WO2020257992A1

WO2020257992A1 - Method for oxidizing and coloring external part of 7000 series aluminum alloy electronic product

Info

Publication number: WO2020257992A1
Application number: PCT/CN2019/092593
Authority: WO
Inventors: 陈文泗; 罗伟浩; 罗铭强; 林丽荧; 李辉; 金娜; 王顺成
Original assignee: 广东兴发铝业有限公司
Priority date: 2019-06-24
Filing date: 2019-06-24
Publication date: 2020-12-30

Abstract

Disclosed is a method for oxidizing and coloring an external part of a 7000 series aluminum alloy electronic product, wherein same belong to the technical field of aluminum alloy surface treatments. The method comprises the following steps in order: mechanical surface pre-treatment; degreasing for oil removal; alkaline washing for film removal; acid washing for ash removal; chemical polishing; using an aluminum alloy external part as an anode in an oxidation liquid, and subjecting same to anodic oxidation using a lead plate or graphite plate as a cathode, such that the surface of the aluminum alloy exterior part is formed into an oxidation film with micropores; after cleaning same, putting the aluminum alloy exterior part into a dye solution for coloring, such that the coloring agent enters the micropores of the oxidation film; and finally, closing the micropores, such that the coloring agent is fixed in the micropores of the oxidation film. The 7000 series aluminum alloy electronic product exterior part obtained from the method has an oxidation film that is dense, has a strong adhesive force, is not easily to shield, and has good wear resistance and corrosion resistance. The oxidation film is transparent and clear, has a smooth texture, can obtain various pure colored color after coloring, and has an excellent surface decoration effect.

Description

Oxidation coloring method for appearance parts of 7000 series aluminum alloy electronic product

Technical field

The invention belongs to the technical field of aluminum alloy surface treatment, and specifically relates to an oxidation coloring method for appearance parts of a 7000 series aluminum alloy electronic product.

Background technique

Aluminum alloy has the advantages of light weight, high specific strength, good heat dissipation performance, recyclability, and unique metal texture. It is widely used in the appearance of smart phones, tablet computers and other electronic products, such as backplanes, middle frames and frames. With the development of economy and society, consumers’ consumption concepts are constantly updated and their needs are becoming more diversified. This puts forward higher requirements on the appearance of electronic products, which require both beautiful decorative effects and excellent wear resistance. Corrosion resistance.

Under normal circumstances, a layer of natural oxide film is formed on the surface of aluminum alloy appearance parts, which has a certain resistance to corrosion, but the natural oxide film is very thin and soft, and is easily damaged and loses its protective effect. In addition, the surface hardness of aluminum alloy is low, and the surface of aluminum alloy appearance parts is easily worn out during use.

In order to improve the wear resistance, corrosion resistance and beautiful decoration effect of aluminum alloy appearance parts, surface treatment is usually required before use. Through anodizing, a dense oxide film is formed on the surface of aluminum alloy appearance parts. High hardness can improve the wear resistance and corrosion resistance of aluminum alloy appearance parts. There are a large number of micropores on the oxide film, which has a strong adsorption capacity for dyeing agents. After coloring treatment, a variety of rich colors can be obtained to achieve the effect of beautification and decoration to meet the needs of different consumer groups.

The appearance parts of existing electronic products such as smart phones and tablet computers are mainly made of 6000 series aluminum alloy. Although 6000 series aluminum alloy has excellent extrusion processing performance and oxidation coloring effect, its strength is generally low. With the development of large screens and thinner electronic products such as smart phones and tablet computers, there is an urgent need for high-strength aluminum alloy backplanes, middle frames or frames to improve the bending resistance of the fuselage to avoid bending when the fuselage is under pressure. , Bending and other phenomena. Especially with the advent of the 5G communication era, because aluminum alloy has a shielding effect on electromagnetic waves, the existing aluminum alloy middle frame + aluminum alloy backplane shell structure can no longer meet the transmission needs of smartphone 5G communication signals, and aluminum must be used. Alloy middle frame + glass or ceramic shell structure. Therefore, in order to prevent the glass and ceramics from cracking due to the deformation of the aluminum alloy frame when the smartphone is dropped, there is an urgent need for high-strength aluminum alloy to make the smartphone frame.

7000 series aluminum alloy is a high-strength aluminum alloy that can be strengthened by heat treatment. The strength of 7000 series aluminum alloy is generally higher, which can meet the development requirements of large-screen and light-weight electronic products such as smart phones and tablet computers. However, the oxidation coloring effect of 7000 series aluminum alloy is relatively poor. The existing commonly used oxidation coloring process generally has the problems of turbid oxide film, poor permeability and low gloss, which makes it impossible to obtain various appearance parts of 7000 series aluminum alloy electronic products. Pure color. In addition, the oxide film generally has problems such as poor compactness, weak adhesion, and easy to fall off, so that the appearance of 7000 series aluminum alloy electronic products cannot obtain good wear resistance and corrosion resistance. Therefore, the oxidation coloring method of the existing 7000 series aluminum alloy electronic product appearance parts still needs to be improved and developed.

