Aggressive Ions Research Articles

Corrosion Behavior of AA70 Reinforced Zea mays Husk Particle in NaCl/H2SO4 Concentrations

The effects of Zea mays husk particle and heat treatment on the corrosion behavior of AA70 matrix composite in 1.5 wt.% NaCl/0.0125 M H2SO4 concentrations were studied using an electrochemical technique and optical microscopy. Results showed that the samples had similar anodic-cathodic polarization behavior after heat treatment, with no passivation. However, the heat-treated AA70 matrix composites were more corrosion-resistant than the untreated AA70 matrix composite material in 1.5 wt.% NaCl/0.0125 M H2SO4 concentrations. The composite with 15 wt.% Zea mays husk and a particle size of 300 μm reinforced AA70 matrix revealed the least corrosive tendency and is the most thermodynamically stable in chloride and sulphate ions conditions. Therefore, the corrosion behavior of heat-treated AA70 matrix composites was better compared to that of AA70 material in 1.5 wt.% NaCl/0.0125 M H2SO4 solution. Furthermore, the presence of a high concentration of aggressive chloride ions increases the corrosion susceptibility, and the Zea mays husk particle breaks down the stable oxide film, resulting in increased chloride ion adsorption. The optical microscopy examination suggested the presence of localized corrosion on the material surface.

Microstructure and anti-corrosion properties of acrylic bone cement-based with MOF nanostructured hybrid coatings on AZ31 Mg alloy

Surface modification of biomedical AZ31 magnesium (Mg) alloy substrates with biocompatible and applicable polymer coatings is an effective and simple method to improve corrosion resistance. Herein, the biodegradable acrylic bone cement incorporation with different content of metal organic frameworks (Ce-MOFs or Zn-MOFs) coated on biodegradable Mg alloy (AZ31) substrates was fabricated by using a dip-coating method. Then, various characterizations like X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) and the water contact angle (WCA) tests were performed to determine the composition, morphology, structure, and wettability of the coatings. The compact acrylic bone cement coatings improve the hydrophilic effect due to the micro/nanostructure of acrylic and hydrophilic groups, but the addition of a small amount of Ce-MOF and Zn-MOFs structures reduces the hydrophilic effect of the coating surface. According to the electro-chemical analysis, prepared acrylic coating has better corrosion behavior compared to AZ31 sample. The PM sample demonstrates the lowest corrosion current density (icorr = 0.095 mA cm−2) compared to other samples. The dense acrylic compact coatings with higher amount of Ce-MOF content blocks the pores in the coating and lead to an inhibitory effect and improved the corrosion behaviors. The dense acrylic bone cement containing MOF coatings with improved electrochemical activity inhibits diffusion of the aggressive ions to the alloy surface.

Effect of Sodium Stearate on the Microstructure and Hydration Process of Alkali-Activated Material

In response to the high water sorptivity of alkali-activated slag–red mud–steel slag cementitious material (AASRSS), water and aggressive ions are easily transferred to the interior of cementitious materials, which poses a significant threat to their durability. In order to limit the transfer of moisture and aggressive ions to the interior of AASRSS, sodium stearate (NaSt) was utilized in this paper to reduce its water sorptivity. The aim of this study was to elucidate the role of NaSt in the AASRSS system. The changes in the compressive strength and water sorptivity of AASRSS mortar were tested by mixing different amounts of NaSt into the mortar. The changes in the hydration process and microstructure of AASRSS after mixing with NaSt were analyzed by using the test methods of the isothermal calorimetry, resistivity, SEM and MIP. The results showed that NaSt plays an important role in the pore structure characteristics of AASRSS and that the use of NaSt significantly reduces its water sorptivity. The improvement in the water sorptivity was caused by two main mechanisms, namely the optimization of the pore structure (reduction in defects of the microstructure and alteration of pore size distribution) and the introduction of a hydrophobic film on the pore surface. The addition of NaSt did not change the type of AASRSS hydration product, but it inhibited the hydration reaction, leading to a reduction in the hydration product. The combination of the increased porosity and reduced hydration products mainly accounts for the decrease in the compressive strength of AASRSS due to NaSt.

