Trivalent chromium passivation solution for maintaining the color of aluminum alloy and its preparation method and passivation method

Abstract

The application provides a trivalent chromium passivation solution for maintaining the original color of aluminum alloy, which is prepared from basic chromium sulfate, zirconium salt, fluoride salt, corrosion inhibitor, organic acid complexing agent and water. The application also provides a preparation method of the trivalent chromium passivation solution for maintaining the original color of aluminum alloy, which comprises the following steps: heating water to 75-85 DEG C, then adding basic chromium sulfate, stirring while adding until completely dissolved, then adding zirconium salt, fluoride salt, corrosion inhibitor, organic acid complexing agent, silane coupling agent, water-soluble resin and nano silicon dioxide in sequence, and stirring for 1-2 h; using a pH regulator to adjust the pH value to 3.8-4.2, and the trivalent chromium passivation solution for maintaining the original color of aluminum alloy is obtained. The application also provides a passivation method for maintaining the original color of aluminum alloy. The application has the advantages of saving raw material cost, simple preparation method, and the like, and the passivated aluminum alloy part has a dense and uniform passivation film, the appearance color is maintained as the original color, the corrosion resistance exceeds 300 hours after neutral salt spray test, and the corrosion resistance is good.

Description

Technical Field

[0001] This invention belongs to the field of chemical engineering and relates to a metal surface treatment technology, specifically a trivalent chromium passivation solution for maintaining the original color of aluminum alloys, its preparation method, and passivation method. Background Technology

[0002] In today's rapidly developing industrial society, high-strength, high-processability aluminum alloys have become an indispensable component of modern industrial society, widely used in various manufacturing industries. Aluminum alloys are composed of multiple elements, the presence of which gives them excellent mechanical properties, but also increases their susceptibility to corrosion. In actual working conditions, especially in chloride-containing environments, they are highly susceptible to localized corrosion, often exhibiting severe corrosion after 24 hours of neutral salt spray testing. Therefore, a series of surface treatments are necessary before practical use. Previously, a common and effective method was to use hexavalent chromium chemical passivation to achieve high corrosion resistance. However, hexavalent chromium is a hazardous chemical with high carcinogenicity and environmental pollution during its production, and its use has been gradually banned in various countries.

[0003] Current research focuses on trivalent chromium passivation. Compared to hexavalent chromium passivation solutions, trivalent chromium passivation solutions have drawbacks such as poor self-healing properties. However, trivalent chromium is only 1% as toxic as hexavalent chromium, the overall treatment process is environmentally friendly and pollution-free, and aluminum alloys also exhibit high corrosion resistance after trivalent chromium passivation. Commercially available trivalent chromium passivation solutions all have good effects, but they all alter the appearance and color of aluminum alloy parts. Some parts require excellent corrosion resistance after passivation while maintaining their original color. This invention satisfies the requirement of excellent corrosion resistance after trivalent chromium passivation while also preserving the original color of the parts. Summary of the Invention

[0004] To address the aforementioned technical problems in the prior art, this invention provides a trivalent chromium passivation solution for maintaining the natural color of aluminum alloys, its preparation method, and passivation method. This trivalent chromium passivation solution for maintaining the natural color of aluminum alloys, its preparation method, and passivation method aim to solve the technical problem that the use of trivalent chromium passivation solutions in the prior art alters the appearance color of aluminum alloy parts, and further enhances their corrosion resistance.

[0005] This invention provides a trivalent chromium passivation solution for maintaining the natural color of aluminum alloys, prepared from the following raw materials:

[0006]

[0007] The remainder is water, and the pH is adjusted to 3.8-4.2 using a pH adjuster.

[0008] The specific water is deionized water.

[0009] Furthermore, the zirconium salt is any one or a combination of two of potassium fluorozirconate or fluorozirconic acid.

[0010] Furthermore, the fluoride salt is any one or a combination of two or more of ammonium bifluoride, sodium fluoride, or ammonium fluoride.

