Super-wear-resistant and corrosion-resistant stainless steel pipe fitting and preparation method thereof

Abstract

The invention relates to an ultra-wear-resistant and corrosion-resistant stainless steel pipe fitting and a preparation method thereof, and belongs to the technical field of metal protection and functional composite materials. A compact composite coating is constructed on the surface of the pipe fitting and is prepared from the following raw materials in parts by weight: 40-60 parts of a modified titanium nitride graphene composite material, 20-35 parts of a 4-(diamino formyl) styrene polymer, 2-5 parts of aluminum triphosphate, 1-2 parts of a fluorosilane coupling agent, 5-10 parts of polyvinylidene fluoride emulsion, 1-3 parts of a surface topography regulating agent and 0.5-1.5 parts of a curing accelerator. The modified composite material induces polydopamine to be self-assembled to form a sheet nested structure after being subjected to chitosan quaternary ammonium salt functionalization treatment, and the compactness, wear resistance and corrosion resistance of the coating are remarkably improved. The preparation process adopts spraying and thermocuring modes, and the coating is uniformly attached to the surface of the stainless steel substrate, is suitable for the fields of oil and gas transmission, deep sea equipment and chemical engineering pipeline extreme working conditions, and has excellent use stability and structure protection performance.

Description

Technical Field

[0001] The present invention relates to the technical field of metal protection and functional composite coatings, and in particular to a super wear-resistant and corrosion-resistant stainless steel pipe fitting suitable for severe corrosion and strong wear conditions and a preparation method thereof. Background Art

[0002] Stainless steel pipe fittings are widely used in the fields of petrochemical engineering, marine engineering, slurry transportation, papermaking, and electric power due to their excellent mechanical properties and certain corrosion resistance. However, in actual service, many working conditions contain not only highly corrosive media such as acids, alkalis, and salts, but also high-speed fluid erosion and solid particle abrasion. Under the synergistic effect of wear and corrosion, stainless steel pipe fittings are prone to failures such as surface peeling, pitting corrosion, and groove wear, which significantly shortens their service life.

[0003] In the existing technology, the wear resistance and corrosion resistance of stainless steel pipe fittings are often improved by spraying ceramic coatings, polymer coatings, laser cladding, etc. However, the above methods generally have problems such as insufficient adhesion, easy cracking or peeling of the coating, high process costs and complex construction. Especially in high temperature, high flow rate and alternating corrosion environments, traditional coating systems often find it difficult to maintain stable performance for a long time.

[0004] Therefore, there is an urgent need to develop a composite functional coating structure that has high wear resistance, excellent corrosion resistance and strong interface adhesion. Through special surface morphology design and firm bonding with the stainless steel substrate, it can achieve dual barrier to corrosive media and abrasive particles, thereby significantly extending the service life of stainless steel pipes under extreme working conditions. Summary of the Invention

[0005] In order to overcome the problems of stainless steel pipe fittings in the background art that they fail quickly under the synergistic effect of wear and corrosion, have poor coating adhesion, and have a short service life, the object of the present invention is to provide a super wear-resistant and corrosion-resistant stainless steel pipe fitting and its preparation method. Titanium nitride nanosheets and graphene oxide are functionalized with chitosan quaternary ammonium salt respectively, and dopamine is introduced under alkaline conditions of pH 8.0-9.0 to form a modified titanium nitride graphene composite material with a nested sheet structure through interface assembly. With 4-(diaminoformyl)styrene polymer as the main component, supplemented by aluminum tripolyphosphate, fluorosilane coupling agent, polyvinylidene fluoride emulsion, silica nanosphere dispersion and curing accelerator, a dense composite functional coating with a nested sheet structure is formed on the surface of the stainless steel substrate through interface assembly and surface morphology control technology. The wear resistance and corrosion resistance of stainless steel pipe fittings are significantly improved, the bonding strength between the coating and the substrate is enhanced, and the service life is extended in high temperature, high flow rate and strong corrosive medium environments.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A super-wear-resistant and corrosion-resistant stainless steel pipe fitting comprises the following raw materials in parts by weight: 40-60 parts of a modified titanium nitride graphene composite material; 20-35 parts of a 4-(diaminoformyl)styrene polymer; 2-5 parts of aluminum tripolyphosphate; 1-2 parts of a fluorosilane coupling agent; 5-10 parts of a polyvinylidene fluoride emulsion; 1-3 parts of a surface morphology controller; and 0.5-1.5 parts of a curing accelerator. The modified titanium nitride graphene composite material is prepared by functionalizing titanium nitride nanosheets and graphene oxide with chitosan quaternary ammonium salt, introducing polydopamine for self-polymerization and coating under alkaline conditions, and constructing a sheet-like nested structure composite material through interface assembly.

[0008] Optionally, the modified titanium nitride graphene composite material includes the following raw materials in parts by weight: 40-60 parts of titanium nitride nanosheets, 15-30 parts of graphene oxide, 5-10 parts of chitosan quaternary ammonium salt, and 0.5-2 parts of polydopamine.

