Method for improving anodic oxidation shielding effect of aluminum alloy

Abstract

The invention relates to a method for improving the anodic oxidation shielding effect of an aluminum alloy, which comprises the following steps: sequentially carrying out polishing treatment, primary acid pickling, primary water washing, primary alkali washing, secondary water washing, secondary acid pickling, tertiary water washing and drying treatment on a to-be-shielded area of the aluminum alloy, and then arranging a shielding material in the to-be-shielded area of the aluminum alloy, and flattening treatment is carried out, and shielding treatment is completed. According to the method, the adhesiveness of the adhesive tape on the aluminum alloy surface can be effectively improved, and the problem of local liquid leakage of the adhesive tape in the anodic oxidation process is effectively solved.

Description

Technical Field

[0001] This invention relates to the field of masking technology for aluminum and aluminum alloy products, and in particular to a method for improving the masking effect of aluminum alloy anodizing. Background Technology

[0002] To overcome the shortcomings of aluminum alloys in terms of surface hardness and wear resistance, and to extend their service life, surface treatment technology has become an indispensable part of aluminum alloy use, and anodizing technology is currently the most widely used and successful. Under appropriate electrolyte and specific process conditions, aluminum and its alloys form an oxide film on aluminum products under the action of an applied current; this means that currently manufactured products must be immersed in a specific solution for a period of time.

[0003] However, traditional local anodizing usually uses tape to mask the non-oxidized surface. The tape masking is usually done before anodizing. Under normal conditions, the tape masking has poor adhesion. During the anodizing process, the tape may peel off or penetrate in some places, causing the non-oxidized surface to be oxidized and then need to be locally polished or stripped and re-anodized.

[0004] CN117721508A discloses a method for masking the roller-printed areas of an aluminum alloy workpiece during hard anodizing, comprising: Step 1, pretreatment: pretreatment of the roller-printed areas of the aluminum alloy workpiece; Step 2, masking and protection: setting masking material on the outside of the roller-printed areas and allowing it to stand for a preset time t; Step 3, determining whether there are gaps at the edges of the roller-printed areas after standing; if yes, applying adhesive and repeating Step 3; otherwise, proceeding to Step 4; Step 4, hard anodizing; Step 5, post-treatment: sealing the holes in the anodized aluminum alloy workpiece and removing the masking material, but this requires the use of adhesive for masking, leading to increased costs.

[0005] CN101403117A discloses a composite oxidation process for the surface of aluminum or aluminum alloy products. The process includes first performing conductive oxidation treatment on all surfaces of the aluminum or aluminum alloy products, then shielding and protecting the surfaces that need to be conductive, then performing anodizing treatment on the products, and finally removing the shielding material from the conductive surfaces. The entire process flow and reagent formulation involve using multiple materials for shielding treatment and require the use of specific removal agents to remove the shielding materials, which leads to increased costs.

[0006] CN112442719A uses degreasing, alkaline washing, one water wash, acid washing, two water washes and drying. After that, the bottom surface and side walls of the sinkhole are polished. Then, tape is applied to the bottom surface of the sinkhole, and finally, sealing and anti-corrosion glue is applied to complete the masking. However, it requires glue to mask the edges of the tape, and a smooth oxidation boundary line cannot be obtained. It is very easy to have jagged edges, which affects the appearance of the product.

[0007] The existing technology described above uses tape and adhesive for masking on vertical surfaces. This method is challenging to control the smoothness of the masked edges, especially on vertical surfaces, easily resulting in jagged edges that affect the product's appearance. Customers may have to accept the masking, or the edges may need to be manually polished. Manual polishing can damage the anodized film, and using high-adhesion tape is costly. Therefore, there is an urgent need for a new masking method for aluminum alloy anodizing that can improve the masking effect and achieve a smooth anodized boundary line. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention provides a method for improving the masking effect of aluminum alloy anodizing. The method of this invention, through a combination of polishing and chemical treatment, achieves a clean aluminum alloy surface, effectively improves the adhesion of the adhesive tape, and prevents leakage at the masked areas during the anodizing process.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] This invention provides a method for improving the masking effect of anodizing aluminum alloys, the method comprising:

[0011] The aluminum alloy area to be shielded is subjected to polishing, pickling, water washing, alkaline washing, water washing, pickling, water washing, and drying in sequence. Then, the shielding material is placed on the aluminum alloy area to be shielded and flattened to complete the shielding process.

