Aluminum-based anodizing nickel-free medium-temperature sealing agent, preparation method thereof and aluminum-based anodizing sealing method

Abstract

This invention provides an aluminum-based nickel-free medium-temperature sealing agent for anodizing, its preparation method, and an aluminum-based anodizing sealing method, belonging to the technical field of sealing agents. By weight, the aluminum-based nickel-free medium-temperature sealing agent provided by this invention comprises the following components: 60-120 parts of lithium salt sealing agent, 2-10 parts of zirconium salt film-forming accelerator, 3-20 parts of titanium salt film-forming accelerator, 10-40 parts of small molecule organic carboxylate, 0.5-5 parts of nonionic surfactant, and 800-1200 parts of water. Using the aluminum-based nickel-free medium-temperature sealing agent provided by this invention, the appearance retention effect of the workpiece can be improved while meeting the nickel-free environmental protection requirements.

Description

Technical Field

[0001] This invention relates to the field of sealing agent technology, and in particular to an aluminum-based anodizing nickel-free medium-temperature sealing agent, its preparation method, and an aluminum-based anodizing sealing method. Background Technology

[0002] Aluminum alloys are widely used in construction, rail transportation, and 3C industries due to their excellent machinability and corrosion resistance. After sulfuric acid anodizing, a porous oxide film forms on the surface of the aluminum alloy. If this film is not sealed, the pores easily adsorb corrosive media and contaminants, resulting in insufficient corrosion resistance and stain resistance. Therefore, sealing treatment is usually required to close the pores and improve corrosion resistance and appearance stability.

[0003] In traditional sealing methods, nickel salt (such as nickel acetate) sealing technology is mature and easy to operate, but it poses a risk of heavy metal emissions. In recent years, there has been research on nickel-free sealing agents and sealing processes, mainly including lithium-ion-based medium-temperature or low-temperature sealing. However, in practical applications, these nickel-free sealing agents still face problems such as white bloom and reduced gloss on the workpiece surface after sealing, and the appearance still needs improvement. Summary of the Invention

[0004] The purpose of this invention is to provide an aluminum-based nickel-free medium-temperature sealing agent for anodizing, its preparation method, and an aluminum-based anodizing sealing method. Using the aluminum-based nickel-free medium-temperature sealing agent provided by this invention, the appearance retention effect of the workpiece can be improved while meeting the requirements of nickel-free environmental protection.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides an aluminum-based anodizing nickel-free medium-temperature sealing agent, comprising the following components by mass parts: The mixture contains 60-120 parts of lithium salt sealing agent, 2-10 parts of zirconium salt film-forming accelerator, 3-20 parts of titanium salt film-forming accelerator, 10-40 parts of small molecule organic carboxylate, 0.5-5 parts of nonionic surfactant, and 800-1200 parts of water.

[0006] Preferably, the lithium salt sealing agent includes one or more of lithium acetate, lithium carbonate, and lithium nitrate.

[0007] Preferably, the zirconium salt film-forming promoter includes one or more of fluorozirconate, zirconium sulfate, and zirconium oxychloride.

[0008] Preferably, the titanium salt film-forming promoter includes titanate and / or titanium-containing complex salt; the titanate is potassium titanate and / or sodium titanate, and the titanium-containing complex salt is one or more of titanium lactate, titanium citrate and titanium oxalate.

[0009] Preferably, the small molecule organic carboxylate includes one or more of citrate, gluconate and tartrate.

[0010] Preferably, the nonionic surfactant includes a polyether-type nonionic surfactant.

[0011] Preferably, the polyether-type nonionic surfactant includes one or more of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, and block polyether.

[0012] This invention provides a method for preparing the nickel-free intermediate-temperature sealing agent for aluminum-based anodizing as described above, comprising the following steps: The lithium salt sealing agent, the small molecule organic carboxylate, and a portion of water were mixed to obtain a first mixture. The first mixture, zirconium salt film-forming accelerator, and titanium salt film-forming accelerator are mixed a second time to obtain a second mixture; The second mixture, the nonionic surfactant, and the remaining water are mixed in a third mixture to obtain the aluminum-based anodizing nickel-free medium-temperature sealing agent.

