Barrier Properties Of Coatings Research Articles

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.

New electrochemical method for the determination of the barrier properties of corrosion protective coatings

A novel electrochemical method evaluates the durability of corrosion protective coatings by measuring the galvanic current between a coated AZ31 Mg alloy and a Pt auxiliary electrode in a 2 M NaCl solution. In this work an organo-inorganic sol-gel film was used. The durability criterion, tsat, was selected as the time where the galvanic current reached 1 mA. Validated using EIS, the method showed 82 % accuracy. However, this difference was not deemed statistically significant. Under the conditions used in this study, results from the new method align with traditional EIS, establishing its viability as a simple and straightforward tool for assessing the barrier properties of corrosion protective coatings.

Boosting the acid penetration barrier of epoxy-silica organic-inorganic hybrid coating via adjusting its molecular structures: Experimental and molecular dynamics simulation study

The permeability barrier property of coatings against corrosive media determines their service life. Herein, the molecular structure of epoxy-silica organic-inorganic hybrid (OIH) coating is regulated to endow the coatings with enhanced barrier properties by a simple sol-gel method. Experiments show that the coating with 8% Si-O-Si structure has the best acid penetration resistance after 45 days of immersion in 10 wt.% H2SO4 solution. In addition, molecular dynamics simulation results show that the molecular structure of OIH affects the densification of the coating, forming a highly cross-linked network structure that inhibits the diffusion and destructive effects of corrosive media and thus affects the acid penetration resistance of the coating.

Freeze Drying of Organically Modified Layered Silicates as Key Step to Improve the Barrier Properties of Organic Coatings for High Power Electronics Protection

AbstractOrganically modified layered silicates can be used as barrier pigments in organic coating systems to reduce the permeation of water vapor and gases, e.g., oxygen as well as harmful gases that promote corrosion. Unmodified layered silicates are not sufficient to reduce the permeation significantly. However, the arrangement and orientation of the particles have an enormous impact on the later performance in the barrier film. In organic solvents or non‐aqueous polymer matrices the non‐modified layered silicates cannot exfoliate adequately. The organic modification influences the layer spacing and the compatibility to organic solvents. Layered silicates are modified with dodecylamine to enhance the spacing layer. The spacing layer is enhanced by 55% caused by the organic modification as it is commonly known. In contrast to previous work freeze drying of the organically modified layered silicates improved the particle distribution and by this barrier properties significantly. The modified particles reduce the diffusion of water and oxygen by ≈99.6% and 97.2%, respectively. The corrosive gas test of electronic circuit boards shows no growth of dendrites and no failure of the electronics in contrast to protective coating without the layered silicates.

Potential of epoxy coating containing ionic liquid as anti-corrosion coating: Evaluation of barrier properties

Barrier properties of innovative epoxy coatings containing 10 or 20 phr of phosphate/phosphonium ionic liquid (IL) were investigated using mainly electrochemical impedance spectroscopy. The impedance diagrams revealed quasi-pure capacitive behavior and the impedance modulus at low frequency, related to corrosion resistance, remains at around 1012 Ω cm2 during immersion time in 0.1 M NaCl solution. The capacitances were graphically extracted from Cole–Cole representations, and the resistances were determined using R//C electric equivalent circuits. Both epoxy–IL coatings were free of porosity and impeded the hydration of the matrix. The results were also compared to those of conventional epoxy coatings, for which hydration occurs owing to their porosity. Results indicate that this new epoxy–IL coating system would offer excellent anticorrosion protection for metallic substrates.

Nanoceramic-based coatings for corrosion protection: a review on synthesis, mechanisms, and applications.

Corrosion is a pervasive issue with significant economic and safety implications across various industries. Nanoceramic-based coatings have emerged as a promising solution for corrosion protection due to their unique properties and mechanisms. This review aims to comprehensively examine the synthesis, mechanisms, and applications of nanoceramic-based coatings for corrosion protection. The review begins by highlighting the importance of corrosion protection and its impact on different industries. It introduces nanoceramic-based coatings as a potential solution to address this challenge. The objective is to provide a thorough understanding of the synthesis methods, mechanisms, and applications of these coatings. The fundamental principles of corrosion and different corrosion mechanisms are discussed, along with the limitations of traditional corrosion protection methods. The review emphasizes how nanoceramic-based coatings can overcome these limitations and provide superior corrosion resistance. Various synthesis methods, including sol-gel, electrodeposition, and physical vapor deposition, are described in detail, along with the factors influencing the synthesis process. Recent advancements and innovations in nanoceramic coating synthesis techniques are also highlighted. This looks at how coatings made with tiny ceramic particles protect against corrosion. It examines the importance of small-scale details like particle size, shape, and what the particles are made of. The formation of passive layers, self-healing mechanisms, and barrier properties of nanoceramic coatings are explained. The diverse applications of nanoceramic coatings for corrosion protection in industries such as automotive, aerospace, and marine are comprehensively discussed. Case studies and examples demonstrating the significant corrosion resistance and improved performance achieved with nanoceramic coatings are presented.