[0012] This invention achieves a clean aluminum alloy surface through a combination of polishing and chemical treatment. Subsequently, a masking material is used for masking and flattening to ensure no gaps between the masking material and the aluminum alloy surface. This effectively solves the problem of insufficient adhesion of ordinary tape, which easily detaches during oxidation. It also avoids localized leakage of the tape during anodizing. The method of this invention has the advantages of low cost, convenient operation, and high practicality.

[0013] The method of the present invention eliminates the need for polishing the aluminum alloy surface after chemical treatment, is not limited to the masking position and can be used for vertical surface masking, and does not require adhesive to mask the edges of the tape, resulting in a smooth oxidation boundary line.

[0014] As a preferred technical solution of the present invention, the acid solution used for the primary pickling and secondary pickling includes nitric acid; the mass concentration of the nitric acid is 5-40%, such as 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, etc., but is not limited to the listed values, and other unlisted values ​​within the above range are also applicable.

[0015] Preferably, the processing temperature for the primary and secondary pickling is 15-25℃, such as 15℃, 17℃, 19℃, 21℃, 23℃, 25℃, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0016] Preferably, the processing time for the first and second pickling is 2-20 minutes, such as 2 minutes, 5 minutes, 8 minutes, 10 minutes, 12 minutes, 15 minutes, 18 minutes, 20 minutes, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0017] As a preferred technical solution of the present invention, the processing time for the first, second and third water washes is 5-20 minutes, such as 5 minutes, 8 minutes, 10 minutes, 12 minutes, 15 minutes, 18 minutes, 20 minutes, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0018] Preferably, the processing temperature for the first, second, and third water washes is 20-25℃, such as 20℃, 21℃, 22℃, 23℃, 24℃, 25℃, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0019] As a preferred technical solution of the present invention, the alkaline solution used in the first alkaline washing includes sodium hydroxide; the mass concentration of the sodium hydroxide is 2-15%, such as 2%, 5%, 8%, 10%, 12%, 15%, etc., but is not limited to the listed values, and other unlisted values ​​within the above range are also applicable.

[0020] Preferably, the treatment temperature of the first alkaline washing is 15-25℃, such as 15℃, 17℃, 19℃, 21℃, 23℃, 25℃, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0021] Preferably, the treatment time for the first alkaline wash is 2-20 minutes, such as 2 minutes, 5 minutes, 8 minutes, 10 minutes, 12 minutes, 15 minutes, 18 minutes, 20 minutes, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0022] As a preferred embodiment of the present invention, the drying process includes drying with compressed air or drying with an oven.

[0023] As a preferred embodiment of the present invention, the shielding material includes adhesive tape; the adhesive tape includes 701 adhesive tape.

[0024] As a preferred technical solution of the present invention, the flattening process includes pressing the edges of the masking material using a special tool or scraper.

[0025] It should be noted that in this invention, if the tape is not immediately covered, dust and other impurities in the air will adhere to the aluminum alloy surface, affecting the adhesion of the tape.

[0026] As a preferred technical solution of the present invention, the method further includes repeatedly performing acid washing, water washing, alkaline washing, water washing, acid washing, water washing, and drying on the aluminum alloy that has undergone the masking treatment, followed by anodizing and sealing treatment to remove the masking material and obtain anodized aluminum alloy.

[0027] It should be noted that, in this invention, the masking material can be removed before or after sealing the holes, and those skilled in the art can make adjustments according to the actual situation.

[0028] As a preferred embodiment of the present invention, the electrolyte for the anodizing treatment is an acidic solution; the acidic solution includes sulfuric acid.

[0029] Preferably, the mass fraction of the acidic solution is 12-18%, such as 12%, 13%, 14%, 15%, 16%, 17%, 18%, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0030] Preferably, the anodizing treatment time is 90-120 min, such as 90 min, 95 min, 100 min, 105 min, 110 min, 115 min, 120 min, etc., but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0031] As a preferred technical solution of the present invention, the method includes:

[0032] The aluminum alloy area to be shielded is subjected to polishing, pickling, water washing, alkaline washing, water washing, pickling, water washing, and drying in sequence. Then, the shielding material is placed on the aluminum alloy area to be shielded and flattened to complete the shielding process.

