Aluminum alloy anodic oxidation coloring process and preparation method of shell of electronic device

Abstract

The invention discloses an aluminum alloy anodic oxidation coloring process and a preparation method of a shell of an electronic device, and the aluminum alloy anodic oxidation coloring process comprises the steps that an oxidation film is formed on the surface of aluminum alloy through anodic oxidation, and the oxidation film has a first pore diameter; the oxidation film is soaked with a pretreatment agent, the pretreatment agent comprises phosphoric acid, and the first pore diameter of the oxidation film is expanded into the second pore diameter; the oxide film having the second aperture is soaked with a colorant, the colorant including a color-developing metal salt, causing at least a portion of the color-developing metal salt to adhere in the oxide film, coloring the aluminum alloy. According to the aluminum alloy anodic oxidation coloring process, the color development metal salt is deposited in the oxidation film for color development, the process is not prone to being influenced by acid liquid left in pretreatment, a good coloring effect can be achieved on gaps in the aluminum-plastic combination position, the process is not prone to being influenced by pH deviation introduced by the residual acid liquid, and the coloring effect is good. The overall coloring effect is improved; and the coloring firmness is improved.

Description

Technical Field

[0001] This application relates to the field of coloring processes, specifically to an aluminum alloy anodizing coloring process and a method for preparing the casing of electronic devices. Background Technology

[0002] In existing technologies, aluminum alloy surfaces are generally colored with organic dyes after anodizing. The color is achieved by the organic dye molecules being chemically or physically adsorbed onto the oxide film and deposited in the pores of the film. Currently, most 3C products use organic dyes for coloring.

[0003] Some 3C products use aluminum-plastic bonding to improve signal performance. However, there may be tiny gaps at the aluminum-plastic bonding point, which can easily cause acid in the pretreatment process (such as anodizing). Therefore, multiple ultrasonic cleaning steps are usually required before coloring to remove residual acid from the gaps. Otherwise, residual acid will cause the product to have an off-color appearance, or the pH deviation introduced by residual acid will cause the coloring result of organic dyes to be unsatisfactory and will also affect the color fastness.

[0004] Therefore, existing aluminum alloy anodizing coloring processes suffer from problems such as high ultrasonic cleaning costs or poor coloring results. Summary of the Invention

[0005] In view of this, this application provides an anodizing coloring process for aluminum alloys to solve at least one of the above-mentioned technical problems. Furthermore, this application also provides a method for manufacturing a casing for an electronic device.

[0006] To achieve the above objectives, in a first aspect, this application provides an aluminum alloy anodizing coloring process, comprising: forming an oxide film on the surface of an aluminum alloy by anodizing, the oxide film having a first pore size; soaking the oxide film with a pretreatment agent, the pretreatment agent including phosphoric acid, to expand the first pore size of the oxide film into a second pore size; and soaking the oxide film having the second pore size with a colorant, the colorant including a coloring metal salt, to make at least a portion of the coloring metal salt adhere to the oxide film, thereby coloring the aluminum alloy.

[0007] Secondly, this application provides a method for preparing the casing of an electronic device, comprising: providing an aluminum alloy, coloring the aluminum alloy by the above-mentioned aluminum alloy anodizing coloring process to obtain a colored aluminum alloy; and bonding the colored aluminum alloy with a plastic material by injection molding to obtain the casing of the electronic device.

[0008] Compared to existing organic dye coloring technologies, the aluminum alloy anodizing coloring process of this application utilizes the deposition of inorganic coloring metal salts within the oxide film. The deposition of these inorganic coloring metal salts primarily occurs through physical adsorption, making them less susceptible to the effects of residual acid from pretreatment. This allows for effective coloring even in the gaps at the aluminum-plastic interface and is less affected by pH deviations introduced by residual acid, thus improving the overall coloring effect and enhancing colorfastness. Therefore, the aluminum alloy anodizing coloring process of this application reduces the reliance on multiple ultrasonic cleaning processes required in conventional organic dye coloring, thereby helping to lower the cost of pretreatment and reduce the risk of poor coloring. Attached Figure Description

[0009] Figure 1 This is a schematic flowchart of an aluminum alloy anodizing coloring process provided in one embodiment of this application.

[0010] The following detailed description, in conjunction with the accompanying drawings, will further illustrate this application. Detailed Implementation

[0011] The embodiments of this application are described in detail below. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application; it should be noted that, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; where there is no conflict, the implementation methods and features of the implementation methods of this application can be combined with each other; many specific details are set forth in the following description in order to provide a full understanding of this application, and the described implementation methods are only a part of the implementation methods of this application, and not all of the implementation methods.

[0012] Please see Figure 1 One embodiment of this application provides an anodizing coloring process for aluminum alloys, including: S1: An oxide film is formed on the surface of an aluminum alloy by anodizing, and the oxide film has a first pore size.

[0013] The oxide film formed by anodizing provides a substrate for coloring aluminum alloys. This oxide film typically possesses a porous structure. In this application, these porous structures provide the basic structure for the subsequent deposition and color development of the coloring metal salt, thereby enhancing the basic adhesion of the coloring agent and improving the stability of the coloring. Furthermore, this oxide film also helps to improve the hardness and corrosion resistance of the aluminum alloy itself, effectively improving its mechanical properties.

[0014] In some embodiments, the voltage for anodizing is between 10 V and 17 V. For example, the voltage for anodizing can be 10 V, 11 V, 12 V, 13 V, 14 V, 15 V, 16 V, 17 V, or any value within the range of any two of the above values. The voltage for anodizing typically affects the pore size and thickness of the formed oxide film. Lower voltages generally result in oxide films with small pore sizes and thinner thicknesses, while higher voltages generally result in oxide films with large pore sizes and thicker thicknesses. This application has found that the pore structure morphology before colorant deposition affects the deposition effect of subsequent coloring metal salt colorants, and the pore size and film thickness of the anodized oxide film, as the basic structure (subsequently treated with pretreatment agents), affect the subsequent shaping of a suitable pore structure morphology. Controlling the anodizing voltage within the above range, by controlling the pore size and film thickness of the anodic oxide film, helps to construct a suitable basic structure for the anodized film, thereby combining with subsequent pretreatment agent treatment to shape a suitable pore structure morphology.

