Anodizing process applied to recycled aluminum alloys

Abstract

The application provides an anodic oxidation process applied to recycled aluminum alloy, which comprises the following steps: performing degreasing treatment on an aluminum alloy part made of recycled aluminum alloy; performing cleaning on the aluminum alloy part after the degreasing treatment and performing pre-activation treatment, so that the aluminum alloy part is contacted with a liquid pre-activation agent and is electrified, the pre-activation agent comprises sulfuric acid and oxalic acid, and the voltage range of the pre-activation treatment is 18-25 V; performing cleaning on the aluminum alloy part after the pre-activation and performing targeted stripping treatment, so that the aluminum alloy part is contacted with a liquid targeted stripping agent, the targeted stripping agent comprises a descaling agent, a stabilizing agent and a complexing agent, and the descaling agent is alkaline liquor; performing cleaning on the aluminum alloy part after the targeted stripping and performing chemical polishing treatment, so that the aluminum alloy part is contacted with a mixed acid liquid containing sulfuric acid and phosphoric acid; performing cleaning on the aluminum alloy part after the chemical polishing and performing anodic oxidation treatment, so that an anodic oxidation film is formed on the surface of the aluminum alloy part, and the electrolyte used in the anodic oxidation treatment comprises sulfuric acid and oxalic acid.

Description

Technical Field

[0001] This application relates to the field of metal processing, and more particularly to an anodizing process for recycled aluminum alloys. Background Technology

[0002] Aluminum alloys, due to their advantages such as low specific gravity, good machinability, and high strength-to-weight ratio, have seen increasing applications in electronic products such as mobile phone casings, computer casings, and frames in recent years. However, because aluminum alloys have low chemical stability and poor corrosion resistance, appropriate surface treatment is usually required. Currently, a commonly used surface treatment method for aluminum alloys is anodizing, which imparts a certain degree of wear resistance and corrosion resistance. The process of placing an aluminum alloy product as the anode in an electrolyte solution and using electrolysis to form a thin film of aluminum oxide on its surface is called anodizing. Anodized aluminum alloy products are called aluminum alloy anodized products, and anodized aluminum alloys have a superior appearance.

[0003] Recycled aluminum refers to aluminum alloys or aluminum metals obtained through sorting, salt smelting, and remelting of scrap aluminum, aluminum alloy materials, or aluminum-containing waste. The main sources of waste include aluminum ingots, aluminum cans, aluminum wire, and aluminum chips. With the rapid development of the aluminum industry and the long-term accumulation of aluminum reserves, my country is about to enter a peak period of aluminum scrapping, leading to a continuous increase in recycled aluminum resources and a maturing potential for scrap aluminum recycling, resulting in a significant increase in recyclable scrap aluminum resources. Recycled aluminum alloy ash is generated during the remelting process of recycled aluminum alloys. It is formed when molten aluminum comes into contact with the atmosphere, causing surface oxidation and forming a semi-solid slag floating on the surface. Compared to electrolytic aluminum ash, recycled aluminum alloy ash has a higher salt content and a darker color, generally appearing grayish-black. This is mainly because salts such as NaCl, KCl, or fluorides (CaF) are usually added as refining agents during the remelting process. The main components of recycled aluminum alloy ash are aluminum (10%–50%), aluminum oxide (30%–50%), salts (5%–15%), and other oxides (Fe, Cu, Mg, Si, Zn, etc.).

[0004] Statistics show that the aluminum recovery rate in my country's recycling process is generally 75% to 85%. Because recycled aluminum alloys contain many impurities and have a rough surface, they are prone to yellowing or blackening after anodizing, resulting in poor product appearance and unusable applications. How to solve these problems is a question that those skilled in the art need to consider. Summary of the Invention

[0005] This application provides an anodizing process for recycled aluminum alloys. The anodized aluminum alloys prepared by this method are less prone to yellowing or blackening and have a better appearance.

[0006] This application provides an anodizing process for recycled aluminum alloys, comprising the following steps:

[0007] Step S1: Degreasing, degreasing the aluminum alloy parts made of recycled aluminum alloy;

[0008] Step S2: Pre-activation. The degreased aluminum alloy parts are cleaned and pre-activated by contacting the aluminum alloy parts with a liquid pre-activating agent and passing electricity through them. The pre-activating agent includes sulfuric acid and oxalic acid. The voltage range of the pre-activation treatment is 18 to 25V.

[0009] Step S3: Targeted peeling. The pre-activated aluminum alloy parts are cleaned and subjected to targeted peeling treatment, so that the aluminum alloy parts come into contact with the liquid targeted release agent. The targeted release agent includes a desiccant, a stabilizer and a complexing agent. The desiccant is an alkaline solution.

