Modified heavy-duty anticorrosive coating containing graphene and preparation method and application thereof

Abstract

The application belongs to the field of coating, and particularly relates to a modified heavy-duty anticorrosive coating containing graphene and a preparation method and application thereof. The modified heavy-duty anticorrosive coating comprises a modified graphene anticorrosive filler, a reactive diluent, an epoxy resin, a curing agent and a defoaming agent. The modified graphene anticorrosive filler is prepared by the following steps: step (1): preparing a modified graphene composite loaded with ZIF-8: tannic acid is used to modify the surface of graphene oxide, a zinc source and an organic ligand are added, and ZIF-8 crystals are in-situ grown on the surface of the graphene oxide; step (2): preparing a polyethyleneimine modified cyclodextrin: polyethyleneimine is grafted onto beta-cyclodextrin by using epichlorohydrin as a crosslinking agent; step (3): loading and coating of the corrosion inhibitor: the GO- TA@ZIF-8 composite prepared in step (1) is dispersed in an organic corrosion inhibitor solution, and vacuum negative pressure is used to force the corrosion inhibitor molecules to enter the ZIF-8 channels; the PEI modified CD aqueous solution prepared in step (2) is added, the pH value is adjusted, and the modified graphene anticorrosive filler is obtained after separation and drying.

Description

Technical Field

[0001] This invention belongs to the field of coatings, specifically relating to a modified heavy-duty anti-corrosion coating containing graphene, its preparation method, and its application. Background Technology

[0002] Metal corrosion causes enormous economic losses and safety hazards every year. In marine engineering, petrochemicals, and infrastructure construction, coating protection is currently the most effective and widely used anti-corrosion method. Among these, epoxy resin has become the preferred matrix resin for heavy-duty anti-corrosion coatings due to its excellent adhesion, chemical resistance, and mechanical strength. However, during the curing process, epoxy resin inevitably produces micropores and cracks, and the cured network structure has free volume. Corrosive media (such as water molecules, chloride ions, and oxygen) can easily penetrate into the metal substrate through these microscopic defects, leading to coating failure.

[0003] To improve the impermeability of coatings, adding layered nanofillers (such as graphene, graphene oxide, and glass flakes) to epoxy resin to create a "maze effect" has become an industry consensus. Graphene, in particular, is hailed as the next-generation "king of anti-corrosion coatings" due to its single-atom-layer thickness, extremely high specific surface area, and excellent physical barrier properties. However, graphene's enormous specific surface area makes it highly prone to agglomeration in the resin matrix. This not only reduces barrier efficiency but may even lead to galvanic corrosion due to the conductivity of the agglomerates, accelerating the damage to the metal substrate.

[0004] In existing technologies, researchers have attempted to improve the dispersibility of graphene by modifying its surface through various physical or chemical methods. For example, existing technologies (such as "Preparation and Performance Study of Graphene Heavy-Duty Anti-corrosion Coatings", Liu Junhua et al., 2025) disclose a method for synergistic modification of graphene oxide using lignin and silane coupling agent (KH550). Although this method improves the dispersibility of graphene by utilizing biomass materials and utilizes the phenolic hydroxyl groups of lignin to play a certain role in rust conversion, this type of technical solution still has the following significant defects in practical applications: a single protective mechanism and a lack of active repair capability: existing modified graphene coatings mainly rely on physical shielding (i.e., extending the diffusion path of corrosive media) and passive rust conversion. Once the coating surface develops microcracks (scratches) due to external impact or environmental stress, or if the medium penetrates to the interface due to long-term immersion, this type of coating cannot actively repair the damaged area, and corrosion will rapidly spread along the interface, leading to blistering and peeling of the coating.

[0005] Poor compatibility of corrosion inhibitors: To impart self-healing properties to coatings, some technologies attempt to directly add organic corrosion inhibitors (such as benzotriazole BTA) to the coating. However, directly added corrosion inhibitors not only easily compromise the density of the resin matrix but also cause uncontrollable leakage in non-corrosive conditions, leading to significant loss of the corrosion inhibitor in the early stages of coating service, insufficient protection in later stages, and environmental pollution. Although some studies have utilized porous materials (such as mesoporous silica and hollonic acid) to load corrosion inhibitors, they often lack effective "capping" mechanisms and still cannot solve the leakage problem.

[0006] There is still room for improvement in interfacial bonding strength: Existing modifiers (such as lignin and traditional silanes) are mostly connected to the epoxy resin matrix through physical entanglement or a small number of chemical bonds, resulting in limited interfacial bonding strength. Under long-term humid and hot or salt spray environments, water molecules tend to accumulate at the filler / resin interface, leading to interfacial delamination and the formation of new corrosion channels.

[0007] Therefore, there is an urgent need to develop a new type of anti-corrosion filler that not only possesses the high barrier properties of graphene and can achieve "on-demand release" of corrosion inhibitors, but also solves the interfacial compatibility problem between fillers and resins through strong chemical bonding, thereby truly achieving long-lasting heavy-duty anti-corrosion coatings. Summary of the Invention

[0008] To address the problems existing in the prior art, this invention provides a modified heavy-duty anti-corrosion coating containing graphene, its preparation method, and its application.

[0009] This invention is achieved through the following technical solution:

[0010] A graphene-modified heavy-duty anti-corrosion coating is prepared from modified graphene anti-corrosion filler, reactive diluent, epoxy resin, curing agent and defoamer; wherein the modified graphene anti-corrosion filler is prepared by the following steps: Step (1): Preparation of modified graphene composite loaded with ZIF-8: Surface modification of graphene oxide is performed using tannic acid, followed by the addition of zinc source and organic ligand, so that ZIF-8 crystals grow in situ on the surface of graphene oxide; Step (2): Preparation of polyethylene Polyethylene imine-modified cyclodextrin: Using epichlorohydrin as a crosslinking agent, polyethyleneimine (PEI) is grafted onto β-cyclodextrin; Step (3): Corrosion inhibitor loading and coating: The GO-TA@ZIF-8 complex obtained in step (1) is dispersed in an organic corrosion inhibitor solution, and the corrosion inhibitor molecules are made to enter the ZIF-8 channels by vacuum negative pressure; then the PEI-modified CD aqueous solution obtained in step (2) is added, the pH value is adjusted, and the modified graphene anticorrosion filler is obtained by separation and drying.

