Trivalent-element-doped layered double-metal hydroxide anti-corrosion coating on surface of magnesium-zinc alloy and preparation method of trivalent-element-doped layered double-metal hydroxide anti-corrosion coating

Abstract

The invention belongs to the field of material preparation, and relates to a trivalent-element-doped layered double-metal hydroxide anti-corrosion coating on the surface of a magnesium-zinc alloy and a preparation method of the trivalent-element-doped layered double-metal hydroxide anti-corrosion coating. The trivalent-element-doped layered double-metal hydroxide anti-corrosion coating on the surface of the magnesium-zinc alloy comprises a magnesium-zinc alloy matrix and a trivalent-element-doped layered double-metal hydroxide coating formed on the surface of the magnesium-zinc alloy matrix in situ, the trivalent elements in the trivalent-element-doped layered double-metal hydroxide coating comprise at least one of aluminum, iron, nickel and lanthanum.

Description

Technical Field

[0001] This invention relates to a method for preparing a layered bimetallic hydroxide anti-corrosion coating on the surface of a magnesium-zinc alloy, specifically to a method for preparing a trivalent element-doped layered bimetallic hydroxide anti-corrosion coating on the surface of a magnesium-zinc alloy in a carbonic acid solution without environmental pollution, and particularly to a method for preparing a trivalent element-doped layered bimetallic hydroxide anti-corrosion coating on the surface of a ZK61M magnesium-zinc alloy, belonging to the field of materials preparation. Background Technology

[0002] Magnesium alloys, with their high specific strength, low density, high thermal conductivity, electromagnetic shielding, and excellent machinability, have gradually replaced aluminum or titanium alloys in certain parts of the automotive, shipbuilding, aerospace, and other fields. However, magnesium has a very low standard electrode potential, approximately -2.372V, making it highly susceptible to corrosion in humid or water-containing environments. Therefore, protective coatings are required on the surfaces of magnesium alloy parts to reduce corrosion. ZK61M is a magnesium-zinc-zirconium alloy with high strength, good plasticity, and corrosion resistance. It is one of the most widely used wrought magnesium alloys in the aerospace field, exhibiting no stress corrosion cracking tendency, simple heat treatment process, good machinability, and the ability to manufacture large forgings with complex shapes.

[0003] Methods for preparing anti-corrosion coatings on magnesium alloy surfaces include electroplating, anodizing, chemical vapor deposition, physical vapor deposition, laser / ion or electron beam treatment, micro-arc oxidation, and chemical conversion. Among these, layered bimetallic hydroxides, with their two-dimensional layered structure, possess inherent ion exchange properties that can capture corrosive anions while releasing corrosion inhibitors, thereby delaying corrosion and improving the corrosion protection capability of magnesium alloys. This has become a research hotspot in recent years and is considered the most effective process for preparing protective chemical conversion coatings on magnesium alloy surfaces. Traditionally, layered bimetallic hydroxides are prepared using a hydrothermal method. The high temperature and high pressure conditions limit the application scenarios of layered bimetallic hydroxides, and the pollution from reaction products and energy consumption are also significant factors restricting their use. Summary of the Invention

[0004] To address the problem of poor anti-corrosion coatings on the surface of magnesium-zinc alloys (e.g., ZK61M (Zn content of 5.43%)), this invention provides an environmentally friendly trivalent element-doped layered bimetallic hydroxide anti-corrosion coating for the surface of magnesium-zinc alloys and its preparation method.

[0005] In a first aspect, the present invention provides a trivalent element-doped layered bimetallic hydroxide anti-corrosion coating on the surface of a magnesium-zinc alloy, comprising: a magnesium-zinc alloy substrate, and a trivalent element-doped layered bimetallic hydroxide coating formed in situ on the surface of the magnesium-zinc alloy substrate; wherein the trivalent element in the trivalent element-doped layered bimetallic hydroxide coating comprises at least one of aluminum, iron, nickel, and lanthanum.

[0006] Preferably, the Zn content in the magnesium-zinc alloy matrix is ​​2-9 mol%, with the balance being Mg.

