Marine environment adapted motor weather-proof anticorrosion composite coating and preparation method thereof

Abstract

The application provides a motor weather-resistant anticorrosion composite coating suitable for marine environment and a preparation method thereof, and belongs to the technical field of coating.The motor weather-resistant anticorrosion composite coating suitable for marine environment is formed by sequentially spraying and solidifying a primer, an intermediate paint and a topcoat on the outer surface of a motor insulation structure, wherein the primer is prepared from the following raw materials in parts by weight: 30-35 parts of water-based epoxy-acrylate hybrid emulsion, 5-6 parts of polypropylene glycol diglycidyl ether, 58-62 parts of zinc powder, 3-5 parts of phytic acid modified alpha-ZrP, 1-1.5 parts of fumed silica, 0.1-0.5 parts of nanocellulose, 1-1.5 parts of silane coupling agent KH-560, 15-18 parts of polyamide curing agent and 0.3-0.5 parts of DMP-30; the mass ratio of flaky zinc powder to spherical zinc powder is 6:4.The application realizes excellent anticorrosion performance and adaptability to various intermediate paints and topcoats while reducing the amount of zinc powder, and is especially suitable for long-term protection of auxiliary motors for marine wind power and other harsh environments.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, specifically relating to a weather-resistant and corrosion-resistant composite coating for motors adapted to marine environments and its preparation method. Background Technology

[0002] Currently, auxiliary motors for offshore wind power typically use zinc-rich epoxy coatings as primers. Their core function is cathodic protection, with a zinc powder content as high as 80%, which forms a conductive zinc layer on the metal substrate surface. When the coating is damaged, the zinc preferentially oxidizes, protecting the steel substrate from corrosion.

[0003] Guan Yingdong et al. (see: Guan Yingdong, Hou Xiaoyan, Sun Chunlong. Research on long-lasting anti-corrosion coating of graphene-zinc powder [J]. Electroplating and Finishing, 2017, 36(14):6) pointed out that zinc-rich primer is one of the most important and widely used heavy-duty anti-corrosion coatings for ships, marine facilities, bridges, large equipment and various large building steel components. The zinc content of epoxy zinc-rich primer with better performance is mostly around 80.0%. The high zinc content also brings the following disadvantages to zinc-rich primer: (1) Zinc oxide fumes and zinc vapors generated during welding, cutting and other hot processing can harm human health and easily lead to "zinc fever"; (2) The paint film has poor density and low strength, and poor compatibility with the topcoat; (3) High density, the density of epoxy zinc-rich primer is generally 3.0 g / cm³. 3 Around 4.0 g / cm³, with a dry film density exceeding 4.0 g / cm³. 3 It is nearly twice as strong as ordinary epoxy primer, which limits its application in special equipment.

[0004] However, existing zinc-rich epoxy primers still have the following problems when applied to auxiliary motors for marine wind power: (1) Zinc powder is not only an important electrochemical rust-preventing material, but its corrosion products can also fill the gaps in the coating and achieve self-healing to a certain extent. Studies have shown that the protective effect of zinc powder on steel largely depends on the self-repairing ability of the corrosion products on the coating. However, this self-healing effect is conditional. When the zinc powder content is moderate and the corrosion rate is controllable, the zinc powder corrosion product, basic zinc carbonate, can effectively fill the pores; but when the zinc powder content is too high, the porosity of the coating increases, the penetration of the corrosive medium accelerates, and zinc corrosion will become uncontrollable. At this time, a large amount of zinc powder will be consumed, and the corrosion products are mainly zinc hydroxide and zinc oxide, whose volume expansion is about 3-5 times that of metallic zinc, generating greater internal stress inside the coating. When the internal stress exceeds the strength or adhesion of the coating, it will lead to blistering, microcrack propagation, interlayer peeling and other forms of damage, ultimately causing the overall failure of the coating. (2) Existing zinc-rich epoxy primers cannot achieve good synergistic effects with many commercially available intermediate and topcoats, resulting in poor interlayer adhesion and limiting the overall protective performance of the coating system.

