Metal matrix black phosphorus derived two-dimensional lamellar layer / zinc phosphating composite coating and preparation method thereof

Abstract

The invention discloses a black phosphorus derived two-dimensional lamella / zinc phosphating composite coating and a preparation method thereof, and belongs to the field of metal surface engineering and interface chemistry. The method comprises the following steps: forming a porous zinc phosphating layer on the surface of a metal matrix, and then further forming the black phosphorus derived two-dimensional lamella / zinc phosphating composite coating by using an RS-H-BP dispersion liquid through a conventional liquid phase deposition method, in order to improve the multi-effect protection performance of the composite coating, preferably, a phosphorus-enriched transition seed layer is formed on the surface of the zinc-series phosphate coating through low-temperature vapor deposition, or the phosphorus-enriched transition seed layer is not prepared, and RS-H-BP dispersion liquid with different solid contents is subjected to graded deposition to form a film, so that the steady-state COF of the composite coating is controlled to be about 0.11, and the fluctuation range of the friction coefficient is very small; and the corrosion-resistant time reaches 720 h or above, the electrochemical impedance is remarkably reduced, the hundred-lattice adhesive force reaches the level 0, and the aluminum alloy material is suitable for antifriction and corrosion-resistant protection of aluminum alloy components in the fields of automobiles, rail transit, aerospace, 3C electronics and the like.

Description

Technical Field

[0001] This invention belongs to the field of metal surface engineering and interface chemistry, specifically relating to a two-dimensional lamellar / zinc phosphating composite coating derived from black phosphorus on a metal substrate and its preparation method. Background Technology

[0002] In existing technologies, zinc-based phosphating solutions are metal surface treatment agents with zinc phosphate salts as the main component, and Zn as the core component. 2+ H2PO 3- NO 3- Phosphating agents, through chemical reactions, form a porous zinc phosphate crystalline film (also known as a phosphating film) on metal surfaces, composed of microcrystalline phases such as Zn3(PO4)2·xH2O. This film provides a good adhesion base and initial corrosion resistance on metal surfaces such as steel, aluminum, and magnesium. However, the inherent brittle microcrystalline structure of traditional phosphating films is prone to breakage or pulverization under boundary lubrication or dry friction environments, leading to an increase in the friction coefficient and inducing secondary corrosion. In addition, the high connectivity of pores in the porous morphology of phosphating films allows for the formation of continuous penetration paths in corrosive environments such as salt spray and humid heat, failing to prevent corrosive media from penetrating the film and entering the metal substrate, thus limiting the long-term corrosion resistance of the phosphating film. To overcome the shortcomings of traditional phosphating films in terms of tribological properties and corrosion resistance, researchers have considered introducing two-dimensional solid lubricating materials, such as graphite, molybdenum disulfide (MoS2), and graphene. Although these materials possess low-shear layered structures and barrier properties, their adhesion and durability remain poor due to significant differences from inorganic conversion films in terms of interfacial chemistry, surface energy matching, and hygrothermal stability. Furthermore, relying on high-content polymer binders to enhance adhesion can lead to problems such as adhesion, carbonization, or failure of the phosphating film under high-temperature or boundary friction conditions, thus limiting the practical application of two-dimensional materials in engineered metal systems.

[0003] Black phosphorus (BP) is a two-dimensional material that has attracted much attention in recent years. Although it possesses significant anisotropy and a low shear energy surface, and its interlayer structure theoretically makes it suitable for use as a drag-reducing, wear-resistant, and barrier functional component, its surface is rich in highly reactive phosphorus atoms, making it prone to oxidation or hydrolysis in air and moisture, producing phosphorus... x O y HPO x Degradation products lead to sheet breakage, decreased dispersion stability, increased agglomeration, and uneven film formation, ultimately resulting in fluctuations in the friction coefficient, film cracking, and a significant reduction in service life. In addition, the interfacial bonding between black phosphorus and inorganic conversion film is weak, and it is prone to overall peeling under vibration, impact, or cyclic friction conditions. Therefore, black phosphorus is currently difficult to use directly in metal matrix phosphating film reinforcement systems.

[0004] Existing methods for introducing two-dimensional materials into phosphating films often employ a combination of "phosphating + two-dimensional material spraying / dipping or organic coating." These methods generally suffer from problems such as insufficient embedding efficiency of two-dimensional sheets within the phosphating micropores, uncontrollable sheet orientation, interfacial energy mismatch, and insufficient long-term stability in humid and hot environments. Although polymer coating or inert encapsulation have moderately improved the stability of black phosphorus, these methods still weaken the low-shear properties of black phosphorus or introduce organic residues that are detrimental to high-temperature / friction service, making it difficult to sustain its tribological advantages. At the same time, the lack of a chemically adjustable transition interface structure between the inorganic phosphating film and the organic two-dimensional material makes the composite coating prone to interfacial decay and peeling under long-term corrosion-friction coupling conditions.

[0005] Currently, industrial applications require coatings to meet the requirements of "low temperature, short cycle time, high repeatability, and compatibility with existing phosphating production lines." At the same time, the coating must maintain stable performance with low friction, low wear, and high impedance in complex service environments under the triple coupling of salt spray, damp heat, and boundary friction. Therefore, simply using traditional phosphating films or introducing two-dimensional materials alone cannot meet the multi-effect protection requirements of metal substrates. There is an urgent need for a composite coating system that can build a stable transition interface under low temperature conditions, achieve controllable orientation of the sheet structure, and has high interface stability. Summary of the Invention

[0006] The first objective of this invention is to provide a method for preparing a metal substrate black phosphorus-derived two-dimensional sheet / zinc-based phosphating composite coating, and the second objective is to provide a metal substrate having a black phosphorus-derived two-dimensional sheet / zinc-based phosphating composite coating.

[0007] The first objective of this invention is achieved as follows: the method for preparing the metal substrate black phosphorus-derived two-dimensional sheet / zinc-based phosphating composite coating includes the following steps: 1) Preparation of zinc-based phosphating layer: First, the metal substrate surface is pretreated by degreasing, alkaline etching and / or acid pickling and activation using conventional methods. Then, the pretreated metal substrate is completely immersed in a zinc-based phosphating solution and reacted at 40-60℃ for 7-12 minutes to form a porous zinc-based phosphating layer with a thickness of 0.3-2.0 μm on the metal substrate surface. The pore size of the zinc-based phosphating layer ranges from 50 to 400 nm. The zinc-based phosphating solution contains Zn... 2+ The concentration is 1.0~1.2g / L, the total acidity is 35~40 points, and the free acidity is 1.5~2.5 points; 2) Preparation of RS-H-BP dispersion: Black phosphorus was dispersed in anhydrous toluene at a concentration of 0.2~1.5 mg / mL, and ultrasonically exfoliated at 400W for 25~30 min to obtain a suspension; carbon chain length C was added to the suspension. 12 ~C 18Alkyl thiols and triethylamine were used in a suspension with an alkyl thiols concentration of 10-50 mM and a triethylamine concentration of 0.3-1.0 vol%. The suspension was reacted at 50-80 °C for 2-8 h under an argon atmosphere. After the reaction, the suspension was centrifuged at 3000-6000 g and the solvent was replaced 3-5 times to remove free alkyl thiols and byproducts. The resulting solid fraction was uniformly redispersed in a mixed solvent of IPA / EA in equal volumes. The solid content in the mixed solvent was adjusted to 0.05-1.0 mg / mL to obtain an RS-H-BP dispersion with an S / P atomic ratio of 0.06-0.12. 3) Liquid phase deposition film formation: The RS-H-BP dispersion is deposited on the zinc phosphate layer of the metal substrate by liquid phase deposition. The liquid phase deposition method includes one or more of the following: spraying, dip coating / coating, spin coating, and electrophoretic deposition. After each film formation, it is pre-dried at 40~80℃ for 3~30min. The total thickness of the film after pre-drying is 250~350nm. 4) Drying and curing of composite coating: After the pre-drying of film formation in step 3), the metal substrate is dried at 50~70℃ for 10~15min, and then cured at 90~120℃ for 10~30min to obtain a metal substrate with a black phosphorus-derived two-dimensional lamellar / zinc phosphating composite coating.

