Composite modified resin anticorrosive paint and preparation method thereof

Abstract

The invention discloses a composite modified resin anticorrosive coating and a preparation method thereof, and belongs to the technical field of coatings. The method comprises the following steps: by taking water-borne epoxy resin as a film forming substrate, firstly preparing graphene oxide, carrying out amination on 2, 5-diaminobenzene sulfonic acid to introduce amino and sulfonic acid groups which are covalently bonded, and then carrying out defect engineering reduction through hydrazine hydrate to obtain defect engineering amino modified graphene oxide with high-density reaction sites; lamellar double hydroxides grow on the surface in situ, molybdate radicals are intercalated to construct a core-shell structure filler, and finally the filler is dispersed in a waterborne epoxy / aliphatic polyamide curing system to prepare the composite anticorrosive coating. According to the invention, the adhesive force and impact resistance of the coating and a metal matrix are remarkably improved, the water absorption rate is reduced, the shielding and slow-release corrosion inhibition capabilities on a corrosive medium are enhanced, and the long-term corrosion resistance superior to that of a conventional waterborne epoxy anticorrosive coating is shown in neutral salt mist and low-frequency impedance tests.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, specifically, it relates to a composite modified resin anticorrosive coating and its preparation method. Background Technology

[0002] Metal corrosion is a key issue restricting the service life and safety of equipment. Statistics show that direct economic losses caused by metal corrosion account for a significant percentage of the GDP of various countries annually. Therefore, long-term protection of steel structures, storage tanks, pipelines, and marine engineering facilities through coatings is of great engineering significance. Traditional solvent-based epoxy anti-corrosion coatings are widely used in heavy-duty anti-corrosion applications due to their dense film formation and good resistance to chemical media. However, their high organic solvent evaporation and volatile organic compound (VOC) emissions make it difficult to meet increasingly stringent environmental regulations. In contrast, water-based epoxy anti-corrosion coatings use water to replace most organic solvents, offering advantages such as low VOCs, high construction safety, and easy tool cleaning, and are gradually becoming an important development direction in the field of heavy-duty anti-corrosion. However, existing water-based epoxy coatings still suffer from insufficient adhesion, high brittleness, poor impact resistance, and limited shielding ability against corrosive media under long-term service conditions, hindering their widespread application in harsh corrosive environments.

[0003] Currently, the main approaches to improving the performance of epoxy anti-corrosion coatings include strategies such as nanoparticle modification, introduction of micro / nano containers, and modification with bio-based materials. These strategies aim to improve the mechanical properties and corrosion resistance of the coating by constructing multi-scale composite structures. Among these, utilizing nanofillers to create a "maze effect" in the coating, extending the diffusion path of corrosive media to the metal matrix, is one of the effective methods to improve shielding performance. Common nanofillers include nano-silica, nano-alumina, carbon nanotubes, and graphene and its derivatives. These materials, with their high specific surface area and excellent mechanical properties, can improve the density and corrosion resistance of the coating to a certain extent. However, some inorganic nanoparticles have poor interfacial compatibility with organic resin matrices, easily forming agglomerates and interfacial defects in the coating, which in turn provides rapid penetration channels for corrosive media, making it difficult to fully realize the long-term protective effect of the coating. Graphene oxide (GO), with its high specific surface area, excellent mechanical properties, and good barrier properties, is considered a potential preferred filler for modified epoxy anti-corrosion coatings. Introducing a small amount of well-dispersed graphene oxide sheets into an epoxy matrix can significantly extend the migration paths of corrosive media such as water, oxygen, and chloride ions, thereby improving the shielding performance and electrochemical impedance of the coating. However, graphene oxide is still prone to interlayer stacking and aggregation in aqueous resin systems, and the interfacial interaction between its oxygen-containing functional groups and the resin matrix is ​​relatively limited, resulting in insufficient dispersion stability in the coating and easily inducing structural defects such as pores and microcracks. To improve this problem, existing studies have attempted to modify the surface of graphene oxide with small molecules, polymers, or silane coupling agents to introduce hydrophilic functional groups or reactive groups, thereby improving its dispersibility and interfacial bonding strength in aqueous epoxy. Although these methods improve the dispersion and compatibility of graphene oxide to some extent, the modified structures are mostly based on physical adsorption or single functional groups, making it difficult to simultaneously meet the multiple requirements of covalent bonding, hydrophilic dispersion, and subsequent directional growth of inorganic shells. On the other hand, to balance physical shielding and chemical corrosion inhibition, inorganic corrosion inhibitors such as layered double hydroxides (LDHs) have attracted widespread attention in waterborne anti-corrosion coatings. LDHs consist of positively charged metal hydroxide layers and exchangeable anions between the layers. They feature adjustable layer composition, easy anion exchange, and diverse preparation methods, making them suitable as corrosion-inhibiting anion carriers for achieving "intelligent release" type corrosion protection. By intercalating corrosion-inhibiting anions such as molybdate and tungstate into LDHs like Zn-Al and adding them to waterborne epoxy coatings, anions can be slowly released when the coating is locally damaged or corrosive media penetrate, forming a protective film on the metal surface and thus inhibiting corrosion propagation.However, traditional LDH powders mostly exist in the form of micron-sized particles, which are prone to sedimentation or agglomeration in water-based resins. Their interfacial bonding with organic matrices is limited, and the shell structure may dissolve or reconstruct in alkaline or chlorine-containing environments, leading to a decline in corrosion inhibition effect over time. In addition, simply adding LDH powder directly to the coating system often makes it difficult to construct a continuous, directional shielding network within the coating, resulting in limited improvement in corrosion resistance.

