A method for electroplating aluminum or aluminum-zinc alloy on the surface of magnesium-lithium alloy using room temperature aprotic solvent

Abstract

A method for electroplating aluminum or aluminum-zinc alloy on the surface of a magnesium-lithium alloy using a room temperature aprotic solvent belongs to the field of metallurgy technology. The present invention uses 1,3-dimethyl-2-imidazolidinone and lithium hexafluorophosphate to prepare a room temperature aprotic solvent, uses anhydrous aluminum chloride as an aluminum salt, and zinc chloride as a zinc salt, and electroplates aluminum or aluminum-zinc alloy on the surface of a magnesium-lithium alloy at 20°C to 50°C. The present invention adopts an aprotic solvent, and does not need to perform zinc immersion and copper plating on the magnesium-lithium alloy. The pretreatment process of the magnesium-lithium alloy is simple and easy to operate. The aluminum or aluminum-zinc alloy coating obtained by electroplating is evenly distributed on the surface of the substrate, which significantly improves the corrosion resistance of the magnesium-lithium alloy and improves the electrical conductivity of the electrolyte. The method provided by the present invention has a low production temperature, can reduce production energy consumption, and at the same time reduce corrosion to equipment, and the operation process is simple.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, and in particular relates to a method for electroplating aluminum or aluminum-zinc alloy on the surface of a magnesium-lithium alloy by utilizing a room temperature aprotic solvent. Background Art

[0002] Magnesium-lithium alloys are the lightest metal structural materials. Due to their low density, high specific strength, excellent electrical and thermal conductivity, strong impact resistance, superior electromagnetic shielding, and good machinability, they are widely used in aerospace, military, nuclear, electronic communications, and transportation. However, magnesium is a very reactive metal and is susceptible to oxidation and corrosion in atmospheric environments. Its poor corrosion resistance severely limits the application of magnesium-lithium alloys in various fields. Currently, methods for preparing metal coatings on workpiece surfaces mainly include thermal spraying, hot-dip plating, physical / chemical vapor deposition (PVD / CVD), and electrochemical deposition. However, during the process of preparing metal coatings on workpiece surfaces using spraying, hot-dip plating, or PVD / CVD techniques, the substrate is heated to a certain temperature. Magnesium-lithium alloys are prone to deformation under high temperature conditions, which affects their mechanical properties. These techniques are not conducive to surface protection of magnesium-lithium alloys. Therefore, electrochemical deposition is commonly used to obtain protective coatings on magnesium-lithium alloy surfaces. Aluminum and zinc, as elements in magnesium-lithium alloys, are the most suitable options for surface protection of magnesium-lithium alloys. Aluminum has a standard reduction potential that is negative compared to hydrogen (-1.67 V vs. SHE), making it difficult to electrodeposit aluminum coatings in aqueous solutions. Traditional zinc plating methods are toxic, produce difficult waste disposal, and are prone to hydrogen embrittlement and low current efficiency. Therefore, high-quality aluminum-zinc coatings can be deposited on magnesium-lithium alloy surfaces in non-aqueous solvents.

[0003] Both organic solvents and ionic liquids can be used for room-temperature electrodeposition of aluminum and aluminum-zinc alloys. The most widely used and studied organic solvent system is tetrahydrofuran (THF)-AlCl3-LiAlH4 as the electrolyte for room-temperature electrodeposition of aluminum. Organic solvent systems have low aluminum deposition rates, poor coating uniformity, are easily affected by external conditions, are highly volatile, produce irritating gases, are flammable and explosive, and are expensive and highly toxic, limiting their in-depth development in the field of metal electrodeposition. Ionic liquids, also known as room-temperature molten salts, are ionic compounds composed entirely of an asymmetric organic cation and an inorganic (or organic) anion. Compared to traditional organic solvents, ionic liquids have a wider electrochemical window, but their viscosity is 1 to 3 orders of magnitude higher than that of organic solvents, and their synthesis process is complex and the cost is relatively high. Aluminum deposition can be achieved in the AlCl3-[EMIm]Cl system. Chang et al. conducted research on aluminum electrodeposition in this ionic liquid system and studied the effect of deposition potential on the microstructure of the deposited coating. [1]. The research results show that as the deposition potential increases, cracks and holes appear in the aluminum coating, affecting the corrosion resistance of the coating. Patent CN109252195A discloses a method for electroplating an aluminum coating on a magnesium alloy surface in a deep eutectic solvent (choline chloride-urea-aluminum chloride). In this system, a corrosion-resistant coating can be obtained, but the deposition temperature needs to be maintained above 70°C. Patent CN104388992A discloses a method for electroplating an Al-Zn alloy coating on an inert electrode copper using a three-electrode system in an imidazole chloride-aluminum chloride system. The system used in the above-mentioned method of electroplating a coating on a magnesium alloy is complex to synthesize, is sensitive to water and air, has high requirements for the operating environment, and is also costly.

[0004] Literature[1]Chang JK, Chen SY, Tsai WT, et al. Electrodeposition ofaluminum on magnesium alloy in aluminum chloride (AlCl3)-1-ethyl-3-methylimidazolium chloride (EMIC) ionic liquid and its corrosion behavior[J]. Electrochemistry Communications, 2007, 9(7): 1602-1606. Summary of the Invention

[0005] To address these issues, the present invention provides a method for electroplating aluminum and aluminum-zinc coatings on magnesium-lithium alloy surfaces at 20°C to 50°C using 1,3-dimethyl-2-imidazolidinone and lithium hexafluorophosphate to prepare a room-temperature aprotic solvent, anhydrous aluminum chloride as the aluminum salt, and anhydrous zinc chloride as the zinc salt. This method efficiently produces aluminum or aluminum-zinc alloy coatings while significantly reducing production costs and improving the corrosion resistance of magnesium-lithium alloys.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] A method for electroplating aluminum or aluminum-zinc alloy on the surface of a magnesium-lithium alloy using a room temperature aprotic solvent comprises the following process steps:

[0008] Pretreatment: pretreating the magnesium-lithium alloy to obtain a magnesium-lithium alloy with no impurities on the surface for standby use;

[0009] Preparation of electrolyte: 1,3-dimethyl-2-imidazolidinone solution and lithium hexafluorophosphate are mixed and stirred to obtain a room temperature aprotic solvent, and aluminum salt and zinc salt are added to the room temperature aprotic solvent and stirred continuously until the mixture is uniform to obtain an electrolyte;

[0010] Electrolysis: Use the pretreated magnesium-lithium alloy as the cathode and the platinum sheet as the anode to perform electrolysis in the electrolyte;

[0011] Cleaning: After the electrolysis is completed, the magnesium-lithium alloy sample is taken out and cleaned with acetonitrile to obtain a magnesium-lithium alloy with aluminum or aluminum-zinc alloy electroplated on the surface.

[0012] The magnesium-lithium alloy is one of LA103Z, LA103M, and LA43M.

