TWI905723B - Processing method for forming aluminum alloy surface with fine texture and matte appearance - Google Patents

Abstract

A processing method for forming an aluminum alloy surface with fine texture and a matte appearance includes the following steps. Firstly, an aluminum alloy surface is chemically polished to have a gloss at a 60° angle between 10 GU and 1000 GU. Next, an electrolytic treatment is performed on the polished aluminum alloy surface. In the electrolytic treatment, a current density ranges from 0.01 A/dm ²to 1.5 A/dm ², a voltage gradually increases from 0V to 50V, and a process time ranges from 3 minutes to 30 minutes. Afterwards, an anodized treatment is performed on the electrolytically treated aluminum alloy surface. In the anodized treatment, a current density ranges from 0.1 A/dm ²to 2.5 A/dm ², a voltage ranges from 10V to 20V, and a process time ranges from 30 minutes to 120 minutes. The anodized aluminum alloy surface has a unique white ceramic texture. The texture is represented by a fine-textured aluminum alloy surface with a matte surface.

Description

Aluminum alloy surface treatment methods with a fine texture and matte finish

This invention relates to a method for treating aluminum alloy surfaces, and more particularly to a method for treating aluminum alloy surfaces with a fine texture and a matte finish, suitable for treating aluminum alloy objects to integrate the texture of ceramics into the aluminum alloy surface, thereby improving the appearance and texture of the product, and the appearance color can be adjusted.

Today's portable electronic products are mostly designed to be thin, light, and compact. Aluminum alloys, with their excellent mechanical properties and light weight, have become a popular material for manufacturing the outer casings or other mechanical parts of portable electronic products. Aluminum alloy parts are generally subjected to surface treatments such as anodizing to enhance their appearance and durability.

CN 102312263 A discloses a ceramic oxidation method for aluminum parts, which uses an oxidation solution containing chromic acid, citric acid, nickel sulfate, etc., to form a ceramic film on the surface of the aluminum parts. However, the oxidation solution contains chromic acid, which is not environmentally friendly, and the obtained film is silvery-gray and cannot be effectively dyed to show a bright color.

CN 102834551 A discloses a method for forming essentially white anodic aluminum oxide, which involves immersion treatment to allow two or more solutions to flow into the pores of the anodic oxide layer and react to form a white precipitate. However, this method is time-consuming and complex to operate.

CN 104428454 B discloses another method for forming a white-looking anodic oxide film, which involves scanning a laser beam onto the anodic oxide film to form an array of uniformly spaced light-diffusing portions (multiple microcracks) within the film. This allows for the production of a white appearance through a combination of spectral reflection and diffuse reflection. However, this method requires more expensive equipment and is not suitable for large-area processing.

The surface treatment of aluminum alloy ceramic texture mostly uses high-voltage micro-arc processing. The operating voltage is high, so the operating cost is high and the process is relatively more complicated. Due to the high density of pores, this process causes problems such as difficulty in dyeing.

There is currently no surface treatment technology in the industry that can be practically applied to treat large areas of complex aluminum alloy parts to create an aluminum alloy surface with a white ceramic texture.

The technical problem to be solved by this invention is to provide a method for treating aluminum alloy surfaces with a fine texture and matte finish, which is suitable for treating aluminum alloy objects. The treated aluminum alloy surface exhibits a fine matte texture while also presenting a ceramic-like aesthetic.

To solve the aforementioned technical problems, one of the technical solutions adopted in this invention is to provide a method for treating an aluminum alloy surface with a fine texture and a matte finish. This method includes: chemically polishing an aluminum alloy surface to give it a 60° gloss level between 10 GU and 1000 GU; electrolyzing the chemically polished aluminum alloy surface; and performing a first anodizing treatment on the electrolyzed aluminum alloy surface. The operating conditions for the electrolytic treatment include: a current density in the range of ^0.01 A/ ^dm² to 1.5 A/dm²; a voltage gradually increasing from 0V to 50V; and a treatment time in the range of 3 to 30 minutes. The operating conditions for the first anodizing treatment include: a current density ranging from 0.1 A/ ^dm² to 2.5 A/ ^dm² ; a voltage ranging from 10V to 20V; and a treatment time ranging from 30 minutes to 120 minutes. According to the CIE L*a*b* color system, the L* value of the aluminum alloy surface after this first anodizing treatment and without coloring is 77 to 85, the a* value is -0.55 to -0.40, and the b* value is -0.7 to +0.3.

In an embodiment of the present invention, the electrolysis is carried out in a first treatment solution, the temperature of which is in the range of 20°C to 80°C and the pH value is in the range of 8 to 11. Based on a total weight of 100 wt%, the first treatment solution contains 3 wt% to 15 wt% sodium carbonate and 1 wt% to 15 wt% fluoride, the fluoride being selected from the group consisting of sodium fluoride, potassium fluoride, hydrogen fluoride, and hydrofluoric acid.

