Chloride Environment Research Articles

Experimental study, numerical simulation and GRNN model for predicting the flexural loading capacity of corroded reinforced concrete beams

The present article is an effort to quantify the flexural strength of corroded reinforced concrete (RC) beams. Eight RC beams with dimensions of 150 × 200 × 2200 mm were tested in four-point bending, including six beams corroded in a chloride environment with average corrosion of longitudinal reinforcement in the range of 5% to 15%. The remaining two beams were used as control beams. The ultimate strength, failure mode and particularly the relationship between crack width and corrosion level are analyzed and discussed. A two-dimensional non-linear finite element model has been presented to simulate the steel bar corrosion considering the deterioration of concrete strength and steel-concrete bond stress. The generalised regression neural network (GRNN)-based model for the ultimate flexural strength of corroded RC beams has been established based on 123 experimental data collected from previous studies. The experimental results were used to separately validate the non-linear finite element model and novel GRNN model. Experimental results indicate that if the overall corrosion rate is used, the corrosion crack width can be a function of the percentage of section loss. The GRNN model provides superior predictive results compared to previous empirical methods with the highest correlation coefficient (r), and the smallest normalised root mean square error.

Chloride Transport and Related Influencing Factors of Alkali-Activated Materials: A Review.

Chloride transport is a vital issue in the research on the durability of alkali-activated materials (AAMs). Nevertheless, due to its miscellaneous types, complex mix proportions, and limitations in testing methods, the reports of different studies are numerous and vary greatly. Therefore, in order to promote the application and development of AAMs in chloride environments, this work systematically reviews the chloride transport behavior and mechanism, solidification of chloride, influencing factors, and test method of chloride transport of AAMs, along with conclusions regarding instructive insights to the chloride transport problem of AAMs in future work.

The Influence of a Corrosive Environment on Fatigue and Mechanical Properties of an Al-Cast Alloy with Higher Fe Content

Al has very good corrosion resistance and corrosion properties. The corrosion resistance of Al-cast alloys is different because these alloys contain a lot of elements, especially in secondary alloys, which contain more impurity elements, of which Fe is the most common. This study deals with secondary AlSi7Mg0.3 cast alloys, which contain more Fe and are affected by a chloride corrosive environment. This environment was selected based on the application of castings in the automotive industry. The main object was to research the effect of such an environment on basic mechanical properties and fatigue properties. The results show that a higher Fe content does not lead to a significant reduction in the properties of the casting, and the chloride environment is not so harmful. Therefore, it can be stated that the investigated secondary sand-cast experimental materials can replace primary alloys without losing the required corrosion and mechanical properties.

Significance of chloride salt type and sulfate salt on chloride transport mechanism of concrete in the presence of corrosion inhibiting admixtures

In this study, the effect of chloride and their cations on free chloride (Clf), chloride diffusion coefficient (Dc), and chloride binding capability (CBC) of concrete treated with inhibitors, subjected to chloride and composite chloride-sulfate environments was investigated. Results revealed that in absence of sulfate, the Clf and Dc were higher for NaCl, while in presence of sulfate they were higher in CaCl2. The Dc increased and CBC decreased in presence of sulfate. Inhibitors were effective in reducing the Clf and Dc of concrete subjected to various environments. Na2HPO4 showed higher CBC in chloride and lower in composite environments than NaNO2.

Investigation of CuAl IMCs Corrosion in Chloride Environment and its Prevention Strategy

Abstract In most current wire-bonding applications, electrical interconnection is accomplished by fine Cu wires bonded to Al bonding pads microfabricated on an IC chip and external contact pins of the PCB board. Corrosion-related failure defects between the Cu wire and Al bond pad have been an ongoing un-trackable reliability issue plaguing the IC packaging industry for the past ten years, despite approaching ppb levels. Most prior studies hypothesized that intermetallic compounds (IMCs) like Cu9Al4, and CuAl2 were responsible for the observed acute wire-bond lift-off corrosion defects. Further studies sought to quantify the rates of corrosion of these IMCs and explore the effects of mitigation efforts of adding Pd, relevant to Pd-coated Cu wire-bonding. However, utilizing a novel real-time corrosion screening approach, we previously established that peripheral bimetallic contact between Cu ball-bonds and Al bond pads also plays a substantial role in the aggressive Al pad corrosion, induced by chloride ion penetration, which often leads to device failure. In this work, we further explored the role of IMCs corrosion in wire-bond lift-off failure utilizing fundamental electrochemical studies to quantify rates of galvanic-induced corrosion of IMCs within the broader context of an interconnected stack of Al bond pad, Cu-Al IMCs and Cu bonding wire. We also explored the use of a corrosion inhibitor to suppress the galvanic corrosion currents of Al bond pad, and Al-rich IMCs when electrically connected to Cu wire or Cu-rich IMCs.