[0011] Furthermore, the corrosion inhibitor is any one or a combination of two or more of benzotriazole, methylbenzotriazole, or cerium nitrate.

[0012] Furthermore, the organic acid complexing agent is any one or a combination of two or more of citric acid, tartaric acid, or oxalic acid.

[0013] Furthermore, the silane coupling agent is any one or a combination of two or more of γ-glycidoxypropyltrimethoxysilane and 1,2-bistrimethoxysilylethane.

[0014] Furthermore, the water-soluble resin is any one or a combination of two or more of water-based modified epoxy resin and water-based polyurethane resin.

[0015] Furthermore, the pH adjuster is selected from a 1:20 sodium hydroxide solution or a 1:20 sulfuric acid solution.

[0016] This invention also provides a method for preparing a trivalent chromium passivation solution for maintaining the natural color of aluminum alloys, comprising the following steps:

[0017] 1) Weigh each raw material according to the material ratio;

[0018] 2) Heat the water to 75-85℃, then add basic chromium sulfate while stirring until completely dissolved. Then add zirconium salt, fluoride salt, corrosion inhibitor, organic acid complexing agent, silane coupling agent, water-soluble resin and nano silica in sequence and stir for 1-2 hours.

[0019] 3) Adjust the pH value to 3.8-4.2 using a pH adjuster to obtain a trivalent chromium passivation solution for maintaining the original color of aluminum alloys.

[0020] The present invention also provides a passivation method for maintaining the natural color of aluminum alloys, comprising the following steps:

[0021] Step 1: Degreasing, using 50-60 g / L borax, 20-30 g / L sodium tripolyphosphate, and 5-8 mL / L 746 surfactant, respectively, to degrease for 5-10 minutes at a temperature of 45-65℃;

[0022] Step 2: Rinse with running water at room temperature;

[0023] Step 3: Acid washing, using sulfuric acid at 10-15 mL / L, reacting at room temperature for 30-60 seconds;

[0024] Step 4: Rinse with deionized water for 20-30 seconds;

[0025] Step 5: Passivation. Immerse the aluminum alloy in a passivation solution at a temperature of 35-45°C for 1-2 minutes.

[0026] Step 6: Rinse with deionized water for 20-30 seconds;

[0027] Step 7: Wash with hot water at a temperature of 50-70℃;

[0028] Step 8: Drying. Place the passivated aluminum alloy in a forced-air drying oven at a temperature of 60-80℃ for 10-15 minutes.

[0029] Compared to traditional inorganic trivalent chromium passivation, this invention adds a silane coupling agent, a water-soluble resin, and nano-silica, increasing the original single-layer passivation film to a multi-layer composite film. This effectively solves the problems of discoloration and brittle passivation films caused by traditional inorganic trivalent chromium passivation. The silane coupling agent enhances the performance of the surfactant in the passivation solution, improving the wettability and adhesion of the passivation film surface, and increasing its corrosion resistance and wear resistance. Adding the film-forming resin improves the flexibility of the passivation film; adding nano-silica reduces the porosity of the passivation film and enhances its density. This invention has advantages such as saving raw material costs and a simple preparation method. Furthermore, the passivated aluminum alloy parts exhibit a dense and uniform passivation film, with a corrosion resistance exceeding 300 hours in a neutral salt spray test, further improving the corrosion resistance of the passivation film. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 A passivated product appearance drawing provided as an exemplary embodiment;

[0032] Figure 2 An exemplary embodiment of the product after a 300-hour neutral salt spray test;

[0033] Figure 3 Appearance drawings of the passivated product provided for comparison;

[0034] Figure 4 The image provided is a comparison of the product's performance after a 300-hour neutral salt spray test. Detailed Implementation

[0035] The present invention will now be described in detail with reference to tables and specific embodiments.

[0036] Unless otherwise specified, the reagents used in the following embodiments are all commercially available products.