[0009] Optionally, the preparation method of the modified titanium nitride graphene composite material comprises the following steps:

[0010] (1) dispersing titanium nitride nanosheets and graphene oxide in a mixed solution, stirring and ultrasonically treating the solution to obtain a titanium nitride dispersion and a graphene oxide dispersion;

[0011] (2) adding chitosan quaternary ammonium salt to the titanium nitride dispersion and the graphene oxide dispersion, respectively, to perform functionalization treatment to obtain a surface-modified titanium nitride suspension and a graphene oxide suspension;

[0012] (3) mixing the surface-modified titanium nitride suspension with the graphene oxide suspension, adding dopamine, and performing an interface-induced self-assembly reaction to form a nested composite structure;

[0013] (4) The mixed liquid after the reaction is centrifuged, washed and dried to obtain a modified titanium nitride graphene composite material.

[0014] Optionally, the stirring and ultrasonic treatment conditions in step (1) are a stirring rate of 300-800 rpm, an ultrasonic power of 100-300 W, and a treatment time of 20-60 minutes; the pH adjustment range in step (3) is 8.0-9.0, and the reaction time is 8-16 hours.

[0015] Optionally, the 4-(diaminoformyl)styrene polymer comprises the following raw materials in parts by weight: 60-80 parts of 4-(diaminoformyl)styrene monomer, 2-5 parts of azobisisobutyronitrile, and 20-35 parts of dimethyl sulfoxide.

[0016] Alternatively, the preparation method of the 4-(diaminoformyl)styrene polymer comprises the following steps:

[0017] (a) dissolving 4-(diaminoformyl)styrene monomer in dimethyl sulfoxide and stirring to form a homogeneous transparent solution;

[0018] (b) adding azobisisobutyronitrile to the homogeneous transparent solution and continuing to stir to fully mix;

[0019] (c) heating the system to a polymerization temperature under an inert atmosphere and maintaining the reaction at a constant temperature to complete the free radical polymerization;

[0020] (d) After the reaction is completed, the product is cooled to room temperature, and precipitation, filtration, and drying steps are performed to obtain the 4-(diaminoformyl)styrene polymer.

[0021] Optionally, the reaction conditions of step (c) are to react at a constant temperature of 70 to 80° C. for 6 to 10 hours under nitrogen protection.

[0022] Optionally, the fluorosilane coupling agent is formed by mixing 1H,1H,2H,2H-perfluorooctyltriethoxysilane and anhydrous ethanol in a mass ratio of 1:4; the polyvinylidene fluoride emulsion is formed by mixing and emulsifying polyvinylidene fluoride resin and deionized water in the presence of an emulsifier in a mass ratio of 1:2; the surface morphology controller is formed by mixing and dispersing silica nanospheres and deionized water in a mass ratio of 1:10; and the curing accelerator is formed by mixing diisopropylbenzene peroxide and dioctyl phthalate in a mass ratio of 1:3.

[0023] Optionally, a method for preparing a super wear-resistant and corrosion-resistant stainless steel pipe fitting comprises the following steps:

[0024] S1, pre-treating the surface of the stainless steel substrate by sandblasting, degreasing, pickling, neutralizing and drying in sequence to obtain a rough active interface;

[0025] S2, uniformly mixing a modified titanium nitride graphene composite material, 4-(diaminoformyl)styrene polymer, aluminum tripolyphosphate, a mixture of 1H,1H,2H,2H-perfluorooctyltriethoxysilane and anhydrous ethanol, a polyvinylidene fluoride emulsion, a silica nanosphere dispersion, and a mixture of diisopropylbenzene peroxide and dioctyl phthalate to prepare a composite coating slurry;

[0026] S3, applying the composite coating slurry evenly to the stainless steel surface by spraying;

[0027] S4, pre-baking the coated pipe fittings at 60-90° C. for 10-30 minutes, then heat curing at 160-200° C. for 30-60 minutes, and cooling to obtain super wear-resistant and corrosion-resistant stainless steel pipe fittings.

[0028] The beneficial effects of the present invention are:

[0029] The present invention functionalizes titanium nitride nanosheets and graphene oxide with chitosan quaternary ammonium salt cations respectively, and introduces dopamine to induce self-polymerization under alkaline conditions to achieve interfacial self-assembly and stable nested composites between multiple components, thereby constructing a sheet network with directional arrangement and high structural integrity, which can maintain continuity and adhesion under conditions of high-speed erosion and particle wear; this nested structure forms a "physical barrier + chemical anchoring" dual protection system on the stainless steel surface, significantly improving the wear resistance and anti-peeling ability of the coating.

[0030] Through its rigid benzene ring and multi-amino side group structure, 4-(diaminoformyl)styrene polymer forms multi-point hydrogen bonds and electrostatic entanglements with nested layers during the coating curing process, forming a dense cross-linked network. This not only improves the integrity and flexibility of the coating, but also enhances the shielding performance against corrosive media and inhibits the propagation of microcracks, thereby achieving a synergistic enhancement of wear resistance, corrosion resistance and interface stability.