Microstructure, Mechanical Properties, and Corrosion Behavior of Co‐Based Stellite 6 Multilayer Overlays Deposited on ASTM A36 Steel by Gas Metal Arc Welding Process

Hardfacing is an effective method for restoring the damaged part. Herein, cobalt‐based superalloy Stellite‐6 is deposited on A36 substrate using gas metal arc welding process. The mechanical properties, microstructure, and corrosion behavior of Stellite‐6 overlays on A36 substrate are examined. Defect‐free hard overlays are obtained, and a dilution ratio of 19.9% is achieved with weaving technique. X‐ray diffraction analysis reveals the presence of M7C3, M23C6, M6C, and martensite in the Stellite‐6 hard overlays. The microstructure of the deposit contains martensite, carbides, and interdendritic precipitates while the mean hardness is 471 HV0.5. Tensile testing with specimens extracted on the longitudinal (LD) and transverse (TD) orientation of the stellite‐6 deposit shows a strength above 950 MPa along with the brittle nature of fracture. Grain growth is epitaxial and shows dendritic morphologies. The higher fraction of high‐angle grain boundaries improves the tensile strength of the deposit and interface region. The localized corrosion behavior of stellite‐6 hard overlays is found to be excellent, and the corrosion analysis exhibits a corrosion rate of 0.10 mils per year (mpy). The outcomes of the study highlight the feasibility of Stellite‐6 hard overlays for extending the service life of A36 steel in chloride environments.

Probabilistic fatigue life prediction for RC beams under chloride environment considering the statistical uncertainty by Bayesian updating

A probabilistic fatigue life prediction model for RC beams under chloride environment is proposed, and the statistical uncertainty is considered by Bayesian inference to determine and update model parameters. In terms of the sparse fatigue data, the Markov-chain Monte-Carlo (MCMC) method is utilized to conduct the Bayesian updating. The prior distribution and posterior distributions are respectively determined by the data in this study and open references. Results show that the fatigue life under chloride environment is accurately predicted by a probabilistic S-N curve, in which as update points increase, predictions get close to tests and the statistical uncertainty is reduced.

Effect of chloride penetration on CFRP sheet, CFRP‐concrete interface, and CFRP‐strengthened concrete beams

AbstractWhether the performance of carbon fiber‐reinforced polymer (CFRP)‐strengthened concrete structure is affected by chloride penetration is the key to the application under chloride environments. In this paper, the effect of chloride penetration on tensile properties of CFRP sheet, bond behavior of CFRP‐concrete, and flexural performance of CFRP‐strengthened concrete beams were studied. Results show that chloride penetration has no effect on the elastic modulus of the CFRP sheet. The tensile strength and elongation of the CFRP sheet decrease with the exposure time increase, reducing by 10% and 12.7% after 240 days. The interface failure of CFRP‐concrete is likely to occur on the concrete surface. As the exposure time increases, the interface failure develops toward the epoxy resin layer; the sliding stiffness and end slip of the interface decrease. However, the ultimate bearing capacity of the interface first increases and then decreases. As the exposure time increase, the effective bonding length gradually increases, and the failure mode of CFRP‐strengthened beams changes from bending failure to shear failure. After 120 days, the ultimate bearing capacity of the beams is significantly reduced. From three parts of materials, interfaces, and components to provide an evaluation basis for the use, regular detection, and life prediction of CFRP‐strengthened reinforced concrete beams under chloride environments.

Study on the damage resistance and deterioration behavior of GO concrete under the harsh environment.