[0013] This invention provides an aluminum-based anodizing sealing method, comprising the following steps: An aluminum-based anode is oxidized to obtain an oxide anode; The oxide anode is immersed in a sealing agent and sealed at 45~70℃; the sealing agent is the nickel-free medium-temperature sealing agent for aluminum-based anodizing as described in the above technical solution or the nickel-free medium-temperature sealing agent for aluminum-based anodizing prepared by the preparation method described in the above technical solution.

[0014] Preferably, the sealing process takes 5 to 25 minutes; The oxidation treatment and the sealing treatment also include a first water wash, the temperature of which is 20~30℃, and the pH value of the washing solution obtained after the first water wash is 6~7. The sealing process includes a second water wash, the temperature of which is 50~80℃ and the time is 30~120s.

[0015] Beneficial Effects: By weight, the nickel-free, medium-temperature sealing agent for aluminum-based anodizing provided by this invention comprises 60-120 parts of lithium salt sealing agent, 2-10 parts of zirconium salt film-forming promoter, 3-20 parts of titanium salt film-forming promoter, 10-40 parts of small molecule organic carboxylate, 0.5-5 parts of nonionic surfactant, and 800-1200 parts of water. This invention, by controlling the ratio of lithium salt, zirconium salt, and titanium salt, and introducing a mild small molecule organic carboxylate as a complexing buffer and a low-foaming nonionic surfactant for wetting and dispersing, enables the sealing process to achieve good pore sealing under medium-temperature conditions of 45-70℃. This reduces the heavy metal emission pressure caused by traditional nickel salt sealing and improves the surface whitening and gloss reduction problems that easily occur with related nickel-free sealing agents, resulting in better appearance retention. Compared with existing sealing methods, this invention improves the appearance retention of workpieces while meeting nickel-free environmental protection requirements, and is suitable for post-treatment of aluminum-based anodized films in building profiles and 3C exterior parts. Detailed Implementation

[0016] This invention provides an aluminum-based anodizing nickel-free medium-temperature sealing agent, comprising the following components by mass parts: The mixture contains 60-120 parts of lithium salt sealing agent, 2-10 parts of zirconium salt film-forming accelerator, 3-20 parts of titanium salt film-forming accelerator, 10-40 parts of small molecule organic carboxylate, 0.5-5 parts of nonionic surfactant, and 800-1200 parts of water.

[0017] The nickel-free, medium-temperature sealing agent for aluminum-based anodizing provided by this invention is suitable for sealing aluminum-based anodized films at temperatures ranging from 45 to 70°C, i.e., "medium temperature," specifically 45 to 70°C. The following is a detailed description of the nickel-free, medium-temperature sealing agent for aluminum-based anodizing according to this invention.

[0018] In this invention, unless otherwise specified, all raw materials used are commercially available products known to those skilled in the art or prepared using methods known to those skilled in the art.

[0019] By weight, the nickel-free, medium-temperature sealing agent for aluminum-based anodizing according to the present invention comprises 60-120 parts of lithium salt sealing agent, specifically 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, or 120 parts. In one embodiment of the present invention, the lithium salt sealing agent may include one or more of lithium acetate, lithium carbonate, and lithium nitrate. The present invention uses the above-mentioned types and amounts of lithium salt sealing agent as the main component of the sealing system. Under medium-temperature conditions, this promotes the hydration and sealing process within the pores of the anodized film, thereby improving the sufficiency of the sealing. Simultaneously, in the nickel-free system, lithium salt can serve as the main source of sealing activity, which is beneficial for meeting environmental protection requirements while also ensuring corrosion resistance and maintaining appearance.

