Universal environment-friendly true black ceramization liquid for aluminum alloy, preparation method of universal environment-friendly true black ceramization liquid and preparation method of black ceramization film

Abstract

The invention belongs to the technical field of aluminum alloy surface treatment, and discloses universal environment-friendly true black vitrification liquid for aluminum alloy, a preparation method of the universal environment-friendly true black vitrification liquid and a preparation method of a black vitrification film. The black vitrification liquid is prepared from the following components: K2ZrF6, K2TiF6, NaOH, phytic acid, La (NO3) 3, sodium glutamate, Al2 (SO4) 3, hexamethylenetetramine, KNO3, sodium dodecyl benzene sulfonate, Na2SiO3. 9H2O, H3PO4, C2H5OH, KH-550 and a water-soluble silicone acrylic resin monomer; a black ceramic liquid is prepared by adopting a step-by-step dissolving and mixing method, and a black ceramic film is plated on the surface of the aluminum alloy by adopting an impregnation method; according to the method, the true black light absorption film is rapidly prepared on the surfaces of aluminum alloy workpieces prepared through different marks and different forming and heat treatment processes at low cost, the method is environmentally friendly and free of pollution, and the problems that an existing black vitrification liquid is poor in universality and cannot give consideration to performance are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of aluminum alloy surface treatment, and relates to a universal environmentally friendly true black ceramic liquid for aluminum alloy and a preparation method thereof, and a black ceramic film preparation method. Background Art

[0002] Aluminum alloy is widely used in the optical instrument industry due to its high strength, high elongation, easy processing, low specific gravity, easy welding, good corrosion resistance, large output, stable price and other advantages. In the core optical path of optical instruments, in order to avoid imaging distortion and optical path pollution caused by multiple reflections, it is generally necessary to process the optical path components into black with high light absorption within a high-precision size range.

[0003] The surface blackening processes of aluminum alloy materials mainly include chemical oxidation blackening, hard anodizing blackening, surface black chrome plating, nickel plating blackening, coating black matte paint, black micro-arc oxidation and other processes. Each of these processes has its own advantages but also has obvious shortcomings. For example, the materials used contain heavy metals such as manganese, iron, chromium, and tungsten, or the process uses organic toxic materials such as aniline for coloring. Moreover, with the emergence of various new grades of aluminum alloys, it is difficult to have a universal process that can achieve this process at low cost and in an environmentally friendly manner. Summary of the invention

[0004] The present invention overcomes the shortcomings of the prior art and provides a universal environmentally friendly true black ceramic liquid for aluminum alloy and a preparation method thereof and a preparation method of a black ceramic film; the present invention is achieved through the following technical solutions: A universal environmentally friendly true black ceramic solution for aluminum alloys, containing the following components in each liter of solution: 8~12g / L K2ZrF6, 4~6g / L K2TiF6, 22~27g / L NaOH, 55~65ml / L phytic acid, 8~12g / L La(NO3)3, 1~3g / L sodium glutamate, 4~6g / L Al2(SO4)3, 4~6g / L hexamethylenetetramine, 4~6g / L KNO3, 0.8~1.2g / L sodium dodecylbenzene sulfonate, 4~6g / L Na2SiO3·9H2O, 60~80ml H3PO4, 80~120ml C2H5OH, 8~12ml KH-550, 8~12g / L water-soluble silicone acrylic resin monomer, and the rest is pure water.

[0005] Preferably, the solution contains the following concentrations per liter: 10g / L K2ZrF6, 5g / L K2TiF6, 25g / L NaOH, 60ml / L phytic acid, 10g / L La(NO3)3, 2g / L sodium glutamate, 5g / L Al2(SO4)3, 5g / L hexamethylenetetramine, 5g / L KNO3, 1g / L sodium dodecylbenzenesulfonate, 5g / L Na2SiO3·9H2O, 70ml H3PO4, 100ml C2H5OH, 10ml KH-550, 10g / L water-soluble silicone acrylic resin monomer, and the rest is pure water.

[0006] Preferably, when the black ceramic liquid is used, the black ceramic liquid is diluted 100 times.

