Corrosion-resistant aluminum alloy pipe

Abstract

The invention relates to the technical field of aluminum alloy pipes, in particular to a corrosion-resistant aluminum alloy pipe which comprises an aluminum alloy pipe and a corrosion-resistant layer coated on the surface of the aluminum alloy pipe, the aluminum alloy pipe comprises the following raw materials: 0.1-0.3% of Mg, 0.06-0.2% of Si, 0.1-0.5% of Fe, 0.005% of Cu, 0.2-0.5% of Mn, less than 0.1% of Cr, 0.1-0.4% of Zn, 0.05-0.2% of Ti, 0.01-0.05% of V and the balance of Al; the corrosion-resistant layer comprises the following components in parts by weight: 100 parts of epoxy resin emulsion, 15-25 parts of composite modified titanium diboride, 3-5 parts of an amino curing agent, 1-3 parts of carbon fibers, 20-30 parts of deionized water, 2-3 parts of a dispersing agent and 0.3-0.5 part of a defoaming agent. According to the technical scheme, the overall corrosion resistance and impact resistance of the aluminum alloy pipe are remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of aluminum alloy pipes, and particularly relates to a corrosion-resistant aluminum alloy pipe. BACKGROUND

[0002] As an important lightweight structural material, the corrosion-resistant aluminum alloy pipe is widely used in fields with extremely high requirements for corrosion resistance, such as petroleum and chemical industry, ocean engineering, aerospace, etc., and also has important applications in new energy and heating, ventilation and air conditioning industries, such as heat exchange equipment such as solar heat exchangers, flat plate collectors and air conditioner condensers. The aluminum alloy itself has good specific strength, thermal conductivity and processing performance, but is prone to electrochemical corrosion in acidic, alkaline, high-salt environments or long-term high-temperature and high-humidity conditions, especially in the complex working conditions of solar heat collection systems and air conditioning systems, the pipeline corrosion problem is more prominent, which leads to equipment failure and seriously affects the system efficiency and service life. Therefore, how to effectively improve the corrosion resistance of aluminum alloy pipes has been an important research topic in the field of material science.

[0003] In the prior art, such as CN202310451965.1, the corrosion-resistant aluminum alloy pipe mainly improves the corrosion resistance through two ways: one is to add Mg, Si, Sr, Mn and other elements, especially rare earth elements Pr, Ce and Nd, to the aluminum alloy raw material to improve the corrosion resistance of the alloy matrix; the other is to use plasma chemical vapor deposition technology to grow Si-B-N ceramic film on the surface of the aluminum alloy. However, this technical solution has obvious defects: the addition of rare earth elements not only significantly increases the cost of raw materials, but also the rare earth elements in the aluminum alloy are prone to form coarse intermetallic compounds, which may become a weak link for corrosion; the plasma chemical vapor deposition process requires high temperature and high vacuum conditions, the equipment investment is huge, the process is complex, and the bonding force between the film and the matrix is limited, which may cause the film to peel off under complex service environment, resulting in corrosion failure. SUMMARY

[0004] Therefore, the present application provides a corrosion-resistant aluminum alloy pipe to solve the technical problems of high cost, poor corrosion-resistant coating bonding force and insufficient stability in the prior art.

[0005] The technical scheme of the present application is implemented as follows: the present application provides a corrosion-resistant aluminum alloy pipe, which comprises an aluminum alloy pipe and a corrosion-resistant layer coated on the surface of the aluminum alloy pipe, and the raw material of the aluminum alloy pipe comprises: 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: the balance; and the corrosion-resistant layer comprises: 100 parts of an epoxy emulsion, 15-25 parts of a composite modified titanium diboride, 3-5 parts of an amino curing agent, 1-3 parts of carbon fibers, 20-30 parts of deionized water, 2-3 parts of a dispersing agent, and 0.3-0.5 parts of a defoaming agent.

[0006] Specifically, the magnesium element mainly exists in the form of solid solution in the aluminum alloy, and produces a significant solid solution strengthening effect by replacing Al atom positions. In a corrosion environment, the magnesium element can preferentially react with oxygen to form a composite oxide film, which has better compactness and stability. The content of magnesium element is limited to 0.1%-0.3%, and exceeding 0.3% will promote the precipitation of brittle phases such as Mg2Si, forming a corrosion channel at the grain boundary, and thus reducing the corrosion resistance.

[0007] The silicon element forms fine and dispersed silicon particles and Mg2Si intermetallic compounds in the aluminum matrix, which plays a dispersion strengthening role. The presence of silicon can refine the casting structure of the aluminum alloy and reduce the formation of coarse dendrites. More importantly, the silicon element can react with Al2O3 in the surface oxide film to form an amorphous Al2O3-SiO2 composite oxide film, which has higher chemical stability and lower diffusion coefficient, effectively preventing the penetration of corrosive ions. The content of silicon element is limited to 0.06-0.2%, and exceeding 0.2% will lead to the precipitation of primary silicon, which forms micro-batteries with the aluminum matrix and accelerates electrochemical corrosion.

