A pretreatment method for preparing porous anodized aluminum template from discarded can aluminum foil

Abstract

The invention discloses a pretreatment method for preparing a porous anodized aluminum template from discarded aluminum foil of an aluminum can in the field of resource recycling technology. First, a solvent is used to wash the surface of the aluminum foil of the can to remove surface grease, then the surface of the aluminum foil of the can is subjected to paint removal treatment, and finally the surface of the aluminum foil of the can is electrochemically polished in a polishing liquid to obtain an aluminum foil sheet with a film layer of microscopic holes on the surface. The invention uses discarded aluminum foil as a substrate for preparing a porous anodized aluminum template, and the raw materials are widely available, which reduces the test cost. At the same time, the discarded aluminum foil is recycled again, which is cleaner and more environmentally friendly. The paint removal method of the invention is simple and has significant effects, which is conducive to large-scale promotion and application.

Description

Technical Field

[0001] The invention relates to the technical field of resource recycling, and in particular to a pretreatment method for preparing a porous anodized aluminum template from discarded aluminum foil of an easy-pull can. Background Art

[0002] In recent years, with the increasing demand for aluminum resources and the increasing prominence of environmental protection issues, the development of the recycled aluminum industry has received widespread attention from the society. The world consumes about 150 billion cans every year, which have become the main source of waste aluminum. Recycling cans can alleviate the shortage of aluminum resources.

[0003] Aluminum cans can be used to produce steelmaking deoxidizers, manufacture hydrogen and potassium alum, and smelt into the original grade 3004 alloy. In the past, high-purity aluminum was used as the experimental raw material for preparing anodized aluminum AAO templates. The purity of aluminum has an important influence on the performance of the template. Aluminum content in discarded cans accounts for more than 95%, and it can be used to prepare AAO templates after pretreatment.

[0004] The paint film layer on the outer surface of the can is mainly composed of chemical coatings with organic hydrocarbon adhesives and titanium dioxide as the main components. During the recycling process, if the paint is directly melted without paint removal, the combustion of the paint film will produce harmful gases to pollute the environment. In the pretreatment process, paint removal is a key step. The cans after paint removal should have conditions such as complete paint removal, low roughness, and high order. The main methods for can paint removal are mechanical paint removal, thermal paint removal, and chemical paint removal. Mechanical paint removal is the simplest to operate, but it has the greatest limitations, and the paint removal process will cause the loss of aluminum alloy; the thermal paint removal method is efficient and low in cost, but it has the disadvantages of large energy loss and the generation of harmful gases. The key point of the chemical paint removal method is the stable paint removal liquid. The microscopic morphology of the aluminum matrix after paint removal and the weight loss mass of the aluminum matrix need to be regulated to ensure the improvement of the order of the AAO template.

[0005] The existing published patent documents record methods and technologies for paint removal or electrochemical polishing. For example, the patent with publication number CN103757649A proposes a paint remover prepared by uniformly mixing 25-45% dimethyl sulfoxide, 30-55% N,N-dimethylformamide, and 5-15% concentrated sulfuric acid; the patent with publication number CN105462337A discloses a paint removal paste for the paint film on the surface of a can, which is prepared by weight parts of 10-40 parts of hydrocarbon solvent oil, 20-80 parts of solid filler, 1-10 parts of sodium salt of dioctyl sulfonate succinate, and 0.1-5 parts of water; the patent with publication number CN107974706A discloses an electrochemical polishing treatment process for aluminum profiles, and the polishing liquid is mainly composed of 25-28 g / L of fluoroboric acid, 5-5.5 g / L of nitric acid, and 6.0-6.1 g / L of boric acid. The above paint removers / pastes and polishing liquids all use a large amount of organic solvents and organic acids, which are dangerous to operate and have insignificant paint removal effects. In addition, the test substrate in the above methods is pure aluminum, which results in high test costs. Summary of the invention

[0006] The purpose of the present invention is to overcome the defects in the prior art and provide a pretreatment method for preparing a porous anodized aluminum template from discarded can aluminum foil. Discarded cans are used as a substrate for preparing the porous anodized aluminum template. The raw materials are widely available, the paint removal method is simple and the effect is significant, which is conducive to large-scale promotion and application.