Effect of loading-induced damage on chloride ingress behavior of recycled aggregate concrete: A comprehensive review

The recycling technology of construction and demolition wastes is an inevitable choice towards the sustainable development of the construction industry, aiming at addressing the problems of raw materials shortage and waste disposal. The utilization of recycled coarse aggregate (RCA) in new concrete production has been identified as an effective way to reasonable application of natural resources replacement and environmental preservation. In service, external mechanical loading can easily cause the initiation and interconnectivity of microcracks inside concrete, specifically the complex multiple interface structures of recycled aggregate concrete (RAC) due to the old adhered mortar at the surface of RCAs, which can remarkably accelerate the process of water penetration and aggressive ions penetration into concrete. Thus, knowledge of mass transport properties in the loading-induced damaged RAC contributes to the durability evaluation of RAC and its extensive application in the practical engineering. This paper reviews the previous findings on the mechanical loading effects on the chloride transport properties of RAC. The effects of loading-induced damage on microstructure evolution of RAC as well as the damage characteristics were discussed. The research progress on the chloride ingress behavior of RAC subjected to mechanical loading was highlighted from the viewpoint of testing method, loading devices and numerical calculation, and the modified effects on the transport properties were further analyzed. On this basis, the future research on the durability-related properties of RAC would be finally proposed, which is helpful to further perfect theoretical development and technological innovation of RAC durability in the aggressive environment.

Exploring the Influence of Biologically Relevant Ions on the Corrosion Behavior of Biodegradable Zinc in Physiological Fluids.

This work presents a study on the influence of biologically relevant ions on the corrosion of zinc (Zn) in physiological fluids. Electrochemical techniques were used to investigate the degradation of pure Zn exposed to different physiological electrolytes containing chlorides, carbonates, sulfates, and phosphates. The corrosion behavior of Zn in the solutions over a 7-day period was also assessed. SEM, EDS, and FTIR were used to analyze corrosion products. With respect to corrosion, the most aggressive ions are chlorides, which induce localized corrosion, while carbonates and phosphates reduce the corrosive attack of the chloride on Zn while inducing uniform corrosion. Sulfates reduce the corrosion rate by disrupting Zn's passive layer. The overall corrosion rate of Zn changed in each electrolyte depending on the nature of the solution and the corrosion product formed. These findings will be useful in predicting the in-service behavior of future biodegradable Zn medical implants.

Evaluation of the Influence of Eggshell (ES) Concentration on the Degradation Behavior of Mg-2.5Zn Biodegradable Alloy in Simulated Body Fluid.

Currently, permanent vascular stents are fabricated using titanium and stainless steel implants that are nondegradable and offer high stability, but they have certain disadvantages. For example, the prolonged exposition of aggressive ions in the physiological media and the existence of defects in the oxide film create conditions for corrosion to occur, thus triggering unwanted biological events and compromising the mechanical integrity of the implants. Moreover, when the implant does not need to be permanent, there is the need to submit the patient for a second surgery for implant removal. As a solution for nonpermanent implants, biodegradable magnesium alloys have been deemed a promising substitute, for example, for cardiovascular-related applications and the construction of orthopedic devices. A biodegradable magnesium alloy (Mg-2.5Zn) reinforced by zinc and eggshell was employed in this study as an environment-conscious magnesium (eco) composite (Mg-2.5Zn-xES). Disintegrated melt deposition (DMD) was used to fabricate the composite. Experimental studies were conducted to investigate the biodegradation performance of Mg-Zn alloys containing 3 and 7 wt % eggshell (ES) in simulated body fluid (SBF) at 37 °C. Different corrosion techniques were used to study the corrosion behavior of the Mg-2.5Zn-xES composites, including weight loss measurements, hydrogen evolution, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and scanning vibrating electrode technique (SVET). Scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) were employed to scrutinize the corroded surfaces' morphology and composition. The outcomes indicated that Mg-2.5Zn-3ES possesses the lowest degradation activity.

