A comprehensive review on anticorrosive/antifouling superhydrophobic coatings: Fabrication, assessment, applications, challenges and future perspectives

Superhydrophobic Fatty Acid-Based Spray Coatings with Dual-Mode Antifungal Activity

Superhydrophobicity, a natural phenomenon commonly observed in plants and insects, imparts diverse functionalities, including self-cleaning capabilities and antibiofouling properties. Nature's design of a superhydrophobic surface relies on a combination of surface chemistry and hierarchical roughness at micro- and nanoscales, inspiring the design of artificial superhydrophobic coatings. These multifunctional coatings offer a promising approach for combating fungal infections that are becoming increasingly prevalent due to global warming and increased resistance to conventional fungicides. Notably, among emerging superhydrophobic surfaces, those made with natural, nontoxic, and environmentally friendly compounds via facile manufacturing methods offer key advantages and support sustainable engineering practices. In this study, we developed easy-to-apply, sprayable bimodal superhydrophobic coatings. The antifungal activity of these coatings, based on long-chain fatty acids, can be further enhanced by incorporating medium-chain fatty acids, as demonstrated against the model phytopathogen Botrytis cinerea. Specifically, we investigate the effect of incorporating sorbic or caprylic medium-chain fatty acids at various concentrations on the structure, physical properties, stability, and applicability of stearic acid-based coatings. Our results show that, depending on the composition, the antifungal activity of the coatings can be tuned, ranging from complete passive antibiofouling to dominant fungicidal action against Botrytis cinerea. Enabled by the synergistic effect of the hierarchical superhydrophobic structure and the incorporation of potent medium-chain fatty acids, these coatings offer a sustainable solution for surface protection against fungal infections and represent a promising alternative to conventional antifungal strategies.

Biomimetic Construction of Robust and Multifunctional-Integrated Superhydrophobic Coatings on Steel Structures via a One-Step Spraying Technique

Nowadays, the contradictions between ideal fire resistance and adequate surface functionality are increasingly highlighted for conventional coatings of steel structures in actual applications. In this context, the introduction of multifunctional coatings has become one of the effective and practical avenues to solve the crucial problem of steel materials. In this paper, superhydrophobic coatings inspired by nature were successfully prepared on steel structures by a simple one-step spraying method, which consisted of a mixture of silicone resin (SR), poly(dimethylsiloxane) (PDMS), diatomaceous earth (DE), titanium dioxide (TiO2), and modified ammonium polyphosphate (MAPP). The results showed that a static water contact angle (WCA) of 157.5° and a water sliding angle (WSA) of 5° were achieved by the as-prepared coatings with good water repellency and self-cleaning ability. Most importantly, the minimum backside temperature of the coated steel structures was decreased to 287 °C during the fire impact tests. Compared with neat EP/PDMS, the peak-to-heat release rate (PHRR) and total heat release rate (THR) were significantly reduced to 26.7 and 26.1%, respectively, indicating that the as-prepared coatings possessed excellent passive fire-resistant capacity. The synergistic effect of fillers in the condensed phase occupied a dominant position in promoting high-quality char layers. Surprisingly, coatings with good robustness could be further endowed with adequate corrosion resistance and oil/water separation ability. Therefore, this work provided a viable and effective strategy for tackling the surface functionality problem of materials, which could extend the application scope of superhydrophobic coatings in more fields.

3D Printing of Objects with Bulk Superhydrophobicity Using Self-Foaming Polydimethylsiloxane-Based Ink

Although bulk superhydrophobic material can maintain durable superhydrophobicity by its micro-nanostructure regeneration for promising application, the 3D printing is still challenging due to the requirement of a large amount of solvent and complicated fabrication processing. Herein, a solvent-free and self-foaming polydimethylsiloxane (PDMS)-based ink is developed for 3D printing bulk superhydrophobic objects. The ink incorporates thermally expandable microspheres (EMs) and polytetrafluoroethylene (PTFE) particles, enabling hierarchical roughness and low surface energy throughout the bulk. During thermal curing, EMs generate cellular pores (20-50 μm) and disrupt the formation of a dense skin layer in the cured PDMS ink, while PTFE particles migrate to the surface, achieving a Cassie-state superhydrophobicity with a water contact angle of 155° and a sliding angle of 9°. The printed foam exhibits exceptional durability, retaining superhydrophobicity after 1000 abrasion cycles due to self-similar porous structures. Rheological optimization ensures printability, and the lightweight foam (density of 0.16 g/cm3) demonstrates versatile applications, including waterproofing, oil-water separation, and waterproof buoyancy carrier for a drone (supporting 7× its weight). This work presents an environmentally benign and facile strategy for fabricating robust, bulk superhydrophobic materials with scalable 3D printing, advancing their potential in sustainable industrial and environmental applications.

