High-efficiency environment-friendly chromium phosphate liquid passivation solution and preparation method thereof

Abstract

The application discloses a preparation method of a high-efficiency environment-friendly chromium phosphate passivation solution, and comprises the following steps: stirring and reacting a chromium phosphate solution, an oxidizing agent and a complexing agent to obtain component A; adding a film forming promoter and a stabilizer into deionized water and heating to obtain component B; slowly adding the component A into the heated component B, mixing, heating and stirring, and filtering to obtain a chromium phosphate passivation solution product. The chromium phosphate passivation solution has excellent passivation effect, can form a dense and uniform passivation film on a metal surface, effectively improves the corrosion resistance of the metal, prolongs the service life of the metal, and has a neutral salt spray resistance time of more than 100 hours. The trivalent chromium in the passivation film will not produce hexavalent chromium to cause harm to the environment with the lapse of time. The preparation method of the chromium phosphate passivation solution is simple, raw materials are easy to obtain, the cost is low, and the method is suitable for industrial production and has good environmental protection performance. The chromium phosphate passivation solution does not contain harmful hexavalent chromium, and harm to the environment and human bodies is reduced.

Description

Technical Field

[0001] This invention belongs to the field of metal surface treatment technology, and more specifically, this invention relates to a method for preparing a highly efficient and environmentally friendly chromium phosphate passivation solution. Background Technology

[0002] With the rapid development of industry, the application of metallic materials in various fields is becoming increasingly widespread. However, metals are susceptible to corrosion during use, leading to a decline in performance and a shortened service life. Traditional metal surface protection treatment mainly involves hexavalent chromium passivation solutions, which react with the metal surface to form a chromium-containing passivation film. This passivation film protects the metal from various types of corrosion. Although this passivation layer can improve corrosion resistance and pretreatment performance before adhesive application, hexavalent chromium is highly toxic, pollutes the environment, and is carcinogenic to humans. With increasing environmental awareness, there is a growing demand for the development and production of hexavalent chromium-free surface treatment solutions and processes.

[0003] The trend is towards replacing highly toxic hexavalent chromium passivation solutions with less toxic trivalent chromium passivation solutions. Early trivalent chromium passivation solutions simply replaced hexavalent chromium compounds with trivalent chromium compounds. However, existing trivalent chromium passivation processes suffer from defects such as unstable product quality, short passivation solution life, difficulty in controlling the passivation process, and poor corrosion resistance of the passivation film. Therefore, developing a highly efficient and environmentally friendly passivation solution has become an urgent problem to be solved in this field. Summary of the Invention

[0004] One object of the present invention is to solve at least the above-mentioned problems and / or defects, and to provide at least the advantages described below.

[0005] To achieve these objectives and other advantages of the present invention, a method for preparing a highly efficient and environmentally friendly chromium phosphate passivation solution is provided, comprising the following steps: Step 1: Mix the chromium phosphate solution, oxidant, and complexing agent according to the mass fractions, stir and react to obtain component A; Step 2: According to the mass proportions, add the film-forming accelerator and stabilizer to deionized water, mix well, and heat for later use; this is component B. Step 3: Slowly add component A to the heated component B according to the volume ratio, mix and heat while stirring, filter to obtain the chromium phosphate passivation solution product.

[0006] Preferably, in step one, the chromium content in the chromium phosphate solution is 5-10%, and the chromium phosphate content is 25-40%.

[0007] Preferably, in step one, the oxidant is one or more of hydrogen peroxide, sodium persulfate, potassium persulfate, and ammonium persulfate.

[0008] Preferably, in step one, the complexing agent is one or more of citric acid, tartaric acid, oxalic acid, aminotrimethylphosphonic acid (ATMP), hydroxyethylidene diphosphonic acid, ethylenediamine, and triethanolamine.

[0009] Preferably, in step one, the mass ratio of chromium phosphate solution, oxidant and complexing agent is 20~30:5~10:2~5, the stirring temperature is 25~30℃, and the stirring is carried out at 300~400 rpm for 1~2 hours.

[0010] Preferably, in step two, the film-forming accelerator is one or more of trimethyl phosphate, triphenyl phosphite, triethanolamine, and N,N-dimethylformamide, the stabilizer is hexadecyltrimethylammonium bromide, the mass ratio of film-forming accelerator, stabilizer and deionized water is 3~8:1~3:50~60, and the temperature is heated to 60~80°C.

[0011] Preferably, in step three, the volume ratio of component A to component B is 1~1.5:1, the heating and stirring temperature is 60~80℃, and the stirring is carried out at a speed of 300~400rpm for 1.5~3h.

