Double-metal hydroxide anti-corrosion coating on surface of magnesium-zinc alloy and preparation method of double-metal hydroxide anti-corrosion coating
By soaking with carbonic acid and alkaline solutions on the magnesium-zinc alloy matrix, the magnesium-zinc bimetallic hydroxide layer is solved, and the environmentally friendly and low-cost anti-corrosion coating process is achieved, which is suitable for applications in multiple fields.
Patent Information
- Application Number
- CN202311477364.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-11-08
- Publication Date
- 2025-05-09
AI Technical Summary
Traditional bimetal hydroxide coatings are prepared under high temperature and high pressure reaction conditions, and there are problems such as usage scenario limitation, reaction product pollution and high energy consumption.
A magnesium-zinc alloy is used as the matrix, and the first soaking is performed in a carbonic acid solution, followed by a second soaking in an alkaline solution to form a magnesium-zinc bimetallic hydroxide layer. This method reacts at room temperature or temperatures less than 100℃ and at normal pressure. The process is simple, the equipment requirements are low, the raw material cost is low, and the reactants are contaminated.
It has achieved the preparation of bimetallic hydroxide coating under environmental protection conditions, with good corrosion resistance, and is suitable for automobiles, ships, aviation, aerospace and other fields. It has simple process operation, low cost, short time, and is easy to promote industrially.
Smart Images
Figure CN119956345A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of preparation of anti-corrosion coating materials, and specifically relates to a double metal hydroxide anti-corrosion coating on the surface of a magnesium-zinc alloy and a preparation method thereof. Background Art
[0002] With its high specific strength, low density, high thermal conductivity, electromagnetic shielding and excellent mechanical processing performance, magnesium alloys have gradually replaced aluminum alloys or titanium alloys in certain parts of various fields such as automobiles, ships, aviation, and aerospace. Among them, ZK61M is a magnesium-zinc-zirconium magnesium alloy with high strength, good plasticity and corrosion resistance. It is one of the most widely used deformable magnesium alloys in the aerospace field. It has no tendency to stress corrosion cracking, simple heat treatment process, good machinability, and can manufacture large forgings with complex shapes. However, the standard electrode potential of magnesium is low (about -2.372V), and it is very easy to corrode in a humid or water-containing environment. Therefore, the surface of magnesium alloy parts generally needs to be prepared with a protective coating to reduce corrosion.
[0003] The main 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, chemical conversion, etc. Among them, the double hydroxide coating has a two-dimensional layered structure, and its inherent ion exchange properties can capture corrosive anions while releasing corrosion inhibitors, thereby delaying the occurrence of corrosion and improving the corrosion protection of magnesium alloys. It has been a hot topic of research in recent years and is considered to be the most effective process for protective chemical conversion coatings on magnesium alloy surfaces. However, traditional double hydroxide coatings are mostly prepared by hydrothermal methods, and the high temperature and high pressure reaction conditions limit the use scenarios of double hydroxide coatings. Reaction product pollution and energy consumption are also important factors limiting their use. Summary of the invention
[0004] In view of the technical problems existing in the above-mentioned anti-corrosion coating on the surface of magnesium-zinc alloy, the purpose of the present invention is to provide an environmentally friendly double metal hydroxide anti-corrosion coating on the surface of magnesium-zinc alloy and a preparation method thereof.
[0005] In a first aspect, the present invention provides a double metal hydroxide anti-corrosion coating on the surface of a magnesium-zinc alloy, comprising: a magnesium-zinc alloy substrate, and a magnesium-zinc double metal hydroxide layer attached to the surface of the magnesium-zinc alloy substrate; Wherein, the corrosion potential of the magnesium-zinc double hydroxide layer is greater than -1.4645 eV.
[0006] Preferably, the content of Zn in the magnesium-zinc alloy substrate is 2-9 mol%, and preferably is a ZK61M magnesium-zinc alloy with a Zn content of 5.43 mol%.