[0031] Through the coordinated construction of interface structure design and functional molecules, the problem of easy shedding and poor durability of traditional stainless steel pipe coatings in high-corrosion and high-wear environments has been solved. The unification of efficient coupling between materials, structural stability and performance superposition has been achieved, showing a comprehensive protection capability that is superior to existing technologies and has significant engineering application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The present invention will be further described below with reference to the accompanying drawings.

[0033] Figure 1 This is a comparison diagram of infrared spectra of titanium nitride graphene composite material and modified titanium nitride graphene composite material;

[0034] Figure 2 This is a comparison of infrared spectra of 4-(diaminoformyl)styrene monomer and 4-(diaminoformyl)styrene polymer;

[0035] Figure 3 This is a scanning electron microscope photo of the composite coating slurry material;

[0036] Figure 4 The bar chart is a comparison of the performance of super wear-resistant and corrosion-resistant stainless steel pipe fittings with different proportions. DETAILED DESCRIPTION

[0037] The present invention will be further described below with reference to specific embodiments. However, the present invention is not limited to the following embodiments. Equivalent adjustments made without departing from the spirit of the present invention should also be deemed to fall within the scope of protection of the present invention.

[0038] Example 1:

[0039] This example uses the lower limit ratio to verify the film-forming integrity and basic performance of the composite coating at the minimum usage of the components.

[0040] Preparation steps:

[0041] S1, weighing 40 parts of titanium nitride nanosheets and 15 parts of graphene oxide, respectively, adding them to a mixture of ethanol and deionized water in equal volume proportions, magnetically stirring for 30 minutes, and treating them at an ultrasonic power of 200 watts for 30 minutes to obtain two uniform dispersions; adding 5 parts of chitosan quaternary ammonium salt to the above dispersions, adjusting the pH to 5.5, and stirring at 40 degrees Celsius for 2 hours for surface functionalization; mixing the two functionalized dispersions in a volume ratio of 1:1, adding 0.5 parts of dopamine, adjusting the pH to 8.5, and reacting at room temperature for 12 hours to allow self-polymerization and coating to form a nested structure; after the reaction, centrifuging at a speed of 6000 rpm for 10 minutes, washing and drying, and finally vacuum drying at 60 degrees Celsius for 12 hours to obtain a modified titanium nitride graphene composite material;

[0042] S2, dissolving 60 parts of 4-(diaminoformyl)styrene monomer in 20 parts of dimethyl sulfoxide and stirring to form a homogeneous transparent solution; adding 2 parts of azobisisobutyronitrile initiator and continuing to stir until homogeneous; and reacting at 70 degrees Celsius for 8 hours under nitrogen protection. After the reaction, the mixture was cooled to room temperature, precipitated with ethanol, filtered, and vacuum dried to obtain the target polymer.

[0043] S3, the following components are mixed to prepare a composite coating slurry: 40 parts of modified titanium nitride graphene composite material, 20 parts of 4-(diaminoformyl)styrene polymer, and 2 parts of aluminum tripolyphosphate; a fluorosilane coupling agent is prepared by mixing 1H,1H,2H,2H-perfluorooctyltriethoxysilane and anhydrous ethanol in a mass ratio of 1:4, and 1 part is added; a polyvinylidene fluoride emulsion is prepared by emulsifying polyvinylidene fluoride resin and deionized water in a mass ratio of 1:2, and 5 parts are added; a surface morphology controller is prepared by mixing and dispersing silica nanospheres and deionized water in a mass ratio of 1:10, and 1 part is added; a curing accelerator is prepared by mixing diisopropyl benzene peroxide and dioctyl phthalate in a mass ratio of 1:3, and 0.5 parts is added; the prepared slurry is sprayed onto the surface of the pretreated stainless steel pipe fittings, pre-baked at 80°C for 20 minutes, and then heat-cured at 180°C for 40 minutes, and the finished pipe fittings are obtained after cooling.

[0044] Example 2:

[0045] This example uses an intermediate ratio to evaluate the balance between coating structure and function.

[0046] Preparation steps:

[0047] S1, weighing 50 parts of titanium nitride nanosheets and 22.5 parts of graphene oxide, respectively, adding them to a mixture of ethanol and deionized water in equal volume proportions, magnetically stirring for 30 minutes, and treating them under an ultrasonic power of 200 W for 30 minutes to obtain two uniform dispersions; adding 7.5 parts of chitosan quaternary ammonium salt to the above dispersions, adjusting the pH to 5.5, and stirring at 40°C for 2 hours for surface functionalization; mixing the two functionalized dispersions in a volume ratio of 1:1, adding 1.0 part of dopamine, adjusting the pH to 8.5, and reacting at room temperature for 12 hours to allow self-polymerization and coating to form a nested structure; after the reaction, centrifuging at a speed of 6000 rpm for 10 minutes, washing and drying, and finally vacuum drying at 60°C for 12 hours to obtain a modified titanium nitride graphene composite material;

