Biomimicking covalent organic frameworks nanocomposite coating for integrated enhanced anticorrosion and antifouling properties of a biodegradable magnesium stent

The utilization of biodegradable magnesium (Mg) alloys in the fabrication of temporary non-vascular stents is an innovative trend in biomedical engineering. However, the heterogeneous degradation profiles of these biomaterials, together with potential bacterial colonization that could precipitate infectious or stenotic complications, are critical obstacles precluding their widespread clinical application. In pursuit of overcoming these limitations, this study applies the principles of biomimicry, particularly the hydrophobic and anti-fouling characteristics of lotus leaves, to pioneer the creation of nanocomposite coatings. These coatings integrate poly-trimethylene carbonate (PTMC) with covalent organic frameworks (COFs), to modify the stent's surface property. The strategic design of the coating's topography, porosity, and self-polishing capabilities collectively aims to decelerate degradation processes and minimize biological adhesion. The protective qualities of the coatings were substantiated through rigorous testing in both in vitro dynamic bile tests and in vivo New Zealand rabbit choledochal models. Empirical findings from these trials confirmed that the implementation of COF-based nanocomposite coatings robustly fortifies Mg implantations, conferring heightened resistance to both biocorrosion and biofouling as well as improved biocompatibility within bodily environments. The outcomes of this research elucidate a comprehensive framework for the multifaceted strategies against stent corrosion and fouling, thereby charting a visionary pathway toward the systematic conception of a new class of reliable COF-derived surface modifications poised to amplify the efficacy of Mg-based stents. STATEMENT OF SIGNIFICANCE: Biodegradable magnesium (Mg) alloys are widely utilized in temporary stents, though their rapid degradation and susceptibility to bacterial infection pose significant challenges. Our research has developed a nanocomposite coating inspired by the lotus, integrating poly-trimethylene carbonate with covalent organic frameworks (COF). The coating achieved self-polishing property and optimal surface energy on the Mg substrate, which decelerates stent degradation and reduces biofilm formation. Comprehensive evaluations utilizing dynamic bile simulations and implantation in New Zealand rabbit choledochal models reveal that the coating improves the durability and longevity of the stent. The implications of these findings suggest the potential COF-based Mg alloy stent surface treatments and a leap forward in advancing stent performance and endurance in clinical applications.

Multiphase Interfacial Regulation Based on Hierarchical Porous Molybdenum Selenide to Build Anticorrosive and Multiband Tailorable Absorbers

Electromagnetic wave (EMW) absorbing materials have an irreplaceable position in the field of military stealth as well as in the field of electromagnetic pollution control. And in order to cope with the complex electromagnetic environment, the design of multifunctional and multiband high efficiency EMW absorbers remains a tremendous challenge. In this work, we designed a three-dimensional porous structure via the salt melt synthesis strategy to optimize the impedance matching of the absorber. Also, through interfacial engineering, a molybdenum carbide transition layer was introduced between the molybdenum selenide nanoparticles and the three-dimensional porous carbon matrix to improve the absorption behavior of the absorber. The analysis indicates that the number and components of the heterogeneous interfaces have a significant impact on the EMW absorption performance of the absorber due to mechanisms such as interfacial polarization and conduction loss introduced by interfacial engineering. Wherein, the prepared MoSe2/MoC/PNC composites showed excellent EMW absorption performance in C, X, and Ku bands, especially exhibiting a reflection loss of - 59.09 dB and an effective absorption bandwidth of 6.96 GHz at 1.9 mm. The coordination between structure and components endows the absorber with strong absorption, broad bandwidth, thin thickness, and multi-frequency absorption characteristics. Remarkably, it can effectively reinforce the marine anticorrosion property of the epoxy resin coating on Q235 steel substrate. This study contributes to a deeper understanding of the relationship between interfacial engineering and the performance of EMW absorbers, and provides a reference for the design of multifunctional, multiband EMW absorption materials.

