Coatings

19 pages, 2117 KB

Open AccessArticle

Machine Learning-Based Prediction of Multi-Year Cumulative Atmospheric Corrosion Loss in Low-Alloy Steels with SHAP Analysis

by Saurabh Tiwari, Seong Jun Heo and Nokeun Park

Coatings 2026, 16(4), 488; https://doi.org/10.3390/coatings16040488 - 17 Apr 2026

Abstract

Atmospheric corrosion of carbon and low-alloy steels causes direct economic losses that are estimated at around 3.4% of the global GDP, and its accurate multi-year prediction is essential for protective coating selection, service-life estimation, and infrastructure maintenance scheduling. In this study, machine learning [...] Read more.

Atmospheric corrosion of carbon and low-alloy steels causes direct economic losses that are estimated at around 3.4% of the global GDP, and its accurate multi-year prediction is essential for protective coating selection, service-life estimation, and infrastructure maintenance scheduling. In this study, machine learning (ML) algorithms, including gradient boosting regressor (GBR), eXtreme gradient boosting (XGBoost), random forest (RF), support vector regression (SVR), and ridge regression, were trained on a 600-sample physics-grounded dataset to predict the cumulative atmospheric corrosion loss (µm) of low-alloy steels over 1–10 years of exposure. The dataset was constructed using the exact ISO 9223:2012 dose–response function (DRF) for a first-year corrosion rate and the ISO 9224:2012 power-law multi-year kinetic model (C(t) = C₁·t0.5), spanning ISO 9223 corrosivity categories C2–CX across 11 environmental and material input features. All models were evaluated on the original (untransformed) corrosion scale under an 80/20 train/test split and five-fold cross-validation. Gradient boosting achieved the best overall performance with test set R² = 0.968, CV-R² = 0.969, RMSE = 10.58 µm, MAE = 5.99 µm, and MAPE = 12.6%. XGBoost was a close second (R² = 0.958, CV-R² = 0.960). RF achieved an R² of 0.944. SHAP (SHapley Additive exPlanations) analysis identified SO₂ deposition rate, exposure time, relative humidity, Cl⁻ deposition rate, and temperature as the five most influential predictors. The dominance of the SO₂ deposition rate (mean |SHAP| = 26.37 µm) and the high second-place ranking of exposure time (13.67 µm) are fully consistent with the ISO 9223:2012 dose–response function and ISO 9224:2012 power-law kinetics, respectively, while among the material features, Cu and Cr contents showed the strongest negative SHAP contributions, confirming their corrosion-inhibiting roles in weathering steels. These results establish a physics-consistent, interpretable ML benchmark exceeding R² = 0.90 for multi-year cumulative corrosion loss prediction and provide a quantitative tool for alloy screening, coating selection in aggressive atmospheric environments, and service-life planning. Full article

(This article belongs to the Special Issue Anti-Corrosion and Anti-Wear Coatings: Fundamentals, Technologies, and Applications)

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16 pages, 2543 KB

Open AccessArticle

Modeling Reversible In Vivo-like Insulin Resistance Using Long-Term Adipocyte Spheroid Culture

by Sheetal Chowdhury, Joshua S. Speed, Gene L. Bidwell III and Amol V. Janorkar

Coatings 2026, 16(4), 487; https://doi.org/10.3390/coatings16040487 - 17 Apr 2026

Abstract

Human adipose biology is strongly influenced by three-dimensional (3D) architecture, cell–cell interactions, and local oxygen availability maintained over a long-term culture period, features that are not reproduced in traditional two-dimensional (2D) culture systems. To address this gap, we established a long-term human adipose-derived [...] Read more.

Human adipose biology is strongly influenced by three-dimensional (3D) architecture, cell–cell interactions, and local oxygen availability maintained over a long-term culture period, features that are not reproduced in traditional two-dimensional (2D) culture systems. To address this gap, we established a long-term human adipose-derived stem cell (hASC) spheroid model using elastin-like polypeptide–polyethyleneimine (ELP-PEI) coating. The ELP-PEI coating facilitated stable spheroid formation and sustained adipogenic differentiation over 56 days. As spheroids enlarged and matured, they exhibited hallmark features of adipocytes, including lipid accumulation, morphological compaction, and transition out of the proliferative state. Glucose uptake increased during maturation and declined as spheroids became larger. This reduction coincided with a marked rise in hypoxia-inducible factor-1α (HIF-1α) expression, indicating the emergence of a hypoxic microenvironment within larger spheroids. Notably, inhibiting HIF-1α restored insulin-stimulated glucose uptake, demonstrating that hypoxia was the primary driver of impaired insulin responsiveness in late-stage spheroids. These findings position ELP-PEI-supported hASC spheroids as a practical and physiologically relevant platform for studying human adipocyte biology, particularly the development and reversibility of hypoxia-associated metabolic dysfunction. This model offers new opportunities for mechanistic studies and for evaluating therapeutic strategies targeting insulin resistance and adipose tissue pathology. Full article

(This article belongs to the Special Issue Films and Coatings with Biomedical Applications)

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17 pages, 3188 KB

Open AccessArticle

Failure Analysis of Corrosion Perforation in P110 Tubing from a Nitrogen-Injection Well Induced by Coating Detachment

by Hanwen Zhang, Wenguang Zeng, Huan Hu, Ke Zhang, Lingfeng Huo, Yujie Guo, Jiangjiang Zhang and Dezhi Zeng

Coatings 2026, 16(4), 486; https://doi.org/10.3390/coatings16040486 - 17 Apr 2026

Abstract

This study investigates the causes and mechanisms of a corrosion-induced perforation failure in P110 tubing from a nitrogen injection well in the Tahe Oilfield. A comprehensive analysis was performed using macroscopic examination, mechanical and chemical property testing, characterization of corrosion product morphology and [...] Read more.