[0020] Based on the mass fraction of the lithium salt sealing agent, the aluminum-based anodizing nickel-free medium-temperature sealing agent of this invention includes 2-10 parts of zirconium salt film-forming accelerator, specifically 2, 3, 4, 5, 6, 7, 8, 9, or 10 parts. In one embodiment of this invention, the zirconium salt film-forming accelerator may include one or more of fluorozirconate, zirconium sulfate, and zirconium oxychloride, wherein the fluorozirconate may include potassium fluorozirconate and / or sodium fluorozirconate. By employing the above-mentioned types and amounts of zirconium salt film-forming accelerators, this invention can regulate the densification process of the sealing layer, which is beneficial for improving film density and corrosion resistance.

[0021] Based on the mass fraction of the lithium salt sealing agent, the aluminum-based anodizing nickel-free medium-temperature sealing agent of this invention includes 3-20 parts of titanium salt film-forming accelerator, specifically 3, 5, 8, 10, 13, 15, 18, or 20 parts. In one embodiment of this invention, the titanium salt film-forming accelerator may include titanates and / or titanium-containing complex salts; the titanates may be potassium titanate and / or sodium titanate, and the titanium-containing complex salts may be one or more of titanium lactate, titanium citrate, and titanium oxalate. This invention uses the above-mentioned types and amounts of titanium salt film-forming accelerators, which can regulate the densification process of the sealing layer, thus improving the sealing rate and workpiece appearance uniformity. When used in combination with zirconium salt film-forming accelerators, it can balance the adequacy of sealing and the uniformity of appearance.

[0022] Based on the mass fraction of the lithium salt sealing agent, the aluminum-based anodizing nickel-free medium-temperature sealing agent of this invention comprises 10-40 parts of small molecule organic carboxylate, specifically 10, 15, 20, 25, 30, 35, or 40 parts. In one embodiment of this invention, the small molecule organic carboxylate may include one or more of citrate, gluconate, and tartrate. The citrate may be sodium citrate, the gluconate may be sodium gluconate, and the tartrate may be sodium potassium tartrate and / or potassium tartrate. This invention uses the above-mentioned types and amounts of small molecule organic carboxylate, which can stabilize metal ions and buffer pH fluctuations during the sealing process. Simultaneously, compared to high-molecular-weight polycarboxylates, the organic carboxylates (such as citrate, gluconate, or tartrate) used in this invention have smaller molecular weights, resulting in lower impact on system viscosity, which is more conducive to maintaining the clarity and low foaming of the aluminum-based anodizing nickel-free medium-temperature sealing agent. Furthermore, their complexation strength is relatively mild, which helps to stabilize metal ions while avoiding excessive complexation that could affect the sealing effect.

[0023] Based on the mass fraction of the lithium salt sealing agent, the aluminum-based anodizing nickel-free medium-temperature sealing agent of this invention comprises 0.5 to 5 parts of nonionic surfactant, specifically 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, or 5 parts. In one embodiment of this invention, the nonionic surfactant may include a polyether-type nonionic surfactant, which may include one or more of fatty alcohol polyoxyethylene ether (AEO), alkylphenol polyoxyethylene ether, and block polyether; specifically, the AEO may be one or more of AEO-3, AEO-5, and AEO-6. The use of the above-mentioned types and amounts of nonionic surfactants in this invention helps reduce bubble adhesion and decrease white bloom and watermarks after sealing. Specifically, the above-mentioned types of nonionic surfactants have low foaming properties and low sensitivity to metal ion systems, reducing foam introduction and surface residue during sealing. Compared with anionic surfactants, they are more effective in mitigating white bloom, watermarks, and gloss fluctuations after sealing.

[0024] Based on the mass fraction of the lithium salt sealing agent, the aluminum-based anodizing nickel-free medium-temperature sealing agent of the present invention comprises 800-1200 parts of water, specifically 800 parts, 850 parts, 900 parts, 950 parts, 1000 parts, 1050 parts, 1100 parts, 1150 parts, or 1200 parts. In one embodiment of the present invention, the water may be deionized water.

[0025] This invention provides a method for preparing the nickel-free intermediate-temperature sealing agent for aluminum-based anodizing as described above, comprising the following steps: The lithium salt sealing agent, the small molecule organic carboxylate, and a portion of water were mixed to obtain a first mixture. The first mixture, zirconium salt film-forming accelerator, and titanium salt film-forming accelerator are mixed a second time to obtain a second mixture; The second mixture, the nonionic surfactant, and the remaining water are mixed in a third mixture to obtain the aluminum-based anodizing nickel-free medium-temperature sealing agent.

