 500 mg/L, with an inhibition efficiency estimated at 97.39%. It is worth indicating that the adsorption of PGPE was found to follow the Langmuir isotherm model. Furthermore, using the principles of quantum chemistry, the adsorption of PGPE constituents on the surface of carbon steel was shown to occur via donor-acceptor interactions.

Chloride sorption of nano-SiO2@MgAl-layered double hydroxides core-shell nanocomposite in simulated concrete pore solution: Equilibrium, thermodynamic and kinetic studies

Nano-SiO2@MgAl-layered double hydroxides (NS@MgAl-LDH) core-shell nano-composites were successfully synthesized by a co-precipitation method. The as-synthesized NS@MgAl-LDH was characterized by SEM, TEM, EDX, TGA and BET. The equilibrium, thermodynamic and kinetic studies on the chloride sorption of NS@MgAl-LDH were performed in simulated concrete pore solution (SCPS). The results show that NS@MgAl-LDH exhibits a higher specific surface area (SSA) compared to MgAl-LDH. Besides, the chloride sorption capacity of NS@MgAl-LDH is significantly higher than that of pure MgAl-LDH, which is obviously influenced by initial pH-value and amount of adsorbents addition. Also, the chloride sorption process can be fitted by the Langmuir-model thermodynamically and the pseudo-second-order kinetics kinetically. The negative values of Gibbs-free energy (ΔG0) and standard enthalpy change (ΔH0) indicate that the chloride sorption is spontaneous and exothermic. Furthermore, the outstanding chloride sorption capacity of NS@MgAl-LDH is mainly contributed to the ion-exchange of chloride ions with interlayer ions in the highly dispersed MgAl-LDH.

Effect of sealing treatment on corrosion resistance of zinc-calcium phosphate coating prepared on HRB335 rebar in simulated concrete pore solution

In order to reduce the corrosion of HRB335 rebar in a concrete environment and ensure the service life of reinforced concrete structures, a zinc-calcium phosphate coating was prepared on the surface of HRB335 rebar. The dehydration antirust oil, chromate solution, and silicate solution were used for the sealing treatment of the phosphate coating. The experimental results show that the zinc-calcium phosphate coating possesses many compact and spherical particles, which evenly and completely cover the surface of rebar substrate. The surface morphology, thickness, composition and corrosion resistance of the phosphate coating do not change significantly after sealing treatment in dehydrating antirust oil. However, sealing treatment in chromate solution and silicate solution can block the intergranular pores, improve the compactness and change the composition of phosphate coating to enhance the corrosion resistance of phosphate coating in simulated concrete pore solution. The main composition of the phosphate coating after sealing treatment in silicate solution are Zn, Ca, P, O, C and Si elements, and the compactness is slightly better than that of the phosphate coating after sealing treatment in chromate solution. Compared with rebar substrate, the corrosion current density of the phosphate coating after sealing treatment in silicate solution is reduced by nearly two orders of magnitude, and the protection efficiency toward rebar substrate reaches 98.2 %, which can enhance the corrosion resistance of rebar substrate in simulated concrete pore solution for a long time. Silicate solution is less harmful to the environment and has a good sealing effect, so it has potential application in the sealing treatment of phosphate coating.

Chloride threshold determination of hybrid inhibitor immersed in simulated concrete pore solution

The hybrid inhibitor performs excellently compared to either organic or inorganic inhibitor individually. In the present studies, a fixed amount i.e. 2 wt% l-arginine (LA) and 0.25 wt% trisodium phosphate dodecahydrate (TSPDH) is considered as hybrid inhibitor and its chloride threshold is determined by open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) in simulated concrete pore solution and the formed passive films are characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy after 240 h of immersion. The chloride threshold of this hybrid inhibitor is 6 wt% NaCl, i.e., C3 until 216 h of immersion, whereas if the amount is increased, the steel rebar leads to corrode severely. 5 wt% NaCl containing sample, i.e., C2 exhibits the noble OCP, highest impedance, and lowest passive current density attributed to the consumption of all zwitterion and phosphate ions in the formation of P-zwitterion-(Cl)-Fe, zwitterion-(Cl)-Fe and FePO4 complexes with NaCl, whereas lower or higher than this amount of NaCl, the Cl- ions either lesser or greater to be formed these complexes.

