Aluminum alloy surface and its treatment method

Abstract

The present invention discloses an aluminum alloy surface and its treatment method, which relates to the technical field of aluminum alloy surface treatment. The surface of the aluminum alloy is cleaned, chemically pretreated, then subjected to pulsed anodic oxidation, and then subjected to a sealing treatment. By mass percentage, the electrolyte composition used for anodic oxidation includes: 10-30% sulfuric acid, 0.5-1% tea polyphenols, 0.1-0.3% cerium nitrate, and 0.2-0.5% nano-aluminum oxide. By mass percentage, the sealing liquid composition used for sealing includes: 0.5-1% chitosan particles, 0.2-0.5% nano-zinc oxide, and 0.1-0.3% cerium complex. Among them, the cerium complex is cerium oxalate or cerium acetylacetonate hydrate. The aluminum alloy surface treatment method of the present invention enables the surface of the aluminum alloy substrate to contain a pulsed oxide layer and a sealing film layer, and the formed aluminum alloy surface has good mechanical properties, insulation properties, and anti-aging properties.

Description

Technical Field

[0001] The present invention belongs to the technical field of aluminum alloy surface treatment, specifically the surface of aluminum alloy and its treatment method. Background Art

[0002] Due to its lightweight, high strength, corrosion resistance and other characteristics, aluminum alloy is widely used in the fields of aerospace, automotive manufacturing, electronic equipment and architectural decoration. However, the surface of untreated aluminum alloy is susceptible to oxidation, wear and corrosion, which limits its performance. Traditional aluminum alloy surface treatment technologies mainly include anodic oxidation, electroplating, spraying, chemical conversion film, etc. Among them, anodic oxidation generates a porous oxide film on the surface of aluminum alloy through an electrochemical reaction, and then forms a stable protective layer through a sealing treatment. The chemical conversion film technology forms a protective film on the surface of aluminum alloy through a chemical reaction, improving its corrosion resistance and coating adhesion, and contributing to the subsequent chemical treatment process of the aluminum alloy surface.

[0003] In recent years, with the development of nanotechnology, nanomaterials have been introduced into the surface treatment of aluminum alloy to further improve its performance. The prior art CN114836805A discloses a method for treating the surface of aluminum alloy, including pretreatment of the substrate surface, preparation of a micro-arc oxidation electrolyte, micro-arc oxidation treatment and sealing. Among them, the micro-arc oxidation electrolyte uses a nanomaterial - nano-graphene. CN105970268A discloses a method for treating the surface of aluminum alloy by anodic oxidation - sealing. The sealing material of this invention contains nano-silica and adopts two sealing treatments. The present invention discloses a nano-aluminum alloy surface treatment process, which can not only effectively improve the corrosion resistance and wear resistance of the aluminum alloy surface, but also enhance the adhesion of the coating, while reducing the impact on the environment in the traditional process. The realization of this technology is expected to bring more efficient and environmentally friendly solutions to the field of aluminum alloy surface treatment. Summary of the Invention

[0004] In order to overcome the above technical problems, the present invention provides the surface of aluminum alloy and its treatment method. The aluminum alloy surface treatment method of the present invention makes the surface of the aluminum alloy substrate contain a pulsed oxide layer and a sealing film layer, and the formed aluminum alloy surface has good mechanical properties, insulation properties and anti-aging properties.

[0005] The present invention solves the above technical problems through the following technical solutions.

[0006] The present invention discloses a method for treating the surface of aluminum alloy, including the following steps:

[0007] Clean and chemically pretreat the surface of the aluminum alloy, then perform pulsed anodic oxidation, and then carry out a sealing treatment;

[0008] By mass percentage, the electrolyte composition used for anodic oxidation includes: 10-30% sulfuric acid, 0.5-1% tea polyphenols, 0.1-0.3% cerium nitrate, and 0.2-0.5% nano-aluminum oxide;

[0009] By mass percentage, the sealing liquid composition used for sealing includes: 0.5-1% chitosan particles, 0.2-0.5% nano-zinc oxide, and 0.1-0.3% cerium complex;

[0010] Among them, the cerium complex is cerium oxalate (15750-47-7) or cerium acetylacetonate hydrate (CAS No.: 206996-61-4).