[0007] A method for preparing a universal environmentally friendly true black ceramic liquid for aluminum alloys comprises the following steps: S1. Take 80-120 ml of pure water and dissolve 8-12 g of K2ZrF6, 4-6 g of K2TiF6 and 4-6 g of Al2(SO4)3 therein to obtain a mixed solution; then take 100 ml of pure water and dissolve 22-27 g of NaOH therein to obtain a NaOH solution; then slowly add the NaOH solution to the mixed solution under stirring while adding, and then filter and retain the precipitate to obtain substance A; S2. Take 80-120 ml of pure water and dissolve 4-6 g of Na2SiO3·9H2O therein to obtain a Na2SiO3 solution. Then take 50 ml of pure water and drop 8-12 ml of H3PO4 thereinto and stir evenly to obtain a H3PO4 solution. Then slowly add the Na2SiO3 solution to the H3PO4 solution while stirring, and let it stand and cool to room temperature to obtain substance B. S3. Add 40-60 ml of pure water to a beaker, then add 80-120 ml of C2H5OH and 8-12 ml of KH-550 and stir evenly, adjust the pH to 1.5-3, then heat the beaker in a water bath to 60-65°C and keep warm for 1.5-2.5 hours, then remove the beaker and cool to room temperature to obtain substance C; S4, take 180-220 ml of pure water, dissolve 8-12 g of La(NO3)3, 1-3 g of sodium glutamate, 4-6 g of KNO3, 8-12 g of water-soluble silicone-acrylic resin monomer, 0.8-1.2 g of sodium dodecylbenzene sulfonate, and 4-6 g of hexamethylenetetramine in it in sequence under stirring, and cool to room temperature to obtain substance D; S5, take 180-220 ml of pure water, add substance A into it and stir thoroughly to form a thin paste, then add 55-65 ml of phytic acid and the remaining H3PO4 into it in sequence and stir to completely dissolve the precipitate, cool to room temperature for use, and obtain substance E; S6. Slowly add substance C, substance E and substance B into substance D respectively under stirring, and make up to 1L with pure water. Transfer the obtained liquid into a glass bottle, cover and seal it, heat it in a 55-65℃ water bath for more than 2h, take out the glass bottle, take out the clarified liquid, cool it to room temperature and set aside to obtain a black ceramic liquid.

[0008] Preferably, 10 ml of the black ceramic liquid is added to 990 ml of pure water and stirred evenly, and then the pH is adjusted to 3-4 with phytic acid or ammonia water for use in the ceramic film plating of aluminum alloy; the temperature for adjusting the pH is 18-30° C. at room temperature.

[0009] A method for preparing a universal environmentally friendly true black ceramic film for aluminum alloys comprises the following steps: using a prepared black ceramic liquid; immersing an aluminum alloy in the black ceramic liquid, treating the aluminum alloy under ultrasonic action for 1 to 2 minutes, and then washing the aluminum alloy with water, blowing the aluminum alloy to dry the aluminum alloy.

[0010] Preferably, the drying temperature is 130-150° C. and the drying time is 20-30 min.

[0011] The beneficial effects of the present invention compared with the prior art are as follows: The present invention is based on the theory of ceramic liquid and has prepared a universal black ceramic liquid. It can quickly and cheaply prepare a true black light-absorbing film on the surface of aluminum alloy workpieces of different grades and different molding and heat treatment processes, and is environmentally friendly and pollution-free. It solves the problem that the existing black ceramic liquid has poor universality and cannot take into account both performance and general purpose.

[0012] 1. The ceramic solution of the present invention introduces Zr and Ti ions as the main film-forming substances and introduces La 3+ Rare earth ions participate in the structural adjustment of film formation and Al 3+ The interstitial treatment of ions fills the three-dimensional network framework formed by Zr and Ti ions with Al 3+ (Flake) and SiO2 colloid particles, through the combination of film layer size particles and different structures, the film layer is made stronger, the bonding force is better, and the corrosion resistance is improved.

[0013] 2. The present invention realizes organic hybrid compounding of ceramic particles, phytic acid organic layer and silane film, making the wear resistance of the film layer more excellent.

[0014] 3. The present invention forms a black film layer by the black coloring property of Zr and Ti ions and phytic acid, instead of forming black color only after adding coloring ions such as Fe, Co, Ni, Cu, Mn, Cr, Mo, and W like other blackening liquids. DETAILED DESCRIPTION

[0015] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer, the present invention is further described in detail in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. The technical solutions of the present invention are described in detail below in conjunction with the embodiments, but the scope of protection is not limited thereto.

