An epoxy zinc-rich primer containing modified graphene and a preparation method thereof

Abstract

The application discloses a modified graphene-containing epoxy zinc-rich primer and a preparation method thereof, and belongs to the technical field of anticorrosive paint. First, graphene oxide is carboxylated on the surface, and then is modified by magnesium and cerium ions to obtain modified graphene oxide. Then, phenyl Janus-SiO2 particles are synthesized and loaded with benzotriazole corrosion inhibitor to obtain corrosion-inhibiting Janus composite particles. Finally, xylene, epoxy resin, zinc powder, dispersant, defoaming agent, heavy calcium carbonate and mica powder are step-by-step stirred to obtain component A. Epoxy curing agent, xylene, carboxylated composite powder, corrosion-inhibiting Janus composite particles and dispersant are ultrasonically prepared to obtain component B. Finally, the components A and B are uniformly mixed to obtain the modified graphene-containing epoxy zinc-rich primer. The primer realizes breakthrough in comprehensive performance in adhesion, long-acting corrosion resistance and cathodic disbonding resistance.

Description

Technical Field

[0001] This invention belongs to the field of anti-corrosion coating technology, specifically relating to an epoxy zinc-rich primer containing modified graphene and its preparation method. Background Technology

[0002] Epoxy zinc-rich primer is a core material in the field of industrial metal corrosion protection. It is made of epoxy resin as film-forming base material, 60%-80% high proportion of zinc powder as rust prevention core, and polyamide curing agent, toughening agent, diluent and other additives. It builds a long-term anti-corrosion barrier for steel and other metal substrates through the dual mechanism of "physical shielding + sacrificial anode cathodic protection". It is the basic layer of the anti-corrosion system in bridges, marine engineering, chemical equipment, steel structures and other scenarios.

[0003] In high humidity / salt environments (ocean, chemical plants), zinc salt rust and paint film blistering are easily caused by accelerated zinc oxidation due to chloride ions. Low temperature and high humidity construction can lead to incomplete curing due to inhibited reaction and moisture mixing. Substandard substrate treatment can cause paint film peeling due to hindered bonding. Improper topcoat matching can cause interlayer delamination due to acid and alkali reactions. With the upgrading of anti-corrosion requirements in extreme environments, the industry has tried to add graphene to strengthen physical shielding, optimize electrochemical protection, improve mechanical properties and extend life. However, direct addition can lead to agglomeration due to van der Waals forces, poor compatibility due to hydrophobic inertness, and interference of the reaction due to high specific surface area adsorption of curing agents. There is also a contradiction between high cost and difficulty in process adaptation.

[0004] Chinese invention patent application CN111777918A discloses a graphene film for improving the salt spray resistance of epoxy zinc-rich primer, its preparation and application. By utilizing the compatibility difference between graphene and epoxy resin matrix, graphene can achieve a highly oriented arrangement in the coating, thereby forming a "conductive bridge" with zinc powder. The layered structure generates a "maze effect", which prolongs the diffusion path of corrosive media, strengthens the cathodic protection effect of zinc powder, and ultimately significantly improves the salt spray resistance of the paint film.

[0005] To avoid damaging the graphene structure, physical blending and directional arrangement are used. However, it is difficult to ensure the uniform orientation of graphene in actual construction. Furthermore, unmodified graphene is still prone to agglomeration in the resin, affecting the continuity of the conductive network and causing the synergistic anti-corrosion system composed of graphene and zinc powder to almost fail. Summary of the Invention

[0006] The purpose of this invention is to provide an epoxy zinc-rich primer containing modified graphene and its preparation method. First, graphene oxide is modified by carboxylation, and then magnesium ion intercalation and cerium compound modification are used to obtain synergistic barrier and corrosion inhibition functions. Then, phenyl Janus-SiO2 particles loaded with benzotriazole corrosion inhibitor are prepared to synergistically achieve a breakthrough in the comprehensive performance of the primer in terms of adhesion, long-term corrosion protection and resistance to cathodic disbondment.

[0007] The objective of this invention can be achieved through the following technical solutions:

[0008] A method for preparing an epoxy zinc-rich primer containing modified graphene includes the following steps:

[0009] Step 1: Graft carboxyl groups onto the surface of graphene oxide, and then use a hydrothermal method to perform composite modification with magnesium and cerium ions to obtain modified graphene oxide.

[0010] Step 2: Phenyl Janus-SiO2 particles were synthesized by emulsion interface method and loaded with benzotriazole corrosion inhibitor to obtain corrosion-inhibited Janus composite particles.