[0008] The iron element forms intermetallic compound phases such as Al3Fe in the aluminum alloy, which have high melting point and high hardness characteristics. During the corrosion process, although the iron phase as a cathode phase will promote local corrosion, its high chemical stability can form a passivation protective layer on the surface. The content of iron element is limited to 0.1-0.5%, which can ensure the formation of a minimum content of sufficient pinning phase, and exceeding 0.5% will form needle-like β-Al5FeSi phase, which seriously deteriorates the corrosion resistance.

[0009] The trace copper element in the aluminum alloy mainly plays a role of grain boundary purification. Copper atoms tend to segregate at the grain boundary, stabilize the grain boundary structure by reducing the grain boundary energy, and reduce the defect concentration at the grain boundary. In a corrosive environment, trace copper can provide cathodic protection for the aluminum matrix through the "sacrificial anode" mechanism. Strictly control at 0.005% because the potential of copper is more positive than that of aluminum, and the content is too high to form a continuous cathode phase network, resulting in serious electrochemical corrosion.

[0010] The manganese element in the aluminum alloy forms Al6Mn intermetallic compounds, which have similar electrochemical properties to the aluminum matrix and do not form significant galvanic corrosion. The main role of the manganese phase is to refine the grain through the pinning effect, and at the same time the manganese element can neutralize the harmful effect of iron. In addition, manganese element can also inhibit the sensitivity of stress corrosion cracking. The manganese content is limited to 0.2-0.5%, which can effectively neutralize the iron phase to produce a refining effect and ensure that the manganese phase remains small and dispersed.

[0011] The chromium element mainly forms Al7Cr intermetallic compound phases, which have very high thermal stability and can effectively inhibit grain growth during recrystallization. Chromium phase can also act as a heterogeneous nucleation core to promote grain refinement. During corrosion, chromium element can form Cr2O3 passivation film on the surface of the alloy, which forms a composite passivation layer with Al2O3, significantly improving corrosion resistance. Limiting to 0.1% or less is because the diffusion coefficient of chromium is very low, and too high content will lead to uneven distribution of chromium phase, forming a corrosion sensitive area.

[0012] Zinc element in aluminum alloy mainly exists in solid solution form, zinc potential is more negative than aluminum, which can provide sacrificial anode protection for aluminum matrix. More importantly, zinc element can form a dense ZnO passivation film on the surface of the alloy, which has excellent self-repairing ability and can quickly re-passivate when local damage occurs. Zinc can also inhibit the pitting tendency of aluminum alloy. Zinc content is limited to 0.1-0.4%, which can provide effective anode protection and prevent excessive anode reaction from causing matrix dissolution.

[0013] Titanium element is a strong carbide and nitride forming element, which can combine with interstitial atoms (C, N, O) in the alloy to form high stability compounds, purifying the matrix composition. In a corrosive environment, titanium oxide has very high chemical stability and can stabilize the oxide film structure. Limiting titanium content to 0.05-0.2% can effectively purify the grain boundary and ensure that the titanium phase remains small and dispersed.

[0014] Vanadium element is a strong carbonitride forming element, which has a significant grain refinement effect, and refines the casting structure by providing heterogeneous nucleation sites. During corrosion, vanadium oxide has self-healing properties and can repair micro-defects in the oxide film.

[0015] The corrosion-resistant layer takes an epoxy resin emulsion as a matrix, adds composite modified titanium diboride as a functional filler, uses the excellent chemical stability and electrochemical inertness of titanium diboride, and combines the organic-inorganic hybrid structure formed after surface modification treatment to build a multiple anticorrosion barrier, wherein the addition of carbon fibers further enhances the mechanical strength and toughness of the coating, the amino curing agent ensures the sufficient cross-linking and curing of the coating, and the dispersant and defoaming agent ensure the uniformity and compactness of the coating. The entire protection system realizes a multilevel anticorrosion mechanism from the inside to the outside 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 pipe, while avoiding the use of rare earth elements and complex vapor deposition processes, and having the remarkable advantages of low cost, simple process, strong coating adhesion, and good long-term stability.

[0016] On the basis of the above technical scheme, preferably, the preparation method of the composite modified titanium diboride comprises:

[0017] S1, disperse 4-allyloxy-4'-hydroxy diphenyl sulfone in anhydrous toluene, add mercapto silane coupling agent and 2, 2-dimethoxy-2-phenyl phenylacetone under nitrogen protection, heat to 40-50 DEG C, and react for 2-4 h to obtain a modifier;

[0018] S2, disperse the acid-treated nano titanium diboride in an ethanol aqueous solution, add the modifier, heat to 50-60 DEG C, and react for 20-24 h to obtain modified titanium diboride;

[0019] S3, disperse the modified titanium diboride in deionized water, add sodium hydroxide solution under ice water bath condition, continue to stir at room temperature for 2-3 h to obtain a modified titanium diboride intermediate;

[0020] S4, disperse the modified titanium diboride intermediate and potassium iodide in DMF, add 4-chloro-3-trifluoromethyl aniline, heat to 90-100 DEG C under nitrogen protection, and stir for 22-24 h to obtain composite modified titanium diboride.