[0010] Step S4: Chemical polishing. The aluminum alloy parts after targeted stripping are cleaned and chemically polished, so that the aluminum alloy parts come into contact with a mixed acid solution containing sulfuric acid and phosphoric acid.

[0011] Step S5: Anodizing. The chemically polished aluminum alloy parts are cleaned and anodized to form an anodized film on the surface of the aluminum alloy parts. The electrolyte used for anodizing includes sulfuric acid and oxalic acid.

[0012] In one possible implementation, the concentration of sulfuric acid in the pre-activator ranges from 60 g / L to 100 g / L.

[0013] In one possible implementation, the concentration of oxalic acid in the pre-activator ranges from 10 g / L to 30 g / L.

[0014] In one possible implementation, the pre-activation time in step S2 ranges from 5 to 10 minutes.

[0015] In one possible implementation, in step S3, the descaling agent is a sodium hydroxide solution with a concentration ranging from 20 g / L to 40 g / L.

[0016] In one possible implementation, in step S3, the stabilizer is a sodium phosphate solution with a concentration ranging from 6 g / L to 12 g / L.

[0017] In one possible implementation, in step S3, the complexing agent is a sodium tartrate solution with a concentration ranging from 1 g / L to 3 g / L.

[0018] In one possible implementation, in step S3, the targeting detachment agent further includes a surface conditioner, which is a sodium thiosulfate solution with a concentration ranging from 1 g / L to 1.5 g / L.

[0019] In one possible implementation, in step S4, the concentration ratio of sulfuric acid to phosphoric acid ranges from 1:4 to 1:7, the chemical polishing temperature is room temperature, and the chemical polishing time is 1 to 4 minutes.

[0020] In one possible implementation, the anodizing process applied to recycled aluminum alloys further includes the following steps:

[0021] Step S6: Sealing. Clean the anodized aluminum alloy parts and seal them. The sealing solution is a nickel sulfate solution or nickel acetate solution with a mass concentration of 5 g / L to 15 g / L. The sealing time is 15 minutes to 60 minutes and the temperature is 85°C to 95°C.

[0022] Step S7: Drying. Clean and dry the sealed aluminum alloy parts. Place the aluminum alloy parts in an oven at a temperature of 65°C to 90°C for 5 to 30 minutes.

[0023] Compared to existing technologies, the anodizing process for recycled aluminum alloys described in this application, by introducing pre-activation and targeted stripping processes before the anodizing process, largely removes insoluble substances such as intermetallic compounds on the outer layer of the aluminum alloy, significantly improving the yellowing and blackening phenomenon after anodizing. Furthermore, the anodizing process for recycled aluminum alloys described in this application, while improving the yellowing and blackening of the aluminum alloy surface, avoids the introduction of chemicals containing elements such as chromium and fluorine, reducing the risk of environmental pollution and making the entire method more environmentally friendly. Attached Figure Description

[0024] Figure 1 This application provides a flowchart of an anodizing process applied to recycled aluminum alloys.

[0025] Figure 2 A schematic scanning electron microscope (SEM) image of an aluminum alloy part after degreasing treatment in the anodizing process of recycled aluminum alloy provided in this application embodiment.

[0026] Figure 3 A schematic scanning electron microscope (SEM) image of an aluminum alloy part after pre-activation treatment in the anodizing process of recycled aluminum alloy provided in this application embodiment.

[0027] Figure 4 A schematic scanning electron microscope (SEM) image of an aluminum alloy part after targeted stripping treatment in the anodizing process of recycled aluminum alloy provided in this application embodiment.

[0028] Figure 5This is a schematic cross-sectional image of an aluminum alloy part after degreasing treatment in the anodizing process of recycled aluminum alloy provided in this application embodiment.

[0029] Figure 6 A schematic cross-sectional image of an aluminum alloy part after pre-activation treatment in the anodizing process of recycled aluminum alloy provided in this application embodiment.

[0030] Figure 7 A schematic cross-sectional image of an aluminum alloy part after targeted stripping treatment in the anodizing process of recycled aluminum alloy provided in this application embodiment.

[0031] The following detailed description, in conjunction with the accompanying drawings, further illustrates this application. Detailed Implementation

[0032] The following description will refer to the accompanying drawings to provide a more complete picture of the present application. The drawings illustrate exemplary embodiments of the present application. However, the present application may be implemented in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. These exemplary embodiments are provided to make the present application thorough and complete, and to fully convey the scope of the present application to those skilled in the art. Similar reference numerals denote the same or similar components.

[0033] The terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to limit the application. As used herein, unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the” are intended to also include the plural forms. Furthermore, when used herein, “comprising” and / or “including” and / or “having,” integers, steps, operations, components, and / or components, but does not exclude the presence or addition of one or more other features, regions, integers, steps, operations, components, and / or groups thereof.