[0011] Step 3: Xylene, epoxy resin, zinc powder, dispersant, defoamer, heavy calcium carbonate and mica powder are stirred in steps to obtain component A. Epoxy curing agent, xylene, carboxylated composite powder, corrosion-inhibiting Janus composite particles and dispersant are ultrasonically mixed to form component B. Components A and B are mixed evenly to obtain epoxy zinc-rich primer containing modified graphene.

[0012] Furthermore, the specific preparation steps for modified graphene oxide are as follows:

[0013] Carboxylated graphene oxide powder was added to a 0.2 mol / L magnesium nitrate solution, sonicated for 60-80 min with constant stirring, and then sonicated for 15-30 min using the sonication function of a cell disruptor to obtain a mixed dispersion.

[0014] Add cerium nitrate hexahydrate to the dispersion, stir for 10-20 min, transfer to a three-necked flask, stir magnetically, heat to 90-100℃ under nitrogen protection, reflux for 1-2 h, filter, wash the filter cake with deionized water until the filtrate is neutral, vacuum dry to constant weight, grind, and pass through a 200-mesh sieve to obtain modified graphene oxide composite powder.

[0015] Furthermore, the ratio of carboxylated graphene oxide powder to 0.2 mol / L magnesium nitrate solution is 1 g: 1 L.

[0016] Furthermore, the ratio of the dispersion to cerium nitrate hexahydrate is 500-800 mL: 43.4-50.2 g.

[0017] Furthermore, the specific preparation steps for carboxylated graphene oxide powder are as follows:

[0018] Add the graphene oxide composite powder to deionized water, sonicate for 1-2 hours, transfer to an ice-water bath, slowly add sodium hydroxide and chloroacetic acid under continuous magnetic stirring, sonicate for 2-3 hours, centrifuge and wash with 1 mol / L dilute hydrochloric acid until the filtrate is neutral, freeze dry to constant weight to obtain carboxylated graphene oxide powder.

[0019] Furthermore, the ratio of graphene oxide composite powder, deionized water, sodium hydroxide, and chloroacetic acid is 1-3g: 1-3L: 50-80g: 10-15g.

[0020] Furthermore, the specific preparation steps for phenyl Janus-SiO2 particles are as follows:

[0021] Hexadecyltrimethylammonium bromide was dissolved in deionized water, and ammonia was added dropwise to adjust the pH of the solution to 10, which served as the aqueous phase; tetraethyl orthosilicate, 3-aminopropyltrimethoxysilane, phenyltrimethoxysilane and toluene were mixed evenly, which served as the oil phase;

[0022] The aqueous and oil phases were mixed and sheared and emulsified at 10,000-12,000 rpm for 5-10 min using a high-speed shear emulsifier. The mixture was then transferred to a three-necked flask and reacted at a stirring rate of 450-600 rpm for 12-15 h in a water bath at 70-80 °C. After filtration, the product was washed three times each with anhydrous ethanol and deionized water, freeze-dried to constant weight, and ground to obtain phenyl Janus-SiO2 particles with an average particle size of 5 μm.

[0023] Furthermore, the ratio of hexadecyltrimethylammonium bromide to deionized water is 1-3g: 200-500mL.

[0024] Furthermore, the mass ratio of tetraethyl orthosilicate, 3-aminopropyltrimethoxysilane, phenyltrimethoxysilane, and toluene is 4-6:1.6-2.2:0.8-1.2:80-100.

[0025] Furthermore, the volume ratio of the aqueous phase to the oil phase is 200-500: 98.5-124.6.

[0026] Furthermore, the specific preparation steps for the corrosion-inhibiting Janus composite particles are as follows:

[0027] Phenyl Janus-SiO2 particles were added to anhydrous ethanol and stirred for 20-30 min. Benzotriazole was added and stirred until homogeneous. The mixture was then transferred to a three-necked flask and reacted at a stirring rate of 300-500 rpm for 8-10 h in a water bath at 25-30 °C. The mixture was washed 5-8 times with anhydrous ethanol, freeze-dried for 24-36 h, and then ground to obtain corrosion-inhibiting Janus composite particles.

[0028] Furthermore, the ratio of phenyl Janus-SiO2 particles, anhydrous ethanol, and benzotriazole is 2-5g: 60-100mL: 2-5g.

