Electrochemical Impedance Spectroscopy Tests Research Articles

Complementary corrosion protection of cast AlSi7Mg0.3 alloy using Zr-Cr conversion and polyacrylic/siloxane-silica multilayer coatings

Aluminium cast alloy AlSi7Mg0.3 is a lightweight metal commonly used in automotive, aeronautical and mechanical applications. It has good corrosion resistance but, under harsh operative conditions, would benefit from additional protection. In this study, a corrosion-protective multilayer coating system for AlSi7Mg0.3 based on hexafluoro-zirconated trivalent chromium coating (Zr-CrCC) and polyacrylic/siloxane-silica (PEHA-SS) coating was developed. The Zr-CrCC was formed by immersion of the substrate in a commercial conversion bath (SurTec® 650). PEHA-SS synthesis was based on organic precursors (2-ethylhexyl acrylate and [3-(methacryloyloxy)propyl]trimethoxysilane) and an inorganic precursor, tetraethyl orthosilicate. After deposition on AlSi7Mg0.3, each coating was first characterised individually, followed by the analysis of the multilayer using scanning electron microscopy and energy-dispersive X-ray spectroscopy. The adhesion of the coatings was evaluated with a cross-hatch cut test. The corrosion studies in sodium chloride solution using electrochemical impedance spectroscopy and salt spray testing showed that the multilayer system is superior to individual Zr-CrCC and PEHA-SS coatings. After 4 months in 0.1 M NaCl, the multilayer-coated samples exhibited the impedance at 10 mHz in the range of GΩ cm2, while scribed samples withstood the corrosion attack in a salt spray chamber for one week. Thus, albeit only about 100 nm thick, the Zr-CrCC deposited between the substrate and a 9-micrometre thick barrier sol-gel PEHA-SS coating acts as an active corrosion protection interlayer and contributes to the overall protectiveness of the multilayer system.

Glycine-Ti3C2Tx Hybrid Material Improves the Electrochemical Corrosion Resistance of a Water-Borne Epoxy Coating.

Improving the dispersibility and compatibility of nanomaterials in water-borne epoxy resins is an important means to improve the protection ability and corrosion resistance of coatings. In this study, glycine-functionalized Ti3C2Tx (GT) was used to prepare an epoxy composite coating. The results of Fourier transform infrared spectroscopy and X-ray diffraction showed that glycine was successfully modified. The scanning electron microscopy and transmission electron microscopy results showed that the aggregation of Ti3C2Tx was alleviated. Electrochemical impedance spectroscopy test results show that, after 60 days of immersion, GT coating still shows the best protection performance, and the composite coating |Z|f = 0.01 Hz is 3 orders of magnitude higher than that of the pure epoxy coating. This is mainly because, after adding glycine, the -COOH group on the surface of glycine binds to the -OH group on the surface of Ti3C2Tx, improving the aggregation of Ti3C2Tx itself. At the same time, the -NH group of glycine can also participate in the curing reaction of epoxy resin to strengthen the bonding strength between the coating and the metal. The good dispersion of GT in epoxy resin makes it fill the pores and holes left by epoxy resin curing and strengthen the corrosion resistance. The easy availability and green properties of glycine provide a simple and environmentally friendly method for the modification of Ti3C2Tx.

Degradation behavior and osteogenic activity of octacalcium phosphate modified MgO coatings on magnesium

To further enhance the corrosion resistance and osteogenic activity of the porous micro-arc oxidation (MAO) derived MgO ceramic coating on biomedical magnesium (Mg), octacalcium phosphate (OCP) layers with different microstucture were prepared on MAO coating by chemical deposition (CD) method to fabricate MAO/CD composite coatings. The in vitro degradation behaviors of MAO/CD-coated samples were evaluated by immersion in simulated body fluid (SBF) and electrochemical impedance spectroscopy (EIS) measurement. Their effects on in vitro MC3T3-E1 cell differentiation were investigated by examining alkaline phosphatase (ALP) activity and expression of main osteogenic-related genes. The in vitro immersion tests show that MAO/CD coatings rarely experience destruction and only micro-cracks occur after 96 h. EIS tests indicate that MAO/CD coatings slow down the degradation rate of Mg observably. In addition, MAO/CD coatings improve osteogenic differentiation of MC3T3-E1 cells compared to MAO coating, which is ascribed the lightened alkalization of the surrounding medium as well as up-regulated intracellular Ca2+. MAO/CD coating deposited in 2 h endows Mg the slowest degradation rate and excellent osteogenic differentiation induction activity.