[0004] Previous studies have reported the use of graphene or graphene oxide composites with LDH to prepare anti-corrosion coatings with both shielding and corrosion-inhibiting functions, further enhancing the coating's corrosion resistance by constructing two-dimensional / two-dimensional hybrid structures. These composites typically utilize the high aspect ratio of graphene sheets and the ion exchange properties of LDH to make the migration path of corrosive media within the coating more tortuous, while simultaneously achieving the localized release of corrosion-inhibiting anions in defect areas of the coating. However, current work largely focuses on organic solvent-based epoxy or laboratory-scale systems. Systematic process design and industrially scalable parameter windows are still lacking for achieving a robust bond between graphene fillers and LDH shells in aqueous epoxy systems, and for balancing dispersion stability, film density, and application adaptability. Molybdate corrosion inhibitors are a widely used class of chromium-free corrosion inhibitors that can form a dense molybdenum-containing protective film on steel surfaces, exhibiting good inhibition of pitting corrosion under chloride environments. Immobilizing molybdate ions in an intercalated form within an LDH shell promises to achieve slow-release corrosion protection during coating service: in undamaged areas, molybdate ions remain stably intercalated; once local pH or chloride ion concentration changes, molybdate ions migrate to the metal surface via ion exchange or leaching, participating in the formation of a passivation film and thus enhancing the coating's self-protective capability. However, if the bond between the LDH shell and the carrier is weak or the structure is unstable, the intercalated anions are prone to premature release or leaching, significantly weakening the corrosion inhibition effect. Therefore, achieving a stable composite between corrosion-inhibiting anions and a high specific surface area carrier at the nanoscale is one of the key issues in enhancing the application value of this type of system.

[0005] In summary, existing waterborne epoxy anti-corrosion coatings still have significant shortcomings in the following aspects: First, pure waterborne epoxy or systems containing only conventional inorganic pigments and fillers are prone to rapid penetration of corrosive media under long-term salt spray or immersion conditions due to pinholes, microcracks, and interface defects within the coating, leading to premature coating failure. Second, while using graphene oxide or graphene alone can improve shielding performance, its dispersibility and interfacial compatibility in waterborne systems are insufficient, resulting in easy agglomeration and local accumulation of nanosheets, and even the introduction of new corrosion channels. Furthermore, directly incorporating LDH powder or single molybdate corrosion inhibitors often results in uneven dispersion, easy sedimentation, and uncontrolled release of corrosion-inhibiting components, making it difficult to form a structurally stable and synergistically efficient protective network within the coating. Summary of the Invention