[0007] The object of the present invention is achieved by: a pretreatment method for preparing a porous anodized aluminum template from discarded can aluminum foil, comprising the following steps:

[0008] (1) Degreasing: Use solvent to rinse the surface of the aluminum foil of the can to remove the surface grease, then use tap water and deionized water to rinse the surface of the aluminum foil of the can, and then dry it;

[0009] (2) Paint removal: prepare a paint removal liquid, put the degreased aluminum foil obtained in step 1 into the paint removal liquid, set the paint removal temperature and time, and wash and dry the aluminum foil after the paint removal is completed;

[0010] (3) Electrochemical polishing: prepare a polishing liquid, use the aluminum foil after paint removal in step 2 as the anode and the platinum electrode as the cathode, and perform electrochemical polishing on a regulated power supply. After polishing, clean and dry the aluminum foil to obtain an aluminum foil sheet with a film layer of microscopic holes on the surface.

[0011] Furthermore, the washing solvent described in step 1 is anhydrous ethanol.

[0012] Furthermore, the paint removal liquid described in step 2 includes 60-80 parts of sulfuric acid solution with a concentration of 600 mL / L, 0-5 parts of auxiliary acid of 1 g / L, and 0-5 parts of surfactant of 3 g / L; the paint removal temperature is 0-60°C, and the paint removal time is 10-60 minutes; after paint removal, first rinse with tap water until it is not greasy to the touch, and then rinse with deionized water 2-3 times.

[0013] Furthermore, the auxiliary acid is one of succinic acid (C4H6O4), malonic acid (C3H4O4), oxalic acid (H2C2O4), tartaric acid (C4H6O6), and ethylenediaminetetraacetic acid (EDTA).

[0014] Furthermore, the surfactant is one of CDEA, AEO-7, fluorocarbon, AES, NP-10, and LAS.

[0015] Furthermore, the polishing liquid in step 3 is composed of 1,2-propylene glycol (PROH) and perchloric acid (HClO4), and the volume ratio of 1,2-propylene glycol (PROH) and perchloric acid (HClO4) is (1~10):1.

[0016] Furthermore, the temperature of the electrochemical polishing is set to 10-40°C, the applied voltage is 10-40 V, and the polishing time is 30-90 s.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] First, using discarded cans as the source of aluminum foil, the raw materials are widely available and easy to obtain, which reduces the cost of testing. At the same time, the discarded cans can be recycled again, which is cleaner and more environmentally friendly.

[0019] Second, the present invention removes paint and electrochemically polishes the surface of discarded aluminum foil of cans, thereby regulating the changes in the self-organized pattern of the aluminum foil surface, and combines the surface morphology of the aluminum substrate after paint removal and the weightlessness of the aluminum substrate to achieve optimization of the self-organization process of the aluminum substrate surface, thereby improving the orderliness of the AAO template prepared from discarded aluminum foil of cans, and providing the possibility for can aluminum alloy to replace pure aluminum. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the Tafel curve of the test piece after paint removal in Example 1.

[0021] Figure 2 1 is the anodic polarization curve after electrochemical polishing at different temperatures in Example 1.

[0022] Figure 3 The electron microscope images (200 times) of the surface of the paint-removed aluminum foil in Example 1 before and after electrochemical polishing.

[0023] Figure 4 This is an electron microscope image (200 times) of the surface of the paint-removed aluminum foil in Example 2 before and after electrochemical polishing.

[0024] Figure 5 This is an electron microscope image (10,000 times) of the surface of the paint-removed aluminum foil in Example 2 before and after electrochemical polishing. DETAILED DESCRIPTION

[0025] Embodiment 1:

[0026] Step 1: Degreasing: Use anhydrous ethanol to clean the grease on the surface of the aluminum foil of the can, then rinse with tap water and deionized water, then use filter paper to wipe off the moisture on the surface of the aluminum foil of the can, and finally use a hair dryer to blow away the moisture and dust;

[0027] Step 2: Paint removal: Prepare paint removal liquid, mix 600 mL / L sulfuric acid solution, 1 g / L succinic acid, and 3 g / L LAS in a weight ratio of 65:2:1, and add distilled water to make up to 100 parts by weight; soak the degreased aluminum foil in the paint removal liquid, control the paint removal temperature at 30°C, and take 8 minutes. After the removal, rinse with tap water until it is not greasy to the touch, and then rinse with deionized water 2 to 3 times;

[0028] Step 3: Electrochemical polishing: prepare the polishing liquid, mix 1,2-propylene glycol (PROH) and perchloric acid (HClO4) in a volume ratio of 5:1, use the depainted aluminum foil as the anode and the platinum electrode as the cathode, place them in a container filled with the polishing liquid, set the external voltage to 26 V, the polishing temperature to 10°C, and the polishing time to 45 s. After the end, rinse with tap water and deionized water for 2 to 3 times respectively, then wipe the moisture on the surface of the aluminum foil with filter paper, and dry it naturally to obtain the pretreated aluminum foil template.