[0012] Preferably, the chromium phosphate solution in step one is replaced with a modified chromium phosphate solution, and the modified chromium phosphate solution is prepared as follows: S11. Polyvinylpyrrolidone is added to anhydrous ethanol, followed by chromium phosphate solution and tetraethyl orthosilicate. Then, ammonia is added to adjust the pH and the mixture is stirred. After the reaction, the solvent is evaporated to obtain the precursor. S12. Disperse the precursor in deionized water, then add polyaspartic acid, ultrasonically disperse until uniform, and then adjust the pH with phosphoric acid to obtain a modified chromium phosphate solution.

[0013] Preferably, in step S11, the ratio of polyvinylpyrrolidone, anhydrous ethanol, chromium phosphate solution and tetraethyl orthosilicate is 5-10g:100-200mL:100-200mL:40-60mL, ammonia is added to adjust the pH to 8-9, and the mixture is stirred at 300-400rpm for 1-2 hours.

[0014] Preferably, in step S12, the precursor is added to deionized water at a mass ratio of chromium content in the precursor to deionized water of 0.05~0.1:1, the ratio of polyaspartic acid to deionized water is 5~10g:100mL, the precursor is ultrasonically dispersed at 20~40kHz for 10~30min, and the pH is adjusted to 3~5 with phosphoric acid.

[0015] The present invention offers at least the following advantages: The chromium phosphate passivation solution of the present invention exhibits excellent environmental performance, containing no harmful hexavalent chromium, thus reducing harm to the environment and human health. The chromium phosphate passivation solution of the present invention provides excellent passivation, forming a dense and uniform passivation film on the metal surface, effectively improving the metal's corrosion resistance and extending its service life. Its resistance to neutral salt spray exceeds 100 hours, and the trivalent chromium in the passivation film does not transform into hexavalent chromium over time, posing no environmental harm. The chromium phosphate passivation solution of the present invention possesses good chemical stability, is not easily oxidized or reduced, and can be stored for extended periods at room temperature and pressure without significant chemical changes, reducing the risk of performance degradation or failure due to chemical changes. Furthermore, the preparation method of the chromium phosphate passivation solution of the present invention is simple, the raw materials are readily available, and the cost is low, making it suitable for industrial production.

[0016] This invention also modifies the chromium phosphate solution, prepares nano-silica using the sol-gel method, and encapsulates chromium phosphate within it, achieving the slow release of trivalent chromium. This, combined with the introduction of polyvinylpyrrolidone, slows down the film formation rate of trivalent chromium on the metal surface, making the film layer more uniform and dense, effectively improving the corrosion resistance and salt spray resistance of the metal. Furthermore, by additionally compounding polyaspartic acid, which has a synergistic corrosion inhibition effect with organic phosphoric acid, the salt spray resistance and corrosion resistance of the film layer formed by the passivation solution on the metal surface are further enhanced.

[0017] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Detailed Implementation

[0019] The present invention will now be described in further detail with reference to embodiments, so that those skilled in the art can implement it based on the description.

[0020] Example 1 A method for preparing a highly efficient and environmentally friendly chromium phosphate passivation solution includes the following steps: Step 1: Mix 100g (100mL) of chromium phosphate solution with a chromium content of 6%, 25g of 30% hydrogen peroxide solution, and 10g of aminotrimethylphosphonic acid (ATMP) thoroughly and stir at 25℃ for 1h to obtain component A. Step 2: Add 15g of trimethyl phosphate and 5g of hexadecyltrimethylammonium bromide to 100mL of deionized water, mix well, and heat to 80℃ for later use. This is component B. Step 3: Slowly add 100 mL of component A to 100 mL of heated component B at a volume ratio of 1:1, maintain the temperature at 80°C and stir for 2 hours, then filter to obtain the chromium phosphate passivation solution product.

[0021] Example 2 A method for preparing a highly efficient and environmentally friendly chromium phosphate passivation solution includes the following steps: Step 1: Mix 100 mL of chromium phosphate solution with a chromium content of 7%, 25 g of 30% hydrogen peroxide solution, and 10 g of aminotrimethylphosphonic acid (ATMP) thoroughly and stir at 25°C for 1 h to obtain component A. Step 2: Add 15g of trimethyl phosphate and 5g of hexadecyltrimethylammonium bromide to 100mL of deionized water, mix well, and heat to 80℃ for later use. This is component B. Step 3: Slowly add 100 mL of component A to 100 mL of heated component B at a volume ratio of 1:1, maintain the temperature at 80°C and stir for 2 hours, then filter to obtain the chromium phosphate passivation solution product.

