A film coating for metal surface of an electric tricycle and a preparation method and application thereof

Abstract

The application discloses a kind of film coating of metal surface of electric tricycle and its preparation method and application, belong to electric vehicle coating coating processing technical field, including the following weight fraction components:70~75 parts single-component acrylic acid epoxy hybrid emulsion, 12~15 parts polydopamine modified curcumin loaded LDH, 8~11 parts double-end amino polydimethylsiloxane modified ZIF-8 / ferroferric oxide nanocomposite, 10~12 parts attapulgite, 5~6 parts sericite powder, 5~6 parts rutile titanium dioxide, 0.8~1 parts dispersing agent, 0.2~0.3 parts defoaming agent, 0.2~0.3 parts leveling agent, 0.5~0.6 parts film forming agent, 20~25 parts deionized water.In the present application, polydopamine modified curcumin loaded LDH, double-end amino polydimethylsiloxane modified ZIF-8 / ferroferric oxide nanocomposite, attapulgite three main components have synergistic effect, if coating crack appears, compared with prior art, corrosion propagation is obviously inhibited.

Description

Technical Field

[0001] This invention belongs to the field of electric vehicle coating technology, and relates to a coating material for the metal surface of an electric tricycle, its preparation method and application. Background Technology

[0002] Electric tricycles suffer from severe corrosion of their metal components (frame, battery compartment base, etc.) due to their heavy loads and complex operating environments (rain, mud, salt spray, stone impact, etc.). Currently, common protective measures include electrophoretic primers, powder coatings, or solvent-based acrylic / epoxy coatings. However, these coatings rely on physical shielding. Once cracks or scratches appear, exposing the metal substrate, corrosive media can quickly penetrate from the cracks or scratches, causing corrosion to spread beneath the coating, damaging the coating structure, and resulting in scratch-induced corrosion. Furthermore, when electric tricycles are used as agricultural vehicles, they frequently come into contact with soil, sewage, and livestock manure. Microbial metabolic activity accelerates metal corrosion at cracks or scratches. As corrosion intensifies, these areas can become entry points for other corrosive media, severely damaging the surface coating and expanding the corrosion range. Summary of the Invention

[0003] The purpose of this invention is to provide a coating material for the metal surface of electric tricycles, its preparation method and application, which solves the problem that when scratches, cracks and other damage occur on the surface coating of existing electric tricycle metal parts, the damaged area becomes a breakthrough point for corrosive media, causing corrosion to spread on the surface of the metal parts and damage to the coating.

[0004] The technical solution adopted in this invention is as follows: A coating for the metal surface of an electric tricycle comprises the following components in parts by weight: 70-75 parts of a single-component acrylic-epoxy hybrid emulsion, 12-15 parts of polydopamine-modified curcumin-loaded LDH, 8-11 parts of bi-amino-terminated polydimethylsiloxane-modified ZIF-8 / ferric oxide nanocomposite, 10-12 parts of attapulgite, 5-6 parts of sericite powder, 5-6 parts of rutile titanium dioxide, 0.8-1 parts of dispersant, 0.2-0.3 parts of defoamer, 0.2-0.3 parts of leveling agent, 0.5-0.6 parts of film-forming agent, and 20-25 parts of deionized water.

[0005] Furthermore, the epoxy-hybrid acrylic emulsion is a single-component acrylic-epoxy hybrid emulsion obtained by hybridizing acrylic acid and epoxy, with a solid content of 40-45%.

[0006] Further, the polydopamine-modified curcumin-loaded LDH was prepared by the following method: Mg(NO3)2·6H2O and Al(NO3)3·9H2O in a molar ratio of 3:1 were dissolved in deionized water, and then NaOH was added dropwise until the pH reached 10.0±0.2. The solution was transferred to a high-pressure reactor for crystallization. After crystallization, the solution was centrifuged, washed until neutral, and vacuum dried to obtain LDH. The LDH was dispersed in anhydrous ethanol, and curcumin was added at a mass ratio of 1:0.3. The solution was stirred at 50°C in the dark for 24 h, centrifuged, washed, and vacuum dried to obtain curcumin-loaded LDH. The curcumin-loaded LDH was dispersed in Tris buffer, and dopamine hydrochloride was added at a mass ratio of 1:0.2. The solution was stirred at room temperature in the dark for 24 h, centrifuged, washed with deionized water until neutral, and freeze-dried to obtain polydopamine-modified curcumin-loaded LDH.

[0007] Further, the dual-amino-terminated polydimethylsiloxane modified ZIF-8 / ferric oxide nanocomposite was prepared by the following method: FeCl3·6H2O and FeSO4·7H2O in a molar ratio of 2:1 were dissolved in deoxygenated water, ammonia was added under heating conditions to pH 10, the reaction was stirred, magnetic separation was performed, the mixture was washed with water until neutral, and vacuum dried to obtain Fe3O4; Fe3O4 was dispersed in methanol, and Zn(NO3)2·6H2O dissolved in methanol was added, with a mass ratio of Fe3O4 to Zn(NO3)2·6H2O of 1:(1.1) ~1.2), after stirring evenly, 2-methylimidazole dissolved in methanol was slowly added dropwise. After the addition was complete, the reaction was stirred at room temperature, magnetically separated, washed with methanol, and vacuum dried to obtain ZIF-8@Fe3O4; ZIF-8@Fe3O4 was dispersed in anhydrous ethanol, and diamino-terminated polydimethylsiloxane was added. The mass ratio of ZIF-8@Fe3O4 to diamino-terminated polydimethylsiloxane was 5:3. The reaction was stirred under nitrogen protection, magnetically separated, washed with ethanol, and vacuum dried to obtain diamino-terminated polydimethylsiloxane modified ZIF-8 / Fe3O4 nanocomposite.

[0008] Further, the biamino-terminated polydimethylsiloxane is prepared by the following method: bihydrogen-terminated polydimethylsiloxane is dissolved in anhydrous ethanol, chloroplatinic acid-isopropanol solution and aluminum isopropoxide are added, the temperature is raised to 85°C under nitrogen protection, allylamine is slowly added dropwise, the reaction is maintained at the temperature and then distilled under reduced pressure, purified by extraction with n-hexane, dried with anhydrous sodium sulfate, and distilled under reduced pressure to obtain biamino-terminated polydimethylsiloxane.

[0009] Furthermore, the attapulgite is a modified attapulgite, specifically γ-aminopropyltriethoxysilane modified attapulgite or polydopamine / KH550 composite modified attapulgite.

