Corrosion resistant aluminum alloy pipe
By optimizing the composition of the aluminum alloy matrix and the surface coating design, a multi-level anti-corrosion system is formed, which solves the problem of electrochemical corrosion of aluminum alloy tubes in complex environments, and achieves high-efficiency corrosion resistance and impact resistance, making it suitable for equipment such as solar heat exchangers and flat plate collectors.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- JIANGSU YUNNENG NEW MATERIAL TECH CO LTD
- Filing Date
- 2025-09-09
- Publication Date
- 2026-05-12
Smart Images
Figure BDA0005587288430000131
Abstract
Description
Technical Field
[0001] This invention relates to the field of aluminum alloy pipe technology, and more particularly to a corrosion-resistant aluminum alloy pipe. Background Technology
[0002] Corrosion-resistant aluminum alloy pipes, as an important lightweight structural material, are widely used in fields with extremely high requirements for corrosion resistance, such as petrochemicals, marine engineering, and aerospace. They also have significant applications in the new energy and HVAC industries, such as solar heat exchangers, flat-plate collectors, and air conditioning condensers. While aluminum alloys possess good specific strength, thermal conductivity, and processing properties, they are prone to electrochemical corrosion in acidic, alkaline, high-salt environments or under prolonged high temperature and humidity conditions. This corrosion problem is particularly pronounced in the complex operating conditions of solar thermal systems and air conditioning systems, leading to equipment failure and severely impacting system efficiency and service life. Therefore, effectively improving the corrosion resistance of aluminum alloy pipes has always been a crucial research topic in materials science.
[0003] In existing technologies, such as the corrosion-resistant aluminum alloy pipe described in CN202310451965.1, corrosion resistance is mainly improved through two methods: one is to add elements such as Mg, Si, Sr, and Mn, especially rare earth elements Pr, Ce, and Nd, to the aluminum alloy raw materials to improve the corrosion resistance of the alloy matrix; the other is to grow Si-BN ceramic films on the aluminum alloy surface using plasma chemical vapor deposition (PCVDC). However, this technical solution has obvious drawbacks: the addition of rare earth elements not only significantly increases the cost of raw materials, but also easily forms coarse intermetallic compounds in aluminum alloys, which may become weak points for corrosion; the PCVDC process requires high temperature and high vacuum conditions, resulting in huge equipment investment and complex processes, and the film-substrate adhesion is limited, making the film prone to peeling off under complex service environments, leading to corrosion failure. Summary of the Invention
[0004] In view of this, the present invention proposes a corrosion-resistant aluminum alloy pipe to solve the technical problems of high cost and poor adhesion and insufficient stability of the anti-corrosion coating in the prior art.
[0005] The technical solution of this invention is achieved as follows: This invention provides a corrosion-resistant aluminum alloy pipe, which includes an aluminum alloy pipe and a corrosion-resistant layer coated on the surface of the aluminum alloy pipe. The raw materials of the aluminum alloy pipe include: Mg: 0.1-0.3%, Si: 0.06-0.2%, Fe: 0.1-0.5%, Cu: 0.005%, Mn: 0.2-0.5%, Cr: <0.1%, Zn: 0.1-0.4%, Ti: 0.05-0.2%, V: 0.01-0.05%, and Al balance. By weight, the corrosion-resistant layer includes: 100 parts of epoxy resin emulsion, 15-25 parts of composite modified titanium diboride, 3-5 parts of amino curing agent, 1-3 parts of carbon fiber, 20-30 parts of deionized water, 2-3 parts of dispersant, and 0.3-0.5 parts of defoamer.
[0006] Specifically, magnesium exists primarily in aluminum alloys as a solid solution, exerting a significant solid solution strengthening effect by substituting Al atoms. In corrosive environments, magnesium preferentially reacts with oxygen to form a composite oxide film, which exhibits better density and stability. The magnesium content is limited to 0.1%-0.3%; exceeding 0.3% promotes the precipitation of brittle phases such as Mg₂Si, forming corrosion channels at grain boundaries and consequently reducing corrosion resistance.
[0007] Silicon forms fine, dispersed silicon particles and Mg2Si intermetallic compounds within the aluminum matrix, acting as a dispersion strengthening agent. The presence of silicon refines the casting microstructure of aluminum alloys and reduces the formation of coarse dendrites. More importantly, silicon reacts with Al2O3 in the surface oxide film to form an amorphous Al2O3-SiO2 composite oxide film. This composite film exhibits higher chemical stability and a lower diffusion coefficient, effectively preventing the penetration of corrosive ions. The silicon content is limited to 0.06-0.2%; exceeding 0.2% leads to the precipitation of primary silicon crystals. These coarse silicon phases form micro-cells with the aluminum matrix, accelerating electrochemical corrosion.
[0008] Iron forms intermetallic compound phases such as Al3Fe in aluminum alloys, which are characterized by high melting points and high hardness. During corrosion, while the iron phase, acting as the cathodic phase, promotes localized corrosion, its high chemical stability allows it to form a passivation protective layer on the surface. Limiting the iron content to 0.1-0.5% ensures the minimum amount required for sufficient pinning phase formation; contents exceeding 0.5% will form acicular β-Al5FeSi phases, severely deteriorating corrosion resistance.