[0011] Further, by weight, it comprises: 1.0 part of modified graphene anticorrosive filler, 10 parts of reactive diluent, 100 parts of epoxy resin, 50 parts of curing agent, and 1.0 part of defoamer; wherein the reactive diluent is preferably butyl glycidyl ether, the epoxy resin is preferably E51 epoxy resin, and the curing agent is preferably 650 type polyamide curing agent.

[0012] Further, the specific preparation method of PEI-modified CD in step (2) is as follows: β-cyclodextrin is dissolved in sodium hydroxide aqueous solution, epichlorohydrin is added dropwise at 0-5℃, polyethyleneimine is added after the reaction is activated, the temperature is raised to 60℃ for reaction, and after the reaction is completed, small molecules are removed by dialysis and freeze-dried to obtain the product; wherein the weight average molecular weight Mw of polyethyleneimine is 1800, and the molecular weight cutoff of the dialysis bag is 1000 Da.

[0013] Further, the specific preparation method of the modified graphene composite loaded with ZIF-8 in step (1) is as follows: the graphene oxide dispersion is mixed and stirred with tannic acid, and modified by π-π conjugation; then zinc nitrate hexahydrate is added and stirred to chelate zinc ions; then 2-methylimidazole solution is added, and the reaction is stirred at room temperature, centrifuged, washed and dried; wherein, the mass ratio of graphene oxide, tannic acid, zinc nitrate hexahydrate and 2-methylimidazole is 200:100:(300-1200):(650-2600).

[0014] Furthermore, the amount of zinc nitrate hexahydrate used is 0.3g to 1.2g, and the amount of 2-methylimidazole used is 0.65g to 2.6g, in order to adjust the loading density of ZIF-8 crystals on the graphene surface accordingly.

[0015] Further, the organic corrosion inhibitor mentioned in step (3) is benzotriazole (BTA) or 2-mercaptobenzothiazole (MBT); the specific process of the vacuum negative pressure operation is as follows: evacuate to -0.1MPa and maintain for 30 minutes, then restore to normal pressure, and repeat the operation 3 times.

[0016] Further, in step (3), the pH value is adjusted to a range of 7.5-8.0; the concentration of the PEI-modified CD aqueous solution is 5 mg / mL; the stirring time of the coating reaction is 4 hours, and the drying conditions are vacuum drying at 50°C for 12 hours.

[0017] This invention also provides a method for preparing a graphene-modified heavy-duty anti-corrosion coating, comprising the following steps: Step S1: Weighing the modified graphene anti-corrosion filler and adding it to an active diluent, ultrasonically dispersing for 30 minutes to obtain a filler pre-dispersion liquid; Step S2: Adding the pre-dispersion liquid to an epoxy resin, and using a high-speed disperser for shearing and stirring until the system is uniform and free of particles; Step S3: Adding a curing agent and a defoamer, stirring at low speed until uniform, and then allowing it to stand for curing to obtain the modified heavy-duty anti-corrosion coating. In Step S2, the high-speed disperser operates at 2000 rpm, and the shearing and stirring time is 20 minutes; in Step S3, the standing curing time is 15 minutes.

[0018] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0019] This invention overcomes the limitations of traditional graphene anti-corrosion coatings that rely solely on physical barriers. By growing a porous ZIF-8 metal-organic framework in situ on the graphene surface as a "nanocontainer," an organic corrosion inhibitor (such as BTA) is densely loaded. When the coating is damaged and corrosion occurs, the localized acidic environment (corrosion causing a pH decrease) induces the ZIF-8 framework to disintegrate and the cyclodextrin gate to open, rapidly releasing the corrosion inhibitor. The released inhibitor forms a dense passivation film on the metal substrate surface, blocking corrosion propagation and achieving a leap from "passive defense" to "active repair." Addressing the industry problem of porous carriers leading to premature leakage of the corrosion inhibitor in non-corrosive conditions, this invention innovatively introduces cyclodextrin-grafted polyethyleneimine (PEI-CD) as a shell. Utilizing the host-guest recognition and electrostatic attraction between cyclodextrin and the ZIF-8 pores, a reversible "molecular valve" is formed. Experiments show that this structure can reduce the leakage rate of corrosion inhibitors in non-corrosive states to an extremely low level, ensuring that the coating still has sufficient repair capabilities in the later stages of long-term service and significantly extending its anti-corrosion life. The outer layer of this invention, polyethyleneimine (PEI), is rich in highly active primary and secondary amine groups. During the coating film formation process, these amine groups directly participate in the ring-opening curing reaction of the epoxy resin, "stitching" the nanofiller into the resin cross-linking network. This chemical bonding eliminates microcracks between the filler and the matrix, significantly improving the pull-out adhesion of the coating (experimental data reach over 16.8 MPa), and also improving impact resistance and toughness. This invention utilizes the π-π conjugation effect of tannic acid (TA) to pre-modify graphene, combined with the steric hindrance effect of ZIF-8, effectively preventing the recombination of graphene sheets. In the coating, well-dispersed graphene sheets and ZIF-8 nanocrystals synergistically construct a dense "labyrinth structure," greatly extending the diffusion path of corrosive media such as water molecules and chloride ions. Neutral salt spray tests show that the coating of this invention has a corrosion resistance time exceeding 2000 hours, far superior to conventional modified graphene coatings. The tannic acid and cyclodextrin used in this invention are both biomass-derived, making them green and environmentally friendly. The "in-situ growth-vacuum loading-electrostatic self-assembly" preparation process employed is mild, requiring no high temperature or high pressure, and the reaction process is controllable, making it easy to achieve industrial-scale production. Detailed Implementation

[0020] 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 embodiments. The illustrative embodiments and descriptions of this invention are only used to explain this invention and are not intended to limit this invention.