Ex Situ pH-Induced Reversible Wettability Switching for an Environmentally Robust and High-Efficiency Stain-Proof Coating

Developing superwetting coatings with environmental adaptability is critical for sustainable industrial applications. However, traditional anti-wetting coatings often fall short due to their susceptibility to environmental factors (UV light, temperature, mold growth, and abrasion) and inadequate stain resistance in complex media. Herein, a durable ex situ pH-responsive coating with reversible wettability switching, engineered by integrating hydrophobic polydimethylsiloxane and tertiary amine structures is presented. The resulting hierarchical micro-nano surface structure, combined with a trapped air cushion, ensures low water adhesion and stable superhydrophobicity. Notably, after ex situ pH treatment, the modulation of surface N+ content synergistically interacts with polydimethylsiloxane chains, enabling a controlled transition in surface wettability from 150° to 68.5°, which can spontaneously revert to a hydrophobic state upon heating and drying. This transition enhances stain resistance in both air and underwater environments, resulting in a 17.2% increase in detergency compared to superhydrophobic controls. Moreover, the coating demonstrates remarkable durability, with no staining, peeling, or mildew growth (grade 0) even after 1500 h of UV radiation and 28 days of mildew resistance testing. This work offers a highly adaptable and stain-resistant coating for applications in building and infrastructure protection, as well as in smart textiles designed for multi-media decontamination.

Smart Polydimethylsiloxane Materials: Versatility for Electrical and Electronic Devices Applications

Bio-inspired autonomous smart polydimethylsiloxane (PDMS) and its composite materials hold immense promise for a wide range of applications in electrical and electronic devices. These materials mimic natural protective mechanisms with self-healing, self-reporting, and self-cleaning properties, enabling innovative and efficient device design. Smart PDMS materials autonomously activate repair mechanisms in response to mechanical or electrical damage, achieving rapid structural and functional recovery and preventing failure due to the accumulation of minor damage. These materials can intuitively report their status through striking color changes, fluorescence, or luminescence when exposed to external stimuli, providing efficient and practical visual feedback for device health monitoring and fault warning. They also have the capacity to effectively eliminate contaminants and ice deposits from their surfaces, thereby ensuring stable device operation. This review aims to introduce the current research progress in self-healing, self-cleaning, and self-reporting PDMS materials. The review systematically discusses the principles, methodological innovations, mechanistic analysis, and applications of these materials, highlighting their significant potential for applications in the field of electrical and electronic devices. Moreover, the review provides an in-depth analysis of the key challenges facing current research and offers insights into future research directions and strategies.

Waterborne Recoatable Transparent Superhydrophobic Coatings with Excellent Self-Cleaning and Anti-Dust Performance

Superhydrophobic surfaces have attracted tremendous attention due to their intriguing lotus-leaf-like water-repelling phenomenon and wide applications, however, most superhydrophobic coatings are prepared with environmentally unfriendly organic solvents and suffer from poor mechanical strength. To solve these issues, waterborne recoatable superhydrophobic (WRSH) coatings are developed based on a novel self-synthesized water-soluble fluorinated acrylic polymer and hydrophobic modified silica nanoparticles. The trade-off between waterborne and superhydrophobicity is well mediated by protonation and deprotonation of the fluorinated acrylic polymer. When the coating is damaged, it can be easily repaired and recoated using WRSH coatings without the need to remove the damaged superhydrophobic layer, providing a sustainable and environmentally friendly solution for maintaining a superhydrophobic surface. The coating exhibits good mechanical properties with the WRSH coating maintaining mechanical stability even after abrasion with 2000 mesh sandpaper for 20 m or impact from 100 g of sand. Additionally, the visible light transmittance of WRSH coating glass reaches as high as ≈94.0%, which is superior to the bare glass of ≈91.7%. Moreover, the WRSH coatings exhibit excellent self-cleaning performance and anti-dust performance when applied on solar panels.