[0009] In aluminum alloys, trace amounts of copper primarily function as grain boundary cleaners. Copper atoms tend to segregate at grain boundaries, stabilizing the grain boundary structure and reducing defect concentration by lowering the grain boundary energy. In corrosive environments, trace amounts of copper can provide cathodic protection to the aluminum matrix through a "sacrificial anode" mechanism. The concentration is strictly controlled at 0.005% because copper has a more positive potential than aluminum; excessively high concentrations would form a continuous cathodic phase network, leading to severe electrochemical corrosion.
[0010] Manganese forms intermetallic compounds such as Al6Mn in aluminum alloys. These compounds possess electrochemical properties similar to the aluminum matrix and do not cause significant galvanic corrosion. The main function of the manganese phase is to refine the grains through a pinning effect, while also neutralizing the harmful effects of iron. Furthermore, manganese can inhibit stress corrosion cracking. A manganese content of 0.2-0.5% effectively neutralizes the iron phase, producing a grain-refining effect, and ensures that the manganese phase remains finely dispersed.
[0011] Chromium primarily forms intermetallic compound phases such as Al7Cr, which possess extremely high thermal stability and effectively inhibit grain growth during recrystallization. The chromium phase also acts as a heterogeneous nucleation site, promoting grain refinement. During corrosion, chromium forms a Cr2O3 passivation film on the alloy surface. This film, together with Al2O3, forms a composite passivation layer, significantly improving corrosion resistance. The content is limited to below 0.1% because chromium has a very low diffusion coefficient; excessively high content leads to uneven chromium phase distribution, creating corrosion-sensitive areas.
[0012] Zinc exists primarily in solid solution form in aluminum alloys. Zinc has a more negative potential than aluminum, providing sacrificial anodic protection to the aluminum matrix. More importantly, zinc can form a dense ZnO passivation film on the alloy surface, which possesses excellent self-healing capabilities, rapidly re-passivating even when locally damaged. Zinc also inhibits the pitting corrosion tendency of aluminum alloys. A zinc content of 0.1-0.4% provides effective anodic protection, preventing excessive anodic reactions that could lead to matrix dissolution.
[0013] Titanium is a strong carbide and nitride forming element, capable of combining with interstitial atoms (C, N, O) in alloys to form highly stable compounds, thus purifying the matrix composition. In corrosive environments, the oxides formed by titanium exhibit extremely high chemical stability, stabilizing the oxide film structure. Limiting the titanium content to 0.05-0.2% effectively purifies grain boundaries, ensuring the titanium phase maintains its fine and dispersed characteristics.
[0014] Vanadium is a strong carbonitride forming element with a significant grain-refining effect, refining the casting microstructure by providing heterogeneous nucleation sites. During corrosion, vanadium oxide exhibits self-healing properties, capable of repairing micro-defects in the oxide film.
[0015] The corrosion-resistant layer uses epoxy resin emulsion as the matrix and adds composite modified titanium diboride as a functional filler. Utilizing the excellent chemical stability and electrochemical inertness of titanium diboride, combined with the organic-inorganic hybrid structure formed after surface modification, a multi-layered anti-corrosion barrier is constructed. The addition of carbon fiber further enhances the mechanical strength and toughness of the coating, while the amino curing agent ensures full cross-linking and curing of the coating. Dispersants and defoamers guarantee the uniformity and density of the coating. The entire protection system achieves a multi-level anti-corrosion mechanism from the inside out through the synergistic cooperation of the matrix self-passivation layer and the surface functional coating. Even in the case of local damage to the coating, the dense oxide film formed by the corrosion-resistant elements in the matrix can still provide effective secondary protection, significantly improving the overall corrosion resistance and long-term service reliability of the aluminum alloy tube. At the same time, it avoids the use of rare earth elements and complex vapor deposition processes, and has significant advantages such as low cost, simple process, strong coating adhesion, and good long-term stability.
[0016] Based on the above technical solutions, the preferred method for preparing composite modified titanium diboride includes:
[0017] S1. 4-Allyloxy-4'-hydroxydiphenyl sulfone is dispersed in anhydrous toluene. Under nitrogen protection, mercaptosilane coupling agent and 2,2-dimethoxy-2-phenylacetophenone are added. The mixture is heated to 40-50℃ and reacted for 2-4 hours to obtain the modifier.
[0018] S2. After acid treatment, nano-titanium diboride is dispersed in an ethanol aqueous solution, a modifier is added, the temperature is raised to 50-60℃, and the reaction is carried out for 20-24 hours to obtain modified titanium diboride.
[0019] S3. Disperse the modified titanium diboride in deionized water, add sodium hydroxide solution under ice-water bath conditions, and continue stirring the reaction at room temperature for 2-3 hours to obtain the modified titanium diboride intermediate.
[0020] S4. The modified titanium diboride intermediate and potassium iodide are dispersed in DMF, 4-chloro-3-trifluoromethylaniline is added, and the mixture is heated to 90-100℃ and stirred for 22-24 hours under nitrogen protection to obtain composite modified titanium diboride.