[0005] Therefore, how to reduce the amount of zinc powder used while building a more stable and efficient synergistic protection system to effectively inhibit the damage to the coating structure caused by zinc corrosion and thus improve the long-term anti-corrosion performance of the coating remains a technical challenge that urgently needs to be solved in the field of corrosion protection for auxiliary motors for marine wind power. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the technical problem to be solved by the present invention is to provide a weather-resistant and corrosion-resistant composite coating for motors that is adapted to the marine environment. It achieves excellent corrosion resistance and compatibility with various intermediate and topcoats while reducing the amount of zinc powder used. It is especially suitable for long-term protection in harsh environments such as auxiliary motors for marine wind power.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a weather-resistant and corrosion-resistant composite coating for motors adapted to marine environments, which is formed by sequentially spraying a primer, an intermediate coat, and a topcoat onto the outer surface of the motor insulation structure and then curing them separately. The primer is prepared from the following raw materials in parts by weight: 30-35 parts of waterborne epoxy-acrylate hybrid emulsion, 5-6 parts of polypropylene glycol diglycidyl ether, 58-62 parts of zinc powder, 3-5 parts of phytic acid-modified α-ZrP, 1-1.5 parts of fumed silica, 0.1-0.5 parts of nanocellulose, 1-1.5 parts of silane coupling agent KH-560, 15-18 parts of polyamide curing agent, and 0.3-0.5 parts of DMP-30; the mass ratio of flakes to spheres in the zinc powder is 6:4.

[0008] Optionally, the nanocellulose has a diameter of 4-20 nm and a length of 1-3 μm.

[0009] Optionally, the phytic acid-modified α-ZrP is prepared by α-ZrP and phytic acid powder at a mass ratio of 1:0.5.

[0010] Optionally, the intermediate paint is an epoxy micaceous iron oxide intermediate paint, and the topcoat is a fluorocarbon topcoat.

[0011] Optionally, the primer is prepared by the following method: Step A: Preparation of phytic acid-modified α-ZrP; Step B: Weigh out the silane coupling agent KH-560 by weight and perform pre-hydrolysis to obtain pre-hydrolyzed silane coupling agent KH-560; Step C: Weigh out the nanocellulose by weight, add deionized water, and perform pre-dispersion treatment to obtain a nanocellulose pre-dispersion slurry with a solid content of 5-6%. Step D: Weigh the following raw materials by weight: waterborne epoxy-acrylate hybrid emulsion, polypropylene glycol diglycidyl ether, zinc powder, phytic acid-modified α-ZrP and fumed silica, mix them evenly, then add nanocellulose pre-dispersed slurry, and continue mixing for 15-20 minutes to obtain component A; Step E: Weigh the following raw materials by weight: polyamide curing agent and DMP-30, mix them evenly to obtain component B; Step F: Mix component A obtained in step D, component B obtained in step E, and pre-hydrolyzed silane coupling agent KH-560 obtained in step B, and stir evenly to obtain the primer. The zinc powder has a flake to spherical mass ratio of 6:4.

[0012] In this invention, zinc powder is mixed in a mass ratio of 6:4 between flake and spherical particles. The flake zinc powder forms a labyrinth effect in the coating, extending the penetration path of corrosive media. The spherical zinc powder ensures point contact between zinc powder particles, maintains the overall conductivity of the coating, and guarantees the continuity of cathodic protection function, thus synergistically achieving physical shielding and electrochemical protection.

[0013] Optionally, the phytic acid-modified α-ZrP is prepared by the following method: α-ZrP and phytic acid powder are mixed at a mass ratio of 1:0.5 and ball-milled at 350-450 rpm for 2-2.5 h to obtain the ball-milled product; the ball-milled product is dispersed in hot water at 80-85℃, the pH is adjusted to 4.0-4.2, the reaction is carried out for 3-3.5 h, the product is centrifuged and washed until neutral, and then dried to obtain the final product.

[0014] This invention employs a two-step process involving ball milling and hot water reaction to introduce phytic acid-modified α-ZrP, solving the problem of α-ZrP's tendency to agglomerate and be difficult to disperse in organic resins. It also compensates for the reduced corrosion resistance of the coating after reducing zinc powder usage. This invention demonstrates that while reducing zinc powder usage by 22.5%-25%, the salt spray resistance of the composite coating is comparable to that of traditional high-zinc primers, and it exhibits significantly greater structural stability in a 63-day corrosion resistance test. Compared to directly adding α-ZrP or using phytic acid alone, this invention's phytic acid-modified α-ZrP achieves a dual effect: providing a physical barrier against corrosive media through the lamellar structure of α-ZrP, and providing chemical passivation through the chelating effect of phytic acid to regulate the zinc corrosion rate, resulting in better long-term corrosion resistance.