[0021] Specifically, titanium diboride as a functional filler has excellent chemical stability, high hardness and good electrical conductivity, and can play a dual role of wear resistance and providing electrochemical protection in the coating, but there are problems such as high surface energy, easy agglomeration, and poor compatibility with organic matrix when directly mixed with epoxy resin. In order to solve the above problems, in step S1, a composite modifier is prepared by thiol-olefin reaction between the double bond on 4-allyloxy-4'-hydroxy diphenyl sulfone and the mercapto silane coupling agent; in step S2, the surface of nano titanium diboride is treated with acid to generate a large number of hydroxyl active sites, and the silane coupling agent in the modifier is condensed to anchor the organic molecule containing the high-temperature-resistant sulfone group structure on the surface of titanium diboride, and the inorganic-organic hybrid modification is initially realized; in step S3, the phenolic hydroxyl group on the modifier is converted into phenolic sodium salt with strong nucleophilic attack ability by adding sodium hydroxide solution; in step S4, the activated phenolic sodium salt reacts with 4-chloro-3-trifluoromethyl aniline to form a stable ether bond to introduce a trifluoromethyl group with corrosion protection function.

[0022] The 4-allyloxy-4'-hydroxy diphenyl sulfone molecule introduced by the mercapto silane coupling agent as a bridge in the composite modified titanium diboride contains benzene ring, sulfone group, ether bond and other structures, which are dispersed in the epoxy resin after being chemically bonded to the surface of titanium diboride. The above structures can effectively improve the impact resistance and thermal stability of the epoxy resin; further, the 4-chloro-3-trifluoromethyl aniline molecule introduced by the hydroxyl group on the modifier, the trifluoromethyl group has strong electronegativity and hydrophobicity, which can significantly improve the chemical corrosion resistance of the coating, and the amino group remaining on the aniline not only can react with the epoxy resin to form a crosslinked network structure to solve the problem of poor compatibility of titanium diboride with the organic matrix; but also can be used as a corrosion inhibitor to passivate the active sites on the metal surface through coordination, and the finally formed composite modified titanium diboride not only has excellent dispersibility, good compatibility with the matrix and multiple corrosion protection mechanisms, but more importantly, the impact resistance of the coating system is significantly improved by the introduction of the sulfone group segment.

[0023] On the basis of the above technical scheme, preferably, in step S1, the molar ratio of 4-allyloxy-4'-hydroxy diphenyl sulfone, mercapto silane coupling agent and 2,2-dimethoxy-2-phenyl phenylacetone is 1:(1.05-1.15):(0.01-0.02), and the mercapto silane coupling agent is 3-mercaptopropyl trimethoxysilane or 3-mercaptopropyl triethoxysilane.

[0024] On the basis of the above technical scheme, preferably, in step S2, the mass ratio of nano titanium diboride and 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] Preferably, in step S3, the mass ratio of the modified titanium diboride and sodium hydroxide is 100:(1.5-2.5).

[0026] Preferably, in step S4, the mass ratio of the modified titanium diboride intermediate, 4-chloro-3-trifluoromethyl aniline, and potassium iodide is 100:(8-12):(0.8-1.2).

[0027] Preferably, the amino curing agent is an aromatic amine curing agent.

[0028] Preferably, the dispersant is any one of a polycarboxylic acid sodium salt, a polyacrylic acid potassium, and a polyacrylic acid sodium.

[0029] Preferably, the defoaming agent is an organic silicon defoaming agent.

[0030] The application provides a preparation method of a corrosion-resistant aluminum alloy pipe.

[0031] (1) Deionized water, a dispersant, and a defoaming agent are added to a reaction kettle with high-speed dispersion stirring, and then uniformly stirred at a medium speed; then, a composite modified titanium diboride and carbon fibers are slowly added, and high-speed dispersion is performed for 25-30 min; finally, an epoxy resin emulsion is added under stirring, and stirring is continuously performed for 15-25 min to obtain a mixed slurry;

[0032] (2) The mixed slurry and an amino curing agent are mixed, uniformly stirred, and then left to stand for 5-10 min for defoaming; then, the mixed slurry is coated on the surface of an aluminum alloy pipe that has been pretreated by removing oil and rust, and cured at room temperature for 70-74 h to obtain a corrosion-resistant aluminum alloy pipe.

[0033] The corrosion-resistant aluminum alloy pipe of the application has the following beneficial effects relative to the prior art:

[0034] (1) By optimizing the component ratio of the aluminum alloy matrix and the synergistic design of the functional surface coating, a multi-level corrosion prevention system is constructed, and a dense self-passivation layer formed by the corrosion-resistant elements in the aluminum alloy matrix and the surface functional coating are synergistically combined through physical shielding, chemical passivation, and electrochemical protection to realize gradient protection from the inside to the outside; even if the coating is partially damaged, the self-passivation layer of the matrix can still provide effective secondary protection, which significantly improves the overall corrosion resistance and impact resistance of the aluminum alloy pipe, and is particularly suitable for complex working conditions such as solar heat exchangers, flat plate collectors, and air conditioners.

