Preparation method of lignin-based friction-resistant, corrosion-resistant and antibacterial multifunctional coating

Abstract

The invention discloses a preparation method of a lignin-based friction-resistant, corrosion-resistant and antibacterial multifunctional coating, and belongs to the field of surface processing coatings, the preparation method comprises the following steps: pretreating a metal substrate to obtain an oil-free and water-free working surface; the metal base material is immersed in the piranha solution for surface activation; the method comprises the following steps: mixing a sodium lignin sulfonate solution and a ferric chloride solution to prepare a mixed solution A; dopamine, polyethyleneimine and a trihydroxymethyl aminomethane buffer solution are mixed, and a mixed solution B is prepared; and the mixed solution A and the mixed solution B are mixed to prepare a coating solution, the completely activated metal base material is immersed in the coating solution to be oscillated and deposited, and the coating is prepared on the surface of the metal base material. The lignin-based anti-friction, anti-corrosion and antibacterial multifunctional coating provided by the invention has the advantages that the surface friction coefficient of an aluminum alloy is reduced, the anti-friction performance of the aluminum alloy is improved, the inhibition rate of electrochemical corrosion exceeds 90%, and the inhibition rate of bacteria reaches 90% or above.

Description

Technical Field

[0001] This invention belongs to the field of surface processing coating technology, specifically relating to a method for preparing a lignin-based multifunctional coating with anti-friction, anti-corrosion, and antibacterial properties. Background Technology

[0002] Key components in mechanical systems (including bearings, guide rails, and gears) inevitably experience friction and wear during dynamic surface contact. Under actual operating conditions, this process accelerates; cyclic loading and continuous sliding can damage the protective film, leading to material loss and potentially premature failure, thus impairing the durability of mechanical components and reducing energy efficiency. Simultaneously, these dynamic interactions cause stress concentration on the surface of mechanical components, and repeated sliding can damage the surface oxide film, causing gradual erosion of the material in the micro-contact areas, inducing adhesive wear and accelerating the wear rate. Given that friction and wear consume nearly 23% of global energy, improving the tribological properties of these mechanical components has become an urgent issue for both industry and the environment.

[0003] Traditional hard ceramic coatings, solid lubricants, and metal-based composite coatings exhibit excellent wear resistance under ideal laboratory conditions. However, in actual use environments with applied loads and repeated sliding, problems often arise, such as stress concentration within the coating leading to brittle fracture, insufficient adhesion causing the coating to peel off easily under cyclic loads, and easy oxidation in humid air making it difficult to form a stable lubricating film.

[0004] Therefore, there is an urgent need in the field for a multifunctional coating that can improve the wear resistance of mechanical parts in order to extend the service life of mechanical parts under complex working conditions. Summary of the Invention

[0005] The purpose of this section is to outline some aspects of the embodiments of the present invention and to briefly describe some preferred embodiments.

[0006] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0007] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing a lignin-based multifunctional coating that is anti-friction, corrosion-resistant, and antibacterial.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for preparing a lignin-based multifunctional coating with anti-friction, corrosion, and antibacterial properties, comprising,

[0009] Pre-treatment of the metal substrate yields an oil-free and water-free working surface;

[0010] The metal substrate was surface activated by immersing it in a piranha solution.

[0011] Mixed solution A is prepared by mixing sodium lignosulfonate solution and ferric chloride solution;

[0012] Dopamine, polyethyleneimine, and tris(hydroxymethyl)aminomethane buffer solution were mixed to prepare mixed solution B;

[0013] Mixing solution A and mixed solution B yields a coating liquid;

[0014] The fully activated metal substrate is immersed in a coating solution and agitated to deposit the coating on the surface of the metal substrate.

[0015] In a preferred embodiment of the preparation method described in this invention, the pretreatment of the metal substrate includes,

[0016] The substrate surface was cleaned sequentially with acetone, anhydrous ethanol, and deionized water to obtain an oil-free and water-free metal substrate.

