Corrosion-resistant magnesium alloy chromium-free passivation solution and preparation method thereof

Abstract

The application discloses a kind of corrosion-resistant magnesium alloy chromium-free passivation solution and preparation method thereof.The corrosion-resistant magnesium alloy chromium-free passivation solution includes the following raw materials by weight percentage 2-10% coupling agent;0.2-1.6% cerium nitrate;0.5-5% fluorotitanic acid ammonia;0.2-3% lauryl betaine;the balance is water.The corrosion-resistant magnesium alloy chromium-free passivation solution of the application has the following advantages: effectively improve the corrosion resistance and coating adhesion of magnesium alloy;Chemical reaction forms stable, uniform, corrosion-resistant protective film, significantly prolongs the service life of magnesium alloy;Since the use of chromium is avoided, the potential harm to the environment and human body is reduced;Raw materials are easy to get, low cost, suitable for large-scale application.The application improves the application value of magnesium alloy, and has wide industrial application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of corrosion-resistant magnesium alloy chromium-free passivation solution and its preparation method. BACKGROUND

[0002] Magnesium alloy, this light metal material, because its lightest metal structure characteristics, high proportion of strength and weight, stiffness and weight ratio, and its strong impact and vibration energy absorption capacity, in aviation, aerospace, automobile, instrument and electronics and other various industrial fields have been widely used.The extensive applicability makes magnesium alloy gradually rise, and develops into the third largest metal engineering material after steel and aluminum.Because of its many advantages, magnesium alloy is known as "the green engineering material of 21st century".

[0003] However, although magnesium alloy has many excellent properties, its corrosion properties in humid environment are worrying.Due to its fast corrosion rate in humid environment, this problem has seriously limited the use of magnesium alloy range.For this problem, how to carry out surface treatment on magnesium alloy to improve its corrosion resistance has become an important research task.In all treatment methods, using passivation solution for treatment is proved to be a significant anticorrosion method.

[0004] Passivation solution is a special solution that can form a solid and stable oxide film or compound film on the metal surface to prevent or slow down the chemical reaction between the metal and the environment medium.Passivation treatment has a significant effect on improving the corrosion resistance of magnesium alloy, but it also affects other properties of the material, such as electrochemical performance, conductivity, etc.

[0005] At present, passivation solution is mainly divided into two categories: solution containing hexavalent chromium (chromate) and solution not containing hexavalent chromium (non-chromate).After treatment with chromium-containing passivation solution, the corrosion resistance and coating adhesion of magnesium alloy surface can be significantly improved, but hexavalent chromium is harmful to the environment and human health.On the other hand, although non-chromium passivation solution is environmentally friendly, the treated product often fails to achieve the expected effect in terms of corrosion resistance, surface resistance and coating adhesion.Therefore, it is urgent to develop a chromium-free passivation solution with high corrosion resistance and good passivation treatment effect.However, such a passivation solution has not yet appeared in the current research.

[0006] Surface treatment technology of magnesium alloy plays a crucial role, which directly determines the service life, maintenance cost and application field of magnesium alloy and many other factors.How to find a new type of passivation solution that can balance environmental protection and performance has become a major challenge in the field of metal surface treatment.

[0007] However, to achieve this goal, we must first understand the working principle and mechanism of passivation solution. Passivation solution can improve the corrosion resistance of metal by forming a protective film on the metal surface. This protective film is composed of oxides or compounds, which can effectively prevent the chemical reaction between metal and environment, thereby achieving the effect of corrosion protection.

[0008] In addition, although the passivation solution can significantly improve the corrosion resistance of metal, it will also affect other properties of the metal, such as electrochemical performance, electrical conductivity, etc. Therefore, when looking for new passivation solution, these factors also need to be considered to ensure that the new passivation solution can not only improve the corrosion resistance of metal, but also will not adversely affect other properties of the metal.

[0009] In summary, for the surface treatment technology of magnesium alloy, it is an urgent task to find a new passivation solution that does not contain chromium, has high corrosion resistance and good passivation treatment effect. This requires us to conduct in-depth research and exploration in order to protect the environment and human health while improving the performance of magnesium alloy and expanding its application range. SUMMARY

[0010] In view of the deficiencies in the prior art, the technical problem to be solved by the present application is to provide a corrosion-resistant magnesium alloy chromium-free passivation solution and a preparation method thereof.

