High shielding type epoxy glass flake anticorrosive coating and preparation process thereof

Abstract

This invention relates to the field of epoxy resin coating technology, specifically to a high-shield epoxy glass flake anti-corrosion coating and its preparation process. This invention overcomes the problem in existing epoxy glass flake anti-corrosion coatings that cannot simultaneously achieve both anti-corrosion performance and adhesion performance. The anti-corrosion coating of this invention is obtained by mixing an epoxy active component and a modified curing agent. The epoxy active component is a mixed epoxy resin of bisphenol A and bisphenol F, with the introduction of a polyurethane-modified epoxy prepolymer and a reactive UV absorber for toughening and chain extension, combined with polydopamine-modified glass flakes and silanized graphene oxide. The modified curing agent is a cashew phenolic amine modified with a silane coupling agent. Through a segmented cooling and stirring process, the glass flakes are arranged in an orderly layered manner within the coating, resulting in a coating with excellent shielding and anti-corrosion properties, suitable for long-term protection of steel structures in extreme corrosive environments.

Description

Technical Field

[0001] This invention relates to the field of epoxy resin coating technology, specifically to a high-shield epoxy glass flake anti-corrosion coating and its preparation process. Background Technology

[0002] Epoxy resin coatings are widely used in heavy-duty anti-corrosion fields such as petrochemicals and marine engineering due to their excellent adhesion and chemical corrosion resistance. At present, epoxy glass flake coatings mainly use glass flakes with a very large aspect ratio added to the coating to block the penetration of water molecules, oxygen and corrosive ions through the labyrinth effect formed by them, which has high application prospects.

[0003] However, existing technologies still face severe challenges in practical applications: First, to achieve high shielding performance, the coating needs to be loaded with a large number of glass flakes, which often leads to a significant increase in coating brittleness. When subjected to mechanical impact or stress caused by curing shrinkage, the substrate is prone to microcracks. Second, the interfacial bonding between glass flakes and epoxy matrix mainly relies on physical molecular chain entanglement or simple silane coupling treatment, resulting in limited bonding strength. Under long-term immersion conditions, the medium is prone to leakage along the debonding interface at the filler edge. In addition, traditional epoxy resins have poor UV aging resistance, and long-term outdoor exposure can lead to coating chalking and loosening of the structure, ultimately causing the shielding performance to fail completely. Finally, existing preparation processes cannot effectively control the arrangement of flakes in the coating film. Randomly distributed flakes cannot form a dense parallel laminate, resulting in a significant shortening of the barrier path and further affecting the overall anti-corrosion performance.

[0004] In summary, existing technologies aim to achieve in-situ toughening while maintaining high crosslinking density through the synergistic use of components, and to construct a good epoxy anti-corrosion system through interfacial chemical modification and precise process control. However, there is still a problem that anti-corrosion performance and adhesion performance cannot be simultaneously achieved.

[0005] To address this, a high-shield epoxy glass flake anti-corrosion coating and its preparation process are proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a high-shield epoxy glass flake anti-corrosion coating and its preparation process. The anti-corrosion coating of this invention is obtained by mixing an epoxy active component and a modified curing agent. The epoxy active component is a mixed epoxy resin of bisphenol A and bisphenol F, with the introduction of a polyurethane-modified epoxy prepolymer and a reactive UV absorber for toughening and chain extension, combined with polydopamine-modified glass flakes and silanized graphene oxide. The modified curing agent is a cashew phenolic amine modified with a silane coupling agent. Through a segmented cooling and stirring process, the glass flakes are arranged in an orderly layered manner within the coating. The resulting coating has excellent shielding and anti-corrosion properties, suitable for long-term protection of steel structures in extreme corrosive environments.

[0007] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a preparation process for a high-shield epoxy glass flake anti-corrosion coating, comprising the following preparation steps: Add 80-90 parts of modified epoxy matrix to the reaction vessel, along with 0.6-1.5 parts of modified graphene oxide. Start a high-shear disperser and disperse at 2500-3500 rpm for 45-60 minutes within a high-temperature, low-viscosity range of 55-65℃ to ensure the nanofiller fully fills the free volume of the matrix. Then, turn on the cooling water jacket and enter the crucial stage of segmented cooling and stirring. Adjust the speed to 400-600 rpm and slowly add 35-45 parts of modified glass flakes, reducing the material temperature to 35-40℃ at a constant rate of 1.5℃ / min. During this cooling process, the system viscosity increases linearly, effectively capturing and locking the horizontally arranged glass flakes induced by shear force, forming a tight... A dense, layered labyrinth structure is formed. 1.5-2.5 parts of polyamide wax thixotropic agent and 0.5 parts of defoamer are added, and the mixture is stirred at 500 rpm for 15 minutes at 30-35°C. This process further stabilizes the gradient stacking morphology of the flakes through a hydrogen bond network. Finally, the mixture is vacuum degassed for 10 minutes under -0.09 MPa pressure and filtered to obtain the active component. Under stirring conditions, 35-42 parts of modified curing agent are slowly added to 100 parts of the active component, and the mixture is stirred at 300 rpm for 20 minutes. After curing for 30 minutes, an epoxy glass flake anti-corrosion coating is obtained. This ensures the curing agent and resin are fully impregnated and releases heat during the induction period. The coating should be used within 2 hours at 25°C to avoid affecting the flake arrangement due to a sudden increase in viscosity.