[0035] (2) The application precisely controls the content ratio of Zn, Mn, Mg, Ti and other elements in the aluminum alloy substrate, the zinc element improves the self-passivation ability of the alloy by forming a dense ZnO film, the manganese element refines the grains and forms stable Al6Mn intermetallic compounds to prevent the diffusion of corrosive media, the magnesium element improves the corrosion resistance of the substrate through the solid solution strengthening mechanism, the titanium element purifies the grain boundary and inhibits intergranular corrosion as a strong carbide forming element, and the synergistic effect of the four elements forms a dense and stable composite oxide film on the surface of the substrate, providing ideal interface conditions for the combination of the surface coating, effectively solving the technical problem that the traditional aluminum alloy pipe is prone to electrochemical corrosion in acidic, alkaline or high-salt environments, and significantly improving the intrinsic corrosion resistance of the substrate material.

[0036] (3) The composite modified titanium diboride is prepared by a multi-step surface modification technology, the sulfonyl structure and the trifluoromethyl structure are grafted on the surface of the titanium diboride in turn through the thiol-olefin click chemistry reaction and the Williamson ether synthesis reaction, the key technical problems of easy agglomeration of nano titanium diboride and poor compatibility with organic matrix are solved, the modified titanium diboride is chemically crosslinked with the epoxy resin through the surface amino group to form a stable organic-inorganic hybrid network structure, the sulfonyl segment significantly improves the impact resistance of the resin, the trifluoromethyl group greatly improves the chemical corrosion resistance of the coating through strong electronegativity and hydrophobicity, the amino group participates in the curing reaction and also plays a corrosion inhibition role, realizing the multi-functional synergistic effect, and significantly improving the comprehensive protection performance of the coating. DETAILED DESCRIPTION

[0037] The technical solutions in the embodiments of the application will be clearly and completely described below in combination with the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0038] It should be noted that the epoxy resin is purchased from Shandong Yi Xin New Material Co., Ltd., and the model number is NPEL-128; the aromatic amine curing agent is m-xylylenediamine, the CAS number is 1477-55-0, and it is purchased from Hubei Xijiecheng Chemical Technology Co., Ltd.; the silicone defoamer is purchased from Shandong Jiayi Chemical Technology Co., Ltd., and the model number is 01; the titanium diboride is purchased from Qinghe County Chaotai Metal Material Co., Ltd., and the particle size is 50 nm.

[0039] Example 1

[0040] The embodiment provides a kind of corrosion-resistant aluminum alloy pipe, corrosion-resistant aluminum alloy pipe includes aluminum alloy pipe and corrosion-resistant layer coated on the surface of aluminum alloy pipe, the raw material of aluminum alloy pipe includes: 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%, Al remainder;Corrosion-resistant layer includes: epoxy resin emulsion 100 parts, composite modified titanium diboride 20 parts, aromatic amine curing agent 4 parts, carbon fiber 2 parts, deionized water 25 parts, potassium polyacrylate 2.5 parts, silicone antifoam 0.4 parts by weight fraction.The preparation method is as follows:

[0041] (1) deionized water, potassium polyacrylate and silicone antifoam are added to the reaction kettle with high-speed dispersion stirring, and stirred evenly at medium speed;Then slowly add composite modified titanium diboride and carbon fiber, high-speed dispersion 25-30min;Finally, under the condition of stirring, add epoxy resin emulsion, continue to stir for 20min, to obtain mixed slurry;

[0042] (2) mix the mixed slurry and aromatic amine curing agent, stir evenly, then stand for 8min to defoam, then coat it on the surface of the aluminum alloy pipe pretreated by removing oil and rust, the coating thickness is controlled at 80-120μm, and the corrosion-resistant aluminum alloy pipe is obtained by curing at room temperature for 72h under the relative humidity of 60-70%.

[0043] The preparation method of the composite modified titanium diboride includes:

[0044] S1, 290g 4-allyloxy-4'-hydroxy diphenyl sulfone (1mol) is dispersed in 500ml anhydrous toluene, 216g 3-mercaptopropyl trimethoxysilane (1.1mol) and 3.84g 2,2-dimethoxy-2-phenyl phenylacetone (0.015mol) are added under nitrogen protection, the temperature is raised to 45℃, and the reaction is carried out for 3h, after the reaction is completed, toluene is removed by vacuum distillation, purified by recrystallization with petroleum ether, and vacuum dried to obtain a modifier;

[0045] S2, 100g nano titanium diboride is dispersed in 200ml 4% nitric acid solution, ultrasonic treatment is carried out for 2h, then washed with deionized water until neutral, and vacuum dried to obtain acid-treated titanium diboride. The acid-treated titanium diboride is dispersed in 300ml ethanol aqueous solution (volume ratio 1:1), 30g modifier is added, the temperature is raised to 55℃, and the reaction is carried out for 22h, after the reaction is completed, centrifugal separation is carried out, washed with ethanol and deionized water in sequence, and vacuum dried to obtain modified titanium diboride;

[0046] S3, dispersing 100 g of modified titanium diboride in 500 ml of deionized water, slowly adding 50 mL of sodium hydroxide solution (prepared from 2.0 g of sodium hydroxide and water) under ice water bath conditions, warming to room temperature, continuing to stir the reaction for 2.5 h, after the reaction is complete, centrifugal separation, washing with deionized water until neutral, obtaining a modified titanium diboride intermediate;

[0047] S4, dispersing 100 g of modified titanium diboride intermediate and 1 g of potassium iodide in 400 ml of DMF, adding 10 g of 4-chloro-3-trifluoromethyl aniline, warming to 95°C under nitrogen protection, stirring for 23 h, after the reaction is complete, cooling to room temperature, centrifugal separation, sequentially washing with DMF, ethanol and deionized water, vacuum drying to obtain a composite modified titanium diboride.