This study investigates the causes and mechanisms of a corrosion-induced perforation failure in P110 tubing from a nitrogen injection well in the Tahe Oilfield. A comprehensive analysis was performed using macroscopic examination, mechanical and chemical property testing, characterization of corrosion product morphology and composition, and electrochemical measurements. The results show that the tubing material met all relevant standard requirements, ruling out intrinsic material defects as a contributing factor. The primary cause of failure was the breakdown of the internal coating. Poor coating adhesion in the older tubing from the shallow section, combined with the tensile stress from the tubing’s suspended weight and the acidic service environment, led to coating blistering and disbondment, thereby exposing the underlying steel. In the presence of H₂S, CO₂, and O₂, severe electrochemical corrosion developed on the exposed metal surface. The process was further accelerated by a high concentration of Cl⁻, which promoted rapid localized corrosion and ultimately resulted in perforation. Based on these findings, several targeted mitigation strategies are proposed. These include optimizing the coating process to improve adhesion and modifying the corrosive environment. The recommendations provide practical guidance for corrosion control in similar oil and gas well applications. Full article

(This article belongs to the Section Metal Surface Process)

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15 pages, 2436 KB

Open AccessArticle

The Coupled Deterioration Effect of Recycled Concrete Aggregate and Seawater Sea Sand on Steel Corrosion: An Electrochemical Study

by Shuyi Miao, Kehua Sun, Xiang Chen, Jiren Xu and Xinxin Cao

Coatings 2026, 16(4), 485; https://doi.org/10.3390/coatings16040485 - 17 Apr 2026

Abstract

To address the shortage of natural aggregates and freshwater, and promote the recycling of construction and demolition waste and localized construction materials for marine engineering, this study explores the electrochemical corrosion characteristics and deterioration mechanism of steel bars in recycled concrete aggregate (RCA)–seawater [...] Read more.

To address the shortage of natural aggregates and freshwater, and promote the recycling of construction and demolition waste and localized construction materials for marine engineering, this study explores the electrochemical corrosion characteristics and deterioration mechanism of steel bars in recycled concrete aggregate (RCA)–seawater sea-sand concrete (SSC) concrete. Using RCA replacement rates (0%, 50%, 100%) as the core variable, specimens were prepared. Vacuum water saturation, open-circuit potential (OCP) monitoring, Tafel polarization scanning and electrochemical impedance spectroscopy (EIS) were adopted to study steel corrosion evolution within 180 days. The results show that RCA incorporation accelerates OCP negative drift and reduces passivation film stability, with more severe corrosion at higher replacement rates: the RCA100 group showed obvious corrosion after 60 days, while the RCA50 and RCA0 groups initiated corrosion at 90 days (RCA50 corroded faster). The surface mortar and internal microcracks of RCA enhance the water absorption and ion permeability of concrete, which, coupled with chloride ions, accelerates steel corrosion. This study clarifies the correlation between RCA replacement rate and corrosion parameters, providing data support for mix ratio optimization and marine engineering applications. Full article

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18 pages, 3285 KB

Open AccessArticle

Research on the Preparation of Red Mud High-Performance Cement Mortar and the Corresponding Resistance to Dry–Wet Alternation Cycles of Exposure to Chloride and Sulfate Solutions

by Ligai Bai, Chunying Zhu, Jian Zhang, Jiameng Wan, Junzhe Liu, Kangshuo Xia, Feiting Shi and Huihui Tong

Coatings 2026, 16(4), 484; https://doi.org/10.3390/coatings16040484 - 17 Apr 2026

Abstract

The accumulation of highly alkaline red mud poses serious environmental risks due to land occupation and potential soil/groundwater contamination. Recycling red mud as a secondary resource offers an eco-friendly solution, yet its influence on the performance of high-performance mortar (HPM) remains incompletely understood, [...] Read more.