[0016] Example 1 This embodiment provides a universal environmentally friendly true black ceramic solution for aluminum alloys, wherein each liter of the solution contains the following components in concentrations: 10g / L K2ZrF6, 5g / L K2TiF6, 25g / L NaOH, 60ml / L phytic acid, 10g / L La(NO3)3, 2g / L sodium glutamate, 5g / L Al2(SO4)3, 5g / L hexamethylenetetramine, 5g / L KNO3, 1g / L sodium dodecylbenzenesulfonate, 5g / L Na2SiO3·9H2O, 70ml H3PO4, 100ml C2H5OH, 10ml KH-550, 10g / L water-soluble silicone acrylic resin monomer, and the rest is pure water.

[0017] Example 2 This embodiment provides a universal environmentally friendly true black ceramic solution for aluminum alloys, wherein each liter of the solution contains the following components in concentrations: 8g / L K2ZrF6, 6g / L K2TiF6, 22g / L NaOH, 65ml / L phytic acid, 8g / L La(NO3)3, 3g / L sodium glutamate, 4g / L Al2(SO4)3, 6g / L hexamethylenetetramine, 4g / L KNO3, 0.8g / L sodium dodecylbenzene sulfonate, 6g / L Na2SiO3·9H2O, 65ml H3PO4, 120ml C2H5OH, 12ml KH-550, 8g / L water-soluble silicone acrylic resin monomer, and the rest is pure water.

[0018] Example 3 This embodiment provides a universal environmentally friendly true black ceramic solution for aluminum alloys, wherein each liter of the solution contains the following components in concentrations: 12g / L K2ZrF6, 4g / L K2TiF6, 27g / L NaOH, 55ml / L phytic acid, 12g / L La(NO3)3, 1g / L sodium glutamate, 6g / L Al2(SO4)3, 4g / L hexamethylenetetramine, 6g / L KNO3, 1.2g / L sodium dodecylbenzene sulfonate, 4g / L Na2SiO3·9H2O, 80ml H3PO4, 80ml C2H5OH, 8ml KH-550, 12g / L water-soluble silicone acrylic resin monomer, and the rest is pure water.

[0019] Example 4 This embodiment provides a method for preparing a universal environmentally friendly true black ceramic liquid for aluminum alloy, comprising the following steps: (using the composition formula of embodiment 1) S1. Take 100 ml of pure water and dissolve 10 g of K2ZrF6, 5 g of K2TiF6 and 5 g of Al2(SO4)3 therein to obtain a mixed solution; then take 100 ml of pure water and dissolve 25 g of NaOH therein to obtain a NaOH solution; then slowly add the NaOH solution to the mixed solution under stirring, stirring while adding, and then filter and retain the precipitate to obtain substance A; S2, take 100 ml of pure water and dissolve 5 g of Na2SiO3·9H2O therein to obtain a Na2SiO3 solution, then take 50 ml of pure water and drop 10 ml of H3PO4 thereinto and stir evenly to obtain a H3PO4 solution, then slowly add the Na2SiO3 solution into the H3PO4 solution while stirring, and let it stand and cool to room temperature to obtain substance B; S3. Add 50 ml of pure water to the beaker, then add 100 ml of C2H5OH and 10 ml of KH-550 to the beaker and stir evenly, adjust the pH to 2, then heat the beaker to 60°C in a water bath and keep it warm for 2 hours, then remove the beaker and cool it to room temperature to obtain substance C; S4, take 200 ml of pure water and dissolve 10 g of La(NO3)3, 2 g of sodium glutamate, 5 g of KNO3, 10 g of water-soluble silicone-acrylic resin monomer, 1 g of sodium dodecylbenzenesulfonate, and 5 g of hexamethylenetetramine in it in sequence under stirring, and cool to room temperature to obtain substance D; S5, take 200 ml of pure water, add substance A into it and stir thoroughly to form a thin paste, then add 60 ml of phytic acid and the remaining H3PO4 into it in sequence and stir to completely dissolve the precipitate, cool to room temperature for use, and obtain substance E; S6. Slowly add substance C, substance E and substance B to substance D respectively under stirring, and add pure water to 1L, transfer the obtained liquid into a glass bottle, seal it with a cover, heat it in a 65°C water bath for 3h, take out the glass bottle, cool the clarified liquid to room temperature for later use to obtain a black ceramic liquid; S7. Take 10 ml of black ceramic liquid and add it into 990 ml of pure water, stir evenly, then adjust the pH to 3.5 with phytic acid or ammonia water at 18°C. It can be used for ceramic film plating on aluminum alloy.

