High-salt-fog-resistance composite anticorrosive paint and preparation method thereof

Abstract

The application discloses a high-salt-fog-resistance composite anticorrosive paint and a preparation method thereof, and relates to the technical field of anticorrosive paint. The anticorrosive paint constructs a synergistic system of pH trigger enzyme catalysis-mineralization-time sequence controlled release cathodic protection-microenvironment regulation-mineralization layer enhancement, modifies Zn-Al powder through tannic acid-zinc (II) complex and poly-L-histidine double-layer coating, matches Tris buffer, fat-soluble oxygen scavenger and functional components such as sodium hyaluronate and KH550, and solves the pain points of existing paint, such as fast consumption of sacrificial anode and brittle fracture of mineralization layer. The preparation process is simple, the salt-fog-resistance life of the coating reaches 12000-15000h, the coating is suitable for harsh environments such as marine engineering, and has a wide application prospect.

Description

Technical Field

[0001] This invention belongs to the field of industrial anti-corrosion materials technology, specifically relating to a high salt spray resistant composite anti-corrosion paint and its preparation method. Background Technology

[0002] In the industrial sector, harsh environments such as high salt spray and humidity can easily lead to corrosion failure of metal substrates, seriously affecting the service life and safety of equipment. As the mainstream protective method, the salt spray resistance and long-term effectiveness of anti-corrosion paint have become core requirements. Existing anti-corrosion paints mostly adopt a single cathodic protection or coating shielding mechanism, but they have significant drawbacks: Zn-Al alloy powder is prone to agglomeration and rapid oxidation consumption, resulting in a short cathodic protection cycle; they lack active repair functions, and the coating cannot be repaired in time after damage, allowing corrosion to continue to spread; enzyme-based repair systems have poor compatibility with sacrificial anodes, are prone to electrochemical conflicts, and enzyme activity is easily lost at low temperatures.

[0003] Meanwhile, traditional metal powder modification methods often involve single coatings or surface treatments, making it difficult to simultaneously address dispersibility, stability, and response timing, resulting in weak synergistic effects in the anti-corrosion system. Furthermore, insufficient microenvironment control can easily lead to problems such as inactivation of repair enzymes and coating layer detachment, further limiting the salt spray resistance life and applicability of anti-corrosion paints. Therefore, developing a highly salt spray resistant composite anti-corrosion paint that combines pH-responsive active repair, time-controlled cathodic protection, and component synergistic compatibility has become an urgent need in the industrial anti-corrosion field. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention proposes a high salt spray resistant composite anti-corrosion paint and its preparation method. This anti-corrosion paint has both pH-responsive mineralization active repair and time-controlled release cathodic protection functions. At the same time, it exhibits excellent performance in terms of component synergistic compatibility, low-temperature enzyme activity retention, and coating stability, and can meet the long-term protection needs of high salt spray and complex corrosive environments in the industrial field.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A high salt spray resistant composite anti-corrosion paint, wherein the anti-corrosion paint is prepared from the following raw materials in parts by weight: 40-60 parts resin matrix, 5-10 parts pH-responsive enzyme-carrying microspheres, 15-25 parts mineralization precursor, 8-15 parts modified nano Zn-Al alloy powder, 3-8 parts microenvironment regulator, and 2-5 parts additives. The pH-responsive enzyme-carrying microspheres are composed of alkaline phosphatase, a cryoprotectant, and a pH-sensitive material. The pH-sensitive material is one or more of polymethacrylate-ethyl acrylate copolymer, chitosan-sodium alginate complex, and poly-L-histidine. The mineralization precursor includes calcium salts, silicates, amino-modified polysiloxanes, sodium hyaluronate, and γ-aminopropyltriethoxysilane. The modified nano-Zn-Al alloy powder has a bilayer coating structure of tannic acid-zinc(II) complex and poly-L-histidine. The microenvironment regulator includes tris(hydroxymethyl)aminomethane buffer and a bentonite complex loaded with lipid-soluble ascorbate palmitate, wherein the loading of ascorbate palmitate is 3-8 wt% of the bentonite mass.

[0006] Optionally, the amino-modified polysiloxane has a mass fraction of 2-3 wt% in the mineralization precursor, and the sodium hyaluronate has a mass fraction of 0.1-0.3 wt%.