[0010] Furthermore, both γ-aminopropyltriethoxysilane-modified attapulgite and polydopamine / KH550 composite-modified attapulgite use acid-treated attapulgite as raw material; the acid-treated attapulgite is prepared by the following method: attapulgite ore is crushed and calcined at 300℃ for 2 h; the calcined attapulgite is taken, a 5% HCl solution is added, the mixture is stirred and reacted at room temperature, centrifuged, washed, dried, ground and sieved to obtain acid-activated attapulgite; γ-aminopropyltriethoxysilane-modified attapulgite was prepared by the following method: acid-activated attapulgite was dispersed in an ethanol / water mixed solvent and ultrasonically dispersed until uniform; the pH was adjusted to 4.0 with glacial acetic acid, KH550 was added, and the reaction was mechanically stirred in a water bath at 70℃~80℃. After the reaction was completed, the mixture was centrifuged, washed three times each with ethanol and deionized water, dried, and ground to obtain KH550-modified attapulgite. The amount of KH550 used was 10~15% of the mass of attapulgite. Polydopamine / KH550 composite modified attapulgite was prepared by the following method: Acid-activated attapulgite was dispersed in Tris buffer and ultrasonically dispersed until uniform. Dopamine hydrochloride was added, with a mass ratio of acid-activated attapulgite to dopamine hydrochloride of 4.8-5:1. The mixture was stirred at room temperature in the dark for 24 h. After the reaction was completed, the mixture was centrifuged, washed with deionized water until neutral, and freeze-dried to obtain PDA@attapulgite. PDA@attapulgite was dispersed in an ethanol / water mixed solvent, the pH was adjusted to 4.0, KH550 was added, and the mixture was stirred at 70-75℃ for 6 h. After centrifugation, the mixture was washed with ethanol and deionized water successively and dried to obtain polydopamine / KH550 composite modified attapulgite.

[0011] Furthermore, the dispersant is a sodium polycarboxylate dispersant, the defoamer is an organosilicon defoamer, the leveling agent is a polyether-modified polydimethylsiloxane, and the film-forming agent is a dodecyl alcohol ester.

[0012] A method for preparing a coating on the metal surface of an electric tricycle includes the following steps: S1. Add deionized water, dispersant, defoamer, and film-forming agent to a dispersion tank according to the weight parts, and stir at 300~500rpm for 5~10 minutes until the mixture is uniform to obtain the basic mixture. S2. Under stirring, add attapulgite, sericite powder, rutile titanium dioxide, polydopamine-modified curcumin-loaded LDH, and double-terminated amino polydimethylsiloxane-modified ZIF-8 / iron tetroxide nanocomposite to the basic mixture in sequence, increase the rotation speed to 800~1200 rpm, disperse for 30~45 min, and obtain a uniform dispersion. S3. Reduce the rotation speed to 400~600 rpm, slowly add the single-component acrylic epoxy hybrid emulsion to the dispersion, continue stirring for 15~20 min after adding to the outer wall, and finally add the leveling agent under stirring and stir for 5~10 min to obtain the coating.

[0013] An application of a coating material for the metal surface of an electric tricycle is disclosed. The coating material is used as a protective coating on the surface of the metal parts of the electric tricycle. The construction method is as follows: the metal part of the electric tricycle is placed with the sprayed surface facing upwards, and the coating material is sprayed or brushed onto the surface of the metal part of the electric tricycle, controlling the wet film thickness to be 40~50μm. After spraying or brushing, in the wet film state, an external magnetic field is applied through a magnet at a distance of 2 mm above the wet film. The direction of the magnetic field is perpendicular to the coating surface, the magnetic field strength is 0.5T, and it is maintained for 20 minutes. Then the magnetic field is removed, and the coating is allowed to air dry at room temperature for 24 hours to obtain the protective coating.

[0014] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: 1. In this invention, a coating for the metal surface of an electric tricycle contains three main components: polydopamine-modified curcumin-loaded LDH, bi-amino-terminated polydimethylsiloxane-modified ZIF-8 / ferric oxide nanocomposite, and attapulgite, which exhibit synergistic effects. After the coating is sprayed or brushed, an external magnetic field is applied, causing the bi-amino-terminated polydimethylsiloxane-modified ZIF-8 / ferric oxide nanocomposite to rearrange and approach the location of the magnetic field, i.e., the outer surface of the coating, away from the metal part. The curcumin-loaded LDH in the polydopamine-modified curcumin-loaded LDH, through polydopamine… After amine modification, on the one hand, it can be uniformly dispersed in a single-component acrylic-epoxy hybrid emulsion system, changing the hydrophilic-hydrophobic properties of curcumin. Combined with LDH, curcumin can be stably dispersed in the coating system. On the other hand, polydopamine has strong adhesion to metal surfaces, which allows polydopamine-modified curcumin-loaded LDH to adhere to the metal layer surface. To avoid delamination in the coating system, attapulgite is introduced. The one-dimensional rod-shaped or fibrous structure of attapulgite can play a penetrating and stabilizing role in the entire system. Modification of attapulgite ensures that attapulgite is uniformly distributed throughout the system.

[0015] 2. In this invention, the three main components—polydopamine-modified curcumin-loaded LDH, biamino-terminated polydimethylsiloxane-modified ZIF-8 / ferric oxide nanocomposite, and attapulgite—have a synergistic effect. When the coating is intact, it provides good protection for the metal surface. If cracks appear in the coating, the polydopamine is easily broken under external force. The curcumin in the polydopamine-modified curcumin-loaded LDH then plays a role in corrosion inhibition and antibacterial activity, providing antibacterial and corrosion-inhibiting effects close to the metal surface. Compared with existing technologies, this significantly inhibits the spread of corrosion. Furthermore, the structures of LDH and ZIF-8 have a significant effect on the corrosion resistance of Cl...- It has a certain adsorption capacity, which can effectively inhibit the penetration of corrosive media and help inhibit the spread of corrosion. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort, wherein: Figure 1 This is a flowchart of a method for preparing a coating on the metal surface of an electric tricycle; Figure 2 This is a magnified electron microscope image comparing the substrate surface at the scratches caused by microbial corrosion according to the present invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention; that is, the described embodiments are merely some embodiments of the invention, and not all embodiments. The components of the embodiments of the invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0018] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0019] It should be noted that relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0020] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0021] This invention discloses a coating for the metal surface of an electric tricycle, comprising the following components in parts by weight: 70-75 parts of a single-component acrylic-epoxy hybrid emulsion, 12-15 parts of polydopamine-modified curcumin-loaded LDH, 8-11 parts of bi-amino-terminated polydimethylsiloxane-modified ZIF-8 / ferric oxide nanocomposite, 10-12 parts of attapulgite, 5-6 parts of sericite powder, 5-6 parts of rutile titanium dioxide, 0.8-1 parts of dispersant, 0.2-0.3 parts of defoamer, 0.2-0.3 parts of leveling agent, 0.5-0.6 parts of film-forming agent, and 20-25 parts of deionized water.

