NaCl Solution Research Articles

Corrosion evaluation of Al-Cu-Mn-Zr cast alloys in 3.5% NaCl solution

Corrosion behavior of cast Al-Cu-Mn-Zr (ACMZ) and RR350 alloys was compared to a cast 319 alloy in 3.5 wt.% NaCl. After 168 h immersion, ACMZ and RR350 alloys suffered from preferential attack adjacent to intermetallic particles decorated at grain boundaries while the attack in 319 occurred in eutectic Al-Si dendritic boundaries. Electrochemical data allowed semiquantitative comparison of alloy resistance to corrosion initiation, and ACMZ type alloys, including RR350 and three alloys with higher Cu, were considered more resistant than 319 due to the absence of deleterious Si particles. In case of 319, such Si particles presumably drove higher micro-galvanic influence to initiate and sustain Al corrosion. With lower susceptibility to corrosion initiation, ACMZ alloys should exhibit higher or at minimum similar resistance compared to cast 319.

NaCl salt stress and PEG water stress differentially affect germination and early seedling growth of two sesame (Sesamum indicum L.) cultivars

Drought stress and salt stress are serious challenges to crop productivity in the arid lands. This work investigates the impact of NaCl-salt stress and PEG-water stress on germination and embryo growth of two sesame (Sesamum indicum L.) cultivars: Sohag 1 (Sohg) and Shandaweel 3 (Shnd). Seed dimensions, volume and weight were measured. The red Sohg seeds were larger with oblong appearance and lower density relative to the white Shnd seeds. Seeds were germinated in isosmotic solutions of NaCl and PEG-6000 at 0, − 0.103, − 0.205, − 0.410 and − 0.615 MPa. The time-based parameters (velocity, uniformity and synchrony of germination) were more reliable measures of germination efficiency than the final germination percentage. The impact of PEG was more severe than that of NaCl particularly on Sohg. The peak of daily germination was lowered and delayed under stress. The genotypic variability in germinability became evident under stress in favor of Shnd. Radicle length–a reliable measure of seedling growth–was subjected to stronger impact of NaCl than PEG. Although Na+ mobilization from seeds to embryos was indifferent in the two cultivars in PEG solutions, Shnd seedlings exhibited higher Na+ uptake from NaCl solutions. Whereas K+ mobilization was restricted by NaCl only in Sohg, it was hastened by PEG equally in the two cultivars. The stress-vulnerable Sohg recovered from stress with higher magnitude than did Shnd, particularly from the more stressing osmoticum (PEG). The indices of germination recovery were highest in PEG-pretreated Sohg while the biomass of recovered seedlings was highest in NaCl-pretreated Sohg.

Microstructure, mechanical behavior, and cavitation erosion-corrosion resistance of the BCC/B2 strengthened FeNiCrMoAl-based multi-principal element alloys

The influence of disordered and ordered body-centered cubic (BCC-β and B2-β′) secondary phases on the mechanical properties and cavitation erosion-corrosion (CE-C) behavior of BCC/B2 strengthened FeNiCrMoAl-based multi-principal element alloy (MPEA) was systematically investigated. An increased β/β′ phases content enhanced the MPEAs’ strengths while maintaining good ductility. However, this increases also led to a higher proportion of loosely bound Al2O3 within the passivation film, resulting in a slight reduction in electrochemical corrosion performance. Remarkably, in a NaCl solution, the increased β/β′ phases significantly improved the MPEAs’ resistance to CE-C, attributed to the outstanding corrosion resistance and mechanical properties which could withstand elastic strain damage and plastic deformation.

Raman Quantitative Measurement on the Cl− Molarity of H2O-NaCl-CO2 System: Application to Fluid Inclusions

In this study, Raman spectroscopy is applied to determine the salinity of fluid inclusions in the H2O-NaCl-CO2 system. In the work, various systems are prepared, such as H2O-NaCl, H2O-CO2, and H2O-NaCl-CO2. For the H2O-NaCl system, the addition of NaCl salts decreases the intensity of the sub-band below 3330 cm−1 but increases the intensity of the sub-band above 3330 cm−1. According to the structural analysis of the H2O-NaCl system, the spectral changes are mainly related to the interactions between Cl− and water. After the Raman OH stretching bands are fitted into two sub-bands, the intensity ratio between them is used to calculate the Cl− concentrations (molarity scale) of NaCl solutions. Additionally, based on the measured Raman spectra, the effects of CO2 on water structure may be weak. It is reasonable to ignore the impact of dissolved CO2 on Raman OH stretching bands. The procedure above can be extended to quantitatively determine the Cl− molarity of the H2O-NaCl-CO2 system. To demonstrate its reliability, this method is applied to determine the salinity of synthetic and natural fluid inclusions containing CO2.

