Nickel-free hole sealing method and aluminum alloy product

Abstract

The invention relates to a nickel-free hole sealing method and an aluminum alloy product. The nickel-free hole sealing method sequentially comprises the steps of degreasing, first nitrogen-free neutralization cleaning, chemical polishing, acid washing, alkali washing, second nitrogen-free neutralization cleaning, anodic oxidation and dyeing hole sealing. The first nitrogen-free neutralization cleaning is added before chemical polishing, and the alkali cleaning and the second nitrogen-free neutralization cleaning are added after chemical polishing, so that the cleaning range is greatly increased, the cleaning strength is improved, the better dust removal effect is achieved, and the better metal surface gloss is obtained; the phenomenon that lime is generated after hole sealing due to the fact that Si ash generated in the hole sealing process is not completely removed is avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, and specifically relates to a metal surface treatment method, and in particular to a nickel-free pore sealing method and an aluminum alloy product. Background Art

[0002] In the existing aluminum alloy anodizing method, the pores of the aluminum alloy anodized film are often filled by sealing treatment to improve the surface quality and corrosion resistance of the aluminum alloy.

[0003] At present, after the surface sealing treatment of aluminum alloy products is completed by the nickel-free sealing method, the product surface can achieve normal gloss and color difference effects, and can ensure that the color difference and gloss drop of the original product are within the range. However, due to the problem of unclean cleaning after chemical polishing, white ash appears on the product surface after nickel-free sealing in the post-process.

[0004] CN117187915A discloses a nickel-free sealing process at room temperature and a nickel-free sealing process with an agent, which adds sodium lignin sulfonate as an anionic surfactant and utilizes its good emulsification, wetting permeability and strong dispersibility and diffusivity to act as a dust suppressant in the sealing agent to suppress the problem of dusting on the surface after sealing. However, it can only play an inhibitory role and cannot eliminate the problem of dusting on the surface after sealing from the source.

[0005] CN103590086A discloses a nickel-free sealing agent for aluminum alloy and a sealing method thereof, which uses fluorotitanic acid as the main component of the sealing agent, increases the sealing speed to more than twice that of nickel salt, and the sealing temperature can be as low as 15°C, thereby improving production efficiency and saving energy. However, the sealing method can only reduce the powder on the surface of the substrate, but cannot completely solve the white ash problem.

[0006] CN109706501A discloses a preparation method and application of a post-sealing deashing agent, which uses the deashing agent to clean the aluminum alloy after sealing to remove the white ash on the surface of the aluminum alloy. However, the deashing method after the sealing process may damage the sealing quality of the oxide film.

[0007] In summary, the sealing methods disclosed in the prior art are unable to suppress the problem of white ash generation on the surface of aluminum alloy products from the source. Therefore, it is of great significance to provide a nickel-free sealing method that can prevent the generation of white ash on the surface of aluminum alloy products after sealing from the source without affecting the color difference and gloss of the product. Summary of the invention

[0008] The invention provides a nickel-free sealing method and an aluminum alloy product, and in particular provides a nickel-free sealing method which can prevent the generation of white ash on the surface of the aluminum alloy product after sealing from the source.

[0009] To achieve this object, the present invention adopts the following technical solutions:

[0010] In a first aspect, the present invention provides a nickel-free sealing method, comprising degreasing, a first nitrogen-free neutralization cleaning, chemical polishing, acid cleaning, alkaline cleaning, a second nitrogen-free neutralization cleaning, anodizing and dyeing sealing performed in sequence.

[0011] The nickel-free sealing process often causes Si elements to remain on the surface of aluminum products, and the cleaning process in the existing sealing method often makes it difficult to completely remove the Si elements, resulting in white ash on the surface of the product after sealing. The present invention improves the phenomenon of white ash on the surface of the material after sealing caused by the residual Si elements by adding a first nitrogen-free neutralization cleaning before chemical polishing, and adding an alkali cleaning and a second nitrogen-free neutralization cleaning after chemical polishing.

[0012] Preferably, the chemical polishing is carried out in a chemical polishing liquid.

[0013] Preferably, the chemical polishing liquid includes H3PO4, H2SO4 and Al 3+ , the Al 3+ Derived from but not limited to Al2(SO4)3.

[0014] Preferably, the concentration of H3PO4 in the polishing liquid is 1200-1450g / L, for example, it can be 1200g / L, 1220g / L, 1240g / L, 1260g / L, 1280g / L, 1300g / L, 1320g / L, 1340g / L, 1360g / L, 1380g / L, 1400g / L, 1420g / L, 1440g / L or 1450g / L, including but not limited to the listed values, and other unlisted values ​​within the numerical range are equally applicable.