[0015] In some embodiments, the anodizing temperature is between 10 °C and 30 °C. For example, the anodizing temperature can be 10 °C, 12 °C, 14 °C, 16 °C, 18 °C, 20 °C, 22 °C, 24 °C, 26 °C, 28 °C, 30 °C, or any value within the range of any two of the above values. The anodizing temperature generally affects the chemical dissolution rate of the oxide film by the electrolyte (such as an acid solution). Anodizing is a dynamic equilibrium process of "film formation" and "dissolution." When the temperature increases, the chemical dissolution effect of the electrolyte on the oxide film is enhanced, and the oxide film tends to be loose, porous, and soft. When the temperature decreases, the chemical dissolution effect of the electrolyte on the oxide film is weakened, and the oxide film tends to be dense and hard. Therefore, different dynamic equilibria affect the density and hardness of the formed oxide film. This application has found that the density and hardness of the oxide film not only affect the improvement of the mechanical properties of aluminum alloys but also affect the effect of subsequent pretreatment agents. By controlling the anodizing temperature within the aforementioned range, the mechanical properties of the aluminum alloy can be improved. Furthermore, by controlling the density and hardness of the anodized film, a suitable basic structure for the anodized film can be formed, which facilitates the improvement of the treatment efficiency of subsequent pretreatment agents and helps to shape a suitable pore structure morphology.

[0016] In some embodiments, the electrolyte for anodizing includes an acid solution with a concentration of 100 g / L to 300 g / L. For example, the concentration of the acid solution may be 100 g / L, 120 g / L, 140 g / L, 160 g / L, 180 g / L, 200 g / L, 220 g / L, 240 g / L, 260 g / L, 280 g / L, 300 g / L, or any value within the range of any two of the above values. The concentration of the acid solution in the anodizing electrolyte determines the oxidizing and solubilizing properties of the electrolyte, which together affect the porosity and growth rate of the oxide film. Generally, the higher the concentration of the acid solution, the stronger the solubility of the electrolyte. Therefore, controlling the concentration of the acid solution in the electrolyte within the above range helps to control the density and hardness of the anodized film, and also helps to construct a suitable basic structure for the anodized film, facilitating the improvement of the treatment efficiency of subsequent pretreatment agents to shape a suitable pore structure morphology.

[0017] In some embodiments, before forming the oxide film by anodizing, the aluminum alloy is further subjected to a pretreatment, which includes one or more of degreasing, alkaline etching, polishing, and black film stripping. The above pretreatment provides a clean, uniform, and highly reactive surface for anodizing, which is beneficial for forming a high-quality oxide film with a dense structure, uniform thickness, transparency, colorlessness, and strong adhesion, thus laying the foundation for subsequent coloring.

[0018] In some embodiments, the aluminum alloy is degreased by immersing it in a degreasing agent at a concentration of 50 g / L to 60 g / L, at a immersion temperature of 50 ℃ to 60 ℃, and for a immersion time of 120 seconds to 300 seconds. For example, the concentration of the degreasing agent can be 50 g / L, 51 g / L, 52 g / L, 53 g / L, 54 g / L, 55 g / L, 56 g / L, 57 g / L, 58 g / L, 59 g / L, 60 g / L, or any value within the range of any two of the above values; the soaking temperature can be 50 ℃, 51 ℃, 52 ℃, 53 ℃, 54 ℃, 55 ℃, 56 ℃, 57 ℃, 58 ℃, 59 ℃, 60 ℃, or any value within the range of any two of the above values; the soaking time can be 120 seconds, 150 seconds, 180 seconds, 210 seconds, 240 seconds, 270 seconds, 300 seconds, or any value within the range of any two of the above values. Degreasing under the above conditions is beneficial to improving the hydrophilicity and uniformity of the aluminum alloy surface, facilitating uniform contact between the reagents and the aluminum alloy in subsequent pretreatment, and also promoting the uniform and firm growth of the anodic oxide film from the aluminum alloy substrate, improving the film-substrate adhesion, and thus improving the stability of subsequent coloring.

[0019] In some embodiments, the aluminum alloy is subjected to alkaline etching treatment by immersing it in an alkaline solution with a concentration of 20 g / L to 40 g / L, an immersion temperature of 30 ℃ to 50 ℃, and an immersion time of 10 seconds to 60 seconds. For example, the concentration of the alkaline solution can be 20 g / L, 22 g / L, 24 g / L, 26 g / L, 28 g / L, 30 g / L, 32 g / L, 34 g / L, 36 g / L, 38 g / L, 40 g / L, or any value within the range of any two of the above values; the immersion temperature can be 30 ℃, 32 ℃, 34 ℃, 36 ℃, 38 ℃, 40 ℃, 42 ℃, 44 ℃, 46 ℃, 48 ℃, 50 ℃, or any value within the range of any two of the above values. The immersion time can be 10 seconds, 15 seconds, 20 seconds, 25 seconds, 30 seconds, 35 seconds, 40 seconds, 45 seconds, 50 seconds, 55 seconds, 60 seconds, or any value within the range of any two of the above values. Controlling the alkaline etching treatment under these conditions facilitates controlled and uniform corrosion of the aluminum alloy surface, removing the natural oxide layer and minor scratches, and imparting a certain degree of micro-roughness to the surface. This provides a more uniform starting point for subsequent anodizing and helps form a uniform oxide film.