Summary of the invention

In view of the above-mentioned problems and deficiencies, the present invention provides a 7000 series aluminum alloy electronic product appearance part oxidation coloring method. By optimizing the composition of the treatment liquid and its treatment process, the gloss, permeability, and permeability of the oxide film are improved. Density and adhesion, improve the wear resistance, corrosion resistance and surface decoration effect of 7000 series aluminum alloy electronic products.

The technical scheme of the present invention is realized as follows:

The oxidation coloring method of the 7000 series aluminum alloy electronic product appearance parts of the present invention is characterized by sequentially including the following steps:

The first step: the surface mechanical pretreatment of the aluminum alloy appearance parts, to remove the surface machining knife marks, burrs, scratches, etc., to obtain a smooth surface, the surface mechanical pretreatment is mechanical polishing or sandblasting;

The purpose of surface mechanical pretreatment of aluminum alloy appearance parts is to remove surface machining knife marks, burrs, scratches, etc., to obtain a smooth surface. Commonly used surface mechanical pretreatment methods include mechanical polishing and sandblasting. Mechanical polishing is performed on a special polishing machine, using the relative grinding and rolling effects between polishing powder, cotton or felt and other polishing materials and aluminum alloy appearance parts. , Remove the convex part of the surface to obtain a flat surface method.

Sandblasting is powered by compressed air to spray abrasive grains on the surface of aluminum alloy appearance parts at high speed. Under the combined action of the impact force and cutting force of the abrasive grains, the surface machining knife marks, burrs, scratches, etc. are removed. The way to get a flat surface. Surface mechanical pretreatment is a conventional pretreatment process for aluminum alloy appearance parts. If you need to obtain a bright and flat surface, you usually choose mechanical polishing. If you need to obtain a matt and flat surface, usually choose sandblasting. For specific requirements, choose mechanical polishing or sandblasting.

Step 2: Put the aluminum alloy exterior parts into a degreasing solution at 80-90°C for 7-8 minutes to remove oil stains on the surface. The degreasing solution is a mixed aqueous solution of sodium carbonate, sodium phosphate and sodium citrate, and carbonated The concentration of sodium is 60～80g/L, the concentration of sodium phosphate is 30～40g/L, and the concentration of sodium citrate is 10～15g/L;

Aluminum alloy appearance parts will inevitably come into contact with oily substances during the manufacturing process. These oily substances must be completely removed by degreasing treatment to provide clean aluminum alloy appearance parts for the subsequent surface treatment process. However, the degreasing treatment can not produce corrosion on the appearance of aluminum alloy parts, otherwise it will affect the effect of the entire surface treatment.

The inventor has conducted a large number of experimental studies on the degreasing treatment process of the appearance parts of 7000 series aluminum alloy electronic products and found that the effect of degreasing treatment is closely related to the composition of the degreasing liquid, the temperature of the degreasing liquid and the degreasing time. Sodium carbonate and The mixed aqueous solution of sodium phosphate is used as the base solution of the degreasing solution. The concentration of sodium carbonate is 60～80g/L, the concentration of sodium phosphate is 30～40g/L, and sodium citrate with the concentration of 10～15g/L is added as anionic surfactant. , Can significantly reduce the surface tension of aluminum alloy appearance parts, improve the emulsification, dispersion and soaking effect of the degreasing solution, and improve the degreasing and degreasing effect. Degreasing treatment in the degreasing solution at 80-90°C for 7-8 minutes can completely remove aluminum Oil stains on the surface of the alloy appearance parts without corroding the aluminum alloy appearance parts. Unreasonable composition of the degreasing solution, too high temperature of the degreasing solution, or too long degreasing treatment time will corrode the appearance of aluminum alloy parts, while the temperature of the degreasing solution is too low or the degreasing time is insufficient, and the surface of the appearance of aluminum alloy parts cannot be completely removed. Of oil.

The third step: Put the cleaned aluminum alloy appearance parts in an alkaline washing solution at 25-30°C for 2 to 3 minutes to remove the natural oxide film on the surface. The alkaline solution is sodium hydroxide and sodium silicate. The mixed aqueous solution, the concentration of sodium hydroxide is 20-25g/L, and the concentration of sodium silicate is 10-15g/L;

Before alkaline washing treatment, it is necessary to clean the aluminum alloy appearance parts with water to remove the degreasing liquid remaining on the surface. A layer of natural oxide film is usually formed on the surface of aluminum alloy appearance parts. This natural oxide film must be removed to expose the clean and well-activated aluminum alloy appearance parts to facilitate subsequent anodization and improve the efficiency of subsequent anodization. And the denseness of the oxide film.

The prior art usually uses an aqueous sodium hydroxide solution as an alkaline washing solution for alkaline washing, but it is often difficult to completely remove the natural oxide film on the surface. The inventor found through a large number of experimental studies that the use of a mixed aqueous solution of sodium hydroxide and sodium silicate as an alkaline washing solution has a better effect than the traditional sodium hydroxide aqueous solution. The sodium hydroxide concentration is 20-20g/L, Sodium silicate concentration is 10～15g/L, alkali washing solution temperature is 25～30℃, alkali washing treatment for 2～3 minutes, it can completely remove the natural oxide film on the surface of aluminum alloy appearance parts, revealing clean and good activation state The appearance of aluminum alloy parts improves the efficiency of subsequent anodization and the compactness of the oxide film.