[0021] Specifically, titanium diboride, as a functional filler, has excellent chemical stability, high hardness and good conductivity, and can play a dual role in coatings as wear resistance and electrochemical protection. However, direct mixing with epoxy resin has problems such as high surface energy, easy agglomeration and poor compatibility with organic matrix. To address the aforementioned issues, in step S1, a composite modifier is prepared by reacting the double bond on 4-allyloxy-4'-hydroxydiphenyl sulfone with a mercaptosilane coupling agent to form a mercapto-olefin reaction. In step S2, after acid treatment, nano-titanium diboride generates abundant hydroxyl active sites on its surface, which undergo a condensation reaction with the silane coupling agent in the modifier, anchoring organic molecules containing high-temperature resistant sulfone structures onto the surface of titanium diboride, thus initially achieving inorganic-organic hybrid modification. In step S3, sodium hydroxide solution is added to convert the phenolic hydroxyl groups on the modifier into sodium phenolate with strong nucleophilic attack capabilities. In step S4, the activated sodium phenolate undergoes a Williamson ether synthesis reaction with 4-chloro-3-trifluoromethylaniline to form a stable ether bond, introducing a trifluoromethyl group with anti-corrosion function.
[0022] In the composite modified titanium diboride, the 4-allyloxy-4'-hydroxydiphenyl sulfone molecule, introduced via a mercaptosilane coupling agent as a bridge, contains structures such as benzene rings, sulfone groups, and ether bonds. After being chemically bonded to the surface of titanium diboride, it is dispersed in epoxy resin. The above structure can effectively improve the impact resistance and thermal stability of epoxy resin. Furthermore, the 4-chloro-3-trifluoromethylaniline molecule introduced through the hydroxyl groups on the surface of the modifier has trifluoromethyl groups with strong electronegativity and hydrophobicity, which can significantly improve the chemical corrosion resistance of the coating. The amino groups retained on the aniline can not only undergo ring-opening curing reaction with epoxy resin to form a cross-linked network structure, solving the problem of poor compatibility between titanium diboride and organic matrix, but also act as corrosion inhibitors to passivate the active sites on the metal surface through coordination. The resulting composite modified titanium diboride not only has excellent dispersibility, good compatibility with the matrix, and multiple anti-corrosion mechanisms, but more importantly, the introduction of sulfone segments significantly improves the impact resistance of the coating system.
[0023] Based on the above technical solutions, preferably, in step S1, the molar ratio of 4-allyloxy-4'-hydroxydiphenyl sulfone, mercaptosilane coupling agent and 2,2-dimethoxy-2-phenylacetophenone is 1:(1.05-1.15):(0.01-0.02), and the mercaptosilane coupling agent is 3-mercaptopropyltrimethoxysilane or 3-mercaptopropyltriethoxysilane.
[0024] Based on the above technical solutions, preferably, in step S2, the mass ratio of nano-titanium diboride to the modifier is 100:(20-40), and the acid used in the acid treatment process is a nitric acid or sulfuric acid solution with a mass fraction of 3-5%.
[0025] Based on the above technical solutions, preferably, in step S3, the mass ratio of modified titanium diboride to sodium hydroxide is 100:(1.5-2.5).
[0026] Based on the above technical solution, preferably, in step S4, the mass ratio of the modified titanium diboride intermediate, 4-chloro-3-trifluoromethylaniline and potassium iodide is 100:(8-12):(0.8-1.2).
[0027] Based on the above technical solutions, preferably, the amino curing agent is an aromatic amine curing agent.
[0028] Based on the above technical solutions, preferably, the dispersant is any one of sodium polycarboxylate, potassium polyacrylate, and sodium polyacrylate.
[0029] Based on the above technical solutions, preferably, the defoamer is an organosilicon defoamer.
[0030] This invention provides a method for preparing a corrosion-resistant aluminum alloy tube, the method comprising the following steps:
[0031] (1) Add deionized water, dispersant and defoamer to a reactor equipped with high-speed dispersion stirring and stir at medium speed until uniform; then slowly add composite modified titanium diboride and carbon fiber and disperse at high speed for 25-30 min; finally add epoxy resin emulsion under stirring and continue stirring for 15-25 min to obtain mixed slurry.
[0032] (2) Mix the mixed slurry and amino curing agent, stir thoroughly and let stand for 5-10 minutes to defoam, then coat it on the surface of the aluminum alloy pipe that has been pretreated for degreasing and rust removal, and cure at room temperature for 70-74 hours to obtain a corrosion-resistant aluminum alloy pipe.
[0033] The corrosion-resistant aluminum alloy pipe of the present invention has the following advantages over the prior art:
[0034] (1) By optimizing the composition ratio of the aluminum alloy matrix and the synergistic design of the functional surface coating, a multi-level anti-corrosion system with internal and external synergy was constructed. The dense self-passivation layer formed by corrosion-resistant elements in the aluminum alloy matrix and the surface functional coating work together through multiple mechanisms of physical shielding, chemical passivation and electrochemical protection to achieve gradient protection from the inside to the outside. Even if the coating is locally damaged, the matrix self-passivation layer can still provide effective secondary protection, which significantly improves the overall corrosion resistance and impact resistance of the aluminum alloy tube. It is particularly suitable for complex working environments such as solar heat exchangers, flat plate collectors and air conditioning condensers.
[0035] (2) In this invention, the content ratio of elements such as Zn, Mn, Mg, and Ti is precisely controlled in the aluminum alloy matrix. Zinc element improves the self-passivation ability of the alloy by forming a dense ZnO film. Manganese element refines the grains and forms a stable Al6Mn intermetallic compound to prevent the diffusion of corrosive media. Magnesium element enhances the corrosion resistance of the matrix through solid solution strengthening mechanism. Titanium element, as a strong carbide forming element, purifies the grain boundaries and inhibits intergranular corrosion. The synergistic effect of the four elements forms a dense and stable composite oxide film on the matrix surface, providing ideal interface conditions for the bonding of surface coatings. This effectively solves the technical problem that traditional aluminum alloy tubes are prone to electrochemical corrosion in acidic, alkaline or high-salt environments, and significantly improves the intrinsic corrosion resistance of the matrix material.
