High-color-fixation medium-temperature hole sealing agent for aluminum alloy anode oxide film and preparation method and application of high-color-fixation medium-temperature hole sealing agent

Abstract

The invention belongs to the technical field of hole sealing reagents, and discloses a high-color-fixation medium-temperature hole sealing agent for an aluminum alloy anodic oxide film as well as a preparation method and application of the high-color-fixation medium-temperature hole sealing agent. The medium-temperature hole sealing agent comprises hole sealing main salt, hole sealing auxiliary salt, a color fixing auxiliary agent and an auxiliary agent, the hole sealing main salt comprises nickel acetate or nickel acetate hydrate; the hole sealing secondary salt comprises at least one of cobalt acetate, magnesium acetate, lithium acetate and calcium acetate; the color fixing auxiliary agent comprises at least one of tannic acid, gallic acid, quercetin, ellagic acid, tannic acid and catechin. According to the medium-temperature hole sealing agent, hole sealing of the aluminum alloy oxidation film is achieved under the medium-temperature (55-65 DEG C) condition, meanwhile, the color fixing process of dye molecules in micropores of the oxidation film is synchronously completed through the effect of the specific color fixing auxiliary, and the problems of uneven hole sealing and color fading caused by a separation technology are solved. And after the hole sealing agent is used for treatment, the binding force of the dye and an oxidation film can be enhanced, and the dye is not easy to fade in a high-temperature and high-humidity environment for a long time.

Description

Technical Field

[0001] The invention belongs to the technical field of sealing agents, and particularly relates to a medium-temperature sealing agent with high color fixation for an aluminum alloy anodized film, and a preparation method and application thereof. Background Art

[0002] Anodizing of aluminum alloys is an important process to improve surface corrosion resistance, decorative properties and other functionalities. A porous oxide film is formed on the surface of the anodized aluminum alloy, and the oxide film can be further colored to enhance decorative properties. Existing aluminum alloy coloring technologies are mainly divided into two methods: electrolytic coloring and dyeing. Electrolytic coloring deposits metal ions in the oxide film through electrolytic reaction. The advantages are stable color and good anti-fading properties, but the process is complicated and the color selection is limited. The dyeing method penetrates the pores of the oxide film through dyes, and the colors are rich. It is suitable for products with high decorative requirements. The process is relatively simple and is a commonly used aluminum alloy anodizing coloring method in industry.

[0003] However, the dyed oxide film is more susceptible to fading due to the dye molecules fixed in the micropores. Sealing becomes an important step to improve the durability of the dyed film, especially for aluminum alloy products with high decorative properties and outdoor use. The quality of sealing directly affects the color stability and weather resistance. Traditional sealing processes are divided into high-temperature sealing (such as steam sealing) and low-temperature sealing (such as chemical sealing). High-temperature sealing can easily lead to cracking of the film layer, while the low-temperature sealing process takes a long time and has low sealing efficiency. Especially during the sealing process, there is still room for improvement in the color fixation effect and anti-fading performance of the dyed film.

[0004] The existing patent CN114059129A discloses a color fixing agent and preparation method after dyeing of aluminum and aluminum alloy anodized film. The color fixing agent is fixed by the sulfonic acid group, carboxylic acid group, etc. in the color fixing agent and the oxide film to produce van der Waals force or hydrogen bonding, but the dye molecule still has strong water solubility, low fastness, and is easy to fade. The color fixing component of the network structure forms an ionic bond with the anionic group of the dye, further sealing the water-soluble group of the dye, thereby improving the color fixing effect. Although the above technology improves the color fastness and anti-fading property of the dyed film, the color fixing and sealing treatment are carried out in steps after dyeing. This separation process leads to the process discontinuity between sealing and color fixing, and the color fixing agent is prone to unevenness or cross interference between the sealing agent and the color fixing agent, thereby affecting the compactness and durability of the dyed film. In addition, although the color fixing agent can enhance the bonding force between the dye and the oxide film, the problem of dye fading still exists under a long-term high temperature and high humidity environment.

[0005] Therefore, it is urgent to provide a sealing agent with good color fixing effect. Summary of the invention

[0006] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention provides a medium-temperature sealing agent with high color fixation for anodized aluminum alloy films and a preparation method and application thereof.

[0007] In view of the defects in the prior art, the purpose of the present invention is to provide a medium temperature (55-65°C) color fixing and sealing agent that combines the color fixing and pore sealing functions. Through the integrated operation of pore sealing and color fixing, not only the pore sealing of the aluminum alloy oxide film is achieved under medium temperature (55-65°C), but also the color fixing process of the dye molecules in the micropores of the oxide film is completed synchronously through the action of a specific color fixing auxiliary agent, thereby avoiding the problems of uneven sealing and fading caused by the separation process. Moreover, after being treated with the sealing agent of the present invention, the bonding force between the dye and the oxide film can be enhanced, and it is not easy to fade even in a long-term high temperature and high humidity environment.

