Coatings

21 pages, 3924 KiB

Open AccessArticle

Influence of Chitosan–Sodium Tripolyphosphate-Coated Tung Oil Microcapsules on the UV Coating Performance of Cherry Wood Surface

by Wenjing Chang, Jinzhe Deng and Xiaoxing Yan

Coatings 2025, 15(8), 949; https://doi.org/10.3390/coatings15080949 - 13 Aug 2025

Abstract

By incorporating microcapsules with self-healing properties into the coating, a self-healing coating can be obtained, which can repair cracks or damage. In this study, chitosan–sodium tripolyphosphate-coated tung oil microcapsules 1# and 2# with a high encapsulation efficiency were incorporated into a UV-cured topcoat [...] Read more.

By incorporating microcapsules with self-healing properties into the coating, a self-healing coating can be obtained, which can repair cracks or damage. In this study, chitosan–sodium tripolyphosphate-coated tung oil microcapsules 1# and 2# with a high encapsulation efficiency were incorporated into a UV-cured topcoat on cherry wood surfaces at different ratios. The results showed that as the microcapsule content increased, the coating’s reflectivity and gloss loss increased, while its impact resistance improved. However, the coating’s adhesion and hardness decreased. The coating containing 6% microcapsule 1# exhibited optimal performance on cherry wood board. The reflectance of the ultraviolet–visible light of the coating was 41.14%, the lightness value was 58.35, the red-green value was 13.96, the yellow-blue value was 25.32, the color difference was 4.47, the gloss reduction rate was 66.84%, the roughness was 1.11 μm, the impact resistance grade was level 4, the adhesion was level 1, the hardness was 3H, and the recovery rate was 17.06%. Comparative analysis revealed that both the chitosan/arabic gum-encapsulated tung oil microcapsules and chitosan–sodium tripolyphosphate-coated tung oil microcapsules could impart self-healing functionality to UV-cured coatings when incorporated into the finish. Notably, the coating system containing 6% chitosan/arabic gum-encapsulated tung oil microcapsules demonstrated optimal performance characteristics when applied to cherry wood substrates. The research findings demonstrate the technical feasibility of achieving self-healing functionality in UV-cured coatings for cherry wood surfaces. Full article

(This article belongs to the Section Functional Polymer Coatings and Films)

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21 pages, 5297 KiB

Open AccessArticle

Construction and Performance Optimization of a Multifunctional CHP-Ti-MAO Composite Coating: Antibacterial Activity, Controlled Drug Release, and Corrosion Resistance

by Liting Mu, Yiqi Lian, Shiyu Zheng, Shuo Chang, Ximeng Li, Changhai Sun and Hongbin Qiu

Coatings 2025, 15(8), 948; https://doi.org/10.3390/coatings15080948 - 13 Aug 2025

Abstract

Titanium and its alloys are widely used in orthopedics because of their excellent mechanical properties and biocompatibility; however, their bioinert surface results in sluggish osseointegration and renders implants susceptible to bacterial infection. This study innovatively constructed a “CHP-Ti-MAO” composite coating, which aims to [...] Read more.

Titanium and its alloys are widely used in orthopedics because of their excellent mechanical properties and biocompatibility; however, their bioinert surface results in sluggish osseointegration and renders implants susceptible to bacterial infection. This study innovatively constructed a “CHP-Ti-MAO” composite coating, which aims to simultaneously improve early osseointegration and antibacterial performance. CHP micron coatings coated with hydroxyapatite (HA) and curcumin (Cur) at different PLGA concentrations (50%, 100%, and 150%) were deposited on the basis of calcium–phosphorus ceramic coatings prepared by micro-arc oxidation (MAO) following the emulsification-solvent volatilization method. It was found that increasing the concentration of PLGA can increase the particle size of the coating, enhance the hydrophilicity, and significantly improve the sustained release performance of the drug. Among them, the 100% PLGA concentration group performed the best: the drug-release half-life reached 75 h, and the corrosion current density was the lowest (9.5 × 10⁻⁹ A/cm²), showing the best corrosion resistance. This group of coatings has a strong and long-term antibacterial effect on Escherichia coli, with an antibacterial rate of more than 95% at 24 h and more than 99% by day 17. The hemolysis rate of all coatings was lower than 5%, indicating good biocompatibility. This study confirmed that 100% CHP-Ti-MAO composite coating successfully solved the limitations of excessive pore size and insufficient antibacterial persistence of an MAO layer and also had excellent slow-release, corrosion resistance, and high-efficiency antibacterial capabilities, which provided an important basis for the development of a new generation of multifunctional titanium-based implants. Full article

(This article belongs to the Special Issue Advanced Metallic Materials: Corrosion Protection and Surface Engineering)

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10 pages, 1885 KiB

Open AccessArticle

Plasma-Induced Amino HBP/Ag Nanoparticle-Grafted PP Melt-Blown Nonwoven Fabric and Its Antibacterial Performance

by Hongxia Chen, Wei Zhang, Weidong Gao and Guangyu Zhang

Coatings 2025, 15(8), 947; https://doi.org/10.3390/coatings15080947 - 13 Aug 2025

Abstract

In this work, polypropylene (PP) melt-blown nonwoven fabric was used as a raw material, which was plasma-treated and grafted with HBP/Ag nanoparticle (NP) solution. The surface wettability, surface morphology, and surface element composition after the treatment were evaluated through a contact angle test, [...] Read more.