[0036] (3) Composite modified titanium diboride was prepared by multi-step surface modification technology. Sulfone and trifluoromethyl structures were grafted onto the surface of titanium diboride through mercapto-olefin click chemistry and Williamson ether synthesis reaction. This solved the key technical problems of easy aggregation of nano titanium diboride and poor compatibility with organic matrix. The modified titanium diboride formed a chemical crosslink with epoxy resin through surface amino groups to build a stable organic-inorganic hybrid network structure. Among them, the sulfone segments significantly improved the impact resistance of the resin, the trifluoromethyl groups greatly improved the chemical corrosion resistance of the coating through strong electronegativity and hydrophobicity, and the amino groups participated in the curing reaction and played a corrosion inhibition role, realizing multi-functional synergistic effect and significantly improving the comprehensive protective performance of the coating. Detailed Implementation
[0037] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.
[0038] It should be noted that the epoxy resin was purchased from Shandong Yiyi New Material Co., Ltd., model NPEL-128; the aromatic amine curing agent was m-phenylenediamine, CAS number 1477-55-0, purchased from Hubei Xinjiecheng Chemical Technology Co., Ltd.; the organosilicon defoamer was purchased from Shandong Jiayi Chemical Technology Co., Ltd., model 01; and titanium diboride was purchased from Qinghe County Chaotai Metal Materials Co., Ltd., with a particle size of 50nm.
[0039] Example 1
[0040] This embodiment provides a corrosion-resistant aluminum alloy pipe, comprising an aluminum alloy pipe and a corrosion-resistant layer coated on the surface of the aluminum alloy pipe. The raw materials of the aluminum alloy pipe include: Mg: 0.2%, Si: 0.12%, Fe: 0.3%, Cu: 0.005%, Mn: 0.35%, Cr: <0.1%, Zn: 0.25%, Ti: 0.1%, V: 0.03%, and Al as the balance. By weight, the corrosion-resistant layer comprises: 100 parts epoxy resin emulsion, 20 parts composite modified titanium diboride, 4 parts aromatic amine curing agent, 2 parts carbon fiber, 25 parts deionized water, 2.5 parts potassium polyacrylate, and 0.4 parts organosilicon defoamer. The preparation method is as follows:
[0041] (1) Add deionized water, potassium polyacrylate and silicone defoamer to a reactor equipped with a high-speed dispersing stirrer and stir at medium speed until uniform; then slowly add composite modified titanium diboride and carbon fiber and disperse at high speed for 25-30 min; finally add epoxy resin emulsion under stirring and continue stirring for 20 min to obtain a mixed slurry.
[0042] (2) Mix the mixed slurry and aromatic amine curing agent, stir thoroughly and let stand for 8 minutes to defoam, and then coat it on the surface of the aluminum alloy pipe that has been pretreated for degreasing and rust removal. The coating thickness is controlled at 80-120μm. Curing is carried out at room temperature and relative humidity of 60-70% for 72 hours to obtain corrosion-resistant aluminum alloy pipe.
[0043] The preparation methods for composite modified titanium diboride include:
[0044] S1. 290g of 4-allyloxy-4'-hydroxydiphenyl sulfone (1mol) was dispersed in 500ml of anhydrous toluene. Under nitrogen protection, 216g of 3-mercaptopropyltrimethoxysilane (1.1mol) and 3.84g of 2,2-dimethoxy-2-phenylacetophenone (0.015mol) were added. The mixture was heated to 45℃ and reacted for 3h. After the reaction was completed, toluene was removed by vacuum distillation, and the mixture was purified by recrystallization with petroleum ether and dried under vacuum to obtain the modifier.
[0045] S2. 100g of nano-titanium diboride was dispersed in 200ml of 4% nitric acid solution, sonicated for 2h, then washed with deionized water until neutral, and vacuum dried to obtain acid-treated titanium diboride. The acid-treated titanium diboride was dispersed in 300ml of ethanol-water solution (volume ratio 1:1), 30g of modifier was added, the temperature was raised to 55℃, and the reaction was carried out for 22h. After the reaction was completed, the mixture was centrifuged, washed with ethanol and deionized water in sequence, and vacuum dried to obtain modified titanium diboride.
[0046] S3. Disperse 100g of modified titanium diboride in 500ml of deionized water. Under ice-water bath conditions, slowly add 50mL of sodium hydroxide solution (prepared from 2.0g of sodium hydroxide and water), heat to room temperature, and continue stirring for 2.5h. After the reaction is complete, centrifuge and wash with deionized water until neutral to obtain the modified titanium diboride intermediate.
[0047] S4. Disperse 100g of modified titanium diboride intermediate and 1g of potassium iodide in 400ml of DMF, add 10g of 4-chloro-3-trifluoromethylaniline, heat to 95℃ under nitrogen protection, stir and react for 23h. After the reaction is complete, cool to room temperature, centrifuge, wash with DMF, ethanol and deionized water in sequence, and vacuum dry to obtain composite modified titanium diboride.