[0048] Example 2

[0049] The embodiment provides a corrosion-resistant aluminum alloy pipe, the corrosion-resistant aluminum alloy pipe comprising an aluminum alloy pipe and a corrosion-resistant layer coated on the surface of the aluminum alloy pipe, and the raw material of the aluminum alloy pipe comprising: 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: the balance; and the corrosion-resistant layer comprising, by weight fraction, 100 parts of an epoxy resin emulsion, 15 parts of composite modified titanium diboride, 3 parts of an aromatic amine curing agent, 1 part of carbon fiber, 20 parts of deionized water, 2 parts of potassium polyacrylate, and 0.3 parts of an organic silicon defoaming agent. The preparation method is as follows:

[0050] (1) adding deionized water, potassium polyacrylate and an organic silicon defoaming agent into a reaction kettle with high-speed dispersion stirring, uniformly stirring at medium speed; then slowly adding composite modified titanium diboride and carbon fiber, high-speed dispersion for 25 min; finally adding an epoxy resin emulsion under stirring, continuing to stir for 15 min, to obtain a mixed slurry;

[0051] (2) mixing the mixed slurry and the aromatic amine curing agent, uniformly stirring, standing for 5 min for defoaming, then coating the mixed slurry on the surface of an aluminum alloy pipe pretreated by removing oil and rust, controlling the coating thickness to be 80-120 μm, curing at room temperature and relative humidity of 60-70% for 70 h, to obtain a corrosion-resistant aluminum alloy pipe.

[0052] The preparation method of the composite modified titanium diboride comprises:

[0053] S1, 290 g of 4-allyloxy-4'-hydroxy diphenyl sulfone (1 mol) was dispersed in 500 ml of anhydrous toluene, 206 g of 3-mercaptopropyl trimethoxysilane (1.05 mol) and 2.56 g of 2,2-dimethoxy-2-phenylacetophenone (0.01 mol) were added under nitrogen protection, the temperature was raised to 40°C, and the reaction was carried out for 4 h. After the reaction was completed, the toluene was removed by distillation under reduced pressure, and the product was purified by recrystallization with petroleum ether and dried under vacuum to obtain the modifier;

[0054] S2, 100 g of nano titanium diboride was dispersed in 200 ml of 3% nitric acid solution, ultrasonic treatment was carried out for 2 h, then washed with deionized water until neutral, and vacuum dried to obtain acid-treated titanium diboride. The acid-treated titanium diboride was dispersed in 300 ml of ethanol aqueous solution (volume ratio 1:1), 20 g of the modifier was added, the temperature was raised to 50°C, and the reaction was carried out for 24 h. After the reaction was completed, centrifugal separation was carried out, and the product was washed with ethanol and deionized water in sequence, and vacuum dried to obtain modified titanium diboride;

[0055] S3, 100 g of modified titanium diboride was dispersed in 500 ml of deionized water, 50 mL of sodium hydroxide solution (prepared from 1.5 g of sodium hydroxide and water) was slowly added under ice water bath condition, the temperature was raised to room temperature, and the reaction was continuously stirred for 2 h. After the reaction was completed, centrifugal separation was carried out, and the product was washed with deionized water until neutral to obtain modified titanium diboride intermediate;

[0056] S4, 100 g of modified titanium diboride intermediate and 0.8 g of potassium iodide were dispersed in 400 ml of DMF, 8 g of 4-chloro-3-trifluoromethyl aniline was added, the temperature was raised to 90°C under nitrogen protection, and the reaction was stirred for 24 h. After the reaction was completed, the temperature was cooled to room temperature, centrifugal separation was carried out, and the product was washed with DMF, ethanol and deionized water in sequence, and vacuum dried to obtain composite modified titanium diboride.

[0057] Example 3

[0058] The present embodiment provides a kind of corrosion-resistant aluminum alloy pipe, corrosion-resistant aluminum alloy pipe includes aluminum alloy pipe and the corrosion-resistant layer coated on the surface of aluminum alloy pipe, the raw material of aluminum alloy pipe includes: 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%, Al balance;Corrosion-resistant layer includes by weight fraction: epoxy resin emulsion 100 parts, composite modified titanium diboride 25 parts, aromatic amine curing agent 5 parts, carbon fiber 3 parts, deionized water 30 parts, potassium polyacrylate 3 parts, silicone antifoaming agent 0.5 parts.The preparation method is as follows:

[0059] (1) Deionized water, potassium polyacrylate and silicone antifoaming agent were added into a reaction kettle with high-speed dispersion stirring, and stirred uniformly at medium speed; then composite modified titanium diboride and carbon fiber were slowly added, and dispersed at high speed for 30 min; finally, the epoxy resin emulsion was added under stirring, and stirred for 25 min to obtain a mixed slurry;

[0060] (2) The mixed slurry and aromatic amine curing agent were mixed, stirred uniformly, and then stood for 10 min to remove bubbles; then it was coated on the surface of an aluminum alloy pipe pretreated by removing oil and rust, and the coating thickness was controlled at 80-120 μm; the coating was cured at room temperature and relative humidity of 60-70% for 74 h to obtain a corrosion-resistant aluminum alloy pipe.