The accumulation of highly alkaline red mud poses serious environmental risks due to land occupation and potential soil/groundwater contamination. Recycling red mud as a secondary resource offers an eco-friendly solution, yet its influence on the performance of high-performance mortar (HPM) remains incompletely understood, particularly in aggressive environments. This study aims to systematically evaluate the effects of red mud on the fresh and hardened properties of HPM, including rheological parameters, setting time, mechanical strength, drying shrinkage, and sulfate dry–wet erosion resistance. The novelty lies in (1) quantifying the nonlinear relationships between red mud content and rheological/setting behaviors, (2) revealing the dual effect of red mud with curing age, and (3) using XRD/SEM-EDS to elucidate the micro-mechanisms related to hydration products and elemental changes (Al and Fe). The results show that increasing red mud content reduces slump flow (max 76.03%), plastic viscosity (46.7%), and yield stress (42.3%) while also shortening initial/final setting times (67.91% and 76.18% max reductions). At curing ages below 7 days, flexural and compressive strength increase (up to 64.53% and 33.35%, respectively), following cubic functions; however, at 7 and 28 days, both strength values decrease (max reductions of 13.43% and 12.98%). Red mud increases drying shrinkage and delays sulfate-induced degradation. Microstructural analysis reveals improved compactness of hydration products at early ages but reduced compactness at later ages, accompanied by increased Al/Fe content and enhanced SiO₂/calcium silicate hydrate crystals. These findings provide valuable insights for applying red mud HPM in marine environments. Full article

(This article belongs to the Special Issue Surface Treatment and Mechanical Properties of Sustainable Pavement Materials, 2nd Edition)

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18 pages, 2531 KB

Open AccessArticle

In Vitro Investigation of Antithrombotic Performance of Bivalirudin and Aspirin Dual-Modified Polycaprolactone Vascular Grafts

by Yuxin Tan, Rui Luan, Jiashuai Zhang, Huilin Mo, Yu Ren, Wei Zhang and Meixian Li

Coatings 2026, 16(4), 483; https://doi.org/10.3390/coatings16040483 - 17 Apr 2026

Abstract

The clinical application of small-diameter vascular grafts (SDVGs; <6 mm) is limited by thrombosis and mediated by protein adsorption, platelet activation, and coagulation. To address this, we develop a dual-modified polycaprolactone (PCL) graft via covalent conjugation of bivalirudin (BV), a direct thrombin inhibitor, [...] Read more.

The clinical application of small-diameter vascular grafts (SDVGs; <6 mm) is limited by thrombosis and mediated by protein adsorption, platelet activation, and coagulation. To address this, we develop a dual-modified polycaprolactone (PCL) graft via covalent conjugation of bivalirudin (BV), a direct thrombin inhibitor, and aspirin (ASA), a cyclooxygenase-1 suppressor. Compared with pure PCL, the BV/ASA-modified PCL graft reduces bovine serum albumin adsorption by 35.7% and fibrinogen adsorption by 36.2%, while maintaining mechanical properties and structural integrity. Platelet adhesion, assessed by LDH viability, is reduced by 42.6%, and the blood clotting index (BCI) is increased by 67.4%, indicating enhanced anticoagulation. The modified surface enhances anticoagulation and exhibits cell viability above 80%, confirming non-toxicity. These in vitro results demonstrate that BV and ASA dual functionalization effectively improves the antithrombotic performance of PCL vascular grafts, suggesting its potential as a candidate for further preclinical evaluation in SDVG applications. Full article

(This article belongs to the Section Surface Coatings for Biomedicine and Bioengineering)

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20 pages, 29515 KB

Open AccessArticle

Finite Element Analysis (FEA) of the Stresses and Strains Occurring in Zirconia Crowns and Tooth Abutments Prepared With or Without a Shoulder Finish Line

by Lucia Alexandra Drăghici, Raluca Monica Comăneanu, Ștefan Eugen Chirsanov-Capanu, Andrei Constantinovici, Anna Maria Pangică, Manuela Victoria Chivu, Mariana Roxana Ciobanu, Mihail Târcolea and Laurența Lelia Mihai

Coatings 2026, 16(4), 482; https://doi.org/10.3390/coatings16040482 - 16 Apr 2026

Abstract

This study aimed to evaluate the stress and strain at the interface between zirconia crowns and prepared tooth abutments, with or without a shoulder finish line. The main objective was to determine which of the two types of preparations provides a more favorable [...] Read more.

This study aimed to evaluate the stress and strain at the interface between zirconia crowns and prepared tooth abutments, with or without a shoulder finish line. The main objective was to determine which of the two types of preparations provides a more favorable long-term prognosis, particularly in the case of single-unit crowns. The Finite Element Analysis (FEA) method was employed to assess the mechanical response of both zirconia and dentin under occlusal forces of 200 N, simulating physiological occlusion. Values from the literature for Young’s modulus, Poisson’s ratio, and Bulk modulus were introduced into the simulations for zirconia and tooth abutments. The simulations demonstrated that zirconia crowns, regardless of the preparation type, experienced higher stress than the tooth abutments. However, preparations with a shoulder finish line demonstrated superior biomechanical behavior. This study provides a detailed biomechanical analysis of zirconia crowns cemented onto tooth abutments prepared with or without a shoulder finish line, highlighting the importance of FEA in optimizing prosthetic design and material selection. Full article

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28 pages, 7860 KB

Open AccessArticle

Study on Interaction Behavior Between Iron Tailings and Asphalt Interface Based on Molecular Dynamics Simulation and Microscopic Test

by Yaning Cui, Chundi Si, Changyu Pu, Ke Zhao and Zhanlin Zhao

Coatings 2026, 16(4), 481; https://doi.org/10.3390/coatings16040481 - 16 Apr 2026

Abstract

With the shortage of natural aggregates and the massive accumulation of iron tailings (ITs) solid waste restricting the sustainable development of asphalt pavement engineering, replacing natural aggregates with ITs has become a promising low-carbon solution with prominent economic and social benefits. However, the [...] Read more.