EIS study on the barrier properties of silicone-epoxy coatings enhanced by different PDA-BN@ZnO nano-pigment contents

To evaluate the barrier properties of the composite coatings reinforced by PDA (polydopamine)-BN@ZnO nano-pigments, the correlation between electrolyte transport characteristics and different nano-pigment contents in the composite coatings was studied. The electrochemical response of composite coatings was mainly controlled by non-Faraday process. A two-layer model based on Young's impedance was established to fit the non-Faraday process of the composite coatings from the 6th day of immersion. The coating resistivity varying with electrolyte transport could be used as a key parameter to describe the barrier properties of the coatings. At the same time, the explanation that different contents of nano-pigments enhance or weaken the barrier performance of composite coatings was given, that is, the nanoconfinement effect of the polymer under the effect of nano-pigments.

Enhancing cathodic protection and barrier properties of zinc-rich epoxy coatings with mesoporous Ti4O7 additive

Searching for an optimal material additive that can enhance both the cathodic protection and barrier properties of zinc-rich epoxy coatings (ZRE) simultaneously remains a significant challenge nowadays. In this study, mesoporous Ti4O7 particles with high conductivity and chemical inertness were synthesised via the thermal reduction method and added to ZRE coating. The impact of different Ti4O7 filler contents on the corrosion resistance of ZRE coating containing 70 wt% zinc was assessed by electrochemical analysis, water uptake measurements, salt spray test and material characterisation techniques. The results demonstrated that the incorporation of mesoporous Ti4O7 significantly enhances the initial cathodic protection and long-term barrier properties of ZRE. The primary mechanism involves the conductive Ti4O7 ameliorating the Zn isolation caused by non-conductive Zn corrosion products and fostering a more efficient network for conductive penetration between zinc particles to improve cathodic protection efficacy. Moreover, mesoporous Ti4O7 promotes the uniform deposition and growth of ZnO/Zn(OH)2 by adsorption and anchoring of Zn(OH)42− and changes the shape of the corrosion product (columnar), thus improving the barrier performance of ZRE coating.

Filiform Corrosion on Polyester Powder-Coated Aluminum

Filiform corrosion initiates and grows locally at macroscopic defects in coatings on metal substrates. While typically not detrimental to the bulk metal properties, the filiform corrosion results in threadlike filaments that propagate parallel to the surface underneath the coating. Herein, we present a study correlating the electrochemical and structural properties of polyester powder coatings onto 6022 aluminum to their associated resistance to filiform corrosion. Filiforms are propagated using a modified EN 3665 method and tracked temporally via bright field microscopy. Results including electrochemical impedance spectroscopy, open-circuit potential tracking, and potentiostatic experiments were used to evaluate coating barrier properties. Coating morphologies of pre- and post-corrosion samples are evaluated using SEM and EDX. Mechanical properties of free-standing polyester films are also characterized. The combined electrochemical and mechanical data are used to derive polyester coating design criterion to maximize resistance to filiform corrosion.

Cellulose nanocrystals-reinforced waterborne epoxy coatings with enhanced corrosion resistance for steel

The practical applications of waterborne epoxy coatings are limited due to their poor barrier properties caused by the formation of numerous micropores and defects during the curing process. Herein, cellulose nanocrystals (CNCs)-reinforced waterborne epoxy coatings were fabricated by the direct addition of 0.2–1.0 wt% CNCs to waterborne epoxy emulsion followed by amine curing agent addition and spray coating. The incorporation of 0.2–0.5 wt% CNCs had no discernible impact on the stability of the waterborne epoxy emulsion. This led to the uniform dispersion of CNCs in the cured coating matrix, as evidenced by differential scanning calorimetry analysis. Because of the good compatibility, 0.2–0.5 wt% CNCs-reinforced epoxy coatings exhibited superior corrosion protection performance for steels. The impedance modulus of these coatings remained at 108 Ω cm2 after being immersed in a 3.5 wt% NaCl solution for 21 d. The hydroxyl groups present on the CNC surface undergo a reaction with the epoxy group, enhancing intermolecular interaction and leading to the formation of a defect-free dense structure that improves coating barrier properties. However, the incorporation of an excessive amount of CNCs (i.e., 0.8 and 1.0 wt%) significantly compromised the corrosion resistance of epoxy coatings due to aggregation-induced coating defects. Overall, this study provides a facile and green strategy for corrosion resistance improvement of waterborne epoxy coatings.