[0048] Figure 1 The changes in infrared absorption peaks of titanium nitride graphene composites before and after modification are compared. The black curve is the unmodified sample, and the red curve is the modified composite material after treatment with components such as chitosan quaternary ammonium salt and fluorosilane. By analyzing the peak position difference of the two curves, the changes in surface functional groups and the modification effect can be clearly identified. At 3430cm -1 Near 1630 cm, the material before modification shows a distinct broad and blunt –OH stretching vibration absorption peak, corresponding to the presence of surface hydroxyl groups and adsorbed water. After modification, this peak is significantly weakened, indicating that the surface hydroxyl content is reduced, the hydrophobicity is enhanced, and the formation of the organic coating layer effectively inhibits water adsorption. -1 In the region of 1570–1470 cm, the H–O–H bending vibration peak of the unmodified material is significantly reduced after modification, which further indicates that the surface moisture content of the material decreases and the structure tends to be stable, which is conducive to the uniformity and adhesion improvement of the subsequent coating process. -1 In the modified sample, the C=C aromatic ring skeleton and C–H bending vibration peaks are enhanced, indicating that the introduction of aromatic structures such as dopamine is successful, which enhances the contribution of organic components at the coating interface and the structural regularity. -1 Newly added C–N nearby + The characteristic peaks indicate that the quaternary ammonium salt functional groups are effectively grafted. This structure provides cationic properties, which helps to improve the surface electrical properties and interfacial compatibility of the material, while also enhancing the potential antibacterial and interfacial binding properties. 1100–1020 cm -1 A significant Si–O–C peak appears in the region, a typical characteristic of the fluorosilane coupling agent structure, indicating that the inorganic silicon-oxygen segments have effectively bonded to the material surface, further enhancing its interfacial bonding ability and chemical stability. Spectral analysis results show that through multi-component synergistic modification, a variety of organic and inorganic functional groups have been introduced to the surface of the titanium nitride graphene composite material, significantly improving its interfacial activity, structural stability, and functional diversity, providing molecular structural support for the construction of high-performance composite coating systems.

[0049] S2, 4-(diaminocarbonyl)styrene monomer 70 parts was dissolved in dimethyl sulfoxide 27.5 parts, stirring to form a uniform transparent solution; azobisisobutyronitrile initiator 2.5 parts was added, and continue to stir evenly; under nitrogen protection, constant temperature reaction at 75°C for 9h, after the reaction was completed, cooled to room temperature, precipitated by ethanol, suction filtration and vacuum drying, the target polymer was obtained;

[0050] Figure 2 The change of structure characteristics of 4-(diaminocarbonyl)styrene before and after polymerization is shown, by comparing the red curve (polymer) with the black curve (monomer), the conversion and retention of functional groups in the polymerization process can be analyzed. In the 3300-3400 cm -1 region, the monomer shows obvious -NH2 stretching vibration absorption peak, indicating that it contains free primary amine group in the molecule. The intensity of this peak in the polymer is obviously weakened and the peak shape is broadened, indicating that part of the -NH2 group participates in the free radical polymerization reaction, and may be converted into amide or form new amine bond, and the structure tends to be complex. In the ~1690 cm -1 region, the peak in the monomer belongs to the C=O stretching vibration peak of -CONH2 structure. After polymerization, the intensity of this peak is enhanced, indicating that the amide group is retained and enriched in the main chain in the polymerization process, further confirming that amide is the main connecting unit in the structure of the polymer. In the range of 1600-1450 cm -1 , the C=C skeleton vibration peak of benzene ring is observed before and after polymerization, reflecting that the styrene main chain structure is retained, and the peak shape is clearer after polymerization, indicating that the molecular regularity is enhanced and the arrangement of aromatic ring is ordered. In the 1250-1000 cm -1 interval, multiple C-N, C-O stretching vibration peaks appear in the polymer, especially the obvious enhancement at ~1160 cm -1 , which is the typical characteristic of amide bond. The enhancement of these peaks proves the large amount of C-N bond generated in the polymerization process, indicating that the polymerization reaction is dominated by amide structure. The benzene ring para C-H bending vibration peak at ~830 cm -1 still exists after polymerization, which proves that the para structure on the benzene ring is not destroyed and the substitution mode of styrene remains stable. Comprehensive analysis shows that the main functional groups are retained in the polymerization process, and a new structure with amide bond as the core is formed, which gives the polymer higher stability and functionality. This structural transformation provides a molecular basis for the dispersion, film forming property and interfacial adhesion of the polymer in the subsequent composite coating.

[0051] S3. Mix the components in the following proportions to prepare a composite coating slurry: 50 parts of modified titanium nitride graphene composite material, 27.5 parts of 4-(diaminoformyl)styrene polymer, and 3.5 parts of aluminum tripolyphosphate; a fluorosilane coupling agent prepared by mixing 1H,1H,2H,2H-perfluorooctyltriethoxysilane and anhydrous ethanol in a mass ratio of 1:4, and adding 1.5 parts; a polyvinylidene fluoride emulsion prepared by emulsifying polyvinylidene fluoride resin and deionized water in a mass ratio of 1:2, and adding 7.5 parts; a surface morphology controller prepared by mixing and dispersing silica nanospheres and deionized water in a mass ratio of 1:10, and adding 2 parts; a curing accelerator prepared by mixing diisopropyl benzene peroxide and dioctyl phthalate in a mass ratio of 1:3, and adding 1.0 part; spray the prepared slurry onto the surface of the pretreated stainless steel pipe fitting, pre-bake at 80°C for 20 minutes, and then heat cure at 180°C for 45 minutes, and obtain the finished pipe fitting after cooling.