[0007] Optionally, the inner layer thickness of the tannic acid-zinc(II) complex is 3-5 nm, and the outer layer thickness of the poly-L-histidine complex is 1-2 nm.

[0008] Optionally, the nano-Zn-Al alloy powder is pre-dispersed in a 0.5wt% Tween-80 solution before being coated with the tannic acid-zinc(II) complex.

[0009] Optionally, the cryoprotectant is a compound of glycerol and propylene glycol in a mass ratio of 1:1, and the amount added is 1-2 wt% of the mass of alkaline phosphatase.

[0010] Optionally, the resin matrix is ​​one or more of epoxy resin, polyurethane resin, and acrylic resin; the additives include polyethylene glycol, dispersant, defoamer, and leveling agent.

[0011] Optionally, the salt spray resistance life of the anti-corrosion paint is 12,000-15,000 hours.

[0012] Optionally, the preparation method of the high salt spray resistant composite anti-corrosion paint is as follows: S1. Alkaline phosphatase, cryoprotectant and pH-sensitive material are mixed at a mass ratio of 1:0.01-0.02:1-2. Deionized water is added to prepare a mixture with a solid content of 10-15wt%. The mixture is stirred at 25-30℃ and 600-800rpm for 1-2 hours. Microspheres are prepared by spray drying. The spray drying inlet temperature is 100-120℃, the outlet temperature is 50-60℃, and the atomization pressure is 0.2-0.3MPa. The pH-responsive enzyme-carried microspheres have a particle size of 1-5μm. S2. After pre-dispersing the nano Zn-Al powder in Tween-80 solution, it was sequentially coated with an inner layer of tannic acid-zinc(II) complex, cross-linked with an acylhydrazine cross-linking agent, and coated with an outer layer of poly-L-histidine containing zinc citrate. Finally, it was dried and sieved to obtain modified nano Zn-Al alloy powder. S3. Heat the resin matrix to 40-50℃, add the mineralization precursor, microenvironment regulator and additives in sequence, and disperse at high speed at 1000-1500 rpm for 30-45 min, keeping the temperature stable during the process. After dispersion, filter with a 1000-mesh filter to obtain a uniform matrix. S4. Add pH-responsive enzyme-carrying microspheres and modified nano-Zn-Al alloy powder to the base material according to the weight ratio, and stir for 20-30 minutes at 30-40℃ and 800-1000rpm. After stirring, treat with an ultrasonic disperser with a power of 100-150W for 5-10 minutes to remove air bubbles, and the high salt spray resistant composite anti-corrosion paint is obtained.

[0013] Optionally, in step S2, the hydrazide crosslinking agent is terephthalohydrazide or adipate dihydrazide, and the amount of crosslinking agent is 5-8 wt% of the mass of the tannic acid-zinc(II) complex; the zinc citrate can slowly release zinc ions to form a coordination structure with poly-L-histidine, improve the density and structural stability of the outer coating layer, and at the same time assist in cathodic protection and improve the salt spray resistance life of the coating, and its addition amount is 0.5-1 wt% of the mass of poly-L-histidine.