An ecofriendly coaxial antibacterial and anticorrosion nanofiber pullulan-ethyl cellulose embedded with carvacrol coating for protection against marine corrosion

Coaxial electrospun coatings with antibacterial and anticorrosion properties have a marked potential to protect against corrosion in marine environments. Ethyl cellulose is a promising biopolymer for corrosion caused by microorganisms owing to its high mechanical strength, nontoxicity, and biodegradability. In this study, a coaxial electrospun coating loaded with antibacterial carvacrol (CV) in the core and anticorrosion pullulan (Pu) and ethyl cellulose (EC) as a shell layer was successfully fabricated. The formation of core-shell structure was confirmed using transmission electron microscopy. Pu-EC@CV coaxial nanofiber had small diameters, uniform distribution, smooth surface, strong hydrophobicity, and no fractures. Electrochemical impedance spectroscopy was used to analyze corrosion of the electrospun coating surface in a medium containing bacterial solution. The results indicated significant corrosion resistance of the coating surface. In addition, the antibacterial activity and mechanism of coaxial electrospun were studied. The Pu-EC@CV nanofiber coating exhibited excellent antibacterial properties by effectively increasing the permeability of cell membranes and killing bacteria, as determined by plate counts, scanning electron microscopy, cell membrane permeability, and the activity of alkaline phosphatase. In summary, the coaxial electrospun pullulan-ethyl cellulose embedded with CV coating can be used as antibacterial and anticorrosion materials and may have potential applications in the field of marine corrosion.

Anticorrosion performance assessment of silane-modified chitosan/epoxy primer coatings on mild steel in saline environment using computational simulation techniques

The anticorrosion performance of silane-modified chitosan/epoxy primer coatings was evaluated using quantum chemical computations (QCC) and molecular dynamics simulation (MDS) techniques. The objective was to appraise the molecular/atomistic level performance of silane-modified chitosan/epoxy primer coating system on mild steel in saline water to be able to design robust anticorrosion epoxy nanocomposite primer coating for marine application. The QCC showed that quantum parameters for (3-aminopropyl) trimethoxy silane-modified chitosan nanocluster (AMCN) are optimum and therefore correspond to high corrosion protective capability. The adsorption energies (E_ads) for AMCN/epoxy, tetraethoxysilane-modified chitosan/epoxy, chitosan-modified epoxy, and unmodified epoxy coatings were found to be - 3094.65, - 2,630.00, - 2,305.77, and - 1,189.33 kcal/mol, respectively. The high negative value of E_ads indicates the coating molecules interacted and adsorbed strongly on the mild steel surface. Hence, AMCN/epoxy coating is potentially most corrosion-resistant than the others. Further, it is established that shorter bond length corresponds to higher bond strength and therefore indicates chemical interaction. Thus, the radial distribution function showed the bond lengths between atoms of the AMCN and mild steel surfaces were shorter than those of other molecules. Overall, AMCN/epoxy coating molecules possess good anticorrosion properties and therefore would perform well if deployed for service in saline environments.

A Gallic Acid-Doped Polypyrrole Coating with Anticorrosion and Antibacterial Properties on Magnesium Alloy

Magnesium (Mg) and its alloys exhibit great potential as biomedical implants due to their excellent biological performance and mechanical properties. However, their clinical applications are limited by their rapid corrosion rate in physiological media and the risk of implant-associated infections. Herein, a multifunctional polypyrrole/gallic acid (PPy/GA) coating was deposited on an AZ31 Mg alloy substrate by electrochemical polymerization to enhance simultaneously the corrosion resistance and antibacterial properties of the Mg alloy. Electrochemical and in vitro immersion tests demonstrated that the anticorrosion performance of the Mg alloy was significantly improved with the PPy/GA coating. The thiazolyl blue tetrazolium bromide (MTT) assay and live-dead staining of L929 cells indicated the acceptable cytocompatibility of the PPy/GA coating. In vitro antibacterial tests revealed a remarkable enhancement in the antibacterial activity of the PPy/GA-coated Mg alloy compared with the PPy-coated material and the bare Mg alloy.

Preparation of photoluminescent and anticorrosive epoxy paints immobilized with nanoscale graphene from sugarcane bagasse agricultural waste