[0013] During the pretreatment process, the surface of the magnesium-lithium alloy substrate is pretreated by mechanical grinding-ultrasonic cleaning-alkali cleaning-acid immersion-activation-cleaning-cold air drying process in sequence; wherein, the grinding treatment is to grind the surface of the magnesium-lithium alloy with 400#, 800#, 1200# and 2000# SiC sandpaper in sequence, and the grinding time is 10min~30min; the ultrasonic cleaning treatment is to perform ultrasonic cleaning in anhydrous ethanol, and the ultrasonic cleaning time is 10min~20min; the alkali washing process is to perform ultrasonic cleaning in anhydrous ethanol containing 15g / L~20g / L sodium hydroxide, 5g / L~10g / L sodium carbonate and 10g / L~15g / L sodium phosphate mixed solution, the alkali washing time is 10min~20min, the temperature is 50℃~60℃; the acid leaching treatment is carried out in a phosphoric acid solution, the concentration of the phosphoric acid solution is 5wt%~10wt%, the acid leaching time is 10s~20s, and the acid leaching temperature is 20℃~30℃; the activation treatment is carried out in a mixed solution containing 5wt%~10wt% phosphoric acid and 0.09g / L~0.12g / L ammonium bifluoride, and the activation time is 10s~20s.

[0014] During the electrolyte preparation process, the stirring speed is 200r / min~400r / min; the concentration of lithium hexafluorophosphate in the room temperature aprotic solvent is 0.1mol / L~0.5mol / L, and the room temperature aprotic solvent conductivity measured at 50°C is between 3.83mS / cm~4.2mS / cm; in the electrolyte, the concentration of aluminum salt is 0.5mol / L~1mol / L, and the concentration of zinc salt is 0~0.5mol / L.

[0015] The aluminum salt is aluminum chloride; the zinc salt is zinc chloride.

[0016] During the electrolysis process, constant potential electrolysis is adopted, the electrolysis temperature is 20°C~50°C, the voltage during the electrolysis process is -1.8V vs Al~-2.4V vs Al, and the electrolysis time is 0.5h~2h; wherein, "vs Al" means that the aluminum electrode is used as the reference electrode.

[0017] The method of the present invention has the following advantages:

[0018] 1. Electrodeposition using a room-temperature aprotic solvent allows for lower production temperatures compared to high-temperature molten salt electrolysis, reducing energy consumption and equipment corrosion, while also simplifying the process. Compared to traditional ionic liquids, the system employed offers simplified synthesis and low raw material costs. Compared to existing processes for electroplating aluminum or aluminum-zinc alloys using room-temperature ionic liquids, the present invention utilizes less toxic raw materials, a simpler synthesis process, and convenient operation, enabling continuous production.

[0019] 2. The present method uses an aprotic solvent, eliminating the need for zinc-copper plating of the magnesium-lithium alloy. The pretreatment process is simple and easy to operate, and the resulting electroplated coating is evenly distributed on the substrate surface. Furthermore, the addition of lithium hexafluorophosphate improves the electrolyte's conductivity. The hexafluorophosphate ion, a relatively large, weakly coordinating anion, inhibits electrolyte decomposition under high-voltage operation, reduces side reactions such as hydrogen evolution, and broadens the system's electrochemical window.

[0020] 3. 1,3-Dimethyl-2-imidazolidinone-LiPF6 polar aprotic solvent is used, which has good solubility and coordination ability for aluminum chloride and zinc chloride. Aluminum and aluminum-zinc alloy are obtained by electroplating on the surface of magnesium-lithium alloy, which significantly improves the corrosion resistance of magnesium-lithium alloy while maintaining the lightweight of magnesium-lithium alloy substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a surface morphology of the electroplated aluminum layer on the magnesium-lithium alloy substrate provided in Example 5 of the present invention.

[0022] Figure 2 This is a composition analysis diagram of the electroplated aluminum layer on the surface of the magnesium-lithium alloy provided in Example 5 of the present invention. DETAILED DESCRIPTION

[0023] The following non-limiting examples may enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0024] The experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials are commercially available unless otherwise specified.

[0025] The purity of 1,3-dimethyl-2-imidazolidinone used in the embodiments of the present invention is greater than 99.0%, the purity of lithium hexafluorophosphate is greater than 97.0%, the purity of anhydrous aluminum chloride is greater than 99.0%, the purity of anhydrous zinc chloride is greater than 98.0%, the purity of sodium hydroxide is greater than 98.0%, the purity of sodium carbonate is greater than 99.5%, the purity of sodium phosphate is greater than 96.0%, the purity of phosphoric acid is 85.0%, and the purity of ammonium bifluoride is not less than 99.99%.

[0026] In the embodiment of the present invention, Shanghai Chenhua electrochemical workstation is used as the electrolysis power source.

[0027] In the embodiment of the present invention, a field emission scanning electron microscope FE-SEM combined with an energy dispersive spectrometer EDS is used to analyze the morphology and composition of the aluminum coating.

[0028] The present invention prepares a room-temperature aprotic solvent by adding varying amounts of lithium hexafluorophosphate to 1,3-dimethyl-2-imidazolidinone to obtain a series of solutions with lithium hexafluorophosphate concentrations ranging from 0.1 mol / L to 0.5 mol / L. Conductivity testing revealed that the lithium hexafluorophosphate had a conductivity of 3.83 mS / cm at a concentration of 0.1 mol / L, 3.97 mS / cm at a concentration of 0.2 mol / L, 4.05 mS / cm at a concentration of 0.3 mol / L, 4.14 mS / cm at a concentration of 0.4 mol / L, and 4.20 mS / cm at a concentration of 0.5 mol / L. This increased conductivity promotes the diffusion of active ions within the electrolyte system, facilitating the electrodeposition of aluminum or aluminum-zinc alloys.

[0029] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0030] Example 1:

[0031] Pretreatment: The surface of the LA103Z magnesium-lithium alloy substrate is pretreated by mechanical grinding-ultrasonic cleaning-alkali cleaning-acid immersion-activation-cleaning-cold air drying to obtain a magnesium-lithium alloy with no impurities on the surface. Among them, LA103Z magnesium-lithium alloy was polished with 400#, 800#, 1200# and 2000# SiC sandpaper in sequence for 10min~30min, and ultrasonically cleaned in anhydrous ethanol for 10min~20min; then alkali washed in a mixed solution containing 15g / L~20g / L sodium hydroxide, 5g / L~10g / L sodium carbonate, and 10g / L~15g / L sodium phosphate for 10min~20min at a temperature of 50℃~60℃; acid soaked in 5wt%~10wt% phosphoric acid solution for 10s~20s at a temperature of 20℃~30℃; finally, activated in a mixed solution containing 5wt%~10wt% phosphoric acid and 0.09g / L~0.12g / L ammonium bifluoride for 10s~20s.

[0032] Electrolyte Preparation: 1,3-Dimethyl-2-imidazolidinone and lithium hexafluorophosphate were mixed and stirred at room temperature at a rate of 200-400 r / min to obtain a uniform, fluid, room-temperature aprotic solvent in the electrolytic cell. The lithium hexafluorophosphate concentration in the room-temperature aprotic solvent was 0.1 mol / L. Aluminum chloride was then added to the room-temperature aprotic solvent to obtain an electrolyte solution. The aluminum chloride concentration in the electrolyte was 0.5 mol / L.

[0033] Electrolysis: A 50ml flat-top beaker served as the electrolytic cell. A surface-free LA103Z magnesium-lithium alloy substrate (effective area 1cm×1cm) served as the cathode, and a high-purity platinum sheet (effective area 1cm×2cm) served as the anode, both fixed in the prepared electrolyte, formed the electrolysis system. The electrolysis reaction was conducted under constant voltage and temperature conditions. The electrolysis temperature was controlled by a magnetic heating stirrer. Electrolysis was conducted for 1 hour at an electrolyte temperature of 50°C and an applied potential of -1.8V vs. Al.