To exploretheeffects of physical, mechanical, anti-deterioration properties of graphene oxide (GO) on cement-based cementitious materials, GO sheet dispersions areprepared by the improved Hummers method and ultrasonic dispersion method. The influence of theGO content on the compressive and flexural strengths of cement paste is investigated, and the penetration process of chloride ions in graphene oxide concrete is discussed by the electric accelerated erosion method. Combined with the rapid freeze-thaw test, the deterioration of graphene oxide concrete ismethodically analyzed. Theobtained results reveal that an appropriate amount of GO improves both the compressive and flexural strengths of cement pastev. In the chloride environment, the chloride diffusion coefficient of 0.03% GO concrete is 18.75% less than that of ordinary concrete.Under the action of freeze-thaw cycles, with the increase of salt freezing times, the deterioration mode of GO concrete is a combination of mortar shedding, micro-crack expansion, denudation, and block shedding; The stress-strain curve of the specimen tends to be flat with the growth of salt freezing times. The peak stress gradually lessens, the peak strain gradually grows, and the elastic modulus remarkably reduces. Compared with ordinary cement paste, theGO is capable of promoting the growth of cement paste hydration crystals, changing the size and shape of crystals, and realizingthe regulation of cement paste microstructure. Incorporating an appropriate amount of theGO could promote the cement hydration process and enhance the chemical water-binding amount in the cement paste. The optimal GO content is reported to be 0.03% of the cement mass.

Tailoring the glass forming ability, mechanical properties and corrosion resistance of Cu–Zr–Al bulk metallic glasses by yttrium addition

The effect of yttrium (Y) on the glass-forming ability (GFA), mechanical properties and corrosion of (Cu50Zr43Al7)100-xYx (x = 0, 2 and 4, in at. %) alloys was investigated. The GFA of Cu50Zr43Al7 alloy was improved by the addition of Y, with a GFA of 15 mm in diameter being obtained for (Cu50Zr43Al7)98Y2. In uniaxial compression, the bulk metallic glasses (BMGs) exhibited a limited plastic strain of less than 1%, however compressive fracture strength and Young's modulus of 1787–2006 MPa and 101–122 GPa were achieved, respectively. Fracture surfaces and shear bands were studied via scanning electron microscopy. The corrosion behavior of BMGs was analyzed by potentiodynamic polarization experiments and electrochemical impedance spectroscopy (EIS) in acidic chloride (1 M HCl) and neutral chloride (0.6 M NaCl) environments. As a result of the Y addition, the corrosion resistance of the base BMG was improved.

Efficient electrocatalytic H2O2 production in simulated seawater on ZnO/reduced graphene oxide nanocomposite

The non-noble metal-based catalysts has been widely studied for two-electron (2e-) oxygen reduction reaction (ORR), and exhibited the excellent 2e- ORR performance in alkaline condition, especially. However, these catalysts are rarely studied at neutral chloride medium. Herein, we synthesized metal oxide nanoparticles supported reduced graphene oxide composites (MxOy/rGO) by adding the precursors of metal salts (Zn, Mn, Co and Fe) and graphene oxide (GO) through a facile lyophilization-pyrolysis strategy. ZnO/rGO exhibits a well 2e- ORR catalytic activity, corresponding to a high 80% H2O2 selectivity and preferable stability in 0.5 M NaCl solution, whereas the MxOy/rGO (M= Mn, Co and Fe) presents even lower selectivity than reduced graphene oxide (rGO). The results suggest that ZnO promotes the 2e- ORR, and the metal oxide (M= Mn, Co and Fe) conducive to 4e- ORR. Interesting finding, the results of rotating ring disk electrode (RRDE) show that chloride ion in the electrolyte promote the H2O2 selectivity of 2e- ORR. These findings provide a promising candidate material for 2e- ORR in neutral chloride environment and valuable insights for future research on seawater-based H2O2 electrosynthesis.