Syntheses of diphenolic resin based anti-corrosion coating material and reinforce its performance through MWCNT-Ag and MWCNT-Ag/PANI nanofillers

In the present work, a novel anti-corrosion coating material was developed using diphenolic resin and multiwalled carbon nanotube (MWCNT) based nanofillers. In this concern, phenylmethylene diphenolic resin (PMD) and its 2-(4-methylbenzyl) oxirane derivative (PMDD) were synthesized using phenol and benzaldehyde. Silver-decorated MWCNT (MWCNT-Ag) and polyaniline (PANI) synthesized on MWCNT-Ag (MWCNT-Ag/PANI) were also fabricated and employed as filler materials to enhance the anti-corrosion performance of PMDD. The resins were analyzed by LC-MS and FT-IR, and the nanofillers were characterized using XRD, SAED, EDX, TEM, and XPS techniques. The synthesized PMD and PMDD and different weight percentages of fillers blended PMDD were coated on the mild steel (MS) sample using doctor blade method. The surface morphology and roughness of the coatings were examined by SEM and AFM analyses. The anti-corrosion ability of the coated samples was assessed by electrochemical impedance spectroscopy (EIS) and salt spray testing (SST). All the results showed an excellent anti-corrosion performance of PMDD by the incorporation of 0.2 wt% of MWCNT-Ag/PANI. Withstanding the 5 wt% NaCl salt spray atmosphere for about 144 h and >460 days in 3.5 wt% NaCl solution reflects its strong barrier property and long-term durability. The cross-linking of resins, blockade of defects by nanofiller and an additional protective layer developed by conductive PANI make the coating material efficient and durable in highly corrosion environments.

Selective laser melting of Hastelloy-X alloy and cerium oxide reinforced Hastelloy-X composite: Microstructural examination and corrosion behavior

The study investigated the microstructures and corrosion behaviors of Hastelloy X (HX) and HX reinforced by cerium oxide particles (HX-C) produced by selective laser melting (SLM) and compared to the wrought equivalent (HX-W). The aim was to eliminate hot cracking and investigate the HX's corrosion behavior in the presence of cerium oxide particles. The HX samples showed fine cellular and columnar solidification structures with uniform-size sub-cells and severe microcracking. Incorporating cerium oxide particles (1 wt%) resulted in finer and relatively equiaxed grains without microcracking. The HX-W alloy contained a micron-sized carbide (Mo-rich M6C type) within the matrix. The HX-C sample displayed higher porosities compared to the HX sample (1.8 % against 0.3 %). Potentiodynamic polarization and electrochemical impedance spectroscopy tests were conducted in a standard NaCl solution at temperatures of 25, 50, and 70 °C to assess the corrosion behavior of Hastelloy samples. The HX-C matrix showed superior corrosion resistance compared to the HX-W and HX samples due to its finer grain structure and stable passive layer formation. Cerium oxide particles were found to be efficient in decreasing hot cracking and improving corrosion resistance.

Selective extraction of molybdenum from an industrial powdery tungsten-molybdenum mixture scraps through ultrasonic-assisted electrochemical dissolution mechanism

Extraction and recovery of W and Mo from waste scraps hold significant importance for sustainable resource utilization and environmental protection. Ultrasonic-assisted leaching was demonstrated to be a clean and efficient method for metal dissolution and separation, and the research emphasis of this work was focused on ultrasonic electrochemical behaviors. The HNO3 leaching behaviors of W and Mo under conventional and ultrasonic-assisted processes from powdery W-Mo mixture scraps generated in the powder metallurgy process were investigated. It’s demonstrated that Mo and W can be selectively separated by the regulation of lixiviant concentration and temperature, in which the Mo is converted into the soluble ions (MoO22+) while the W particle is kept in original metallic state and covered with insoluble WO3·H2O. Experiment results indicated that 96.38 % Mo and 8.03 % W were rapidly leached in 2 mol/L HNO3 within ultrasonic-assisted leaching for 10 min at 25 °C, showing a favorable pre-separation effect. Phase transformation and microstructure evolution of the leaching residues under conventional and ultrasonic-assisted leaching processes were analyzed. It’s suggested that Mo can precipitate in the form of molybdenum oxide hydrates, covering the unreacted particle surfaces and further hindering the Mo leaching, especially at higher temperature. This unfavorable situation can be relieved by the introduction of ultrasonic cavitation effect. Importantly, the electrochemical dissolution behaviors of pure W, pure Mo, and W-Mo alloy sheets in HNO3 solution were compared employing the potentiodynamic polarization and electrochemical impedance spectroscopy testing to reveal the ultrasonic intensifying mechanism in this study. Eventually, the ultrasonic electrochemical intensifying mechanism can be referential for the efficient dissolution of metal-based scraps for resource recycling.