[0033] The acid solution used for the first and second pickling processes includes nitric acid; the mass concentration of the nitric acid is 5-40%; the processing temperature for the first and second pickling processes is 15-25℃; the processing time for the first and second pickling processes is 2-20 minutes; the processing time for the first, second, and third water rinsing processes is 5-20 minutes; the processing temperature for the first, second, and third water rinsing processes is 20-25℃; the alkaline solution used for the first alkaline wash includes sodium hydroxide; the mass concentration of the sodium hydroxide is 2-15%; the processing temperature for the first alkaline wash is 15-25℃; the processing time for the first alkaline wash is 2-20 minutes.

[0034] The drying process includes drying with compressed air or drying in an oven; the masking material includes tape; the tape includes 701 tape; the flattening process includes pressing the edges of the masking material with a special tool or scraper;

[0035] The method further includes repeatedly subjecting the masked aluminum alloy to a series of processes: pickling, water washing, alkaline washing, water washing, pickling, and water washing, followed by drying. Then, anodizing and sealing are performed to remove the masking material, resulting in an anodized aluminum alloy. The electrolyte for the anodizing process is an acidic solution, including sulfuric acid. The mass fraction of the acidic solution is 12-18%. The anodizing time is 90-120 minutes.

[0036] Compared with the prior art, the present invention has at least the following beneficial effects:

[0037] The method of this invention obtains a clean aluminum alloy surface through polishing combined with chemical treatment; subsequently, a masking material is used for masking and flattening treatment to improve the adhesion of the tape and avoid the problem of local leakage of the tape during the anodizing process. The method of this invention has the advantages of low cost, convenient operation and strong practicality. Detailed Implementation

[0038] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0039] Example 1

[0040] This embodiment provides a method for improving the masking effect of aluminum alloy anodizing, the method comprising:

[0041] After polishing the aluminum alloy area to be masked, it is pickled once with 5% nitric acid at 15°C for 2 minutes; then rinsed with pure water at 20°C for 5 minutes; then alkali-washed once with 2% sodium hydroxide at 15°C for 2 minutes; then rinsed a second time with pure water at 20°C for 5 minutes; then pickled again with 5% nitric acid at 15°C for 2 minutes; then rinsed a third time with pure water at 20°C for 5 minutes; then dried with compressed air; the tape is placed on the aluminum alloy area to be masked, and the edges of the tape are pressed with a scraper to complete the masking process;

[0042] The method further includes repeatedly performing pickling, water washing, alkaline washing, water washing, acid washing, and drying on the masked aluminum alloy, followed by anodizing treatment with 12% sulfuric acid for 90 minutes, then sealing treatment, and removing the masking material to obtain anodized aluminum alloy.

[0043] Example 2

[0044] This embodiment provides a method for improving the masking effect of aluminum alloy anodizing, the method comprising:

[0045] After polishing the aluminum alloy area to be masked, it is pickled once with 20% nitric acid at 20°C for 10 minutes; then rinsed once with pure water at 22°C for 10 minutes; then alkali-washed once with 10% sodium hydroxide at 20°C for 10 minutes; then rinsed a second time with pure water at 22°C for 10 minutes; then pickled again with 20% nitric acid at 20°C for 10 minutes; and finally rinsed a third time with pure water at 22°C for 10 minutes. Afterwards, it is dried in an oven. Adhesive tape is then placed on the aluminum alloy area to be masked, and the edges of the tape are pressed down using a special tool to complete the masking process.

[0046] The method further includes repeatedly performing pickling, water washing, alkaline washing, water washing, acid washing, and drying on the masked aluminum alloy, followed by anodizing treatment with 15% sulfuric acid for 100 minutes, then sealing treatment, and removing the masking material to obtain anodized aluminum alloy.

[0047] Example 3

[0048] This embodiment provides a method for improving the masking effect of aluminum alloy anodizing, the method comprising:

[0049] After polishing the aluminum alloy area to be masked, it is pickled once with 40% nitric acid at 25°C for 20 minutes; then rinsed once with pure water at 25°C for 20 minutes; then alkali-washed once with 15% sodium hydroxide at 25°C for 20 minutes; then rinsed a second time with pure water at 25°C for 20 minutes; then pickled again with 40% nitric acid at 25°C for 20 minutes; and finally rinsed a third time with pure water at 25°C for 20 minutes. Afterwards, it is dried in an oven. Adhesive tape is then placed on the aluminum alloy area to be masked, and the edges of the tape are pressed down using a special tool to complete the masking process.

