Two-Dimensional Nanomaterials for Anticorrosive Polymeric Coatings: A Review

Emerging two dimensional MXene for corrosion protection in new energy systems: Design and mechanisms

With the development of new and clean energy (offshore wind power, fuel cells, aqueous zinc ion batteries, lithium-ion batteries, etc.), the corrosion and security problems in special environments of the new energy system have attracted much attention. Corrosion protection on the metals applied in new energy system can reduce the economic loss, security risk, and energy consumption, as well as guarantee the efficiency of energy system. Traditional coatings face challenges in agglomeration of nano fillers, structural control, environmental issues, and poor conductivity, which limits the applications. With features in controllable surface chemistry and composition, rich surface terminations, better conductivity than graphene oxide, high aspect-ratio, strong impermeability, and low friction coefficient, the two-dimensional (2D) MXene presents potential for applications in corrosion protection in new energy systems. Despite progress has been made in the MXene for corrosion protection, there is still a lack of comprehensive review regarding the design and mechanisms of anti-corrosive MXene-based materials for corrosion protection in new energy system. In this review, a brief induction of MXene and the specially four corrosive environments (offshore wind power at deep sea, bipolar plates in PEMFC environments, zinc anode in AZIBs, and current collectors in Li-ion battery) are presented. Importantly, the design strategies and mechanisms of the MXene-based anti-corrosive coatings on metals used in the special environments are discussed in detail. Finally, the challenges and research trends in the MXene-based coatings for new energy systems are prospected. This review provides further understanding of corrosion in new energy and would expand the application prospects of MXene.

Block Architectures in 2D Polymer Networks Fabricated via Sequential Copolymerization in a Metal-Organic Framework

Two-dimensional (2D) polymer network monolayers with novel block architectures were fabricated via sequential copolymerization within a pillared-layer metal-organic framework (MOF) that served as the reaction template. The MOF provides a confined 2D nanospace, restricting the crosslinking copolymerization of vinyl monomers to two dimensions. Sequential crosslinking copolymerization of methyl methacrylate and styrene, regulated by the reversible addition-fragmentation chain transfer (RAFT) process, resulted in the formation of 2D block architectures with 'patchy' domains consisting of crosslinked poly(methyl methacrylate) and polystyrene segments. Atomic force microscopy revealed that the resulting block monolayers exhibited varied morphologies on substrates, attributed to their intrinsic flexibility in 2D conformation, which facilitated microphase separation of the 2D segments within monolayers, leading to the unique aggregation morphologies. The unprecedented block topology in 2D polymeric monolayers presented in this study introduces a novel strategy for designing 2D polymeric nanomaterials with flexible yet anisotropic properties.

Triggering the Interplay of sp2-sp3 Carbon-Assisted Sustained Tribofilm via Two-Dimensional Surface Modulation for Exceptional Wear Resistance of Steel Surfaces

The relentless wear and friction of steel-based moving machinery have created ongoing challenges that hinder their industrial applications. One promising solution is the use of reduced graphene oxide (rGO) as a lubricant due to its excellent mechanical strength and promising tribological properties. However, its tendency to self-agglomerate presents a major hurdle for its practical use. This study aims to combat the restacking of rGO nanosheets by strategically intercalating self-assembled α-ZrP between the rGO layers, unlocking exceptional wear resistance in mild steel through hot-dip galvanization. The multilayer architecture of the developed coatings ensures lubrication through layer slippage during friction, while the coexistence of sp2-sp3 hybridized carbons further extends wear life, with the Zn-0.22/ZP_5@G coating exhibiting the highest wear resistance (0.277 × 10-7 mm3 N-1 m-1). The as-tailored composite coating, featuring a tribolayer composed of graphitic sp2 carbons, ZrO2, Zr(PO4)2, and Fe2O3, serves as an effective dissipative medium for contact stress. The formation of diamond-like sp3 carbons induced by the tribological process further contributes to the increased hardness of the resulting tribofilm. The reduced generation of the π-conjugated system in the composite prevents the movement of electrons toward the cathodic site, while the passivation effect induced by the composite effectively inhibits electrolyte permeation, resulting in substantial corrosion resistance. The exemplary wear resistance with remarkable anticorrosion performance achieved in this study offers significant improvement in the realm of hard coatings for mechanical applications, including moving machinery and manufacturing. Hence, the system can find effective use in such industries following the completion of relevant case studies.