[0021] Example 1

[0022] A modified heavy-duty anti-corrosion coating containing graphene is prepared from modified graphene anti-corrosion filler, reactive diluent, epoxy resin, curing agent and defoamer.

[0023] The preparation method of the modified graphene anti-corrosion filler is as follows:

[0024] Prepare an ethanol solution of benzotriazole (BTA) with a concentration of 20 mg / mL;

[0025] 0.5 g of the GO-TA@ZIF-8 complex was dispersed in 50 mL of the above BTA solution;

[0026] The mixture was placed in a vacuum drying oven, evacuated to -0.1 MPa and maintained for 30 minutes, then restored to normal pressure. This cycle was repeated three times to force BTA molecules into the pores of ZIF-8 using the pressure difference. 100 mL of PEI-modified CD aqueous solution (concentration 5 mg / mL) was added directly to the above mixture, and the pH was adjusted to 7.5-8.0 with dilute hydrochloric acid. Stirring was continued at room temperature for 4 hours to complete the coating using the electrostatic attraction between PEI-modified CD and the ZIF-8 surface and the host-guest recognition of cyclodextrin. The product was separated by centrifugation, washed once with deionized water, and dried in a vacuum oven at 50 °C for 12 hours to obtain the final modified graphene anticorrosive filler.

[0027] The preparation method of the PEI-modified CD is as follows:

[0028] 5.0 g of β-cyclodextrin (β-CD) was dissolved in 100 mL of 1.0 mol / L sodium hydroxide aqueous solution and cooled to 0-5 °C in an ice-water bath. Under magnetic stirring, 2.0 mL of epichlorohydrin (ECH) was slowly added dropwise as a crosslinking agent. After the addition was complete, the reaction was stirred for 2 hours to activate the β-cyclodextrin. 3.0 g of polyethyleneimine (PEI, weight-average molecular weight Mw = 1800) was added to the above solution, and the reaction system was heated to 60 °C and stirred continuously for 6 hours. After the reaction was completed, the product solution was placed in a dialysis bag (molecular weight cutoff of 1000 Da) and dialyzed in deionized water for 48 hours, with the deionized water being replaced every 8 hours to remove unreacted small molecules. The dialyzed solution was freeze-dried to obtain a pale yellow powder of PEI-modified CD.

[0029] Preparation of the ZIF-8-loaded modified graphene composite:

[0030] 200 mg of graphene oxide (GO) powder was weighed and dispersed in 200 mL of deionized water. The mixture was sonicated for 1 hour (300 W) to obtain a uniform graphene oxide dispersion. 100 mg of tannic acid (TA) was added to the dispersion and the mixture was magnetically stirred at room temperature for 2 hours to utilize the π-π conjugation effect of tannic acid to perform non-covalent surface modification of graphene. 0.6 g of zinc nitrate hexahydrate Zn(NO3)2·6H2O was added to the mixture and stirred for 30 minutes to allow zinc ions to fully chelate at the phenolic hydroxyl sites of tannic acid. A methanol solution (100 mL) containing 1.3 g of 2-methylimidazole was quickly poured in and the mixture was magnetically stirred at room temperature for 12 hours to allow ZIF-8 crystals to nucleate and grow in situ on the surface of graphene oxide. After the reaction, the precipitate was collected by centrifugation (8000 rpm, 5 min), washed three times with methanol, and vacuum dried to obtain the modified graphene composite loaded with ZIF-8 (GO-TA@ZIF-8).

[0031] A method for preparing a graphene-modified heavy-duty anti-corrosion coating:

[0032] Step S1: Weigh 1.0g of the modified graphene anticorrosive filler prepared above, add it to 10g of reactive diluent (butyl glycidyl ether), and ultrasonically disperse for 30 minutes to obtain the filler pre-dispersion liquid;

[0033] Step S2: Add the pre-dispersion liquid to 100g of epoxy resin E51, and use a high-speed disperser to shear and stir at 2000rpm for 20 minutes until the system is uniform and free of particles.

[0034] Step S3: Add 50g of polyamide curing agent (type 650) and 1.0g of defoamer, stir evenly at low speed, and let stand for 15 minutes to mature.

[0035] Example 2

[0036] The difference between this embodiment and Example 1 is that the content of zinc nitrate hexahydrate and the corresponding ligands in the modified graphene composite loaded with ZIF-8 is reduced.

[0037] A modified heavy-duty anti-corrosion coating containing graphene is prepared from modified graphene anti-corrosion filler, reactive diluent, epoxy resin, curing agent and defoamer.

[0038] The preparation method of the modified graphene anti-corrosion filler is as follows:

[0039] Prepare an ethanol solution of benzotriazole (BTA) with a concentration of 20 mg / mL;

[0040] 0.5 g of the GO-TA@ZIF-8 complex was dispersed in 50 mL of the above BTA solution;

[0041] The mixture was placed in a vacuum drying oven, evacuated to -0.1 MPa and maintained for 30 minutes, then restored to normal pressure. This cycle was repeated three times to force BTA molecules into the pores of ZIF-8 using the pressure difference. 100 mL of PEI-modified CD aqueous solution (concentration 5 mg / mL) was added directly to the above mixture, and the pH was adjusted to 7.5-8.0 with dilute hydrochloric acid. Stirring was continued at room temperature for 4 hours to complete the coating using the electrostatic attraction between PEI-modified CD and the ZIF-8 surface and the host-guest recognition of cyclodextrin. The product was separated by centrifugation, washed once with deionized water, and dried in a vacuum oven at 50 °C for 12 hours to obtain the final modified graphene anticorrosive filler.