Influence of AC-DC-AC Cycling with Hydrostatic Pressure on Accelerated Protective Performance Test of Glass Flake Epoxy Coating

To achieve fast testing of the barrier properties of organic coatings, immersion tests, AC-DC-AC tests, and coupled tests of AC-DC-AC with hydrostatic pressure were conducted in seawater for a glass flake epoxy coating. Electrochemical impedance spectroscopy (EIS) was used to characterize the degradation processes of the coating during the tests, and the surface of the coating was analyzed using an optical microscope, scanning electron microscope (SEM), and a Fourier transform infrared spectrometer (FTIR). The results showed that periodic cathodic polarization coupled with high hydrostatic pressure can accelerate the degradation of a coating by facilitating the diffusion and uptake of electrolyte and the delamination of the coating. The coupled test method has the largest acceleration due to the synergetic effect of AC-DC-AC and hydrostatic pressure.

Influence of pre-treatments on adhesion, barrier and mechanical properties of epoxy coatings: A comparison between steel, AA7075 and AA2024

In this work five independent pre-treatments – mechanical polishing, alkaline and acid etching, sol-gel primer, and anodizing – were applied on mild steel and aluminum (AA7075 and AA2024) substrates before the deposition of epoxy coatings. The results demonstrate that efficient adhesion can be achieved by simple methodologies and widely available chemicals as an alternative to toxic conversion layers or highly energetic processes. All the treatments provided higher adhesion (up to 75%, 61% and 14% on AA7075, AA2024 and steel, respectively) and better anti-corrosion performance (increase of impedance values at low frequency up to four orders of magnitude) than the polished reference. The anodizing of aluminum alloys yielded good anti-corrosion performance, but slightly lower mechanical properties compared to sol-gel primer and alkaline etching. The hydroxyls density was found to play a major role in strong adhesion prevailing over surface roughness, contact area, oxide thickness and hydrophobicity. Despite the efficient performance of hydrogen bonds from acid and alkaline etching on aluminum, these connections do not yield sufficiently stable bonds that make an impermeable barrier of epoxy coatings on steel. Covalent bonds (Me-O-Si) represent the key to achieve a significant improvement in mechanical and chemical resistance against the ingress of water and polymer chain relaxation. This makes the sol-gel primer a simple, economical, and environmentally alternative towards efficient bonding at a molecular level.

Barrier and Antimicrobial Properties of Coatings Based on Xylan Derivatives and Chitosan for Food Packaging Papers

This paper analyzes the potential of coatings based on xylan derivatives and chitosan to provide barrier properties and antimicrobial protection for paper food packaging and also to substitute the synthetic materials currently used in the food packaging industry. Colloidal dispersions of xylan derivatives (hydrophobized xylan with alkyl ketene dimers—XyAKD—and acetylated xylan—XyAc) and a chitosan biopolymer (Ch) were applied as coatings in single and two successive layers on a paper substrate using a laboratory automatic film applicator. The assessment of the water and fatty compound barrier properties of coated paper samples showed differences in effectiveness among xylan derivatives and their combination with chitosan. Generally, xylan derivative coatings improved the barrier and antimicrobial features of coated papers compared with native xylan. However, important improvements were obtained by adding to the coating formula a chitosan biopolymer. Thus, the best barrier properties for water, water vapors, oils and greases were obtained for paper coated with the acetylated xylan and chitosan formula in a single layer, where values of 30 g/m2.day for the water vapor transmission rate (WVTR), a 92.8° contact angle (CA) and a KIT rating of 8 were achieved. All coated paper samples exhibited the total inhibition of Bacillus sp. both after 24 and 48 h. Based on the obtained results in this study, one can conclude that the area of application of xylan hemicelluloses could be extended. Their utilization in appropriate chemical structures and combinations as coatings for paper can be a sustainable alternative for the food packaging industry.

