Sprayable composition for forming superhydrophobic coating on steel surfaces

Abstract

The present invention relates to a sprayable composition and method (100) for forming a durable, transparent, and cost-effective superhydrophobic coating on metal surfaces, such as steel, applied through a simple spray process. The sprayable composition comprises a titanium alkoxide, such as titanium butoxide, which forms a titanium dioxide (TiO₂) nanocoating on the metal surface through hydrolysis. The hydrophobicity is achieved by self-assembly of organic silane agents, such as hexadecyltrimethoxysilane, onto the TiO₂ layer. Methanol is used as a solvent to prevent premature hydrolysis, and a binder, such as methyl-2-cyanoacrylate, enhances the adhesion and durability of the coating. The method (100) is energy-efficient, scalable, and requires minimal equipment, such as a conventional spray gun. The resulting coating demonstrates excellent durability, withstanding over 25 washing cycles and maintaining hydrophobic performance across a wide temperature range from 4°C to 120°C.

Description

SPRAYABLE COMPOSITION FOR FORMING SUPERHYDROPHOBIC COATING ON STEEL SURFACESFIELD OF THE INVENTION

[0001] The present invention relates to the field of surface coating. More specifically, the present invention relates to a sprayable composition and a method of applying durable, transparent, and superhydrophobic coatings on metal surfaces, such as steel, using a low-cost, sprayable liquid composition.BACKGROUND OF THE INVENTION

[0002] The development of superhydrophobic surfaces has been inspired by a self-cleaning property observed in lotus leaves. Such leaves are known to exhibit remarkable water repellence due to their unique micro-nano structured surface.

[0003] Since the discovery of this phenomenon in the late 20th century, significant efforts have been made to create artificial superhydrophobic surfaces for practical applications. These surfaces are defined by their ability to achieve a water contact angle (CA) greater than 150° and a rolling angle (RA) less than 10°. The combination of surface roughness and low surface energy is essential to achieve such properties.

[0004] Moreover, superhydrophobic materials have garnered considerable attention due to their potential in industrial and domestic applications, including corrosion resistance, anti- icing, self-cleaning, drag reduction, and waterproofing. Fluoropolymers are widely used to achieve hydrophobicity because of their low surface energy, high thermal stability, and excellent chemical resistance.

[0005] It will be apparent to those skilled in the art that stainless steel is extensively used in various industries, such as medical devices, food processing, kitchenware, and construction due to their corrosion resistance and mechanical strength.

[0006] However, despite their advantages, stainless steel surfaces are prone to bacterial growth, which poses challenges in meeting health standards. To address this issue, antibacterial and corrosion-resistant coatings have been developed, including those incorporating nanoparticles such as Silver (Ag) and Titanium Dioxide (TiO₂). These coatings enhance the antibacterial properties of the surface but often suffer from a loss of antibacterial effectiveness over time. That is the anti-bacterial properties wane after some period of time.

[0007] Nevertheless, Titanium dioxide (TiO₂), a low-cost, non-toxic, and chemically stable material, has emerged as a promising candidate for fabricating superhydrophobic surfaces. Specifically, the ability of TiO₂ to create micro-nano structures and its compatibility with silane compounds make it suitable for modifying surface properties. Additionally, TiO₂-based coatings have shown potential in antibacterial and self-cleaning applications, particularly in medical devices and industrial equipment.

[0008] Despite advances in superhydrophobic coatings, several challenges remain. A major challenge is to achieve a long-term antibacterial performance. Other challenges include maintaining hydrophobicity under mechanical and environmental stresses, and developing low-cost, scalable, and environmentally friendly fabrication methods. Current fabrication techniques, including chemical etching, sol-gel processing, and electrophoretic deposition, require optimization to balance cost, durability, and industrial feasibility.

[0009] Therefore, there is a pressing need for a durable, low-cost, and scalable method to fabricate superhydrophobic coatings on stainless steel surfaces, particularly stainless steel. Such coatings may combine hydrophobicity, antibacterial properties, and corrosion resistance while retaining transparency and surface aesthetics.

[0010] Various prior art has tried to overcome the challenges. For example, prior art Japanese publication number 2014214061 discloses a hydrophobic inorganic oxide powder produced using a sol-gel method. The disclosed composition results in particles with a narrow particle size distribution, small primary particle size, excellent crushability, and dispersibility in resins.