Corrosion Behavior of SLMed Ti6Al4V-Equine Bone Nanocomposites

Ti6Al4V is one of the most widely used Ti alloys in biomedical applications, such as orthopedic and dental implants, due to its excellent mechanical properties, biocompatibility, and high corrosion resistance. Metal implants require high bonding strength between the implant and bone for long-term use in the human body; Hydroxyapatite (HAp) has generally been used as it can be expected to provide high osseointegration. However, in this study, Equine Bone (EB), which is a biowaste with a similar chemical composition to HAp and is environmentally friendly, was used instead. Ti6Al4V and EB were mixed through ball milling and then fabricated into Ti6Al4V-0.05EB composites using Selective Laser Melting (SLM). During the SLM process, localized high thermal gradients and rapid cooling rates leads to high strength and low ductility, making it challenging to use as a biomaterial. To overcome these issues, heat treatment was performed at temperatures corresponding to the <i>β</i> phase transformation. Subsequently, to evaluate the corrosion behavior after implantation in the body, the corrosion resistance of the Ti6Al4V-0.05EB nanocomposites was assessed through potentiodynamic polarization tests in a 0.9% NaCl solution, which simulates the physiological environment of the human body. Additionally, the effects of EB addition and heat treatment temperature on the corrosion behavior were also observed.

Improving electrochemical corrosion resistance of AISI 304 using tungsten carbide-cobalt/silicon carbide high-velocity oxygen fuel coatings

This study offers an in-depth analysis of the electrochemical corrosion behaviour of tungsten carbide-cobalt/silicon carbide coatings on AISI 304 stainless steel, applied using high-velocity oxygen fuel spraying. The coatings were produced with varying silicon carbide concentrations (25%, 40%, 60% and 75%) to evaluate their effectiveness in enhancing corrosion resistance. Microstructural analyses were conducted using SEM and EDS, while corrosion behaviour was assessed through open-circuit potential and Tafel tests in a NaCl solution. The findings indicate that increasing the silicon carbide content increases surface roughness and coating thickness. Additionally, the corrosion results revealed that coatings with higher silicon carbide concentrations exhibited more negative potential values, indicating improved corrosion resistance due to passivation effects.

Quickly Calculating the Activity Coefficient of a NaCl Solution Based on Machine Learning Algorithms

Quickly Calculating the Activity Coefficient of a NaCl Solution Based on Machine Learning Algorithms

Electrospun Membranes of Hydrophobic Polyimide and NH2‐UiO‐66 Nanocomposite for Desalination

Hydrophobic nanofiber composite membranes comprising polyimide and metal–organic frameworks are developed for desalination via direct contact membrane distillation (DCMD). Our study demonstrates the synthesis of hydrophobic polyimides with trifluoromethyl groups, along with superhydrophobic UiO‐66 (hMOF) prepared by phenylsilane modification on the metal‐oxo nodes. These components are then combined to create nanofiber membranes with improved hydrophobicity, ensuring long‐term stability while preserving a high water flux. Integration of hMOF into the polymer matrix further increases membrane hydrophobic properties and provides additional pathways for vapor transport during MD. The resulting nanofiber composite membranes containing 20 wt% of hMOFs (PI‐1‐hMOF‐20) were able to desalinate hypersaline feed solution of up to 17 wt% NaCl solution, conditions that are beyond the capability of reverse osmosis systems. These membranes demonstrated a water flux of 68.1 kg m−2 h−1 with a rejection rate of 99.98% for a simulated seawater solution of 3.5 wt% NaCl at 70 °C, while maintaining consistent desalination performance for 250 h.

