Color aluminum alloy coating film and preparation method thereof

Abstract

According to the color aluminum alloy coating film and the preparation method thereof, the light green and golden yellow aluminum oxide film which is particularly stable in color is prepared through the processes of pretreatment, anodic oxidation, inorganic salt soaking and electrolytic dyeing and hole sealing, good corrosion resistance and excellent protection performance are achieved, and on the whole, the color of the oxidation film is bright and uniform, and the service life of the oxidation film is prolonged. The color difference is small, and the corrosion resistance and the weather resistance are good.

Description

Technical Field

[0001] The present invention relates to the technical field of surface treatment of metals, in particular to an aluminum alloy film with stable color on the surface of aluminum alloy. Background Art

[0002] Aluminum, as the most abundant metallic element on earth, exists in ores in the form of chemical compounds, with low price and rich production. Aluminum and its alloys have characteristics such as high ductility, good machinability, and low density, and are widely used in many manufacturing fields such as aircraft and automobile manufacturing, architectural aluminum profiles, daily light industrial products, computer and communication components, optoelectronic and semiconductor components, etc.

[0003] Anodic oxidation of aluminum alloy is a process of electrochemical reaction in an electrolyte to generate an anodic oxidation film that has a protective effect on the substrate. There are many micropores on the grown anodic oxidation film, and these micropores have extremely strong adsorption properties. The adsorption property can be used to apply a layer of color on the oxide film to enhance the decoration of the anodic oxidation film of aluminum alloy and expand the application range of the anodic oxidation film.

[0004] The coloring methods of aluminum alloy oxide film include natural coloring method, electrolytic coloring method, and organic dye staining method. The natural coloring method is a method in which aluminum alloy shows color while undergoing anodic oxidation treatment under given electrolytes containing certain additives (such as carboxylic acids, aminosulfonic acid, tartaric acid, etc.) and electrolysis conditions. The change in the depth of hue can be achieved by selecting different alloy compositions and adjusting anodic oxidation parameters. However, due to the high energy consumption of this method, the electrolytic coloring process with relatively low energy consumption is often used now.

[0005] The electrolytic coloring method places the anodized aluminum alloy material in a coloring solution. The method in which coloring ions undergo a reduction reaction at the bottom of the oxide film pores under the action of an externally applied AC or DC electric field to generate a coloring substance and deposit is called electrolytic coloring. The types of colors and color brightness of the obtained colored film are determined by the types of metal salts, the deposition amount in the pores, the morphology and particle size distribution of the formed metal complexes. Due to different process conditions, electrolytic coloring can be divided into the following four types: (1) Natural coloring The method of coloring the aluminum alloy oxide film by oxidizing alloy elements by adjusting the operating conditions of anodic oxidation of aluminum alloy is called natural coloring. During the natural coloring process, the concentration of aluminum ions in the electrolyte should be strictly controlled. If the concentration of aluminum ions is too high, the conductivity of the electrolyte will be reduced, and then the quality of the formed colored film will be affected.

[0006] (2) Primary electrolytic coloring The method of adding inorganic salts during anodization and using an organic acid solution as the electrolyte to attach a colored film to the surface of aluminum alloy is called primary electrolytic coloring, and this method is also known as solution coloring. The color of the colored film formed by primary electrolytic coloring is related to the aluminum alloy material, oxidation operating conditions, and organic acid system.

[0007] (3)Secondary electrolytic coloring The method of using a metal salt solution as the electrolyte and performing electrolytic coloring treatment on an anodized product under the action of an external electric field to deposit coloring substances on the oxide film barrier layer is called secondary electrolytic coloring. According to the different compositions of the electrolyte, it can be divided into: mixed salt and single salt electrolytic coloring; according to the output waveform of the external electric field power supply, it can be divided into: direct current electrolytic coloring and alternating current electrolytic coloring.