[0011] Preferably, by mass percentage, the electrolyte composition used for anodic oxidation includes: 10-20% sulfuric acid, 0.5-1% tea polyphenols, 0.1-0.3% cerium nitrate, and 0.2-0.5% nano-aluminum oxide.

[0012] Sulfuric acid in the electrolyte serves as the basis of the electrolyte, providing hydrogen ions and sulfate ions to form an acidic environment, promoting the occurrence of anodic oxidation reactions, and helping to generate a porous Al2O3 oxide layer on the surface of aluminum alloy. The phenolic hydroxyl groups of tea polyphenols can adsorb on the surface of aluminum alloy, and this adsorption can inhibit local corrosion and excessive dissolution, especially in high current density areas, to avoid non-uniform growth of the oxide film. In addition, the antioxidant property of tea polyphenols can reduce the occurrence of side reactions in the electrolyte and improve the stability of the electrolyte. Cerium (III) ions in cerium nitrate will be embedded in the alumina lattice during anodic oxidation to form a rare earth-doped oxide layer. This doping can refine the grain structure of alumina, improve the hardness and density of the oxide layer. At the same time, the embedding of cerium (III) ions can improve the corrosion resistance and self-healing ability of the oxide layer. The adsorption of tea polyphenols helps the uniform distribution of cerium (III) ions on the surface of aluminum alloy, thereby enhancing the effect of rare earth doping. Nano-aluminum oxide particles are dispersed in the electrolyte and are embedded in the pores of the oxide layer during anodic oxidation. These nano-particles can fill the micropores in the oxide film, reduce the pore diameter, and thus improve the density and wear resistance of the oxide layer.

[0013] Preferably, the sealing liquid composition used for sealing includes: 0.5-1% chitosan particles, 0.2-0.5% nano-zinc oxide, and 0.1-0.3% cerium complex.

[0014] The nano-zinc oxide in the sealing solution has antibacterial and anti-ultraviolet properties. It can also fill the micropores of the pulsed anodic oxidation film, improve the surface density and hardness, and enhance the wear resistance of the sealing film layer. The amino and hydroxyl groups in the chitosan molecule have strong adsorption ability. As a film-forming matrix, it can disperse nano-zinc oxide, prevent the aggregation of nano-sized particles, and to a certain extent, improve the density of the sealing film layer through the filling effect with nano-zinc oxide. Moreover, compared with traditional chromium-containing sealing agents, chitosan has the advantage of being environmentally friendly and non-toxic. When the cerium complex is exposed to an oxidative environment (such as containing oxygen and water) for a long time, the cerium complex releases cerium(III) ions. These ions migrate to the damaged area, and the deposition of the oxide of cerium(III) ions can actively repair the damaged area and delay corrosion. The chemical interaction between cerium and chitosan can also enhance the stability of the sealing film layer. Therefore, cerium and zinc form a double-metal protective layer, which can significantly improve the comprehensive performance of the sealing film layer and enhance the durability of the coating.

[0015] In some preferred embodiments, D99 of the chitosan particles ≤ 180 μm.

[0016] In some preferred embodiments, the particle size of the nano-zinc oxide is 30 ± 10 nm.

[0017] In some preferred embodiments, the purity of the tea polyphenols ≥ 98%.

[0018] In some preferred embodiments, D50 of the nano-aluminum oxide is 10 - 60 nm, preferably D50 is 20 - 30 nm.

[0019] In some preferred embodiments, the temperature of the pulsed anodic oxidation is 20 - 45 °C, preferably 20 - 25 °C.

[0020] In some preferred embodiments, the time of the pulsed anodic oxidation is 30 - 60 min.

[0021] In some preferred embodiments, the frequency of the pulsed anodic oxidation is 100 - 500 Hz, preferably 300 - 500 Hz.

[0022] In some preferred embodiments, the duty cycle of the pulsed anodic oxidation is 40 - 50%.

[0023] In some preferred embodiments, the method of the sealing treatment is immersion.

[0024] In some preferred embodiments, the temperature of the sealing treatment is 50 - 60 °C.

[0025] In some preferred embodiments, the time of the sealing treatment is 20 - 30 min.

[0026] In some preferred embodiments, the sealing treatment is carried out with the assistance of ultrasonic waves at a frequency of 15 - 40 kHz; preferably, the sealing treatment is carried out with the assistance of ultrasonic waves at a frequency of 20 - 40 kHz.