Sugarcane bagasse agricultural waste has been one of the most common solid pollutants worldwide. Thus, introducing a simple method to convert sugarcane bagasse into value-added materials has been highly significant. Herein, we develop a simple and green strategy to reprocess sugarcane bagasse as a starting material for the preparation of graphene oxide nanosheets toward the preparation of novel photoluminescent, hydrophobic, and anticorrosive epoxy nanocomposite coatings integrated with lanthanide-doped aluminate nanoparticles. Environmentally friendly graphene oxide (GO) nanostructures were provided by a single-step preparation procedure from sugarcane bagasse (SCB) agricultural waste using ferrocene-based oxidation under muffled conditions. The oxidized SCB nanostructures were applied as a drier, anticorrosion, and crosslinking agent for epoxy coatings. Different concentrations of pigment phosphor were applied onto the epoxy coating. The generated epoxy-graphene-aluminate (EGA) paints were then coated onto mild steel. The hydrophobic properties and hardness as well as resistance to scratch of the EGA paints were examined. The transparency and colorimetric screening of the EGA nanocomposite paints were determined by the absorption spectral analysis and CIE Lab parameters. The luminescent translucent paints demonstrated a bright green emission at 520 nm when excited at 372 nm. The anticorrosion properties of the painted steel submerged in NaCl_(aq) were inspected by the electrochemical impedance spectral (EIS) method. The EGA paints with phosphor (11% w/w) exhibited the most distinct anti-corrosion properties and long-persistent luminescence. The produced paints displayed high durability and photostability.

Metal organic frameworks (MOFs) as multifunctional nanoplatform for anticorrosion surfaces and coatings

Corrosion of metallic materials is a long-standing problem in many engineering fields. Various organic coatings have been widely applied in anticorrosion of metallic materials over the past decades. However, the protective performance of many organic coatings is limited due to the undesirable local failure of the coatings caused by micro-pores and cracks in the coating matrix. Recently, metal organic frameworks (MOFs)-based surfaces and coatings (MOFBSCs) have exhibited great potential in constructing protective materials on metallic substrates with efficient and durable anticorrosion performance. The tailorable porous structure, flexible composition, numerous active sites, and controllable release properties of MOFs make them an ideal platform for developing various protective functionalities, such as self-healing property, superhydrophobicity, and physical barrier against corrosion media. MOFs-based anticorrosion surfaces and coatings can be divided into two categories: the composite surfaces/coatings using MOFs-based passive/active nanofillers and the surfaces/coatings using MOFs as functional substrate support. In this work, the state-of-the-art fabrication strategies of the MOFBSCs are systematically reviewed. The anticorrosion mechanisms of MOFBSCs and functions of the MOFs in the coating matrix are discussed accordingly. Additionally, we highlight both traditional and emerging electrochemical techniques for probing protective performances and mechanisms of MOFBSCs. The remaining challenging issues and perspectives are also discussed.

Control of chloride ion corrosion by MgAlOx/MgAlFeOx in the process of chloride deicing

Adding a corrosion inhibitor to the chloride deicing salt can prevent the corrosion and pollution of Cl^-, which is very important. Layered double hydroxide (LDHs), calcined at high temperature is used as adsorbents to remove various anionic contaminants, and it can reduce the freezing point of solution after adsorbing anions. Therefore, this paper reports the use of calcined LDHs as corrosion inhibitors in deicing salts, which are denoted as MgAlO_x or MgAlFeO_x depending on the preparation element. By analyzing the removal efficiency and the freezing point of MgAlO_x and MgAlFeO_x to Cl^-, the feasibility of the study was determined. Resulted that the removal efficiency to Cl^- of MgAlFeO_x at low temperature (0 ± 2 °C) and room temperature (25 ± 2 °C) was higher than that of MgAlO_x, reaching 39.4% and 85.60%, respectively. And the freezing point of MgAlFeO_x was lower than that of MgAlO_x, the value was -12.0 °C. At the same time, we also found that CaCl₂-MgAlO_x and CaCl₂-MgAlFeO_x significantly reduced the corrosion of carbon steel and concrete compared with chloride salts, and CaCl₂-MgAlFeO_x had the lowest corrosion degree. Hence, MgAlFeO_x was chosen as the corrosion inhibitor in chloride deicing salt. The metal molar ratio, synthesis temperature, and calcination temperature for preparation of MgAl/MgAlFe-LDHs were determined by XRD and TG-DSC analysis that were 9/2/1, 120 °C, and 500 °C, respectively. Characterization methods such as Zeta, XRD, XPS, BET, and SEM were used to study in detail the characteristic changes of MgAlFe-LDHs and MgAlFeO_x after Fe³⁺ was added, and the mechanism of corrosion inhibitors was further determined that was achieved by adsorption and neutralization.