[0015] Preferably, the concentration of H2SO4 in the polishing liquid is 140-220g / L, for example, it can be 140g / L, 150g / L, 160g / L, 170g / L, 180g / L, 190g / L, 200g / L, 210g / L or 220g / L, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0016] Preferably, Al in the polishing liquid 3+ The concentration is 10-40g / L, for example, it can be 10g / L, 12g / L, 14g / L, 16g / L, 18g / L, 20g / L, 22g / L, 24g / L, 26g / L, 28g / L, 30g / L, 32g / L, 34g / L, 36g / L, 38g / L or 40g / L, including but not limited to the listed values, and other unlisted values ​​within the numerical range are equally applicable.

[0017] Preferably, the polishing temperature is 70-80°C, for example, it can be 70°C, 71°C, 72°C, 73°C, 74°C, 75°C, 76°C, 77°C, 78°C, 79°C or 80°C, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0018] Preferably, the first nitrogen-free neutralization cleaning is performed in a first nitrogen-free neutralizer solution.

[0019] Preferably, the first nitrogen-free neutralizing solution comprises a first nitrogen-free neutralizing agent.

[0020] Preferably, the raw materials of the first nitrogen-free neutralizer include 25-35 parts of sulfuric acid, for example, 25 parts, 26 parts, 27 parts, 28 parts, 29 parts, 30 parts, 31 parts, 32 parts, 33 parts, 34 parts or 35 parts, by mass; 5-15 parts of additives, for example, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, 11 parts, 12 parts, 13 parts, 14 parts or 15 parts, 0.5-1 parts of catalyst, for example, 0.5 parts, 0.6 parts, 0.7 parts, 0.8 parts, 0.9 parts or 1 parts, 3-8 parts of oxidant, for example, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts or 8 parts, and 45-55 parts of pure water, for example, 45 parts, 46 parts, 47 parts, 48 ​​parts, 49 parts, 50 parts, 51 parts, 52 parts, 53 parts, 54 parts or 55 parts. The mass parts of each raw material in the above-mentioned first nitrogen-free neutralizer include but are not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0021] Preferably, the additive comprises any one of tartaric acid, oxalic acid, malic acid, citric acid, ascorbic acid, citric acid, acetic acid, succinic acid, benzoic acid or salicylic acid.

[0022] Preferably, the catalyst includes any one of lecithin, sodium lauryl sulfate, polyethylene glycol, propylene glycol, fatty alcohol glyceride, and polysorbate. The catalyst of the present invention is a substance that can reduce the activation energy of the reaction, make the reaction easier to proceed, and thus achieve a catalytic effect. The present invention does not specifically limit the type of the catalyst, as long as it can achieve the catalytic function.

[0023] Preferably, the oxidant comprises any one of potassium permanganate, hydrogen peroxide, peracetic acid, sodium dichromate, chromic acid or ammonium persulfate, or a combination of at least two thereof.

[0024] Preferably, the concentration of the first nitrogen-free neutralizer is 250-350 g / L, for example, it can be 250 g / L, 260 g / L, 270 g / L, 280 g / L, 290 g / L, 300 g / L, 310 g / L, 320 g / L, 330 g / L, 340 g / L or 350 g / L, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0025] Preferably, the temperature of the first nitrogen-free neutralization cleaning is 20-40°C, for example, it can be 20°C, 22°C, 24°C, 26°C, 28°C, 30°C, 32°C, 34°C, 36°C, 38°C or 40°C, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0026] Preferably, the time for the first nitrogen-free neutralization cleaning is 120-180s, for example, it can be 120s, 125s, 130s, 135s, 140s, 145s, 150s, 155s, 160s, 165s, 170s, 175s or 180s, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0027] In the present invention, the first nitrogen-free neutralization cleaning can effectively reduce the dust on the surface of the product after degreasing and bring it into the chemical polishing tank, thereby causing a large amount of dust accumulation during the chemical polishing process, thereby affecting the gloss and cleanliness of the product surface and the generation of white ash.

[0028] Preferably, the alkali washing is carried out in an alkali solution.

[0029] Preferably, the alkaline solution is one of NaOH solution, KOH solution, NaHCO3 solution or a combination of at least two thereof. Typical but non-limiting combinations include a combination of NaOH solution and KOH solution, a combination of NaOH solution and NaHCO3 solution, a combination of KOH solution and NaHCO3 solution, or a combination of NaOH solution, KOH solution and NaHCO3 solution, preferably NaOH solution.

[0030] Preferably, the concentration of the alkaline solution is 30-50 g / L, for example, it can be 30 g / L, 32 g / L, 34 g / L, 36 g / L, 38 g / L, 40 g / L, 42 g / L, 44 g / L, 46 g / L, 48 g / L or 50 g / L, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0031] Preferably, the alkali washing time is 30-70s, for example, it can be 30s, 35s, 40s, 45s, 50s, 55s, 60s, 65s or 70s, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0032] Preferably, the alkali washing temperature is 30-35°C, for example, 30°C, 31°C, 32°C, 33°C, 34°C or 35°C, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0033] In the present invention, the purpose of alkali washing is to further remove surface dirt and completely remove the natural oxide film on the aluminum surface to reveal a pure metal matrix, thereby laying a good foundation for subsequent anodizing to uniformly conduct electricity and form a uniform anodized film.