Biomineralisation to improve properties of polymer modified concrete for chloride environments

This research compares the performance of three types of polymer-modified concrete (TPE, LDPE/EVA, and PCL) if bacteria-based solutions are used for reinforced concrete (RC) structures designed for a compressive strength higher than 50 MPa in chloride environments. The aim is to understand the impact on mechanical and durability performance of concrete. These recyclable polymers' use is crucial to increasing the strength at 28 and 60 days. At 60 days, all polymer-modified concrete reached a compressive strength higher than 60 MPa. The use of bioproducts is crucial to lowering the open porosity values to 4%. However, the use of bioproducts tends to delay the increase of concrete's compressive strength with time, especially until the 14 days. The existence of tetrahedron and pyramid structures in polymer-modified bio concrete indicates that calcite is present, and the quantity of calcium carbonate in the polymer-modified bio concrete is significantly higher than in plain bio-concrete or even plain. The bioproduct plays a dominant role in the capillary control and prevents water migration more effectively in comparison to the use of different polymers in concrete. The bioproduct substantially minimise the migration of chlorides to 7 × 10−12 m2/s, a water-soluble ion in wet/humid concrete porous medium environments, but also at low relative humidity environments, as it happens when the concrete is exposed to capillary suction. The highest electrical resistivity values have been recorded in TPE bio-concrete.

Research on Corrosion Rate Model of Reinforcement in Concrete under Chloride Ion Environments

In a chloride environment, taking reinforced concrete structures as the research object, the corrosion rate of reinforcement determines its corrosion expansion because multiple coupling parameters will affect the corrosion rate of reinforcement, which is extremely difficult to effectively predict. In this paper, 144 sets of experimental data were collected and sorted out by reading the relevant literature, and six empirical models for predicting the corrosion rate of steel bars were compared and analyzed based on these experimental data. Based on the investigations, a new empirical model is proposed for predicting the corrosion rate of reinforcement, and the relevant influencing factors are considered in the new model. By comparing the 144 sets of experimental data and 90 experimental data for this paper, the new prediction model can well predict the corrosion rate of reinforcement. Furthermore, the time variability of the new prediction model is verified. The probability distribution characteristics of seven prediction models are obtained through model error analysis, which provides a theoretical basis for the next step of concrete cover cracking and reliability analysis.

Eco-friendly Silane-Based Coating for Mitigation of Carbon Steel Corrosion in Marine Environments.

Losses from corrosion contribute roughly 3-5% of the gross domestic product of developed nations, and among the many methods used to avoid corrosion, using silane-based coatings is seen to be of the biggest importance due to their low toxicity and superior adhesive qualities. It is essential to develop an anti-corrosion coating that is efficient, economical, and eco-friendly. The corrosion resistance and durability of various silane-based coatings such as 1,2-bis(triethoxysilyl)ethane (BTSE), bis[3-(triethoxysilyl)propyl]tetrasulfide (TESPT), and vinyltrimethylsilane (VTES) for carbon steel 1018 substrates were investigated in a high-salinity environment (4.5 wt % NaCl). The corrosion resistance performance was evaluated via potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) techniques. Results revealed that the TESPT film (pH ≈ 7) has the best corrosion resistance performance on the carbon steel surface in the aggressive chloride environment, that is, 99.6%. The high corrosion resistance of the TESPT film is due to the hydrophobic nature of this silane, which leads to the formation of a stable and dense film. These results were supported by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDX) analyses.

Graphene coatings for corrosion resistance of nickel and copper in acidic, alkaline and neutral environments