[0015] Optionally, the preparation steps of the pre-hydrolyzed silane coupling agent KH-560 are as follows: anhydrous ethanol and water are mixed at a volume ratio of (8-9):1, and the pH is adjusted to 4.0-4.5 with acetic acid to obtain an alcohol-water mixture; silane coupling agent KH-560 is added dropwise to the alcohol-water mixture, and the mixture is stirred at 25±2℃ for 2-4 hours to obtain the pre-hydrolyzed silane coupling agent KH-560; wherein the total mass of the alcohol-water mixture is 3-4 times the mass of the silane coupling agent KH-560.

[0016] In this invention, the silane coupling agent KH-560 (γ-glycidoxypropyltrimethoxysilane) exhibits poor affinity between its methoxy groups and the aqueous resin when not hydrolyzed, easily leading to phase separation. This invention enhances compatibility with the resin matrix by controlling the alcohol-to-water ratio and dosage under weakly acidic conditions through pre-hydrolysis.

[0017] Optionally, the mixing in step D is carried out using a high-speed disperser with a dispersion speed of 800-1200 rpm and a dispersion time of 15-30 min.

[0018] Optionally, the stirring speed in step F is 300-500 rpm, and the stirring time is 10-20 min.

[0019] This invention also provides a method for preparing a weather-resistant and corrosion-resistant composite coating for motors adapted to marine environments, comprising the following steps: Step 1: Pre-treat the outer surface of the motor insulation structure to be sprayed, remove surface defects and clean it thoroughly; Step 2: Spray primer onto the pretreated surface and cure to form a base layer with a thickness ≥ 60 μm; Step 3: Spray an intermediate paint onto the base layer and cure it to form an intermediate layer with a thickness ≥120μm; Step 4: Spray a topcoat onto the intermediate layer and cure it to form a surface layer with a thickness ≥60μm, thus obtaining the weather-resistant and corrosion-resistant composite coating for the motor.

[0020] After each coat of paint has completely dried, the dry film thickness is measured. After all coatings are completed, the overall dry film thickness is inspected again. If it meets the requirements, the weather-resistant and corrosion-resistant composite coating for the motor is obtained.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a weather-resistant and corrosion-resistant composite coating for motors adapted to marine environments. It is composed of a primer, an intermediate coat, and a topcoat applied sequentially. The primer contains a water-based epoxy-acrylate hybrid emulsion, zinc powder in a 6:4 ratio of flakes and spheres, phytic acid-modified α-ZrP, fumed silica, and nanocellulose, etc. This invention addresses the dual nature of zinc corrosion in zinc-rich primers, achieving excellent corrosion resistance and compatibility with various intermediate and topcoats while reducing the amount of zinc powder used. It is particularly suitable for long-term protection in harsh environments such as auxiliary motors for marine wind power.

[0022] First, this invention reduces the zinc powder content in the primer and introduces phytic acid-modified α-ZrP. Utilizing the chemical passivation effect of phytic acid-modified α-ZrP, the corrosion rate of zinc is controlled, enabling it to maintain its self-healing function for a longer period. Simultaneously, it avoids the potential problems of uncontrolled zinc corrosion and excessive volume expansion in traditional zinc-rich primers. The coating showed no blistering or cracking after a 63-day salt spray test. The phytic acid-modified α-ZrP of this invention is prepared using a combination of ball milling and low-temperature hot water reaction. The localized high temperature, high pressure, and strong shear field generated by ball milling expose the active sites of α-ZrP and promote the reaction between α-ZrP and phytic acid. The low-temperature hot water environment further promotes chemical bonding, achieving more efficient and uniform chemical modification.

[0023] Secondly, by optimizing the zinc powder content and introducing flake-shaped zinc powder (flake: spherical = 6:4), the present invention enables the flake-shaped zinc powder to form a labyrinth effect in the coating, significantly extending the diffusion path of the corrosive medium. Simultaneously, the phytic acid-modified α-ZrP nanosheets further fill the micropores, and the fumed silica and nanocellulose form a fiber-particle dual network, achieving a balance between density and cathodic protection.

[0024] Furthermore, this invention uses a water-based epoxy-acrylate hybrid emulsion as the film-forming resin and pre-hydrolyzes KH-560 to enhance the adhesion of the primer. Simultaneously, the low porosity of the primer surface provides a good adhesion substrate for intermediate and topcoats, enabling the primer of this invention to form a good interlayer adhesion system with various commercially available epoxy micaceous iron oxide intermediate coats and fluorocarbon topcoats, overcoming the poor compatibility of traditional zinc-rich primers.