[0034] Cleaning: After the electrolysis is completed, the cathode is removed, cleaned with acetonitrile, and vacuum dried to obtain the aluminum-magnesium-lithium alloy. The EDS test results show that the mass percentage of aluminum is 29.58%.

[0035] Example 2:

[0036] Pretreatment: The surface of the LA103Z magnesium-lithium alloy substrate is pretreated by mechanical grinding-ultrasonic cleaning-alkali cleaning-acid immersion-activation-cleaning-cold air drying to obtain a magnesium-lithium alloy with no impurities on the surface. Among them, LA103Z magnesium-lithium alloy was polished with 400#, 800#, 1200# and 2000# SiC sandpaper in sequence for 10min~30min, and ultrasonically cleaned in anhydrous ethanol for 10min~20min; then alkali washed in a mixed solution containing 15g / L~20g / L sodium hydroxide, 5g / L~10g / L sodium carbonate, and 10g / L~15g / L sodium phosphate for 10min~20min at a temperature of 50℃~60℃; acid soaked in 5wt%~10wt% phosphoric acid solution for 10s~20s at a temperature of 20℃~30℃; finally, activated in a mixed solution containing 5wt%~10wt% phosphoric acid and 0.09g / L~0.12g / L ammonium bifluoride for 10s~20s.

[0037] Electrolyte Preparation: 1,3-Dimethyl-2-imidazolidinone and lithium hexafluorophosphate were mixed and stirred at room temperature at a rate of 200-400 r / min to obtain a uniform, fluid, room-temperature aprotic solvent in the electrolytic cell. The lithium hexafluorophosphate concentration in the room-temperature aprotic solvent was 0.5 mol / L. Aluminum chloride was then added to the room-temperature aprotic solvent to obtain an electrolyte solution. The aluminum chloride concentration in the electrolyte was 0.5 mol / L.

[0038] Electrolysis: A 50ml flat-top beaker served as the electrolytic cell. A surface-free LA103Z magnesium-lithium alloy substrate (effective area 1cm×1cm) served as the cathode, and a high-purity platinum sheet (effective area 1cm×2cm) served as the anode, both fixed in the prepared electrolyte, formed the electrolysis system. The electrolysis reaction was conducted under constant voltage and temperature conditions. The electrolysis temperature was controlled by a magnetic heating stirrer. Electrolysis was conducted for 1 hour at an electrolyte temperature of 50°C and an applied potential of -1.8V vs. Al.

[0039] Cleaning: After the electrolysis is completed, the cathode is removed, cleaned with acetonitrile, and vacuum dried to obtain the aluminum-magnesium-lithium alloy. The EDS test results show that the mass percentage of aluminum is 37.39% and the current efficiency reaches 85.71%.

[0040] From the results of Examples 1 and 2 above, it can be seen that when the addition amount of lithium hexafluorophosphate increases from 0.1 mol / L to 0.5 mol / L, the aluminum content in the obtained deposition product increases from 29.58% to 37.39%.

[0041] Example 3:

[0042] Pretreatment: The surface of the LA103Z magnesium-lithium alloy substrate is pretreated by mechanical grinding-ultrasonic cleaning-alkali cleaning-acid immersion-activation-cleaning-cold air drying to obtain a magnesium-lithium alloy with no impurities on the surface. Among them, LA103Z magnesium-lithium alloy was polished with 400#, 800#, 1200# and 2000# SiC sandpaper in sequence for 10min~30min, and ultrasonically cleaned in anhydrous ethanol for 10min~20min; then alkali washed in a mixed solution containing 15g / L~20g / L sodium hydroxide, 5g / L~10g / L sodium carbonate, and 10g / L~15g / L sodium phosphate for 10min~20min at a temperature of 50℃~60℃; acid soaked in 5wt%~10wt% phosphoric acid solution for 10s~20s at a temperature of 20℃~30℃; finally, activated in a mixed solution containing 5wt%~10wt% phosphoric acid and 0.09g / L~0.12g / L ammonium bifluoride for 10s~20s.

[0043] Electrolyte Preparation: 1,3-Dimethyl-2-imidazolidinone and lithium hexafluorophosphate were mixed and stirred at room temperature at a rate of 200-400 r / min to obtain a uniform, fluid, room-temperature aprotic solvent in the electrolytic cell. The lithium hexafluorophosphate concentration in the room-temperature aprotic solvent was 0.5 mol / L. Aluminum chloride was then added to the room-temperature aprotic solvent to obtain an electrolyte solution. The aluminum chloride concentration in the electrolyte was 1 mol / L.

[0044] Electrolysis: A 50ml flat-top beaker served as the electrolytic cell. An LA103Z magnesium-lithium alloy cathode (effective area 1cm×1cm) and a high-purity platinum sheet anode (effective area 1cm×2cm) were fixed in the prepared electrolyte to form the electrolysis system. The electrolysis reaction was carried out under constant voltage and temperature conditions. The electrolysis temperature was controlled by a magnetic heating stirrer. Electrolysis was conducted for 1 hour at an electrolyte temperature of 50°C and an applied potential of -1.8V vs. Al.

[0045] Cleaning: After the electrolysis is completed, the cathode is removed, cleaned with acetonitrile, and vacuum dried to obtain the aluminum-magnesium-lithium alloy. The EDS test results show that the mass percentage of aluminum is 35.48% and the current efficiency reaches 83.75%.

[0046] Example 4:

[0047] Pretreatment: The surface of the LA103Z magnesium-lithium alloy substrate is pretreated by mechanical grinding-ultrasonic cleaning-alkali cleaning-acid immersion-activation-cleaning-cold air drying to obtain a magnesium-lithium alloy with no impurities on the surface. Among them, LA103Z magnesium-lithium alloy was polished with 400#, 800#, 1200# and 2000# SiC sandpaper in sequence for 10min~30min, and ultrasonically cleaned in anhydrous ethanol for 10min~20min; then alkali washed in a mixed solution containing 15g / L~20g / L sodium hydroxide, 5g / L~10g / L sodium carbonate, and 10g / L~15g / L sodium phosphate for 10min~20min at a temperature of 50℃~60℃; acid soaked in 5wt%~10wt% phosphoric acid solution for 10s~20s at a temperature of 20℃~30℃; finally, activated in a mixed solution containing 5wt%~10wt% phosphoric acid and 0.09g / L~0.12g / L ammonium bifluoride for 10s~20s.

[0048] Electrolyte Preparation: 1,3-Dimethyl-2-imidazolidinone and lithium hexafluorophosphate were mixed and stirred at room temperature at a rate of 200-400 r / min to obtain a uniform, fluid, room-temperature aprotic solvent in the electrolytic cell. The lithium hexafluorophosphate concentration in the room-temperature aprotic solvent was 0.5 mol / L. Aluminum chloride was then added to the room-temperature aprotic solvent to obtain an electrolyte solution. The aluminum chloride concentration in the electrolyte was 0.5 mol / L.

[0049] Electrolysis: A 50ml flat-top beaker served as the electrolytic cell. A surface-free LA103Z magnesium-lithium alloy substrate (effective area 1cm×1cm) served as the cathode, and a high-purity platinum sheet (effective area 1cm×2cm) served as the anode, both fixed in the prepared electrolyte, formed the electrolysis system. The electrolysis reaction was conducted under constant voltage and temperature conditions. The electrolysis temperature was controlled by a magnetic heating stirrer. Electrolysis was conducted for 1 hour in the electrolyte at 50°C and an applied deposition potential of -2.0V vs. Al.