Development of silica-coated rare-earth doped strontium aluminate toward superhydrophobic, anti-corrosive and long-persistent photoluminescent epoxy coating

Long-persistent phosphorescent smart paints have the ability to continue glowing in the dark for a prolonged time period to function as energy-saving products. Herein, new epoxy/silica nanocomposite paints were prepared with different concentrations of lanthanide-doped aluminate nanoparticles (LAN; SrAl₂ O₄ : Eu²⁺ , Dy³⁺ ). The LAN pigment was firstly coated with SiO₂ utilizing the heterogeneous precipitation technique to provide LAN-encapsulated between SiO₂ nanoparticles (LAN@SiO₂ ). The epoxy/silica/lanthanide-doped aluminate nanoparticles (ESLAN) nanocomposite paints were coated on steel. The prepared ESLAN paints were studied by transmission electron microscope (TEM), infrared spectra (FTIR), scanning electron microscope (SEM), X-ray fluorescence analysis (XRF), and energy-dispersive X-ray spectra (EDS). The transparency and coloration properties of the nanocomposite coated films were explored by CIE Lab parameters and photoluminescence spectra. The ultraviolet-induced luminescence properties of the transparent coated films demonstrated greenish phosphorescence at 518 nm upon excitation at 368 nm. Both hardness and hydrophobic activities were investigated. The anticorrosion activity of the nanocomposite films coated onto mild steel substrates immersed in NaCl_(aq) (3.5%) was studied by the electrochemical impedance spectral (EIS) analysis. The silica-containing coatings were monitored to exhibit anticorrosion properties. Additionally, the nanocomposite films with LAN@SiO₂ (25%) exhibited the optimized long-lasting luminescence properties in the dark for 90 minutes. The nanocomposite films showed highly reversible and durable long-lived phosphorescence.

Benzimidazole loaded β-cyclodextrin as a novel anti-corrosion system; coupled experimental/computational assessments

HYPOTHESIS

Silane (sol-gel)-based coatings have been introduced as an eco-friendly system for reducing the metals' corrosion in NaCl solutions. However, due to the lack of active protection property for this type of coatings, their modification is totally recommended for achieving durable protection properties. The present study introduces Beta-cyclodextrin (β-CD) as a novel/effective organic nano-container for Benzimidazole (BM) encapsulation to obtain reliable active protection property via a controlled-release property.

EXPERIMENTS

The chemical structure of the β-CD-BM macromolecule was explored by Fourier-transform infrared spectroscopy (FT-IR), X-Ray diffraction (XRD), and Ultraviolet-visible spectroscopy (UV-Vis). Besides, the Electrochemical Impedance Spectroscopy (EIS) and polarization (potentiodynamic) tests were carried out for investigating the inhibition impacts of the constructed containers. The exposed and unexposed samples' surfaces were analyzed by Field Emission Scanning Electron Microscope (FE-SEM), Energy Dispersive Spectroscopy (EDS)/mapping, and Grazing incidence X-ray diffraction (GIXRD) experiments. Also, the EIS test was conducted over the Silane-based composite film (SCF) for analyzing the anti-corrosion performance of the constructed composites.

FINDINGS

The EIS achievements demonstrated that by the addition of β-CD-BM complexes to the saline solution, the mild steel corrosion was mitigated by about 84%. The EIS results also displayed that the total resistance of the modified composite was enhanced from 5540 Ω.cm² to 10967 Ω.cm² and the intact coating provided a total resistance of 80254 Ω.cm². The dispersion-corrected Density Functional Theory (DFT)-D explorations ascertained the inclusion capacity of benzimidazole inside the β-CD. The Monte Carlo/Molecular Dynamics (MC/MD) calculations strongly affirmed the adsorption of BM and β-CD-BM over the substrate.

Chitosan-sodium alginate-based coatings for self-strengthening anticorrosion and antibacterial protection of titanium substrate in artificial saliva

A self-strengthening coating with silver nanoparticles (Ag NPs) doped chitosan (CHI) and sodium alginate (SA) polyelectrolytes was constructed on the surface of polydopamine (PDA) coated Ti substrate by a layer-by-layer assembly method. The PDA coating exhibited an excellent bond with Ti substrate, and also can uniformly deposit Ag NPs via a mild method without introducing any exogenous reductant. The CHI coating was assembled through a spin-coating method for controlling Ag⁺ release. The SA was introduced to enhance the anticorrosion performance by forming calcium alginate (CA) in a corrosive medium. The corrosion protection was investigated with electrochemical impedance spectroscopy and polarization curves tests in fluorine-containing artificial saliva. During immersion, the charge-transfer resistance and the protection efficiency (ŋ) presented a continuous increase with the immersion time, demonstrating that this coating possessed a remarkable self-strengthening capability, and the compositions of the outermost film changed from SA to CA with the Ca²⁺ cations of the corrosive medium as a crosslinker by SEM and EDS analysis. Furthermore, the ŋ remained up to 96.8% after immersion of 30 days, and then the coating also displayed a distinct inhibition zone on S. mutans. These results prove this coating possesses an excellent anticorrosion performance and antibacterial property.