[0026] In one embodiment of the present invention, the volume of the water portion is 70-85% of the total water volume, specifically 70%, 75%, 80%, or 85%. In another embodiment of the present invention, the first mixing can be: adding a small molecule organic carboxylate and a lithium salt sealing agent sequentially to the water portion, and stirring until all components are completely dissolved to obtain the first mixture.

[0027] In one embodiment of the present invention, the second mixing can be: adding zirconium salt film-forming promoter and titanium salt film-forming promoter to the first mixture, stirring until the material is clear, and obtaining the second mixture.

[0028] In one embodiment of the present invention, the third mixing can be: adding a nonionic surfactant and the remaining water to the second mixture in sequence, stirring and mixing evenly to obtain the aluminum-based anodizing nickel-free medium-temperature sealing agent.

[0029] This invention provides an aluminum-based anodizing sealing method, comprising the following steps: An aluminum-based anode is oxidized to obtain an oxide anode; The oxide anode is immersed in a sealing agent and sealed at 45~70℃; the sealing agent is the nickel-free medium-temperature sealing agent for aluminum-based anodizing as described in the above technical solution or the nickel-free medium-temperature sealing agent for aluminum-based anodizing prepared by the preparation method described in the above technical solution.

[0030] This invention involves oxidizing an aluminum-based anode to obtain an oxide anode. In one embodiment, the aluminum-based anode can be an aluminum anode or an aluminum alloy anode, specifically a 6063, 6061, or 6060 aluminum alloy anode. In another embodiment, the aluminum-based anode is placed in a sulfuric acid anodizing solution for oxidation to form an anodic oxide film, thus obtaining the oxide anode. The concentration of the sulfuric acid anodizing solution can be 150-200 g / L, specifically 180 g / L; the oxidation temperature can be 18-22°C, specifically 20°C; the voltage can be 12-18V, specifically 15V; and the time can be 20-40 min, specifically 30 min.

[0031] After obtaining the oxide anode, the present invention immerses the oxide anode in a sealing agent and performs sealing treatment at 45~70℃; the sealing agent is the nickel-free medium-temperature sealing agent for aluminum-based anodizing described in the above technical solution or the nickel-free medium-temperature sealing agent for aluminum-based anodizing prepared by the preparation method described in the above technical solution. As an embodiment of the present invention, the oxidation treatment and the sealing treatment preferably include a first water wash, the temperature of the first water wash is 20~30℃, specifically the first water wash can be performed at room temperature (25℃); the pH value of the washing solution obtained after the first water wash is preferably 6~7. As an embodiment of the present invention, the first water wash includes sequential tap water washing and deionized water washing; the number of tap water washings can be 1~2 times, the time of each tap water washing can be 20~60s, specifically 20s, 30s, 40s, 50s or 60s; the number of deionized water washings can be 1 time, and after deionized water washing, the workpiece surface should have no obvious liquid residue, no acidic odor residue, and the pH value of the washing solution should be 6~7.

[0032] The sealing temperature described in this invention is 45~70℃, specifically 45℃, 50℃, 55℃, 60℃, 65℃, or 70℃; the sealing time is 5~25min, specifically 5min, 10min, 15min, 20min, or 25min. As one embodiment of this invention, the sealing treatment preferably includes a second water rinse, which can be a rinsing process; the temperature of the second water rinse can be 50~80℃, specifically 50℃, 60℃, 70℃, or 80℃, and the time can be 30~120s, specifically 30s, 50s, 80s, 100s, or 120s. As one embodiment of this invention, the second water rinse preferably includes drying. This invention, through the second water rinse, can remove residual aluminum-based anodized nickel-free medium-temperature sealing agent from the workpiece surface and reduce watermarks after drying.