Photocatalytic Activity and Mechanical Properties of Cement Slurries Containing Titanium Dioxide

The effect of titanium dioxide (TiO2) on the mechanical properties of cement slurries including their benefits on air purification and abatement of pollutants is not well documented. Cementitious-based slurries are typically applied in thin layers as decorative coatings for existing facades, protection against an ingress of aggressive ions, or rainproof covers to minimize water penetration. Different parameters including the TiO2 concentration, dispersion time during batching, and applied thickness on top of existing mortar blocks are investigated in this paper. Tested properties included the flow, colorimetry, compressive/flexural strengths, bond to existing substrates, water absorption, and photocatalytic activity evaluated using an ISO 22197-1:2007 reactor. The results showed that the mechanical properties remarkably improved with TiO2 additions, up to 8% of the cement mass. This was attributed to two concomitant phenomena including a micro-filler effect that enhances the packing density and nucleation sites to promote strength development. The removal of nitrogen oxides from the atmosphere reached 92% when the TiO2 was added at a rate of 5% of the cement mass. Such data can be of particular interest to consultants and environmental activists searching for innovative materials capable of maintaining better ambient air quality in urban and modern cities.

A novel cerium organic network modified graphene oxide prepared multifunctional waterborne epoxy-based coating with excellent mechanical and passive/active anti-corrosion properties

Effectively reducing microdefects and endowing coatings with active protection are critical factors in prolonging the service life of coatings. Herein, a novel ceria nanoparticle decorated cerium organic network (GO-CN/CON-U) is in-situ prepared on graphene oxide (GO) via a simple one-step method. Then, a multifunctional coating is obtained by introducing GO-CN/CON-U into the epoxy resin matrix. The coating surprisingly exhibits exceptional mechanical properties and hydrophobicity attributing to the optimized crosslinking degree, compactness, and toughness due to the interaction between composite materials and epoxy resin, while its sustained anti-corrosion performance (around 109 Ω·cm2) also displays three orders of magnitude higher than that of pure epoxy coating (less than 106 Ω·cm2) even after 60 d of immersion in the aggressive media. An active protective mechanism was further proposed according to the UV–Vis and microelectrochemical test results, revealing that a shielding film can be promptly formed on the surface of Q235 steel when damage occurs against the attack of aggressive ions due to the release of Ce3+/Ce4+ and organic inhibitors from GO-CN/CON-U under acidic responsiveness. In brief, the present work provides a simple but attractive strategy for the preparation of long-lasting multifunctional protective coatings.

Investigations on corrosion inhibition performance of self-healing nano-clay modified epoxy coatings

Motivated by the need to mitigate corrosion and improve the lifespan of concrete structures, we report in this paper the results of our experimental investigation using hybrid nano-modified epoxy coatings for mild steel bars in concrete using a combination of nano-clay and self-healing tung-oil microcapsules. The prepared nano-modified coatings were characterized by Field Emission Scanning Electron Microscopy (FE-SEM) and Fourier Transform Infrared Spectroscopy (FT-IR). They were applied on plain mild steel bars and subjected to accelerated impressed current corrosion. Their performance was assessed by non-destructive electrochemical corrosion current and ultrasonic guided wave measurements. These assessments were corroborated by visual inspection and destructive testing parameters of residual mass loss and tensile strength. Coated rebars were also subjected to simulated damage to investigate the self-healing capabilities of the prepared coatings. Both non-destructive and destructive results demonstrate that hybrid nano-modified coatings utilizing nano-clay (2 wt% of epoxy resin) with self-healing tung-oil microcapsules (10 wt% of epoxy matrix) are effective in inhibiting initiation as well as progression of corrosion made possible by a dual-protection mechanism. Initiation of corrosion was delayed effectively due to the paths of diffusing aggressive ions made tortuous by nano-clay modification. In addition, the progression of corrosion was arrested by self-healing tung-oil microcapsules. We believe these results could provide an important tool in reaching the goal of sustainable construction.

