Epoxy Coatings Research Articles

Effect of Acrylic Resin on the Protection Performance of Epoxy Coating for Magnesium Alloy

Effect of Acrylic Resin on the Protection Performance of Epoxy Coating for Magnesium Alloy

Experimental Investigation of Producer Gas Effects on Coated Pipelines in Biomass Downdraft Gasifier System

Abstract This research examines the performance of epoxy, ceramic, and graphene coatings on stainless steel 316 in a producer gas environment, focusing on corrosion and erosion resistance. This research aimed to identify the most effective coating for applications in harsh gasification environments. In this research, various analyses, including microstructural examination, hardness and weight measurements, FESEM analysis, and EDAX analysis, were conducted to evaluate the performance of the coatings. The producer gas was passed on to all the coated samples for a period of 100 hours. The significant findings include the superior corrosion and erosion resistance of ceramic-coated stainless steel, as evidenced by low weight fluctuations, maintained hardness levels, and elemental stability. Graphene coatings exhibit high hardness but increased porosity, raising concerns about durability, while epoxy coatings are vulnerable to gas-induced structural alterations. The inclusion rating analysis underscored the ceramic coatings' ability to preserve consistent material properties. Overall, ceramic coatings have emerged as the preferred option for gasification environments due to their structural resilience, inclusion integrity, and elemental stability. Considering the inclusion integrity, mechanical strength, weight stability, and elemental stability, ceramic-coated stainless steel 316 samples exhibit better resistance toward producer gas influence. This research contributes valuable insights for material selection in applications exposed to harsh gasification environments, emphasizing the importance of coating selection for long-term durability and performance.

Cu(II) complexes using acylhydrazones or cyclen for biocidal antifouling coatings

Abstract Copper and copper-based compounds have broad spectrum antimicrobial activity, but concerns about leaching into the environment and toxicity on non-target organisms is leading the use of copper-based coatings being restricted. Our objective was to develop coatings that used the biocidal activity of copper, but with low negative impacts by reducing its leaching into the environment. This study reports the synthesis and characterisation of copper coordinating ligands, their formulation into coatings and testing of their antibacterial activity. A polyacylhydrazone and a series of simple acylhydrazones were synthesised and coordinated to Cu(II), but were considered unsuitable due to either their poor water-solubility or high levels of copper leaching. In an alternative approach, copper was successfully chelated to the tetraazamacrocycle, cyclen, and used to synthesise Cu(II)-cyclen functionalised silica particles, which were successfully combined with commercial paint formulations. These functionalised products showed poor antibacterial activity when incorporated into epoxy coatings, probably due to the low copper content of the formulations. However, these ligands may have other applications, such as removal of heavy metals from contaminated effluent steams.

Evaluation of Antimicrobial Properties in Coatings for Operating Room Surfaces

This article highlights the crucial significance of upholding sterility in operating rooms (ORs) to minimize infection risks and uphold patient safety. Putting a spotlight on the pivotal role of antimicrobial coatings, the research delves into the examination of four frequently used coatings—polyurethane, acrylic, alkyd, and epoxy—across various surfaces within ORs. The study evaluates the antimicrobial properties of these coatings against 20 contaminant bacteria, uncovering diverse impacts on different strains. While these coatings may not inherently possess antimicrobial characteristics, formulations enriched with agents like 1,2-benzisothiazol-3(2H)-one (BIT) and 2-octyl-2H-isothiazol-3-one (OIT) demonstrate active resistance against bacterial growth. The results highlight the efficacy of acrylic and epoxy coatings, specifically in impeding bacterial proliferation. These findings affirm the practical utility of antimicrobial coatings in vital healthcare settings, providing valuable insights into their potential to elevate hygiene, safety, and efficiency in ORs. The study advocates for ongoing exploration of innovative coatings and antimicrobial agents, underscoring the importance of adhering to cleaning protocols and healthcare regulations for optimal effectiveness.