[0007] Preferably, the trivalent element-doped layered bimetallic hydroxide coating comprises Mg-Zn layered bimetallic hydroxide and a trivalent element doped in the Mg-Zn layered bimetallic hydroxide; the trivalent element exists in the form of hydroxides (e.g., aluminum hydroxide, iron hydroxide, nickel hydroxide, lanthanum hydroxide, etc.). The trivalent element doping content in the layered bimetallic hydroxide coating is 20-70 mol% (e.g., 20 mol%, 30 mol%, 40 mol%, 45 mol%, 50 mol%, 55 mol%, 60 mol%, 65 mol%, 70 mol%, etc., i.e., the molar ratio of trivalent element to (trivalent element + Mg element + Zn element)). Preferably, the molar ratio of Mg to Zn in the Mg-Zn layered bimetallic hydroxide is (4-6):1, more preferably 5:1.

[0008] Preferably, the thickness of the trivalent element-doped layered bimetallic hydroxide coating is 2–10 μm.

[0009] Preferably, the corrosion potential of the trivalent element-doped layered bimetallic hydroxide coating is > -1.4645 eV.

[0010] Secondly, the present invention provides a method for preparing a trivalent element-doped layered bimetallic hydroxide anti-corrosion coating on the surface of a magnesium-zinc alloy, comprising: (1) The sample is obtained by soaking at least one of the elements, oxides and hydroxides of the trivalent element and the magnesium-zinc alloy matrix in a carbonic acid solution. (2) After the soaking treatment is completed, an alkaline solution is added dropwise to the carbonic acid solution for a second soaking treatment, and then dried to obtain a layered bimetallic hydroxide anti-corrosion coating doped with trivalent elements.

[0011] In this invention, magnesium-zinc alloy and trivalent elements, oxides, or hydroxides are immersed in a carbonic acid solution. During the corrosion reaction of the magnesium alloy in the carbonic acid solution at atmospheric pressure and 20–90°C, the cathodic reaction is: 2e - +2H + (aq)→H2(g), the anodic reaction is: Mg(s)-2e - →Mg 2+ (aq), Zn(s)-2e - →Zn 2+(aq) combines with carbonate ions in the solution to form magnesium carbonate and zinc carbonate. After adding an alkaline solution or transferring the sample to an alkaline solution, OH- - The addition of these substances gradually transforms magnesium carbonate and zinc carbonate into a dense film of magnesium hydroxide and zinc hydroxide, thereby improving corrosion resistance.

[0012] Preferably, the magnesium-zinc alloy substrate is pretreated before immersion treatment; the pretreatment includes grinding and cleaning. Preferably, the polishing is performed by sequentially using 120-grit, 500-grit, and 2000-grit grinding wheels; The cleaning method is ultrasonic cleaning.

[0013] Preferably, in step (1): the ratio of at least one of the trivalent element, the oxide of the trivalent element, and the hydroxide of the trivalent element to the carbonic acid solution is 0.01 M / L to 0.5 M / L; the concentration of the carbonic acid solution is greater than 0.02 mol / L, and the pH is less than 4.0; preferably, the carbonic acid solution is prepared by heating deionized water to 20–90°C (50°C), and then continuously introducing CO2 gas to obtain the carbonic acid solution; the flow rate of the introduced CO2 gas is 0.5–1.5 L / min (e.g., 1 L / min); The parameters for the soaking treatment include: atmospheric pressure, temperature of 20-90°C, and time of more than 1 hour, preferably 1-4 hours, and most preferably 1-2 hours.

[0014] Preferably, in step (2): an alkaline solution is added dropwise until the pH value of the solution is greater than 8, preferably 9 to 12, and most preferably 10 to 11; The temperature of the secondary soaking treatment is 20-90℃, preferably 50℃; the time of the secondary soaking treatment is more than 1 hour, preferably 2-8 hours, and most preferably 3-4 hours. The drying temperature is 40–60°C (e.g., 50°C), and the time is no less than 1 hour.

[0015] Preferably, in step (2): the pH value of the alkaline solution (meaning the alkaline solution to be added) (NaOH) is greater than 8, preferably 9-12, and most preferably 10-11; the composition of the alkaline solution includes at least one of NaOH, KOH, LiOH, NH4OH, Ca(OH)2, Ba(OH)2, Sr(OH)2, CsOH, and FrOH.

[0016] Thirdly, the present invention provides a method for preparing a trivalent element-doped layered bimetallic hydroxide anti-corrosion coating on the surface of a magnesium-zinc alloy, comprising: (1) The sample is obtained by soaking at least one of the elements, oxides and hydroxides of the trivalent element and the magnesium-zinc alloy matrix in a carbonic acid solution. (2) The obtained sample was transferred to an alkaline solution for a second soaking treatment and then dried to obtain a trivalent element-doped layered bimetallic hydroxide anti-corrosion coating.