Waterborne Polyurethane Treated with Flame Retardant Based on Polydimethylsiloxanes and Boron Phenolic Resin for Improving the Char Residue and Anti-Dripping Performance

Waterborne polyurethane (WPU) was cured with a flame retardant composed of polydimethylsiloxanes and boron phenolic resin. In comparison to unmodified WPU, the heat resistance of the cured WPU film was significantly improved by approximately 40.0 °C, and the limited oxygen index (LOI) increased from 21.9% to 32.6%. The outcomes reveal that the char residue yield of the cured WPU reached a substantial 8.93 wt.% at 600 °C, which is 60 times that of the unmodified WPU. The flame retardant facilitates the creation of char residue with a high degree of graphitization. Furthermore, the total smoke production (TSP), average effective heat of combustion (AEHC), total heat release (THR), and peak heat release rate (pHRR) of the cured WPU were diminished by 66.29%, 48.89%, 28.01%, and 27.96%, respectively, compared to the unmodified WPU. The CO/CO2 emission ratio was elevated by 46.32%, and the total flue gas emission was cut by 66.29%, demonstrating a remarkable smoke suppression effect. The cured WPU attained the UL-94 V0 rating without melt-dripping. These results indicate that the combined flame retardants (2.0 wt.%) can endow WPU with outstanding flame retardant properties.

Recent advances and perspectives for intercalation layered compounds. Part 2: applications in the field of catalysis, environment and health

Intercalation compounds represent a unique class of materials that can be anisotropic (1D and 2D-based topology) or isotropic (3D) through their guest/host superlattice repetitive organisation. Intercalation refers to the reversible introduction of guest species with variable natures into a crystalline host lattice. Different host lattice structures have been used for the preparation of intercalation compounds, and many examples are produced by exploiting the flexibility and the ability of 2D-based hosts to accommodate different guest species, ranging from ions to complex molecules. This reaction is then carried out to allow systematic control and fine tuning of the final properties of the derived compounds, thus allowing them to be used for various applications. This review mainly focuses on the recent applications of intercalation layered compounds (ILCs) based on layered clays, zirconium phosphates, layered double hydroxides and graphene as heterogeneous catalysts, for environmental and health purposes, aiming at collecting and discussing how intercalation processes can be exploited for the selected applications.

Amino-Modified Graphene Oxide from Kish Graphite for Enhancing Corrosion Resistance of Waterborne Epoxy Coatings

Waterborne epoxy (WEP) coatings with enhanced corrosion resistance were prepared using graphene oxide (GO) that was obtained from kish graphite, and amino-functionalized graphene oxide (AGO) was modified by 2-aminomalonamide. The structural characteristics of the GO and AGO were analyzed using X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). And the anti-corrosive performance of waterborne epoxy-cased composite coatings with different addition amounts of AGO was investigated using electrochemical measurements, pull-off adhesion tests, and salt spray tests. The results indicate that AGO15/WEP with 0.15 wt.% of AGO has the best anti-corrosive performance, and the lowest frequency impedance modulus increased from 1.03 × 108 to 1.63 × 1010 ohm·cm-2 compared to that of WEP. Furthermore, AGO15/WEP also demonstrates the minimal corrosion products or bubbles in the salt spray test for 200 h, affirming its exceptional long-term corrosion protection capability.