[0034] Preferably, the second nitrogen-free neutralization cleaning is performed in a second nitrogen-free neutralizing agent.

[0035] Preferably, the second nitrogen-free neutralizer solution comprises a second nitrogen-free neutralizer.

[0036] Preferably, the raw materials of the second nitrogen-free neutralizer include, by weight:

[0037]

[0038] The second nitrogen-free neutralizing agent used in the present invention includes 3-5 parts of sulfuric acid, for example, 3 parts, 3.2 parts, 3.4 parts, 3.6 parts, 3.8 parts, 4 parts, 4.3 parts, 4.5 parts, 4.7 parts, 4.8 parts or 5 parts by weight; 0.1-0.3 parts of surfactant, for example, 0.1 parts, 0.12 parts, 0.14 parts, 0.16 parts, 0.18 parts, 0.2 parts, 0.21 parts, 0.22 parts by weight; 20-25 parts of oxidant, for example, 20 parts, 20.5 parts, 21 parts, 21.5 parts, 22 parts, 22.5 parts, 23 parts, 23.5 parts, 24 parts, 24.5 parts or 25 parts; 60-80 parts of pure water, for example, 62 parts, 64 parts, 66 parts, 68 parts, 70 parts, 72 parts, 74 parts, 76 parts, 78 parts or 80 parts. The mass parts of each raw material in the second nitrogen-free neutralizer include but are not limited to the listed values, and other values ​​not listed in the numerical range are also applicable.

[0039] Preferably, the surfactant includes any one of sodium dodecyl sulfate, lauryl ether phosphate, coconut acid monoethanolamide, phenylethyl alcohol, isobutyl hydroxyphenyl ether, isopentyl hydroxyphenyl ether, hydroxyethyl phenyl ether, polyethylene glycol ether, polyethylene glycol sulfate, polyoxyethylene ethyl ether or lauryl amide propyl amine oxide, or a combination of at least two thereof.

[0040] Preferably, the oxidant comprises any one of potassium permanganate, hydrogen peroxide, peracetic acid, sodium dichromate, chromic acid or ammonium persulfate, or a combination of at least two thereof.

[0041] Preferably, the concentration of the second nitrogen-free neutralizer is 250-350 g / L, for example, it can be 250 g / L, 260 g / L, 270 g / L, 280 g / L, 290 g / L, 300 g / L, 310 g / L, 320 g / L, 330 g / L, 340 g / L or 350 g / L, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0042] Preferably, the temperature of the second nitrogen-free neutralization cleaning is 20-40°C, for example, it can be 20°C, 22°C, 24°C, 26°C, 28°C, 30°C, 32°C, 34°C, 36°C, 38°C or 40°C, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0043] Preferably, the time for the second nitrogen-free neutralization cleaning is 120-180s, for example, it can be 120s, 125s, 130s, 135s, 140s, 145s, 150s, 155s, 160s, 165s, 170s, 175s or 180s, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0044] In the present invention, the second nitrogen-free neutralization cleaning is performed after the alkali cleaning, which can remove the dust attachments remaining on the surface of the product after the alkali cleaning to prevent them from being brought into the electrolyte in the anode tank, thereby polluting the electrolyte; and the second nitrogen-free neutralization cleaning process can effectively dissolve some impurities generated by the alkali cleaning and a small amount of insoluble attachments such as copper, magnesium, and iron, so as to obtain a better metal surface gloss and prevent the generation of white ash after sealing.

[0045] Preferably, the pickling is carried out in a solution containing sulfuric acid and Fe 3+ The Fe 3+ From iron sulfate.

[0046] Preferably, the concentration of sulfuric acid is 130-220 g / L, for example, 130 g / L, 140 g / L, 150 g / L, 160 g / L, 170 g / L, 180 g / L, 190 g / L, 200 g / L, 210 g / L or 220 g / L, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0047] Preferably, the Fe 3+ The concentration is 1.5-3.5 g / L, for example, it can be 1.5 g / L, 1.7 g / L, 1.9 g / L, 2 g / L, 2.2 g / L, 2.4 g / L, 2.6 g / L, 2.8 g / L, 3.0 g / L, 3.3 g / L or 3.5 g / L, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0048] Preferably, the pickling time is 180s-200s, for example, it can be 180s, 182s, 184s, 186s, 188s, 190s, 192s, 194s, 196s, 198s or 200s, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0049] Preferably, the pickling temperature is 30-35°C, for example, 30°C, 31°C, 32°C, 33°C, 34°C or 35°C, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0050] In the present invention, acid washing with a mixed solution of sulfuric acid and ferric sulfate can preliminarily clean Si ash and other impurities generated after chemical polishing. In combination with subsequent alkali washing and the second nitrogen-free neutralization cleaning method, the cleaning range can be greatly enhanced, the cleaning strength can be improved, a better ash removal effect can be achieved, and the phenomenon of white ash generated after sealing due to incomplete removal of Si ash generated during the sealing process can be avoided.