[0017] In a preferred embodiment of the preparation method described in this invention, the metal substrate is a commonly used mechanical component metal material, including stainless steel, aluminum alloy, and copper alloy.

[0018] As a preferred embodiment of the preparation method described in this invention, the concentration of the sodium lignosulfonate solution is 5 wt%.

[0019] The ferric chloride solution has a concentration of 0.1M;

[0020] The volume ratio of the sodium lignosulfonate solution to the ferric chloride solution is 95:5.

[0021] In a preferred embodiment of the preparation method described in this invention, the dopamine has a molecular weight of 153.18 and the polyethyleneimine has a molecular weight of 189.64.

[0022] The concentration of dopamine in mixed solution B is 2 mg / mL, and the concentration of polyethyleneimine is 1 mg / mL.

[0023] In a preferred embodiment of the preparation method described in this invention, the volume ratio of the mixed solution A to the mixed solution B is 3:1.

[0024] In a preferred embodiment of the preparation method described in this invention, the oscillating deposition occurs at a reaction temperature of 50°C.

[0025] Another objective of this invention is to overcome the shortcomings of the prior art and provide a lignin-based multifunctional coating that is anti-friction, corrosion-resistant, and antibacterial.

[0026] Another objective of this invention is to overcome the shortcomings of the prior art and provide an application of a multifunctional coating with anti-friction, anti-corrosion, and antibacterial properties on the surface of mechanical parts.

[0027] Beneficial effects of this invention:

[0028] (1) The lignin-based anti-friction, corrosion and antibacterial multifunctional coating provided by the present invention reduces the friction coefficient of aluminum alloy surface and improves its anti-friction performance. The coating applied to the aluminum alloy surface is subjected to friction and wear test, and has the lowest average friction coefficient and the narrowest and shallowest scratch.

[0029] (2) The lignin-based anti-friction, anti-corrosion and antibacterial multifunctional coating provided by the present invention has strong adhesion, and the adhesion level of the coating deposited on the aluminum alloy surface reaches 4B.

[0030] (3) The lignin-based anti-friction, anti-corrosion and antibacterial multifunctional coating provided by the present invention has the effect of reducing the corrosion current density on the aluminum alloy surface and the electrochemical corrosion inhibition rate exceeds 90%.

[0031] (4) The lignin-based anti-friction, anti-corrosion and antibacterial multifunctional coating provided by the present invention has an inhibition rate of more than 90% against bacteria. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0033] Figure 1 This is a schematic diagram of the preparation and reaction mechanism of the lignin-based anti-friction, anti-corrosion, and antibacterial multifunctional coating in this invention. In the diagram, A is the preparation schematic diagram and B is the corresponding reaction mechanism diagram.

[0034] Figure 2 The lignin-Fe of this invention 3+ See the accompanying diagram.

[0035] Figure 3 This is a schematic diagram of the molecular structure formed by the reaction of dopamine and polyethyleneimine via Michael addition and Schiff base reaction.

[0036] Figure 4These are typical two-dimensional surface morphology diagrams of the original sample, examples, and comparative examples under different sliding times according to the present invention. Among them, A-1 to A-3 are morphology diagrams of bare aluminum alloy after sliding for 15 minutes, 30 minutes, and 60 minutes, respectively; B-1 to B-3 are morphology diagrams of Comparative Example 1 sample after sliding for 15 minutes, 30 minutes, and 60 minutes, respectively; C-1 to C-3 are morphology diagrams of Example 1 sample after sliding for 15 minutes, 30 minutes, and 60 minutes, respectively; D-1 to D-3 are morphology diagrams of Comparative Example 2 sample after sliding for 15 minutes, 30 minutes, and 60 minutes, respectively; and E-1 to E-3 are morphology diagrams of Comparative Example 3 sample after sliding for 15 minutes, 30 minutes, and 60 minutes, respectively.