[0042] The preparation method of the PEI-modified CD is as follows:

[0043] 5.0 g of β-cyclodextrin (β-CD) was dissolved in 100 mL of 1.0 mol / L sodium hydroxide aqueous solution and cooled to 0-5 °C in an ice-water bath. Under magnetic stirring, 2.0 mL of epichlorohydrin (ECH) was slowly added dropwise as a crosslinking agent. After the addition was complete, the reaction was stirred for 2 hours to activate the β-cyclodextrin. 3.0 g of polyethyleneimine (PEI, weight-average molecular weight Mw = 1800) was added to the above solution, and the reaction system was heated to 60 °C and stirred continuously for 6 hours. After the reaction was completed, the product solution was placed in a dialysis bag (molecular weight cutoff of 1000 Da) and dialyzed in deionized water for 48 hours, with the deionized water being replaced every 8 hours to remove unreacted small molecules. The dialyzed solution was freeze-dried to obtain a pale yellow powder of PEI-modified CD.

[0044] Preparation of the ZIF-8-loaded modified graphene composite:

[0045] 200 mg of graphene oxide (GO) powder was weighed and dispersed in 200 mL of deionized water. The mixture was sonicated for 1 hour (300 W) to obtain a uniform graphene oxide dispersion. 100 mg of tannic acid (TA) was added to the dispersion and the mixture was magnetically stirred at room temperature for 2 hours to utilize the π-π conjugation effect of tannic acid to perform non-covalent surface modification of graphene. 0.3 g of zinc nitrate hexahydrate (Zn(NO3)2·6H2O) was added to the mixture and stirred for 30 minutes to allow zinc ions to fully chelate at the phenolic hydroxyl sites of tannic acid. A methanol solution (100 mL) containing 0.65 g of 2-methylimidazole was quickly poured in and the mixture was magnetically stirred at room temperature for 12 hours to allow ZIF-8 crystals to nucleate and grow in situ on the surface of graphene oxide. After the reaction, the precipitate was collected by centrifugation (8000 rpm, 5 min), washed three times with methanol, and vacuum dried to obtain the modified graphene composite loaded with ZIF-8 (GO-TA@ZIF-8).

[0046] A method for preparing a graphene-modified heavy-duty anti-corrosion coating:

[0047] Step S1: Weigh 1.0g of the modified graphene anticorrosive filler prepared above, add it to 10g of reactive diluent (butyl glycidyl ether), and ultrasonically disperse for 30 minutes to obtain the filler pre-dispersion liquid;

[0048] Step S2: Add the pre-dispersion liquid to 100g of epoxy resin E51, and use a high-speed disperser to shear and stir at 2000rpm for 20 minutes until the system is uniform and free of particles.

[0049] Step S3: Add 50g of polyamide curing agent (type 650) and 1.0g of defoamer, stir evenly at low speed, and let stand for 15 minutes to mature.

[0050] Example 3

[0051] The difference between this embodiment and Example 1 is that the content of zinc nitrate hexahydrate and the corresponding ligands in the modified graphene composite loaded with ZIF-8 is increased.

[0052] A modified heavy-duty anti-corrosion coating containing graphene is prepared from modified graphene anti-corrosion filler, reactive diluent, epoxy resin, curing agent and defoamer.

[0053] The preparation method of the modified graphene anti-corrosion filler is as follows:

[0054] Prepare an ethanol solution of benzotriazole (BTA) with a concentration of 20 mg / mL;

[0055] 0.5 g of the GO-TA@ZIF-8 complex was dispersed in 50 mL of the above BTA solution;

[0056] The mixture was placed in a vacuum drying oven, evacuated to -0.1 MPa and maintained for 30 minutes, then restored to normal pressure. This cycle was repeated three times to force BTA molecules into the pores of ZIF-8 using the pressure difference. 100 mL of PEI-modified CD aqueous solution (concentration 5 mg / mL) was added directly to the above mixture, and the pH was adjusted to 7.5-8.0 with dilute hydrochloric acid. Stirring was continued at room temperature for 4 hours to complete the coating using the electrostatic attraction between PEI-modified CD and the ZIF-8 surface and the host-guest recognition of cyclodextrin. The product was separated by centrifugation, washed once with deionized water, and dried in a vacuum oven at 50 °C for 12 hours to obtain the final modified graphene anticorrosive filler.

[0057] The preparation method of the PEI-modified CD is as follows:

[0058] 5.0 g of β-cyclodextrin (β-CD) was dissolved in 100 mL of 1.0 mol / L sodium hydroxide aqueous solution and cooled to 0-5 °C in an ice-water bath. Under magnetic stirring, 2.0 mL of epichlorohydrin (ECH) was slowly added dropwise as a crosslinking agent. After the addition was complete, the reaction was stirred for 2 hours to activate the β-cyclodextrin. 3.0 g of polyethyleneimine (PEI, weight-average molecular weight Mw = 1800) was added to the above solution, and the reaction system was heated to 60 °C and stirred continuously for 6 hours. After the reaction was completed, the product solution was placed in a dialysis bag (molecular weight cutoff of 1000 Da) and dialyzed in deionized water for 48 hours, with the deionized water being replaced every 8 hours to remove unreacted small molecules. The dialyzed solution was freeze-dried to obtain a pale yellow powder of PEI-modified CD.

[0059] Preparation of the ZIF-8-loaded modified graphene composite:

[0060] 200 mg of graphene oxide (GO) powder was weighed and dispersed in 200 mL of deionized water. The mixture was sonicated for 1 hour (300 W) to obtain a uniform graphene oxide dispersion. 100 mg of tannic acid (TA) was added to the dispersion and the mixture was magnetically stirred at room temperature for 2 hours to utilize the π-π conjugation effect of tannic acid to perform non-covalent surface modification of graphene. 1.2 g of zinc nitrate hexahydrate (Zn(NO3)2·6H2O) was added to the mixture and stirred for 30 minutes to allow zinc ions to fully chelate at the phenolic hydroxyl sites of tannic acid. A methanol solution (100 mL) containing 2.6 g of 2-methylimidazole was quickly poured in and the mixture was magnetically stirred at room temperature for 12 hours to allow ZIF-8 crystals to nucleate and grow in situ on the surface of graphene oxide. After the reaction was completed, the precipitate was collected by centrifugation (8000 rpm, 5 min), washed three times with methanol, and vacuum dried to obtain the modified graphene composite loaded with ZIF-8 (GO-TA@ZIF-8).