[0051] Preferably, after the anodizing, a surface conditioning treatment is also included.

[0052] In a second aspect, the present invention provides an aluminum alloy product, wherein the surface of the aluminum alloy product is sealed using the nickel-free sealing method described in the first aspect.

[0053] Preferably, the color difference drop point L value of the aluminum alloy product is 0.03-0.13, for example, it can be 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12 or 0.13, the a value is 0-0.03, for example, it can be 0, 0.005, 0.01, 0.015, 0.02, 0.025 or 0.03, and the b value is 0.05- 0.23, for example, it can be 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2, 0.21, 0.22 or 0.23, and the values ​​of L value, a value and b value include but are not limited to the listed values, and other values ​​not listed in the numerical range are also applicable.

[0054] Preferably, the gloss drop point of the aluminum alloy product is 0.2-0.9GU, for example, it can be 0.2GU, 0.23GU, 0.3GU, 0.36GU, 0.4GU, 0.42GU, 0.5GU, 0.58GU, 0.6GU, 0.64GU, 0.7GU, 0.8GU or 0.9GU, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0055] Preferably, the film thickness of the aluminum alloy product is 0.02-0.12μm, for example, it can be 0.02μm, 0.23μm, 0.03μm, 0.04μm, 0.05μm, 0.57μm, 0.06μm, 0.07μm, 0.08μm, 0.09μm, 0.1μm, 0.11μm or 0.12μm, including but not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0056] Compared with the prior art, the present invention has at least the following beneficial effects:

[0057] The present invention adds a first nitrogen-free neutralization cleaning before chemical polishing, and adds alkali cleaning and a second nitrogen-free neutralization cleaning after chemical polishing. On the one hand, the first nitrogen-free neutralization cleaning can effectively avoid bringing dust on the surface of the product after degreasing into the chemical polishing tank, thereby causing a large amount of dust accumulation during the chemical polishing process, thereby affecting the glossiness and neatness of the product surface and the generation of white ash. On the other hand, the second nitrogen-free neutralization cleaning is performed after alkali cleaning, and the ash attachments remaining on the surface of the product after alkali cleaning can be removed to avoid being brought into the electrolyte in the anode tank, thereby polluting the electrolyte. In addition, the second nitrogen-free neutralization cleaning process can effectively dissolve some impurities generated by alkali cleaning and a small amount of insoluble attachments such as copper, magnesium, and iron. The present invention greatly enhances the cleaning range, improves the cleaning strength, achieves a better dust removal effect, obtains a better metal surface gloss, and avoids the phenomenon of white ash generation after sealing caused by incomplete removal of Si ash generated in the sealing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 The figure is a flow chart of the nickel-free pore sealing method of the present invention.

[0059] Figure 2 This is a SEM image of the final aluminum alloy product obtained by the nickel-free sealing method in Example 1.

[0060] Figure 3 This is the SEM image of the final aluminum alloy product obtained by the nickel-free sealing method in Example 1.

[0061] Figure 4 This is the SEM image of the final aluminum alloy product obtained by the nickel-free sealing method in Example 5.

[0062] Figure 5 This is the SEM image of the final aluminum alloy product obtained by the nickel-free sealing method in Example 6. DETAILED DESCRIPTION

[0063] For the convenience of understanding the present invention, the present invention lists the following embodiments. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0064] Example 1

[0065] This embodiment provides a nickel-free sealing method, comprising the following steps:

[0066] (1) at 30° C., placing the degreased aluminum alloy substrate in a first nitrogen-free neutralizing cleaning solution having a first nitrogen-free neutralizing agent concentration of 300 g / L for first nitrogen-free neutralizing cleaning, and the cleaning time is 150 s; the first nitrogen-free neutralizing agent is composed of 30 parts of sulfuric acid, 10 parts of tartaric acid, 0.7 parts of sodium dodecyl sulfate, 5 parts of potassium permanganate and 50 parts of pure water in parts by mass;

[0067] (2) The aluminum alloy substrate after the first nitrogen-free neutralization cleaning in step (1) was placed in a solution containing 1350 g / L H3PO4, 180 g / L H2SO4 and 25 g / L Al 3+ Chemical polishing is carried out in the chemical polishing liquid;