[0017] In this invention, magnesium-zinc alloy and trivalent elements, oxides, or hydroxides are immersed in a carbonic acid solution. During the corrosion reaction of the magnesium alloy in the carbonic acid solution at atmospheric pressure and 20–90°C, the cathodic reaction is: 2e - +2H + (aq)→H2(g), the anodic reaction is: Mg(s)-2e - →Mg 2+ (aq), Zn(s)-2e - →Zn 2+ (aq) combines with carbonate ions in the solution to form magnesium carbonate and zinc carbonate. After adding an alkaline solution or transferring the sample to an alkaline solution, OH- - The addition of these substances gradually transforms magnesium carbonate and zinc carbonate into a dense film of magnesium hydroxide and zinc hydroxide, thereby improving corrosion resistance.

[0018] Preferably, the magnesium-zinc alloy substrate is pretreated before immersion treatment; the pretreatment includes grinding and cleaning. Preferably, the polishing is performed by sequentially using 120-grit, 500-grit, and 2000-grit grinding wheels; The cleaning method is ultrasonic cleaning.

[0019] Preferably, in step (1): the ratio of at least one of the trivalent element, the oxide of the trivalent element, and the hydroxide of the trivalent element to the carbonic acid solution is 0.01 M / L to 0.5 M / L; the concentration of the carbonic acid solution is greater than 0.02 mol / L, and the pH is less than 4.0; preferably, the carbonic acid solution is prepared by heating deionized water to 20–90°C (50°C), and then continuously introducing CO2 gas to obtain the carbonic acid solution; the flow rate of the introduced CO2 gas is 0.5–1.5 L / min (e.g., 1 L / min); The parameters for the soaking treatment include: atmospheric pressure, temperature of 20-90°C, and time of more than 1 hour, preferably 1-4 hours, and most preferably 1-2 hours.

[0020] Preferably, in step (2): the pH value of the alkaline solution (meaning the alkaline solution used for transfer) (NaOH) is greater than 8, preferably 9-12, and most preferably 10-11; the composition of the alkaline solution includes at least one of NaOH, KOH, LiOH, NH4OH, Ca(OH)2, Ba(OH)2, Sr(OH)2, CsOH, and FrOH; The temperature of the secondary soaking treatment is 20-90℃, preferably 50℃; the time of the secondary soaking treatment is more than 1 hour, preferably 2-8 hours, and most preferably 3-4 hours. The drying temperature is 40–60°C (e.g., 50°C), and the time is no less than 1 hour.

[0021] The beneficial effects of this invention are: The anti-corrosion coating of the present invention has good anti-corrosion performance and can be applied to automobiles, ships, aviation, aerospace and other fields. The method for preparing the anti-corrosion coating on the surface of magnesium-zinc alloy described in the present invention is simple to operate, low in cost, short in time, and easy to promote and apply in industrial applications. Attached Figure Description

[0022] Figure 1 SEM image of the surface of the anti-corrosion coating prepared in Example 1; Figure 2 The image shows the XRD pattern of the anti-corrosion coating prepared in Example 1. Detailed Implementation

[0023] The present invention will be further illustrated by the following embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the present invention.

[0024] In this disclosure, the trivalent element-doped layered bimetallic hydroxide anti-corrosion coating on the surface of a magnesium-zinc alloy includes: a trivalent element-doped layered bimetallic hydroxide formed on the surface of the magnesium-zinc alloy; the composition of the trivalent element-doped layered bimetallic hydroxide coating includes magnesium hydroxide, zinc hydroxide, and hydroxides of doped trivalent elements (e.g., iron, nickel, lanthanum, etc.).

[0025] The following is an example illustrating the preparation method of an anti-corrosion coating on a magnesium-zinc alloy surface.

[0026] After grinding the ZK61M magnesium-zinc alloy parts or samples, clean them in ethanol and then dry them. The magnesium alloy parts or samples are ground using a grinding wheel, for example, successively using 120-grit, 500-grit, and 2000-grit grinding wheels. Preferably, the samples are ultrasonically cleaned at 80–300 W for at least 1 hour. The drying temperature is 50℃, and the drying time is no less than 1 hour.

[0027] A certain amount of deionized water was measured, heated, and CO2 gas was bubbled through it to obtain a carbonic acid solution. The heating temperature was 50℃. After bubbling CO2 gas, the pH value of the solution was below 4.0.