[0037] Figure 5 The images show the wear trace depth profiles of the original sample, examples, and comparative examples under different sliding times according to the present invention. Among them, the wear trace depth profiles (A-4)-(A-6) correspond to A-1 to A-3, respectively; the wear trace depth profiles (B-4)-(B-6) correspond to B-1 to B-3; the wear trace depth profiles (C-4)-(C-6) correspond to the wear trace depth profiles corresponding to C-1 to C-3; (D-4)-(D-6) correspond to the wear trace depth profiles of D-1 to D-3; and (E-4)-(E-6) correspond to the wear trace depth profiles of E-1 to E-3.

[0038] Figure 6 This is a laser confocal microscope image used to characterize the antibacterial effect of the coating in this invention. Detailed Implementation

[0039] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0040] In this embodiment of the invention, sodium lignosulfonate was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0041] Anhydrous ferric chloride was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0042] Dopamine hydrochloride was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0043] Polyethyleneimine was purchased from Shanghai Maclean Biochemical Technology Co., Ltd.

[0044] Tris(hydroxymethyl)aminomethane was purchased from Aladdin Reagent Co., Ltd.

[0045] The lignin-based anti-friction, anti-corrosion, and antibacterial multifunctional coating of the present invention is achieved through, for example... Figure 1 The process shown is illustrated in Figure A, where A is a schematic diagram of the preparation and B is the corresponding reaction mechanism diagram. It can be seen that the completely dissolved acidic FeC3 solution acts as a chelating agent to form an Fe-lignin complex, in which Fe...3+ As a coordination center, it connects the phenolic hydroxyl terminal groups in the lignin macromolecular network; simultaneously, through the co-deposition process of dopamine and polyethyleneimine, a dense cross-linked structure is formed via Michael addition and Schiff base reactions. During the mixing and oscillating deposition process, Fe... 3+ It forms a stable complex with DA, and subsequent oxidation reactions promote the co-deposition of all components.

[0046] Using aluminum alloy as the research substrate, the surface of the aluminum alloy was cleaned, then the aluminum alloy was activated and immersed in a solution of sodium lignosulfonate, ferric chloride and functional co-deposition solution for oscillation deposition to obtain the coating.

[0047] In this embodiment of the invention, the aluminum alloy substrate has dimensions of 10×10×1mm. Staphylococcus aureus and Escherichia coli were selected as common Gram-positive and Gram-negative bacteria, respectively, to evaluate the antibacterial properties of the coating.

[0048] (1) Friction and wear test in this invention:

[0049] P800 grade abrasive paper with an average abrasive particle size of 21.8 micrometers was used as the grinding surface. The abrasive paper was attached to a horizontal platform with double-sided tape, abrasive side facing up and coated sample side facing down. A 20g load was applied to the back of the sample, and a 20cm linear reciprocating motion was performed at a constant speed of 40cm / min, maintaining continuous and uniform contact throughout the process. Wear resistance was evaluated after 20, 40, 60, and 80 friction cycles. After the test, the wear surface morphology was analyzed using a three-dimensional optical profilometer (Contour GT-K), and the surface roughness parameters Ra (arithmetic mean) and Rz (maximum height) were calculated using the following formula:

[0050]

[0051] L is the length measured along the contour line, and Z(x) is the perpendicular distance between a point on the contour line and the reference plane. pi Z represents the summit height of the five peaks within the sampling length L. vi This represents the depth of the five lowest valleys within the sampling length L.

[0052] (2) Lubrication performance test:

[0053] Dry sliding wear tests were conducted using a tribostudio (Yangzhou University) friction and wear testing machine, employing 6 mm diameter GCr15 steel balls as the friction elements. Tests were performed under a 2 N load for durations of 15, 30, and 60 minutes. The reciprocating sliding frequency of the coating was set to 2 Hz, with a stroke length of 5 mm. The coefficient of friction (COF) was collected in real-time throughout the test.