[0008] The invention provides a novel medium-temperature sealing agent, which can significantly improve the sealing rate of a dyed oxide film, enhance the color fixing effect and weather resistance, and has good operational stability and environmental adaptability.

[0009] A first aspect of the present invention provides a medium-temperature sealing agent with high color fixation for anodized aluminum alloy films.

[0010] Specifically, a medium-temperature sealing agent with high color fixation for anodized aluminum alloy film comprises a sealing main salt, a sealing secondary salt, a color fixation aid, and an auxiliary agent;

[0011] The sealing main salt includes nickel acetate or nickel acetate hydrate;

[0012] The sealing secondary salt includes at least one of cobalt acetate, magnesium acetate, lithium acetate and calcium acetate;

[0013] The color fixing auxiliary agent includes at least one of tannic acid, gallic acid, quercetin, ellagic acid, tannic acid and catechin.

[0014] Preferably, the auxiliary agent includes at least one of a pH stabilizer, a complexing agent, a corrosion inhibitor, a promoter, an ash inhibitor, and a surfactant; further preferably, the auxiliary agent includes a pH stabilizer, a complexing agent, a corrosion inhibitor, a promoter, an ash inhibitor, and a surfactant.

[0015] Preferably, the medium temperature sealing agent further comprises water. The water may be deionized water. The water may also be added when the medium temperature sealing agent is used.

[0016] Preferably, the nickel acetate hydrate comprises nickel acetate tetrahydrate. Nickel acetate generates nickel hydroxide through hydrolysis reaction under medium temperature conditions and is deposited in the micropores of the aluminum alloy oxide film to seal the pores of the film layer. Nickel ions react with aluminum oxide groups in the oxide film to further improve the sealing efficiency and increase the density of the film layer, thereby significantly improving the corrosion resistance. The hydrolysis reaction rate of nickel acetate is moderate and is suitable for use at a sealing temperature of 50-65°C.

[0017] The cobalt, magnesium, lithium and calcium ions in the sealing secondary salt play a role similar to that of nickel ions in the oxide film, which can form a stable oxide layer and increase the sealing effect of the film layer. The use of sealing secondary salt in conjunction with the sealing primary salt can significantly improve the sealing effect.

[0018] The color fixing auxiliary agent selected by the present invention, during the dyeing process, the dye molecules are attached to the inner wall of the micropores of the aluminum alloy oxide film through electrostatic attraction or van der Waals force. The traditional sealing agent does not have a strong color fixing ability during the sealing process, which causes the dye molecules to migrate or fall off in the later environment. The color fixing auxiliary agent of the present invention enhances the binding force between the dye molecules and the inner pore wall of the oxide film by generating coordination or hydrogen bonding with the dye molecules, and locks the dye firmly in the micropores. For example, tannic acid, which contains multiple hydroxyl and phenolic hydroxyl structures, can be combined with the sulfonic acid group or carboxylic acid group in the dye molecule through hydrogen bonding or covalent bonding, further enhancing the binding force between the dye molecule and the surface of the oxide film. Tannic acid fixes the dye molecules in the micropores of the oxide film through this chemical action, thereby preventing the dye from migrating and fading, and significantly improving the color fastness of the dye. Gallic acid is a strong antioxidant with a structure similar to tannic acid, having multiple phenolic hydroxyl groups, which can form a strong bond with the dye molecule, increase the color fixing effect, and also inhibit the oxidation and fading of the dye. Ellagic acid has good antioxidant and color-fixing effects. It can combine with the active groups in the dye molecules to improve color fastness.

[0019] In addition to reacting with dye molecules, the hydroxyl, carboxyl, and phenolic hydroxyl groups in the color fixing agent molecules can also play a chelating role, that is, they form complexes or ionic bonds with metal ions such as nickel or cobalt ions in the sealing salt, further forming a network structure, which can improve the density of the film layer and reduce the gaps in the micropores, thereby blocking the invasion of external moisture, oxygen, etc. into the interior of the film layer. This not only improves the corrosion resistance of the dye, but also enhances the film's antioxidant and UV resistance. It is suitable for aluminum alloy products in outdoor environments or high humidity environments.

[0020] Preferably, the pH stabilizer is selected from at least one of boric acid, ammonium acetate, tartaric acid, and potassium hydrogen phthalate. The pH of the medium-temperature sealing agent is adjusted within a neutral to slightly acidic range to ensure that nickel ions and other components are in a suitable pH range during the sealing process.