[0020] Example 5 This embodiment provides a method for preparing a universal environmentally friendly true black ceramic liquid for aluminum alloy, comprising the following steps: (using the composition formula of embodiment 1) S1. Take 80 ml of pure water and dissolve 12 g of K2ZrF6, 4 g of K2TiF6 and 4 g of Al2(SO4)3 therein to obtain a mixed solution; then take 120 ml of pure water and dissolve 27 g of NaOH therein to obtain a NaOH solution; then slowly add the NaOH solution to the mixed solution under stirring, stirring while adding, and then filter and retain the precipitate to obtain substance A; S2, take 120 ml of pure water and dissolve 6 g of Na2SiO3·9H2O therein to obtain a Na2SiO3 solution, then take 60 ml of pure water and drop 12 ml of H3PO4 thereinto and stir evenly to obtain a H3PO4 solution, then slowly add the Na2SiO3 solution to the H3PO4 solution while stirring, and let it stand and cool to room temperature to obtain substance B; S3. Add 60 ml of pure water to the beaker, then add 120 ml of C2H5OH and 12 ml of KH-550 to the beaker and stir evenly, adjust the pH to 3, then heat the beaker to 65°C in a water bath and keep it warm for 2 hours, then remove the beaker and cool it to room temperature to obtain substance C; S4, take 220 ml of pure water and dissolve 8 g of La(NO3)3, 3 g of sodium glutamate, 6 g of KNO3, 12 g of water-soluble silicone-acrylic resin monomer, 0.8 g of sodium dodecylbenzenesulfonate, and 6 g of hexamethylenetetramine in it in sequence under stirring, and cool to room temperature to obtain substance D; S5, take 180 ml of pure water, add substance A into it and stir thoroughly to form a thin paste, then add 65 ml of phytic acid and the remaining H3PO4 into it in sequence and stir to completely dissolve the precipitate, cool to room temperature for use, and obtain substance E; S6. Slowly add substance C, substance E and substance B to substance D respectively under stirring, and add pure water to 1L, transfer the obtained liquid into a glass bottle, seal it with a cover, heat it in a 60°C water bath for 2.5h, take out the glass bottle, cool the clarified liquid to room temperature for later use to obtain a black ceramic liquid; S7. Take 10 ml of black ceramic liquid and add it into 990 ml of pure water, stir evenly, then use phytic acid or ammonia water at 25°C to adjust the pH to 3.2. It can be used for ceramic film plating on aluminum alloy.

[0021] Example 6 This embodiment provides a method for preparing a universal environmentally friendly true black ceramic liquid for aluminum alloy, comprising the following steps: (using the composition formula of embodiment 1) S1. Take 120 ml of pure water and dissolve 8 g of K2ZrF6, 6 g of K2TiF6 and 6 g of Al2(SO4)3 therein to obtain a mixed solution; then take 80 ml of pure water and dissolve 22 g of NaOH therein to obtain a NaOH solution; then slowly add the NaOH solution to the mixed solution under stirring, stirring while adding, and then filter and retain the precipitate to obtain substance A; S2, take 80 ml of pure water and dissolve 4 g of Na2SiO3·9H2O therein to obtain a Na2SiO3 solution, then take 40 ml of pure water and drop 8 ml of H3PO4 thereinto and stir evenly to obtain a H3PO4 solution, then slowly add the Na2SiO3 solution to the H3PO4 solution while stirring, and let it stand and cool to room temperature to obtain substance B; S3. Add 40 ml of pure water to the beaker, then add 80 ml of C2H5OH and 8 ml of KH-550 to the beaker and stir evenly, adjust the pH to 1.5, then heat the beaker to 65°C in a water bath and keep it warm for 2 hours, then remove the beaker and cool it to room temperature to obtain substance C; S4, take 180 ml of pure water and dissolve 12 g of La(NO3)3, 1 g of sodium glutamate, 4 g of KNO3, 8 g of water-soluble silicone-acrylic resin monomer, 1.2 g of sodium dodecylbenzenesulfonate, and 4 g of hexamethylenetetramine in it in sequence under stirring, and cool to room temperature to obtain substance D; S5, take 220 ml of pure water, add substance A into it and stir thoroughly to form a thin paste, then add 55 ml of phytic acid and the remaining H3PO4 into it in sequence and stir to completely dissolve the precipitate, cool to room temperature for use, and obtain substance E; S6. Slowly add substance C, substance E and substance B to substance D respectively under stirring, and add pure water to 1L, transfer the obtained liquid into a glass bottle, seal it with a cover, heat it in a 55°C water bath for 4h, take out the glass bottle, cool the clarified liquid to room temperature for later use to obtain a black ceramic liquid; S7. Take 10 ml of black ceramic liquid and add it into 990 ml of pure water, stir evenly, then use phytic acid or ammonia water at 30°C to adjust the pH to 4. It can be used for ceramic film plating on aluminum alloy.