[0048] Example 2
[0049] This embodiment provides a corrosion-resistant aluminum alloy pipe, comprising an aluminum alloy pipe and a corrosion-resistant layer coated on the surface of the aluminum alloy pipe. The raw materials of the aluminum alloy pipe include: Mg: 0.1%, Si: 0.06%, Fe: 0.1%, Cu: 0.005%, Mn: 0.2%, Cr: <0.1%, Zn: 0.1%, Ti: 0.05%, V: 0.01%, and Al as the balance. By weight, the corrosion-resistant layer comprises: 100 parts epoxy resin emulsion, 15 parts composite modified titanium diboride, 3 parts aromatic amine curing agent, 1 part carbon fiber, 20 parts deionized water, 2 parts potassium polyacrylate, and 0.3 parts organosilicon defoamer. The preparation method is as follows:
[0050] (1) Add deionized water, potassium polyacrylate and organosilicon defoamer to a reactor equipped with a high-speed dispersing stirrer and stir at medium speed until uniform; then slowly add composite modified titanium diboride and carbon fiber and disperse at high speed for 25 min; finally add epoxy resin emulsion under stirring and continue stirring for 15 min to obtain a mixed slurry.
[0051] (2) Mix the mixed slurry and aromatic amine curing agent, stir thoroughly and let stand for 5 minutes to defoam, and then coat it on the surface of the aluminum alloy pipe that has been pretreated for degreasing and rust removal. The coating thickness is controlled at 80-120μm. Curing is carried out at room temperature and relative humidity of 60-70% for 70 hours to obtain corrosion-resistant aluminum alloy pipe.
[0052] The preparation methods for composite modified titanium diboride include:
[0053] S1. 290g of 4-allyloxy-4'-hydroxydiphenyl sulfone (1mol) was dispersed in 500ml of anhydrous toluene. Under nitrogen protection, 206g of 3-mercaptopropyltrimethoxysilane (1.05mol) and 2.56g of 2,2-dimethoxy-2-phenylacetophenone (0.01mol) were added. The mixture was heated to 40℃ and reacted for 4h. After the reaction was completed, toluene was removed by vacuum distillation, and the mixture was purified by recrystallization with petroleum ether and dried under vacuum to obtain the modifier.
[0054] S2. 100g of nano-titanium diboride was dispersed in 200ml of 3% nitric acid solution, sonicated for 2h, then washed with deionized water until neutral, and vacuum dried to obtain acid-treated titanium diboride. The acid-treated titanium diboride was dispersed in 300ml of ethanol-water solution (volume ratio 1:1), 20g of modifier was added, the temperature was raised to 50℃, and the reaction was carried out for 24h. After the reaction was completed, the mixture was centrifuged, washed with ethanol and deionized water in sequence, and vacuum dried to obtain modified titanium diboride.
[0055] S3. Disperse 100g of modified titanium diboride in 500ml of deionized water. Under ice-water bath conditions, slowly add 50mL of sodium hydroxide solution (prepared from 1.5g of sodium hydroxide and water), heat to room temperature, and continue stirring for 2h. After the reaction is complete, centrifuge and wash with deionized water until neutral to obtain the modified titanium diboride intermediate.
[0056] S4. Disperse 100g of modified titanium diboride intermediate and 0.8g of potassium iodide in 400ml of DMF, add 8g of 4-chloro-3-trifluoromethylaniline, heat to 90℃ under nitrogen protection, stir and react for 24h. After the reaction is complete, cool to room temperature, centrifuge, wash with DMF, ethanol and deionized water in sequence, and vacuum dry to obtain composite modified titanium diboride.
[0057] Example 3
[0058] This embodiment provides a corrosion-resistant aluminum alloy pipe, comprising an aluminum alloy pipe and a corrosion-resistant layer coated on the surface of the aluminum alloy pipe. The raw materials of the aluminum alloy pipe include: Mg: 0.3%, Si: 0.2%, Fe: 0.5%, Cu: 0.005%, Mn: 0.5%, Cr: <0.1%, Zn: 0.4%, Ti: 0.2%, V: 0.05%, and Al as the balance. By weight, the corrosion-resistant layer comprises: 100 parts epoxy resin emulsion, 25 parts composite modified titanium diboride, 5 parts aromatic amine curing agent, 3 parts carbon fiber, 30 parts deionized water, 3 parts potassium polyacrylate, and 0.5 parts silicone defoamer. The preparation method is as follows:
[0059] (1) Add deionized water, potassium polyacrylate and organosilicon defoamer to a reactor equipped with a high-speed dispersing stirrer and stir at medium speed until uniform; then slowly add composite modified titanium diboride and carbon fiber and disperse at high speed for 30 min; finally add epoxy resin emulsion under stirring and continue stirring for 25 min to obtain a mixed slurry.
[0060] (2) Mix the mixed slurry and aromatic amine curing agent, stir thoroughly and let stand for 10 minutes to defoam, and then coat it on the surface of the aluminum alloy pipe that has been pretreated for degreasing and rust removal. The coating thickness is controlled at 80-120μm. Curing is carried out at room temperature and relative humidity of 60-70% for 74 hours to obtain corrosion-resistant aluminum alloy pipe.