An investigation on the mechanical and corrosion protection properties of poly(arylene ether nitrile) reinforced epoxy coating

To follow the current industrial demand, epoxy coatings which feature extraordinary comprehensive properties have been considered as a versatile and promising thermosetting resin for application in various middle and high-end sectors of multitudinous industries. Regrettably, epoxy coatings possess the inherent shortcoming of poor durability to external force and deformation, severely restricting further introjection in various fields. Herein, this study employs poly(arylene ether nitrile) with bisphenol A structure (PENBA) as superior intensifying agent to ameliorate the toughness and corrosion resistance of brittle epoxy coatings. As a linear thermoplastic polymer with satisfying mechanical performances, PENBA serves as epoxy's energy-dissipating medium and forms a semi-interpenetrating polymer network (SIPN) with epoxy matrix, efficiently impeding epoxy's fracture and crack propagation. As a result, the tensile strength, elongation at break, impact strength, and flexural strength of PENBA-modified epoxy possess considerable increments of 214 %, 360 %, 148 %, and 295 % in sequence by contrast with the pristine epoxy. Meanwhile, according to the potentiodynamic polarization analysis, the PENBA with outstanding chemical resistance also significantly promoted the epoxy's corrosion resistance, endowing the epoxy coating with the most positive Ecorr and icorr of −0.453 V and 9.439 × 10−10 A/cm2 when PENBA reached 15 % (mass percent) at the end of entire soaking process.

Construction of functional epoxy resin coatings based on acid-doping polyaniline coated APP: Preparation, characterization and properties

Waterborne epoxy resin (WER) coatings have attracted more and more attention because of their excellent physical and chemical properties, however, WER's flammability and high insulation limit its application. In this paper, polyaniline (PANI) doped with four different acids (sulfuric acid, phosphoric acid, citric acid and amino trimethylene phosphonic acid) was used as the shell material to coat ammonium polyphosphate (APP), and a series of multifunctional WER fillers (PANIacids/APP) integrating flame retardant, smoke suppression and antistatic properties were prepared. Then, the PANIacids/APP was compounded with WER to prepare a functional WER coating. The structures and morphologies of the PANIacids/APP fillers were characterized by Fourier transform infrared spectrometer (FTIR), scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS), the results showed that acids doping could promote the formation of polyaniline coating on the surface of APP, and the PANIacids/APP filler doped by amino trimethylene phosphonic acid (ATMP) exhibits the best coating effect. Furthermore, the effects of PANIacids/APP fillers on the flame retardant property, smoke suppression property, electrical property and adhesion property of waterborne epoxy resins were explored. The results indicated that the carbon residue of WER coatings with PANIacids/APP fillers at 800 °C could reach 24.1 %-29.6 %, among which ATMP doping group has a residual carbon of 27.3 %. Also, the WER coating containing PANIATMP/APP filler possesses the best comprehensive performance, the coating has a limiting oxygen index of 31.7 % and passed V-0 level in the vertical burning test (UL-94). Compared with pure EP coating, the peak heat release rate of the PANIATMP/APP modified coating decreased by 78.1 % and the total heat release decreased by 37.8 %. Additionally, the surface resistance and adhesive force of the PANIATMP/APP modified coating reached 3.14×106 Ω and 11.8 MPa, respectively, which could meet the usage needs of anti-static application of the WER coatings.

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.