In this work, polypropylene (PP) melt-blown nonwoven fabric was used as a raw material, which was plasma-treated and grafted with HBP/Ag nanoparticle (NP) solution. The surface wettability, surface morphology, and surface element composition after the treatment were evaluated through a contact angle test, field emission scanning electron microscopy (FE-SEM), energy-dispersive spectrometer (EDS), and Fourier transform infrared spectroscopy (FTIR), respectively. The antibacterial activity of PP fabrics treated with Ag NPs against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) was measured. SEM and EDS results showed that Ag NPs were evenly dispersed on the surface of the PP fabrics. The PP fabrics treated with Ag NPs exhibited excellent antibacterial performance. Full article

(This article belongs to the Special Issue Recent Progress on Functional Films and Surface Science)

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16 pages, 5272 KiB

Open AccessArticle

Molecular Dynamics Study on the Synergistic Compatibilization Mechanism of MAH-g-SBS in Epoxy Asphalt

by Pan Liu, Kaimin Niu, Bo Tian, Binbin Wang, Kai Li, Jiaxin Wan and Bailin Shan

Coatings 2025, 15(8), 946; https://doi.org/10.3390/coatings15080946 - 13 Aug 2025

Abstract

Epoxy asphalt is a superior polymer-modified asphalt material; however, significant differences in physicochemical properties, such as solubility parameters and dielectric constants, between epoxy resin and asphalt have led to compatibility issues that hinder its development. This study employed molecular dynamics simulations to investigate [...] Read more.

Epoxy asphalt is a superior polymer-modified asphalt material; however, significant differences in physicochemical properties, such as solubility parameters and dielectric constants, between epoxy resin and asphalt have led to compatibility issues that hinder its development. This study employed molecular dynamics simulations to investigate the effect of maleic anhydride-grafted styrene-butadiene-styrene (MAH-g-SBS) on the compatibility of epoxy asphalt. By analyzing parameters such as cohesive energy density, solubility parameters, energy distribution, interaction energy, radial distribution function, free volume fraction, and mean square displacement, the molecular mechanism underlying the enhanced compatibility was elucidated. The results indicate that the amphiphilic molecular structure of MAH-g-SBS significantly improves the thermodynamic compatibility between asphalt and epoxy resin, enhances interfacial affinity and stability, reduces the system’s total interaction and nonbonded energies, facilitates the dispersion and permeation of epoxy molecules into asphalt, and increases molecular mobility, thereby comprehensively enhancing the compatibility of the epoxy asphalt blend. Segregation tests and fluorescence microscopy further verified the simulation results, demonstrating that MAH-g-SBS improves the storage stability and phase uniformity of the epoxy asphalt system. Full article

(This article belongs to the Special Issue Novel Cleaner Materials for Pavements)

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23 pages, 6682 KiB

Open AccessArticle

Study on Live Temperature Rise and Electrical Characteristics of Composite Insulators with Internal Conductive Defects

by Jianghai Geng, Zhongfeng He, Yuming Zhang, Hao Zhang, Zheng Zhong and Ping Wang

Coatings 2025, 15(8), 945; https://doi.org/10.3390/coatings15080945 - 13 Aug 2025

Abstract

Internal conductive defects in composite insulators severely degrade their insulation performance and are considered concealed defects, posing a significant threat to the safe and stable operation of the power grid. Focusing on this issue, this study develops an electro-thermal multi-physical field simulation model [...] Read more.