[0068] (3) The aluminum alloy substrate after chemical polishing in step (2) was placed in a mixture of 180 g / L H2SO4 and Fe 3+ Acid washing for 190s in a 2.5g / L ferric sulfate solution;

[0069] (4) placing the aluminum alloy substrate after acid washing in step (3) in a 45 g / L NaOH solution at 32° C. and performing alkaline washing for 45 seconds;

[0070] (5) at 32° C., placing the aluminum alloy substrate after alkali washing in step (4) into a second nitrogen-free neutralizing cleaning solution with a second nitrogen-free neutralizing agent concentration of 280 g / L for a second nitrogen-free neutralizing cleaning, and the cleaning time is 160 s; in terms of mass parts, the second nitrogen-free neutralizing agent is composed of 4 parts of sulfuric acid, 0.2 parts of sodium dodecyl sulfate, 23 parts of hydrogen peroxide, and 70 parts of pure water;

[0071] (6) Anodizing and dyeing the aluminum alloy substrate after the second nitrogen-free neutralization cleaning to obtain a final aluminum alloy product.

[0072] The SEM image of the final aluminum alloy product obtained by the nickel-free pore sealing method provided in this embodiment is as follows: Figure 2 shown.

[0073] Example 2

[0074] This embodiment provides a nickel-free sealing method, comprising the following steps:

[0075] (1) At 20° C., the degreased aluminum alloy substrate is placed in a first nitrogen-free neutralization cleaning solution with a first nitrogen-free neutralizer concentration of 250 g / L for first nitrogen-free neutralization cleaning for 120 s; the first nitrogen-free neutralizer is composed of 25 parts of sulfuric acid, 5 parts of ascorbic acid, 0.5 parts of polyethylene glycol, 3 parts of hydrogen peroxide and 45 parts of pure water in parts by mass;

[0076] (2) The aluminum alloy substrate after the first nitrogen-free neutralization cleaning in step (1) was placed in a solution containing 1200 g / L H3PO4, 140 g / L H2SO4 and 10 g / L Al 3+ Chemical polishing is carried out in the chemical polishing liquid;

[0077] (3) The aluminum alloy substrate after chemical polishing in step (2) was placed in a mixture of H2SO4 with a concentration of 130 g / L and Fe 3+ Acid wash for 180s in 1.5g / L ferric sulfate solution;

[0078] (4) placing the aluminum alloy substrate after acid washing in step (3) into a 30 g / L KOH solution at 30° C. and performing alkaline washing for 30 seconds;

[0079] (5) at 20° C., placing the aluminum alloy substrate after alkali washing in step (4) into a second nitrogen-free neutralizing cleaning solution with a second nitrogen-free neutralizing agent concentration of 250 g / L for a second nitrogen-free neutralizing cleaning, and the cleaning time is 120 s; in terms of mass parts, the second nitrogen-free neutralizing agent is composed of 3 parts of sulfuric acid, 0.1 parts of isobutyl hydroxyphenyl ether, 20 parts of peracetic acid, and 60 parts of pure water;

[0080] (6) Anodizing and dyeing the aluminum alloy substrate after the second nitrogen-free neutralization cleaning to obtain a final aluminum alloy product.

[0081] Example 3

[0082] This embodiment provides a nickel-free sealing method, comprising the following steps:

[0083] (1) At 40° C., the degreased aluminum alloy substrate is placed in a first nitrogen-free neutralization cleaning solution with a first nitrogen-free neutralizer concentration of 350 g / L for first nitrogen-free neutralization cleaning, and the cleaning time is 180 s; in terms of mass parts, the first nitrogen-free neutralizer is composed of 35 parts of sulfuric acid, 15 parts of succinic acid, 1 part of fatty alcohol glyceride, 8 parts of sodium dichromate and 55 parts of pure water;

[0084] (2) The aluminum alloy substrate after the first nitrogen-free neutralization cleaning in step (1) was placed in a solution containing 1450 g / L H3PO4, 220 g / L H2SO4 and 40 g / L Al 3+ Chemical polishing is carried out in the chemical polishing liquid;

[0085] (3) The aluminum alloy substrate after chemical polishing in step (2) was placed in a mixture of H2SO4 with a concentration of 220 g / L and Fe 3+ Acid wash for 200s in 3.5g / L ferric sulfate solution;

[0086] (4) placing the aluminum alloy substrate after acid washing in step (3) into a 50 g / L NaOH solution at 35° C. and performing alkaline washing for 70 seconds;

[0087] (5) at 40° C., placing the aluminum alloy substrate after alkali washing in step (4) into a second nitrogen-free neutralizing cleaning solution with a second nitrogen-free neutralizing agent concentration of 350 g / L for a second nitrogen-free neutralizing cleaning, and the cleaning time is 180 s; in terms of mass parts, the second nitrogen-free neutralizing agent is composed of 5 parts of sulfuric acid, 0.3 parts of polyethylene glycol ether, 25 parts of ammonium persulfate, and 80 parts of pure water;

[0088] (6) Anodizing and dyeing the aluminum alloy substrate after the second nitrogen-free neutralization cleaning to obtain a final aluminum alloy product.

