A general-purpose environmentally friendly true black phosphatizing solution for aluminum alloys, its preparation method, and a method for preparing a black phosphatized film

Abstract

The present invention belongs to the technical field of aluminum alloy surface treatment, and discloses a general-purpose environmentally friendly true black ceramic conversion solution for aluminum alloy, its preparation method, and a method for preparing a black ceramic conversion film; the components of the black ceramic conversion solution include K2ZrF6, K2TiF6, NaOH, phytic acid, La(NO3)3, sodium glutamate, Al2(SO4)3, hexamethylenetetramine, KNO3, sodium dodecylbenzenesulfonate, Na2SiO3·9H2O, H3PO4, C2H5OH, KH-550, and a water-soluble silicone-acrylic resin monomer; the black ceramic conversion solution is prepared by a method of stepwise dissolution and mixing, and the black ceramic conversion film is plated on the surface of the aluminum alloy by an immersion method; the present invention can rapidly and low-costly prepare a true black light-absorbing film on the surface of aluminum alloy workpieces prepared in different grades, different forming, and heat treatment processes, and is environmentally friendly and pollution-free, solving the problems of poor versatility and inability to balance performance of the existing black ceramic conversion solution.

Description

Technical Field

[0001] The present invention belongs to the technical field of surface treatment of aluminum alloys, and relates to a general-purpose environmental protection true black ceramic conversion solution for aluminum alloys, a preparation method thereof, and a preparation method of a black ceramic conversion film. Background Technique

[0002] Aluminum alloys are widely used in the optical instrument industry due to their high strength, high elongation rate, easy processing, low specific gravity, easy welding, good corrosion resistance, etc., as well as large output and stable price. 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 a black color with a high light absorption rate within a high-precision size range.

[0003] In the surface blackening process of aluminum alloy materials, there are mainly chemical oxidation blackening, hard anodization blackening, surface black chromium plating, blackening treatment of nickel plating layer, coating black matte paint, black micro-arc oxidation and other processes. These processes have their own advantages but also obvious deficiencies. For example, the materials used contain heavy metals such as manganese, iron, chromium, tungsten, or organic toxic materials such as aniline are used for coloring in the process. Moreover, with the endless emergence of various new grades of aluminum alloys, it is difficult to have a general process to achieve this process with low cost and environmental protection. Summary of the Invention

[0004] The present invention overcomes the deficiencies of the prior art and provides a general-purpose environmental protection true black ceramic conversion solution for aluminum alloys, a preparation method thereof, and a preparation method of a black ceramic conversion film. The present invention is realized through the following technical solutions:

[0005] A general-purpose environmental protection true black ceramic conversion solution for aluminum alloys, each liter of the solution contains the following components in the following concentrations:

[0006] 8 - 12 g / L of K2ZrF6, 4 - 6 g / L of K2TiF6, 22 - 27 g / L of NaOH, 55 - 65 ml / L of phytic acid, 8 - 12 g / L of La(NO3)3, 1 - 3 g / L of sodium glutamate, 4 - 6 g / L of Al2(SO4)3, 4 - 6 g / L of hexamethylenetetramine, 4 - 6 g / L of KNO3, 0.8 - 1.2 g / L of sodium dodecylbenzenesulfonate, 4 - 6 g / L of Na2SiO3·9H2O, 60 - 80 ml of H3PO4, 80 - 120 ml of C2H5OH, 8 - 12 ml of KH-550, 8 - 12 g / L of water-soluble silicone acrylic resin monomer, and the rest is pure water.

[0007] Preferably, each liter of the solution contains the following components in the following concentrations:

[0008] 10 g / L of K2ZrF6, 5 g / L of K2TiF6, 25 g / L of NaOH, 60 ml / L of phytic acid, 10 g / L of La(NO3)3, 2 g / L of sodium glutamate, 5 g / L of Al2(SO4)3, 5 g / L of hexamethylenetetramine, 5 g / L of KNO3, 1 g / L of sodium dodecylbenzenesulfonate, 5 g / L of Na2SiO3·9H2O, 70 ml of H3PO4, 100 ml of C2H5OH, 10 ml of KH-550, 10 g / L of water-soluble silicone acrylic resin monomer, and the balance is pure water.