Brownian Diffusion of Hexagonal Boron Nitride Nanosheets and Graphene in Two Dimensions

Two-dimensional (2D) nanomaterials have numerous interesting chemical and physical properties that make them desirable building blocks for the manufacture of macroscopic materials. Liquid-phase processing is a common method for forming macroscopic materials from these building blocks including wet-spinning and vacuum filtration. As such, assembling 2D nanomaterials into ordered functional materials requires an understanding of their solution dynamics. Yet, there are few experimental studies investigating the hydrodynamics of disk-like materials. Herein, we report the lateral diffusion of hexagonal boron nitride nanosheets (h-BN and graphene) in aqueous solution when confined in 2-dimensions. This was done by imaging fluorescent surfactant-tagged nanosheets and visualizing them by using fluorescence microscopy. Spectroscopic studies were conducted to characterize the interactions between h-BN and the fluorescent surfactant, and atomic force microscopy (AFM) was conducted to characterize the quality of the dispersion. The diffusion data under different gap sizes and viscosities displayed a good correlation with Kramers' theory. We propose that the yielded activation energies by Kramers' equation express the magnitude of the interaction between fluorescent surfactant tagged h-BN and glass because the energies remain constant with changing viscosity and decrease with increasing confinement size. The diffusion of graphene presented a similar trend with similar activation energy as the h-BN. This relationship suggests that Kramers' theory can also be applied to simulate the diffusion of other 2D nanomaterials.

Multifunctional liquid-like magnetic nanofluids mediated coating with anticorrosion and self-healing performance

The long-term protective efficacy of organic coatings against corrosion can be diminished by the presence of micropores/cracks and poor self-healing capabilities. To address these issues, Ti3C2 MXene was subjected to liquefaction-like treatment to maintain a two-dimensional lamellar structure in water and polymer matrix for a long time, as well as improve the dispersion stability and loading capacity of MXene. The inorganic corrosion inhibitor ferroferric oxide (Fe3O4) was then electrostatically loaded onto MXene nanofluids to obtain a hybrid material. Through hydrogen bonding, polyvinyl alcohol (PVA) molecular chains were bridged to the hybrid material, resulting in a self-healing anti-corrosion coating. The coating exhibited excellent corrosion protection, as well as self-healing properties attributed to the labyrinth effect and corrosion inhibition of MXene@Fe3O4 hybrids. Notably, electrochemical testing demonstrated outstanding corrosion resistance of this coating on diverse substrate surfaces. In addition, the anti-corrosion coating will strongly coalesce on the surface of B-NdFeB under magnetic stimulation, realizing the localized corrosion protection of metal materials. The anti-corrosion coating can be quickly repaired under the stimulation of water as well as recovery, the anti-corrosion repair efficiency on the surface of permanent magnets is up to 92%, and the mechanical properties after recovery can be restored to 97% of the original sample. This innovative coating offers a convenient, green synthesis strategy for the construction of self-healing coatings with superior anti-corrosion properties.

Advanced materials for smart protective coatings: Unleashing the potential of metal/covalent organic frameworks, 2D nanomaterials and carbonaceous structures

The detrimental impact of corrosion on metallic materials remains a pressing concern across industries. Recently, intelligent anti-corrosive coatings for safeguarding metal infrastructures have garnered significant interest. These coatings are equipped with micro/nano carriers that store corrosion inhibitors and release them when triggered by external stimuli. These advanced coatings have the capability to elevate the electrochemical impedance values of steel by 2-3 orders of magnitude compared to the blank coating. However, achieving intelligent, durable, and reliable anti-corrosive coatings requires careful consideration in the design of these micro/nano carriers. This review paper primarily focuses on investigating the corrosion inhibition mechanism of various nano/micro carriers/barriers and identifying the challenges associated with using them for achieving desired properties in anti-corrosive coatings. Furthermore, the fundamental aspects required for nano/micro carriers, including compatibility with the coating matrix, high specific surface area, stability in different environments, stimuli-responsive behavior, and facile synthesis were investigated. To achieve this aim, we explored the properties of micro/nanocarriers based on oxide nanoparticles, carbonaceous and two-dimensional (2D) nanomaterials. Finally, we reviewed recent literature on the application of state-of the art nanocarriers based on metal-organic frameworks (MOFs) and covalent-organic frameworks (COFs). We believe that the outcomes of this review paper offer valuable insights for researchers in selecting appropriate materials that can effectively enhance the corrosion resistance of coatings.