With the shortage of natural aggregates and the massive accumulation of iron tailings (ITs) solid waste restricting the sustainable development of asphalt pavement engineering, replacing natural aggregates with ITs has become a promising low-carbon solution with prominent economic and social benefits. However, the poor interfacial adhesion between ITs and asphalt severely restricts the engineering application of tailings, and the micro-interaction mechanism at their interface still lacks systematic clarification, which is the key research gap addressed in this work. Different from conventional macro road performance tests, this study innovatively combined molecular dynamics (MD) simulation with microscopic characterization, including Fourier transform infrared spectroscopy (FT-IR) and atomic force microscopy (AFM), to comprehensively reveal the interfacial interaction mechanism between ITs and asphalt at the molecular and microscales. The results indicate that asphalt molecules exhibit higher aggregation concentration and diffusivity on Al₂O₃ and Fe₂O₃ surfaces than on SiO₂ surfaces, proving stronger interfacial interaction between asphalt and iron-rich oxide minerals. Moderate temperature optimizes the adhesion performance of asphalt with Al₂O₃ and Fe₂O₃, while the interfacial bonding of asphalt on CaCO₃ and SiO₂ weakens as temperature rises. The silane coupling agent KH-550 can effectively react with acidic minerals, SiO₂ minerals in ITs, which significantly increases the concentration, diffusion coefficient, and distribution uniformity of asphalt molecules at the interface. FT-IR results verify that the combination of ITs and asphalt mainly relies on physical adsorption without generating new chemical bonds. AFM tests further confirm that alkaline minerals improve the surface roughness of asphalt mastic, and KH-550 greatly enhances the micro-adhesion force of the interface. The novelty of this work lies in clarifying the mechanism of typical mineral components in ITs and revealing the modification enhancement law of silane coupling agent and alkali minerals at the micro level. This study provides a scientific theoretical support for the high-value engineering utilization of ITs in asphalt pavement, and offers a reference for optimizing the interfacial modification design of solid waste aggregate. Full article

(This article belongs to the Section Architectural and Infrastructure Coatings)

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14 pages, 4033 KB

Open AccessArticle

Microstructural Evolution and Hardening Behavior of a Low-Activation Ti-Nb-Zr-O Film Under He⁺ Irradiation

by Wanmin Yu, Ranshang Guo, Tianyu Zhao, Guanzhi Wang, Yanhui Li, Youping Lu, Zhenjie Liu, Juan Du, Zhiqiang Cao and Li Jiang

Coatings 2026, 16(4), 480; https://doi.org/10.3390/coatings16040480 - 16 Apr 2026

Abstract

The development of accident-tolerant fuels has significantly enhanced the safety of fission reactors. The TiNbZrO alloy system has garnered considerable attention due to its excellent mechanical properties and outstanding irradiation resistance. Its unique compositional design enables effective suppression of irradiation-induced defect formation. In [...] Read more.

The development of accident-tolerant fuels has significantly enhanced the safety of fission reactors. The TiNbZrO alloy system has garnered considerable attention due to its excellent mechanical properties and outstanding irradiation resistance. Its unique compositional design enables effective suppression of irradiation-induced defect formation. In this study, TiNbZrO thin films are fabricated via radio-frequency magnetron sputtering and irradiated with 50 keV He ions to fluences of 5 × 10¹⁶, 1 × 10¹⁷, and 2 × 10¹⁷ ions/cm². The microstructural evolution before and after irradiation is characterized by Transmission Electron Microscopy (TEM) and Grazing Incidence X-ray Diffraction (GIXRD), and the changes in mechanical properties are evaluated by nanoindentation. With increasing irradiation fluence, the average size of He bubbles increases from 1.10 nm to 2.06 nm, the number density decreases from 5.27 × 10²⁴ m⁻³ to 1.39 × 10²⁴ m⁻³, and the swelling rate rises from 0.37% to 0.64%. Although significant irradiation hardening is observed in all samples, the maximum hardening rate reaches only 31.91%, a value substantially lower than that reported for many conventional nuclear materials. This demonstrates the superior irradiation resistance of TiNbZrO thin films. The superior irradiation resistance of TiNbZrO thin films stems from two synergistic effects: high-entropy lattice distortion suppresses atomic diffusion, while oxygen complexes pin defects. Full article

(This article belongs to the Special Issue Modification and Technology of Thin Films)

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20 pages, 2790 KB

Open AccessArticle

Comparative Effects of Tung Oil/Chitosan–Gum Arabic Microcapsules Prepared Under Two Feed Efficiencies on Surface Coating Performance of Bamboo

by Xiang Liu, Jingyi Hang, Hongxia Yang, Xiaoxing Yan and Jun Li

Coatings 2026, 16(4), 479; https://doi.org/10.3390/coatings16040479 - 16 Apr 2026

Abstract

Bamboo surfaces are susceptible to scratches and contamination during service, which limits their durability and aesthetic performance. To address this issue, this study aims to develop a natural self-healing coating based on tung oil microcapsules. Tung oil microcapsules encapsulated within chitosan and gum [...] Read more.