[0006] To address the shortcomings of existing waterborne epoxy anticorrosion coatings in terms of long-term service performance, particularly limited adhesion, brittleness, insufficient shielding against corrosive media, and lack of stable and efficient corrosion inhibition, this invention proposes a composite modified resin anticorrosion coating based on defect-engineered amino-modified graphene oxide / zinc-aluminum layered double hydroxide intercalated molybdate core-shell structure filler, and its preparation method. In existing waterborne epoxy graphene anticorrosion coatings, graphene oxide sheets often exhibit problems such as easy agglomeration, high conductivity, and limited functional sites, resulting in poor dispersion stability and the formation of defect channels within the coating, thus limiting its long-term corrosion resistance in heavy-duty anticorrosion applications. Furthermore, using Zn-Al layered double hydroxides or molybdate corrosion inhibitors alone can easily lead to particle sedimentation, insufficient interfacial bonding with the resin matrix, and uncontrolled release of corrosion-inhibiting anions, making it difficult to balance shielding, slow-release corrosion inhibition, and coating mechanical properties. Therefore, it is necessary to design a novel composite anti-corrosion filler and its coating system that can achieve stable dispersion in aqueous systems, has good interfacial compatibility with resins and metal matrices, and possesses both physical shielding and chemical corrosion inhibition functions. The purpose of this invention is to provide a method for preparing a composite modified resin anti-corrosion coating. This method involves amination and defect engineering of graphene oxide, followed by the in-situ construction of a zinc-aluminum layered double hydroxide intercalated molybdate shell on its surface. This yields a core-shell structure filler with high specific surface area, multifunctional reaction sites, and stable corrosion inhibition capabilities. This filler is then combined with an aqueous epoxy / aliphatic polyamide amine curing system, significantly improving the coating's adhesion, impact resistance, and long-term corrosion resistance. Another objective of this invention is to provide a composite modified resin anti-corrosion coating prepared by the above method. This coating, while maintaining the low VOC and application-friendly nature of the aqueous system, achieves efficient and durable protection of the metal matrix by precisely controlling the graphene oxide defect density, LDH shell composition and thickness, molybdate intercalation amount, and filler addition amount. This results in the construction of a continuous and dense shielding network and a controlled-release corrosion inhibition system within the coating.

[0007] The present invention adopts the following technical solution: A method for preparing a composite modified resin anti-corrosion coating, which, by weight, includes the following steps: (1) Preparation of graphene oxide: 2-8 parts of graphite powder (CAS No.: 7782-42-5, particle size <44μm), 10-30 parts of concentrated sulfuric acid (CAS No.: 7664-93-9), 1 part of sodium nitrate (CAS No.: 7631-99-4), and 2-10 parts of potassium permanganate (CAS No.: 7722-64-7) are reacted in an ice bath, then heated to 40-80℃ and stirred for 8h, 2-4 parts of hydrogen peroxide (CAS No.: 7722-84-1) are added for reduction, and the mixture is centrifuged (5000g, 10min) and washed until neutral. (1) Vacuum drying at 50-70℃ for 8-16h to obtain graphene oxide; (2) Preparation of amino-modified graphene oxide: Disperse 1 part of the graphene oxide obtained in step (1) and 1 part of 2,5-diaminobenzenesulfonic acid (CAS No.: 89-57-6) in ultrapure water respectively, mix and stir mechanically at 70-90℃ for 30-50min, and vacuum dry at 50-70℃ to obtain amino-modified graphene oxide; (3) Preparation of defect-engineered amino-modified graphene oxide: Disperse 1 part of the amino-modified graphene oxide obtained in step (2) in water, add 0.1 part of hydrazine hydrate (CAS No.: 7803-57-8), reduce at 60℃ for 2h, centrifuge (8000g, 20min), wash and dry. (3) Preparation of defect-engineered amino-modified graphene oxide; (4) Preparation of core-shell structure filler: Disperse 1 part of defect-engineered amino-modified graphene oxide obtained in step (3), 2-6 parts of zinc nitrate hexahydrate (CAS No.: 7779-88-6), 1-3 parts of aluminum nitrate nonahydrate (CAS No.: 7784-27-2), and 1 part of sodium molybdate dihydrate (CAS No.: 10102-48-4) in 50-150 parts of deionized water, add 2 mol / L sodium hydroxide (CAS No.: 1310-73-2) solution to adjust pH to 10, age at 70-90℃ for 8-16h, centrifuge (6000g, 15min), wash, and dry at 70-90℃ to obtain core-shell structure filler. The shell is a layered double hydroxide intercalated molybdate, with a shell thickness of 5-10 nm. It grows by self-assembly through coordination between zinc and aluminum salts and amino sites. In addition, the conventional LDH intercalation method usually involves first co-precipitating zinc and aluminum salts to form LDH-NO3, and then introducing molybdate through ion exchange. Alternatively, at a constant pH (e.g., pH=10), zinc and aluminum salt solutions and NaOH solutions are "double-dropped" into the bottom solution containing molybdate. (5) Preparation of composite coating: 60-80 parts of waterborne epoxy resin emulsion (solid content 50-55wt%, viscosity at 25℃ 0.5-2.5Pa·s, average particle size 400-600nm, pH 8-8.8, epoxy value 410-425g / eq, density at 25℃ 1.05, Bisphenol A type waterborne epoxy dispersion, Zhejiang Hongli New Material Co., Ltd., model: HongLi®2055), 20-40 parts of waterborne epoxy curing agent (solid content 40±2%, viscosity at 25℃ 15-25Pa·s, pH 8.5-9, density at 25℃ 1.03, amine value 320-380mgKOH / g, active hydrogen equivalent 130-160g / eq, Guangzhou Guanzhi New Material Technology Co., Ltd., model EC-1880), 0.1-0.5 parts of the core-shell structure filler obtained in step (4) ultrasonically dispersed for 0.5-1.5h (power 200-400W), mechanically stirred evenly, sprayed onto the substrate, and cured at room temperature for 12-36h to obtain a composite modified resin anti-corrosion coating.