2D hexagonal boron nitride (h-BN) nanosheets in protective coatings: A literature review

The layered 2D hexagonal boron nitride (h-BN) nanosheets (BNNSs) have received significant attention as effective fillers for composite protective coatings in anti-corrosion, anti-oxidation and anti-wear applications. Vapour deposited h-BN mono/multilayers are related classes well-recognized as protective thin films and coatings. This review comprehensively accounts for the research and development of BNNSs in protective coatings. Chemical vapour deposited (CVD) BN thin films and exfoliated BNNSs-incorporated composite polymer coatings are primarily discussed. Inorganic and nanocarbon-based composite coatings are also covered. Future research potentials are presented.

Control and prevention of microbially influenced corrosion using cephalopod chitosan and its derivatives: A review

Microbially influenced corrosion (MIC) of metals is an important industrial problem, causing 300-500 billion dollars of economic loss worldwide each year. It is very challenging to prevent or control the MIC in the marine environment. Eco-friendly coatings embedded with corrosion inhibitors developed from natural products may be a successful approach for MIC prevention or control. As a natural renewable resource, cephalopod chitosan has a number of unique biological properties, such as antibacterial, antifungal and non-toxicity effects, which attract scientific and industrial interests for potential applications. Chitosan is a positively charged molecule, and the negatively charged bacterial cell wall is the target of its antimicrobial action. Chitosan binds to the bacterial cell wall and disrupts the normal functions of the membrane by, for example, facilitating the leakage of intracellular components and impeding the transport of nutrients into the cells. Interestingly, chitosan is an excellent film-forming polymer. Chitosan may be applied as an antimicrobial coating substance for the prevention or control of MIC. Furthermore, the antimicrobial chitosan coating can serve as a basal matrix, in which other antimicrobial or anticorrosive substances like chitosan nanoparticles, chitosan silver nanoparticles, quorum sensing inhibitors (QSI) or the combination of these compounds, can be embedded to achieve synergistic anticorrosive effects. A combination of field and laboratory experiments will be conducted to test this hypothesis for preventing or controlling MIC in the marine environment. Thus, the proposed review will identify new eco-friendly MIC inhibitors and will assay their potential in future applications in the anti-corrosion industry.

Prospective applications of two-dimensional materials beyond laboratory frontiers: A review

The development of nanotechnology has been advancing for decades and gained acceleration in the 21st century. Two-dimensional (2D) materials are widely available, giving them a wide range of material platforms for technological study and the advancement of atomic-level applications. The design and application of 2D materials are discussed in this review. In order to evaluate the performance of 2D materials, which might lead to greater applications benefiting the electrical and electronics sectors as well as society, the future paradigm of 2D materials needs to be visualized. The development of 2D hybrid materials with better characteristics that will help industry and society at large is anticipated to result from intensive research in 2D materials. This enhanced evaluation might open new opportunities for the synthesis of 2D materials and the creation of devices that are more effective than traditional ones in various sectors of application.

Superior Anticorrosion Performance of Well-Dispersed MXene-Polymer Composite Coatings Enabled by Covalent Modification and Ambient Electron-Beam Curing