[0011] The sol-gel process disclosed in JP 2014214061 publication involves hydrolysis and polycondensation of metal alkoxides such as tetramethoxysilane in an organic solvent with water, using acidic or basic catalysts. The resulting fine inorganic oxide particles have a spherical shape and uniform size. The powder is particularly useful as an additive in electrophotographic technologies to improve toner durability and transferability. The method also includes hydrophobizing the silica using a silane compound, though the recovery process disclosed may be impractical for large-scale production.

[0012] Further, another prior art, German publication number 4025215 discloses a preparation of a wear-resistant coating with alkaline stability. The coating composition involves a reaction between a non-hydrolyzable primary silane and an organic epoxide, with or without the inclusion of amino groups. The coating solution contains at least one amino component and acompound with at least two epoxy groups. The resulting coating demonstrates alkali resistance, as tested in a dishwashing machine with a 3% Somat solution for 2 hours, with no visible changes to the layer.

[0013] Further, another prior art, Chinese publication number 110885592 discloses a super¬ hydrophobic, antibacterial cationic fluoropolymer nano-coating composed of an antibacterial cationic fluoropolymer microsphere emulsion, a water-based curing agent, and a solvent.

[0014] The emulsion is prepared by emulsion polymerization of an antibacterial cationic monomer, fluorine-containing monomer, styrene, and acrylic acid. The antibacterial cationic monomer is synthesized by reacting alkyl-dimethyl tertiary amine with 3-chIoropropene. The process results in a microsphere emulsion with an average particle size of 100-200 nano meters (nm), offering a durable and effective hydrophobic and antibacterial coating.

[0015] Further, another prior art, Chinese publication number 109967322 discloses a method for preparing a super-hydrophobic composite coating that improves surface hydrophobicity and stability,

[0016] The process disclosed involves applying an adhesive coating to a substrate, partially curing it, and then using a dipping and pulling method to form a film by immersing the pre¬ cured layer in a hydrophobic nanoparticle dispersion. The nanoparticles create a micro-nano composite structure, enhancing the coating’s hydrophobicity with a contact angle over 150 degrees. This method ensures strong adhesion, stability, and uniformity, making it ideal for industrial applications.

[0017] Further, another prior art, U S publication number 20090163647 discloses a composition and method for preparing a hybrid metal oxide coating, consisting of an aqueous carrier and the condensation product of a silicon peroxide and a transition metal peroxi de.

[0018] The disclosed composition forms crystalline nanoparticles, less than 10 nm in diameter, including hybrid metal oxides or transition metal oxides. The preparation involves boiling a mixture under pressure to create the coating, which can be applied to substrates. The composition may also include additives like organometallic compounds, wetting agents, and fillers to enhance the coating’s properties, with potential applications in various fields.

[0019] Further, yet another prior art, Chinese publication number 110257801 discloses a super¬ hydrophobic titanium carbide nano coating with a holey nanowall structure, featuring carbon content of 30-80 wt.% and titanium content of 20-70 wt%.

[0020] The disclosed coating is created using a vapor deposition process on a pretreated substrate, typically made of steel or high-speed steel. The pretreatment includes surface polishing, cleaning with acetone, and drying. The nanowall structure has a thickness of 10-150 nm and is formed with a combination of amorphous and crystalline phases.

[0021] Additionally, certain other methods are available such as the solidification of alkyl ketene dimer [1] the fabrication of aligned polymer nano-fibers by the template extrusion [2] and the preparation of a hydrophobic poly(vinyl-chloride) surface via solvent-non-solvent coating, Phase separation [3] plasma etching [4] sol-gel method [5,6] solution-immersing method [7,8] and electrospinning method.