[0020] In some embodiments, the aluminum alloy is polished by immersing it in a chemical polishing solution, which includes phosphoric acid, the specific gravity of which is 1.70 to 1.75. The immersion temperature is 70°C to 100°C, and the immersion time is 30 to 90 seconds. For example, the specific gravity of phosphoric acid in the chemical polishing solution can be 1.70, 1.71, 1.72, 1.73, 1.74, 1.75, or any value within the range of any two of the above values; the soaking temperature can be 70 ℃, 73 ℃, 76 ℃, 79 ℃, 82 ℃, 85 ℃, 88 ℃, 91 ℃, 94 ℃, 97 ℃, 100 ℃, or any value within the range of any two of the above values; the soaking time can be 30 seconds, 35 seconds, 40 seconds, 45 seconds, 50 seconds, 55 seconds, 60 seconds, 65 seconds, 70 seconds, 75 seconds, 80 seconds, 85 seconds, 90 seconds, or any value within the range of any two of the above values. This application uses chemical polishing solution to polish aluminum alloys. By controlling the specific gravity of phosphoric acid, the soaking temperature, and the soaking time in the chemical polishing solution, the dissolving intensity of the solution can be controlled, achieving micron-level leveling of the aluminum alloy surface, filling micro-scratches, and obtaining higher gloss. This helps to achieve the mirror or high-gloss surface required for 3C electronic products. At the same time, the high gloss also helps to make the oxide film itself more transparent and pure, better showcasing the original texture of the aluminum metal, and making the subsequent dyeing colors more vivid and saturated.

[0021] In some embodiments, the aluminum alloy is subjected to a black film removal process by immersing it in an acid solution with a concentration of 10wt% to 40wt% and an immersion time of 120 seconds to 300 seconds. For example, the acid solution concentration can be 10wt%, 13wt%, 16wt%, 19wt%, 22wt%, 25wt%, 28wt%, 31wt%, 34wt%, 37wt%, 40wt%, or any value within the range of any two of the above values; the immersion time can be 120 seconds, 140 seconds, 160 seconds, 180 seconds, 200 seconds, 220 seconds, 240 seconds, 260 seconds, 280 seconds, 300 seconds, or any value within the range of any two of the above values. This black film removal process removes the blackish-gray residue remaining on the aluminum alloy surface after alkaline etching. Controlling the acid solution concentration and immersion time within the above ranges helps to expose a cleaner, brighter aluminum alloy surface, thereby improving the color brightness and purity of the finished product.

[0022] S2: Soak the oxide film with a pretreatment agent, including phosphoric acid, to expand the first pore size of the oxide film into a second pore size.

[0023] First, an oxide film with a basic pore structure is formed through anodizing. Then, the chemical dissolution effect of phosphoric acid helps to uniformly erode the pore walls of the pore structure on the anodized film. This allows the pore size to gradually and controllably expand from the first pore size to the second pore size while maintaining the basic pore structure on the anodized film, thereby shaping a pore structure with a suitable morphology, which facilitates the subsequent deposition of coloring metal salts.

[0024] Understandably, if only anodizing is used to construct the oxide film, the morphology of the pore structure ultimately used for colorant deposition is difficult to control. Furthermore, the methods required to enlarge the pore size (such as increasing voltage or temperature) usually result in sparse pores. A sparse pore structure with simply enlarged pore size is not conducive to the full deposition and color development of the coloring metal salt in the coloring process of this application; instead, it increases the risk of uneven and unstable color development, leading to poor color development. Therefore, the coloring process of this application combines anodizing and pretreatment agent immersion treatment. Based on the oxide film formed by anodizing with a dense and abundant pore structure, the pore size of these pores is further enlarged, resulting in an oxide film with a dense, abundant, and large-pore-size morphology. This provides a large specific surface area and anchoring points for colorant deposition, thereby improving the color development quality of the colorant.

[0025] In some embodiments, the mass percentage of phosphoric acid in the pretreatment agent is 1 wt% to 10 wt%. For example, the mass percentage of phosphoric acid in the pretreatment agent can be 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 10 wt%, or any value within the range of any two of the above values. This application has found that when anodic oxide films are treated with phosphoric acid immersion, the amount of phosphoric acid used not only affects the efficiency of pore expansion and film thickness, but also the overall pore structure morphology of the oxide film. For example, excessive phosphoric acid may increase the risk of excessive corrosion and bridging of the current pore structure, as well as reducing the thickness of the anodic oxide film. Furthermore, when the amount of phosphoric acid is excessive, the dissolution effect of phosphoric acid on the oxide film becomes intense and less controllable, leading to rough pore walls, numerous pits, or even "penetration" of the pore structure. This causes adjacent pores to merge into an irregular large pore, which may cause the entire ordered porous structure to collapse, becoming loose and powdery, which is not conducive to shaping a suitable pore structure morphology. By controlling the mass ratio of phosphoric acid within the aforementioned range, this application maintains a suitable oxide film thickness and simultaneously performs controllable pore-enlarging treatment on the oxide film, expanding the pore size from a first pore diameter to a second pore diameter. This reduces the risk of adjacent pores connecting together and facilitates uniform and isotropic dissolution of the pore walls. The internal shape of the pore structure gradually evolves from its initial shape to a larger, more regular, and smooth shape, maintaining smooth pore walls. This, in turn, helps to create a suitable pore structure morphology, providing a suitable deposition structure for subsequent coloring metal salt colorants. Furthermore, controlling the mass ratio of phosphoric acid within the aforementioned range improves the controllability of phosphoric acid dissolution, which in turn enhances the repeatability of the coloring process, thereby increasing the yield of the final colored product.

[0026] In some embodiments, the soaking time of the oxide film with the pretreatment agent is greater than 0 seconds and less than or equal to 60 seconds. For example, the soaking time of the oxide film with the pretreatment agent can be 5 seconds, 10 seconds, 15 seconds, 20 seconds, 25 seconds, 30 seconds, 35 seconds, 40 seconds, 45 seconds, 50 seconds, 55 seconds, 60 seconds, or any value within the range of any two of the above values. In this application, using the above-mentioned soaking time range is beneficial for producing the desired pore structure morphology after soaking the oxide film with a pretreatment agent of appropriate phosphoric acid content.