[0025] Furthermore, this invention combines nanocellulose with fumed silica to enhance coating density. The two components prevent zinc powder sedimentation through steric hindrance and hydrogen bonding networks, while the fiber network fills micropores, reducing coating porosity and enhancing corrosion resistance. This invention reduces zinc powder usage while achieving superior salt spray resistance compared to traditional zinc-rich primers, and further reduces VOC content to below 50 g / L, resulting in better environmental performance. Detailed Implementation

[0026] To better understand the present invention, the following embodiments further illustrate the content of the invention, but the scope of protection of the present invention is not limited to the following embodiments. Numerous specific details are set forth in the following description to provide a more thorough understanding of the invention. However, it will be apparent to those skilled in the art that the present invention can be practiced without one or more of these details.

[0027] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention.

[0028] Unless otherwise specified, all raw materials are derived from commercially available products and do not contain any unspecified components other than unavoidable impurities.

[0029] In the following examples, the aqueous epoxy-acrylate hybrid emulsion has a solids content of 45±5%; polypropylene glycol diglycidyl ether, CAS: 26142-30-3; and zinc flake powder: D. 50 Spherical zinc powder, 10-15μm in diameter and 0.2-0.5μm in thickness: D 50 4-9μm; α-ZrP (α-zirconium phosphate), CAS: 13772-29-7; phytic acid, CAS: 83-86-3; fumed silica, CAS: 7631-86-9; nanocellulose (CNF), diameter 4-20nm, length 1-3μm; silane coupling agent KH-560, CAS: 2530-83-8; polyamide curing agent 650, CAS: 19438-64-3; DMP-30, CAS: 90-72-2.

[0030] Examples 1-3 below are specific implementation schemes for phytic acid-modified α-ZrP.

[0031] Example 1: α-ZrP and phytic acid powder were mixed at a mass ratio of 1:0.5 and placed in a planetary ball mill. The mixture was ball-milled at 400 rpm for 2 hours to obtain the ball-milled product. The ball-milled product was dispersed in hot water at 80°C (solid-liquid ratio 1:20), and the pH was adjusted to 4.1 with acetic acid. The mixture was reacted in a constant temperature water bath for 3 hours. The mixture was repeatedly centrifuged and washed with deionized water until neutral. The mixture was then vacuum dried at 80°C for 12 hours to obtain phytic acid-modified α-ZrP.

[0032] Example 2: α-ZrP and phytic acid powder were mixed at a mass ratio of 1:0.5 and placed in a planetary ball mill. The mixture was ball-milled at 350 rpm for 2.5 h to obtain the ball-milled product. The ball-milled product was dispersed in hot water at 85°C (solid-liquid ratio 1:20), and the pH was adjusted to 4.0 with acetic acid. The mixture was reacted in a constant temperature water bath for 3.5 h. The mixture was repeatedly centrifuged and washed with deionized water until neutral, and then vacuum dried at 80°C for 12 h to obtain phytic acid-modified α-ZrP.

[0033] Example 3: α-ZrP and phytic acid powder were mixed at a mass ratio of 1:0.5 and placed in a planetary ball mill. The mixture was ball-milled at 450 rpm for 2 hours to obtain the ball-milled product. The ball-milled product was dispersed in hot water at 82°C (solid-liquid ratio 1:20), and the pH was adjusted to 4.2 with acetic acid. The mixture was reacted in a constant temperature water bath for 3.2 hours. The mixture was repeatedly centrifuged and washed with deionized water until neutral. The mixture was then vacuum dried at 80°C for 12 hours to obtain phytic acid-modified α-ZrP.

[0034] Examples 4-6 below are specific implementation schemes for the pre-hydrolyzed silane coupling agent KH-560.

[0035] Example 4: Anhydrous ethanol and water were mixed at a volume ratio of 8.5:1, and the pH was adjusted to 4.2 with acetic acid to obtain an alcohol-water mixture. The total mass of the alcohol-water mixture was 3.5 times the mass of KH-560. KH-560 was added dropwise to the alcohol-water mixture, and the mixture was stirred at 25°C for 3 hours to obtain the pre-hydrolyzed silane coupling agent KH-560.

[0036] Example 5: Anhydrous ethanol and water were mixed at a volume ratio of 8:1, and the pH was adjusted to 4.0 with acetic acid to obtain an alcohol-water mixture. The total mass of the alcohol-water mixture was 3 times the mass of KH-560. KH-560 was added dropwise to the alcohol-water mixture, and the mixture was stirred at 25°C for 2 hours to obtain the pre-hydrolyzed silane coupling agent KH-560.