[0061] The preparation methods for composite modified titanium diboride include:
[0062] S1. 290g of 4-allyloxy-4'-hydroxydiphenyl sulfone (1mol) was dispersed in 500ml of anhydrous toluene. Under nitrogen protection, 225.8g of 3-mercaptopropyltrimethoxysilane (1.15mol) and 5.13g of 2,2-dimethoxy-2-phenylacetophenone (0.02mol) were added. The mixture was heated to 50℃ and reacted for 2h. After the reaction was completed, toluene was removed by vacuum distillation, and the mixture was purified by recrystallization with petroleum ether and dried under vacuum to obtain the modifier.
[0063] S2. 100g of nano-titanium diboride was dispersed in 200mol of 5% nitric acid solution, sonicated for 2h, then washed with deionized water until neutral, and vacuum dried to obtain acid-treated titanium diboride. The acid-treated titanium diboride was dispersed in 300ml of ethanol-water solution (volume ratio 1:1), 40g of modifier was added, the temperature was raised to 60℃, and the reaction was carried out for 20h. After the reaction was completed, the mixture was centrifuged, washed with ethanol and deionized water in sequence, and vacuum dried to obtain modified titanium diboride.
[0064] S3. Disperse 100g of modified titanium diboride in 500ml of deionized water. Under ice-water bath conditions, slowly add 50mL of sodium hydroxide solution (prepared from 2.5g of sodium hydroxide and water), heat to room temperature, and continue stirring for 3h. After the reaction is complete, centrifuge and wash with deionized water until neutral to obtain the modified titanium diboride intermediate.
[0065] S4. Disperse 100g of modified titanium diboride intermediate and 1.2g of potassium iodide in 400ml of DMF, add 12g of 4-chloro-3-trifluoromethylaniline, heat to 100℃ under nitrogen protection, stir and react for 22h. After the reaction is complete, cool to room temperature, centrifuge, wash with DMF, ethanol and deionized water in sequence, and vacuum dry to obtain composite modified titanium diboride.
[0066] Comparative Example 1
[0067] This comparative example provides a corrosion-resistant aluminum alloy pipe, comprising an aluminum alloy pipe and a corrosion-resistant layer coated on the surface of the aluminum alloy pipe. The raw materials of the aluminum alloy pipe include: Mg: 0.2%, Si: 0.12%, Fe: 0.3%, Cu: 0.005%, Mn: 0.35%, Cr: <0.1%, Zn: 0.25%, Ti: 0.1%, V: 0.03%, and Al as the balance. By weight, the corrosion-resistant layer comprises: 100 parts epoxy resin emulsion, 20 parts composite modified titanium diboride, 4 parts aromatic amine curing agent, 2 parts carbon fiber, 25 parts deionized water, 2.5 parts potassium polyacrylate, and 0.4 parts organosilicon defoamer. The preparation method is the same as in Example 1, except that the composite modified titanium diboride is not grafted with 4-allyloxy-4'-hydroxydiphenyl sulfone, as detailed below:
[0068] S1. 100g of nano-titanium diboride was dispersed in 200ml of 4% nitric acid solution, sonicated for 2h, then washed with deionized water until neutral, and vacuum dried to obtain acid-treated titanium diboride. The acid-treated titanium diboride was dispersed in 300ml of ethanol-water solution (volume ratio 1:1), 30g of 3-mercaptopropyltrimethoxysilane was added, the temperature was raised to 55℃, and the reaction was carried out for 22h. After the reaction was completed, the mixture was centrifuged, washed with ethanol and deionized water sequentially, and vacuum dried to obtain modified titanium diboride.
[0069] S2. Disperse 100g of modified titanium diboride in 500ml of deionized water. Under ice-water bath conditions, slowly add 50mL of sodium hydroxide solution (prepared from 2.0g of sodium hydroxide and water), heat to room temperature, and continue stirring for 2.5h. After the reaction is complete, centrifuge and wash with deionized water until neutral to obtain the modified titanium diboride intermediate.
[0070] S3. 100g of modified titanium diboride intermediate was dispersed in 400ml of DMF, and 10g of 4-chloro-3-trifluoromethylaniline was added. Under nitrogen protection, the temperature was raised to 95℃ and the mixture was stirred for 23h. After the reaction was completed, the mixture was cooled to room temperature, centrifuged, washed successively with DMF, ethanol and deionized water, and vacuum dried to obtain composite modified titanium diboride.
[0071] Comparative Example 2
[0072] This comparative example provides a corrosion-resistant aluminum alloy pipe, comprising an aluminum alloy pipe and a corrosion-resistant layer coated on the surface of the aluminum alloy pipe. The raw materials of the aluminum alloy pipe include: Mg: 0.2%, Si: 0.12%, Fe: 0.3%, Cu: 0.005%, Mn: 0.35%, Cr: <0.1%, Zn: 0.25%, Ti: 0.1%, V: 0.03%, and Al as the balance. By weight, the corrosion-resistant layer comprises: 100 parts epoxy resin emulsion, 20 parts composite modified titanium diboride, 4 parts aromatic amine curing agent, 2 parts carbon fiber, 25 parts deionized water, 2.5 parts potassium polyacrylate, and 0.4 parts organosilicon defoamer. The preparation method is the same as in Example 1, except that the composite modified titanium diboride is not grafted with 4-chloro-3-trifluoromethylaniline, as detailed below:
[0073] S1. 290g of 4-allyloxy-4'-hydroxydiphenyl sulfone (1mol) was dispersed in 500ml of anhydrous toluene. Under nitrogen protection, 216g of 3-mercaptopropyltrimethoxysilane (1.1mol) and 3.84g of 2,2-dimethoxy-2-phenylacetophenone (0.015mol) were added. The mixture was heated to 45℃ and reacted for 3h. After the reaction was completed, toluene was removed by vacuum distillation, and the mixture was purified by recrystallization with petroleum ether and dried under vacuum to obtain the modifier.