[0008] Preferably, the preparation of the modified epoxy resin includes the following steps: 45-55 parts of bisphenol A type epoxy resin and 20-30 parts of bisphenol F type epoxy resin are placed in a reaction vessel, heated to 60-70℃ and mixed evenly. Then, 10-18 parts of polyurethane modified epoxy prepolymer and 0.5-1 parts of DMP-30 are slowly added dropwise, the temperature is raised to 80-85℃, and the modification reaction is carried out for 1.5-2.0 h to obtain the modified system. After cooling to 60℃ at a cooling rate of 1.5-3℃ / min, 2-4 parts of ultraviolet absorber are slowly added, followed by the addition of BTAC. 0.1-0.2 parts were heated to 100℃ for chain extension reaction for 3-4 hours. After the reaction was completed, the vacuum pump was turned on and degassing was carried out at -0.09MPa to remove trace bubbles mixed in during the reaction. After the system cooled naturally to below 40℃, the modified epoxy matrix was obtained by filtering through a 200-mesh stainless steel filter screen. Its viscosity was maintained at 8000-12000 mPa·s at 25℃, providing a low viscosity platform for high-proportion loading of subsequent fillers.

[0009] Preferably, the preparation of modified glass flakes includes the following steps: dispersing 28 parts of 150-mesh C-type glass flakes and 12 parts of 400-mesh C-type glass flakes in a Tris-HCl buffer solution with a pH of 8.5; adding 0.5 parts of dopamine hydrochloride monomer, and stirring the mixture at 25-30°C for 12-24 hours; utilizing the self-polymerization reaction of dopamine under weakly alkaline conditions, forming a polydopamine film with high adhesion on the surface of the glass flakes; after the reaction, obtaining modified glass flakes by separation and centrifugation, washing with deionized water, and vacuum drying at 60°C. This process achieves a physical stacking basis of large shielding and small filling through the compounding of different particle sizes, while the PDA layer enhances the interfacial compatibility between the flakes and the resin.

[0010] Preferably, the preparation of modified graphene oxide includes the following steps: dispersing 0.5-1.0 parts of graphene oxide in 100 parts of 70% ethanol aqueous solution, and ultrasonically dispersing for 45-60 min to obtain a mixed system; the ultrasonic dispersion power is 400W and the ultrasonic dispersion frequency is 30Hz; adding 0.1-0.2 parts of silane coupling agent KH-560 to the mixed system, and refluxing at 65-75℃ for 4 h to obtain modified graphene oxide. By grafting with silane coupling agent, the surface polarity of GO is changed, giving it excellent exfoliation and dispersion stability in epoxy resin, thus constructing a nanoscale two-dimensional barrier.

[0011] Preferably, the preparation of the modified curing agent includes the following steps: In a reactor equipped with a stirrer and a condenser, 100 parts of cashew nut shell powder and 20-25 parts of ethylenediamine are added, the temperature is raised to 80-90°C, and the mixture is stirred to obtain a mixture; 15-20 parts of paraformaldehyde are added dropwise to the mixture in batches, the temperature is raised to 100-110°C, the reaction is maintained at this temperature for 3 hours, and dehydration is carried out under reduced pressure, wherein the pressure is reduced to -0.08 MPa; After cooling to 60°C at 2°C / min, 5-8 parts of KH-550 are added, and the grafting reaction is maintained at this temperature for 2 hours to obtain the modified curing agent; This curing agent combines the wet curing characteristics of cashew nut shell powder with the strong adhesion of siloxane bonds.

[0012] The anti-corrosion coating of this invention consists of active components and modified curing agents. Before use, the steel surface is sandblasted and sprayed using a high-pressure airless sprayer with a pressure ratio of 45:1, employing a cross-spraying method. The spray gun is perpendicular to the substrate, with a distance of 40-60cm. The thickness of a single dry film is controlled at 300-500μm. At this thickness, the thixotropic network formed by the gradient cooling process can guide the scales to spontaneously stack and form a parallel shielding layer of 50-100 layers. The surface drying time of the coating is tested at 25℃ for 4-6 hours, and the actual drying time is 24 hours. The coating performance is tested after 7 days of curing.

[0013] This invention also provides a high-shield epoxy glass flake anti-corrosion coating. The raw materials for preparing the anti-corrosion coating include bisphenol A type epoxy resin, bisphenol F type epoxy resin, ultraviolet absorber, glass flakes, dopamine hydrochloride, graphene oxide, cashew phenol and paraformaldehyde.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention achieves in-situ toughening of the coating by introducing polyurethane-modified epoxy prepolymer into the epoxy curing network. Unlike traditional physical addition of toughening agents, which can easily lead to a decrease in strength, this process utilizes the condensation reaction of epoxy groups to embed flexible segments in the cross-linked network, forming an interpenetrating network structure. This effectively absorbs external impact energy and releases the shrinkage internal stress during the curing process, solving the problems of easy cracking and poor impact resistance of high-content glass flake coatings, and achieving a perfect balance between rigid shielding and tough protection.