[0011] The specific technical solutions of the present application are as follows:

[0012] A corrosion-resistant magnesium alloy chromium-free passivation solution comprises the following raw materials by weight percentage:

[0013] 2-10% coupling agent;

[0014] 0.2-1.6% cerium nitrate;

[0015] 0.5-5% fluorotitanic acid ammonia;

[0016] 0.2-3% lauryl betaine;

[0017] The balance is water.

[0018] Preferably, a corrosion-resistant magnesium alloy chromium-free passivation solution comprises the following raw materials by weight percentage:

[0019] 3-7% coupling agent;

[0020] 0.4-1.2% cerium nitrate;

[0021] 1-3% fluorotitanic acid ammonia;

[0022] 0.4-2% lauryl betaine;

[0023] The balance is water.

[0024] Preferably, the chromium-free passivation solution for corrosion-resistant magnesium alloy comprises the following raw materials by weight percentage:

[0025] 4-6% coupling agent;

[0026] 0.6-1.0% cerium nitrate;

[0027] 1.5-2.5% ammonium fluorotitanate;

[0028] 0.7-1.5% lauryl betaine;

[0029] and the balance is water.

[0030] Preferably, the coupling agent is at least one selected from the group consisting of γ-methacryloxy methyl dimethoxy silane, ethyl acetate trimethoxy silane, 3-nitropropyl trimethoxy silane, 3-methyl benzoate trimethoxy silane, γ-glycerate trimethoxy silane, 3-methyl propionate triethoxy silane, 3-vinyloxy propyl triethoxy silane, 3-isopropylate triethoxy silane, 3-ethyl phenylacetate trimethoxy silane, 3-ethyl hexanoate trimethoxy silane, γ-methacryloxy propyl trimethoxy silane, silane coupling agent KH-560 (γ-aminopropyl triethoxy silane), 3-chloropropyl methyl dimethyl silane, 3-mercuric propyl trimethoxy silane, 3-mercuric propyl triethoxy silane, ethyl silicate, methyl disilazane, isocyanate silane coupling agent, 3-methyl methyl propionate trimethoxy silane and 3-ethyl sulfate trimethoxy silane.

[0031] Preferably, the coupling agent consists of isocyanate silane coupling agent and γ-aminopropyl triethoxy silane. Further preferably, the coupling agent consists of 0.5-2 parts by weight of isocyanate silane coupling agent and 1 part by weight of γ-aminopropyl triethoxy silane.

[0032] The isocyanate silane coupling agent is one of γ-isocyanate propyl triethoxy silane, 3-isocyanate propyl trimethoxy silane, 3-isocyanate propyl methyl dimethoxy silane and 1,3,5-tri (trimethoxy silane propyl) isocyanurate.

[0033] Further preferably, the chromium-free passivation solution for corrosion-resistant magnesium alloy further comprises 0.4-1.4% zirconium ammonium carbonate.

[0034] The application also provides a preparation method of the chromium-free passivation solution for corrosion-resistant magnesium alloy, and the specific steps are as follows: uniformly mixing the raw materials.

[0035] The application also provides an application of the chromium-free passivation solution for corrosion-resistant magnesium alloy in the passivation treatment of the surface of magnesium alloy.

[0036] Specifically, the magnesium alloy is immersed in a corrosion-resistant, chromium-free passivation solution at room temperature for 10-300 seconds (preferably 60-240 seconds) or coated, and then dried. Ideally, the magnesium alloy surface should be pre-treated by cleaning before passivation.