Properties and corrosion protection of polypyrrole prepared by electrochemical polymerization on aluminum

AbstractIn a one‐step procedure that did not require any surface preparation, polypyrrole (PPy) films doped with 3‐nitrosalicylic acid (3Nisa) became effectively electropolymerized on the aluminum substrate in aqueous solutions. Fourier transform infrared, scanning electron microscopy, and thermal gravimetric analysis were used to analyze the properties of PPy‐based films. Open circuit potential (OCP), electrochemical impedance spectroscopy, Tafel polarization, and salt spray tests were used to study the corrosion‐resistant efficiency of the coatings. The as‐prepared PPy films performed corrosion resistance on aluminum in the 3% NaCl solution. However, the PPy films prepared in the 0.01 m solution of 3Nisa showed the best protection ability on aluminum. The self‐healing characteristic of the PPy films was recorded by varying the potential in the OCP measurement. The findings indicate the potential of using 3‐nitrosalicylic acid‐doped PPy films for applications as anti‐corrosion coatings for aluminum.

Enhanced pseudocapacitance performance of conductive polymer in the presence of synthesized mesoporous MnO2@Zeolite-Y

In the current study, mesoporous MnO2@Zeolite-Y (MOZ) was synthesized using the ultrasonic method. Then, MOZ was utilized to enhance the electrochemical behavior of poly ortho-aminophenol (POAP) conducting polymer. The POAP/MnO2@Zeolite-Y (MOZ/POAP) composite was synthesized by electropolymerization over the zeolite-modified working electrode surface. To investigate and compare the electrochemical behavior of the synthesized materials, two electrodes of MOZ and MOZ/POAP were designed. Subsequently, the electrochemical characteristics of the two mentioned electroactive compounds were evaluated by galvanostatic charge/discharge (GCD), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) tests in a three-electrode setup. The comparison of the results revealed that the MOZ/POAP electrode had a more significant performance and recorded a specific capacitance (Cs) of 422 F g−1 at 1 A g−1 and cyclic stability of 97.2 % over 10,000 cycles. After verifying this electrode's remarkable efficacy, a symmetric supercapacitor of MOZ/POAP was designed and analyzed by CV and GCD techniques in a two-electrode system. This electrode revealed a Cs of 184 F g−1 at 1 A g−1, energy density of 12.02 Wh kg−1, power density of 275 W kg−1, and cyclic stability of 95.7 % over 10,000 cycles. This impressive performance was due to the presence of the manganese metal in MOZ and nitrogen and oxygen species of POAP in improving the pseudocapacitance behavior, POAP as a conductive chemical and mesoporous zeolite-Y for enhancing the electrical double-layer behavior of the electrode by providing a medium for electrochemical reactions.

A novel organic-inorganic two-dimensional filler for composite coating with excellent mechanical and high-pressure CO2 anti-corrosion performance

organic-inorganic composite fillers were successfully prepared by a simple one-pot film-like coating of poly (α-cyanoethyl acrylate) (PECA) on mica. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and thermogravimetric analysis (TG) were used to analyze the structure, morphology, and chemical composition of the organic-inorganic composite filler and pure mica in detail. The organic-inorganic composite filler was added to epoxy resin to prepare a composite coating with long-lasting anti-corrosion and wear-resistance properties. The composite coating was characterized by electrochemical impedance spectroscopy (EIS), high-pressure CO2 corrosion tests, friction performance tests, differential scanning calorimetry (DSC), and adhesion performance tests. The mechanical test results showed that the average wear quality of the EP/P30&M(8/2) composite coating prepared with the modified filler was reduced to 65.7 % of that of the EP/MICA(8/2) coating. The addition of the modified filler to the coating substantially improved the wear resistance and crosslinking of the composite coating, reduced the porosity, increased the density, and effectively improved the overall performance of the composite coating. The results of high-pressure CO2 corrosion tests in harsh environments and electrochemical impedance spectroscopy showed that the composite coating had excellent barrier capacity. After high-pressure CO2 corrosion tests, the EP/P20&M(9/1) composite coating still has a high impedance modulus value of 6.348 × 1010 Ω/cm2 at 0.01 Hz, which is 5 orders of magnitude higher than that of the pure epoxy coating, and showsed excellent long-lasting corrosion resistance in EIS tests. This study provides new ideas for the industrial application of mica and the preparation of long-lasting anti-corrosion coatings.