[0022] Example 7 This embodiment provides a method for preparing a universal environmentally friendly true black ceramic film for aluminum alloy, using the black ceramic liquid prepared in Example 4; taking a number of 6061, 6063, A356, and A380 aluminum alloy test pieces respectively, immersing the different aluminum alloy test pieces in the black ceramic liquid, treating them under ultrasonic wave for 2 minutes, washing them with water after taking them out of the bath, drying them, and then drying them at 140° C. for 30 minutes.

[0023] Experimental Example 1 The A380 aluminum alloy test piece coated with the black ceramic film in Example 7 was used to perform performance tests to test the bonding strength, light absorption rate and corrosion resistance: 1. The bonding strength is tested by the cross-cut method; the cross-cut method is carried out according to the cross-cut test method in GB / T9286-2021 paints and varnishes; the test result of Example 7 is grade 0, the cutting edge is completely smooth, and there is no shedding in the grid.

[0024] 2. The absorbance is detected by a colorimeter, and the results are shown in Table 1. The colorimeter detection is based on the color description method of the Lab color space recommended by CIE (International Commission on Illumination), and the colorimeter is used to perform detection according to the color description method.

[0025] 3. The corrosion resistance is tested by a neutral salt spray test. The neutral salt spray test is carried out according to GB / T10125-2021 artificial atmosphere corrosion test salt spray test. The rating is carried out according to GB / T6461-2002 rating of samples and test pieces after corrosion test of metal and other inorganic covering layers on metal substrates. The black ceramic film prepared in Example 7 is tested for grade 9 after 96 hours of neutral salt spray test.

[0026] Table 1 L (a + b) values ​​of the front and back surfaces of A380 aluminum alloy specimens coated with black ceramic film Experimental Example 2 The 6063 aluminum alloy test piece coated with the black ceramic film in Example 7 was used to test the absorbance. The method of testing the absorbance was the same as that in Example 1. The test results are shown in Table 2: Table 2 L (a + b) values ​​of the front and back surfaces of 6063 aluminum alloy specimens coated with black ceramic film The Lab color model is composed of three elements: luminance (L) and a and b related to color. L stands for luminosity, which is equivalent to brightness, a stands for the range from red to green, and b stands for the range from blue to yellow. The value range of L is from 0 to 100, and when L=50, it is equivalent to 50% black; the value ranges of a and b are both from +120 to -120, where +120a is red, and gradually turns to green when it transitions to -120a; by the same principle, +120b is yellow and -120b is blue. All colors are composed of the interactive changes of these three values.

[0027] The L* values ​​of Experimental Examples 1 and 2 are between 37 and 40, a* is between 0.6 and 1.5, and b* is between -1.3 and -0.9, indicating that it is a stable black film layer with universal applicability.

[0028] The above content is a further detailed description of the present invention in combination with a specific preferred embodiment. It cannot be determined that the specific embodiments of the present invention are limited to this. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the present invention, which should be regarded as belonging to the present invention and the scope of patent protection determined by the submitted claims.

Claims

1. A universal environmentally friendly true black ceramic liquid for aluminum alloy, characterized in that: The solution contains the following concentrations per liter: 8~12g / L K2ZrF6, 4~6g / L K2TiF6, 22~27g / L NaOH, 55~65ml / L phytic acid, 8~12g / L La(NO3)3, 1~3g / L sodium glutamate, 4~6g / L Al2(SO4)3, 4~6g / L hexamethylenetetramine, 4~6g / L KNO3, 0.8~1.2g / L sodium dodecylbenzene sulfonate, 4~6g / L Na2SiO3·9H2O, 60~80ml H3PO4, 80~120ml C2H5OH, 8~12ml KH-550, 8~12g / L water-soluble silicone acrylic resin monomer, and the rest is pure water.