MXene-reinforced composite coatings have recently shown promise for metal anticorrosion due to their large aspect ratio and antipermeability; however, the challenges of the poor dispersion, oxidation, and sedimentation of MXene nanofillers in a resin matrix that are often encountered in the existing curing methods have greatly limited practical applications. Herein, we reported an efficient, ambient, and solvent-free electron beam (EB) curing technology to fabricate PDMS@MXene filled acrylate-polyurethane (APU) coatings for anticorrosion of 2024 Al alloy, a common aerospace structural material. We showed that the dispersion of MXene nanoflakes modified by PDMS-OH was dramatically improved in EB-cured resin and enhanced the water resistance through the additional water-repellent groups of PDMS-OH. Moreover, the controllable irradiation-induced polymerization enabled a unique high-density cross-linked network, presenting a large physical barrier against corrosive media. The newly developed APU-PDMS@MX₁ coatings achieved excellent corrosion-resistance with the highest protection efficiency of 99.9957%. The coating filled with uniformly distributed PDMS@MXene promoted the corrosion potential, corrosion current density, and corrosion rate to be -0.14 V, 1.49 × 10^-9 A/cm², and 0.0004 mm/year, respectively, and the impedance modulus was increased by 1-2 orders of magnitude compared to that of APU-PDMS coating. This work combining 2D material with EB curing technology broadens the avenue for designing and fabricating composite coatings for metal corrosion protection.

Recent Advances in the Development of Oxidoreductase-Based Biosensors for Detection of Phenolic Antioxidants in Food and Beverages

Antioxidants are known to exhibit a protective effect against reactive oxygen species (ROS)-related oxidative damage. As a result, inclusion of exogenous antioxidants in the diet has greatly increased. In this sense, detection and quantification of such antioxidants in various food and beverage items are of eminent importance. Monophenols and polyphenols are among the most prominent natural antioxidants. In this regard, biosensors have emerged as a simple, fast, and economical method for determination of such antioxidants. Owing to the fact that majority of the phenolic antioxidants are electroactive, oxidoreductase enzymes are the most extensively availed bioreceptors for their detection. Herein, the different types of oxidoreductases that have been utilized in biosensors for the biorecognition and quantification of natural phenolic compounds commonly present in foods and beverages are discussed. Apart from the most accustomed electrochemical biosensors, this review sheds light on the alternative transduction systems for the detection of phenolic antioxidants. Recent advances in the strategies involved in enzyme immobilization and surface modification of the biosensing platform are analyzed. This review aims to provide a brief overview of the latest developments in biosensor technology for phenolic antioxidant analysis in foodstuffs and future directions in this field.

Development of Metallo (Calcium/Magnesium) Polyurethane Nanocomposites for Anti-Corrosive Applications

Long-term corrosion protection of metals might be provided by nanocomposite coatings having synergistic qualities. In this perspective, rapeseed oil-based polyurethane (ROPU) and nanocomposites with calcium and magnesium ions were designed. The structure of these nanocomposites was established through Fourier-transform infrared spectroscopy (FT-IR). The morphological studies were carried out using scanning electron microscopy (SEM) as well as transmission electron microscopy (TEM). Their thermal characteristics were studied using thermogravimetric analysis (TGA). Electrochemical experiments were applied for the assessment of the corrosion inhibition performance of these coatings in 3.5 wt. % NaCl solution for 7 days. After completion of the test, the results revealed a very low i_corr value of 7.73 × 10^-10 A cm^-2, a low corrosion rate of 8.342 × 10^-5 mpy, impedance 1.0 × 10⁷ Ω cm², and phase angle (approx 90°). These findings demonstrated that nanocomposite coatings outperformed ordinary ROPU and other published methods in terms of anticorrosive activity. The excellent anti-corrosive characteristic of the suggested nanocomposite coatings opens up new possibilities for the creation of advanced high-performance coatings for a variety of metal industries.

