Self-sealing anodizing solution for adc12 cast aluminum alloy and its preparation and application

Abstract

The application discloses a self-sealing anodic oxidation solution for ADC12 cast aluminum alloy, which comprises phosphate or / and borate, cerium salt, corrosion inhibitor, pH buffer, sulfonated wetting agent and deionized water. The application also discloses preparation and application of the self-sealing anodic oxidation solution. The self-sealing anodic oxidation solution for ADC12 cast aluminum alloy can ensure smooth production of anodic oxidation layer of ADC12 cast aluminum alloy, and can obtain a sealing layer with excellent self-healing performance, bonding force and compactness, thereby reducing a process flow, improving efficiency and reducing cost. In addition, the preparation and application operation of the self-sealing anodic oxidation solution are simple and environment-friendly and pollution-free.

Description

Technical Field

[0001] This invention relates to the field of metal surface treatment technology, specifically to ADC12 cast aluminum alloy self-sealing anodizing solution and its preparation and application. Background Technology

[0002] Aluminum alloys, due to their low density, excellent mechanical properties, and good machinability, are widely used in aerospace, chemical, shipbuilding, and automotive industries. Among them, ADC12 cast aluminum alloy, a high-performance Al-Si-Cu die-cast aluminum alloy, typically has a Si content of 9.6-12.0 wt% and a Cu content of 1.9-3.5 wt%. Its excellent fluidity, die-castability, and dimensional stability make it frequently used in 3C electronic casings, mechanical components, and automotive parts. However, excessively high copper content (≥2 wt%) reduces the corrosion resistance and fatigue life of aluminum alloys. This is because copper forms galvanic cells with the aluminum substrate, leading to localized pitting corrosion around copper-rich deposits, thus reducing the alloy's corrosion resistance. Simultaneously, excessive copper in the as-cast state forms coarse and incompletely dissolved Al2Cu plates, becoming stress concentration points and further reducing fatigue life. In practical applications, surface anodizing of aluminum alloys is typically performed to improve their corrosion resistance and service life. Generally, after anodizing, aluminum alloys are often sealed; otherwise, the final performance and cost of the aluminum alloy will be affected.

[0003] Currently used sealing technologies mainly include high-pressure steam sealing, boiling water sealing, nickel salt sealing, cold nickel fluoride sealing, and hexavalent chromium sealing. These technologies all share a common characteristic: they all require a separate sealing process after anodizing, which increases both cost and operational difficulty and complexity. Existing sealing technologies also have their own drawbacks. For example, high-pressure steam sealing and boiling water sealing are not only extremely costly, but in practical applications, the mismatch in expansion coefficients between the sealing material and the porous structure often leads to the former being damaged by the oxide film, ultimately affecting or limiting the improvement in oxide layer performance, thus severely limiting their application. Heavy metal salt sealing technologies (nickel salt sealing, cold nickel fluoride sealing, and hexavalent chromium sealing) will face restrictions or elimination due to the advocacy of green chemistry and the improvement of relevant laws and regulations.

[0004] Therefore, developing an electrolyte that can seal pores simultaneously during anodizing has become one of the current research hotspots in the field of aluminum alloy anodizing technology.

[0005] Chinese Patent CN 119932669 A (publication date May 6, 2025) discloses a method for preparing a self-sealing micro-arc oxidation ceramic film on 6063 aluminum alloy. This invention involves placing a pretreated aluminum alloy in an electrolyte for micro-arc oxidation, then placing the micro-arc-oxidized aluminum alloy in a carbonate precursor (hydrotalcite) to prepare a sample containing a layered bimetallic hydroxide (LDH) coating. Finally, the sample containing the LDH coating is placed in a modified hydroxyquinoline solution to prepare a self-sealing micro-arc oxidation ceramic film. Although this invention uses micro-arc oxidation self-sealing technology, it still uses LDH for secondary sealing, thus failing to ensure the effectiveness of the self-sealing technology.

[0006] Chinese invention patent CN 108468077 A (publication date August 13, 2018) discloses a method for self-sealing anodizing of magnesium alloys. The self-sealing anodizing electrolyte provided in this invention mainly consists of potassium hydroxide, potassium fluoride, sodium silicate, water-soluble organosilicon monomer, HK550, and deionized water. This invention involves placing a pretreated magnesium alloy in a specific anodizing electrolyte for anodizing to obtain a self-sealing anodized layer. The anodized layer prepared by this invention exhibits high adhesion, hardness, and excellent abrasion resistance and corrosion resistance. However, it is essentially a micro-arc oxidation self-sealing technology, and its sealing technology is a sol-gel sealing technology. A well-known drawback of sol-gel sealing technology is insufficient mechanical strength, and its use of high voltage (150-180V) poses safety hazards. Summary of the Invention

[0007] The purpose of this invention is to provide a self-sealing anodizing solution for ADC12 cast aluminum alloy, its preparation and application, in order to overcome the shortcomings of the prior art.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A self-sealing anodizing solution for ADC12 cast aluminum alloy comprises: phosphate and / or borates, cerium salts, corrosion inhibitors, pH buffers, sulfonating wetting agents, and deionized water;

[0010] The phosphate and / or borate is one or more of sodium phosphate, sodium pyrophosphate, sodium metaphosphate, sodium tripolyphosphate, sodium tetraborate, sodium metaborate, aluminum borate, and aluminum metaborate.