[0029] Embodiment 2:

[0030] Step 1: Degreasing: Use anhydrous ethanol to clean the grease on the surface of the aluminum foil of the can, then rinse with tap water and deionized water, then use filter paper to wipe off the moisture on the surface of the aluminum foil of the can, and finally use a hair dryer to blow away the moisture and dust;

[0031] Step 2: Paint removal: Prepare paint removal liquid, mix 600 mL / L sulfuric acid solution, 1 g / L tartaric acid, and 3 g / L CDEA in a weight ratio of 80:1:1, and add distilled water to 100 parts by weight; soak the degreased can aluminum foil in the paint removal liquid, control the paint removal temperature at 40°C, and take 6 minutes. After the paint removal is completed, rinse with tap water until it is not greasy to the touch, and then rinse with deionized water 2 to 3 times;

[0032] Step 3: Electrochemical polishing: prepare the polishing liquid, mix 1,2-propylene glycol (PROH) and perchloric acid (HClO4) in a volume ratio of 1:1, use the depainted aluminum foil as the anode and the platinum electrode as the cathode, place them in a container filled with the polishing liquid, set the applied voltage to 35 V, the polishing temperature to 20°C, and the polishing time to 60 s. After the end, rinse with tap water and deionized water for 2 to 3 times respectively, then wipe the moisture on the surface of the aluminum foil with filter paper, and dry it naturally to obtain the pretreated aluminum foil template.

[0033] Embodiment 3:

[0034] Step 1: Degreasing: Use anhydrous ethanol to clean the grease on the surface of the aluminum foil of the can, then rinse with tap water and deionized water, then use filter paper to wipe off the moisture on the surface of the aluminum foil of the can, and finally use a hair dryer to blow away the moisture and dust;

[0035] Step 2: Paint removal: Prepare paint removal liquid, mix 600 mL / L sulfuric acid solution, 1 g / L malonic acid, and 3 g / L AEO-7 in a weight ratio of 70:3:3, and make up to 100 parts by weight with distilled water; soak the degreased aluminum foil of the can in the paint removal liquid, control the paint removal temperature at 20°C, and take 20 minutes. After the removal, rinse with tap water until it is not greasy to the touch, and then rinse with deionized water 2 to 3 times;

[0036] Step 3: Electrochemical polishing: prepare the polishing liquid, mix 1,2-propylene glycol (PROH) and perchloric acid (HClO4) in a volume ratio of 3:1, use the depainted aluminum foil as the anode and the platinum electrode as the cathode, place them in a container filled with the polishing liquid, set the external voltage to 10 V, the polishing temperature to 30°C, and the polishing time to 55 s. After the end, rinse with tap water and deionized water for 2 to 3 times respectively, then wipe the moisture on the surface of the aluminum foil with filter paper, and dry it naturally to obtain the pretreated aluminum foil template.

[0037] Embodiment 4:

[0038] Step 1: Degreasing: Use anhydrous ethanol to clean the grease on the surface of the aluminum foil of the can, then rinse with tap water and deionized water, then use filter paper to wipe off the moisture on the surface of the aluminum foil of the can, and finally use a hair dryer to blow away the moisture and dust;

[0039] Step 2: Paint removal: Prepare paint removal liquid, mix 600 mL / L sulfuric acid solution, 1 g / L oxalic acid, and 3 g / L fluorocarbon in a weight ratio of 75:1:4, and make up to 100 parts by weight with distilled water; soak the degreased aluminum foil of the can in the paint removal liquid, control the paint removal temperature at 10°C, and take 40 minutes. After the removal, rinse with tap water until it is not greasy to the touch, and then rinse with deionized water 2 to 3 times;

[0040] Step 3: Electrochemical polishing: prepare the polishing liquid, mix 1,2-propylene glycol (PROH) and perchloric acid (HClO4) in a volume ratio of 7:1, use the depainted aluminum foil as the anode and the platinum electrode as the cathode, place them in a container filled with the polishing liquid, set the external voltage to 20 V, the polishing temperature to 40°C, and the polishing time to 65 s. After the end, rinse with tap water and deionized water for 2 to 3 times respectively, then wipe the moisture on the surface of the aluminum foil with filter paper, and dry it naturally to obtain the pretreated aluminum foil template.