[0021] Preferably, the complexing agent is selected from at least one of potassium sodium tartrate, ethylenediaminetetraacetic acid, sodium polyphosphate, and sodium citrate. Further, the complexing agent is potassium sodium tartrate and sodium polyphosphate. As a multifunctional complexing agent, potassium sodium tartrate can effectively prevent the metal ions in the medium-temperature sealing agent from reacting with impurities, maintain the stability of the medium-temperature sealing agent, and extend the service life of the bath liquid; sodium polyphosphate, as a polymer compound, can form a stable complex with the metal ions in the oxide film, and its long-chain molecular structure can fill the micropores of the oxide film to form a protective film layer to prevent the migration of dye molecules. By forming a phosphate film, the stability and corrosion resistance of the film layer are further enhanced, and the cracking of the film layer is reduced.

[0022] Preferably, the corrosion inhibitor is selected from at least one of benzotriazole and its derivatives, glycerol, and ammonium dihydrogen phosphate to prevent corrosion of the oxide film during the sealing process.

[0023] Preferably, the promoter is selected from at least one of ammonium sulfate, thiourea and urea. As a promoter, ammonium sulfate can accelerate the hydrolysis and deposition rate of nickel ions, reduce the sealing time, and reduce the cracks and pores of the film layer after sealing, effectively improving the density of the film layer. In addition, ammonium sulfate can promote the oxide film and other components in the medium-temperature sealer to form a more uniform sealing effect. Urea can slowly decompose in the medium-temperature sealer, provide additional amino groups, promote the hydrolysis of nickel ions and increase the sealing rate.

[0024] Preferably, the ash suppressant is selected from organic phosphonic acid, specifically including at least one of HEDP (hydroxyethylidene diphosphonic acid) and ATMP (amino trimethylene phosphonic acid). Although the conventionally used macromolecular organic compounds such as carboxylates and phosphates can suppress the generation of sealing ash, they will also suppress the deposition of nickel salts in the sealing reaction, thus reducing the sealing quality; the ash suppressant used in the present invention has a small amount and good effect, and can be adsorbed on the surface of the oxide film without entering the micropores, does not affect the deposition of nickel, and significantly reduces the generation of sealing ash.

[0025] Preferably, the surfactant includes at least one of polyethylene glycol laurate, sodium lignin sulfonate, sodium dodecyl sulfate, and γ-aminopropyl triethoxysilane (silane coupling agent KH-500). Polyethylene glycol laurate is a nonionic surfactant with good emulsification, wetting, solubilization and low foaming properties, which can enhance the smoothness and fineness of the sealing surface, retain the metallic texture and improve the brightness; if other types of nonionic surfactants are selected, the sealing surface is likely to become dull or the surface is white and lacks metallic texture. Sodium lignin sulfonate is an anionic surfactant with good emulsification, wetting permeability and strong dispersibility and diffusivity. At the same time, as an ash suppressant in the medium-temperature sealing agent, it can suppress the problem of easy ash formation on the surface after sealing. If other types of anionic surfactants are selected, the surface after sealing is prone to white ash formation, and there is no ash suppression effect.

[0026] Preferably, the medium-temperature sealing agent, calculated by weight, includes 65-85 parts of the main sealing salt, 4-10 parts of the secondary sealing salt, 2-9 parts of the color fixing aid, and 5-20 parts of the auxiliary agent; further preferably, the medium-temperature sealing agent, calculated by weight, includes 70-85 parts of the main sealing salt, 5-8 parts of the secondary sealing salt, 3-5 parts of the color fixing aid, and 8.4-19.1 parts of the auxiliary agent.

[0027] Preferably, the medium-temperature sealing agent includes, by weight, 70-85 parts of a main sealing salt, 5-8 parts of a secondary sealing salt, 3-5 parts of a color fixing aid, 2-3 parts of a pH stabilizer, 5-8 parts of a complexing agent, 0.2-0.5 parts of a corrosion inhibitor, 0.1-0.3 parts of an accelerator, 0.1-0.3 parts of a ash suppressant, and 1-2 parts of a surfactant.

[0028] The second aspect of the present invention provides a method for preparing a medium-temperature sealing agent with high color fixation for anodized aluminum alloy films.

[0029] Specifically, a method for preparing a medium-temperature sealing agent with high color fixation for anodized aluminum alloy films comprises the following steps:

[0030] The components are mixed to obtain the medium-temperature sealing agent.

[0031] A third aspect of the present invention provides an application of a medium-temperature sealing agent with high color fixation property for anodized aluminum alloy films.

[0032] The above-mentioned medium-temperature sealing agent is used in the surface treatment of aluminum alloys containing oxide films on the surface.

[0033] A method for using a medium-temperature sealing agent comprises the following steps:

[0034] The aluminum alloy workpiece with an oxide film on the surface is dyed and then placed in an aqueous solution of a medium-temperature sealing agent for sealing.