[0008] Preferably, step 1) further includes forming a phosphorus-enriched transition seed layer on the surface of the zinc-based phosphating layer using a low-temperature remote plasma-assisted chemical vapor deposition method. During preparation, the plasma mode is selected as remote / downstream plasma, the radio frequency power is 60~100W, the metal substrate temperature is 120~250℃, red phosphorus is used as the phosphorus-containing precursor, and deposition is carried out in an argon atmosphere for 30~600s to form a phosphorus-enriched transition seed layer with a thickness of 2~20nm; in step 3), RS-H-BP dispersion is liquid-phase deposited on the surface of the phosphorus-enriched transition seed layer of the metal substrate to form a film.

[0009] Preferably, a phosphorus enrichment transition seed layer is not prepared. In step 2), when preparing the RS-H-BP dispersion, dispersions A and B with solid contents of 0.05~0.1 mg / mL and 0.2~0.4 mg / mL, respectively, are prepared. In step 3), a liquid phase deposition film is formed on the surface of the zinc-based phosphating layer using spin coating. The bottom and top layers of the film are prepared with dispersion A, and the middle layer of the film is prepared with dispersion B. When preparing the bottom, middle, and top layers, the concentration is 60~100 μL / cm. 2Add the amount of dispersion A or B dropwise. After the addition, spin coat each layer at 300-500 r / min for 8-10 s, and then spin coat at 1800-2500 r / min for 20-30 s. After the two spin coats, pre-dry at 60-70℃ for 5-10 min. The total thickness of the film after pre-drying is 250-350 nm. Step 4) After the surface layer of the film in step 3) is pre-dried, heat-curing at 90-120℃ for 10-30 min to obtain a metal substrate with a black phosphorus-derived two-dimensional sheet / zinc phosphating composite coating.

[0010] The second objective of this invention is achieved by obtaining a metal substrate with a black phosphorus-derived two-dimensional lamellar / zinc-based phosphating composite coating by the preparation method described in this invention.

[0011] To overcome the shortcomings of existing zinc-based phosphating layers on metal substrates, this invention optimizes the thickness and pore size range of the zinc-based phosphating layer based on traditional phosphating. Then, black phosphorus (BP) is modified with alkyl thiols (RS-H) to obtain an RS-H-BP dispersion. The RS-H-BP dispersion is an alkyl thiols-modified BP dispersion, in which the solid portion consists of RS-H-BP nanosheets (i.e., modified BP nanosheets, hereinafter referred to as RS-H-BP). A liquid phase deposition method is used to form a film (non-gradient) on the surface of the zinc-based phosphating layer using the RS-H-BP dispersion, obtaining a black phosphorus-derived two-dimensional sheet / zinc-based phosphating composite coating. Experiments show that after 5000 dry friction cycles, the steady-state COF is 0.14~0.17, with COF fluctuating within the range of 0.12~0.18, and the corrosion resistance time is approximately 600 hours. The electrochemical impedance spectroscopy (EIS) is also high. 0.01 Hz is between 3.3 and 3.4 × 10⁻⁶. 7 Ω·cm 2 Within the specified range, the adhesion of the cross-link is between 0 and 1. Compared with the composite coating obtained by forming a film with unmodified BP dispersion, it significantly reduces steady-state COF, increases wear life, and significantly improves corrosion resistance and coating adhesion, thus providing multi-effect protection for the metal substrate.

[0012] To further improve the performance of zinc-based phosphate layers, this invention adopts two optimization technical solutions: Firstly, the bottom, middle, and top layers of the film were prepared by gradient spin-coating of RS-H-BP dispersions with different solid contents onto the surface of a zinc-based phosphate layer. XRD analysis showed that the bottom layer material was uniformly distributed on the surface of the zinc-based phosphate layer and partially embedded in the pores, while the middle layer formed a dense barrier structure. The lotgering orientation factor in the top layer was about 30-40% higher than that of the non-gradient film formed by RS-H-BP dispersion, indicating that a low-shear orientation structure was formed on the surface of the composite coating, which is conducive to reducing the friction coefficient. The experiment showed that, compared with the non-gradient film, even after 10,000 dry friction cycles, the steady-state COF of the composite coating was 0.11 with a fluctuation range of ±0.01, the corrosion resistance time was extended to more than 720 hours, the electrochemical impedance was significantly improved, and the cross-cut adhesion reached level 0. Secondly, a phosphorus-enriched transition seed layer was prepared on the surface of a zinc-based phosphate layer using low-temperature long-range plasma-assisted chemical vapor deposition (PECVD). Then, an RS-H-BP dispersion was used to form a non-gradient film on the surface of the phosphorus-enriched transition seed layer. The experiment showed that, compared with the phosphorus-free transition seed layer, even after 8000 dry friction cycles, the steady-state COF of the composite coating was 0.12~0.13, the COF fluctuated in the range of 0.11~0.145, the corrosion resistance time was extended to more than 720 hours, the electrochemical impedance was also significantly improved, and the cross-cut adhesion reached level 0.

[0013] This invention also found that although the relevant protective indicators deteriorate slightly with decreasing carbon chain length, the protection index remains relatively stable at a certain carbon chain length (C0). 12 ~C 18 It can maintain COF at 0.115~0.18, has a corrosion resistance time of over 480h, and an electrochemical impedance of 2.6×10⁻⁶. 7 Ω·cm 2 The adhesion of the cross-linked polymer (CLP) is within grade 1, which is significantly improved compared to the application of C8SH-BP dispersion. To achieve better application results, this invention preferably uses a carbon chain length of C... 16 ~C 18 Especially octadecyl mercaptan (ODT).

[0014] In summary, the present invention has the following advantages over the prior art: (1) Significantly enhances the wear resistance and friction reduction properties of the composite coating: By adding a phosphorus-enriched transition seed layer to the surface of the zinc phosphate layer, and with the application of RS-H-BP dispersion, the shear orientation of the layer structure on the surface of the composite coating is optimized, the steady-state COF is significantly improved, and the fluctuation is kept small during cyclic friction. In addition, by gradient spin coating of dispersions with different RS-H-BP contents, a low shear orientation structure that is beneficial to reducing the friction coefficient is formed on the surface of the composite coating. Even without the preparation of the phosphorus-enriched transition seed layer, the tribological properties of the composite coating are similar to or even better than those of the composite coating with the addition of the phosphorus-enriched transition seed layer. According to the test, the static water contact angle of the composite coating obtained by the present invention is not less than 95°, and even reaches 107°. (2) Significantly improves the corrosion resistance of the composite coating: RS-H-BP improves the orientation of the surface layers of the composite coating. Some RS-H-BP is embedded in the pores of the zinc phosphate layer and forms a multi-scale barrier network together with the surface RS-H-BP, which significantly tortuous the diffusion path of the corrosive medium, improves the overall impedance of the composite coating, significantly increases the low-frequency impedance of EIS, and achieves a corrosion resistance time of more than 480h, or even more than 720h. (3) Improve the adhesion and interface stability of the composite coating: Since some RS-H-BP enters the pores of the zinc phosphate layer and forms a mechanical lock with the crystal structure of the phosphate layer, especially the phosphorus enrichment transition seed layer provides P-related chemical anchoring points, which can be combined with weak coordination or bonding of Zn-S, P-Zn and other weak coordination or bonding to enhance the interface bonding force. The adhesion of the 100-grid coating is maintained in the range of 0~1, or even reaches 0, and can remain stable under complex working conditions such as vibration and impact. (4) Significantly improves the stability of black phosphorus: During the research, it was found that alkyl thiols (especially ODT) effectively inhibited the oxidation and hydrolysis of black phosphorus through PS linkage and long-chain hydrophobic self-assembly structure. The improvement in the stability of black phosphorus can be seen from the extension of wear resistance and corrosion resistance time. At the same time, it was also found that RS-H-BP dispersion can be stable for 30-60 days at 4~10℃, thus ensuring the repeatability of the coating preparation process.