Bamboo surfaces are susceptible to scratches and contamination during service, which limits their durability and aesthetic performance. To address this issue, this study aims to develop a natural self-healing coating based on tung oil microcapsules. Tung oil microcapsules encapsulated within chitosan and gum arabic (TO/CS–GA MCs) were prepared by spray drying at two feed rates (100 and 200 mL h⁻¹) and incorporated into tung oil coatings applied on bamboo substrates. The effects of microcapsule content (1.0–11.0 wt%) and feed rate on the optical performance, mechanical performance, and self-healing performance of the coatings were systematically investigated. The results showed that increasing the microcapsule content gradually increased the color difference (ΔE) and surface roughness of the coatings, while the gloss decreased. The hardness, impact resistance, adhesion grade, and self-healing efficiency of the coatings exhibited a similar trend, initially increasing and then decreasing with increasing microcapsule content. This behavior indicates that an appropriate amount of microcapsules can enhance the coating performance, whereas excessive addition leads to particle agglomeration and structural defects. Under the better condition of 5.0 wt% microcapsule content and a spray-drying feed rate of 100 mL h⁻¹, the coating exhibited the best overall performance, including higher gloss retention, a hardness of 2H, an impact resistance of 3 kg·cm, relatively low surface roughness, and a self-healing efficiency of 28.16 ± 0.63%. These results suggest that the spray-drying feed rate plays an important role in regulating the particle size distribution and encapsulation efficiency of the microcapsules, which in turn affects their dispersion and rupture–release behavior within the coating matrix. Therefore, controlling the spray-drying parameters is crucial for optimizing the performance of microcapsule-based self-healing coatings. Overall, this study provides a sustainable strategy for developing natural polymer-based self-healing coatings and offers useful insights into the design of functional microcapsules for bamboo surface protection. Full article

(This article belongs to the Section Cultural Heritage and Protective Coatings)

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23 pages, 4096 KB

Open AccessArticle

Prediction of the Surface Quality Obtained by Milling Using Artificial Intelligence Methods

by Andrei Osan, Mihai Banica and Cornel Florian

Coatings 2026, 16(4), 478; https://doi.org/10.3390/coatings16040478 - 16 Apr 2026

Abstract

The paper explores the use of artificial neural networks for surface roughness parameter Ra prediction when milling the finishing of flat surfaces with toroidal milling on C45 steel. The experiments were conducted on a 5-axis CNC center, varying three main parameters: cutting speed, [...] Read more.

The paper explores the use of artificial neural networks for surface roughness parameter Ra prediction when milling the finishing of flat surfaces with toroidal milling on C45 steel. The experiments were conducted on a 5-axis CNC center, varying three main parameters: cutting speed, feed per tooth, and tool axis tilt angle. In total, 70 surfaces were processed, with multiple measurements of Ra roughness. The data were preprocessed in MATLAB (noise reduction by Z-score and augmentation to 630 values) and used to train an artificial feedforward neural network with Bayesian regularization. The resulting model showed good performance on the dataset and was experimentally validated on three new parameter combinations, processed and measured independently with a 3D scanner. The results confirm the network’s ability to estimate Ra roughness based on varying process parameters. The paper proposes the model as a useful tool for assessing surface quality in finishing milling and recommends extending the experimental base as the main direction of continuation. Full article

(This article belongs to the Special Issue Surface Integrity and Engineering Optimization in Advanced Manufacturing and Mechanical Systems)

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21 pages, 9521 KB

Open AccessArticle

An Active Protective Waterborne Epoxy Coating with Mesoporous Silica-1,10-Phenanthroline Microcontainers on Carbon Steel

by Ruinong Xu and Hongwei Shi

Coatings 2026, 16(4), 477; https://doi.org/10.3390/coatings16040477 - 16 Apr 2026

Abstract

This study reported highly dispersible mesoporous silica (MSP) with a uniform particle size, which was used as host to load 1,10-Phenanthroline (Phen) to prepare Phen@MSP microcontainer. Improving the dispersion of microcontainers prevents performance degradation caused by their agglomeration. Phen can form a red-colored [...] Read more.

This study reported highly dispersible mesoporous silica (MSP) with a uniform particle size, which was used as host to load 1,10-Phenanthroline (Phen) to prepare Phen@MSP microcontainer. Improving the dispersion of microcontainers prevents performance degradation caused by their agglomeration. Phen can form a red-colored complex with Fe²⁺ ions generated during corrosion of steel substrate, enabling early corrosion warning while also acting as a corrosion inhibitor to suppress further corrosion of the substrate. Phen@MSP microcontainers were incorporated into a waterborne epoxy (EP) resin to construct a coating with dual functionality of corrosion self-diagnosing and self-healing. As a key component, the average diameter of Phen@MSP microcontainers is approximately 1 μm, with a Phen loading rate of 18.45 wt.% in the microcontainers. Surface observation shows that substrate corrosion can be detected within 10 min by the appearance of red color. After 30 d of immersion in 3.5 wt.% NaCl solution, the impedance modulus value (|Z|_0.01Hz) of the 5 wt.% Phen@MSP coating (2.27 × 10⁹ Ω·cm²) on Q235 carbon steel substrate is five orders of magnitude higher than that of the blank coating (8.79 × 10³ Ω·cm²). Salt spray tests demonstrate that the 5 wt.% Phen@MSP coating effectively suppressed corrosion propagation on the substrate. Full article