[0037] The chromium-free passivation solution for corrosion-resistant magnesium alloys of the present invention has the following advantages: 1) It effectively improves the corrosion resistance and coating adhesion of magnesium alloys; 2) The chemical reaction forms a stable, uniform, and corrosion-resistant protective film, significantly extending the service life of magnesium alloys; 3) By avoiding the use of chromium, it reduces potential harm to the environment and human health; 4) The raw materials are readily available and the cost is low, making it suitable for large-scale applications. This invention enhances the application value of magnesium alloys and has broad prospects for industrial application. Detailed Implementation

[0038] This invention provides a corrosion-resistant, chromium-free passivation solution for magnesium alloys, comprising the following raw materials by weight percentage:

[0039] 2-10% coupling agent;

[0040] 0.2-1.6% cerium nitrate;

[0041] 0.5-5% Ammonium fluorotitanate;

[0042] 0.2-3% lauryl betaine;

[0043] The remainder is water.

[0044] Preferably, a corrosion-resistant magnesium alloy chromium-free passivation solution comprises the following raw materials by weight percentage:

[0045] 2-10% coupling agent;

[0046] 0.2-1.6% cerium nitrate;

[0047] 0.5-5% Ammonium fluorotitanate;

[0048] 0.2-3% lauryl betaine;

[0049] 0.4-1.4% ammonium zirconium carbonate;

[0050] The remainder is water.

[0051] The coupling agent is selected from at least one of γ-methacrylate oxymethyl dimethoxysilane, ethyl acetate trimethoxysilane, 3-nitropropyltrimethoxysilane, methyl 3-benzoate trimethoxysilane, γ-glycerate trimethoxysilane, methyl 3-propionate triethoxysilane, 3-vinyloxypropyltriethoxysilane, 3-isopropionate triethoxysilane, ethyl 3-phenylacetate trimethoxysilane, ethyl 3-hexanoate trimethoxysilane, γ-methacrylate oxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, 3-chloropropylmethyldimethylsilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, ethyl silicate, methyldisilazane, isocyanate silane coupling agent, methyl 3-methylpropionate trimethoxysilane, and 3-ethyltrimethoxysilane sulfate.

[0052] Preferably, the coupling agent is composed of isocyanate-based silane coupling agent and γ-aminopropyltriethoxysilane. More preferably, the coupling agent is composed of 0.5-2 parts by weight of isocyanate-based silane coupling agent and 1 part by weight of γ-aminopropyltriethoxysilane.

[0053] The isocyanate-based silane coupling agent is one of γ-isocyanate-propyltriethoxysilane, 3-isocyanate-propyltrimethoxysilane, 3-isocyanate-propylmethyldimethoxysilane, and 1,3,5-tris(trimethoxysilylpropyl)isocyanurate.

[0054] Coupling agents play a crucial role in forming passivation films. One end of the coupling agent contains functional groups that can chemically react with the magnesium alloy surface, while the other end contains silicon-oxygen bonds that can react with other components. In this way, the coupling agent can form a uniform silicon oxide film on the magnesium alloy surface, significantly enhancing the adhesion between the coating and the magnesium alloy surface. In an aqueous environment, the coupling agent generates SiOH groups, which react with the magnesium alloy surface to form a silicon oxide film. This film effectively prevents direct contact between external substances and the magnesium alloy surface, reducing its corrosion rate.

[0055] The addition of cerium nitrate further enhances the performance of the protective film. Its cerium ions can form stable compounds on the magnesium alloy surface and crystallize into a robust film. This film not only has excellent corrosion resistance to various environmental conditions, but also has strong hardness and adhesion, making the bond between the magnesium alloy surface and other coating materials tighter.

[0056] Ammonium fluorotitanate is an effective film-forming substance. It can form a stable compound film containing titanium on the surface of magnesium alloys. This compound film has very high stability and corrosion resistance, and is a key component in improving the corrosion resistance of magnesium alloys.

[0057] Lauryl betaine, as a surfactant, can reduce the surface tension of the passivation solution and increase its wettability on the magnesium alloy surface, allowing coupling agents and other inorganic substances to adhere uniformly to the magnesium alloy surface, thus forming a more uniform and dense protective film. Simultaneously, as a crosslinking agent between organic and inorganic substances, lauryl betaine can promote the chemical reaction between the coupling agent and inorganic substances such as cerium nitrate, further enhancing the density and adhesion of the protective film.