[0037] It should be understood that the described embodiments are merely some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0038] Example 1: In this example, the aluminum alloy natural trivalent chromium passivation solution includes the following raw materials: basic chromium sulfate 6g / L, fluorozirconic acid 2g / L, ammonium hydrogen fluoride 0.1g / L, benzotriazole 0.6g / L, citric acid 0.2g / L, γ-glycidyl etheroxypropyltrimethoxysilane 2g / L, water-based modified epoxy resin 1g / L, nano silica 1g / L, and the balance being water.

[0039] The pH value of the trivalent chromium passivation solution for aluminum alloys is adjusted by a 1:20 sodium hydroxide solution or a 1:20 sulfuric acid solution.

[0040] Example 2: In this example, the aluminum alloy natural trivalent chromium passivation solution includes the following raw materials: basic chromium sulfate 7g / L, fluorozirconic acid 1.5g / L, ammonium hydrogen fluoride 0.15g / L, benzotriazole 0.7g / L, citric acid 0.3g / L, γ-glycidyl etheroxypropyltrimethoxysilane 2g / L, water-based modified epoxy resin 1g / L, nano silica 1g / L, and the balance being water.

[0041] The pH value of the trivalent chromium passivation solution for aluminum alloys is adjusted by a 1:20 sodium hydroxide solution or a 1:20 sulfuric acid solution.

[0042] Example 3: In this example, the aluminum alloy natural trivalent chromium passivation solution includes the following raw materials: basic chromium sulfate 5g / L, fluorozirconic acid 1g / L, ammonium hydrogen fluoride 0.2g / L, benzotriazole 0.8g / L, citric acid 0.4g / L, γ-glycidyl etheroxypropyltrimethoxysilane 1.5g / L, water-based modified epoxy resin 1.5g / L, nano silica 0.5g / L, and the balance is water.

[0043] The pH value of the trivalent chromium passivation solution for aluminum alloys is adjusted by a 1:20 sodium hydroxide solution or a 1:20 sulfuric acid solution.

[0044] Example 4: In this example, the aluminum alloy natural trivalent chromium passivation solution includes the following raw materials: basic chromium sulfate 6 g / L, potassium fluorozirconate 1.5 g / L, sodium hydrogen fluoride 0.1 g / L, benzotriazole 0.6 g / L, citric acid 0.2 g / L, 1,2-bis(trimethoxysilyl)ethane 1.5 g / L, water-based modified epoxy resin 1.5 g / L, nano silica 0.5 g / L, and the balance is water.

[0045] The pH value of the trivalent chromium passivation solution for aluminum alloys is adjusted by a 1:20 sodium hydroxide solution or a 1:20 sulfuric acid solution.

[0046] Example 5: In this example, the aluminum alloy natural trivalent chromium passivation solution includes the following raw materials: basic chromium sulfate 5g / L, potassium fluorozirconate 1g / L, sodium hydrogen fluoride 0.2g / L, benzotriazole 0.7g / L, citric acid 0.3g / L, 1,2-bis(trimethoxysilyl)ethane 2g / L, water-based modified epoxy resin 1g / L, nano silica 1g / L, and the balance is water.

[0047] The pH value of the trivalent chromium passivation solution for aluminum alloys is adjusted by a 1:20 sodium hydroxide solution or a 1:20 sulfuric acid solution.

[0048] Example 6: In this example, the aluminum alloy natural trivalent chromium passivation solution includes the following raw materials: basic chromium sulfate 7g / L, potassium fluorozirconate 1g / L, ammonium fluoride 0.2g / L, benzotriazole 0.6g / L, citric acid 0.4g / L, 1,2-bis(trimethoxysilyl)ethane 1.5g / L, waterborne polyurethane resin 1.5g / L, nano silica 0.5g / L, and the balance is water.