[0015] The preparation method of this invention features low overall temperature, fewer steps, and a wide parameter window. The phosphating step is fully compatible with traditional zinc-based phosphating production lines. The liquid phase deposition of the RS-H-BP dispersion can be completed using conventional spraying, dip coating, spin coating, or electrophoresis equipment. The phosphorus enrichment transition seed layer can be achieved through low-temperature PECVD or other low-temperature gas phase equipment. No high-temperature curing oven or complex high-temperature CVD system is required. This method is suitable for large-scale surface treatment of various metal components such as steel, aluminum, and magnesium, and has significant engineering application value and promotion prospects. Attached Figure Description

[0016] Figure 1The Fourier transform infrared spectrum (FT-IR) of ODT-BP in Example 2 shows that the thiol group introduces CH, CS and PS related absorption peaks; Figure 2 The X-ray photoelectron spectrum (XPS) of ODT-BP in Example 2 is shown in Figure a. The full spectrum is shown in the Survey, and the high-resolution P2p spectrum is shown in Figure b (Al Kα, Pass Energy 20eV). Figure 3 The surface microstructure of the zinc phosphate layer in Example 2 is shown under a scanning electron microscope (SEM) at 500× magnification (accelerating voltage 15kV, scale bar 100μm). Figure 4 The surface microstructure of ODT-BP in Example 2 is shown under a scanning electron microscope (SEM) at 30,000x magnification (accelerating voltage 2kV, scale bar 300nm). Detailed Implementation

[0017] The present invention will be further described in detail below with reference to embodiments and comparative examples, but the scope of protection of the present invention is not limited to these embodiments.

[0018] The method for preparing the metal substrate black phosphorus-derived two-dimensional lamellar / zinc-based phosphating composite coating of the present invention includes the following steps: 1) Preparation of zinc-based phosphating layer: First, the metal substrate surface is pretreated by degreasing, alkaline etching and / or acid pickling and activation using conventional methods. Then, the pretreated metal substrate is completely immersed in zinc-based phosphating solution and reacted at 40~60℃ for 7~12 min to form a porous zinc-based phosphating layer (referred to as phosphating layer) with a thickness of 0.3~2.0μm on the metal substrate surface. The pore size range of the zinc-based phosphating layer is 50~400nm; Zn in the zinc-based phosphating solution... 2+ The concentration is 1.0~1.2g / L, the total acidity is 35~40 points (pt), and the free acidity is 1.5~2.5 points (pt). 2) Preparation of RS-H-BP dispersion: Black phosphorus (BP) was dispersed in anhydrous toluene at a concentration of 0.2~1.5 mg / mL, and ultrasonically exfoliated at 400 W for 25~30 min to obtain a suspension; carbon chain length C was added to the suspension. 12 ~C 18Alkyl thiols (RS-H) and triethylamine were reacted in an argon atmosphere at 50-80℃ for 2-8 hours. After the reaction, the mixture was centrifuged at 3000-6000g and the solvent was replaced 3-5 times to remove free alkyl thiols and byproducts. The resulting solid fraction (RS-H-BP) was uniformly redispersed in an equal volume ratio of IPA / EA mixed solvent (isopropanol / ethyl acetate mixed solvent, the same below). The solid content in the mixed solvent was adjusted to 0.05-1.0 mg / mL to obtain RS-H-BP dispersion (alkyl thiols modified BP dispersion). The S / P atomic ratio in the dispersion was 0.06-0.12. 3) Liquid phase deposition film formation: The RS-H-BP dispersion is deposited on the zinc phosphate layer of the metal substrate by liquid phase deposition. Liquid phase deposition includes one or more of the following methods: spraying, dip coating / coating, spin coating, and electrophoretic deposition. After each film formation, it is pre-dried at 40~80℃ for 3~30min (except for electrophoretic deposition, the other three methods are multiple film formations, and pre-drying is performed after each film formation; for electrophoretic deposition, pre-drying is performed after film formation). The total thickness of the film after pre-drying is 250~350nm. 4) Drying and curing of composite coating: After the pre-drying of film formation in step 3), the metal substrate is dried at 50~70℃ for 10~15min, and then cured at 90~120℃ for 10~30min to obtain a metal substrate with a black phosphorus-derived two-dimensional lamellar / zinc phosphating composite coating.

[0019] Furthermore, in step 1), the metal matrix is ​​an aluminum matrix or an aluminum alloy matrix, and the zinc-based phosphating solution also contains 0.10 g / L of Ni. 2+ or Mn 2+ (Ni) 2+ or Mn 2+ As a crystallizing agent).

[0020] Furthermore, in step 3), the alkyl thiol has a carbon chain length of C0. 16 ~C 18 Alkyl thiols.

[0021] Furthermore, in step 3), the alkyl thiol is n-octadecyl thiol (ODT).

[0022] Preferably, step 1) further includes forming a phosphorus-enriched transition seed layer on the surface of the zinc-based phosphating layer using low-temperature remote plasma-assisted chemical vapor deposition (PECVD). During preparation, the plasma mode is selected as remote / downstream plasma, the radio frequency power is 60~100W, the metal substrate temperature is 120~250℃, red phosphorus is used as the phosphorus-containing precursor, and deposition is carried out in an argon atmosphere for 30~600s to form a phosphorus-enriched transition seed layer (hereinafter referred to as the seed layer) with a thickness of 2~20nm; in step 3), RS-H-BP dispersion is deposited in liquid phase on the surface of the phosphorus-enriched transition seed layer of the metal substrate to form a film.

[0023] Furthermore, a phosphorus-enriched transition seed layer with a thickness of 3-10 nm is formed.

[0024] Furthermore, in step 3): When using the spraying method, apply RS-H-BP dispersion to the surface of the metal substrate with an existing coating (phosphating layer or seed layer) using air pressure spraying or ultrasonic atomization. The distance between the nozzle and the metal substrate is 10~25cm, the spraying pressure is 0.05~0.25MPa, the spray gun is moved at a speed of 50~300mm / s and the spraying is repeated 3~10 times. After each spraying, pre-dry at 40~80℃ for 3~5min until the total thickness of the film after drying is 250~350nm. When using the dip-coating / coating method, the metal substrate is completely immersed in the RS-H-BP dispersion. After immersion for 10~120s, it is lifted off the liquid surface at a speed of 0.5~5.0mm / s and pre-dried at 40~80℃ for 5~10min. Then, the immersion, lifting, and pre-drying are repeated for 3~5 cycles until the total thickness of the film after drying is 250~350nm. When using spin coating, apply at a concentration of 60~100 μL / cm. 2 The RS-H-BP dispersion was added dropwise to the surface of the metal substrate with an existing coating (phosphating layer or seed layer). After the first addition, the coating was spin-coated at a speed of 300-500 r / min for 8-10 s. After subsequent additions, the coating was spin-coated at a speed of 1800-2500 r / min for 20-30 s. After each spin-coating, the film was pre-dried at 40-80℃ for 5-10 min. The addition, spin-coating, and pre-drying were repeated 3-5 times until the total thickness of the film after drying was 250-350 nm. When using electrophoretic deposition, the metal substrate (including the existing phosphating layer or phosphating layer + seed layer) is used as the negative electrode of the working electrode and placed in an RS-H-BP dispersion containing 0.02 mol / L Mg(NO3)2·6H2O (electrolyte). Electrophoretic deposition is carried out at a voltage of 10~100V for 10~300s. After electrophoresis, the metal substrate is removed and pre-dried at 40~80℃ for 10~30min. The total thickness of the film after drying is 250~350nm.