Organic carbon dot coating for superhydrophobic aluminum alloy surfaces

A novel fluorine-free and silicon-free superhydrophobic aluminum alloy (treated-Al) is fabricated by chemical etching using hydrochloric acid and hydrogen peroxide and modified with an organic carbon dot (OCD) coating. The water contact angle (CA) of the treated-Al surface increases with the OCD concentration. When etched aluminum (etched-Al) is modified with 0.5 mg/ml OCDs, a CA of 161.4° is achieved, which indicates good nonwettability. SEM results verify that porous microstructures with cavities are uniformly distributed on the surface of etched-Al, in contrast to the bare aluminum alloy, which forms a primary rough structure. After treatment with 0.5 mg/ml OCDs, a nanoparticle coating is dispersed on the rough structures of treated-Al-0.5, which can trap air and make a water droplet essentially rest on a layer of air. The treated-Al-0.5 material has good self-cleaning properties and can sweep away contaminants at both 20 and 0°C. The Ecorr and Icorr of treated-Al-0.5 are - 0.56 V and 2.82 × 10^-6 A/cm², respectively, which shows good anticorrosion performance.

Organic carbon dot coating for superhydrophobic aluminum alloy surfaces

A novel fluorine-free and silicon-free superhydrophobic aluminum alloy (treated-Al) is fabricated by chemical etching using hydrochloric acid and hydrogen peroxide and modified with an organic carbon dot (OCD) coating. The water contact angle (CA) of the treated-Al surface increases with the OCD concentration. When etched aluminum (etched-Al) is modified with 0.5 mg/ml OCDs, a CA of 161.4° is achieved, which indicates good nonwettability. SEM results verify that porous microstructures with cavities are uniformly distributed on the surface of etched-Al, in contrast to the bare aluminum alloy, which forms a primary rough structure. After treatment with 0.5 mg/ml OCDs, a nanoparticle coating is dispersed on the rough structures of treated-Al-0.5, which can trap air and make a water droplet essentially rest on a layer of air. The treated-Al-0.5 material has good self-cleaning properties and can sweep away contaminants at both 20 and 0°C. The Ecorr and Icorr of treated-Al-0.5 are - 0.56 V and 2.82 × 10^-6 A/cm², respectively, which shows good anticorrosion performance.

Immobilization of bioactive complex on the surface of magnesium alloy stent material to simultaneously improve anticorrosion, hemocompatibility and antibacterial activities

Magnesium alloy represents one of the most potential biodegradable vascular stent materials due to its good biodegradability, biocompatibility and suitable mechanical properties, whereas the rapid degradation in physiological environment and the limited biocompatibility remain the challenges. In this study, graphene oxide (GO) was firstly functionalized by chitosan (GOCS), followed by loading zinc ions and propranolol to obtain GOCS@Zn/Pro complex, which was finally covalently immobilized on the self-assembled modified magnesium alloy surface to enhance the corrosion resistance and biocompatibility. The multi-functional coating can significantly improve the corrosion resistance and reduce the degradation rate of the magnesium alloy. Furthermore, the coating can significantly inhibit platelet adhesion and activation, reduce hemolysis rate, prolong activated partial thromboplastin time (APTT), and thus improve the blood compatibility of the magnesium alloy. In addition, the modified magnesium alloy can not only significantly promote the endothelial cell adhesion and proliferation, up-regulate the expression of vascular endothelial growth factor (VEGF) and nitric oxide (NO), but also endow the materials with good antibacterial properties. Therefore, the method of the present study can be used to modify magnesium alloy stent materials to simultaneously enhance corrosion resistance and blood compatibility, promote endothelialilization, and inhibit infections.