[0027] In some preferred embodiments, the chemical pretreatment is carried out by soaking in a zirconium-titanium conversion solution for 5 - 10 minutes at a soaking temperature of 50 - 60 °C.

[0028] In some preferred embodiments, the zirconium-titanium conversion solution contains 1 - 3 g / L of zirconium hexafluoride acid (H2ZrF6), 0.5 - 2 g / L of titanium hexafluoride acid (H2TiF6), 1 - 2 g / L of ammonium fluoride (NH4F), 0.5 - 1 g / L of citric acid, and 0.1 - 0.5 g / L of surfactant.

[0029] In some preferred embodiments, the cleaning includes degreasing and pickling.

[0030] In some preferred embodiments, after the degreasing and pickling, water washing is also required.

[0031] In some preferred embodiments, the temperature of the degreasing is 60 - 70 °C, and the time of the degreasing is 180 - 300 s.

[0032] In some preferred embodiments, the degreasing agent used for degreasing includes 10 - 20 g / L of sodium hydroxide, 10 - 20 g / L of trisodium phosphate, 20 - 30 g / L of sodium carbonate, and 1 - 3 g / L of surfactant.

[0033] In some preferred embodiments, the temperature of the pickling is 15 - 30 °C, and the time of the pickling is 60 - 120 s.

[0034] In some preferred embodiments, by mass fraction, the pickling agent used for pickling includes 30 - 50 g / L of concentrated sulfuric acid (98% concentrated sulfuric acid), 3 - 8 g / L of ammonium bifluoride, 2 - 4 g / L of citric acid, 1 - 3 g / L of sodium nitrate, 0.5 - 1 g / L of ferric sulfate, and 1 - 2 g / L of dipropylene glycol.

[0035] The present invention also discloses an aluminum alloy surface obtained by the aforementioned treatment method for the aluminum alloy surface.

[0036] The aluminum alloy surface includes an aluminum alloy substrate, an anodic oxidation layer, and a sealing film layer.

[0037] The thickness of the pulsed anodic oxidation film layer is 5 - 15 μm, preferably 5 - 11 μm; the pulsed anodic oxidation film layer is the film layer formed after the pulsed anodic oxidation.

[0038] The thickness of the sealing film layer is 0.3-1.0 μm, preferably 0.3-0.8 μm; the sealing film layer is the film layer formed after the sealing treatment.

[0039] On the basis of conforming to the common knowledge in the art, the above preferred conditions can be combined arbitrarily to obtain various preferred examples of the present invention.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] 1. During the pulse anodic oxidation process of the present invention, tea polyphenols inhibit corrosion and side reactions through adsorption, and at the same time help the cerium (III) ions to be evenly distributed; the cerium (III) ions in cerium nitrate are embedded in the alumina lattice, refining the grains, enhancing the hardness, compactness and corrosion resistance; the nano-alumina particles fill the micropores, further improving the compactness and wear resistance. These components act synergistically to optimize the performance of the pulse anodic oxidation film layer.

[0042] 2. In the sealing solution, nano-zinc oxide can fill the micropores of the pulse anodic oxidation film due to its antibacterial and ultraviolet resistance properties, improving the surface compactness and hardness and enhancing the wear resistance. Chitosan has strong adsorption ability of amino and hydroxyl groups, and can be used as a film-forming matrix to disperse nano-zinc oxide, preventing agglomeration and improving the compactness of the sealing film layer, and it is environmentally friendly and non-toxic. The cerium complex releases cerium (III) ions in an oxidative environment, migrates to the damaged area and deposits oxides to repair the damage, delaying corrosion, and at the same time the chemical interaction between cerium and chitosan further enhances the film layer stability. Finally, the double-metal protective layer formed by cerium and zinc significantly improves the comprehensive performance and durability of the sealing film layer.

[0043] 3. The surface treatment of the aluminum alloy of the present invention also includes a cleaning and chemical pretreatment process. The degreasing process can remove the grease, oil stains and other organic substances on the surface of the aluminum alloy, preventing these substances from forming an isolation layer during the subsequent treatment process and hindering the progress of chemical reactions; after soaking in the zirconium-titanium-based conversion solution in the chemical pretreatment, a zirconium-titanium-based conversion film will be formed on the surface of the aluminum alloy. This conversion film can improve the corrosion resistance of the aluminum alloy surface, and at the same time enhance the adhesion and uniformity of the subsequent anodic oxidation film.