[0025] Preferably, a phosphorus enrichment transition seed layer is not prepared. In step 2), when preparing the RS-H-BP dispersion, dispersions A and B with solid contents of 0.05~0.1 mg / mL and 0.2~0.4 mg / mL, respectively, are prepared. In step 3), a liquid phase deposition film is formed on the surface of the zinc-based phosphating layer using spin coating. The bottom and top layers of the film are prepared with dispersion A, and the middle layer of the film is prepared with dispersion B. When preparing the bottom, middle, and top layers, the concentration is 60~100 μL / cm. 2 Add the amount of dispersion A or B dropwise. After the addition, spin coat each layer at 300-500 r / min for 8-10 s, and then spin coat at 1800-2500 r / min for 20-30 s. After the two spin coats, pre-dry at 60-70℃ for 5-10 min. The total thickness of the film after pre-drying is 250-350 nm. Step 4) After the surface layer of the film in step 3) is pre-dried, heat-curing at 90-120℃ for 10-30 min to obtain a metal substrate with a black phosphorus-derived two-dimensional sheet / zinc phosphating composite coating.

[0026] Furthermore, the solid contents in dispersions A and B are 0.05 mg / mL and 0.3 mg / mL, respectively.

[0027] The metal substrate with a black phosphorus-derived two-dimensional sheet / zinc phosphating composite coating obtained by the preparation method described in this invention.

[0028] Example 1: Pretreatment of Metal Matrix 6xxx series aluminum alloy plates are selected as the metal substrate. The surface of the metal substrate is degreased, alkali etched and / or acid-washed and activated according to conventional methods to pretreat the metal substrate to a state of smooth surface, no oil and no oxide layer.

[0029] Example 2: Preparation of aluminum alloy substrate with composite coating 1) Preparation of zinc-based phosphating layer: The pretreated metal substrate from Example 1 is completely immersed in a zinc-based phosphating solution, wherein the zinc-based phosphating solution contains Zn 2+ The concentration is 1.0 g / L and contains 0.1 g / L Mn. 2+ (Crystallization agent), total acidity 35 points (pt), free acidity 2 points (pt); react at 45℃ for 10 min to form a porous zinc phosphate layer with a thickness of 1.0 μm on the surface of the metal substrate, with a pore size range of 50~360 nm; 2) Preparation of ODT-BP dispersion: Black phosphorus (BP) was dispersed in anhydrous toluene at a concentration of 0.5 mg / mL and ultrasonically exfoliated at 400 W for 27 min to obtain a suspension. Odadectothiol (ODT) was added to the suspension to a concentration of 30 mM, and triethylamine was added to a concentration of 0.5 vol%. The mixture was reacted at 60 °C for 4 h under an argon atmosphere. After the reaction, the mixture was centrifuged at 4000 g to remove the supernatant. Anhydrous toluene was added, and the mixture was centrifuged again (solvent replacement) to remove free alkyl thiols and byproducts. After four centrifugation and solvent replacement cycles, the solid fraction (ODT-BP) was redispersed in an IPA / EA mixed solvent (volume ratio 1:1). The solid content in the mixed solvent was adjusted to 0.2 mg / mL to obtain the ODT-BP dispersion. XPS analysis showed a significant enhancement of the S2p (162~164 eV) peak in ODT-BP, with an S / P atomic ratio of 0.08 (see Table 2). 3) Liquid Phase Deposition Film Formation: The ODT-BP dispersion obtained in step 2) was sprayed onto the zinc phosphate layer surface of the metal substrate obtained in step 2) using a pneumatic spray gun. The nozzle was 15 cm away from the metal substrate, the spraying pressure was 0.10 MPa, and the spray gun was moved at a speed of 100 mm / s for 5 sprays. After each spray, the substrate was pre-dried at 60°C for 3 min. The total equivalent deposition amount was 0.08 mg / cm³. 2 The pre-dried film thickness is 315 nm; 4) Film drying and curing: After step 3), dry at 70℃ for 10 min, and then keep at 110℃ for 20 min to obtain an aluminum alloy substrate with a black phosphorus-derived two-dimensional lamellar / zinc phosphating composite coating; the static water contact angle of the composite coating is 104°.

[0030] Example 3: Preparation of aluminum alloy substrate with composite coating 1) When preparing the zinc-based phosphating layer according to step 1) of Example 2, the Zn in the zinc-based phosphating solution... 2+ The concentration is 1.1 g / L and contains 0.1 g / L Ni. 2+ (Crystallization agent), total acidity 37 points (pt), free acidity 1.5 points (pt); react at 40℃ for 7 min to form a porous zinc phosphate layer with a thickness of 0.3 μm on the surface of the metal substrate, with a pore size range of 90~400 nm; 2) Preparation of ODT-BP dispersion: Black phosphorus (BP) was dispersed in anhydrous toluene at a concentration of 0.2 mg / mL and ultrasonically exfoliated at 400 W for 25 min to obtain a suspension. Odadectothiol (ODT) was added to the suspension to a concentration of 10 mM, and triethylamine was added to a concentration of 0.3 vol%. The mixture was reacted at 80 °C for 2 h under an argon atmosphere. After the reaction, the mixture was centrifuged at 3000 g to remove the supernatant. Anhydrous toluene was added, and the mixture was centrifuged again (solvent replacement) to remove free alkyl thiols and byproducts. After three centrifugations and solvent replacements, the solid fraction (ODT-BP) was redispersed in an IPA / EA mixed solvent (volume ratio 1:1). The solid content in the mixed solvent was adjusted to 0.05 mg / mL to obtain the ODT-BP dispersion. XPS analysis showed a significant enhancement of the S2p (162~164 eV) peak in ODT-BP, with an S / P atomic ratio of 0.06 (see Table 2). 3) Referring to step 3) of Example 2, during liquid phase deposition, the nozzle was 25 cm away from the metal substrate, the spraying pressure was 0.05 MPa, and the spray gun was moved at a speed of 300 mm / s for 10 sprays. After each spray, the film was pre-dried at 40°C for 5 min, resulting in a total equivalent deposition amount of 0.07 mg / cm³. 2 The film thickness after pre-drying is 303 nm; 4) Drying and curing: After step 3), dry at 50℃ for 15 min, and then keep at 120℃ for 10 min to obtain an aluminum alloy substrate with a black phosphorus-derived two-dimensional lamellar / zinc phosphating composite coating; the static water contact angle of the composite coating is 99°.

[0031] Example 4: Preparation of aluminum alloy substrate with composite coating 1) When preparing the zinc-based phosphating layer according to step 1) of Example 2, the Zn in the zinc-based phosphating solution... 2+ The concentration is 1.2 g / L and contains 0.1 g / L Mn. 2+ (Crystallization agent), total acidity 40 points (pt), free acidity 2.5 points (pt); react at 60℃ for 12 min to form a porous zinc phosphate layer with a thickness of 2.0 μm on the surface of the metal substrate, with a pore size range of 70~390 nm; 2) Preparation of ODT-BP dispersion: Black phosphorus (BP) was dispersed in anhydrous toluene at a concentration of 1.5 mg / mL and ultrasonically exfoliated at 400 W for 30 min to obtain a suspension. Odadectothiol (ODT) was added to the suspension to a concentration of 50 mM, and triethylamine was added to a concentration of 1.0 vol%. The mixture was reacted at 50 °C for 8 h under an argon atmosphere. After the reaction, the mixture was centrifuged at 6000 g to remove the supernatant. Anhydrous toluene was added, and the mixture was centrifuged again (solvent replacement) to remove free alkyl thiols and byproducts. After five centrifugation and solvent replacement cycles, the solid fraction (ODT-BP) was redispersed in an IPA / EA mixed solvent (volume ratio 1:1). The solid content in the mixed solvent was adjusted to 1.0 mg / mL to obtain the ODT-BP dispersion. XPS analysis showed a significant enhancement of the S2p (162~164 eV) peak in ODT-BP, with an S / P atomic ratio of 0.10 (see Table 2). 3) Liquid phase deposition film formation: The metal substrate was used as the negative electrode of the working electrode and placed in an ODT-BP dispersion containing 0.02 mol / L Mg(NO3)2·6H2O (electrolyte). Electrophoretic deposition was carried out at 80V for 200s. After electrophoresis, the substrate was removed and pre-dried at 80℃ for 10min. The total thickness of the film after pre-drying was 331nm. 4) Drying and curing: After step 3), dry at 60℃ for 13 min, and then keep warm at 90℃ for 30 min to obtain an aluminum alloy substrate with a black phosphorus-derived two-dimensional lamellar / zinc phosphating composite coating; the static water contact angle of the composite coating is 107°.