[0034] Unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. Furthermore, unless expressly defined herein, terms such as those defined in a general dictionary should be interpreted as having the same meaning as they have in the relevant art and in the content of this application, and will not be interpreted as having an idealized or overly formal meaning.

[0035] The specific embodiments of this application will be further described in detail below with reference to the accompanying drawings.

[0036] like Figure 1 As shown in the figure, this application provides an anodizing process for recycled aluminum alloys, including the following steps:

[0037] Step S1: Degreasing, degreasing the aluminum alloy parts made of recycled aluminum alloy.

[0038] Furthermore, degreasing removes grease, dust, and other contaminants from the surface of the aluminum alloy parts, making the surface of the aluminum alloy parts hydrophilic. Sodium phosphate can be used as the degreasing solution, with a mass concentration of 5 to 90 g / L. The degreasing temperature is 20 to 60°C, and the time is 3 to 10 minutes.

[0039] Step S2: Pre-activation. The degreased aluminum alloy parts are cleaned and pre-activated by contacting the aluminum alloy parts with a liquid pre-activating agent and passing electricity through them. The pre-activating agent includes sulfuric acid and oxalic acid, and the voltage range of the pre-activation treatment is 18 to 25V.

[0040] In one embodiment, the concentration of sulfuric acid in the pre-activator ranges from 60 g / L to 100 g / L.

[0041] Furthermore, the concentration range of sulfuric acid can be 62 g / L, 64 g / L, 66 g / L, 68 g / L, 70 g / L, 72 g / L, 74 g / L, 76 g / L, 78 g / L, 80 g / L, 82 g / L, 84 g / L, 86 g / L, 88 g / L, 90 g / L, 92 g / L, 94 g / L, 96 g / L, and 98 g / L.

[0042] In one embodiment, the concentration of oxalic acid in the pre-activator ranges from 10 g / L to 30 g / L.

[0043] Furthermore, the concentration range of sulfuric acid can be 11 g / L, 12 g / L, 13 g / L, 14 g / L, 15 g / L, 16 g / L, 17 g / L, 18 g / L, 19 g / L, 21 g / L, 22 g / L, 23 g / L, 24 g / L, 25 g / L, 26 g / L, 27 g / L, 28 g / L, and 29 g / L.

[0044] In one embodiment, the pre-activation time in step S2 ranges from 5 to 10 minutes.

[0045] Furthermore, the pre-activation time range can be 5.5 minutes, 6 minutes, 6.5 minutes, 7 minutes, 7.5 minutes, 8 minutes, 8.5 minutes, 9 minutes, and 9.5 minutes.

[0046] Understandably, recycled aluminum alloys contain numerous metallic impurities, which can form insoluble intermetallic compounds on the alloy surface. These compounds, in the form of oxides, are embedded in the aluminum oxide film. Ordinary processes such as blackening, alkaline etching, and chemical polishing are insufficient to remove these impurities, especially silicon oxides, leading to potential yellowing or blackening of recycled aluminum alloys after anodizing. By placing the aluminum alloy parts in a pre-activator and applying electricity and pressure, the potential energy of some electrons in the crystal lattice of the metallic elements in the intermetallic compounds is reduced, allowing these insoluble intermetallic compounds to be removed during subsequent targeted stripping.

[0047] By placing the aluminum alloy parts in a pre-activator and applying electricity and pressure, the electrons of the metal in the part of the aluminum alloy parts in contact with the electrolyte transition to a higher energy level, which increases the potential energy of some electrons in the lattice of the metal elements in the intermetallic compound. This makes it easier to remove the insoluble intermetallic compound in the subsequent targeted stripping process. At the same time, the pre-activation process pulls oxygen atoms into the barrier layer to form a relatively stable protective layer structure, which prepares for the removal of impurities in the subsequent targeted stripping.

[0048] Step S3: Targeted peeling. The pre-activated aluminum alloy parts are cleaned and subjected to targeted peeling treatment, so that the aluminum alloy parts come into contact with the liquid targeted release agent. The targeted release agent includes a desiccant, a stabilizer and a complexing agent. The desiccant is an alkaline solution.

[0049] In one embodiment, the ash remover is a sodium hydroxide solution with a concentration ranging from 20 g / L to 40 g / L.

[0050] Furthermore, the concentration of the ash removal agent can be 21 g / L, 22 g / L, 23 g / L, 24 g / L, 25 g / L, 26 g / L, 27 g / L, 28 g / L, 29 g / L, 31 g / L, 32 g / L, 33 g / L, 34 g / L, 35 g / L, 36 g / L, 37 g / L, 38 g / L, and 39 g / L.

[0051] In one embodiment, the stabilizer is a sodium phosphate solution with a concentration ranging from 6 g / L to 12 g / L.