[0089] Comparative Example 1

[0090] This comparative example provides a nickel-free pore sealing method, comprising the following steps:

[0091] (1) The aluminum alloy substrate after degreasing in step (1) was placed in a solution containing 1350 g / L H3PO4, 180 g / L H2SO4 and 25 g / L Al 3+ Chemical polishing is carried out in the chemical polishing liquid;

[0092] (2) The aluminum alloy substrate after chemical polishing in step (2) was placed in a mixture of H2SO4 with a concentration of 180 g / L and Fe 3+ Acid washing for 190s in a 2.5g / L ferric sulfate solution;

[0093] (3) The pickled aluminum alloy substrate is anodized and dyed to obtain a final aluminum alloy product.

[0094] Compared with Example 1, this comparative example does not perform the first nitrogen-free neutralization cleaning before chemical polishing, nor does it perform alkali cleaning and the second nitrogen-free neutralization cleaning after chemical polishing.

[0095] The SEM image of the final aluminum alloy product obtained by the nickel-free sealing method provided in this comparative example is as follows: Figure 3 shown.

[0096] Comparative Example 2

[0097] This comparative example provides a nickel-free pore sealing method, comprising the following steps:

[0098] (1) The degreased aluminum alloy substrate was placed in a solution containing 1350 g / L H3PO4, 180 g / L H2SO4, and 25 g / L Al 3+ Chemical polishing is carried out in the chemical polishing liquid;

[0099] (2) The aluminum alloy substrate after chemical polishing in step (1) was placed in a mixture of 180 g / L H2SO4 and Fe 3+ Acid washing for 190s in a 2.5g / L ferric sulfate solution;

[0100] (3) placing the aluminum alloy substrate after acid washing in step (2) in a 45 g / L NaOH solution at 32° C. and performing alkaline washing for 45 seconds;

[0101] (4) at 32° C., placing the aluminum alloy substrate after alkali washing in step (3) into a second nitrogen-free neutralizing cleaning solution with a second nitrogen-free neutralizing agent concentration of 280 g / L for a second nitrogen-free neutralizing cleaning, and the cleaning time is 160 s; in terms of mass parts, the second nitrogen-free neutralizing agent is composed of 4 parts of sulfuric acid, 0.2 parts of sodium dodecyl sulfate, 23 parts of hydrogen peroxide, and 70 parts of pure water;

[0102] (5) Anodizing and dyeing the aluminum alloy substrate after the second nitrogen-free neutralization cleaning to obtain a final aluminum alloy product.

[0103] Compared with Example 1, this comparative example did not perform the first nitrogen-free neutralization cleaning before chemical polishing.

[0104] Comparative Example 3

[0105] This comparative example provides a nickel-free pore sealing method, comprising the following steps:

[0106] (1) at 30° C., placing the degreased aluminum alloy substrate in a first nitrogen-free neutralizing cleaning solution having a first nitrogen-free neutralizing agent concentration of 300 g / L for first nitrogen-free neutralizing cleaning, and the cleaning time is 150 s; the first nitrogen-free neutralizing agent is composed of 30 parts of sulfuric acid, 10 parts of tartaric acid, 0.7 parts of sodium dodecyl sulfate, 5 parts of potassium permanganate and 50 parts of pure water in parts by mass;

[0107] (2) The aluminum alloy substrate after the first nitrogen-free neutralization cleaning in step (1) was placed in a solution containing 1350 g / L H3PO4, 180 g / L H2SO4 and 25 g / L Al 3+ Chemical polishing is carried out in the chemical polishing liquid;

[0108] (3) The aluminum alloy substrate after chemical polishing in step (2) was placed in a mixture of 180 g / L H2SO4 and Fe 3+ Acid washing for 190s in a 2.5g / L ferric sulfate solution;

[0109] (4) placing the aluminum alloy substrate after acid washing in step (3) in a 45 g / L NaOH solution at 32° C. and performing alkaline washing for 45 seconds;

[0110] (5) The alkali-washed aluminum alloy substrate is anodized and dyed to obtain a final aluminum alloy product.

[0111] Compared with Example 1, this comparative example did not perform the second nitrogen-free neutralization cleaning after the alkali cleaning.

[0112] Comparative Example 4

[0113] This comparative example provides a nickel-free sealing method, which is the same as comparative example 1 except that the pickling time is adjusted to 200 seconds.