[0033] The nickel-free, medium-temperature sealing agent for aluminum-based anodizing provided by this invention uses lithium salt as the main medium-temperature sealing system, introduces a small amount of zirconium salt and titanium salt as pore densification promoting components, and is compounded with a mild small-molecule organic carboxylic acid complexing buffer and a low-foaming nonionic surfactant. Using this nickel-free, medium-temperature sealing agent for aluminum-based anodizing to seal the anodized anode results in a lower white bloom defect rate, higher gloss retention, reduced anodic oxide film weight loss, and improved salt spray corrosion resistance. Furthermore, this nickel-free, medium-temperature sealing agent for aluminum-based anodizing also exhibits good clarity and stability. The preparation method of the nickel-free, medium-temperature sealing agent for aluminum-based anodizing provided by this invention is simple to operate, suitable for mass production, and has a wide medium-temperature sealing process window, good sealing uniformity and batch consistency, improving corrosion resistance and appearance retention under the premise of nickel-free environmental protection.

[0034] The technical solutions of this invention will be clearly and completely described below with reference to the embodiments thereof. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0035] Examples 1-3 Small molecule organic carboxylate and lithium salt sealing agent were added sequentially to a portion of water (80% of the total water volume) and stirred until all components were completely dissolved to obtain a first mixture. Zirconium salt film-forming accelerator and titanium salt film-forming accelerator were added to the first mixture and stirred until the material was clear to obtain a second mixture. Nonionic surfactant and remaining water were added sequentially to the second mixture and stirred until uniform to obtain an aluminum-based anodizing nickel-free medium-temperature sealing agent. The formulations of the aluminum-based anodizing nickel-free medium-temperature sealing agents in each embodiment are shown in Table 1.

[0036] Table 1. Formulations (parts by mass) of nickel-free medium-temperature sealing agents for aluminum-based anodizing in Examples 1-3

[0037] Comparative Example 1 A nickel-free medium-temperature sealing agent for aluminum-based anodizing was prepared according to Example 1, except that the titanium salt film-forming promoter was replaced with deionized water.

[0038] Comparative Example 2 A nickel-free medium-temperature sealing agent for aluminum-based anodizing was prepared according to Example 1, except that the zirconium salt film-forming accelerator and the titanium salt film-forming accelerator were replaced with deionized water.

[0039] Comparative Example 3 A nickel-free, medium-temperature sealing agent for aluminum-based anodizing was prepared according to Example 1, except that the small molecule organic carboxylate was replaced with deionized water.

[0040] Comparative Example 4 A nickel-free medium-temperature sealing agent for aluminum-based anodizing was prepared according to Example 1, except that the nonionic surfactant was replaced with an anionic surfactant (specifically sodium dodecyl sulfonate).

[0041] Test Example 1 The 6063 aluminum alloy anode was placed in a sulfuric acid anodizing solution (specifically, sulfuric acid with a concentration of 180 g / L) and oxidized for 30 min at a temperature of 20°C and a voltage of 15 V. After that, it was washed twice with tap water at room temperature (25°C) for 40 s each time, and then washed once with deionized water until the pH of the resulting washing solution was 7, thus obtaining the oxidized anode. The sealing agents prepared in each example and comparative example were placed in sealing tanks, and the oxidized anodes were immersed in the sealing agents respectively. The sealing treatment was carried out at 55°C for 15 min, followed by rinsing with hot water at 70°C for 80 s, and then drying to obtain the workpiece to be tested.

[0042] The workpiece under test was subjected to performance testing, and the results are shown in Table 2. The testing items were performed as follows: White frost defect rate: The percentage of samples with visible white frost on the surface of the workpiece under test is statistically analyzed. Gloss retention rate: The gloss value at 60° of the workpiece before and after the sealing treatment is measured and calculated as a percentage; Weight loss by phosphochromic acid method: The sealing quality is tested according to the phosphochromic acid method; Salt spray test: Conducted according to the GB / T 10125 Neutral Salt Spray Test (NSS) method; Tank solution clarity: Observe whether the tank solution is clear and whether there are any suspended matter or sediment; 7-day stability of the solution: After standing at room temperature for 7 days, observe whether it becomes cloudy, precipitates sediment, and returns to the state after stirring.