In an embodiment of the present invention, the first treatment solution further comprises 5 wt% to 50 wt% glycerol, 0.1 wt% to 10 wt% chelating agent, and 0.1 wt% to 10 wt% additive. The chelating agent is selected from the group consisting of sodium gluconate, ethylenediaminetetraacetic acid, citric acid, and potassium sodium tartrate, and the additive is selected from the group consisting of boric acid, sodium citrate, and triethanolamine.

In an embodiment of the present invention, the first anode treatment is carried out in a second treatment solution, the temperature of which is in the range of 5°C to 20°C. The second treatment solution contains 5% to 25% sulfuric acid, 5% to 20% oxalic acid, or a combination thereof, based on a total weight of 100 wt%.

In an embodiment of the present invention, the processing method further includes: after performing the first anodic treatment, performing a sealing treatment on the aluminum alloy surface that has undergone the first anodic treatment.

In embodiments of the present invention, the sealing treatment may be a nickel sealing treatment, a hot water sealing treatment, or a coating sealing treatment; the sealing material used in the coating sealing treatment is a UV-curable or thermosetting material, including polyurethane polymer, polycarbonate polymer, aminosiloxane, epoxysiloxane, nanosilicone compound, or any combination thereof.

In an embodiment of the present invention, the processing method further includes: between the step of performing the first anodizing treatment and the step of performing the sealing treatment, performing a first dyeing treatment on the aluminum alloy surface after the first anodizing treatment. The first anodizing treatment includes forming a porous alumina layer on the aluminum alloy surface, and the first dyeing treatment includes filling at least one dye into a plurality of openings in the porous alumina layer.

In an embodiment of the present invention, the processing method further includes: after performing the sealing process, forming a diamond-cut surface on the aluminum alloy surface that has undergone the sealing process.

In an embodiment of the present invention, the processing method further includes: after forming the diamond facet, performing a second anodizing treatment on the diamond facet, wherein the operating conditions of the second anodizing treatment include a current density in the range of 0.1 A/ ^dm² to 1.5 A/ ^dm² ; a voltage in the range of 10V to 20V; and a treatment time in the range of 10 minutes to 60 minutes. Furthermore, the second anodizing treatment is carried out in a third treatment solution, the temperature of which is in the range of 5°C to 20°C; and based on a total weight of 100 wt% of the third treatment solution, the second treatment solution contains 5 wt% to 20 wt% sulfuric acid, 5 wt% to 20 wt% oxalic acid, or a combination thereof.

In an embodiment of the present invention, the processing method further includes: after performing the second anodic treatment, performing a second staining treatment on the diamond facet that has undergone the second anodic treatment.

In general, the method for treating aluminum alloy surfaces with a fine texture and matte finish provided by this invention can produce an aluminum alloy surface with a unique white ceramic texture by "chemically polishing the aluminum alloy surface (which may have undergone pretreatment such as sandblasting or uniform polishing) to give it a 60° gloss (measured at a 60° angle) between 10 GU and 1000 GU", "electrolyzing the chemically polished aluminum alloy surface under special conditions", and "performing a first anodic treatment on the electrolyzed aluminum alloy surface under special conditions". The white color difference can be controlled by adjusting the operating condition parameters, and the appearance color of the aluminum alloy surface can also be changed as needed. In addition, the processing method of this invention can be practically applied to the processing of complex aluminum alloy parts over a large area, and the processed products are highly reliable and can directly meet product testing specifications.

To further understand the features and technical content of this invention, please refer to the following detailed description and drawings of this invention. However, the drawings provided are for reference and illustration only and are not intended to limit this invention.

The following specific embodiments illustrate the implementation of the "method for treating aluminum alloy surfaces with a fine texture and matte finish" disclosed in this invention. Those skilled in the art can understand the advantages and effects of this invention from the content disclosed in this specification. This invention can be implemented or applied through other different specific embodiments, and various details in this specification can also be modified and changed based on different viewpoints and applications without departing from the concept of this invention. Furthermore, the accompanying drawings of this invention are for simple illustrative purposes only and are not depictions based on actual dimensions, as stated in advance. The following embodiments will further explain the relevant technical content of this invention in detail, but the disclosed content is not intended to limit the scope of protection of this invention.

Unless otherwise defined, the terms used herein have the same meanings as commonly understood by one of ordinary skill in the art. The materials involved in the embodiments are, unless otherwise specified, commercially available or manufactured according to prior art. The processes involved in the embodiments are, unless otherwise specified, conventionally used processes in the art.

It should be understood that although the multiple steps in the method flowchart are described in a specific order in this document, this does not require or imply that these steps must be performed in that specific order, or that all steps must be performed to achieve the desired result. Optionally, multiple steps can be combined into one step, or a single step can be broken down into multiple steps.