[0114] Comparative Example 5

[0115] This comparative example provides a nickel-free sealing method, which is the same as comparative example 1 except that the pickling time is adjusted to 260s.

[0116] The SEM image of the final aluminum alloy product obtained by the nickel-free sealing method provided in this comparative example is as follows: Figure 4 shown.

[0117] Comparative Example 6

[0118] This comparative example provides a nickel-free sealing method, which is the same as comparative example 1 except that the pickling time is adjusted to 360s.

[0119] The SEM image of the final aluminum alloy product obtained by the nickel-free sealing method provided in this comparative example is as follows: Figure 5 shown.

[0120] Cleaning effect verification:

[0121] The aluminum alloy products prepared in Examples 1 to 3 and Comparative Examples 1 to 6 were subjected to appearance inspection, SEM and EDS analysis, and the test results are shown in Table 1.

[0122] The color difference, gloss and film thickness drop points of the aluminum alloy products before and after sealing in Examples 1 to 3 and Comparative Examples 1 to 6 were tested, wherein:

[0123] Color difference drop point = color difference before sealing - color difference after sealing, which is characterized by L value, a value and b value;

[0124] Gloss loss = before sealing - after sealing;

[0125] Membrane thickness drop point = before sealing - after sealing. The test results are shown in Table 2.

[0126] The aluminum alloy products in Examples 1 to 3 and Comparative Examples 1 to 6 were subjected to a salt spray test. The temperature of the salt spray test was (35±2)°C, the concentration of the sodium chloride solution used was (50±5) g / L, the pH value of the sedimentation salt solution was 6.5-7.2, and the sedimentation amount of the salt spray was (1.5±0.5) ml / h / 80cm2 , spray pressure is 0.7-1.1kg / cm 2 , the saturated barrel temperature is 47+2℃, the test spray mode is continuous spray, the angle between the sample and the vertical line is 15°-30°, and the test cycles are 2h, 6h, 24h, 48h, 72h, 96h, 144h, 168h, 720h and 1000h. After the test is completed, take out the sample and dry it naturally in the room for 0.5-1h, and clean the salt spray solution remaining on the surface with running water.

[0127] Table 1

[0128]

[0129]

[0130] Table 2

[0131]

[0132] From the data results of Example 1 in Table 1, it can be seen that according to the nickel-free pore sealing method provided by the present invention, a first nitrogen-free neutralization cleaning is performed before chemical polishing, and an alkali cleaning and a second nitrogen-free neutralization cleaning are performed after chemical polishing. The aluminum alloy product obtained by the treatment is subjected to EDS analysis, and no Si element is detected, indicating that the residual Si element in the pore sealing process is completely removed. Figure 2 It can be seen from the SEM image that the surface of the aluminum alloy product is in good condition, without any corrosion or white ash, and the appearance inspection has passed. From the data of the embodiment in Table 2, it can be seen that the aluminum alloy product obtained by the sealing method provided by the present invention has a color difference drop point L value of less than 0.13, a value of less than 0.03, b value of less than 0.23, gloss drop point of less than 0.9GU, film thickness drop point of less than 0.12μm, and successfully passed the REL test.

[0133] According to the data of Comparative Examples 1 to 3, if the first nitrogen-free neutralization cleaning is not performed before chemical polishing, and the alkali cleaning and the second nitrogen-free neutralization cleaning are not performed after chemical polishing according to the present invention, the Si element cannot be completely removed. The Si element in the aluminum alloy product obtained in Comparative Example 1 is as high as 4.6wt%. Figure 3 It can also be seen from the SEM image that the surface of the aluminum alloy product is significantly deteriorated, there are serious corrosion marks, there is white ash on the surface, and the appearance inspection fails. The color difference, gloss and film thickness drop are also much higher than the aluminum alloy product treated by the sealing method of the present invention, and all fail to pass the REL test.

[0134] It can be seen from the EDS detection data of Comparative Examples 4 to 6 in Table 1 that, on the basis of Comparative Example 1, the cleaning time of sulfuric acid and ferric sulfate solution is extended, and the content of Si element decreases to a certain extent, but even if the cleaning time of sulfuric acid and ferric sulfate is increased to twice the original, the Si element cannot be completely removed. In Comparative Examples 5 and 6, after the cleaning time of sulfuric acid and ferric sulfate is increased from 180s to 260s and 360s respectively, the surface state of the aluminum alloy product is significantly improved compared with Comparative Example 1, but there are still obvious corrosion marks, and because the Si element cannot be completely removed, although the appearance inspection is passed, there is still a risk of producing white ash phenomenon. According to the data results of Table 2, extending the cleaning time of sulfuric acid and ferric sulfate does not improve the color difference, gloss and thickness drop, and the prepared aluminum alloy product still cannot pass the REL test.