Study on the durability of eco-friendly recycled aggregate concrete with supplementary cementitious materials: The combined action of compound salt solution of MgSO4, Na2SO4, and NaCl and dry-wet cycles

Focusing on eco-friendliness and sustainability, recycled aggregate concrete (RAC) has been recently substituted for natural aggregate concrete (NAC) in new constructions. In Northwest China, high-concentration corrosive ions of magnesium, sulfate, and chloride exist in soil and groundwater, which have a severe adverse effect of exposing RAC’s durability. To improve the efficient utilization of RAC in the environment of the aggressive ion, the durability experiment of eco-friendly RAC with supplementary cementitious materials (SCMs) under the combined action of 7.5 %Na2SO4 + 7.5 %MgSO4 + 5 %NaCl and dry-wet cycles was investigated. Results show that RAC with the ternary blend of cement-fly ash-granulated blast furnace slag had the best durability among all the RAC mixtures. The 10 % fly ash + 20 % silica fume and 10 % fly ash + 20 % metakaolin negatively affected the durability improvement of RAC. At the same D&W cycles, the relative content of hydration and corrosive products of RAC with SCMs was lower than that of RAC without SCMs, and Friedel’s salt and Mg10(OH)18Cl2·5H2O were not found. The mineral phase composition of RAC exposed to the compound salt solution was related to the relative content of portlandite. Furthermore, grain volume increasing from brucite and gypsum, salt crystallization pressure from blödite and MgCl2, and solid volume changing from thenardite to mirabilite mainly degraded RAC’s durability.

Influence of seawater and sea sand on the performance of Anti-washout underwater concrete: The overlooked significance of Mg2+

Seawater and sea sand are widely used in marine concrete to overcome the shortage of freshwater and river sand. However, the effect of the various salts in seawater and sea sand on the performance of anti-washout underwater concrete (AWC) is unclear. In this study, the influence of seawater and sea sand, as well as the aggressive ions in seawater, on the anti-washout ability, mechanical performance, and microscopic structure of AWC mortar are studied systematically. The AWC mortar molded in seawater has a lower compressive strength even though its indicators of anti-washout ability perform better than that in freshwater. This is because Mg2+ in seawater chemically binds with OH– in cement to form Mg(OH)2 film absorbed by anti-washout admixture(AWA), which inhibits the release of substances in AWC while also introducing more defects in AWC. This study lays the foundation for promoting the application of seawater and sea sand AWC in marine engineering.

Electrochemical study on the effect of hydrogen on the passive film of selective laser melted 316L stainless steel in a proton exchange membrane water electrolyzer environment

The effect of hydrogen on the passivation behavior and electrochemical characteristics of selective laser melted (SLMed) 316L stainless steel in a simulated anode environment for a proton exchange membrane water electrolyzer (PEMWE) was studied. The results indicate that hydrogen charged into the sample increased the ratio of superficial Fe2+/Fe3+ and OH−/O2−, increased the concentration of point defects, reduced the film thickness, and weakened its protective effect. The film near 0.6 VSCE showed n-type semiconductor behavior. Hydrogen charging resulted in a higher defect density and thinner space charge layer in the film, which promoted the invasion of aggressive ions.

Electrochemical corrosion protection of neat and zinc phosphate modified epoxy coating: A comparative physical aging study on Al alloy 6101.

Optimizing the pigment volume concentration of zinc phosphate pigments can protect Al alloy 6101 from alkaline media. Additionally, zinc phosphate pigments form a shielding film on the substrate and facilitate stopping the penetration of aggressive corrosion ions. The efficiency of eco-friendly zinc phosphate pigments is almost 98% during the corrosion analysis. A comparative study of physical aging of neat epoxy and Zinc Phosphate (ZP) pigment-modified epoxy coatings on Al alloy 6101 was conducted in Xi'an, China, for one year in all four seasons, where in summer for 3 months, results degraded more due to high UV radiation and humidity; it is found that peeling force of ZP pigments modified epoxy coatings is 50% higher of than that of the neat epoxy coatings though both peel-off adhesion strength and scratch test visibility decreased in both coatings; The electrochemical resistance of ZP pigments modified epoxy coatings is about 30% higher of than that of neat epoxy coatings, the corrosion rate of ZP pigments modified epoxy coatings is about 70% lower of than that of neat epoxy coatings, moreover the gloss retention is 20% higher in the modified epoxy; Optical surface observation of the coatings showed that the ZP modified epoxy coating could effectively restrict the crack and shrinkage in coatings after aging experimentation in the natural environment.