[0037] Example 6: Anhydrous ethanol and water were mixed at a volume ratio of 9:1, and the pH was adjusted to 4.5 with acetic acid to obtain an alcohol-water mixture. The total mass of the alcohol-water mixture was 4 times the mass of KH-560. KH-560 was added dropwise to the alcohol-water mixture and stirred at 25°C for 4 hours to obtain the pre-hydrolyzed silane coupling agent KH-560.

[0038] Examples 7-9 below are specific implementation schemes for nanocellulose predispersed slurry.

[0039] Example 7: Weigh nanocellulose powder and deionized water at a mass ratio of 1:18, slowly add nanocellulose to water while stirring, and disperse at 8500 rpm for 10 min using a high-speed disperser to obtain a nanocellulose pre-dispersed slurry with a solid content of about 5.3% and a particle size D50≤1.0μm.

[0040] Example 8: Weigh nanocellulose powder and deionized water at a mass ratio of 1:19. Slowly add nanocellulose to the water while stirring. Use a high-speed disperser to disperse at 8000 rpm for 15 min to obtain a nanocellulose pre-dispersed slurry with a solid content of about 5.0% and a particle size D50≤1.0μm.

[0041] Example 9: Weigh nanocellulose powder and deionized water at a mass ratio of 1:16, slowly add nanocellulose to water while stirring, and disperse at 8200 rpm for 12 min using a high-speed disperser to obtain a nanocellulose pre-dispersed slurry with a solid content of about 5.9% and a particle size D50≤1.0μm.

[0042] Examples 10-13 below are specific implementation schemes for the preparation of primer.

[0043] Examples 10-13: The primer was prepared from the following raw materials in parts by weight: 30-35 parts of waterborne epoxy-acrylate hybrid emulsion, 5-6 parts of polypropylene glycol diglycidyl ether, 58-62 parts of zinc powder, 3-5 parts of phytic acid-modified α-ZrP, 1-1.5 parts of fumed silica, 0.1-0.5 parts of nanocellulose, 1-1.5 parts of silane coupling agent KH-560, 15-18 parts of polyamide curing agent, and 0.3-0.5 parts of DMP-30; the mass ratio of flake to spherical zinc powder was 6:4. The primer was prepared by weighing each raw material according to the parts by weight composition shown in Table 1.

[0044] Table 1. Composition of primer by weight The preparation steps of the primer in Example 10 are as follows: phytic acid-modified α-ZrP is prepared according to the method of Example 1; pre-hydrolyzed KH-560 is prepared according to the method of Example 4; nanocellulose pre-dispersion slurry is prepared according to the method of Example 7; waterborne epoxy-acrylate hybrid emulsion, polypropylene glycol diglycidyl ether, zinc powder, phytic acid-modified α-ZrP, and fumed silica are added to a dispersion tank and dispersed at 1000 rpm for 20 min using a high-speed disperser; then the nanocellulose pre-dispersion slurry is added and dispersed for another 15 min to obtain component A; polyamide curing agent and DMP-30 are mixed and stirred for 10 min to obtain component B; before use, component A, component B, and pre-hydrolyzed KH-560 are mixed and stirred at 400 rpm for 15 min to obtain the primer.

[0045] The preparation steps of the primer in Example 11 above are as follows: Phytic acid modified α-ZrP is prepared according to the method of Example 2; pre-hydrolyzed KH-560 is prepared according to the method of Example 5; nanocellulose pre-dispersion slurry is prepared according to the method of Example 8; waterborne epoxy-acrylate hybrid emulsion, polypropylene glycol diglycidyl ether, zinc powder, phytic acid modified α-ZrP, and fumed silica are added to a dispersion tank and dispersed at 800 rpm for 30 min using a high-speed disperser; then nanocellulose pre-dispersion slurry is added and dispersed for another 20 min to obtain component A; polyamide curing agent and DMP-30 are mixed and stirred for 10 min to obtain component B; before use, component A, component B and pre-hydrolyzed KH-560 are mixed and stirred at 300 rpm for 20 min to obtain the primer.

[0046] The preparation steps of the primer in Example 12 above are as follows: phytic acid-modified α-ZrP is prepared according to the method of Example 3; pre-hydrolyzed KH-560 is prepared according to the method of Example 6; nanocellulose pre-dispersion slurry is prepared according to the method of Example 9; waterborne epoxy-acrylate hybrid emulsion, polypropylene glycol diglycidyl ether, zinc powder, phytic acid-modified α-ZrP, and fumed silica are added to a dispersion tank and dispersed at 1200 rpm for 15 min using a high-speed disperser; then the nanocellulose pre-dispersion slurry is added and dispersed for another 20 min to obtain component A; polyamide curing agent and DMP-30 are mixed and stirred for 10 min to obtain component B; before use, component A, component B, and pre-hydrolyzed KH-560 are mixed and stirred at 500 rpm for 10 min to obtain the primer.