Seamlessly embedded microcapsules in self-repairing coatings: Improved compatibility and enhanced corrosion resistance recovery

Microcapsules, with polyether amine as the core repairing agent and polyether amine-cured epoxy as the shell, were prepared via the multiple emulsion polymerization and applied in an epoxy/polyether amine coating system on carbon steel surfaces. The microcapsules and the coating substrate have the same composition and are seamlessly connected by chemical bonds, akin to the direct injection of liquid healing agents into the substrate. When the repairing agent flows out, it will crosslink and cure with the epoxy groups in the substrate to achieve no difference self-repair. The characteristics of microcapsules were studied by scanning electron microscope (SEM), Fourier transform infrared (FTIR) and Thermal gravimetric (TG). The mechanical properties and corrosion resistance recovery of coatings loaded of coatings with different weight percentages of loaded microcapsules were investigated using tensile testing, electrochemical impedance spectroscopy (EIS) and neutral salt spray test (NSS). Results indicate that the 7 wt% microcapsules composite coating shows a 37.7 % increase in tensile strength and a 71.4 % increase in fracture toughness over pure epoxy coating. After immersing in saltwater for 7 days, the scratch sealing efficiency can reach 99.85 %. The coating system not only improved the compatibility between microcapsules and the substrate, but also enhanced the toughness of thermosetting brittle epoxy materials, giving it long-lasting anti-corrosion capability.

The influence of rolling on the corrosion and wear resistance of the MAO coating on ZM5 alloy

PurposeThe impact of rolling on the performance of micro arc oxidation (MAO) coatings on ZM5 alloy has been underreported. The purpose of this study is to explore the correlation between rolling and the failure mechanism of MAO coatings in greater depth.Design/methodology/approachThe influence of rolling on the corrosion and wear properties of MAO coating was investigated by phase structure, bond strength test (initial bond strength and wet adhesion), electrochemical impedance spectroscopy and wear test. The change of the surface electrochemical properties was studied by first principles analysis.FindingsThe results showed that the MAO coating on rolled alloy had better corrosion and wear resistance compared to cast alloy, although the structure and component content of two kinds of MAO coating are nearly identical. The difference in interface bonding between MAO coating and Mg substrate is the primary factor contributing to the disparity in performance between the two types of samples. Finally, the impact of the rolling process on MAO coating properties is explained through first-principle calculation.Originality/valueA comprehensive explanation of the impact of the rolling process on MAO coating properties will provide substantial support for enhancing the application of Mg alloy anticorrosion.Graphical abstract

Frequency varying heating strategy for lithium-ion battery rapid preheating under subzero temperature considering the limitation of on-board current

The electrical performance of lithium-ion battery gradually deteriorates with the temperature decrease. Alternating current (AC) heating is an efficient manner to improve the lithium-ion battery (LIB) discharge ability at low temperature. This paper proposes an effective method to quickly preheat battery under low temperature based on sinusoidal AC. An electrothermal coupled model is established to precisely characterize the battery electrical and thermal behavior characteristics. Subsequently, the impedance characteristics of large format prismatic LIB are investigated through electrochemical impedance spectroscopy testing. The amplitude and frequency of sine wave current exploited for battery pack heating are optimized at different temperatures and SOC based on the analysis of AC impedance. Finally, the sinusoidal AC heating for battery pack is achieved leveraging the designed full bridge inverter circuit-based heater and the heating efficiency with respect to different amplitudes and frequencies are comprehensively compared. On this basis, a frequency varying heating strategy with fixed amplitude considering the current limitation of hardware circuit is proposed. The experimental results show that the battery pack can be rapidly heated from −30 °C to 0 °C with the maximum average temperature rise rate of 3.78 °C/min, and the heating energy consumption rate is less than 0.27% SOC/°C with the proposed strategy. On this account, the battery pack discharge capacity under frigid environment can be distinctly enhanced based on the proposed heating strategy.