[0022] Example 3 A method for preparing a highly efficient and environmentally friendly chromium phosphate passivation solution includes the following steps: Step 1: Mix 100 mL of chromium phosphate solution with a chromium content of 6%, 25 g of ammonium persulfate, and 10 g of aminotrimethylphosphonic acid (ATMP) thoroughly and stir at 25 °C for 1 h to obtain component A. Step 2: Add 15g of trimethyl phosphate and 5g of hexadecyltrimethylammonium bromide to 100mL of deionized water, mix well, and heat to 80℃ for later use. This is component B. Step 3: Slowly add 100 mL of component A to 100 mL of heated component B at a volume ratio of 1:1, maintain the temperature at 80°C and stir for 2 hours, then filter to obtain the chromium phosphate passivation solution product.

[0023] Example 4 A method for preparing a highly efficient and environmentally friendly chromium phosphate passivation solution includes the following steps: Step 1: Mix 150 mL of chromium phosphate solution with a chromium content of 6%, 25 g of 30% hydrogen peroxide solution, and 10 g of aminotrimethylphosphonic acid (ATMP) thoroughly and stir at 25°C for 1 h to obtain component A. Step 2: Add 15g of trimethyl phosphate and 5g of hexadecyltrimethylammonium bromide to 100mL of deionized water, mix well, and heat to 80℃ for later use. This is component B. Step 3: Slowly add 100 mL of component A to 100 mL of heated component B at a volume ratio of 1.5:1, maintain the temperature at 80°C and stir for 2 hours, then filter to obtain the chromium phosphate passivation solution product.

[0024] Example 5 A method for preparing a highly efficient and environmentally friendly chromium phosphate passivation solution includes the following steps: Step 1: Mix 150 mL of chromium phosphate solution with a chromium content of 7%, 25 g of hydrogen peroxide, and 10 g of aminotrimethylphosphonic acid (ATMP) thoroughly and stir at 25 °C for 1 h to obtain component A. Step 2: Add 15g of trimethyl phosphate and 5g of hexadecyltrimethylammonium bromide to 100mL of deionized water, mix well, and heat to 80℃ for later use. This is component B. Step 3: Slowly add 100 mL of component A to 100 mL of heated component B at a volume ratio of 1.5:1, maintain the temperature at 80°C and stir for 2 hours, then filter to obtain the chromium phosphate passivation solution product.

[0025] Example 6 A method for preparing a highly efficient and environmentally friendly chromium phosphate passivation solution includes the following steps: Step 1: Mix 150 mL of chromium phosphate solution with a chromium content of 7%, 25 g of ammonium persulfate, and 10 g of aminotrimethylphosphonic acid (ATMP) thoroughly and stir at 25 °C for 1 h to obtain component A. Step 2: Add 15g of trimethyl phosphate and 5g of hexadecyltrimethylammonium bromide to 100mL of deionized water, mix well, and heat to 80℃ for later use. This is component B. Step 3: Slowly add 100 mL of component A to 100 mL of heated component B at a volume ratio of 1.5:1, maintain the temperature at 80°C and stir for 2 hours, then filter to obtain the chromium phosphate passivation solution product.

[0026] Example 7 A method for preparing a highly efficient and environmentally friendly chromium phosphate passivation solution includes the following steps: Step 1: Mix 150 mL of chromium phosphate solution with a chromium content of 7%, 25 g of 30% hydrogen peroxide solution, and 10 g of aminotrimethylphosphonic acid (ATMP) thoroughly and stir at 25°C for 1 h to obtain component A. Step 2: Add 15g of triphenyl phosphite and 5g of hexadecyltrimethylammonium bromide to 100mL of deionized water, mix well, and heat to 80℃ for later use. This is component B. Step 3: Slowly add 100 mL of component A to 100 mL of heated component B at a volume ratio of 1.5:1, maintain the temperature at 80°C and stir for 2 hours, then filter to obtain the chromium phosphate passivation solution product.