Internal conductive defects in composite insulators severely degrade their insulation performance and are considered concealed defects, posing a significant threat to the safe and stable operation of the power grid. Focusing on this issue, this study develops an electro-thermal multi-physical field simulation model and uses finite element analysis to investigate the electric field distribution and temperature rise characteristics. Composite insulator specimens with varying defect lengths were fabricated using the electrical erosion test. Charged tests were then conducted on these defective specimens, as well as on field-decommissioned specimens. The impact of internal conductive defects on the infrared, ultraviolet, and electric field distribution characteristics of composite insulators during operation was analyzed. The results indicate that the surface electric field of composite insulators with internal conductive defects becomes highly concentrated along the defect path, with a significant increase in electric field strength at the defect’s end. The maximum field strength migrates toward the grounded end as the defect length increases. Conductive defects lead to partial discharge and abnormal temperature rise at the defect’s end and the bending points of the composite insulator. The temperature rise predominantly manifests as “bar-form temperature rise,” with temperature rise regions correlating well with discharge areas. Conductive defects accelerate the decay-like degradation process of composite insulators through a positive feedback loop formed by the coupling of electric field distortion, Joule heating, material degradation, and discharge activity. This study identifies the key characteristics of electrical and temperature rise changes in insulators with conductive defects, reveals the deterioration evolution process and degradation mechanisms of insulators, and provides effective criteria for on-site diagnosis of conductive defects. Full article

(This article belongs to the Collection Feature Paper Collection for Topic Editors and Invited Scholars in Coatings)

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15 pages, 4949 KiB

Open AccessArticle

The Synergistic Influence of Trace Impurities and Temperature on the Corrosion Behavior of Tubing in Supercritical CO₂ Environment

by Mifeng Zhao, Zaipeng Zhao, Junfeng Xie, Xuanpeng Li, Wenwen Song, Jinjie Zhou and Qiyao He

Coatings 2025, 15(8), 944; https://doi.org/10.3390/coatings15080944 - 13 Aug 2025

Abstract

Carbon dioxide capture, utilization, and storage for enhanced oil recovery (CCUS-EOR) represents an effective strategy for reducing CO₂ emissions while improving oil recovery efficiency. However, harsh environmental conditions during the process can induce a supercritical state in captured CO₂, which [...] Read more.

Carbon dioxide capture, utilization, and storage for enhanced oil recovery (CCUS-EOR) represents an effective strategy for reducing CO₂ emissions while improving oil recovery efficiency. However, harsh environmental conditions during the process can induce a supercritical state in captured CO₂, which may undermine the structural integrity of tubular components through corrosion. This study systematically investigated the corrosion behaviors of two tubing steels (P110 and Super 13Cr) in 20 MPa supercritical CO₂ containing trace H₂S/O₂ impurities at 60–120 °C using weight loss tests and surface analysis. The results demonstrate that in water-unsaturated supercritical CO₂ with ≤500 ppmv H₂S, both steels exhibited low general corrosion rates (P110: 0.03 mm/y; S13Cr: 0.01 mm/y), with incomplete surface films partially covering grinding traces. However, S13Cr suffered pitting corrosion at >500 ppmv H₂S. Oxygen introduction triggered severe general/localized corrosion characterized by cracked, non-protective surface films. Reducing O₂ to 500 ppm yielded thin, continuous protective films, eliminating pitting. Temperature critically influenced S13Cr corrosion: decreasing from 120 °C to 60 °C increased the corrosion rates from 0.0031 mm/y to 0.08 mm/y due to enhanced water precipitation and impurity gas dissolution. These findings establish impurity thresholds to ensure acceptable corrosion performance. Full article

(This article belongs to the Section Corrosion, Wear and Erosion)

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14 pages, 4807 KiB

Open AccessArticle

Effect of Technological Parameters of Detonation Spraying on the Properties of Cr₂O₃ Coatings

by Bauyrzhan Rakhadilov, Dauir Kakimzhanov, Aibol Mural and Yernar Turabekov

Coatings 2025, 15(8), 943; https://doi.org/10.3390/coatings15080943 - 12 Aug 2025

Abstract

In the present work, the influence of technological parameters of detonation sputtering, in particular the degree of barrel filling, on the properties of chromium oxide (Cr₂O₃) coatings was investigated. Coatings were obtained under different sputtering conditions and analyzed comprehensively [...] Read more.

In the present work, the influence of technological parameters of detonation sputtering, in particular the degree of barrel filling, on the properties of chromium oxide (Cr₂O₃) coatings was investigated. Coatings were obtained under different sputtering conditions and analyzed comprehensively using X-ray phase analysis, optical and electron microscopy, and measurements of microhardness, porosity, and tribological characteristics. The results showed that the degree of barrel filling significantly affects the microstructure, thickness, porosity, and mechanical properties of the coatings. The sample obtained at 58% barrel filling showed the lowest porosity (0.01%), uniform distribution of chromium oxide, and the best adhesion, which makes it possible to consider this mode as optimal for the formation of wear-resistant coatings by detonation spraying. Full article

(This article belongs to the Special Issue Advanced Ceramic Materials and Coatings: Synthesis, Properties and Applications)

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19 pages, 4847 KiB

Open AccessArticle

Promoted Mechanical Properties and LBE Corrosion Resistance of FeCrAlTi-ODS Coatings Deposited by Magnetron Sputtering

by Hongtao Huang, Jinfeng Li, Bao Zhang, Jianwei Zhang, Zhigang Li and Hongtao Zhao

Coatings 2025, 15(8), 942; https://doi.org/10.3390/coatings15080942 - 12 Aug 2025

Abstract

A key issue with lead-cooled fast reactors is the corrosion vulnerability of fuel cladding and core components, which will endanger the structural materials’ integrity and the operational safety of the reactor system. The FeCrAlTi-ODS (Oxide Dispersion Strengthened) alloy coatings are prepared by the [...] Read more.