[0022] In the following examples, the epoxy-hybrid acrylic emulsion is a single-component acrylic-epoxy hybrid emulsion obtained by hybridizing acrylic acid and epoxy, specifically Joncryl PRO 1556 single-component acrylic-epoxy hybrid emulsion with a solid content of 44%.

[0023] The polydopamine-modified curcumin-loaded LDH was prepared by the following method: Mg(NO3)2·6H2O and Al(NO3)3·9H2O in a molar ratio of 3:1 were dissolved in deionized water, and then NaOH was added dropwise until the pH reached 10.0±0.2. The solution was transferred to a high-pressure reactor for crystallization. After crystallization, the solution was centrifuged, washed until neutral, and vacuum dried to obtain LDH. LDH was dispersed in anhydrous ethanol, and curcumin was added at a mass ratio of 1:0.3. The solution was stirred at 50°C in the dark for 24 h, centrifuged, washed, and vacuum dried to obtain curcumin-loaded LDH. The curcumin-loaded LDH was dispersed in Tris buffer, and dopamine hydrochloride was added at a mass ratio of 1:0.2. The solution was stirred at room temperature in the dark for 24 h, centrifuged, washed with deionized water until neutral, and freeze-dried to obtain polydopamine-modified curcumin-loaded LDH.

[0024] In the following examples, the specific preparation method of polydopamine-modified curcumin-loaded LDH is as follows: 0.75 mol Mg(NO3)2·6H2O and 0.25 mol Al(NO3)3·9H2O were dissolved in 1 L of deionized water, and 1 M NaOH was added dropwise under nitrogen protection until the pH reached 10.0 ± 0.2. The solution was transferred to a high-pressure reactor and crystallized at 100 °C for 24 h. After centrifugation and washing until neutral, the solution was dried under vacuum at 60 °C to obtain LDH. 2 g of LDH was dispersed in 100 mL of anhydrous ethanol, and 0.6 g of curcumin was added. The solution was stirred at 50 °C in the dark for 24 h, centrifuged, washed three times with ethanol, and dried under vacuum at 40 °C to obtain curcumin-loaded LDH. 1 g of curcumin-loaded LDH was dispersed in 200 mL of Tris buffer (0.05 M, pH = 8.5), and 0.2 g of dopamine hydrochloride was added. The solution was stirred at room temperature in the dark for 24 h. h, centrifuged, washed with deionized water until neutral, freeze-dried to obtain polydopamine-modified curcumin-loaded LDH.

[0025] The dual-amino-terminated polydimethylsiloxane modified ZIF-8 / ferric oxide nanocomposite was prepared by the following method: FeCl3·6H2O and FeSO4·7H2O in a molar ratio of 2:1 were dissolved in deoxygenated water, ammonia was added under heating conditions to pH 10, the reaction was stirred, magnetic separation was performed, the mixture was washed with water until neutral, and vacuum dried to obtain Fe3O4; Fe3O4 was dispersed in methanol, and Zn(NO3)2·6H2O dissolved in methanol was added, with a mass ratio of Fe3O4 to Zn(NO3)2·6H2O of 1:(1.1~1) 2) After stirring evenly, 2-methylimidazole dissolved in methanol was slowly added dropwise. After the addition was complete, the mixture was stirred at room temperature, magnetically separated, washed with methanol, and vacuum dried to obtain ZIF-8@Fe3O4. ZIF-8@Fe3O4 was dispersed in anhydrous ethanol, and diamino-terminated polydimethylsiloxane was added. The mass ratio of ZIF-8@Fe3O4 to diamino-terminated polydimethylsiloxane was 5:3. The mixture was stirred under nitrogen protection, magnetically separated, washed with ethanol, and vacuum dried to obtain diamino-terminated polydimethylsiloxane modified ZIF-8 / Fe3O4 nanocomposite.

[0026] In the following examples, the specific preparation method of the dual-amino-terminated polydimethylsiloxane modified ZIF-8 / Fe3O4 nanocomposite is as follows: 0.02 mol FeCl3·6H2O and 0.01 mol FeSO4·7H2O were dissolved in 100 mL of deoxygenated water, and 25% ammonia was rapidly added at 80°C until the pH reached 10. The mixture was stirred for 1 h, magnetically separated, washed with water until neutral, and vacuum dried at 60°C to obtain Fe3O4; 0.5 g of Fe3O4 was dispersed in 50 mL of methanol, and 0.59 g of Zn(NO3)2·6H2O dissolved in 10 mL of methanol was added, and the mixture was stirred for 10 min; 1.17 g of 2-methylimidazole dissolved in 20 mL of methanol was slowly added dropwise, and the mixture was stirred at room temperature for 2 h after the addition was complete, magnetically separated, washed three times with methanol, and vacuum dried at 60°C to obtain ZIF-8@Fe3O4; 0.5 g of ZIF-8@Fe3O4 was dispersed in 30 mL of anhydrous ethanol, and 0.3 g of ZIF-8@Fe3O4 was added. g of amino-terminated polydimethylsiloxane was stirred at 50℃ under nitrogen protection for 8 h, magnetically separated, washed twice with ethanol, and dried under vacuum at 40℃ to obtain amino-terminated polydimethylsiloxane-modified ZIF-8 / iron tetroxide nanocomposite.

[0027] The diamino-terminated polydimethylsiloxane was prepared by the following method: dihydrogen-terminated polydimethylsiloxane was dissolved in anhydrous ethanol, chloroplatinic acid-isopropanol solution and aluminum isopropoxide were added, the temperature was raised to 85°C under nitrogen protection, allylamine was slowly added dropwise, the reaction was maintained at the temperature and then distilled under reduced pressure, purified by extraction with n-hexane, dried with anhydrous sodium sulfate, and distilled under reduced pressure to obtain diamino-terminated polydimethylsiloxane.