Investigating novel thin-film nanocomposite membranes for sustainable water recovery using fertilizer-driven forward osmosis – Experimental and machine learning approaches

Water recovery from municipal wastewater can augment freshwater resources to meet increasing demand. An osmotic-driven membrane separation process- forward osmosis (FO) is currently being explored as a sustainable technology. This work proposes to address the challenges associated with FO namely (i) robust membrane and (ii) draw solute (DS) recovery. Robust thin-film nanocomposite membranes incorporating a) nickel ferrite or b) nitrogen-enriched nanoporous polytriazine (NENP-1) covalent organic framework were fabricated with enhanced hydrophilicity, surface roughness and anti-fouling properties. The optimum membranes M2 and C2 displayed a pure water flux of 4.86 ± 0.11 and 5.4 ± 0.2 L/m2h respectively and a specific reverse solute flux (SRSF) <<1 when using 1 M NaCl solution as the DS (feed solution – DI water). Fertilizer-driven FO (FDFO) was proposed as the diluted DS need not be recovered but could be used directly for irrigation. The pure water flux for both M2 and C2 membranes were in the following order for the fertilizers used as DS (1 M) - (NH4)2SO4 + (NH₄)₂HPO₄ > (NH4)2SO4 > (NH₄)₂HPO₄ which indicates that the mixed ions in the DS enhanced the water permeance. In all cases, the SRSF was < 1 g/L indicating the feasibility of the process. The membranes exhibited a TOC removal of > 90 % from synthetic municipal wastewater containing persistent organic pollutants and personal & pharmaceutical care products and the membranes could be regenerated after washing with a 10 mM solution of SDS for 5 cycles of operation. Further, ANN was used to develop a predictive model for water flux in FO membranes and the optimized architecture of 7–5–50–40–1 displayed a remarkable overall R2 value of 0.98 (MSE= 0.027). The FDFO process using the fabricated thin-film nanocomposite membranes holds enormous potential to be investigated in larger-scale studies.

Effects of Na2SiO3/NaOH ratio in alkali activator on the microstructure, strength and chloride ingress in fly ash and GGBS based alkali activated concrete

In this study, the impact of alkaline solutions composed of various Na2SiO3/NaOH ratio and NaOH molarity on the strength, chloride ingress and chloride binding capacity of fly ash (FA) and ground granulated blast furnace slag (GGBS) based alkali activated concrete (AAC) was investigated. The microstructural properties of alkali activated binders (AAB) composites was also studied to understand its influence on the chloride permeability of AAC. Chloride permeability of concrete was tested by using the rapid chloride penetration test (RCPT) and by immersing concrete in NaCl solution (ASTM C1556). The compressive strength, chloride ingress and chloride binding capacity of AAC was compared with Portland cement-based concrete (OPC). Results showed that higher Na2O/SiO2 ratio in alkaline solutions resulted in a weak microstructure with, low strength and high chloride ingress. Concrete activated by alkaline solutions with Na2O/SiO2 molar ratio =1 (+3), exhibited greater compressive strength and resistance to chloride ion penetration. The increase of SiO2 concentration in alkaline solution greatly reduces the binding capacity of AAC while the bound chlorides increased with the NaOH molarity. No chemical chloride binding was observed in AAC but for OPC concrete, calcium salts formed in the microstructure after immersion in NaCl solution. Compared to OPC concrete, AAC showed superior performance in terms of strength and chloride diffusion making it a potential candidate for application in marine structures.

Synergy analysis of tribocorrosion behaviour of aluminum alloy under different hydrostatic pressures

Static corrosion, tribocorrosion tests, and potentiostat polarization tests were carried out on aluminum alloy 7075-T6 in 3.5 wt.% NaCl solution. The influence of hydrostatic pressure on the tribocorrosion of the aluminum alloy in 3.5 wt.% NaCl solution was studied, and the synergy relationship between its corrosion and wear was quantitatively analyzed. The results showed that the material loss of the aluminum alloy was not simply a superposition of corrosion and wear. The wear rate of corrosion-accelerated wear increased with the hydrostatic pressure, and when the hydrostatic pressure increased from 0.1 MPa to 30 MPa, the contribution of corrosion-accelerated wear increased by 15.43%. This research will help provide theoretical support for the selection of materials for deep-sea equipment.