[0041] Embodiment 5:

[0042] Step 1: Degreasing: Use anhydrous ethanol to clean the grease on the surface of the aluminum foil of the can, then rinse with tap water and deionized water, then use filter paper to wipe off the moisture on the surface of the aluminum foil of the can, and finally use a hair dryer to blow away the moisture and dust;

[0043] Step 2: Paint removal: Prepare paint removal liquid, mix 600 mL / L sulfuric acid solution, 1 g / L EDTA, and 3 g / L NP-10 in a weight ratio of 80:4:5, and add distilled water to make up to 100 parts by weight; soak the degreased aluminum foil in the paint removal liquid, control the paint removal temperature at 0°C, and take 60 minutes. After the removal, rinse with tap water until it is not greasy to the touch, and then rinse with deionized water 2 to 3 times;

[0044] Step 3: Electrochemical polishing: prepare the polishing liquid, mix 1,2-propylene glycol (PROH) and perchloric acid (HClO4) in a volume ratio of 9:1, use the depainted aluminum foil as the anode and the platinum electrode as the cathode, place them in a container filled with the polishing liquid, set the external voltage to 40 V, the polishing temperature to 15°C, and the polishing time to 30 s. After the end, rinse with tap water and deionized water for 2 to 3 times respectively, then wipe the moisture on the surface of the aluminum foil with filter paper, and dry it naturally to obtain the pretreated aluminum foil template.

[0045] Embodiment 6:

[0046] Step 1: Degreasing: Use anhydrous ethanol to clean the grease on the surface of the aluminum foil of the can, then rinse with tap water and deionized water, then use filter paper to wipe off the moisture on the surface of the aluminum foil of the can, and finally use a hair dryer to blow away the moisture and dust;

[0047] Step 2: Paint removal: Prepare paint removal liquid, mix 600 mL / L sulfuric acid solution, 1 g / L tartaric acid, and 3 g / L LAS in a weight ratio of 75:4:1, and add distilled water to 100 weight parts; soak the degreased aluminum foil in the paint removal liquid, control the paint removal temperature at 50°C, and the time for 10 min. After the paint removal is completed, rinse with tap water until it is not greasy to the touch, and then rinse with deionized water 2 to 3 times;

[0048] Step 3: Electrochemical polishing: prepare the polishing liquid, mix 1,2-propylene glycol (PROH) and perchloric acid (HClO4) in a volume ratio of 10:1, use the depainted aluminum foil as the anode and the platinum electrode as the cathode, place them in a container filled with the polishing liquid, set the applied voltage to 10 V, the polishing temperature to 10°C, and the polishing time to 90 s. After the end, rinse with tap water and deionized water for 2 to 3 times respectively, then wipe the moisture on the surface of the aluminum foil with filter paper, and dry it naturally to obtain the pretreated aluminum foil template.

[0049] Embodiment 7:

[0050] Step 1: Degreasing: Use anhydrous ethanol to clean the grease on the surface of the aluminum foil of the can, then rinse with tap water and deionized water, then use filter paper to wipe off the moisture on the surface of the aluminum foil of the can, and finally use a hair dryer to blow away the moisture and dust;

[0051] Step 2: Paint removal: Prepare paint removal liquid, mix 600 mL / L sulfuric acid solution, 1 g / L EDTA, and 3 g / L AES in a weight ratio of 60:1:2, and add distilled water to 100 weight parts; soak the degreased aluminum foil in the paint removal liquid, control the paint removal temperature at 60℃, and the time for 50 min. After the removal, rinse with tap water until it is not greasy to the touch, and then rinse with deionized water 2~3 times;

[0052] Step 3: Electrochemical polishing: prepare the polishing liquid, mix 1,2-propylene glycol (PROH) and perchloric acid (HClO4) in a volume ratio of 4:1, use the depainted aluminum foil as the anode and the platinum electrode as the cathode, place them in a container filled with the polishing liquid, set the applied voltage to 10 V, the polishing temperature to 20°C, and the polishing time to 70 s. After the end, rinse with tap water and deionized water for 2 to 3 times respectively, then wipe the moisture on the surface of the aluminum foil with filter paper, and dry it naturally to obtain the pretreated aluminum foil template.

[0053] Comparative Example 1:

[0054] The specific preparation steps are the same as those in Example 1, except that the temperature during paint removal is changed to 30°C, 50°C, and 60°C.

[0055] Comparative Example 2:

[0056] The specific preparation steps are the same as those in Example 2, except that the temperature during electrochemical polishing is changed to 10°C, 20°C, and 30°C.

[0057] Figure 1 The Tafel curves of the test pieces after paint removal at different temperatures of Example 1 and Comparative Example 1 are shown. The smaller the corrosion current, the better the corrosion resistance of the material; the higher the corrosion potential, the smaller the corrosion rate of the material, and the stronger the corrosion resistance of the material; Figure 1As shown, from the perspective of corrosion current, the corrosion current at 30°C is the smallest, and the paint removal temperature for Example 1 is determined to be 30°C.

