Competitive adsorption and unexpected corrosion inhibition effect of 316 L stainless steel in NaClO₃ and NaCl environment of chlor-alkali industry

The demand for environmentally sustainable methods to enhance the performance of low-carbon steel (LCS) has led to increased interest in organic waste-derived carburizing agents. This study explores the potential of using a blend of Shea Nut Shell (SNS) and Eggshell (ES) ash, mixed in a 1:3 ratio, as an eco-friendly carburizing medium for improving the mechanical and corrosion-resistant properties of LCS. Carburization was carried out at 900°C for 30 minutes, and the effects were assessed through comprehensive characterization. Mechanical properties such as hardness, tensile strength, and impact energy were evaluated alongside microstructural analysis using X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy-dispersive spectroscopy (EDS), and wear rate testing. Corrosion resistance was investigated in H₂SO₄ and NaCl environments over a 21-day period. Results show that carburized LCS achieved significantly higher hardness (514.55 HB) compared to the uncarburized counterpart (399.05 HB), with improved toughness as indicated by increased impact energy absorption. However, un-carburized LCS maintained higher tensile strength. Microstructural examination revealed enhanced carbon diffusion and pearlite formation, contributing to reduced wear in carburized samples. EDS confirmed increased surface carbon content, while corrosion behavior varied: carburized LCS performed better in saline (NaCl) conditions, whereas uncarburized LCS offered better resistance in acidic (H₂SO₄) environments. In conclusion, the SNS-ES ash mixture presents a promising route for sustainable carburization of LCS, particularly for components exposed to saline environments such as agricultural tools and automotive parts. Future work will focus on optimizing treatment durations, expanding corrosion testing in simulated service environments, and scaling the process for industrial applications.

This study comparatively evaluates the corrosion behaviour of binary magnesium–titanium (MgTi) and aluminium–vanadium (AlV) alloys recovered from automotive scrap in dilute H 2 SO 4 (0.000625–0.1 M), NaCl (0.5–4.5 wt%) and mixed H 2 SO 4 /NaCl environments. Corrosion performance was assessed using gravimetric weight-loss, potentiodynamic and cyclic polarisation, open-circuit potential monitoring, electrochemical impedance spectroscopy (EIS) and post-exposure optical microscopy. AlV alloy exhibited markedly superior corrosion resistance in all tested media, forming a compact, self-healing oxide film that conferred high polarisation resistance and partial passivation capability. In contrast, MgTi alloy underwent rapid active dissolution, displaying very high corrosion rates, low impedance, unstable open-circuit potentials and severe surface degradation dominated by pitting and general attack. The presence of vanadium in the aluminium matrix was responsible for the stable passive layer, whereas the MgTi system formed only porous and non-protective corrosion products. The results demonstrate that, among the two lightweight binary alloys examined, AlV possesses significantly greater resistance to acidic, chloride-containing and mixed corrosive environments, making it considerably more suitable for structural applications where exposure to de-icing salts, acidic condensation or marine atmospheres is anticipated. MgTi, however, requires additional protective measures (coatings, inhibitors or further alloying) for practical use in aggressive service conditions.

Plant growth-promoting endophytes (PGPE) in halophytes have the potential to enhance plant stress resistance and promote growth, demonstrating broad application prospects in agriculture. The culturable microorganisms inhabiting in halophytes and their potential roles in enhancing salt-stress resistance of crops remain limited. This study isolated culturable endophytic bacteria from the roots of two dominant desert halophytes, Haloxylon ammodendron and Halostachys caspica, determined their growth-promoting abilities, and evaluated their capability in improving wheat performance under salt stress. Five saline-alkali tolerant bacterial strains-identified as Priestia endophyticus (S1, Y5), Priestia licheniformis (S2), Streptomyces griseorubens (S7), and Nocardiopsis aegyptia (Y6)-were characterized. These bacterial strains exhibited robust survival in 1.4 mol/L NaCl and high-pH environments (pH > 11.0), while demonstrating multiple growth-promoting traits, including indole-3-acetic acid (IAA) production and inorganic phosphate solubilization. All of the five strains (except for S2) and mixed culture improved the germination potential at 100 mmol/L NaCl. The strains S7, Y5, and mixed culture significantly increased plant height, root length, above ground fresh and dry weight compared to 200 mmol/L NaCl stressed seedlings (200CK)(p < 0.05). Salt stress significantly decreased chlorophyll content by 25.82% and 34.06% under 100 and 200mmol/L NaCl in comparison to CK. Conversely, PGPE inoculation significantly promoted chlorophyll synthesis of seedlings under salt stress. PGPE inoculation reduced enzyme activities of peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) relative to the salt stressed seedlings. All inoculation treatments significantly decreased SOD activity by 20.2%-34.62%, and POD activity by 30.79%-53.38%, relative to 200CK. These findings demonstrate that these strains isolated from halophytic plants exhibit positive effects in ameliorating salt stress and improving the growth of wheat seedlings, highlighting their potential for enhancing agricultural productivity in saline-alkali soils.