[0043] As shown in Table 2, the sealing agents used in Examples 1-3 of this invention have excellent sealing effects on the oxide anodes. While meeting the nickel-free environmental protection requirements, they also improve the appearance retention of the workpiece, and the bath solution exhibits good clarity and stability. In contrast, Comparative Examples 1-2, which do not use titanium or zirconium salts, show a significant increase in the white bloom defect rate and weight loss in the phosphochromic acid method, resulting in a decrease in the appearance retention of the workpiece and a certain impact on the clarity and stability of the bath solution. Comparative Example 3, which does not use small-molecule organic carboxylate salts, shows a decrease in the appearance retention of the workpiece. Comparative Example 4, which uses anionic surfactants, shows a significant increase in the white bloom defect rate, a decrease in gloss retention, and a significant decrease in the appearance retention of the workpiece.

[0044] Table 2. Effects of sealing agents prepared in each example and comparative example

[0045] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An aluminum-based anodizing nickel-free medium-temperature sealing agent, comprising the following components by mass parts: The mixture contains 60-120 parts of lithium salt sealing agent, 2-10 parts of zirconium salt film-forming accelerator, 3-20 parts of titanium salt film-forming accelerator, 10-40 parts of small molecule organic carboxylate, 0.5-5 parts of nonionic surfactant, and 800-1200 parts of water.

2. The aluminum-based anodizing nickel-free medium-temperature sealing agent according to claim 1, characterized in that, The lithium salt sealing agent includes one or more of lithium acetate, lithium carbonate, and lithium nitrate.

3. The aluminum-based anodizing nickel-free medium-temperature sealing agent according to claim 1, characterized in that, The zirconium salt film-forming promoter includes one or more of fluorozirconate, zirconium sulfate, and zirconium oxychloride.

4. The aluminum-based anodizing nickel-free medium-temperature sealing agent according to claim 1, characterized in that, The titanium salt film-forming promoter includes titanates and / or titanium-containing complex salts; the titanates are potassium titanate and / or sodium titanate, and the titanium-containing complex salts are one or more of titanium lactate, titanium citrate, and titanium oxalate.

5. The aluminum-based anodizing nickel-free medium-temperature sealing agent according to claim 1, characterized in that, The small molecule organic carboxylic acid salts include one or more of citrate, gluconate, and tartrate.

6. The aluminum-based anodizing nickel-free medium-temperature sealing agent according to claim 1, characterized in that, The nonionic surfactant includes polyether-type nonionic surfactants.

7. The aluminum-based anodizing nickel-free medium-temperature sealing agent according to claim 6, characterized in that, The polyether-type nonionic surfactant includes one or more of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, and block polyether.

8. A method for preparing the aluminum-based anodizing nickel-free medium-temperature sealing agent according to any one of claims 1 to 7, comprising the following steps: The lithium salt sealing agent, the small molecule organic carboxylate, and a portion of water were mixed to obtain a first mixture. The first mixture, zirconium salt film-forming accelerator, and titanium salt film-forming accelerator are mixed a second time to obtain a second mixture; The second mixture, the nonionic surfactant, and the remaining water are mixed in a third mixture to obtain the aluminum-based anodizing nickel-free medium-temperature sealing agent.

9. A method for sealing pores in aluminum-based anodizing, comprising the following steps: An aluminum-based anode is oxidized to obtain an oxide anode; The oxide anode is immersed in a sealing agent and sealed at 45-70°C; the sealing agent is the aluminum-based anodizing nickel-free medium-temperature sealing agent according to any one of claims 1-7 or the aluminum-based anodizing nickel-free medium-temperature sealing agent prepared by the preparation method of claim 8.

10. The aluminum-based anodizing sealing method according to claim 9, characterized in that, The sealing process takes 5 to 25 minutes. The oxidation treatment and the sealing treatment also include a first water wash, the temperature of which is 20~30℃, and the pH value of the washing solution obtained after the first water wash is 6~7. The sealing process includes a second water wash, the temperature of which is 50~80℃ and the time is 30~120s.

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