Superhydrophobic Coating for Aluminum Alloy Surface with Durable Wear Resistance and Corrosion Resistance and its Preparation Method

Abstract

This invention discloses a superhydrophobic and oleophobic coating for aluminum alloy surfaces with durable wear resistance and corrosion resistance, and its preparation method. The coating, by weight, comprises: 10-15 parts of nano-sized silica particles, 10-15 parts of nano-sized titanium dioxide particles, 5-10 parts of polytetrafluoroethylene (PTFE), and an epoxy resin matrix as a carrier. The preparation method involves pre-mixing the raw materials, then uniformly depositing the components of the premixed solution onto the aluminum alloy surface using electrophoresis, followed by drying to form the superhydrophobic and oleophobic coating. The coating of this invention is pollution-free during production and use. The resulting coating exhibits high crosslinking density, low curing shrinkage, and high wear resistance, high hardness, and superhydrophobic and oleophobic properties. Furthermore, by pre-treating the aluminum alloy surface, a stable and dense coating film is formed, which can isolate oxygen to improve the corrosion resistance of the coated surface, providing long-lasting protection. This method has broad application prospects.

Description

Technical Field

[0001] This invention relates to the field of coating technology, specifically to a superhydrophobic coating for aluminum alloy surfaces with durable wear resistance and corrosion resistance, and its preparation method. Background Technology

[0002] Aluminum alloys possess numerous advantages, including light weight, excellent thermal and electrical conductivity, good plasticity and formability, and ease of processing. They are widely used in aerospace, automotive manufacturing, electronics manufacturing, instrumentation, light industry, and building materials. Especially in recent years, the rapid development of my country's industry has placed high demands on lightweighting, energy conservation, and emission reduction. Today, aluminum alloys can replace steel in many applications, becoming a widely used metallic material in industrial development. However, aluminum alloys contain other metallic elements such as Mg and Zn on their surface, making them more chemically reactive, especially when rich in active Cl. - In marine environments with high dissolved oxygen levels, aluminum alloys are more susceptible to corrosion, severely limiting their service life and application areas. With increasing industrial demands, their low hardness, poor wear resistance, and poor corrosion resistance have become increasingly prominent drawbacks. Therefore, effectively improving the wear resistance and corrosion resistance of aluminum alloy surfaces has become a crucial issue that urgently needs to be addressed.

[0003] Traditional surface treatment methods, such as electroplating, anodizing, and organic coatings, while improving the wear resistance and corrosion resistance of aluminum alloys to some extent, still have some shortcomings. For example, electroplated layers are prone to cracking during long-term use, leading to a decrease in corrosion resistance; anodized layers are easily worn in frictional environments; and organic coatings are prone to failure in high-temperature or strong acid / alkali environments. In recent years, superhydrophobic surfaces have attracted widespread attention due to their unique surface wettability, which can reduce interfacial interactions, especially in areas such as corrosion resistance, anti-icing, anti-fouling, and oil-water separation. Superhydrophobic coatings fundamentally reduce the possibility of corrosion and friction by reducing the contact area between liquids and solid surfaces, preventing liquid adhesion and reducing surface contamination. However, achieving durable wear resistance and corrosion resistance on aluminum alloy surfaces remains a significant challenge.

[0004] The invention patent CN117210094A discloses a superhydrophobic composite coating with wear resistance, thermal conductivity, and corrosion resistance, and its preparation method. The composite coating components, by weight, include 8-10 parts flake graphite, 8-10 parts Al₂O₃, 1-3 parts long-chain silane coupling agent, 15-20 parts fluorinated resin particles, 70-80 parts solvent, and 30-35 parts epoxy resin. The epoxy resin serves as the film-forming agent, the fluorinated resin as a low surface energy material, and the long-chain silane coupling agent improves the coating's mechanical and film-forming properties. This coating achieves excellent wear resistance, thermal conductivity, and corrosion resistance through a unique material ratio and preparation process. However, the low surface energy modified flake graphite and low surface energy modified spherical alumina used in the preparation process are expensive, and the modification steps involved in the coating preparation are complex. This not only increases production costs and the difficulty of technology popularization but may also reduce production efficiency, making it unsuitable for widespread application.