[0015] 2. This invention utilizes polydopamine to treat the surface of glass flakes, constructing an active transition layer rich in hydroxyl and amino groups on the surface of inorganic flakes. This design changes the traditional coating method where the flakes and resin are only physically entangled. During the curing process, the silanoxy groups in the modified curing agent undergo a coupling reaction with the PDA layer to form chemical bonds, tightly stitching the organic resin phase and the inorganic filler phase together, significantly improving adhesion and ensuring that the coating will not delaminate or peel off when faced with complex mechanical loads or alternating environmental stresses.

[0016] 3. This invention constructs a dense micro-nano composite shielding network by mixing glass flakes of different particle sizes with silanized modified graphene oxide. The glass flakes achieve physical stacking with large shielding and small filling, while the modified graphene oxide further fills the microscopic gaps between the flakes using its two-dimensional sheet structure. By using a segmented cooling and stirring process, the flakes are induced to be arranged in a parallel layered orientation, which greatly extends the penetration path of corrosive media. The resulting coating has a significantly improved resistance time to neutral salt spray, demonstrating a good synergistic effect of physical barrier and chemical protection.

[0017] 4. This invention introduces a reactive UV absorber into the resin molecular chain and locks it onto the main chain of the film-forming substance through chemical co-extension. The introduction of this structured aging-resistant component avoids the physical migration and precipitation of traditional additive absorbers during long-term use, ensuring that the coating has high gloss retention and does not chalk under UV irradiation. At the same time, the labyrinth structure formed by the highly ordered array of scales greatly reduces the transmittance of water molecules, significantly extending the service life in outdoor and humid environments, and solving the technical bottleneck of easy aging of epoxy coatings.

[0018] 5. This invention utilizes the characteristic that the viscosity of the system changes with the temperature gradient to effectively capture and lock the parallel flakes arranged under shear force at a specific rotation speed, avoiding the problem of disordered flake arrangement caused by traditional stirring. This ensures that the coating has excellent sag limit thickness and support when applied in thick coating. The modified curing agent combines the wet curing characteristics of cashew phenol with the strong adhesion of siloxane, which improves the coating's workability in harsh environments. Attached Figure Description

[0019] Figure 1 The graph shows the changes in the aging resistance impact strength retention rate of Examples 1-5 and Comparative Examples 8-10 of the present invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] In this invention, the bisphenol A type epoxy resin is E-51, CAS number 25068-38-6, epoxy equivalent is 184-195 g / eq, and viscosity (25℃) is 11000-14000 mPa·s; the bisphenol F type epoxy resin has an epoxy equivalent of 160-180 g / eq and viscosity (25℃) of 2000-5000 mPa·s; the polyurethane modified epoxy prepolymer is an epoxy-terminated polyurethane modified epoxy toughening agent, formed by reacting polyethylene glycol with excess hexamethylene isocyanate to form an NCO-terminated prepolymer, which is then end-capped with epoxy resin E51, wherein the epoxy value is 0.38-0.42 and the viscosity is 10000-15000 mPa·s. mPa·s; the polyamide wax thixotropic agent is an oligomer, CAS number 68412-14-6, melting point 120-130℃, fineness ≤15μm; cashew phenol CAS number 8007-24-7, iodine value 250-290g / 100g, hydroxyl value 180-200mgKOH / g; C-type glass flakes are selected, of which 150 mesh glass flakes have an average particle size of 80-100μm, a thickness of 2-5μm, and an aspect ratio ≥40; 400 mesh glass flakes have an average particle size of 30-38μm, a thickness of 1-3μm, and an aspect ratio ≥30; the transverse dimension of graphene oxide is 0.5-5μm, thickness... The wavelength is 1-3 nm, and the number of layers is 1-5; KH-560 is 3-glycidyl etheroxypropyltrimethoxysilane, CAS number 2530-83-8; KH-550 is 3-aminopropyltriethoxysilane, CAS number 919-30-2; dopamine hydrochloride CAS number 62-31-7; the ultraviolet absorber is a reactive ultraviolet absorber, specifically ultraviolet absorber UV-1300, CAS number 104810-48-2; DMP-30 is 2,4,6-tris(dimethylaminomethyl)phenol, CAS number 90-72-2; BTAC is benzyltrimethylammonium chloride, CAS number 56-93-9.