[0052] Furthermore, the concentration of the stabilizer can be 6.5 g / L, 7 g / L, 7.5 g / L, 8 g / L, 8.5 g / L, 9 g / L, 9.5 g / L, 10 g / L, 10.5 g / L, 11 g / L, and 11.5 g / L.

[0053] In one embodiment, the complexing agent is a sodium tartrate solution with a concentration ranging from 1 g / L to 3 g / L.

[0054] Furthermore, the concentration range of the complexing agent can be 1.1 g / L, 1.2 g / L, 1.3 g / L, 1.4 g / L, 1.5 g / L, 1.6 g / L, 1.7 g / L, 1.8 g / L, 1.9 g / L, 2.0 g / L, 2.1 g / L, 2.2 g / L, 2.3 g / L, 2.4 g / L, 2.5 g / L, 2.6 g / L, 2.7 g / L, 2.8 g / L, and 2.9 g / L.

[0055] In one embodiment, the targeting detachment agent further includes a surface conditioner, which is a sodium thiosulfate solution with a concentration range of 1 g / L to 1.5 g / L.

[0056] Understandably, in the targeted stripping process, a uniform and smooth oxide film is more stable, while irregular metal oxide structures with high impurity content are more easily selectively stripped. Sodium phosphate solution primarily serves to slow the reaction rate and stabilize the reaction; sodium tartrate solution is used for the complexation of irregular metal oxides, which is more conducive to the forward reaction.

[0057] Furthermore, a barrier layer and a porous layer are sequentially formed on the aluminum alloy surface. During the targeted stripping stage, impurities such as Si and Al6Mn are typically inert and are not preferentially oxidized or dissolved. They are squeezed to the outer layer by the uniform alumina film, forming an irregular outer film (porous layer side) with more impurities, appearing yellowish or blackish. After the outermost layer preferentially contacts the oxidation bath solution, an impurity oxide film (gray film) is formed. The targeted stripping agent can remove the outer gray film. The uniform inner oxide film layer peels off more slowly, while the disordered and loose oxide film structure is preferentially peeled off, forming a smooth and uniform oxide film surface, similar to reshaping the oxide film structure. Alkaline substances target and strip the intermetallic compounds containing insoluble Si oxides and other impurities from the porous layer and the aluminum alloy surface. By selectively stripping oxides of intermetallic compounds with lower potential, the crystal structure of the aluminum alloy oxide film surface is changed, and impurities such as Si / Mn / C in the outermost layer are removed. The barrier layer is likely to be an aluminum alloy oxide film containing relatively impurities. After re-oxidation, it is equivalent to removing the impurities of intermetallic compounds in the outer layer of the aluminum alloy in advance, which greatly improves the yellowing and blackening phenomenon in the oxide film obtained by subsequent anodizing.

[0058] Step S4: Chemical polishing. The aluminum alloy parts after targeted stripping are cleaned and chemically polished, so that the aluminum alloy parts come into contact with a mixed acid solution containing sulfuric acid and phosphoric acid.

[0059] In one embodiment, the concentration ratio of sulfuric acid to phosphoric acid ranges from 1:4 to 1:7, the chemical polishing temperature is room temperature, and the chemical polishing time is 1 to 4 minutes.

[0060] In this embodiment, the concentration ratio of sulfuric acid to phosphoric acid is 1:6, the chemical polishing temperature is room temperature, and the chemical polishing time is 2 minutes.

[0061] Understandably, chemical polishing of aluminum alloy parts can result in a finer surface finish and better flatness. Furthermore, to enhance the effectiveness of chemical polishing, it is often performed at a temperature of 80 to 90°C under stirring conditions. For example, a shaking motion can be used, with a shaking frequency of 10 to 60 times per minute.

[0062] Step S5: Anodizing. The chemically polished aluminum alloy parts are cleaned and anodized to form an anodized film on the surface of the aluminum alloy parts. The electrolyte used for anodizing includes sulfuric acid and oxalic acid.

[0063] Understandably, by adjusting the parameters of the anodizing process, the resulting oxide film becomes denser, thinner, and has better light transmittance.

[0064] In one embodiment, during the anodizing process, the bath solution of the oxidation tank can be a mixture of sulfuric acid and oxalic acid, wherein the concentration of sulfuric acid is in the range of 80 to 120 g / L and the concentration of oxalic acid is in the range of 10 to 30 g / L; the voltage of the oxidation tank can be in the range of 0.6 to 0.8 A, the temperature of the bath solution of the oxidation tank can be in the range of 25 to 28°C, and the oxidation time of the oxidation tank can be in the range of 45 to 55 minutes.

[0065] Step S6: Sealing. Clean the anodized aluminum alloy parts and seal them. The sealing solution is a nickel sulfate solution or nickel acetate solution with a mass concentration of 5 g / L to 15 g / L. The sealing time is 30 minutes to 60 minutes and the temperature is 85°C to 95°C.