[0135] The applicant declares that the present invention illustrates the detailed method of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed method, that is, it does not mean that the present invention must rely on the above-mentioned detailed method to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of various raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A nickel-free sealing method, characterized in that: The nickel-free sealing method comprises degreasing, first nitrogen-free neutralization cleaning, chemical polishing, acid cleaning, alkali cleaning, second nitrogen-free neutralization cleaning, anodizing and dyeing sealing which are performed in sequence.

2. The nickel-free sealing method according to claim 1, characterized in that: The chemical polishing is carried out in a chemical polishing liquid; Preferably, the chemical polishing liquid includes H3PO4, H2SO4 and Al 3+ ; Preferably, the concentration of H3PO4 in the polishing liquid is 1200-1450g / L; Preferably, the concentration of H2SO4 in the chemical polishing liquid is 140-220g / L; Preferably, Al in the polishing liquid 3+ The concentration is 10-40g / L; Preferably, the temperature of the polishing is 70-80°C.

3. The nickel-free sealing method according to claim 1, characterized in that: The first nitrogen-free neutralization cleaning is performed in a first nitrogen-free neutralizer solution; Preferably, the first nitrogen-free neutralizing solution comprises a first nitrogen-free neutralizing agent; Preferably, the raw materials of the first nitrogen-free neutralizer include, by weight: Preferably, the additive comprises any one of tartaric acid, oxalic acid, malic acid, citric acid, ascorbic acid, citric acid, acetic acid, succinic acid, benzoic acid or salicylic acid; Preferably, the catalyst includes any one of lecithin, sodium lauryl sulfate, polyethylene glycol, propylene glycol, fatty alcohol glyceride, and polysorbate; Preferably, the oxidant comprises any one or a combination of at least two of potassium permanganate, hydrogen peroxide, peracetic acid, sodium dichromate, chromic acid or ammonium persulfate; Preferably, the concentration of the first nitrogen-free neutralizer is 250-350 g / L.

4. The nickel-free sealing method according to claim 1, characterized in that: The temperature of the first nitrogen-free neutralization cleaning is 23-27° C.; Preferably, the first nitrogen-free neutralization cleaning time is 120-180 seconds.

5. The nickel-free sealing method according to claim 1, characterized in that: The alkali washing is carried out in an alkali solution; Preferably, the alkaline solution comprises one or a combination of at least two of a NaOH solution, a KOH solution, and a NaHCO3 solution; Preferably, the concentration of the alkaline solution is 30-50 g / L; Preferably, the alkali washing time is 30-70s; Preferably, the temperature of the alkali washing is 30-35°C.

6. The nickel-free sealing method according to claim 1, characterized in that: The second nitrogen-free neutralization cleaning is performed in a second nitrogen-free neutralizer solution; Preferably, the second nitrogen-free neutralizer solution comprises a second nitrogen-free neutralizer; Preferably, the raw materials of the second nitrogen-free neutralizer include, by weight: Preferably, the surfactant includes any one of sodium dodecyl sulfate, lauryl ether phosphate, coconut acid monoethanolamide, phenylethyl alcohol, isobutyl hydroxyphenyl ether, isopentanediyl hydroxyphenyl ether, hydroxyethyl phenylethyl ether, polyethylene glycol ether, polyethylene glycol sulfate, polyoxyethylene ethyl ether or lauryl amide propyl amine oxide, or a combination of at least two thereof; Preferably, the oxidant comprises any one or a combination of at least two of potassium permanganate, hydrogen peroxide, peracetic acid, sodium dichromate, chromic acid or ammonium persulfate; Preferably, the concentration of the second nitrogen-free neutralizer is 250-350 g / L.

7. The nickel-free sealing method according to claim 1, characterized in that: The temperature of the second nitrogen-free neutralization cleaning is 20-40° C.; Preferably, the second nitrogen-free neutralization cleaning time is 120-180 seconds.

8. The nickel-free sealing method according to claim 1, characterized in that: The pickling process comprises H2SO4 and Fe 3+ in a mixed solution; Preferably, the concentration of the sulfuric acid is 130-220 g / L; Preferably, the Fe 3+ The concentration is 1.5-3.5g / L; Preferably, the pickling time is 180s-200s; Preferably, the pickling temperature is 30-35°C.

9. The nickel-free sealing method according to claim 1, characterized in that: After the anodizing, a surface conditioning treatment is also included.

10. An aluminum alloy product, characterized in that: The aluminum alloy product is subjected to surface sealing treatment using the nickel-free sealing method described in any one of claims 1 to 9; The color difference drop point L value of the aluminum alloy product is in the range of 0.03-0.13, the a value is in the range of 0-0.03, and the b value is in the range of 0.05-0.23; The gloss drop point of the aluminum alloy product is 0.2-0.9GU; The film thickness of the aluminum alloy product is 0.02-0.12 μm.

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