[0027] Example 8 A method for preparing a highly efficient and environmentally friendly chromium phosphate passivation solution includes the following steps: Step 1: Prepare the modified chromium phosphate solution: S11. Add 5g of polyvinylpyrrolidone to 100mL of anhydrous ethanol, then add 150mL of chromium phosphate solution with a chromium content of 7% and 40mL of tetraethyl orthosilicate. Then add ammonia water to adjust the pH to 8 and stir at 300rpm for 1h. After the reaction, evaporate the solvent to obtain the precursor. S12. Disperse the precursor in 150 mL of deionized water at a mass ratio of chromium content in the precursor to deionized water of 0.07:1, then add 7.5 g of polyaspartic acid, sonicate at 20 kHz for 10 min, and then adjust the pH to 3 with phosphoric acid to obtain a modified chromium phosphate solution with a chromium content of 7%. 150 mL of modified chromium phosphate solution with a chromium content of 7%, 25 g of hydrogen peroxide, and 10 g of aminotrimethylphosphonic acid (ATMP) were thoroughly mixed and stirred at 25 °C for 1 h to obtain component A. Step 2: Add 15g of trimethyl phosphate and 5g of hexadecyltrimethylammonium bromide to 100mL of deionized water, mix well, and heat to 80℃ for later use. This is component B. Step 3: Slowly add 100 mL of component A to 100 mL of heated component B at a volume ratio of 1.5:1, maintain the temperature at 80°C and stir for 2 hours, then filter to obtain the chromium phosphate passivation solution product.

[0028] Example 9: A method for preparing a highly efficient and environmentally friendly chromium phosphate passivation solution includes the following steps: Step 1: Prepare the modified chromium phosphate solution: S11. Add 5g of polyvinylpyrrolidone to 100mL of anhydrous ethanol, then add 150mL of chromium phosphate solution with a chromium content of 7% and 40mL of tetraethyl orthosilicate. Then add ammonia water to adjust the pH to 8 and stir at 300rpm for 1h. After the reaction, evaporate the solvent to obtain the precursor. S12. Disperse the precursor in 150 mL of deionized water at a mass ratio of chromium content in the precursor to deionized water of 0.07:1, sonicate at 20 kHz for 10 min, and then adjust the pH to 3 with phosphoric acid to obtain a modified chromium phosphate solution with a chromium content of 7%. 150 mL of modified chromium phosphate solution with a chromium content of 7%, 25 g of hydrogen peroxide, and 10 g of aminotrimethylphosphonic acid (ATMP) were thoroughly mixed and stirred at 25 °C for 1 h to obtain component A. Step 2: Add 15g of trimethyl phosphate and 5g of hexadecyltrimethylammonium bromide to 100mL of deionized water, mix well, and heat to 80℃ for later use. This is component B. Step 3: Slowly add 100 mL of component A to 100 mL of heated component B at a volume ratio of 1.5:1, maintain the temperature at 80°C and stir for 2 hours, then filter to obtain the chromium phosphate passivation solution product.

[0029] Example 10: A method for preparing a highly efficient and environmentally friendly chromium phosphate passivation solution includes the following steps: Step 1: First, prepare the modified chromium phosphate solution: Add 7.5g of polyaspartic acid to 150mL of chromium phosphate solution with a chromium content of 7%, and ultrasonically disperse at 20kHz for 10min to obtain a modified chromium phosphate solution with a chromium content of 7%. 150 mL of modified chromium phosphate solution with a chromium content of 7%, 25 g of hydrogen peroxide, and 10 g of aminotrimethylphosphonic acid (ATMP) were thoroughly mixed and stirred at 25 °C for 1 h to obtain component A. Step 2: Add 15g of trimethyl phosphate and 5g of hexadecyltrimethylammonium bromide to 100mL of deionized water, mix well, and heat to 80℃ for later use. This is component B. Step 3: Slowly add 100 mL of component A to 100 mL of heated component B at a volume ratio of 1.5:1, maintain the temperature at 80°C and stir for 2 hours, then filter to obtain the chromium phosphate passivation solution product.

[0030] The chromium phosphate passivation solutions prepared in Examples 1-10 were subjected to a 5% NaCl neutral salt spray test (NSS) according to GB / T10125 1997 "Artificial Atmosphere Corrosion Test". The test conditions were: 5% NaCl, pH value of 6.8-7.2, temperature in the spray chamber of 33℃-37℃, sample at 15°-30° to the vertical direction, continuous spraying, and periodic observation of the corrosion of the passivated parts. The neutral salt spray time (the time when corrosion begins) was recorded to determine the corrosion resistance of the passivation film. The results are shown in Table 1.

[0031] Table 1 1 2 3 4 5 6 7 8 9 10 Neutral salt spray time 187h 169h 179h 168h 210h 196h 178h 255h 241h 226h Based on Example 5, Examples 8-10 of this invention modify the chromium phosphate solution. In Example 8, nano-silica was prepared using the sol-gel method and chromium phosphate was coated inside, achieving the slow release of trivalent chromium. This, combined with the introduction of polyvinylpyrrolidone, slowed down the film formation rate of trivalent chromium on the metal surface, making the film layer more uniform and dense, effectively improving the corrosion resistance and salt spray resistance of the metal. Furthermore, by additionally compounding polyaspartic acid, which has a synergistic corrosion inhibition effect with organic phosphoric acid, the salt spray resistance and corrosion resistance of the film layer formed by the passivation solution on the metal surface were further enhanced. The passivated part treated with the passivation solution of Example 8 achieved a neutral salt spray time of 255 hours, and its salt spray resistance and corrosion resistance were significantly improved. In Example 9, only nano-silica was used to coat chromium phosphate and polyvinylpyrrolidone was introduced, which also improved the salt spray resistance, but was slightly inferior to that of Example 8. In Example 10, only polyaspartic acid, which has a synergistic corrosion inhibition effect with organic phosphoric acid, was compounded, resulting in the smallest improvement in salt spray resistance.