[0049] The pH value of the trivalent chromium passivation solution for aluminum alloys is adjusted by a 1:20 sodium hydroxide solution or a 1:20 sulfuric acid solution.

[0050] Example 7: In this example, the aluminum alloy natural trivalent chromium passivation solution includes the following raw materials: basic chromium sulfate 5g / L, fluorozirconic acid 1.5g / L, ammonium hydrogen fluoride 0.3g / L, methylbenzotriazole 0.7g / L, tartaric acid 0.3g / L, 1,2-bis(trimethoxysilyl)ethane 1.5g / L, waterborne polyurethane resin 1.5g / L, nano silica 1g / L, and the balance is water.

[0051] The pH value of the trivalent chromium passivation solution for aluminum alloys is adjusted by a 1:20 sodium hydroxide solution or a 1:20 sulfuric acid solution.

[0052] Example 8: In this example, the aluminum alloy natural trivalent chromium passivation solution includes the following raw materials: basic chromium sulfate 7g / L, fluorozirconic acid 1g / L, ammonium hydrogen fluoride 0.2g / L, methylbenzotriazole 0.6g / L, oxalic acid 0.2g / L, γ-glycidyl etheroxypropyltrimethoxysilane 1.5g / L, waterborne polyurethane resin 1.5g / L, nano silica 1g / L, and the balance is water.

[0053] The pH value of the trivalent chromium passivation solution for aluminum alloys is adjusted by a 1:20 sodium hydroxide solution or a 1:20 sulfuric acid solution.

[0054] Example 9: In this example, the aluminum alloy natural trivalent chromium passivation solution includes the following raw materials: basic chromium sulfate 6g / L, fluorozirconic acid 2g / L, ammonium bifluoride 0.4g / L, cerium nitrate 0.6g / L, tartaric acid 0.4g / L, γ-glycidyl etheroxypropyltrimethoxysilane 2g / L, waterborne polyurethane resin 1g / L, nano silica 0.5g / L, and the balance is water.

[0055] The pH value of the trivalent chromium passivation solution for aluminum alloys is adjusted by a 1:20 sodium hydroxide solution or a 1:20 sulfuric acid solution.

[0056] Example 10: In this example, the aluminum alloy natural trivalent chromium passivation solution comprises the following raw materials: basic chromium sulfate 5 g / L, fluorozirconic acid 1 g / L, potassium fluorozirconate 0.5 g / L, ammonium hydrogen fluoride 0.1 g / L, sodium hydrogen fluoride 0.1 g / L, benzotriazole 0.7 g / L, citric acid 0.2 g / L, γ-glycidyl etheroxypropyltrimethoxysilane 1 g / L, waterborne polyurethane resin 1.5 g / L, nano silica 0.5 g / L, with the balance being water.

[0057] The pH value of the trivalent chromium passivation solution for aluminum alloys is adjusted by a 1:20 sodium hydroxide solution or a 1:20 sulfuric acid solution.

[0058] Example 11: In this example, the aluminum alloy natural trivalent chromium passivation solution includes the following raw materials: basic chromium sulfate 6 g / L, fluorozirconic acid 1 g / L, potassium fluorozirconate 1 g / L, ammonium hydrogen fluoride 0.1 g / L, ammonium fluoride 0.1 g / L, benzotriazole 0.8 g / L, tartaric acid 0.4 g / L, γ-glycidoxypropyltrimethoxysilane 1 g / L, 1,2-bistrimethoxysilylethane 1 g / L, waterborne polyurethane resin 1 g / L, waterborne modified epoxy resin 1 g / L, nano silica 1 g / L, and the balance is water.

[0059] The pH value of the trivalent chromium passivation solution for aluminum alloys is adjusted by a 1:20 sodium hydroxide solution or a 1:20 sulfuric acid solution.