[0028] In the following examples, the specific preparation method of the double-amino-terminated polydimethylsiloxane is as follows: 20 g of octamethylcyclotetrasiloxane, 1.5 g of 1,1,3,3-tetramethyldisiloxane (hydrogen-containing double-terminated) and 50 mL of toluene are added to a dry three-necked flask. Under nitrogen protection, the temperature is raised to 80°C, and 0.05 g of tetramethylammonium hydroxide silanolate catalyst is added. The reaction is maintained at this temperature for 6-8 hours. After the reaction is completed, the temperature is raised to 150°C and stirring is continued for 1 hour. Subsequently, the mixture is distilled under reduced pressure, with the vacuum degree controlled at no less than -0.095 MPa and the temperature at 140-150°C, to obtain the double-hydrogen-terminated polydimethylsiloxane. 10 g of hydrogen-terminated polydimethylsiloxane was dissolved in 30 mL of anhydrous ethanol. 0.01 g of chloroplatinic acid-isopropanol solution (with a platinum content of 2%) and 0.2 g of aluminum isopropoxide were added. Under nitrogen protection, the mixture was heated to 85 °C, and 1.5 g of allylamine was slowly added dropwise. The reaction was maintained at this temperature for 6 hours. After the reaction was complete, the mixture was cooled to below 40 °C, followed by vacuum distillation at 50–60 °C and a vacuum of -0.08 to -0.09 MPa to obtain the crude product. The crude product was cooled to room temperature, and 50 mL of n-hexane was added. After stirring thoroughly, the mixture was transferred to a 250 mL separatory funnel, and 30 mL of deionized water was added. The mixture was vigorously shaken for 2 min, allowed to stand for separation, and the lower layer was removed. The mixture was washed twice with water (30 mL of deionized water each time) until the pH of the lower aqueous phase reached 7. The upper n-hexane phase was collected, and 5 g of anhydrous sodium sulfate was added. The mixture was shaken and allowed to stand for 30 minutes. After filtration, the filtrate was distilled under reduced pressure at 40-45°C until constant weight was obtained, yielding a diamino-terminated polydimethylsiloxane. FTIR: Compared to the reactant dihydrogen-terminated polydimethylsiloxane, the product showed a higher filtration rate at 2160 cm⁻¹. -1 The Si-H stretching peaks at the 3300~3500 cm⁻¹ have largely disappeared, while the peaks at the 3300~3500 cm⁻¹ have also disappeared. -1 A new absorption peak appears in the region, and at 1620 cm⁻¹. -1 Deformation vibration peaks appeared nearby; ¹H NMR (CDCl3, 300 MHz): δ 0.05-0.15 (m, Si-CH3), 0.45-0.55 (m, Si-CH2-), 1.42-1.52 (m, -CH2-CH2-CH2-), 2.55-2.65 (t, -CH2-NH2), 1.15 (broad peak, NH2).

[0029] The attapulgite is a modified attapulgite, specifically γ-aminopropyltriethoxysilane modified attapulgite or polydopamine / KH550 composite modified attapulgite.

[0030] In the following examples, γ-aminopropyltriethoxysilane-modified attapulgite or polydopamine / KH550 composite-modified attapulgite were both prepared using acid-treated attapulgite as raw material. The acid-treated attapulgite was prepared by the following method: the raw attapulgite ore was crushed, passed through a 200-mesh sieve, and calcined at 300°C for 2 h; 50 g of the calcined attapulgite was taken, 500 mL of 5% HCl solution was added, and the mixture was stirred at room temperature for 3 h. After the reaction was completed, the mixture was centrifuged, washed repeatedly with deionized water until no chloride ions were detected by 0.1 M AgNO3, and then vacuum dried at 60°C for 24 h. After grinding and sieving, acid-activated attapulgite was obtained. In the following examples, γ-aminopropyltriethoxysilane-modified attapulgite was prepared by the following method: 10 g of acid-activated attapulgite was dispersed in 100 mL of ethanol / water mixed solvent (ethanol / water volume ratio 9:1) and ultrasonically dispersed for 20 min; the pH was adjusted to 4.0 with glacial acetic acid, 1.2 g of KH550 was added, and the mixture was mechanically stirred in a 70℃ water bath for 6 h. After the reaction was completed, the mixture was centrifuged, washed 3 times each with ethanol and deionized water, and finally vacuum dried at 80℃ for 12 h. KH550-modified attapulgite was then obtained by grinding. In the following examples, polydopamine / KH550 composite modified attapulgite was prepared by the following method: 10 g of acid-activated attapulgite was dispersed in 200 mL of Tris buffer (0.05 M, pH=8.5), ultrasonically dispersed for 20 min, 2 g of dopamine hydrochloride was added, and stirred at room temperature in the dark for 24 h. After the reaction was completed, the mixture was centrifuged, washed with deionized water until neutral, and freeze-dried to obtain PDA@attapulgite; 10 g of PDA@attapulgite was dispersed in 100 mL of ethanol / water (9:1) mixed solvent, the pH was adjusted to 4.0, 1.0 g of KH550 was added, stirred at 70 °C for 6 h, centrifuged, washed successively with ethanol and deionized water, and vacuum dried at 80 °C for 12 h to obtain polydopamine / KH550 composite modified attapulgite; In the following examples, the dispersant is BYK-190 sodium polycarboxylate dispersant, the defoamer is BYK-024 silicone defoamer, the leveling agent is poly(BYK-333) ether-modified polydimethylsiloxane, and the film-forming agent is dodecyl alcohol ester.

[0031] Example 1 Based on the above, the present invention provides a coating for the metal surface of an electric tricycle, comprising the following components in parts by weight: 70 parts of a single-component acrylic-epoxy hybrid emulsion, 12 parts of polydopamine-modified curcumin-loaded LDH, 8 parts of bi-amino-terminated polydimethylsiloxane-modified ZIF-8 / ferric oxide nanocomposite, 10 parts of attapulgite, 5 parts of sericite powder, 5 parts of rutile titanium dioxide, 0.8 parts of dispersant, 0.2 parts of defoamer, 0.2 parts of leveling agent, 0.5 parts of film-forming agent, and 20 parts of deionized water; wherein the attapulgite is a polydopamine / KH550 composite modified attapulgite.

[0032] like Figure 1 As shown, the preparation method of the above-mentioned coating includes the following steps: S1. According to the weight proportions, add deionized water, dispersant, defoamer and film-forming agent into a dispersion tank, stir at 400 rpm for 8 min until the mixture is uniform, and obtain the basic mixture. S2. Under stirring, add attapulgite, sericite powder, rutile titanium dioxide, polydopamine-modified curcumin-loaded LDH, and double-terminated amino polydimethylsiloxane-modified ZIF-8 / iron tetroxide nanocomposite to the basic mixture in sequence, increase the rotation speed to 1000 rpm, disperse for 40 min, and obtain a uniform dispersion. S3. Reduce the rotation speed to 400 rpm, slowly add the single-component acrylic epoxy hybrid emulsion to the dispersion, continue stirring for 20 min after adding it to the outer wall, and finally add the leveling agent under stirring and stir for 10 min to obtain the coating.

[0033] The above-mentioned coating is used for a protective coating on the surface of metal parts of electric tricycles. The construction method is as follows: the metal parts of the electric tricycle are placed with the sprayed surface facing upwards, and the coating is sprayed onto the surface of the metal parts of the electric tricycle, controlling the wet film thickness to 45μm. After spraying, in the wet film state, an external magnetic field is applied by a magnet at a distance of 2 mm above the wet film. The direction of the magnetic field is perpendicular to the coating surface, the magnetic field strength is 0.5T, and it is maintained for 20 minutes. Then the magnetic field is removed, and the metal parts are allowed to air dry at room temperature for 24 hours to obtain a protective coating on the surface of the metal parts.