[0027] In other embodiments, the immersion time of the oxide film in the pretreatment agent is between 80 and 120 seconds. For example, the immersion time of the oxide film in the pretreatment agent can be 80 seconds, 85 seconds, 90 seconds, 95 seconds, 100 seconds, 105 seconds, 110 seconds, 115 seconds, 120 seconds, or any value within the range of any two of the above values. This application has found that extending the immersion time of the pretreatment agent with a suitable phosphoric acid content to the above range helps to increase the deposition rate of some coloring metal salts in the pore structure after immersion treatment, thereby improving the coloring efficiency.

[0028] S3: The aluminum alloy is colored by soaking an oxide film with a second pore size in a colorant, the colorant comprising a coloring metal salt, such that at least a portion of the coloring metal salt adheres to the oxide film.

[0029] After the preliminary treatment, this application uses an immersion method to allow the coloring metal salt to adhere and deposit within the porous structure of the oxide film through material adsorption, thereby producing a coloring effect. By selecting the coloring metal salt, the target color is achieved. In particular, the preliminary step forms a dense, abundant, and relatively large pore structure, providing sufficient deposition structure for the coloring metal salt and contributing to improved coloring stability and uniformity.

[0030] Current technologies use organic dyes for dyeing, but these dyes are susceptible to acidic residues. When a workpiece is placed in the dyeing tank, strong acid hidden in the crevices slowly releases into the surrounding dyeing solution, creating a highly acidic microenvironment in a localized area. Many organic dyes undergo chemical structural changes at low pH levels, leading to decreased solubility and a change from a dissolved state to a precipitated or aggregated state, making them unadsorbable. Furthermore, commonly used organic dye molecules, when dissolved in water, generally exist as negatively charged anions. In acidic localized areas, the negatively charged groups on the organic dye molecules are subjected to a large amount of H+. + Protonation transforms dye molecules into uncharged groups, eliminating the electrostatic repulsion between them. The solubility of these uncharged dye molecules drops sharply, causing them to aggregate and precipitate directly from the solution. Although the oxide film containing acidic regions is positively charged, some dyes remain charged and attracted. However, the dominant physical adsorption and hydrogen bonding are significantly weakened due to the structural change (protonation) of the dye molecules. Therefore, organic dyes are significantly affected by acidic residues, resulting in poor coloring. In contrast, the deposition of inorganic color-developing metal salts in this application is primarily through physical adsorption and is not affected by acidic residues. The pretreatment process only requires phosphoric acid immersion, eliminating the need for multiple ultrasonic cleaning steps, thus reducing the cost of the coloring process and the risk of poor coloring. Furthermore, the coloring process in this application is achieved through immersion, making it simpler and more efficient.

[0031] In some embodiments, the coloring metal salt includes one or more of Cu2Fe(CN)6, Fe4[Fe(CN)6]3, and CoS. As an example, the colorant of this application may employ the aforementioned coloring metal salt. Specifically, coloring with Cu2Fe(CN)6 can give the aluminum alloy surface a light gold-related color, coloring with Fe4[Fe(CN)6]3 can give the aluminum alloy surface a light blue-related color, and coloring with CoS can give the aluminum alloy surface a yellow-related color.

[0032] In some embodiments, the colorant further includes a precursor of a color-developing metal salt. The precursor forms the color-developing metal salt through a chemical reaction during the immersion process. The precursor is used for immersion one by one to induce the chemical reaction and form the color-developing metal salt. In the coloring process of this application, the precursor required for the chemical reaction can also be distributed on the oxide film by immersing one by one. Finally, a chemical reaction occurs during the immersion process to form the color-developing metal salt, which then adheres and deposits within the porous structure of the oxide film to produce a coloring effect. Forming the color-developing metal salt through a chemical reaction is beneficial for obtaining a more uniformly dispersed color-developing metal salt. The preliminary step forms a dense, abundant, and relatively large pore structure, providing sufficient deposition structure for the color-developing metal salt formed by the reaction, and also helps to improve the stability and uniformity of the coloring.

[0033] In some embodiments, the precursor comprises copper sulfate and potassium ferrocyanide, wherein the concentration of copper sulfate is from 0.3 g / L to 0.6 g / L and the concentration of potassium ferrocyanide is from 0.3 g / L to 0.6 g / L. For example, the concentration of copper sulfate can be 0.3 g / L, 0.33 g / L, 0.36 g / L, 0.39 g / L, 0.42 g / L, 0.45 g / L, 0.48 g / L, 0.51 g / L, 0.54 g / L, 0.57 g / L, 0.6 g / L, or any value within the range of any two of the above values; the concentration of potassium ferrocyanide can be 0.3 g / L, 0.33 g / L, 0.36 g / L, 0.39 g / L, 0.42 g / L, 0.45 g / L, 0.48 g / L, 0.51 g / L, 0.54 g / L, 0.57 g / L, 0.6 g / L, or any value within the range of any two of the above values. As an example, the precursors copper sulfate and potassium ferrocyanide can undergo the following chemical reaction: 2CuSO4 + K4Fe(CN)6 → Cu2Fe(CN)6 + 2K2SO4, forming Cu2Fe(CN)6. Controlling the concentrations of copper sulfate and potassium ferrocyanide within the aforementioned range during the soaking process, controlling the reaction rate, and forming an appropriate amount of coloring metal salt product helps to make the color closer to the corresponding target color. It also helps the coloring metal salt product to adhere evenly and fully to the oxide film, forming a stable coloring effect.