Electrochemical investigation of electrophoretically deposited graphene-oxide coating on AZ31 alloy prepared using in-house synthesized few-layer graphene-oxide nanosheets

Magnesium and its alloys possess low density and superior specific strength making it a potential structural metal to be used in different engineering fields. However, its proneness to corrosion limits its applications. In this novel study, an eco-friendly graphene-oxide coating was prepared on AZ31 magnesium alloy via electrophoretic deposition to enhance its anti-corrosion properties. Scanning electron microscopy coupled with energy dispersive spectroscopy, atomic force microscopy, and scratch test were adopted to investigate surface morphology, roughness, chemical composition, and adherence of the coating. The corrosion behaviour of graphene-oxide coated alloy was studied using potentio-dynamic polarization and electrochemical impedance spectroscopy tests in 3.5 wt% NaCl and Borate Buffer solutions. The obtained results demonstrate that the coating developed on AZ31 alloy is smooth and adherent with the hardness of the as-deposited coating measuring as high as 6.0 GPa. In addition, the electrochemical corrosion behaviour studies revealed that the coating significantly increased the corrosion potential (Ecorr) of the alloy towards more noble values (−0.65 V < Ecorr < −0.35 V), with the coated alloys possessing a charge transfer resistance nearly two orders of magnitude greater than their non-coated counterparts. Consequently, the corrosion rate of the coated alloy decreased substantially, indicating that the coating exhibits exceptional corrosion resistance (0.045–0.09 mm/a in 3.5 wt% NaCl and 0.002–0.006 mm/a in Borate Buffer). These findings challenge the conventional beliefs that graphene exhibits strong cathodic behaviour towards anodic materials such as AZ31 alloy. Thus, the outcomes not only have the potential to revolutionize the advancement of graphene-oxide coatings for corrosion resistance but could also possibly expand AZ31 alloy’s applications in the aerospace and automotive sectors.

Improvement of corrosion resistance of 7075 aluminum alloy by ceria coating modified by zinc oxide nanoparticles

Purpose This paper aims to investigate the corrosion resistance of two types of coatings – one is ceria sol coating and the other is ceria sol coating modified by ZnO nanoparticles on 7075 aluminum alloy in 3.5% NaCl solution. Design/methodology/approach Aluminum alloys were dipped into ceria sol and ceria sol modified by ZnO nanoparticles separately and removed after 10 min from the solutions and dried at 110°C for 30 min and heated at 500 °C for 30 min to form the coatings. The coatings have been characterized by using field emission scanning electron microscopy (FE-SEM), electrochemical impedance spectroscopy (EIS), X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS). The EIS tests were performed in a corrosive solution of 3.5% NaCl. Findings The results showed that the coating of ceria sol modified by ZnO nanoparticles has higher corrosion resistance than the ceria sol coating and the bare sample. Also, the best efficiency is related to aluminum sample immersion after 1 h in NaCl corrosive solution for coating modified by ZnO nanoparticles. Originality/value In this research, the modification of ceria sol coating by ZnO nanoparticles had an effect on improving the corrosion behavior of aluminum alloy. It is also understood that modification of coatings is an effective parameter on corrosion resistance.

Effect of hydrostatic pressure on the anodic dissolution process of X80 steel

Based on the fact that hydrostatic pressure affects chemical potentials of reaction species and the structure evolution of electric double layer (EDL), the authors propose a generalized-BV equation to analyze the anodic dissolution process of X80 steel in deep-sea environment. Combined with the results of potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests, the following conclusions can be drawn: hydrostatic pressure can compress the electric double layer non-uniformly. The CHCD (CD: capacitance of diffused layer; CH: capacitance of compact layer) value increases first and then decreases with increasing hydrostatic pressure and reaches its maximum at 15 MPa, which is sure to influence the difference in electrical potential that drives chemical reaction at interface. Ultimately, the anodic dissolution current increases and then decreases with rising hydrostatic pressure at the same anodic polarized potential. Besides, low hydrostatic pressure may contribute to forming a dense corrosion product film and inducing a good inhibiting effect on further dissolution of X80 steel; However, when the hydrostatic pressure exceeds the critical value of 20Mpa, too high anodic dissolution rate along with promoted Cl− adsorption will deteriorate the protection performance of corrosion product film, and exacerbate local corrosion process.