A composite epoxy coating with a newly synthetic BN@SiO2 filler and its improvement on the durability of cement-based materials

In order to improve the durability of cement-based materials, a composite epoxy coating with a newly synthetic BN@SiO2 filler was developed using nanosilica (SiO2) and hexagonal boron-nitride (h-BN). In this study, the BN@SiO2 was synthesized through grafting SiO2 nanoparticles onto surface of h-BN, while the BN@SiO2 were verified by using Fourier transform infrared (FTIR) spectrum, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and transmission electron microscopy (TEM). Results showed that, the BN@SiO2 as a filler can outperform the SiO2 and h-BN for improving the thermostability and waterproofing performance of the coating. Three composite coatings prepared by SiO2, h-BN and developed BN@SiO2 can effectively prevent mortar from carbonation and chloride attack, but the coating with BN@SiO2 filler has more effectively performance than that with SiO2 and h-BN fillers. After the mortar sample covered with BN@SiO2 coating undergoes 180 days of chloride attack and 28 days of carbonization, its chloride penetration and carbonization depths were reduced by 50% and 64% compared to pure coating, respectively. In general, optimizing the properties of the filler can significantly enhance the barrier properties of coatings, which is beneficial for improving the durability of cement-based materials.

Dual function of rare earth carboxylate compounds on the barrier properties and active corrosion inhibition of epoxy coatings on mild steel

In this work, two rare earth carboxylate compounds, lanthanum 4-hydroxycinnamate (La(4-OHcin)3) and yttrium 3-(4-methylbenzoyl)propanoate (Y(mbp)3), were incorporated into bisphenol-based epoxy resin to investigate their effectiveness in coating barrier properties and active corrosion inhibition. EIS results showed that the incorporation of rare earth carboxylate inhibitors significantly improved corrosion resistance compared to the inhibitor free coating, with the global impedance modulus remaining at a level higher than 1 GΩ cm2 after 219 days immersion. Following EIS experiments, cross-sectional views of the coatings exhibited a pore-plugging behavior by rare earth containing precipitates, which reinforced the coating barrier properties and delayed the electrolyte diffusion process. These effects were also reflected from the electrochemical parameters extracted from breakpoint frequency analysis and equivalent circuit modelling. Filiform corrosion experiments for artificially scratched coatings suggest that the addition of rare earth carboxylates effectively suppressed the initiation and growth of filaments as well as the development of the coating delamination front. The active corrosion inhibition is possibly related to the formation of a surface protective film consisting of bimetallic complexes and rare earth metal rich precipitates. The electrochemical measurements and surface analyses evidence the dual function of rare earth carboxylate species for enhancing coating barrier properties against electrolyte penetration and providing active corrosion inhibition for the underlying AS1020 mild steel.

Antibacterial efficiency over time and barrier properties of wood coatings with colloidal silver

This work aims to represent a standard application for understanding the extent of the antibacterial efficacy of coatings with different amounts of colloidal silver on wooden surfaces over time. The key variable that was intended to be evaluated in this study was the “time efficiency,” with concerns about the possible efficacy in the durability of the surfaces. By highlighting the “expiry date” of the agents, as in the case with other products, the study aimed to confirm the validity of the simulation tests conducted in the laboratory with degradation tests. Furthermore, the role of the silver amount on the barrier performance of the coatings was assessed by liquid resistance, water uptake, and perspiration tests, evaluating the aesthetic durability of the coatings by means of colorimetric analyses. Ultimately, this work demonstrates that these coatings may represent alternatives in terms of prolonged antimicrobial activity when compared with the biocide agents currently in use, capable to offer good resistance to detergent solutions and to water. Nevertheless, due to silver’s susceptibility to extended exposure to acidic solutions, the findings of the research discourage the utilization of colloidal silver in wood paints intended for use in public settings.Key points• Colloidal silver does not alter the deposition process and does not introduce defects in the wood paint.• Coatings containing silver show high antimicrobial activity over time, against both E.coli and S.aureus.• The silver-based filler resists contact with detergents and aqueous solutions but suffers oxidation processes in acidic environments.

Super-anticorrosion epoxy nanocomposites prepared with P-doped carbon dots functionalized large-size boron nitride nanosheets