[0011] The cerium salt is one or more of cerium trichloride, cerium triiodide, cerium carbonate, cerium acetate, and cerium phosphate;

[0012] The corrosion inhibitor is one or more of benzotriazole, polyaspartic acid, and pyridine;

[0013] The pH buffer is one of sodium tetraborate-sodium hydroxide buffer, tris(hydroxymethyl)aminomethane-phosphate buffer, and potassium chloride-sodium hydroxide buffer.

[0014] The sulfonated wetting agent is one or more of succinate sulfonate, lignin sulfonate, alkyl sulfonate, α-olefin sulfonate, and fatty alcohol polyoxyethylene ether sulfonate.

[0015] The phosphate and / or borate concentration is 35–45 g / L, the cerium salt concentration is 15–30 g / L, the corrosion inhibitor concentration is 1–8 g / L, the pH buffer concentration is 15–20 g / L, the sulfonated wetting agent concentration is 1–5 g / L, and the balance is deionized water. The mass of the pH buffer is calculated as the mass of sodium tetraborate + sodium hydroxide, or the mass of tris(hydroxymethyl)aminomethane + phosphate, or the mass of potassium chloride + sodium hydroxide.

[0016] A method for preparing a self-sealing anodizing solution for ADC12 cast aluminum alloy includes the following steps:

[0017] (1) Weigh each component according to the formula amount, and dissolve each component except cerium salt in deionized water to obtain phosphate and / or borate solution, corrosion inhibitor solution, pH buffer solution, and sulfonated wetting agent solution.

[0018] (2) Under stirring conditions, add cerium salt to the corrosion inhibitor solution and stir thoroughly;

[0019] (3) Under stirring conditions, phosphate and / or borate solution, sulfonated wetting agent solution and pH buffer solution are added to the solution obtained in step (2) in sequence and stirred until the solution is homogeneous;

[0020] (4) Use sodium hydroxide solution to adjust the pH value of the solution obtained in step (3) to 7.5 to 10.5, and thus obtain the ADC12 cast aluminum alloy self-sealing anodizing solution.

[0021] Further, the sodium hydroxide solution mentioned in step (4) is a sodium hydroxide solution with a concentration of 80 g / L to 120 g / L.

[0022] Application of a self-sealing anodizing solution for ADC12 cast aluminum alloy in the anodizing of ADC12 cast aluminum alloy.

[0023] Further, the application includes the following steps: Anodizing: The pretreated ADC12 cast aluminum alloy substrate is placed in the ADC12 cast aluminum alloy self-sealing anodizing solution for anodizing, and then taken out and washed with water; the anodizing temperature is 20-55℃, the DC power supply is 55-75V, and the time is 10-30min; the oxide film thickness obtained by anodizing is 7-35μm.

[0024] Furthermore, the pretreatment includes degreasing, alkaline etching, and ash removal.

[0025] Furthermore, the degreasing and alkaline etching process involves immersing the ADC12 cast aluminum alloy substrate in a degreasing and alkaline etching solution for degreasing and alkaline etching, followed by rinsing with water. The degreasing and alkaline etching solution comprises 30–40 g / L NaOH, 25–35 g / L Na2CO3, 15–30 g / L NaHCO3, 25–40 g / L NaH2PO4, 5–8 g / L Tween-60, 25–35 g / L Na2SiO3, with the remainder being deionized water. The working temperature of the degreasing and alkaline etching solution is 65–75°C, and the time is 5–10 minutes. During operation, an 80–120 g / L sodium hydroxide solution is used to adjust the pH value of the degreasing and alkaline etching solution to 6.5–8.5.

[0026] Furthermore, the ash removal process involves immersing the degreased and alkali-etched ADC12 cast aluminum alloy substrate in an ash removal solution for ash removal, followed by rinsing with water. The ash removal solution comprises 65–80 mL / L H2SO4, 3–5 mL / L HF, and the remainder being deionized water. The H2SO4 is 98 wt% H2SO4, and the HF is 40 wt%–45 wt% HF. The working temperature of the ash removal solution is 25–55°C, and the time is 45–180 s.

[0027] Furthermore, the anodizing process includes post-treatment, which includes hot water washing, hot air blowing, and drying.

[0028] Furthermore, the temperature of the hot water wash is 50-65℃ and the time is 30-120s; the temperature of the hot air blower is 80-90℃ and the time is 3-5min; the temperature of the drying is 100-150℃ and the time is 5-10min.

[0029] The beneficial effects of this invention are:

[0030] 1. The self-sealing anodizing solution for ADC12 cast aluminum alloy of the present invention ensures the smooth production of anodized layer of ADC12 cast aluminum alloy, while also obtaining a sealing layer with excellent self-healing properties, bonding strength and density, reducing process steps, improving efficiency and reducing costs, and its preparation and application are simple, environmentally friendly and pollution-free.