[0022] However, it is very difficult to fabricate durable hydrophobic surface on steel and metal surfaces by means of the above methods, because developed hydrophobic films and coatings on surfaces easi ly fall off from the stain less-steel substrate. Furthermore, most of these methods do not produce transparent coatings which limits some applications.Refer:[1] Onda, T.; Shibuichi, S.; Satoh, N.; Tsujii, K. Super- Water-Repellent Fractal Surfaces. Langmuir 1996, 12, 2125-2127.[2] Feng, L.; Li, S.; Li, H.; Zhai, J.; Song, Y.; Jiang, L.; Zhu, D. Super-hydrophobic surface of aligned polyacrylonitrile nanofibers. Angew Chem Int Ed Engl 2002, 41, 1221-1223.[3] Zhao, N.; Xie, Q.; Weng, L.; Wang, S.; Zhang, X.; Xu, J. Superhydrophobic Surface from Vapor-Induced Phase Separation of Copolymer Micel lar Solution. Macromolecules 2005, 38, 8996-8999.[4] Park, J.; Lim, H.; Kim, W.; Ko, J. S. Design and fabrication of a superhydrophobic glass surface with micro-network of nanopillars. J Colloid Interface Sci 2011, 360, 272-279.[5] Budunoglu, IL; Yildirim, A,; Guler, M. O.; Bayindir, M. Highly Transparent, Flexible, and Thermally Stable Superhydrophobic ORMOSIL Aerogel Thin Films. ACS Appl. Mater. & Interfaces 2011, 3, 539-545.[6] Feng, X,; Feng, L.; Jin, M.; Zhai, J.; Jiang, L.; Zhu, D. Reversible Super-hydrophobicity to Super-hydrophilicity Transition of Aligned ZnO Nanorod Films. J. Am. Chem. Soc. 2004, 126, 62-63.[7] Gong, Z.; Wang, J.; Wu, L.; Wang, X.; LU, G.; Liao, L, Fabrication of Super Hydrophobic Surfaces on Copper by Solution-immersion. Chinese J. Chem. Eng. 2013, 21, 920-926.[8] Ishizaki, T.; Saito, N. Rapid Formation of a Superhydrophobic Surface on a Magnesium Alloy Coated with a Cerium Oxide Film by a Simple Immersion Process at Room Temperature and Its Chemical Stability. Langmuir 2010, 26, 9749-9755.

[0023] Based on the analysis of the prior art literature, it may be appreciated that the development of superhydrophobic coatings faces several key challenges, including ensuring long-term durability under harsh conditions such as abrasion, chemical exposure, and extreme temperatures,

[0024] Moreover, achieving a strong bond between the coating and metal surfaces, particularly stainless steel, is critical to prevent delamination. Combining dual functionalities, such as antibacterial properties and hydrophobicity, without compromising performance or longevity, remains difficult.

[0025] The present invention addresses key challenges in superhydrophobic coatings by providing a low-cost, sprayable liquid that forms a durable, transparent, and self-cleaning nanocoating on metal surfaces, including stainless steel, at room temperatureOBJECT OF THE INVENTION

[0026] The main objective invention of the present invention is to develop a durable, transparent, and cost-effective hydrophobic coating for metal surfaces, applied easily through a spray process, while preserving the surface appearance and ensuring long-lasting resistance to contaminants.

[0027] Yet another objective of the present invention is to enhance the durability' of the superhydrophobic coating, allowing it to withstand washing cycles and perform effectively across a wide temperature range from 4°C to 120°C.

[0028] Yet another objective of the present invention is to offer a scalable, energy-efficient solution for manufacturing and applying the superhydrophobic coating without the need for high-end equipment or damaging processes.

[0029] Lastly, another objective of the present invention is to create a multi-functional coating that resists water, mud, dust, dyes, and oil repellence.SUMMARY OF THE INVENTION

[0030] In various aspects of the present invention, a method and a sprayable composition are provided for obtaining a durable superhydrophobic coating on metal surfaces, such as steel.

[0031] In an embodiment of the present invention, the method utilizes a combination of hydrophobicity substrate, organic silane agents, solvent, water, and a binder to form a nanocoating on the metal surface.

[0032] In another aspect, the organic silane agent, self-assembles on the coating through coordinating and hydrogen bonding interactions, thereby providing the hydrophobic properties.

[0033] In a further aspect, the preparation of the hydrophobic coating involves dissolving the hydrophobici ty substrate and silane agents in solvent, followed by the gradual addition of water to initiate hydrolysis.

[0034] In yet another aspect, the method is simple, cost-effective, and can be carried out with minimal equipment, such as a standard spray gun.

[0035] Specifically, in one aspect, the present invention provides a sprayable composition for coating a metal surface such as steel. The sprayable composition comprises a hydrophobicity substrate comprising ti tanium alkoxide (such as titanium butoxide) capable of hydrolyzing to form a nano-sized titanium alkoxide layer bonded to the metal surface. The said titanium alkoxide is added in a range of about 0,05 wt% to 5 wt% of the composition.

[0036] Specifically, titanium butoxide hydrolyzes to form titanium dioxide nanocoating as the titanium dioxide layer enabling bonding of hydrophobic molecules to the metal surface through coordinating bonds and hydrogen bonds,

[0037] Further, in various embodiments, the sprayable composition comprises an organic silane agent comprising trimethoxysilane (specifically hexadecyltrimethoxysilane). The saidagent capable of hydrolyzing in water and self-assembling onto the titanium dioxide layer via hydrogen bonding to provide hydrophobicity.

[0038] In another aspect, the present invention discloses a method of forming a superhydrophobic coating.