[0035] Preferably, the sealing treatment temperature is 55-65°C.

[0036] Preferably, the concentration of the aqueous solution of the medium-temperature sealing agent is 8-10 g / L.

[0037] Preferably, the pH of the aqueous solution of the medium-temperature sealing agent is 5.3-6.5, and more preferably 5.5-6.2.

[0038] Preferably, the sealing treatment lasts for 5-20 minutes, and further for 10-20 minutes.

[0039] Preferably, the sealing speed during the sealing treatment is 0.5-2.5 min / μm, further 1-2 min / μm.

[0040] Preferably, the method of use comprises the following steps:

[0041] The aluminum alloy workpiece is placed in an oxidant solution after degreasing, water washing, alkaline etching, water washing, deashing and water washing, and powered on for anodizing. After water washing, a workpiece with an anodized film on the surface is obtained, and then the workpiece is dyed. The dyed workpiece is immersed in a pre-heated aqueous solution of a medium-temperature sealing agent for sealing. During the process, the aqueous solution of the medium-temperature sealing agent is stirred regularly to ensure uniform temperature and full contact between the surface of the aluminum alloy workpiece and the aqueous solution of the medium-temperature sealing agent. After the sealing is completed, the workpiece is taken out of the solution, quickly rinsed with deionized water, and air-dried.

[0042] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0043] The medium-temperature sealing agent of the present invention includes a sealing main salt, a sealing secondary salt, a color fixing auxiliary agent, and an auxiliary agent; by specifically selecting the sealing main salt, the sealing secondary salt, and the color fixing auxiliary agent, and matching the auxiliary agent, the medium-temperature sealing agent of the present invention not only achieves the sealing of the aluminum alloy oxide film under medium temperature (55-65°C), but also, through the action of the specific color fixing auxiliary agent, the color fixing process of the dye molecules in the micropores of the oxide film can be completed synchronously, avoiding the uneven sealing and fading problems caused by the separation process. After the sealing agent of the present invention is treated, it can enhance the binding force between the dye and the oxide film, and is not easy to fade in a long-term high temperature and high humidity environment. DETAILED DESCRIPTION

[0044] In order to make the technical scheme of the present invention more clearly understood by those skilled in the art, the following embodiments are listed for illustration. It should be pointed out that the following embodiments do not limit the protection scope of the present invention.

[0045] Unless otherwise specified, the raw materials, reagents or devices used in the following examples can be obtained from conventional commercial sources or by existing known methods.

[0046] Example 1

[0047] A medium-temperature sealing agent with high color fixation for anodized aluminum alloy films, which is composed of the following components in parts by weight: 75 parts of a main sealing salt (nickel acetate), 6 parts of a secondary sealing salt (cobalt acetate), 4 parts of a color fixation aid (tannic acid), 2.5 parts of a pH stabilizer (boric acid), 6 parts of a complexing agent (potassium sodium tartrate), 0.4 parts of a corrosion inhibitor (benzotriazole), 0.2 parts of an accelerator (thiourea), 0.2 parts of a ash suppressant (hydroxyethylidene diphosphonic acid), and 1.5 parts of a surfactant (sodium lignin sulfonate).

[0048] A method for preparing a medium-temperature sealing agent with high color fixation of anodized aluminum alloy films comprises the following steps:

[0049] The components are mixed to obtain a medium-temperature sealing agent with high color fixation property for anodized aluminum alloy films.

[0050] Example 2

[0051] A medium-temperature sealing agent with high color fixation for anodized aluminum alloy films, which is composed of the following components in parts by weight: 80 parts of a main sealing salt (nickel acetate), 5 parts of a secondary sealing salt (cobalt acetate), 3 parts of a color fixation aid (gallic acid), 3 parts of a pH stabilizer (boric acid), 7 parts of a complexing agent (ethylenediaminetetraacetic acid), 0.3 parts of a corrosion inhibitor (ammonium dihydrogen phosphate), 0.15 parts of an accelerator (thiourea), 0.25 parts of a ash suppressant (hydroxyethylidene diphosphonic acid), and 1.8 parts of a surfactant (polyethylene glycol laurate).

[0052] A method for preparing a medium-temperature sealing agent with high color fixation of anodized aluminum alloy films comprises the following steps:

[0053] The components are mixed to obtain a medium-temperature sealing agent with high color fixation property for anodized aluminum alloy films.