[0050] The method further includes repeatedly performing pickling, water washing, alkaline washing, water washing, acid washing, and drying on the masked aluminum alloy, followed by anodizing treatment with 18% sulfuric acid for 120 minutes, then sealing treatment, and removing the masking material to obtain anodized aluminum alloy.

[0051] Example 4

[0052] This embodiment provides a method for improving the masking effect of aluminum alloy anodizing. The only difference from Embodiment 1 is that the mass concentration of the alkaline solution used in the first alkaline washing is adjusted to 0.5%, while the other steps and conditions are the same as in Embodiment 1.

[0053] Example 5

[0054] This embodiment provides a method for improving the masking effect of aluminum alloy anodizing. The only difference from Embodiment 1 is that the mass concentration of the alkaline solution used in the first alkaline washing is adjusted to 20%, while the other steps and conditions are the same as in Embodiment 1.

[0055] Example 6

[0056] This embodiment provides a method for improving the masking effect of aluminum alloy anodizing. The only difference from Embodiment 1 is that the mass concentration of the acid solution used in the first pickling is adjusted to 2%, while the other steps and conditions are the same as in Embodiment 1.

[0057] Example 7

[0058] This embodiment provides a method for improving the masking effect of aluminum alloy anodizing. The only difference from Embodiment 1 is that the mass concentration of the acid solution used in the first pickling is adjusted to 50%, while the other steps and conditions are the same as in Embodiment 1.

[0059] Comparative Example 1

[0060] This comparative example provides a method for improving the masking effect of aluminum alloy anodizing. The only difference from Example 1 is that the flattening treatment is not performed, while the other steps and conditions are the same as in Example 1.

[0061] Comparative Example 2

[0062] This comparative example provides a method for improving the masking effect of aluminum alloy anodizing. The only difference from Example 1 is that the polishing treatment, one acid pickling, one water washing, one alkali washing, two water washing, two acid pickling, three water washing and drying treatment are not performed. The masking material is simply placed on the aluminum alloy area to be masked. All other steps and conditions are the same as in Example 1.

[0063] Comparative Example 3

[0064] This comparative example provides a method for improving the masking effect of aluminum alloy anodizing. The only difference from Example 1 is that polishing is not performed, while the other steps and conditions are the same as in Example 1.

[0065] Comparative Example 4

[0066] This comparative example provides a method for improving the masking effect of aluminum alloy anodizing. The only difference from Example 1 is that the secondary pickling and tertiary water washing are not performed, while the other steps and conditions are the same as in Example 1.

[0067] Comparative Example 5

[0068] This comparative example provides a method for improving the masking effect of aluminum alloy anodizing. The only difference from Example 1 is that no acid pickling and water washing are performed, while the other steps and conditions are the same as in Example 1.

[0069] Performance testing

[0070] The masking effect on aluminum alloy anodizing was tested in Examples 1-7 and Comparative Examples 1-5, and the test results are shown in Table 1.

[0071] Table 1

[0072]

[0073] The test results show that:

[0074] (1) As can be seen from Examples 1 to 3, the present invention can obtain a clean aluminum alloy surface by combining polishing and chemical treatment; then, a masking material is used for masking and flattening treatment is performed to improve the adhesion of the tape and effectively avoid the problem of local leakage of the tape during the anodizing process.

[0075] (2) By comparing Example 1 with Examples 4-7, it can be seen that by optimizing the mass concentration of the solutions used for acid washing and alkaline washing, the present invention can further improve the adhesion of the tape and effectively avoid the problem of local leakage of the tape during the anodizing process.

[0076] (3) As can be seen from Example 1 and Comparative Examples 1-5, in Comparative Example 1, no flattening treatment was performed, which caused leakage at the edge of the masking material, resulting in a jagged edge that affected the product's appearance. In Comparative Example 2, no polishing, first pickling, first water washing, first alkaline washing, second water washing, second pickling, third water washing, and drying treatment were performed. The masking material was only placed in the aluminum alloy area to be masked, which caused serious leakage during the anodizing process. Local grinding or deplating and re-anodizing were required, increasing the processing cost. In Comparative Example 3, no polishing treatment was performed, which caused a decrease in the adhesion of the masking material and local leakage. In Comparative Example 4, no second pickling and third water washing were performed, which caused a decrease in the adhesion of the masking material and local leakage. In Comparative Example 5, no first pickling and first water washing were performed, which also caused a decrease in the adhesion of the masking material and local leakage.