[0054] (3) Adhesion test:

[0055] To assess the adhesion strength of the coating according to ASTM D3359, use a multi-blade cutter to score a cross grid consisting of six parallel cuts in the vertical direction on the coating surface, ensuring that the cuts penetrate to the substrate. Gently remove loose debris from the grid with a soft brush at a 45° angle. Firmly cover the scored area with 25 mm wide pressure-sensitive tape (3M™ 600, adhesion strength 10.0 ± 1.0 N / 25 mm), press three times to ensure even contact, and let stand for 90 ± 30 seconds.

[0056] Then, the tape is quickly torn off at a 180° angle within 1 second, and the degree of coating peeling is evaluated according to the classification standard specified in ASTM D3359 to determine the adhesion level.

[0057] (4) Antibacterial performance test:

[0058] The antimicrobial properties of the coating were evaluated using *Escherichia coli* (ATCC PTA-10989) and *Staphylococcus aureus* (ATCC PTA-10989), representing Gram-negative and Gram-positive bacteria, respectively. Glycerol-preserved strains were streaked onto LB agar plates using an inoculation loop and incubated at 37°C aerobic conditions for 24 hours to activate and purify the strains.

[0059] Single colonies were inoculated into LB broth and incubated at 37°C with shaking for approximately 3 hours. The resulting bacterial suspension was diluted 1:100 for subsequent attachment experiments, incubated at 37°C for 24 hours, fixed with 2.5% glutaraldehyde for 4 hours, and stained with sterile PBS containing 50 μg / mL PI under dark conditions. Bacterial attachment was observed using a confocal laser scanning microscope (CLSM).

[0060] Quantitative analysis of biofilms: 1 mL of bacterial suspension was added to a 24-well plate and incubated at 37°C for 24 hours. After 3 hours of adhesion, the sample surface was gently washed with PBS to remove loosely attached bacteria. The samples were stained with 0.1% crystal violet (500 μL per well) at room temperature for 15 minutes. Washing with PBS until the eluent was colorless was performed to remove unbound dye. After the stained samples were allowed to air dry, the adsorbed dye was dissolved in 30% acetic acid solution for 15 minutes. Then, 3 mL of the eluent from each sample was placed in a cuvette, and the absorbance was measured at 590 nm using a UV-Vis spectrophotometer.

[0061] (5) Corrosion resistance test:

[0062] An electrochemical workstation equipped with a standard three-electrode system, the Gamry Interface 1010E, was used. The reference electrode was a saturated calomel electrode, and the counter electrode was a platinum sheet electrode. The electrode polarization curves of the coated electrode in 3.5% NaCl solution were measured. The corrosion potential and corrosion current density were determined by Tafel extrapolation using Origin software, and the corrosion inhibition rate was calculated.

[0063] Example 1

[0064] (1) Prepare a 5wt% solution of sodium lignosulfonate at 60℃ and 600rpm.

[0065] (2) Add 0.1M ferric chloride to the solution in step (1) and prepare a mixed solution of sodium lignosulfonate and ferric chloride at a volume ratio of 95:5. Stir for 2 hours to mix thoroughly and name it L5 mixture.

[0066] (3) Prepare functional deposition solution. Prepare 2 mg / mL dopamine and 1 mg / mL polyethyleneimine at 25℃ and 600 rpm. Add weakly alkaline tris(hydroxymethyl)aminomethane buffer solution together at 25℃ and 600 rpm. Name it DA / PEI mixture.

[0067] (4) At 25°C and 600 rpm, mix the L5 mixture from step (2) and the DA / PEI mixture from step (3) at a volume ratio of 3:1. Name it L5 / DA / PEI mixture;

[0068] Lignin-Fe 3+ See the diagram for details. Figure 2 See the schematic diagram of the molecular structure formed by the Michael addition and Schiff base reaction of dopamine and polyethyleneimine. Figure 3 ;

[0069] from Figure 2 As can be seen, the acidic FeCl3 solution acts as a chelating agent, in which Fe... 3+ As a coordination center, it connects the phenolic hydroxyl terminal groups in the lignin macromolecular network; from Figure 3 As can be seen, in the air, dopamine oxidizes catechol to catechol, which then undergoes a lower Schiff base reaction and a Michael addition reaction with the amino group of PEI.