[0044] 4. Through pulse anodic oxidation and sealing treatment, a pulse anodic oxidation film layer and a sealing film layer are respectively formed on the surface of the aluminum alloy. The pulse anodic oxidation film layer has good corrosion resistance and wear resistance, and at the same time, the surface of the aluminum alloy also has good toughness, which can effectively resist external mechanical impacts. The sealing film layer further enhances the corrosion resistance and wear resistance of the aluminum alloy surface. In addition, the nano-zinc oxide in the sealing film layer endows the surface with antibacterial and anti-ultraviolet aging capabilities, while the cerium complex has self-healing ability and can maintain good protection performance during long-term use. The sealing film layer of the present invention eliminates the use of traditional chromium-containing sealants and instead uses chitosan, a natural material, making the entire treatment process more environmentally friendly. Detailed Embodiments

[0045] To facilitate the understanding of the present invention, the following will describe the present invention more comprehensively and in detail in combination with preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

[0046] Unless otherwise defined, all professional terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention.

[0047] The "range" disclosed in the present invention is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a specific range. The range defined in this way can include the end values or not include the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, ranges of 60 - 110 and 80 - 120 are also contemplated. In addition, if the minimum range values of 1 and 2 are listed, and if the maximum range values of 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5. In the present invention, unless otherwise specified, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" have been fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0048] If there is no special indication, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0049] Unless otherwise specified, all technical features and optional technical features of the present invention can be combined with each other to form new technical solutions.

[0050] Unless otherwise specified, all steps of the present invention can be carried out sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) carried out sequentially, or may include steps (b) and (a) carried out sequentially. For example, when it is mentioned that the method may further include step (c), it means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0051] Unless otherwise specified, the terms "comprising" and "including" mentioned in the present invention mean open-ended or may also be closed-ended. For example, the "comprising" and "including" may mean that other components not listed may also be included or contained, or may only include or contain the listed components.

[0052] Unless otherwise specified, in the present invention, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) while B is true (or exists); or both A and B are true (or exist).

[0053] The test method for the thickness of the anodic oxidation film layer and the thickness of the sealing film layer on the surface of the aluminum alloy in the following examples and comparative examples is the beam microscope method, specifically referring to GB / T 8014.3.

[0054] The degree of deacetylation of chitosan particles ≥ 85%, D99 = 177 - 180 μm.

[0055] Nanometer zinc oxide was purchased from Shanghai Dingfen Chemical Technology Co., Ltd., and the particle size is 30 ± 10 nm.

[0056] Tea polyphenols were purchased from Nanjing Daosifu Biotechnology Co., Ltd., and the purity > 98%.

[0057] Nanometer aluminum oxide was purchased from Bohuasi Nanotechnology (Ningbo) Co., Ltd., and D50 of the nanometer aluminum oxide = 20 nm.

[0058] Example 1

[0059] The treatment method for the surface of the aluminum alloy in this example is as follows:

[0060] (1) Cleaning:

[0061] Clean the surface of the aluminum alloy, i.e., perform degreasing, water washing, pickling, and water washing in sequence;

[0062] Perform degreasing at 60 °C for 220 s, then wash with water twice at 20 °C, with each water washing time being 30 s; perform pickling at 20 °C for 110 s, then wash with water twice at 20 °C, with each water washing time being 30 s; both degreasing and pickling are carried out by immersion;

[0063] The components of the degreasing agent used for degreasing are 20 g / L sodium hydroxide, 14 g / L trisodium phosphate, 21 g / L sodium carbonate, and 2.7 g / L surfactant (sodium dodecyl sulfonate), and the solvent is water;

[0064] The components of the pickling agent used for pickling are 45 g / L concentrated sulfuric acid (concentration 98%), 6 g / L ammonium bifluoride, 3.5 g / L citric acid, 2.8 g / L sodium nitrate, 0.7 g / L ferric sulfate, and 1.2 g / L dipropylene glycol (CAS No.: 25265 - 71 - 8), and the solvent is water;

[0065] (2) Chemical pretreatment:

[0066] Immerse the surface of the aluminum alloy cleaned in step (1) in a zirconium - titanium conversion solution for 8 min, and the immersion temperature is 60 °C;

[0067] The components of the zirconium - titanium conversion solution are 2 g / L fluozirconic acid, 0.8 g / L fluotitanic acid, 1.5 g / L ammonium fluoride, 0.6 g / L citric acid, and 0.3 g / L sodium dodecyl sulfonate (surfactant).