[0077] In summary, this invention provides a method for improving the masking effect of aluminum alloy anodizing. By combining polishing with chemical treatment, a clean aluminum alloy surface can be obtained. Subsequently, a masking material is used for masking and flattening to ensure that there are no gaps between the masking material and the aluminum alloy surface. This effectively solves the problem of insufficient adhesion of ordinary tape, which makes it easy to fall off during the oxidation process. At the same time, it avoids the problem of local leakage of tape during the anodizing process. The method of this invention has the advantages of low cost, convenient operation, and strong practicality.

[0078] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for improving the masking effect of aluminum alloy anodizing, characterized in that, The method includes: sequentially polishing the aluminum alloy area to be shielded, performing a first pickling, a first water washing, a first alkaline washing, a second water washing, a second pickling, a third water washing, and drying; then placing the shielding material on the aluminum alloy area to be shielded and flattening it to complete the shielding process.

2. The method according to claim 1, characterized in that, The acid solution used in the primary and secondary pickling processes includes nitric acid; the mass concentration of the nitric acid is 5-40%. Preferably, the processing temperature for the primary and secondary pickling is 15-25℃; Preferably, the processing time for the first and second pickling is 2-20 minutes.

3. The method according to claim 1 or 2, characterized in that, The processing time for the first, second, and third water washes in step (1) is 5-20 minutes; Preferably, the processing temperature for the first, second, and third water washes is 20-25°C.

4. The method according to any one of claims 1-3, characterized in that, The alkaline solution used in the primary alkaline washing includes sodium hydroxide; the mass concentration of the sodium hydroxide is 2-15%. Preferably, the treatment temperature for the first alkaline washing is 15-25℃; Preferably, the treatment time for the first alkaline wash is 2-20 minutes.

5. The method according to any one of claims 1-4, characterized in that, The drying process includes drying with compressed air or drying in an oven.

6. The method according to any one of claims 1-5, characterized in that, The shielding material includes adhesive tape; the adhesive tape includes 701 adhesive tape.

7. The method according to any one of claims 1-6, characterized in that, The flattening process involves pressing the edges of the masking material using a special tool or scraper.

8. The method according to any one of claims 1-7, characterized in that, The method further includes repeatedly performing pickling, water washing, alkaline washing, water washing, acid washing, and drying on the shielded aluminum alloy, followed by anodizing and sealing treatment, removing the shielding material, and obtaining anodized aluminum alloy.

9. The method according to any one of claims 1-8, characterized in that, The electrolyte for the anodic oxidation treatment is an acidic solution; the acidic solution includes sulfuric acid. Preferably, the acidic solution has a mass fraction of 12-18%; Preferably, the anodizing treatment time is 90-120 min.

10. The method according to any one of claims 1-9, characterized in that, The method includes: The aluminum alloy area to be shielded is subjected to polishing, pickling, water washing, alkaline washing, water washing, pickling, water washing, and drying in sequence. Then, the shielding material is placed on the aluminum alloy area to be shielded and flattened to complete the shielding process. The acid solution used for the primary and secondary pickling includes nitric acid; the mass concentration of the nitric acid is 5-40%; the processing temperature for the primary and secondary pickling is 15-25℃; and the processing time for the primary and secondary pickling is 2-20 minutes. The processing time for the first, second, and third water washes is 5-20 minutes; the processing temperature for the first, second, and third water washes is 20-25°C. The alkaline solution used in the first alkaline wash includes sodium hydroxide; the mass concentration of the sodium hydroxide is 2-15%; the treatment temperature of the first alkaline wash is 15-25℃; the treatment time of the first alkaline wash in step (1) is 2-20 min; The drying process includes drying with compressed air or drying in an oven; the masking material includes tape; the tape includes 701 tape; the flattening process includes pressing the edges of the masking material with a special tool or scraper; The method further includes repeatedly subjecting the masked aluminum alloy to a series of processes: pickling, water washing, alkaline washing, water washing, pickling, and drying; followed by anodizing and sealing to remove the masking material, resulting in an anodized aluminum alloy. The electrolyte for the anodizing process is an acidic solution, which includes sulfuric acid. The mass fraction of the acidic solution is 12-18%. The anodizing time is 90-120 minutes.

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