[0031] 2. The self-sealing anodizing solution for ADC12 cast aluminum alloy of this invention uses unconventional alkaline anodizing, which effectively avoids the defect that ADC12 cast aluminum alloy cannot be anodized in acidic electrolyte due to its high copper content (because the dissolution of copper and aluminum will cause the oxide film to be loose, thus affecting the bonding force and other mechanical properties). At the same time, the sulfonated wetting agent in the anodizing solution can effectively suppress the graying phenomenon caused by high Si content (because the empty electron sites of sulfur atoms in sulfonate ions actively attack silicon atoms and share electrons, thereby suppressing the appearance of silica ash), thus giving full play to the performance and advantages after anodizing.

[0032] 3. The self-sealing anodizing solution for ADC12 cast aluminum alloy of the present invention utilizes cerium ions in the anodizing solution to simultaneously generate corresponding oxides and hydroxides to fill the porous layer of the anodizing film while anodizing the ADC12 cast aluminum alloy, thereby playing a sealing role. Furthermore, the corrosion inhibitor in the electrolyte first complexes with the cerium ions to avoid premature precipitation of cerium ions, which would affect the stability and service life of the anodizing solution.

[0033] 4. In the self-sealing anodizing solution for ADC12 cast aluminum alloy of the present invention, the corrosion inhibitor coordinated with cerium actively adheres to the surface of the ADC12 cast aluminum alloy substrate during the anodizing stage, avoiding the need to use additives such as tartaric acid to control the pore size of the porous layer (because the presence of the inhibitor causes different oxidation corrosion rates at different locations in the porous structure due to the different radii of curvature, and this phenomenon can be used to indirectly control the pore size). The inhibitor also migrates into the porous layer during its formation, indirectly ensuring the stability of the sealing layer (because the corrosion inhibitor actively adheres to the surface of the ADC12 cast aluminum alloy substrate, and the corrosion inhibitor and cerium...). Ion complexation ensures that the sealing layer is formed on the ADC12 cast aluminum alloy substrate and enhances the bonding force between the sealing layer and the ADC12 cast aluminum alloy substrate (it can be confirmed that the corrosion inhibitor is attached to the surface of the ADC12 cast aluminum alloy substrate, and since the corrosion inhibitor and cerium ions have been pre-coordinated, it indirectly ensures that the cerium ions are connected to the ADC12 cast aluminum alloy substrate, thus ensuring that the bonding force is enhanced to a certain extent). The subsequent heat treatment further enhances the bonding force of the sealing layer (heat treatment will cause crystallization of the microstructure, and the presence of crystallization is obviously beneficial to the improvement of the bonding force).

[0034] 5. The self-sealing anodic oxide solution for ADC12 cast aluminum alloy of this invention provides a sealing layer with excellent self-healing properties. That is, if the sealing layer structure is damaged, it can spontaneously repair itself within a short period of time without external action, effectively ensuring the corrosion resistance of the ADC12 cast aluminum alloy anodic oxide film. The self-healing principle of the sealing layer of this invention is as follows:

[0035] 2Ce(OH)3→Ce2O3+3H2O (1)

[0036] 4Ce 3+ +O2+12OH - +2H2O→4Ce(OH)4 (2)

[0037] Ce(OH)4 → CeO2 + 2H2O (3)

[0038] When the ADC12 cast aluminum alloy substrate is scratched and punctured, the Ce(OH)3 inside is exposed and reacts (1) to release trivalent cerium ions (Ce). 3+ The trivalent cerium ion (Ce) 3+ It will further react with hydroxide ions to generate Ce(OH)4 (the self-sealing anodizing solution for ADC12 cast aluminum alloy of this invention avoids the use of oxidants such as hydrogen peroxide. Through the electron-withdrawing effect of the corrosion inhibitor in this anodizing solution, it promotes the growth of Ce). 3+ To Ce 4+ (The transformation), in which a portion of Ce(OH)4 is subsequently transformed into CeO2, so the new sealing layer composed of Ce(OH)4 and CeO2 will once again seal the exposed ADC12 cast aluminum alloy substrate, i.e., self-healing sealing effect.

[0039] 6. The self-sealing anodizing solution for ADC12 cast aluminum alloy of the present invention can obtain a porous layer different from acidic anodizing by controlling the corrosion inhibitor. That is, the porous layer obtained by the present invention exhibits a feather-like shape on a macroscopic scale (because the presence of the inhibitor causes the oxidation corrosion rate to be different in different places in the porous structure due to the different radii of curvature, thus exhibiting a feather-like shape). This provides a basis for the anodizing layer to have dual-repellent properties (the above-mentioned macroscopic feather-like shape exhibits a micro-nano structure on a microscopic scale, and the micro-nano structure is a necessary condition for dual-repellent properties). At the same time, it can further enhance the performance of the sealing layer (the presence of dual-repellent properties can avoid or reduce the residence time of oil stains and water stains, that is, reduce the degree of "corrosion" on the sealing layer, thus further enhancing its own performance). Detailed Implementation

[0040] The present invention will be further explained below with reference to the embodiments. The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0041] The water of crystallization in the following compounds is not included in the mass calculation.