Experimental and Theoretical Studies toward Superior Anti-corrosive Nanocomposite Coatings of Aminosilane Wrapped Layer-by-Layer Graphene Oxide@MXene/Waterborne Epoxy

Herein, layer-by-layer MXene/graphene oxide nanosheets wrapped with 3-aminopropyltriethoxy silane (abbreviated as F-GO@MXene) are proposed as an anti-corrosion promoter for waterborne epoxies. The GO@MXene nanohybrid is synthesized by a solvothermal reaction to produce a multi-layered 2D structure without defects. Then, the GO@MXene is modified by silane wrapping under a reflux reaction, in order to achieve chemical stability and to create active sites on the nanohybrid surface for reaction with the polymer matrix of the coating. The organic coating modified with 0.1 wt % F-GO@MXene has revealed superior corrosion protection efficiency than the organic coatings modified with either F-GO or F-MXene nanosheets. The impedance modulus at low frequency for the pure epoxy, epoxy/F-MXene, epoxy/F-GO, and epoxy/F-GO@MXene coatings is 4.17 × 10⁵, 5.5 × 10⁸, 4.46 × 10⁸, and 1.14 × 10¹⁰ Ω·cm² after 30 days of immersion in the corrosive media, respectively. The remarkable anti-corrosion property is assigned to the intense effect of the nanohybrid on the barrier performance, surface roughness, and adhesion strength of the epoxy coating. The complemental analysis based on first-principles density functional theory reveals that the adhesion strength related to the silane functional groups in its complexes follows the order F-GO@MXene > F-MXene > F-GO. The enhanced stabilization predicted on the GO@MXene nanohybrid ultimately stems from the combined role of the electrostatic and van der Waals forces, suggesting an increase in the penetration path of the corrosive media.

Rising of MXenes: Novel 2D-functionalized nanomaterials as a new milestone in corrosion science - a critical review

Corrosion is a natural process between a metal and its environment that can gradually cause catastrophic damage to the metal equipment, which would have economic implications. Consequently, several protective methods have been utilized to prevent metals from severe degradation. Organic polymeric coatings have been widely used as the most convenient and cost-effective method to boost metals' anti-corrosion properties. Nonetheless, these coatings have a significant amount of solvent, resulting in shrinkage and micro defects in the films during the curing process. Many studies have verified that transition metal carbides/nitrides (MXenes) can form a "labyrinth effect" in the polymeric coatings due to their "nano-barrier effect". Furthermore, based on their sheet-like structures, they can considerably cover the surface defects of the polymeric films. Therefore, the penetration of corrosive elements can be substantially curbed. It is the first review that specifically focused on the new family of 2D nanomaterials, i.e., MXenes, and discussed their applications in corrosion protection systems. The MXenes' pros and cons in the polymeric matrixes as nanofillers will be clarified. Moreover, the synthesis and functionalization methods of the MXenes, their applications, and corrosion protection mechanism will be explored. Subsequently, the MXenes' superiority over other 2D nanomaterials will be highlighted while their future perspectives and industrial applications will be predicted.

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.

Graphene-Oxide-Based Fluoro- and Chromo-Genic Materials and Their Applications

Composite materials and their applications constitute a hot field of research nowadays due to the fact that they comprise a combination of the unique properties of each component of which they consist. Very often, they exhibit better performance and properties compared to their combined building blocks. Graphene oxide (GO), as the most widely used derivative of graphene, has attracted widespread attention because of its excellent properties. Abundant oxygen-containing functional groups on GO can provide various reactive sites for chemical modification or functionalization of GO, which in turn can be used to develop novel GO-based composites. This review outlines the most recent advances in the field of novel dyes and pigments encompassing GO as a key ingredient or as an important cofactor. The interactions of graphene with other materials/compounds are highlighted. The special structure and unique properties of GO have a great effect on the performance of fabricated hybrid dyes and pigments by enhancing the color performance of dyes, the anticorrosion properties of pigments, the viscosity and rheology of inks, etc., which further expands the applications of dyes and pigments in dyeing, optical elements, solar-thermal energy storage, sensing, coatings, and microelectronics devices. Finally, challenges in the current development as well as the future prospects of GO-based dyes and pigments are also discussed. This review provides a reference for the further exploration of novel dyes and pigments.