[0039] The method involves preparing the sprayable composition, ensuring precise hydrolysis and integration of components, and applying the coating with high adherence and durability.

[0040] In one embodiment, a hydrophobicity substrate is prepared by dissolving titanium alkoxide and an organic silane agent, for example hexadecyltrimethoxysilane, in a methanol¬ based solvent at room temperature.

[0041] The methanol solvent, added in the range of 85 wt% to 99.5 wt%, ensures dissolution of the hydrophobic agents. Titanium alkoxide is used in concentrations ranging from 0.05 wt% to 5 wt%, while hexadecyltrimethoxysilane is added at 0.1 wt% to 10 wt%. The solution is stirred thoroughly to ensure dissolution and prevent premature hydrolysis.

[0042] Furthermore, water is added dropwise to the mixture over 0.5 to 3 hours while stirring at room temperature which allows hydrolysis of the titanium alkoxide and the organic silane agent, forming a robust titanium alkoxide layer essential for hydrophobic properties.

[0043] A binder, methyl-2-cyanoacrylate, is incorporated into the solution and stirred for an additional 30 to 60 minutes. This step ensures integration of the binder, which enhances the coating’s adhesion and durability on the metal surface.

[0044] Finally, the prepared solution is applied to the metal surface using a conventional spray gun. The coating is allowed to dry at room temperature for 1 to 2 hours. This step facilitates the strong adhesion of the coating and the formation of a superhydrophobic layer.

[0045] The hydrophobic coating demonstrates excellent durability, withstanding over 25 washing cycles and a wide temperature range of 4°C to 120°C.

[0046] This together with the other aspects of the present invention along with the various features of novelty that characterize the present disclosure is pointed out with particularity.

[0047] For a better understanding of the present disclosure, its operating advantages, and the specified objective attained by its uses, reference should be made to the accompanyingdescriptive matter in which there are illustrated exemplary embodiments of the present invention.DESCRIPTION OF THE DRAWINGS

[0048] The advantages and features of the present invention will become better understood with reference to the following detailed description taken in conjunction with the accompanying drawings, in which:

[0049] Fig. 1 is a flow chart illustrating a method for preparing and applying the hydrophobic coating on metal surfaces, such as steel, according to various embodiments of the present invention;

[0050] Fig. 2 is a scanning electron microscopic view 200 of hydrophobic transparent layer applied on steel surface, according to various embodiments of the present invention;

[0051] Fig. 3 is an illustration 300 (derived from the electron microscope data) showing washing cycles of hydrophobic surfaces obtained, according to various embodiments of the present invention;

[0052] Fig. 4 is an illustration 400 (derived from the electron microscope data) showing temperature durability of hydrophobic surfaces, according to various embodiments of the present invention; and

[0053] Fig. 5 is a depiction 500 of an experimental test showing mud repellency of a steel piece treated with the sprayable composition, according to various embodiments of the present invention.

[0054] Like numerals denote like elements throughout the figures.DESCRIPTION OF THE INVENTION

[0055] The exemplar}? embodiments described herein detail for illustrative purposes are subjected to many variations. It should be emphasized, however, that the present invention is not limited to as disclosed.

[0056] It is understood that various omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient, but these are intended to coverthe application or implementation without departing from the spirit or scope of the present invention.

[0057] Specifically, the following terms have the meanings indicated below.

[0058] The terms “a” and “an” herein do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced items.

[0059] The terms “having”, “comprising”, “including”, and variations thereof signify the presence of a component.

[0060] The inventive aspects of the invention along with various components and engineering involved will now be explained with reference to Figs. 1---5 herein.

[0061] The present invention introduces a sprayable composition designed to coat metal surfaces, offering enhanced durability, transparency, and hydrophobic protection.

[0062] In various embodiments, the sprayable composition comprises a hydrophobicity substrate comprising titanium alkoxide, such as titanium butoxide. However, such example of the titanium alkoxide should not be construed as a limitation to the present invention.

[0063] Accordingly, the hydrophobicity substrate comprises titanium tetraethoxide, or titanium tetraisopropoxide, or titanium tetrabutoxide, wherein such titanium alkoxide forms the foundation of the composition.

[0064] In various embodiments, the hydrophobicity substrate undergoes a hydrolysis reaction to produce a titanium dioxide (TiO₂) nanocoating that adheres strongly to the metal surface when applied thereto. This nanocoating establishes a durable and well-bonded layer due to its ability to form coordination and hydrogen bonds with the substrate.