Encapsulating polyaniline within porous MIL-101 for high-performance corrosion protection

The metal corrosion possesses a serious threat to the safety and loss of property. The anticorrosion study on metal-organic frameworks (MOFs) remains rarely reported. Therefore, it is desirable to build MOFs-based anticorrosion coating with long-term corrosion resistance. Herein, we prepared a novel MOF-polymer anticorrosion composite PANI@MIL-101 by encapsulating polyaniline (PANI) within the pores of MIL-101 with in-situ polymerization of aniline monomer. The N₂ adsorption-desorption and transmission electron microscopy (TEM) of PANI@MIL-101 illustrate that PANI is successfully encapsulated in the pores of MIL-101 with in-situ polymerization. PANI@MIL-101 was dispersed in epoxy resin (EP) to prepare anti-corrosive coatings. The Tafel potentiodynamic polarization measurements and electrochemical impedance spectroscopy show that PANI@MIL-101/EP coating system has superior corrosion protection with the lowest i_corr value and the highest |Z|_0.01 value compared with MIL-101/EP coating, PANI/EP coating and EP coating. A possible anticorrosion mechanism of PANI@MIL-101 was discussed. This work reveals that MOF-polymer composite materials are superb candidates for high-performance corrosion protection.

Chitosan nanocomposite coatings with enhanced corrosion inhibition effects for copper

A biopolymer coating on copper was prepared based on chitosan nanocomposite and its corrosion inhibition efficiency was investigated. Inclusion of silica nanoparticles substantially reduces swelling ratio of chitosan coating while enhancing its thermal stability. The corrosion resistance of chitosan-based coatings is improved by introducing 2-mercaptobenzothiazole and silica in the matrix. It is found that upon crosslinking the chitosan coatings, a higher corrosion resistance could be achieved and the highest inhibition efficiency for chitosan nanocomposite coatings is calculated as 85%. The corrosion mechanism is found closely related to mass transition and diffusion process, and also the polarization resistance contributes to the impedance. Calculated impedance using Kramers-Kronig transformation shows good agreement with experimental values, thus validating the impedance measurements. This study exhibits the enhanced efficiency of nanocomposite and potential of chitosan coatings in corrosion prevention for copper.

Synthesis of thiophene derivatives and their anti-microbial, antioxidant, anticorrosion and anticancer activity

Background

A new series of thiophene analogues was synthesized and checked for their in vitro antibacterial, antifungal, antioxidant, anticorrosion and anticancer activities.

Results

A series of ethyl-2-(substituted benzylideneamino)-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxylate derivatives were synthesized by using Gewald synthesis and their structures were confirmed by FTIR, MS and ¹H-NMR. The synthesized compounds were further evaluated for their in vitro biological potentials i.e. antimicrobial activity against selected microbial species using tube dilution method, antiproliferative activity against human lung cancer cell line (A-549) by sulforhodamine B assay, antioxidant activity by using DPPH method and anticorrosion activity by gravimetric method.

Conclusion

Antimicrobial screening results showed that compound S ₁ was the most potent antibacterial agent against Staphylococcus aureus, Bacillus subtilis, Escherichia coli and Salmonella typhi having MIC value 0.81 µM/ml and compound S ₄ also displayed excellent antifungal activity against both Candida albicans and Aspergillus niger (MIC = 0.91 µM/ml) when compared with cefadroxil (antibacterial) and fluconazole (antifungal) as standard drug. The antioxidant screening results indicated that compound S ₄ and S ₆ exhibited excellent antioxidant activity with IC₅₀ values 48.45 and 45.33 respectively when compared with the ascorbic acid as standard drug. Anticorrosion screening results indicated that compound S ₇ showed more anticorrosion efficiency (97.90%) with low corrosion rate. Results of anticancer screening indicated that compound S ₈ showed effective cytotoxic activity against human lung cancer cell line (A-549) at dose of 10^-4 M when compared with adriamycin as standard.

Synthesis of anticorrosion nanohybrid films based on bioinspired dopamine, L-cys/CNT@PDA through self-assembly on 304 stainless steel in 3.5% NaCl

Nanohybrid films containing multiwalled carbon nanotubes (MWCNTs) were successfully coated on 304-stainless steel (304ss) for anti-corrosion use. The nanocompositewas made by a self-assembly of poly (dopamine), wrapped with MWCNTs (CNT@PDA) through a mussel inspired method. In order to enhance the corrosion protection, an inner layer of L-cysteine, an adhesive amino acid to 304ss surface through thiol (-SH) functional group were constructed through a dip-coating process. Potentiodynamic polarization measurements and electrochemical impedance spectroscopy revealed that the double nano-layer could act as a noble anticorrosive coating in 3.5% NaCl, which was assigned to the hydrophobicity, robustness, and dense double layer coating.