[0034] Example 2 This embodiment, based on Example 1, provides a coating for the metal surface of an electric tricycle, comprising the following components in parts by weight: 73 parts of a single-component acrylic-epoxy hybrid emulsion, 13.5 parts of polydopamine-modified curcumin-loaded LDH, 9.5 parts of a bi-amino-terminated polydimethylsiloxane-modified ZIF-8 / ferric oxide nanocomposite, 11 parts of attapulgite, 5.5 parts of sericite powder, 5.5 parts of rutile titanium dioxide, 0.9 parts of dispersant, 0.3 parts of defoamer, 0.3 parts of leveling agent, 0.6 parts of film-forming agent, and 23 parts of deionized water; wherein the attapulgite is a polydopamine / KH550 composite modified attapulgite. The preparation method and application are the same as in Example 1.

[0035] Example 3 This embodiment, based on Example 1, provides a coating for the metal surface of an electric tricycle, comprising the following components in parts by weight: 75 parts of a single-component acrylic-epoxy hybrid emulsion, 15 parts of polydopamine-modified curcumin-loaded LDH, 11 parts of biamino-terminated polydimethylsiloxane-modified ZIF-8 / ferric oxide nanocomposite, 12 parts of attapulgite, 6 parts of sericite powder, 6 parts of rutile titanium dioxide, 1 part of dispersant, 0.3 parts of defoamer, 0.3 parts of leveling agent, 0.6 parts of film-forming agent, and 25 parts of deionized water; wherein the attapulgite is a polydopamine / KH550 composite modified attapulgite. The preparation method and application are the same as in Example 1.

[0036] Example 4 This embodiment, based on Example 1, provides a coating for the metal surface of an electric tricycle, comprising the following components in parts by weight: 70 parts of a single-component acrylic-epoxy hybrid emulsion, 12 parts of polydopamine-modified curcumin-loaded LDH, 8 parts of biamino-terminated polydimethylsiloxane-modified ZIF-8 / ferric oxide nanocomposite, 10 parts of attapulgite, 5 parts of sericite powder, 5 parts of rutile titanium dioxide, 0.8 parts of dispersant, 0.2 parts of defoamer, 0.2 parts of leveling agent, 0.5 parts of film-forming agent, and 20 parts of deionized water; wherein the attapulgite is γ-aminopropyltriethoxysilane-modified attapulgite. The preparation method and application are the same as in Example 1.

[0037] Comparative Example 1 This comparative example provides a coating for the metal surface of an electric tricycle, comprising the following components in parts by weight: 70 parts of a single-component acrylic-epoxy hybrid emulsion, 5 parts of sericite powder, 5 parts of rutile titanium dioxide, 0.8 parts of dispersant, 0.2 parts of defoamer, 0.2 parts of leveling agent, 0.5 parts of film-forming agent, and 20 parts of deionized water. The preparation method is the same as in Example 1, with appropriate adjustments. The application method is as follows: place the metal part of the electric tricycle with the sprayed surface facing upwards, spray the coating onto the surface of the metal part, controlling the wet film thickness to 45 μm; after spraying, allow it to air dry at room temperature for 24 hours to obtain a protective coating on the metal surface.

[0038] Comparative Example 2 Based on Example 1, but differing from Example 1, this comparative example provides a coating for the metal surface of an electric tricycle, comprising the following components in parts by weight: 70 parts of a single-component acrylic-epoxy hybrid emulsion, 5 parts of sericite powder, 5 parts of rutile titanium dioxide, 3.6 parts of curcumin, 0.8 parts of dispersant, 0.2 parts of defoamer, 0.2 parts of leveling agent, 0.5 parts of film-forming agent, and 20 parts of deionized water. The preparation method is the same as in Example 1, with appropriate adjustments. The application method is as follows: place the metal part of the electric tricycle with the sprayed surface facing upwards, spray the coating onto the surface of the metal part, controlling the wet film thickness to 45 μm; after spraying, allow it to air dry at room temperature for 24 hours to obtain a protective coating on the metal surface.

[0039] Comparative Example 3 Based on Example 1, the difference from Example 1 is that the coating on the metal surface of an electric tricycle provided in this comparative example does not include polydopamine-modified curcumin-loaded LDH, but all other aspects are the same, and the preparation method and application are the same as in Example 1.

[0040] Comparative Example 4 Based on Example 1, the difference from Example 1 is that the coating on the metal surface of an electric tricycle provided in this comparative example does not include the double-terminated amino polydimethylsiloxane modified ZIF-8 / iron tetroxide nanocomposite, but all other aspects are the same, and the preparation method and application are the same as in Example 1.

[0041] Comparative Example 5 Based on Example 1, the difference from Example 1 is that the coating on the metal surface of an electric tricycle provided in this comparative example does not include attapulgite, but all other aspects are the same, and the preparation method and application are the same as in Example 1.

[0042] Comparative Example 6 Based on Example 1, the difference from Example 1 is that the curcumin-loaded LDH in the coating of the metal surface of an electric tricycle provided in this comparative example is not modified by polydopamine, but otherwise it is the same; the curcumin-loaded LDH is prepared by the following method: 0.75 mol Mg(NO3)2·6H2O and 0.25 mol Al(NO3)3·9H2O are dissolved in 1 L of deionized water, and 1 M NaOH is added dropwise under nitrogen protection until pH=10.0±0.2. The solution is transferred to a high-pressure reactor, crystallized at 100℃ for 24 h, centrifuged and washed until neutral, and dried under vacuum at 60℃ to obtain LDH; 2 g of LDH is dispersed in 100 mL of anhydrous ethanol, 0.6 g of curcumin is added, stirred at 50℃ in the dark for 24 h, centrifuged, washed 3 times with ethanol, and dried under vacuum at 40℃ to obtain curcumin-loaded LDH.

[0043] Comparative Example 7 Based on Example 1, the difference from Example 1 is that the ZIF-8 / Fe3O4 nanocomposite in the coating of the metal surface of an electric tricycle provided in this comparative example is not modified with diamino-terminated polydimethylsiloxane, while the rest are the same; the specific preparation method of ZIF-8 / Fe3O4 nanocomposite is as follows: 0.02 mol FeCl3·6H2O and 0.01 mol FeSO4·7H2O are dissolved in 100 mL of deoxygenated water, 25% ammonia is rapidly added at 80°C until the pH is 10, stirred for 1 h, magnetically separated, washed with water until neutral, and vacuum dried at 60°C to obtain Fe3O4; 0.5 g of Fe3O4 is dispersed in 50 mL of methanol, and 0.59 g of Zn(NO3)2·6H2O dissolved in 10 mL of methanol is added, and stirred for 10 min; 1.17 g of 2-methylimidazole dissolved in 20 mL of methanol is slowly added dropwise, and after the addition is complete, the reaction is stirred at room temperature for 2 minutes. h, magnetic separation, washing with methanol 3 times, vacuum drying at 60℃ to obtain ZIF-8 / Fe3O4 nanocomposite.