Corrosion Resistance of CoCrFeMnNi High Entropy Alloy Compared with 2205 Duplex Stainless Steel in a Simulated Concrete Pore Solution

Corrosion Resistance of CoCrFeMnNi High Entropy Alloy Compared with 2205 Duplex Stainless Steel in a Simulated Concrete Pore Solution

Sodium lignosulfonate biomolecule application as an effective steel-rebar corrosion inhibitor in a chloride induced–simulated concrete pore solution

Sodium lignosulfonate biomolecule application as an effective steel-rebar corrosion inhibitor in a chloride induced–simulated concrete pore solution

Influence of tensile stress on chloride-induced depassivation of carbon steel in simulated concrete pore solution

To study the influence of tensile stress on the depassivation behaviour of carbon steel, the critical chloride threshold CCl,crit, chemical composition, surface morphology, thickness, and shedding rate of carbon steel passive films were investigated using electrochemical tests and XPS and SEM analyses. The results showed that CCl,crit decreased gradually, and the shedding rate of the passive film increased remarkably with the applied tensile stress. Slight change of Fe0 content can be found under less tensile stress. As the tensile stress increased to 200 MPa, the content of Fe0 increased significant by about 57%. A correlation model between CCl,crit and the characteristic evolution of the passive film is proposed to describe the depassivation process of carbon steel under tensile stress. The decrease in CCl,crit could be attributed to the degradation of the passive films. Additionally, a relationship between CCl,crit and tensile stress is proposed, and a method for determining the depassivation of carbon steel under stress based on electrochemical parameters is established.

Corrosion Behaviors of Tetrasodium Iminodisuccinate (IDS) as an Environmentally Friendly Inhibitor: Experimental and Theoretical Studies

An environmentally friendly chelating agent, tetrasodium iminodisuccinate (IDS), was investigated as an inhibitor in the simulated concrete pore solution on Q235 carbon steel by using Tafel polarization (TF), electrochemical impedance spectroscopy (EIS) and surface morphology tests. The EIS and TF results indicate that the IDS is a mixed type of inhibitor and exhibits excellent protection efficiency (97.54%) at 200 mg/L. Furthermore, based on the Langmuir adsorption isotherm, IDS protects carbon steel through physical and chemical adsorption. Besides, density functional theory (DFT) and molecular dynamics (MD) simulations are applied to explore the inhibition mechanism to support the experimental data, indicating that IDS can be used as a new green corrosion inhibitor.

Improving corrosion resistance of epoxy coating by optimizing the stress distribution and dispersion of SiO2 filler

The steel fiber textile overcomes mostly the shortcomings of traditional reinforcement materials. However, the poor corrosion resistance severely limits service life. In this study, based on the mechanism of stress corrosion and electrochemical corrosion, the epoxy resin anti-corrosion coating was designed and prepared. First, the von Mises stress distribution of lamellar and spherical fillers in epoxy resin was studied by finite element simulation, which confirmed that the stress distribution of spherical SiO2 filler was more uniform when it was stressed. In addition, to optimize the dispersion of spherical SiO2 in epoxy resin, the spherical polyaniline@SiO2 (PANI@SiO2) composites with core-shell structure were produced with in situ polymerization method. Ultrasonic C scanning results showed that the addition of PANI@SiO2 nano-filler can effectively reduce the defects in epoxy resin. Compared with bare steel fiber, the composites coating of 2 wt% PANI@SiO2/epoxy showed the most excellent resistance to stress corrosion and electrochemical corrosion. The capacitance diameter is two orders of magnitude higher, which has good stability in simulated concrete pore solution. This is due to the fact that the addition of PANI@SiO2 nanomaterials improves the physical shielding properties of epoxy, creating a labyrinth effect, and that PANI can produce passivation on the metal surface.