[0022] Please see Figure 1 This invention provides a high-shield epoxy glass flake anti-corrosion coating and its preparation process, the technical solution of which is as follows: Example 1 By mass, 50 parts of bisphenol A epoxy resin and 25 parts of bisphenol F epoxy resin were placed in a reactor and heated to 65°C. The mixture was stirred until homogeneous. After the resin was fully mixed and the viscosity decreased, 12 parts of polyurethane modified epoxy prepolymer and 0.8 parts of DMP-30 were slowly added dropwise. The temperature was raised to 80°C and the modification reaction was carried out for 2 hours to obtain the modified system. The temperature was lowered to 60°C at a rate of 2°C / min. Then, 3 parts of UV absorber and 0.2 parts of BTAC were slowly added. The temperature was raised to 100°C and the chain extension reaction was carried out for 3.5 hours to obtain the reaction product. The vacuum pump was then turned on and degassing was carried out under reduced pressure of -0.09 MPa. After the system cooled naturally to below 40°C, it was filtered through a 200-mesh stainless steel filter to obtain the modified epoxy matrix. 28 parts of 150-mesh C-type glass flakes and 12 parts of 400-mesh C-type glass flakes were dispersed in a Tris-HCl buffer solution with a pH of 8.5; 0.5 parts of dopamine hydrochloride monomer were added, and the mixture was stirred at 30°C for 20 h; after the reaction was completed, the modified glass flakes were obtained by separation and centrifugation, washing with deionized water, and vacuum drying at 60°C for 2 h. 0.8 parts of graphene oxide were dispersed in 100 parts of 70% ethanol aqueous solution and ultrasonically dispersed for 60 min to obtain a mixed system; the ultrasonic dispersion power was 400 W and the ultrasonic dispersion frequency was 30 Hz; 0.15 parts of silane coupling agent KH-560 were added to the mixed system and refluxed at 70 °C for 4 h to obtain modified graphene oxide.

[0023] In a reactor equipped with a stirrer and a condenser, 100 parts of cashew phenol and 25 parts of ethylenediamine were added, the temperature was raised to 80°C, and the mixture was stirred to obtain a mixture. 18 parts of paraformaldehyde were added dropwise to the mixture, the temperature was raised to 110°C, the reaction was maintained at this temperature for 3 hours, and the mixture was dehydrated under reduced pressure, with the pressure dropping to -0.08 MPa. After cooling to 60°C at a rate of 2°C / min, 6 parts of KH-550 were added, and the grafting reaction was carried out for 2 hours to obtain a modified curing agent.

[0024] 82.5 parts of modified epoxy matrix were added to the reaction vessel, along with 0.8 parts of modified graphene oxide. A high-shear disperser was turned on and dispersed at 3000 rpm for 50 min in a high-temperature, low-viscosity range of 60℃ to ensure that the nanofiller fully filled the free volume of the matrix. Subsequently, the cooling water jacket was turned on, and the critical gradient cooling and stirring stage was entered: the speed was adjusted to 500 rpm, 42 parts of modified glass flakes were slowly added, and the material temperature was reduced to 35℃ at a constant rate of 1.5℃ / min, and stirred for 30 min. Then, 1.8 parts of polyamide wax thixotropic agent and 0.5 parts of defoamer were added, and stirred at 500 rpm for 20 min at 32℃. Finally, vacuum degassing was performed at -0.09 MPa pressure for 10 min, and the active component was obtained by filtration. 37 parts of modified curing agent were slowly added to 100 parts of active component, and stirred at 300 rpm for 20 min, followed by curing for 30 min to obtain epoxy glass flake anti-corrosion coating.

[0025] Examples 2-5 follow the same preparation method and parameters as Example 1, with differences shown in Table 1.

[0026] Table 1. Parameter variations in Examples 1-5 Example Example 1 Example 2 Example 3 Example 4 Example 5 Modified resin matrix mass dosage / part 84 82 85 80 90 Modified graphene oxide mass dosage / part 0.8 0.6 1.2 0.5 1.5 Modified glass flakes mass dosage / part 42 40 45 35 45 Polyamide wax thixotropic agent mass dosage / part 1.8 1.6 2.2 1.5 2.5 Modified curing agent mass dosage / part 38 36 40 35 42 Temperature of high-temperature dispersion section / ℃ 60 58 62 55 65 Cooling termination temperature / ℃ 35 38 33 40 36 Thixotropic building block temperature / °C 32 34 30 35 30 Bisphenol A type epoxy resin mass dosage / part 50 45 52 55 48 Bisphenol F type epoxy resin mass dosage / part 25 30 20 22 28 Polyurethane modified epoxy mass dosage / part 12 10 15 10 18 UV absorber dosage (parts) 3 2.5 3.5 2 4 Dispersion stage stirring speed / rpm 3000 2500 3500 2000 3800

[0027] Comparative Example 1: Refer to Example 1, except that modified graphene oxide is not added to the active component of the coating, while the amounts of the other components remain unchanged.

[0028] Comparative Example 2 is the same as Example 1, except that the cooling rate during the preparation of the active component of the coating is set to 5.0°C / min.

[0029] Comparative Example 3 is the same as Example 1, except that no bisphenol F epoxy resin is added during the preparation of the modified resin matrix, and only 75 parts of bisphenol A epoxy resin are used, while the amounts of the other components remain unchanged.

[0030] Comparative Example 4 is the same as Example 1, except that the modified resin matrix does not use a reactive UV absorber, but instead adds an equal mass of UV absorber UV-9.

[0031] Comparative Example 5 is the same as Example 1, except that no modified curing agent is used, and an equal amount of conventional cashew phenol amine curing agent is used instead, while the amounts of other components remain unchanged.