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

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16 pages, 7426 KB

Open AccessArticle

Mg Doping Gradient Engineering by MOCVD for Threshold Voltage Enhancement in Si-Based p-GaN E-Mode HEMTs

by Changyao Chen, Shuhan Zhang, Qian Fan, Xianfeng Ni and Xing Gu

Coatings 2026, 16(4), 476; https://doi.org/10.3390/coatings16040476 - 16 Apr 2026

Abstract

The threshold voltage (Vth) of p-GaN gate enhancement-mode (E-mode) high electron mobility transistors (HEMTs) on silicon substrates grown by metal–organic chemical vapor deposition (MOCVD) is often limited to 1.0–1.5 V. Apart from the low Mg acceptor activation rate, the non-uniform vertical Mg distribution [...] Read more.

The threshold voltage (Vth) of p-GaN gate enhancement-mode (E-mode) high electron mobility transistors (HEMTs) on silicon substrates grown by metal–organic chemical vapor deposition (MOCVD) is often limited to 1.0–1.5 V. Apart from the low Mg acceptor activation rate, the non-uniform vertical Mg distribution in thin p-GaN layers is also a key bottleneck limiting Vth. This work reveals that the vertical distribution (not only magnitude) of Mg doping fundamentally influences Vth by modulating the charge centroid and electric field coupling to the heterointerface. Through bis(cyclopentadienyl)magnesium (Cp₂Mg) flow modulation, surfactant-assisted growth, and growth rate adjustment, the vertical Mg doping uniformity within the 80 nm p-GaN layer was improved while effectively suppressing Mg out-diffusion. A short-cycle gate-first self-aligned process was used to fabricate the devices, and the results showed that the improved Mg vertical distribution led to a significant Vth enhancement by 0.75 V. Technology Computer-Aided Design (TCAD) simulations further demonstrated that the uniform doping profile builds a stronger negative space charge field beneath the gate, raising the energy band and increasing Vth. This work not only presents practical strategies, but also establishes a direct physical link between vertical Mg doping distribution and Vth in Si-based E-mode HEMTs. Full article

(This article belongs to the Special Issue Advanced Functional Nanostructured Films and Coatings for Energy Applications, 2nd Edition)

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18 pages, 2577 KB

Open AccessArticle

Preparation of Composite Resin Coatings and Its Performance Improvement on Ti-Based Dental Implants

by Siqi Zhu, Chao Yao, Xiaopan Li, Yifan Yuan, Mengmeng Chen, Yiyun Kong, Yujie Fan, Jing Xia and Chun Yao

Coatings 2026, 16(4), 475; https://doi.org/10.3390/coatings16040475 - 15 Apr 2026

Abstract

Titanium alloys are widely used in dental implants due to their excellent mechanical properties. However, their inertness and poor antibacterial activity cause interfacial loosening and failure, shortening service life. This study integrates surface microtexturing with coating technologies, employing modified light-curing composite resins to [...] Read more.

Titanium alloys are widely used in dental implants due to their excellent mechanical properties. However, their inertness and poor antibacterial activity cause interfacial loosening and failure, shortening service life. This study integrates surface microtexturing with coating technologies, employing modified light-curing composite resins to boost the bioactivity of medical titanium alloys via surface modification. The results reveal that surface microtexturing enlarges the coating-substrate contact area by 42.5% compared with rough surfaces, concurrently diminishing stress per unit area, and the coating on microtextured Ti-6Al-4V (TC4) surfaces achieves adhesion with a damaged area of only 0.5%, thereby notably enhancing adhesion between the coating and TC4 matrix. In comparison, with rough surfaces (surface roughness of 0.658 μm), smooth TC4 planes (surface roughness of 0.014 μm) show a significantly reduced bacterial colony count (from 130 ± 6 to 42 ± 3) with an antibacterial rate of 67.7%, as the water contact angle on TC4 surfaces increases with decreasing roughness (reaching 80.95° on the smoothest surface), making bacterial adhesion more challenging and reducing colonization. The composite resin coating based on a mixture of titanium-doped hydroxyapatite and titanium dioxide (Ti-HA/TiO₂) further improves the antibacterial rate to 74.6% through a photocatalytic synergistic effect and endows TC4 with excellent remineralization capacity—mineralization deposits appear on the coated surface after 3 days of immersion in artificial saliva, while no obvious deposits are found on uncoated rough and smooth surfaces even after 7 days—thereby enhancing its bioactivity effectively. This study on the modification of Ti-based implant surfaces will enrich the field by introducing new technologies and methodologies. These advancements provide a theoretical basis for improvement of the remineralization capacity and antibacterial properties of Ti-based dental implants, thereby promoting broader biomedical applications. Full article