[0029] Furthermore, the specific preparation steps of the epoxy zinc-rich primer containing modified graphene are as follows:

[0030] Component A: Add xylene and epoxy resin to a beaker and stir at low speed until homogeneous. Add zinc powder and stir at 750-850 rpm for 10-20 min. Then add dispersant, defoamer, heavy calcium carbonate and mica powder and stir at 2000-3000 rpm for 15-25 min. Vacuum dry to constant weight and set aside.

[0031] Component B: Mix the epoxy curing agent, xylene, carboxylated composite powder, corrosion-inhibiting Janus composite particles and dispersant and ultrasonically disperse them evenly; add Component A to Component B and stir evenly at 750-800 rpm to obtain an epoxy zinc-rich primer containing modified graphene.

[0032] Furthermore, the mass ratio of xylene, epoxy resin, zinc powder, dispersant, defoamer, heavy calcium carbonate and mica powder is 5-8:8.5-9.8:60-70:0.5-0.8:0.5-0.8:8-10:8-10.

[0033] Furthermore, the mass ratio of epoxy curing agent, xylene, carboxylated composite powder, corrosion-inhibiting Janus composite particles and dispersant is 4.5-6.5: 4-6: 0.3-0.5: 0.2-0.3: 0.1-0.2.

[0034] Furthermore, the mass ratio of component A to component B is 85.5-101.4:9.1-13.5.

[0035] The beneficial effects of this invention are:

[0036] 1. This invention constructs a three-dimensional synergistic protection system of "layered barrier - interface anchoring - intelligent corrosion inhibition" through material selection and multi-level spatial structure design. When corrosive media invade, the modified graphene oxide distributed throughout the coating not only constructs a dense physical barrier network, but the cerium compounds anchored on its surface can also form a Ce(OH)3 / CeO2 passivation film in situ, achieving early inhibition of corrosion initiation points. In conjunction with zinc powder as a sacrificial anode, it continuously provides electrochemical protection. As the corrosion process progresses, the oriented corrosion-inhibiting Janus composite particles intelligently release benzotriazole corrosion inhibitors through a pH response mechanism, forming a molecular protective film and strengthening interface protection. This breaks through the technical limitations of traditional zinc-rich coatings that rely on single cathodic protection, achieving a comprehensive breakthrough in primer adhesion, salt spray resistance, and cathodic disbondment resistance.

[0037] 2. The modified graphene oxide composite powder of this invention constructs a stable nanoscale interlayer spacing through magnesium ion intercalation, enhancing the physical barrier effect of the sheet structure and forcing the corrosive medium to penetrate through a more tortuous and lengthy path. At the same time, with the help of the electrochemical activity of cerium compounds, a self-healing passivation film is formed on the surface of the metal substrate, which produces a synergistic protection mechanism with the cathodic protection effect of zinc powder. Carboxylation treatment provides anchoring sites for the modification reaction and promotes metal ion complexation, further optimizing the modification of magnesium and cerium ions, constructing a uniform and stable conductive network, and ensuring the balanced distribution of cathodic protection current. This fundamentally solves the technical problems of low barrier efficiency and single protection mechanism of traditional zinc-rich coatings.

[0038] 3. The corrosion-inhibiting Janus composite particles in this invention, with their amphiphilic structure, can spontaneously orient themselves at the coating-metal interface, forming a molecular-level "rivet" anchoring effect, enhancing adhesion and constructing a dense interface barrier. The benzotriazole corrosion inhibitor loaded on them can sense changes in the local corrosion microenvironment, achieving pH-responsive intelligent release and targeted repair, forming a protective adsorption film at defect sites, forming a multi-dimensional complementarity with the sheet barrier of modified graphene oxide, jointly constructing a complete corrosion protection network, endowing the coating with long-lasting interface stability and dynamic self-healing ability. Detailed Implementation

[0039] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments in the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0040] Example 1: A method for preparing an epoxy zinc-rich primer containing modified graphene, comprising the following steps:

[0041] S1: Add 1g of graphene oxide composite powder to 1L of deionized water, sonicate for 1h, transfer to an ice-water bath, slowly add 50g of sodium hydroxide and 10g of chloroacetic acid under continuous magnetic stirring, sonicate for 2h, centrifuge and wash with 1mol / L dilute hydrochloric acid until the filtrate is neutral, freeze dry to constant weight to obtain carboxylated graphene oxide powder.

[0042] Under ice-water bath and strong alkaline conditions, the hydroxyl groups on the surface of graphene oxide powder are activated into highly reactive alkoxy anions, which then initiate a nucleophilic substitution reaction with chloroacetic acid molecules, thereby grafting carboxyl functional groups onto the material surface through strong ether bonds.