[0042] A self-sealing anodizing solution for ADC12 cast aluminum alloy comprises: phosphate and / or borates, cerium salts, corrosion inhibitors, pH buffers, sulfonating wetting agents, and deionized water;

[0043] The phosphate and / or borate is one or more of sodium phosphate, sodium pyrophosphate, sodium metaphosphate, sodium tripolyphosphate, sodium tetraborate, sodium metaborate, aluminum borate, and aluminum metaborate.

[0044] The cerium salt is one or more of cerium trichloride, cerium triiodide, cerium carbonate, cerium acetate, and cerium phosphate;

[0045] The corrosion inhibitor is one or more of benzotriazole, polyaspartic acid, and pyridine;

[0046] The pH buffer is one of sodium tetraborate-sodium hydroxide buffer, tris(hydroxymethyl)aminomethane-phosphate buffer, and potassium chloride-sodium hydroxide buffer.

[0047] The sulfonated wetting agent is one or more of succinate sulfonate, lignin sulfonate, alkyl sulfonate, α-olefin sulfonate, and fatty alcohol polyoxyethylene ether sulfonate.

[0048] The phosphate and / or borate concentration is 35–45 g / L, the cerium salt concentration is 15–30 g / L, the corrosion inhibitor concentration is 1–8 g / L, the pH buffer concentration is 15–20 g / L, the sulfonated wetting agent concentration is 1–5 g / L, and the balance is deionized water. The mass of the pH buffer is calculated as the mass of sodium tetraborate + sodium hydroxide, or the mass of tris(hydroxymethyl)aminomethane + phosphate, or the mass of potassium chloride + sodium hydroxide.

[0049] A method for preparing a self-sealing anodizing solution for ADC12 cast aluminum alloy includes the following steps:

[0050] (1) Weigh each component according to the formula amount, and dissolve each component except cerium salt in deionized water to obtain phosphate and / or borate solution, corrosion inhibitor solution, pH buffer solution, and sulfonated wetting agent solution.

[0051] (2) Under stirring conditions, add cerium salt to the corrosion inhibitor solution and stir thoroughly;

[0052] (3) Under stirring conditions, phosphate and / or borate solution, sulfonated wetting agent solution and pH buffer solution are added to the solution obtained in step (2) in sequence and stirred until the solution is homogeneous;

[0053] (4) Use sodium hydroxide solution of 80g / L to 120g / L to adjust the pH value of the solution obtained in step (3) to 7.5 to 10.5, and thus obtain the self-sealing anodizing solution of ADC12 cast aluminum alloy.

[0054] The application of a self-sealing anodizing solution for ADC12 cast aluminum alloy in the anodizing of ADC12 cast aluminum alloy includes the following steps:

[0055] (1) Degreasing and alkaline etching: The ADC12 cast aluminum alloy substrate is placed in a degreasing and alkaline etching solution for degreasing and alkaline etching, and then taken out and washed with water; the composition of the degreasing and alkaline etching solution is 30-40 g / L NaOH, 25-35 g / L Na2CO3, 15-30 g / L NaHCO3, 25-40 g / L NaH2PO4, 5-8 g / L Tween-60, 25-35 g / L Na2SiO3, and the balance is deionized water; the working temperature of the degreasing and alkaline etching solution is 65-75℃, the time is 5-10 min, and the pH value of the degreasing and alkaline etching solution is adjusted to 6.5-8.5 using 80-120 g / L sodium hydroxide solution during operation;

[0056] (2) Descaling: The ADC12 cast aluminum alloy substrate after degreasing and alkaline etching is placed in a descaling solution for descaling, and then taken out and washed with water; the composition of the descaling solution is 65-80 mL / L H2SO4, 3-5 mL / L HF, and the balance is deionized water, wherein the H2SO4 is 98 wt% H2SO4 and the HF is 40 wt%-45 wt% HF; the working temperature of the descaling solution is 25-55℃ and the time is 45-180 s;

[0057] (3) Anodizing: The ADC12 cast aluminum alloy substrate after ash removal is placed into the ADC12 cast aluminum alloy self-sealing anodizing solution for anodizing, and then taken out and washed with water; the anodizing temperature is 20-55℃, the DC power supply is 55-75V, and the time is 10-30min; the oxide film thickness obtained by anodizing is 7-35μm.

[0058] (4) Post-treatment: The anodized ADC12 cast aluminum alloy substrate is sequentially washed with hot water, blown with hot air and dried. The temperature of the hot water washing is 50-65℃ and the time is 30-120s; the temperature of the hot air blowing is 80-90℃ and the time is 3-5min; the temperature of the drying is 100-150℃ and the time is 5-10min.