[0065] In a preferable but non-limiting embodiment, the said titanium alkoxide is added in a range of about 0.05 wt% to 5 wt% of the composition. The said titanium butoxide hydrolyzes to form titanium dioxide nanocoating as the titanium dioxide layer enabling bonding of hydrophobic molecules to the metal surface through coordinating bonds and hydrogen bonds.

[0066] To impart hydrophobic properties, the sprayable composition includes silanes. Various examples of silanes comprise but are not limited to hexadecyltrimethoxysilane or hexadecyltrimethoxy or Cetyl-trimethoxysilane or hexadecyl(trimethoxy)silane, and the like.However, it should be understood that such examples of the silanes listed are not exhaustive, and are only exemplary in nature.

[0067] In a preferable but non-limiting example, the sprayable composition includes hexadecyltrimethoxysilane, added to the composition in a range of about 0.1 wt% to 10 wt% of the composition, and more preferably, the organic silane agent is a silane compound that hydrolyzes in water, and is added in a range of about 0.01 wt% to 5 wt%, wherein the silane agent self-assembles onto the titanium dioxide layer through hydrogen bonding.

[0068] In various embodiments, the silanes added to the composition hydrolyzes in water and self-assembles on the TiO₂ nanocoating. This process creates a layer of hydrophobic molecules that repel water, ensuring water droplets do not spread on the surface. The silane layer also enhances the water-repellent characteristics of the coating through a combination of hydrogen bonding and molecular organization.

[0069] In a preferable but non-limiting example, an important aspect of the formulation is the use of Ethanol, or Methanol, or Propanol as a solvent. Accordingly, the sprayable composition includes a solvent which is capable of dissolving both hydrophobicity substrate and organic silane agent for preventing premature hydrolysis and ensuring a uniform, stable solution. This ensures that the coating can be applied smoothly and effectively using standard spray equipment, making it suitable for industrial-scale applications.

[0070] In a preferable but non-limiting embodiment, the solvent is methanol and is present in a range of about 85 wt% to 99.5 wt% for maintaining the stability of the titanium alkoxide and silane during the application process and preventing premature hydrolysis of the composition.

[0071] Furthermore, in various embodiments of the present invention, the sprayable composition further includes a binder. In various embodiments, the binder comprises cyanoacrylate, and preferably methyl-2 -cyanoacrylate or ethyl 2-cyanoacrylate or the like.

[0072] It will be apparent to a person skilled in the art that such cyanides are used as the main component of certain cyanoacrylate glues and serves as a binder, playing a pivotal role in maintaining the adhesion of the hydrophobic layers to the metal surface. The binder strengthens the bond between the titanium dioxide nanocoating, the silane layer, and the substrate. This enhances the durability of the coating, ensuring resists environmental stresses such as washing, abrasion, and temperature variations.

[0073] The sprayable composition as obtained in the embodiments disclosed above is designed to be sprayed on a metal surface, such as on steel to form a coating. The method of obtaining superhydrophobic coating will now be explained with reference to Fig. 1.

[0074] Referring to Fig. 1, the method (100) begins with step 102. At step 102 the method begins by accurately measuring the required amounts of each component: hydrophobicity substrate (0.05wt%-5wt% by weight) serves as the precursor for forming nanocoating (such as titanium dioxide nanocoatings) on the metal surface, while hexadecyltrimethoxysilane (0.1wt%-10wt% by weight) provides hydrophobic properties to the coating. Methanol (85 wt%-99.5wt% by weight) acts as the solvent to dissolve the titanium butoxide and silane compounds, preventing premature hydrolysis. Moreover, Water (0.01wt%-5% by weight) is measured for addition to facilitate the hydrolysis of these compounds during mixing, and Methyl-2-cyanoacrylate binder (0.01wt%-5% by weight) is measured for addition to enhance the adhesion of the coating to the metal surface, ensuring long-term durability.

[0075] Referring to Fig, 1, the method (100) moves to step 104, wherein the measured quantities of Titanium Butoxide and Hexadecyltrimethoxysilane are combined in methanol and stirred thoroughly to ensure complete dissolution of the compounds. It should be noted that methanol acts as a stabilizing solvent, preventing premature hydrolysis and maintains the stability of the mixture. Uniform dissolution is essential to prepare a stable precursor solution for the subsequent steps in the coating process.

[0076] The method (100) then moves to step 106, wherein water is slowly added dropwise to the solution while continuously stirring to initiate hydrolysis. This is a crucial step that facilitates the formation of nanocoating (titanium dioxide nanocoating) and activates the silane compounds. The solution is stirred for 0.5–3 hours to ensure complete hydrolysis of both titanium butoxide and silane, allowing their functional groups to form essential coordination and hydrogen bonds. Proper stirring ensures uniform reactions and stability of the solution, preventing uneven chemical processes critical for the coating’s functionality.