[0005] The invention patent with publication number CN114703456A proposes a novel corrosion-resistant superhydrophobic coating for aluminum and aluminum alloy surfaces and its preparation method. Specifically, the method involves sequentially subjecting aluminum or aluminum alloy to cleaning pretreatment, immersion-coating, and in-situ chemical curing, achieving uniform coating adhesion and effectively enhancing the interfacial bonding between the two materials, thus obtaining a novel corrosion-resistant superhydrophobic coating with superior stability. However, the preparation process involves the presence of metal salts such as copper, chromium, and nickel, which may cause environmental pollution. Chromium salts, in particular, have certain forms (such as hexavalent chromium) that are highly toxic. Improper handling could result in chemical waste that poses a serious environmental hazard, making this method unsuitable for widespread application. Summary of the Invention

[0006] To address the aforementioned problems, the present invention aims to provide a superhydrophobic coating for aluminum alloy surfaces with durable wear resistance and corrosion resistance, and a method for preparing the same.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] In a first aspect, the present invention provides a superhydrophobic coating for aluminum alloy surfaces with durable wear resistance and corrosion resistance, comprising, by weight, the following components: 10-15 parts of nano-sized silica particles, 10-15 parts of nano-sized titanium dioxide particles, 5-10 parts of polytetrafluoroethylene (PTFE), and an epoxy resin matrix as a carrier, accounting for the remaining weight percentage. This combination effectively provides durable corrosion resistance, anti-fouling properties, and wear resistance.

[0009] The nano-sized silica particles (SiO2) have an average particle size of 20-22 nm and a concentration of 1-1.5 wt%; the nano-sized titanium dioxide particles (TiO2) have an average particle size of 25-28 nm and a concentration of 0.5-0.6 wt%; and the polytetrafluoroethylene (PTFE) powder has an average particle size of 200-220 nm and a concentration of 0.5-0.6 wt%. The nano-sized silica particles and nano-sized titanium dioxide particles together provide superhydrophobic and superoleophobic properties, while the addition of PTFE enhances the coating's wear resistance and reduces surface energy, thus giving the coating superhydrophobic and superoleophobic properties and increasing its antifouling ability.

[0010] Secondly, the present invention provides a method for preparing a superhydrophobic coating on an aluminum alloy surface with durable wear resistance and corrosion resistance, comprising the following steps:

[0011] S1) The nanoparticles are mixed with the modifier and stirred or ultrasonically dispersed to make the modifier uniformly coat the particle surface. Then, the unreacted residues are removed by washing to obtain charged nanoparticles.

[0012] S2) Surface-modified nano-sized silica particles, modified nano-sized titanium dioxide particles, polytetrafluoroethylene (PTFE) powder and epoxy resin matrix are mixed to form a premixed liquid;

[0013] S3) The premixed liquid is treated with ultrasonic dispersion technology to ensure that the modified nanoparticles and PTFE are uniformly dispersed in the epoxy resin matrix to form a stable suspension system.

[0014] S4) The components in the premixed solution are uniformly deposited on the aluminum alloy surface by electrophoresis: The pretreated aluminum alloy material is placed in the electrophoresis tank, and the appropriate electric field parameters are adjusted so that the charged particles in the premixed solution are uniformly deposited on the aluminum alloy surface to form a uniform coating.

[0015] S5) Remove the aluminum alloy material from the electrophoresis tank and rinse it with deionized water to remove excess deposits;

[0016] S6) The prepared aluminum alloy plate is baked and cured at 80-120℃ to obtain a superhydrophobic coating.

[0017] In step S1), the proportions of each raw material component are as follows: 10-15 parts modified silica particles, 10-15 parts modified titanium dioxide particles, 5-10 parts polytetrafluoroethylene (PTFE) powder, and the remaining 60-75 parts are epoxy resin matrix as a carrier. The modifier is an aminosilane coupling agent (such as one or more of 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane) or a positively charged polymer (one or more of polyethyleneimine, polydiallylammonium chloride, and chitosan).

[0018] In step S2), the ultrasonic dispersion time is 30-35 min and the ultrasonic power is 200-220 W to ensure that the nanoparticles in the premixed liquid are uniformly dispersed.