[0032] Example 5: Preparation of an aluminum alloy substrate with a composite coating 1) Prepare an aluminum alloy substrate with a porous zinc-based phosphate layer with a thickness of 1.0 μm according to step 1) of Example 2; 2) When preparing the ODT-BP dispersion according to step 2) of Example 2, ODT-BP dispersions A and B with solid contents of 0.05 mg / mL and 0.30 mg / mL respectively were prepared; 3) A staged liquid phase deposition film is formed using spin coating, consisting of a bottom layer, a middle layer, and a surface layer: Apply 80 μL / cm to the zinc-based phosphate coating surface. 2 Add the amount of ODT-BP dispersion A dropwise, spin coat at 500 r / min for 10 s, then spin coat at 2000 r / min for 20 s, and pre-dry at 60℃ for 5 min to obtain the bottom layer of the membrane; Apply 80 μL / cm to the bottom surface of the membrane. 2 Add the amount of ODT-BP dispersion B dropwise, spin coat at 400 r / min for 10 s, then spin coat at 1800 r / min for 30 s, and pre-dry at 60℃ for 8 min to obtain the middle layer of the membrane. Apply 80 μL / cm to the middle layer surface of the membrane. 2 The amount of ODT-BP dispersion A was added dropwise, and the mixture was first spin-coated at 300 r / min for 8 s, then at 2500 r / min for 25 s, and pre-dried at 70℃ for 10 min to obtain the surface layer of the film. The total thickness of the film after pre-drying was 332 nm. 4) After pre-drying the surface of the film, it is cured at 110℃ for 20 minutes to obtain an aluminum alloy substrate with a black phosphorus-derived two-dimensional sheet / zinc phosphating composite coating.

[0033] Example 6 Preparation of aluminum alloy substrate with composite coating 1) After forming a porous zinc phosphate layer with a thickness of 1.0 μm on the surface of the aluminum alloy substrate according to step 1) of Example 2, the metal substrate is placed in a low-temperature remote plasma-assisted chemical vapor deposition (PECVD) device with a radio frequency power of 80 W and an aluminum alloy substrate temperature of 180 °C. Red phosphorus is used as a phosphorus-containing precursor, and deposition is carried out for 180 s in an argon atmosphere to form a phosphorus-enriched transition seed layer with a thickness of 5 nm on the surface of the zinc phosphate layer. 2) Prepare an ODT-BP dispersion according to step 2) of Example 2, wherein the solid content in the dispersion is 0.2 mg / mL; 3) Following step 3) of Example 2, a film was formed on the surface of the phosphorus-enriched transition seed layer by liquid phase deposition using a spraying method. The operation method was the same, and the total thickness of the film after pre-drying was 339 nm. 4) Complete the drying and curing according to step 4) of Example 2 to obtain an aluminum alloy substrate with a black phosphorus-derived two-dimensional lamellar / zinc phosphating composite coating.

[0034] Example 7 Preparation of aluminum alloy substrate with composite coating 1) Following step 1) of Example 6, a porous zinc phosphate layer with a thickness of 1.0 μm and a phosphorus enrichment transition seed layer with a thickness of 5 nm are sequentially formed on the surface of the aluminum alloy substrate; 2) Prepare an ODT-BP dispersion according to step 2) of Example 2, with a solid content of 0.1 mg / mL in the dispersion; 3) The metal substrate obtained in step 1) is completely immersed in the ODT-BP dispersion. After immersion for 60 seconds, it is vertically lifted off the liquid surface at a speed of 1.0 mm / s. After lifting, it is pre-dried at 60℃ for 10 min. The dip-coating, lifting and drying process is repeated 4 times. The film thickness after pre-drying is 327 nm. 4) After step 3) is completed, the metal substrate is dried at 90℃ for 15 min and then cured at 120℃ for 15 min to obtain an aluminum alloy substrate with a black phosphorus-derived two-dimensional lamellar / zinc phosphating composite coating.

[0035] Example 8: Preparation of an aluminum alloy substrate with a composite coating 1) Prepare an aluminum alloy substrate with a porous zinc-based phosphate layer with a thickness of 1.0 μm according to step 1) of Example 2; 2) When preparing the ODT-BP dispersion according to step 2) of Example 2, n-hexadecyl mercaptan (HDT) was used instead of n-octadecyl mercaptan (ODT), and other operations were the same, resulting in an HDT-BP dispersion with a solid content of 0.20 mg / mL; the S / P atomic ratio in HDT-BP was measured to be 0.07 (see Table 2). 3) Referring to step 3) of Example 2, HDT-BP dispersion was used to deposit a film on the surface of a zinc-based phosphate layer on an aluminum alloy substrate. After pre-drying, the film thickness was 320 nm. 4) Dry and cure according to step 4) of Example 2 to obtain an aluminum alloy substrate with a black phosphorus-derived two-dimensional lamellar / zinc phosphating composite coating; the static water contact angle of the composite coating is 100°.

[0036] Example 9 Preparation of aluminum alloy substrate with composite coating 1) Prepare an aluminum alloy substrate with a porous zinc-based phosphate layer with a thickness of 1.0 μm according to step 1) of Example 2; 2) When preparing the ODT-BP dispersion according to step 2) of Example 2, n-dodecyl mercaptan (DDT) was used instead of n-octadecyl mercaptan (ODT), and the other operations were the same, resulting in a DDT-BP dispersion with a solid content of 0.20 mg / mL. The S / P atomic ratio in DDT-BP was found to be 0.06 (see Table 2). 3) Referring to step 3) of Example 2, a film was formed by liquid phase deposition of DDT-BP dispersion on the surface of zinc phosphate layer on aluminum alloy substrate, and the film thickness was 300 nm after pre-drying; 4) Dry and cure according to step 4) of Example 2 to obtain an aluminum alloy substrate with a black phosphorus-derived two-dimensional lamellar / zinc phosphating composite coating; the static water contact angle of the composite coating is 95°.

[0037] Comparative Example 1: Preparation of an aluminum alloy substrate with a black phosphorus / zinc phosphating composite coating 1) Prepare an aluminum alloy substrate with a porous zinc-based phosphate layer with a thickness of 1.0 μm according to step 1) of Example 2; 2) Black phosphorus (BP) was dispersed in a mixed solvent of IPA / EA (volume ratio 1:1), with a solid content of 0.20 mg / mL in the mixed solvent, to obtain a BP dispersion; 3) Referring to step 3) of Example 2, a film was formed by liquid-phase deposition of BP dispersion on the surface of zinc phosphate layer on aluminum alloy substrate, and the film thickness was 310 nm after pre-drying; 4) Dry and cure according to step 4) of Example 2 to obtain an aluminum alloy substrate with black phosphorus / zinc phosphating composite coating.

[0038] Comparative Example 2: Preparation of an aluminum alloy substrate with a black phosphorus-derived two-dimensional lamellar coating The zinc phosphate layer preparation in step 1) of Example 2 is omitted. An ODT-BP dispersion with a solid content of 0.2 mg / mL is obtained according to step 2) of Example 2. Referring to step 3) of Example 2, the ODT-BP dispersion is used to deposit a film on the surface of the aluminum alloy substrate pretreated in Example 1. After pre-drying, the film thickness is 319 nm. The substrate is dried and cured according to step 4) of Example 2 to obtain an aluminum alloy substrate with a black phosphorus-derived two-dimensional sheet coating.