Step 4: Put the cleaned aluminum alloy appearance parts in a pickling solution at 25-30°C for 1 to 2 minutes to remove dirt on the surface. The acid solution is a mixed aqueous solution of nitric acid, sulfuric acid and formic acid , The concentration of nitric acid is 110～130g/L, the concentration of sulfuric acid is 30～40g/L, and the concentration of formic acid is 10～20g/L;

Before pickling treatment, it is necessary to clean the aluminum alloy appearance parts with water to remove the residual alkali lotion on the surface. 7000 series aluminum alloy electronic products usually contain Si, Cu, Fe, Mn and other elements and their intermetallic compounds. These elements and their intermetallic compounds are insoluble in alkaline solution. After the third step of alkaline washing treatment, It is usually attached to the surface of aluminum alloy appearance parts in the state of tiny particles, which is called fouling. Fouling will not only affect the subsequent chemical polishing effect, but also reduce the gloss and permeability of the oxide film. Therefore, it must be removed Dirt on the surface.

In the prior art, a single nitric acid or sulfuric acid solution is usually used for pickling to remove the dirt on the surface. The problem is that the dirt is not completely removed or the surface of the aluminum alloy appearance part is left with black spots and other defects. Reduce the gloss and permeability of the anodic oxide film.

The inventor has conducted a large number of experimental studies on this problem and found that the use of a mixed aqueous solution of nitric acid, sulfuric acid and formic acid as the pickling solution has a better effect than a single nitric acid or sulfuric acid solution, and the pickling efficiency is higher and can be significantly shortened. Pickling time, under the conditions of nitric acid concentration of 110～130g/L, sulfuric acid concentration of 30～40g/L, formic acid concentration of 10～20g/L, and pickling solution temperature of 25～30℃, pickling treatment 1～2 Minutes, can completely remove the dirt on the surface of aluminum alloy appearance parts, and significantly improve the gloss and permeability of the oxide film.

Step 5: Put the cleaned aluminum alloy appearance parts into a 50-60°C polishing solution for chemical polishing for 30-40 seconds to obtain a smooth and bright surface. The polishing solution is made of phosphoric acid, sulfinic acid and phenylacetic acid. In the mixed solution, the volume percentage of phosphoric acid is 65 to 70%, the volume percentage of sulfinic acid is 20 to 22%, and the volume percentage of phenylacetic acid is 10 to 13%;

Before chemical polishing, it is necessary to clean the aluminum alloy appearance parts with water to remove the pickling solution remaining on the surface. Chemical polishing is the process of putting aluminum alloy in a polishing liquid, and selectively dissolving uneven areas on the surface through the chemical etching of the polishing liquid, etching and leveling, and obtaining a smooth and bright surface. The effect of chemical polishing is closely related to the composition of the polishing liquid, the temperature of the polishing liquid and the time of chemical polishing.

The existing commonly used polishing liquids usually contain nitric acid, and the biggest problem is that it generates NOx gas, which causes serious environmental pollution. In addition, the chemical polishing effect of the existing phosphoric acid-sulfuric acid system polishing liquid is still difficult to obtain high-gloss aluminum alloy appearance parts, which seriously affects the beautiful decorative effect.

The inventor has conducted a lot of experimental research on the chemical polishing process of the appearance parts of 7000 series aluminum alloy electronic products and found that a mixture of phosphoric acid, sulfinic acid, and phenylacetic acid is used as the polishing liquid, and the volume percentage of phosphoric acid is 65-70%. The volume percentage of sulfinic acid is 20-22%, the volume percentage of phenylacetic acid is 10-13%, and the chemical polishing is 30-40 seconds in the polishing liquid at 50-60℃. It can be etched and leveled thoroughly to obtain a bright and smooth surface. , At the same time, it will not produce NOx gas and cause environmental pollution. If the temperature of the polishing liquid is too high or the polishing time is too long, it is easy to cause defects such as pitting, local stains or spots on the surface of the aluminum alloy appearance part. If the temperature of the polishing liquid is too low or the polishing time is not enough, it will not be completely etched and leveled. Eventually, the oxide film will be loose, which will reduce the wear resistance and corrosion resistance of aluminum alloy appearance parts and beautify the decoration effect.

Step 6: Put the cleaned aluminum alloy appearance parts into an oxidizing solution at 20-22°C for 30-40 minutes to form a microporous oxide film on the surface. The oxidizing solution is sulfuric acid, oxalic acid, Mixed aqueous solution of aluminum sulfate and alkylphenol, sulfuric acid concentration is 140～150g/L, oxalic acid concentration is 8-9g/L, aluminum sulfate concentration is 15-20g/L, alkylphenol concentration is 2～3g/L, anode The oxidized direct current density is 1.6～1.8A/dm2, the voltage is 8～10V, and the anodized cathode is lead plate or graphite plate;

Before anodizing, it is necessary to clean the aluminum alloy appearance parts with water to remove the remaining polishing liquid on the surface. Anodizing is to put the aluminum alloy appearance part as an anode into an oxidation solution, with a lead plate or graphite plate as a cathode, and under the action of an external current, a layer of microporous oxide film is formed on the surface of the aluminum alloy appearance part. The formation of the oxide film is the result of the following two reactions simultaneously. One is the electrochemical formation process of the oxide film, that is, the oxygen atoms ionized on the surface of the aluminum alloy appearance part react with aluminum to form an Al2O3 oxide film, and the other is formed The chemical dissolution process of the oxide film, that is, the generated oxide film is partially dissolved by the oxidizing liquid at the same time.