[0008] Preferably, in step (1), the ice bath temperature is 0-5℃, the heating rate is 1-2℃ / min, the stirring speed is 200-300rpm, and the interlayer spacing of graphene oxide is 0.7-0.8nm.

[0009] Preferably, in step (2), the concentration after dispersion is 0.5-1.5 mg / mL, and the stirring speed is 300-500 rpm; after amino modification, CN bonds (1500 cm⁻¹) appear. -1 ) and S=O bond (1400cm) -1 ).

[0010] Preferably, in step (3), the reduction temperature is 55-65℃, the mass ratio of reducing agent to DGO is 0.05-0.15:1, and the ID / IG ratio after the defect is introduced is 2.5-3.5.

[0011] Preferably, in step (4), the aging temperature is 75-85℃ and the aging speed is 100-200rpm; the LDH shell is formed by coordination of zinc ions with amino groups, co-precipitation of aluminum salts, and exchange of molybdate anions, and the shell crystal form is hexagonal.

[0012] Preferably, in step (5), the amount of core-shell filler added is 0.2 parts; the ultrasonic dispersion frequency is 20-40kHz; the thickness of the spray coating is 30-50μm; and the curing humidity is <60%RH.

[0013] Preferably, in step (4), the sodium hydroxide dropping rate is 0.1-0.5 mL / min, the pH is controlled at 9.5-10.5, and the core-shell packing has a specific surface area of ​​150-250 m². 2 / g.

[0014] A composite modified resin anticorrosive coating, wherein the composite modified resin anticorrosive coating is obtained by the preparation method according to any one of claims 1-7.

[0015] Compared to existing technologies, this invention has at least the following beneficial effects: First, by amylating graphene oxide with 2,5-diaminobenzenesulfonic acid, amino groups that can react with epoxy resin and sulfonic acid groups that impart good hydrophilic dispersibility are simultaneously introduced onto the surface of the sheets. This significantly improves the dispersion stability and interfacial compatibility of graphene oxide in aqueous epoxy systems, avoiding the problems of easy agglomeration and defect channel formation of traditional graphene / graphene oxide in aqueous coating systems. Second, based on amino-modified graphene oxide, this invention uses hydrazine hydrate for moderate defect engineering treatment. By controlling the degree of reduction and defect density, high-density active sites are formed on the surface of the sheets. This is beneficial for the subsequent directional in-situ growth of zinc-aluminum layered double hydroxides and enhances the mechanical interlocking and chemical coupling between the sheets and the aqueous epoxy resin matrix, thereby improving the adhesion and impact resistance of the coating. Furthermore, this invention utilizes defect-engineered amino-modified graphene oxide as the "core," constructing a layered double hydroxide shell of Zn:Al=2:1 on its surface, and intercalating molybdate anions into the shell to form a core-shell structure filler with dual functions of "two-dimensional shielding and slow-release corrosion inhibition." Compared with existing schemes that simply physically mix graphene / LDH or add molybdate corrosion inhibitors alone, the inorganic shell and organic functionalized sheets in this core-shell structure achieve a tight bond through coordination and electrostatic interaction. This not only improves the dispersion stability of LDH in the aqueous system but also increases the carrying capacity and controllability of molybdate release, which is beneficial for forming a dense passivation film in the damaged area of ​​the coating and achieving long-term corrosion inhibition protection. Furthermore, this invention optimizes and controls key process parameters such as the Zn:Al molar ratio, pH range of 9.5-10.5, aging temperature of 75-85℃, and ultrasonic dispersion power and frequency. This ensures that the formed LDH shell has a moderate thickness, complete crystal structure, and high specific surface area, avoiding structural defects and performance degradation caused by insufficient shell crystallization or excessive coarsening. This results in the construction of a continuous and dense labyrinthine shielding network within the coating. Regarding the coating formulation, this invention uniformly disperses the aforementioned core-shell structure filler at a low addition amount in an aqueous epoxy / aliphatic polyamide amine curing system. By controlling the filler dosage and dispersion conditions, the zeta potential of the coating system is kept below -30mV. This ensures good storage stability and application adaptability while avoiding localized agglomeration and microporous defects caused by excessive filler content. Compared to existing solutions that rely on high-content lamellar fillers to improve shielding performance, this invention achieves superior overall anti-corrosion effects with lower filler dosage, demonstrating greater economic efficiency and engineering feasibility.As can be seen from the test results of the examples, under the same waterborne epoxy system and substrate conditions, the adhesion, impact resistance, low-frequency impedance, and rust propagation width of the coating of the present invention are significantly better than those of the unmodified or single-modified filler coatings. The water absorption rate is also significantly reduced, which fully demonstrates the effectiveness and superiority of the synergistic design of "ammoniation, defect engineering, LDH intercalated molybdate core-shell structure and controlled filler dosage" in improving the long-term corrosion resistance of waterborne epoxy anti-corrosion coatings. Attached Figure Description