[0043] S2: Add 1g of carboxylated graphene oxide powder to 1L of 0.2mol / L magnesium nitrate solution, sonicate for 60min with continuous stirring, and then sonicate for 15min using the sonication function of a cell disruptor to obtain a mixed dispersion; add 43.4g of cerium nitrate hexahydrate to 500mL of dispersion, stir for 10min, transfer to a three-necked flask, stir magnetically, heat to 90℃ under nitrogen protection, reflux for 1h, filter, wash the filter cake with deionized water until the filtrate is neutral, vacuum dry to constant weight, grind, and pass through a 200-mesh sieve to obtain modified graphene oxide composite powder.

[0044] Through a one-step hydrothermal method, magnesium ions are first intercalated between graphene oxide sheets by electrostatic adsorption, while cerium ions are anchored on the surface of graphene oxide and hydrolyzed, ultimately yielding magnesium / cerium co-modified graphene oxide composite powder.

[0045] S3: Dissolve 1g of hexadecyltrimethylammonium bromide in 200mL of deionized water, and adjust the pH of the solution to 10 by adding ammonia dropwise, as the aqueous phase; mix 4g of tetraethyl orthosilicate, 1.6g of 3-aminopropyltrimethoxysilane, 0.8g of phenyltrimethoxysilane and 80g of toluene evenly, as the oil phase;

[0046] 200 mL of aqueous phase and 98.5 mL of oil phase were mixed and sheared and emulsified at 10,000 rpm for 5 min using a high-speed shear emulsifier. The mixture was then transferred to a three-necked flask and reacted at 450 rpm for 12 h in a water bath at 70 °C. After filtration, the product was washed three times each with anhydrous ethanol and deionized water, freeze-dried to constant weight, and ground to obtain phenyl Janus-SiO2 particles with an average particle size of 5 μm.

[0047] Using an oil-water emulsion interface as a template, hydrophilic 3-aminopropyltrimethoxysilane and hydrophobic phenyltrimethoxysilane undergo directional self-assembly at the interface under alkaline conditions due to their polarity difference. They then undergo synergistic hydrolysis and condensation with tetraethyl orthosilicate at the interface to form asymmetric amphiphilic silica particles.

[0048] S4: Add 2g of phenyl Janus-SiO2 particles to 60mL of anhydrous ethanol and stir for 20min. Add 2g of benzotriazole and stir until homogeneous. Transfer to a three-necked flask and react at 300rpm for 8h in a water bath at 25℃. Wash 5 times with anhydrous ethanol, freeze dry for 24h, and grind to obtain corrosion-inhibiting Janus composite particles.

[0049] S5: Component A: Add 5g xylene and 8.5g epoxy resin to a beaker, stir at low speed until homogeneous, add 60g zinc powder, stir at 750rpm for 10min, then add 0.5g dispersant, 0.5g defoamer, 8g heavy calcium carbonate and 8g mica powder, stir at 2000rpm for 15min, vacuum dry to constant weight, and set aside.

[0050] Component B: Mix 4.5g epoxy curing agent, 4g xylene, 0.3g carboxylated composite powder, 0.2g corrosion-inhibiting Janus composite particles and 0.1g dispersant and ultrasonically disperse evenly; add 85.5g of component A to 9.1g of component B and stir evenly at 750rpm to obtain epoxy zinc-rich primer containing modified graphene.

[0051] Example 2: A method for preparing an epoxy zinc-rich primer containing modified graphene, comprising the following steps:

[0052] S1: Add 2g of graphene oxide composite powder to 2L of deionized water, sonicate for 1.5h, transfer to an ice-water bath, slowly add 65g of sodium hydroxide and 12.5g of chloroacetic acid under continuous magnetic stirring, sonicate for 2.5h, centrifuge and wash with 1mol / L dilute hydrochloric acid until the filtrate is neutral, freeze dry to constant weight to obtain carboxylated graphene oxide powder.

[0053] S2: Add 2g of carboxylated graphene oxide powder to 2L of 0.2mol / L magnesium nitrate solution, sonicate for 70min with continuous stirring, and then sonicate for 22.5min using the sonication function of a cell disruptor to obtain a mixed dispersion; add 46.8g of cerium nitrate hexahydrate to 650mL of dispersion, stir for 15min, transfer to a three-necked flask, stir magnetically, heat to 95℃ under nitrogen protection, reflux for 1.5h, filter, wash the filter cake with deionized water until the filtrate is neutral, vacuum dry to constant weight, grind, and pass through a 200-mesh sieve to obtain modified graphene oxide composite powder.