Enhancement of Anticorrosive Performance of Cardanol Based Polyurethane Coatings by Incorporating Magnetic Hydroxyapatite Nanoparticles

The present investigation demonstrates renewable cardanol-based polyol for the formulation of nanocomposite polyurethane (PU) coatings. The functional and structural features of cardanol polyol and nanoparticles were studied using FT-IR and 1H NMR spectroscopic techniques. The magnetic hydroxyapatite nanoparticles (MHAPs) were dispersed 1–5% in PU formulations to develop nanocomposite anticorrosive coatings. An increase in the strength of MHAP increased the anticorrosive performance as examined by immersion and electrochemical methods. The nanocomposite PU coatings showed good coating properties, viz., gloss, pencil hardness, flexibility, cross-cut adhesion, and chemical resistance. Additionally, the coatings were also studied for surface morphology, wetting, and thermal properties by scanning electron microscope (SEM), contact angle, and thermogravimetric analysis (TGA), respectively. The hydrophobic nature of PU coatings increased by the addition of MHAP, and an optimum result (105°) was observed in 3% loading. The developed coatings revealed its hydrophobic nature with excellent anticorrosive performance.

Eco-friendly functionalization of hexagonal boron nitride nanosheets with carbon dots towards reinforcement of the protective performance of water-borne epoxy coatings

A h-BN@CDs/WEP coating shows superior corrosion protection under intact or damaged status owing to the improved barrier properties and interfacial bonding of the coating.

Long-term corrosion protection of styrene acrylic coatings enhanced by fluorine and nitrogen co-doped graphene oxide

Graphene materials are widely used as a physical barrier when applying anticorrosion polymer coatings due to their large surface area and layered structure. However, the electrical conductivity of intrinsic graphene can accelerate galvanic corrosion and shorten the protection period. In this work, fluorine and nitrogen co-doped graphene oxide (FNGO) was synthesized by a hydrothermal process and acted as an anticorrosion filler in waterborne styrene acrylic coatings. Styrene acrylic coatings with 0.4 wt% FNGO showed a corrosion current density that was two orders of magnitude lower than the other samples in the potential polarization test and the largest impedance modulus in the electrochemical impedance spectroscopy results. The outstanding corrosion protection was attributed to the graphene acting as a physical barrier and the synergistic effect of the doped fluorine and nitrogen. In addition to the 'labyrinth effect' of the graphene matrix, the nitrogen atoms inserted in the graphene plane and fluorine atoms grafted on the graphene simultaneously adjusted the electrical properties of graphene, prohibiting electron transport between it and the styrene acrylic resin matrix. This result indicates that doped graphene oxide has great potential to increase the corrosion resistance of waterborne coatings.

Poly(m-phenylenediamine) encapsulated graphene for enhancing corrosion protection performance of epoxy coatings

Graphene (G) is regarded as a tremendous potential corrosion protection material owing to its perfect impermeability. However, the tendency of graphene nanosheets to agglomerate and the corrosion-promotion effect brought by its native high electrical conductivity seriously affect its anti-corrosion application. In this paper, high-energy ball milling was used to prepare graphene with excellent impermeability. Then, insulating poly(m-phenylenediamine) encapsulated graphene (G@PmPD, conductivity of 1.2 × 10^-7S cm^-1) was prepared through non-covalentπ-πinteraction. The resulting amino-rich G@PmPD exhibits stable dispersibility and excellent compatibility in organic solvents and polymer matrix. Embedding 0.5 wt% of G@PmPD into the epoxy matrix, and the composite coating can effectively protect the steel substrate for up to 60 d. This superior corrosion resistance is attributed to the impermeability inherited by G@PmPD and the compactness improved by the cross-linking of G@PmPD and EP. Especially in the damaged state, the composite coating embedded with low conductivity G@PmPD triumphantly eliminated graphene's corrosion-promotion effect. This study provides promising inspiration for the application of graphene in anti-corrosion field.