• Multilayer graphene coating provides robust and similar corrosion resistance to Ni irrespective of the aggressiveness of the environment. • Improvement in corrosion resistance of bare Ni due to multilayer graphene coating is greatest in the most aggressive environment of 0.5M H 2 SO 4 . • Improvement in corrosion resistance of bare Ni due to multilayer graphene coating is least in 0.5M NaOH because Ni develops a robust passive layer. • The improvement in corrosion resistance of bare Cu is limited because Cu develops only 1-2 layers of graphene. Graphene coatings have been reported to provide impressive corrosion resistance to nickel (Ni) and copper (Cu), because of remarkable characteristics of inertness and impermeablity of graphene. However, the earlier investigations have generally been carried out in chloride environment, and it is important to understand the performance of graphene coating in more aggressive environments such as acids and alkali. This study investigated the electrochemical corrosion behaviour of bare and graphene-coated (by chemical vapour deposition (CVD)) Ni and Cu in 0.5 M H 2 SO 4 , 0.1 M NaCl and 0.5 M NaOH solutions. Electrochemical tests and post corrosion characterisation revealed the improvement in the corrosion resistance of Ni due to multilayer graphene coating to be similar in the three solutions, i.e., the robustness of the barrier property of the multilayer graphene is largely unaffected by the aggressiveness of the corrosive environment. However, the improvement in corrosion resistance of bare Ni due to multilayer graphene is considerably greater (nearly 3 orders of magnitude) in the most aggressive of the test solutions (0.5 M H 2 SO 4 ). The improvement is considerably less in 0.5M NaOH because bare Ni develops a robust passive layer in highly alkaline solutions. The improvement in corrosion resistance of bare Cu is limited (within an order of magnitude) in the three solutions because Cu develops only 1-2 layers of graphene.

Durability assessment of quaternary blended recycled aggregate concrete under chloride environment

This article describes the durability of Normally Vibrated Concrete (NVC) containing Recycled Coarse Aggregate (RCA) using different mineral admixtures under extreme chloride environment. Further, to make concrete more sustainable by replacing cement and Natural Coarse Aggregates (NCA) with supplementary cementitious materials and RCA respectively without compromising the performance of concrete. For this, cement is replaced partially with Fly Ash (FA), Silica Powder (SP) and Ground Granulated Blast Furnace Slag (GGBS). The percentage of admixtures (FA, GGBS and silica powder) are decided based on the fresh) and hardened (compressive - strength) properties. M30 concrete is prepared using binary mix (OPC + FA), (OPC + GGBS), ternary mix (OPC + FA + GGBS) and quaternary mix (OPC + FA + GGBS + silica powder). Fresh and mechanical properties of concrete prepared from these mixes are determined. Further the best result of the outcomes based on the above mechanical properties is opted as optimum proportion of (FA, GGBS and silica powder) and is replaced in conventional mix to make concrete more sustainable. This optimum proportion is now used as a new conventional mix for replacing natural coarse aggregate with RCA by % weight varying in proportion 0%, 20%, 40%, 60%, 80% and 100%. For the assessment of durability of concrete Rapid Chloride Permeability Test (RCPT) is carried out. Charge passed through the concrete mix, ingress depth, migration coefficient is noted and relationship between compressive - strength and total charge passed for varying percentage of RCA with optimum proportion of admixtures is analysed. From experimental results it is observed that fly ash, GGBS and silica powder significantly improve the mechanical and durability properties of concrete. Moreover, it is also concluded that up to some extent RCA can be used as alternative of coarse aggregate.

Comparative Studies on Steel Corrosion Resistance of Different Inhibitors in Chloride Environment: The Effects of Multi-Functional Protective Film

A corrosion inhibitor was widely used to improve corrosion resistance of steel bar in reinforcement concrete structure. A kind of multi-component corrosion inhibitor, which is composed of organic and inorganic substances, was developed in this research. This corrosion inhibitor was comparatively studied with various other inhibitors by using open circuit potential (OCP), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) methods. The results show that the OCP values and charge transfer resistance (calculated by EIS curves) of the multi-component corrosion inhibitor remain, respectively, as high as −0.45 V and 932.19 kΩ·cm−2 after 60 days immersion, which are significantly better than other groups. Wide passivation interval and various peaks in cyclic voltammograms (CV) were applied to analyze the mechanism of adsorption (organic substance) and oxidation–reduction reactions (inorganic substance). The functional groups -OH in triethanolamine (TEA) and tri-isopropanolamine (TIPA) bond to the steel bar surface quickly, behaving as an adsorbent of organic substance in early age. An additional protective precipitate related to the reactions of Fe3+ was formed by inorganic substances (Fe2(MoO4)3 and FePO4), which is consistent with the EIS results and equivalent electrochemical circuits. As an eco-friendly substitute, multi-component corrosion inhibitors possess similar or even better protecting effects on steel bars in comparison to calcium nitrite. In addition, the concept of a “multi-functional protective film” was proposed, providing a new insight to achieve modified anti-corrosion capacity of inhibitors.