[0068] (3) Pulse anodic oxidation:

[0069] Perform pulse anodic oxidation on the surface of the aluminum alloy pretreated chemically in step (2) at 25 °C for 50 min, with a pulse frequency of 500 Hz and a pulse duty cycle of 50%; after pulse anodic oxidation, wash with water at 20 °C for 40 s, twice;

[0070] By mass percentage, the components of the electrolyte are 15% sulfuric acid, 0.6% tea polyphenols, 0.3% cerium nitrate, and 0.35% nano - alumina, and the solvent is water.

[0071] (4) Sealing treatment:

[0072] Perform sealing treatment on the surface of the aluminum alloy after pulse anodic oxidation in step (3) at 50 °C for 25 min, with ultrasonic assistance at a frequency of 30 kHz; after sealing treatment, wash with water at 20 °C for 40 s, twice;

[0073] The components of the sealing solution are 0.8% chitosan particles, 0.45% nano - zinc oxide, and 0.15% cerium complex (cerium acetylacetonate hydrate).

[0074] (5) Drying: Dry at 120 °C for 25 min.

[0075] The thickness of the pulsed anodic oxidation film layer in this example is 8 μm; the thickness of the sealing film layer is 0.6 μm.

[0076] Example 2

[0077] The difference between this example and Example 1 is only that:

[0078] Pulsed anodic oxidation: Perform pulsed anodic oxidation at 25 °C for 40 min, with a pulse frequency of 500 Hz and a pulse duty cycle of 40%;

[0079] By mass percentage, the electrolyte composition is 10% sulfuric acid, 1.0% tea polyphenols, 0.25% cerium nitrate, and 0.5% nano-aluminum oxide, and the solvent is water.

[0080] The thickness of the pulsed anodic oxidation film layer in this example is 5 μm.

[0081] All other steps and parameters are the same as in Example 1.

[0082] Example 3

[0083] The difference between this example and Example 1 is only that:

[0084] Sealing treatment: Perform sealing treatment at 60 °C for 20 min, with 30 kHz ultrasonic assistance;

[0085] By mass percentage, the sealing solution composition is 1.0% chitosan particles, 0.3% nano-zinc oxide, and 0.3% cerium complex (cerium oxalate).

[0086] The thickness of the sealing film layer in this example is 0.75 μm.

[0087] All other steps and parameters are the same as in Example 1.

[0088] Example 4

[0089] The difference between this example and Example 1 is that:

[0090] The degreaser composition is 20 g / L sodium hydroxide, 10 g / L trisodium phosphate, 30 g / L sodium carbonate, and 2 g / L surfactant, and the solvent is water;

[0091] The pickling agent composition is 50 g / L concentrated sulfuric acid (concentration 98%), 5 g / L ammonium bifluoride, 2 g / L citric acid, 1.5 g / L sodium nitrate, 0.5 g / L ferric sulfate, and 1.8 g / L dipropylene glycol, and the solvent is water.

[0092] The thickness of the pulsed anodic oxidation film layer in this example is 9 μm; the thickness of the sealing film layer is 0.65 μm.

[0093] All other steps and parameters are the same as those in Example 1.

[0094] Example 5

[0095] The difference between this example and Example 1 lies only in that:

[0096] It is immersed in the zirconium-titanium conversion liquid for 5 min at an immersion temperature of 50 °C;

[0097] The composition of the zirconium-titanium conversion liquid is 2.4 g / L zirconium fluoroacid, 1.5 g / L titanium fluoroacid, 1.0 g / L ammonium fluoride, 1.0 g / L citric acid, and 0.5 g / L surfactant (sodium dodecyl sulfonate).

[0098] The thickness of the pulsed anodic oxidation film layer in this example is 8.4 μm; the thickness of the sealing film layer is 0.61 μm.

[0099] All other steps and parameters are the same as those in Example 1.

[0100] Comparative Example 1

[0101] The difference between this comparative example and Example 1 is that:

[0102] By mass percentage, the electrolyte composition is 15% sulfuric acid, 0.3% cerium nitrate, and 0.5% nano-aluminum oxide, and the solvent is water.