[0032] Comparative Example 6 is the same as Example 1, except that the amount of modified curing agent is 20 parts, while the amount of other components remains unchanged.

[0033] Comparative Example 7 is the same as Example 1, except that 400-mesh glass flakes are not used in the active components of the coating, and 40 parts of 150-mesh glass flakes are used instead.

[0034] Comparative Example 8 is the same as Example 1, except that polyurethane-modified epoxy is not added to the modified resin matrix, and the balance is made up by E51, while the amount of other components remains unchanged.

[0035] Comparative Example 9 is the same as Example 1, except that ordinary glass flakes without PDA modification were used, while the amounts of other components remained unchanged.

[0036] Comparative Example 10 is the same as Example 1, except that the gradient cooling process is not used in the preparation of the active components of the coating, and the material is discharged directly after dispersion at 60°C.

[0037] Example 1 The epoxy glass flake anti-corrosion coatings prepared in Examples 1-5 and Comparative Examples 1-6 were sprayed onto pretreated Q235 steel plates using a cross-spraying method. High-pressure airless spraying was employed, controlling the single-pass dry film thickness to be 300-500 μm. The coatings were allowed to dry at 25°C for 24 hours, and then cured for 7 days before testing. The bending strength of the coating was tested using the three-point bending method according to GB / T 1731-2020, with the support spacing set according to the sample thickness and a loading speed of 2 mm / min. The impact strength of the coating was tested according to GB / T 1732-2020. The pull-off adhesion was tested using an automatic adhesion tester at 25°C at a uniform speed not exceeding 1 MPa / s. The adhesion was tested according to GB / T 5210-2006. 9286-2021, a grid with a spacing of 2mm was drawn on the coating surface using a cross-cutting tool. The peeling of the grid edges was observed by tearing with pressure-sensitive adhesive tape to verify the contribution of polyurethane modified epoxy prepolymer to the interfacial bonding force; the test results are shown in Table 2.

[0038] Table 2 Test results of the examples and comparative examples Example Bending strength / MPa Impact strength / kg·cm Pull-off adhesion / MPa Intercoating adhesion / grade Example 1 92.4 55.3 18.6 0 Example 2 88.5 52.1 17.3 0 Example 3 94.7 54.8 18.9 0 Example 4 85.2 48.4 16.2 1 Example 5 90.6 53.7 17.9 0 Comparative Example 1 85.3 46.2 16.1 1 Comparative Example 2 78.4 38.6 14.2 2 Comparative Example 3 82.1 42.7 15.4 1 Comparative Example 4 91.2 53.2 17.1 0 Comparative Example 5 86.6 50.4 11.5 3 Comparative Example 6 65.7 30.2 8.3 4

[0039] As shown in Table 2, the epoxy glass flake anticorrosion coating prepared in the examples exhibits excellent mechanical properties and adhesion, showing a significant improvement in performance compared to the comparative example. In the examples, the introduction of polyurethane-modified epoxy prepolymer into the modified resin matrix enables the formation of flexible segments within the epoxy curing network through toughening, effectively absorbing impact energy and releasing curing stress. Furthermore, during coating application, the silanoxy groups in the modified curing agent can chemically couple with the polar groups on the surface of the modified glass flakes through a chemical reaction, forming a cross-interfacial chemical bridge at the resin-filler interface, tightly bonding the organic and inorganic phases. The gradient cooling process induces the glass flakes to be arranged in a layered, parallel pattern. This highly ordered structure not only enhances the shielding performance of the coating but also resembles the microstructure of reinforced concrete. The structure also significantly enhances the overall mechanical strength and crack resistance of the film. In Comparative Example 1, because no modified graphene oxide is added to the active component, the micro-regions inside the coating lack effective filling of nanoscale fillers, resulting in the inability to effectively compensate for the tiny free volume pores in the resin matrix. This makes it easy to generate microcrack sources during the stress process, leading to a significant decrease in flexural strength and impact strength. In Comparative Example 2, when the cooling rate increases, the rapid cooling speed prevents the molecular chains of the resin matrix from undergoing stress relaxation during the curing process, resulting in huge thermal stress concentration inside the coating. This high internal stress not only makes the coating... The brittleness significantly weakens impact resistance and disrupts effective wetting between interfaces, resulting in a marked decrease in adhesion. Comparative Example 3 shows that when using single-component epoxy resin E51, the initial viscosity of the system increases significantly, leading to poorer encapsulation and wetting of micron-sized glass flakes and nanofillers. The tiny voids at the interface become mechanically weak points, resulting in reduced adhesion and flexural strength. In Comparative Example 4, since UV-9 exists only as a physical dopant and does not participate in the construction of the epoxy network, it interferes to some extent with the tight cross-linking of the polymer long chains and is prone to migration at the interface, leading to reduced adhesion. Slightly reduced; in Comparative Example 5, after using a conventional cashew phenol amine curing agent, the coating and substrate, as well as the layers, were only bonded by physical van der Waals forces. Under high loads or alternating environmental stresses, the lack of interfacial chemical bonding resulted in extremely low bonding strength and a significant reduction in adhesion. Combined with the results of Comparative Example 6, it can be seen that the reduction in the amount of modified curing agent prevented the epoxy groups in the matrix from obtaining enough amine hydrogen for ring-opening reactions, resulting in a severe deficiency in the crosslinking density of the coating. The uncured soft segment components played a negative plasticizing role in the system, leading to a significant reduction in the mechanical strength and adhesion performance of the coating, making it extremely prone to delamination and peeling.