A new strategy to improve the anticorrosion performance of waterborne polyurethane coating on AA7075

In this study, Ce3+ functionalised halloysite nanotubes (HNTs) were prepared, and their impact on the anticorrosion properties of waterborne polyurethane (WPU) coating on 7075 aluminium alloy (AA7075) was investigated. HNTs were grafted by 3-aminopropyltriethoxysilane (APTES) to enhance Ce3+ loading, which was confirmed by X-ray diffraction (XRD) and Fourier-transform infrared (FT-IR) spectrum. The release behaviour of Ce3+ from HNTs was tested by inductively coupled plasma optical emission spectrometry (ICP-OES), and the inhibition effect of Ce3+-loaded HNTs for AA7075 was tested by polarization plots. The anticorrosion property of WPU doped with Ce3+-loaded HNTs was investigated by electrochemical impedance spectroscopy (EIS) and pull-off adhesion test. The results showed that APTES modification improved the Ce3+ loading amount on HNTs, and Ce3+ acts as an effective cathodic inhibitor for AA7075. After soaking for 40 days, the |Z|0.01Hz of Ce-HNTs/WPU was two orders of magnitude higher than that of pure WPU, while wet put-off adhesion was higher than pure WPU.

Corrosion Behavior of 30 ppi TAD3D/5A05Al Composite in Neutral Salt Spray Corrosion

This study created ceramic preforms with a 3D network structure (TAD3D) by using treated aluminum dross (TAD) and kaolin slurry, with 30 ppi polyurethane foam as a template via the sacrificial template method. TAD3D/5A05Al composites were then produced via pressureless infiltration of 5A05Al aluminum alloy into TAD3D. The corrosion behavior and resistance of TAD3D/5A05Al in salt spray were assessed via neutral salt spray corrosion (NSS), scanning electron microscopy (SEM), potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS) tests. The results showed that after 24 to 360 h of NSS corrosion, the corrosion of the 5A05 matrix was primarily pitting, with pits expanding and deepening over time, and showing a tendency to interconnect. The main corrosion products were MgAl2O4, Al(OH)3, and Al2O3. As corrosion progressed, these products increased and filled cracks, pits, and grooves at the composite interface on the material’s surface. Corrosion products transferred to the grooves at the composite interface and grew on the ceramic surface. Corrosion products on the ceramic framework and the Al matrix can form a continuous passivation film covering the composite surface. PDP and EIS results indicated that the composite’s corrosion resistance decreased by 240 h but increased after that time. After 240 h, the surface passivation film can weaken corrosion effects and enhance the composite’s resistance, although it remained weaker than that of the uncorroded samples. Additionally, grooves at the composite interface deepened over time, with loosely structured corrosion products inside, potentially leading to severe localized corrosion.

Mussel-inspired synergistic anticorrosive coatings for steel substrate prepared basing on fully bio-based epoxy resin and biomass modified graphene nanoparticles

Traditional epoxy anticorrosive coatings face challenges such as reliance on non-renewable petroleum resources, environmental pollution, brittleness and poor long-term anticorrosion performance. In this work, the bio-based coatings are fabricated to address the above issues by using epoxidized soybean oil (ESO) as the resin matrix, tannic acid (TA) as curing agent and modified graphene (TH-rGO) nanoparticles as functional fillers. Inspired by mussels, the phenolic hydroxyl groups of TA are fully used, so that the coating has in-situ adhesion to the steel substrate. The TH-rGO nanoparticles, formed by grafting L-histidine onto GO and reducing them with TA, exhibit favourable dispersion stability in epoxy coating suspension. And the prepared coating films exhibit favourable tensile ductility with the strain of higher than 14%, thermostability with the initial degradation temperature above 300 ℃, as well as impervious performance and antimicrobial activity. Furthermore, the results of electrochemical impedance spectroscopy test demonstrate that after 8 weeks of immersion in simulated seawater, the low-frequency impedance modulus at 0.01 Hz of the nanocomposite coating with optimal nanoparticles content reaches 4.42×109 Ω cm2, resulting in favourable durability of anticorrosion performance. This study presents a facile fabrication approach of bio-based epoxy coatings with durable anticorrosion performance, demonstrating potential for industrial applications.