[0070] (5) The aluminum alloy surface was cleaned with acetone, anhydrous ethanol and deionized water in sequence to obtain an oil-free and water-free metal substrate. The aluminum alloy substrate was then immersed in piranha solution for surface activation for 24 hours. The aluminum alloy surface was then rinsed with deionized water until there was no piranha solution on the aluminum alloy surface. The substrate was then allowed to stand and dry to obtain a pre-treated aluminum alloy substrate (the same below).

[0071] The pretreated aluminum alloy substrate was immersed in the L5 / DA / PEI mixture of step (4) at 50°C and reacted with shaking for 6 hours.

[0072] (6) Remove the fully vibrated aluminum alloy substrate, gently rinse the surface of the residual mixture with deionized water, repeat the rinsing 3 times to obtain the desired coating, named L5 / DA / PEI.

[0073] Comparative Example 1

[0074] (1) Prepare a 1wt% solution of sodium lignosulfonate at 60℃ and 600rpm.

[0075] (2) Add 0.1M ferric chloride to the solution in step (1) and prepare a mixed solution of sodium lignosulfonate and ferric chloride at a volume ratio of 95:5. Stir for 2 hours to mix thoroughly and name it L1 mixture.

[0076] (3) Prepare functional deposition solution. Prepare 2 mg / mL dopamine and 1 mg / mL polyethyleneimine at 25℃ and 600 rpm. Add weakly alkaline tris(hydroxymethyl)aminomethane buffer solution together at 25℃ and 600 rpm. Name it DA / PEI mixture.

[0077] (4) At 25°C and 600 rpm, the L1 mixture from step (2) and the DA / PEI mixture from step (3) are mixed at a volume ratio of 3:1 and named L1 / DA / PEI mixture.

[0078] (5) Immerse the aluminum alloy substrate in the L1 / DA / PEI mixture of step (4) at 50°C and shake for 6 hours.

[0079] (6) Remove the fully vibrated aluminum alloy substrate, gently rinse the surface of the residual mixture with deionized water, repeat the rinsing 3 times to obtain the desired coating, named L1 / DA / PEI.

[0080] Compared with Example 1, this comparative example added 1 wt% sodium lignosulfonate solution, and the rest was the same as Example 1.

[0081] The coating was observed to have high Ra and Rz values, indicating poor anti-friction properties.

[0082] The coating was observed to inhibit bacterial growth, but its antibacterial properties were not strong.

[0083] Comparative Example 2

[0084] (1) Prepare a 10wt% solution of sodium lignosulfonate at 60℃ and 600rpm.

[0085] (2) Add 0.1M ferric chloride to the solution in step (1) and prepare a mixed solution of sodium lignosulfonate and ferric chloride at a volume ratio of 95:5. Stir for 2 hours to mix thoroughly and name it L10 mixture.

[0086] (3) Prepare functional deposition solution. Prepare 2 mg / mL dopamine and 1 mg / mL polyethyleneimine at 25℃ and 600 rpm. Add weakly alkaline tris(hydroxymethyl)aminomethane buffer solution together at 25℃ and 600 rpm. Name it DA / PEI mixture.

[0087] (4) At 25°C and 600 rpm, the L10 mixture from step (2) and the DA / PEI mixture from step (3) are mixed at a volume ratio of 3:1 and named L10 / DA / PEI mixture.

[0088] (5) Immerse the aluminum alloy substrate in the L10 / DA / PEI mixture of step (4) at 50°C and shake for 6 hours.

[0089] (6) Remove the fully vibrated aluminum alloy substrate, gently rinse the surface of the residual mixture with deionized water, repeat the rinsing 3 times to obtain the desired coating, named L10 / DA / PEI.

[0090] Compared with Example 1, this comparative example added 10wt% sodium lignosulfonate solution, and the rest was the same as Example 1.