[0054] Example 3

[0055] A medium-temperature sealing agent with high color fixation for anodized aluminum alloy films, which is composed of the following components in parts by weight: 72 parts of a main sealing salt (nickel acetate), 6.5 parts of a secondary sealing salt (magnesium acetate), 3.5 parts of a color fixation aid (ellagic acid), 3 parts of a pH stabilizer (potassium hydrogen phthalate), 6.5 parts of a complexing agent (sodium polyphosphate), 0.4 parts of a corrosion inhibitor (ammonium dihydrogen phosphate), 0.2 parts of an accelerator (ammonium sulfate), 0.2 parts of a ash suppressant (aminotrimethylenephosphonic acid), and 1.2 parts of a surfactant (γ-aminopropyltriethoxysilane).

[0056] A method for preparing a medium-temperature sealing agent with high color fixation of anodized aluminum alloy films comprises the following steps:

[0057] The components are mixed to obtain a medium-temperature sealing agent with high color fixation property for anodized aluminum alloy films.

[0058] Example 4

[0059] A medium-temperature sealing agent with high color fixation for anodized aluminum alloy films, which is composed of the following components in parts by weight: 72 parts of a main sealing salt (nickel acetate), 6.5 parts of a secondary sealing salt (magnesium acetate), 3.5 parts of a color fixation aid (tannic acid), 2.8 parts of a pH stabilizer (boric acid), 6.5 parts of a complexing agent (sodium potassium tartrate), 0.4 parts of a corrosion inhibitor (ammonium dihydrogen phosphate), 0.2 parts of an accelerator (ammonium sulfate), 0.2 parts of a ash suppressant (aminotrimethylenephosphonic acid), and 1.2 parts of a surfactant (γ-aminopropyltriethoxysilane).

[0060] A method for preparing a medium-temperature sealing agent with high color fixation of anodized aluminum alloy films comprises the following steps:

[0061] The components are mixed to obtain a medium-temperature sealing agent with high color fixation property for anodized aluminum alloy films.

[0062] Comparative Example 1

[0063] A medium-temperature sealing agent with high color fixation for anodized aluminum alloy films, which is composed of the following components in parts by weight: 77 parts of a sealing main salt (nickel acetate), 4.5 parts of a color fixation aid (tannic acid), 2 parts of a pH stabilizer (boric acid), 5 parts of a complexing agent (potassium sodium tartrate), 0.4 parts of a corrosion inhibitor (benzotriazole), 0.25 parts of an accelerator (thiourea), 0.15 parts of a ash suppressant (hydroxyethylidene diphosphonic acid), and 1 part of a surfactant (sodium lignin sulfonate).

[0064] A method for preparing a medium-temperature sealing agent with high color fixation of anodized aluminum alloy films comprises the following steps:

[0065] The components are mixed to obtain a medium-temperature sealing agent with high color fixation property for anodized aluminum alloy films.

[0066] Comparative Example 2

[0067] Compared with Example 1, the difference of Comparative Example 2 is that an equal amount of calcium acetate is used instead of nickel acetate as the main sealing salt, and other components and processes are the same as those of Example 1.

[0068] Comparative Example 3

[0069] Compared with Example 1, the difference of Comparative Example 3 is that an equal amount of acrylic acid polymer is used instead of tannic acid as a color fixing auxiliary agent, and other components and processes are the same as those of Example 1.

[0070] Product effect testing

[0071] The medium-temperature sealing agent with high color fixation property for anodized aluminum alloy films (hereinafter referred to as medium-temperature sealing agent) prepared in the above-mentioned Examples 1-4 and Comparative Examples 1-3 were mixed with deionized water respectively to prepare a medium-temperature sealing agent solution with a concentration of 9 g / L. The pH values ​​of the medium-temperature sealing agent solutions corresponding to Examples 1-4 and Comparative Examples 1-2 were 5.7, 5.7, 6.0, 6.5, 5.5 and 5.7, respectively.

[0072] Then, the medium-temperature sealing agent solutions corresponding to the above-mentioned embodiments 1-4 and comparative examples 1-3 are respectively used according to the following method of use, and the method of use comprises the following steps:

[0073] The aluminum alloy workpiece is degreased, washed, alkaline etched, washed, deashed and washed, then placed in a sulfuric acid solution, powered on for anodizing, and washed with water to obtain a workpiece with an anodized film on the surface. The workpiece is then dyed and the dyed workpiece is immersed in a pre-heated medium-temperature sealing agent solution (the temperatures of the medium-temperature sealing agent solutions corresponding to Examples 1-4 and Comparative Examples 1-3 are 55°C, 60°C, 55°C, 65°C, 55°C, 55°C, and 55°C, respectively) for sealing (the sealing time is 10 minutes). During this period, the medium-temperature sealing agent solution is stirred regularly to ensure uniform temperature and sufficient contact between the surface of the aluminum alloy workpiece and the medium-temperature sealing agent solution. After the sealing is completed, the workpiece is taken out of the solution, quickly rinsed with deionized water, and air-dried.