[0050] Cleaning: After the electrolysis is completed, the cathode is removed, cleaned with acetonitrile, and vacuum dried to obtain the aluminum-magnesium-lithium alloy. The EDS test results show that the mass percentage of aluminum is 40.18% and the current efficiency reaches 87.37%.

[0051] Example 5:

[0052] Pretreatment: The surface of the LA103Z magnesium-lithium alloy substrate is pretreated by mechanical grinding-ultrasonic cleaning-alkali cleaning-acid immersion-activation-cleaning-cold air drying to obtain a magnesium-lithium alloy with no impurities on the surface. Among them, LA103Z magnesium-lithium alloy was polished with 400#, 800#, 1200# and 2000# SiC sandpaper in sequence for 10min~30min, and ultrasonically cleaned in anhydrous ethanol for 10min~20min; then alkali washed in a mixed solution containing 15g / L~20g / L sodium hydroxide, 5g / L~10g / L sodium carbonate, and 10g / L~15g / L sodium phosphate for 10min~20min at a temperature of 50℃~60℃; acid soaked in 5wt%~10wt% phosphoric acid solution for 10s~20s at a temperature of 20℃~30℃; finally, activated in a mixed solution containing 5wt%~10wt% phosphoric acid and 0.09g / L~0.12g / L ammonium bifluoride for 10s~20s.

[0053] Electrolyte Preparation: 1,3-Dimethyl-2-imidazolidinone and lithium hexafluorophosphate were mixed and stirred at room temperature at a rate of 200-400 r / min to obtain a uniform, fluid, room-temperature aprotic solvent in the electrolytic cell. The lithium hexafluorophosphate concentration in the room-temperature aprotic solvent was 0.5 mol / L. Aluminum chloride was then added to the room-temperature aprotic solvent to obtain an electrolyte solution. The aluminum chloride concentration in the electrolyte was 0.5 mol / L.

[0054] Electrolysis: A 50ml flat-top beaker served as the electrolytic cell. A surface-free LA103Z magnesium-lithium alloy substrate (effective area 1cm×1cm) served as the cathode, and a high-purity platinum sheet (effective area 1cm×2cm) served as the anode, both fixed in the prepared electrolyte, formed the electrolysis system. The electrolysis reaction was carried out under constant voltage and temperature conditions. The electrolysis temperature was controlled by a magnetic heating stirrer. Electrolysis was conducted for 1 hour at an electrolyte temperature of 50°C and an applied deposition potential of -2.2V vs. Al.

[0055] Cleaning: After the electrolysis is completed, the cathode is removed, cleaned with acetonitrile, and vacuum dried to obtain the aluminum-magnesium-lithium alloy. The EDS test results show that the mass percentage of aluminum is 44.54% and the current efficiency reaches 90.24%.

[0056] Example 6:

[0057] Pretreatment: The surface of the LA103Z magnesium-lithium alloy substrate is pretreated by mechanical grinding-ultrasonic cleaning-alkali cleaning-acid immersion-activation-cleaning-cold air drying to obtain a magnesium-lithium alloy with no impurities on the surface. Among them, LA103Z magnesium-lithium alloy was polished with 400#, 800#, 1200# and 2000# SiC sandpaper in sequence for 10min~30min, and ultrasonically cleaned in anhydrous ethanol for 10min~20min; then alkali washed in a mixed solution containing 15g / L~20g / L sodium hydroxide, 5g / L~10g / L sodium carbonate, and 10g / L~15g / L sodium phosphate for 10min~20min at a temperature of 50℃~60℃; acid soaked in 5wt%~10wt% phosphoric acid solution for 10s~20s at a temperature of 20℃~30℃; finally, activated in a mixed solution containing 5wt%~10wt% phosphoric acid and 0.09g / L~0.12g / L ammonium bifluoride for 10s~20s.

[0058] Electrolyte Preparation: 1,3-Dimethyl-2-imidazolidinone and lithium hexafluorophosphate were mixed and stirred at room temperature at a rate of 200-400 r / min to obtain a uniform, fluid, room-temperature aprotic solvent in the electrolytic cell. The lithium hexafluorophosphate concentration in the room-temperature aprotic solvent was 0.5 mol / L. Aluminum chloride was then added to the room-temperature aprotic solvent to obtain an electrolyte solution. The aluminum chloride concentration in the electrolyte was 0.5 mol / L.

[0059] Electrolysis: A 50ml flat-top beaker served as the electrolytic cell. A surface-free LA103Z magnesium-lithium alloy substrate (effective area 1cm×1cm) served as the cathode, and a high-purity platinum sheet (effective area 1cm×2cm) served as the anode, both fixed in the prepared electrolyte, formed the electrolysis system. The electrolysis reaction was conducted under constant voltage and temperature conditions. The electrolysis temperature was controlled by a magnetic heating stirrer. Electrolysis was conducted for 1 hour at an electrolyte temperature of 50°C and an applied deposition potential of -2.4V vs. Al.

[0060] Cleaning: After the electrolysis is completed, the cathode is removed, cleaned with acetonitrile, and vacuum dried to obtain the aluminum-magnesium-lithium alloy. The EDS test results show that the mass percentage of aluminum is 43.69% and the current efficiency reaches 90.02%.

[0061] From the results of Examples 2, 4 to 6 above, it can be seen that under the conditions of the same material ratio and concentration, the same electrolysis temperature and time, the aluminum content in the deposited product obtained when the deposition potential increases from -1.8 V to -2.2 V increases significantly, and the current efficiency increases from 85.71% to 90.24%. When the deposition potential continues to shift negatively to -2.4 V, there is a downward trend, so the deposition potential is selected to be -2.2 V.

[0062] The SEM image of the product obtained on the cathode plate in Example 5 is as follows: Figure 1 As shown. Figure 1 It can be seen that there is no dendrite structure during the formation of the aluminum coating, and spherical particles are accumulated on the magnesium-lithium alloy sheet, and the coating surface is uniform and flat. Figure 2 It can be seen that the EDS spectrum of the aluminum coating shows that the coating mainly contains elements such as Al, O and Mg, as well as a small amount of Cl element.

[0063] Example 7:

[0064] Pretreatment: The surface of the LA103Z magnesium-lithium alloy substrate is pretreated by mechanical grinding-ultrasonic cleaning-alkali cleaning-acid immersion-activation-cleaning-cold air drying to obtain a magnesium-lithium alloy with no impurities on the surface. Among them, LA103Z magnesium-lithium alloy was polished with 400#, 800#, 1200# and 2000# SiC sandpaper in sequence for 10min~30min, and ultrasonically cleaned in anhydrous ethanol for 10min~20min; then alkali washed in a mixed solution containing 15g / L~20g / L sodium hydroxide, 5g / L~10g / L sodium carbonate, and 10g / L~15g / L sodium phosphate for 10min~20min at a temperature of 50℃~60℃; acid soaked in 5wt%~10wt% phosphoric acid solution for 10s~20s at a temperature of 20℃~30℃; finally, activated in a mixed solution containing 5wt%~10wt% phosphoric acid and 0.09g / L~0.12g / L ammonium bifluoride for 10s~20s.

[0065] Electrolyte Preparation: 1,3-Dimethyl-2-imidazolidinone and lithium hexafluorophosphate were mixed and stirred at room temperature at a rate of 200-400 r / min to obtain a uniform, fluid, room-temperature aprotic solvent in the electrolytic cell. The lithium hexafluorophosphate concentration in the room-temperature aprotic solvent was 0.5 mol / L. Aluminum chloride was then added to the room-temperature aprotic solvent to obtain an electrolyte solution. The aluminum chloride concentration in the electrolyte was 0.5 mol / L.