[0059] The corrosion resistance of the components in the following embodiments and comparative examples was tested according to the neutral salt spray test (NSS) and copper accelerated acetic acid salt spray test (CASS) in GB / T12967.3-2022 "Test Methods for Anodized Films and Organic Polymer Films of Aluminum and Aluminum Alloys - Part 3: Salt Spray Test"; the sealing quality was tested according to the sodium phosphate molybdate method in GB / T 8753.1-2017 "Evaluation Method for Sealing Quality of Anodized Films of Aluminum and Aluminum Alloys - Part 1: Acid Immersion Weight Loss Method"; the impact resistance was tested according to the impact test in GB / T 12967.5-2022 "Test Methods for Anodized Films and Organic Polymer Films of Aluminum and Aluminum Alloys - Part 5: Determination of Bursting Resistance"; and the corrosion resistance was tested according to JB / T 7901-2023, "Metallic Materials Laboratory Uniform Corrosion Full Immersion Test Method," involves making scratches on the workpiece with a utility knife, ensuring the scratches reach the aluminum alloy substrate (i.e., penetrate the anodic oxide film). The workpiece is then immersed in a 3.5wt% NaCl solution (with the pH adjusted to 9.0 using 100g / L NaOH solution) for different times (12h, 24h, 48h, 72h, 96h, and 120h). The scratches are then checked for self-healing and corrosion of the workpiece. The 3.5wt% NaCl solution (pH=9.0) is changed daily.

[0060] The dimensions of the ADC12 cast aluminum alloy substrate used in the following embodiments and comparative examples are 0.5 dm in length, 0.5 dm in width, and approximately 1 mm in thickness.

[0061] The degreasing and alkaline etching solutions in the following examples and comparative examples consist of 35 g / L NaOH, 35 g / L Na2CO3, 25 g / L NaHCO3, 35 g / L NaH2PO4, 5 g / L Tween-60, and 30 g / L Na2SiO3, with the remainder being deionized water. The pH is adjusted using a 100 g / L sodium hydroxide solution during operation. The ash removal solutions consist of 65 mL / L 98 wt% H2SO4 and 4 mL / L 40 wt%–45 wt% HF.

[0062] Example 1

[0063] The composition of the ADC12 cast aluminum alloy self-sealing anodizing solution is 45 g / L sodium phosphate, 15 g / L cerium phosphate, 1 g / L benzotriazole, 1 g / L sodium succinate sulfonate (purchased from Shanghai Yiwan Chemical Co., Ltd.) and 15 g / L pH slow-release agent (5 g / L potassium chloride + 10 g / L sodium hydroxide), with the balance being deionized water.

[0064] The preparation process of ADC12 cast aluminum alloy self-sealing anodizing solution is as follows:

[0065] (1) Weigh each component according to the formula amount, and dissolve each component except cerium phosphate in deionized water to obtain sodium phosphate solution, benzotriazole solution, sodium succinate sulfonate solution, and pH slow-release agent solution.

[0066] (2) Under stirring conditions, cerium phosphate was added to the benzotriazole solution and stirred thoroughly;

[0067] (3) Under stirring conditions, sodium phosphate solution, sodium succinate sulfonate solution and pH slow-release agent solution are added to the solution obtained in step (2) in sequence and stirred continuously until the solution is homogeneous;

[0068] (4) Use 100g / L sodium hydroxide solution to adjust the pH value of the solution obtained in step (3) to 10.0 to obtain the ADC12 cast aluminum alloy self-sealing anodizing solution.

[0069] The application of a self-sealing anodizing solution for ADC12 cast aluminum alloy anodizing includes the following steps:

[0070] (1) Degreasing and alkaline etching: The ADC12 cast aluminum alloy substrate was placed in a degreasing and alkaline etching solution at a temperature of 75℃ and a pH value of 7.5 for 5 minutes for degreasing and alkaline etching, and then taken out and washed with water.

[0071] (2) Descaling: The ADC12 cast aluminum alloy substrate after degreasing and alkaline etching is placed in a descaling solution at 35°C for 55 seconds to remove ash, and then taken out and washed with water.

[0072] (3) Anodizing: The ADC12 cast aluminum alloy substrate after ash removal is placed in the ADC12 cast aluminum alloy self-sealing anodizing solution at 45℃ for 30 minutes, and at the same time, a DC power supply is used to apply a voltage of 75V to it for anodizing. The thickness of the anodized film is 25μm. Then it is taken out and washed with water.

[0073] (4) Post-treatment: The anodized ADC12 cast aluminum alloy substrate is washed with hot water at 60℃ for 30s, then blown with hot air at 85℃ for 3min, and finally dried in an oven at 120℃ for 10min.

[0074] Example 2

[0075] The composition of the ADC12 cast aluminum alloy self-sealing anodizing solution is 45g / L sodium phosphate, 15g / L cerium phosphate, 1.5g / L pyridine, 1g / L sodium fatty alcohol polyoxyethylene ether sulfonate (provided by Central South University) and 15g / L pH slow-release agent (5g / L potassium chloride + 10g / L sodium hydroxide), with the balance being deionized water.

[0076] The preparation process of ADC12 cast aluminum alloy self-sealing anodizing solution is as follows:

[0077] (1) Weigh each component according to the formula amount, and dissolve each component except cerium phosphate in deionized water to obtain sodium phosphate solution, pyridine solution, sodium fatty alcohol polyoxyethylene ether sulfonate solution, and pH slow-release agent solution.