Synergistic inhibition of benzotriazole and sodium D-gluconate on steel corrosion in simulated concrete pore solution

Synergistic inhibition of benzotriazole and sodium D-gluconate on steel corrosion in simulated concrete pore solution

Macrocell Corrosion Currents in Simulated Concrete Pore Solution and Reinforced Concrete

Chloride-induced rebar corrosion is one of the main causes of damage in reinforced concrete structures (RCS). Chloride attacks lead to depassivation creating pits, which can imply major losses of sections. The current generated at these spots (microcell) is contributed by the current produced between corroded and uncorroded areas (macrocell). The influence of both currents has been deeply investigated based on solution studies, which do not actually represent the behaviour of concrete-embedded elements. The studies about macrocell currents in solution are interesting to analyse this phenomenon quickly and simply. However, they must not be interpreted as the reality of RCS because this requires studies using rebars embedded in concrete. The performed experimental plan verified this fact. In addition, another objective of this study was to analyse the influence of concrete’s electrical resistance and the limiting effect of the cathode/anode surface (Cs/As) ratio on macrocell currents in solution and in concrete. For this study, specimens manufactured using concretes with different properties were used: standard concrete (SC), high-performance concrete (HPC), very high-performance concrete (VHPC) and ultra-high performance-fibre reinforced concrete (UHPFRC). The conclusions show how the Cs/As ratio plays a key role in regulating macrocell current intensity, but what really governs this phenomenon is concrete resistivity because it regulates the participation of a bigger or smaller cathode surface. The influence of this parameter as a limiting factor of macrocell currents is fundamental, especially in high resistivity concretes like VHPC and UHPFRC.

Corrosion of Steel Fibers in Chloride-Contaminated Simulated Concrete Pore Solutions

The corrosion of steel fibers is a direct cause of the deterioration of steel fiber-reinforced concrete in chloride environments. This study mainly investigated the corrosion behavior of steel fibers exposed to NaCl solutions with pH=7, 10, 11, 12, and 13. The corrosion rate of the steel fibers was calculated according to the change of the diameter and ultimate tensile load. The electrochemical parameters of the steel fibers corrosion were continuously monitored. The morphology of the steel fibers affected by chloride attack was observed by scanning electron microscope (SEM). The results reveal that the corrosion rate of the steel fibers decreased as the pH of the NaCl solution increased from 7 to 13, and it was very small at pH≥12. According to the open circuit potential, corrosion potential, corrosion current density, and electrochemical impedance spectroscopy, the steel fibers exhibited a high corrosion tendency and corrosion rate when exposed to NaCl solutions with pH≤12. However, they exhibited low corrosion tendency in the chloride solution with pH=13. The surface roughness of the steel fibers exhibited only a slight increase after exposure to the NaCl solution with pH=13 for 180 days.

Characterization of single-mode multimode single-mode fiber optic sensors for steel rebar corrosion monitoring in NaCl and simulated concrete pore solutions

Single-mode multimode single-mode (SMS) fiber optic sensors are characterized for corrosion monitoring of steel rebars in NaCl and simulated concrete pore solutions. Three diameters of the multimode fiber (MMF) are considered including 125 µm, 90 µm, and 60 µm. Steel rebar specimens were first cast in epoxy resin and then polished to expose a rectangular section. The SMS fiber optic sensors are directly attached on the polished surface of the steel rebar and then immersed in solutions for corrosion monitoring. Two types of solution are prepared, including 3.5 wt.% NaCl solution and simulated concrete pore solutions. During the immersion tests, the corrosion evolution of the steel rebar was measured with open circuit potential and linear polarization resistance. The change of the transmission spectrum of the SMS fiber optic sensors is recorded with an optical spectra analyzer. The change of the characteristic wavelength is correlated with the corrosion-induced mass loss of the steel rebars. Results show that linear relationships are present between the corrosion-induced mass loss of the steel rebars and the shift of the characteristic wavelength of the SMS fiber optic sensors. The corrosion monitoring sensitivity of SMS fiber optic sensors increases with a decrease of the diameter of the MMF.