[0091] An increase in the density and size of the microstructure on the coating surface was observed, along with some agglomeration and numerous micro-defects.

[0092] The coating was observed to have high Ra and Rz values, indicating poor anti-friction properties.

[0093] Comparative Example 3

[0094] (1) Add 0.1M ferric chloride to deionized water, stir and mix thoroughly, and name it ferric chloride solution.

[0095] (2) Prepare functional deposition solution. Prepare 2 mg / mL dopamine and 1 mg / mL polyethyleneimine at 25℃ and 600 rpm. Add weakly alkaline tris(hydroxymethyl)aminomethane buffer solution together at 25℃ and 600 rpm. Name it DA / PEI mixture.

[0096] (3) At 25°C and 600 rpm, the ferric chloride solution from step (1) and the DA / PEI mixture from step (2) are mixed at a volume ratio of 3:1 and named as DA / PEI mixture.

[0097] (4) Immerse the aluminum alloy substrate in the DA / PEI mixture of step (3) at 50°C and shake for 6 hours.

[0098] (5) Remove the fully vibrated aluminum alloy substrate, gently rinse the surface of the residual mixture with deionized water, repeat the rinsing 3 times to obtain the desired coating, named DA / PEI.

[0099] Compared with Example 1, this comparative example did not include sodium lignosulfonate solution, but was otherwise the same as Example 1.

[0100] The coating was found to have a high average coefficient of friction and poor lubrication performance.

[0101] Table 1. Characterization of mechanical properties of lignin-based multifunctional coatings with anti-friction, anti-corrosion, and antibacterial properties

[0102]

[0103] Table 2 Characterization of the antibacterial and anticorrosion properties of lignin-based multifunctional coatings with anti-friction, anti-corrosion, and antibacterial properties

[0104]

[0105] Friction and wear tests on the original samples, examples, and comparative examples are as follows: Figure 4 As shown.

[0106] Based on the data in Table 1 and Figure 4 , Figure 6 It can be seen that the lignin-based anti-friction, anti-corrosion, and antibacterial multifunctional coating prepared by the formulation in Example 1 of the present invention has the lowest Ra and Rz values ​​under friction and wear conditions, exhibiting excellent wear resistance. This is because the phenolic hydroxyl groups in lignin react with Fe... 3+ Ion coordination occurs, and PEI and DA react with Schiff bases via Michael addition to form a cross-linked structure. The lignin-iron complex is embedded in this framework through multiple intermolecular interactions, significantly improving tear resistance and reducing surface abrasion.

[0107] As shown in Table 1, the lignin-based anti-friction, anti-corrosion, and antibacterial multifunctional coating prepared by the formulation of Example 1 of the present invention exhibits a significantly reduced coefficient of friction and significantly enhanced lubrication performance. This is because the oxygen-containing functional groups in lignin promote the formation of a boundary lubrication film at the friction interface during sliding. This layer acts as a protective barrier, minimizing direct contact between metals and forming a stable self-lubricating friction interface.

[0108] As can be seen from the data in Table 1, the lignin-based anti-friction, anti-corrosion, and antibacterial multifunctional coating prepared by the formulation in Example 1 of the present invention has the highest adhesion level and excellent adhesion performance.

[0109] Antimicrobial performance tests on the original samples, examples, and comparative examples are as follows: Figure 6 As shown.

[0110] Based on the data in Table 2 and Figure 6 It is known that a large number of bacteria adhere to the original aluminum alloy surface. However, the lignin-based anti-friction, anti-corrosion, and antibacterial multifunctional coating prepared by the formulation in Example 1 of the present invention has an inhibition rate of more than 90% against bacteria and a high PD value, exhibiting excellent antibacterial performance. This is due to the ability of lignin to capture active free radicals. When combined with iron ions, it can generate reactive oxygen species through Fenton or Fenton-like reactions. These processes together induce oxidative stress in microbial cells, thereby enhancing antibacterial activity.