Referring to Figure 1, this invention provides a method for treating an aluminum alloy surface with a fine texture and matte finish. The method mainly includes: step S100, chemically polishing the aluminum alloy surface; step S102, electrolytically treating the chemically polished aluminum alloy surface; and step S104, performing a first anodizing treatment on the electrolytically treated aluminum alloy surface. Specifically, this invention's method is a surface treatment method for aluminum alloy objects, primarily employing electrolytic treatment under special conditions combined with anodizing treatment to integrate a ceramic texture into the aluminum alloy surface and impart tunable color appearance.

The aforementioned aluminum alloy articles may be made of 5000 series (e.g., 5052), 6000 series (e.g., 6063), or 7000 series (e.g., 7075) aluminum alloys, and may be formed into desired shapes (e.g., sheet metal) by die casting, extrusion, forging, or cutting, thereby being used for the appearance components of electronic products such as housings. However, the present invention is not limited to the examples mentioned above.

The steps of the processing method of the present invention will be described in detail below with reference to Figures 3 and 5.

In step S100, the aluminum alloy object can be placed in a chemical polishing solution to remove minor fine lines on the aluminum alloy surface, making the surface smoother and brighter. In embodiments of the present invention, the aluminum alloy surface after chemical polishing can have a gloss level between 10 GU and 1000 GU (measured at a 60° angle). The chemical polishing solution may contain phosphoric acid or a combination of phosphoric acid and sulfuric acid, but the present invention is not limited thereto.

In practical applications, the present invention may also include a pretreatment step, that is, pretreating the aluminum alloy surface before chemical polishing. The pretreatment method varies depending on the purpose, and may include sandblasting, degreasing, pickling and alkaline washing steps, and the above steps may be performed sequentially.

Furthermore, the sandblasting material can be rounded steel grit, iron sand, or zirconium sand. Degreasing can be performed by immersing the aluminum alloy object in a 50°C solution containing a degreasing agent for 1 to 3 minutes. Pickling can be performed by immersing the aluminum alloy object in a 20°C to 40°C solution containing a pickling agent for 1 to 3 minutes. Alkali pickling can be performed by immersing the aluminum alloy object in a 40°C to 60°C solution containing an alkaline detergent for 0.5 to 2 minutes. However, the above descriptions are merely feasible embodiments and are not intended to limit the invention.

In step S102, the aluminum alloy object may be placed in a first treatment solution containing an alkaline agent and electrolyzed under specific conditions. The temperature of the first treatment solution is in the range of 20°C to 80°C and the pH value is in the range of 8 to 11. Based on a total weight of 100 wt%, the first treatment solution contains 3 wt% to 15 wt% sodium carbonate and 1 wt% to 15 wt% fluoride; the fluoride may be selected from the group consisting of sodium fluoride, potassium fluoride, hydrogen fluoride and hydrofluoric acid. In embodiments of the present invention, the first treatment solution may further comprise 0.1 wt% to 10 wt% of a chelating agent and 0.1 wt% to 10 wt% of an additive; the chelating agent may be selected from the group consisting of sodium gluconate, ethylenediaminetetraacetic acid, citric acid, and potassium sodium tartrate, and the additive may be selected from the group consisting of boric acid, sodium citrate, and triethanolamine. If necessary, the first treatment solution may further comprise 5 wt% to 50 wt% of glycerol. However, the present invention is not limited to the examples described above.

As shown in Figures 3 and 5, during the electrolytic treatment process, the aluminum alloy object 1 being treated serves as the anode, while the cathode is made of corrosion-resistant materials (such as stainless steel plates, carbon plates, titanium plates, lead-antimony plates, etc.). A certain current and a gradually increasing voltage are applied to form a well-adhered first porous alumina layer 2 on the aluminum alloy surface 100. Specifically, the operating conditions for the electrolytic treatment include: a current density in the range of 0.01 A/ ^dm² to 1.5 A/ ^dm² ; a voltage gradually increasing from 0V to a target voltage Vt, which can be 10~50V; and a treatment time in the range of 3 to 30 minutes.

In embodiments of the present invention, the current density for electrolysis can be 0.01 A/ ^dm² , 0.05 A/ ^dm² , 0.1 A/ ^dm² , 0.5 A/ ^dm² , 1.0 A/ ^dm² , or 1.5 A/ ^dm² . The electrolysis time can be 3 minutes, 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, or 30 minutes.

In step S104, the aluminum alloy object may be placed in a second treatment solution containing an acidic agent and subjected to a first anodic treatment under specific conditions, the temperature of which is in the range of 5°C to 20°C. The second treatment solution contains, by a total weight of 100 wt%, 5 wt% to 25 wt% sulfuric acid, 5 wt% to 20 wt% oxalic acid, or a combination thereof.