[0066] It is understandable that sealing is performed on anodized aluminum alloy parts to improve the corrosion resistance of the anodized film.

[0067] Step S7: Drying. Clean and dry the sealed aluminum alloy parts. Place the aluminum alloy parts in an oven at a temperature of 65°C to 90°C for 5 to 30 minutes.

[0068] Figure 2 This is a schematic diagram of a scanning electron microscope (SEM) image of an aluminum alloy part after degreasing treatment. Figure 3 This is a schematic diagram of a scanning electron microscope (SEM) image of an aluminum alloy part after pre-activation treatment. Figure 4 This is a schematic scanning electron microscope (SEM) image of an aluminum alloy part after targeted abrasion treatment. Figures 2 to 4 It can be seen that the surface of the aluminum alloy parts after targeted peeling is significantly more uniform.

[0069] Figure 5This is a schematic cross-sectional image of an aluminum alloy part after degreasing treatment via ion cutting (FBI). Figure 6 This is a schematic cross-sectional image of an aluminum alloy part after pre-activation treatment via ion cutting (FBI). Figure 7 This is a schematic cross-sectional image of an aluminum alloy part after targeted ablation (FBI) cutting. Figures 5 to 7 It can be seen that the oxide layer on the surface of the aluminum alloy parts after targeted peeling is significantly smoother and has a more uniform thickness.

[0070] Furthermore, the aluminum alloy parts were tested after degreasing, pre-activation, and targeted stripping. The content mapping results show: after degreasing, (1% CK; 1% OK; 97% Al K); after pre-activation, (13% OK; 84% Al K; 3% SK); and after targeted stripping, (0% CK; 1% OK; 99% Al K). The mapping results show that after targeted stripping, the carbon content on the aluminum alloy surface decreased by 1%, and other impurities decreased by 1%. Based on the content of the recycled aluminum raw materials, it is speculated that the 1% reduction mainly consists of silicon. It is understandable that the combination of pre-activation and targeted stripping can effectively remove impurities from the surface of aluminum alloy parts.

[0071] The anodizing process for recycled aluminum alloys described in this application can solve the problem of color difference (too yellow / too dark) in recycled aluminum after sulfuric acid oxidation. Aluminum alloy parts treated by the anodizing process for recycled aluminum alloys described in this application can achieve the same oxide film appearance standards as non-recycled aluminum alloys.

[0072] The anodizing process for recycled aluminum alloys described in this application is simple, easy to mass-produce, convenient to operate, and does not damage the anodized film.

[0073] Compared to existing technologies, the anodizing process for recycled aluminum alloys described in this application, by introducing pre-activation and targeted stripping processes before the anodizing process, largely removes insoluble substances such as intermetallic compounds on the outer layer of the aluminum alloy, significantly improving the yellowing and blackening phenomenon after anodizing. Furthermore, the anodizing process for recycled aluminum alloys described in this application, while improving the yellowing and blackening of the aluminum alloy surface, avoids the introduction of chemicals containing elements such as chromium and fluorine, reducing the risk of environmental pollution and making the entire method more environmentally friendly.

[0074] Example 1

[0075] An anodizing process for recycled aluminum alloys includes the following steps:

[0076] Step S1: Degrease the aluminum alloy parts made from recycled aluminum alloy. The degreasing solution can be an alkaline degreasing agent (e.g., a mixture of sodium carbonate, sodium pyrophosphate, and surfactants), with an alkaline concentration of 55 g / L, a degreasing temperature of 60°C, and a degreasing time of 6 minutes.

[0077] Step S2: Clean the degreased aluminum alloy parts and perform pre-activation treatment by contacting the aluminum alloy parts with the liquid pre-activator and applying electricity. The concentration of sulfuric acid is 90 g / L, the concentration of oxalic acid is 25 g / L, the voltage of the pre-activation treatment is 20V, and the time is 5 minutes.

[0078] Step S3: Clean the pre-activated aluminum alloy parts and perform targeted stripping treatment. The concentration of sodium hydroxide solution is 35 g / L, the concentration of sodium phosphate solution is 7 g / L, the concentration of sodium tartrate is 2 g / L, the concentration of sodium thiosulfate is 1 g / L, and the time is 0.5 minutes.

[0079] Step S4: Clean the aluminum alloy parts after targeted stripping and perform chemical polishing treatment. The concentration ratio of sulfuric acid to phosphoric acid is 1:5.5, the chemical polishing temperature is 82℃, and the chemical polishing time is 130s.

[0080] Step S5: Clean the chemically polished aluminum alloy parts and perform anodizing treatment. The electrolyte is a mixture of sulfuric acid (90g / L) and oxalic acid (25g / L). The anodizing temperature is 26℃, the current density is 0.8A / dm2, and the anodizing time is 50 minutes.