[0060] Example 12: In this example, the aluminum alloy natural trivalent chromium passivation solution comprises the following raw materials: basic chromium sulfate 7 g / L, fluorozirconic acid 0.5 g / L, potassium fluorozirconate 1.5 g / L, sodium hydrogen fluoride 0.1 g / L, ammonium fluoride 0.1 g / L, benzotriazole 0.3 g / L, methylbenzotriazole 0.3 g / L, oxalic acid 0.3 g / L, γ-glycidoxypropyltrimethoxysilane 0.5 g / L, 1,2-bistrimethoxysilylethane 0.5 g / L, waterborne polyurethane resin 0.5 g / L, waterborne modified epoxy resin 0.5 g / L, nano silica 1 g / L, with the balance being water.

[0061] The pH value of the trivalent chromium passivation solution for aluminum alloys is adjusted by a 1:20 sodium hydroxide solution or a 1:20 sulfuric acid solution.

[0062] Example 13: In this example, the aluminum alloy natural trivalent chromium passivation solution includes the following raw materials: basic chromium sulfate 5g / L, fluorozirconic acid 0.5g / L, potassium fluorozirconate 1.5g / L, ammonium bifluoride 0.1g / L, ammonium fluoride 0.1g / L, benzotriazole 0.4g / L, cerium nitrate 0.3g / L, citric acid 0.4g / L, γ-glycidoxypropyltrimethoxysilane 1.5g / L, 1,2-bistrimethoxysilylethane 0.5g / L, waterborne polyurethane resin 1.5g / L, waterborne modified epoxy resin 0.5g / L, nano silica 0.5g / L, with the balance being water.

[0063] The pH value of the trivalent chromium passivation solution for aluminum alloys is adjusted by a 1:20 sodium hydroxide solution or a 1:20 sulfuric acid solution.

[0064] Example 14: In this example, the aluminum alloy natural trivalent chromium passivation solution comprises the following raw materials: basic chromium sulfate 6 g / L, fluorozirconic acid 1 g / L, potassium fluorozirconate 1 g / L, ammonium bifluoride 0.1 g / L, ammonium bifluoride 0.1 g / L, methylbenzotriazole 0.3 g / L, cerium nitrate 0.4 g / L, tartaric acid 0.2 g / L, γ-glycidoxypropyltrimethoxysilane 0.5 g / L, 1,2-bistrimethoxysilylethane 1.5 g / L, waterborne polyurethane resin 0.5 g / L, waterborne modified epoxy resin 1.5 g / L, nano silica 0.5 g / L, with the balance being water.

[0065] The pH value of the trivalent chromium passivation solution for aluminum alloys is adjusted by a 1:20 sodium hydroxide solution or a 1:20 sulfuric acid solution.

[0066] In one embodiment, a method for preparing a natural-colored trivalent chromium passivating agent for aluminum alloys is provided, comprising the following steps:

[0067] Heat deionized water to 75-85℃, then slowly add basic chromium sulfate while stirring until completely dissolved. Then add the required zirconium salt, fluoride salt, corrosion inhibitor and organic acid complexing agent in sequence and stir for 1-2 hours. Finally, adjust the pH value to 3.8-4.2 with a pH adjuster to obtain the trivalent chromium passivation solution used to maintain the original color of aluminum alloy.

[0068] The entire configuration process is simple and convenient.

[0069] In the above embodiments regarding the passivation method for aluminum alloys, the passivation method for aluminum alloys is as follows:

[0070] Step 1: Degreasing, using 50-60 g / L borax, 20-30 g / L sodium tripolyphosphate, and 5-8 mL / L 746 surfactant, respectively, to degrease for 5-10 minutes at a temperature of 45-65℃;

[0071] Step 2: Rinse with running water at room temperature;

[0072] Step 3: Acid washing, using sulfuric acid at 10-15 mL / L, reacting at room temperature for 30-60 seconds;

[0073] Step 4: Rinse with deionized water for 20-30 seconds;

[0074] Step 5: Passivation. Immerse the aluminum alloy in a passivation solution at a temperature of 35-45°C for 2-4 minutes.