The quality of the oxide film is firstly closely related to the composition of the oxidizing solution. Although the existing common sulfuric acid anodizing process has the advantages of simple oxidizing solution composition, easy operation, porous oxide film, and strong adsorption capacity, it has loose oxide film, Defects such as poor permeability and low gloss.

The inventor conducted a lot of experimental research on the composition of the oxidation solution for the appearance of the 7000 series aluminum alloy electronic products, and found that on the basis of the traditional sulfuric acid oxidation solution, oxalic acid with a concentration of 8-9g/L and a concentration of 15-20g was added. /L aluminum sulfate and alkylphenol with a concentration of 2～3g/L. Among them, oxalic acid is an organic acid. During the formation of the oxide film, oxalate ions compete with sulfate ions for adsorption, and sulfate ions are mainly adsorbed in oxidation The bottom of the membrane pores, and oxalate ions are mainly adsorbed on the pore walls of the oxide film pores. Oxalic acid dissolves the oxide film weaker than sulfuric acid, thereby reducing the dissolution of the micropore pore walls and forming a fine and uniform oxide film The micropores improve the adsorption capacity of the oxide film and improve the subsequent coloring effect.

Aluminum sulfate can separate aluminum ions in the oxidizing solution, increase the current stability of the oxidizing solution, accelerate the film formation speed, and avoid the oxide film's defects such as looseness, powdering and cracking, and increase the integrity and thickness of the oxide film. Obtain a continuous, uniform and dense oxide film layer, and improve the wear and corrosion resistance of the oxide film. As an ionic surfactant, alkyl phenol has a cleaning effect on the oxide film, which can avoid dark spots, black spots and chromatic aberrations on the oxide film, thereby significantly improving the gloss and permeability of the oxide film, so that the oxide film can be colored Obtain gorgeous colors and improve beautification and decoration effects.

Since the formation of the oxide film is the result of the simultaneous production and dissolution of the oxide film, the quality of the oxide film is also closely related to the process parameters of anodization. The higher the temperature of the oxidation solution, the faster the dissolution rate of the oxide film, and the thinner the oxide film. The higher the voltage, the larger the pore size of the oxide film, the smaller the number of micropores, and the poorer the adsorption capacity of the oxide film. Increasing the current density can speed up the growth rate of the oxide film, but if the current density is too large, the growth rate of the oxide film will not speed up, but will tend to stop. During the oxidation period, the thickness of the oxide film is thin, the oxidation time is too long, the oxide film is too thick, and the permeability of the oxide film is poor.

After a lot of experiments, the inventor found that the temperature of the oxidizing solution is 20-22°C, the direct current density is 1.6-1.8A/dm2, the voltage is 8-10V, and the oxidation time is 30-40 minutes. The appearance of electronic products is anodized, and finally a continuous oxide film with high density, high gloss and good permeability with micropores can be obtained. The oxide film has excellent coloring effect and wear resistance and corrosion resistance.

Step 7: Put the cleaned aluminum alloy appearance parts in a dyeing solution for coloring, so that the dye is deposited into the holes of the oxide film to obtain a brilliant color, and the coloring is organic dyeing or electrolytic dyeing;

Before coloring, it is necessary to clean the aluminum alloy appearance parts with water to remove the residual oxidation liquid on the surface. The fresh oxide film obtained by anodic oxidation is very easy to be polluted. It should be colored immediately after washing to obtain various gorgeous colors to achieve beautification and decoration effect.

The commonly used methods for coloring the oxide film of aluminum alloy exterior parts include organic dyeing and electrolytic coloring. Organic dyeing is a coloring method that uses the high porosity and strong adsorption capacity of the oxide film to adsorb chemical dyes in the pores of the film. Electrolytic coloring is to put anodized aluminum alloy appearance parts into a metal salt solution, and under the action of electric current, metal particles or metal compounds are electrolytically deposited in the film pores of the oxide film, and the incident light is affected by the metal particles and metal compounds. It absorbs and scatters to produce a color rendering effect, and the color depth is mainly determined by the amount of metal particles deposited. Organic dyeing is fast, diverse in color and easy to operate. After the sealing process, the dye can be firmly attached to the film hole. The weather resistance, light resistance and service life of electrolytic coloring are better than those of organic dyeing, but the color of electrolytic coloring is currently more monotonous. You can choose organic dyeing or electrolytic coloring according to the specific color requirements of 7000 series aluminum alloy electronic products. Get gorgeous colors.

Step 8: Put the cleaned aluminum alloy appearance parts into boiling water with a pH of 4.5-5.0 and a temperature of 80-85°C for sealing treatment for 3 to 5 minutes, sealing the micropores on the oxide film, and washing and drying The appearance part of the 7000 series aluminum alloy electronic product is obtained.