A key issue with lead-cooled fast reactors is the corrosion vulnerability of fuel cladding and core components, which will endanger the structural materials’ integrity and the operational safety of the reactor system. The FeCrAlTi-ODS (Oxide Dispersion Strengthened) alloy coatings are prepared by the Magnetron Sputtering technique under different bias voltages to shield structural elements in lead-cooled fast reactors from corrosion caused by lead-bismuth eutectic (LBE). A comprehensive study examines their mechanical attributes and resistance to LBE-induced corrosion. Compared to the bare substrate of austenitic 316L steel, the FeCrAlTi-ODS alloy coatings exhibit significantly improved binding force and hardness. The hardness (H) reaches 11.52 GPa (twice that of the bare substrate), and the elastic modulus (E) reaches 172.89 GPa. After the corrosion of bare substrate 316L steel by LBE, the oxygen element penetrated was obvious, and the Nickel element underwent selective migration. The FeCrAlTi-ODS alloy coatings show promising LBE corrosion resistance, and the FeCrAlTi-ODS alloy coating prepared under different bias can effectively protect the substrate material, which is attributed to the formation of protective FeCr₂O₄ film on the surface. The compact oxide film significantly prevents the further infiltration of the oxygen element and the migration of metal elements. Full article

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16 pages, 3635 KiB

Open AccessArticle

Properties and Diffusion Plugging Mechanism of Modified Sodium Bentonite

by Sen Hu, Bo Tian, Kaimin Niu, Haowu Wang and Zhihao Li

Coatings 2025, 15(8), 941; https://doi.org/10.3390/coatings15080941 - 12 Aug 2025

Abstract

With rising global temperatures, roads in the permafrost regions of the Qinghai–Tibet Plateau are exhibiting issues such as subsidence, water accumulation alongside the roads and in their foundations, and ongoing permafrost degradation. Among these issues, water accumulation has emerged as a prominent challenge [...] Read more.

With rising global temperatures, roads in the permafrost regions of the Qinghai–Tibet Plateau are exhibiting issues such as subsidence, water accumulation alongside the roads and in their foundations, and ongoing permafrost degradation. Among these issues, water accumulation has emerged as a prominent challenge in road management. In this study, sodium-based-bentonite-modified cementitious waterproof grouting materials were prepared and utilized as functional barrier layers. The rheological properties, mechanical strength, flowability, and setting time of the materials were tested under different sodium bentonite dosages. The feasibility of the application of these materials was evaluated, accounting for the evolution of pressure, flow rate, and diffusion distance of permafrost subgrades over different time scales when the materials were applied as functional barrier layers. The results indicate that, when used as a functional barrier layer, the modified cement-based grouting material exhibits a fluidity that meets the upper limit of grouting requirements, with a controllable setting time. Both compressive strength and apparent viscosity rise with the addition of sodium-based bentonite (Na-bentonite). Notably, an appropriate viscosity range of 0.35–0.50 Pa·s was found to effectively resist groundwater erosion while satisfying the critical performance requirements for grouting applications, demonstrating excellent applicability. In the field grouting test, the effects of grouting pressure and flow rate over different time scales on soil cracking, spreading distance, and the crack-filling process were further analyzed. Based on these findings, a technical solution using a new type of subgrade treatment material (functional barrier layer) was proposed, providing a reference for related theoretical research and engineering practice. Full article

(This article belongs to the Section Environmental Aspects in Colloid and Interface Science)

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13 pages, 3005 KiB

Open AccessArticle

Temperature-Dependent Performance of Thermally Oxidized Zr2.5Nb Alloy for Orthopedic Implants: Mechanical Properties, Wear Resistance, and Biocompatibility

by Yunpeng Xiao, Hanke Song, Tangqing Hu, Yong Luo, Hao Xu and Xiaolei Sun

Coatings 2025, 15(8), 940; https://doi.org/10.3390/coatings15080940 - 11 Aug 2025

Abstract

This study investigates the critical influence of oxidation temperature on the intrinsic characteristics and surface properties of thermally oxidized Zr2.5Nb alloy. The resulting oxide layers were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), surface hardness, and nanoindentation. [...] Read more.