[0078] (2) Under stirring conditions, cerium phosphate was added to the pyridine solution and stirred thoroughly;

[0079] (3) Under stirring conditions, sodium phosphate solution, sodium fatty alcohol polyoxyethylene ether sulfonate solution and pH slow-release agent solution are added to the solution obtained in step (2) in sequence and stirred continuously until the solution is homogeneous;

[0080] (4) Use 100g / L sodium hydroxide solution to adjust the pH value of the solution obtained in step (3) to 9.5 to obtain the ADC12 cast aluminum alloy self-sealing anodizing solution.

[0081] The application of a self-sealing anodizing solution for ADC12 cast aluminum alloy anodizing includes the following steps:

[0082] (1) Degreasing and alkaline etching: The ADC12 cast aluminum alloy substrate was placed in a degreasing and alkaline etching solution at a temperature of 75℃ and a pH value of 7.5 for 5 minutes for degreasing and alkaline etching, and then taken out and washed with water.

[0083] (2) Descaling: The ADC12 cast aluminum alloy substrate after degreasing and alkaline etching is placed in a descaling solution at 35°C for 60 seconds to remove ash, and then taken out and washed with water.

[0084] (3) Anodizing: The ADC12 cast aluminum alloy substrate after ash removal is placed in the ADC12 cast aluminum alloy self-sealing anodizing solution at 45℃ for 25 minutes, and at the same time, a DC power supply is used to apply a voltage of 75V to it for anodizing. The thickness of the anodized film is 21μm. Then it is taken out and washed with water.

[0085] (4) Post-treatment: The anodized ADC12 cast aluminum alloy substrate is washed with hot water at 60℃ for 30s, then blown with hot air at 85℃ for 3min, and finally dried in an oven at 120℃ for 10min.

[0086] Example 3

[0087] The composition of the ADC12 cast aluminum alloy self-sealing anodizing solution is 40 g / L sodium tetraborate, 20 g / L cerium carbonate, 2.5 g / L polyaspartic acid (purchased from Jinan Delan Chemical Co., Ltd.), 3 g / L sodium lignosulfonate (purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., S140863) and 15 g / L pH slow-release agent (5 g / L potassium chloride + 10 g / L sodium hydroxide), with the balance being deionized water.

[0088] The preparation process of ADC12 cast aluminum alloy self-sealing anodizing solution is as follows:

[0089] (1) Weigh each component according to the formula amount, and dissolve each component except cerium carbonate in deionized water to obtain sodium tetraborate solution, polyaspartic acid solution, sodium lignosulfonate solution and pH slow release agent solution.

[0090] (2) Under stirring conditions, cerium carbonate is added to the polyaspartic acid solution and stirred thoroughly;

[0091] (3) Under stirring conditions, sodium tetraborate solution, sodium lignosulfonate solution and pH slow-release agent solution are added to the solution obtained in step (2) in sequence and stirred continuously until the solution is homogeneous;

[0092] (4) Use 100g / L sodium hydroxide solution to adjust the pH value of the solution obtained in step (3) to 9.5 to obtain the ADC12 cast aluminum alloy self-sealing anodizing solution.

[0093] The application of a self-sealing anodizing solution for ADC12 cast aluminum alloy anodizing includes the following steps:

[0094] (1) Degreasing and alkaline etching: The ADC12 cast aluminum alloy substrate was placed in a degreasing and alkaline etching solution at a temperature of 75℃ and a pH value of 7.5 for 5 minutes for degreasing and alkaline etching, and then taken out and washed with water.

[0095] (2) Ash removal: The ADC12 cast aluminum alloy substrate after degreasing and alkaline etching is placed in a 35°C ash removal solution for 60 seconds to remove ash, and then taken out and washed with water.

[0096] (3) Anodizing: The ADC12 cast aluminum alloy substrate after ash removal is placed in the ADC12 cast aluminum alloy self-sealing anodizing solution at 50℃ for 30 minutes, and at the same time, a DC power supply is used to apply a voltage of 65V to it for anodizing. The thickness of the anodized film is 21μm. Then it is taken out and washed with water.

[0097] (4) Post-treatment: The anodized ADC12 cast aluminum alloy substrate is washed with hot water at 60℃ for 30s, then blown with hot air at 85℃ for 3min, and finally dried in an oven at 120℃ for 10min.

[0098] Comparative Example 1

[0099] The anodizing solution consists of 40 g / L sodium tetraborate, 25 g / L cerium carbonate, 3 g / L sodium lignosulfonate (purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., S140863) and 15 g / L pH slow-release agent (5 g / L potassium chloride + 10 g / L sodium hydroxide), with the remainder being deionized water.

[0100] The preparation process of the anodizing solution is as follows:

[0101] (1) Weigh each component according to the formula amount, and dissolve each component except cerium carbonate in deionized water to obtain sodium tetraborate solution, sodium lignosulfonate solution and pH slow release agent solution.