[0040] Experimental Example 2: Shielding and Corrosion Resistance The epoxy glass flake anticorrosive coatings prepared in Examples 1-5 and Comparative Examples 3-9 were used to prepare coatings according to the method in Experimental Example 1. Shielding and anticorrosive performance tests were conducted. The neutral salt spray resistance time was tested according to GB / T 1771-2007. According to GB / T 7790-2008, an artificial defect with a diameter of 6 mm was drilled from the center of the coating sample down to the substrate. The sample was placed in a 3% NaCl solution, a constant potential of -1.05 V was applied, and the solution was maintained at 30°C for 28 days. After the test, the coating was cut and pried open along the defect, and the peel radius was measured. According to GB / T 36724-2018, a three-electrode system was constructed using an electrochemical workstation, with the coating sample as the working electrode, a platinum electrode as the auxiliary electrode, a saturated calomel electrode as the reference electrode, and a 3.5% electrolyte. NaCl solution was used, and a sinusoidal disturbance signal with an amplitude of 20mV was used. The frequency range was from 100kHz to 0.01Hz. The impedance modulus at the low-frequency end of 0.01Hz was recorded. The test results are shown in Table 3.

[0041] Table 3 Test Results of Examples and Comparative Examples Example Neutral salt spray tolerance time / h Anti-cathode stripping diameter / mm <![CDATA[Electrochemical impedance modulus / Ω·cm 2 > Example 1 6500 3.2 <![CDATA[1.2×10 11 ]]> Example 2 5800 4.1 <![CDATA[8.5×10 10 ]]> Example 3 6200 3.6 <![CDATA[9.8×10 10 ]]> Example 4 5200 5.4 <![CDATA[4.6×10 10 ]]> Example 5 6100 3.9 <![CDATA[9.1×10 10 ]]> Comparative Example 3 4200 6.5 <![CDATA[1.4×10 10 ]]> Comparative Example 4 5500 4.8 <![CDATA[5.3×10 10 ]]> Comparative Example 5 3200 15.7 <![CDATA[9.1×10 9 ]]> Comparative Example 6 1800 22.3 <![CDATA[6.3×10 8 ]]> Comparative Example 7 3500 7.2 <![CDATA[4.8×10 9 ]]> Comparative Example 8 4500 5.9 <![CDATA[1.1×10 10 ]]> Comparative Example 9 2200 12.8 <![CDATA[3.5×10 9 ]]>

[0042] As shown in Table 3, the comparative example, through adjustments to the components and process, exhibited significant differences in shielding and anti-corrosion performance compared to the example. In the example, the modified resin matrix, through the compounding of bisphenol A and bisphenol F epoxy resins, significantly reduced the system viscosity, ensuring sufficient wetting of the high aspect ratio glass flakes and nanoscale modified graphene oxide. Simultaneously, the modified glass flakes, using different particle sizes, formed a dense, large-shielding, small-filling labyrinth structure within the coating. Furthermore, the silane segments in the modified curing agent formed stable covalent bonds with the PDA modified layer and metal substrate during curing, greatly enhancing the coating's electrochemical properties. The anti-stripping ability under corrosive environments was tested. In Comparative Example 3, because bisphenol F epoxy resin was not added to the modified resin matrix, and only high-viscosity bisphenol A epoxy resin was used, the fluidity of the system when dispersing glass flakes decreased significantly. Without the wetting of low-viscosity components, the resin could not completely remove microbubbles from the filler surface. These micro-defects at the interface became rapid channels for the penetration of corrosive media in the salt spray test, resulting in a significant reduction in salt spray resistance time. The results of Comparative Example 4 showed that because UV-9 was physically added instead of reactive absorbents to the modified resin matrix, although the initial decline in anti-corrosion performance was slower, UV-9 existed only in the form of physical doping and did not participate in the epoxy network. In the construction of this small molecule substance, molecular migration easily occurs during long-term immersion, disrupting the continuity of the coating structure and resulting in a decrease in the electrochemical impedance modulus compared to the previous example. In Comparative Example 5, without the use of the siloxane bond chemical bridge provided by the modified curing agent, the coating-substrate interface relies solely on physical molecular chain entanglement and conventional Candle Waals forces. Due to the attack of hydroxide ions generated during cathodic polarization, the physical bonding is insufficient to maintain interface stability, resulting in extremely low cathodic disbondment resistance and a significantly increased disbondment diameter. Combined with the results of Comparative Example 6, it can be seen that reducing the amount of modified curing agent fails to form a three-dimensional network structure with high cross-linking density, making it easy for small molecule corrosive media to penetrate the resin gaps, thus affecting the shielding performance. Complete failure; In Comparative Example 7, the absence of 400-mesh fine flakes resulted in a lack of effective filling of the gaps between the 150-mesh large flakes within the coating. During the penetration of corrosive media, the path that should have been blocked by the small flakes became straight, significantly weakening the labyrinth effect. The thicker single-size particle layer was prone to uneven distribution and arrangement, thus weakening the overall anti-corrosion effect. In Comparative Example 8, the lack of polyurethane-modified epoxy meant that the matrix lacked flexible buffer segments, leading to micro-stress concentration phenomena under curing shrinkage and environmental stress. Although the shielding performance was acceptable in the short term, the generation of micro-cracks provided shortcuts for water molecule penetration, thereby reducing its protective effect in long-term salt spray environments. In Comparative Example 9, the surface of ordinary glass flakes lacked polar functional groups and active bridging points, resulting in extremely poor wetting and bonding forces with the resin matrix. The loss of adhesion at the interface caused corrosive media to easily leak along the filler edges, causing severe electrochemical corrosion and interface peeling.