[0014] The beneficial effects of this invention are as follows: the high salt spray resistant composite anti-corrosion paint prepared by this invention has a salt spray resistant life of 12,000-15,000 hours, achieving efficient pH-responsive mineralization repair; the multi-modified nano-Zn-Al alloy powder solves the problems of agglomeration and rapid consumption of traditional metal powders, and the time-controlled release mechanism and mineralization repair work synergistically to extend the cathodic protection cycle; the microenvironment regulator improves component compatibility, avoids electrochemical conflicts, and enhances the stability of the coating layer; the dense protective network effectively blocks the penetration of corrosive media, giving the coating excellent overall corrosion resistance and environmental adaptability. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0016] Example 1: This Example 1 describes a high salt spray resistant composite anti-corrosion paint, prepared from the following raw materials in parts by weight: 50 parts of resin matrix (polyurethane resin), 8 parts of pH-responsive enzyme-carrying microspheres (ALP: chitosan-sodium alginate complex: cryoprotectant = 1:0.015:1.5), 20 parts of mineralization precursor (2.5wt% amino-modified polysiloxane, 0.2wt% sodium hyaluronate, 57.3wt% calcium carbonate, 30wt% sodium silicate and 10wt% KH550), 12 parts of modified nano-Zn-Al alloy powder, 5 parts of microenvironment regulator (Tris buffer: bentonite complex loaded with ascorbate palmitate = 2:8), and 3 parts of additives (polyethylene glycol: dispersant: defoamer: leveling agent = 7:6:4:3). The preparation method of the chitosan-sodium alginate complex is as follows: S1. Weigh chitosan and sodium alginate in a mass ratio of 1:1. Add chitosan to a 1wt% acetic acid aqueous solution (solid-liquid ratio 1:50g / mL) and stir at 25℃ and 600rpm for 2 hours until completely dissolved. Add sodium alginate to deionized water (solid-liquid ratio 1:40g / mL) and stir at 25℃ and 500rpm for 1 hour until completely dissolved. S2. Add the chitosan solution dropwise to the sodium alginate solution at a rate of 1 mL / min, stir at 25°C and 700 rpm for 1.5 h, then add 10% of the volume of the composite solution of 2 wt% calcium chloride solution, stir for 30 min to crosslink and solidify. S3. Centrifuge at 3500 rpm for 15 min to collect the precipitate, wash with deionized water 3 times, vacuum dry at 60℃ for 3 h, grind and pass through a 200 mesh sieve, seal and refrigerate for later use.

[0017] The preparation method of pH-responsive enzyme-carrying microspheres is as follows: S1. Weigh ALP, cryoprotectant (glycerol: propylene glycol = 1:1), and chitosan-sodium alginate complex at a mass ratio of 1:0.015:1.5 and mix them. Add deionized water to prepare a 12wt% mixture. Stir at 28℃ and 700rpm for 1.5h to ensure no agglomeration. During this period, use a glass rod to lift and observe every 30min to ensure that there are no visible agglomerated particles in the mixture and that ALP is uniformly dispersed in the pH-sensitive material matrix. S2. The mixture is continuously fed into the feed port of a high-pressure homogenizer, with a working pressure of 20MPa. A single cycle is performed (the feed rate and discharge rate are kept consistent, about 10mL / min). The high-pressure shearing action refines the particle size of the dispersed phase to 1-2μm, improving the uniformity of subsequent microsphere coating. S3. Start the spray dryer for preheating. After the inlet temperature stabilizes at 110℃ and the outlet temperature stabilizes at 55℃, feed the homogenized mixture into the atomizer at a feed rate of 5mL / min using a peristaltic pump. Under an atomization pressure of 0.25MPa, fine droplets are formed. The droplets dry rapidly upon contact with the hot airflow, forming core-shell structured microcapsules. During the drying process, the inlet and outlet temperatures are monitored in real time, and the fluctuation range is controlled within ±2℃. S4. Collect the microsphere product from the spray dryer outlet. First, use a 100-mesh standard sieve for preliminary sieving to remove large agglomerated particles; then use a 200-mesh standard sieve to sieve and collect the fine powder that passes through the sieve, namely pH-responsive enzyme-carried microspheres with a particle size of 2-4 μm. S5. Place the product in a brown bottle and store it at 4°C away from light.