A methodology to assess the evolution of mechanical performance of UHPC as affected by autogenous healing under sustained loadings and aggressive exposure conditions

This study investigates the evolution of the performance of an Ultra-High Performance Concrete (UHPC) under simultaneous action of sustained loading and aggressive environmental exposure. UHPC mixes were investigated containing different functionalizing micro- and nano-scale components to promote autogenous self-healing. In order to assess the healing capabilities in the different multi-action scenarios and the evolution of the mechanical response of the material over time, a tailored methodology was implemented, including non-destructive and destructive tests performed all along the scheduled exposure/healing times up to 12 months. In particular, an innovative set-up was designed to reproduce on the specimens the sustained flexural loading conditions a structure undergoes during its service life; the load was applied simultaneously with each of the three selected different exposures, to simulate the chloride and sulphate aggressive environments, besides a reference one. Multiple indices were defined to quantify the self-healing efficiency, which were further calibrated against experimental microscope crack observation as well as cross correlated with each other, as a further proof of the reliability of the proposed methodology. The results confirmed the material durability, especially in the cracked state, through its capacity of sealing the cracks and restoring original properties in short periods and preserving its load bearing capacity, thus providing solid argument for UHPC as the ideal candidate material for highly durable and sustainable structural applications in aggressive scenarios.

Corrosion-Effected Bond Behavior between PVA-Fiber-Reinforced Concrete and Steel Rebar under Chloride Environment

Corrosion-effected bond behavior between polyvinyl-alcohol-fiber-reinforced concrete and steel rebar under a chloride environment is the experimental subject studied in the present work. Twenty-four pull-out specimens are designed and subjected firstly to an accelerated corrosion test. The effects of polyvinyl alcohol fibers on the cracking behavior, chloride penetration of concrete members and the corrosion loss of steel rebars during the corrosion test are discussed. After this, these corroded specimens are subjected to a pull-out test. The failure mode, the bond-slip curves and the typical bond-stress values are measured during the test. The effects of polyvinyl alcohol fibers and corrosion loss on bond behavior between polyvinyl-alcohol-fiber-reinforced concrete and steel rebar are clarified. Results show that the polyvinyl-alcohol-fiber-reinforced concrete exhibits worse resistance to corrosion damage than plain concrete. The cracking width, chloride penetration depth in concrete and the corrosion loss of steel rebar are more serious for the specimens with more polyvinyl alcohol fibers. The polyvinyl alcohol fibers also negatively affect bonding in ascending branches for both the specimens, but improve the bonding in descending branches after peak stress in the case of splitting. In the present test, the bond strength of corrosive specimens is increased slightly and then decreases gradually with the deepening of corrosion loss. The failures of specimens change from pull-out to splitting-pull-out as the corrosion time exceeds 30 days. Compared with uncorroded specimens, the maximum degradation of bond strength is about 50.1% when the corrosion is increased from 0% to 15%.

The Effect of Curing Temperature and Thickness of Polybutyl Methacrylate Siloxane Coatings on the Corrosion Protection of Structural Steel S355

This study aimed to determine the effects of coating thickness and curing temperature on the properties of a polybutyl methacrylate-siloxane coating deposited on structural steel S355. First, the thermal properties of the sol as a function of temperature were investigated using thermogravimetric analysis coupled with mass spectrometry and differential scanning calorimetry. After coating deposition on structural steel S355 using a dip-coating process, the coating composition and porosity were evaluated using Fourier transform infrared spectroscopy and photothermal beam deflection spectroscopy. In the second part, coating thickness, topography, and corrosion properties were studied as functions of withdrawal rate during deposition. The corrosion properties of variously prepared coatings were evaluated using electrochemical impedance measurements in 3.5 wt.% NaCl and salt spray testing according to the ASTM B117 standard. An elevated curing temperature (at 150 °C) of the polybutyl methacrylate siloxane sol-gel coating impairs greater crosslinking and lower porosity, while the optimal thickness of 4 μm is achieved with the appropriate withdrawal rate to obtain a homogeneous, defect-free surface. Under these optimal conditions, the protection of structural steel against corrosion in a chloride environment lasting for more than 6 months can be achieved.