Before sealing, it is necessary to clean the aluminum alloy appearance parts with water to remove the staining solution remaining on the surface. In order to maintain the color of the colored oxide film, avoid contamination, and improve the abrasion and corrosion resistance of the oxide film, sealing should be carried out in time after washing. At present, aluminum alloy appearance parts are mainly sealed by boiling water, that is, the aluminum alloy appearance parts are placed in boiling water. The anhydrous Al2O3 on the surface of the oxide film and the pore walls is first hydrated into a monohydrate compound, and the volume is increased by more than 30%. When it is converted into a trihydrate, the volume will increase by more than 100% compared to the original, thereby sealing the micropores on the oxide film. After sealing, the dye is fixed in the membrane pores and the oxide film becomes non-porous and dense.

The effect of boiling water sealing is closely related to the pH value, temperature and sealing treatment time of boiling water. The inventor conducted a large number of experiments on the boiling water sealing process of the appearance parts of 7000 series aluminum alloy electronic products and found that the use of boiling water with a pH value of 4.5 to 5.0 and a temperature of 80 to 85°C, sealing treatment for 3 to 5 minutes, can completely Close the micropores on the oxide film to obtain a uniform and dense oxide film on the surface, and improve the wear and corrosion resistance of the oxide film. If the water temperature is lower than 80°C or the time is less than 3 minutes, the micropores cannot be completely sealed. If the water temperature is higher than 85°C or the time is longer than 5 minutes, although the micropores can be closed, the surface will be uneven, which will reduce the quality of the sealing, resulting in the corrosion and wear resistance of the oxide film.

The 7000 series aluminum alloy in the present invention refers to an aluminum alloy with Zn as the main alloy element.

Preferably, the 7000 series aluminum alloy is composed of the following components by mass percentage: Zn 5.0-6.0%, Mg 0.5-1.0%, Zr 0.15-0.25%, Fe≤0.15%, Si≤0.1%, Ti≤0.1%, The rest is Al and other unavoidable impurity elements. The individual content of other impurity elements is ≤0.05%, and the total amount is ≤0.15%.

Preferably, the 7000 series aluminum alloy is composed of the following components by mass percentage: Zn 4.0-5.0%, Mg 1.2-1.8%, Mn 0.3-0.6%, Fe≤0.15%, Si≤0.1%, Ti≤0.1%, The rest is Al and other unavoidable impurity elements. The individual content of other impurity elements is ≤0.05%, and the total amount is ≤0.15%.

Preferably, the 7000 series aluminum alloy is composed of the following components by mass percentage: Zn 5.5~6.5%, Mg 1.5~2.5%, Cu 1.5~2.5%, Fe≤0.15%, Si≤0.1%, Ti≤0.1%, The rest is Al and other unavoidable impurity elements. The individual content of other impurity elements is ≤0.05%, and the total amount is ≤0.15%.

Compared with the prior art, the present invention has the following beneficial effects: the present invention uses the degreasing liquid, alkaline washing liquid, pickling liquid, polishing liquid, oxidizing liquid composition and its treatment process of the appearance parts of 7000 series aluminum alloy electronic products. Parameters are optimized to improve the density of the oxide film. The oxide film has strong adhesion, not easy to fall off, good permeability, and high gloss. After coloring and sealing, the color is pure and bright, which can significantly improve the 7000 series aluminum alloy electronics The wear resistance, corrosion resistance and surface decoration effect of the appearance parts of the product.

Detailed ways

In order to make the objectives, technical solutions, and effects of the present invention clearer and clearer, the present invention will be further described in detail below in conjunction with specific embodiments and comparative examples.

Example 1

A 7000 series aluminum alloy electronic product appearance part oxidation coloring method, the 7000 series aluminum alloy is composed of the following mass percentages: Zn 5.6%, Mg 0.8%, Zr 0.19%, Fe 0.14%, Si 0.08%, Ti 0.06, the rest is Al and other unavoidable impurity elements. The individual content of other impurity elements is ≤0.05%, and the total amount is ≤0.15%; the oxidation coloring method includes the following steps in sequence:

The first step: mechanically polish the surface of the aluminum alloy appearance parts to remove the machining knife marks, burrs, scratches, etc. on the surface to obtain a smooth surface;

Step 2: Put the aluminum alloy exterior parts into a degreasing solution at 85°C for 8 minutes to remove oil stains on the surface. The degreasing solution is a mixed aqueous solution of sodium carbonate, sodium phosphate and sodium citrate, with a sodium carbonate concentration of 70g /L, the concentration of sodium phosphate is 35g/L, and the concentration of sodium citrate is 12g/L;

The third step: Put the cleaned aluminum alloy appearance parts into an alkaline washing solution at 30°C for 2.5 minutes to remove the natural oxide film on the surface. The alkaline solution is a mixed aqueous solution of sodium hydroxide and sodium silicate. The concentration of sodium hydroxide is 23g/L and the concentration of sodium silicate is 12g/L;

Step 4: Put the cleaned aluminum alloy appearance parts into a pickling solution at 25°C for 1.5 minutes to remove dirt on the surface. The acid solution is a mixed aqueous solution of nitric acid, sulfuric acid and formic acid, and the concentration of nitric acid is 120g/L, sulfuric acid concentration is 35g/L, formic acid concentration is 15g/L;