[0074] Then the aluminum alloy workpieces after the sealing treatment of the above-mentioned Examples 1-4 and Comparative Examples 1-2 were subjected to the following performance tests, and the results are shown in Table 1:

[0075] 1. Appearance inspection: Use a clean cotton cloth to wipe the aluminum alloy surface after sealing (called sample), and observe whether it is smooth, whether there is gray film or color difference, discoloration, white spots and other poor appearance. Place the sample under white light, visually inspect and record the uniformity of the film layer after sealing, whether there is peeling, roughness or gray film.

[0076] 2. Boiling test: GB / T12967.6-2022, immerse the sealed aluminum alloy (sample) in boiling water at 100°C for 1 hour. Take out the sample, rinse it with clean water and dry it, and observe whether the dyed film has obvious fading or color difference.

[0077] 3. Anti-pollution test (ink residue test): Apply methyl violet solution (1g methyl violet dissolved in 100mL alcohol) to the surface of the sealed aluminum alloy (sample), then wipe it clean with a damp cloth. The anti-pollution performance is judged based on the depth of the stains left.

[0078] 4. Weight loss test: According to the nitric acid pre-immersion phosphochromic acid mass loss method specified in GB / T8753.2-2005 standard, the nitric acid pre-immersion solution for measuring mass loss is 650mL / L nitric acid solution (HNO3, density ρ 20 =1.4 g / mL), temperature T is (19 ± 1) °C, t is 10 min; the mass loss etching solution is 20 g / L chromium trioxide (CrO3) and 35 mL / L phosphoric acid solution (H3PO4, density ρ 20 =1.7g / mL), temperature T is (38±1)℃, t is 15min. And the mass loss of nitric acid pre-immersion phosphochromic acid specified in the architectural aluminum profile standard (GB / T5237.2-2008) is ≤30mg / dm 2 The sealing quality is judged to be qualified.

[0079] 5. Salt spray test: According to GB / T12967.3-2022, the copper accelerated acetate salt spray test is carried out on the sealed aluminum alloy (sample) using a salt spray box. The sample is sprayed with a spray device to make the salt spray settle on the surface of the sample (the salt spray is a sodium chloride solution with a concentration of 5% and a pH of 7). After 48 hours, the surface condition of the sample is observed. If there is no color flow, fading, cracks, bubbles, whitening, discoloration, corrosion points, etc. after salt spray treatment, it is OK (OK means qualified), otherwise it is NG (NG means unqualified).

[0080] Table 1

[0081]

[0082]

[0083] As can be seen from Table 1, the sealing secondary salt used in Example 1 and Example 2 is cobalt acetate, which can significantly improve the sealing effect and enhance the corrosion resistance of the oxide film. In the salt spray test, the corrosion resistance of the film layer of Example 1 and Example 2 is better than that of other examples and comparative examples, the sealing rate is high in the ink residue experiment, and the film layer is complete, smooth and has no obvious fading after sealing.

[0084] The film layer after sealing corresponding to Example 1 is the most dense, has a high sealing rate, and has a smooth surface without ash film. Compared with Comparative Example 1, the auxiliary salt (cobalt acetate) has a significant auxiliary effect on sealing, while the use of nickel acetate alone (Comparative Example 1) leads to a decrease in the density of the sealing film layer and a decrease in the sealing rate.

[0085] The sealing ability of Example 3 and Example 4 is slightly inferior to that of Example 1, but the color fixing auxiliary agent thereof has an obvious effect, and the color fastness of the film layer is acceptable, especially the color fixing effect is enhanced under high temperature sealing.

[0086] Example 1 uses tannic acid, and the color fixing effect is better. In the water boiling test, the fading phenomenon is very rare. The color of the film layer is maintained for a long time after sealing. In the ink residue experiment, the sealing rate is maintained at more than 95%.

[0087] Example 2 uses gallic acid, which has a slightly poor color fixation ability and slightly fades in the water boiling test. In contrast, tannic acid shows better dye molecule binding ability among color fixation aids.

[0088] Examples 3 and 4 use tannic acid and ellagic acid as color-fixing aids, which provide stable color fastness during the sealing process, and the effect is better when the sealing temperature is slightly higher (65° C.), which can further inhibit fading.

[0089] Example 1 is the optimal formula with high sealing rate, good color fastness, strong corrosion resistance, best sealing appearance, and excellent comprehensive performance under medium temperature sealing.

[0090] The sealing effect of Example 2 is close to the optimal formula, but the color fixing effect is slightly inferior, and it is suitable for the sealing process under high temperature conditions.

[0091] Examples 3 and 4 have better performance, especially in terms of color fastness, but their sealing rate and corrosion resistance are slightly inferior to those of Example 1.

[0092] Due to the lack of secondary salt, the overall performance of Comparative Example 1 is not as good as that of other embodiments, showing problems of poor sealing rate and corrosion resistance.