As shown in Figure 3, in the first anodizing process, the aluminum alloy object 1 being treated serves as the anode, while the cathode is made of corrosion-resistant materials (such as stainless steel plates, carbon plates, titanium plates, lead-antimony plates, etc.). A certain current and voltage are applied to form a well-adhered second porous alumina layer 3 on the aluminum alloy surface 100. Specifically, the operating conditions for the first anodizing process include: a current density in the range of 0.1 A/ ^dm² to ^2.5 A/dm²; a voltage in the range of 10V to 20V; and a treatment time in the range of 30 minutes to 120 minutes.

In embodiments of the present invention, the current density of the first anode treatment can be 0.01 A/ ^dm² , 0.05 A/ ^dm² , 0.1 A/ ^dm² , 0.5 A/ ^dm² , 1.0 A/ ^dm² , 1.5 A/ ^dm² , 2.0 A/ ^dm² , or 2.5 A/ ^dm² . The voltage of the first anode treatment can be 10V, 11V, 12V, 13V, 14V, 15V, 16V, 17V, 18V, 19V, or 20V. The duration of the first anodizing treatment can be 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, or 120 minutes.

Furthermore, the second porous alumina layer 3 is located between the aluminum alloy surface 100 and the first porous alumina layer 2, wherein the first porous alumina layer 2 is thinner and the second porous alumina layer 3 is thicker. In addition, the first porous alumina layer 2 and the second porous alumina layer 3 have different pore structures (such as pore shape, size or aspect ratio), different pore arrangement, and different porosities. It is worth noting that the aluminum alloy surface 100 after the first anodizing treatment can have a unique white ceramic texture; according to the CIE L*a*b* color system, the L* value of the aluminum alloy surface 100 after the first anodizing treatment and without dyeing is 77 to 85, the a* value is -0.55 to -0.40, and the b* value is -0.7 to +0.3.

Referring again to Figure 1, the processing method of the present invention may further include: step S105, performing a dyeing treatment on the aluminum alloy surface after the first anodizing treatment; and performing a sealing treatment on the aluminum alloy surface after the first anodizing treatment. The dyeing treatment can change the appearance color of the aluminum alloy surface, and the sealing treatment can provide sufficient protection for the aluminum alloy surface and ensure that the dyed aluminum alloy surface does not fade or change color.

In step S105, the aluminum alloy object can be placed in a dyeing solution containing dye to dye the aluminum alloy surface after the first anodic treatment. After dyeing, excess dye on the aluminum alloy surface can be removed by washing with water. The dye suitable for step S105 can be Okuno dye, but the present invention is not limited to it.

As shown in Figure 3, during the dyeing process, the dye in the dyeing solution can deposit in the pores of the first porous alumina layer 2 and the second porous alumina layer 3, causing a color change on the aluminum alloy surface 100. The portion of the dye remaining outside the pores of the first porous alumina layer 2 can be easily removed by the washing water.

In practical applications, a second pickling can be performed on the aluminum alloy surface that has undergone the first anodizing treatment before dyeing. The second pickling can be performed by immersing the diamond-cut CE surface that has undergone the second anodizing treatment in a solution containing 5-15 wt% nitric acid for 1-3 minutes at a solution temperature of 20-35°C.

In step S106, the dyed aluminum alloy surface can be brought into contact with a sealing material containing a sealing agent (the contact time is controllable) for sealing treatment. The sealing treatment can be a nickel sealing treatment, a hot water sealing treatment, or a coating sealing treatment. The coating sealing treatment may include curing the sealing material under UV irradiation or heating conditions, thereby allowing the dye to adhere firmly to the aluminum alloy surface without peeling off. Specifically, the sealing material used in the coating sealing treatment is a UV-curable or thermosetting material, including polyurethane polymers, polycarbonate polymers (such as polycarbonate), aminosiloxanes, epoxysiloxanes, nanosilicone compounds, or any combination thereof. The contact method of the sealing material in step S106 includes coating. However, this invention is not limited to the examples given above.

As shown in Figure 3, during the sealing process, a coating is applied to bring the sealing material into contact with the aluminum alloy surface 100, forming a transparent sealing layer 4 on the first porous alumina layer 2 and sealing its pores. With the presence of the transparent sealing layer 4, the dye can be stably retained within the pores of the first porous alumina layer 2 for a long period.

It should be noted that, depending on the product appearance requirements, the processing method of this invention can skip the dyeing treatment in step S105 after completing the first anodic oxidation treatment in step S104, and directly proceed to the sealing treatment in step S106.