[0061] A method for preparing a graphene-modified heavy-duty anti-corrosion coating:

[0062] Step S1: Weigh 1.0g of the modified graphene anticorrosive filler prepared above, add it to 10g of reactive diluent (butyl glycidyl ether), and ultrasonically disperse for 30 minutes to obtain the filler pre-dispersion liquid;

[0063] Step S2: Add the pre-dispersion liquid to 100g of epoxy resin E51, and use a high-speed disperser to shear and stir at 2000rpm for 20 minutes until the system is uniform and free of particles.

[0064] Step S3: Add 50g of polyamide curing agent (type 650) and 1.0g of defoamer, stir evenly at low speed, and let stand for 15 minutes to mature.

[0065] Example 4

[0066] The difference between this embodiment and Example 1 is that BTA is replaced with an equal mass of 2-mercaptobenzothiazole (MBT), while the other steps are the same as in Example 1.

[0067] A modified heavy-duty anti-corrosion coating containing graphene is prepared from modified graphene anti-corrosion filler, reactive diluent, epoxy resin, curing agent and defoamer.

[0068] The preparation method of the modified graphene anti-corrosion filler is as follows:

[0069] Prepare a 20 mg / mL 2-mercaptobenzothiazole ethanol solution;

[0070] 0.5 g of the GO-TA@ZIF-8 complex was dispersed in 50 mL of the above 2-mercaptobenzothiazole solution;

[0071] The mixture was placed in a vacuum drying oven, evacuated to -0.1 MPa and maintained for 30 minutes, then restored to normal pressure. This cycle was repeated three times to force 2-mercaptobenzothiazole molecules into the pores of ZIF-8 using the pressure difference. 100 mL of PEI-modified CD aqueous solution (concentration 5 mg / mL) was added directly to the above mixture, and the pH was adjusted to 7.5-8.0 with dilute hydrochloric acid. Stirring was continued at room temperature for 4 hours to complete the coating using the electrostatic attraction between PEI-modified CD and the ZIF-8 surface and the host-guest recognition of cyclodextrin. The product was separated by centrifugation, washed once with deionized water, and dried in a vacuum oven at 50 °C for 12 hours to obtain the final modified graphene anticorrosive filler.

[0072] The preparation method of the PEI-modified CD is as follows:

[0073] 5.0 g of β-cyclodextrin (β-CD) was dissolved in 100 mL of 1.0 mol / L sodium hydroxide aqueous solution and cooled to 0-5 °C in an ice-water bath. Under magnetic stirring, 2.0 mL of epichlorohydrin (ECH) was slowly added dropwise as a crosslinking agent. After the addition was complete, the reaction was stirred for 2 hours to activate the β-cyclodextrin. 3.0 g of polyethyleneimine (PEI, weight-average molecular weight Mw = 1800) was added to the above solution, and the reaction system was heated to 60 °C and stirred continuously for 6 hours. After the reaction was completed, the product solution was placed in a dialysis bag (molecular weight cutoff of 1000 Da) and dialyzed in deionized water for 48 hours, with the deionized water being replaced every 8 hours to remove unreacted small molecules. The dialyzed solution was freeze-dried to obtain a pale yellow powder of PEI-modified CD.

[0074] Preparation of the ZIF-8-loaded modified graphene composite:

[0075] 200 mg of graphene oxide (GO) powder was weighed and dispersed in 200 mL of deionized water. The mixture was sonicated for 1 hour (300 W) to obtain a uniform graphene oxide dispersion. 100 mg of tannic acid (TA) was added to the dispersion and the mixture was magnetically stirred at room temperature for 2 hours to utilize the π-π conjugation effect of tannic acid to perform non-covalent surface modification of graphene. 1.2 g of zinc nitrate hexahydrate (Zn(NO3)2·6H2O) was added to the mixture and stirred for 30 minutes to allow zinc ions to fully chelate at the phenolic hydroxyl sites of tannic acid. A methanol solution (100 mL) containing 2.6 g of 2-methylimidazole was quickly poured in and the mixture was magnetically stirred at room temperature for 12 hours to allow ZIF-8 crystals to nucleate and grow in situ on the surface of graphene oxide. After the reaction was completed, the precipitate was collected by centrifugation (8000 rpm, 5 min), washed three times with methanol, and vacuum dried to obtain the modified graphene composite loaded with ZIF-8 (GO-TA@ZIF-8).

[0076] A method for preparing a graphene-modified heavy-duty anti-corrosion coating:

[0077] Step S1: Weigh 1.0g of the modified graphene anticorrosive filler prepared above, add it to 10g of reactive diluent (butyl glycidyl ether), and ultrasonically disperse for 30 minutes to obtain the filler pre-dispersion liquid;

[0078] Step S2: Add the pre-dispersion liquid to 100g of epoxy resin E51, and use a high-speed disperser to shear and stir at 2000rpm for 20 minutes until the system is uniform and free of particles.

[0079] Step S3: Add 50g of polyamide curing agent (type 650) and 1.0g of defoamer, stir evenly at low speed, and let stand for 15 minutes to mature.

[0080] Example 5

[0081] The difference between this embodiment and Embodiment 1 is that the amount of β-cyclodextrin used is changed; the other steps are the same as in Embodiment 1.

[0082] A modified heavy-duty anti-corrosion coating containing graphene is prepared from modified graphene anti-corrosion filler, reactive diluent, epoxy resin, curing agent and defoamer.