Purpose This study aims to introduce the efficacy of zein-oleic acid (ZO) nanobiocomposite coatings as an environmentally friendly inhibitor of corrosion on copper substrates in a 3.5% NaCl environment. Design/methodology/approach The composition of proposed biopolymer-based coating as a copper corrosion inhibitor was optimized using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and Fourier-transform infrared (FTIR) techniques. Findings Polarization studies show that the inhibitor decreases the corrosion current density by mixed mode mechanism. An equivalent circuit model was used to analyze the EIS data of electrode /electrolyte interface. SEM images reveal the presence of an adsorbed protective film of green inhibitor. Supplementing these observations, FTIR spectroscopy exhibits chemical behavior and integrity of a protective film, corroborating ZO’s role in providing a barrier to corrosive species. The biopolymer’s stability and synergistic interaction with the hydrophobicity of fatty acids position ZO as an environmentally friendly alternative for corrosion inhibition in chloride environments. The thin-film coating prepared from casting solution 0.5% w/v-0.03% oleic acid and 1.5% w/v-0.03% oleic acid show high inhibition efficiencies (η) of 92.31% and 92.64%, respectively, after 2 h of immersion in saltwater. Practical implications Considering the wide applications of copper in various industrial technologies, introducing an effective corrosion protector can significantly reduce damage caused by metal corrosion. The ZO nanobiocomposite film on copper can be used as a green and inexpensive corrosion protective layer on copper in humid and dry media. Originality/value The outstanding advantages of the ZO nanobiocomposite include ease of preparation, good adhesion to the copper surface, acceptable stability, transparency and high efficiency in inhibiting copper corrosion.

Aluminium (Al) plays a vital role in many industrial and engineering applications. But Al undergoes severe corrosion in NaCl environment. The corrosion of metals can be controlled by chromium coating, but the toxicity hinders their applications. Now-a-days sol–gel based silane coatings are considered as best alternative for toxic chromium conversion coatings. In the present study, 3-glycidoxypropyltrimethoxysilane (GPTMS) and 3-aminopropyltrimethoxysilane (APTMS) based sol–gel coatings were prepared to control the corrosion of Al in 3.5% NaCl environment. Further, nano titanium oxide (TiO2) was added with both GPTMS and APTMS to improve the corrosion protection performance of Al in NaCl. The corrosion protection efficiency of the sol–gel coatings was evaluated by electrochemical impedance and Tafel polarization studies. The impedance study suggested that the protection efficiency of TiO2 doped GPTMS and TiO2 doped APTMS are about 97% and 95%, respectively. This work revealed that TiO2 doped GPTMS and APTMS based sol–gel coating protects the Al from corrosion to a significant extent.

Laser Powder Bed Fusion (LPBF) in Additive Manufacturing (AM) has become a transformative method for creating metallic parts, especially Stainless Steel (SS) 316L shows compatibility. Since SS316L, with its constituent elements, offers excellent mechanical strength, biocompatibility, and corrosion resistance, it is suitable for several applications. Nevertheless, enhancements in mechanical strength and corrosion resistance are essential for its application in biomedical fields. Shot Peening (SP), a Severe Plastic Deformation (SPD) technique, was used to enhance these properties on Unpeened (UP) and Shot-Peened (SPed) samples with exposure times of 6 (SP1), 8 (SP2), and 10 minutes (SP3). The characterized results indicate that the contact angles increased hydrophilicity for SPed samples in PBS and Deionized water, maintaining the trend and indicating higher wettability compared to the UP sample. Surface roughness values gradually decreased from SP1 (8.27 μm) to SP3 (7.6 μm) compared to the UP sample (10.93 μm). The micro-hardness increased after SP; among all the samples, the maximum value was exhibited by SP2 (395.7 ± 5.8 Hv). The tensile properties, such as YTS and UTS, are increased for SPed samples of SP1 and SP2, but slightly decreased for SP3 compared to the UP sample. In contrast, the percentage elongation gradually reduced for the SPed samples compared to the UP, except for SP1. The corrosion tests conducted in a 0.5 M NaCl environment using PDP and EIS methods showed that the SPed samples exhibited lower Icorr and higher Ecorr. Consequently, the corrosion resistance varies in the order of SP3 &gt; SP2 &gt; SP1 &gt; UP. Hence, the corrosion resistance of LPBF SS316L is not influenced by a single parameter, but it is controlled by the combined effects of surface properties imparted by SP. Major Findings: SP played a crucial role in the varying durations of the mechanical properties and corrosion behavior of LPBF 316L, along with the distinct surface morphological features.