Glutenin phase transition as a method of fabricating primer for superhydrophobic and corrosion-resistant coating

Concerns over food safety arising from conventional plastic and resin-based corrosion barriers cannot be underestimated, particularly in light of the potential for plasticizer migration. We introduce an environmental-friendly and sustainable approach to develop superhydrophobic and anticorrosion coatings. This involved a unique process where glutenin, post-reduction with tris(2-carboxyethyl)phosphine, underwent a phase transition, naturally adhering to diverse surfaces to form a foundational primer. The core mechanism of this adhesion lied the β-sheet stacking configuration, confirmed by grazing-incidence wide-angle X-ray scattering. To further elevate the performance, carnauba wax was easily incorporated as a topcoat, forming a superhydrophobic coating that surpassed standalone wax coatings in durability against wear, impact, high temperature, and corrosion. This enhancement was derived from the intricate intermolecular interactions, including hydrogen bonding and hydrophobic interactions, established between the primer and carnauba wax. Notably, the phase-transited coating and superhydrophobic coating maintained a low-frequency impedance of 0.1 and 2.1 MΩ/cm2, respectively, even after prolonged immersion in a 3.5 % NaCl solution for 21 days. The superhydrophobic coating was ideally applicated in an extensive range of canned food products, such as beverages, fruits, etc., that undergo pasteurization. Additionally, both the primer and the superhydrophobic coating exhibited outstanding biocompatibility, as evidenced by red blood cell hemolysis and cytotoxicity assessments. In summary, this research contributes significant knowledge to the development of superhydrophobic coatings and expand applications of protein-based assembly materials.

Development of a Multifunctional Antimicrobial Peptide for Marine Antifouling by Theoretical Calculations and Experimental Approaches

Marine biofouling poses significant challenges to the economy, safety, and reliability of marine infrastructure. While antimicrobial peptides (AMPs) have emerged as green and efficient antifouling agents, their single functionality and the complexity of preparing antifouling surfaces remain key challenges. This study introduces a multifunctional AMP with combined adhesion and antimicrobial properties, derived from 3,4-dihydroxy-l-phenylalanine (DOPA) and IP12 (sequence IRLRWRWKWPWP). The directional recombination of AMP was guided by theoretical calculations. Density functional theory (DFT) simulations identify that the hydroxyl groups of DOPA were the main activating groups that react with aluminum alloy. Coarse-grained molecular dynamics (CG MD) and all-atom molecular dynamics (AA MD) simulations revealed that amino acid residues near the N-terminal of the IP12 could induce cell membrane bending and rupture. The AMP surfaces were fabricated to validate the accurate calibration of the simulations and performance of multifunctional AMP. Atomic force microscopy, Fourier transform infrared, and X-ray photoelectron spectroscopy results confirm the successful construction of AMP surfaces through adhesion function. Antifouling evaluations demonstrated the antifouling properties of AMP surfaces against Escherichia coli (Gram-negative) and Bacillus sp. (Gram-positive), achieving antifouling rates of 85.8 and 82.4%, respectively. This study provides valuable insights into the design of multifunctional AMPs.

Laser-Induced Superhydrophobic Polymer Surface for Droplet Manipulation, Controllable Light-Driven Actuator, and Underwater Motion Monitoring

In the field of smart materials, there is a demand to fabricate surfaces with superhydrophobic and conductive features in a cost-effective and efficient fabrication manner. In this study, a high-efficiency approach for fabricating superhydrophobic and multifunctional surfaces is presented. By using a cost-effective fiber laser and ablating the PDMS/CNT nanocomposite surface, superhydrophobic (WCA = 157°, SA = 7.35°) unidirectional groove structures were fabricated with a high efficiency of 3.5 s/cm2 under a laser spacing of 75 μm and a scanning speed of 500 mm/s. Three separate application scenarios for superhydrophobic PDMS/CNT nanocomposite are demonstrated. The results showed that the superhydrophobic PDMS/CNT nanocomposite facilitated nondestructive droplet transfer and enabled fluid manipulation via self-floating. Its load-bearing capacity was increased by 49.8%. The movement of the PDMS/CNT nanocomposite on water was accelerated by 116% after laser irradiation, and it achieved optically controllable motion of complex paths as light-driven actuators. Notably, they maintained exceptional superhydrophobic properties, even when stretched to a strain of 75%. PDMS/CNT nanocomposite can effectively monitor various underwater motion signals such as underwater finger flexion, wrist flexion, and fist clenching, which exhibited great potential application in underwater sensor monitoring.