An experimental characterization of the properties of graphene oxide—Waterborne epoxy resin coating of concrete after chloride erosion

The durability of concrete surfaces is frequently compromised by adverse external factors, such as freeze-thaw cycles and ionic corrosion among others. This study aims to investigate the comparative performance of three concrete coating techniques independently applied uniformly to concrete surfaces, namely the Graphene Oxide—Waterborne Epoxy Resin Coating (GO-WEP) coating and two commercially available WEP coatings (S1, S2). The corrosion resistances of the coatings were evaluated under various conditions: chloride drying-wetting cycles, chloride freeze-thaw cycles, and chloride immersion tests. In this study, the changes in color difference and adhesion of the coating after chloride erosion were studied. And after five drying-wetting cycles, the GO-WEP coating exhibited a color difference value approximately 56 % and 45 % lower compared to S1 and S2 coatings respectively. The S1 and S2 coatings demonstrated adhesive strength below 1.50 MPa after the 3rd and 4th cycles respectively, indicating a loss of protective capabilities. Conversely, the GO-WEP coating maintained adhesive strength greater than 1.50 MPa after five cycles, implying sustained protective capabilities. Following freeze-thaw cycles, the color difference value in GO-WEP was about 16 % and 7 % lower than S1 and S2 coatings respectively. S1 and S2 coatings lost their protective ability after the 4th and 5th cycles respectively, while GO-WEP maintained an adhesive strength greater than 1.50 MPa. Furthermore, following chloride immersion, the GO-WEP coating had a color difference value approximately 20 % and 17 % lower than S1 and S2 respectively. The adhesive strength reduced by 39.7 %, 46.4 %, and 43.1 % for the three coatings respectively, signaling the superior performance of GO-WEP in all tested properties. The surface morphology and compressive strength variations of the coated concrete were also studied. As the experimental cycles progressed, both S1 and S2 coatings suffered noticeable surface damage, while the GO-WEP coating demonstrated no significant changes until the end of the experimental cycles. During the chloride drying-wetting and chloride immersion tests, the concrete specimens showed an increase in strength. Initially, uncoated concrete showed a faster rate of strength increase than coated concrete. However, this rate slowed down and even reversed in later stages. Coated concrete on the other hand, exhibited a steady increase in strength over the experimental cycles, with GO-WEP coated concrete showing the slowest growth rate. In the chloride freeze-thaw cycle test, concrete strength decreased progressively. And by the fifth cycle, the compressive strengths of GO-WEP, S1, and S2 were 31.5 MPa, 30.8 MPa, and 30 MPa, respectively, a 9 %, 6 %, and 3 % improvement over the 29 MPa of uncoated concrete. These findings further reinforce the superior protective effect of the GO-WEP coating on concrete.

In-situ Zn-Al layered double hydroxide conversion coatings prepared on galvanized steels by a two-step electrochemical method

Zn-Al layered double hydroxide (LDH) pretreatment layer was prepared by a novel two-step electrochemical method on galvanized steel surface from a precursor solution containing Al3+-only. In the first step, anodic currents are applied to Zn deposit to produce Zn2+ in solution near the substrate surface. Cathodic currents are then applied to ensure the cathodic deposition of LDH film. The obtained LDH coatings not only provide excellent adhesion to the metal surface, but also enhance the adhesion between metal substrate and the top epoxy coatings. The “LDH/epoxy” painting system can protect galvanized steel from rusting for at least 150 days.

Tailoring exfoliated 2D Mo-PDA nanopetals as sustainable intelligent anti-corrosion nanoreservoir for upgrading the self-healing/barrier function of epoxy coatings