[0054] S3: Dissolve 2g of hexadecyltrimethylammonium bromide in 350mL of deionized water, and adjust the pH of the solution to 10 by adding ammonia dropwise, as the aqueous phase; mix 5g of tetraethyl orthosilicate, 1.9g of 3-aminopropyltrimethoxysilane, 1.0g of phenyltrimethoxysilane and 90g of toluene evenly, as the oil phase;

[0055] 350 mL of aqueous phase and 111.6 mL of oil phase were mixed and sheared and emulsified at 11000 rpm for 7.5 min using a high-speed shear emulsifier. The mixture was then transferred to a three-necked flask and reacted at a stirring rate of 525 rpm for 13.5 h in a water bath at 75 °C. After filtration, the product was washed three times each with anhydrous ethanol and deionized water, freeze-dried to constant weight, and ground to obtain phenyl Janus-SiO2 particles with an average particle size of 5 μm.

[0056] S4: Add 3.5g of phenyl Janus-SiO2 particles to 80mL of anhydrous ethanol and stir for 25min. Add 3.5g of benzotriazole and stir until homogeneous. Transfer to a three-necked flask and react at 400rpm for 9h in a water bath at 27.5℃. Wash with anhydrous ethanol 6.5 times, freeze-dry for 30h, and grind to obtain corrosion-inhibiting Janus composite particles.

[0057] S5: Component A: Add 6.5g xylene and 9.15g epoxy resin to a beaker, stir at low speed until homogeneous, add 65g zinc powder, stir at 800rpm for 15min, then add 0.65g dispersant, 0.65g defoamer, 9g heavy calcium carbonate and 9g mica powder, stir at 2500rpm for 20min, vacuum dry to constant weight, and set aside.

[0058] Component B: Mix 5.5g epoxy curing agent, 5g xylene, 0.4g carboxylated composite powder, 0.25g corrosion-inhibiting Janus composite particles and 0.15g dispersant and ultrasonically disperse evenly; add 93.45g of component A to 11.3g of component B and stir evenly at 775rpm to obtain an epoxy zinc-rich primer containing modified graphene.

[0059] Example 3: A method for preparing an epoxy zinc-rich primer containing modified graphene, comprising the following steps:

[0060] S1: Add 3g of graphene oxide composite powder to 3L of deionized water, sonicate for 2h, transfer to an ice-water bath, slowly add 80g of sodium hydroxide and 15g of chloroacetic acid under continuous magnetic stirring, sonicate for 3h, centrifuge and wash with 1mol / L dilute hydrochloric acid until the filtrate is neutral, freeze dry to constant weight to obtain carboxylated graphene oxide powder.

[0061] S2: Add 3g of carboxylated graphene oxide powder to 3L of 0.2mol / L magnesium nitrate solution, sonicate for 80min with continuous stirring, and then sonicate for 30min using the sonication function of a cell disruptor to obtain a mixed dispersion; add 50.2g of cerium nitrate hexahydrate to 800mL of dispersion, stir for 20min, transfer to a three-necked flask, stir magnetically, heat to 100℃ under nitrogen protection, reflux for 2h, filter, wash the filter cake with deionized water until the filtrate is neutral, vacuum dry to constant weight, grind, and pass through a 200-mesh sieve to obtain modified graphene oxide composite powder.

[0062] S3: Dissolve 3g of hexadecyltrimethylammonium bromide in 500mL of deionized water, and add ammonia dropwise to adjust the pH of the solution to 10, as the aqueous phase; mix 6g of tetraethyl orthosilicate, 2.2g of 3-aminopropyltrimethoxysilane, 1.2g of phenyltrimethoxysilane and 100g of toluene evenly, as the oil phase;

[0063] 500 mL of aqueous phase and 124.6 mL of oil phase were mixed and sheared and emulsified at 12000 rpm for 10 min using a high-speed shear emulsifier. The mixture was then transferred to a three-necked flask and reacted at 600 rpm for 15 h in an 80 °C water bath. After filtration, the product was washed three times each with anhydrous ethanol and deionized water, freeze-dried to constant weight, and ground to obtain phenyl Janus-SiO2 particles with an average particle size of 5 μm.

[0064] S4: Add 5g of phenyl Janus-SiO2 particles to 100mL of anhydrous ethanol and stir for 30min. Add 5g of benzotriazole and stir until homogeneous. Transfer to a three-necked flask and react at 500rpm for 10h in a 30℃ water bath. Wash 8 times with anhydrous ethanol, freeze dry for 36h, and grind to obtain corrosion-inhibiting Janus composite particles.