[0043] Experiment Example 3 Barrier Performance Test

[0044] The epoxy glass flake anticorrosive coatings prepared in Examples 1-5 and Comparative Examples 8-10 were used to prepare coatings according to the method in Experimental Example 1. Barrier performance tests were conducted in a QUV aging test chamber according to GB / T 1865-2009. The cycle was set as follows: 4 hours of UV irradiation at 60°C (wavelength 340nm), 4 hours of static treatment at 50°C, for a total of 2000 hours. The gloss level before and after aging was measured using a 60° gloss meter. The impact strength before and after aging was tested using GB / T 1732-2020 from Experimental Example 1, and the impact strength retention rate was calculated. According to GB / T 1037-2021, the prepared coating was sealed in a test cup containing desiccant using the cup method and placed in a constant temperature and humidity chamber at 38°C and 90% relative humidity. The mass change of the test cup was measured, and the water vapor transmission rate was calculated. According to GB / T... 9264-2012 Test of the Sag Limit of Anticorrosive Coatings: A sag meter (50-1000μm gradient) is placed on top of a horizontally fixed sample. The mixed coating is poured into the grooves and then continuously scraped downwards at a uniform speed. Within 1 second of scraping, the sample is placed vertically with the groove stripes horizontal, maintaining this vertical position until the coating is surface dry. The maximum gap thickness between the stripes where the coating does not flow to the next stripe is observed; this is the construction sag limit thickness. The test results are shown in Table 4, where the changes in the aging impact strength retention rate of Examples 1-5 and Comparative Examples 8-10 are as follows: Figure 1 As shown.

[0045] Table 4 Test Results of Examples and Comparative Examples Example Impact strength retention rate / % Artificial accelerated aging gloss retention rate / % <![CDATA[Water vapor transmission rate / g / (m 2 ·24 h)]]> Construction sag limit thickness / μm Example 1 92.4 88.6 <![CDATA[0.85×10 -3 ]]> 850 Example 2 90.1 85.3 <![CDATA[1.12×10 -3 ]]> 720 Example 3 93.7 89.2 <![CDATA[0.94×10 -3 ]]> 910 Example 4 86.5 82.8 <![CDATA[1.46×10 -3 ]]> 650 Example 5 91.2 90.4 <![CDATA[0.78×10 -3 ]]> 980 Comparative Example 8 65.8 86.4 <![CDATA[1.62×10 -3 ]]> 780 Comparative Example 9 82.3 80.5 <![CDATA[3.41×10 -3 ]]> 740 Comparative Example 10 88.7 84.1 <![CDATA[2.19×10 -3 ]]> 320

[0046] Through Table 4, Figure 1The results show that the overall barrier performance of the epoxy glass flake anti-corrosion coating obtained in the comparative example, through adjustments to the components and process, is significantly different from that in the example. In the example, a reactive UV absorber was introduced into the modified resin matrix, which can undergo a chemical co-chain extension reaction with the epoxy resin matrix through the hydroxyl groups in its molecular structure. This chemical bonding permanently locks the UV absorber groups onto the molecular backbone of the film-forming material, preventing physical migration or precipitation during artificial accelerated aging, thus giving the coating extremely high gloss retention and strength retention after aging. At the same time, the introduction of polyurethane-modified epoxy prepolymer forms an interpenetrating network inside the matrix. The structure achieves in-situ toughening through the condensation reaction of isocyanate groups and epoxy groups, effectively absorbing the micro-stress generated by ultraviolet degradation during aging. Furthermore, the segmented cooling and stirring process, combined with the use of polyamide wax thixotropic agents, effectively captures and locks the parallel glass flakes induced by shear force during the linear increase of material viscosity, forming an extremely dense, layered labyrinth structure. This highly ordered arrangement greatly extends the diffusion path of water molecules, significantly reducing water vapor permeability, and the resulting parallel shielding layer significantly improves the maximum thickness for construction sag. In Comparative Example 8, because no polyurethane-modified epoxy prepolymer was added to the modified resin matrix, Lacking the protection of flexible chain extenders, the cross-linked network of the system exhibits significant brittleness. During artificial accelerated aging, the microscopic internal stress generated by photo-oxidative degradation in the matrix cannot be effectively relaxed, leading to a severe decline in impact strength retention and reduced barrier performance. In Comparative Example 9, the lack of polydopamine modification means the glass flake surface possesses only weak polarity. During coating preparation, the unmodified flake surface lacks active amino and hydroxyl groups, preventing the formation of cross-interfacial molecular bonds with the resin matrix. Bonding relies solely on physical van der Waals forces, making the interfacial adhesion highly susceptible to the combined attack of moisture and ultraviolet radiation in the aging environment, ultimately leading to failure. This leads to a sharp increase in water vapor transmission rate, and the gloss retention rate also decreases due to the increased scattering of light by interface reflection. In Comparative Example 10, the material is discharged directly at high temperature without a segmented cooling process. Due to the extremely low viscosity of the system at the time of discharge, the rheological properties of the material in the initial stage of spraying cannot maintain the horizontal orientation of the flakes. The lack of viscosity gradient locking effect causes the glass flakes, which were originally arranged under shear force, to move and tilt in disorder under the influence of gravity, and cannot form a tight layered structure. This not only leads to an increase in water vapor transmission rate, but also makes the coating lack the mechanical support provided by the layered arrangement during thick coating construction. The maximum thickness of the coating is extremely low, and the sagging phenomenon is very easy to occur.