[0058] In this invention, the addition of ammonium zirconium carbonate plays a crucial role. Ammonium zirconium carbonate plays an extremely critical role in this invention, enhancing the stability and corrosion resistance of the passivation film through its reaction with the SiOH groups in the coupling agent. (1) Providing a zirconium source: Ammonium zirconium carbonate is an important zirconium source, which can release Zr4+ ions in a liquid environment. These ions can form a protective oxide film on the surface of magnesium alloys. This oxide film plays a key role in preventing corrosion of magnesium alloys and protecting their physical and chemical properties. At the same time, this oxide film has strong hardness and adhesion, which makes it possible to combine with other coating materials. (2) Promoting crosslinking: Due to the high activity of zirconium hydroxyl (Zr-OH), it can react with the SiOH groups in the coupling agent to form a stable zirconium silicate structure, which plays an important role in improving the stability and adhesion of the passivation film. This crosslinking reaction not only makes the internal structure of the passivation film more uniform, but also greatly improves the stability and corrosion resistance of the film. (3) Hydrogen bond formation: The zirconium hydroxyl group (Zr-OH) of ammonium zirconium carbonate can form hydrogen bonds with water, SiOH groups in coupling agents, etc. The formation of these hydrogen bonds is beneficial to the structural stability of the passivation film, preventing film rupture and peeling, thereby improving the durability of the film. In summary, ammonium zirconium carbonate in this invention greatly improves the stability, adhesion, and corrosion resistance of the passivation film by providing a zirconium source, promoting cross-linking, and forming hydrogen bonds, thereby protecting the physical and chemical properties of the magnesium alloy and extending its service life.

[0059] In summary, each raw material plays a unique role in the passivation process of magnesium alloys. However, these raw materials do not exist in isolation, but rather interact and promote each other through various complex chemical reactions, forming a synergistic effect. For example, coupling agents, cerium nitrate, and ammonium fluorotitanate all contribute to the formation of a stable and dense passivation film, while lauryl betaine enhances the adhesion of these raw materials to the magnesium alloy surface, making the protective film more uniform and compact. Simultaneously, because lauryl betaine promotes the cross-linking reaction between organic and inorganic substances, it allows inorganic substances such as cerium nitrate and ammonium fluorotitanate to better combine with the coupling agent, enhancing the density and adhesion of the protective film.

[0060] The above analysis shows that the raw materials in the chromium-free passivation solution for magnesium alloys are not simply stacked together, but rather interact to form a highly efficient, stable, and corrosion-resistant protective film. This protective film not only prevents the magnesium alloy from being oxidized and corroded by oxygen in the environment, but also enhances the adhesion between the magnesium alloy and other coating materials, further extending the service life of the magnesium alloy and improving its application value. Therefore, this corrosion-resistant chromium-free passivation solution for magnesium alloys has high practical value and broad application prospects.

[0061] Example 1

[0062] A corrosion-resistant magnesium alloy chromium-free passivation solution comprises the following raw materials by weight percentage: 5% coupling agent; 0.8% cerium nitrate; 2.0% ammonium fluorotitanate; 1.0% lauryl betaine; and the balance being water.

[0063] The coupling agent is γ-aminopropyltriethoxysilane.

[0064] Lauryl betaine was dissolved in water at room temperature, and then a coupling agent, cerium nitrate, and ammonium fluorotitanate were added. The mixture was stirred at 500 rpm for 2 hours to obtain the corrosion-resistant magnesium alloy chromium-free passivation solution of the present invention.

[0065] Example 2

[0066] A corrosion-resistant magnesium alloy chromium-free passivation solution comprises the following raw materials by weight percentage: 5% coupling agent; 0.8% cerium nitrate; 2.0% ammonium fluorotitanate; 1.0% lauryl betaine; 0.9% ammonium zirconium carbonate; and the balance being water.

[0067] The coupling agent is γ-aminopropyltriethoxysilane.

[0068] Lauryl betaine was dissolved in water at room temperature, and then a coupling agent, cerium nitrate, ammonium fluorotitanate, and ammonium zirconium carbonate were added. The mixture was stirred at 500 rpm for 2 hours to obtain the corrosion-resistant magnesium alloy chromium-free passivation solution of the present invention.