[0019] In step S3), the pretreatment of the aluminum alloy material includes surface cleaning and micro-roughening treatment to increase the adhesion strength between the coating and the aluminum alloy surface; the conductivity of the premixed liquid in the electrophoresis tank is 100-110 μS / cm, the electrophoresis voltage is 50-55V, and the electrophoresis time is 10-12min.

[0020] The baking process in step S5) adopts a gradual heating method to avoid the nanoparticles in the premixed liquid from agglomerating due to rapid heating, thus ensuring the uniformity and performance stability of the coating.

[0021] In the technical solution of this invention, the micro-nano structure formed by polytetrafluoroethylene (PTFE) in the coating can effectively reduce friction and surface wear. Specifically, the strong van der Waals forces between PTFE molecules ensure a sliding effect when the surface is subjected to friction. When the coating surface is rubbed, the interaction between PTFE molecules allows the PTFE molecular layer to slide relatively easily under external force. Furthermore, the fluorine atoms on the PTFE surface form an almost completely smooth surface, further reducing friction. Nanoscale silica and titanium dioxide particles have better compatibility with epoxy resin, forming a dense protective layer on the coating surface. This layer not only blocks corrosive media but also, through the photocatalytic effect of titanium dioxide, generates free radicals using ultraviolet irradiation, destroying organic matter adsorbed on the aluminum alloy surface, further preventing corrosion. Simultaneously, the nanoscale silica and titanium dioxide particles form a multi-layered rough structure on the surface at the micron to nanometer scale, while PTFE provides the necessary low surface energy. These factors work together to increase the contact angle between droplets and the coating surface, causing water and oil droplets to form beads upon contact with the coating instead of spreading out, achieving a self-cleaning effect. Its core innovations are mainly reflected in the following aspects:

[0022] 1. Innovative Material Combination: The coating of this invention comprises nano-sized silica particles, nano-sized titanium dioxide particles, polytetrafluoroethylene (PTFE), and an epoxy resin matrix. While nano-silica and titanium dioxide have been used in traditional coatings for wear resistance and hydrophobic / oleophobic applications, many researchers have not delved into the performance improvements resulting from precise control of particle size. This invention achieves optimal micro / nano surface structure effects by optimizing the particle size of nano-silica (20-22 nm) and nano-titanium dioxide (25-28 nm). This combination effectively provides durable corrosion, fouling, and wear resistance, particularly through the synergistic effect of nano-sized silica and titanium dioxide particles with epoxy resin. The tiny particle size of silica and titanium dioxide nanoparticles allows them to form micro-nano-level rough structures on the epoxy resin surface, increasing the proportion of gas adhering to the coating surface and creating a "gas pocket" effect. Furthermore, the combination of the micro-nano structure with low surface energy materials increases the water-oil contact angle, forming a superhydrophobic and superoleophobic coating. This additional "barrier layer" increases the pathway for corrosive media (such as water and oxygen) to penetrate below the coating, thereby improving its corrosion resistance. In addition, the high hardness of silica and titanium dioxide nanoparticles (especially titanium dioxide) effectively enhances the overall hardness and wear resistance of the coating when dispersed in the epoxy resin matrix. When the coating is subjected to friction or scratching, the nanoparticles act as "barriers," reducing surface wear. Secondly, the nanoparticles can also disperse stress in the matrix, reducing crack propagation caused by localized stress concentration.

[0023] 2. Innovation in Preparation Process: This invention employs electrophoresis to uniformly deposit the components of a premixed solution onto the surface of an aluminum alloy. Through a specific baking temperature and curing process, coating stabilization is achieved at a lower temperature, resulting in a tighter bond between particles and the matrix. This avoids damage to material properties caused by excessively high temperatures, ensuring the uniformity and performance stability of the coating. Compared to traditional spraying methods, electrophoresis offers significant advantages in coating uniformity, density, and adhesion: ① During electrophoresis, charged particles move along a fixed direction and deposit on the substrate under the influence of an electric field, allowing for close packing and reducing the porosity of the coating; ② The electric field strength and deposition time in electrophoretic deposition can be precisely controlled, resulting in a uniform coating thickness. Because the charged particles experience relatively uniform forces in the electric field, the coating thickness is uniform, the edges are smooth, and it achieves good coverage even on complex surfaces; ③ Electrophoretic deposition typically occurs in a solution, where the coating material gradually deposits under the influence of an electric field, forming a strong interfacial bond. During the deposition process, the particles gradually approach the substrate material, and the layer-by-layer deposition method results in higher mechanical interlocking force and intermolecular interaction between the coating and the substrate.