[0016] Figure 1 This is a transmission electron microscope (TEM) image of the graphene oxide prepared in Example 1. Figure 2 This is the infrared spectrum of the amino-modified graphene oxide prepared in Example 1. Figure 3 This is an application diagram of the composite modified resin anti-corrosion coating prepared in Example 1. Detailed Implementation

[0017] The present invention will now be described in detail through specific embodiments. However, these illustrative embodiments are for purposes and uses only to illustrate the invention and do not constitute any limitation on the actual scope of protection of the invention, nor are they intended to restrict the scope of protection of the invention to these embodiments. For parameter ranges not mentioned, intermediate values ​​are selected. Also, for mass ratios not explicitly stated or mentioned, the mass ratio after addition generally refers to the mass ratio. Furthermore, in the present invention, the unit of weight parts is grams (g). The main equipment used in this invention is as follows: a low-temperature constant temperature reaction tank (model: DC-0506), a mechanical stirrer (model: JJ-1), an ultrasonic disperser (model: JY92-IIN), a vacuum drying oven (model: DZF-6050), a pH meter (model: PHS-3C), a spray gun (model: W-71), an electrochemical workstation (model: PGSTAT302N), a neutral salt spray test chamber (model: YWX / Q-250), a pull-off adhesion tester (model: PosiTest AT-A), and a film impact tester (model: QCJ). For ease of reproduction, the waterborne epoxy resin emulsions described in this invention all use bisphenol A type waterborne epoxy dispersions; the 70.0g waterborne epoxy resin emulsion used in Example 1 contains 38.5g of solid resin, and the 30.0g waterborne epoxy curing agent used is an aliphatic polyamide amine curing agent; the mass ratio of component A to component B is 2.33:1. Unless otherwise specified, the substrate in each embodiment is a sandblasted Q235 steel plate with dimensions of 150mm×70mm×2mm and a surface treatment grade of Sa2.5. Example 1 Example 1 is a preferred embodiment of the present invention. Table 1 Steps of Example 1 (1) Feeding Formulation

[0018] Graphite powder, concentrated sulfuric acid, sodium nitrate, and potassium permanganate were sequentially added to a four-necked flask equipped with a mechanical stirrer and reacted in an ice bath at 3°C ​​with a stirring speed of 300 rpm. After the system was thoroughly mixed, the temperature was increased to 60°C at a rate of 2°C / min and stirred continuously for 8 hours; then hydrogen peroxide was slowly added and the reaction continued for another 20 minutes. After the reaction was completed, the filtrate was centrifuged and washed with deionized water until it was neutral, and then dried under vacuum at 60°C for 12 hours to obtain 6.6 g of graphene oxide. Figure 1 As shown, the interlayer spacing is 0.76 nm, according to the test results. Table 2. Feeding formulations for steps (2) and (3) of Example 1