The Corrosion-Inhibitory Influence of Graphene Oxide on Steel Reinforcement Embedded in Concrete Exposed to a 3.5M NaCl Solution

Steel reinforcement corrosion significantly reduces the durability and service life of concrete structures, particularly in chloride-rich environments such as marine and coastal areas. This study aims to reduce the corrosion rate using graphene oxide (GO) as a corrosion inhibitor. Two GO dosages (0.0005 and 0.005 wt.%) were evaluated for their effectiveness in mitigating corrosion in reinforced concrete exposed to a 3.5M NaCl solution. To assess the corrosion behavior of the steel reinforcement, Open Circuit Potential (OCP), Electrochemical Impedance Spectroscopy (EIS), and Linear Polarization Resistance (LPR) were evaluated to monitor corrosion over one year by of wetting/drying cycles. Oxygen permeability and electrical resistivity tests were also conducted to evaluate the concrete's susceptibility to corrosion. Both GO content demonstrated significant corrosion inhibition, with the 0.005 wt.% dosage providing the most effective protection. This was evidenced by the lowest icorr values recorded during the final cycle (52), larger capacitive loops, and higher impedance in EIS results, indicating enhanced corrosion resistance. Visual inspection of steel bars further confirmed these findings, showing no signs of deterioration or discoloration in GO-modified concrete compared to steel bars extracted from reference concrete. SEM-EDS analysis revealed higher carbon content on the steel surface, suggesting GO adsorption and the formation of a protective passive layer. These results suggest that GO is a promising nanomaterial for inhibiting corrosion in steel-reinforced concrete exposed to aggressive environmental conditions.

2D hollow leaf shaped mesoporous carbon derived from ZIF-L for efficient capacitive deionization

Electrochemical treatment of saline or brackish water by capacitive deionization (CDI) is a novel resource-saving solution to ensure the availability of freshwater resources in the environment. MOF (metal–organic framework) derived carbon as a novel carbonaceous material in CDI has received considerable research attention. Among them, ZIF-L-derived carbon (ZC) suffers from problems such as self-aggregation, poor mesoporous structure, and low electrical conductivity, which lead to poor CDI performance. In this paper, a strategy of ZIF-L coated with polydopamine (PDA) is proposed to solve the above problems. When the amount of PDA was 0.5 g, ZIF-L@PDA0.5-derived carbon composite (ZPC0.5) is obtained for efficient capacitive deionization. The ZPC0.5 composite not only maintains the 2D leaf shaped structure consistent with ZIF-L, exposing more active sites, but also has an elevated mesopore occupancy ratio to promote solution diffusion. Meanwhile, the interaction between PDA and ZIF-L makes the ZPC0.5 have a cavity structure, which improves the mass transfer capacity. The resulting ZPC0.5 composite has a specific capacitance (165.8F g−1) that is 3.86 times higher than that of ZC (42.9F g−1). Consequently, in 1.2 V, 500 mg/L NaCl solution, the symmetric CDI cell ZPC0.5//ZPC0.5 exhibits an excellent desalination capacity (29.6 mg/g), which is 2.69 times that of the ZC//ZC.

Photoaging-induced variations in heteroaggregation of nanoplastics and suspended sediments in aquatic environments: a case study on nanopolystyrene

Photoaging of nanoplastics (NPs) and heteroaggregate with suspended sediments (SS) determines transport processes and ecological risks of NPs in aquatic environments. This study investigated the disruption of photoaging on the heteroaggregation behavior of polystyrene NPs (PSNPs) and SS in different valence electrolyte solutions and deduced the interaction mechanisms by integrating aggregation kinetics and molecular dynamics (MD) simulation. Increasing the electrolyte concentration significantly enhanced the heteroaggregation between PSNPs and SS, and the divalent electrolytes induced the heteroaggregation more efficiently. MD simulation at the molecular level revealed that PS and SS could spontaneously form clusters, and photoaged PS has a stronger potential to fold into a dense state with SS. Photoaging for 30 d retarded heteroaggregation due to the steric hindrance produced by the leached organic matter in NaCl solutions, and the critical coagulation concentration (CCC) increased by more than 85.44%. Contrarily, photoaging caused more oxygen-containing functional groups produced on the surface of PSNPs through Ca2+ bridging promoting heteroaggregation and thus destabilizing in CaCl2 solutions, the CCC decreased by 23.53% ∼ 35.29%. These findings provide mechanistic insight into the environmental process of NPs and SS and are crucial for a comprehensive understanding of the environmental fate and transport of NPs in aquatic environments.