[0065] S5: Component A: Add 8g xylene and 9.8g epoxy resin to a beaker and stir at low speed until homogeneous. Add 70g zinc powder and stir at 850rpm for 20min. Then add 0.8g dispersant, 0.8g defoamer, 10g heavy calcium carbonate and 10g mica powder and stir at 3000rpm for 25min. Vacuum dry to constant weight and set aside.

[0066] Component B: Mix 6.5g epoxy curing agent, 6g xylene, 0.5g carboxylated composite powder, 0.3g corrosion-inhibiting Janus composite particles and 0.2g dispersant and ultrasonically disperse evenly; add 101.4g of component A to 13.5g of component B and stir evenly at 800rpm to obtain an epoxy zinc-rich primer containing modified graphene.

[0067] Example 4: This example provides a method for preparing an epoxy zinc-rich primer containing modified graphene. The difference from Example 1 is that bromoacetic acid is used instead of chloroacetic acid in step S1 to prepare the epoxy zinc-rich primer containing modified graphene.

[0068] Example 5: This example provides a method for preparing an epoxy zinc-rich primer containing modified graphene. The difference from Example 1 is that in step S4, urotropine is used instead of benzotriazole to prepare the epoxy zinc-rich primer containing modified graphene.

[0069] In Examples 1-5, the graphene oxide powder was selected from Zhongke Leiming (Beijing) Technology Co., Ltd., with a sheet diameter of 1-5 μm, a thickness of 0.8-1.2 nm, and approximately 3-4 layers; phenyltrimethoxysilane was selected from Yunsheng Chemical (Shandong) Co., Ltd., brand name Yunsheng Chemical, model number 201; dispersant was selected from Dongguan Ruikun Materials Technology Co., Ltd., brand name Tianderun, model number 4117; defoamer was selected from Hubei Maidehao Biotechnology Co., Ltd., brand name Maidehao, model number MDH; epoxy curing agent was selected from Shandong Luxing Chemical Co., Ltd., brand name Luxing Chemical, product name curing agent T31; heavy calcium carbonate was selected from Jiangxi Chenxin New Materials Co., Ltd., with a particle size of 1250 mesh; mica powder was selected from Lingshou Yongqi Mineral Products Co., Ltd., brand name Baofeng; zinc powder was selected from Shijiazhuang Xinri Zinc Industry Co., Ltd., with an average particle size of 5-7 μm; the remaining raw materials were commercially available products.

[0070] Comparative Example 1: The difference from Example 1 is that step S1 is omitted, and in step S2, graphene oxide powder is used instead of carboxylated graphene oxide powder. The remaining steps remain unchanged, and an epoxy zinc-rich primer containing modified graphene is prepared.

[0071] Comparative Example 2: The difference from Example 1 is that step S2 is omitted, and in step S5, carboxylated graphene oxide powder is used instead of modified graphene oxide composite powder. The remaining steps remain unchanged, and an epoxy zinc-rich primer containing modified graphene is prepared.

[0072] Comparative Example 3: The difference from Example 1 is that step S3 is omitted, and in step S4, conventional symmetrical SiO2 particles are used instead of phenyl Janus-SiO2 particles. The remaining steps remain unchanged, and an epoxy zinc-rich primer containing modified graphene is prepared.

[0073] The following performance tests were conducted on the modified graphene-containing zinc-rich epoxy primers prepared in Examples 1-5 and Comparative Examples 1-3:

[0074] Adhesion: The test is conducted in accordance with GB / T9286-2021 "Paints and Varnishes Cross-cut Test". The blade spacing is selected according to the film thickness (usually 1 mm for thickness <60μm, and 2 mm for thickness 60μm-120μm). The adhesion grade is divided into 0-5 levels. The lower the grade, the better the adhesion.

[0075] Salt spray resistance time: The test was conducted in accordance with GB / T1771-2007 "Determination of resistance to neutral salt spray of paints and varnishes". The standard was that the paint film did not bubble, rust, crack, or peel off. The time that the paint film could maintain its resistance to blistering, rust, cracking, and peeling was recorded.

[0076] Cathodic disbondment resistance: The test was conducted in accordance with GB / T7790-2023 "Determination of cathodic disbondment resistance of coatings of paints and varnishes exposed to seawater". The maximum and minimum disbondment distance (mm) from the edge of the defect to the still firmly attached paint film was measured and recorded. The average disbondment radius or disbondment area was calculated. The smaller the disbondment distance, the better the cathodic disbondment resistance of the coating.