[0019] 1.0 g of graphene oxide and 1.0 g of 2,5-diaminobenzenesulfonic acid were added separately to 1000.0 g of ultrapure water. After pre-dispersing using an ultrasonic disperser for 20 min, the two liquids were combined and mechanically stirred at 500 r / min for 40 min at 80 °C. The reaction solution was then centrifuged and vacuum dried at 60 °C for 10 h to obtain 1.7 g of amino-modified graphene oxide. Figure 2 As shown, the FTIR test results indicate that at 1502 cm⁻¹... -1 A CN absorption peak appears at 1408 cm⁻¹. -1 The presence of an S=O absorption peak indicates successful amination modification. 1.0 g of amino-modified graphene oxide was added to 500.0 g of deionized water, ultrasonically dispersed for 15 min, and then 0.1 g of hydrazine hydrate was added. Reduction was carried out at 60 °C for 2 h. After centrifugation and washing, the sample was vacuum dried at 60 °C for 8 h to obtain 0.82 g of defect-engineered amino-modified graphene oxide. Tests showed that the sample's ID / IG ratio was 3.0, indicating the introduction of an appropriate number of defect sites, which is beneficial for the subsequent directional growth of layered double hydroxide shells. Table 3 Step (4) of Example 1: Feeding Formulation

[0020] The aforementioned defect-modified amino-modified graphene oxide, zinc nitrate hexahydrate, aluminum nitrate nonahydrate, and sodium molybdate dihydrate were added to 100.0 g of deionized water and ultrasonically dispersed for 20 min. The mixture was then stirred at 200 r / min at 80 °C. Subsequently, an aqueous sodium hydroxide solution was added dropwise to the reaction system at a rate of 0.5 g / min to adjust the pH to 10.0, and aging was continued for 12 h. After aging, the mixture was centrifuged, washed, and dried at 80 °C for 10 h to obtain 3.6 g of core-shell structured filler. The shell thickness of the obtained filler was approximately 8 nm; BET testing showed that its specific surface area was 198.6 m². 2 / g. The above results indicate that the amino sites on the surface of defect-engineered amino-modified graphene oxide can serve as initial coordination sites for zinc ions, promoting the self-assembly growth of zinc-aluminum layered double hydroxide shells, while molybdate ions are intercalated into the shells, improving the corrosion inhibition capability of the coating during service. Table 4 Step (5) of Example 1: Coating Formulation

[0021] First, 0.2g of core-shell structured filler was added to 70.0g of waterborne epoxy resin emulsion and ultrasonically dispersed for 1h at 300W and 30kHz. The Zeta potential of the dispersion system was measured to be -36.4mV, indicating good dispersion stability. Then, 30.0g of waterborne epoxy curing agent was added, and the mixture was mechanically stirred at 400r / min for 10min to obtain a composite modified resin anti-corrosion coating. The resulting coating was uniformly sprayed onto the surface of a Q235 steel plate using a spray gun, controlling the dry film thickness to be 40μm. The ambient temperature was 25℃, the relative humidity was 55%, and the coating was cured at room temperature for 24h to obtain the composite modified resin anti-corrosion coating. Figure 3 As shown, the resulting coating surface is smooth, without obvious pinholes or sagging, and cross-sectional observation shows that the filler is evenly distributed in the resin matrix. Examples 2-12 Except for the changes listed in the table below, the types of raw materials, the quality of feed, the operating steps and the post-processing conditions are the same as in Example 1. Table 5. Parameter changes in Examples 2-6

[0022] Table 6. Parameter variations in Examples 7-12

[0023] Comparative Examples 1-12 Except for the changes listed in the table below, all other parameters are the same as in Example 1.

[0024] Table 7. Parameter variations in Comparative Examples 1–6 Table 8. Parameter variations in Comparative Examples 7–12 Test methods To verify the corrosion resistance and mechanical properties of the coatings of this invention, the coatings prepared in Examples 1-12 and Comparative Examples 1-12 were subjected to the following tests. All test samples were cured at 25℃ and 50% relative humidity for 7 days before testing. Three samples were prepared in parallel for each group, and the average value was taken. Adhesion test: The test was conducted according to GB / T 5210-2006 "Paints and Varnishes - Pull-off Adhesion Test". A pull-off adhesion tester was used, with an aluminum pull-off head diameter of 20mm. Two-component epoxy adhesive was used for bonding. After curing for 24 hours, the coating was pulled off at a loading rate of 1MPa / s, and the adhesion value at failure was recorded in MPa. Impact resistance test: The test was conducted according to GB / T 1732-2020 "Paint Film Impact Resistance Test". A QCJ type paint film impactor with a punch mass of 1000g was used. The coating was dropped freely from different heights, and the presence of cracks and peeling was observed. The maximum impact height without failure was recorded in cm. Neutral Salt Spray Test: Conducted according to GB / T 1771-2007 "Determination of Neutral Salt Spray Resistance of Paints and Varnishes". An 80mm long scratch was made in the center of the sample, which was then placed in a salt spray chamber. The spray solution was prepared by adding 50.0g of sodium chloride to 950.0g of deionized water. The test temperature was 35℃, and the test was conducted continuously for 720 hours. After the test, the width of rust spread on one side of the scratch was measured in mm; a smaller value indicates better corrosion resistance. Low-Frequency Impedance Testing: Electrochemical impedance spectroscopy was measured using an electrochemical workstation after immersion in a 3.5% sodium chloride solution for 30 days. A three-electrode system was used, with the coated sample as the working electrode and an exposed area of ​​1.0cm². 2 The reference electrode was a saturated calomel electrode, and the counter electrode was a platinum sheet. The test frequency range was 100kHz to 0.01Hz, with a sinusoidal perturbation amplitude of 10mV. The logarithm of the impedance modulus at 0.01Hz was recorded. The larger this value, the stronger the shielding effect of the coating. Water absorption test: The test was conducted according to the method of GB / T 1733-1993 "Determination of Water Resistance of Paint Film". A known mass of free paint film sample was immersed in deionized water at 25℃ for 168h. After removal, the surface moisture was wiped dry and the sample was weighed quickly. The water absorption rate was calculated using the following formula:

[0025] in, For the quality of the paint film before soaking, This refers to the quality of the paint film after immersion. The lower the water absorption rate, the denser the coating structure.

[0026] Test Results Table 9 Performance results of Examples 1-6

[0027] Table 10 Performance results of Examples 7-12

[0028] Table 11 Performance results of Comparative Examples 1–6 Table 12 Performance results of Comparative Examples 7–12 Results Analysis: Examples 1-12 all achieved good overall performance. Among them, Examples 3 and 9 showed the best performance, indicating that when the defect site density is high, the shell is relatively intact, and the filler addition is at a high but not excessive level, the lamellar labyrinth effect, slow-release corrosion inhibition effect, and interface enhancement effect can be exerted simultaneously. Although the performance of Examples 2, 4, 6, 8, and 10 was slightly lower than that of Example 1, it was still significantly better than each comparative example. This indicates that when the reduction degree is low, the shell is thin, or the filler addition is close to the lower limit, the material can still form a continuous protective network. However, the lamellar stacking path increases and the shell ion exchange protection effect is relatively weakened, so the salt spray spread width and water absorption rate increase slightly. Comparative Examples 1 and 2 show that the aminated modified component in step (2) is a key component. Without amination modification, the coordination and self-assembly capabilities between graphene oxide and subsequent zinc and aluminum salts are significantly weakened, resulting in weak shell bonding. Although replacing 2,5-diaminobenzenesulfonic acid with ordinary p-phenylenediamine can still provide certain amino sites, the corrosion resistance is still significantly reduced due to the lack of sulfonic acid groups to assist hydrophilic dispersion and interfacial interaction. Comparative Example 3 illustrates that the defect engineering treatment in step (3) is an important step in forming high-density reaction sites. Without appropriate reduction, the number of active sites available for shell nucleation on the sheet surface is reduced, resulting in an uneven core-shell structure. The interfacial compatibility of the filler in the epoxy system also decreases, thus simultaneously reducing adhesion, low-frequency impedance, and impact resistance. Comparative Example 4 further illustrates that molybdate intercalation is another key factor in obtaining excellent corrosion resistance in this invention. Without sodium molybdate dihydrate, even if a zinc-aluminum layered double hydroxide shell is still formed, it is difficult to provide effective slow-release and corrosion inhibition when the coating is damaged or the medium penetrates, thus significantly increasing rust spread in the salt spray test. Comparative Examples 5-9 illustrate that the Zn:Al ratio, pH, and aging temperature in step (4) must be controlled within a reasonable range. When the Zn:Al ratio deviates from 2:1, the growth of layered double hydroxide crystals tends to be disordered; when the pH is too low, co-precipitation is insufficient, and when the pH is too high, coarse by-products are easily formed or lamellar agglomeration occurs; when the aging temperature is too low, crystallization is insufficient, and when it is too high, the shell layer grows excessively and structural defects are generated. Therefore, the impedance and adhesion of these comparative examples all show a significant decrease. Comparative Examples 10-12 illustrate that the filler addition amount and dispersion conditions in step (5) should also not be changed arbitrarily. When the filler addition amount is too low, it is impossible to form an effective barrier channel in the resin matrix; when the addition amount is too high, it is easy to cause local agglomeration and introduce microporous defects; when the ultrasonic power and frequency are below the limit range, it is difficult to fully peel off and uniformly disperse the core-shell filler, resulting in an increase in internal defects of the coating, leading to an increase in water absorption, a decrease in low-frequency impedance, and a significant increase in salt spray propagation.In summary, this invention, through amination modification of graphene oxide, appropriate defect engineering, and the construction of a zinc-aluminum layered double hydroxide intercalated molybdate shell, combined with controlled filler dosage, pH, aging temperature, and dispersion conditions, can significantly improve the adhesion, impact resistance, and corrosion resistance of waterborne epoxy anti-corrosion coatings, and demonstrates a clear synergistic relationship among the key characteristics. This technical solution can be repeatedly implemented by those skilled in the art to achieve stable technical results.