[0052] Figure 3 The microscopic morphology of the composite particles can be intuitively observed. The main structure is a rough, flaky structure, with small, flocculent and spherical particles adhering to the surface. These particles, presumably composed of graphene oxide and polydopamine, demonstrate good interfacial coating and dispersion. The overall structure is dense, with multi-level pores and surface roughness, which enhances the coating's mechanical integrity and wear and corrosion resistance.

[0053] Example 3:

[0054] This example uses the upper limit ratio to verify the film formation uniformity and coating performance limit under high filler content conditions.

[0055] Preparation steps:

[0056] S1, weighing 60 parts of titanium nitride nanosheets and 30 parts of graphene oxide, respectively, adding them to a mixture of ethanol and deionized water in equal volume proportions, magnetically stirring for 30 minutes, and treating them under an ultrasonic power of 200W for 30 minutes to obtain two uniform dispersions; adding 10 parts of chitosan quaternary ammonium salt to the above dispersions, adjusting the pH to 5.5, and stirring at 40°C for 2 hours for surface functionalization; mixing the two functionalized dispersions in a volume ratio of 1:1, adding 2.0 parts of dopamine, adjusting the pH to 8.5, and reacting at room temperature for 12 hours to allow self-polymerization and coating to form a nested structure; after the reaction, centrifuging at a speed of 6000 rpm for 10 minutes, washing and drying, and finally vacuum drying at 60°C for 12 hours to obtain a modified titanium nitride graphene composite material;

[0057] S2, 80 parts of 4-(diaminocarbonyl)styrene monomer was dissolved in 35 parts of dimethyl sulfoxide, and stirred to form a uniform transparent solution; 5 parts of azobisisobutyronitrile initiator was added, and the stirring was continued to be uniform; under nitrogen protection, the reaction was carried out at 80℃ for 10h, after the reaction was completed, it was cooled to room temperature, precipitated by ethanol, filtered and vacuum dried to obtain the target polymer;

[0058] S3, the composite coating slurry was prepared by mixing the components in the following proportions: modified titanium nitride graphene composite material 60 parts, 4-(diaminocarbonyl)styrene polymer 35 parts, aluminum tripolyphosphate 5 parts; fluorosilane coupling agent was prepared by mixing 1H, 1H, 2H, 2H-perfluorooctyltriethoxysilane and anhydrous ethanol at a mass ratio of 1:4, and 2 parts were added; polyvinylidene fluoride emulsion was prepared by emulsifying polyvinylidene fluoride resin and deionized water at a mass ratio of 1:2, and 10 parts were added; the surface morphology modifier was prepared by mixing and dispersing silica nanospheres and deionized water at a mass ratio of 1:10, and 3 parts were added; the curing accelerator was prepared by mixing dicumyl peroxide and dioctyl phthalate at a mass ratio of 1:3, and 1.5 parts were added; the prepared slurry was sprayed onto the surface of the pretreated stainless steel pipe, pre-baked at 90℃ for 30min, and then heat-cured at 200℃ for 60min, and the finished product pipe was obtained after cooling.

[0059] Comparative Example 1 (titanium nitride graphene composite material without functionalization treatment)

[0060] This comparative example aims to verify the influence of titanium nitride graphene material without functionalization modification by chitosan quaternary ammonium salt and dopamine on the performance of the coating, and highlight the structure-activity relationship of the nested structure modified material in the present application.

[0061] Preparation steps:

[0062] S1, 50 parts of titanium nitride nanosheet and 22.5 parts of graphene oxide were weighed and added into equal volume of ethanol and deionized water mixture respectively, and then magnetically stirred for 30min, and treated under ultrasonic power of 200W for 30min to obtain two kinds of uniform dispersion; 7.5 parts of chitosan quaternary ammonium salt was added into each of the above dispersion, and the pH was adjusted to 5.5, and then stirred at 40℃ for 2h for surface functionalization; then the functionalized titanium nitride and graphene oxide were mixed, and the pH was adjusted to 8.5, but dopamine was not added, and no self-polymerization coating reaction occurred; after centrifugal separation, washing and drying, the mixture was vacuum dried at 60℃ for 12h to obtain the modified composite material without introducing the nested structure.

[0063] S2, dissolving 70 parts of 4-(diaminoformyl)styrene monomer in 27.5 parts of dimethyl sulfoxide and stirring to form a uniform transparent solution; adding 2.5 parts of azobisisobutyronitrile initiator and continuing to stir until uniform; reacting at 75°C under nitrogen for 9 hours. After the reaction, cooling to room temperature, precipitating with ethanol, filtering, and vacuum drying to obtain the target polymer;