[0102] (2) Under stirring conditions, sodium tetraborate solution, sodium lignosulfonate solution and pH buffer solution are mixed, and then cerium carbonate is added to it and stirred continuously until the solution is homogeneous;

[0103] (3) Adjust the pH of the solution obtained in step (2) to 9.5 using a 100 g / L sodium hydroxide solution to obtain the anodic oxide solution.

[0104] The application of anodizing solution to ADC12 cast aluminum alloy anodizing includes the following steps:

[0105] (1) Degreasing and alkaline etching: The ADC12 cast aluminum alloy substrate was placed in a degreasing and alkaline etching solution at a temperature of 75℃ and a pH value of 7.5 for 5 minutes for degreasing and alkaline etching, and then taken out and washed with water.

[0106] (2) Ash removal: The ADC12 cast aluminum alloy substrate after degreasing and alkaline etching is placed in a 35°C ash removal solution for 60 seconds to remove ash, and then taken out and washed with water.

[0107] (3) Anodizing: The ADC12 cast aluminum alloy substrate after ash removal is placed in anodizing solution at 50℃ for 30 minutes, and a DC power supply is used to apply a voltage of 65V to it for anodizing. The thickness of the anodized film is 20μm. Then it is taken out and washed with water.

[0108] (4) Post-treatment: The anodized ADC12 cast aluminum alloy substrate is washed with hot water at 60℃ for 30s, then blown with hot air at 85℃ for 3min, and finally dried in an oven at 120℃ for 10min.

[0109] Comparative Example 2

[0110] The anodizing solution consists of 40 g / L sodium tetraborate, 3 g / L sodium lignosulfonate (purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., S140863), and 15 g / L pH slow-release agent (5 g / L potassium chloride + 10 g / L sodium hydroxide), with the remainder being deionized water.

[0111] The preparation process of the anodizing solution is as follows:

[0112] (1) Weigh each component according to the formula amount, and dissolve each component in deionized water to obtain sodium tetraborate solution, sodium lignosulfonate solution and pH slow release agent solution.

[0113] (2) Under stirring conditions, the sodium tetraborate solution, sodium lignosulfonate solution and pH slow-release agent solution are mixed and stirred continuously until the solution is homogeneous;

[0114] (3) Use 100g / L sodium hydroxide solution to adjust the pH of the solution obtained in step (2) to 9.5 to obtain the anodic oxide solution.

[0115] The application of anodizing solution to ADC12 cast aluminum alloy anodizing includes the following steps:

[0116] (1) Degreasing and alkaline etching: The ADC12 cast aluminum alloy substrate was placed in a degreasing and alkaline etching solution at a temperature of 75℃ and a pH value of 7.5 for 5 minutes for degreasing and alkaline etching, and then taken out and washed with water.

[0117] (2) Ash removal: The ADC12 cast aluminum alloy substrate after degreasing and alkaline etching is placed in a 35°C ash removal solution for 60 seconds to remove ash, and then taken out and washed with water.

[0118] (3) Anodizing: The ADC12 cast aluminum alloy substrate after ash removal is placed in anodizing solution at 50℃ for 30 minutes, and a DC power supply is used to apply a voltage of 65V to it for anodizing. The thickness of the anodized film is 22μm. Then it is taken out and washed with water.

[0119] (4) Post-treatment: The anodized ADC12 cast aluminum alloy substrate is washed with hot water at 60℃ for 30s, then blown with hot air at 85℃ for 3min, and finally dried in an oven at 120℃ for 10min.

[0120] The components obtained from each embodiment and comparative example were subjected to performance tests, and the test results are shown in Table 1.

[0121] Table 1

[0122] Neutral Salt Spray Test (NSS) Copper-Accelerated Acetic Acid Salt Spray Test (CASS) Acid etching weight loss method - sodium molybdate phosphate method Impact resistance test Self-healing performance Example 1 Level 10 Level 10 0 mg / dm 2 ]] No cracks, no peeling The scratch initially healed after 24 hours and was completely healed after 72 hours, with no signs of corrosion. Example 2 Level 10 Level 10 0 mg / dm 2 ]] No cracks, no peeling The scratch initially healed after 24 hours and was completely healed after 72 hours, with no signs of corrosion. Example 3 Level 10 Level 10 0 mg / dm 2 ]] No cracks, no peeling The scratch initially healed after 24 hours and was completely healed after 72 hours, with no signs of corrosion. Comparative Example 1 9 levels Level 8 0.2 mg / dm 2 ]]> No peeling, slight cracking The scratches show no signs of healing, and the corrosion at the scratches is severe, with the corrosion area expanding. Comparative Example 2 Level 0 Level 0 Severe corrosion, weight not calculated. slight peeling Not tested (its corrosion resistance doesn't even meet the standards).

[0123] A comparison of Examples 1-3 with Comparative Example 1 shows that, due to the lack of corrosion inhibitor, the sealing layer has no self-healing properties. A comparison of Examples 1-3, Comparative Example 1, and Comparative Example 2 shows that, without cerium salt, the anodic oxide solution lacks the properties of a sealing layer, let alone self-healing properties.