As shown in Figure 3, after the above steps are completed, a finished product Z is obtained, which includes an aluminum alloy object 1, a first porous alumina layer 2, a second porous alumina layer 3, and a transparent sealing layer 4. The aluminum alloy object 1 has an aluminum alloy surface 100, and the first porous alumina layer 2, the second porous alumina layer 3, and the transparent sealing layer 4 are formed on the aluminum alloy surface 100. The second porous alumina layer 3 is located between the aluminum alloy surface 100 and the first porous alumina layer 2, and the transparent sealing layer 4 covers the first porous alumina layer 2.

Referring to Figure 2, the present invention may also include a post-processing step, namely, post-processing the aluminum alloy surface after the sealing treatment. In an embodiment of the present invention, the present invention may further include: step S108, forming a diamond-cut surface on the sealed aluminum alloy surface; step S110, performing a second anodizing treatment on the diamond-cut surface; and step S112, performing a second staining treatment on the diamond-cut surface after the second anodizing treatment.

As shown in Figure 4, in step S118, the finished product Z can be partially drilled (such as edge drilling) in the presence of cutting oil, and the resulting drilled surface CE can have a gloss between 200 GU and 1000 GU (measured at an angle of 60°).

In step S110, the second anodic treatment can use essentially the same treatment solution and operating conditions as the first anodic treatment, the only difference being that the treatment solution can contain a lower concentration of sulfuric acid, and the second anodic treatment can be completed in a shorter time. Specifically, the treatment solution for the second anodic treatment can contain 5 wt% to 20 wt% sulfuric acid, 5 wt% to 20 wt% oxalic acid, or a combination thereof. The duration of the second anodic treatment is in the range of 10 to 60 minutes. In addition, the operating conditions for the second anode treatment may include: a current density in the range of 0.1 A/ ^dm² to ^1.5 A/dm²; a voltage in the range of 10V to 20V; and a treatment time in the range of 10 minutes to 60 minutes.

In step S112, the treated product Z can be placed in a dyeing solution containing dye, and the diamond facet CE, which has undergone a second anodic treatment, can be dyed at a temperature of 45~60°C for 3~20 minutes. After dyeing, excess dye on the diamond facet CE can be removed by washing with water. The dye suitable for step S112 can be Okuno dye, but the present invention is not limited to this.

In practical applications, the CE facets can be pretreated before the second anodizing treatment. The pretreatment method varies depending on the purpose and may include surface degreasing and a first pickling step, which can be performed sequentially. Additionally, the CE facets after the second anodizing treatment can be pickled a second time before dyeing; and after dyeing, the dyed CE facets can be sealed.

Furthermore, surface degreasing can be performed by immersing the treated product Z with diamond-cut CE facets in a 50°C solution containing a degreasing agent for 3 minutes to remove surface dirt and oil stains. A first pickling process involves immersing the treated product Z with diamond-cut CE facets in a 30°C solution containing a pickling agent for 1 minute to remove surface oxides and contaminants. A second pickling process involves immersing the diamond-cut CE facets, which have undergone a second anodic treatment, in a solution containing 5-15 wt% nitric acid for 1-3 minutes at a temperature of 20-35°C. Hole sealing can be performed using nickel sealing at a temperature of 90°C for 30-40 minutes; alternatively, nickel-free sealing processes, such as color fixing or spraying, can be used. However, the above description is only a possible implementation method and is not intended to limit the invention.

[Specific Example 1]

The 6063 aluminum alloy object was surface-blasted using rounded steel pebbles (grit size 120#). Subsequently, the aluminum alloy object underwent surface degreasing (50°C, 3 minutes) to remove surface dirt and oil stains. Next, the aluminum alloy object was pickled (30°C, 1 minute) to remove surface oxides and contaminants. Finally, the aluminum alloy object was alkaline-washed (60°C, 0.5 minutes) to improve surface cleanliness. Subsequently, the aluminum alloy objects were chemically polished using a phosphoric acid-based chemical polishing solution at 85°C to 95°C to remove surface contaminants and increase surface gloss and uniformity; the chemically polished aluminum alloy surface had a gloss level between 40 GU and 100 GU (measured at a 60° angle). Next, the aluminum alloy objects underwent electrolytic treatment with a treatment solution at a temperature of 20°C to 40°C and a pH of 8 to 11, containing 5 wt% to 10 wt% sodium carbonate and 5 wt% to 10 wt% sodium fluoride; operating conditions included a current density of 0.01 A/ ^dm² , a voltage gradually increasing from 0.1V to 35V, and a treatment time ranging from 3 to 30 minutes. Subsequently, the aluminum alloy object undergoes anodizing treatment in a solution at a temperature of 5°C to 20°C, containing 15 wt% sulfuric acid, 15 wt% oxalic acid, or a combination thereof. Operating conditions include a current density of 1 A/ ^dm² , a voltage of 14V to 19V, and a treatment time ranging from 30 to 60 minutes. Following this, the aluminum alloy object undergoes pickling treatment (temperature 20–35°C, time 1–3 minutes, nitric acid concentration in the treatment solution 5–15%). Next, the aluminum alloy object is dyed using Okuno dye (temperature 45–60°C, dyeing time 3–20 minutes). Finally, the aluminum alloy object undergoes sealing treatment (temperature 90°C, time 30–40 minutes).