[0081] Step S6: Clean and seal the anodized aluminum alloy parts. The sealing solution is a nickel acetate sealing agent with a mass concentration of 14 g / L. The sealing treatment time is 40 minutes and the temperature is 95℃.

[0082] Step S7: Clean and dry the sealed aluminum alloy parts.

[0083] Example 2

[0084] An anodizing process for recycled aluminum alloys includes the following steps:

[0085] Step S1: Degrease the aluminum alloy parts made from recycled aluminum alloy. The degreasing solution can be an acidic degreasing agent, which can be a commercially available, compliant acidic degreasing agent. The volume concentration of the acidic degreasing agent is 10%, the degreasing temperature is 60°C, and the time is 4 minutes.

[0086] Step S2: Clean the degreased aluminum alloy parts and perform pre-activation treatment by contacting the aluminum alloy parts with the liquid pre-activator and applying electricity. The concentration of sulfuric acid is 90 g / L, the concentration of oxalic acid is 25 g / L, the voltage of the pre-activation treatment is 20V, and the time is 5 minutes.

[0087] Step S3: Clean the pre-activated aluminum alloy parts and perform targeted stripping treatment. The concentration of sodium hydroxide solution is 35 g / L, the concentration of sodium phosphate solution is 7 g / L, the concentration of sodium tartrate is 2 g / L, the concentration of sodium thiosulfate is 1 g / L, and the time is 0.5 minutes.

[0088] Step S4: Clean the aluminum alloy parts after targeted stripping and perform chemical polishing treatment. The concentration ratio of sulfuric acid to phosphoric acid is 1:5.5, the chemical polishing temperature is 82℃, and the chemical polishing time is 130s.

[0089] Step S5: Clean the chemically polished aluminum alloy parts and perform anodizing treatment. The electrolyte is a mixture of sulfuric acid (90g / L) and oxalic acid (25g / L). The anodizing temperature is 26℃, the current density is 0.8A / dm2, and the anodizing time is 50 minutes.

[0090] Step S6: Clean and seal the anodized aluminum alloy parts. The sealing solution is a nickel acetate sealing agent with a mass concentration of 14 g / L. The sealing treatment time is 40 minutes and the temperature is 95℃.

[0091] Step S7: Clean and dry the sealed aluminum alloy parts.

[0092] Example 3

[0093] An anodizing process for recycled aluminum alloys includes the following steps:

[0094] Step S1: Degrease the aluminum alloy parts made from recycled aluminum alloy. The degreasing solution can be an alkaline degreasing agent (e.g., a mixture of sodium carbonate, sodium pyrophosphate, and surfactants), with an alkaline concentration of 55 g / L, a degreasing temperature of 60°C, and a degreasing time of 6 minutes.

[0095] Step S2: Clean the degreased aluminum alloy parts and perform pre-activation treatment by contacting the aluminum alloy parts with the liquid pre-activator and applying electricity. The concentration of sulfuric acid is 100g / L, the concentration of oxalic acid is 20g / L, the voltage of the pre-activation treatment is 18V, and the time is 8 minutes.

[0096] Step S3: Clean the pre-activated aluminum alloy parts and perform targeted stripping treatment. The concentration of sodium hydroxide solution is 35 g / L, the concentration of sodium phosphate solution is 7 g / L, the concentration of sodium tartrate is 2 g / L, the concentration of sodium thiosulfate is 1 g / L, and the time is 0.5 minutes.

[0097] Step S4: Clean the aluminum alloy parts after targeted stripping and perform chemical polishing treatment. The concentration ratio of sulfuric acid to phosphoric acid is 1:5.5, the chemical polishing temperature is 82℃, and the chemical polishing time is 130s.

[0098] Step S5: Clean the chemically polished aluminum alloy parts and perform anodizing treatment. The electrolyte is a mixture of sulfuric acid (90g / L) and oxalic acid (25g / L). The anodizing temperature is 26℃, the current density is 0.8A / dm2, and the anodizing time is 50 minutes.

[0099] Step S6: Clean and seal the anodized aluminum alloy parts. The sealing solution is a nickel acetate sealing agent with a mass concentration of 14 g / L. The sealing treatment time is 40 minutes and the temperature is 95℃.

[0100] Step S7: Clean and dry the sealed aluminum alloy parts.

[0101] Example 4

[0102] An anodizing process for recycled aluminum alloys includes the following steps:

[0103] Step S1: Degrease the aluminum alloy parts made from recycled aluminum alloy. The degreasing solution can be an alkaline degreasing agent (e.g., a mixture of sodium carbonate, sodium pyrophosphate, and surfactants), with an alkaline concentration of 55 g / L, a degreasing temperature of 60°C, and a degreasing time of 6 minutes.