[0039] Comparative Example 3: Preparation of aluminum alloy substrate coated with a thiol small molecule / zinc phosphating composite coating An aluminum alloy substrate with a porous zinc phosphate layer of 1.0 μm thickness was prepared according to step 1) of Example 2; step 2) of Example 2 was omitted, and octadecyl mercaptan (ODT) was dissolved in a mixed solvent of IPA / EA (volume ratio 1:1) to obtain a mixed solution A with an ODT concentration of 30 mM; according to step 3) of Example 2, an equal amount of mixed solution A was sprayed onto the surface of the zinc phosphate layer of the aluminum alloy substrate, and the film thickness was 312 nm after pre-drying; the substrate was dried and cured according to step 4) of Example 2 to obtain an aluminum alloy substrate coated with a thiol small molecule / zinc phosphate composite coating.

[0040] Comparative Example 4: Preparation of aluminum alloy substrate with composite coating 1) Prepare an aluminum alloy substrate with a porous zinc-based phosphate layer with a thickness of 1.0 μm according to step 1) of Example 2; 2) When preparing the ODT-BP dispersion according to step 2) of Example 2, short-chain n-octyl mercaptan (C8SH) was used instead of n-octadecyl mercaptan (ODT), and other operations were the same, resulting in a C8SH-BP dispersion with a solid content of 0.20 mg / mL; the S / P atomic ratio in C8SH-BP was detected to be 0.05 (see Table 2). 3) Referring to step 3) of Example 2, a film was formed by liquid phase deposition of C8SH-BP dispersion on the surface of zinc phosphate layer on aluminum alloy substrate, and the film thickness was 320 nm after pre-drying; 4) Dry and cure according to step 4) of Example 2 to obtain an aluminum alloy substrate with a black phosphorus-derived two-dimensional lamellar / zinc phosphating composite coating; the static water contact angle of the composite coating is tested to be 88°.

[0041] The present invention conducted the following detection experiments on the ODT-BP and zinc phosphating layers in Examples 2, 3, and 4: Experiment I: Fourier Transform Infrared Spectroscopy (FT-IR) Test The ODT-BP in Example 2 was tested using a known method; Experiment II: X-ray photoelectron spectroscopy (XPS) test The ODT-BP in Examples 2, 3, and 4 were tested using a Thermo ESCALAB 250Xi X-ray photoelectron spectrometer (Al Kα, 1486.6 eV); full spectrum and P2p high-resolution spectrum (Al Kα, Pass Energy 20 eV) were obtained with C1s=284.8 eV as the energy calibration. Experiment III: Detection of Microscopic Morphology of Coating Surface The surface microstructure of the zinc phosphate layer and ODT-BP in Example 2 was examined using scanning electron microscopy (SEM).

[0042] Experimental results: The results of Experiment I are as follows Figure 1 As shown: Figure 1 A significantly enhanced -CH2- stretching vibration absorption peak appeared at 2920 cm⁻¹. -1 2850cm -1 and the CH2 shear peak at 1465 cm⁻¹ -1 Low wavenumber region (approximately 650~600 cm⁻¹) -1 CS / PS-related absorption peaks can be observed in the region, and these features together indicate that alkyl thiols have been introduced into the surface of black phosphorus (BP).

[0043] The results of Experiment II are as follows Figure 2 As shown, Figure 2 Characteristic peaks such as C1s, O1s, P2p, and S2p can be seen in the full spectrum (survey) shown in Figure a. Figure 2 The high-resolution P2p spectrum shown in Figure b, after peak fitting, reveals that in addition to the PP bond corresponding to the black phosphorus host (P2p3 / 2 binding energy ≈ 129.5 eV), a component belonging to the PS bond also appears. This result corroborates the characteristic peak at 162.8 eV in the S2p high-resolution spectrum, clearly confirming the successful formation of PS chemical bonds in the ODT-BP of Example 2. Further quantitative analysis shows that the S / P atomic ratio on the sample surface reaches 0.08, which provides direct evidence for the effective grafting of alkyl thiols onto BP. In addition, the ODT-BP in Examples 3 and 4 were simultaneously detected in this invention, and their characteristics were similar to those of the ODT-BP in Example 2, with S / P atomic ratios of 0.06 and 0.10, respectively (see Table 2).

[0044] In Experiment III: like Figure 3As shown, under SEM magnification of 500× (accelerating voltage 15kV, scale bar 100μm), it can be clearly seen that the surface of the zinc phosphate layer is composed of microcrystalline aggregates with open pores, exhibiting a typical morphology of zinc phosphate film. Interconnected channels are formed between the grains, providing a channel basis for the capillary penetration of RS-H-BP nano-two-dimensional sheet material into the pores. When the RS-H-BP nano-two-dimensional sheet material penetrating into the pores and covering the surface forms a mechanical lock, it inevitably leads to the tortuosity of the interconnected channels, thereby forming a multi-scale barrier against corrosive media and effectively improving the corrosion resistance of the composite coating. like Figure 4 As shown, under SEM magnification of 30,000× (accelerating voltage 2kV, scale bar 300nm), it can be clearly seen that the sheet / layer nanosheets in ODT-BP are mainly distributed in parallel or semi-parallel orientation, and locally in a stacked and spread morphology; the parallel or semi-parallel orientation structure of the sheet / layer nanosheets in the morphology provides a structural basis for obtaining a low shear interface after liquid phase deposition film formation.

[0045] Using the coated metal substrates of Examples 2-9 and Comparative Examples 1-4 as experimental subjects, the present invention also conducted the following experiments: Experiment IV, Tribological Experiment UMT-2MT friction and wear testing machine was selected, and ball-disc dry sliding test was carried out according to ASTM G99. Under a load of 5N and a sliding speed of 0.10m / s, a steel ball was used to dry rub the coated surface of the test object, and the friction coefficient was recorded at different times and different numbers of friction cycles. The steady-state friction coefficient (steady-state COF) and COF-t dynamic curve (the curve of COF fluctuating with time) were calculated. Experiment V, X-ray diffraction analysis (XRD) X-ray diffraction analysis was performed on the metal matrix composite coatings obtained in Examples 2 and 5 using conventional X-ray diffraction testing methods (Cu Kα target, θ-2θ scanning mode). Experiment VI, Neutral Salt Spray Experiment The coatings of the above-mentioned experimental objects were subjected to neutral salt spray tests according to GB / T 10125-2021, and the corrosion conditions at different time periods were recorded. Experiment VII, Electrochemical Impedance Testing In accordance with the data acquisition requirements of ISO 16773-2, a three-electrode system (the coated metal substrate as the working electrode, the platinum sheet as the counter electrode, and the saturated calomel electrode as the reference electrode) was used to conduct electrochemical impedance spectroscopy (EIS) tests on the coating of the above-mentioned experimental objects in a 3.5wt% NaCl aqueous solution using conventional AC electrochemical impedance spectroscopy (EIS) testing methods. Experiment VIII, Cross-cut adhesion test The coatings of the above-mentioned test objects were subjected to a cross-cut adhesion test according to GB / T 9286-1998, and the adhesion level was recorded.

[0046] Experimental results: The results of Experiment IV are shown in Table 1: After 5000 dry friction cycles, the steady-state COF of the composite coating in Example 2 was 0.14, and the COF-t fluctuation range was ±0.02. After 5000 dry friction cycles, the steady-state COF of the composite coating in Example 3 was 0.17, and the COF-t fluctuation range was ±0.01. After 5000 dry friction cycles, the steady-state COF of the composite coating in Example 4 was 0.15, and the COF-t fluctuation range was ±0.02. After 10,000 dry friction cycles, the steady-state COF of the composite coating in Example 5 was 0.11, and the COF-t fluctuation range was ±0.01. After 8000 dry friction cycles, the steady-state COF of the composite coating in Example 6 was 0.12, and the COF-t fluctuation range was ±0.01. After 8000 dry friction cycles, the steady-state COF of the composite coating in Example 7 was 0.13, and the COF-t fluctuation range was ±0.015. After 5000 dry friction cycles, the steady-state COF of the composite coating in Example 8 was 0.14, and the COF-t fluctuation range was ±0.025. After 5000 dry friction cycles, the steady-state COF of the composite coating in Example 9 was 0.15, and the COF-t fluctuation range was ±0.03. In Comparative Example 1, the COF of the composite coating slowly increased from an initial 0.18 to 0.24 during 5000 dry friction cycles, with a steady-state COF of 0.22 and a COF-t fluctuation range of ±0.06. In Comparative Example 2, the initial COF of the coating was 0.16 during 3000 dry friction cycles. After 1000-1500 cycles, local coating peeling occurred, and the COF suddenly increased to 0.30-0.40. The steady-state COF value simulated using the approximate value after local coating peeling was about 0.25, and the COF-t fluctuation range was ±0.08. The COF of the composite coating in Comparative Example 3 was approximately 0.18 during the initial 500 dry friction cycles. Subsequently, the COF increased rapidly and stabilized at 0.30 (steady-state COF) after 3000 cycles. The COF-t fluctuation range was ±0.04. After 5000 dry friction cycles, the COF of the composite coating in Comparative Example 4 was 0.21, and the COF-t fluctuation range was ±0.04.