[0083] The preparation method of the modified graphene anti-corrosion filler is as follows:

[0084] Prepare an ethanol solution of benzotriazole (BTA) with a concentration of 20 mg / mL;

[0085] 0.5 g of the GO-TA@ZIF-8 complex was dispersed in 50 mL of the above BTA solution;

[0086] The mixture was placed in a vacuum drying oven, evacuated to -0.1 MPa and maintained for 30 minutes, then restored to normal pressure. This cycle was repeated three times to force BTA molecules into the pores of ZIF-8 using the pressure difference. 100 mL of PEI-modified CD aqueous solution (concentration 5 mg / mL) was added directly to the above mixture, and the pH was adjusted to 7.5-8.0 with dilute hydrochloric acid. Stirring was continued at room temperature for 4 hours to complete the coating using the electrostatic attraction between PEI-modified CD and the ZIF-8 surface and the host-guest recognition of cyclodextrin. The product was separated by centrifugation, washed once with deionized water, and dried in a vacuum oven at 50 °C for 12 hours to obtain the final modified graphene anticorrosive filler.

[0087] The preparation method of the PEI-modified CD is as follows:

[0088] 8.0 g of β-cyclodextrin (β-CD) was dissolved in 100 mL of 1.0 mol / L sodium hydroxide aqueous solution and cooled to 0-5 °C in an ice-water bath. Under magnetic stirring, 2.0 mL of epichlorohydrin (ECH) was slowly added dropwise as a crosslinking agent. After the addition was complete, the reaction was stirred for 2 hours to activate the β-cyclodextrin. 3.0 g of polyethyleneimine (PEI, weight-average molecular weight Mw = 1800) was added to the above solution, and the reaction system was heated to 60 °C and stirred continuously for 6 hours. After the reaction was completed, the product solution was placed in a dialysis bag (molecular weight cutoff of 1000 Da) and dialyzed in deionized water for 48 hours, with the deionized water being replaced every 8 hours to remove unreacted small molecules. The dialyzed solution was freeze-dried to obtain a pale yellow powder of PEI-modified CD.

[0089] Preparation of the ZIF-8-loaded modified graphene composite:

[0090] 200 mg of graphene oxide (GO) powder was weighed and dispersed in 200 mL of deionized water. The mixture was sonicated for 1 hour (300 W) to obtain a uniform graphene oxide dispersion. 100 mg of tannic acid (TA) was added to the dispersion and the mixture was magnetically stirred at room temperature for 2 hours to utilize the π-π conjugation effect of tannic acid to perform non-covalent surface modification of graphene. 0.6 g of zinc nitrate hexahydrate (Zn(NO3)2·6H2O) was added to the mixture and stirred for 30 minutes to allow zinc ions to fully chelate at the phenolic hydroxyl sites of tannic acid. A methanol solution (100 mL) containing 1.3 g of 2-methylimidazole was quickly poured in and the mixture was magnetically stirred at room temperature for 12 hours to allow ZIF-8 crystals to nucleate and grow in situ on the surface of graphene oxide. After the reaction, the precipitate was collected by centrifugation (8000 rpm, 5 min), washed three times with methanol, and vacuum dried to obtain the modified graphene composite loaded with ZIF-8 (GO-TA@ZIF-8).

[0091] A method for preparing a graphene-modified heavy-duty anti-corrosion coating:

[0092] Step S1: Weigh 1.0g of the modified graphene anticorrosive filler prepared above, add it to 10g of reactive diluent (butyl glycidyl ether), and ultrasonically disperse for 30 minutes to obtain the filler pre-dispersion liquid;

[0093] Step S2: Add the pre-dispersion liquid to 100g of epoxy resin E51, and use a high-speed disperser to shear and stir at 2000rpm for 20 minutes until the system is uniform and free of particles.

[0094] Step S3: Add 50g of polyamide curing agent (type 650) and 1.0g of defoamer, stir evenly at low speed, and let stand for 15 minutes to mature.

[0095] Comparative Example 1

[0096] The difference between Comparative Example 1 and Example 1 is that PEI modification of CD is not used for coating.

[0097] A modified heavy-duty anti-corrosion coating containing graphene is prepared from modified graphene anti-corrosion filler, reactive diluent, epoxy resin, curing agent and defoamer.

[0098] The preparation method of the modified graphene anti-corrosion filler is as follows:

[0099] Prepare an ethanol solution of benzotriazole (BTA) with a concentration of 20 mg / mL;

[0100] 0.5 g of the GO-TA@ZIF-8 complex was dispersed in 50 mL of the above BTA solution;

[0101] The mixture was placed in a vacuum drying oven, evacuated to -0.1 MPa and maintained for 30 minutes, and then restored to normal pressure. This cycle was repeated 3 times to force BTA molecules into the pores of ZIF-8 using the pressure difference. The product was separated by centrifugation, washed once with deionized water, and dried in a vacuum oven at 50°C for 12 hours to obtain the final modified graphene anticorrosive filler.

[0102] Preparation of the ZIF-8-loaded modified graphene composite:

[0103] 200 mg of graphene oxide (GO) powder was weighed and dispersed in 200 mL of deionized water. The mixture was sonicated for 1 hour (300 W) to obtain a uniform graphene oxide dispersion. 100 mg of tannic acid (TA) was added to the dispersion and the mixture was magnetically stirred at room temperature for 2 hours to utilize the π-π conjugation effect of tannic acid to perform non-covalent surface modification of graphene. 0.6 g of zinc nitrate hexahydrate (Zn(NO3)2·6H2O) was added to the mixture and stirred for 30 minutes to allow zinc ions to fully chelate at the phenolic hydroxyl sites of tannic acid. A methanol solution (100 mL) containing 1.3 g of 2-methylimidazole was quickly poured in and the mixture was magnetically stirred at room temperature for 12 hours to allow ZIF-8 crystals to nucleate and grow in situ on the surface of graphene oxide. After the reaction, the precipitate was collected by centrifugation (8000 rpm, 5 min), washed three times with methanol, and vacuum dried to obtain the modified graphene composite loaded with ZIF-8 (GO-TA@ZIF-8).