[0007] Preferably, the thickness of the magnesium zinc double hydroxide layer is 2 to 10 μm.
[0008] In a second aspect, the present invention provides a method for preparing the double metal hydroxide anti-corrosion coating on the surface of the magnesium-zinc alloy, the preparation method comprising the following steps: The pretreated magnesium-zinc alloy substrate is immersed in a carbonate solution for the first time; then, an alkaline solution is added dropwise thereto or the magnesium-zinc alloy substrate after the first immersion is transferred to an alkaline solution for a second immersion; after the immersion is completed, the magnesium-zinc alloy substrate is taken out and dried to obtain a double metal hydroxide anti-corrosion coating on the surface of the magnesium-zinc alloy.
[0009] Preferably, the pretreatment includes grinding, cleaning and drying processes performed in sequence; wherein the grinding is performed using 120 mesh, 500 mesh and 2000 mesh grinding wheels in sequence, and the cleaning method is ultrasonic cleaning, preferably ultrasonic cleaning at 80-300W for not less than 1 hour, the drying temperature is 50°C, and the drying time is not less than 1 hour.
[0010] Preferably, the concentration of the carbonate solution is greater than 0.02 mol / L and the pH is less than 4.0; The preparation process of the carbonate solution is: heating deionized water to 40-60° C., and then continuously introducing CO 2 gas to obtain a carbonate solution; preferably, the flow rate of the introduced CO 2 gas is 0.5-1.5 L / min.
[0011] Preferably, the first immersion is carried out under normal pressure; the temperature of the first immersion is 20-50°C, preferably 50°C; the time of the first immersion is more than 1 hour, preferably 1-4 hours, most preferably 1-2 hours.
[0012] Preferably, the alkaline solution is selected from sodium hydroxide, potassium hydroxide, and ammonia solution; The pH value of the mixed solution after the alkaline solution is added dropwise and the pH value of the alkaline solution is greater than 8, preferably 9-12, and most preferably 10-11.
[0013] Preferably, the second immersion is carried out under normal pressure; the temperature of the second immersion is 30-90°C, preferably 50°C; the time of the second immersion is more than 1 hour, preferably 2-8 hours, most preferably 3-4 hours.
[0014] Preferably, the drying temperature is 40-60°C, preferably 50°C; and the drying time is not less than 1 hour.
[0015] Beneficial Effects The present invention uses a magnesium-zinc alloy matrix as a source of double metal hydroxides and a carbonic acid solution as an acidic solution. The reaction can be carried out at room temperature or a temperature less than 100° C. and normal pressure. The process is simple, the equipment requirements are low, the raw material cost is low, the reactants are pollution-free, and the reaction process is mild. The anti-corrosion coating provided by the present invention has good anti-corrosion performance and can be applied to the fields of automobiles, ships, aviation, aerospace, etc. The method for preparing the anti-corrosion coating on the surface of the magnesium-zinc alloy provided by the invention is simple to operate, low in cost, short in time, and easy to be popularized and applied in industry. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Figure 1 This is a SEM image of the surface of the double metal hydroxide anti-corrosion coating on the surface of the magnesium-zinc alloy prepared in Example 1; Figure 2 This is a SEM image of the surface of the double metal hydroxide anti-corrosion coating on the magnesium-zinc alloy prepared in Example 2. DETAILED DESCRIPTION
[0017] The present invention is further described by way of embodiments. It should be understood that the following embodiments are only used to illustrate the present invention, rather than to limit the present invention.
[0018] First, the present invention provides a double metal hydroxide anti-corrosion coating on the surface of a magnesium-zinc alloy, comprising: a magnesium-zinc alloy substrate, and a magnesium-zinc double metal hydroxide layer attached to the surface of the magnesium-zinc alloy substrate; wherein the corrosion potential of the magnesium-zinc double metal hydroxide layer is greater than -1.4645 eV.