[0044] Comparative Example 8 Based on Example 1, the difference from Example 1 is that the attapulgite in the coating on the metal surface of the electric tricycle provided in this comparative example is not modified with γ-aminopropyltriethoxysilane or polydopamine / KH550 composite, but directly uses acid-treated attapulgite. The rest are the same. The acid-treated attapulgite is prepared by the following method: the raw attapulgite ore is crushed, passed through a 200-mesh sieve, and calcined at 300°C for 2 h; 50 g of calcined attapulgite is taken, 500 mL of 5% HCl solution is added, and the mixture is stirred at room temperature for 3 h. After the reaction is completed, the mixture is centrifuged, washed repeatedly with deionized water until no chloride ions are detected by 0.1 MAgNO3, and then vacuum dried at 60°C for 24 h. After grinding and sieving, acid-activated attapulgite is obtained. The acid-activated attapulgite is acid-treated attapulgite.

[0045] Experimental Example 1 The basic performance of the protective coatings prepared in Examples 1-4 and Comparative Examples 1-8 was tested, and the results are shown in Table 1.

[0046] Test substrate: Q235 carbon steel plate for electric tricycles (150mm×75mm×2mm), surface sandblasted to Sa2.5 grade, roughness 45~50μm; Coating and curing: Spray according to the construction methods of each embodiment and comparative example (wet film 45μm), air dry at room temperature for 24 hours, and continue to cure in a constant temperature and humidity room (25±2℃, RH 50±5%) for 7 days before testing; Each sample group consists of 5 parallel samples, and the average value of the data is taken. Test items and test methods: Adhesion: Refer to ISO 2409 cross-cut adhesion test, 1mm spacing, 6-level grading, ranging from level 0 (no peeling, best) to level 5 (peeling area greater than 65%, worst).

[0047] Pencil hardness: Refer to GB / T 6739-2022 Pencil method for determining the hardness of paint and varnish film.

[0048] Impact resistance: Refer to GB / T 1732-2020 Test method for impact resistance of paint film (positive impact, 1kg weight). The maximum height from which the weight falls on the test plate without causing damage to the paint film is measured in cm. If the paint film is not damaged at a height of 50 cm, the result is recorded as >50 cm. Water contact angle: JC2000D contact angle meter, room temperature static drop method (5μL deionized water, average of 5 test points); Abrasion resistance: The Taber test method was used, with a CS-10 rubber grinding wheel and a 500 g weight applied. The coated sample was fixed on a turntable, the turntable speed was set to 60 rpm, and the total number of revolutions was 500. The wear mass loss was calculated. Initial weight Weight after deducting wear The wear mass loss is obtained as follows: (Unit: mg)

[0049] Table 1. Basic Performance Testing of Protective Coatings Adhesion Pencil hardness Impact resistance (cm) Water contact angle Wear and tear quality loss Example 1 Level 0 2H >50 cm 103° 28.5 Example 2 Level 0 3H >50 cm 105° 30.2 Example 3 Level 0 3H >50 cm 104° 29.8 Example 4 Level 0 2H >50 cm 98° 35.6 Comparative Example 1 Level 3 HB 33cm 68° 78 Comparative Example 2 Level 3 HB 38cm 72° 72.1 Comparative Example 3 Level 1 H 48cm 102° 45.5 Comparative Example 4 Level 1 H 47cm 78° 48.7 Comparative Example 5 Level 2 H 43cm 95° 60.4 Comparative Example 6 Level 2 2H 49cm 99° 55.2 Comparative Example 7 Level 1 2H 48cm 82° 44.3 Comparative Example 8 Level 2 H 44cm 88° 65.6 As shown in Table 1, the three main components of this application—polydopamine-modified curcumin-loaded LDH, bi-amino-terminated polydimethylsiloxane-modified ZIF-8 / iron tetroxide nanocomposite, and attapulgite—have a synergistic effect, which can balance the impact resistance, pencil hardness, and adhesion of the coating, so that all three are maintained at a high level; moreover, the coating of this application has certain hydrophobic and waterproof properties as well as wear resistance.

[0050] Experimental Example 2 The corrosion propagation test after scratching was carried out on the protective coatings prepared in Examples 1-4 and Comparative Examples 1-8. The results are shown in Table 2.

[0051] Reference standard: ISO 12944-6, Salt spray system: controllable salt spray deposition rate (1-2 mL / (80 cm⁻¹)). 2 The salt solution is 5% NaCl (pH 6.5-7.2); the ultraviolet irradiation system uses a UVA-340 fluorescent ultraviolet lamp (simulating outdoor ultraviolet radiation, wavelength 315-400 nm, peak 340 nm), and the irradiance can be controlled at 0.77 W / (m²). 2 ·nm)±0.05 W / (m 2 •nm) (at 340 nm); Salt spray stage temperature 35℃±2℃, UV stage temperature 60℃±3℃; Substrate treatment: Low carbon steel plate Q235 is used, with dimensions typically 150 mm × 70 mm × 3 mm, and surface treatment reaches Sa 2.5 grade; Coating preparation: Prepare coatings according to Examples 1-4 and Comparative Examples 1-8; Scratch treatment: An X-shaped scratch (deep to the substrate, scratch width ≤ 0.3 mm, length approximately 50 mm, and included angle 60°) is made on the coating surface to simulate corrosion expansion after coating damage; the edges of the test panel are sealed with an aging-resistant sealant (such as epoxy resin), exposing only the coating surface and the scratched area; Each sample group consists of 5 parallel samples, and the average value of the data is taken. Test cycle setup: Refer to ISO 12944-6, Phase 1: Salt spray test (ISO 9227 NSS conditions): 35℃±2℃, lasting 72 hours; Phase 2: UV irradiation + condensation cycle: 60℃±3℃ (UV irradiation for 8 hours) → 40℃±2℃ (condensation for 4 hours), lasting 72 hours; Cycle duration 144 hours, repeated 5 times for a total of 720 hours. After the cycle, remove the test plate, rinse the surface salt with deionized water, and place it in a standard environment (23℃±2℃, 50%±5%RH) for 1 hour. Test the adhesion of the coating on the test plate surface (refer to ISO 2409 cross-cut test, 6-level classification, level 0 is optimal), and observe whether blistering or spots appear on the sample surface (including the coated area and the scratched area). Blistering level (GB / T GB / T 1766-2008, Method for evaluating bubbling grade: Bubble density grade and bubble size grade (in parentheses); Example: Bubble 2 (S3), indicating that the paint film bubbling density is grade 2 and the bubble size is grade S3); Spot grade (GB / T 1766-2008, Method for evaluating spot grade: Spot quantity grade and spot size grade (in parentheses); Example: Spot 2 (S3), indicating that the coating spot quantity is grade 2 and the spot size is grade S3); and detect the maximum single-sided erosion width (mm) at the scratch, and take the average value.