Step 5: Put the cleaned aluminum alloy appearance parts into a polishing solution at 55°C for 35 seconds to obtain a smooth and bright surface. The polishing solution is a mixture of phosphoric acid, sulfinic acid, and phenylacetic acid. The volume percentage is 67%, the volume percentage of sulfinic acid is 21%, and the volume percentage of phenylacetic acid is 12%;

Step 6: Put the cleaned aluminum alloy appearance parts into an oxidizing solution at 21°C for 35 minutes to form an oxide film with micropores on the surface. The oxidizing solution is sulfuric acid, oxalic acid, aluminum sulfate and alkane. The mixed aqueous solution of base phenol, the concentration of sulfuric acid is 15g/L, the concentration of oxalic acid is 8g/L, the concentration of aluminum sulfate is 18g/L, the concentration of alkylphenol is 2.5g/L, the direct current density of anodizing is 1.7A/dm2, the voltage 9V, the anodized cathode is lead plate;

Step 7: Put the cleaned aluminum alloy appearance parts into the dyeing solution for organic dyeing and coloring, so that the dye is deposited into the holes of the oxide film;

Step 8: Put the cleaned aluminum alloy appearance parts into boiling water with a pH of 4.8 and a temperature of 82°C for sealing treatment for 4 minutes to close the micropores on the oxide film, and obtain the 7000 series aluminum after cleaning and drying Appearance of alloy electronic products.

Example 2

A 7000 series aluminum alloy electronic product appearance part oxidation coloring method, the 7000 series aluminum alloy is composed of the following mass percentages: Zn 4.7%, Mg 1.5%, Mn 0.5%, Fe 0.13%, Si 0.07%, Ti 0.5%, the rest is Al and other unavoidable impurity elements. The individual content of other impurity elements is ≤0.05%, and the total amount is ≤0.15%; the oxidation coloring method includes the following steps in sequence:

Step 2: Put the aluminum alloy exterior parts into a degreasing solution at 80°C for 8 minutes to remove oil stains on the surface. The degreasing solution is a mixed aqueous solution of sodium carbonate, sodium phosphate and sodium citrate, with a sodium carbonate concentration of 80g /L, the concentration of sodium phosphate is 30g/L, and the concentration of sodium citrate is 15g/L;

The third step: Put the cleaned aluminum alloy appearance parts into an alkaline washing solution at 30°C for 2 minutes to remove the natural oxide film on the surface. The alkaline solution is a mixed aqueous solution of sodium hydroxide and sodium silicate. The concentration of sodium hydroxide is 20g/L, and the concentration of sodium silicate is 15g/L;

Step 4: Put the cleaned aluminum alloy appearance parts into a pickling solution at 25°C for 2 minutes to remove the dirt on the surface. The acid solution is a mixed aqueous solution of nitric acid, sulfuric acid and formic acid, and the concentration of nitric acid is 130g/L, sulfuric acid concentration is 30g/L, formic acid concentration is 20g/L;

Step 5: Put the cleaned aluminum alloy appearance parts into a 60°C polishing solution for chemical polishing for 30 seconds to obtain a smooth and bright surface. The polishing solution is a mixture of phosphoric acid, sulfinic acid, and phenylacetic acid. The volume percentage is 70%, the volume percentage of sulfinic acid is 20%, and the volume percentage of phenylacetic acid is 10%;

Step 6: Put the cleaned aluminum alloy appearance parts into an oxidizing solution at 20°C for 40 minutes to form an oxide film with micropores on the surface. The oxidizing solution is sulfuric acid, oxalic acid, aluminum sulfate and alkane. A mixed aqueous solution of base phenol, the concentration of sulfuric acid is 140g/L, the concentration of oxalic acid is 9g/L, the concentration of aluminum sulfate is 20g/L, the concentration of alkylphenol is 2g/L, the direct current density of anodizing is 1.6A/dm2, and the voltage is 10V, the anodized cathode is lead plate;

Step 8: Put the cleaned aluminum alloy appearance parts into boiling water with a pH of 5.0 and a temperature of 80°C for sealing treatment for 5 minutes to seal the micropores on the oxide film, and obtain the 7000 series aluminum after washing and drying Appearance of alloy electronic products.

Example 3

A 7000 series aluminum alloy electronic product appearance part oxidation coloring method, the 7000 series aluminum alloy is composed of the following mass percentages: Zn 6.3%, Mg 2.1%, Cu 1.9%, Fe 0.15%, Si 0.07%, Ti 0.08%, the rest is Al and other unavoidable impurity elements. The individual content of other impurity elements is ≤0.05%, and the total amount is ≤0.15%; the oxidation coloring method includes the following steps in sequence:

Step 2: Put the aluminum alloy appearance parts into a 90°C degreasing solution for 7 minutes to remove oil stains on the surface. The degreasing solution is a mixed aqueous solution of sodium carbonate, sodium phosphate and sodium citrate, with a sodium carbonate concentration of 60g /L, the concentration of sodium phosphate is 40g/L, and the concentration of sodium citrate is 10g/L;

The third step: Put the cleaned aluminum alloy appearance parts into an alkaline washing solution at 25°C for 2 minutes to remove the natural oxide film on the surface. The alkaline solution is a mixed aqueous solution of sodium hydroxide and sodium silicate. The concentration of sodium hydroxide is 25g/L, and the concentration of sodium silicate is 10g/L;