[0024] 3. Performance Improvement: The coating of this invention features high wear resistance, high hardness, and superhydrophobicity and oleophobicity. By pre-treating the aluminum alloy surface, a stable and dense coating film is formed, which can isolate oxygen and improve the corrosion resistance of the coated surface. This coating can provide long-lasting protection in harsh environments and has significant application value.

[0025] 4. Environmental friendliness: Electrophoretic deposition is a closed system that can recover unused deposited materials. The material utilization rate of the entire process is close to 100%. Compared with traditional surface treatment methods, the coating provided by this invention is pollution-free during production and use, and the process is simple. This not only reduces production costs but also reduces the impact on the environment, thus exhibiting good environmental friendliness.

[0026] In summary, the innovation of this invention is mainly reflected in the innovation of material combination, the innovation of preparation process, the improvement of performance and environmental friendliness. These innovations together constitute the important contribution of this invention to the field of coating technology.

[0027] The advantages and beneficial effects of this invention are as follows:

[0028] The coating provided by this invention is pollution-free during production and use, and the process is simple. The resulting coating has high crosslinking density and low curing shrinkage, and features high wear resistance, high hardness, and superhydrophobicity and oleophobicity. At the same time, by pre-treating the aluminum alloy surface, a stable and dense coating film is formed, which can isolate oxygen to improve the corrosion resistance of the coated surface, so that it can provide long-term protection for the coated surface. Attached Figure Description

[0029] Figure 1 Images showing the contact angles of water and oil droplets on a superhydrophobic coating; where: water (left) and sunflower oil (right).

[0030] Figure 2 This is a graph showing the change in contact angle of the coating after 200 cycles of friction. Detailed Implementation

[0031] The technical solution of the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0032] A superhydrophobic coating for aluminum alloy surfaces with durable wear resistance and corrosion resistance comprises, by weight, the following components: 10-15 parts SiO2, 10-15 parts TiO2, 5-10 parts PTFE, and an epoxy resin matrix as a carrier, accounting for the remaining weight percentage. This combination effectively provides durable corrosion resistance, antifouling properties, and wear resistance.

[0033] The SiO2 has an average particle size of 20-22 nm and a concentration of 1-1.5 wt%; the TiO2 has an average particle size of 25-28 nm and a concentration of 0.5-0.6 wt%; and the PTFE powder has an average particle size of 200-220 nm and a concentration of 0.5-0.6 wt%. SiO2 and TiO2 together provide superhydrophobic and superoleophobic properties, while the addition of PTFE enhances the coating's wear resistance and reduces surface energy, thus giving the coating superhydrophobic and superoleophobic properties and increasing its antifouling ability.

[0034] This coating system achieves high performance and multifunctionality primarily through the synergistic effect of PTFE, SiO2, TiO2, and epoxy resin. The multi-layered rough structure at the micron to nanometer scale formed by SiO2 and TiO2 on the surface, combined with the low surface energy of PTFE, enables the coating to achieve a self-cleaning effect. This characteristic is significant for improving the coating's durability and ease of maintenance in harsh environments.

[0035] The method for preparing this superhydrophobic coating includes the following steps:

[0036] S1) SiO2, TiO2, and PTFE powders are mixed with an epoxy resin matrix to form a premix;

[0037] S2) Ultrasonic dispersion technology is used to ensure uniform dispersion of nanoparticles in the premixed solution;

[0038] S3) Place the pretreated aluminum alloy material into an electrophoresis tank and uniformly deposit the components in the premixed solution onto the aluminum alloy surface by electrophoresis.

[0039] S4) Remove the aluminum alloy material from the electrophoresis tank and rinse it with deionized water to remove excess deposits;

[0040] S5) The prepared aluminum alloy plate is baked and cured at 80°C to 120°C to obtain a superhydrophobic coating.