This study investigates the critical influence of oxidation temperature on the intrinsic characteristics and surface properties of thermally oxidized Zr2.5Nb alloy. The resulting oxide layers were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), surface hardness, and nanoindentation. The tribological behavior of the untreated and thermally oxidized Zr2.5Nb alloy was evaluated via reciprocating ball-on-disc wear tests under a load of 29.4 N. MC3T3-E1 cells were employed to assess the biocompatibility. The results show that oxide layers primarily composed of m-ZrO₂ formed on the alloy surface, with thickness increasing from 2.43 µm to 13.59 µm as the oxidation temperature rose from 500 °C to 700 °C. However, this thickness increase was accompanied by elevated defect density. Compared to the untreated alloy, thermally oxidized samples exhibited significantly enhanced hardness and wear resistance. Notably, oxidation at 600 °C produced a dense 5.31 µm oxide layer with optimal structural integrity, achieving an 85% reduction in wear rate and a superior MC3T3-E1 cell relative activity of 123.07 ± 6.02%. These findings provide foundational data for developing zirconium-based implants with improved stability. Full article

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16 pages, 6498 KiB

Open AccessArticle

Near-Nozzle Atomization Characteristics in Air-Assisted Spraying: Integrated VOF-DPM Modeling and Experimental Validation

by Shiming Chen, Yu Zhang, Zhaojie Wu, Gang Fang, Yan Chen and Jimiao Duan

Coatings 2025, 15(8), 939; https://doi.org/10.3390/coatings15080939 - 11 Aug 2025

Abstract

Near-nozzle atomization characteristics in air-assisted spraying were investigated through a novel 3D transient model integrating Volume-of-Fluid and Large Eddy Simulation (VOF-DPM) methods, with experimental validation of droplet distributions (Malvern analyzer) and coating thickness profiles. Key findings reveal that (1) the spray field stabilizes [...] Read more.

Near-nozzle atomization characteristics in air-assisted spraying were investigated through a novel 3D transient model integrating Volume-of-Fluid and Large Eddy Simulation (VOF-DPM) methods, with experimental validation of droplet distributions (Malvern analyzer) and coating thickness profiles. Key findings reveal that (1) the spray field stabilizes within 30 mm downstream, achieving 80% atomization efficiency (droplets ≤ 100 μm) at 27.5 mm axial distance; (2) radial momentum originates dually from fan-shaped airflow (max 595 m/s) and transverse motion induced by central atomizing air entrainment—a previously unreported mechanism; (3) paint loading delays flow stabilization to 2.5 ms (vs. 0.7 ms for gas-only flow) while reducing peak axial velocity by 18%–22% due to gas–liquid momentum exchange; (4) auxiliary and fan airflows synergistically constrain dispersion, forming elliptical sprays with characteristic cone angles of 61.7° (short axis) and 99.1° (long axis). Significantly, surface tension plays a dual role in inhibiting droplet atomization while promoting ligament pinch-off at 8.1 mm breakup length. These results provide the first quantitative characterization of gas–liquid interactions in near-nozzle regions, enabling precise parameter control for enhanced coating uniformity on complex surfaces. Full article

(This article belongs to the Section Surface Characterization, Deposition and Modification)

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22 pages, 8634 KiB

Open AccessArticle

Effect of Tea Tree Essential Oil@Chitosan Microcapsules on Surface Coating Properties of Pine Wood

by Nana Zhang, Ye Zhu and Xiaoxing Yan

Coatings 2025, 15(8), 938; https://doi.org/10.3390/coatings15080938 - 11 Aug 2025

Abstract

Pine wood has a natural, rustic, and environmentally friendly style and is used in a large number of applications in the furniture industry. However, its soft and porous texture makes it susceptible to bacteria, mould, and other micro-organisms. Pine wood was selected as [...] Read more.

Pine wood has a natural, rustic, and environmentally friendly style and is used in a large number of applications in the furniture industry. However, its soft and porous texture makes it susceptible to bacteria, mould, and other micro-organisms. Pine wood was selected as the test substrate, and tea tree essential oil@chitosan (TTO@CS) microcapsules with emulsifier concentrations of 4%, 5%, and 6% were added to the waterborne topcoat at a content of 1%–9% (in 2% intervals) to investigate their effect on the surface coating properties of pine wood. With the increase in microcapsule content, there was an overall increase in colour difference and light loss rate of pine wood surface coating, and the reflectance showed an increase and then decrease. The overall performance of the pine wood surface coatings containing 7% of 13# microcapsules was found to be excellent: the antimicrobial activity of the coatings was 62.58% for Escherichia coli and 61.29% for Staphylococcus aureus after 48 h, and the antimicrobial activity of the coatings was 40.14% for Escherichia coli and 38.89% for Staphylococcus aureus after 4 months. The colour difference in the coating was 2.37, and the light loss was 63.71%. The reflectance value was found to be 0.6860, while the hardness was determined to be 2H and the adhesion class was categorised as one. The impact resistance class was determined to be three, while the roughness was measured at 1.320 μm. The waterborne coating on the surface of pine wood was modified by microencapsulation technology with the objective of enhancing the antimicrobial properties of pine wood and expanding its scope of application. Full article