[0052] Table 2 Results of corrosion propagation test Adhesion after corrosion Foaming level Spot grading Maximum erosion width on one side of the scratch (mm) Example 1 Level 0 0（S0） 1（S1） 0.7 Example 2 Level 0 0（S0） 1（S1） 0.6 Example 3 Level 0 0（S0） 1（S1） 0.7 Example 4 Level 1 0（S0） 1（S1） 0.9 Comparative Example 1 Level 4 3（S3） 3（S3） 5.5 Comparative Example 2 Level 4 3（S3） 3（S3） 5 Comparative Example 3 Level 2 2（S2） 2（S2） 3 Comparative Example 4 Level 2 2（S1） 2（S2） 2.8 Comparative Example 5 Level 3 3（S2） 3（S2） 4 Comparative Example 6 Level 2 2（S2） 2（S2） 3.2 Comparative Example 7 Level 2 2（S1） 2（S1） 2.2 Comparative Example 8 Level 3 3（S2） 3（S2） 3.8 The spots in this application are mainly in the scratched areas; no spots visible to the naked eye were observed on other coated surfaces.

[0053] Experimental Example 3 Microbial corrosion tests were conducted on the protective coatings prepared in Examples 1-4 and Comparative Examples 1-8 after scratching. The results are shown in Table 3. The preparation of the test panels was based on Test Example 2, including substrate treatment, coating preparation, scratch treatment, etc., and sterilization treatment was performed to obtain sterile coating test panels. Test strains: Aspergillus flavus, Aspergillus niger, and Aspergillus versicolor (provided by Shanghai Beinuo Biotechnology Co., Ltd.) were selected, and each strain was prepared at a concentration of 1×10⁻⁶. 7 CFU / mL Aspergillus flavus spore suspension, Aspergillus niger spore suspension, and Aspergillus versicolor spore suspension were mixed uniformly at a volume ratio of 1:1:1, and vigorously shaken to ensure thorough mixing. The mixed spore suspension was then diluted to a final concentration of 1×10⁻⁶. 6 CFU / mL; Blank nutrient solution: Use blank nutrient solution instead of mixed spore suspension. The blank nutrient solution contains 0.7 g·L⁻¹ KH₂PO₄. −1 0.3 g·L K2HPO4 −1MgSO4 0.5 g·L −1 NaNO3 2.0 g·L −1 KCl 0.5 g·L −1 FeSO4 0.01 g·L −1 C 12 H 22 O 11 30 g·L −1 ; Test Method: The prepared mixed spore suspension was evenly sprayed onto the sterilized coated test plates corresponding to each example and comparative example, ensuring that the bacterial suspension completely covered the coating surface and scratched areas. The amount of mixed spore suspension used in each test plate was basically the same. Sterile nutrient solution was evenly sprayed onto the sterilized coated test plate of Example 1 instead of the mixed spore suspension, serving as a blank control group. The coated test plates were then placed in a mold incubator (model MJX-128) at a temperature of 30°C and a relative humidity of 95% for 28 days. After 28 days of incubation, the results were compared with the standard (GB / T). 1766-2008), to evaluate the mold growth level of the entire test plate surface (including the coated area and the scratched area). The mold growth level is expressed as: the level of the number of mold growths and the level of the mold spot size (in parentheses); Example: Mold growth 2 (S3) indicates that the number of mold growths on the coating is level 2 and the mold spot size is level S3; After removing corrosion products from the sample surface, the maximum erosion width (mm) on one side of the scratch is measured and the average value is taken (5 parallel samples per test group).

[0054] Table 3 Microbial Corrosion Test Mold level Maximum erosion width (mm) on one side of the scratch. Example 1 0（S0） 0.4 Example 2 0（S0） 0.3 Example 3 0（S0） 0.3 Example 4 0（S0） 0.6 Comparative Example 1 4（S4） 3 Comparative Example 2 3（S3） 2.3 Comparative Example 3 3（S3） 2.5 Comparative Example 4 2（S2） 1.4 Comparative Example 5 3（S3） 2.2 Comparative Example 6 2（S3） 1.7 Comparative Example 7 2（S1） 1.2 Comparative Example 8 3（S1） 1.9 Blank control group - ＜0.2 This application shows no visible mold spots, and the scratched area shows virtually no erosion on one side. After mold inoculation and culture, the corrosion morphology of the substrate surface with a single-sided scratch in the sample corresponding to Example 1 and the substrate surface with a scratch in the sample corresponding to Comparative Example 1 were observed under electron microscopy magnification as follows: Figure 2 As shown, the degree of corrosion on the surface of the scratched substrate of Comparative Example 1 is more severe than that on the surface of the scratched substrate of Example 1. After inoculation with mold, the surface of the scratched substrate of Example 1 has slight corrosion, and spots can be seen under an electron microscope, but the spots and other corrosion morphologies are basically not visible to the naked eye.

[0055] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A coating for the metal surface of an electric tricycle, characterized in that: The product comprises the following components in parts by weight: 70-75 parts of single-component acrylic epoxy hybrid emulsion, 12-15 parts of polydopamine-modified curcumin-loaded LDH, 8-11 parts of biamino-terminated polydimethylsiloxane-modified ZIF-8 / ferric oxide nanocomposite, 10-12 parts of attapulgite, 5-6 parts of sericite powder, 5-6 parts of rutile titanium dioxide, 0.8-1 parts of dispersant, 0.2-0.3 parts of defoamer, 0.2-0.3 parts of leveling agent, 0.5-0.6 parts of film-forming agent, and 20-25 parts of deionized water.

2. The coating material for the metal surface of an electric tricycle according to claim 1, characterized in that: The epoxy-hybrid acrylic emulsion is a single-component acrylic-epoxy hybrid emulsion obtained by hybridizing acrylic acid and epoxy, with a solid content of 40-45%.

3. The coating material for the metal surface of an electric tricycle according to claim 1, characterized in that: The polydopamine-modified curcumin-loaded LDH was prepared by the following method: Mg(NO3)2·6H2O and Al(NO3)3·9H2O in a molar ratio of 3:1 were dissolved in deionized water, and then NaOH was added dropwise until the pH reached 10.0±0.