Synthesis, biological evaluation and corrosion inhibition studies of transition metal complexes of Schiff base

Background

The transition metal complexes formed from Schiff base is regarded as leading molecules in medicinal chemistry. Because of the preparative availability and diversity in the structure of central group, the transition metals are important in coordination chemistry. In the present work, we have designed and prepared Schiff base and its metal complexes (MC₁–MC₄) and screened them for antimicrobial, anticancer and corrosion inhibitory properties.

Methodology

The synthesized metal complexes were characterized by physicochemical and spectral investigation (UV, IR, ¹H and ¹³C-NMR) and were further evaluated for their antimicrobial (tube dilution) and anticancer (SRB assay) activities. In addition, the corrosion inhibition potential was determined by electrochemical impedance spectroscopy (EIS) technique.

Results and discussion

Antimicrobial screening results found complexes (MC₁–MC₄) to exhibit less antibacterial activity against the tested bacterial species compared to ofloxacin while the complex MC₁ exhibited greater antifungal activity than the fluconazole. The anticancer activity results found the synthesized Schiff base and its metal complexes to elicit poor cytotoxic activity than the standard drug (5-fluorouracil) against HCT116 cancer cell line. Metal complex MC₂ showed more corrosion inhibition efficiency with high R_ct values and low C_dl values.

Conclusion

From the results, we can conclude that complexes MC₁ and MC₂ may be used as potent antimicrobial and anticorrosion agents, respectively.

Self-healing polyelectrolyte multilayered coating for anticorrosion on carbon paper

Ideally, if the corrosion resistance coating on carbon paper (CP) can be endowed with the self-healing property, the service life and the reliability of the carbon paper will be greatly increased as the gas diffusion layer. In this paper, different cycles of s branched poly (ethyleneimine) (bPEI) and poly (acrylic acid) (PAA) were modified on the surface of the carbon paper via layer-by-layer (LbL) self-assembly technology. The prepared polyelectrolyte multilayered coatings can not only protect the carbon fiber from corrosion, but also take advantages of the surrounding water to quickly repair themselves after damaged. The effects of the assembly cycles on morphology, resistance, air permeability and the contact angle of carbon papers were investigated, then the differences of the carbon papers in electrolysis process were explored. The results reveal that all the prepared coatings can protect carbon papers from corrosion, while when the assembly cycles was 10, the coatings are most efficient.

Corrosion resistance of biodegradable Mg with a composite polymer coating

Degrading Mg and its alloys are a category of implant materials for bone surgery, but rapid corrosion in physiological environment limits their clinical applications. To improve the corrosion resistance of Mg-based implants, a biodegradable composite polymer coating is deposited on an Mg rod in this work. The strategy is to decorate Mg surfaces with poly(γ-glutamic acid)-g-7-amino-4-methylcoumarin/hydroxyapatite (γ-PGA-g-AMC/HAp) composite nanoparticles through electrophoretic deposition in ethanol. The morphology and chemical composition of the resulting coating material are determined by scanning electron microscopy and Fourier transform infrared spectroscopy. Sample rods of bare Mg and coated Mg are implanted intramedullary into the femora of New Zealand white rabbits, periodic radiography and post-autopsy histopathology of each sample are analyzed. The obtained in vivo results clearly confirm that the coating material decreases degradation rate of the underlying Mg sample and appears good histocompatibility and osteoinductivity. The main aim of this work is to investigate the degradation process of bare Mg and coated Mg samples in bone environment and their effect on the surrounding bone tissue.

Effect of molecular structure of aniline-formaldehyde copolymers on corrosion inhibition of mild steel in hydrochloric acid solution

Aniline-formaldehyde copolymers with different molecular structures have been prepared and investigated for the purpose of corrosion control of mild steel in hydrochloric acid. The copolymers were synthesized by a condensation polymerization process with different ratios of aniline to formaldehyde in acidic precursor solutions. The corrosion inhibition efficiency of as-synthesized copolymers for Q235 mild steel was investigated in 1.0 mol L(-1) hydrochloric acid solution by weight loss measurement, potentiodynamic polarization, and electrochemical impedance spectroscopy, respectively. All the results demonstrate that as-prepared aniline-formaldehyde copolymers are efficient mixed-type corrosion inhibitors for mild steels in hydrochloric acid. The corrosion inhibition mechanism is discussed in terms of the role of molecular structure on adsorption of the copolymers onto the steel surface in acid solution.