[0061] The preparation method of the composite modified titanium diboride comprises:

[0062] S1, 290g of 4-allyloxy-4'-hydroxy diphenyl sulfone (1mol) was dispersed in 500ml of anhydrous toluene, 225.8g of 3-mercaptopropyl trimethoxysilane (1.15mol) and 5.13g of 2,2-dimethoxy-2-phenyl phenylacetone (0.02mol) were added under nitrogen protection, and the temperature was raised to 50°C, and the reaction was carried out for 2h; after the reaction was completed, the toluene was removed by distillation under reduced pressure, and the modified agent was purified by recrystallization with petroleum ether and vacuum drying.

[0063] S2, 100g of nano-titanium diboride was dispersed in 200ml of 5% nitric acid solution, and ultrasonic treatment was carried out for 2h; then it was 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 aqueous solution (volume ratio 1:1), 40g of the modified agent was added, the temperature was raised to 60°C, and the reaction was carried out for 20h; after the reaction was completed, centrifugal separation was carried out, and the product was washed with ethanol and deionized water in sequence, and vacuum dried to obtain modified titanium diboride.

[0064] S3, 100g of modified titanium diboride was dispersed in 500ml of deionized water, 50ml of sodium hydroxide solution (prepared by dissolving 2.5g of sodium hydroxide in water) was slowly added under ice water bath condition, the temperature was raised to room temperature, and the reaction was continued to stir for 3h; after the reaction was completed, centrifugal separation was carried out, and the product was washed with deionized water until neutral to obtain a modified titanium diboride intermediate.

[0065] S4, 100g of the modified titanium diboride intermediate and 1.2g of potassium iodide were dispersed in 400ml of DMF, 12g of 4-chloro-3-trifluoromethyl aniline was added, the temperature was raised to 100°C under nitrogen protection, and the reaction was carried out for 22h; after the reaction was completed, the temperature was cooled to room temperature, centrifugal separation was carried out, and the product was washed with DMF, ethanol and deionized water in sequence, and vacuum dried to obtain composite modified titanium diboride.

[0066] Comparative Example 1

[0067] The comparative example 1 provides a kind of corrosion-resistant aluminum alloy pipe, corrosion-resistant aluminum alloy pipe includes aluminum alloy pipe and corrosion-resistant layer coated on the surface of aluminum alloy pipe, the raw material of aluminum alloy pipe includes: 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%, Al remainder;With weight fraction, corrosion-resistant layer includes: epoxy resin emulsion 100 parts, composite modified titanium diboride 20 parts, aromatic amine curing agent 4 parts, carbon fiber 2 parts, deionized water 25 parts, potassium polyacrylate 2.5 parts, silicone antifoam 0.4 parts.Preparation method is same with example 1, the difference is that composite modified titanium diboride is not grafted 4-allyloxy-4'-hydroxy diphenyl sulfone, as follows:

[0068] S1, 100g nano titanium diboride is dispersed in 200ml 4% mass fraction nitric acid solution, ultrasonic treatment 2h, then washed to neutral with deionized water, vacuum drying to obtain acid treated titanium diboride.The acid treated titanium diboride is dispersed in 300ml ethanol aqueous solution (volume ratio 1:1), 30g 3-mercaptopropyl trimethoxysilane is added, and the temperature is raised to 55℃, and the reaction is carried out for 22h.After reaction, centrifugal separation is carried out, and ethanol and deionized water are sequentially washed, and vacuum drying is carried out to obtain modified titanium diboride;

[0069] S2, 100g modified titanium diboride is dispersed in 500ml deionized water, 50mL sodium hydroxide solution (prepared by 2.0g sodium hydroxide and water) is slowly added under ice water bath condition, the temperature is raised to room temperature, and the stirring reaction is continued for 2.5h, after reaction, centrifugal separation is carried out, and deionized water is washed to neutral to obtain modified titanium diboride intermediate;

[0070] S3, 100g modified titanium diboride intermediate is dispersed in 400ml DMF, 10g 4-chloro-3-trifluoromethyl aniline is added, under nitrogen protection, the temperature is raised to 95℃, stirring reaction is carried out for 23h, after reaction, the temperature is cooled to room temperature, centrifugal separation is carried out, and DMF, ethanol and deionized water are sequentially washed, and vacuum drying is carried out to obtain composite modified titanium diboride.