The present study unfurled novel route to tailor cutting-edge molybdenum-polydopamine (AHPDA) and molybdenum-polydopamine-Ce3+/4+ nanocarriers (AHPDA@Ce) using in-situ self-nucleophilic polymerization techniques and scrutinized their intelligent anti-corrosion and physicomechanical properties in solution and coating phases. The manageable emancipation of Ce3+/4+,MoO42-, polydopamine (PDA) derivatives from exfoliated AHPDA and AHPDA@Ce nanocarriers at the extract solutions brilliantly reduced the icorr from 5.14 to 2.22 and 1.45 µA/cm2, respectively. Afterward, the derivatives assembled intricate barrier films at the electrochemical active sites, outstandingly restricting the severe corrosion on steel panels immersed in AHPDA@Ce and AHPDA extract solutions. Moreover, even after 48 h immersion, not only did the scratched EAHC (containing AHPDA@Ce nanocarriers) and EAHM (including AHPDA nanocarriers) coatings exhibit superior self-healing protection by 382 % and 327 % promotion in RTotal towards NE coatings (neat epoxy), but also intelligent EAHC and EAHM coatings tolerated the salt spray condition up to 1000 h exposure rather than 400 h of NE coating. Also, the intact EAHC and EAHM coatings after 24 weeks of submersion with noteworthy log|Z|0.01Hz of 10.51 and 9.98 Ω cm2 showcased boosted barrier-passive function lifetime with respect to the NE coatings (5.68 Ω cm2). Furthermore, smart EAHM and EAHC nanocomposites flaunted lower adhesion loss of 2.3 and 5.2 times, respectively, as well as, an incredible 76.11 % and 31.50 % improvement in the reduction of cathodic peel-off area regarding the NE coating. Ultimately, smart EAHC and EAHM coatings could be employed as eco-friendly effective anti-corrosion coatings with terrific self-healing/barrier function and durable service life in strategic knowledge edge applications.

Ultrathin Al2O3 film modification on waterborne epoxy coatings by atomic layer deposition for augmenting the corrosion resistance.

The polar channels formed by the curing of waterborne anticorrosive coatings compromise their water resistance, leading to coating degradation and metal corrosion. To enhance the anticorrosive performance of waterborne coatings, this study proposed a novel method of depositing ultrathin Al2O3 films on the surface of waterborne epoxy coatings by atomic layer deposition (ALD), a technique that can modify the surface properties of polymer materials by depositing functional films. The Al2O3-modified coatings exhibited improved sealing and barrier properties by closing the polar channels and surface defects and cracks. The surface structure and morphology of the modified coatings were characterized by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The hydrophilicity and corrosion resistance of the modified coatings were evaluated by water contact angle measurement, Tafel polarization curve, and electrochemical impedance spectroscopy. The results indicated that the water contact angle of the Al2O3-modified coating increased by 48° compared to the unmodified coating, and the protection efficiency of the modified coating reached 99.81%. The Al2O3-modified coating demonstrated high anticorrosive efficiency and potential applications for metal anticorrosion in harsh marine environments.&#xD.

Synthesis and Characterization of Superhydrophobic Epoxy Resin Coating with SiO2@CuO/HDTMS for Enhanced Self-Cleaning, Photocatalytic, and Corrosion-Resistant Properties.

The exceptional corrosion resistance and combined physical and chemical self-cleaning capabilities of superhydrophobic photocatalytic coatings have sparked significant interest among researchers. In this paper, we propose an economical and eco-friendly superhydrophobic epoxy resin coating that incorporates SiO2@CuO/HDTMS nanoparticles modified with Hexadecyltrimethoxysilane (HDTMS). The application of superhydrophobic coatings effectively reduces the contact area between the metal surface and corrosive media, leading to a decreased corrosion rate. Additionally, the incorporation of nanomaterials, exemplified by SiO2@CuO core-shell nanoparticles, improves the adhesion and durability of the coatings on aluminum alloy substrates. Experimental data from Tafel curve analysis and electrochemical impedance spectroscopy (EIS) confirm the superior corrosion resistance of the superhydrophobic modified aluminum alloy surface compared to untreated surfaces. Estimations indicate a significant reduction in corrosion rate after superhydrophobic treatment. Furthermore, an optical absorption spectra analysis of the core-shell nanoparticles demonstrates their suitability for photocatalytic applications, showcasing their potential contribution to enhancing the overall performance of the coated surfaces. This research underscores the promising approach of combining superhydrophobic properties with photocatalytic capabilities to develop advanced surface modification techniques for enhanced corrosion resistance and functional properties in diverse industrial settings.