Volatile organic compounds (VOCs) are key aroma determinants in pork, and gas chromatography-ion mobility spectrometry (GC-IMS) is an effective technique for their detection. However, the detection conditions for pork using GC-IMS have yet to be standardized. This study employed GC-IMS to investigate the effects of incubation (temperature/duration) and medium (water and different concentrations of NaCl) environments on VOCs in pork. Statistical analyses including t-tests, PLS-DA, and OPLS-DA were employed to assess VOC differences. The results showed that: (1) VOC diversity and intensity increased with incubation temperature and time, with optimal signals obtained at 100 °C for 20 min. (2) The sample medium significantly influenced aroma release. When the medium contained 10% NaCl, the relative content of aldehydes increased, showing that these compounds were optimally released. (3) Under the optimized conditions, 15 key differential VOCs were identified from different muscle tissues, including 10 aldehydes, 2 esters, 1 ketone, 1 alcohol and 1 ether. This work establishes practical GC-IMS parameters for pork VOC analysis and provides a reliable reference for flavor-related studies.

This study aims to improve the corrosion resistance of steel in a 3.5% NaCl environment by developing epoxy coatings containing surface-modified Fe3O4 nanoparticles. Fe3O4 was synthesized via co-precipitation, functionalized with 3-aminopropyltriethoxysilane (APTES) to improve dispersion, and combined with triethanolamine (TEA) as a surfactant to stabilize morphology. Five coating systems, pure epoxy, epoxy–Fe3O4, epoxy–Fe3O4/TEA, epoxy–APTES–Fe3O4, and epoxy–APTES–Fe3O4/TEA, were prepared. The nanoparticle structure and morphology were analyzed using XRD, FT-IR, SEM and EDX, while corrosion resistance was evaluated via potentiodynamic polarization (PDP) và electrochemical impedance spectroscopy (EIS). Results showed that APTES functionalization improved nanoparticle dispersion and interfacial bonding, while TEA reduced particle size and prevented agglomeration. The epoxy–APTES–Fe3O4/TEA system exhibited the best corrosion protection. These findings highlight the potential of modified epoxy nanocomposite coatings for marine steel protection.

A malignant leakage presents a significant challenge in drilling engineering, particularly within carbonate formations, where such a leakage is frequently encountered. Currently, there is no effective solution to this problem. In this study, a water-reactive polyurethane sealing agent was developed using multifunctional polypropylene glycol and 1,4-butanediol (BDO) as soft segments, diphenylmethane diisocyanate (MDI) as the hard segment, and a composite catalyst consisting of N, N-dimethyl cyclohexylamine (PC-8) and dibutyltin dilaurate (T-12). The material reacts rapidly with water to form a high-strength gel, with the reaction time being controllable. Through experimental optimization, it was determined that the BDO mass fraction was 1%, and the molar ratio of isocyanate group to hydroxyl group was 1.8. Additionally, the gelation time can be controlled by adjusting the mass fraction of the composite catalyst. Experimental results from sand-bed and fracture-plate tests indicated that the material could withstand pressures exceeding 3 MPa at 93 °C and exhibited resistance to saturated NaCl and CaCl2 environments. The plugging mechanism was investigated using scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and Fourier-transform infrared (FTIR) spectroscopy. The results demonstrated that the agent formed a compact, micron-scale porous structure upon reacting with water, exhibiting excellent thermal stability and dual plugging performance through both physical and chemical mechanisms. Due to its water-reactive characteristics, a multi-stage injection process was adopted for field application design. This material shows promising potential for mitigating large-fracture-type malignant leakages in drilling operations.