Investigation of the hydrophobicity and microstructure of fly ash-slag geopolymer modified by polydimethylsiloxane

The replacement of geopolymer for Portland cement exhibits the potential for reducing the CO2 footprint and saving natural resources during the production of building materials. However, geopolymer is a class of inorganic cementitious material, easy to suffer water intrusion with aggressive ions, such as chloride and sulphate, resulting in the destruction of structural integrity. In this study, hydroxyl-terminated polydimethylsiloxane (PDMS) was used as an additive to improve the hydrophobicity of fly ash-slag geopolymer. The microstructure was characterized using mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FT-IR). The results showed that the contact angle (CA) of the geopolymers increased from 57.32° to 127.64°, and the water absorption decreased from 6.96% to 1.61% as a function of the dosages of PDMS, contributing to the hydrophobic nature of the geopolymers. On the other hand, the addition of PDMS led to the formation of a less compact pore structure of geopolymers, accompanied by a transformation from internal gel pores into capillary pores and macropores. The pore enlargement will have adverse effects on the compressive strength of the geopolymers, but it can still meet the requirements for daily work. According to the analysis of microscopic test results, PDMS and N-A-S-H gel were likely to undergo dehydration condensation reaction in a strong alkaline environment, they were connected in the form of covalent bonds, so that the geopolymers have hydrophobicity.

Revealing the Corrosion Resistance of 316 L Stainless Steel by an In Situ Grown Nano Oxide Film.

It is widely accepted that the corrosion resistance of stainless steel originates from a compact Cr2O3 layer in the native passive film that serves as a barrier to aggressive ions. However, this suggestion has been questioned by some researchers. They believe that protectiveness might be related to the film recovery. Herein, the pitting development of bare 316 L stainless steel was compared with a corrosion-resistance enhanced steel obtained by tuning the native passive film of the alloy. Statistical software was employed for tracing the size and number of pits on the alloy surface. The statistical results for 12 weeks in 1 M sodium chloride solution (80 °C) revealed that there was a crossover in the growing rates of stable pits (diameter > 9 µm) between the bare alloy and the film-enhanced one. Stable pits on bare 316 L occurred early but showed a comparatively slow increase in the following weeks, demonstrating that self-repairability of metastable pits rather than impermeability of the native passive film plays the key role in the early stage of pitting corrosion.

Assessment of the Laser Beam Welding of Galvanized Car Body Steel with an Additional Organic Protective Layer.

This study discusses the effect of laser beam welding parameters on the structure, mechanical properties and corrosion resistance of 1.2 mm thick galvanized sheets made of low-carbon steel DC04 provided with a ZE36/36 GardoprotectOC2BU organic coating. The test laser beam butt welded joints were made without the filler metal, using a variable welding rate, where linear welding energy was restricted within the range of 30 J/mm to 90 J/mm. The joints were subjected to non-destructive tests, destructive tests and corrosion resistance tests. The tests revealed the possibility of making joints meeting the criteria specified in the ISO 15614-11 standard. Regardless of the value of linear welding energy applied in the process, all the joints were characterised by high mechanical and plastic properties. It was noticed that an increase in linear welding energy from 30 J/mm to 90 J/mm was accompanied by the widening of the weld and that of the heat-affected zone (HAZ). In addition, an increase in linear welding energy was accompanied by a decrease in the maximum weld hardness to approximately 250 HV0.2. In the HAZ, hardness was restricted within the range of 190 HV0.2 to 230 HV0.2 and decreased along with increasing linear welding energy. In the static tensile test, regardless of the value of linear welding energy, the test specimen ruptured in the base material. In the bend test, regardless of the value of linear welding energy, a bend angle of 180° was obtained without partial tear or scratches; unit elongation was restricted within the range of 29% to 42%. The electrochemical tests and experiments performed in the salt spray chamber revealed the very high effectiveness of the corrosion protections against aggressive chloride ions.