Melamine-Modified Graphene Oxide as a Corrosion Resistance Enhancing Additive for Waterborne Epoxy Resin Coatings

Waterborne epoxy resin (WEP) coatings are widely used in various fields due to their environmentally friendly properties, yet their corrosion resistance and shielding properties demand further refinement. In this work, melamine-modified graphene oxide (MGO) was synthesized using surface covalent functionalization, and a novel waterborne epoxy/modified graphene oxide coating (WEP/MGO) was prepared. The optimal modification effect was obtained by exploring different proportions of melamine, which led to significant improvements in the corrosion resistance of WEP. Furthermore, the corrosion protection efficiency of WEP/MGO coatings was systematically evaluated by examining the impact of different additions of MGO. The impedance modulus at the lowest frequency was increased from 3.77 × 108 Ω·cm2 of WEP to 2.85 × 109 Ω·cm2 after immersion in 3.5% NaCl for 48 h, when the addition of MGO was 0.1 wt.%. And the corrosion expansion at both the scratch and corrosion spot frequencies of the WEP-coated samples displayed a remarkable attenuation following exposure to salt spray for 300 h. The corrosion resistance and barrier properties of WEP coatings have been considerably enhanced.

Nanocellulose Grades with Different Morphologies and Surface Modification as Additives for Waterborne Epoxy Coatings.

While adding different micro- and nanocellulose types into epoxy coating formulations with waterborne phenalkamine crosslinker, effects on processing conditions and coating performance were systematically investigated. The variations in viscosity, thermal and thermomechanical properties, mechanical behavior, abrasive wear, water contact angles, and coating morphologies were evaluated. The selected additives include microcrystalline cellulose (MCC) at 1 to 10 wt.% and cellulose nanocrystals (CNC), cellulose nanofibers (CNF), cellulose microfibers (CMF), and hydrophobically modified cellulose microfibers (mCMF) at 0.1 to 1.5 wt.%. The viscosity profiles are determined by the inherent additive characteristics with strong shear thinning effects for epoxy/CNF, while the epoxy/mCMF provides lower viscosity and better matrix compatibility owing to the lubrication of encapsulated wax. The crosslinking of epoxy/CNF is favored and postponed for epoxy/(CNC, CMF, mCMF), as the stronger interactions between epoxy and CNF are confirmed by an increase in the glass transition temperature and reduction in the dampening factor. The mechanical properties indicate the highest hardness and impact strength for epoxy/CNF resulting in the lowest abrasion wear rates, but ductility enhances and wear rates mostly reduce for epoxy/mCMF together with hydrophobic protection. In addition, the mechanical reinforcement owing to the specific organization of a nanocellulose network at percolation threshold concentrations of 0.75 wt.% is confirmed by microscopic analysis: the latter results in a 2.6 °C (CNF) or 1.6 °C (CNC) increase in the glass transition temperature, 50% (CNF) or 20% (CNC) increase in the E modulus, 37% (CNF) or 32% (CNC) increase in hardness, and 58% (CNF) or 33% (CNC) lower abrasive wear compared to neat epoxy, while higher concentrations up to 1.5 wt.% mCMF can be added. This research significantly demonstrates that nanocellulose is directly compatible with a waterborne phenalkamine crosslinker and actively contributes to the crosslinking of waterborne epoxy coatings, changing the intrinsic glass transition temperatures and hardness properties, to which mechanical coating performance directly relates.

Corrosion Protection of Q235 Steel Using Epoxy Coatings Based on Polyaniline Loaded with Benzotriazole

Polyaniline (PANI) doped with hydrochloric acid and phytic acid are prepared as benzotriazole (BTA) inhibitor carriers, and their anticorrosion properties are studied on epoxy resin-coated Q235 steel. The structure and morphology of the prepared PANI materials are investigated by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The thermal stability of PANI and its release rate of corrosion inhibitor are measured, and the test results indicate that hydrochloric acid-doped PANI can accommodate a larger amount of corrosion inhibitor. The results of contact angle and water absorption tests show that the PANI loaded with BTA can improve the hydrophobicity and reduce the water absorption of the coating. The anticorrosion performances of epoxy coatings with 0.6 wt% PANI are investigated in 3.5 wt% NaCl solution using electrochemical tests. The experimental results reveal that PANI loaded with BTA shows a good anticorrosion effect in the epoxy coating. Particularly, phytic acid-doped PANI loaded with BTA has a better inhibition efficiency (93.6%), which is superior to hydrochloric acid-doped PANI loaded with BTA (86.4%).