[0104] A method for preparing a graphene-modified heavy-duty anti-corrosion coating:

[0105] Step S1: Weigh 1.0g of the modified graphene anticorrosive filler prepared above, add it to 10g of reactive diluent (butyl glycidyl ether), and ultrasonically disperse for 30 minutes to obtain the filler pre-dispersion liquid;

[0106] Step S2: Add the pre-dispersion liquid to 100g of epoxy resin E51, and use a high-speed disperser to shear and stir at 2000rpm for 20 minutes until the system is uniform and free of particles.

[0107] Step S3: Add 50g of polyamide curing agent (type 650) and 1.0g of defoamer, stir evenly at low speed, and let stand for 15 minutes to mature.

[0108] Comparative Example 2

[0109] The difference between this comparative example and Example 1 is that ZIF-8 is not used; instead, BTA and GO-TA are directly mixed and then PEI-CD is added for coating.

[0110] A modified heavy-duty anti-corrosion coating containing graphene is prepared from modified graphene anti-corrosion filler, reactive diluent, epoxy resin, curing agent and defoamer.

[0111] The preparation method of the modified graphene anti-corrosion filler is as follows:

[0112] Prepare an ethanol solution of benzotriazole (BTA) with a concentration of 20 mg / mL;

[0113] Disperse 0.5 g GO-TA in 50 mL of the above BTA solution;

[0114] Add 100 mL of PEI-modified CD aqueous solution (concentration of 5 mg / mL) directly to the above mixture, and adjust the pH value to 7.5-8.0 with dilute hydrochloric acid; continue stirring at room temperature for 4 hours; centrifuge to separate the product, wash once with deionized water, and dry in a vacuum oven at 50℃ for 12 hours to obtain the final modified graphene anticorrosive filler.

[0115] The preparation method of the PEI-modified CD is as follows:

[0116] 5.0 g of β-cyclodextrin (β-CD) was dissolved in 100 mL of 1.0 mol / L sodium hydroxide aqueous solution and cooled to 0-5 °C in an ice-water bath. Under magnetic stirring, 2.0 mL of epichlorohydrin (ECH) was slowly added dropwise as a crosslinking agent. After the addition was complete, the reaction was stirred for 2 hours to activate the β-cyclodextrin. 3.0 g of polyethyleneimine (PEI, weight-average molecular weight Mw = 1800) was added to the above solution, and the reaction system was heated to 60 °C and stirred continuously for 6 hours. After the reaction was completed, the product solution was placed in a dialysis bag (molecular weight cutoff of 1000 Da) and dialyzed in deionized water for 48 hours, with the deionized water being replaced every 8 hours to remove unreacted small molecules. The dialyzed solution was freeze-dried to obtain a pale yellow powder of PEI-modified CD.

[0117] Preparation of the modified graphene composite:

[0118] Weigh 200 mg of graphene oxide (GO) powder and disperse it in 200 mL of deionized water. Sonicate the mixture for 1 hour (300 W) to obtain a uniform graphene oxide dispersion. Add 100 mg of tannic acid (TA) to the dispersion and stir magnetically at room temperature for 2 hours to perform non-covalent surface modification of graphene using the π-π conjugation effect of tannic acid. After the reaction is complete, centrifuge to collect the precipitate (8000 rpm, 5 min), wash it three times with methanol, and vacuum dry it to obtain GO-TA.

[0119] A method for preparing a graphene-modified heavy-duty anti-corrosion coating:

[0120] Step S1: Weigh 1.0g of the modified graphene anticorrosive filler prepared above, add it to 10g of reactive diluent (butyl glycidyl ether), and ultrasonically disperse for 30 minutes to obtain the filler pre-dispersion liquid;

[0121] Step S2: Add the pre-dispersion liquid to 100g of epoxy resin E51, and use a high-speed disperser to shear and stir at 2000rpm for 20 minutes until the system is uniform and free of particles.

[0122] Step S3: Add 50g of polyamide curing agent (type 650) and 1.0g of defoamer, stir evenly at low speed, and let stand for 15 minutes to mature.

[0123] Comparative Example 3

[0124] A modified heavy-duty anti-corrosion coating containing graphene is prepared from modified graphene anti-corrosion filler, reactive diluent, epoxy resin, curing agent and defoamer.

[0125] The modified graphene anticorrosive filler is prepared by mechanically mixing 200 mg of graphene oxide, 400 mg of commercial ZIF-8 nanoparticle powder (average particle size 100 nm), 100 mg of benzotriazole (BTA) powder, 100 mg of tannic acid, 100 mg of polyethyleneimine, and 150 mg of β-cyclodextrin to obtain the modified graphene anticorrosive filler.

[0126] A method for preparing a graphene-modified heavy-duty anti-corrosion coating:

[0127] Step S1: Weigh 1.0g of the modified graphene anticorrosive filler prepared above, add it to 10g of reactive diluent (butyl glycidyl ether), and ultrasonically disperse for 30 minutes to obtain the filler pre-dispersion liquid;

[0128] Step S2: Add the pre-dispersion liquid to 100g of epoxy resin E51, and use a high-speed disperser to shear and stir at 2000rpm for 20 minutes until the system is uniform and free of particles.

[0129] Step S3: Add 50g of polyamide curing agent (type 650) and 1.0g of defoamer, stir evenly at low speed, and let stand for 15 minutes to mature.

[0130] Test Example 1

[0131] To verify the performance of the anti-corrosion coating described in this invention, we used the air spraying method to apply the coatings prepared in Examples 1-5 and Comparative Examples 1-3 to the surface of Q235 carbon steel samples that had undergone sandblasting and rust removal. The samples were allowed to surface dry at room temperature for 24 hours, then placed in a 60°C oven for complete curing for 2 hours before testing. Each example and comparative example was tested three times.

[0132] The test standards included: adhesion: GB / T5210-2006 "Paints and Varnishes - Pull-off Adhesion Test"; and neutral salt spray resistance: GB / T1771-2007 "Determination of Neutral Salt Spray Resistance of Paints and Varnishes". The results are shown in Table 1.

[0133] Table 1 Performance Tests.