[0009] Preferably, when using the black phosphatizing solution, dilute the black phosphatizing solution 100 times.

[0010] A preparation method of a general-purpose environmentally friendly true black phosphatizing solution for aluminum alloy, comprising the following steps:

[0011] 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 in it to obtain a mixed solution; then take 100 ml of pure water and dissolve 22 - 27 g of NaOH in it to obtain a NaOH solution; then slowly add the NaOH solution to the above-mentioned mixed solution under stirring, stir while adding, and then filter to retain the precipitate to obtain substance A;

[0012] S2. Take 80 - 120 ml of pure water and dissolve 4 - 6 g of Na2SiO3·9H2O in it to obtain a Na2SiO3 solution, then take 50 ml of pure water and drop 8 - 12 ml of H3PO4 into it and stir evenly to obtain an H3PO4 solution, and then slowly add the Na2SiO3 solution to the H3PO4 solution under stirring, stir while adding, and let it stand and cool to room temperature to obtain substance B;

[0013] 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 to the beaker and stir evenly, adjust the pH to 1.5 - 3, then heat the beaker in a water bath to 60 - 65 °C and keep it warm for 1.5 - 2.5 h, then remove the beaker and cool it to room temperature to obtain substance C;

[0014] 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 dodecylbenzenesulfonate, and 4 - 6 g of hexamethylenetetramine in it in turn under stirring, and cool it to room temperature to obtain substance D;

[0015] S5. Take 180 - 220 ml of pure water, add substance A to it and stir well to form a thin paste. Then, add 55 - 65 ml of phytic acid and the remaining H3PO4 to it in sequence and stir until the precipitate is completely dissolved. Cool it to room temperature for standby to obtain substance E.

[0016] S6. Slowly add substance C, substance E, and substance B to substance D respectively under stirring, and make up pure water to 1 L. Transfer the obtained liquid into a glass bottle, seal it with a lid, heat it in a water bath at 55 - 65 °C for more than 2 h. Take out the glass bottle, take the clarified liquid, cool it to room temperature for standby to obtain a black ceramic conversion solution.

[0017] Preferably, take 10 ml of the black ceramic conversion solution, add it to 990 ml of pure water, stir evenly, and adjust the pH to 3 - 4 with phytic acid or ammonia water for use in the preparation of a ceramic conversion film on aluminum alloy; the temperature for adjusting the pH is 18 - 30 °C at room temperature.

[0018] A preparation method of a general-purpose environmentally friendly true black ceramic conversion film for aluminum alloy, using the prepared black ceramic conversion solution; immerse the aluminum alloy into the black ceramic conversion solution, carry out treatment for 1 - 2 min under the action of ultrasonic waves, then wash with water, blow dry, and perform drying treatment.

[0019] Preferably, the temperature of the drying is 130 - 150 °C, and the drying time is 20 - 30 min.

[0020] The beneficial effects of the present invention compared with the prior art are as follows:

[0021] Based on the research of the theory of ceramic conversion solution, the present invention prepares a general-purpose black ceramic conversion solution, which can quickly and low-costly prepare a true black light-absorbing film on the surface of aluminum alloy workpieces prepared by different grades, different forming and heat treatment processes currently common, and is environmentally friendly and pollution-free; it solves the problems of poor versatility and inability to balance performance of the existing black ceramic conversion solutions.

[0022] 1. When introducing Zr and Ti ions as the main film-forming substances in the ceramic conversion solution of the present invention, La 3+ rare earth ions participate in the structural adjustment of film formation and the interstitial treatment of Al 3+ ions, so that Al 3+ (flake-shaped) and SiO2 colloidal particles are filled into the three-dimensional network framework formed by Zr and Ti ions. Through the combination of large and small particles of the film layer and different structures, the film layer is made more firm, the bonding force is more excellent, and the corrosion resistance is improved.