[0069] Example 3

[0070] A corrosion-resistant magnesium alloy chromium-free passivation solution comprises the following raw materials by weight percentage: 5% coupling agent; 0.8% cerium nitrate; 2.0% ammonium fluorotitanate; 1.0% lauryl betaine; 0.9% ammonium zirconium carbonate; and the balance being water.

[0071] The coupling agent is 3-isocyanate-propyltrimethoxysilane.

[0072] Lauryl betaine was dissolved in water at room temperature, and then a coupling agent, cerium nitrate, ammonium fluorotitanate, and ammonium zirconium carbonate were added. The mixture was stirred at 500 rpm for 2 hours to obtain the corrosion-resistant magnesium alloy chromium-free passivation solution of the present invention.

[0073] Example 4

[0074] A corrosion-resistant magnesium alloy chromium-free passivation solution comprises the following raw materials by weight percentage: 5% coupling agent; 0.8% cerium nitrate; 2.0% ammonium fluorotitanate; 1.0% lauryl betaine; 0.9% ammonium zirconium carbonate; and the balance being water.

[0075] The coupling agent is a combination of 3-isocyanate-propyltrimethoxysilane and γ-aminopropyltriethoxysilane in a 1:1 mass ratio.

[0076] Lauryl betaine was dissolved in water at room temperature, and then a coupling agent, cerium nitrate, ammonium fluorotitanate, and ammonium zirconium carbonate were added. The mixture was stirred at 500 rpm for 2 hours to obtain the corrosion-resistant magnesium alloy chromium-free passivation solution of the present invention.

[0077] Test Example 1:

[0078] Wipe the surface of the AZ31B magnesium alloy plate (100mm×50mm×5mm) provided by Dongguan Feitai Metal Products Co., Ltd. clean, ultrasonically clean it with distilled water, and dry it for later use.

[0079] The magnesium alloy plate was immersed in a corrosion-resistant chromium-free passivation solution for 150 seconds at room temperature (25°C), then dried at 70°C for 10 minutes and then naturally cooled to room temperature.

[0080] (a) Corrosion resistance test:

[0081] The neutral salt spray test, as defined in GB / T 10125-2021 (Artificial Atmosphere Corrosion Test - Salt Spray Test), involves subjecting the material to a 5% sodium chloride solution spray. Observations are taken every 2 hours to monitor the corroded area. If the corrosion exceeds 5%, the salt spray test is stopped, and the duration (in hours) is recorded. This test method is a rapid way to assess the corrosion resistance of materials, simulating the corrosion process in a real environment. A longer salt spray duration indicates better corrosion resistance in magnesium alloys.

[0082] (II) Electrochemical Testing:

[0083] Sample preparation: Select a magnesium alloy sample covered with a passivation film. Then, seal most of the sample surface with epoxy resin, leaving only a 10mm × 10mm area for the experiment. This part is the working surface for the electrochemical reaction.

[0084] Solution preparation: Prepare a 5% sodium chloride (NaCl) solution. This solution simulates corrosive conditions that may be encountered in the natural environment.

[0085] Sample immersion: Immerse the partially sealed sample in a prepared 5% NaCl solution. The experiment should be conducted at room temperature and no degassing is required.

[0086] Electrochemical measurements: The immersed samples were tested using an advanced electrochemical workstation (AUTOLAB 302N electrochemical workstation, Switzerland). First, the samples were kept still until the corrosion potential stabilized.

[0087] Polarization curve determination: After the corrosion potential stabilizes, the polarization curve is determined using a scan rate of 1 mV / s, thereby obtaining the polarization resistance (kΩ·cm). 2 ) and corrosion current density (μA·cm) -2 (Data).

[0088] Data Analysis: By analyzing the obtained polarization resistance and corrosion current density data, the corrosion resistance of the magnesium alloy passivation film can be evaluated. Ideally, the film should exhibit high polarization resistance and low corrosion current density to demonstrate its good corrosion resistance.