[0111] As can be seen from the data in Table 2, the lignin-based anti-friction, anti-corrosion, and antibacterial multifunctional coating prepared by the formulation in Example 1 of the present invention has the effect of reducing the surface corrosion current density.

[0112] In summary, the lignin-based multifunctional coating of the present invention, possessing significantly enhanced anti-friction, anti-corrosion, and antibacterial properties, achieves this through the interaction of lignin and Fe. 3+ The core mechanism is the synergistic effect, while PEI and DA form a cross-linked network through Michael addition and Schiff base reaction, lignin-Fe 3+ By embedding multiple functions into the network structure, the coating's anti-friction, anti-corrosion, and antibacterial properties are greatly enhanced.

[0113] Currently, traditional ceramic coating preparation typically relies on conventional physical vapor deposition (PVD) or chemical vapor deposition (CVD) processes. These methods require precise control of temperature, gas flow rate, and vacuum conditions, resulting in high energy consumption. This limitation hinders their application in manufacturing more economical or energy-efficient mechanical components. Therefore, biocomposite materials are receiving increasing attention. However, to achieve widespread application, inherent defects must be overcome: biocomposite coatings exhibit low cohesive strength and poor wear resistance, and are prone to rapid failure under shear stress. This defect severely restricts their transformation into high-wear-resistant and lubrication applications. Simultaneously, research on applying lignin to wear-resistant properties is generally limited. This invention provides a method for preparing a lignin-based multifunctional coating with anti-friction, corrosion, and antibacterial properties, improving the wear-resistant and lubrication performance of the lignin biocomposite coating while also possessing excellent antibacterial properties and strong adhesion. The coating deposited on the aluminum alloy surface achieves an adhesion rating of 4B, and the coating exhibits an inhibition rate of over 90% against bacteria.

[0114] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.

Claims

1. A method for preparing a lignin-based multifunctional coating with anti-friction, corrosion, and antibacterial properties, characterized in that: include, Pre-treatment of the metal substrate yields an oil-free and water-free working surface; The metal substrate was surface activated by immersing it in a piranha solution. Mixed solution A is prepared by mixing sodium lignosulfonate solution and ferric chloride solution; Dopamine, polyethyleneimine, and tris(hydroxymethyl)aminomethane buffer solution were mixed to prepare mixed solution B; Mixing solution A and mixed solution B yields a coating liquid; The fully activated metal substrate is immersed in a coating solution and agitated to deposit the coating on the surface of the metal substrate.

2. The preparation method according to claim 1, characterized in that: The metal substrate is pretreated. include, The substrate surface was cleaned sequentially with acetone, anhydrous ethanol, and deionized water to obtain an oil-free and water-free metal substrate.

3. The preparation method according to claim 1 or 2, characterized in that: The metal substrate is a commonly used metal material for mechanical parts, including stainless steel, aluminum alloy, and copper alloy.

4. The preparation method according to claim 3, characterized in that: The concentration of the sodium lignosulfonate solution is 5 wt%. The ferric chloride solution has a concentration of 0.1M; The volume ratio of the sodium lignosulfonate solution to the ferric chloride solution is 95:

5.

5. The preparation method according to claim 1 or 4, characterized in that: The dopamine has a molecular weight of 153.18, and the polyethyleneimine has a molecular weight of 189.

64. The concentration of dopamine in mixed solution B is 2 mg / mL, and the concentration of polyethyleneimine is 1 mg / mL.

6. The preparation method according to claim 5, characterized in that: The volume ratio of the mixed solution A to the mixed solution B is 3:

1.

7. The preparation method according to claim 1 or 6, characterized in that: The oscillating deposition process is carried out at a reaction temperature of 50°C.

8. A lignin-based anti-friction, corrosion-resistant, and antibacterial multifunctional coating prepared by any of the preparation methods described in claims 1 to 7.

9. The application of the anti-friction, corrosion, and antibacterial multifunctional coating as described in claim 8 on the surface of mechanical parts for anti-friction, corrosion, and antibacterial purposes.

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