Salt spray tests with 0.1 wt% NaCl and 1 wt% NaCl solutions were used to investigate the corrosion behavior of LA141 Mg-Li alloy in different Cl− environments. The study used corrosion weight loss analysis, macro/micromorphological analysis, x-ray diffraction, and electrochemical tests. The results showed that in the 0.1 wt% NaCl salt spray environment, the corrosion weight loss rate of the alloy continuously decreased, whereas in the 1 wt% NaCl environment, it initially decreased and then increased. The corrosion products on the LA141 alloy surface were mainly composed of Mg(OH)2 and Li2CO3, along with minor amounts of MgCO3, LiOH, and Al2O3. Among these, the Li2CO3 in the corrosion product layer was stable and exhibited good corrosion resistance, contributing to the mitigation of substrate corrosion in low Cl− environments. However, when the Cl− concentration was high, this layer provided almost no protection to the substrate. In addition to Li2CO3, this study suggests that a small amount of Al2O3 also played a protective role at low Cl− concentrations. Nevertheless, when the concentration became excessively high, Al2O3 was destroyed, and Li2CO3 no longer provided significant protection.

As the core component of offshore wind power converter, the encapsulated silicone gel insulation material of insulated gate bipolar transistor (IGBT) module is prone to deterioration under the long-term action of ocean salt fog operation environment. In order to study the surface discharge of silicone gel in salt fog environment, this article designs a discharge experimental platform and measurement samples. Based on the partial discharge measurement results along the sample surface under square wave voltages, it is found that the number and phase of surface discharge of silicone gel under the salt fog environment are positively correlated with the voltage frequency. Meanwhile, the amplitude and the phase of discharge under the ocean standard condition show an increase of 54.4% and 32.8% compared with those under the condition without salt fog. Furthermore, the measurement finds that there is a special frequency-induced inflection point phenomenon of surface breakdown voltage at 15 kHz under the salt fog environment. Therefore, a mathematical model of the inflection point is established by further combining the influencing mechanism of salt fog ions and voltage frequency on the discharge, and the calculated inflection frequency of 16.99 kHz is close to the measurement result. The results of this article can provide theoretical support for the characteristics and mechanism of surface discharge of IGBT silicone gel insulation under salt fog environment.

Marine organisms such as barnacles rely on a complex underwater adhesive system, driven by self-assembly and intermolecular associations between cement proteins, for permanent attachment to a variety of surface types. In this study, we investigated the influence of environmental parameters on the self-assembly of recombinant cp19k, a key adhesive protein in Pollicipes pollicipes. Using TEM imaging, a low pH (4.0) and high salt concentration (600 mM NaCl) environment, mimicking P. pollicipes gland conditions, was identified to promote the formation of extended, needle-like fibrils by the cp19k protein. The β-amyloid nature of fibrils formed under these conditions and at high pH/low salt concentration was confirmed by Thioflavin T assay. Non-fibrillar cp19k adhered most effectively to hydrophilic and hydrophobic surfaces under low pH/low salt concentration conditions, while pre-formed fibrils retained their adhesion ability upon switching to a high pH/high salt concentration environment, which was designed to mimic the change in the protein environment upon secretion in vivo. These findings support the hypothesis that fibril formation occurs in the acidic, iso-osmotic gland of the barnacle, with delayed cement curing enabling fibril secretion for sustained adhesion of the organism. The study provides insight into the environmental sensitivity of cp19k structure–function dynamics and may support the design of bioinspired adhesives and biomaterials.

Aiming at the energy bottleneck of long-term operation of deep-sea equipment, this paper proposes a high-voltage self-powered power generation device with new Ag₁.₉₉₅Au₀.₀₀₅Te₀.₇S₀.₃ nano-thermoelectric materials as the core. Through Au doping and Te/S ratio control, the ZT value of the material reaches 1.2 at 300 K, and the thermal conductivity of the lattice decreases below 0.4 W/m·K; Adopt TA32 titanium alloy shell+vacuum potting +Inconel 718 metal seal to realize 30 MPa pressure resistance. Trapezoidal array layout and micro-channel water cooling design make the thermal efficiency of the system reach 85%, and the output power density is 320 W/m² and the conversion efficiency is 8.5% under the temperature difference of 10 K deep sea, which is 407% and 124% higher than that of the traditional Bi₂Te₃ system respectively. Integrating 1850 kWh Ferrous lithium phosphate energy storage and SiC inverter, the end-to-end energy utilization rate of 72 h system is 7.8%. After 500 h aging in 30 MPa and 3.5% NaCl environment, the power attenuation is only 4.7%, which verifies the stability and engineering application potential of the device under extreme conditions in deep sea.