Triple Corrosion Protection: Dual-Layer Coating with Simultaneous Superhydrophobicity, Intelligent Self-Healing, and Shape Memory

In this paper, a self-healing superhydrophobic smart two-layer coating, ZOA/SMP-S, was developed. ZIF-8 was surface hydrophobically modified by octadecylphosphoric acid (OPA) to obtain Z-OPA and then encapsulated with a corrosion inhibitor, AMT ( 2-Amino-5-mercapto-1,3,4-thiadiazole), to obtain the superhydrophobic nanocontainers, ZOA. ZOA was embedded into the SMP (shape memory coating) to obtain the smart coating, and Z-OPA was sprayed to obtain the second superhydrophobic coating. SEM showed that the scratch coatings were rapidly reduced by scratches after a simple heat treatment. The prepared composite coatings showed excellent performance in corrosion inhibitor release, immersion, superhydrophobicity, and self-healing experiments. The contact angle of the superhydrophobic coating reached 158.2°, and the sliding angle was 2.8°. The low-frequency impedance value |Z|f=0.01 Hz of ZOA/SMP-S is as high as 1.58 × 1010 Ω·cm2 after 40 days of immersion test, which indicates that the triple protection greatly enhances the corrosion resistance of the coating.

Binding Kinetics of Self-Assembled Monolayers of Fluorinated Phosphate Ester on Metal Oxides for Underwater Aerophilicity

The term "aerophilic surface" is used to describe superhydrophobic surfaces in the Cassie-Baxter wetting state that can trap air underwater. To create aerophilic surfaces, it is essential to achieve a synergy between a low surface energy coating and substrate surface roughness. While a variety of techniques have been established to create surface roughness, the development of rapid, scalable, low-cost, waste-free, efficient, and substrate-geometry-independent processes for depositing low surface energy coatings remains a challenge. This study demonstrates that fluorinated phosphate ester, with a surface tension as low as 15.31 mN m-1, can form a self-assembled monolayer on metal oxide substrates within seconds using a facile wet-chemical approach. X-ray photoelectron spectroscopy was used to analyze the formed self-assembled monolayers. Using nanotubular morphology as a rough substrate, we demonstrate the rapid formation of a superhydrophobic surface with a trapped air layer underwater.

Preparation of Robust, Antireflective and Superhydrophobic Hierarchical Coatings on PMMA Substrates via Mechanical Locking and Chemical Bonding

Antireflection (AR) coatings with mechanical robustness and superhydrophobic properties have wide potential applications in optical, electronic, and automotive fields. However, the fabrication of large-sized, robust, and multifunctional AR coatings on plastic/polymer substrates has been a challenging problem. In this study, we developed a bottom-up approach to produce mechanically robust, enhanced transmittance, and superhydrophobic coatings on poly(methyl methacrylate) (PMMA) substrate. Their AR structure is composed of two layers: acid-catalyzed silica and base-catalyzed silica nanoparticles to construct a three-dimensional porous structure as the top layer; the connecting layer consists of monolayer mesoporous silica nanoparticles (MSNs) that are partially embedded in the PMMA substrate. The lower part of mesoporous silica nanoparticles is mechanically locked in the PMMA substrate by organic vapor phase treatment, while the upper part is chemically bonded to the top layer, forming a solid double-layer structure. Finally, the AR structure surface is treated by chemical vapor deposition of hexamethyldisilazane (HMDS). The obtained double-layer coating exhibits outstanding light transmission (Tave: 98.96% in the wavelength range of 400-800 nm), superhydrophobicity (water contact angle (WCA): 157.6°, rolling angle (RA): 3.3°), mechanical robustness (pencil hardness: 4H), and weather resistance (3 months of outdoor exposure). This work offers a novel approach to the synthesis of multifunctional coatings on polymer substrates with robust mechanical properties.

Heterogeneous micro-architectonic integration of SU-8 and highly entangled polyacrylamide hydrogel to realize cut-resistant soft superhydrophobic surfaces

This paper presents a novel idea to create cut-resistant superhydrophobic (SHPo) surfaces by integrating an array of SU-8 micropillars on a highly entangled polyacrylamide (PAAm) hydrogel substrate. We begin by demonstrating that this highly entangled PAAm hydrogel exhibits superior resistance to cutting while being as transparent, flexible, and stretchable as other polymeric substrates like polydimethylsiloxane (PDMS). Currently, there are no well-known methods or chemicals to directly integrate SU-8 and PAAm with a covalent bond. To overcome this challenge, we introduce a thin layer of chemically modified PDMS between the SU-8 and PAAm so that covalent bonds can be formed between both the SU-8/PDMS interface and the PDMS/PAAm interface. After validating the reliability of the bonding in our experiments, we develop a heterogeneous integration process to fabricate the desired SHPo surface. To demonstrate the critical role of PAAm hydrogel in achieving the cut-resistant SHPo surface, we contrast this new SHPo surface with a reference version that uses a PDMS substrate instead. We conduct microscopic inspections using scanning electron microscopy (SEM) and a contact angle goniometer before and after cutting the two surfaces. These evaluations show significant differences in their structural integrity and behavior in water interaction.