GO-Ti3C2 two-dimensional heterojunction nanomaterial for anticorrosion enhancement of epoxy zinc-rich coatings

MXenes are a unique family of two-dimensional (2D) transition metal carbides and/or nitrides, which have been proven useful for energy storage, water purification, and biomedical applications. Herein, a kind of heterojunction structure was designed by grafting highly conductive MXene (Ti₃C₂) on the graphene oxide (GO) nanosheets， which was confirmed by Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectronic spectroscopy (XPS) and Raman results. Open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and salt spray measurements corroborated that inclusion of 0.5 wt% Ti₃C₂ or GO-Ti₃C₂ into epoxy zinc-rich coating (ZRC) effectively enhance the cathodic protection capability. Additionally, superior corrosion resistance was achieved by incorporation of GO-Ti₃C₂ into ZRC since GO-Ti₃C₂ in the coating improved the utilization rate of zinc particles and GO provided barrier protection for inhibiting the diffusion of corrosive agents. At the end of immersion, R_c value of ZRC/GO-Ti₃C₂ coating was 3.047 × 10⁴ Ω·cm², which was one order of magnitude higher than that of ZRC coating. Scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) measurements demonstrated that ZRC/GO-Ti₃C₂ coating exhibited lower speed of zinc particles oxidation and intact steel substrate. Hence, ZRC/GO-Ti₃C₂ coating exhibited the optimal corrosion resistance among the four kinds of coatings.

Epoxy-matrix polyaniline/p-phenylenediamine-functionalised graphene oxide coatings with dual anti-corrosion and anti-fouling performance

This research work reports on the anti-corrosion and anti-fouling properties of epoxy (E) coatings reinforced with polyaniline (PANI)/p-phenylenediamine-functionalised graphene oxide (PGO) composites. The mass ratio of graphene oxide/p-phenylenediamine in any PGO was assumed to be 1 : 1, but different PANI-PGO composites containing various loadings of PGO were prepared. An ultrasonic-assisted in situ polymerization method was employed to produce PANI-PGO at low temperature (0 °C). Several analytical and microscopical techniques, i.e., Fourier-transfer infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and field emission scanning electron microscopy (FESEM), were used to confirm that PANI-PGO composites were successfully synthesized. The epoxy-based coatings (E/PANI-PGO (x), x = 0.05-0.4 g) were applied by brushing them onto carbon steel substrates, which exhibited dual anti-corrosion and anti-fouling performance. Electrochemical impedance spectroscopy (EIS) results show that E/PANI-PGO (0.2) has the highest corrosion resistance (8.87 × 10⁶ Ω cm²) after 192 h of immersion in 3.5 wt% NaCl amongst all the coatings compared with neat epoxy (1.00 × 10⁴ Ω cm²) and E/PANI (6.82 × 10³ Ω cm²). Efficient antifouling performance at the macroscopic level under simulated marine conditions was observed for the epoxy-based PANI-PGO coatings with a range of PGO compositions, in particular for the 0.1 and 0.2 g PGO coatings.

Waterborne Polyurea Coatings Filled with Sulfonated Graphene Improved Anti-Corrosion Performance

In this paper, an environmentally friendly waterborne polyurea (WPUA) emulsion and its corresponding coating were prepared, which was characterized by dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), and scanning electron microscopy (SEM). To improve the performance of the coating, we doped sulfonated graphene (SG) into WPUA to prepare composite coating (SG/WPUA). SG can be uniformly dispersed in WPUA emulsion and is stable for a long time (28 days) without delamination. The water resistance of the composite coating with 0.3 wt.% SG nanofiller was improved; the water contact angle (WCA) result was SG/WPUA (89°) > WPUA (48.5°), and water absorption result was SG/WPUA (2.90%) < WPUA (9.98%). After water immersion treatment, SEM observation revealed that the SG/WPUA film only generated enlarged microcracks (100 nm) instead of holes (150–400 nm, WPUA film). Polarization curves and electrochemical impedance spectroscopy (EIS) tests show that SG nanosheets with low doping content (0.3 wt.%) are more conducive to the corrosion resistance of WPUA coatings, and the model was established to explain the mechanism.