[0077] Referring to Fig. 1, the method (100) then moves to step 108, wherein the measured amount of Methyl-2-cyanoacrylate binder is added to the hydrolyzed solution and stirred thoroughly for a period of about 30-60 minutes to ensure complete integration with the hydrolyzed compounds. The binder significantly improves the coating’s adhesion to the metal surface, enhancing its durability and resistance to external stresses such as washing, abrasion, and temperature fluctuations.

[0078] Referring to Fig. 1, the method (100) then moves to step 110, wherein the prepared solution is evenly sprayed onto the cleaned metal surface using a conventional spray gun, ensuring uniform coverage to create a transparent super-hydrophobic coating.

[0079] Moreover, the coating is then allowed to dry and cure at room temperature, enabling the formation of strong chemical bonds between the titanium dioxide nanocoating, silane layer, and metal surface. This drying process results in a durable superhydrophobic layer that preserves the surface’s original appearance while providing long-lasting protection.

[0080] The coating is designed to be highly durable, withstanding repeated washing cycles and harsh environmental conditions. The hydrophobic properties of coating are achieved by creating a surface with high water contact angles, effectively repelling water.

[0081] Furthermore, the transparent nature of the coating ensures the original appearance of the metal surface remains unchanged. Additionally, the inclusion of solvent facilitates efficient application and rapid drying, making the coating practical and scalable.

[0082] The sprayable composition leverages the hydrolysis of titanium alkoxide to form a uniform TiO2layer, which is integral to its structural integrity. The self-assembly of silane molecules creates a hydrophobic surface topology, critical for achieving superhydrophobicity. The binder, in turn, provides mechanical stability and ensures the coating remains intact under mechanical or environmental stress.

[0083] The efficacy of the coating obtained by spraying the sprayable composition will be better understood by referring to Figs. 2-5.

[0084] Particularly, referring to Fig. 2, the scanning electron microscopic (SEM) image 200 illustrates the hydrophobic transparent coating formed on a steel surface, showing the presence of titanium dioxide (TiO2) particles (200).

[0085] The titanium dioxide (TiO2) particles, produced by the hydrolysis of titanium alkoxide (e.g., titanium butoxide), adhere strongly to the steel surface through coordinating bonds. The SEM reveals a rough hierarchical structure comprising micro- and nanoscale spherical and irregularly shaped particles, as seen at the 5 μm scale. The roughness is critical for achieving hydrophobicity, as titanium dioxide (TiO2) reduces the contact area between water droplets and the surface, creating a Cassie-Baxter state where water droplets remain on top of the rough structure without fully wetting.

[0086] Referring to Fig. 3, there is shown an illustration (300) obtained from the SEM image which exhibits the durability of the hydrophobic coating when applied on a steel surface. The angles shown in the illustration are measured using a contact angle goniometer,

[0087] As shown in Fig. 3, the water contact angle is shown across multiple washing cycles, reflecting the coating’s ability to retain its hydrophobicity over time. Before washing, the water contact angle is approximately 157°, indicating excellent initial hydrophobicity. After the first washing cycle, the contact angle slightly decreases to 147°, demonstrating some loss in performance but still maintaining a high level of water repellence.

[0088] Moreover, as the number of washing cycles increases, the contact angle gradually declines further. By the 15th washing cycle, the contact angle reduces to 136°, and after 25 washing cycles, contact angle stabilizes around 135°. This steady decline highlights the robustness of the coating and retains significant hydrophobic properties even after prolonged washing. The minor reduction in water contact angle over time indicates that the coating is durable and able to withstand repeated washing without a complete loss of functionality.

[0089] Referring to Fig. 4, there is shown an illustration (400) obtained from SEM image which demonstrates the temperature stability of the hydrophobic coating. The angles are measured using a contact angle goniometer to evaluate water contact angles at different temperatures.

[0090] As shown, initially, at room temperature, the coating exhibits excellent hydrophobicity with a contact angle of 158°, indicating ability to repel water effectively. When exposed to elevated temperatures of 100°C, the contact angle decreases slightly to 148°, reflecting minor changes in hydrophobicity but still maintaining strong water-repellent properties.

[0091] Moreover, at even higher temperatures of 120°C, the coating continues to perform well, with a contact angle of 149°, showing resilience under thermal stress. This slight fluctuation in contact angles across varying temperatures highlights the coating’s durability and ability to withstand heat without significant degradation in its hydrophobic performance.