[0018] The preparation method of the modified nano-Zn-Al alloy powder is as follows: S1. Clean the nano Zn-Al alloy powder (80nm) twice with ethanol at 80W ultrasonic cleaning (5min each time), centrifuge at 3500rpm for 10min, and vacuum dry at 60℃ for 1h for later use. S2. Add 0.5wt% Tween-80 aqueous solution (solid-liquid ratio 1:12 g / mL), stir at 35℃ and 600 rpm for 25 min to form a uniform suspension; S3. Weigh the raw materials according to the molar ratio of tannic acid to zinc chloride of 1:2. Dissolve the tannic acid in an ethanol-water mixed solvent (volume ratio 1:20) to prepare a solution with a mass-volume ratio of 1:25 g / mL. Add zinc chloride and stir at 600 rpm for 15 min until completely dissolved to obtain a homogeneous and transparent complex solution. Use a peristaltic pump to dropwise add it to the homogeneous suspension at a rate of 2 mL / min. In a constant temperature water bath at 40℃, stir at 700 rpm for 1.2 h. During this period, sonicate at 80W for 5 min every 20 min (for a total of 3 times). After the reaction is completed, centrifuge at 3500 rpm for 12 min to collect the precipitate. Wash twice with deionized water (each time add 10 mL of deionized water, shake to mix, centrifuge at 3500 rpm for 10 min and discard the supernatant) to remove unreacted raw materials and residual solvent. S4. The precipitate was redispersed in deionized water (solid-liquid ratio 1:15 g / mL), and 6 wt% of adipic acid dihydrazide (tannic acid-zinc(II) complex) was added. The mixture was stirred at 32°C and 500 rpm for 35 min. The cross-linking modification of adipic acid dihydrazide improved the interfacial bonding strength and structural stability of the coating membrane. The cross-linked precipitate was then collected by centrifugation at 3500 rpm for 12 min and vacuum dried for 30 min. S5. Prepare a poly-L-histidine aqueous solution with a mass-to-volume ratio of 1:20 g / mL, add 0.8 wt% zinc citrate and stir until completely dissolved, add the cross-linked precipitate to the solution, stir at 45℃ and 900 rpm for 1.8 h to form an outer coating membrane through electrostatic adsorption and coordination, and collect the double-layer coated product by centrifugation at 4000 rpm for 15 min. S6. The product was dried in a vacuum drying oven at 70℃ and -0.085MPa for 2.5h. After grinding, it was passed through a 200-mesh standard sieve to obtain modified nano Zn-Al alloy powder with a particle size of 80-150nm. The inner layer thickness of the tannic acid-zinc(II) complex was 4.2nm, the outer layer thickness of the poly-L-histidine was 1.5nm, and the coating layer was uniform and dense.

[0019] The preparation method of the mineralization precursor is as follows: S1. Add calcium carbonate and sodium silicate to a high-speed mixer, set the speed to 1000 rpm, and stir at room temperature for 15 minutes to fully mix the two main powders and form a basic powder mixture. S2. Slowly add KH550 to the basic powder mixture, maintain a speed of 800 rpm, and continue stirring for 10 minutes; then add amino-modified polysiloxane and sodium hyaluronate, adjust the speed to 600 rpm, and stir for 8 minutes. S3. Pass the mixed product through a 1000-mesh standard filter to remove undispersed agglomerates and impurities. Collect the uniform and fine powder that has passed through the filter, which is the mineralization precursor. Store it in a sealed and moisture-proof package.

[0020] This embodiment describes a method for preparing a high salt spray resistant composite anti-corrosion paint. The specific preparation steps are as follows: S1. Add bentonite powder to deionized water to prepare a suspension with a solid content of 10 wt%. Stir at 600 rpm for 30 min to fully swell and disperse. Then add ascorbate palmitate (5 wt% of the bentonite mass), heat to 50℃, and stir at 800 rpm for 2 h for adsorption. After the reaction is completed, centrifuge at 3500 rpm for 15 min, discard the supernatant, vacuum dry at 60℃ to constant weight, grind through a 200-mesh sieve to obtain the bentonite composite loaded with ascorbate palmitate, and seal for later use. S2. Weigh each component precisely according to the formula: 50 parts polyurethane resin, 8 parts pH-responsive enzyme-carrying microspheres, 12 parts modified nano Zn-Al alloy powder, 20 parts mineralization precursor, 5 parts microenvironment regulator, and 3 parts additives. S3. Add all the above components to the reactor in sequence, maintain room temperature, turn on the stirring device, set the speed to 600 rpm, and stir continuously for 30 minutes to make the components initially mixed evenly and form a homogeneous suspension system, so as to avoid local high concentrations that may lead to agglomeration. S4. Heat the reactor to 45°C, adjust the stirring speed to 1200 rpm, and maintain this temperature and speed for high-speed dispersion for 60 min; after the high-speed dispersion is completed, use 80W power ultrasonic-assisted dispersion for 20 min. S5. After the reaction is complete, let the system cool naturally to room temperature, then filter the material through a 200-mesh filter to remove any possible impurities or large particles that are not fully dispersed, and obtain a high salt spray resistant self-healing anti-corrosion paint.