[0008] (4)Tertiary electrolytic coloring Tertiary electrolytic coloring is a newly developed electrolytic coloring method in recent years, also known as photointerference electrolytic coloring. Compared with the secondary electrolytic coloring process, a "pore expansion" process is added on this basis. Before electrolytic coloring treatment and after anodization treatment, the aluminum alloy profile is placed in an acid solution for membrane pore modification treatment until the micropores are expanded into trumpet-shaped pores, and then the aluminum alloy material is electrolytically colored. This process is to adjust the morphological structure of the pores on the surface of the oxide film, and then change the deposition of metal complexes on the surface, so as to obtain various bright colors on the surface of aluminum alloy.

[0009] Although the colored film obtained by electrolytic coloring has good wear resistance and light resistance, and is less affected by the composition and morphology of the aluminum alloy material, the disadvantages of complex process and high energy consumption shown by the electrolytic coloring film still restrict its application range.

[0010] Organic dye staining method: It is a method that utilizes the porosity and adsorption of the oxide film to adhere organic dye molecules in the pores of the anodic aluminum oxide film to achieve a coloring effect. The characteristics of the AAO colored film obtained by this method are: there is a bonding effect between the organic coloring agent and the aluminum in the AAO film, and the process is simple, the operation is convenient, and the color is bright. However, the obtained colored film layer has extremely poor light and weather resistance, is not suitable for outdoor use, and the coloring process often requires heating to above 70°C, and the energy consumption is also relatively serious. Inorganic adsorption coloring is to immerse the aluminum material with a porous oxide film formed on its surface into two inorganic salt solutions successively, so that some ions contained in the two solutions undergo a chemical reaction to generate a new colored inorganic salt, which precipitates in the pore structure of the oxide film surface on the aluminum material, making the surface of the aluminum material present the color of the generated inorganic salt. Taking the example of coloring blue with Prussian blue (KFe[Fe(CN)6]) on aluminum material, the anodic aluminum oxide film of aluminum alloy is first immersed in an aqueous solution of potassium ferrocyanide (K4[Fe(CN)6]), and K enters the porous layer film structure of the oxide film+ and [Fe(CN)6] 4- ions, and then immersed in an aqueous solution containing Fe 3+ . At this time, the entering Fe 3+ will react with K + and [Fe(CN)6] 4- in the pore structure of the membrane to form blue KFe[Fe(CN)6] and adsorb it in the porous layer structure of the oxide film, making the aluminum material finally blue.

[0011] The colored oxide film prepared by the inorganic adsorption coloring method has good light resistance and weather resistance, is suitable for outdoor use, and has a simple process and less energy consumption during the coloring process, which can save labor and energy costs. However, the coloring degree of inorganic adsorption coloring is relatively shallow. To improve the coloring degree of inorganic adsorption coloring, a secondary pore expansion process is used to increase the micropore diameter on the oxide film, increase the adsorption amount of the coloring substance by the oxide film, enable more coloring substances to enter the oxide film, and enhance the inorganic adsorption coloring effect of the oxide film. Summary of the Invention

[0012] The present invention provides a color aluminum alloy coating film and a preparation method thereof, and a light green and golden yellow aluminum oxide film with particularly stable color is prepared through a process of pretreatment - anodic oxidation - inorganic salt immersion and electrolytic coloring - sealing hole, and it has good corrosion resistance and excellent protection performance.

[0013] A preparation method of a color aluminum alloy coating film includes the following steps: (1) Pretreatment: including ultrasonic degreasing, alkali washing, chemical polishing and water washing.

[0014] (2) Anodic oxidation: The anodic oxidation solution includes 3 - 4 mol / L sulfuric acid, 0.05 - 0.1 mol / L ferric sulfate, 0.1 - 0.5 mol / L aluminum sulfate and deionized water, the voltage is 20 - 30 V, the time is 20 - 30 min, and the temperature is 20 - 25 °C.

[0015] (3) Inorganic salt immersion: The immersion solution includes 0.5 - 0.7 mol / L sulfuric acid, 0.1 - 1 mol / L ferrous sulfate, 0.05 - 0.1 mol / L ferric sulfate, deionized water, the immersion time is 5 - 7 min, and the temperature is 10 - 15 °C.