[0029] The above description, in conjunction with specific embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of the present invention, and all such deductions or substitutions should be considered to fall within the scope of protection defined by the claims submitted herein.

Claims

1. A method for preparing a composite modified resin anticorrosive coating, characterized in that: The process, by weight, includes the following steps: (1) Reacting 2-8 parts of graphite powder, 10-30 parts of concentrated sulfuric acid, 1 part of sodium nitrate, and 2-10 parts of potassium permanganate in an ice bath, then heating to 40-80℃ and stirring for 8 hours, adding 2-4 parts of hydrogen peroxide for reduction, centrifuging and washing until neutral, and vacuum drying at 50-70℃ for 8-16 hours to obtain graphene oxide; (2) Dispersing 1 part of the graphene oxide obtained in step (1) and 1 part of 2,5-diaminobenzenesulfonic acid separately in ultrapure water, mixing and mechanically stirring at 70-90℃ for 30-50 minutes, and vacuum drying at 50-70℃ to obtain amino-modified graphene oxide; (3) Dispersing 1 part of the amino-modified graphene oxide obtained in step (2) in water, adding 0.1 parts of hydrazine hydrate, reducing at 60℃ for 2 hours, centrifuging and washing, (3) Dry to obtain defect-engineered amino-modified graphene oxide; (4) Disperse 1 part of defect-engineered amino-modified graphene oxide obtained in step (3), 2-6 parts of zinc nitrate hexahydrate, 1-3 parts of aluminum nitrate nonahydrate, and 1 part of sodium molybdate dihydrate in 50-150 parts of deionized water, add 2 mol / L sodium hydroxide solution to adjust the pH to 10, age at 70-90℃ for 8-16h, centrifuge and wash, dry at 70-90℃ to obtain core-shell structure filler; (5) Disperse 60-80 parts of waterborne epoxy resin emulsion, 20-40 parts of waterborne epoxy curing agent, and 0.1-0.5 parts of core-shell structure filler obtained in step (4) ultrasonically for 0.5-1.5h, stir mechanically until uniform, spray on substrate, and cure at room temperature for 12-36h to obtain composite modified resin anti-corrosion coating.

2. The method for preparing the composite modified resin anticorrosive coating according to claim 1, characterized in that; In step (1), the ice bath temperature is 0-5℃, the heating rate is 1-2℃ / min, the stirring speed is 200-300rpm, and the interlayer spacing of graphene oxide is 0.7-0.8nm.

3. The method for preparing the composite modified resin anticorrosive coating according to claim 1, characterized in that: In step (2), the concentration after dispersion is 0.5-1.5 mg / mL, and the stirring speed is 300-500 rpm.

4. The method for preparing the composite modified resin anticorrosive coating according to claim 1, characterized in that: The reduction temperature in step (3) is 55-65℃.

5. The method for preparing the composite modified resin anticorrosive coating according to claim 1, characterized in that: In step (4), the aging temperature is 75-85℃ and the aging speed is 100-200rpm.

6. The method for preparing the composite modified resin anticorrosive coating according to claim 1, characterized in that: In step (5), the amount of core-shell filler added is 0.2 parts; the ultrasonic dispersion frequency is 20-40kHz; the spraying thickness is 30-50μm; and the curing humidity is <60%RH.

7. The method for preparing the composite modified resin anticorrosive coating according to claim 1, characterized in that: In step (4), the sodium hydroxide dropping rate is 0.1-0.5 mL / min, and the pH is controlled at 9.5-10.5; the specific surface area of ​​the core-shell packing is 150-250 m². 2 / g.

8. A composite modified resin anticorrosive coating, characterized in that: The composite modified resin anticorrosive coating is obtained by the preparation method described in any one of claims 1-7.

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