[0041] The prepared superhydrophobic coating was tested for contact angle according to the standard GB / T 26490-2011 "Test Method for Superhydrophobic Properties of Nanomaterials" to obtain its superhydrophobic properties. The coated specimens were then tested for corrosion resistance according to GB / T 10125-2012 "Artificial Atmosphere Corrosion Test - Salt Spray Test" using a neutral NaCl solution for accelerated corrosion testing via continuous spraying. Finally, the coating's abrasion resistance was tested according to GB / T 23988-2009 "Determination of Abrasion Resistance of Coatings - Falling Sand Method" by cyclically rubbing the superhydrophobic coating sample with 1000-mesh SiC sandpaper under a 200g load, with each cycle covering a distance of 10cm.

[0042] Example 1

[0043] Super hydrophobic coating I comprises the following components: 10g SiO2, 10g TiO2, 5g PTFE and 60g epoxy resin.

[0044] The preparation method of the superhydrophobic coating I is as follows: 1) Take an appropriate amount of SiO2, TiO2, PTFE powder and mix with epoxy resin matrix to form a premix; 2) Ensure that the nanoparticles in the premix are uniformly dispersed by ultrasonic dispersion technology; 3) Put the pretreated aluminum alloy material into the electrophoresis tank and uniformly deposit the components in the premix onto the aluminum alloy surface by electrophoresis; 4) Take out the aluminum alloy material from the electrophoresis tank and rinse with deionized water to remove excess deposits; 5) Bake the obtained aluminum alloy plate at 80℃ to 120℃ to obtain the superhydrophobic coating I.

[0045] Example 2

[0046] Super hydrophobic coating II comprises the following components: 10g SiO2, 12.5g TiO2, 7.5g PTFE and 67.5g epoxy resin.

[0047] The preparation and application methods of the superhydrophobic coating II are the same as those in Example 1, resulting in the superhydrophobic coating II.

[0048] Example 3

[0049] Super hydrophobic coating III comprises the following components: 10g SiO2, 15g TiO2, 10g PTFE and 75g epoxy resin.

[0050] The preparation and application methods of the superhydrophobic coating III are the same as those in Example 1, resulting in the superhydrophobic coating III.

[0051] Example 4

[0052] Superhydrophobic coating IV comprises the following components: 12.5g SiO2, 10g TiO2, 7.5g PTFE and 75g epoxy resin.

[0053] The preparation and application methods of the superhydrophobic coating IV are the same as those in Example 1, resulting in the superhydrophobic coating IV.

[0054] Example 5

[0055] Superhydrophobic coating V comprises the following components: 12.5g SiO2, 12.5g TiO2, 10g PTFE and 60g epoxy resin.

[0056] The preparation and application methods of the superhydrophobic coating V are the same as in Example 1, resulting in the superhydrophobic coating V.

[0057] Example 6

[0058] Super hydrophobic coating VI comprises the following components: 12.5g SiO2, 15g TiO2, 5g PTFE and 67.5g epoxy resin.

[0059] The preparation and application methods of the superhydrophobic coating VI are the same as those in Example 1, resulting in the superhydrophobic coating VI.

[0060] Example 7

[0061] Super hydrophobic coating VII comprises the following components: 15g SiO2, 10g TiO2, 10g PTFE and 67.5g epoxy resin.

[0062] The preparation and application methods of the superhydrophobic coating VII are the same as those in Example 1, resulting in the superhydrophobic coating VII.

[0063] Example 8

[0064] Super hydrophobic coating VIII comprises the following components: 15g SiO2, 12.5g TiO2, 5g PTFE and 75g epoxy resin.

[0065] The preparation and application methods of the superhydrophobic coating VIII are the same as those in Example 1, resulting in the superhydrophobic coating VIII.

[0066] Example 9

[0067] Super hydrophobic coating IX comprises the following components: 15g SiO2, 15g TiO2, 7.5g PTFE and 60g epoxy resin.

[0068] The preparation and application methods of the superhydrophobic coating IX are the same as those in Example 1, resulting in the superhydrophobic coating IX.

[0069] The performance of the superhydrophobic coatings prepared in each embodiment was tested according to the test method described above, and the performance test results are shown in Table 1.