[Specific Example 2]

The 5052 or 6063 aluminum alloy object is surface-blasted using rounded steel pebbles (grit size 120#). Subsequently, the aluminum alloy object undergoes surface degreasing treatment (50°C, 3 minutes) to remove surface dirt and oil stains. Next, the aluminum alloy object undergoes pickling treatment (30°C, 1 minute) to remove surface oxides and contaminants. Finally, the aluminum alloy object undergoes alkaline washing (60°C, 0.5 minutes) to improve surface cleanliness. Subsequently, the aluminum alloy objects were chemically polished using a phosphoric acid-based chemical polishing solution at 85°C to 95°C to remove surface contaminants and increase surface gloss and uniformity; the chemically polished aluminum alloy surface had a gloss level between 40 GU and 1000 GU (measured at a 60° angle). Next, the aluminum alloy objects underwent electrolytic treatment with a treatment solution at a temperature of 40°C to 75°C and a pH of 8 to 11, containing 5 wt% to 10 wt% sodium carbonate and 5 wt% to 10 wt% sodium fluoride; operating conditions included a current density of 0.1 A/ ^dm² , a voltage gradually increasing from 0.1 V to 40 V, and a treatment time ranging from 3 to 30 minutes. Subsequently, the aluminum alloy object undergoes anodizing treatment in a solution at a temperature of 5°C to 20°C, containing 15 wt% sulfuric acid, 15 wt% oxalic acid, or a combination thereof. Operating conditions include: current density of 0.1–1.5 A/ ^dm² , voltage of 14V to 19V, and treatment time ranging from 30 to 60 minutes. Following this, the aluminum alloy object undergoes pickling treatment (temperature of 20–35°C, time of 1–3 minutes, nitric acid concentration of 5–15% in the treatment solution). Finally, the aluminum alloy object is dyed using Okuno dye (temperature of 45–60°C, dyeing time of 3–20 minutes). Subsequently, the aluminum alloy object is sealed (at a temperature of 90°C for 30-40 minutes).

[Specific Example 3]

The 5052 or 6063 aluminum alloy object is surface-blasted using rounded steel pebbles (grit size 120#). Subsequently, the aluminum alloy object undergoes surface degreasing treatment (50°C, 3 minutes) to remove surface dirt and oil stains. Next, the aluminum alloy object undergoes pickling treatment (30°C, 1 minute) to remove surface oxides and contaminants. Finally, the aluminum alloy object undergoes alkaline washing (60°C, 0.5 minutes) to improve surface cleanliness. Subsequently, the aluminum alloy objects were chemically polished using a phosphoric acid-based chemical polishing solution at 85°C to 95°C to remove surface contaminants and increase surface gloss and uniformity; the aluminum alloy surface after chemical polishing had a gloss between 40 GU and 100 GU (measured at a 60° angle). Subsequently, the aluminum alloy object is subjected to electrolytic treatment in a treatment solution at a temperature of 25°C to 40°C and a pH of 8 to 11, containing 3 wt% to 15 wt% sodium carbonate, 1 wt% to 10 wt% sodium fluoride, 0.1 wt% to 5 wt% sodium gluconate, 0.1 wt% to 5 wt% boric acid, and 15 wt% to 45 wt% glycerol. The operating conditions include a current density of 0.01 A/ ^dm² , a voltage gradually increasing from 0.1V to 35V, and a treatment time ranging from 3 minutes to 30 minutes. Subsequently, the aluminum alloy object undergoes anodizing treatment in a solution at a temperature of 5°C to 20°C, containing 15 wt% sulfuric acid, 15 wt% oxalic acid, or a combination thereof. Operating conditions include: current density of 0.01–1.5 A/ ^dm² , voltage of 14V to 19V, and treatment time of 30–60 minutes. Following this, the aluminum alloy object undergoes pickling treatment (temperature of 20–35°C, time of 1–3 minutes, nitric acid concentration of 5–15% in the treatment solution). Finally, the aluminum alloy object is dyed using Okuno dye (temperature of 45–60°C, dyeing time of 3–20 minutes). Subsequently, the aluminum alloy object is sealed (at a temperature of 90°C for 30-40 minutes).