[0066] Electrolysis: A 50ml flat-top beaker served as the electrolytic cell. A surface-free LA103Z magnesium-lithium alloy substrate (effective area 1cm×1cm) served as the cathode, and a high-purity platinum sheet (effective area 1cm×2cm) served as the anode, both fixed in the prepared electrolyte, formed the electrolysis system. The electrolysis reaction was carried out under constant voltage and temperature conditions. The electrolysis temperature was controlled by a magnetic heating stirrer. The applied deposition potential was -2.2V vs. Al, and the electrolyte temperature was 20°C. Electrolysis was performed in the electrolyte for 1 hour.

[0067] Cleaning: After the electrolysis is completed, the cathode is removed, cleaned with acetonitrile, and vacuum dried to obtain the aluminum-magnesium-lithium alloy. EDS monitoring results show that the mass percentage of aluminum is 30.17% and the current efficiency reaches 83.28%.

[0068] Example 8:

[0069] Pretreatment: The surface of the LA103Z magnesium-lithium alloy substrate is pretreated by mechanical grinding-ultrasonic cleaning-alkali cleaning-acid immersion-activation-cleaning-cold air drying to obtain a magnesium-lithium alloy with no impurities on the surface. Among them, LA103Z magnesium-lithium alloy was polished with 400#, 800#, 1200# and 2000# SiC sandpaper in sequence for 10min~30min, and ultrasonically cleaned in anhydrous ethanol for 10min~20min; then alkali washed in a mixed solution containing 15g / L~20g / L sodium hydroxide, 5g / L~10g / L sodium carbonate, and 10g / L~15g / L sodium phosphate for 10min~20min at a temperature of 50℃~60℃; acid soaked in 5wt%~10wt% phosphoric acid solution for 10s~20s at a temperature of 20℃~30℃; finally, activated in a mixed solution containing 5wt%~10wt% phosphoric acid and 0.09g / L~0.12g / L ammonium bifluoride for 10s~20s.

[0070] Electrolyte Preparation: 1,3-Dimethyl-2-imidazolidinone and lithium hexafluorophosphate were mixed and stirred at room temperature at a rate of 200-400 r / min to obtain a uniform, fluid, room-temperature aprotic solvent in the electrolytic cell. The lithium hexafluorophosphate concentration in the room-temperature aprotic solvent was 0.5 mol / L. Aluminum chloride was then added to the room-temperature aprotic solvent to obtain an electrolyte solution. The aluminum chloride concentration in the electrolyte was 0.5 mol / L.

[0071] Electrolysis: A 50ml flat-top beaker served as the electrolytic cell. A surface-free LA103Z magnesium-lithium alloy substrate (effective area 1cm×1cm) served as the cathode, and a high-purity platinum sheet (effective area 1cm×2cm) served as the anode, both fixed in the prepared electrolyte, formed the electrolysis system. The electrolysis reaction was carried out under constant voltage and temperature conditions. The electrolysis temperature was controlled by a magnetic heating stirrer. The applied deposition potential was -2.2V vs. Al, and the electrolyte temperature was 30°C. Electrolysis was performed in the electrolyte for 1 hour.

[0072] Cleaning: After the electrolysis is completed, the cathode is removed, cleaned with acetonitrile, and vacuum dried to obtain the aluminum-magnesium-lithium alloy. The EDS test results show that the mass percentage of aluminum is 35.78% and the current efficiency reaches 85.52%.

[0073] Example 9:

[0074] Pretreatment: The surface of the LA103Z magnesium-lithium alloy substrate is pretreated by mechanical grinding-ultrasonic cleaning-alkali cleaning-acid immersion-activation-cleaning-cold air drying to obtain a magnesium-lithium alloy with no impurities on the surface. Among them, LA103Z magnesium-lithium alloy was polished with 400#, 800#, 1200# and 2000# SiC sandpaper in sequence for 10min~30min, and ultrasonically cleaned in anhydrous ethanol for 10min~20min; then alkali washed in a mixed solution containing 15g / L~20g / L sodium hydroxide, 5g / L~10g / L sodium carbonate, and 10g / L~15g / L sodium phosphate for 10min~20min at a temperature of 50℃~60℃; acid soaked in 5wt%~10wt% phosphoric acid solution for 10s~20s at a temperature of 20℃~30℃; finally, activated in a mixed solution containing 5wt%~10wt% phosphoric acid and 0.09g / L~0.12g / L ammonium bifluoride for 10s~20s.

[0075] Electrolyte Preparation: 1,3-Dimethyl-2-imidazolidinone and lithium hexafluorophosphate were mixed and stirred at room temperature at a rate of 200-400 r / min to obtain a uniform, fluid, room-temperature aprotic solvent in the electrolytic cell. The lithium hexafluorophosphate concentration in the room-temperature aprotic solvent was 0.5 mol / L. Aluminum chloride was then added to the room-temperature aprotic solvent to obtain an electrolyte solution. The aluminum chloride concentration in the electrolyte was 0.5 mol / L.

[0076] Electrolysis: A 50ml flat-top beaker served as the electrolytic cell. A surface-free LA103Z magnesium-lithium alloy substrate (effective area 1cm×1cm) served as the cathode, and a high-purity platinum sheet (effective area 1cm×2cm) served as the anode, both fixed in the prepared electrolyte, formed the electrolysis system. The electrolysis reaction was carried out under constant voltage and temperature conditions. The electrolysis temperature was controlled by a magnetic heating stirrer. The applied deposition potential was -2.2V vs. Al, and the electrolyte temperature was 40°C. Electrolysis was performed in the electrolyte for 1 hour.

[0077] Cleaning: After the electrolysis is completed, the cathode is removed, cleaned with acetonitrile, and vacuum dried to obtain the aluminum-magnesium-lithium alloy. The EDS test results show that the mass percentage of aluminum is 41.46% and the current efficiency reaches 89.28%.

[0078] The results of Examples 5, 7, and 9 above demonstrate that, under the same material ratios, deposition potential, and deposition time, increasing the deposition temperature from 20°C to 50°C gradually increases the aluminum content and current efficiency of the deposited layer. Appropriately increasing the temperature facilitates the deposition of the aluminum coating.

[0079] Example 10:

[0080] Pretreatment: The surface of the LA103Z magnesium-lithium alloy substrate is pretreated by mechanical grinding-ultrasonic cleaning-alkali cleaning-acid immersion-activation-cleaning-cold air drying to obtain a magnesium-lithium alloy with no impurities on the surface. Among them, LA103Z magnesium-lithium alloy was polished with 400#, 800#, 1200# and 2000# SiC sandpaper in sequence for 10min~30min, and ultrasonically cleaned in anhydrous ethanol for 10min~20min; then alkali washed in a mixed solution containing 15g / L~20g / L sodium hydroxide, 5g / L~10g / L sodium carbonate, and 10g / L~15g / L sodium phosphate for 10min~20min at a temperature of 50℃~60℃; acid soaked in 5wt%~10wt% phosphoric acid solution for 10s~20s at a temperature of 20℃~30℃; finally, activated in a mixed solution containing 5wt%~10wt% phosphoric acid and 0.09g / L~0.12g / L ammonium bifluoride for 10s~20s.