[0092] Referring to Fig. 5, there is shown an illustration (500) depicting an experiment which demonstrates the excellent mud repellence of a steel surface treated with the superhydrophobic spray coating.

[0093] As shown in Fig. 5, the treated steel surface prevents mud from adhering, as the hydrophobic layer causes water and mud particles to bead up and slide off the surface easily. This is a result of the high-water contact angle created by the coating, which reduces the interaction between the surface and contaminants such as mud. The titanium dioxide nanocoating, combined with the self-assembled organic silane layer, forms a rough and water- repellent surface that minimizes the adhesion of mud particles.The following examples will now be explained which explains the sprayable composition and the superhydrophobic coating obtained from the said composition.EXAMPLES:Example- 1: Mud and water-repellent sprayable composition

[0094] 0.5 mL of titanium butoxide and 0.5 mL of 1H,1H,2H,2H- Perfluorodecyltriethoxysilane in 98.8 mL of absolute methanol are dissolved while stirring continuously to ensure proper dissolution. Gradually 0.1 mL of water is dropwise added to the mixture and stirred for 1 hour to allow hydrolysis of the compounds.

[0095] Thereafter, 0.1 mL of methyl-2-cyanoacrylate binder is added to the solution and stir for an additional 30 minutes to achieve uniform integration,

[0096] Finally, the sprayable composition is sprayed evenly onto the metal surface using a spray gun or similar spraying technique.Example-2: Oil repellent sprayable composition

[0097] 0.5 mL of titanium butoxide and 0.5 mL of Hexadecyltrimethoxysilane in 98.8 mL of absolute methanol is dissolved with continuous stirring to ensure proper dissolution. Gradually 0.1 mL of water is dropwise added to the mixture and stirred for 2 hours to allow thorough hydrolysis. Then, 0.1 mL of methyl-2-cyanoacrylate binder is added and the solution is stirred for an additional 30 minutes to ensure uniform mixing.

[0098] Finally, spray the prepared solution evenly onto the metal surface using a spray gun or similar spraying technique,

[0099] Table 1 below highlights the abrasion resistance of three coatings — conventional epoxy, polyurethane coatings, and that in Example 1 — based on testing performed according to ASTM D 968._ Table 1.. Abrasion test resul —ts _ according _ to ASTM D 968Sample Average abrasion value (L / mm) Epoxy coating 150 (±10)* Polyurethane coating 90 (±10)*Example 1 156.3 (±8.5)

[0100] The abrasion value, measured in liters per millimeter (L / mm), reflects the volume of abrasive material required to erode 1 mm of coating thickness. The epoxy coating demonstrates a robust average value of 150 (±10) L / mm, indicating good durability under abrasive conditions. In contrast, the polyurethane coating shows a lower abrasion value of 90 (±10) L / mm, revealing a weaker resistance to wear.

[0101] Example 1, an advanced superhydrophobic composition, outperforms both with an exceptional average abrasion value of 156.3 (±8.5) L / mm, reflecting superior durability and consistency. This performance is attributed to the innovative combination of titanium dioxide nanocoating and methyl-2-cyanoacrylate binder, which synergistically enhance structural integrity and resistance to wear. These results position example 1 as a highly durable coating suitable for demanding environments such as aerospace, automotive, and marine industries, where abrasion resistance is critical.Advantageous effects of the present in vention

[0102] In one embodiment of the present invention, the present invention allows for easy and efficient application of the superhydrophobic coating using a conventional spray gun.

[0103] Moreover, in the present invention, the coating demonstrates exceptional durability, capable of withstanding over 25 washing cycles and remaining effective across a broad temperature range from 4°C to 120°C.

[0104] Further, in the present invention, the coating is transparent, ensuring that the original appearance of the metal surface is maintained after application.

[0105] Further, in the present invention, the coating provides strong resistance to water, mud, dust, dyes, dissolved substances, and colloidal dispersions.

[0106] Further, in the present invention, the use of a binder, such as methyl-2-cyanoacrylate, ensures strong attachment of the titanium dioxide layer and silane compounds to the metal surface, contributing to the coating's long-term stability and performance.

[0107] Lastly, in the present invention, the liquid formulation is prepared at room temperature with readily available materials, making the manufacturing process cost-effective and suitable for large-scale production.

[0108] It is understood that various omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient. Still, such omissions and substitutions are intended to cover the application or implementation without departing from the spirit or scope of the present invention.

[0109] The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and many modifications and variations are possible in light of the above teaching.

[0110] Further, the embodiments were chosen and described to best explain the principles of the present invention and its practical application, and thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated.