[0047] The preparation steps of the primer in Example 13 are the same as those in Example 10.

[0048] Example 14: A weather-resistant and corrosion-resistant composite coating for motors adapted to marine environments, which is formed by sequentially spraying a primer, an intermediate coat and a topcoat onto the outer surface of the motor insulation structure and curing them separately. The primer is the primer prepared in Example 10, the intermediate coat is Jotun epoxy micaceous iron oxide intermediate coat and the topcoat is Jotun fluorocarbon topcoat.

[0049] The preparation method of the weather-resistant and corrosion-resistant composite coating for motors adapted to marine environments is carried out according to the following steps: Step 1: Pre-treat the outer surface of the motor insulation structure to be coated, remove surface defects and clean it; Step 2: Spray primer on the pre-treated surface, cure to form the underlayer, the thickness of the underlayer is ≥60μm; Step 3: Spray intermediate paint on the underlayer, cure to form the intermediate layer, the thickness of the intermediate layer is ≥120μm; Step 4: Spray topcoat on the intermediate layer, cure to form the top layer, the thickness of the top layer is ≥60μm; After all coatings are completed, the overall dry film thickness is inspected. If it meets the requirements, the weather-resistant and corrosion-resistant composite coating for motors is obtained.

[0050] Example 15: A weather-resistant and corrosion-resistant composite coating for motors adapted to marine environments, which is formed by sequentially spraying a primer, an intermediate coat and a topcoat onto the outer surface of the motor insulation structure and curing them separately. The primer is the primer prepared in Example 11, the intermediate coat is Tiannv epoxy micaceous iron oxide intermediate coat and the topcoat is Tiannv fluorocarbon topcoat.

[0051] Example 16: A weather-resistant and corrosion-resistant composite coating for motors adapted to marine environments, which is formed by sequentially spraying a primer, an intermediate coat and a topcoat onto the outer surface of the motor insulation structure and curing them separately. The primer is the primer prepared in Example 12, the intermediate coat is Zog epoxy micaceous iron oxide intermediate coat and the topcoat is Zog fluorocarbon topcoat.

[0052] Example 17: A weather-resistant and corrosion-resistant composite coating for motors adapted to marine environments, which is formed by sequentially spraying a primer, an intermediate coat and a topcoat onto the outer surface of the motor insulation structure and curing them separately. The primer is the primer prepared in Example 13, and the intermediate coat and topcoat are the same as in Example 14.

[0053] The preparation methods of the composite coatings in Examples 15-17 are the same as those in Example 14.

[0054] The following are comparative examples.

[0055] Comparative Example 1: The weather-resistant and corrosion-resistant composite coating for motors differs from Example 14 only in that phytic acid is not added to modify α-ZrP when preparing the primer.

[0056] Comparative Example 2: Weather-resistant and corrosion-resistant composite coating for motors, differing from Example 14 only in that the content of phytic acid-modified α-ZrP in the preparation of the primer is 2 parts by weight.

[0057] Comparative Example 3: Weather-resistant and corrosion-resistant composite coating for motors, differing from Example 14 only in that: when preparing the primer, the content of phytic acid-modified α-ZrP is 6 parts by weight.

[0058] Comparative Example 4: Weather-resistant and corrosion-resistant composite coating for motors. The only difference from Example 14 is that when preparing the primer, all the zinc powder in the primer is made up of spherical particles.

[0059] Comparative Example 5: Weather-resistant and corrosion-resistant composite coating for motors. The only difference from Example 14 is that the zinc powder content in the primer is increased to 80 parts by weight, and the phytic acid modification of α-ZrP is omitted.

[0060] The preparation methods of the coatings in Comparative Examples 1-5 were all carried out in accordance with Example 14.

[0061] The following is an evaluation of the effectiveness.

[0062] Using Q235A steel plate (150mm×150mm×3mm) as the substrate, the surface was treated to Sa2.5 grade. Dirt and other defects adhering to the sample surface were cleaned using a grinder, and the sample was then cleaned with a cleaning agent. Composite coatings of Examples 14-16 and Comparative Examples 1-5 were prepared on the treated substrate surface, respectively.

[0063] The above composite coatings were subjected to the following performance tests: (1) Paint film thickness: After the sample is painted, the overall dry film thickness of the sample is inspected using an ultrasonic paint film thickness measuring instrument (GB / T13452.2-2008).