[0089] Table 1: Performance Test Table

[0090] Salt spray time, h Polarization resistance, x 10 3 kΩ·cm 2 ]]> Corrosion current density, x 10 -2 μA-cm -2 ]]> Example 1 88 1.29 5.9 Example 2 112 1.54 4.2 Example 3 116 1.58 4.0 Example 4 128 1.72 3.3

[0091] As can be seen from the data in Table 1, the choice of coupling agent and the addition of ammonium zirconium carbonate have a significant impact on the corrosion resistance of the chromium-free passivation solution for magnesium alloys. In Example 2, the addition of ammonium zirconium carbonate resulted in a significantly better corrosion resistance than in Example 1. In Example 3, changing the type of coupling agent also improved the corrosion resistance.

[0092] First, regarding the selection of coupling agents: Two different coupling agents were used in these four examples. A coupling agent is a compound that can improve interfacial compatibility, thereby improving the adhesion between the coating and the substrate. The coupling agent used in Examples 1 and 2 was γ-aminopropyltriethoxysilane, while in Examples 3 and 4, 3-isocyanate-propyltrimethoxysilane or a combination of both were used. The main function of the coupling agent is to improve the adhesion between the chromium-free passivation solution and the magnesium alloy surface, thereby making the passivation layer more compact and reducing the direct contact between the corrosive medium and the magnesium alloy surface. Therefore, changing the type or combination of coupling agents can significantly affect the corrosion resistance of the magnesium alloy.

[0093] Then, regarding the addition of ammonium zirconium carbonate: ammonium zirconium carbonate was added in Examples 2 / 3 / 4, but not in Example 1. Ammonium zirconium carbonate has a high melting point, high electrical conductivity, and stable chemical properties, which can effectively improve the thermal and electrochemical stability of the coating, thereby extending the corrosion time of the magnesium alloy.

[0094] Comparing Example 2 and Example 1, it can be seen that the addition of ammonium zirconium carbonate significantly improves the anti-corrosion effect, increasing the salt spray time from 88 hours to 112 hours. This may be because the addition of ammonium zirconium carbonate improves the stability and thermal stability of the passivation solution.

[0095] Comparing Example 3 and Example 2, it can be seen that changing the coupling agent improves the corrosion protection effect, and the salt spray time increases from 112 hours to 116 hours. This may be because 3-isocyanate-propyltrimethoxysilane has better compatibility with the magnesium alloy surface and can form a more stable protective layer.

[0096] In corrosion resistance testing, polarization resistance measures the impedance of a material to current. Generally, the higher the polarization resistance, the better the corrosion resistance of the material. Comparing the four examples, we can see that the polarization resistance increases from 1.29 × 10⁻⁶ in Example 1. 3 kΩ·cm 2 Increased to 1.72 × 10 in Example 4 3 kΩ·cm 2 This addition demonstrates that by changing the coupling agent and adding ammonium zirconium carbonate, the polarization resistance of the chromium-free passivation solution for magnesium alloys was increased, thereby improving the corrosion resistance of the material.

[0097] On the other hand, corrosion current density is a parameter used to measure the corrosion rate of a material; the lower the corrosion current density, the better the corrosion resistance of the material. From the test results, we can see that the corrosion current density decreased from 5.9 × 10⁻⁶ in Example 1. -2 μA·cm -2 Reduced to 3.3 × 10⁻⁶ in Example 4 -2 μA·cm -2 This reduction indicates that by changing the coupling agent and adding ammonium zirconium carbonate, the corrosion rate of the material was slowed down, thereby improving the material's corrosion resistance.

[0098] Therefore, based on the above analysis, we can conclude that by changing the type of coupling agent and adding ammonium zirconium carbonate, the corrosion resistance of chromium-free passivation solutions for corrosion-resistant magnesium alloys can be significantly improved.