[0023] 2. The present invention realizes the organic hybridization and compounding of ceramic conversion particles, phytic acid organic layer, and silane film, making the wear resistance of the film layer more excellent.

[0024] 3. The black film layer of the present invention is formed by the characteristic that Zr and Ti ions react with phytic acid to show black, rather than forming black in the case of adding color-developing ions such as Fe, Co, Ni, Cu, Mn, Cr, Mo, and W like other blackening liquids. Detailed implementation manners

[0025] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clear and understandable, the present invention will be further described in detail in combination with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. The technical solutions of the present invention will be described in detail below in combination with embodiments, but the protection scope is not limited by this.

[0026] Embodiment 1

[0027] This embodiment provides a general-purpose environmentally friendly true black phosphatizing solution for aluminum alloy, and each liter of the solution contains the following components in the following concentrations:

[0028] 10 g / L of K2ZrF6, 5 g / L of K2TiF6, 25 g / L of NaOH, 60 ml / L of phytic acid, 10 g / L of La(NO3)3, 2 g / L of sodium glutamate, 5 g / L of Al2(SO4)3, 5 g / L of hexamethylenetetramine, 5 g / L of KNO3, 1 g / L of sodium dodecylbenzenesulfonate, 5 g / L of Na2SiO3·9H2O, 70 ml of H3PO4, 100 ml of C2H5OH, 10 ml of KH-550, 10 g / L of water-soluble silicone acrylic resin monomer, and the rest is pure water.

[0029] Embodiment 2

[0030] This embodiment provides a general-purpose environmentally friendly true black phosphatizing solution for aluminum alloy, and each liter of the solution contains the following components in the following concentrations:

[0031] 8 g / L of K2ZrF6, 6 g / L of K2TiF6, 22 g / L of NaOH, 65 ml / L of phytic acid, 8 g / L of La(NO3)3, 3 g / L of sodium glutamate, 4 g / L of Al2(SO4)3, 6 g / L of hexamethylenetetramine, 4 g / L of KNO3, 0.8 g / L of sodium dodecylbenzenesulfonate, 6 g / L of Na2SiO3·9H2O, 65 ml of H3PO4, 120 ml of C2H5OH, 12 ml of KH-550, 8 g / L of water-soluble silicone acrylic resin monomer, and the rest is pure water.

[0032] Embodiment 3

[0033] This embodiment provides a general-purpose environmentally friendly true black phosphatizing solution for aluminum alloy, and each liter of the solution contains the following components in the following concentrations:

[0034] 12 g / L of K2ZrF6, 4 g / L of K2TiF6, 27 g / L of NaOH, 55 ml / L of phytic acid, 12 g / L of La(NO3)3, 1 g / L of sodium glutamate, 6 g / L of Al2(SO4)3, 4 g / L of hexamethylenetetramine, 6 g / L of KNO3, 1.2 g / L of sodium dodecylbenzenesulfonate, 4 g / L of Na2SiO3·9H2O, 80 ml of H3PO4, 80 ml of C2H5OH, 8 ml of KH-550, 12 g / L of water-soluble silicone-acrylic resin monomer, and the balance is pure water.

[0035] Example 4

[0036] This example presents a preparation method for a general-purpose environmentally friendly true black ceramic conversion solution for aluminum alloys, including the following steps: (using the ingredient formulation of Example 1)

[0037] S1. Take 100 ml of pure water and dissolve 10 g of K2ZrF6, 5 g of K2TiF6, and 5 g of Al2(SO4)3 in it to obtain a mixed solution; then take 100 ml of pure water and dissolve 25 g of NaOH in it to obtain an NaOH solution; then slowly add the NaOH solution to the mixed solution under stirring, stirring while adding, and then filter to retain the precipitate to obtain Substance A;

[0038] S2. Take 100 ml of pure water and dissolve 5 g of Na2SiO3·9H2O in it to obtain an Na2SiO3 solution, then take 50 ml of pure water and drop 10 ml of H3PO4 into it and stir evenly to obtain an H3PO4 solution, and then slowly add the Na2SiO3 solution to the H3PO4 solution under stirring, stirring while adding, and let it stand and cool to room temperature to obtain Substance B;