[0019] In some embodiments, the Zn content in the Mg-Zn alloy substrate can be controlled to be 2-9 mol %, preferably a ZK61M Mg-Zn alloy with a Zn content of 5.43 mol %.
[0020] In some embodiments, the thickness of the magnesium zinc double hydroxide layer may be 2 to 10 μm.
[0021] The following is an exemplary description of the preparation method of the double metal hydroxide anti-corrosion coating on the surface of the magnesium-zinc alloy provided by the present invention. The preparation method may include the following steps: soaking the pretreated magnesium-zinc alloy substrate in a carbonate solution for the first time; then, adding an alkaline solution thereto for continuous soaking or transferring the magnesium-zinc alloy substrate after the first soaking to an alkaline solution for a second soaking; after the soaking is completed, taking out the magnesium-zinc alloy substrate and drying it to obtain the double metal hydroxide anti-corrosion coating on the surface of the magnesium-zinc alloy.
[0022] In the present invention, the magnesium-zinc alloy substrate undergoes corrosion reaction when it is immersed in the carbonate solution for the first time, and the cathode reaction is: 2e - +2H+ (aq)→H2(g), the anode reaction is: Mg(s)-2e - →Mg 2+ (aq), Zn(s)-2e - →Zn 2+ (aq). Among them, Mg 2+ 、Zn 2+ Combined with carbonate ions in the solution to form magnesium carbonate and zinc carbonate, after adding alkaline solution or transferring the magnesium-zinc alloy substrate sample after the first immersion to the alkaline solution, OH - The increase causes magnesium carbonate and zinc carbonate to gradually transform into dense magnesium hydroxide and zinc hydroxide films, and finally forms a magnesium-zinc double hydroxide layer on the surface of the zinc-magnesium alloy substrate, greatly improving the corrosion resistance of the zinc-magnesium alloy.
[0023] Carbonates can corrode the substrate to produce double hydroxide precursors. The raw material price is low, the product is non-corrosive to magnesium-zinc alloys, and the product is pollution-free, which is conducive to industrial green production.
[0024] In some embodiments, the pretreatment may include a grinding, cleaning and drying process performed sequentially; wherein the grinding may be performed sequentially with 120 mesh, 500 mesh and 2000 mesh grinding wheels, the cleaning method may be ultrasonic cleaning, preferably ultrasonic cleaning at 80-300W for not less than 1 hour, the drying temperature may be 50°C, and the drying time may be not less than 1 hour.
[0025] In some embodiments, the concentration of the carbonate solution can be controlled to be greater than 0.02 mol / L and the pH value can be less than 4.0. The carbonate solution is weakly acidic and the reaction is relatively mild, which will not cause excessive corrosion to the magnesium alloy; moreover, the product of the carbonate product after the later reaction with the alkaline solution has basically no corrosive effect on the magnesium alloy.
[0026] Among them, the preparation process of the carbonate solution can be: heating deionized water to 40-60°C (such as 50°C), and then continuously introducing CO2 gas to obtain a carbonate solution; preferably, the flow rate of the introduced CO2 gas can be 0.5-1.5L / minute (such as 1L / minute).
[0027] In some embodiments, the first immersion can be carried out under normal pressure; the temperature of the first immersion can be 20-50°C, preferably 50°C; the time of the first immersion can be more than 1 hour, preferably 1-4 hours, and most preferably 1-2 hours. The reaction is easier to control at room temperature. Exceeding 50°C will result in too fast a reaction speed and too strong acid corrosion effect, which is not conducive to the second step reaction to form a dense anti-corrosion film layer; at the same time, if the first immersion time is too short, the corrosion effect will be insufficient, the second step anti-corrosion film layer will be too thin or unable to form a film, and if the time is too long, the corrosion will be too strong, the second step film formation time will be too long, and even the film formation effect will be affected.
[0028] In some embodiments, the alkaline solution can be selected from sodium hydroxide, potassium hydroxide, and ammonia solution.