Inhibition Mechanism of Oxalhydrazide on Reinforcing Steel in Pore Solution Contaminated by 3.5%NaCl - Experimental and Theoretical Study

Concrete is one among the most consumed materials on the planet secondary to water. However, the degradation of concrete happens due to the corrosion of reinforcement. Although the pore solution of concrete is alkaline, the corrosion of rebars in concrete is triggered due to aggressive ions like chlorides entering the concrete. The most common method of corrosion inhibition is by utilising corrosion inhibitors which when added to the concrete stays in the pore solution and prevents the corrosion of surface of rebars from aggressive ions. Although there are number of inhibitors, the rise in corrosion deterioration demands the need for new potential inhibitors which are highly effective in different aggressive environments. This study is based on the corrosion of rebars in simulated concrete pore solution in the presence of 3.5% NaCl with oxalhydrazide as the potential inhibiting material. The corrosion behaviour of rebar is obtained by electrochemical studies using EIS and potentiodynamic polarization and theoretically analysed employing molecular mechanics and molecular dynamics simulations. The experimental results revealed that the inhibitor is effective in reducing the corrosion and the values of binding energy of the inhibitors on rebar surface also go well with the experimental results. Oxalhydrazide is found effective in minimizing the attack of chloride ion on rebar in pore solution.

Atomic diffusion of sulfate and chloride ions in the nanometer cavity of C-S-H/Nanoclay

Concrete is notably vulnerable to aggressive ions such as sulfate and chloride penetrating its inner nanopores and damaging its microstructure or the reinforcements it encompasses. Nanoclay particles, being impermeable to...

Osvrt na samozaceljujući beton - biološki pristup

Concrete is one of the most popular and used construction materials. It is strong, durable, and relatively inexpensive, but it has a higher tendency to form cracks. The cracks provide a low service life for the concrete and high maintenance costs. The penetration of aggressive ions through cracks results in corrosion of steel reinforcement, carbonation, sulphate attack, alkali-aggregate reaction, etc. However, prevention of cracks formation is impossible, however, they can be controlled or repaired by various methods. Self-healing concrete is well known as a suitable remedial method to improve concrete's long-term durability. It is a new, rapid, and environmentally friendly approach. In this technology, when concrete is exposed to water, the healing agent material produces calcium carbonate (CaCO3), which fills in the cracks and decreases permeability while enhancing concrete durability. The materials that are used as the healing agents are mostly bacteria, polymers, and chemical compounds. Bacteria are the most preferred material in concrete for healing. Therefore, bio concrete or bacterial concrete is another name for self-healing concrete. This article provides a comprehensive overview of self-healing concrete including, the system, process, mechanical properties, and durability of healed concrete.

Efeito da duração e pressão da cura por carbonatação do concreto em perfis de cloreto

Abstract Carbonation curing alters the characteristics of the concrete's microstructure and can interfere with the penetration of aggressive ions. The objective of this article was to evaluate the influence of CO2 pressure and carbonation cure time on chloride profiles. Concrete specimens were cured by carbonation with CO2 pressures ranging from 5 to 25 Psi, for a time within the carbonation chamber of 8, 24, and 36 hours. These concretes were subjected to 30 wetting and drying cycles in NaCl solution to stimulate the chloride ingress. The carbonation depth and the microstructure of the concrete were monitored over time. Chloride profiles were obtained and modeled by 4 mathematical equations. The results showed that the combination of less time and CO2 pressure during carbonation curing potentiated the reduction of chloride penetration in concrete. Also, the carbonation curing conditions of 5 and 10 Psi for 8 hours reduced the chloride diffusion coefficient.