Surface patterned polyvinyl alcohol/CNT hydrogels for sustained solar powered high concentration brine desalination and salt harvesting

Solar-driven interfacial evaporation is an attractive way to achieve water purification. However, high water evaporation rates often result in the precipitation of salt crystals on the surface of the evaporator leading to decay of the evaporation efficiency over time, which makes it difficult to balance high water evaporation rates with salt resistance. Herein, an anisotropic polyvinyl alcohol/CNT hydrogel is constructed by directional freezing and surface patterning. The polymer backbone formed by the polyvinyl alcohol chains interacts with the water clusters to reduce the evaporation enthalpy of water and the absorbed water can be released by squeezing the hydrogels due to the micron-sized vertically aligned pores. More importantly, by designing the structure of the hydrogels surface, the gas–liquid interface of the evaporators can be increased while the growth direction of the salt crystals can be controlled. As a result, the water evaporation rate can be increased from 3.26 kg m-2h−1 to 3.69 kg m-2h−1 under one sun irradiation through surface patterning. After 50 h of continuous operation in 10 wt% NaCl solution under one sun irradiation, the water evaporation rate gradually increases and a large amount of salt collection is collected, which proves its satisfactory salt resistance.

Effect of Graphene and Fe3O4 on the Protection Efficiency of Polyeugenol Conducted Coating for Stainless Steel 316L in NaCl solution

التآكل هو مصطلح يطلق على عملية تفكك سطح المعادن والسبائك في بيئة معينة. تتغير الخواص الكيميائية للسبائك المعدنية بعد عملية التأكل وكذلك سلوكها الميكانيكي. لغرض الحماية من التأكل تم تطبيق إستراتيجية جديدة تعتمد على تخليق مادة بوليميرية من خلال البلمرة الكهربائية لليوجينول لتكوين للبولي يوجينول / المركب النانوي (Graphgene ، Fe3O4 )على الفولاذ المقاوم للصدأ نوع (SS316L) ، والذي يربط كقطب كهربائي انود ، باستخدام عملية البلمرة الكهربائية ، فإن البوليمر الموصل الناتج يعطي حماية جيدة ضد التآكل. تم اجراء الفحوصات المختبرية من التشخيص بتقنية الاشعة التحت الحمراء ومطيافية القوة الذرية للبوليمر المحضر لوحده مرة ومع المواد النانوية مرة اخرى. أظهرت النتائج أنه بالمقارنة مع SS316L الغير مطلي ، يوفر البولي يوجينول مع الكرافين أفضل حماية للمعدن المستخدم من التآكل.

Ultrahigh tribocorrosion resistance of hydrogenated amorphous carbon coating via trace gradient W incorporation

In this work, we manipulated the trace gradient W incorporation combined with a increment top-layer thickness for the hydrogenated amorphous carbon (a-C:H) coating on thermally sprayed WC-based cermet. The tribocorrosion resistance of the modified a-C:H coating was investigated in terms of structural evolution during friction under 3.5wt.% NaCl solution. Regardless of introduction of gradient W doping, although the a-C:H coating maintained the sp2/sp3 atomic bond structure, the stress reduction and plasticity increase were obtained for coatings. Moreover, the stable open-circuit potential revealed that the tribocorrosion resistance of modified coating was significantly improved, as identified by the quite low wear rate and coefficient of friction at 1.46×10-8 mm3/N·m and COF of 0.067, respectively. Different with the traditional failure of worn-out and pitting corrosion of a-C:H coating in chloride solution, the designed robust interfaces and the functional top-layer enabled the coating to withstand longest sliding distance over 2100m at heavy contacting pressure of 1.67GPa. These observations offer the promising strategy to fabricate advanced carbon-based coatings with required extremely strong wear resistance and anticorrosion capability for mechanical components used in harsh marine environment.