[0064] (2) Adhesion: In accordance with GB / T9286-2021, the adhesion between the paint film and the sample was tested using a pull-out tester.

[0065] (3) Hardness: According to GB / T6739-2022, the hardness of the sample paint was tested by using a Zhonghua brand 2H pencil (≥2H required).

[0066] (4) Salt spray test: The sample was subjected to neutral salt spray (NSS) test according to test method 1 in GB / T2423.18-2021. Each cycle of spraying was 2h + wet heat storage for 6d22h. The changes in the sample were observed at the end of the 4th and 9th cycles.

[0067] (5) Acid and alkali resistance test: According to GB / T9274-1988, the sample was immersed in 10% oxalic acid / 10% sodium hydroxide solution for 30 days and the changes were observed.

[0068] The results of the above tests are shown in Table 2. Table 2 Performance Test Results The results showed that the thickness of each layer in the composite coating of this invention met the requirements, the adhesion was greater than 7.0 MPa, the hardness was 2H, and there was no change after 63 days of salt spray testing. The coating also showed no change in resistance to 10% oxalic acid and 10% sodium hydroxide, indicating that the composite coating of this invention has excellent resistance to salt spray corrosion and acid / alkali corrosion. Furthermore, the primer of this invention has good compatibility with topcoats and intermediate coats from different brands, and its corrosion resistance and acid / alkali corrosion performance remain consistent.

[0069] Compared to Example 14, Comparative Example 1, which lacks phytic acid-modified α-ZrP in its primer, exhibits reduced coating adhesion, a decrease in hardness from 2H to H, and noticeable rust and slight blistering at scratches after 28 days of salt spray corrosion. Rust spots increase after 63 days, and slight whitening occurs after acid and alkali immersion. These phenomena indicate that the absence of phytic acid-modified α-ZrP in the formulation system of this invention accelerates the penetration of corrosive media, leading to noticeable rust at scratches and slight blistering of the coating after 28 days of salt spray corrosion. Simultaneously, the chemical passivation effect of phytic acid-modified α-ZrP is lost, resulting in decreased acid and alkali resistance.

[0070] Compared to Example 14, Comparative Example 2 showed a lower content of phytic acid-modified α-ZrP in the primer, resulting in an adhesion strength of 6.21 MPa, which was lower than that of Example 14. While short-term corrosion resistance was acceptable, rust appeared at the scratches after 63 days of salt spray testing. The possible reason for these phenomena is that insufficient phytic acid-modified α-ZrP leads to limited passivation and weakened long-term corrosion resistance, resulting in rust.

[0071] Compared to Example 14, Comparative Example 3 showed an increased content of phytic acid-modified α-ZrP in the primer, resulting in an adhesion of 6.64 MPa, a hardness of H, slight rust after 28 days of salt spray testing with no blistering, and slight blistering after 63 days. These phenomena may be due to excessive addition of phytic acid-modified α-ZrP, leading to an imbalance in its interaction with zinc. Furthermore, excessive phytic acid-modified α-ZrP reduces its dispersibility, decreases adhesion, and ultimately lowers overall corrosion resistance.

[0072] Compared to Example 14, Comparative Example 4 used spherical zinc powder in its primer, exhibiting an adhesion of 6.37 MPa, a hardness of H, and no blistering during 28 days of salt spray corrosion; however, pitting increased after 63 days, and slight whitening was observed during acid and alkali treatment. The possible reason for these phenomena is that when all zinc powder is spherical, the labyrinth effect of the flake-shaped zinc powder disappears, reducing its physical shielding ability, accelerating the penetration of corrosive media, and decreasing corrosion resistance.

[0073] Compared to Example 14, Comparative Example 5 used a conventional high-zinc primer without phytic acid-modified α-ZrP. The adhesion was 5.86 MPa, and after 63 days of salt spray testing, the unscratched area remained intact, while the scratched areas showed corrosion. In this formulation, the high zinc content provided good cathodic protection, exhibiting excellent short-term salt spray resistance, but its long-term performance was inferior to Example 14, indicating that the present invention offers superior long-term protection.

[0074] In summary, the weather-resistant and corrosion-resistant composite coating for motors adapted to marine environments of this invention has excellent corrosion resistance and superior long-term protective performance. It is suitable for auxiliary motors for marine wind power, marine platform equipment, ships and other fields, and has good industrial application prospects and promotion value.

[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention, as long as they do not depart from the spirit and scope of the technical solutions of the present invention, should be covered within the scope of the claims of the present invention.