Unfolded graphene riveted on layered double hydroxide as a highly efficient enhancer for the corrosion protective performance of zinc-rich epoxy coatings

The performance enhancement of zinc-rich epoxy coating brought by embedding conventional graphene nanosheets (GNs) is severely restricted due to the inevitable crumpling and folding nature of two-dimensional GNs. Herein, unfolded GNs are riveted on both sides of MgAl-layered double hydroxides (LDHs) via chemical graft method, achieving a novel LDHs/GNs nanocomposites (LGs). Experimental results reveal that, compared with pristine zinc-rich epoxy coatings (ZREs), the cathodic protection duration of LG/ZREs is roughly tripled under an ultra-low loading of net GNs (0.007 wt%), and this performance is even better than 0.2 wt% GNs-embedded ZRE. Compared with conventional GNs with crumpling and folding morphology, unfolded GNs riveted on LDHs perform better in “bridging” the available zinc powders into integrated conductive pathway and twisting the diffusion path of diffusing species in coating matrix.

Experimental and theoretical insights on long-term corrosion protection performance of MXene Nanosheets decorated with graphene quantum dots in epoxy coatings

In this study, MXene nanosheets decorated with zero-dimensional graphene quantum dots and functionalized with 3-aminopropyltriethoxysilane (APTES-MXene@GQDs) are used as a nanofiller in epoxy coatings. The MXene@GQDs and APTES-MXene@GQDs are characterized by X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The results prove that the GQDs with spherical size (≤ 10 nm) have covered the MXene nanosheets through creating C-O-Ti covalent bonds. The Si-O-C and Ti-O-Si bonds in the APTES-MXene@GQDs indicate that both MXene and GQDs have reacted with the APTES molecules. The results of electrochemical impedance spectroscopy reveal that the low-frequency impedance modulus of epoxy coatings loaded with 0.1 wt% APTES-MXene@GQDs is 4.4 × 109 and 6.4 × 108 Ω.cm2 after 1 day and 7 weeks of immersion in NaCl solution, respectively. Meanwhile, hydrophobic coatings with high adhesion strength are achieved by adding the modified nanofillers. Density Functional Theory calculations emphasize the potential of MXene@GQDs nanohybrids in corrosion protection. The COO covalent bond significantly bolsters stability, making it a strong contender. An efficient electron transfer, as revealed in charge transfer dynamics, reinforces the interactions. The presence of MXene reshapes the electronic landscape, facilitating robust charge transfer processes. Conversely, the systems lacking MXene exhibit less advantageous energy level placement.

Constructing PANI@CF hybrids enhanced epoxy coatings with integrated functionalities of interfacial enhancement, erosion wear resistance and anti-corrosion