[0021] Example 2: This Example 2 describes a high salt spray resistant composite anti-corrosion paint, prepared from the following raw materials in parts by weight: 50 parts of resin matrix (polyurethane resin), 10 parts of pH-responsive enzyme-carrying microspheres (ALP: chitosan-sodium alginate complex: cryoprotectant = 1:0.015:1.5), 20 parts of mineralization precursor (2.5wt% amino-modified polysiloxane, 0.2wt% sodium hyaluronate, 57.3wt% calcium carbonate, 30wt% sodium silicate and 10wt% KH550), 12 parts of modified nano-Zn-Al alloy powder, 5 parts of microenvironment regulator (Tris buffer: bentonite complex loaded with ascorbate palmitate = 2:8), and 3 parts of additives (polyethylene glycol: dispersant: defoamer: leveling agent = 7:6:4:3). The preparation methods of pH-responsive enzyme-carrying microspheres, mineralization precursors and modified nano-Zn-Al alloy powder are the same as in Example 1; The preparation method of the high salt spray resistant composite anti-corrosion paint in this embodiment is the same as that in Example 1, except that the amount of pH-responsive enzyme-loaded microspheres is increased to 10 parts.

[0022] Example 3: A high salt spray resistant composite anti-corrosion paint of Example 3 is prepared from the following raw materials in parts by weight: 50 parts of resin matrix (polyurethane resin), 8 parts of pH-responsive enzyme-carrying microspheres (ALP: chitosan-sodium alginate complex: cryoprotectant = 1:0.015:1.5), 20 parts of mineralization precursor (2.5wt% amino-modified polysiloxane, 0.2wt% sodium hyaluronate, 57.3wt% calcium carbonate, 30wt% sodium silicate and 10wt% KH550), 15 parts of modified nano-Zn-Al alloy powder, 5 parts of microenvironment regulator (Tris buffer: bentonite complex loaded with ascorbate palmitate = 2:8), and 3 parts of additives (polyethylene glycol: dispersant: defoamer: leveling agent = 7:6:4:3). The preparation methods of pH-responsive enzyme-carrying microspheres, mineralization precursors and modified nano-Zn-Al alloy powder are the same as in Example 1; The preparation method of the high salt spray resistant composite anti-corrosion paint in this embodiment is the same as that in Example 1, except that the amount of modified nano Zn-Al alloy powder is increased to 15 parts.

[0023] Comparative Example 1: The anti-corrosion paint of Comparative Example 1 was prepared from the following raw materials in parts by weight: 58 parts of resin matrix (polyurethane resin), 20 parts of mineralized precursor (2.5wt% amino-modified polysiloxane, 0.2wt% sodium hyaluronate, 57.3wt% calcium carbonate, 30wt% sodium silicate and 10wt% KH550), 12 parts of modified nano Zn-Al alloy powder, 5 parts of microenvironment regulator (Tris buffer: bentonite complex loaded with ascorbate palmitate = 2:8), and 3 parts of additives (polyethylene glycol: dispersant: defoamer: leveling agent = 7:6:4:3). The preparation methods of the mineralization precursor and the modified nano-Zn-Al alloy powder are the same as in Example 1; In this comparative example, the preparation method of the anti-corrosion paint is the same as that in Example 1, except that pH-responsive enzyme-carrying microspheres are not added, and an equal amount of polyurethane resin is used instead.

[0024] Comparative Example 2: The anti-corrosion paint of Comparative Example 2 was prepared from the following raw materials in parts by weight: 50 parts of resin matrix (polyurethane resin), 8 parts of pH-responsive enzyme-carrying microspheres (ALP: chitosan-sodium alginate complex: cryoprotectant = 1:0.015:1.5), 20 parts of mineralization precursor (2.5wt% amino-modified polysiloxane, 0.2wt% sodium hyaluronate, 57.3wt% calcium carbonate, 30wt% sodium silicate and 10wt% KH550), 12 parts of nano Zn-Al alloy powder, 5 parts of microenvironment regulator (Tris buffer: bentonite complex loaded with ascorbate palmitate = 2:8), and 3 parts of additives (polyethylene glycol: dispersant: defoamer: leveling agent = 7:6:4:3). The preparation methods of pH-responsive enzyme-carrying microspheres and mineralized precursors are the same as in Example 1; The preparation method of the anti-corrosion paint in this comparative example is the same as that in Example 1, except that the modified nano-Zn-Al alloy powder is replaced with unmodified nano-Zn-Al alloy powder.