[0071] Comparative example 2

[0072] The comparative example 1 provides a kind of corrosion-resistant aluminum alloy pipe, corrosion-resistant aluminum alloy pipe includes aluminum alloy pipe and the corrosion-resistant layer coated on the surface of aluminum alloy pipe, the raw material of aluminum alloy pipe includes: 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%, Al balance;By weight parts, corrosion-resistant layer includes: epoxy resin emulsion 100 parts, composite modified titanium diboride 20 parts, aromatic amine curing agent 4 parts, carbon fiber 2 parts, deionized water 25 parts, potassium polyacrylate 2.5 parts, silicone defoamer 0.4 parts.The preparation method is same with example 1, the difference is that composite modified titanium diboride is not grafted 4-chloro-3-trifluoromethylaniline, as follows:

[0073] S1, 290g 4-allyloxy-4'-hydroxy diphenyl sulfone (1mol) is dispersed in 500ml anhydrous toluene, 216g 3-mercaptopropyl trimethoxysilane (1.1mol) and 3.84g 2,2-dimethoxy-2-phenyl phenylacetone (0.015mol) are added under nitrogen protection, the temperature is raised to 45 DEG C, and the reaction is carried out for 3h. After the reaction is completed, toluene is removed by distillation under reduced pressure, purified by recrystallization with petroleum ether, and vacuum dried to obtain a modifier.

[0074] S2, 100g nano titanium diboride is dispersed in 200ml 4% mass fraction nitric acid solution, ultrasonic treatment is carried out for 2h, then washed with deionized water until neutral, and vacuum dried to obtain acid-treated titanium diboride. The acid-treated titanium diboride is dispersed in 300ml ethanol aqueous solution (volume ratio 1:1), 30g modifier is added, the temperature is raised to 55 DEG C, and the reaction is carried out for 22h. After the reaction is completed, centrifugal separation is carried out, washed with ethanol and deionized water in sequence, and vacuum dried to obtain modified titanium diboride, which is composite modified titanium diboride.

[0075] Comparative example 3

[0076] The comparative example 1 provides a kind of corrosion-resistant aluminum alloy pipe, corrosion-resistant aluminum alloy pipe includes aluminum alloy pipe and the corrosion-resistant layer coated on the surface of aluminum alloy pipe, the raw material of aluminum alloy pipe includes: 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%, Al balance;By weight parts, corrosion-resistant layer includes: epoxy resin emulsion 100 parts, composite modified titanium diboride 20 parts, aromatic amine curing agent 4 parts, carbon fiber 2 parts, deionized water 25 parts, potassium polyacrylate 2.5 parts, silicone defoamer 0.4 parts.The preparation method is same with example 1, the difference is that composite modified titanium diboride is not grafted 4-chloro-3-trifluoromethylaniline, as follows:

[0077] 100 g of nanometer titanium diboride, 30 g of 4-allyloxy-4'-hydroxy diphenyl sulfone and 10 g of 4-chloro-3-trifluoromethyl aniline were physically mixed in a planetary ball mill, the ball milling speed was 300 r / min, the ball milling time was 2 h, the ball-to-material ratio was 10:1, to obtain the physically mixed composite modified titanium diboride. To improve the mixing uniformity, the ball mill was stopped for 10 min every 30 min to prevent overheating. After ball milling, the product was sieved through a 200-mesh screen and vacuum dried at 60°C for 4 h to obtain the composite modified titanium diboride.

[0078] Comparative Example 4

[0079] The present comparative example provides a corrosion-resistant aluminum alloy pipe, which comprises an aluminum alloy pipe and a corrosion-resistant layer coated on the surface of the aluminum alloy pipe. The raw material of the aluminum alloy pipe comprises: 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%, Al: balance; the corrosion-resistant layer comprises, by weight fraction: 100 parts of epoxy emulsion, 20 parts of nanometer titanium diboride, 4 parts of aromatic amine curing agent, 2 parts of carbon fiber, 25 parts of deionized water, 2.5 parts of potassium polyacrylate, and 0.4 parts of silicone defoamer. The preparation method is the same as that of Example 1.

[0080] Performance detection

[0081] The sample of the corrosion-resistant aluminum alloy pipe prepared by the examples and the comparative examples is subjected to performance detection, and the detection indexes include corrosion resistance, wear resistance, impact resistance and adhesion. The corrosion resistance detection method is: the salt spray resistance is detected according to the standard GB / T10125, and the judgment standard is 1-10 levels, wherein 1 level is almost completely corroded, 2-3 levels are severely discolored, a large number of corrosion points are connected into a piece, and the bubbling is serious and obvious peeling; 4-5 levels have relatively serious discoloration, the corrosion points increase and the diameter becomes larger, the bubbling and slight peeling; 6-7 levels have obvious discoloration, a small amount of corrosion points with small diameter or slight bubbling phenomenon appear; 8-9 levels have slight discoloration or a small amount of very small corrosion points; 10 level has no any visible change. The wear resistance detection method is: a sample with a diameter of 20 mm and a thickness of 3 mm is cut, the mass is weighed, a vertical universal friction tester is used, 150# metallographic sandpaper is used as abrasive material, 150N load is applied on the sample, the sample is contacted with the wear carrier, the test equipment is started, the sample is worn at a speed of 150r / min under the load of 150N, after 5min, the weight difference before and after the wear test is calculated as the wear amount, and the average value of three wear amounts is taken as the experimental data. The impact resistance is detected according to the standard GB / T1732, the adhesion is detected according to GB / T9286, and the adhesion atmosphere is 0-5 levels, wherein 0 level is without any peeling, 1 level is with a peeling area of not more than 5%, 2 level is with a peeling area of 5%-15%, 3 level is with a peeling area of 15-35%, 4 level is with a peeling area of 35%-65%, and 5 level is with a peeling area of more than 65%. The detection results are shown in Table 1.