[0016] (4) Electrolytic coloring: The electrolytic coloring solution includes 1.2 - 1.4 mol / L sulfuric acid, 0.1 - 0.2 mol / L ferrous oxide dihydrate, 0.1 - 0.5 mol / L KH2PO4, 0.1 - 0.2 mol / L K2HPO4, 0.05 - 0.07 mol / L aluminum hexafluorophosphate, 0.01 - 0.03 mol / L SDS, use NaHCO3 to adjust the pH = 4.2 - 4.8, and perform electrolytic coloring.

[0017] (5) Sealing the holes: Sealing with water vapor.

[0018] In some embodiments, the electrolytic coloring includes three times of electrolytic coloring: The first electrolytic coloring: voltage 12 - 14 V, temperature 60 - 65 °C, time 12 - 14 min; The second electrolytic coloring: voltage 10 - 12 V, temperature 55 - 60 °C, time 10 - 12 min; The third electrolytic coloring: voltage 8 - 10 V, temperature 50 - 55 °C, time 8 - 10 min.

[0019] In some embodiments, the alkaline cleaning solution is 1 mol / L NaOH solution. The sample is immersed in the alkaline cleaning solution at room temperature for 3 min.

[0020] In some embodiments, the chemical polishing solution includes 80 ml / L H3PO4, 100 ml / L HNO3, 80 ml / L H2SO4, at a temperature of 95 °C for 2 - 3 min.

[0021] In some embodiments, between the first electrolytic coloring and the second electrolytic coloring, and between the second electrolytic coloring and the third electrolytic coloring, there are water washing and drying treatment processes.

[0022] In some embodiments, water vapor is used for sealing the holes.

[0023] The base material selected in the present invention is aluminum alloy, and the pretreatment means include ultrasonic degreasing, alkaline cleaning, chemical polishing and water washing.

[0024] (1) Ultrasonic degreasing In fact, most of the various quality problems that occur after the surface treatment of aluminum and its alloy products do not come from the treatment solution, materials and process conditions, but are caused by the grease and stains that are not thoroughly cleaned on the metal surface before various surface treatments. The adhesion force between the oil stain on the surface of the sample of the present invention and the substrate surface is small, and it can be removed as long as a suitable method is used, and the cleaning difficulty is small. The present invention uses ultrasonic degreasing, and the degreasing solution is anhydrous ethanol for 10 min. This method has a fast degreasing speed and no corrosive effect on the metal. After ultrasonic degreasing, the sample is directly dried.

[0025] The main function of the alkaline cleaning process is to remove the natural oxide film on the surface of metallic aluminum, exposing the fresh substrate structure of the sample to ensure the smooth progress of anodic oxidation. In addition, the alkaline cleaning can also remove the residual grease on the surface of the sample. In the present invention, the alkaline cleaning solution is 1 mol / L NaOH solution. The sample is immersed in the alkaline cleaning solution at room temperature for 3 min.

[0026] Chemical polishing: During processing, cutting, transportation, and sample preparation, scratches or grooves of varying depths will remain on the surface of the aluminum sheet, resulting in a rough and uneven surface of the sample. Generally speaking, the uniformity of the film layer on a rough surface is inferior to that on a smooth surface, which will have an adverse effect on the corrosion resistance and wear resistance of the film layer. Therefore, polishing treatment should be carried out before anodization. Water washing: The water washing after alkali washing and polishing is to prevent the solution of the former process from being carried into the solution of the latter process between two adjacent processes, thereby affecting each other and destroying the treatment effect, which will affect the microscopic morphology of the sample after anodization. The designed water washing process is to rinse the sample thoroughly in tap water after taking it out, and then rinse it three times with distilled water. The distilled water cannot be reused between processes and should be replaced in time. The alkali washing and polishing processes are very simple, but since the surface of high-purity aluminum after alkali washing is more likely to be oxidized in the air, it is necessary to strictly control the time for transferring the sample from the alkali washing solution to the polishing solution, and from the polishing solution to the anodization electrolyte. At the same time, the water washing must ensure that there is no residual liquid from the previous process on the surface of the sample.