2. The universal environmentally friendly true black ceramic liquid for aluminum alloy according to claim 1, characterized in that: The solution contains the following concentrations per liter: 10g / L K2ZrF6, 5g / L K2TiF6, 25g / L NaOH, 60ml / L phytic acid, 10g / L La(NO3)3, 2g / L sodium glutamate, 5g / L Al2(SO4)3, 5g / L hexamethylenetetramine, 5g / L KNO3, 1g / L sodium dodecylbenzenesulfonate, 5g / L Na2SiO3·9H2O, 70ml H3PO4, 100ml C2H5OH, 10ml KH-550, 10g / L water-soluble silicone acrylic resin monomer, and the rest is pure water.

3. A universal environmentally friendly true black ceramic liquid for aluminum alloy according to claim 1 or 2, characterized in that: When the black ceramic liquid is used, the black ceramic liquid is diluted 100 times.

4. The method for preparing a universal environmentally friendly true black ceramic liquid for aluminum alloy as claimed in claim 1, characterized in that: The following steps are involved: S1. Take 80-120 ml of pure water and dissolve 8-12 g of K2ZrF6, 4-6 g of K2TiF6 and 4-6 g of Al2(SO4)3 therein to obtain a mixed solution; then take 80-120 ml of pure water and dissolve 22-27 g of NaOH therein to obtain a NaOH solution; Then, the NaOH solution is slowly added into the mixed solution under stirring, while stirring, and then the precipitate is filtered to obtain substance A; S2, take 80-120 ml of pure water and dissolve 4-6 g of Na2SiO3·9H2O therein to obtain a Na2SiO3 solution, then take 45-65 ml of pure water and drop 8-12 ml of H3PO4 thereinto and stir evenly to obtain a H3PO4 solution, then slowly add the Na2SiO3 solution to the H3PO4 solution while stirring, and let it stand and cool to room temperature to obtain substance B; S3. Add 40-60 ml of pure water to a beaker, then add 80-120 ml of C2H5OH and 8-12 ml of KH-550 and stir evenly, adjust the pH to 1.5-3, then heat the beaker in a water bath to 60-65°C and keep warm for 1.5-2.5 hours, then remove the beaker and cool to room temperature to obtain substance C; S4, take 180-220 ml of pure water and dissolve 8-12 g of La(NO3)3, 1-3 g of sodium glutamate, 4-6 g of KNO3, 8-12 g of water-soluble silicone-acrylic resin monomer, 0.8-1.2 g of sodium dodecylbenzene sulfonate, and 4-6 g of hexamethylenetetramine in it in sequence under stirring, and cool to room temperature to obtain substance D; S5, take 180-220 ml of pure water, add substance A into it and stir thoroughly to form a thin paste, then add 55-65 ml of phytic acid and the remaining H3PO4 into it in sequence and stir to completely dissolve the precipitate, cool to room temperature for use, and obtain substance E; S6. Slowly add substance C, substance E and substance B into substance D respectively under stirring, and make up to 1L with pure water. Transfer the obtained liquid into a glass bottle, cover and seal it, heat it in a 55-65℃ water bath for more than 2h, take out the glass bottle, cool the clarified liquid to room temperature for use to obtain a black ceramic liquid.

5. The method for preparing a universal environmentally friendly true black ceramic liquid for aluminum alloy according to claim 4, characterized in that: Take 10ml of black ceramic liquid and add it to 990ml of pure water, stir evenly, then use phytic acid or ammonia water at room temperature 18-30℃ to adjust the pH to 3~4 for use in aluminum alloy ceramic film plating.

6. A method for preparing a universal environmentally friendly true black ceramic film for aluminum alloy, characterized in that: The black ceramic liquid prepared as claimed in claim 5 is used; the aluminum alloy is immersed in the black ceramic liquid, treated under ultrasonic wave for 1 to 2 minutes, then washed with water, blown dry, and dried.

7. The method for preparing a universal environmentally friendly true black ceramic film for aluminum alloy according to claim 6, characterized in that: The drying temperature is 130-150° C., and the drying time is 20-30 minutes.

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