[0032] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A method for preparing a highly efficient and environmentally friendly chromium phosphate passivation solution, characterized in that, Includes the following steps: Step 1: Mix the chromium phosphate solution, oxidant, and complexing agent according to the mass fractions, stir and react to obtain component A; Step 2: According to the mass proportions, add the film-forming accelerator and stabilizer to deionized water, mix well, and heat for later use; this is component B. Step 3: Slowly add component A to the heated component B according to the volume ratio, mix and heat while stirring, filter to obtain the chromium phosphate passivation solution product.

2. The high-efficiency and environmentally friendly chromium phosphate passivation solution as described in claim 1, characterized in that, In step one, the chromium content in the chromium phosphate solution is 5-10%, and the chromium phosphate content is 25-40%.

3. The high-efficiency and environmentally friendly chromium phosphate passivation solution as described in claim 1, characterized in that, In step one, the oxidant is one or more of hydrogen peroxide, sodium persulfate, potassium persulfate, and ammonium persulfate.

4. The high-efficiency and environmentally friendly chromium phosphate passivation solution as described in claim 1, characterized in that, In step one, the complexing agent is one or more of citric acid, tartaric acid, oxalic acid, aminotrimethylphosphonic acid, hydroxyethylidene diphosphonic acid, ethylenediamine, and triethanolamine.

5. The high-efficiency and environmentally friendly chromium phosphate passivation solution as described in claim 1, characterized in that, In step one, the mass ratio of chromium phosphate solution, oxidant and complexing agent is 20~30:5~10:2~5, the stirring temperature is 25~30℃, and the stirring is carried out at a speed of 300~400rpm for 1~2 hours.

6. The high-efficiency and environmentally friendly chromium phosphate passivation solution as described in claim 1, characterized in that, In step two, the film-forming accelerator is one or more of trimethyl phosphate, triphenyl phosphite, triethanolamine, and N,N-dimethylformamide, the stabilizer is hexadecyltrimethylammonium bromide, and the mass ratio of film-forming accelerator, stabilizer and deionized water is 3~8:1~3:50~60, and the temperature is heated to 60~80℃.

7. The high-efficiency and environmentally friendly chromium phosphate passivation solution as described in claim 1, characterized in that, In step three, the volume ratio of component A to component B is 1~1.5:1, the heating and stirring temperature is 60~80℃, and the stirring is carried out at a speed of 300~400rpm for 1.5~3h.

8. The method for preparing the efficient and environmentally friendly chromium phosphate passivation solution as described in claim 1, characterized in that, The chromium phosphate solution in step one is replaced with a modified chromium phosphate solution, and the modified chromium phosphate solution is prepared as follows: S11. Polyvinylpyrrolidone is added to anhydrous ethanol, followed by chromium phosphate solution and tetraethyl orthosilicate. Then, ammonia is added to adjust the pH and the mixture is stirred. After the reaction, the solvent is evaporated to obtain the precursor. S12. Disperse the precursor in deionized water, then add polyaspartic acid, ultrasonically disperse until uniform, and then adjust the pH with phosphoric acid to obtain a modified chromium phosphate solution.

9. The method for preparing the efficient and environmentally friendly chromium phosphate passivation solution as described in claim 8, characterized in that, In step S11, the ratio of polyvinylpyrrolidone, anhydrous ethanol, chromium phosphate solution, and tetraethyl orthosilicate is 5-10g:100-200mL:100-200mL:40-60mL. Ammonia water is added to adjust the pH to 8-9, and the mixture is stirred at 300-400rpm for 1-2 hours.

10. The method for preparing the efficient and environmentally friendly chromium phosphate passivation solution as described in claim 8, characterized in that, In step S12, the precursor is added to deionized water at a mass ratio of chromium content in the precursor to deionized water of 0.05~0.1:1, and the ratio of polyaspartic acid to deionized water is 5~10g:100mL. The precursor is ultrasonically dispersed at 20~40kHz for 10~30min, and the pH is adjusted to 3~5 with phosphoric acid.