[0034] In some embodiments, the precursor comprises an iron salt and potassium ferrocyanide, wherein the iron salt comprises at least one of ferric sulfate and ferric chloride, the concentration of the iron salt is from 0.7 g / L to 0.9 g / L, and the concentration of potassium ferrocyanide is from 0.6 g / L to 0.8 g / L. For example, the concentration of iron salt can be 0.7 g / L, 0.72 g / L, 0.74 g / L, 0.76 g / L, 0.78 g / L, 0.8 g / L, 0.82 g / L, 0.84 g / L, 0.86 g / L, 0.88 g / L, 0.9 g / L, or any value within the range of any two of the above values; the concentration of potassium ferrocyanide can be 0.6 g / L, 0.62 g / L, 0.64 g / L, 0.66 g / L, 0.68 g / L, 0.7 g / L, 0.72 g / L, 0.74 g / L, 0.76 g / L, 0.78 g / L, 0.8 g / L, or any value within the range of any two of the above values. As an example, the precursor iron salt and potassium ferrocyanide can undergo the following chemical reaction: 2Fe₂(SO₄)₃ + 3K₄Fe(CN)₆ → Fe₄[Fe(CN)₆]₃ + 6K₂SO₄, forming Fe₄[Fe(CN)₆]₃. Controlling the concentrations of iron salt and potassium ferrocyanide within the aforementioned range during the soaking process, controlling the reaction rate, and forming an appropriate amount of coloring metal salt product helps to make the color closer to the corresponding target color. It also helps the coloring metal salt product to adhere evenly and fully to the oxide film, forming a stable coloring effect.

[0035] In some embodiments, the precursor comprises cobalt acetate and sodium sulfide, wherein the concentration of cobalt acetate is from 0.3 g / L to 0.6 g / L, and the concentration of sodium sulfide is from 0.4 g / L to 0.8 g / L. For example, the concentration of cobalt acetate may be 0.3 g / L, 0.33 g / L, 0.36 g / L, 0.39 g / L, 0.42 g / L, 0.45 g / L, 0.48 g / L, 0.51 g / L, 0.54 g / L, 0.57 g / L, 0.6 g / L, or any value within the range of any two of the above values; the concentration of sodium sulfide may be 0.4 g / L, 0.45 g / L, 0.5 g / L, 0.55 g / L, 0.6 g / L, 0.65 g / L, 0.7 g / L, 0.75 g / L, 0.8 g / L, or any value within the range of any two of the above values. As an example, the precursors cobalt acetate and sodium sulfide can undergo the following chemical reaction: CoAc₂ + Na₂S → CoS + 2NaAc, forming CoS. Controlling the concentrations of cobalt acetate and sodium sulfide within the aforementioned range during the soaking process, controlling the reaction rate, and forming an appropriate amount of coloring metal salt product helps to make the color closer to the corresponding target color. It also helps the coloring metal salt product to adhere evenly and fully to the oxide film, forming a stable coloring effect. It should be noted that within the above concentration range, the deposited coloring metal salt product CoS exhibits a near-grayish-yellow color effect.

[0036] In some embodiments, the precursor comprises cobalt acetate and sodium sulfide, wherein the concentration of cobalt acetate is from 1.8 g / L to 2.2 g / L, and the concentration of sodium sulfide is from 2 g / L to 2.4 g / L. For example, the concentration of cobalt acetate may be 1.8 g / L, 1.85 g / L, 1.9 g / L, 1.95 g / L, 2 g / L, 2.05 g / L, 2.1 g / L, 2.15 g / L, 2.2 g / L, or any value within the range of any two of the above values; the concentration of sodium sulfide may be 2 g / L, 2.05 g / L, 2.1 g / L, 2.15 g / L, 2.2 g / L, 2.25 g / L, 2.3 g / L, 2.35 g / L, 2.4 g / L, or any value within the range of any two of the above values. As an example, by controlling the concentrations of cobalt acetate and sodium sulfide within the above range during the soaking process, the resulting colored metal salt product CoS exhibits a brownish-yellow color effect after deposition.

[0037] In some embodiments, when impregnating an oxide film having a second pore size with a colorant, the method further includes: aerating the colorant to form bubbles. This application has found that aerating the colorant and forming bubbles makes the precursors in the reaction more uniformly mixed or the colored metal salts more uniformly distributed, thus helping to further improve the uniformity of the colorant distribution, thereby further improving the uniformity of coloring.

[0038] In some embodiments, the coloring depth of the aluminum alloy is changed from a first depth to a second depth by altering the soaking time and / or concentration of the colorant. In the coloring process of this application, based on the specific color effect produced by a specific coloring metal salt, the degree of deposition of the specific coloring metal salt can be changed by altering the soaking time and / or concentration of the colorant, thereby changing the coloring depth. Understandably, a greater degree of deposition results in a deeper coloring depth. However, excessive deposition may also cause some of the deposited coloring metal salt to diffuse and overflow, reducing the degree of deposition and decreasing the coloring depth.

[0039] In some embodiments, after coloring the aluminum alloy, the colored aluminum alloy is further treated with a sealing agent at a concentration of 8 g / L to 16 g / L, at a temperature of 90 °C to 97 °C, and for a time of 1800 seconds to 3000 seconds. For example, the concentration of the sealing agent can be 8 g / L, 9 g / L, 10 g / L, 11 g / L, 12 g / L, 13 g / L, 14 g / L, 15 g / L, 16 g / L, or any value within the range of any two of the above values; the temperature at which the sealing agent is used to treat the aluminum alloy can be 90 ℃, 91 ℃, 92 ℃, 93 ℃, 94 ℃, 95 ℃, 96 ℃, 97 ℃, or any value within the range of any two of the above values; and the time can be 1800 seconds, 1900 seconds, 2000 seconds, 2100 seconds, 2200 seconds, 2300 seconds, 2400 seconds, 2500 seconds, 2600 seconds, 2700 seconds, 2800 seconds, 2900 seconds, 3000 seconds, or any value within the range of any two of the above values. In this application, a precipitate is formed to fill the pores through a combined mechanism of chemical adsorption and hydration reaction of the sealing agent. This not only further improves the mechanical properties of the aluminum alloy but also helps maintain the stability of the coloring effect. Controlling the concentration of the sealing agent, the treatment temperature, and the time within the above-mentioned ranges is beneficial for fully sealing the pores and forming a dense sealing layer. This reduces color changes or fading caused by improper sealing processes and improves the repeatability of the coloring process through controllable conditions.