(This article belongs to the Special Issue Advanced Biomaterials, Coatings and Techniques: Applications in Medicine and Dentistry, 2nd Edition)

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16 pages, 8567 KB

Open AccessArticle

The Influence of Flow Rate on the Erosion–Corrosion Behavior of 304 Stainless Steel in Sulfur-Containing and Sand-Containing Sodium Aluminate Solutions

by Sixuan Li, Bianli Quan and Dongyu Li

Coatings 2026, 16(4), 474; https://doi.org/10.3390/coatings16040474 - 15 Apr 2026

Abstract

Regarding the erosion–corrosion problem of 304 stainless steel, which is commonly used in the production of alumina, in high-temperature, high-pressure, and strongly alkaline aluminum ammonium solutions, a detailed study was conducted on the erosion–corrosion behavior and damage mechanism of 304 stainless steel in [...] Read more.

Regarding the erosion–corrosion problem of 304 stainless steel, which is commonly used in the production of alumina, in high-temperature, high-pressure, and strongly alkaline aluminum ammonium solutions, a detailed study was conducted on the erosion–corrosion behavior and damage mechanism of 304 stainless steel in a sodium aluminate solution with varying S²⁻ concentrations at 65 °C and pH = 14 under the influence of key factors such as erosion speed. This study quantitatively revealed, for the first time, the flow rate threshold effect (critical point at 2 m/s) of 304 stainless steel during scouring corrosion in a strongly alkaline aluminum ammonium solution, identified its peak weight loss rate (1.892 × 10⁻³ g/m²·d), and innovatively elucidated the mechanism reversal phenomenon: below the threshold, passive film destruction and corrosion synergistically dominate, while above the threshold, high oxygen mass transfer promotes film regeneration. These findings provide a critical theoretical basis for precise flow rate control and equipment life prediction in alumina production processes. Full article

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

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18 pages, 15954 KB

Open AccessArticle

Effect of CrN Layer Composition on the Microstructure, Mechanical and Tribological Properties of TiN/CrN Multilayer Coatings

by Aidar Kenzhegulov, Kenzhegali Smailov, Nauryzbek Bakhytuly, Diana Karim, Azamat Yessengaziyev, Alma Uskenbayeva and Zhasulan Alibekov

Coatings 2026, 16(4), 473; https://doi.org/10.3390/coatings16040473 - 15 Apr 2026

Abstract

With increasingly stringent requirements for wear resistance and reliability of functional coatings for heavily loaded friction units, a relevant challenge in materials science is to establish the relationships between the parameters of reactive pulsed magnetron sputtering and the tribo-mechanical properties of TiN/CrN multilayer [...] Read more.

With increasingly stringent requirements for wear resistance and reliability of functional coatings for heavily loaded friction units, a relevant challenge in materials science is to establish the relationships between the parameters of reactive pulsed magnetron sputtering and the tribo-mechanical properties of TiN/CrN multilayer systems. In this study, TiN/CrN multilayer coatings were deposited by reactive pulsed magnetron sputtering using separate titanium and chromium targets. The effect of the nitrogen flow rate (0.20–0.36 L/h) during chromium sputtering on the structure, phase composition, and mechanical and tribological properties of the coatings was investigated at a fixed nitrogen flow rate of 0.08 L/h for titanium. SEM, EDS, and XRD showed that increasing the nitrogen flow rate leads to a non-monotonic change in coating thickness (2.0–2.6 µm), caused by the transition of the chromium target from the metallic to the poisoned sputtering mode. At low N₂ flow rates, a subnitride Cr₂N phase forms in the structure, whereas at the optimal flow rate of 0.32 L/h the coating consists of stable TiN, CrN, and (Cr_0.5Ti_0.5)N phases. The coating nanohardness was 20–23 GPa and the Young’s modulus was 250–300 GPa. The best tribological performance was achieved at a nitrogen flow rate of 0.32 L/h, coefficient of friction μ ≈ 0.5 and a minimum wear rate of 1 × 10⁻⁵ mm³/(m·N), which correlates with the highest H³/E² value. It is shown that independent control of the CrN layer stoichiometry using separate targets can affect the tribo-mechanical properties of the TiN/CrN multilayer system. Full article

(This article belongs to the Section Tribology)

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15 pages, 1791 KB

Open AccessArticle

Numerical Optimization of Wind Turbine Blade Profiles for Aeroacoustic Noise Reduction Using ANSYS Simulations

by Yll Ibrahimi, Luis Rubio Rodriguez and Levente Csóka

Coatings 2026, 16(4), 472; https://doi.org/10.3390/coatings16040472 - 15 Apr 2026

Abstract

The global push for sustainable energy has elevated wind power as a key renewable source; however, turbine noise remains a critical barrier to deployment near populated areas. This study investigates the optimization of symmetric and asymmetric trailing-edge profiles to minimize aeroacoustic emissions. The [...] Read more.