[0075] Step 6: Rinse with deionized water for 20-30 seconds;

[0076] Step 7: Wash with hot water at a temperature of 50-70℃;

[0077] Step 8: Drying. Place the passivated aluminum alloy in a forced-air drying oven at a temperature of 60-80℃ for 10-15 minutes.

[0078] Comparative examples: basic chromium sulfate 6 g / L, fluorozirconic acid 2 g / L, ammonium hydrogen fluoride 0.1 g / L, benzotriazole 0.6 g / L, citric acid 0.2 g / L.

[0079] The pH value of the trivalent chromium passivation solution for aluminum alloys is adjusted by a 1:20 sodium hydroxide solution or a 1:20 sulfuric acid solution.

[0080] Salt spray test results data:

[0081]

[0082]

Claims

1. A trivalent chromium passivation solution for maintaining the natural color of aluminum alloys, characterized in that Prepared from the following raw materials: Basic chromium sulfate 5~7g / L; Zirconium salt 1~2g / L; Fluoride salt 0.1~0.2g / L; Corrosion inhibitor 0.6~0.8g / L; Organic acid complexing agent 0.2~0.4g / L; Silane coupling agent 1~2g / L; Water-soluble resin 1~2g / L; Nano-silicon dioxide 0.5~1g / L; The balance is water, and a pH adjuster is used to adjust the pH value to 3.8-4.2; The zirconium salt is any one or a combination of two of potassium fluorozirconate or fluorozirconic acid; The fluoride salt is any one or a combination of two or more of ammonium fluoride, sodium fluoride or ammonium fluoride; The corrosion inhibitor is any one or a combination of two or more of benzotriazole, methyl benzotriazole or cerium nitrate; The organic acid complexing agent is any one or a combination of two or more of citric acid, tartaric acid or oxalic acid; The silane coupling agent is any one or a combination of two or more of γ-glycidoxypropyltrimethoxysilane and 1,2-bistrimethoxysilylethane; The water-soluble resin is any one or a combination of two or more of water-based modified epoxy resin and water-based polyurethane resin; The pH adjuster is selected from 1:20 sodium hydroxide solution or 1:20 sulfuric acid solution; The above preparation method of the trivalent chromium passivation solution for maintaining the original color of aluminum alloy includes the following steps: 1) Weigh each raw material according to the material ratio; 2) Heat the water to 75-85℃, then add the basic chromium sulfate, stir while adding until completely dissolved, then add the zirconium salt, fluoride salt, corrosion inhibitor, organic acid complexing agent, silane coupling agent, water-soluble resin and nano-silicon dioxide in turn and stir for 1-2 h; 3) Adjust the pH value to 3.8-4.2 using a pH adjuster, and the trivalent chromium passivation solution for maintaining the original color of aluminum alloy is obtained.

2. The passivation method of maintaining the color of an aluminum alloy using the trivalent chromium passivation solution according to claim 1, characterized in that The above preparation method of the trivalent chromium passivation solution for maintaining the original color of aluminum alloy includes the following steps: Step one: degreasing, respectively using borax 50~60 g / L, sodium tripolyphosphate 20~30 g / L, 746 surfactant 5~8 mL / L, carrying out oil removal at a temperature of 45~65 ℃ for 5~10 minutes; Step two: rinsing, water washing at room temperature; Step three: pickling, using sulfuric acid 10~15 mL / L, reacting at room temperature for 30~60 s; Step four: rinsing, deionized water washing for 20~30 s; Step five: passivation, immersing the aluminum alloy in the passivation solution, the immersion temperature is 35~45℃, and the immersion time is 1~2 min; Step six: rinsing, deionized water washing for 20~30 s; Step seven: hot water washing, water washing at a temperature of 50~70℃; Step eight: drying, placing the passivated aluminum alloy in a forced air drying oven, the temperature is 60~80℃, and the time is 10~15 min.

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