[Specific Example 4]

The 5052 or 6063 aluminum alloy object is surface-blasted using rounded steel pebbles (grit size 120#). Subsequently, the aluminum alloy object undergoes surface degreasing treatment (50°C, 3 minutes) to remove surface dirt and oil stains. Next, the aluminum alloy object undergoes pickling treatment (30°C, 1 minute) to remove surface oxides and contaminants. Finally, the aluminum alloy object undergoes alkaline washing (60°C, 0.5 minutes) to improve surface cleanliness. Subsequently, the aluminum alloy object was chemically polished using a phosphoric acid-based chemical polishing solution at 95°C to remove surface contaminants and increase surface gloss and uniformity; the aluminum alloy surface after chemical polishing had a gloss between 40 GU and 100 GU (measured at a 60° angle). Subsequently, the aluminum alloy object is subjected to electrolytic treatment in a treatment solution at a temperature of 40°C to 75°C and a pH of 8 to 11, containing 3 wt% to 15 wt% sodium carbonate, 1 wt% to 10 wt% sodium fluoride, 0.1 wt% to 5 wt% sodium gluconate, 0.1 wt% to 5 wt% boric acid, and 15 wt% to 45 wt% glycerol. The operating conditions include a current density of 0.1 A/ ^dm² , a voltage gradually increasing from 0.1 V to 35 V, and a treatment time ranging from 3 to 30 minutes. Subsequently, the aluminum alloy object undergoes anodizing treatment in a solution at a temperature of 5°C to 20°C, containing 15 wt% sulfuric acid, 15 wt% oxalic acid, or a combination thereof. Operating conditions include: current density of 0.01–1.5 A/ ^dm² , voltage of 14V to 19V, and treatment time of 30–60 minutes. Following this, the aluminum alloy object undergoes pickling treatment (temperature of 20–35°C, time of 1–3 minutes, nitric acid concentration of 5–15% in the treatment solution). Finally, the aluminum alloy object is dyed using Okuno dye (temperature of 45–60°C, dyeing time of 3–20 minutes). Subsequently, the aluminum alloy object is sealed (at a temperature of 90°C for 30-40 minutes).

[Specific Example 5]

The finished product of one of Examples 1-4 is drilled to form a diamond-cut facet with a gloss level between 200 GU and 1000 GU (measured at a 60° angle). Subsequently, the finished product undergoes surface degreasing (at 50°C for 3 minutes) to remove surface dirt and oil stains. Then, the finished product is pickled (at 30°C for 1 minute) to remove surface oxides and contaminants. Subsequently, the finished product undergoes anodizing treatment in a solution at a temperature of 5°C to 20°C, containing 15 wt% sulfuric acid, 15 wt% oxalic acid, or a combination thereof. Operating conditions include: current density of 0.01~1.5 A/ ^dm² , voltage of 10V to 20V, and treatment time ranging from 10 to 60 minutes. Following this, the aluminum alloy object undergoes pickling treatment (temperature of 20~35°C, time of 1~3 minutes, nitric acid concentration of 5~15% in the treatment solution). Finally, the aluminum alloy object is dyed using Okuno dye (temperature of 45~60°C, dyeing time of 3~20 minutes). Subsequently, the aluminum alloy object is sealed (at a temperature of 90°C for 30-40 minutes).

[Beneficial effects of the implementation]

The present invention provides a method for treating aluminum alloy surfaces with a fine texture and matte finish. This method involves "chemically polishing the aluminum alloy surface to achieve a gloss level between 10 GU and 1000 GU (measured at a 60° angle)," "electrolytically treating the chemically polished aluminum alloy surface under special conditions," and "performing a first anodizing treatment on the electrolytically treated aluminum alloy surface under special conditions." This process produces an aluminum alloy surface with a unique white ceramic texture. The white color difference can be controlled by adjusting the operating parameters, and the appearance color of the aluminum alloy surface can be changed as needed. Furthermore, the method of the present invention can be practically applied to the large-area processing of complex aluminum alloy parts, and the finished products are highly reliable and directly meet product testing specifications.

The above-disclosed content is merely a preferred feasible embodiment of the present invention and is not intended to limit the scope of the patent application of the present invention. Therefore, all equivalent technical changes made using the contents of the present invention's description and drawings are included within the scope of the patent application of the present invention.

Z: Finished Product 1: Aluminum Alloy Part 100: Aluminum Alloy Surface 2: First Porous Alumina Layer 3: Second Porous Alumina Layer 4: Transparent Sealing Layer CE: Drill Facet S100, S102, S104, S105, S106, S108, S110, S112: Processing Steps

Figure 1 is a flowchart of the main steps of the method for treating an aluminum alloy surface with a fine texture and matte finish according to the present invention.

Figure 2 is a flowchart of the post-processing steps of the method for treating aluminum alloy surfaces with a fine texture and matte finish according to the present invention.

Figure 3 is a schematic diagram of the finished product obtained by the surface treatment method of aluminum alloy with fine texture and matte finish of the present invention.

Figure 4 is a process diagram of step S108 of the method for treating an aluminum alloy surface with a fine texture and matte finish according to the present invention.