2. The solution was transferred to a high-pressure reactor for crystallization. After crystallization, the solution was centrifuged, washed until neutral, and vacuum dried to obtain LDH. LDH was dispersed in anhydrous ethanol, and curcumin was added at a mass ratio of 1:0.

3. The solution was stirred at 50°C in the dark for 24 h, centrifuged, washed, and vacuum dried to obtain curcumin-loaded LDH. The curcumin-loaded LDH was dispersed in Tris buffer, and dopamine hydrochloride was added at a mass ratio of 1:0.

2. The solution was stirred at room temperature in the dark for 24 h, centrifuged, washed with deionized water until neutral, and freeze-dried to obtain polydopamine-modified curcumin-loaded LDH.

4. The coating material for the metal surface of an electric tricycle according to claim 1, characterized in that: The dual-amino-terminated polydimethylsiloxane modified ZIF-8 / ferric oxide nanocomposite was prepared by the following method: FeCl3·6H2O and FeSO4·7H2O in a molar ratio of 2:1 were dissolved in deoxygenated water, ammonia was added under heating conditions to pH 10, the reaction was stirred, magnetic separation was performed, the mixture was washed with water until neutral, and vacuum dried to obtain Fe3O4; Fe3O4 was dispersed in methanol, and Zn(NO3)2·6H2O dissolved in methanol was added, with a mass ratio of Fe3O4 to Zn(NO3)2·6H2O of 1:(1.1~1) 2) After stirring evenly, 2-methylimidazole dissolved in methanol was slowly added dropwise. After the addition was complete, the mixture was stirred at room temperature, magnetically separated, washed with methanol, and vacuum dried to obtain ZIF-8@Fe3O4. ZIF-8@Fe3O4 was dispersed in anhydrous ethanol, and diamino-terminated polydimethylsiloxane was added. The mass ratio of ZIF-8@Fe3O4 to diamino-terminated polydimethylsiloxane was 5:

3. The mixture was stirred under nitrogen protection, magnetically separated, washed with ethanol, and vacuum dried to obtain diamino-terminated polydimethylsiloxane modified ZIF-8 / Fe3O4 nanocomposite.

5. The coating material for the metal surface of an electric tricycle according to claim 4, characterized in that: The diamino-terminated polydimethylsiloxane was prepared by the following method: dihydrogen-terminated polydimethylsiloxane was dissolved in anhydrous ethanol, chloroplatinic acid-isopropanol solution and aluminum isopropoxide were added, the temperature was raised to 85°C under nitrogen protection, allylamine was slowly added dropwise, the reaction was maintained at the temperature and then distilled under reduced pressure, purified by extraction with n-hexane, dried with anhydrous sodium sulfate, and distilled under reduced pressure to obtain diamino-terminated polydimethylsiloxane.

6. The coating material for the metal surface of an electric tricycle according to claim 1, characterized in that: The attapulgite is a modified attapulgite, specifically γ-aminopropyltriethoxysilane modified attapulgite or polydopamine / KH550 composite modified attapulgite.

7. The coating material for the metal surface of an electric tricycle according to claim 6, characterized in that: γ-aminopropyltriethoxysilane-modified attapulgite or polydopamine / KH550 composite-modified attapulgite both use acid-treated attapulgite as raw material; the acid-treated attapulgite is prepared by the following method: attapulgite ore is crushed and calcined at 300℃ for 2 h; the calcined attapulgite is taken, 5% HCl solution is added, the mixture is stirred and reacted at room temperature, centrifuged, washed, dried, ground and sieved to obtain acid-activated attapulgite; γ-aminopropyltriethoxysilane-modified attapulgite was prepared by the following method: acid-activated attapulgite was dispersed in an ethanol / water mixed solvent and ultrasonically dispersed until uniform; the pH was adjusted to 4.0 with glacial acetic acid, KH550 was added, and the reaction was mechanically stirred in a water bath at 70℃~80℃. After the reaction was completed, the mixture was centrifuged, washed three times each with ethanol and deionized water, dried, and ground to obtain KH550-modified attapulgite. The amount of KH550 used was 10~15% of the mass of attapulgite. Polydopamine / KH550 composite modified attapulgite was prepared by the following method: Acid-activated attapulgite was dispersed in Tris buffer and ultrasonically dispersed until uniform. Dopamine hydrochloride was added, with a mass ratio of acid-activated attapulgite to dopamine hydrochloride of 4.8-5:

1. The mixture was stirred at room temperature in the dark for 24 h. After the reaction was completed, the mixture was centrifuged, washed with deionized water until neutral, and freeze-dried to obtain PDA@attapulgite. PDA@attapulgite was dispersed in an ethanol / water mixed solvent, the pH was adjusted to 4.0, KH550 was added, and the mixture was stirred at 70-75℃ for 6 h. After centrifugation, the mixture was washed with ethanol and deionized water successively and dried to obtain polydopamine / KH550 composite modified attapulgite.

8. The coating material for the metal surface of an electric tricycle according to claim 1, characterized in that: The dispersant is a sodium polycarboxylate dispersant, the defoamer is an organosilicon defoamer, the leveling agent is a polyether-modified polydimethylsiloxane, and the film-forming agent is a dodecyl alcohol ester.

9. The method for preparing a coating on the metal surface of an electric tricycle according to claim 1, characterized in that: Includes the following steps: S1. According to the weight proportions, add deionized water, dispersant, defoamer and film-forming agent into a dispersion tank, stir at 300~500 rpm for 5~10 min until the mixture is uniform, and obtain the basic mixture; S2. Under stirring, add attapulgite, sericite powder, rutile titanium dioxide, polydopamine-modified curcumin-loaded LDH, and double-terminated amino polydimethylsiloxane-modified ZIF-8 / iron tetroxide nanocomposite to the basic mixture in sequence, increase the rotation speed to 800~1200 rpm, disperse for 30~45 min, and obtain a uniform dispersion. S3. Reduce the rotation speed to 400~600 rpm, slowly add the single-component acrylic epoxy hybrid emulsion to the dispersion, continue stirring for 15~20 min after adding to the outer wall, and finally add the leveling agent under stirring and stir for 5~10 min to obtain the coating.

10. The application of a coating on the metal surface of an electric tricycle according to claim 1, characterized in that: The coating is used as a protective coating on the surface of metal parts of electric tricycles; The construction method is as follows: Place the metal parts of the electric tricycle with the sprayed surface facing upwards, and spray or brush the coating onto the surface of the metal parts of the electric tricycle, controlling the wet film thickness to be 40~50μm; after spraying or brushing, in the wet film state, apply an external magnetic field through a magnet at a distance of 2 mm above the wet film, with the magnetic field direction perpendicular to the coating surface and the magnetic field strength of 0.5T, and maintain it for 20 minutes, then remove the magnetic field and let it air dry at room temperature for 24 hours to obtain the protective coating.

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