[0047] It is not difficult to find that the black phosphorus-derived two-dimensional sheet / zinc-based phosphating composite coatings formed according to Examples 2-4 have a steady-state COF of 0.14-0.17 after 5000 dry friction cycles, with a fluctuation range of 0.12-0.18. Combined with the experimental results of Comparative Examples 1-3, it can be seen that the zinc-based phosphating layer, combined with the alkyl thiol-modified BP dispersion, plays an important role in improving the friction coefficient and friction resistance life of the composite coating. In Example 5, the bottom layer, middle layer, and top layer of the film were prepared by gradient spin coating using dispersions A and B with different ODT-BP contents. Even after 10 dry friction cycles, the film showed good performance. After 8000 cycles of dry friction, the steady-state COF of the composite coating was 0.11, with a fluctuation range of ±0.01. This not only significantly reduced the coefficient of friction but also extended the wear resistance life. In Examples 6 and 7, a phosphorus-enriched transition seed layer was added to the zinc-based phosphating layer of Example 2. Even after 8000 cycles of dry friction, the steady-state COF of the composite coating was 0.12~0.13, with a fluctuation range of 0.11~0.145, which also reduced the coefficient of friction and extended the wear resistance life. Although the steady-state COF increased with the decrease of C in Examples 2, 8, and 9, the carbon chain length C... 12 ~C 18 The friction coefficient can still be controlled within the range of 0.115~0.18, which is significantly better than the BP modification with C8SH in Comparative Example 4 and Comparative Examples 1~3.

[0048] XRD analysis of Experiment V showed that, compared with Example 2, the bottom layer material of the film formed in Example 5 was uniformly distributed on the surface of the zinc phosphate layer and partially embedded in the pores, while the middle layer formed a dense barrier structure. XRD characterization of BP-related peaks showed that the Lotgering orientation factor in the surface layer of the composite coating was increased by about 30-40% compared with that of Example 2 with non-gradient spraying, indicating that gradient spin coating according to the method of Example 5 can form a low-shear orientation structure on the surface of the composite coating that is beneficial to reducing COF.

[0049] The results of Experiment VI are shown in Table 1. During the neutral salt spray experiment: The composite coatings in Examples 2, 3, and 4 showed no large-area whitening or pitting in the area outside the scratches after 600 hours, with only slight corrosion spots near the cut. The composite coating in Example 5 showed no obvious whitening or corrosion extension in the area outside the scratch after 720 hours. The composite coatings in Examples 6 and 7 showed no obvious whitening or pitting in the area outside the scratches after 720 hours. The composite coating in Example 8 showed no significant corrosion extension outside the scratch area after 600 hours; In Example 9, the composite coating only showed a small amount of pitting in the area outside the scratch after 480 hours. The composite coating in Comparative Example 1 showed obvious whitening / pitting in the scratch and edge areas after 120 hours, and the corrosion area expanded significantly after 240 hours. In Comparative Example 2, the coating continued to show obvious corrosion spots for 48-72 hours, and the coating failed after 96 hours, resulting in partial exposure of the aluminum alloy substrate. The composite coating of Comparative Example 3 showed obvious corrosion spots for 96-120 hours, and the corrosion area increased significantly after 240 hours. The composite coating in Comparative Example 4 showed obvious corrosion near the scratch after 360 hours, and the corrosion area further expanded after 480 hours.

[0050] It is not difficult to see that the black phosphorus-derived two-dimensional lamellar / zinc-based phosphating composite coatings formed according to Examples 2-4 can control the corrosion resistance time to about 600 hours, which is a significant improvement in corrosion resistance compared to Comparative Examples 1-3. The corrosion resistance time is extended to more than 720 hours by gradient spin coating and graded film formation in Example 5. The addition of phosphorus enrichment transition seed layers in Examples 6 and 7 can also extend the corrosion resistance time to more than 720 hours. Although the corrosion resistance of Examples 2, 8, and 9 decreases as the number of C atoms in alkyl thiols decreases, it can still be maintained at more than 480 hours, which is a significant improvement compared to the C8SH-BP dispersion in Comparative Example 4 and Comparative Examples 1-3.

[0051] The results of Experiment VII are shown in Table 1. The electrochemical impedance |Z| of the coatings of each experimental object is shown in Table 1. 0.01 The Hz values ​​are as follows: In Examples 2, 3, and 4, the composite coatings had a thickness of 3.3~3.4 × 10⁻⁶. 7 Ω·cm 2 Within the range; In Example 5, the composite coating is 5.5 × 10 7 Ω·cm 2 ; In Examples 6 and 7, the composite coatings have a thickness of 4.7~5.4×10⁻⁶. 7 Ω·cm 2 Within the range; In Example 8, the composite coating is 3.1 × 10⁻⁶. 7 Ω·cm 2 ; In Example 9, the composite coating is 2.6 × 10⁻⁶. 7 Ω·cm 2 ; In Comparative Example 1, the composite coating has a thickness of 7.7 × 10⁻⁶. 6 Ω·cm 2 ; In Comparative Example 2, the coating thickness was 2.7 × 10⁻⁶. 6 Ω·cm 2 ; In Comparative Example 3, the composite coating was 1.5 × 10⁻⁶. 7 Ω·cm 2 It is only slightly higher than the phosphate layer of the aluminum alloy sample; In Comparative Example 4, the composite coating was 2.0 × 10⁻⁶. 7 Ω·cm 2 .

[0052] It is not difficult to observe that the electrochemical impedance |Z| of the black phosphorus-derived two-dimensional lamellar / zinc-based phosphating composite coatings formed according to Examples 2-4 is... 0.01 Hz is between 3.3 and 3.4 × 10⁻⁶. 7 Ω·cm 2 Within the range, the electrochemical impedance is significantly improved compared to comparative examples 1-3; the gradient spin-coating stepwise film formation in Example 5, or the addition of a phosphorus-enriched transition seed layer in Examples 6 and 7, both significantly improve the electrochemical impedance; although the electrochemical impedance decreases somewhat in Examples 2, 8, and 9 as the number of carbon atoms in the alkyl thiols decreases, it still remains at 2.6 × 10⁻⁶. 7 Ω·cm 2 The above results show a significant improvement compared to the C8SH-BP dispersion and comparative examples 1-3.

[0053] The results of Experiment VIII are shown in Table 1. The cross-cut adhesion ratings of the coatings for each experimental object are as follows: In Examples 2, 3, and 4, the composite coatings are between level 0 and 1; In Example 5, the composite coating is grade 0; In Examples 6 and 7, the composite coating is grade 0; In Example 8, the composite coating is between level 0 and 1; In Example 9, the composite coating is Grade 1; In Comparative Example 1, the composite coating is grade 2, and flaky peeling is visible at the grid lines. In Comparative Example 2, the coating was at level 3-4, and large areas of the gridded areas showed peeling off. In Comparative Example 3, the composite coating was between level 1 and 2. However, after friction, the coated thiol molecule layer was almost completely worn away, lacking continuous barrier and friction reduction capabilities. In Comparative Example 4, the composite coating is between level 1 and 2.