[0058] Figure 2 The anodic polarization curves of the test pieces after electrochemical polishing at different temperatures for Example 1 and Comparative Example 2 are shown in the figure. The limiting current density shows an upward trend. The limiting current density increases with increasing temperature. The figure also shows that the anodic polarization curves under different temperature conditions show the same trend: the current density first increases rapidly with increasing potential, which is the active dissolution zone of the anode; then the anode surface begins to passivate, and the current density decreases rapidly with increasing potential and fluctuates, which is the interval oscillation zone or passivation zone; when the potential is further increased, the current density remains constant, which is the limiting current density zone. Figure 2 It can be seen that in the limiting current density region, when the electrolyte temperature rises from 0°C to 30°C, the limiting current density increases accordingly, and its limiting potential range also changes. This is because as the temperature increases, the viscosity coefficient of the polishing liquid decreases, the diffusion rate of the dissolved metal ions accelerates, the concentration polarization on the anode surface is weakened, and the electrochemical reaction rate accelerates. Therefore, as the temperature increases, the time required for polishing will be shortened and the effect will be better. However, when the temperature continues to rise, due to the rapid diffusion rate of the dissolved metal ions, pores on the surface of the aluminum foil appear sharply, resulting in irregular pits on the surface of the aluminum foil, which does not meet the basic requirements for preparing the AAO template.

[0059] Figure 3 , 4 The surface electron microscope images of the aluminum foil of Example 1 and Example 2 before and after polishing (200 times) are respectively. Before electrochemical polishing, the surface of the aluminum foil is rough, with pits and protrusions of varying degrees, and the points are raised. When the polishing potential reaches 35 V, it can be seen that the surface of the aluminum foil changes, and spots and air stripes appear. This is due to the retention of oxygen bubbles on the surface of the aluminum foil and the movement of bubbles. It can be observed in the figure that the aluminum foil of Example 2 has the best flatness after electrochemical polishing, and almost no scratches and unevenness can be seen on the surface. The aluminum foil of Example 2 was scanned and magnified 10,000 times under an electron microscope, as shown in the figure. Figure 5 As shown, a film layer with microscopic holes on its surface can be clearly observed. The film layer is formed after paint removal and electrochemical polishing. The pre-formed film layer is a self-organized form of the aluminum foil surface after electrochemical polishing, which can lay a good foundation for improving the orderliness of the film layer pores in the subsequent anodizing process.

[0060] The present invention is not limited to the above-mentioned embodiments. On the basis of the technical solution disclosed in the present invention, technicians in this field can make some substitutions and deformations to some technical features therein according to the disclosed technical content without creative labor, and these substitutions and deformations are all within the protection scope of the present invention.

Claims

1. A pretreatment method for preparing a porous anodized aluminum template from discarded can aluminum foil, characterized in that: The following steps are involved: (1) Degreasing: Use solvent to rinse the surface of the aluminum foil of the can to remove the surface grease, then use tap water and deionized water to rinse the surface of the aluminum foil of the can, and then dry it; (2) Paint removal: prepare a paint removal solution, which includes 60-80 parts of a sulfuric acid solution with a concentration of 600 mL / L, 0-5 parts of an auxiliary acid with a concentration of 1 g / L, and 0-5 parts of a surfactant with a concentration of 3 g / L; Put the degreased aluminum foil obtained in step 1 into the paint removal liquid, set the paint removal temperature to 0-60°C and the paint removal time to 10-60 minutes, rinse with tap water until it is not greasy to touch, then rinse with deionized water 2-3 times, and dry; The auxiliary acid is one of succinic acid (C4H6O4), malonic acid (C3H4O4), oxalic acid (H2C2O4), tartaric acid (C4H6O6), and ethylenediaminetetraacetic acid (EDTA), and the surfactant is one of CDEA, AEO-7, fluorocarbon, AES, NP-10, and LAS; (3) Electrochemical polishing: prepare a polishing solution consisting of 1,2-propylene glycol (PROH) and perchloric acid (HClO4), with the volume ratio of 1,2-propylene glycol (PROH) to perchloric acid (HClO4) being (1-10):1; The aluminum foil after paint removal in step 2 is used as the anode and the platinum electrode is used as the cathode. Electrochemical polishing is performed on a stabilized power supply. After polishing, the aluminum foil is cleaned and dried to obtain an aluminum foil sheet with a film layer of microscopic holes on the surface. The temperature of electrochemical polishing is set to 10~40℃, the applied voltage is 10~40 V, and the polishing time is 30~90s.

2. The pretreatment method for preparing a porous anodized aluminum template from discarded can aluminum foil according to claim 1, characterized in that: The washing solvent described in step 1 is anhydrous ethanol.

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