[0103] The thickness of the pulsed anodic oxidation film layer in this comparative example is 7.1 μm.

[0104] All other steps and parameters are the same as those in Example 1.

[0105] Comparative Example 2

[0106] The difference between this comparative example and Example 1 is that:

[0107] By mass percentage, the electrolyte composition is 15% sulfuric acid, 0.6% tea polyphenols, and 0.3% cerium nitrate, and the solvent is water.

[0108] The thickness of the pulsed anodic oxidation film layer in this comparative example is 7.4 μm.

[0109] All other steps and parameters are the same as those in Example 1.

[0110] Comparative Example 3

[0111] The difference between this comparative example and Example 1 is that:

[0112] By mass percentage, the electrolyte composition includes: 15% sulfuric acid, 0.15% tea polyphenols, 0.3% cerium nitrate, 0.6% nano-aluminum oxide, and the solvent is water.

[0113] The thickness of the pulsed anodic oxidation film layer in this comparative example is 7.8 μm.

[0114] All other steps and parameters are the same as those in Example 1.

[0115] Comparative Example 4

[0116] The difference between this comparative example and Example 1 is that:

[0117] By mass percentage, the composition of the sealing solution is 0.5% nano-zinc oxide and 0.2% cerium complex.

[0118] The thickness of the sealing film layer in this comparative example is 0.47 μm.

[0119] All other steps and parameters are the same as those in Example 1.

[0120] Comparative Example 5

[0121] The difference between this comparative example and Example 1 is that:

[0122] By mass percentage, the composition of the sealing solution is 2% chitosan particles, 0.5% nano-zinc oxide and 0.3% cerium complex.

[0123] The thickness of the sealing film layer in this comparative example is 0.77 μm.

[0124] All other steps and parameters are the same as those in Example 1.

[0125] Comparative Example 6

[0126] The difference between this comparative example and Example 1 is that:

[0127] This comparative example does not include the step of (2) chemical pretreatment.

[0128] The thickness of the pulsed anodic oxidation film layer in this comparative example is 7.2 μm, and the thickness of the sealing film layer is 0.56 μm.

[0129] All other steps and parameters are the same as those in Example 1.

[0130] Test Example

[0131] The insulation, wear resistance and light and heat resistance of the aluminum alloy surfaces in the above examples and comparative examples were tested, and the test results are shown in Table 1.

[0132] The insulation test was carried out under the conditions of temperature 23°C ± 2°C and relative humidity ≤ 65%. The specific test method refers to GB / T 8754.

[0133] The wear resistance test was carried out using a load of 19.6 N and 240-mesh silicon carbide sandpaper for three experiments, and the average value was taken as the final result. The unit of wear rate is times (double stroke) / 5 μm, and the specific reference is GB / T 12967.2.

[0134] The light and heat resistance performance test is carried out in a thermostatic and humidistatic chamber with a temperature of 47°C ± 1°C and a relative humidity of 96% ± 2%. It is irradiated with a 313B fluorescent ultraviolet lamp for 800 h. The specific method refers to GB / T 12967.4. Whether there are phenomena such as color change, gloss change, crack peeling, etc. on the aluminum alloy surface is judged according to the grading standard of GB / T 1766.

[0135] Among them, the aluminum alloy in the blank group is only the aluminum alloy after cleaning, without going through the technological processes of chemical pretreatment, pulse anodic oxidation, and sealing treatment.

[0136] 。

[0137] In Comparative Example 1, the electrolyte does not contain tea polyphenols, and the hardness and densification performance of the formed pulse anodic oxidation film layer decrease. In Comparative Example 2, the electrolyte does not contain nano-aluminum oxide, the porosity of the pulse anodic oxidation film layer increases, and both the wear resistance and hardness decrease. In Comparative Example 3, the content of tea polyphenols in the electrolyte is too high, and excessive tea polyphenols will form excessive organic deposits on the surface of the oxide film, which will not only increase the conductivity of the film layer but also reduce its wear resistance.

[0138] In Comparative Example 4, the absence of chitosan in the sealing liquid causes a slight decrease in the adhesion of the coating, and at the same time, the nano-zinc oxide particles are prone to agglomeration, thus weakening the ultraviolet protection ability of the sealing film layer. In Comparative Example 5, the content of chitosan in the sealing liquid is too high, and excessive chitosan will reduce the mechanical properties of the sealing film layer and increase brittleness.