[0104] Step S2: Clean the degreased aluminum alloy parts and perform pre-activation treatment by contacting the aluminum alloy parts with the liquid pre-activator and applying electricity. The concentration of sulfuric acid is 90 g / L, the concentration of oxalic acid is 25 g / L, the voltage of the pre-activation treatment is 20V, and the time is 5 minutes.

[0105] Step S3: Clean the pre-activated aluminum alloy parts and perform targeted stripping treatment. The concentration of sodium hydroxide solution is 40 g / L, the concentration of sodium phosphate solution is 8 g / L, the concentration of sodium tartrate is 3 g / L, the concentration of sodium thiosulfate is 1 g / L, and the time is 0.5 minutes.

[0106] Step S4: Clean the aluminum alloy parts after targeted stripping and perform chemical polishing treatment. The concentration ratio of sulfuric acid to phosphoric acid is 1:5.5, the chemical polishing temperature is 82℃, and the chemical polishing time is 130s.

[0107] Step S5: Clean the chemically polished aluminum alloy parts and perform anodizing treatment. The electrolyte is a mixture of sulfuric acid (90g / L) and oxalic acid (25g / L). The anodizing temperature is 26℃, the current density is 0.8A / dm2, and the anodizing time is 50 minutes.

[0108] Step S6: Clean and seal the anodized aluminum alloy parts. The sealing solution is a nickel acetate sealing agent with a mass concentration of 14 g / L. The sealing treatment time is 40 minutes and the temperature is 95℃.

[0109] Step S7: Clean and dry the sealed aluminum alloy parts.

[0110] Example 5

[0111] An anodizing process for recycled aluminum alloys includes the following steps:

[0112] Step S1: Degrease the aluminum alloy parts made from recycled aluminum alloy. The degreasing solution can be an alkaline degreasing agent (e.g., a mixture of sodium carbonate, sodium pyrophosphate, and surfactants), with an alkaline concentration of 55 g / L, a degreasing temperature of 60°C, and a degreasing time of 6 minutes.

[0113] Step S2: Clean the degreased aluminum alloy parts and perform pre-activation treatment by contacting the aluminum alloy parts with the liquid pre-activator and applying electricity. The concentration of sulfuric acid is 90 g / L, the concentration of oxalic acid is 25 g / L, the voltage of the pre-activation treatment is 20V, and the time is 5 minutes.

[0114] Step S3: Clean the pre-activated aluminum alloy parts and perform targeted stripping treatment. The concentration of sodium hydroxide solution is 35 g / L, the concentration of sodium phosphate solution is 7 g / L, the concentration of sodium tartrate is 2 g / L, the concentration of sodium thiosulfate is 1 g / L, and the time is 0.5 minutes.

[0115] Step S4: Clean the aluminum alloy parts after targeted stripping and perform chemical polishing treatment. The concentration ratio of sulfuric acid to phosphoric acid is 1:6.5, the chemical polishing temperature is 85℃, and the chemical polishing time is 120s.

[0116] Step S5: Clean the chemically polished aluminum alloy parts and perform anodizing treatment. The electrolyte is a mixture of sulfuric acid (90g / L) and oxalic acid (25g / L). The anodizing temperature is 26℃, the current density is 0.8A / dm2, and the anodizing time is 50 minutes.

[0117] Step S6: Clean the anodized aluminum alloy parts and seal them. The sealing solution is a nickel acetate sealing agent with a mass concentration of 12g / L. The sealing treatment time is 50 minutes and the temperature is 95℃.

[0118] Step S7: Clean and dry the sealed aluminum alloy parts.

[0119] Example 6

[0120] An anodizing process for recycled aluminum alloys includes the following steps:

[0121] Step S1: Degrease the aluminum alloy parts made from recycled aluminum alloy. The degreasing solution can be an alkaline degreasing agent (e.g., a mixture of sodium carbonate, sodium pyrophosphate, and surfactants), with an alkaline concentration of 55 g / L, a degreasing temperature of 60°C, and a degreasing time of 6 minutes.

[0122] Step S2: Clean the degreased aluminum alloy parts and perform pre-activation treatment by contacting the aluminum alloy parts with the liquid pre-activator and applying electricity. The concentration of sulfuric acid is 90 g / L, the concentration of oxalic acid is 25 g / L, the voltage of the pre-activation treatment is 20V, and the time is 5 minutes.

[0123] Step S3: Clean the pre-activated aluminum alloy parts and perform targeted stripping treatment. The concentration of sodium hydroxide solution is 35 g / L, the concentration of sodium phosphate solution is 7 g / L, the concentration of sodium tartrate is 2 g / L, the concentration of sodium thiosulfate is 1 g / L, and the time is 0.5 minutes.

[0124] Step S4: Clean the aluminum alloy parts after targeted stripping and perform chemical polishing treatment. The concentration ratio of sulfuric acid to phosphoric acid is 1:5.5, the chemical polishing temperature is 82℃, and the chemical polishing time is 130s.