[0027] Then, anodization treatment is carried out on the aluminum alloy that has undergone surface pretreatment. The anodization solution includes 3 - 4 mol / L sulfuric acid, 0.05 - 0.1 mol / L ferric sulfate, 0.1 - 0.5 mol / L aluminum sulfate, and deionized water. The voltage is 20 - 30 V, the time is 20 - 30 min, and the temperature is 20 - 25 °C. Possible reasoning: Among them, sulfuric acid provides an acidic environment for anodization and promotes the anodization reaction. The presence of sulfuric acid can adjust the pH value of the solution to ensure that the reaction environment is suitable for the oxidation reaction on the surface of the aluminum material; Ferric sulfate (0.05 - 0.1 mol / L): Releases ferric ions onto the surface of the aluminum material, improves the activity and efficiency of the oxidation reaction, shortens the oxidation time, can promote the introduction and dispersion of aluminum sulfate, and improves the denseness of the oxide film. Aluminum sulfate is one of the key components of anodization. It reacts with aluminum to form a dense oxide film, and at the same time provides the effect of sacrificial anode. After anodization, aluminum will be oxidized to aluminum ions by the way of sacrificial anode and embedded in the oxide film. The aluminum ions help to enhance the corrosion inhibition effect of the solution on the aluminum material. The oxide film obtained after the above anodization is a light yellowish-green oxide film, and the pore size of the obtained aluminum oxide film is 30 - 50 nm.

[0028]

[0029] (3) Inorganic salt immersion: The immersion solution includes 0.5 - 0.7 mol / L sulfuric acid, 0.1 - 1 mol / L ferrous sulfate, 0.05 - 0.1 mol / L ferric sulfate, and deionized water. The immersion time is 5 - 7 min, and the temperature is 10 - 15 °C.

[0030] ​Inorganic salt immersion provides an ideal condition for subsequent electrolytic staining by cleaning and adjusting the matrix environment. At the same time, by adjusting the composition and concentration of inorganic salts, the color characteristics of the anodic oxidation film can be controlled to present the desired color effect. For example, brine can increase the conductivity of the material, contribute to the subsequent electrolytic staining process, or ensure uniform coverage on the surface of the anodic oxidation layer, reducing the influence of impurities on the color. Specifically, the possible influencing factors are as follows: in an acidic environment, sulfuric acid provides appropriate medium conditions, which helps aluminum combine with aluminum oxide to form bound aluminum, and bound aluminum is the basis for the golden yellow film. Metal ions in ferrous sulfate and ferric sulfate may affect the formation rate or quality of bound aluminum; or by adjusting the pH value and ion concentration on the surface of the anodic oxidation film, the formation rate and quality of bound aluminum can be optimized, thereby affecting the color depth and uniformity of the film.

[0031] Electrolytic staining: The electrolytic staining solution includes 1.2 - 1.4 mol / L sulfuric acid, 0.1 - 0.2 mol / L ferrous oxide dihydrate, 0.1 - 0.5 mol / L KH2PO4, 0.1 - 0.2 mol / L K2HPO4, 0.05 - 0.07 mol / L aluminum hexafluorophosphate, 0.01 - 0.03 mol / L SDS, and the pH is adjusted to 4.2 - 4.8 using NaHCO3 for electrolytic staining. Possible reasoning: The main role of sulfuric acid is to provide an acidic environment. The role of ferrous oxide dihydrate is to introduce Fe 2+ ions into the solution. Fe 2+ will be reduced to metallic iron by aluminum during electrolysis, forming a brown or yellowish-brown deposition layer. At the same time, Fe 2+ will combine with SO4 in sulfuric acid 2- to form ferrous sulfate (FeSO4), further affecting the color. Potassium dihydrogen phosphate and phosphate mainly function to adjust the pH value of the solution. Aluminum hexafluorophosphate introduces PF6 - anions into the solution to form a hexafluoride delocalized bond. PF6 - has good dispersion performance and combines with Al 3+ to form aluminum hexafluorophosphate complex ([Al(PF6)3] - ), which will affect the final staining effect. Aluminum hexafluorophosphate will also inhibit other metal ions in the solution (such as Fe 2+Precipitates are formed to reduce the impact on color. The main role of SDS is to act as an emulsifier and surfactant, preventing the deposits generated during the electrolysis process from coking. It also helps to maintain the viscosity and stability of the electrolyte, reducing the impact on the electrode reaction. NaHCO3 is used to adjust the pH to 4.2 - 4.8. Sodium bicarbonate helps to maintain the pH value of the solution between 4.2 and 4.8. This pH range is crucial for the electrochemical reaction of aluminum, as it will neither make the system too alkaline to cause passivation nor make the system too acidic to affect the dissolution of aluminum.