[0028] The treated ZK61M magnesium-zinc alloy parts or samples, trivalent elements, oxides, or hydroxides are immersed in a carbonic acid solution for a certain period of time. The immersion time in the carbonic acid solution can be more than 1 hour, preferably 1 to 4 hours, and most preferably 1 to 2 hours. The immersion temperature is 50°C.

[0029] Add an alkaline solution dropwise or transfer the sample to an alkaline solution for soaking for a certain period of time. Maintain the initial pH value of the solution greater than 8, preferably 9-12, and most preferably 10-11. The soaking time is more than 1 hour, preferably 2-8 hours, and most preferably 3-4 hours. The soaking temperature is 30-90℃, preferably 90℃. The alkaline solution comprises at least one of NaOH, KOH, LiOH, NH4OH, Ca(OH)2, Ba(OH)2, Sr(OH)2, CsOH, and FrOH.

[0030] Remove the ZK61M magnesium-zinc alloy parts or samples and dry them. The drying temperature can be 50℃, and the drying time should not be less than 1 hour.

[0031] All of the above steps are carried out under heating and normal pressure.

[0032] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are all within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below. In the following examples and comparative examples, corrosion potential is used to represent the corrosion resistance of the coating. The higher this value, the stronger the corrosion resistance and the better the corrosion resistance effect. Generally, an electrochemical workstation is used to test the corrosion potential.

[0033] Example 1 (1) A 20×20mm ZK61M magnesium-zinc alloy (Zn content of 5.43%) sample was polished with 120 mesh, 500 mesh and 2000 mesh grinding wheels in sequence, then ultrasonically cleaned with ethanol for 60 minutes and dried in an oven at 50℃ for 1 hour. (2) Take a certain amount of deionized water, heat it to 50°C, and pass CO2 gas at 1L / min to obtain a carbonic acid solution with a pH value of less than 4 (carbonic acid concentration of about 0.04mol / L). (3) Immerse the treated ZK61M magnesium-zinc alloy sample and Fe2O3 powder (0.3mol) in a carbonic acid solution (1000mL) for 1 hour (continuously pass CO2 gas through the solution and keep the carbonic acid solution at 50℃). (4) Transfer the ZK61M magnesium-zinc alloy sample to an alkaline solution (solute NaOH, 0.0001 mol / L) at pH 10 at 50℃ for 4 hours. (5) Take out the ZK61M magnesium-zinc alloy sample and dry it in an oven at 50℃ for 1 hour.

[0034] Example 2 Repeat the method of Example 1, but with the difference that: in step (3), Fe2O3 powder is replaced with aluminum powder (0.3 mol), and in step (4), the time is 24 hours.

[0035] Example 3 Repeat the method of Example 1, but with the difference that in step (3), Fe2O3 powder is replaced with Al2O3 powder (0.3 mol).

[0036] Example 4 Repeat the method of Example 1, but with the difference that in step (3), Fe2O3 powder is replaced with La2O3 powder (0.3 mol).

[0037] Example 5 Repeat the method of Example 1, but with the difference that in step (3), Fe2O3 powder is replaced with Ni2O3 powder (0.3 mol).

[0038] Example 6 Repeat the method of Example 1, but with the difference that the temperature of the alkaline solution is 90°C.

[0039] Example 7 Repeat the method of Example 1, but with the difference that the pH of the alkaline solution is 9 (the solute is NaOH, 0.00001 mol / L).

[0040] Example 8 The method of Example 1 was repeated, but the difference was that the mass of Fe2O3 powder was 0.2 mol.

[0041] Example 9 The method of Example 1 was repeated, but the difference was that the mass of Fe2O3 powder was 0.4 mol.

[0042] Example 10 The method of Example 1 was repeated, but the difference was that the mass of Fe2O3 powder was 0.5 mol.

[0043] Comparative Example 1 The corrosion potential of ZK61M magnesium-zinc alloy was tested, and the test results are listed in Table 1.

[0044] Comparative Example 2 Repeat the method of Example 1, but with the difference that Fe2O3 powder is not added.

[0045] Table 1 shows the test data for corrosion potential in each embodiment and comparative example.

[0046] As shown in Table 1, the corrosion potential of the anti-corrosion coating of the present invention is significantly higher than that of Comparative Example 1.