[0070] Figure 1 Images showing the contact angles of water and oil (sunflower seed oil) dropped onto a superhydrophobic coating are displayed. Figure 2 The diagram shows the change in the contact angle of the coating after 200 cycles of friction. After 200 cycles of friction, the water contact angle (WCA) of the coating is greater than 150°, and it still maintains excellent water repellency, indicating that the coating has excellent superhydrophobic properties and abrasion resistance.

[0071] The coating performance test results show that the superhydrophobic coating III in Example 3 has the best overall performance. Specifically, after 200 cycles of friction, the water contact angle (WCA) of the coating is greater than 150° (159.4°), no corrosion was observed after 2000 hours of salt spray testing, and the coating did not blister, wrinkle, peel, or crack, exhibiting excellent and durable hydrophobicity, oleophobicity, abrasion resistance, and corrosion resistance. (The hydrophobicity, oleophobicity, and abrasion resistance test results are all characterized by contact angle values, where abrasion resistance is the contact angle value after 200 cycles of friction; in the corrosion resistance test results, "excellent" means no corrosion occurred, and "good" means the corrosion area is less than 3%).

[0072] Table 1. Coating performance test results

[0073]

Claims

1. A superhydrophobic coating for aluminum alloy surfaces with durable wear resistance and corrosion resistance, characterized in that: Based on parts by weight, it comprises the following components: 10 parts modified silica particles, 15 parts modified titanium dioxide particles, 10 parts polytetrafluoroethylene (PTFE), and 75 parts epoxy resin matrix as a carrier. The modified silica particles have an average particle size of 20-22 nm; the modified titanium dioxide particles have an average particle size of 25-28 nm. The average particle size of the polytetrafluoroethylene (PTFE) powder is 200-220 nm. The method for preparing the superhydrophobic coating on the aluminum alloy surface includes the following steps: S1) The nanoparticles are mixed with the modifier and stirred or ultrasonically dispersed to make the modifier uniformly coat the particle surface. Then, the unreacted residues are removed by washing to obtain charged nanoparticles. S2) The surface-modified nano-sized silica particles, modified nano-sized titanium dioxide particles, polytetrafluoroethylene powder and epoxy resin matrix are mixed to form a premixed liquid. S3) The premixed liquid is treated with ultrasonic dispersion technology to ensure that the modified nanoparticles and polytetrafluoroethylene are uniformly dispersed in the epoxy resin matrix to form a stable suspension system. S4) The components in the premixed solution are uniformly deposited on the aluminum alloy surface by electrophoresis: The pretreated aluminum alloy material is placed in the electrophoresis tank, and the appropriate electric field parameters are adjusted so that the charged particles in the premixed solution are uniformly deposited on the aluminum alloy surface to form a uniform coating. S5) Remove the aluminum alloy material from the electrophoresis tank and rinse it with deionized water to remove excess deposits; S6) The prepared aluminum alloy plate is baked and cured at 80-120℃ to obtain a superhydrophobic coating; In step S1), the modifier is an aminosilane coupling agent or a positively charged polymer.

2. The superhydrophobic coating on the aluminum alloy surface according to claim 1, characterized in that: the aminosilane coupling agent is one or more of 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane; and the positively charged polymer is one or more of polyethyleneimine, polydimethyldiallylammonium chloride, and chitosan.

3. The superhydrophobic coating on the aluminum alloy surface according to claim 2 is characterized in that: in step S2), the ultrasonic dispersion time is 30-35 min and the ultrasonic power is 200-220 W to ensure that the nanoparticles in the premixed liquid are uniformly dispersed.

4. The superhydrophobic coating on the aluminum alloy surface according to claim 3, characterized in that: in step S3), the pretreatment of the aluminum alloy material includes surface cleaning and micro-roughening treatment to increase the adhesion strength between the coating and the aluminum alloy surface; the conductivity of the premixed liquid in the electrophoresis tank is 100-110 μS / cm, the electrophoresis voltage is 50-55V, and the electrophoresis time is 10-12min.

5. The superhydrophobic coating on the aluminum alloy surface according to claim 4 is characterized in that: the baking process in step S5) adopts a gradual heating method to avoid the nanoparticles in the premixed liquid from agglomerating due to rapid heating, thereby ensuring the uniformity and performance stability of the coating.

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