Step 4: Put the cleaned aluminum alloy appearance parts into a 30°C pickling solution for 1 minute to remove dirt on the surface. The acid solution is a mixed aqueous solution of nitric acid, sulfuric acid and formic acid, and the concentration of nitric acid is 110g/L, sulfuric acid concentration is 40g/L, formic acid concentration is 10g/L;

Step 5: Put the cleaned aluminum alloy appearance parts into a 50°C polishing solution for chemical polishing for 40 seconds to obtain a smooth and bright surface. The polishing solution is a mixture of phosphoric acid, sulfinic acid, and phenylacetic acid. The volume percentage is 65%, the volume percentage of sulfinic acid is 22%, and the volume percentage of phenylacetic acid is 13%;

Step 6: Put the cleaned aluminum alloy exterior parts into an oxidizing solution at 22°C for 30 minutes to form an oxide film with micropores on the surface. The oxidizing solution is sulfuric acid, oxalic acid, aluminum sulfate and alkane. A mixed aqueous solution of base phenol, the concentration of sulfuric acid is 150g/L, the concentration of oxalic acid is 8g/L, the concentration of aluminum sulfate is 15g/L, the concentration of alkylphenol is 3g/L, the direct current density of anodizing is 1.8A/dm2, and the voltage is 8V, the anodized cathode is lead plate;

Step 8: Put the cleaned aluminum alloy appearance parts into boiling water with a pH of 4.5 and a temperature of 85°C for sealing treatment for 3 minutes to close the micropores on the oxide film, and obtain the 7000 series aluminum after cleaning and drying. Appearance of alloy electronic products.

Comparative example 1

The third step: Put the cleaned aluminum alloy appearance parts into alkaline washing solution at 30°C for 2.5 minutes to remove the natural oxide film on the surface. The alkaline solution is a mixed aqueous solution of sodium hydroxide and sodium nitrate, hydrogen The concentration of sodium oxide is 23g/L and the concentration of sodium nitrate is 12g/L;

Step 5: Put the cleaned aluminum alloy appearance parts into a polishing solution at 55°C for 35 seconds to obtain a smooth and bright surface. The polishing solution is a mixture of phosphoric acid, sulfinic acid and phenylacetic acid. The percentage is 67%, the volume percentage of sulfinic acid is 21%, and the volume percentage of phenylacetic acid is 12%;

Comparative example 2

Step 5: Put the cleaned aluminum alloy appearance parts into a 60°C polishing solution for chemical polishing for 30 seconds to obtain a smooth and bright surface. The polishing solution is a mixture of phosphoric acid and sulfuric acid, and the volume percentage of phosphoric acid is 67%. The volume percentage of sulfuric acid is 33%;

Comparative example 3

Step 6: Put the cleaned aluminum alloy appearance parts into an oxidizing solution at 22°C for 30 minutes to form an oxide film with micropores on the surface. The oxidizing solution is an aqueous sulfuric acid solution with a sulfuric acid concentration of 150g/ L, the anodized direct current density is 1.8A/dm2, the voltage is 8V, and the anodized cathode is a lead plate;

The oxide film of the appearance parts of the 7000 series aluminum alloy electronic product of the example and the comparative example was observed on the JCX-1250 Shimadzu scanning electron microscope, and the cross-sectional thickness of the oxide film was measured. The test results are shown in Table 1. According to GB/T 20503-2006 "Aluminum and Aluminum Alloy Anodized Anodic Oxide Film Specular Reflectance and Specular Gloss Measurement", the 7000 series aluminum alloy electronic product appearance part oxide film was measured and tested at 60° specular gloss GS value. The results are shown in Table 1. According to the national standard GB/T12967.6-2008 "Aluminum and aluminum alloy anodic oxide film detection method Part 6: Visual observation method to inspect the color difference and appearance quality of colored anodic oxide film", the test results are shown in Table 1.

Table 1 Test results of appearance parts of 7000 series aluminum alloy electronic products of the embodiment and the comparative example

It can be seen from Table 1 that the oxide film of the appearance part of the 7000 series aluminum alloy electronic product of the present invention is dense, the oxide film thickness is greater than 25 microns, the gloss GS value is greater than 718, and the color is pure and colorful after coloring. It can be seen from Table 1 that Comparative Example 1 is due to the common sodium hydroxide and sodium nitrate aqueous solution, Comparative Example 2 is due to the ordinary phosphoric acid and sulfuric acid mixture, and Comparative Example 3 is due to the oxidizing solution used. It is a common sulfuric acid aqueous solution, which causes the oxide film of the comparative example to be loose, the oxide film thickness is uniformly less than 25 microns, the gloss GS value is less than 18, and the color is cloudy and the color is dim after coloring. Through comparison, it can be seen that the present invention can significantly improve the compactness, thickness, gloss and coloring of the oxide film of the appearance parts of 7000 series aluminum alloy electronic products by optimizing the composition ratio of the alkaline washing liquid, polishing liquid and oxidation liquid. The effect is pure and colorful after coloring.

The present invention is described through the embodiments, but does not limit the present invention. With reference to the description of the present invention, other changes to the disclosed embodiments are easily conceivable by those skilled in the art. Such changes should belong to Within the scope defined by the claims of the present invention.