Claims

CLAIMS:

1. A sprayable composition for spraying on a metal surface such as steel to obtain a superhydrophobic coating thereon, the sprayable composition comprising:a hydrophobicity substrate comprising titanium alkoxide capable of hydrolyzing to form a nano-sized titanium alkoxide layer bonded to the metal surface;an organic silane agent comprising trimethoxysilane, the said agent capable of hydrolyzing in water and self-assembling onto the titanium alkoxide layer via hydrogen bonding to provide hydrophobicity;a solvent consisting of methanol for preventing premature hydrolysis of the titanium alkoxide and silane and enabling a smooth application process; anda binder comprising cyanoacrylate for improving adhesion and enhancing the durability of the coating on the metal surface.

2. The sprayable composition as claimed in claim 1, wherein the said titanium alkoxide comprises titanium butoxide,3. The sprayable composition as claimed in claim 2, wherein the said titanium butoxide is added in a range of about 0.05 wt% to 5 wt% of the composition, the said titanium butoxide hydrolyzing to form titanium dioxide nanocoating as the titanium dioxide layer enabling bonding of hydrophobic molecules to the metal surface through coordinating bonds and hydrogen bonds.

4. The sprayable composition as claimed in claim 1, wherein the organic silane agent comprises hexadecyltrimethoxysilane, added to the composition in a range of about 0.1 wt% to 10 wt% of the composition.

5. The sprayable composition as claimed in claim 4, wherein the organic silane agent is a silane compound that hy drolyzes in water, and is added in a range of about 0.01 wt% to 5 wt%, wherein the silane agent self-assembles onto the titanium dioxide layer through hydrogen bonding.

6. The sprayable composition as claimed in claim 1, wherein methanol is present in a range of about 85 wt% to 99.5 wt% and is provided for maintaining the stability of the titanium alkoxide and silane during the application process and preventing premature hydrolysis of the composition.

7. The sprayable composition as claimed in claim 1, wherein the cyanoacrylate is methyl-2- cyanoacrylate, which is present in a range of about 0.01wt% to 5wt% of the composition, the said binder enhancing the adhesion and durability of the coating on the metal surface, and ensuring long-term performance.

8. A method (100) for preparing a superhydrophobic coating on a metal surface such as steel, the method comprising:preparing a sprayable composition comprising dissolving (at step 104) hydrophobicity substrate comprising titanium alkoxide and organic silane agent comprising trimethoxysilane in solvent and stirring the mixture for complete dissolution;adding water (at step 106) dropwise to the mixture while stirring for about 0.5 to 3 hours to allow proper hydrolysis of the hydrophobicity substrate and organic silane agent;adding binder (at step 108) comprising cyanoacrylate to the solution and stirring for a period of 30-60 minutes to achieve uniform integration;spraying (at step 110) the prepared solution onto the metal surface using a spraying mechanism such as spray gun; andallowing the coated solution to dry at room temperature to ensure strong adhesion and the formation of a superhydrophobic coating on the metal surface.

9. The method (100) as claimed in claim 8, wherein the hydrophobicity substrate comprises a titanium alkoxide added in a range of about 0.05 wt% to 5 wt% of the solution, and dissolved in a solvent comprising methanol, wherein the methanol content is in a range of about 85 wt% to 99.5 wt%, to ensure complete dissolution of the titanium alkoxide.

10. The method (100) as claimed in claim 8-9, wherein the organic silane agent comprises hexadecyltrimethoxysilane added in a range of about 0.1 wt% to 10 wt%, dissolved in a solvent comprising methanol, wherein the methanol content is in a range of about 85wt% to 99.5wt%, wherein the mixture is maintained at room temperature to prevent premature hydrolysis.

11. The method as claimed in claim 8-10, wherein water is added dropwise to the mixture while stirring for 0.5 to 3 hours at room temperature to allow hydrolysis of the titanium alkoxide and hexadecyltrimethoxysilane, ensuring the formation of a titanium alkoxide layer.

12. The method (100) as claimed in claim 8-11, wherein the binder comprises methyl-2- cyanoacrylate, added to the solution and stirred for about additional 30-60 minutes at room temperature to ensure uniform integration, thereby enhancing the adhesion and durability of the superhydrophobic coating.

13. The method (100) as claimed in claim 8-12, wherein the prepared solution is sprayed onto the metal surface using a spraying mechanism such as spray gun, and the coated surface is allowed to dry at room temperature for 1 to 2 hours to ensure strong adhesion and the formation of a superhydrophobic titanium dioxide layer bonded with hydrophobic molecules.

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