Corrosion behavior of mechanically alloyed Cu-Zn and Cu-15Al-Zn alloys in NaCl environment

The main features of anodic potentiostatic treatment of austenitic stainless steel grade 12Cr18Ni10Ti (AISI 321 equivalent) in deep eutectic solvents ethaline and reline, which are eutectic mixtures of choline chloride with ethylene glycol and urea, respectively, have been studied. Based on cyclic voltammetry data, two anodic treatment potentials were selected: 0.2 V and 1.0 V in ethaline, and 2.0 V and 2.7 V in reline (vs. Ag quasi-reference electrode). The treatment duration was 150 minutes at a temperature of 250C. Scanning electron microscopy, surface micro-roughness measurements, and visual inspection confirmed that electropolishing of the steel occurred in all cases. Energy-dispersive X-ray microanalysis showed that electropolishing of 12Cr18Ni10Ti steel in ethaline and reline is accompanied by selective iron dissolution and some surface enrichment with carbon and oxygen. It was found that the electropolished surface exhibits enhanced resistance to corrosion damage in an aggressive 3% NaCl environment. In some cases, electropolishing slightly enhanced the electrocatalytic activity of the steel surface toward the anodic reaction coupled with cathodic hydrogen evolution in an aqueous alkaline medium.

Innovative application of electro-polymerized polyaniline for enhanced corrosion protection of aluminum alloys in chloride environments

The role of Nb2O5-based coatings in improving the corrosion resistance of friction stir welded 2198-T8 aluminium alloy in NaCl environment

This study explores the thermodynamic behavior and adsorption mechanism of Sclerocarya birrea leaf extract as a sustainable corrosion inhibitor for mild steel in simulated seawater (3.5 % NaCl). Corrosion inhibition efficiency and corrosion rate were assessed using the weight-loss method over a temperature range of 303-323 K. Thermodynamic parameters such as activation energy (Ea), enthalpy (ΔH°), entropy (ΔS°), and Gibbs free energy (ΔG°) were calculated to evaluate the adsorption nature and spontaneity of the inhibition process. Adsorption isotherms (Langmuir, Temkin, and Freundlich) were applied to model the inhibitor-metal surface interactions. The results show that increasing extract concentration enhanced inhibition efficiency, while increasing the temperature reduced it, indicating a temperature-sensitive physisorption process. Inhibited samples exhibited Ea values below 80 kJ/mol and positive ΔH° values, confirming endothermic adsorption. ΔG° values ranged from -6.653 to -21.765 kJ/mol, consistent with spontaneous physical adsorption. Among the isotherm models evaluated, the Temkin isotherm best described the adsorption behavior (R² = 0.932 at 303 K). These findings demonstrate that Sclerocarya birrea extract offers a viable, eco-friendly approach to corrosion mitigation through thermodynamically favorable physisorption.

Calcium ameliorates salt-related growth defects in plants. The objective of this study was to determine whether supplying calcium through a seed enrichment technique enhances the germinability and early growth of timothy (Phleum pratense L.) under saline conditions. For seed enrichment, timothy seeds were soaked in CaCl2 solutions at concentrations of 50 mM or 100 mM for 24 h at room temperature. Seeds treated with distilled water served as the control. Under distilled water conditions, germination rates among the seeds showed minimal variation, approximately 95% on average. However, in a 200 mM NaCl environment, the germination rate of the control seeds significantly decreased to 25%, while the germination rates of the Ca-enriched seeds remained high, exceeding 86%. Additionally, the Ca-enriched seeds germinated more quickly than the control seeds. When plants were grown with distilled water, the total dry matter weights did not differ significantly among the treatment types. However, under salt stress with 100 mM NaCl, the plants derived from Ca-enriched seeds thrived and exhibited higher dry matter weights compared to the control plants. The Ca-enriched seeds contained more soluble sugars and demonstrated higher catalase activity than the control seeds, and their corresponding plants accumulated less sodium under salt stress compared to the control plants. Seed enrichment is an effective technique for supplying calcium to timothy, and a concentration of 50 mM of CaCl2 in the treatment solution is sufficient to achieve salt tolerance.