[0081] Electrolyte Preparation: 1,3-Dimethyl-2-imidazolidinone and lithium hexafluorophosphate were mixed and stirred at room temperature at a rate of 200-400 r / min to obtain a uniform, fluid, room-temperature aprotic solvent in the electrolytic cell. The lithium hexafluorophosphate concentration in the room-temperature aprotic solvent was 0.5 mol / L. Aluminum chloride was then added to the room-temperature aprotic solvent to obtain an electrolyte solution. The aluminum chloride concentration in the electrolyte was 0.5 mol / L.

[0082] Electrolysis: A 50ml flat-top beaker served as the electrolytic cell. A surface-free LA103Z magnesium-lithium alloy substrate (effective area 1cm×1cm) served as the cathode, and a high-purity platinum sheet (effective area 1cm×2cm) served as the anode, both fixed in the prepared electrolyte, formed the electrolysis system. The electrolysis reaction was carried out under constant voltage and temperature conditions. The electrolysis temperature was controlled by a magnetic heating stirrer. The applied deposition potential was -2.2V vs. Al, and the electrolyte temperature was 50°C. Electrolysis was performed in the electrolyte for 0.5h.

[0083] Cleaning: After the electrolysis is completed, the cathode is removed, cleaned with acetonitrile, and vacuum dried to obtain the aluminum-magnesium-lithium alloy. The EDS test results show that the mass percentage of aluminum is 30.18% and the current efficiency is 84.46%.

[0084] Example 11:

[0085] Pretreatment: The surface of the LA103Z magnesium-lithium alloy substrate is pretreated by mechanical grinding-ultrasonic cleaning-alkali cleaning-acid immersion-activation-cleaning-cold air drying to obtain a magnesium-lithium alloy with no impurities on the surface. Among them, LA103Z magnesium-lithium alloy was polished with 400#, 800#, 1200# and 2000# SiC sandpaper in sequence for 10min~30min, and ultrasonically cleaned in anhydrous ethanol for 10min~20min; then alkali washed in a mixed solution containing 15g / L~20g / L sodium hydroxide, 5g / L~10g / L sodium carbonate, and 10g / L~15g / L sodium phosphate for 10min~20min at a temperature of 50℃~60℃; acid soaked in 5wt%~10wt% phosphoric acid solution for 10s~20s at a temperature of 20℃~30℃; finally, activated in a mixed solution containing 5wt%~10wt% phosphoric acid and 0.09g / L~0.12g / L ammonium bifluoride for 10s~20s.

[0086] Electrolyte Preparation: 1,3-Dimethyl-2-imidazolidinone and lithium hexafluorophosphate were mixed and stirred at room temperature at a rate of 200-400 r / min to obtain a uniform, fluid, room-temperature aprotic solvent in the electrolytic cell. The lithium hexafluorophosphate concentration in the room-temperature aprotic solvent was 0.5 mol / L. Aluminum chloride was then added to the room-temperature aprotic solvent to obtain an electrolyte solution. The aluminum chloride concentration in the electrolyte was 0.5 mol / L.

[0087] Electrolysis: A 50ml flat-top beaker served as the electrolytic cell. A surface-free LA103Z magnesium-lithium alloy substrate (effective area 1cm×1cm) served as the cathode, and a high-purity platinum sheet (effective area 1cm×2cm) served as the anode, both fixed in the prepared electrolyte, formed the electrolysis system. The electrolysis reaction was carried out under constant voltage and temperature conditions. The electrolysis temperature was controlled by a magnetic heating stirrer. The applied deposition potential was -2.2V vs. Al, and the electrolyte temperature was 50°C. Electrolysis was performed in the electrolyte for 2 hours.

[0088] Cleaning: After the electrolysis is completed, the cathode is removed, cleaned with acetonitrile, and vacuum dried to obtain the aluminum-magnesium-lithium alloy. The EDS test results show that the mass percentage of aluminum is 40.62% and the current efficiency is 88.43%.

[0089] From the results of Examples 5, 10, and 11 above, it can be seen that, under the same conditions of material ratio and concentration, electrolysis voltage, and electrolysis temperature, the aluminum content in the deposited layer obtained by extending the electrolysis time from 0.5 h to 1 h significantly increases, and the aluminum content decreases when the time is further extended to 2 h, indicating that the electrolyte begins to decompose at this time. Therefore, the electrodeposition time should not be too long, and 1 h is most suitable.

[0090] Example 12:

[0091] Pretreatment: The surface of the LA103M magnesium-lithium alloy substrate is pretreated by mechanical grinding-ultrasonic cleaning-alkali cleaning-acid immersion-activation-cleaning-cold air drying to obtain a magnesium-lithium alloy with no impurities on the surface. Among them, LA103M magnesium-lithium alloy was polished with 400#, 800#, 1200# and 2000# SiC sandpaper in sequence for 10min~30min, and ultrasonically cleaned in anhydrous ethanol for 10min~20min; then alkali washed in a mixed solution containing 15g / L~20g / L sodium hydroxide, 5g / L~10g / L sodium carbonate, and 10g / L~15g / L sodium phosphate for 10min~20min at a temperature of 50℃~60℃; acid soaked in 5wt%~10wt% phosphoric acid solution for 10s~20s at a temperature of 20℃~30℃; finally, activated in a mixed solution containing 5wt%~10wt% phosphoric acid and 0.09g / L~0.12g / L ammonium bifluoride for 10s~20s.

[0092] Electrolyte Preparation: 1,3-Dimethyl-2-imidazolidinone and lithium hexafluorophosphate were mixed and stirred at room temperature at a rate of 200-400 r / min to obtain a uniform, fluid, room-temperature aprotic solvent in the electrolytic cell. The lithium hexafluorophosphate concentration in the room-temperature aprotic solvent was 0.5 mol / L. Aluminum chloride was then added to the room-temperature aprotic solvent to obtain an electrolyte solution. The aluminum chloride concentration in the electrolyte was 0.5 mol / L.

[0093] Electrolysis: A 50ml flat-top beaker served as the electrolytic cell. A surface-free LA103M magnesium alloy substrate (effective area 1cm x 1cm) served as the cathode, and a high-purity platinum sheet (effective area 1cm x 2cm) served as the anode, both fixed in the prepared electrolyte, formed the electrolysis system. The electrolysis reaction was carried out under constant voltage and temperature conditions. The electrolysis temperature was controlled by a magnetic heating stirrer. The applied deposition potential was -2.2V vs. Al, and the electrolyte temperature was 50°C. Electrolysis was performed in the electrolyte for 1 hour.

[0094] Cleaning: After the electrolysis is completed, the cathode is removed, cleaned with acetonitrile, and vacuum dried to obtain the aluminum-magnesium-lithium alloy. The EDS test results show that the mass percentage of aluminum is 38.87% and the current efficiency reaches 87.46%.

[0095] Example 13:

[0096] Pretreatment: The surface of the LA43M magnesium-lithium alloy substrate is pretreated by mechanical grinding-ultrasonic cleaning-alkali cleaning-acid immersion-activation-cleaning-cold air drying to obtain a magnesium-lithium alloy with no impurities on the surface. Among them, LA43M magnesium-lithium alloy was polished with 400#, 800#, 1200# and 2000# SiC sandpaper for 10min~30min in sequence, and ultrasonically cleaned in anhydrous ethanol for 10min~20min; then alkali washed in a mixed solution containing 15g / L~20g / L sodium hydroxide, 5g / L~10g / L sodium carbonate, and 10g / L~15g / L sodium phosphate for 10min~20min at a temperature of 50℃~60℃; acid soaked in 5wt%~10wt% phosphoric acid solution for 10s~20s at a temperature of 20℃~30℃; finally, activated in a mixed solution containing 5wt%~10wt% phosphoric acid and 0.09g / L~0.12g / L ammonium bifluoride for 10s~20s.