[0039] S3. Add 50 ml of pure water to a 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 in a water bath to 60 °C and keep it warm for 2 h, then remove the beaker and cool it to room temperature to obtain Substance C;

[0040] 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 turn under stirring, and cool it to room temperature to obtain Substance D;

[0041] S5. Take 200 ml of pure water and add Substance A to it and stir well to form a thin paste, then add 60 ml of phytic acid and the remaining H3PO4 to it in turn and stir until the precipitate is completely dissolved, cool it to room temperature and set aside to obtain Substance E;

[0042] S6. Slowly add Substance C, Substance E, and Substance B to Substance D separately under stirring, and make up pure water to 1 L. Transfer the obtained liquid into a glass bottle, seal it with a cap, heat it in a water bath at 65 °C for 3 h, take out the glass bottle, and take the clarified liquid and cool it to room temperature for standby to obtain a black phosphatizing solution.

[0043] S7. Take 10 ml of the black phosphatizing solution and add it to 990 ml of pure water, stir evenly, and then adjust the pH to 3.5 with phytic acid or ammonia water at a temperature of 18 °C, which can be used for aluminized ceramic film.

[0044] Example 5

[0045] This example proposes a preparation method of a general-purpose environmentally friendly true black phosphatizing solution for aluminum alloy, including the following steps: (using the component formula of Example 1)

[0046] S1. Take 80 ml of pure water and dissolve 12 g of K2ZrF6, 4 g of K2TiF6, and 4 g of Al2(SO4)3 in it to obtain a mixed solution; then take 120 ml of pure water and dissolve 27 g of NaOH in it to obtain a NaOH solution; then slowly add the NaOH solution to the above-mentioned mixed solution under stirring, stir while adding, and then filter to retain the precipitate to obtain Substance A.

[0047] S2. Take 120 ml of pure water and dissolve 6 g of Na2SiO3·9H2O in it to obtain a Na2SiO3 solution, then take 60 ml of pure water and drop 12 ml of H3PO4 into it and stir evenly to obtain an H3PO4 solution, and then slowly add the Na2SiO3 solution to the H3PO4 solution under stirring, stir while adding, and let it stand and cool to room temperature to obtain Substance B.

[0048] S3. Add 60 ml of pure water to a beaker, then add 120 ml of C2H5OH and 12 ml of KH-550 to the beaker and stir evenly, adjust the pH = 3, then heat the beaker in a water bath to 65 °C, keep it warm for 2 h, then take down the beaker and cool it to room temperature to obtain Substance C.

[0049] 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 propylene resin monomer, 0.8 g of sodium dodecylbenzenesulfonate, and 6 g of hexamethylenetetramine in it in turn under stirring, and cool it to room temperature to obtain Substance D.

[0050] S5. Take 180 ml of pure water and add Substance A to it and stir well to form a thin paste, then add 65 ml of phytic acid and the remaining H3PO4 to it in turn and stir to completely dissolve the precipitate, and cool it to room temperature for standby to obtain Substance E.

[0051] S6. Slowly add Substance C, Substance E, and Substance B to Substance D separately under stirring, and make up pure water to 1 L. Transfer the obtained liquid into a glass bottle, seal it with a cap, heat it in a water bath at 60 °C for 2.5 h. Take out the glass bottle, and take the clarified liquid and cool it to room temperature for standby to obtain a black phosphatizing solution.

[0052] S7. Take 10 ml of the black phosphatizing solution and add it to 990 ml of pure water, stir evenly, and then adjust the pH to 3.2 with phytic acid or ammonia water at a temperature of 25 °C, which can be used for the aluminum alloy to be coated with a black phosphatized film.

[0053] Example 6

[0054] This example proposes a preparation method of a general-purpose environmentally friendly true black phosphatizing solution for aluminum alloy, including the following steps: (using the component formula of Example 1)

[0055] S1. Take 120 ml of pure water and dissolve 8 g of K2ZrF6, 6 g of K2TiF6, and 6 g of Al2(SO4)3 in it to obtain a mixed solution; then take 80 ml of pure water and dissolve 22 g of NaOH in it to obtain a NaOH solution; then slowly add the NaOH solution to the above-mentioned mixed solution under stirring, stir while adding, and then filter to retain the precipitate to obtain Substance A.