The global push for sustainable energy has elevated wind power as a key renewable source; however, turbine noise remains a critical barrier to deployment near populated areas. This study investigates the optimization of symmetric and asymmetric trailing-edge profiles to minimize aeroacoustic emissions. The primary novelty lies in the comparative analysis of a novel Pressure-Side Intruding Divergent model against standard sinusoidal serrations. Employing finite volume analysis in ANSYS, the preliminary results revealed that these targeted modifications significantly reduced noise propagation by 51.1% to 75.4%. By altering vortex shedding patterns and turbulent boundary-layer interactions, these findings provide actionable guidelines for balancing aerodynamic efficiency with environmental noise standards. Full article

(This article belongs to the Section Surface Engineering for Energy Harvesting, Conversion, and Storage)

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15 pages, 5441 KB

Open AccessArticle

A Simple and Scalable Two-Step Process for Durable Hydrophobic and Stain-Resistant Leather Coatings

by Susana A. F. Neves, Silvia Pinho, Manuel F. Almeida, Maria A. Lopes and Carlos Fonseca

Coatings 2026, 16(4), 471; https://doi.org/10.3390/coatings16040471 - 15 Apr 2026

Abstract

There is a strong and growing need for low environmental impact, fluorine-free finishes that deliver durable water repellency and stain resistance to leather while preserving its original appearance. This work successfully addresses this need by introducing a simple, robust, and scalable two-step coating [...] Read more.

There is a strong and growing need for low environmental impact, fluorine-free finishes that deliver durable water repellency and stain resistance to leather while preserving its original appearance. This work successfully addresses this need by introducing a simple, robust, and scalable two-step coating strategy that endows leather surfaces with excellent hydrophobic and self-cleaning properties. The process relies on a straightforward spray application of functionalized silica nanoparticles followed by a hydrophobic silane, namely hexadecyltrimethoxysilane (HDTMS), enabling precise control over surface properties through the number of applied layers. Comprehensive characterization by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM–EDS) confirmed the effective formation and uniformity of the coating. Performance testing demonstrated excellent functional outcomes: the optimized coating achieved a water contact angle (WCA) of 128° and maintained values above 125° even after abrasion, highlighting its durability. Treated leather exhibited resistance to common liquid stains such as tea and coffee, maintaining a clean surface. These functional gains were achieved without compromising the leather’s natural look or soft feel, even after multiple coating cycles. This work delivers a fluorine-free solution offering an effective route to high-value water- and stain-resistant leather finishes that respect both environmental and aesthetic requirements. Full article

(This article belongs to the Section Composite Coatings)

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37 pages, 10729 KB

Open AccessArticle

Surface Microstructural Characteristics of Textured Multicomponent TiN-Based Coated Cemented Carbides

by Xin Tong, Xiaolong Cao, Shucai Yang and Dongqi Yu

Coatings 2026, 16(4), 470; https://doi.org/10.3390/coatings16040470 - 14 Apr 2026

Abstract

To address the issues of high cutting temperatures and severe tool wear during titanium alloy machining, this study proposes a hybrid surface modification strategy combining micro-textures and multicomponent titanium nitride (TiN)-based coatings on cemented carbide tools. Using YG8 cemented carbide as the substrate, [...] Read more.

To address the issues of high cutting temperatures and severe tool wear during titanium alloy machining, this study proposes a hybrid surface modification strategy combining micro-textures and multicomponent titanium nitride (TiN)-based coatings on cemented carbide tools. Using YG8 cemented carbide as the substrate, micro-dimple textures were fabricated by fiber laser, and three coatings with different architectures (TiAlSiN, TiSiN/TiAlN, and TiSiN/TiAlSiN/TiAlN) were deposited via multi-arc ion plating technology. Based on a two-factor (texture diameter and texture spacing) and three-level orthogonal experiment, the evolution behaviors of surface morphology, phase composition, and mechanical properties of the textured multicomponent TiN-based coatings were systematically characterized and comparatively analyzed. The results reveal that: compared to the monolithic-structured TiAlSiN coating, the TiSiN/TiAlSiN/TiAlN and TiSiN/TiAlN composite coatings with multilayered composite structures can effectively relieve the residual stress inside the film–substrate system, and significantly suppress the phenomena of coating cracking and localized spallation caused by irregular protrusions of the recast layer at the micro-texture edges. X-ray diffraction (XRD) and crystallite size analyses indicate that the amorphous Si₃N₄ phase promoted by the Si element in the composite coatings effectively impedes the growth of TiN columnar crystals, achieving significant grain refinement. Mechanical property tests confirm that the existence of multicomponent composite interfaces effectively hinders dislocation movement. Among them, the textured TiSiN/TiAlSiN/TiAlN composite coating exhibits the optimal comprehensive performance; its microhardness, nanohardness, and H/E ratio (characterizing the resistance to plastic deformation) are increased by 17.94%, 8%, and approximately 45%, respectively, compared to those of the textured TiAlSiN coating. This study deeply elucidates the synergistic strengthening and toughening mechanisms between micro-texture parameters and the internal structures of the coatings, providing important theoretical guidance and experimental data support for the surface design of long-lifespan tools oriented towards the high-efficiency machining of titanium alloys. Full article

(This article belongs to the Special Issue Cutting Performance of Coated Tools)

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