[0025] Performance testing 1. Neutral salt spray test Neutral salt spray (NSS) tests were conducted according to GB / T 10125-2021 standard: The anti-corrosion paint samples from Examples 1-3 and Comparative Examples 1-2 were uniformly coated onto the surface of Q235 steel test pieces that had undergone rust removal, degreasing, and sanding pretreatment. The dry film thickness was controlled to be 80-100 μm. After the coating was fully cured, cross-shaped scratches (50 mm length, 1 mm width, and 2 mm spacing) were made on the test piece surface using a scratching tool, penetrating the coating to the substrate. The test pieces were then placed in the salt spray test chamber at an angle of 15°-30° to the vertical plane. A 5wt% solution of analytical grade sodium chloride and deionized water was used to prepare the solution. NaCl aqueous solution was used to adjust the pH value of the solution to 6.5-7.2 using a pH meter. The test chamber temperature was set at 35℃±2℃, the salt spray deposition rate was 1.0-2.0mL / (80cm2·h), and the relative humidity inside the chamber was ≥95%. Continuous spraying was carried out without interruption. The blistering, rusting, peeling, and corrosion spread at scratches of the test piece coating were observed and recorded regularly. The cumulative spraying time when the test piece showed obvious corrosion (blistering level ≥2 or scratch corrosion width ≥2mm) was taken as the salt spray resistance time of the sample.

[0026] Table 1. Neutral Salt Spray Test Data for Different Samples

[0027] Examples 1-3 all exhibited salt spray resistance times exceeding 12,000 hours, with coating blistering and rusting grades both at level 0, and scratches spreading only 0.5 mm wide, demonstrating exceptionally long-lasting salt spray corrosion resistance. In contrast, Comparative Examples 1 and 2 showed significantly shorter salt spray resistance times, with noticeable blistering, rusting, and spreading of corrosion on the coating. This indicates that the present invention, by introducing a pH-responsive self-healing system and modified nano-Zn-Al alloy powder, can significantly improve the salt spray resistance of the coating and effectively inhibit the erosion of the substrate by corrosive media.

[0028] 2. Self-healing performance test Straight scratches (40 mm in length and approximately 0.5 mm in width) were prepared on the cured coating specimens of Examples 1-3 and Comparative Examples 1-2 using a utility knife to penetrate the coating to the substrate. The initial volume of the scratches was weighed and recorded. The specimens were then immersed in a 3.5 wt% sodium chloride solution at room temperature for 72 h. After drying, the changes in the morphology of the scratches were observed using a three-dimensional video microscope. The scratch repair rate was calculated by the change in cross-sectional area before and after scratch repair.

[0029] Table 2. Test data on the self-healing performance of different samples

[0030] Examples 1-3, after soaking in a 3.5wt% sodium chloride solution for 72 hours, all showed a self-repair rate of over 85%, with significant repair of the scratch morphology, demonstrating excellent environmentally responsive self-repair capabilities. Comparative Example 1, lacking pH-responsive enzyme-carried microspheres, exhibited almost no self-repair effect, with a self-repair rate of only 4.8%. This demonstrates that the enzyme-catalyzed mineralization self-repair system constructed in this invention can effectively achieve in-situ repair of coating damage under corrosive environments, thereby improving the service life of the coating.

[0031] 3. Electrochemical Impedance Spectroscopy (EIS) Test According to the general specifications for electrochemical testing, a three-electrode system was adopted (saturated calomel electrode as reference electrode, platinum sheet as counter electrode, and coated Q235 steel as working electrode). 3.5wt% sodium chloride solution was used as the corrosion medium. Electrochemical impedance spectroscopy was performed after the open circuit potential stabilized. The test frequency range was set to 105Hz-10-2Hz, and the AC excitation signal amplitude was 10mV. The low-frequency impedance modulus |Z| of 0.01Hz was obtained by fitting the equivalent circuit to characterize the anti-corrosion barrier performance of the coating.

[0032] Table 3 EIS test data for different samples

[0033] The low-frequency impedance modulus |Z|0.01Hz of Examples 1-3 all reached the order of 109Ω⋅cm2, which is much higher than that of Comparative Example 1 and Comparative Example 2, indicating that the composite anti-corrosion paint prepared by the present invention has excellent barrier ability against corrosive media and interface protection stability. The comparative examples, due to the lack of self-healing components or the use of unmodified alloy powder, showed a significant decrease in coating density and protective effect, and a significant reduction in impedance value, further verifying the highly efficient anti-corrosion effect of the synergistic protection system of the present invention.