[0029] In some embodiments, the pH value of the mixed solution after the alkaline solution is added and the pH value of the alkaline solution can be controlled to be greater than 8, preferably 9-12, and most preferably 10-11.
[0030] In some embodiments, the second soaking can be carried out under normal pressure; the temperature of the second soaking can be 30-90°C, preferably 50°C; the time of the second soaking can be more than 1 hour, preferably 2-8 hours, and most preferably 3-4 hours. Improper parameters of the second soaking conditions will result in poor film bonding.
[0031] In some embodiments, the drying temperature may be 40-60° C., preferably 50° C.; and the drying time is not less than 1 hour.
[0032] The following examples are further listed to illustrate the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention belong to the scope of protection of the present invention. The specific process parameters and the like in the following examples are only examples in a suitable range, that is, those skilled in the art can make a selection within a suitable range through the description herein, and are not limited to the specific values exemplified below.
[0033] Example 1
[0034] The method for preparing the double metal hydroxide anti-corrosion coating on the surface of the magnesium-zinc alloy provided in Example 1 of the present invention comprises the following steps: (1) A 20×20 mm ZK61M magnesium-zinc alloy (Zn content: 5.43 mol%) sample was polished with 120 mesh, 500 mesh, and 2000 mesh grinding wheels in sequence, ultrasonically cleaned in ethanol for 60 minutes, and then dried in an oven at 50°C for 1 hour to obtain a pretreated magnesium-zinc alloy substrate; Take a certain amount of deionized water, heat it to 50°C, and introduce 1L / min of CO2 gas to obtain a carbonate solution with a pH value less than 4; (2) The pretreated magnesium-zinc alloy substrate is immersed in a carbonic acid solution for 1 hour (CO2 gas is continuously introduced and the carbonic acid solution is kept at 50°C) for the first immersion; then the magnesium-zinc alloy substrate after the first immersion is transferred to a 50°C alkaline solution with a pH of 10 for 4 hours for the second immersion; after the second immersion, the magnesium-zinc alloy substrate is taken out and dried in an oven at 50°C for 1 hour to obtain a double metal hydroxide anti-corrosion coating on the surface of the magnesium-zinc alloy.
[0035] Figure 1 This is a SEM image of the surface of the double metal hydroxide anti-corrosion coating on the surface of the magnesium-zinc alloy prepared in Example 1. It can be seen from the figure that an obvious double hydroxide structure is generated on the surface of the magnesium-zinc alloy.
[0036] Example 2
[0037] The preparation method of this Example 2 refers to that of Example 1, with the main difference being that the pH of the alkaline solution is 12.
[0038] Figure 2 This is a SEM image of the surface of the double metal hydroxide anti-corrosion coating on the surface of the magnesium-zinc alloy prepared in Example 2. It can be seen from the figure that an obvious double hydroxide structure is generated on the surface of the magnesium-zinc alloy.
[0039] Example 3
[0040] The preparation method of this Example 3 refers to that of Example 1, with the main difference being that the second immersion time is 1 hour.
[0041] Example 4
[0042] The preparation method of this Example 4 refers to that of Example 1, with the main difference being that the temperature of the second immersion is 30°C.
[0043] Example 5
[0044] The preparation method of this Example 5 refers to that of Example 1, with the main difference being that the temperature of the second immersion is 90°C.
[0045] Example 6
[0046] The preparation method of this Example 6 refers to that of Example 1, with the main difference being that the pH of the alkaline solution is 9.
[0047] Comparative Example 1
[0048] Directly test the corrosion potential of ZK61M magnesium-zinc alloy.
[0049] Table 1 is the test data of the corrosion potential of the double metal hydroxide anti-corrosion coating on the surface of the magnesium-zinc alloy prepared in Examples 1-6 and the ZK61M magnesium-zinc alloy used in Comparative Example 1: sample pH of alkaline solution Second soaking temperature / ℃ Second soaking time / h Corrosion potential (eV) Example 1 10 50 4 -1.3362 Example 2 12 50 4 -1.4090 Example 3 10 50 1 -1.4348 Example 4 10 30 4 -1.4471 Example 5 10 90 4 -1.3565 Example 6 9 50 4 -1.3459 Comparative Example 1 - - - -1.4645 .