[0077] The results are shown in Table 1:

[0078] Table 1. Performance test results of epoxy zinc-rich primer containing modified graphene

[0079]

[0080] As can be seen from Table 1, the epoxy zinc-rich primers containing modified graphene prepared in Examples 1-5 are significantly better than those in Comparative Examples 1-3. The modified graphene oxide uses carboxylated graphene oxide as a substrate, and magnesium ion intercalation and cerium-based compounds form synergistic modification. Then, phenyl Janus-SiO2 particles loaded with benzotriazole corrosion inhibitor are prepared, which synergistically achieves a breakthrough in the comprehensive performance of the primer in terms of adhesion, long-term corrosion protection and resistance to cathodic disbondment.

[0081] The severe degradation in adhesion, salt spray resistance, and cathodic stripping resistance in Comparative Example 1 may be due to the lack of carboxylation modification. The uncarboxylated graphene oxide surface lacks uniformly distributed carboxyl anchoring sites, which prevents magnesium ions from achieving effective intercalation and makes it difficult for cerium ions to be stably loaded and subsequently hydrolyzed. This ultimately results in a defective composite material with a loose modified layer and weak bonding force. As a result, the material cannot provide effective active corrosion inhibition through cerium compounds, nor can it build a dense sheet barrier network. Furthermore, it becomes a weak link at the interface when combined with epoxy resin, ultimately leading to a complete loss of the coating's barrier function, electrochemical protection capability, and interface stability.

[0082] The degradation in adhesion, salt spray resistance, and cathodic disbondment resistance in Comparative Example 2 may be due to the lack of magnesium / cerium synergistic modification. The absence of magnesium ion intercalation prevents the graphene oxide sheets from being fully expanded, weakening their physical barrier ability to construct the "maze effect," making it easier for corrosive media to penetrate. The lack of cerium-based compounds causes the coating to lose the active corrosion inhibition function unique to cerium ions, making it unable to form an effective passivation film on the surface of the metal substrate, and also unable to produce a synergistic electrochemical protective effect with zinc powder.

[0083] In Comparative Example 3, the adhesion, salt spray resistance, and cathodic disbondment resistance were significantly deteriorated. This may be because traditional symmetrical SiO2 particles were used instead of phenyl Janus-SiO2 particles with an asymmetric structure. The traditional symmetrical SiO2 particles are randomly distributed in the coating, which directly leads to a decrease in adhesion. The symmetrical particles lack the amphiphilic asymmetric structure, which limits their loading and controlled release capacity for the corrosion inhibitor (benzotriazole). They cannot trigger the intelligent release of the corrosion inhibitor through pH changes when corrosion occurs, causing the coating to lose its key "active repair" function and significantly reduce its salt spray resistance.

[0084] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for preparing an epoxy zinc-rich primer containing modified graphene, characterized in that, Includes the following steps: Step 1: Graft carboxyl groups onto the surface of graphene oxide. Add carboxylated graphene oxide powder to a 0.2 mol / L magnesium nitrate solution, sonicate for 60-80 min with constant stirring, and then sonicate for 15-30 min using the sonication function of a cell disruptor to obtain a mixed dispersion. Add cerium nitrate hexahydrate to the dispersion, stir for 10-20 min, transfer to a three-necked flask, stir magnetically, heat to 90-100℃ under nitrogen protection, reflux for 1-2 h, filter, wash the filter cake with deionized water until the filtrate is neutral, vacuum dry to constant weight, grind, and pass through a 200-mesh sieve to obtain modified graphene oxide composite powder. Step 2: Phenyl Janus-SiO2 particles were synthesized by emulsion interface method and loaded with benzotriazole corrosion inhibitor to obtain corrosion-inhibited Janus composite particles; Step 3: Xylene, epoxy resin, zinc powder, dispersant, defoamer, heavy calcium carbonate and mica powder are stirred in steps to obtain component A. Epoxy curing agent, xylene, modified graphene oxide composite powder, corrosion-inhibiting Janus composite particles and dispersant are ultrasonically mixed to form component B. Components A and B are mixed evenly to obtain epoxy zinc-rich primer containing modified graphene.

2. The method for preparing a modified graphene-containing epoxy zinc-rich primer according to claim 1, characterized in that, The ratio of the carboxylated graphene oxide powder to the 0.2 mol / L magnesium nitrate solution is 1 g: 1 L; The ratio of the dispersion to cerium nitrate hexahydrate is 500-800 mL: 43.4-50.2 g.