[0097] Electrolyte Preparation: 1,3-Dimethyl-2-imidazolidinone and lithium hexafluorophosphate were mixed and stirred at room temperature at a rate of 200-400 r / min to obtain a uniform, fluid, room-temperature aprotic solvent in the electrolytic cell. The lithium hexafluorophosphate concentration in the room-temperature aprotic solvent was 0.5 mol / L. Aluminum chloride was then added to the room-temperature aprotic solvent to obtain an electrolyte solution. The aluminum chloride concentration in the electrolyte was 0.5 mol / L.

[0098] Electrolysis: A 50ml flat-top beaker served as the electrolytic cell. A surface-free LA43M magnesium-lithium alloy substrate (effective area 1cm×1cm) served as the cathode, and a high-purity platinum sheet (effective area 1cm×2cm) served as the anode, both fixed in the prepared electrolyte, formed the electrolysis system. The electrolysis reaction was carried out under constant voltage and temperature conditions. The electrolysis temperature was controlled by a magnetic heating stirrer. The applied deposition potential was -2.2V vs. Al, and the electrolyte temperature was 50°C. Electrolysis was performed in the electrolyte for 1 hour.

[0099] Cleaning: After the electrolysis is completed, the cathode is removed, cleaned with acetonitrile, and vacuum dried to obtain the aluminum-magnesium-lithium alloy. The EDS test results show that the mass percentage of aluminum is 37.26% and the current efficiency reaches 86.39%.

[0100] Comparative Example 1:

[0101] Pretreatment: The surface of the LA103Z magnesium-lithium alloy substrate is pretreated by mechanical grinding-ultrasonic cleaning-alkali cleaning-acid immersion-activation-cleaning-cold air drying to obtain a magnesium-lithium alloy with no impurities on the surface. Among them, LA103Z magnesium-lithium alloy was polished with 400#, 800#, 1200# and 2000# SiC sandpaper in sequence for 10min~30min, and ultrasonically cleaned in anhydrous ethanol for 10min~20min; then alkali washed in a mixed solution containing 15g / L~20g / L sodium hydroxide, 5g / L~10g / L sodium carbonate, and 10g / L~15g / L sodium phosphate for 10min~20min at a temperature of 50℃~60℃; acid soaked in 5wt%~10wt% phosphoric acid solution for 10s~20s at a temperature of 20℃~30℃; finally, activated in a mixed solution containing 5wt%~10wt% phosphoric acid and 0.09g / L~0.12g / L ammonium bifluoride for 10s~20s.

[0102] Preparation of electrolyte: At room temperature, aluminum chloride was added to 1,3-dimethyl-2-imidazolidinone and mixed with stirring at a stirring speed of 200 r / min to 400 r / min to obtain a uniform electrolyte with good fluidity in the electrolytic cell. The aluminum chloride concentration in the electrolyte was 0.5 mol / L.

[0103] Electrolysis: A 50ml bottle-top beaker was used as the electrolytic cell. A surface-free LA103Z magnesium-lithium alloy substrate (effective area 1cm×1cm) was used as the cathode, and a high-purity platinum sheet (effective area 1cm×2cm) was used as the anode. These elements were fixed in the prepared electrolyte to form the electrolysis system. The electrolysis reaction was carried out under constant voltage and temperature conditions. The electrolysis temperature was controlled by a magnetic heating stirrer. Electrolysis was conducted in the electrolyte for 1 hour at a temperature of 50°C and an applied deposition potential of -2.4V vs. Al.

[0104] Cleaning: After the electrolysis is completed, the cathode is removed, cleaned with acetonitrile, and vacuum dried to obtain the aluminum-magnesium-lithium alloy. The EDS test results show that the mass percentage of aluminum is 23.18% and the current efficiency is 70.49%.

[0105] It can be seen that when lithium hexafluorophosphate is not added to 1,3-dimethyl-2-imidazolidinone, the current efficiency of the electroplated aluminum layer is only 70.49%. Using 1,3-dimethyl-2-imidazolidinone-lithium hexafluorophosphate as the electrolyte system promotes the electrodeposition of aluminum in the electrolyte and improves the current efficiency.

[0106] Example 14:

[0107] Pretreatment: The surface of the LA103Z magnesium-lithium alloy substrate is pretreated by mechanical grinding-ultrasonic cleaning-alkali cleaning-acid immersion-activation-cleaning-cold air drying to obtain a magnesium-lithium alloy with no impurities on the surface. Among them, LA103Z magnesium-lithium alloy was polished with 400#, 800#, 1200# and 2000# SiC sandpaper in sequence for 10min~30min, and ultrasonically cleaned in anhydrous ethanol for 10min~20min; then alkali washed in a mixed solution containing 15g / L~20g / L sodium hydroxide, 5g / L~10g / L sodium carbonate, and 10g / L~15g / L sodium phosphate for 10min~20min at a temperature of 50℃~60℃; acid soaked in 5wt%~10wt% phosphoric acid solution for 10s~20s at a temperature of 20℃~30℃; finally, activated in a mixed solution containing 5wt%~10wt% phosphoric acid and 0.09g / L~0.12g / L ammonium bifluoride for 10s~20s.

[0108] Electrolyte Preparation: 1,3-Dimethyl-2-imidazolidinone and lithium hexafluorophosphate were mixed and stirred at room temperature at a rate of 200-400 r / min to obtain a uniform, fluid, room-temperature aprotic solvent in the electrolytic cell. The lithium hexafluorophosphate concentration in the room-temperature aprotic solvent was 0.5 mol / L. Aluminum chloride was added to the room-temperature aprotic solvent and, after complete dissolution, zinc chloride was added to obtain an electrolyte. The concentrations of aluminum chloride and zinc chloride in the electrolyte were 0.5 mol / L and 0.02 mol / L, respectively.

[0109] Electrolysis: A 50ml flat-top beaker served as the electrolytic cell. A surface-free LA103Z magnesium-lithium alloy substrate (effective area 1cm×1cm) served as the cathode, and a high-purity platinum sheet (effective area 1cm×2cm) served as the anode, both fixed in the prepared electrolyte, formed the electrolysis system. The electrolysis reaction was carried out under constant voltage and temperature conditions. The electrolysis temperature was controlled by a magnetic heating stirrer. Electrolysis was conducted for 1 hour at an electrolyte temperature of 50°C and an applied deposition potential of -2.2V vs. Al.

[0110] Cleaning: After the electrolysis is completed, the cathode is removed, cleaned with acetonitrile, and vacuum dried to obtain the aluminum-zinc coating. The EDS test results show that the mass percentages of aluminum and zinc are 41.72% and 25.06%, respectively.

[0111] Example 15:

[0112] Pretreatment: The surface of the LA103Z magnesium-lithium alloy substrate is pretreated by mechanical grinding-ultrasonic cleaning-alkali cleaning-acid immersion-activation-cleaning-cold air drying to obtain a magnesium-lithium alloy with no impurities on the surface. Among them, LA103Z magnesium-lithium alloy was polished with 400#, 800#, 1200# and 2000# SiC sandpaper in sequence for 10min~30min, and ultrasonically cleaned in anhydrous ethanol for 10min~20min; then alkali washed in a mixed solution containing 15g / L~20g / L sodium hydroxide, 5g / L~10g / L sodium carbonate, and 10g / L~15g / L sodium phosphate for 10min~20min at a temperature of 50℃~60℃; acid soaked in 5wt%~10wt% phosphoric acid solution for 10s~20s at a temperature of 20℃~30℃; finally, activated in a mixed solution containing 5wt%~10wt% phosphoric acid and 0.09g / L~0.12g / L ammonium bifluoride for 10s~20s.