[0082] Table 1 Performance detection

[0083]

[0084] As shown in Table 1, the wear-resistant layer of the corrosion-resistant aluminum alloy pipe prepared by the technical scheme of the examples has good adhesion, and has good corrosion resistance, wear resistance and impact resistance. The reason is analyzed as follows: in the comparative example 1, the sulfonyl structure unit is lacked, the coating system loses important high-temperature resistance and impact resistance structure support, which promotes the coating to be more easily broken and degraded under the action of the corrosion medium, and thus the corrosion resistance and the impact resistance are reduced; in the comparative example 2, the lack of trifluoromethyl protection makes the coating unable to effectively prevent the penetration of corrosive ions and the charge transfer process, and the chemical crosslinking effect of the amino group and the epoxy resin is also lost, resulting in reduced corrosion resistance and adhesion, and reduced interfacial bonding force of the coating and the substrate; in the comparative example 3, the physical mixing cannot realize uniform dispersion and chemical bonding at the molecular level, resulting in overall performance decline, especially the adhesion, which is significantly deteriorated; in the comparative example 4, the nano titanium diboride is not modified, resulting in factors such as easy agglomeration and poor matrix compatibility, and thus the performance is low.

[0085] The above merely provides the preferred embodiment of the present application, and is not used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A corrosion resistant aluminum alloy pipe characterized by, 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, and the raw material of the aluminum alloy pipe comprises: 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: the balance; and the corrosion-resistant layer comprises, by weight fraction: 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 defoaming agent.

2. A corrosion resistant aluminum alloy pipe as claimed in claim 1, wherein: The preparation method of the composite modified titanium diboride comprises the following steps: S1, dispersing 4-allyloxy-4'-hydroxy diphenyl sulfone in anhydrous toluene, adding mercapto silane coupling agent and 2,2-dimethoxy-2-phenyl phenylacetone under nitrogen protection, warming to 40-50 DEG C, and reacting for 2-4 h to obtain a modifier; S2, dispersing nano titanium diboride in ethanol aqueous solution after acid treatment, adding the modifier, warming to 50-60 DEG C, and reacting for 20-24 h to obtain modified titanium diboride; S3, dispersing the modified titanium diboride in deionized water, adding sodium hydroxide solution under ice water bath condition, and continuously stirring and reacting for 2-3 h at room temperature to obtain a modified titanium diboride intermediate; S4, dispersing the modified titanium diboride intermediate and potassium iodide in DMF, adding 4-chloro-3-trifluoromethyl aniline, warming to 90-100 DEG C under nitrogen protection, and stirring and reacting for 22-24 h to obtain the composite modified titanium diboride.

3. A corrosion resistant aluminum alloy pipe as claimed in claim 2, wherein: In step S1, the molar ratio of 4-allyloxy-4'-hydroxy diphenyl sulfone, mercapto silane coupling agent and 2,2-dimethoxy-2-phenyl phenylacetone is 1:(1.05-1.15):(0.01-0.02), and the mercapto silane coupling agent is 3-mercaptopropyl trimethoxysilane or 3-mercaptopropyl triethoxysilane.

4. A corrosion resistant aluminum alloy pipe as claimed in claim 2, wherein: In step S2, the mass ratio of nano titanium diboride and the modifier is 100:(20-40), and the acid used in the acid treatment process is a 3-5% mass fraction nitric acid or sulfuric acid solution.

5. A corrosion resistant aluminum alloy pipe as claimed in claim 2, wherein: In step S3, the mass ratio of the modified titanium diboride and sodium hydroxide is 100:(1.5-2.5).

6. A corrosion resistant aluminum alloy pipe as claimed in claim 2, wherein: In step S4, the mass ratio of the modified titanium diboride intermediate, 4-chloro-3-trifluoromethyl aniline and potassium iodide is 100:(8-12):(0.8-1.2).

7. A corrosion resistant aluminum alloy pipe as claimed in claim 1 wherein: The amino curing agent is an aromatic amine curing agent.

8. A corrosion resistant aluminum alloy pipe as claimed in claim 1 wherein: The dispersant is any one of polycarboxylic acid sodium salt, potassium polyacrylate and sodium polyacrylate.

9. A corrosion resistant aluminum alloy pipe as claimed in claim 1 wherein: The defoaming agent is an organic silicon defoaming agent.

10. A method of producing a corrosion resistant aluminium alloy pipe according to any one of claims 1 to 9, characterized in that: The preparation method comprises the following steps: (1) adding deionized water, dispersant and defoaming agent into a reaction kettle with high-speed dispersion stirring, uniformly stirring at medium speed, then slowly adding the composite modified titanium diboride and carbon fiber, high-speed dispersing for 25-30 min, finally adding the epoxy resin emulsion under stirring, continuously stirring for 15-25 min to obtain a mixed slurry; (2) the mixed slurry and amino curing agent are mixed, stirred uniformly, and then left to stand for 5-10 min to remove bubbles, and then coated on the surface of the aluminum alloy pipe which has been pretreated by removing oil and rust, and cured at room temperature for 70-74 h to obtain the corrosion-resistant aluminum alloy pipe.

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