[0056] S2. Take 80 ml of pure water and dissolve 4 g of Na2SiO3·9H2O in it to obtain a Na2SiO3 solution, then take 40 ml of pure water and add 8 ml of H3PO4 dropwise thereto and stir evenly to obtain an H3PO4 solution, and then slowly add the Na2SiO3 solution to the H3PO4 solution under stirring, stir while adding, and let it stand and cool to room temperature to obtain Substance B.

[0057] S3. Add 40 ml of pure water to a beaker, then add 80 ml of C2H5OH and 8 ml of KH-550 to the beaker and stir evenly, adjust the pH = 1.5, then heat the beaker in a water bath to 65 °C and keep it warm for 2 h, then remove the beaker and cool it to room temperature to obtain Substance C.

[0058] 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 propylene resin monomer, 1.2 g of sodium dodecylbenzenesulfonate, and 4 g of hexamethylenetetramine in it in sequence under stirring, and cool it to room temperature to obtain Substance D.

[0059] S5. Take 220 ml of pure water and add Substance A to it and stir well to form a thin paste, then add 55 ml of phytic acid and the remaining H3PO4 to it in sequence and stir to completely dissolve the precipitate, and cool it to room temperature for standby to obtain Substance E.

[0060] S6. Slowly add Substance C, Substance E, and Substance B to Substance D separately under stirring, and make up pure water to 1 L. Transfer the obtained liquid into a glass bottle, seal it with a lid, heat it in a water bath at 55 °C for 4 h. Take out the glass bottle, and take the clarified liquid, cool it to room temperature for standby to obtain a black phosphatizing solution.

[0061] S7. Take 10 ml of the black phosphatizing solution and add it to 990 ml of pure water, stir evenly, and then adjust the pH to 4 at 30 °C with phytic acid or ammonia water for use in aluminized black phosphatizing film.

[0062] Example 7

[0063] This example proposes a preparation method of a general-purpose environmentally friendly true black phosphatizing film for aluminum alloy, using the black phosphatizing solution prepared in Example 4; take several pieces of 6061, 6063, A356, and A380 aluminum alloy test pieces respectively, immerse different aluminum alloy test pieces into the said black phosphatizing solution respectively, perform a 2-min treatment under ultrasonic wave action, wash with water after taking out of the bath, dry, and then perform a 30-min drying treatment at 140 °C.

[0064] Experimental Example 1

[0065] Perform performance tests on the A380 aluminum alloy test piece plated with a black phosphatizing film in Example 7, and detect the bonding strength, light absorption rate, and corrosion resistance:

[0066] 1. Among them, the bonding strength is detected by the cross-cut method; the cross-cut method is carried out according to the method of cross-cut test in GB / T 9286-2021 Paints and varnishes; the test result of Example 7 is Grade 0, the cutting edge is completely smooth, and there is no peeling off in the grid.

[0067] 2. The light absorption rate is detected by a color difference meter, and the results are shown in Table 1; the color difference meter detection is based on the color description method of the CIE (International Commission on Illumination) recommended Lab color space, and the color difference meter is used for detection according to the said color description method.

[0068] 3. The corrosion resistance is detected by the neutral salt spray test. The neutral salt spray test is carried out according to GB / T 10125-2021 Corrosion tests in artificial atmospheres - Salt spray tests; the rating is carried out according to GB / T 6461-2002 Rating of specimens and test pieces after corrosion tests for metallic and other inorganic coatings on metallic substrates; after the black phosphatizing film prepared in Example 7 passes through the neutral salt spray test for 96 h, the test result is Grade 9.