[0040] In some embodiments, after coloring the aluminum alloy, the process further includes drying the colored aluminum alloy. In some embodiments, the drying temperature is 50°C to 80°C, and the drying time is 1200 seconds to 3600 seconds. For example, the drying temperature can be 50°C, 53°C, 56°C, 59°C, 62°C, 65°C, 68°C, 71°C, 74°C, 77°C, 80°C, or any value within the range of any two of the above values; the drying time can be 1200 seconds, 1400 seconds, 1600 seconds, 1800 seconds, 2000 seconds, 2200 seconds, 2400 seconds, 2600 seconds, 2800 seconds, 3000 seconds, 3200 seconds, 3400 seconds, 3600 seconds, or any value within the range of any two of the above values. By controlling the temperature and time mentioned above to dry the colored aluminum alloy, it is helpful to make the moisture evaporate quickly and evenly, avoid local concentration of minerals, reduce watermarks caused by uneven evaporation of moisture, and obtain a clean colored aluminum alloy surface.

[0041] One embodiment of this application also provides a method for preparing a housing of an electronic device, comprising: providing an aluminum alloy, coloring the aluminum alloy by the above-mentioned aluminum alloy anodizing coloring process to obtain a colored aluminum alloy; and bonding the colored aluminum alloy with a plastic material by injection molding to obtain a housing of the electronic device.

[0042] The aluminum alloy anodizing coloring process of this application involves the deposition of coloring metal salts within the oxide film. This process is less susceptible to the effects of residual acid from the pretreatment, achieving good coloring results even at the gaps between aluminum and plastic joints. Furthermore, it is less affected by pH deviations introduced by residual acid, which helps improve the overall coloring effect and enhances the colorfastness. Therefore, the electronic device casing of this application exhibits excellent coloring, with normal coloring at the aluminum-plastic joints.

[0043] The present application's solution will be explained below with reference to embodiments. Those skilled in the art will understand that the following examples are for illustrative purposes only and should not be construed as limiting the present application. Unless otherwise stated, reagents, software, and instruments involved in the following embodiments that are not specifically mentioned are all conventional commercially available products or open-source materials.

[0044] Example 1: An anodizing coloring process for aluminum alloys, comprising: S1: Degreasing treatment, using 50 g / L to 60 g / L of R105 agent to immerse the material at 50°C to 60°C for 120 to 300 seconds to clean the surface of oil and other dirt, ensuring surface cleanliness; wash with water at room temperature for 30 to 120 seconds in preparation for the next step.

[0045] S2: Alkali treatment, immersing in sodium hydroxide at 20 g / L to 40 g / L at 30°C to 50°C for 10 to 60 seconds to remove the original oxide film on the surface; then rinsing with water at room temperature for 30 to 120 seconds in preparation for subsequent steps.

[0046] S3: The first black film removal process involves soaking the material in 10wt% to 40wt% nitric acid at room temperature for 120 to 300 seconds to remove ash and neutralize it, ensuring a uniform surface condition. The material is then washed with water at room temperature for 30 to 120 seconds to prepare for subsequent steps.

[0047] S4: Polishing treatment, immersing the aluminum surface in a chemical polishing solution with a specific gravity of 1.70 to 1.75 phosphoric acid as a base at 70°C to 100°C for 30 to 90 seconds to enhance the gloss, for example, to 40 GU to 100 GU; then rinsing with water at 50°C to 60°C for 30 to 120 seconds in preparation for the next step.

[0048] S5: Second black film stripping treatment, using 10wt% to 40wt% nitric acid to soak at room temperature for 120 to 300 seconds to remove ash and neutralize, so as to make the surface state of the material uniform; wash with water at room temperature for 30 to 120 seconds in order to proceed with the next step.

[0049] S6: Anodizing, using a sulfuric acid solution of 100 g / L to 300 g / L at 10°C to 30°C, and a voltage of 10 V to 17 V, to control the oxide film thickness to 8 μm to 18 μm. The electrolyte can be phosphoric acid, oxalic acid, tartaric acid, lactic acid, citric acid, or a mixture of two or more components, in addition to sulfuric acid. Wash with water at room temperature for 30 to 120 seconds to prepare for subsequent steps.

[0050] S7: Soak the oxide film in a pretreatment agent, including phosphoric acid, to expand the first pore size of the oxide film into a second pore size. Specifically, soak the film in a 1wt% to 10wt% phosphoric acid solution at room temperature for 0 to 60 seconds, followed by ultrasonic washing with pure water for 2 to 5 minutes to increase the pore size of the oxide film; then wash with water at room temperature for 30 to 120 seconds to prepare for subsequent steps.

[0051] S8: The aluminum alloy is colored by immersing it in an oxide film with a second pore size using a colorant, which includes a coloring metal salt. At least a portion of the coloring metal salt adheres to the oxide film. Specifically, at room temperature, the aluminum alloy with the oxide film having a second pore size is immersed in a copper sulfate solution of 0.3 g / L to 0.6 g / L. After rinsing with water, it is then immersed in a potassium ferrocyanide solution of 0.3 g / L to 0.6 g / L. During the coloring process, both solutions A and B can be repeatedly used, but the product surface must be rinsed with pure water after each immersion to avoid solution residue. The immersion time needs to be controlled according to the target color value. The depth of the color is adjusted by the change in the deposition degree of the metal salt generated in the oxide film to achieve the final target color value.