(This article belongs to the Section Functional Polymer Coatings and Films)

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24 pages, 4598 KiB

Open AccessArticle

Microbial Biosurfactant as Sustainable Inhibitor to Mitigate Biocorrosion in Metallic Structures Used in the Offshore Energy Sector

by Yslla Emanuelly S. Faccioli, Irinan B. França, Kaio Wêdann Oliveira, Bruno Augusto C. Roque, Alexandre Augusto P. Selva Filho, Attilio Converti, Rita de Cássia F. Soares da Silva and Leonie A. Sarubbo

Coatings 2025, 15(8), 937; https://doi.org/10.3390/coatings15080937 - 11 Aug 2025

Abstract

Microbiologically influenced corrosion (MIC) represents a critical challenge to the integrity of pipelines, piping, and metal structures in offshore environments, directly affecting the safety and operational costs of companies in the energy sector. However, conventional control methods, such as the use of chemical [...] Read more.

Microbiologically influenced corrosion (MIC) represents a critical challenge to the integrity of pipelines, piping, and metal structures in offshore environments, directly affecting the safety and operational costs of companies in the energy sector. However, conventional control methods, such as the use of chemical inhibitors, raise environmental and economic concerns. To face this problem, a biosurfactant produced by Pseudomonas cepacia CCT 6659 was tested as a biocorrosion inhibiting agent on carbon steel specimens immersed in seawater. For this purpose, static and dynamic conditions were simulated using different concentrations of the biosurfactant. Furthermore, analyses were performed using Scanning Electron Microscopy paired with Energy Dispersive Spectroscopy (SEM/EDS) to visualize the morphology of the biofilm and its chemical components. Laboratory tests indicated that the biosurfactant formulated in a 1:5 (v/v) ratio reduced the mass loss of test specimens (119.72 ± 2.64 g/m²) by no less than 57.3% compared to the control (280.28 ± 4.58 g/m²). Under dynamic conditions, the 1:2 (v/v) formulation showed greater protection, being able to reduce specimen corrosion (578.87 ± 7.01 g/m²) by 69.6% compared to the control (1901.41 ± 13.53 g/m²). SEM/EDS analyses revealed changes in surface composition and a reduction in corrosive elements associated with sulfur in the formed biofilms, which may be associated with a decrease in sulfate-reducing bacteria (SRB) activity, suggesting microbial inhibition by the biosurfactant. The results obtained in this study highlight the biosurfactant as a viable and ecological alternative to synthetic inhibitors, with potential application in the protection of metal structures exposed to corrosive environments in offshore energy systems, promoting greater durability, sustainability, and less environmental impact. Full article

(This article belongs to the Section Corrosion, Wear and Erosion)

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17 pages, 2677 KiB

Open AccessArticle

Study of Polyhedral Oligomeric Silsesquioxane-Modified Superwetting Transparent Coating for Anti-Fogging, Stain Resistance, Self-Cleaning and Anti-Biological Application

by Weibiao Zhu, Jinxin He and Xia Dong

Coatings 2025, 15(8), 936; https://doi.org/10.3390/coatings15080936 - 11 Aug 2025

Abstract

Transparent coatings with superwetting properties (superhydrophilicity or superhydrophobicity) have broad application prospects. Usually, most studies have been carried out separately on superhydrophobic coatings or superhydrophilic coatings. In our work, superhydrophilic transparent coatings were prepared by the four-mercapto and four-polyethylene glycol monomethyl acrylate modified [...] Read more.

Transparent coatings with superwetting properties (superhydrophilicity or superhydrophobicity) have broad application prospects. Usually, most studies have been carried out separately on superhydrophobic coatings or superhydrophilic coatings. In our work, superhydrophilic transparent coatings were prepared by the four-mercapto and four-polyethylene glycol monomethyl acrylate modified POSS (POSS-(SH)₄-(PEGMA)₄) (designated as I-coating) as well as superhydrophobic transparent coating (designated as O-coating) were prepared with the mercapto and seven-heptyl decafluoroheptyl acrylate modified POSS (POSS-SH-(DFMA)₇). The similarities and differences in anti-fogging, stain resistance, self-cleaning and anti-biological application between superhydrophobic and superhydrophilic coatings were compared systematically. The results show that superhydrophilic coatings performed better at preventing fog and facilitating self-cleaning; nevertheless, superhydrophobic coatings exhibited superior efficacy in the removal of contaminants such as markers and lipsticks. Both superwetting coatings demonstrated proficiency in self-cleaning and in deterring biological adhesion with respect to low-viscosity oil droplets. The relevant research of this paper provided a reference for the subsequent study on the advantages and disadvantages of superhydrophilic and superhydrophobic as well as its specific application. Full article