Figure 5 is a schematic diagram of the operating conditions of step S102 of the method for treating an aluminum alloy surface with a fine texture and matte finish according to the present invention.

S100, S102, S104, S105, S106: Processing steps

Claims (9)

A method for treating an aluminum alloy surface with a fine texture and matte finish includes: chemically polishing an aluminum alloy surface to achieve a 60° gloss level between 10 GU and 1000 GU; and electrolyzing the chemically polished aluminum alloy surface, wherein the operating conditions of the electrolyzing treatment include: a current density in the range ^of 0.01 A/ ^dm² to 1.5 A/dm²; a voltage gradually increasing from 0V to 50V; and a treatment time in the range of 3 minutes to 30 minutes; wherein the electrolyzing treatment is carried out in a first treatment solution, the temperature of which is in the range of 20°C to 80°C and the pH value is in the range of 8 to 11; wherein the total weight of the first treatment solution is 100... The first treatment solution, by weight, comprises 3 wt% to 15 wt% sodium carbonate and 1 wt% to 15 wt% fluoride, wherein the fluoride is selected from the group consisting of sodium fluoride, potassium fluoride, hydrogen fluoride, and hydrofluoric acid; and a first anodic treatment is performed on the surface of the electrolyzed aluminum alloy, wherein the operating conditions for the first anodic treatment include: a current density in the range of 0.1 A/ ^dm² to 2.5 A/ ^dm² ; a voltage in the range of 10V to 20V; and a treatment time in the range of 30 minutes to 120 minutes; wherein, according to CIE The L*a*b* color system indicates that the aluminum alloy surface after the first anodic treatment has an L* value of 77 to 85, an a* value of -0.55 to -0.40, and a b* value of -0.7 to +0.3. The method for treating an aluminum alloy surface with a fine texture and matte finish as described in claim 1, wherein the first treatment solution further comprises 5 wt% to 50 wt% glycerol, 0.1 wt% to 10 wt% chelating agent and 0.1 wt% to 10 wt% additive; the chelating agent is selected from the group consisting of sodium gluconate, ethylenediaminetetraacetic acid, citric acid and potassium sodium tartrate, and the additive is selected from the group consisting of boric acid, sodium citrate and triethanolamine. The method for treating an aluminum alloy surface with a fine texture and matte finish as described in claim 1, wherein the first anodic treatment is performed in a second treatment solution, the temperature of which is in the range of 5°C to 20°C; and the second treatment solution contains 5% to 25% sulfuric acid, 5% to 20% oxalic acid, or a combination thereof, based on a total weight of 100 wt%. The method for treating an aluminum alloy surface with a fine texture and matte finish as described in claim 1, wherein after performing the first anodizing step, the method further includes: performing a sealing treatment on the aluminum alloy surface treated with the first anodizing. The method for treating an aluminum alloy surface with a fine texture and matte finish as described in claim 4, wherein the sealing treatment is a nickel sealing treatment, a hot water sealing treatment, or a coating sealing treatment; the sealing material used in the coating sealing treatment is a UV-curable or thermosetting material, including polyurethane polymer, polycarbonate polymer, aminosiloxane, epoxysiloxane, nanosilicone compound, or any combination thereof. The method for treating an aluminum alloy surface with a fine texture and matte finish as described in claim 4, wherein, between the step of performing the first anodizing treatment and the step of performing the sealing treatment, the method further includes: performing a first dyeing treatment on the aluminum alloy surface after the first anodizing treatment; wherein the first anodizing treatment includes forming a porous alumina layer on the aluminum alloy surface, and the first dyeing treatment includes filling at least one dye into a plurality of openings in the porous alumina layer. The method for treating an aluminum alloy surface with a fine texture and a matte finish as described in any of claims 4 to 6, wherein, after performing the sealing treatment step, it further includes: forming a diamond-cut surface on the aluminum alloy surface that has undergone the sealing treatment. The method for treating an aluminum alloy surface with a fine texture and matte finish as described in claim 7, further comprising, after the step of forming the diamond facet, performing a second anodizing treatment on the diamond facet, wherein the operating conditions for the second anodizing treatment include: a current density in the range of 0.1 A/ ^dm² to 1.5 A/ ^dm² ; a voltage in the range of 10V to 20V; and a treatment time in the range of 10 minutes to 60 minutes; wherein the second anodizing treatment is performed in a third treatment solution, the temperature of which is in the range of 5°C to 20°C; and, based on a total weight of 100 wt% of the third treatment solution, the second treatment solution contains 5 wt% to 20 wt% sulfuric acid and 5 wt% to 20 wt% sulfuric acid. wt% of oxalic acid or combinations thereof. The method for treating an aluminum alloy surface with a fine texture and a matte finish as described in claim 8, wherein after performing the second anodizing step, the method further includes performing a second staining treatment on the diamond facet that has undergone the second anodizing treatment.