[0032] In some embodiments, the electrolytic coloring includes three times of electrolytic coloring: The first electrolytic coloring: voltage 12 - 14 V, temperature 60 - 65 °C, time 12 - 14 min; The second electrolytic coloring: voltage 10 - 12 V, temperature 55 - 60 °C, time 10 - 12 min; The third electrolytic coloring: voltage 8 - 10 V, temperature 50 - 55 °C, time 8 - 10 min.

[0033] The voltage used in the electrolytic coloring is a three-stage voltage. The three-stage stepped-down voltage can avoid the following problems: (1) Local peroxidation: High voltage may cause excessive local oxidation, producing black or gray areas; (2) Film non-uniformity: Higher voltage may cause uneven film growth, affecting the final effect; (3) Color stability: Slowly reducing the voltage allows the oxidation reaction to be completed step by step, reducing the color difference caused by rapid oxidation. The stepped control of the voltage helps the oxidation reaction to proceed within a controllable range, ensuring the denseness and uniformity of the oxide film.

[0034] Sealing is required after coloring. The methods of sealing are not limited to hot water sealing treatment, steam sealing treatment or metal salt sealing treatment, which are not the focus of this invention and will not be elaborated further.

[0035] Beneficial technical effects: The present invention provides a colored aluminum alloy film and its preparation method. By means of the processes of pretreatment - anodic oxidation - inorganic salt immersion and electrolytic coloring - sealing, a light green and golden yellow aluminum oxide film with particularly stable color is prepared, and it has good corrosion resistance and excellent protective performance. Generally speaking, the color of the oxide film is bright and uniform, with small color difference, good corrosion resistance and weather resistance. Detailed implementation mode Embodiment

[0036] A preparation method of a colored aluminum alloy film includes the following steps: (1) Pretreatment: including ultrasonic degreasing, alkali washing, chemical polishing and water washing.

[0037] (2) Anodic oxidation: The anodic oxidation solution includes 3 mol / L sulfuric acid, 0.05 mol / L ferric sulfate, 0.1 mol / L aluminum sulfate and deionized water, with a voltage of 20 V, a time of 20 min, and a temperature of 20 - 25 °C.

[0038] (3) Inorganic salt immersion: The immersion solution includes 0.5 mol / L sulfuric acid, 0.1 mol / L ferrous sulfate, 0.05 mol / L ferric sulfate, and deionized water. The immersion time is 5 min, and the temperature is 10 °C.

[0039] (4) Electrolytic coloring: The electrolytic coloring solution includes 1.2 mol / L sulfuric acid, 0.1 mol / L ferrous oxide dihydrate, 0.1 mol / L KH2PO4, 0.1 mol / L K2HPO4, 0.05 mol / L aluminum hexafluorophosphate, 0.01 mol / L SDS. Use NaHCO3 to adjust the pH to 4.2 and perform electrolytic coloring. The electrolytic coloring includes three times of electrolytic coloring. The first electrolytic coloring: voltage 12 V, temperature 60 °C, time 12 min; the second electrolytic coloring: voltage 10 V, temperature 55 °C, time 10 min; the third electrolytic coloring: voltage 8 V, temperature 50 °C, time 8 min.

[0040] (5) Sealing: Sealing with steam. Example

[0041] A preparation method of a color - tinted aluminum alloy film includes the following steps: (1) Pretreatment: including ultrasonic degreasing, alkali washing, chemical polishing and water washing.