[0034] 4. Adhesion test Adhesion tests were conducted according to GB / T 5210-2006 "Paints and Varnishes - Pull-off Adhesion Test": Coating specimens from Examples 1-3 and Comparative Examples 1-2 were placed at a temperature of (23±2)℃ and a relative humidity of (50±5)% for 24 hours. The test column was uniformly bonded to the coating surface using a special adhesive. After the adhesive was completely cured, the specimen was clamped in the pull-off tester. The tensile rate was set to (10±2) mm / min, and a tensile force was applied uniformly until the test column separated from the specimen. The maximum tensile force value when the specimen was damaged was recorded, and the adhesion strength was calculated. At the same time, the failure mode and the proportion of the failure area were observed and recorded to evaluate the adhesion performance of the coating.

[0035] Table 4 Adhesion test data for different samples

[0036] The adhesion strength of Examples 1-3 was all above 12.8 MPa, and the failure mode was cohesive failure. The failure area accounted for more than 95%, indicating that the coating and the metal substrate were firmly bonded and had excellent adhesion. The adhesion strength of Comparative Examples 1 and 2 was significantly lower, and the failure mode was adhesion failure. This indicates that the introduction of self-healing components and modified Zn-Al alloy powder can effectively improve the interfacial bonding state between the coating and the substrate and improve the overall adhesion of the coating.

[0037] 5. Impact resistance test According to GB / T 1732-2020 standard for testing the impact resistance of paints and varnishes, the coating test piece is placed on the test piece holder of the impact tester, and a weight is dropped freely from a specified height to impact the coating surface of the test piece. The coating in the impact area is observed to see whether cracks, peeling, wrinkling or other damage occurs. The product of the maximum weight of the weight that does not cause damage and the drop height is taken as the impact resistance strength of the coating, and the unit is kg·cm.

[0038] Table 5 Impact resistance test data for different samples

[0039] The impact strength of Examples 1-3 all reached 50 kg·cm. After impact, the coating showed no cracks, peeling, or wrinkling, demonstrating good toughness and impact resistance. The impact strength of Comparative Examples 1 and 2 was only 30 kg·cm and 35 kg·cm, respectively. After impact, the coating showed slight cracks or wrinkling defects. This indicates that the formulation system of the present invention can effectively improve the mechanical properties and resistance to external damage of the coating, and ensure the integrity of the coating in complex usage environments.

[0040] 6. Pencil hardness test According to the GB / T 6739-2022 standard for pencil hardness test of paints and varnishes, pencils of different hardness grades were used. Under the condition that the pencil lead was ground flat and at a 45° angle to the coating surface, a constant load of 750g was used to push the pencil across the coating surface, and the pencil hardness was gradually increased. The highest pencil hardness grade that did not produce scratches on the coating surface was taken as the pencil hardness of the sample.

[0041] Table 6. Test data of pencil hardness for different samples

[0042] The pencils in Examples 1-3 all reached a hardness grade of 2H. After testing, the coating surface showed no scratches or damage, demonstrating good surface hardness and scratch resistance. The pencils in Comparative Examples 1 and 2 had a hardness of only H, and slight scratches appeared on the surface. This indicates that the present invention can effectively improve the surface hardness of the coating and enhance the scratch resistance and wear resistance of the coating during use through the synergistic effect of the mineralized precursor and the modified filler.

[0043] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high salt spray resistant composite anti-corrosion paint, characterized in that, The anti-corrosion paint is prepared from the following raw materials in parts by weight: 40-60 parts resin matrix, 5-10 parts pH-responsive enzyme-carrying microspheres, 15-25 parts mineralization precursor, 8-15 parts modified nano Zn-Al alloy powder, 3-8 parts microenvironment regulator, and 2-5 parts additives. The pH-responsive enzyme-carrying microspheres are composed of alkaline phosphatase, a cryoprotectant, and a pH-sensitive material. The pH-sensitive material is one or more of polymethacrylate-ethyl acrylate copolymer, chitosan-sodium alginate complex, and poly-L-histidine. The mineralization precursor includes calcium salts, silicates, amino-modified polysiloxanes, sodium hyaluronate, and γ-aminopropyltriethoxysilane. The modified nano-Zn-Al alloy powder has a bilayer coating structure of tannic acid-zinc(II) complex and poly-L-histidine. The microenvironment regulator includes tris(hydroxymethyl)aminomethane buffer and a bentonite complex loaded with lipid-soluble ascorbate palmitate, wherein the loading of ascorbate palmitate is 3-8 wt% of the bentonite mass.