[0052] S9: Sealing treatment, using a sealing agent (Okuno DX-500) with a concentration of 8 g / L to 16 g / L, immersing at 90°C to 97°C for 1800 to 3000 seconds to seal the oxide film formed by oxidation and ensure the performance of the anode layer; washing with water at room temperature for 30 to 120 seconds in preparation for subsequent steps.

[0053] S10: Drying treatment, drying for 1200 to 3600 seconds in an air-circulating oven at 50°C to 80°C.

[0054] The colored aluminum alloy obtained in Example 1 was subjected to visual inspection, and the alloy exhibited a light gold color. Colorimetric analysis showed that the color difference values ​​of the light gold color of the colored aluminum alloy in Example 1 under different immersion times are shown in Table 1. Based on the color difference values ​​of the standard light gold (L*: 88.68, a*: 1.49, b*: 4.66), it can be seen that the alloy after immersion in copper sulfate solution for 4 minutes and potassium ferrocyanide solution for 2 minutes is quite close to the standard light gold color.

[0055] Table 1. Color difference values ​​of light gold color exhibited under different soaking times in Example 1 of this application. This application also uses organic dyes for coloring, comparing it with Example 1. Five products were made for each example, each based on a light gold color scheme, and the color difference values ​​are shown in Table 2. It can be seen that the color difference value of the coloring process in Example 1 is very close to the color difference value of traditional organic dyeing, basically meeting the required color difference value. This application also produced 20 more products from Example 1 and inspected their appearance, finding no discoloration in the gaps between the aluminum and plastic.

[0056] Table 2. Color difference values ​​between aluminum alloys colored with organic dyes and those colored with light gold in Example 1 of this application. Example 2: The difference from Example 1 is that in S8, the aluminum alloy with the oxide film having the second pore size is immersed in a ferric sulfate solution of 0.7 g / L to 0.9 g / L, washed with water, and then immersed in a potassium ferrocyanide solution of 0.6 g / L to 0.8 g / L. The immersion time needs to be controlled by the target color value. The depth of color is adjusted by the change in the degree of deposition of the metal salt generated in the oxide film to achieve the final target color value.

[0057] The colored aluminum alloy obtained in Example 2 was subjected to visual inspection, and the alloy exhibited a light blue color. Colorimetric analysis showed that the light blue color difference values ​​of the colored aluminum alloy from Example 2 under different immersion times are shown in Table 3. In Table 3, the L value represents brightness; a larger L value indicates a brighter color, and a smaller L value indicates a darker color. A positive a value indicates a reddish tint, and a negative a value indicates a greenish tint. A positive b value indicates a yellowish tint, and a negative b value indicates a bluish tint. In Table 3, all b values ​​are negative, indicating that the combination of ferric sulfate solution and potassium ferrocyanide solution used in the process provided in this application can achieve a light blue coloring effect.

[0058] Table 3. Color difference values ​​of light blue color exhibited at different soaking times in Example 2 of this application. Example 3: The difference from Example 1 is as follows: In step S8, an aluminum alloy with an oxide film having a second pore size is immersed in a cobalt acetate solution of 0.3 g / L to 0.6 g / L, washed with water, and then immersed in a sodium sulfide solution of 0.4 g / L to 0.8 g / L. The immersion time needs to be controlled according to the target color value. The depth of color is adjusted by the change in the degree of deposition of the metal salt generated in the oxide film to achieve the final target color value.

[0059] Example 4: The difference from Example 3 is that in S8, the aluminum alloy with the oxide film having the second pore size is immersed in a cobalt acetate solution of 1.8 g / L to 2.2 g / L, washed with water, and then immersed in a sodium sulfide solution of 2 g / L to 2.4 g / L. The immersion time needs to be controlled by the target color value. The depth of color is adjusted by the change in the degree of deposition of the metal salt generated in the oxide film to achieve the final target color value.

[0060] The colored aluminum alloys obtained from Examples 3 and 4 were subjected to visual inspection, and the alloys exhibited a yellowish hue. Colorimetric analysis revealed color differences in the yellow color of the colored aluminum alloys from Examples 3 and 4 under different immersion times, as shown in Tables 4 and 5. Under the conditions of Example 3, the aluminum alloy exhibited a grayish-yellow color, while under the conditions of Example 4, the aluminum alloy exhibited a brownish-yellow color after the precursor solution concentration was increased.

[0061] Table 4. Color difference values ​​of grayish-yellow color exhibited at different soaking times in Example 3 of this application. Table 5. Color difference values ​​of brownish-yellow color exhibited at different soaking times in Example 4 of this application. Compared to existing organic dye coloring techniques, the aluminum alloy anodizing coloring process in Examples 1-4 of this application, which uses color-developing metal salts deposited within the oxide film, is less susceptible to the effects of residual acid from pretreatment. It achieves good coloring results even in the gaps at the aluminum-plastic joint, producing various color effects such as light gold, light blue, and brown tones. Furthermore, it is less affected by pH deviations introduced by residual acid, which helps improve the overall coloring effect and enhance colorfastness. Therefore, the aluminum alloy anodizing coloring process of this application reduces the reliance on multiple ultrasonic cleaning processes required in conventional organic dye coloring, thereby helping to reduce the cost of pretreatment and the risk of poor coloring.

[0062] Furthermore, in existing organic dye coloring processes, after anodizing and before dyeing, the process requires sequential steps: 2-7 minutes of ultrasonic cleaning, 1-3 minutes of ultrasonic rinsing, 2-7 minutes of ultrasonic cleaning, 1-3 minutes of ultrasonic rinsing, 0-2 minutes of degreasing, 0-2 minutes of black film removal, 2-7 minutes of ultrasonic cleaning, 1-3 minutes of ultrasonic rinsing, 2-7 minutes of chemical soaking, and 1-3 minutes of ultrasonic rinsing. The average pretreatment time for this stage is approximately 30 minutes. In contrast, in this application, after anodizing and before dyeing, only approximately 1 minute of phosphoric acid soaking and 2-7 minutes of ultrasonic rinsing are required, with an average pretreatment time of 5.5 minutes, significantly reducing the pretreatment time for this stage.