Synthesis and evaluation of a novel pyridinyl thiazolidine derivative as an antioxidant and corrosion inhibitor for mild steel in acidic environments

A new synthesized (Z)-2-((3,5-dichloropyridin-2-yl)imino)thiazolidin-4-one (DICPT) was evaluated as an antioxidant and a corrosion inhibitor for mild steel (M.STL) in a 0.5 M HCl solution. The antioxidant activity of newly synthesized DICPT was screened using a DPPH assay, and the results showed that DICPT has good antioxidant activity. Electrochemical assessments were conducted utilizing potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS). A new compound, DICPT, was synthesized, and its chemical structure was established and validated through various spectroscopic techniques, including including infrared (FTIR), nuclear magnetic resonance (NMR), and mass spectroscopy. PDP measurements revealed DICPT to be a mixed-type inhibitor. Charge transfer resistance (Rct) increased when inhibitor concentrations increased, according to EIS tests. The inhibition efficiency (%I) showed a corresponding rise with increasing inhibitor concentration, peaking at approximately 94.2 % at 3 × 10−5 M. Langmuir’s adsorption isotherm was found to govern the preferred adsorption mode of DICPT molecules onto the metal surface. UV–visible spectra confirmed the chemical interaction between DICPT molecules and the M.STL surface. AFM investigation indicated the formation of a protective layer on the metal surface, shielding it from corrosive environmental factors. Quantum chemical calculations were compared to experimental results to learn more about how corrosion is stopped and how well it works. Our study demonstrates the innovation of DICPT as a dual-function compound, offering both antioxidant and corrosion protection properties. This research contributes to the development of effective corrosion inhibitors for industrial applications.

The effect of copper doping in α-MnO2 as cathode material for aqueous Zinc-ion batteries

Copper-doped Manganese Dioxide has been synthesised through a simple hydrothermal method at different doping levels. The synthesised materials have been characterized by X-ray diffraction (XRD), and scanning electron microscopy (SEM) to determine the composition, structure, and morphology. All the Cu doped MnO2 are found to be single phased. Their electrochemical properties as cathode for Zinc-ion batteries are studied by cyclic voltammetry (CV), galvano-static charge / discharge (GCD) and electrochemical impedance spectroscopy (EIS), using 3 M ZnSO4 + 0.3 MnSO4 solution as the electrolyte. 3.8% Cu doped MnO2 has shown the highest initial capacity of 379.5 mAh g−1 at 0.02 A·g−1, and 304.4 mA h g−1 at 0.5 A g−1, but experienced fast fading with a poor capacity retention of 56.8% after 100 cycles. 7.4% Cu doping gives lower capacity, while 5.9% doping shows a higher discharging capacity (320.0 mAh·g−1 at 0.02 A·g−1 and 269.3 mAh·g−1 at 0.5 A·g−1) and improved stability (85.8% capacity retention after 100 cycles), better than non-doped MnO2 electrode (284.4 mAh g−1 at 0.02 A g−1 and 252.1 mAh·g−1 at 0.5 A g−1, capacity retention 76.7%). The samples show satisfactory capacity and rate capability while the cycling stability is not ideal, which may relate to the needle like morphology and nanoscale particle size. CV tests revealed that the electrochemical process is mainly diffusion controlled. The zinc ion diffusion coefficient is tested to be in the range of 10−12 cm2·s−1 from both CV and EIS tests and showed the same trend in their electrochemical capacity. Doping of Copper in MnO2 reduced the polarization on electrode, improved the electrochemical reversibility, as evidenced by the reduction of the redox peak potential difference from 0.31 to 0.24 V at 1.1 mV·s−1, and from 0.45 V to 0.31 V at 5 mV·s−1. Whilst the cell resistance of non-doped MnO2 increased from 1.78 Ω to 7.39 Ω after cycling, the cell resistances of all Cu-doped cathodes reduced, indicating improved electronic conductivities after cycling. These results indicate that Cu-doping is effective to increase the conductivity of the materials, reduce the polarization during charge and discharge, and improve the cycling stability of MnO2 cathode.