2. The high salt spray resistant composite anticorrosive paint according to claim 1, characterized in that, The amino-modified polysiloxane has a mass fraction of 2-3 wt% in the mineralization precursor, and the sodium hyaluronate has a mass fraction of 0.1-0.3 wt%.

3. The high salt spray resistant composite anticorrosive paint according to claim 1, characterized in that, The inner layer thickness of the tannic acid-zinc(II) complex is 3-5 nm, and the outer layer thickness of the poly-L-histidine complex is 1-2 nm.

4. The high salt spray resistant composite anticorrosive paint according to claim 1, characterized in that, The nano-Zn-Al alloy powder was pre-dispersed in a 0.5wt% Tween-80 solution before being coated with tannic acid-zinc(II) complex.

5. The high salt spray resistant composite anticorrosive paint according to claim 1, characterized in that, The cryoprotectant is a compound of glycerol and propylene glycol in a mass ratio of 1:1, and the amount added is 1-2 wt% of the mass of alkaline phosphatase.

6. The high salt spray resistance composite anticorrosive paint according to claim 1, characterized in that, The resin matrix is ​​one or more of epoxy resin, polyurethane resin and acrylic resin; the additives include polyethylene glycol, dispersant, defoamer and leveling agent.

7. The high salt spray resistant composite anticorrosive paint according to claim 1, characterized in that, The salt spray resistance life of the anti-corrosion paint is 12,000-15,000 hours.

8. A method for preparing a high salt spray resistant composite anticorrosive paint, used to prepare the high salt spray resistant composite anticorrosive paint according to any one of claims 1-7, characterized in that, The specific preparation method is as follows: S1. Alkaline phosphatase, cryoprotectant and pH-sensitive material are mixed at a mass ratio of 1:0.01-0.02:1-2. Deionized water is added to prepare a mixture with a solid content of 10-15wt%. The mixture is stirred at 25-30℃ and 600-800rpm for 1-2 hours. Microspheres are prepared by spray drying. The spray drying inlet temperature is 100-120℃, the outlet temperature is 50-60℃, and the atomization pressure is 0.2-0.3MPa. The pH-responsive enzyme-carried microspheres have a particle size of 1-5μm. S2. After pre-dispersing the nano Zn-Al powder in Tween-80 solution, it was sequentially coated with an inner layer of tannic acid-zinc(II) complex, cross-linked with an acylhydrazine cross-linking agent, and coated with an outer layer of poly-L-histidine containing zinc citrate. Finally, it was dried and sieved to obtain modified nano Zn-Al alloy powder. S3. Heat the resin matrix to 40-50℃, add the mineralization precursor, microenvironment regulator and additives in sequence, and disperse at high speed at 1000-1500 rpm for 30-45 min, keeping the temperature stable during the process. After dispersion, filter with a 1000-mesh filter to obtain a uniform matrix. S4. Add pH-responsive enzyme-carrying microspheres and modified nano-Zn-Al alloy powder to the base material according to the weight ratio, and stir for 20-30 minutes at 30-40℃ and 800-1000rpm. After stirring, treat with an ultrasonic disperser with a power of 100-150W for 5-10 minutes to remove air bubbles, and the high salt spray resistant composite anti-corrosion paint is obtained.

9. The method for preparing a high salt spray resistant composite anticorrosive paint according to claim 8, characterized in that, In step S2, the hydrazide crosslinking agent is terephthalohydrazide or adipate dihydrazide, and the amount of crosslinking agent is 5-8 wt% of the mass of the tannic acid-zinc(II) complex; the zinc citrate is used as a zinc ion slow-release agent, and its addition amount is 0.5-1 wt% of the mass of poly-L-histidine.

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