Claims

1. A trivalent element doped layered double hydroxide anticorrosion coating on a magnesium-zinc alloy surface, characterized in that, The application relates to a magnesium-zinc alloy substrate and a trivalent element-doped layered double hydroxide coating formed in situ on the surface of the magnesium-zinc alloy substrate. The trivalent element in the trivalent element-doped layered double hydroxide coating comprises at least one of aluminum, iron, nickel and lanthanum. The content of Zn in the magnesium-zinc alloy substrate is 2-9 mol%, and the balance is Mg.

2. The trivalent element doped layered double hydroxide corrosion protective coating on a magnesium zinc alloy surface according to claim 1, characterized in that, The composition of the trivalent element-doped layered double hydroxide coating comprises Mg-Zn layered double hydroxide and trivalent elements doped in the Mg-Zn layered double hydroxide; and the trivalent elements exist in the form of hydroxide.

3. The trivalent element doped layered double hydroxide corrosion protective coating on a magnesium zinc alloy surface according to claim 1 or 2, characterized in that The doping content of the trivalent element in the trivalent element-doped layered double hydroxide coating is 20-70 mol%. Preferably, the molar ratio of Mg to Zn in the Mg-Zn layered double hydroxide is (4-6):1, preferably 5:

1. The thickness of the trivalent element-doped layered double hydroxide coating is 2-10 microns.

4. The trivalent element doped layered double hydroxide corrosion protective coating on a magnesium zinc alloy surface according to any one of claims 1 to 3, characterized in that The corrosion potential of the trivalent element-doped layered double hydroxide coating is greater than -1.4645 eV.

5. The trivalent element doped layered double hydroxide corrosion protective coating on a magnesium zinc alloy surface according to any one of claims 1 to 4, characterized in that, The application relates to a magnesium-zinc alloy substrate and a trivalent element-doped layered double hydroxide coating formed in situ on the surface of the magnesium-zinc alloy substrate.

6. A method for producing a trivalent element-doped layered double hydroxide anticorrosion coating layer on a surface of a magnesium-zinc alloy, characterized by, The application relates to a magnesium-zinc alloy substrate and a trivalent element-doped layered double hydroxide coating formed in situ on the surface of the magnesium-zinc alloy substrate. Before the soaking treatment, the magnesium-zinc alloy substrate is pretreated; the pretreatment comprises polishing and cleaning. Preferably, the polishing is carried out by using 120-mesh, 500-mesh and 2000-mesh grinding wheels in sequence.

7. The production method according to claim 6, wherein The cleaning is carried out by ultrasonic cleaning. In step (1), the ratio of the at least one of the trivalent element, the oxide of the trivalent element and the hydroxide of the trivalent element to the carbonic acid solution is 0.01 M / L-0.5 M / L. The concentration of the carbonic acid solution is greater than 0.02 mol / L, and the pH is less than 4.0; preferably, the carbonic acid solution is prepared by heating deionized water to 20-90 DEG C and continuously introducing CO2 gas to obtain the carbonic acid solution; the flow rate of the introduced CO2 gas is 0.5-1.5 L / min.

8. The production method according to claim 6 or 7, characterized by, The parameters of the soaking treatment include normal pressure, a temperature of 20-90 DEG C, a time of more than 1 hour, preferably 1-4 hours, and most preferably 1-2 hours. In step (2), the alkaline solution is added dropwise until the pH of the solution is greater than 8, preferably 9-12, and most preferably 10-11. The temperature of the secondary soaking treatment is 20-90 DEG C, preferably 50 DEG C; the time of the secondary soaking treatment is more than 1 hour, preferably 2-8 hours, and most preferably 3-4 hours.

9. The production method according to any one of claims 6 to 8, characterized by, The drying temperature is 40-60 DEG C, and the drying time is not less than 1 hour. ​ ​ 10. The production method according to any one of claims 6 to 9, characterized by, In step (2), the pH of the basic solution is greater than 8, preferably 9-12, most preferably 10-11; the composition of the basic solution comprises at least one of NaOH, KOH, LiOH, NH4OH, Ca(OH)2, Ba(OH)2, Sr(OH)2, CsOH, FrOH. In step (2), the pH of the basic solution is greater than 8, preferably 9-12, most preferably 10-11; the composition of the basic solution comprises at least one of NaOH, KOH, LiOH, NH4OH, Ca(OH)2, Ba(OH)2, Sr(OH)2, CsOH, FrOH. In step (2), the pH of the basic solution is greater than 8, preferably 9-12

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