[0064] S3, the components are mixed in the following proportions to prepare a composite coating slurry: 50 parts of modified titanium nitride graphene composite material, 27.5 parts of 4-(diaminoformyl)styrene polymer, 3.5 parts of aluminum tripolyphosphate; 1.5 parts of fluorosilane coupling agent is prepared by mixing 1H,1H,2H,2H-perfluorooctyltriethoxysilane and anhydrous ethanol in a mass ratio of 1:4; polyvinylidene fluoride emulsion is prepared by emulsifying polyvinylidene fluoride resin and deionized water in a mass ratio of 1:2 7.5 parts of the above-mentioned material were added; 2 parts of the above-mentioned material were added to form a surface morphology control agent prepared by mixing and dispersing silica nanospheres and deionized water in a mass ratio of 1:10; 1.0 part of the above-mentioned material was added to form a curing accelerator prepared by mixing dicumyl peroxide and dioctyl phthalate in a mass ratio of 1:3; the obtained coating slurry was sprayed onto the surface of the pretreated stainless steel pipe fitting, pre-baked at 80°C for 20 minutes, and then heat-cured at 180°C for 45 minutes. After cooling, a comparative sample pipe fitting was obtained.

[0065] Comparative Example 2 (4-(diaminoformyl)styrene polymer not introduced, only conventional binder resin used)

[0066] This comparative example is used to verify the changes in the bonding strength and density of the composite coating when the unique functional polymer is not used, highlighting the key role of the polymer in the construction of the coating structure.

[0067] Preparation steps:

[0068] S1, weighing 50 parts of titanium nitride nanosheets and 22.5 parts of graphene oxide, adding them to a mixture of ethanol and deionized water in equal volume proportions, stirring them magnetically for 30 minutes, and treating them under ultrasonic power of 200 W for 30 minutes to obtain two uniform dispersions; directly mixing the two dispersions, adding 1.0 parts of dopamine, adjusting the pH to 8.5, reacting them at room temperature for 12 hours, and performing self-polymerization and coating to form a nested structure; after the reaction, centrifuging at a speed of 6000 rpm for 10 minutes, washing and drying, and finally vacuum drying at 60°C for 12 hours to obtain a modified titanium nitride graphene composite material without surface functionalization;

[0069] S2, dissolving 70 parts of 4-(diaminoformyl)styrene monomer in 27.5 parts of dimethyl sulfoxide and stirring to form a uniform transparent solution; adding 2.5 parts of azobisisobutyronitrile initiator and continuing to stir until uniform; reacting at 75°C under nitrogen for 9 hours. After the reaction, cooling to room temperature, precipitating with ethanol, filtering, and vacuum drying to obtain the target polymer;

[0070] S3, the components are mixed in the following proportions to prepare a composite coating slurry: 50 parts of modified titanium nitride graphene composite material, 27.5 parts of 4-(diaminoformyl)styrene polymer, 3.5 parts of aluminum tripolyphosphate; 1.5 parts of fluorosilane coupling agent is prepared by mixing 1H,1H,2H,2H-perfluorooctyltriethoxysilane and anhydrous ethanol in a mass ratio of 1:4; polyvinylidene fluoride emulsion is prepared by emulsifying polyvinylidene fluoride resin and deionized water in a mass ratio of 1:2 7.5 parts of the above-mentioned material were added; 2 parts of the above-mentioned material were added to form a surface morphology control agent prepared by mixing and dispersing silica nanospheres and deionized water in a mass ratio of 1:10; 1.0 part of the above-mentioned material was added to form a curing accelerator prepared by mixing dicumyl peroxide and dioctyl phthalate in a mass ratio of 1:3; the obtained coating slurry was sprayed onto the surface of the pretreated stainless steel pipe fitting, pre-baked at 80°C for 20 minutes, and then heat-cured at 180°C for 45 minutes. After cooling, a comparative sample pipe fitting was obtained.

[0071] Performance Testing

[0072] Wear resistance test

[0073] This test evaluates the wear resistance of composite coatings under dry grinding conditions. During the test, a 25 mm x 75 mm sample is mounted on a grinding wheel holder, in contact with a rubber wheel. A 40 N load is applied, using dry quartz sand with a particle size of 200 to 300 μm as the abrasive. The speed is set at 200 rpm, and the abrasion is continued for 6000 revolutions. The sample is weighed before and after the test, and the mass loss (abrasion loss, in mg) is recorded. Lower values ​​indicate better wear resistance.

[0074] Adhesion test

[0075] This test evaluates the bond strength between a coating and a stainless steel substrate. The test involves scratching an 11x11 grid pattern with 1mm spacing on the sample surface, ensuring the scratches penetrate the coating to the substrate. After removing any flaking debris with a soft brush, standard 3M tape is applied to the gridded area and quickly removed vertically. The test is graded on a scale of 0 to 5, based on the number of remaining coating grids, with 0 indicating the strongest adhesion with no flaking.

[0076] Corrosion resistance test

[0077] The test simulates the corrosion of stainless steel in a high-salt environment. The sample is placed in a salt spray test chamber, and a 5wt% sodium chloride solution is continuously sprayed at 35°C, with the pH maintained at 6.5-7.2, and the test period is 500 hours. During the test, the sample surface is periodically inspected for signs of failure such as rust, blistering, peeling, etc., and the corrosion area is quantitatively rated according to ASTM D1654 standard, with smaller corrosion area indicating better protection effect.