(This article belongs to the Section Bioactive Coatings and Biointerfaces)

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21 pages, 4980 KiB

Open AccessArticle

Strength Development of Bottom Ash-Based Geopolymer-Stabilized Recycled Concrete Aggregate as a Pavement Base Material

by Menglim Hoy, Chokchai Traiyasut, Suksun Horpibulsuk, Avirut Chinkulkijniwat, Apichat Suddeepong, Apinun Buritatum, Teerasak Yaowarat, Mantana Julvorawong and Thanaset Savetviwat

Coatings 2025, 15(8), 935; https://doi.org/10.3390/coatings15080935 - 11 Aug 2025

Abstract

This study investigated a 100% waste-derived material system, using bottom ash (BA) and recycled concrete aggregate (RCA) for sustainable pavement base applications. This innovative approach diverts both construction and power plant waste from landfills while replacing conventional natural aggregates and cement-based binders. Five [...] Read more.

This study investigated a 100% waste-derived material system, using bottom ash (BA) and recycled concrete aggregate (RCA) for sustainable pavement base applications. This innovative approach diverts both construction and power plant waste from landfills while replacing conventional natural aggregates and cement-based binders. Five RCA:BA replacement ratios (90:10 to 50:50) were evaluated with three Na₂SiO₃:NaOH alkaline activator ratios (1:1, 1:1.5, and 1:2) through unconfined compressive strength (UCS) testing, scanning electron microscopy, energy dispersive X-ray spectroscopy (SEM-EDX), and X-ray diffraction (XRD) analysis. The RCA90BA10 composition with a G/N ratio of 1:2 achieved exceptional performance, reaching 9.14 MPa UCS at 7 days while exceeding the Department of Highways, Thailand, requirement of 2.413 MPa. All geopolymer-stabilized mixtures substantially surpassed minimum specifications, validating the technology for high-traffic pavement applications. Toughness evaluation confirmed superior energy absorption capacity of 107.89 N·m for the optimal formulation. Microstructural characterization revealed that higher G/N ratios promoted extensive sodium aluminosilicate hydrate and calcium silicate hydrate gel formation, creating dense, well-integrated matrices. XRD patterns confirmed successful geopolymerization through pronounced amorphous gel development between 20° and 35° 2θ, correlating directly with mechanical performance improvements. The RCA90BA10 formulation demonstrated optimal balance between reactive aluminosilicate content and structural aggregate framework. This technology offers significant environmental benefits by diverting construction and power plant waste from landfills while achieving mechanical properties superior to conventional materials, providing a scalable solution for sustainable infrastructure development. Full article

(This article belongs to the Section Environmental Aspects in Colloid and Interface Science)

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14 pages, 10162 KiB

Open AccessArticle

Corrosion Behavior of Porcelain Enamels in Water Tank Storage

by Nicolò Mattei, Luca Benedetti and Stefano Rossi

Coatings 2025, 15(8), 934; https://doi.org/10.3390/coatings15080934 - 11 Aug 2025

Abstract

Recent updates to European Union directives on drinking water have extended safety limits to hot water, increasing the need to assess materials commonly used in water storage systems, such as porcelain enamel. This study investigates the interaction between enameled surfaces and aqueous environments, [...] Read more.

Recent updates to European Union directives on drinking water have extended safety limits to hot water, increasing the need to assess materials commonly used in water storage systems, such as porcelain enamel. This study investigates the interaction between enameled surfaces and aqueous environments, focusing on element release and microstructural alterations. The mass loss and chemical stability of the enamel were evaluated through a combination of surface characterization and Inductively Coupled Plasma (ICP) analysis. Time-resolved quantification of selected elements confirmed that all concentrations remained within EU regulatory thresholds. Additionally, the enamel was subjected to acidic and alkaline environments to explore the influence of pH on degradation mechanisms. Scanning electron microscopy (SEM) revealed that while the enamel undergoes surface-level modifications, the bulk structure remains intact. Notably, alkaline exposure had the strongest impact, dissolving needle-like calcium-rich structures and altering the surface more significantly than water or acid alone. These structures appear to facilitate localized corrosion once degraded. The correlation between surface morphology and elemental release dynamics highlights the critical role of microstructural features in determining long-term chemical resistance. Overall, the results underscore the importance of optimizing both the composition and structure of enamel coatings for applications involving prolonged contact with potable water. Full article

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19 pages, 4696 KiB

Open AccessArticle

Ductile–Brittle Mode Classification for Micro-End Milling of Nano-FTO Thin Film Using AE Monitoring and CNN

by Hee-hwan Lee, Hyo-jeong Kim, Jae-hyeon Nam and Seoung-hwan Lee

Coatings 2025, 15(8), 933; https://doi.org/10.3390/coatings15080933 - 10 Aug 2025

Abstract

This study introduces a real-time acoustic emission (AE) monitoring system for the micro-milling of fluorine-doped tin oxide (FTO) thin films, a critical transparent conductive oxide (TCO) material. The system uses AE sensors to capture high-frequency elastic waves generated during the micro-milling process. We [...] Read more.