Factors such as sediment erosion and diffusion of corrosive ions in the splash zone result in a serious decrease in the protective performance of organic coatings. Carbon fiber (CF) reinforced polymer coatings have attracted much attention due to the impressive high mechanical strength and reliable chemical stability, but their protection period for steel structures is usually limited by the surface inertness and poor interfacial compatibility of the original CF. Herein, we created a composite coating with excellent erosion and wear resistance and corrosion resistance through simple self-polymerization of polyaniline on carbon fibers. The PANI layer not only helped to improve the interfacial compatibility between fibers/resin, but also exerted its corrosion inhibition effect. The interfacial shear strength (IFSS) value of the modified PANI4@CF monofilament and resin (60.63 MPa) was 46.73 % larger than that of the unmodified CF monofilament. In the simulated splash zone, PANI4@CF5/EP composite coating showed the best erosion resistance and corrosion resistance, and the mass loss and volume loss after erosion test were reduced by 53.39 % and 50.10 %, respectively, compared with pure epoxy coating. The local electrochemical impedance spectroscopy (LEIS) value of PANI4@CF5/EP coating with artificial defect was one order of magnitude higher than the epoxy coating after 48 h immersion. Finally, the environmental conditions of the splash zone were simulated to evaluate the anti-corrosion performance and erosion resistance of the CF reinforced composite coatings, and the protective mechanism was discussed in depth, which has great significance to the development of protective coatings for the splash zone under extreme marine environments.

Synergistic enhancement: Ammonium Polyphosphate's impact on hybrid coating performance against corrosion and fire

AbstractThis research demonstrated the impact of ammonium polyphosphate (APP) content on corrosion resistance and flame retardancy properties of hybrid graphene oxide/halloysite/intumescent flame retardant (GO‐HNT‐IFR) coatings. Electrochemical impedance spectroscopy studied indicates that the GO0.6‐H0.3 coating exhibited superior corrosion resistance (Rct = 2.490 × 109 Ω·cm) compared with hybrid GO‐HNT‐IFR coatings. Tafel polarization data revealed a decrease in polarization resistance, Rp simultaneously increases the corrosion rate, Rcorr of the epoxy coatings containing APP compare with GO0.6‐H0.3 coating. Salt spray test result demonstrated that all epoxy coating filled with hybrid nanofillers maintained excellent surface integrity, preventing corrosion for up to 500 h under controlled accelerated corrosive conditions. A reasonable increment of limited oxygen index up to 12.5% was reported by the addition of 1 phr APP, indicating its best flame retardancy and thermal stability properties among coating samples. The appropriate addition of APP (1 phr) enhanced the flame retardancy and thermal stability properties of hybrid GO‐HNT‐IFR coatings to a certain extent but it is impaired by increasing the APP loading. Transmission electron microscopy results validated the formation of aggregation at high APP loading, consequently affecting coating performances as well as its adhesion strength.

Self-healing epoxy coatings via microencapsulation of aromatic diisocyanate in lignin stabilized Pickering emulsions

Isocyanate-filled microcapsules are gaining increased attention for their role in developing self-healing materials, thereby reducing maintenance costs and increasing polymer durability. Nevertheless, microencapsulating highly reactive -NCO groups remains a challenging task in the literature. Likewise, considerable efforts have been directed towards developing polymers from renewable and biobased sources, which could also be applied to microcapsule synthesis. In this work, lignin, an abundant biopolymer, was used as a solid stabilizer for oil-in-water (O/W) interfaces, enabling the encapsulation of highly reactive isocyanate. Hybrid polyurethane/polyurea microcapsules containing reactive methylenediphenyl diisocyanate (MDI) were obtained via optimized O/W Pickering emulsions using lignin for system stabilization. This optimized process facilitated shell formation via the reaction of diisocyanate with lignin and water, eliminating the need for additional chain extenders. Scanning electron microscopy revealed the formation of spherical and rough microcapsules, while infrared spectroscopy confirmed the presence of residual free -NCO groups, indicating effective encapsulation of MDI. Additionally, a core -NCO concentration of 11 wt% was confirmed by titration. The microcapsules were further assessed as components in self-healing epoxy coatings. Their incorporation resulted in the retardation of corrosion on a low carbon steel panel after 72 h of submersion in a saline solution. Electrochemical impedance spectroscopy (EIS) confirmed a significant increase of approximated 620% in impedance modulus after 83 days of immersion in a 3.5 wt% NaCl solution, compared to the neat epoxy coating. These findings suggest a promising technological application of this material for the advancement of self-healing epoxy-based coatings and composites.