[0078] Hydrophobicity test

[0079] The test reflects the hydrophilic / hydrophobic properties and self-cleaning potential of the coating surface. During the test, a contact angle measuring instrument is used to drop 5 μL of deionized water on the sample surface, the water droplet profile is photographed, and the contact angle is recorded. Three different areas of each sample are selected for repeated testing and the average value is taken. If the water contact angle is > 90°, it is hydrophobic, and > 120°, it is strongly hydrophobic. The larger the contact angle, the more difficult it is to wet the surface, and the stronger the anti-pollution property.

[0080] Coating adhesion test

[0081] The test is used to evaluate the interfacial bonding strength between the composite coating and the stainless steel substrate. The standard GB / T9286-2021 "Cross-hatch test for paint and varnish film" is referred to for operation. A special cross-hatch device is used to draw 6x6 grids (cutting interval is 1 mm) on the sample surface, cutting to the substrate but not damaging the substrate. Then a strong adhesive tape is evenly applied to the cross-hatch area, and after compaction, it is quickly peeled off at an angle of 60°, and the paint film peeling condition of the grid area is observed. The peeling grade is rated from 0 to 5, with 0 indicating no paint film peeling and the strongest adhesion, and 5 indicating large area of paint film peeling and the worst adhesion. The adhesion grades of the examples and the comparative examples are compared to reflect the contribution of different structural material systems to the coating bonding performance.

[0082] Table 1 Composite coating performance test results

[0083]

[0084] By testing the abrasion amount, adhesion grade, salt spray corrosion area, water contact angle and coating adhesion grade of the stainless steel pipe samples of Examples 1-3 and Comparative Examples 1-2, the comprehensive performance improvement brought by the structural design and material combination of the composite coating of the present application is verified. According to Figure 4 and the test results in Table 1 show that the intermediate value ratio used in Example 2 performs the best in all indicators, reflecting the synergistic balance advantage between structure and components.

[0085] In terms of wear resistance, the wear loss of Example 2 is only 3.9 mg, which is significantly better than that of Example 1 (6.3 mg) and Example 3 (4.5 mg). Compared with Comparative Example 1 (13.7 mg) which does not adopt a nested composite structure and Comparative Example 2 (10.9 mg) which does not introduce a functional polymer, the wear loss is reduced by more than 60%, indicating that the modified titanium nitride graphene has a significant effect in enhancing the wear resistance of the coating, especially its self-assembled nested structure can effectively prevent the expansion of the abrasive cutting path. In the cross-hatch adhesion test, Example 2 is level 0, indicating that there is no obvious paint film shedding in its grid area and the bonding strength is optimal; while Example 1 and Example 3 are both level 1, which have good bonding performance. In contrast, the adhesion grades of Comparative Examples 1 and 2 are level 3 and level 2, respectively, indicating that when there is a lack of a synergistic modified structure or a high-polarity polymer, the bonding strength between the coating and the metal substrate is significantly reduced, and interface peeling is prone to occur. In the salt spray corrosion test, the corrosion area of ​​Example 2 is only 0.1%, which is much better than Example 1 (0.4%) and Example 3 (0.2%), and is also significantly better than Comparative Example 1 (3.6%) and Comparative Example 2 (2.7%). This shows that the dense coating structure synergistically constructed by additives such as aluminum tripolyphosphate, fluorosilane and PVDF can effectively shield the penetration of corrosive ions, delay metal oxidation, and enhance the protective function of the coating. The hydrophobicity test results show that the composite coating of the present invention has excellent water-repellent properties. The water contact angle of Example 2 reaches 136.8°, which is higher than Example 1 (127.5°) and Example 3 (131.2°), and has a significant hydrophobic improvement compared to Comparative Example 1 (92.5°) and Comparative Example 2 (96.0°). This result is attributed to the micro-nano surface structure synergistically constructed by the fluorosilane coupling agent and the silica microspheres, which effectively reduces the surface free energy and improves the self-cleaning and anti-pollution capabilities of the coating. In the adhesion test under the GB / T9286 standard, Example 2 maintained level 0, showing extremely high interface bonding stability, which is consistent with the above-mentioned cross-hatch test results, verifying the bonding enhancement effect of the functional polymer and the nested structure filler under the joint action of the interface layer.

[0086] To sum up, the composite coating system composed of the modified titanium nitride graphene composite material and 4-(diaminoformyl)styrene polymer designed in the present invention shows significant advantages over the traditional unmodified coating system in key properties such as wear resistance, adhesion, corrosion resistance, and hydrophobicity. In particular, it achieves the optimal balance between performance and process under the intermediate ratio, verifying the effectiveness and practicality of the innovative structural design.

Claims

1. A super wear-resistant and corrosion-resistant stainless steel pipe, characterized in that: The invention comprises the following raw materials in parts by weight: 40-60 parts of a modified titanium nitride graphene composite material; 20-35 parts of a 4-(diaminoformyl)styrene polymer; 2-5 parts of aluminum tripolyphosphate; 1-2 parts of a fluorosilane coupling agent; 5-10 parts of a polyvinylidene fluoride emulsion; 1-3 parts of a surface morphology regulator; and 0.5-1.5 parts of a curing accelerator. The modified titanium nitride graphene composite material has a sheet-like nested structure, and is formed by self-polymerization of titanium nitride nanosheets and graphene oxide after functionalization with chitosan quaternary ammonium salt and introduction of polydopamine at the interface.