Optimizing laser parameters and exploring building direction dependence of corrosion behavior in NiTi alloys fabricated by laser powder bed fusion

The microstructure and materials performance of Laser Powder Bed Fusion-fabricated (LPBFed) NiTi shape memory alloys (SMAs) varies depending on the laser parameters and building directions. This study initially optimized the laser processing parameters (laser power and scanning speed) for LPBFed NiTi SMAs to enhance their printing quality and mechanical properties. We determined that with fixed hatch spacing of 80 μm and layer thickness of 30 μm, the laser power of 105 W, and scanning speed of 600 mm/s produced the best results. Subsequently, the corrosion behavior of LPBFed NiTi SMAs built in three different building directions (0°, 45°, 90°) was investigated in 0.9 wt.% NaCl solution at 37 °C. The electrochemical data revealed that the corrosion current density (Icorr) decreased with increasing building direction angle (Icorr-90° <Icorr-45° <Icorr-0°). The corrosion resistance followed the order of 0° sample ˂ 45° sample ˂ 90° sample. These findings were attributed to the difference in the grain size and boundary density. Higher boundary densities enhanced the electron activity capacity and the element diffusion rates, facilitating the rapid formation of a protective film and thus improving the corrosion resistance. This new insight into the anisotropy of corrosion behavior relative to building directions can inform the design of NiTi-SMA products and improve their reliability in tissue engineering applications.

Pagoda solar evaporators with an alternating hot-cold pattern for rapid, scaling-free desalination of hypersaline brines

Solar-driven evaporation holds significant potential for desalinating hypersaline brines, which pose challenges for traditional reverse osmosis. However, achieving both rapid evaporation and scaling prevention remains a key obstacle. In this study, we introduce a pagoda-like solar evaporator designed to optimize heat and mass transfer during the evaporation process of hypersaline brines. The interconnected multi-layer structure creates an alternating hot–cold pattern that integrates solar and environmental evaporation, enhancing the overall evaporation rate. This pattern also induces thermal Marangoni convection within the evaporator, mitigating local ion accumulation and providing durable scaling resistance. The pagoda evaporator sustains an evaporation rate of approximately 1.70 kg·m−2·h−1 over 8 h with a 20 wt% NaCl solution and produces 7.78 L·m−2·day−1 of fresh water without surface scaling in outdoor experiments. This innovative and facile design marks a significant advancement in the sustainable and efficient desalination of highly saline brines.

Evaluation of the bactericidal activity of plasma-activated NaCl solution (PAN) against foodborne pathogens: Inactivation mechanism and application to mackerel

The objective of this study was to assess the bactericidal effect of plasma-activated NaCl solution (PAN) against Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes and apply PAN as a brine salting solution for mackerel. To enhance the bactericidal effect of plasma-activated water (PAW), NaCl solutions (0, 3.5, 7, and 10 %) were treated with plasma for 20 and 40 min to generate PAN. Plasma-activated glycerol solution (PAG) was also included to evaluate the influence of water activity on plasma activation and its effect on microbial activity. Physicochemical analysis revealed that elevating the NaCl concentration of PAN led to a decrease in pH, an increase in oxidation–reduction potential, and higher levels of reactive species such as H2O2 and HOCl. PAN showed greater antibacterial activity compared to PAW and PAG, except for L. monocytogenes, where 40 min activation time and treatment time exceeding 20 min was required for significantly higher reduction to occur. PAN exhibited greater antibacterial activity at higher NaCl concentrations, which was attributed to increased ionic strength and reactive chlorine species. Additionally, we evaluated the microbial mechanisms of PAN by assessing cellular damage and alterations. The common observation across the three pathogens was that PAN resulted in increased cell membrane damage, reduced intermembrane enzyme activity, higher intracellular ROS levels, and changes in zeta potential values, while DNA damage was observed only in PAN-treated L. monocytogenes. Furthermore, when PAW and PAN were stored for up to four weeks, PAN showed higher efficacy compared to PAW. 10 % PAN was also effective against foodborne pathogens on mackerel, achieving log reductions of 3.62 for E. coli O157:H7, 4.62 for S. Typhimurium, and 3.18 for L. monocytogenes after a 20 min treatment without adversely affecting quality. Our results demonstrated the antibacterial activity and action mechanism of PAN, presenting its potential application in the seafood industry.