Large-size ultrathin 2D nanosheets show huge advantages in improving the barrier and anticorrosion properties of organic coatings. However, the irreversible agglomeration of large-size nanosheets has become a key scientific issue restricting their practical applications. Herein the in situ phosphorus-doped carbon dots (PCDs) are synthesized and decorated on large-size boron nitride nanosheets (BNNSs) matrix, to empower excellent dispersion of BNNSs (stable for a few weeks) and superlative nanosheet-matrix bonding with matrix. When served as the functional fillers for epoxy (EP) coatings, the resultant PCD@BNNS/EP composite coating shows greatly enhanced corrosion resistance due to the long-range ordered self-alignment of large-size PCD@BNNSs and strong interfacial bind with coating matrix. Typically, after 5 weeks of exposure in 3.5 wt% NaCl(aq), the coating resistance of the PCD@BNNS/EP composite coating maintained 6.3 × 109 O cm2, 2 ∼ 3 orders of magnitude higher than those of unmodified BNNS/EP composite (8.0 × 107 O cm2) and blank (4.2 × 106 O cm2) coatings, revealing exceptional long-term anticorrosion performance. The anticorrosion mechanism was unlocked in detail by the chemical reactions at the coating-metal interfaces, owing to the arrested incursion of aggressive species through the multi-effect synergies of superior shielding property and passivation function by the intercalated large-size and self-aligned PCD@BNNSs. Our work introduces a unique binary hybrid material system to construct high-performance coatings for future marine and aviation protection.

Green Approaches on Modification of Xylan Hemicellulose to Enhance the Functional Properties for Food Packaging Materials-A Review.

Based on the environmental concerns, the utilisation of hemicelluloses in food packaging has become a sustainable alternative to synthetic polymers and an important method for the efficient utilisation of biomass resources. After cellulose, hemicellulose is a second component of agricultural and forestry biomass that is being taken advantage of given its abundant source, biodegradability, nontoxicity and good biocompatibility. However, due to its special molecular structure and physical and chemical characteristics, the mechanical and barrier properties of hemicellulose films and coatings are not sufficient for food packaging applications and modification for performance enhancement is needed. Even though there are many studies on improving the hydrophobic properties of hemicelluloses, most do not meet environmental requirements and the chemical modification of these biopolymers is still a challenge. The present review examines emerging and green alternatives to acetylation for xylan hemicellulose in order to improve its performance, especially when it is used as biopolymer in paper coatings or films for food packaging. Ionic liquids (ILs) and enzymatic modification are environmentally friendly methods used to obtain xylan derivatives with improved thermal and mechanical properties as well as hydrophobic performances that are very important for food packaging materials. Once these novel and green methodologies of hemicellulose modifications become well understood and with validated results, their production on an industrial scale could be implemented. This paper will extend the area of hemicellulose applications and lead to the implementation of a sustainable alternative to petroleum-based products that will decrease the environmental impact of packaging materials.

A novel smart coating with hexacyanoferrate intercalated layered double hydroxides nanoadditive for early detection of carbon steel corrosion

The detection of corrosion at early stages could increase the service life of metal-based infrastructures in a cost-effective manner. Despite the recent progress in “smart” self-reporting corrosion sensing coatings, the development of environmentally friendly systems appropriate for steel substrate used in offshore applications remains a relevant challenge. In this study, a novel smart corrosion sensing coating, based on hexacyanoferrate intercalated Mg-Al LDH nanoadditive, was developed, aiming at the detection of early-stage corrosion of carbon steel. The detection mechanism is based on the ability of hexacyanoferrate ions to react with iron cations generated during the corrosion process, giving rise to a colorimetric signal, while LDH carriers provide a controlled release of active ions under corrosion conditions. The sensing nanoadditive was embedded into a commercial pigment-free water-based acrylic polyurethane coating. The nanomaterial was characterized structurally (XRD) and morphologically (STEM). The compatibility of the additive with the polymer formulation and its influence on the resulting coating performance was investigated in terms of rheological behavior, structure (FTIR), morphology (SEM/EDS), thermal (TGA, DSC) and mechanical (adhesion, hardness) properties. The corrosion protection ability of the coating was evaluated via EIS, while the sensing functionality was analyzed by visual analysis of the surface. The developed coating successfully detects early-stage corrosion of steel substrate at a lab scale, in conditions relevant to the use of metallic structures in offshore applications, demonstrating a correlation between the level of material degradation and the spectroscopic signal associated with the presence of the LDH functional nanoadditive. Furthermore, the observed decrease in coating barrier properties, caused by the presence of LDH, was overcome by the subsequent development of a multilayer coating system. Two different topcoats (epoxy- and polyurethane-based) were surveyed for this purpose, showing an improvement in the coating barrier properties without influencing the corrosion detection functionality of the sensing layer. The results were successfully validated by standard salt spray tests. The multilayer approach opens up the possibility to model coatings with different characteristics for various operating conditions.

Influence of impingement flows with sand particles on the barrier properties of organic coatings

Influence of impingement flows with sand particles on the barrier properties of organic coatings