[0063] In summary, the aluminum alloy anodizing coloring process provided in this application can effectively save the steps of frequently cleaning acidic residues in conventional organic dyeing processes, optimize the overall process time, and does not produce discoloration at the aluminum-plastic joint.

[0064] The above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to the above preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of this application should not depart from the spirit and scope of the technical solutions of this application.

Claims

1. An anodizing coloring process for aluminum alloys, characterized in that, include: An oxide film is formed on the surface of an aluminum alloy by anodizing, the oxide film having a first pore size; The oxide film is soaked in a pretreatment agent, including phosphoric acid, to expand the first pore size of the oxide film into a second pore size. The aluminum alloy is colored by soaking the oxide film having the second pore size in a colorant comprising a coloring metal salt, such that at least a portion of the coloring metal salt adheres to the oxide film.

2. The aluminum alloy anodizing coloring process as described in claim 1, characterized in that, The phosphoric acid in the pretreatment agent accounts for 1 wt% to 10 wt% by mass.

3. The aluminum alloy anodizing coloring process as described in claim 1, characterized in that, The time for immersing the oxide film with the pretreatment agent meets one of the following conditions: (1) Greater than 0 seconds and less than or equal to 60 seconds; (2) 80 to 120 seconds.

4. The aluminum alloy anodizing coloring process as described in claim 1, characterized in that, The color-developing metal salt includes one or more of Cu2Fe(CN)6, Fe4[Fe(CN)6]3, and CoS.

5. The aluminum alloy anodizing coloring process as described in claim 3, characterized in that, The colorant also includes the precursor of the color-developing metal salt, which forms the color-developing metal salt through a chemical reaction during the soaking process. The soaking is performed one by one using the precursor to cause the chemical reaction to form the color-developing metal salt. The precursor satisfies at least one of the following conditions: (1) The precursor comprises copper sulfate and potassium ferrocyanide, wherein the concentration of copper sulfate is from 0.3 g / L to 0.6 g / L and the concentration of potassium ferrocyanide is from 0.3 g / L to 0.6 g / L; (2) The precursor comprises an iron salt and potassium ferrocyanide, wherein the iron salt comprises at least one of ferric sulfate and ferric chloride, the concentration of the iron salt is from 0.7 g / L to 0.9 g / L, and the concentration of the potassium ferrocyanide is from 0.6 g / L to 0.8 g / L; (3) The precursor comprises cobalt acetate and sodium sulfide, wherein the concentration of cobalt acetate is 0.3 g / L to 0.6 g / L and the concentration of sodium sulfide is 0.4 g / L to 0.8 g / L; (4) The precursor includes cobalt acetate and sodium sulfide, wherein the concentration of cobalt acetate is from 1.8 g / L to 2.2 g / L and the concentration of sodium sulfide is from 2 g / L to 2.4 g / L.

6. The aluminum alloy anodizing coloring process as described in claim 1, characterized in that, When impregnating the oxide film having the second pore size with the colorant, the method further includes: aerating the colorant to form bubbles; and / or, By changing the soaking time and / or the concentration of the colorant, the coloring depth of the aluminum alloy is changed from a first depth to a second depth.

7. The aluminum alloy anodizing coloring process according to any one of claims 1-6, characterized in that, The anodizing process satisfies at least one of the following conditions: (1) The voltage for the anodizing is 10 V to 17 V; (2) The anodizing temperature is 10 ℃ to 30 ℃; (3) The electrolyte for the anodic oxidation includes an acid solution with a concentration of 100 g / L to 300 g / L.

8. The aluminum alloy anodizing coloring process according to any one of claims 1-6, characterized in that, After coloring the aluminum alloy, the process further includes treating the colored aluminum alloy with a sealing agent. The concentration of the sealing agent is from 8 g / L to 16 g / L, and the temperature at which the sealing agent is used to treat the aluminum alloy is from 90 ℃ to 97 ℃, and the treatment time is from 1800 seconds to 3000 seconds.

9. The aluminum alloy anodizing coloring process according to any one of claims 1-6, characterized in that, Before forming the oxide film through anodizing, the aluminum alloy undergoes a pretreatment process, which includes one or more of the following: degreasing, alkaline etching, polishing, and black film stripping. The aluminum alloy is degreased by immersing it in a degreasing agent at a concentration of 50 g / L to 60 g / L, at a immersion temperature of 50 ℃ to 60 ℃, and for a immersion time of 120 seconds to 300 seconds. The aluminum alloy is subjected to alkaline etching treatment by immersing it in an alkaline solution with a concentration of 20 g / L to 40 g / L, an immersion temperature of 30 ℃ to 50 ℃, and an immersion time of 10 seconds to 60 seconds. The aluminum alloy is polished by immersing it in a chemical polishing solution, the chemical polishing solution including phosphoric acid, the specific gravity of the phosphoric acid in the chemical polishing solution being 1.70 to 1.75, the immersion temperature being 70 ℃ to 100 ℃, and the immersion time being 30 seconds to 90 seconds; The aluminum alloy is subjected to the black film removal process by immersing it in an acid solution with a concentration of 10wt% to 40wt% for a duration of 120 to 300 seconds.

10. A method for manufacturing a housing of an electronic device, characterized in that, include: An aluminum alloy is provided, and the aluminum alloy is colored by the aluminum alloy anodizing coloring process as described in any one of claims 1-9 to obtain a colored aluminum alloy; The colored aluminum alloy and plastic are combined by injection molding to obtain the housing of the electronic device.

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