[0047] 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 alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A process for the preparation of high shielding epoxy glass flake anticorrosive coating characterized in that, The preparation process includes the following: The modified epoxy group and modified graphene oxide were sheared and dispersed, and modified glass flakes were added. The mixture was then cooled and stirred in stages, degassed under vacuum, and filtered to obtain the active component. A modified curing agent was added to the active component, stirred and mixed, and cured to obtain the anti-corrosion coating. The modified epoxy group was obtained by reacting bisphenol A type epoxy resin, bisphenol F type epoxy resin, polyurethane modified epoxy prepolymer, and ultraviolet absorber. The modified glass flakes were obtained by stirring and polymerizing glass flakes and dopamine hydrochloride. The modified graphene oxide was obtained by reflux reaction of graphene oxide and 3-glycidyl etheroxypropyltrimethoxysilane. The modified curing agent was obtained by grafting cashew nut shell powder, paraformaldehyde, and 3-aminopropyltriethoxysilane.

2. The preparation process of the high shielding type epoxy glass flake anticorrosive coating according to claim 1, characterized in that, The preparation of the active component includes the following steps: adding the modified epoxy matrix into a reaction vessel, adding the modified graphene oxide, and dispersing at 55-65°C; then adding the modified glass flakes, and lowering the temperature to 35-40°C; finally adding polyamide wax and defoamer, and stirring and mixing at 30-35°C; and obtaining the active component by vacuum degassing and filtration.

3. The preparation process of the high shielding type epoxy glass flake anticorrosive coating according to claim 1, characterized in that, The preparation of the modified epoxy body includes the following steps: placing the bisphenol A type epoxy resin and the bisphenol F type epoxy resin in a reaction vessel, mixing them evenly, adding the polyurethane modified epoxy prepolymer dropwise, and performing a modification reaction to obtain a modified system; then adding the ultraviolet absorber and benzyltrimethylammonium chloride, and performing a chain extension reaction to obtain the modified epoxy body.

4. The preparation process of the high shielding type epoxy glass flake anticorrosive coating according to claim 1, characterized in that, The preparation of the modified glass flakes includes the following steps: dispersing 150-mesh C-type glass flakes and 400-mesh C-type glass flakes in a buffer solution; adding the dopamine hydrochloride and stirring the reaction; and obtaining the modified glass flakes by separation and centrifugation, washing with deionized water, and vacuum drying.

5. The preparation process of a high-shield epoxy glass flake anti-corrosion coating according to claim 1, characterized in that, The preparation of the modified graphene oxide includes the following steps: dispersing the graphene oxide in an aqueous ethanol solution and ultrasonically dispersing it to obtain a mixed system; adding the 3-glycidyl etheroxypropyltrimethoxysilane to the mixed system and refluxing to obtain the modified graphene oxide.

6. The preparation process of a high-shield epoxy glass flake anti-corrosion coating according to claim 1, characterized in that, The preparation of the modified curing agent includes the following steps: adding cashew phenol and ethylenediamine to a reaction vessel and stirring to obtain a mixture; then adding paraformaldehyde dropwise, keeping it at a constant temperature for reaction, and dehydrating it under reduced pressure; then adding 3-aminopropyltriethoxysilane and performing a grafting reaction to obtain the modified curing agent.

7. A high-shield epoxy glass flake anti-corrosion coating, characterized in that, The raw materials for preparing the anti-corrosion coating include bisphenol A type epoxy resin, bisphenol F type epoxy resin, ultraviolet absorber, glass flakes, dopamine hydrochloride, graphene oxide, cashew phenol and paraformaldehyde; the anti-corrosion coating is prepared by the preparation process described in any one of claims 1-6.

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