Chloride binding of monosulfate hydrate (AFm) and its effect on steel corrosion in simulated concrete pore solution

The impact of monosulfate hydrate (AFm) on chloride (Cl−) binding and steel corrosion in simulated concrete pore solutions (SCPSs) was evaluated. In the SCPS with AFm added, a high concentration of Cl− promoted the Cl− binding amount per unit AFm without producing Kuzel's salt. The Cl− binding capacity of AFm could be improved by appropriately changing the amount of AFm with a constant Cl− concentration. The addition of AFm to the SCPS shortened the passivation time and created a more stable passivation film of the steel. The SO42− produced by the AFm binding with Cl− preferentially reacted with AFm to form AFt, and it affected the stability of the Friedel's salt to release Cl−. The addition of AFm raised the chloride threshold value (CTV) for steel corrosion. However, after reaching the CTV, the corrosion rate of steels increased dramatically, due to the release of the bound Cl−.

High-efficiency photocathodic protection performance of novel MnIn2S4/TiO2 n-n heterojunction films for Q235 carbon steel in chloride-containing simulated concrete pore solution

In this work, the n-type TiO2 nanotube film was modified successfully by n-type MnIn2S4 nanoparticles with one-step hydrothermal method, and a novel MnIn2S4/TiO2 heterojunction material with excellent photoelectrochemical properties was constructed firstly. Owing to the modification, the light response range of MnIn2S4/TiO2 nanocomposites was extended to the visible light region. Benefiting from the presence of type II n-n heterojunction with built-in electric field effects in the nanocomposites, the photogenerated carriers recombination rate decreased significantly. In addition, the photocathodic protection effects of MnIn2S4/TiO2 (MIS/T) photoanodes on Q235 carbon steel (Q235 CS) immersed in simulated concrete pore solution containing chloride were investigated. Under visible light irradiation, the cathodic protection current density of MIS/T-2 photoanode was found to be more than 30 μA/cm2 and over 10 times that of T photoanode. The MIS/T-2 photoanode has good long-term photochemical stability and maintains excellent photocathodic protection effect on Q235 CS (OCP value are about - 870 mV (vs. SCE)) under visible light irradiation. The amount of MnIn2S4 nanoparticles deposited on the TiO2 film could affect the photoelectrochemical properties of MnIn2S4/TiO2 n-n heterojunctions and an appropriate number of the nanoparticles, corresponding to the best cathodic protection performance was revealed.

The Effect of Temperatures on the Passivation Behavior of Q235 Steel in the Simulated Concrete Pore Solution.

Concrete, especially mass concrete, releases a large amount of heat during the hydration process, resulting in the passivation of reinforcement at high temperatures. However, the passivation study of reinforced concrete is mostly conducted at room temperature, and the influence of temperature on passive film behavior is not clear at present. The passivation film of reinforcing steel directly determines the corrosion resistance of reinforcing steel and affects the service life of reinforced concrete. Herein, the passivation of Q235 steel soaking in simulated concrete pore (SCP) solution at 20 °C, 40 °C, and 60 °C is explored. It is found that the passivation process is divided into two stages, with 24 h as the boundary; within 24 h the passivation was carried out rapidly, and the passive film is in a relatively stable state after 24 h. In addition, the higher the temperature, the faster the passivation. Moreover, under the condition of higher temperatures, more Fe3+ compounds are produced, and the semiconductor properties of passivated films are more stable. Based on experiments, the passivation mechanism affected by temperature was analyzed in detail.