[0134]

[0135] The test results in Table 1 show that the intelligent self-healing coating prepared in this invention outperforms the comparative examples in all aspects. Its neutral salt spray resistance life exceeds 1850 hours (up to 2400 hours), and its pull-out adhesion is consistently above 16.2 MPa. In contrast, the comparative examples (lacking a complete core-shell structure or using physical blending) have a salt spray resistance life of only 600-1300 hours, and their adhesion is significantly reduced (down to a minimum of 8.5 MPa). This fully demonstrates that the synergistic system constructed by in-situ growth of ZIF-8 and PEI-CD gated coating in this invention can significantly improve the long-term corrosion protection and interfacial bonding performance of the coating. Example 2 (reduced zinc source): Although the performance decreased slightly (1850h / 16.2MPa), it still far exceeded the comparative examples, indicating that the low-cost formulation remains effective. Example 4 (corrosion inhibitor replaced with MBT): 2150h / 16.5MPa, proving the universality of different corrosion inhibitors. Comparative Example 1: Salt spray resistance life shortened to 1300h. This indicates that the corrosion inhibitor was lost prematurely, reducing long-term protection capabilities. Comparative Example 2 (without ZIF-8 structure): Salt spray lifespan was only 1100 h. This indicates that the lack of a MOF porous carrier resulted in insufficient corrosion inhibitor loading and uncontrolled release. Comparative Example 3 (worst performance): Salt spray lifespan was only 600 h, and adhesion dropped to 8.5 MPa. Based on the data characteristics, this group corresponds to the "physical blending" scheme described in the article, confirming that simple mixing without chemical bonding and micro-assembly severely damages coating performance.

Claims

1. A modified heavy-duty anticorrosive coating containing graphene, characterized by, The coating includes modified graphene anticorrosive filler, active diluent, epoxy resin, curing agent and defoaming agent; wherein the modified graphene anticorrosive filler is prepared by the following steps: step (1): preparing modified graphene composite loaded with ZIF-8: using tannic acid to modify the surface of graphene oxide, then adding zinc source and organic ligand to make ZIF-8 crystals grow in situ on the surface of graphene oxide; step (2): preparing polyethyleneimine modified cyclodextrin: using epichlorohydrin as a crosslinking agent, grafting polyethyleneimine onto beta-cyclodextrin; step (3): inhibitor loading and coating: dispersing the GO-TA@ZIF-8 composite prepared in step (1) in an organic inhibitor solution, using vacuum negative pressure to force the inhibitor molecules into the ZIF-8 channels; then adding the PEI modified CD aqueous solution prepared in step (2), adjusting the pH value, stirring, and obtaining the modified graphene anticorrosive filler after separation and drying. The raw material components of the coating include, by weight: modified graphene anticorrosive filler 1.0 part, active diluent 10 parts, epoxy resin 100 parts, curing agent 50 parts, and defoaming agent 1.0 part; the active diluent is butyl glycidyl ether, the epoxy resin is E51 epoxy resin, and the curing agent is 650 type polyamide curing agent. The specific preparation method of PEI modified CD in step (2) is: dissolving beta-cyclodextrin in sodium hydroxide aqueous solution, adding epichlorohydrin dropwise at 0-5℃, adding polyethyleneimine after reaction activation, heating to 60℃ for reaction, removing small molecules by dialysis after reaction is completed, and freeze-drying to obtain; wherein the weight average molecular weight Mw of polyethyleneimine is 1800, and the molecular weight cut-off of the dialysis bag is 1000 Da. The specific preparation method of the modified graphene composite loaded with ZIF-8 in step (1) is: mixing and stirring the graphene oxide dispersion liquid with tannic acid to modify by π-π conjugation; then adding zinc nitrate hexahydrate and stirring to chelate zinc ions; then adding 2-methyl imidazole solution and stirring at room temperature; centrifuging, washing and drying; wherein the mass ratio of graphene oxide, tannic acid, zinc nitrate hexahydrate and 2-methyl imidazole is 200:100:(300-1200):(650-2600).

2. The modified heavy-duty anticorrosive coating containing graphene according to claim 1, characterized in that, The amount of zinc nitrate hexahydrate is 0.3g to 1.2g, and the amount of 2-methyl imidazole is 0.65g to 2.6g, which corresponds to adjusting the loading density of ZIF-8 crystals on the surface of graphene.

3. The modified heavy-duty anticorrosive coating containing graphene according to claim 1, characterized in that, The organic corrosion inhibitor in step (3) is benzotriazole or 2-mercaptobenzothiazole; the specific process of vacuum negative pressure operation is: vacuumizing to-0.1MPa and maintaining for 30 minutes, then restoring normal pressure, and repeating the operation for 3 times.

4. The modified heavy-duty anticorrosive coating containing graphene according to claim 1, characterized in that, The pH value in step (3) is adjusted to a range of 7.5-8.0; the concentration of the PEI modified CD aqueous solution is 5mg / mL; the stirring time of the coating reaction is 4 hours, and the drying condition is vacuum drying at 50℃ for 12 hours.

5. A method for preparing a modified heavy-duty anticorrosive paint containing graphene according to any one of claims 1 to 4, characterized in that, The method comprises the following steps: step S1: weighing modified graphene anticorrosive filler and adding into active diluent, ultrasonic dispersion for 30 minutes to prepare filler pre-dispersion liquid; step S2: adding the pre-dispersion liquid into epoxy resin, using a high-speed dispersion machine for shearing stirring until the system is uniform and no particles; step S3: adding curing agent and defoaming agent, uniformly stirring at low speed and then standing and curing to obtain the modified heavy-duty anticorrosive coating.

6. The production method according to claim 5, wherein The rotating speed of the high-speed dispersion machine in step S2 is 2000 rpm, and the shearing stirring time is 20 minutes; the standing and curing time in step S3 is 15 minutes.

7. Application of the modified heavy-duty anticorrosive coating containing graphene in the field of high-salt, high-humidity, difficult-to-maintain and long-life anticorrosive coating as claimed in any one of claims 1-4.

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