Claims

1. A self-sealing anodizing solution for ADC12 cast aluminum alloy, characterized in that, include: Phosphates and / or borates, cerium salts, corrosion inhibitors, pH buffers, sulfonated wetting agents, and deionized water; The phosphate and / or borate is one or more of sodium phosphate, sodium pyrophosphate, sodium metaphosphate, sodium tripolyphosphate, sodium tetraborate, sodium metaborate, aluminum borate, and aluminum metaborate. The cerium salt is one or more of cerium trichloride, cerium triiodide, cerium carbonate, cerium acetate, and cerium phosphate; The corrosion inhibitor is one or more of benzotriazole, polyaspartic acid, and pyridine; The pH buffer is one of sodium tetraborate-sodium hydroxide buffer, tris(hydroxymethyl)aminomethane-phosphate buffer, and potassium chloride-sodium hydroxide buffer. The sulfonated wetting agent is one or more of succinate sulfonate, lignin sulfonate, alkyl sulfonate, α-olefin sulfonate, and fatty alcohol polyoxyethylene ether sulfonate. The phosphate and / or borate concentration is 35–45 g / L, the cerium salt concentration is 15–30 g / L, the corrosion inhibitor concentration is 1–8 g / L, the pH buffer concentration is 15–20 g / L, the sulfonated wetting agent concentration is 1–5 g / L, and the balance is deionized water. The mass of the pH buffer is calculated as the mass of sodium tetraborate + sodium hydroxide, or the mass of tris(hydroxymethyl)aminomethane + phosphate, or the mass of potassium chloride + sodium hydroxide.

2. The method for preparing a self-sealing anodizing solution for ADC12 cast aluminum alloy according to claim 1, characterized in that, Includes the following steps: (1) Weigh each component according to the formula amount, and dissolve each component except cerium salt in deionized water to obtain phosphate and / or borate solution, corrosion inhibitor solution, pH buffer solution, and sulfonated wetting agent solution. (2) Under stirring conditions, add cerium salt to the corrosion inhibitor solution and stir thoroughly; (3) Under stirring conditions, phosphate and / or borate solution, sulfonated wetting agent solution and pH buffer solution are added to the solution obtained in step (2) in sequence and stirred until the solution is homogeneous; (4) Use sodium hydroxide solution to adjust the pH value of the solution obtained in step (3) to 7.5 to 10.5, and thus obtain the ADC12 cast aluminum alloy self-sealing anodizing solution.

3. The method for preparing a self-sealing anodizing solution for ADC12 cast aluminum alloy according to claim 2, characterized in that, The sodium hydroxide solution mentioned in step (4) is a sodium hydroxide solution with a concentration of 80 g / L to 120 g / L.

4. The application of the self-sealing anodizing solution for ADC12 cast aluminum alloy as described in claim 1 in the anodizing of ADC12 cast aluminum alloy.

5. The application according to claim 4, characterized in that, When applying, Includes the following steps: Anodizing: The pretreated ADC12 cast aluminum alloy substrate is placed in the ADC12 cast aluminum alloy self-sealing anodizing solution for anodizing, and then taken out and washed with water; the anodizing temperature is 20-55℃, the DC power supply is 55-75V, and the time is 10-30min; the oxide film thickness obtained by anodizing is 7-35μm.

6. The application according to claim 5, characterized in that, The pretreatment includes degreasing, alkaline etching, and ash removal.

7. The application according to claim 6, characterized in that, The degreasing and alkaline etching process involves immersing the ADC12 cast aluminum alloy substrate in a degreasing and alkaline etching solution for degreasing and alkaline etching, followed by rinsing with water. The composition of the degreasing and alkaline etching solution is 30–40 g / L NaOH, 25–35 g / L Na2CO3, 15–30 g / L NaHCO3, 25–40 g / L NaH2PO4, 5–8 g / L Tween-60, 25–35 g / L Na2SiO3, with the remainder being deionized water. The working temperature of the degreasing and alkaline etching solution is 65–75°C, and the time is 5–10 minutes. During operation, an 80–120 g / L sodium hydroxide solution is used to adjust the pH value of the degreasing and alkaline etching solution to 6.5–8.

5.

8. The application according to claim 6, characterized in that, The ash removal process involves immersing the degreased and alkali-etched ADC12 cast aluminum alloy substrate in an ash removal solution for ash removal, followed by rinsing with water. The ash removal solution consists of 65–80 mL / L H2SO4, 3–5 mL / L HF, with the remainder being deionized water. The H2SO4 is 98 wt% H2SO4, and the HF is 40 wt%–45 wt% HF. The working temperature of the ash removal solution is 25–55°C, and the time is 45–180 seconds.

9. The application according to claim 5, characterized in that, Anodizing is followed by post-treatment, which includes hot water washing, hot air blowing, and drying.

10. The application according to claim 9, characterized in that, The hot water washing temperature is 50-65℃, and the time is 30-120s; the hot air blowing temperature is 80-90℃, and the time is 3-5min; the drying temperature is 100-150℃, and the time is 5-10min.