[0074] S2. 100g of nano-titanium diboride was dispersed in 200ml of 4% nitric acid solution, sonicated for 2h, then washed with deionized water until neutral, and vacuum dried to obtain acid-treated titanium diboride. The acid-treated titanium diboride was dispersed in 300ml of ethanol-water solution (volume ratio 1:1), 30g of modifier was added, the temperature was raised to 55℃, and the reaction was carried out for 22h. After the reaction was completed, the mixture was centrifuged, washed sequentially with ethanol and deionized water, and vacuum dried to obtain modified titanium diboride, which is the composite modified titanium diboride.
[0075] Comparative Example 3
[0076] This comparative example provides a corrosion-resistant aluminum alloy pipe, comprising an aluminum alloy pipe and a corrosion-resistant layer coated on the surface of the aluminum alloy pipe. The raw materials of the aluminum alloy pipe include: Mg: 0.2%, Si: 0.12%, Fe: 0.3%, Cu: 0.005%, Mn: 0.35%, Cr: <0.1%, Zn: 0.25%, Ti: 0.1%, V: 0.03%, and Al as the balance. By weight, the corrosion-resistant layer comprises: 100 parts epoxy resin emulsion, 20 parts composite modified titanium diboride, 4 parts aromatic amine curing agent, 2 parts carbon fiber, 25 parts deionized water, 2.5 parts potassium polyacrylate, and 0.4 parts organosilicon defoamer. The preparation method is the same as in Example 1, except that the specific preparation method of the composite modified titanium diboride is as follows:
[0077] 100g of nano-titanium diboride, 30g of 4-allyloxy-4'-hydroxydiphenyl sulfone, and 10g of 4-chloro-3-trifluoromethylaniline were physically mixed in a planetary ball mill at 300 rpm for 2 hours with a ball-to-material ratio of 10:1 to obtain a physically mixed composite modified titanium diboride. To improve mixing uniformity, the mill was stopped for 10 minutes every 30 minutes of milling to prevent overheating. After milling, the mixture was passed through a 200-mesh sieve and vacuum dried at 60℃ for 4 hours to obtain the composite modified titanium diboride.
[0078] Comparative Example 4
[0079] This comparative example provides a corrosion-resistant aluminum alloy pipe, comprising an aluminum alloy pipe and a corrosion-resistant layer coated on the surface of the aluminum alloy pipe. The raw materials of the aluminum alloy pipe include: Mg: 0.2%, Si: 0.12%, Fe: 0.3%, Cu: 0.005%, Mn: 0.35%, Cr: <0.1%, Zn: 0.25%, Ti: 0.1%, V: 0.03%, and Al as the balance. By weight, the corrosion-resistant layer comprises: 100 parts epoxy resin emulsion, 20 parts nano-titanium diboride, 4 parts aromatic amine curing agent, 2 parts carbon fiber, 25 parts deionized water, 2.5 parts potassium polyacrylate, and 0.4 parts organosilicon defoamer. The preparation method is the same as in Example 1.
[0080] Performance testing
[0081] The corrosion-resistant aluminum alloy tube samples prepared in the examples and comparative examples were subjected to performance testing. The test indicators included corrosion resistance, wear resistance, impact resistance, and adhesion. Corrosion resistance testing method: Salt spray resistance performance was tested according to standard GB / T10125, with a judgment standard of 1-10. Level 1 is almost complete corrosion; Levels 2-3 are severely discolored, with numerous corrosion spots merging into patches, severe blistering, and obvious peeling; Levels 4-5 show relatively severe discoloration, an increase in the number and diameter of corrosion spots, blistering, and slight peeling; Levels 6-7 show obvious discoloration, with a small number of small-diameter corrosion spots or slight blistering; Levels 8-9 show slight discoloration or a small number of very fine corrosion spots; Level 10 shows no visible changes. Abrasion resistance testing method: Cut a Ф20mm×3mm sample, weigh it, and use a vertical universal friction testing machine with 150-grit metallographic sandpaper as the abrasive material. Apply a load of 150N to the sample, making it contact the wear carrier. Start the testing equipment and allow the sample to be worn at a speed of 150r / min under a load of 150N for 5 minutes. After the test, calculate the weight difference before and after the wear test as the wear amount, and use the average of three wear amounts as the experimental data. Impact resistance is tested according to standard GB / T1732, and adhesion is tested according to GB / T9286. Adhesion is classified into grades 0-5, where grade 0 is no peeling, grade 1 is peeling area not exceeding 5%, grade 2 is peeling area between 5% and 15%, grade 3 is peeling area between 15% and 35%, grade 4 is peeling area between 35% and 65%, and grade 5 is peeling area greater than 65%. The test results are shown in Table 1.