2. The super wear-resistant and corrosion-resistant stainless steel pipe fitting according to claim 1, characterized in that: The modified titanium nitride graphene composite material comprises the following raw materials in parts by weight: 40-60 parts of titanium nitride nanosheets, 15-30 parts of graphene oxide, 5-10 parts of chitosan quaternary ammonium salt, and 0.5-2 parts of polydopamine.

3. A super wear-resistant and corrosion-resistant stainless steel pipe fitting according to claim 1 or 2, characterized in that: The preparation method of the modified titanium nitride graphene composite material comprises the following steps: (1) dispersing titanium nitride nanosheets and graphene oxide in a mixed solution, stirring and ultrasonically treating the solution to obtain a titanium nitride dispersion and a graphene oxide dispersion; (2) adding chitosan quaternary ammonium salt to the titanium nitride dispersion and the graphene oxide dispersion, respectively, to perform functionalization treatment to obtain a surface-modified titanium nitride suspension and a graphene oxide suspension; (3) mixing the surface-modified titanium nitride suspension with the graphene oxide suspension, adding dopamine, and performing an interface-induced self-assembly reaction to form a nested composite structure; (4) The mixed liquid after the reaction is centrifuged, washed and dried to obtain a modified titanium nitride graphene composite material.

4. The super wear-resistant and corrosion-resistant stainless steel pipe fitting according to claim 3, characterized in that: The stirring and ultrasonic treatment conditions in step (1) are as follows: a stirring rate of 300-800 rpm, an ultrasonic power of 100-300 W, and a treatment time of 20-60 minutes; the pH adjustment range in step (3) is 8.0-9.0, and the reaction time is 8-16 hours.

5. The super wear-resistant and corrosion-resistant stainless steel pipe fitting according to claim 1, characterized in that: The 4-(diaminoformyl)styrene polymer comprises the following raw materials in parts by weight: 60-80 parts of 4-(diaminoformyl)styrene monomer, 2-5 parts of azobisisobutyronitrile, and 20-35 parts of dimethyl sulfoxide.

6. The super wear-resistant and corrosion-resistant stainless steel pipe fitting according to claim 1 or 5, characterized in that: The preparation method of the 4-(diaminoformyl)styrene polymer comprises the following steps: (a) dissolving 4-(diaminoformyl)styrene monomer in dimethyl sulfoxide and stirring to form a homogeneous transparent solution; (b) adding azobisisobutyronitrile to the homogeneous transparent solution and continuing to stir to fully mix; (c) under an inert atmosphere, heating the system to a polymerization temperature and maintaining the reaction at a constant temperature to complete the free radical polymerization; (d) After the reaction is completed, the product is cooled to room temperature, and precipitation, filtration, and drying steps are performed to obtain the 4-(diaminoformyl)styrene polymer.

7. The super wear-resistant and corrosion-resistant stainless steel pipe fitting according to claim 6, characterized in that: The reaction conditions of step (c) are as follows: reacting at a constant temperature of 70-80° C. for 6-10 hours under nitrogen protection.

8. The super wear-resistant and corrosion-resistant stainless steel pipe fitting according to claim 1, characterized in that: The fluorosilane coupling agent is formed by mixing 1H,1H,2H,2H-perfluorooctyltriethoxysilane and anhydrous ethanol in a mass ratio of 1:4; the polyvinylidene fluoride emulsion is formed by mixing and emulsifying polyvinylidene fluoride resin and deionized water in a mass ratio of 1:2 under the action of an emulsifier; the surface morphology controller is formed by mixing silica nanospheres and deionized water in a mass ratio of 1:10; and the curing accelerator is formed by mixing diisopropylbenzene peroxide and dioctyl phthalate in a mass ratio of 1:

3.

9. A method for preparing a super wear-resistant and corrosion-resistant stainless steel pipe fitting, wherein the super wear-resistant and corrosion-resistant stainless steel pipe fitting is as described in any one of claims 1 to 8, characterized in that: The following steps are involved: S1, pre-treating the surface of the stainless steel substrate by sandblasting, degreasing, pickling, neutralizing and drying in sequence to obtain a rough active interface; S2, uniformly mixing a modified titanium nitride graphene composite material, 4-(diaminoformyl)styrene polymer, aluminum tripolyphosphate, a mixture of 1H,1H,2H,2H-perfluorooctyltriethoxysilane and anhydrous ethanol, a polyvinylidene fluoride emulsion, a silica nanosphere dispersion, and a mixture of diisopropylbenzene peroxide and dioctyl phthalate to prepare a composite coating slurry; S3, applying the composite coating slurry evenly to the stainless steel surface by spraying; S4, pre-baking the coated pipe fittings at 60-90° C. for 10-30 minutes, then heat curing at 160-200° C. for 30-60 minutes, and cooling to obtain super wear-resistant and corrosion-resistant stainless steel pipe fittings.

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