[0099] In particular, Example 4, which combined 3-isocyanate-propyltrimethoxysilane and γ-aminopropyltriethoxysilane as coupling agents, exhibited the best anti-corrosion effect. Whether in terms of salt spray time, polarization resistance, or corrosion current density, it was better than Examples 2 and 3 using the same amount of either 3-isocyanate-propyltrimethoxysilane or γ-aminopropyltriethoxysilane as a single coupling agent, demonstrating a synergistic effect. The reasons for this synergistic effect can be theoretically explained from the following aspects:

[0100] Complementary Chemical Properties: These two silane coupling agents each contain different functional groups, resulting in complementary protective effects on magnesium alloy surfaces. 3-Isocyanopropyltrimethoxysilane contains isocyanate groups, which are highly polar and reactive, allowing it to form stable chemical bonds with the oxide layer on the magnesium alloy surface, enhancing the adhesion of the protective film. Meanwhile, γ-aminopropyltriethoxysilane contains amino groups, which are polar and enhance the hydrophilicity of the coating, making it more difficult for liquid corrosive media to penetrate the metal surface.

[0101] Optimization of protective layer structure: Protective films formed by different coupling agents may differ in microstructure. Combining two coupling agents can potentially create a more complex protective film structure, better resisting the penetration of corrosive media and enhancing the protective effect.

[0102] Interaction with ammonium zirconium carbonate: Ammonium zirconium carbonate can release Zr 4+ The ions can form stable zirconium silicate structures with the two coupling agents, making the internal structure of the passivation film more uniform and improving the stability and corrosion resistance of the film. At the same time, the zirconium hydroxyl groups (Zr-OH) of ammonium zirconium carbonate can form hydrogen bonds with water and SiOH groups in the coupling agent, further enhancing the stability and corrosion resistance of the protective film.

[0103] Enhanced chemical bonding: When two silane coupling agents coexist, they may form tighter and more continuous chemical bonds on the surface, strengthening the bond between the magnesium alloy surface and the coating, thereby improving corrosion resistance.

[0104] Therefore, by using two silane coupling agents and ammonium zirconium carbonate, a more complex, uniform, and stable protective film can be formed, effectively reducing corrosion current density, improving corrosion protection, and achieving synergistic effects.

[0105] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A corrosion-resistant, chromium-free passivation solution for magnesium alloys, characterized in that, Including the following raw materials by weight percentage: 2-10% coupling agent; 0.2-1.6% cerium nitrate; 0.5-5% ammonium fluorotitanate; 0.2-3% lauryl betaine; 0.4-1.4% ammonium zirconium carbonate; The remainder is water.

2. The corrosion-resistant magnesium alloy chromium-free passivation solution as described in claim 1, characterized in that, Including the following raw materials by weight percentage: 3-7% coupling agent; 0.4-1.2% cerium nitrate; 1-3% ammonium fluorotitanate; 0.4-2% lauryl betaine; 0.4-1.4% ammonium zirconium carbonate; The remainder is water.

3. The corrosion-resistant magnesium alloy chromium-free passivation solution as described in claim 1, characterized in that, Including the following raw materials by weight percentage: 4-6% coupling agent; 0.6-1.0% cerium nitrate; 1.5-2.5% ammonium fluorotitanate; 0.7-1.5% lauryl betaine; 0.4-1.4% ammonium zirconium carbonate; The remainder is water.

4. The corrosion-resistant magnesium alloy chromium-free passivation solution according to any one of claims 1-3, characterized in that, The coupling agent is selected from at least one of 3-isocyanatopropyltrimethoxysilane and γ-aminopropyltriethoxysilane.

5. The method for preparing the corrosion-resistant magnesium alloy chromium-free passivation solution according to any one of claims 1-4, characterized in that, Mix all ingredients thoroughly.

6. The application of the corrosion-resistant chromium-free passivation solution for magnesium alloys according to any one of claims 1-4 in the passivation treatment of magnesium alloy surfaces.

7. The application of the corrosion-resistant chromium-free passivation solution for magnesium alloys as described in claim 6 in the passivation treatment of magnesium alloy surfaces, characterized in that, The magnesium alloy is immersed or coated at room temperature for 10-300 seconds using the corrosion-resistant chromium-free passivation solution described in any one of claims 1-4, and then dried.

8. The application of the corrosion-resistant chromium-free passivation solution for magnesium alloys as described in claim 7 in the passivation treatment of magnesium alloy surfaces, characterized in that, Before passivating the magnesium alloy surface, a cleaning pretreatment is performed on the magnesium alloy surface.