3. The method for preparing a modified graphene-containing epoxy zinc-rich primer according to claim 1, characterized in that, The specific preparation steps for the carboxylated graphene oxide powder are as follows: Add graphene oxide powder to deionized water, sonicate for 1-2 hours, transfer to an ice-water bath, slowly add sodium hydroxide and chloroacetic acid under continuous magnetic stirring, sonicate for 2-3 hours, centrifuge and wash with 1 mol / L dilute hydrochloric acid until the filtrate is neutral, freeze dry to constant weight to obtain carboxylated graphene oxide powder.

4. The method for preparing a modified graphene-containing epoxy zinc-rich primer according to claim 3, characterized in that, The ratio of graphene oxide powder, deionized water, sodium hydroxide, and chloroacetic acid is 1-3g: 1-3L: 50-80g: 10-15g.

5. The method for preparing a modified graphene-containing epoxy zinc-rich primer according to claim 1, characterized in that, The specific preparation steps for the phenyl Janus-SiO2 particles are as follows: Hexadecyltrimethylammonium bromide was dissolved in deionized water, and ammonia was added dropwise to adjust the pH of the solution to 10, which served as the aqueous phase; tetraethyl orthosilicate, 3-aminopropyltrimethoxysilane, phenyltrimethoxysilane and toluene were mixed evenly, which served as the oil phase; The aqueous and oil phases were mixed and sheared and emulsified at 10,000-12,000 rpm for 5-10 min using a high-speed shear emulsifier. The mixture was then transferred to a three-necked flask and reacted at a stirring rate of 450-600 rpm for 12-15 h in a water bath at 70-80 °C. The mixture was filtered, and the product was washed three times each with anhydrous ethanol and deionized water. The product was freeze-dried to constant weight and then ground to obtain phenyl Janus-SiO2 particles with an average particle size of 5 μm. The ratio of hexadecyltrimethylammonium bromide to deionized water is 1-3g: 200-500mL; The mass ratio of tetraethyl orthosilicate, 3-aminopropyltrimethoxysilane, phenyltrimethoxysilane, and toluene is 4-6:1.6-2.2:0.8-1.2:80-100; The volume ratio of the aqueous phase to the oil phase is 200-500: 98.5-124.

6.

6. The method for preparing a modified graphene-containing epoxy zinc-rich primer according to claim 1, characterized in that, The specific preparation steps for the corrosion-inhibiting Janus composite particles are as follows: Phenyl Janus-SiO2 particles were added to anhydrous ethanol and stirred for 20-30 min. Benzotriazole was added and stirred until homogeneous. The mixture was then transferred to a three-necked flask and reacted at a stirring rate of 300-500 rpm for 8-10 h in a water bath at 25-30 °C. The mixture was washed 5-8 times with anhydrous ethanol, freeze-dried for 24-36 h, and then ground to obtain corrosion-inhibiting Janus composite particles. The ratio of the phenyl Janus-SiO2 particles, anhydrous ethanol, and benzotriazole is 2-5g: 60-100mL: 2-5g.

7. The method for preparing a modified graphene-containing epoxy zinc-rich primer according to claim 1, characterized in that, The specific preparation steps of the epoxy zinc-rich primer containing modified graphene are as follows: Component A: Add xylene and epoxy resin to a beaker and stir at low speed until homogeneous. Add zinc powder and stir at 750-850 rpm for 10-20 min. Then add dispersant, defoamer, heavy calcium carbonate and mica powder and stir at 2000-3000 rpm for 15-25 min. Vacuum dry to constant weight and set aside. Component B: Mix epoxy curing agent, xylene, modified graphene oxide composite powder, corrosion-inhibiting Janus composite particles and dispersant and ultrasonically disperse evenly; add component A to component B and stir evenly at 750-800 rpm to obtain epoxy zinc-rich primer containing modified graphene.

8. The method for preparing a modified graphene-containing epoxy zinc-rich primer according to claim 7, characterized in that, The mass ratio of xylene, epoxy resin, zinc powder, dispersant, defoamer, heavy calcium carbonate and mica powder is 5-8:8.5-9.8:60-70:0.5-0.8:0.5-0.8:8-10:8-10; The mass ratio of the epoxy curing agent, xylene, modified graphene oxide composite powder, corrosion-inhibiting Janus composite particles, and dispersant is 4.5-6.5:4-6:0.3-0.5:0.2-0.3:0.1-0.2; The mass ratio of component A to component B is 85.5-101.4:9.1-13.

5.

9. An epoxy zinc-rich primer containing modified graphene, prepared according to any one of claims 1-8.

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