[0050] It can be seen from Table 1 that the corrosion potential of the double metal hydroxide anti-corrosion coating on the surface of the magnesium-zinc alloy obtained by the preparation method provided by the present invention is significantly higher than the corrosion potential of Comparative Example 1.
[0051] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited by the appended claims.
Claims
1. A double metal hydroxide anti-corrosion coating on the surface of a magnesium-zinc alloy, characterized in that: include: A magnesium-zinc alloy substrate, and a magnesium-zinc double metal hydroxide layer attached to the surface of the magnesium-zinc alloy substrate; Wherein, the corrosion potential of the magnesium-zinc double hydroxide layer is greater than -1.4645 eV.
2. The double metal hydroxide anti-corrosion coating on the surface of magnesium-zinc alloy according to claim 1, characterized in that: The content of Zn in the magnesium-zinc alloy substrate is 2-9 mol%, and preferably is a ZK61M magnesium-zinc alloy with a Zn content of 5.43 mol%.
3. The double metal hydroxide anti-corrosion coating on the surface of magnesium-zinc alloy according to claim 1 or 2, characterized in that: The thickness of the magnesium zinc double hydroxide layer is 2 to 10 μm.
4. A method for preparing a double metal hydroxide anti-corrosion coating on a magnesium-zinc alloy surface according to any one of claims 1 to 3, the preparation method comprising the following steps: The pretreated magnesium-zinc alloy substrate is immersed in a carbonic acid solution for the first time; Then, an alkaline solution is added dropwise thereto or the magnesium-zinc alloy substrate after the first immersion is transferred to an alkaline solution for a second immersion; after the immersion is completed, the magnesium-zinc alloy substrate is taken out and dried to obtain a double metal hydroxide anti-corrosion coating on the surface of the magnesium-zinc alloy.
5. The preparation method according to claim 4, characterized in that: The pretreatment includes grinding, cleaning and drying processes performed in sequence; wherein the grinding is performed using 120 mesh, 500 mesh and 2000 mesh grinding wheels in sequence, and the cleaning method is ultrasonic cleaning, preferably ultrasonic cleaning at 80-300W for not less than 1 hour, the drying temperature is 50°C, and the drying time is not less than 1 hour.
6. The preparation method according to claim 4 or 5, characterized in that: The concentration of the carbonate solution is greater than 0.02 mol / L, and the pH is less than 4.0; The preparation process of the carbonate solution is: heating deionized water to 40-60° C., and then continuously introducing CO 2 gas to obtain a carbonate solution; preferably, the flow rate of the introduced CO 2 gas is 0.5-1.5 L / min.
7. The preparation method according to any one of claims 4 to 6, characterized in that: The first immersion is carried out under normal pressure; the temperature of the first immersion is 20-50°C, preferably 50°C; the time of the first immersion is more than 1 hour, preferably 1-4 hours, most preferably 1-2 hours.
8. The preparation method according to any one of claims 4 to 7, characterized in that: The alkaline solution is selected from sodium hydroxide, potassium hydroxide, and ammonia solution; The pH value of the mixed solution after the alkaline solution is added dropwise and the pH value of the alkaline solution is greater than 8, preferably 9-12, and most preferably 10-11.
9. The preparation method according to any one of claims 4 to 8, characterized in that: The second immersion is carried out under normal pressure; the temperature of the second immersion is 30-90°C, preferably 50°C; the time of the second immersion is more than 1 hour, preferably 2-8 hours, and most preferably 3-4 hours.
10. The preparation method according to any one of claims 4 to 9, characterized in that: The drying temperature is 40-60° C., preferably 50° C.; the drying time is not less than 1 hour.