Preparation and performance control of ultra-low near-infrared reflectivity coatings with super-hydrophobic and outstanding mechanical properties

The development of ultra-low near-infrared reflectivity coatings with outstanding engineering properties remains a challenge in laser stealth materials research. Herein, we reported a laser stealth coating with outstanding mechanical properties, super-hydrophobicity, and an ultra-low near-infrared reflectivity for 1.06 μm wavelength. The effects of the mass ratio of graphene to nano-SiO2, the proportion of total filler, the addition of KH560, the mass ratio of Polydimethylsiloxane (PDMS) to acrylic-modified polyurethane (APU), and the addition of dioctyl phthalate (DOP) on the coating properties were thoroughly discussed. The coating can achieve a low reflectivity of 9.3% at 1.06 μm and a high water contact angle of 152° at a mass ratio of 7:3 for PDMS to APU and 6:4 for graphene to nano-SiO2 with a total filler amount of 40 wt%. KH560 can play a bridging role between the blended resin matrix and nano-SiO2, which can significantly improve the impact strength of the coating. The DOP, which contains a polar ester group and a non-polar carbon chain structure, can be inserted between the molecular chains of the resin to weaken the intermolecular force of the resin, so that the flexibility of the coating can be significantly improved. Adding KH560 at 4 wt% and DOP at 1 wt%, resulted in a coating with ultra-low near-infrared reflectivity of 1.06 μm (9.3%), super-hydrophobic properties, outstanding adhesion strength (grade 2), flexibility (2 mm), and impact strength (50 kg cm). The above super-hydrophobic ultra-low near-infrared reflectivity coating has significant potential for use in the field of laser stealth equipment, and it can serve as a useful reference for optimizing the mechanical properties of super-hydrophobic functional coatings.

One-Step Spraying Strategy for Fabricating Bioinspired, Graphene-Based, and Multifunctional-Integrated Coatings on Structural Steel with Good Water Repellency, Fireproofing, Anticorrosion, and Durability

Traditionally, many coatings were merely concentrated on settling the inherent fire protection problem of steel structures, while surface contamination and corrosion susceptibility should also be considered. Concurrently addressing these problems in fireproof efficiency and surface multifunctionality has become an issue of great significance in further expanding the application value in industrial and daily scenarios. Based on this condition, ecofriendly, graphene-based, and superhydrophobic coatings with multifunctional integration were constructed on steel via a one-step spraying method. The as-prepared coatings mainly consist of epoxy resin (EP), silicone resin (SR), a cyclodextrin-based flame retardant (MCDPM), expandable graphite (EG), and multilayered graphene (MG). The results demonstrate that the water contact angle (WCA) and water sliding angle (WSA) of as-prepared coatings can reach 156.8 ± 1.6 and 5.8 ± 0.7°, respectively, revealing good water repellency and self-cleaning properties. The coatings can also exhibit adequate adaptability for various substrates including wood, polyurethane foam, and cotton fabrics. Besides, good durability and robustness of coatings have been also verified via acid/alkali immersion, outdoor exposure, O2/plasma etching, and linear abrasion tests. Simultaneously, the coatings can exhibit excellent anticorrosion capacity for steel materials via a double barrier effect. Most importantly, the coatings have exhibited the lowest backside temperature (234.5 °C) during fire impact tests, suggesting excellent fireproof and heat insulation performance. This fact can be ascribed to the conjunct action between the physical/chemical charring process of flame retardants and the remarkable thermal stability of graphene. Consequently, this article can be expected to further promote the development and application of multifunctional-integrated coatings for steel structures in more fields.

A review of experimental Assessment Processes of material resistance to marine and freshwater biofouling

Biofouling presents hazards to a variety of freshwater and marine underwater infrastructures and is one of the direct causes of species invasion. These negative impacts provide a unified goal for both industry practitioners and researchers: the development of novel antifouling materials to prevent the adhesion of biofouling. The prohibition of tributyltin (TBT) by the International Maritime Organization (IMO) in 2001 propelled the research and development of new antifouling materials. However, the evaluation process and framework for these materials remain incomplete and unsystematic. This mini-review starts with the classification and principles of new antifouling materials, discussing and summarizing the methods for assessing their biofouling resistance. The paper also compiles the relevant regulations and environmental requirements from different countries necessary for developing new antifouling materials with commercial potential. It concludes by highlighting the current challenges in antifouling material development and future outlooks. Systematic evaluation of newly developed antifouling materials can lead to the emergence of more genuinely applicable solutions, transitioning from merely laboratory products to materials that can be effectively used in real-world applications.