[0093] After calcium acetate was used instead of nickel acetate in Comparative Example 2, the surface quality was significantly reduced, and the film layer after sealing was rough and had a gray film. The performance of calcium acetate in the color fixation process was significantly poor, and obvious fading occurred in the boiling test, indicating that the color fixation effect was poor. The large amount of ink residue indicated that the oxide film formed by calcium acetate in the sealing process was not dense enough. The results of the salt spray test and the weight loss test both showed that the corrosion resistance was significantly reduced after calcium acetate replaced nickel acetate. Comparative Example 2 shows that calcium acetate as the main salt for sealing cannot achieve the effect of nickel acetate, especially in terms of sealing rate and corrosion resistance, which proves the importance of using nickel acetate as the main salt in the present invention.

[0094] Comparative Example 3 uses acrylic polymer as a color fixing agent, which shows obvious deficiencies compared with the tannic acid in Example 1, especially in key indicators such as color fastness, sealing rate, and corrosion resistance. The molecular structure of acrylic polymer is relatively stable, but the ionic bond or complexation between it and the main sealing salt (nickel acetate) is weak, resulting in its adsorption force in the micropores of the anodized film being not as good as tannic acid. This makes it easier for the dye molecules to detach from the film layer, and a slight fading phenomenon is shown in the boiling test. The sealing effect of acrylic polymer in the micropores is poor, so that the sealing rate fails to reach the effect of Example 1, and at the same time, the compactness of the film layer is not as good as the tannic acid sealing agent solution, thereby reducing the corrosion resistance and showing a slight corrosion phenomenon in the salt spray test. When acrylic polymer is used as a color fixing agent, the surface gloss of the aluminum alloy after sealing is poor, resulting in uneven sealing appearance, dim surface, slight color difference, and affecting the overall appearance effect. The addition of tannic acid not only improves the color fastness and sealing rate, but also improves the compactness and corrosion resistance of the film layer. This further demonstrates the importance of the selection of the specific dye fixation aid of the present invention.

[0095] Finally, Example 1 is the optimal formula, which is suitable for sealing at a medium temperature of 55°C and has significant advantages in industrial applications.

[0096] Traditional sealers are mostly based on a single chemical component, usually based on nickel acetate or other simple sealer ingredients. This single-component sealer is easily affected by fluctuations in process parameters such as pH and temperature of the sealing liquid during the sealing process, resulting in a decrease in the sealing rate, fading of the dyed film, or a loose structure of the sealing film. The present invention adopts a composite formula system, the main component of which is nickel acetate, supplemented by sealing secondary salts, color fixing aids, gray suppressants, pH buffers, promoters, chelating agents, and surfactants. This compounding technology makes the sealer more stable in multiple functions, especially more flexible in the sealing process under different environmental conditions.

[0097] The traditional sealing process usually requires a relatively high temperature (usually around 90°C), a long sealing time and high process energy consumption. In addition, in the traditional high-temperature sealing process, the fading problem of the sample after dyeing is more serious, and the sealing is not stable enough. The medium-temperature sealing agent of the present invention improves the dispersibility and wetting ability of the medium-temperature sealing agent on the oxide film through various components, accelerates the sealing process, thereby improving the sealing efficiency, and realizes the medium-temperature sealing process (55°C-65°C), which not only reduces energy consumption, but also ensures the high efficiency and stability of the sealing process, effectively improves the simplicity and energy efficiency of the process flow, and is suitable for industrial-scale production.

[0098] In the traditional sealing process, the film layer after dyeing is often not dense enough due to the uneven distribution of the sealing agent, especially the formation of yellow film on the surface of aluminum. This not only affects the appearance, but also reduces the corrosion resistance. The present invention introduces different surfactants into the medium-temperature sealing agent, and the synergistic effect significantly improves the dispersion uniformity of the sealing agent and the penetration ability of the oxide film, prevents the formation of yellow film, and improves the sealing effect. The surfactant can also reduce the surface tension of the sealing liquid, ensure that the sealing liquid is evenly covered on the surface of the aluminum alloy, and improve the density and corrosion resistance of the sealing film. After 120 hours of sealing with the agent, a copper-accelerated acetic acid salt spray test was performed, and it reached level 10 in 96 hours, which greatly improved the salt spray resistance of the aluminum alloy; the required tank liquid temperature during sealing is relatively low, there is no obvious corrosion mark, the durability is good, and it is suitable for long-term outdoor use.