[0042] (2) Anodic oxidation: The anodic oxidation solution includes 3.5 mol / L sulfuric acid, 0.075 mol / L ferric sulfate, 0.075 mol / L aluminum sulfate and deionized water, with a voltage of 25 V, a time of 25 min, and a temperature of 22.5 °C.

[0043] (3) Inorganic salt immersion: The immersion solution includes 0.6 mol / L sulfuric acid, 0.4 mol / L ferrous sulfate, 0.07 mol / L ferric sulfate, and deionized water. The immersion time is 6 min, and the temperature is 12.5 °C.

[0044] (4) Electrolytic coloring: The electrolytic coloring solution includes 1.3 mol / L sulfuric acid, 0.15 mol / L iron(II) oxide dihydrate, 0.3 mol / L KH2PO4, 0.15 mol / L K2HPO4, 0.06 mol / L aluminum hexafluorophosphate, 0.02 mol / L SDS. Use NaHCO3 to adjust the pH to 4.5 and perform electrolytic coloring. The electrolytic coloring includes three times of electrolytic coloring. The first electrolytic coloring: voltage 13 V, temperature 62.5 °C, time 13 min; the second electrolytic coloring: voltage 11 V, temperature 57.5 °C, time 11 min; the third electrolytic coloring: voltage 9 V, temperature 52.5 °C, time 9 min.

[0045] (5) Sealing: Sealing with steam. Example

[0046] A method for preparing a colored aluminum alloy film includes the following steps: (1) Pretreatment: including ultrasonic degreasing, alkali washing, chemical polishing and water washing.

[0047] (2) Anodizing: The anodizing solution includes 4 mol / L sulfuric acid, 0.1 mol / L ferric sulfate, 0.5 mol / L aluminum sulfate and deionized water. The voltage is 30 V, the time is 30 min, and the temperature is 25 °C.

[0048] (3) Inorganic salt immersion: The immersion solution includes 0.7 mol / L sulfuric acid, 0.8 mol / L ferrous sulfate, 0.09 mol / L ferric sulfate, deionized water. The immersion time is 7 min and the temperature is 15 °C.

[0049] (4) Electrolytic coloring: The electrolytic coloring solution includes 1.4 mol / L sulfuric acid, 0.2 mol / L iron(II) oxide dihydrate, 0.5 mol / L KH2PO4, 0.2 mol / L K2HPO4, 0.07 mol / L aluminum hexafluorophosphate, 0.03 mol / L SDS. Use NaHCO3 to adjust the pH to 4.8 and perform electrolytic coloring. The electrolytic coloring includes three times of electrolytic coloring. The first electrolytic coloring: voltage 14 V, temperature 65 °C, time 14 min; the second electrolytic coloring: voltage 12 V, temperature 60 °C, time 12 min; the third electrolytic coloring: voltage 10 V, temperature 55 °C, time 10 min.

[0050] (5) Sealing: Sealing with steam.

[0051] A method for preparing a colored aluminum alloy film includes the following steps: (1) Pretreatment: including ultrasonic degreasing, alkali washing, chemical polishing and water washing.

[0052] (2) Anodic oxidation: The anodic oxidation solution includes 3.5 mol / L sulfuric acid, 0.075 mol / L ferric sulfate, 0.075 mol / L aluminum sulfate and deionized water. The voltage is 25 V, the time is 25 min, and the temperature is 22.5 °C.

[0053] (3) Electrolytic dyeing: The electrolytic dyeing solution includes 1.3 mol / L sulfuric acid, 0.15 mol / L ferrous oxide dihydrate, 0.3 mol / L KH2PO4, 0.15 mol / L K2HPO4, 0.06 mol / L aluminum hexafluorophosphate, 0.02 mol / L SDS. Use NaHCO3 to adjust the pH to 4.5 and perform electrolytic dyeing. The electrolytic dyeing includes three times of electrolytic dyeing. The first electrolytic dyeing: voltage 13 V, temperature 62.5 °C, time 13 min; the second electrolytic dyeing: voltage 11 V, temperature 57.5 °C, time 11 min; the third electrolytic dyeing: voltage 9 V, temperature 52.5 °C, time 9 min.