This study introduces a real-time acoustic emission (AE) monitoring system for the micro-milling of fluorine-doped tin oxide (FTO) thin films, a critical transparent conductive oxide (TCO) material. The system uses AE sensors to capture high-frequency elastic waves generated during the micro-milling process. We combine experimental and theoretical analyses to investigate how various milling parameters influence the AE signals. To address the crucial challenge of ensuring ductile mode cutting in brittle materials like FTO, we employed a convolutional neural network (CNN) to identify the transition between ductile and brittle machining modes. A CNN was trained on energy-based features extracted from the AE signals, achieving a classification accuracy of 97.37%. This high accuracy demonstrates the effectiveness of integrating AE sensing with deep learning for interpreting complex micro-machining data. The results confirm that this combined approach offers a powerful, non-destructive, and intelligent monitoring solution for improving process control and understanding in the micro-milling of fragile conductive thin films. Full article

(This article belongs to the Special Issue Advances in Coating Tribology: Smart, Sustainable and High-Performance Coatings for Next-Generation Applications)

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12 pages, 14320 KiB

Open AccessArticle

Effect of Scanning Speed on Microstructure and Properties of Ni/B₄C/TiC Coating

by Yan Tong, Bo Cui, Yu Liu, You Lv, Qimeng Liu and Dongdong Zhang

Coatings 2025, 15(8), 932; https://doi.org/10.3390/coatings15080932 - 9 Aug 2025

Abstract

Ni/B₄C/TiC coating was prepared using laser cladding technology with 45 steel as substrate material. The effects of different scanning speeds on phase composition, microstructure, microhardness, and tribological properties were investigated. It was found that the coating is primarily composed of Fe [...] Read more.

Ni/B₄C/TiC coating was prepared using laser cladding technology with 45 steel as substrate material. The effects of different scanning speeds on phase composition, microstructure, microhardness, and tribological properties were investigated. It was found that the coating is primarily composed of Fe₃B, Fe₃C, B₂Fe₃Ni₃, TiC, and solid solution of [Fe, Ni]. TiC particles are not completely dissolved, which promotes grain refinement. The microhardness increases with the increase in scanning speed and reaches the maximum value at 240 mm/min. The wear resistance test revealed that the coating exhibited the best wear resistance at 240 mm/min. The main wear mechanisms were fatigue wear, abrasive wear, and a small amount of oxidative wear. Full article

(This article belongs to the Special Issue Additive Manufacturing of Metallic Components for Hard Coatings, 2nd Edition)

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21 pages, 745 KiB

Open AccessReview

Sustainable Marine Coatings: Comparing the Costs, Benefits, and Impacts of Biocidal and Biocide-Free Paints

by Oskar Kontus and Jonne Kotta

Coatings 2025, 15(8), 931; https://doi.org/10.3390/coatings15080931 - 9 Aug 2025

Abstract

Biofouling presents a major challenge for maritime industries, leading to the widespread use of copper-based biocidal coatings that, while effective, release harmful substances into marine environments. Biocide-free alternatives, such as silicone-based, hydrogel, and natural product-derived coatings, offer more sustainable solutions. This systematic review [...] Read more.

Biofouling presents a major challenge for maritime industries, leading to the widespread use of copper-based biocidal coatings that, while effective, release harmful substances into marine environments. Biocide-free alternatives, such as silicone-based, hydrogel, and natural product-derived coatings, offer more sustainable solutions. This systematic review and meta-analysis assesses the functional, economic, and environmental performance of both coating types using PRISMA guidelines and literature from Scopus and ISI Web of Knowledge (2003–2025). Data from experimental, field, and modeling studies were synthesized, covering fouling intensity, coating durability, toxicity, cost-effectiveness, and regulatory compliance. Biocidal coatings generally performed better short-term, but biocide-free options showed comparable efficacy in some cases and clear environmental benefits. Although initial costs for biocide-free coatings are higher, they may yield savings over time. The meta-analysis found no significant differences in fouling or hydrodynamic performance, though quantitative evidence is limited. Research gaps remain, particularly in long-term studies, highlighting the need for standardized testing and lifecycle assessments to guide sustainable antifouling practices. The outcome of the review also showed that some evidence was excluded due to being in non-indexed sources. This highlights the importance of combining systematic and traditional review methods to ensure a more comprehensive assessment. Full article

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