Claims

1. A weather-resistant and corrosion-resistant composite coating for motors adapted to marine environments, comprising a primer, an intermediate coat, and a topcoat sequentially sprayed onto the outer surface of the motor's insulation structure and then cured and bonded together, characterized in that: The primer is prepared from the following raw materials in parts by weight: 30-35 parts of waterborne epoxy-acrylate hybrid emulsion, 5-6 parts of polypropylene glycol diglycidyl ether, 58-62 parts of zinc powder, 3-5 parts of phytic acid-modified α-ZrP, 1-1.5 parts of fumed silica, 0.1-0.5 parts of nanocellulose, 1-1.5 parts of silane coupling agent KH-560, 15-18 parts of polyamide curing agent, and 0.3-0.5 parts of DMP-30; the mass ratio of flake to spherical zinc powder is 6:

4. The nanocellulose has a diameter of 4-20 nm and a length of 1-3 μm; The phytic acid-modified α-ZrP was prepared by the following method: α-ZrP and phytic acid powder were mixed at a mass ratio of 1:0.5 and ball-milled at 350-450 rpm for 2-2.5 h to obtain the ball-milled product; the ball-milled product was dispersed in hot water at 80-85℃, the pH was adjusted to 4.0-4.2, the reaction was carried out for 3-3.5 h, the product was centrifuged and washed until neutral, and then dried to obtain the final product. The silane coupling agent KH-560 undergoes pre-hydrolysis treatment, the steps of which are as follows: anhydrous ethanol and water are mixed at a volume ratio of (8-9):1, and the pH is adjusted to 4.0-4.5 with acetic acid to obtain an alcohol-water mixture; silane coupling agent KH-560 is added dropwise to the alcohol-water mixture, and the mixture is stirred at 25±2℃ for 2-4 hours to obtain the pre-hydrolyzed silane coupling agent KH-560; wherein, the total mass of the alcohol-water mixture is 3-4 times the mass of the silane coupling agent KH-560.

2. The weather-resistant and corrosion-resistant composite coating for motors adapted to marine environments according to claim 1, characterized in that: The intermediate paint is an epoxy micaceous iron oxide intermediate paint, and the topcoat is a fluorocarbon topcoat.

3. The weather-resistant and corrosion-resistant composite coating for motors adapted to marine environments according to claim 1, characterized in that: The primer is prepared by the following method: Step A: Preparation of phytic acid-modified α-ZrP; Step B: Weigh out the silane coupling agent KH-560 by weight and perform pre-hydrolysis to obtain pre-hydrolyzed silane coupling agent KH-560; Step C: Weigh out the nanocellulose by weight, add deionized water, and perform pre-dispersion treatment to obtain a nanocellulose pre-dispersion slurry with a solid content of 5-6%. Step D: Weigh the following raw materials by weight: waterborne epoxy-acrylate hybrid emulsion, polypropylene glycol diglycidyl ether, zinc powder, phytic acid-modified α-ZrP and fumed silica, mix them evenly, then add nanocellulose pre-dispersed slurry, and continue mixing for 15-20 minutes to obtain component A; Step E: Weigh the following raw materials by weight: polyamide curing agent and DMP-30, mix them evenly to obtain component B; Step F: Mix component A obtained in step D, component B obtained in step E, and pre-hydrolyzed silane coupling agent KH-560 obtained in step B, and stir evenly to obtain the primer. The mass ratio of flakes to spheres in the zinc powder is 6:

4.

4. The weather-resistant and corrosion-resistant composite coating for motors adapted to marine environments according to claim 3, characterized in that: The mixing in step D is carried out using a high-speed disperser with a dispersion speed of 800-1200 rpm and a dispersion time of 15-30 min.

5. The weather-resistant and corrosion-resistant composite coating for motors adapted to marine environments according to claim 3, characterized in that: The stirring speed in step F is 300-500 rpm, and the stirring time is 10-20 min.

6. A method for preparing a weather-resistant and corrosion-resistant composite coating for motors adapted to marine environments as described in any one of claims 1-5, characterized in that: Includes the following steps: Step 1: Pre-treat the outer surface of the motor insulation structure to be sprayed, remove surface defects and clean it thoroughly; Step 2: Spray primer onto the pretreated surface and cure to form a base layer with a thickness ≥ 60 μm; Step 3: Spray an intermediate paint onto the base layer and cure it to form an intermediate layer with a thickness ≥120μm; Step 4: Spray a topcoat onto the intermediate layer and cure it to form a surface layer with a thickness ≥60μm, thus obtaining the weather-resistant and corrosion-resistant composite coating for the motor.

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