[0054] (4) Sealing: Steam sealing.

[0055] Characterize the dyeing effects of Examples 1-3 and the comparative examples.

[0056] According to the existing knowledge or classification in CN114544514B, for color defect points, when 1.0 ≤ △E < 2.0, the severity of the color defect is considered medium; when 2.0 ≤ △E < 4.0, the severity of the color defect is considered relatively large, and there are clearly visible differences to the naked eye; when △E ≥ 4.0, the severity of the color defect is very large, and the color difference is very significant; for the comparative analysis points, when △E < 0.25, it is considered that there is no color difference from the test standard sample point; when 0.25 ≤ △E < 0.5, it is considered that the color difference from the test standard sample point is very small; when 0.5 ≤ △E < 1.0, it is considered that the color difference from the test standard sample point is small to medium. And for the Lab values, L represents brightness. When it is necessary to change the color brightness, only adjust L. The L value increases to become brighter, and the L value decreases to become darker; a and b represent color components. Changing the values of a and b can change the color tone and color saturation.

[0057] Referring to the above content, it can be seen that the color of the oxide film prepared in the embodiment of the present invention is yellowish green, with more yellow, corresponding to a smaller color difference, bright and uniform color, and a small color difference.

[0058] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a color-coated aluminum alloy film, characterized in that It includes the following steps: (1) Pretreatment: including ultrasonic degreasing, alkali washing, chemical polishing and water washing; (2) Anodic oxidation: the anodic oxidation solution includes 3 - 4 mol / L sulfuric acid, 0.05 - 0.1 mol / L ferric sulfate, 0.1 - 0.5 mol / L aluminum sulfate and deionized water, the voltage is 20 - 30 V, the time is 20 - 30 min, and the temperature is 20 - 25 °C; (3) Inorganic salt immersion: the immersion solution includes 0.5 - 0.7 mol / L sulfuric acid, 0.1 - 1 mol / L ferrous sulfate, 0.05 - 0.1 mol / L ferric sulfate, deionized water, the immersion time is 5 - 7 min, and the temperature is 10 - 15 °C; (4) Electrolytic coloring: the electrolytic coloring solution includes 1.2 - 1.4 mol / L sulfuric acid, 0.1 - 0.2 mol / L ferrous oxide dihydrate, 0.1 - 0.5 mol / L KH2PO4, 0.1 - 0.2 mol / L K2HPO4, 0.05 - 0.07 mol / L aluminum hexafluorophosphate, 0.01 - 0.03 mol / L SDS, use NaHCO3 to adjust the pH = 4.2 - 4.8, and perform electrolytic coloring; (5) Sealing.

2. The preparation method of a color aluminum alloy film as described in claim 1, characterized in that The electrolytic coloring includes three times of electrolytic coloring. The first electrolytic coloring: the voltage is 12 - 14 V, the temperature is 60 - 65 °C, and the time is 12 - 14 min; the second electrolytic coloring: the voltage is 10 - 12 V, the temperature is 55 - 60 °C, and the time is 10 - 12 min; the third electrolytic coloring: the voltage is 8 - 10 V, the temperature is 50 - 55 °C, and the time is 8 - 10 min.

3. The preparation method of a color-coated aluminum alloy film as claimed in claim 1, wherein The alkali washing solution is 1 mol / L NaOH solution, and the sample is immersed in the alkali washing solution at room temperature for 3 min.

4. The preparation method of a color aluminum alloy coating as claimed in claim 1, characterized in that The chemical polishing solution includes 80 ml / L H3PO4, 100 ml / L HNO3, 80 ml / L H2SO4, the temperature is 95 °C, and the time is 2 - 3 min.

5. The preparation method of a color aluminum alloy film as described in claim 1, characterized in that Between the first electrolytic coloring and the second electrolytic coloring, and between the second electrolytic coloring and the third electrolytic coloring, there are water washing and drying treatment processes.

6. The preparation method of a color aluminum alloy film as described in claim 1, characterized in that The sealing is steam sealing.

7. A color aluminum alloy coating film, characterized in that Obtained by the preparation method according to any one of claims 1 - 6.