[0099] In view of the fading problem of dyed oxide film in long-term use in the prior art, the present invention uses specially designed color fixing aids (such as tannic acid, gallic acid, quercetin, ellagic acid, catechin, etc.), and the active ingredients in the color fixing aids form stable chemical bonds with the dye molecules. At the same time, the water-soluble groups of the dye are blocked during the sealing process to generate stable color lakes, effectively lock the dye molecules, and prevent the dye from migrating, so that the dyed film can maintain excellent color stability and anti-fading ability even when exposed to high temperature and high humidity for a long time. This innovation solves the fading problem of dyed oxide film and is suitable for aluminum alloy products used outdoors. The dyed film treated with the medium-temperature sealing agent of the present invention was tested for fading under high temperature and high humidity conditions. The results show that after 96 hours of copper accelerated salt spray test and ultraviolet accelerated aging test, the color retention rate of the film layer reaches more than 90%, compared with the film layer that does not use the medium-temperature sealing agent of the present invention, and its color retention rate is only about 70%.

[0100] The current technology usually performs color fixation and sealing in steps after dyeing. This separation process leads to process discontinuity between sealing and color fixation, and is prone to uneven color fixation or cross interference between the sealer and the color fixer, which in turn affects the compactness and durability of the oxide film. The medium-temperature sealer of the present invention realizes the process improvement of color fixation and sealing integration. During the sealing process, the color fixation auxiliary agent acts on the oxide film and the dye molecules at the same time, realizing the simultaneous color fixation of the dye and the sealing of the oxide film, simplifying the process steps and greatly improving the color fixation effect of the dyed film. The surface condition of the aluminum alloy after sealing shows that the surface is smooth and spotless, there is no sealing powder frost, no sticky fingerprints and film, and the appearance of the anodized film does not change. The ink is easy to wipe off, and the weight loss results also meet the requirements of national standards, with good corrosion resistance.

Claims

1. A medium-temperature sealing agent, characterized in that: Including sealing main salt, sealing secondary salt, color fixing agent, auxiliary agent; The sealing main salt includes nickel acetate or nickel acetate hydrate; The sealing secondary salt includes at least one of cobalt acetate, magnesium acetate, lithium acetate and calcium acetate; The color fixing auxiliary agent includes at least one of tannic acid, gallic acid, quercetin, ellagic acid, tannic acid and catechin.

2. The medium-temperature sealing agent according to claim 1, characterized in that: The auxiliary agent includes at least one of a pH stabilizer, a complexing agent, a corrosion inhibitor, a promoter, an ash suppressant, and a surfactant.

3. The medium-temperature sealing agent according to claim 1, characterized in that: The nickel acetate hydrate includes nickel acetate tetrahydrate.

4. The medium-temperature sealing agent according to claim 1, characterized in that: The pH stabilizer is selected from at least one of boric acid, ammonium acetate, tartaric acid, and potassium hydrogen phthalate; and / or the complexing agent is selected from at least one of potassium sodium tartrate, ethylenediaminetetraacetic acid, sodium polyphosphate, and sodium citrate.

5. The medium-temperature sealing agent according to claim 1, characterized in that: The corrosion inhibitor is selected from at least one of benzotriazole, glycerol, and ammonium dihydrogen phosphate; and / or the accelerator is selected from at least one of ammonium sulfate, thiourea, and urea; and / or the ash suppressant is selected from organic phosphonic acid; and / or the surfactant includes at least one of polyethylene glycol laurate, sodium lignin sulfonate, sodium dodecyl sulfate, and γ-aminopropyltriethoxysilane.

6. The medium-temperature sealing agent according to any one of claims 1 to 5, characterized in that: The medium-temperature sealing agent comprises, by weight, 65-85 parts of a main sealing salt, 4-10 parts of a secondary sealing salt, 2-9 parts of a color fixing auxiliary agent, and 5-20 parts of an auxiliary agent.

7. The medium-temperature sealing agent according to claim 2, characterized in that: The auxiliary agents include pH stabilizers, complexing agents, corrosion inhibitors, promoters, ash inhibitors and surfactants, and the medium-temperature sealing agent, by weight, includes 70-85 parts of sealing main salt, 5-8 parts of sealing secondary salt, 3-5 parts of color fixing auxiliary agent, 2-3 parts of pH stabilizer, 5-8 parts of complexing agent, 0.2-0.5 parts of corrosion inhibitor, 0.1-0.3 parts of promoter, 0.1-0.3 parts of ash inhibitor and 1-2 parts of surfactant.

8. The preparation method according to any one of claims 1 to 7, characterized in that: The following steps are involved: The components are mixed to obtain the medium-temperature sealing agent.

9. Use of the medium-temperature sealing agent according to any one of claims 1 to 7 in the surface treatment of aluminum alloys containing oxide films on the surface.

10. The method for using the medium-temperature sealing agent according to any one of claims 1 to 7, characterized in that: The following steps are involved: The aluminum alloy workpiece with an oxide film on the surface is dyed and then placed in an aqueous solution of a medium-temperature sealing agent for sealing.

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