[0069] Table 1 L(a + b) values of the front and back sides of the A380 aluminum alloy test piece A plated with a black phosphatizing film

[0070]

[0071] Experimental Example 2

[0072] The light absorption rate of the 6063 aluminum alloy test piece plated with a black ceramic film in Example 7 was detected. The method for detecting the light absorption rate was the same as that in Example 1. The detection results are shown in Table 2:

[0073] Table 2 L(a + b) values of the front and back sides of the 6063 aluminum alloy test piece plated with a black ceramic film

[0074]

[0075] The Lab color model consists of three elements: illuminance (L) and a and b related to color. L represents illuminance (Luminosity), equivalent to brightness. a represents the range from red to green, and b represents the range from blue to yellow. The value range of L is from 0 to 100. When L = 50, it is equivalent to 50% black; the value ranges of a and b are both from +120 to -120. Among them, +120a is red, and when gradually transitioning to -120a, it becomes green; by the same principle, +120b is yellow, and -120b is blue. All colors are composed of the interactive changes of these three values.

[0076] The L* values in 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 and has universality.

[0077] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific embodiments of the present invention are limited to this. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the premise of the present invention, several simple deductions or substitutions can still be made, and all should be regarded as belonging to the patent protection scope determined by the claims submitted for the present invention.

Claims

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

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

3. A general-purpose environmentally friendly true black phosphatizing solution for aluminum alloy according to claim 1 or 2, characterized in that, When using the black phosphatizing solution, dilute the black phosphatizing solution 100 times.

4. The preparation method of a general-purpose environmentally friendly true black phosphatizing solution for aluminum alloy according to claim 1, characterized in that, It includes 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 in it to obtain a mixed solution; then take 80 - 120 ml of pure water and dissolve 22 - 27 g of NaOH in it to obtain a NaOH solution; After that, slowly add the NaOH solution to the above-mentioned mixed solution under stirring, stir while adding, and then filter to retain the precipitate to obtain substance A; S2. Take 80 - 120 ml of pure water and dissolve 4 - 6 g of Na2SiO3·9H2O in it to obtain a Na2SiO3 solution, then take 45 - 65 ml of pure water and drop 8 - 12 ml of H3PO4 into it and stir evenly to obtain an H3PO4 solution, and then slowly add the Na2SiO3 solution to the H3PO4 solution under stirring, stir while adding, 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 to the beaker and stir evenly, adjust the pH to 1.5 - 3, then heat the beaker in a water bath to 60 - 65 °C and keep it warm for 1.5 - 2.5 h, then remove the beaker and cool it 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 dodecylbenzenesulfonate, and 4 - 6 g of hexamethylenetetramine in it successively under stirring, and cool to room temperature to obtain Substance D; S5. Take 180 - 220 ml of pure water and add Substance A to it, stir well to form a thin paste, then add 55 - 65 ml of phytic acid and the remaining H3PO4 to it successively and stir until the precipitate completely dissolves, cool to room temperature and set aside to obtain Substance E; S6. Slowly add Substance C, Substance E and Substance B to Substance D respectively under stirring, make up pure water to 1 L, transfer the obtained liquid into a glass bottle, seal it with a cap, heat it in a water bath at 55 - 65 °C for more than 2 h, take out the glass bottle, take the clarified liquid, cool to room temperature and set aside to obtain a black phosphatizing solution.

5. The preparation method of a general-purpose environmentally friendly true black phosphatizing solution for aluminum alloy according to claim 4, characterized in that, Take 10 ml of the black phosphatizing solution and add it to 990 ml of pure water, stir evenly, and adjust the pH to 3 - 4 at room temperature of 18 - 30 °C with phytic acid or ammonia water for use in aluminizing the ceramic film.

6. A preparation method of a general-purpose environmentally friendly true black ceramic conversion film for aluminum alloy, characterized in that, Use the black phosphatizing solution prepared as claimed in claim 5; immerse the aluminum alloy in the said black phosphatizing solution, carry out treatment for 1 - 2 min under the action of ultrasonic waves, then wash with water, blow dry, and carry out drying treatment.

7. The preparation method of a general-purpose environmentally friendly true black ceramic conversion film for aluminum alloy according to claim 6, characterized in that, The temperature of the said drying is 130 - 150 °C, and the drying time is 20 - 30 min.

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