[0054] It is not difficult to find that the cross-cut adhesion of the black phosphorus-derived two-dimensional sheet / zinc phosphating composite coatings formed according to Examples 2-4 is maintained between level 0 and 1. Compared with Comparative Examples 1-3, the bonding force between the composite coating and the metal substrate is significantly improved. Through gradient spin coating in Example 5 or adding a phosphorus-enriched transition seed layer in Examples 6 and 7, the cross-cut adhesion can reach level 0. Although the cross-cut adhesion of Examples 2, 8, and 9 decreased with the reduction of C in alkyl thiols, it is still within level 1, which is significantly improved compared with C8SH-BP dispersion and Comparative Examples 1-3.

[0055] Table 1. Comparison of tribological properties, corrosion resistance, and coating adhesion strength of different experimental objects.

[0056] Note: 0.25* refers to the steady-state COF value simulated by approximation after partial peeling of the coating.

[0057] Table 2. Effect of different chain lengths of alkyl thiols on coating performance

[0058] The above experimental results are only used to illustrate the performance advantages of the composite coating obtained by the present invention, and are not intended to limit the scope of protection.

Claims

1. A method for preparing a metal matrix black phosphorus derived two-dimensional sheet layer / zinc-based phosphide composite coating, characterized in that, Comprising the following steps: 1) Preparation of zinc-based phosphating layer: first, the metal substrate surface is pretreated by conventional method of degreasing, alkali etching and / or acid pickling and activation, then the pretreated metal substrate is completely immersed in zinc-based phosphating solution, reacted at 40-60℃ for 7-12min, forming a porous zinc-based phosphating layer with thickness of 0.3-2.0μm on the surface of the metal substrate, the pore size of the zinc-based phosphating layer ranges from 50-400nm; the concentration of Zn 2+ in the zinc-based phosphating solution is 1.0-1.2g / L, the total acidity is 35-40 points, and the free acidity is 1.5-2.5 points; 2) Preparation of RS-H-BP dispersion: black phosphorus was dispersed in anhydrous toluene at a black phosphorus concentration of 0.2-1.5 mg / mL, and ultrasonic exfoliation was performed for 25-30 min at a power of 400 W to obtain a suspension; alkyl mercaptan with a carbon chain length C 12 ~C 18 of 2-8 h at 50-80 °C in an argon atmosphere; after the reaction was completed, centrifugation was performed at a centrifugal force of 3000-6000 g, and solvent replacement was performed for 3-5 times to remove free alkyl mercaptan and byproducts, and the obtained solid part was uniformly redispersed in a mixed solvent of IPA / EA in a ratio of equal volumes, the solid content in the mixed solvent was adjusted to 0.05-1.0 mg / mL, and an RS-H-BP dispersion was obtained, the S / P atomic ratio in the dispersion being 0.06-0.12; 3) Liquid deposition film forming: the RS-H-BP dispersion liquid is deposited on the surface of the zinc-based phosphating layer of the metal substrate by liquid deposition method, which includes one or more of spraying, dip coating / tape pulling, spin coating, and electrophoretic deposition. After each film forming, pre-drying is performed at 40-80℃ for 3-30min, and the total thickness of the dried film is 250-350nm; 4) Composite coating drying and curing: after the pre-drying of step 3) is completed, the metal substrate is dried at 50-70℃ for 10-15min, and then cured at 90-120℃ for 10-30min, obtaining a metal substrate with black phosphorus derived two-dimensional sheet / zinc-based phosphating composite coating.

2. The production method according to claim 1, characterized by, The metal base in step 1) is an aluminum base or an aluminum alloy base, and the zinc-based phosphating solution further contains 0.10 g / L of Ni 2+ or Mn 2+ .

3. The preparation method according to claim 1, characterized in that, The alkyl mercaptan in step 3) is an alkyl mercaptan having a carbon chain length C 16 ~C 18 of 1 to 4.

4. The production method according to claim 1 or 3, characterized by, The alkyl mercaptan in step 3) is n-octadecyl mercaptan.

5. The preparation method according to claim 1, characterized in that, Step 1) also includes forming a phosphorus-rich transition seed layer on the surface of the zinc-based phosphating layer by low-temperature remote plasma-assisted chemical vapor deposition. When preparing, the plasma mode is selected as remote / downstream plasma, the radio frequency power is 60-100W, the metal substrate temperature is 120-250℃, red phosphorus is used as the phosphorus-containing precursor, and the phosphorus-rich transition seed layer with a thickness of 2-20nm is deposited under argon atmosphere for 30-600s. In step 3), the RS-H-BP dispersion liquid is deposited on the surface of the phosphorus-rich transition seed layer of the metal substrate by liquid deposition.

6. The preparation method according to claim 5, characterized in that, A phosphorus-rich transition seed layer with a thickness of 3-10nm is formed.

7. The production method according to claim 1 or 5, characterized by, In step 3): When spraying is used, the RS-H-BP dispersion liquid is sprayed on the existing coating surface of the metal substrate by gas pressure spraying or ultrasonic atomization. The distance between the nozzle and the metal substrate is 10-25cm, the spraying pressure is 0.05-0.25MPa, the spray gun is moved at a speed of 50-300mm / s and sprayed repeatedly for 3-10 times, and after each spraying, pre-drying is performed at 40-80℃ for 3-5min until the total thickness of the dried film is 250-350nm; When dip coating / tape pulling is used, the metal substrate is completely immersed in the RS-H-BP dispersion liquid, pulled away from the liquid surface at a speed of 0.5-5.0mm / s after soaking for 10-120s, and then pre-dried at 40-80℃ for 5-10min. Then, the soaking, pulling, and pre-drying are repeated for 3-5 cycles until the total thickness of the dried film is 250-350nm; When spin coating is used, the RS-H-BP dispersion solution is added dropwise to the surface of the existing coating of the metal substrate in an amount of 60-100 μL / cm 2 After the initial dropwise addition, spin coating is performed at a speed of 300-500 r / min for 8-10 s. After subsequent dropwise addition, spin coating is performed at a speed of 1800-2500 r / min for 20-30 s. After each spin coating, pre-drying is performed at 40-80 °C for 5-10 min. The dropwise addition, spin coating, and pre-drying are repeated 3-5 times until the total thickness of the dried film is 250-350 nm. When electrophoretic deposition is used, the metal substrate is placed as the negative electrode of the working electrode in the RS-H-BP dispersion liquid containing 0.02mol / L Mg(NO3)2·6H2O, and electrophoretic deposition is performed at a voltage of 10-100V for 10-300s. After electrophoresis, the metal substrate is taken out and pre-dried at 40-80℃ for 10-30min, and the total thickness of the dried film is 250-350nm.

8. The method of claim 1, wherein, Step 2) when preparing the RS-H-BP dispersion liquid, dispersion liquids A and B with solid content of 0.05-0.1 mg / mL and 0.2-0.4 mg / mL respectively are prepared; Step 3) the spin coating method is used to deposit a film on the surface of the zinc-based phosphating layer, and dispersion liquid A is used to prepare the bottom layer and surface layer of the film, and dispersion liquid B is used to prepare the middle layer of the film; when preparing the bottom layer, middle layer and surface layer, dispersion liquid A or B is added in an amount of 60-100 μL / cm 2 , after adding, each layer is spin coated at 300-500 r / min for 8-10 s, and then spin coated at 1800-2500 r / min for 20-30 s, after two times of spin coating, each layer is pre-dried at 60-70 °C for 5-10 min, and after pre-drying, the total thickness of the film is 250-350 nm; Step 4) then the surface layer of the film in Step 3) is pre-dried and cured at 90-120 °C for 10-30 min, to obtain a metal substrate with a black phosphorus derived two-dimensional sheet layer / zinc-based phosphating composite coating.

9. The production method according to claim 8, characterized by, The solid content in the dispersion liquids A and B is 0.05mg / mL and 0.3mg / mL, respectively.

10. A metal substrate with black phosphorus derived two-dimensional sheet / zinc-based phosphating composite coating prepared by the method of any one of claims 1-9.

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