[0125] Step S5: Clean the chemically polished aluminum alloy parts and perform anodizing treatment. The electrolyte is a mixture of sulfuric acid (100g / L) and oxalic acid (20g / L). The anodizing temperature is 27℃, the current density is 0.7A / dm2, and the anodizing time is 50 minutes.

[0126] Step S6: Clean and seal the anodized aluminum alloy parts. The sealing solution is a nickel acetate sealing agent with a mass concentration of 14 g / L. The sealing treatment time is 40 minutes and the temperature is 95℃.

[0127] Step S7: Clean and dry the sealed aluminum alloy parts.

[0128] The aluminum alloy parts obtained in Examples 1 to 6 were tested for color difference and gloss, and the data are shown in Table 1 below:

[0129]

[0130]

[0131] As shown in Table 1 above, the surface parameters of the aluminum alloy parts obtained in Examples 1 to 6 are better than those of the aluminum alloy parts obtained using conventional anodizing processes (not the technical solution of this application). Specifically, the dL and db values ​​of the aluminum alloy parts treated in Examples 1 to 6 are closer to or deviate less from the target values, which is reflected in the product as a significant improvement in the yellowing or blackening of the color. This solves the problem of yellowing and blackening of recycled aluminum alloys, meets customer appearance quality requirements, and ensures that the gloss and film thickness are within the expected range.

[0132] The specific embodiments of this application have been described above with reference to the accompanying drawings. However, those skilled in the art will understand that various changes and substitutions can be made to the specific embodiments of this application without departing from the scope of this application. All such changes and substitutions fall within the scope defined by this application.

Claims

1. An anodizing process for recycled aluminum alloys, characterized in that, Includes the following steps: Step S1: Degreasing, degreasing the aluminum alloy parts made of recycled aluminum alloy; Step S2: Pre-activation. The degreased aluminum alloy parts are cleaned and pre-activated by contacting the aluminum alloy parts with a liquid pre-activating agent and passing electricity through them. The pre-activating agent includes sulfuric acid and oxalic acid. The voltage range of the pre-activation treatment is 18 to 25V. Step S3: Targeted peeling. The pre-activated aluminum alloy parts are cleaned and subjected to targeted peeling treatment, so that the aluminum alloy parts come into contact with the liquid targeted peeling agent. The targeted peeling agent includes a desiccant, a stabilizer, a complexing agent and a surface conditioner. The desiccant is an alkaline solution, the stabilizer is a sodium phosphate solution with a concentration range of 6 g / L to 12 g / L, the complexing agent is a sodium tartrate solution with a concentration range of 1 g / L to 3 g / L, and the surface conditioner is a sodium thiosulfate solution with a concentration range of 1 g / L to 1.5 g / L. Step S4: Chemical polishing. The aluminum alloy parts after targeted stripping are cleaned and chemically polished, so that the aluminum alloy parts come into contact with a mixed acid solution containing sulfuric acid and phosphoric acid. and Step S5: Anodizing. The chemically polished aluminum alloy parts are cleaned and anodized to form an anodized film on the surface of the aluminum alloy parts. The electrolyte used for anodizing includes sulfuric acid and oxalic acid.

2. The anodizing process for recycled aluminum alloys as described in claim 1, characterized in that, The concentration of sulfuric acid in the pre-activator ranges from 60 g / L to 100 g / L.

3. The anodizing process for recycled aluminum alloys as described in claim 1, characterized in that, The concentration of oxalic acid in the pre-activator ranges from 10 g / L to 30 g / L.

4. The anodizing process for recycled aluminum alloys as described in claim 1, characterized in that, In step S2, the pre-activation time ranges from 5 to 10 minutes.

5. The anodizing process for recycled aluminum alloys as described in claim 1, characterized in that, In step S3, the ash remover is a sodium hydroxide solution with a concentration ranging from 20 g / L to 40 g / L.

6. The anodizing process for recycled aluminum alloys as described in claim 1, characterized in that, In step S4, the concentration ratio of sulfuric acid to phosphoric acid is in the range of 1:4 to 1:7, the chemical polishing temperature is room temperature, and the chemical polishing time is 1 to 4 minutes.

7. The anodizing process for recycled aluminum alloys as described in claim 1, characterized in that, It also includes the following steps: Step S6: Sealing. Clean the anodized aluminum alloy parts and seal them. The sealing solution is a nickel sulfate solution or nickel acetate solution with a mass concentration of 5 g / L to 15 g / L. The sealing time is 15 minutes to 60 minutes and the temperature is 85°C to 95°C. Step S7: Drying. Clean and dry the sealed aluminum alloy parts. Place the aluminum alloy parts in an oven at a temperature of 65°C to 90°C for 5 to 30 minutes.

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