[0113] Electrolyte Preparation: 1,3-Dimethyl-2-imidazolidinone and lithium hexafluorophosphate were mixed and stirred at room temperature at a rate of 200-400 r / min to obtain a uniform, fluid, room-temperature aprotic solvent in the electrolytic cell. The lithium hexafluorophosphate concentration in the room-temperature aprotic solvent was 0.5 mol / L. Aluminum chloride was added to the room-temperature aprotic solvent and dissolved completely, followed by zinc chloride to obtain an electrolyte solution. The concentrations of aluminum chloride and zinc chloride in the electrolyte were 0.5 mol / L and 0.1 mol / L, respectively.

[0114] Electrolysis: A 50ml flat-top beaker served as the electrolytic cell. A surface-free LA103Z magnesium-lithium alloy substrate (effective area 1cm×1cm) served as the cathode, and a high-purity platinum sheet (effective area 1cm×2cm) served as the anode, both fixed in the prepared electrolyte, formed the electrolysis system. The electrolysis reaction was carried out under constant voltage and temperature conditions. The electrolysis temperature was controlled by a magnetic heating stirrer. Electrolysis was conducted for 1 hour at an electrolyte temperature of 50°C and an applied deposition potential of -2.2V vs. Al.

[0115] Cleaning: After the electrolysis is completed, the cathode is removed, cleaned with acetonitrile, and vacuum dried to obtain the aluminum-zinc coating. The EDS test results show that the mass percentages of aluminum and zinc are 44.16% and 26.88%, respectively.

[0116] Example 16:

[0117] Pretreatment: The surface of the LA103Z magnesium-lithium alloy substrate is pretreated by mechanical grinding-ultrasonic cleaning-alkali cleaning-acid immersion-activation-cleaning-cold air drying to obtain a magnesium-lithium alloy with no impurities on the surface. Among them, LA103Z magnesium-lithium alloy was polished with 400#, 800#, 1200# and 2000# SiC sandpaper in sequence for 10min~30min, and ultrasonically cleaned in anhydrous ethanol for 10min~20min; then alkali washed in a mixed solution containing 15g / L~20g / L sodium hydroxide, 5g / L~10g / L sodium carbonate, and 10g / L~15g / L sodium phosphate for 10min~20min at a temperature of 50℃~60℃; acid soaked in 5wt%~10wt% phosphoric acid solution for 10s~20s at a temperature of 20℃~30℃; finally, activated in a mixed solution containing 5wt%~10wt% phosphoric acid and 0.09g / L~0.12g / L ammonium bifluoride for 10s~20s.

[0118] Electrolyte Preparation: 1,3-Dimethyl-2-imidazolidinone and lithium hexafluorophosphate were mixed and stirred at room temperature at a rate of 200-400 r / min to obtain a uniform, fluid, room-temperature aprotic solvent in the electrolytic cell. The lithium hexafluorophosphate concentration in the room-temperature aprotic solvent was 0.5 mol / L. Aluminum chloride was added to the room-temperature aprotic solvent and dissolved completely, followed by zinc chloride to obtain an electrolyte solution. The concentrations of aluminum chloride and zinc chloride in the electrolyte were 0.5 mol / L and 0.5 mol / L, respectively.

[0119] Electrolysis: A 50ml flat-top beaker served as the electrolytic cell. A surface-free LA103Z magnesium-lithium alloy substrate (effective area 1cm×1cm) served as the cathode, and a high-purity platinum sheet (effective area 1cm×2cm) served as the anode, both fixed in the prepared electrolyte, formed the electrolysis system. The electrolysis reaction was carried out under constant voltage and temperature conditions. The electrolysis temperature was controlled by a magnetic heating stirrer. Electrolysis was conducted for 1 hour at an electrolyte temperature of 50°C and an applied deposition potential of -2.2V vs. Al.

[0120] Cleaning: After the electrolysis is completed, the cathode is removed, cleaned with acetonitrile, and vacuum dried to obtain the aluminum-zinc coating. The EDS test results show that the mass percentages of aluminum and zinc are 43.75% and 25.94%, respectively.

[0121] It can be seen from Examples 14 to 16 that, keeping other conditions the same, zinc chloride is added to the electrolyte and the zinc chloride concentration is controlled to be 0.02 mol / L to 0.5 mol / L, and an aluminum-zinc coating can be obtained by electroplating.

Claims

1. A method for electroplating aluminum or aluminum-zinc alloy on the surface of a magnesium-lithium alloy using a room temperature aprotic solvent, characterized in that: The process steps include: Pretreatment: pretreating the magnesium-lithium alloy to obtain a magnesium-lithium alloy with no impurities on the surface for standby use; Preparation of electrolyte: 1,3-dimethyl-2-imidazolidinone solution and lithium hexafluorophosphate are mixed and stirred to obtain a room temperature aprotic solvent, and aluminum salt and zinc salt are added to the room temperature aprotic solvent and stirred continuously until the mixture is uniform to obtain an electrolyte; Electrolysis: Use the pretreated magnesium-lithium alloy as the cathode and the platinum sheet as the anode to perform electrolysis in the electrolyte; Cleaning: After the electrolysis is completed, the magnesium-lithium alloy sample is taken out and cleaned with acetonitrile to obtain a magnesium-lithium alloy with aluminum or aluminum-zinc alloy electroplated on the surface; The magnesium-lithium alloy is one of LA103Z, LA103M, and LA43M. During the pretreatment process, the surface of the magnesium-lithium alloy substrate is pretreated by mechanical grinding-ultrasonic cleaning-alkali cleaning-acid immersion-activation-cleaning-cold air drying. The room temperature aprotic solvent conductivity measured at 50°C is between 3.83 mS / cm and 4.2 mS / cm.

2. The method of electroplating aluminum or aluminum-zinc alloy on the surface of a magnesium-lithium alloy using a room temperature aprotic solvent according to claim 1, characterized in that: During the electrolyte preparation process, the stirring speed is 200 r / min to 400 r / min.

3. The method of electroplating aluminum or aluminum-zinc alloy on the surface of magnesium-lithium alloy using a room temperature aprotic solvent according to claim 1, characterized in that: The concentration of lithium hexafluorophosphate in the aprotic solvent at room temperature is 0.1 mol / L to 0.5 mol / L.

4. The method of electroplating aluminum or aluminum-zinc alloy on the surface of a magnesium-lithium alloy using a room temperature aprotic solvent according to claim 1, characterized in that: In the electrolyte, the aluminum salt concentration is 0.5 mol / L to 1 mol / L, and the zinc salt concentration is 0 to 0.5 mol / L; The aluminum salt is aluminum chloride, and the zinc salt is zinc chloride.

5. The method of electroplating aluminum or aluminum-zinc alloy on the surface of magnesium-lithium alloy using a room temperature aprotic solvent according to claim 1, characterized in that: During the electrolysis process, constant potential electrolysis is adopted, the electrolysis temperature is 20° C. to 50° C., the voltage during the electrolysis process is -1.8 V vs Al to -2.4 V vs Al, and the electrolysis time is 0.5 h to 2 h.

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