[0139] In Comparative Example 6, due to the absence of the chemical pretreatment step, the bonding degree between the cleaned aluminum alloy and the pulse anodic oxidation film layer is low, and serious wear and large-area peeling will occur on the surface of the aluminum alloy during the wear resistance test.

[0140] Unless otherwise specifically stated, all kinds of raw materials, reagents, instruments, and equipment used in the present invention can be obtained through market purchase or can be prepared by existing methods. The specific embodiments described above further elaborate on the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for treating the surface of an aluminum alloy, characterized in that: The following steps are involved: The surface of the aluminum alloy is cleaned, chemically pretreated, pulse anodized, and then sealed; The electrolyte used in the anodizing process comprises, by mass percentage, 10-30% sulfuric acid, 0.5-1% tea polyphenols, 0.1-0.3% cerium nitrate and 0.2-0.5% nano-aluminum oxide; The sealing liquid used for sealing comprises, by mass percentage, 0.5-1% chitosan particles, 0.2-0.5% nano zinc oxide and 0.1-0.3% cerium complex; Wherein, the cerium complex is cerium oxalate or hydrated cerium acetylacetonate.

2. The method for treating the surface of an aluminum alloy according to claim 1, characterized in that: Meet at least one of the following conditions ①~③: ① The D99 of the chitosan particles is ≤180 μm; ② The particle size of the nano zinc oxide is 30±10nm; ③ The D50 of the nano-alumina is 10~60nm.

3. The method for treating the surface of an aluminum alloy according to claim 1, characterized in that: Meet at least one of the following conditions ①~④: ① The temperature of the pulse anodizing is 20~45°C; ② The pulse anodizing time is 30 to 60 minutes; ③ The frequency of the pulse anodizing is 100~500Hz; ④ The duty cycle of the pulse anodizing is 40-50%.

4. The method for treating the surface of an aluminum alloy according to claim 1, characterized in that: Meet at least one of the following conditions ①~④: ① The sealing treatment method is immersion; ② The temperature of the sealing treatment is 50~60℃; ③ The sealing treatment time is 20 to 30 minutes; ④ The sealing treatment is carried out with the assistance of ultrasound at a frequency of 15~40kHz.

5. The method for treating the surface of an aluminum alloy according to claim 1, characterized in that: The chemical pretreatment method is to soak in a zirconium-titanium conversion solution for 5-10 minutes at a soaking temperature of 50-60°C; The zirconium-titanium conversion solution contains 1-3 g / L fluorozirconic acid, 0.5-2 g / L fluorotitanic acid, 1-2 g / L ammonium fluoride, 0.5-1 g / L citric acid and 0.1-0.5 g / L surfactant.

6. The method for treating the surface of an aluminum alloy according to claim 1, characterized in that: The cleaning includes degreasing and pickling; After the degreasing and pickling, water washing is required.

7. The method for treating the surface of an aluminum alloy according to claim 6, characterized in that: Meet at least one of the following conditions ①~②: ① The degreasing temperature is 60-70°C and the degreasing time is 180-300s; ② The degreasing agent used in the degreasing comprises 10-20 g / L sodium hydroxide, 10-20 g / L trisodium phosphate, 20-30 g / L sodium carbonate and 1-3 g / L surfactant.

8. The method for treating the surface of an aluminum alloy according to claim 6, characterized in that: Meet at least one of the following conditions ①~②: ① The pickling temperature is 15-30°C and the pickling time is 60-120s; ② Calculated by mass fraction, the pickling agent used in the pickling includes 30~50g / L concentrated sulfuric acid, 3~8g / L ammonium bifluoride, 2~4g / L citric acid, 1~3g / L sodium nitrate, 0.5~1g / L ferric sulfate and 1~2g / L dipropylene glycol.

9. Aluminum alloy surface, characterized in that The aluminum alloy surface is obtained by the aluminum alloy surface treatment method as described in any one of claims 1 to 8.

10. The aluminum alloy surface according to claim 9, characterized in that It includes an aluminum alloy substrate, a pulse anodized layer and a sealing film layer; The thickness of the pulse anodized film is 5~15μm; The thickness of the sealing film layer is 0.3-1.0 μm.