[0082] Table 1 Performance Testing
[0083]
[0084] As shown in Table 1, the wear-resistant layer of the corrosion-resistant aluminum alloy pipe prepared by the technical solution of the present invention has good adhesion and good corrosion resistance, wear resistance, and impact resistance. The reasons for this are as follows: Comparative Example 1 lacks sulfone structural units, causing the coating system to lose important high-temperature resistance and impact resistance structural support, making the coating more susceptible to molecular chain breakage and degradation under corrosive media, thus reducing corrosion resistance and impact resistance; Comparative Example 2 lacks trifluoromethyl protection, preventing the coating from effectively preventing the penetration and charge transfer of corrosive ions, and also losing the chemical cross-linking effect between amino groups and epoxy resin, resulting in reduced corrosion resistance and adhesion, and decreased interfacial bonding between the coating and the substrate; Comparative Example 3's physical mixing cannot achieve uniform dispersion and chemical bonding at the molecular level, leading to a comprehensive decline in all properties, especially adhesion, which deteriorates significantly; Comparative Example 4 uses unmodified nano-titanium diboride, resulting in easy agglomeration and poor substrate compatibility, leading to low overall performance.
[0085] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A corrosion-resistant aluminum alloy pipe, characterized in that, The corrosion-resistant aluminum alloy pipe comprises an aluminum alloy pipe and a corrosion-resistant layer coated on the surface of the aluminum alloy pipe. The raw materials of the aluminum alloy pipe include: Mg: 0.1-0.3%, Si: 0.06-0.2%, Fe: 0.1-0.5%, Cu: 0.005%, Mn: 0.2-0.5%, Cr: <0.1%, Zn: 0.1-0.4%, Ti: 0.05-0.2%, V: 0.01-0.05%, and Al balance. By weight, the corrosion-resistant layer comprises: 100 parts epoxy resin emulsion, 15-25 parts composite modified titanium diboride, 3-5 parts amino curing agent, 1-3 parts carbon fiber, 20-30 parts deionized water, 2-3 parts dispersant, and 0.3-0.5 parts defoamer. The preparation methods of composite modified titanium diboride include: S1. 4-Allyloxy-4'-hydroxydiphenyl sulfone is dispersed in anhydrous toluene. Under nitrogen protection, mercaptosilane coupling agent and 2,2-dimethoxy-2-phenylacetophenone are added. The mixture is heated to 40-50℃ and reacted for 2-4 hours to obtain the modifier. S2. After acid treatment, nano-titanium diboride is dispersed in an ethanol aqueous solution, a modifier is added, the temperature is raised to 50-60℃, and the reaction is carried out for 20-24 hours to obtain modified titanium diboride. S3. Disperse the modified titanium diboride in deionized water, add sodium hydroxide solution under ice-water bath conditions, and continue stirring the reaction at room temperature for 2-3 hours to obtain the modified titanium diboride intermediate. S4. The modified titanium diboride intermediate and potassium iodide are dispersed in DMF, 4-chloro-3-trifluoromethylaniline is added, and the mixture is heated to 90-100℃ and stirred for 22-24 hours under nitrogen protection to obtain composite modified titanium diboride.
2. The corrosion-resistant aluminum alloy pipe as described in claim 1, characterized in that: In step S1, the molar ratio of 4-allyloxy-4'-hydroxydiphenyl sulfone, mercaptosilane coupling agent, and 2,2-dimethoxy-2-phenylacetophenone is 1 : (1.05-1.15) : (0.01-0.02), and the mercaptosilane coupling agent is 3-mercaptopropyltrimethoxysilane or 3-mercaptopropyltriethoxysilane.
3. The corrosion-resistant aluminum alloy pipe as described in claim 1, characterized in that: In step S2, the mass ratio of nano-titanium diboride to modifier is 100 : (20-40), and the acid used in the acid treatment process is a nitric acid or sulfuric acid solution with a mass fraction of 3-5%.
4. The corrosion-resistant aluminum alloy pipe as described in claim 1, characterized in that: In step S3, the mass ratio of modified titanium diboride to sodium hydroxide is 100 : (1.5-2.5).
5. The corrosion-resistant aluminum alloy pipe as described in claim 1, characterized in that: In step S4, the mass ratio of the modified titanium diboride intermediate, 4-chloro-3-trifluoromethylaniline and potassium iodide is 100 : (8-12) : (0.8-1.2).
6. The corrosion-resistant aluminum alloy pipe as described in claim 1, characterized in that: The amino curing agent is an aromatic amine curing agent.
7. The corrosion-resistant aluminum alloy pipe as described in claim 1, characterized in that: The dispersant is any one of sodium polycarboxylate, potassium polyacrylate, and sodium polyacrylate.
8. The corrosion-resistant aluminum alloy pipe as described in claim 1, characterized in that: The defoamer is an organosilicon defoamer.
9. A method for preparing a corrosion-resistant aluminum alloy tube as described in any one of claims 1-8, characterized in that: The preparation method includes the following steps: (1) Add deionized water, dispersant and defoamer to a reactor equipped with high-speed dispersion stirring and stir at medium speed until uniform; then slowly add composite modified titanium diboride and carbon fiber and disperse at high speed for 25-30 min; finally add epoxy resin emulsion under stirring and continue stirring for 15-25 min to obtain mixed slurry. (2) Mix the mixed slurry and amino curing agent, stir thoroughly and let stand for 5-10 minutes to defoam, then coat it on the surface of the aluminum alloy pipe that has been pretreated for degreasing and rust removal, and cure at room temperature for 70-74 hours to obtain a corrosion-resistant aluminum alloy pipe.