Claims

A method for oxidizing and coloring appearance parts of 7000 series aluminum alloy electronic products, which is characterized by including the following steps in sequence:

The first step: the surface mechanical pretreatment of the aluminum alloy appearance parts, remove the surface machining knife marks, burrs, scratches, etc., to obtain a smooth surface;

Step 2: Put the aluminum alloy exterior parts into a degreasing solution at 80-90°C for 7-8 minutes to remove oil stains on the surface. The degreasing solution is a mixed aqueous solution of sodium carbonate, sodium phosphate and sodium citrate, and carbonated The concentration of sodium is 60～80g/L, the concentration of sodium phosphate is 30～40g/L, and the concentration of sodium citrate is 10～15g/L;

The third step: Put the cleaned aluminum alloy appearance parts in an alkaline washing solution at 25-30°C for 2 to 3 minutes to remove the natural oxide film on the surface. The alkaline solution is sodium hydroxide and sodium silicate. The concentration of sodium hydroxide is 20-25g/L and the concentration of sodium silicate is 10-15g/L;

Step 4: Put the cleaned aluminum alloy appearance parts in a pickling solution at 25-30°C for 1 to 2 minutes to remove dirt on the surface. The acid solution is a mixed aqueous solution of nitric acid, sulfuric acid and formic acid , The concentration of nitric acid is 110～130g/L, the concentration of sulfuric acid is 30～40g/L, and the concentration of formic acid is 10～20g/L;

Step 5: Put the cleaned aluminum alloy appearance parts into a 50-60°C polishing solution for chemical polishing for 30-40 seconds to obtain a smooth and bright surface. The polishing solution is made of phosphoric acid, sulfinic acid and phenylacetic acid. In the mixed solution, the volume percentage of phosphoric acid is 65 to 70%, the volume percentage of sulfinic acid is 20 to 22%, and the volume percentage of phenylacetic acid is 10 to 13%;

Step 6: Put the cleaned aluminum alloy appearance parts into an oxidizing solution at 20-22°C for 30-40 minutes to form a microporous oxide film on the surface. The oxidizing solution is sulfuric acid, oxalic acid, Mixed aqueous solution of aluminum sulfate and alkylphenol, sulfuric acid concentration is 140-150g/L, oxalic acid concentration is 8-9g/L, aluminum sulfate concentration is 15-20g/L, alkylphenol concentration is 2-3g/L;

Step 7: Put the cleaned aluminum alloy appearance parts into the dyeing solution for coloring, so that the dyeing agent is deposited into the holes of the oxide film to obtain brilliant colors;

Step 8: Put the cleaned aluminum alloy appearance parts into boiling water with a pH of 4.5-5.0 and a temperature of 80-85°C for sealing treatment for 3 to 5 minutes, sealing the micropores on the oxide film, and washing and drying with water The appearance part of the 7000 series aluminum alloy electronic product is obtained.
The oxidation coloring method for appearance parts of 7000 series aluminum alloy electronic products according to claim 1, characterized in that: the 7000 series aluminum alloy is composed of the following components by mass percentage: Zn 5.0-6.0%, Mg 0.5-1.0%, Zr 0.15～0.25%, Fe≤0.15%, Si≤0.1%, Ti≤0.1%, the rest is Al and other unavoidable impurity elements. The individual content of other impurity elements is ≤0.05%, and the total amount is ≤0.15%.
The oxidation coloring method for appearance parts of 7000 series aluminum alloy electronic products according to claim 1, characterized in that: the 7000 series aluminum alloy is composed of the following components by mass percentage: Zn 4.0-5.0%, Mg 1.2-1.8%, Mn 0.3-0.6%, Fe≤0.15%, Si≤0.1%, Ti≤0.1%, the rest is Al and other unavoidable impurity elements, the individual content of other impurity elements is ≤0.05%, and the total amount is ≤0.15%.
The oxidation coloring method for appearance parts of 7000 series aluminum alloy electronic products according to claim 1, characterized in that: the 7000 series aluminum alloy is composed of the following components by mass percentage: Zn 5.5 to 6.5%, Mg 1.5 to 2.5%, Cu 1.5～2.5%, Fe≤0.15%, Si≤0.1%, Ti≤0.1%, the rest is Al and other unavoidable impurity elements, the individual content of other impurity elements is ≤0.05%, and the total amount is ≤0.15%.
The oxidation coloring method for appearance parts of 7000 series aluminum alloy electronic products according to claim 1, characterized in that: in the first step, the surface mechanical pretreatment includes surface mechanical polishing or sandblasting.
The oxidation coloring method of the appearance part of the 7000 series aluminum alloy electronic product according to claim 1, wherein in the sixth step, the direct current density of the anodization is 1.6 to 1.8 A/dm2, and the voltage is 8 to 10V.
The oxidation coloring method of the appearance part of the 7000 series aluminum alloy electronic product according to claim 1, wherein in the sixth step, the anodized cathode comprises a lead plate or a graphite plate.
The oxidation coloring method for appearance parts of 7000 series aluminum alloy electronic products according to claim 1, wherein in the seventh step, the coloring includes organic coloring or electrolytic coloring.