A method of electroplating zinc on a magnesium alloy

Abstract

The application discloses a magnesium alloy zinc electroplating method and belongs to the technical field of magnesium alloy surface treatment. The method comprises the following steps: 1. substrate pretreatment: AZ31B magnesium alloy is polished by sandpaper and then is washed by anhydrous ethanol and dried; 2. alkali washing: the micro specific surface area of the substrate is increased, and the mechanical bite effect of the coating and the substrate is strengthened; 3. acid washing activation: a protective film is formed on the surface of the magnesium alloy, so that the alloy is not corroded in the electroplating solution; 4. pre-plating zinc: an initial zinc layer with uniformity, compactness and strong adhesion is rapidly established on the surface by adopting impact current; and 5. zinc electroplating: the magnesium alloy with the initial zinc layer is electroplated. The zinc coating of the magnesium alloy is uniform and compact and is silver-white. The process is synergistically controlled by pretreatment and impact current pre-plating, the coating is uniform and compact, is bright silver-white, is firmly combined with the substrate and is not easy to peel off, and the obtained zinc coating has excellent corrosion resistance and welding adaptability.

Description

Technical Field

[0001] This invention relates to a method for electroplating zinc onto magnesium alloys. More particularly, it relates to a method for electroplating zinc onto AZ31B magnesium alloys, belonging to the field of magnesium alloy surface treatment technology. Background Technology

[0002] Magnesium alloys, with their advantages of low density, high specific strength, and high specific stiffness, have great potential for application in lightweight fields such as aerospace, automotive, and electronics. AZ31B magnesium alloy, as a typical wrought magnesium alloy, has excellent forming and processing performance, making it a preferred material for lightweight structural components. However, magnesium alloys are chemically reactive and have a low standard electrode potential, making them highly susceptible to corrosion in humid and salt spray environments. Furthermore, their welding process is prone to defects such as hot cracking and porosity, severely limiting their industrial application. Welding AZ31B magnesium alloy often employs sheet-assisted welding, a process that easily introduces oxygen inclusions, affecting the mechanical properties of the joint. While ultrasonic-assisted cavitation to remove the oxide layer has size limitations and increases costs, electroplating an intermediate layer is expected to mitigate the impact of the oxide layer, thereby improving joint performance. Electroplating zinc, due to its low cost, mature process, and good protective effect, can not only improve the corrosion resistance of AZ31B magnesium alloy, but the resulting zinc coating can also serve as a welding intermediate layer, optimizing the weld interface characteristics. However, existing electroplating zinc technology has bottlenecks: the substrate is easily corroded in the plating solution, the coating has poor adhesion and is easy to fall off; conventional electroplating is difficult to obtain a uniform and dense coating, pre-plating nucleation is slow, and high current electroplating aggravates hydrogen evolution and stress. There is an urgent need to develop an electroplating zinc process that is suitable for welding requirements. Summary of the Invention

[0003] The purpose of this invention is to provide a method for electroplating zinc onto magnesium alloys to solve the above-mentioned technical problems.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A method for electroplating zinc onto magnesium alloys includes the following steps: Step 1: Pretreatment of the substrate: The AZ31B magnesium alloy was sanded with sandpaper, rinsed with anhydrous ethanol, and then dried. Step 2: Alkali washing: Increases the specific surface area of ​​the substrate and strengthens the mechanical bonding between the coating and the substrate; Step 3: Pickling and activation: This process forms a protective film on the surface of the magnesium alloy, preventing corrosion in the electroplating solution. Step 4: Pre-galvanizing: Using an impact current, a uniform, dense, and strongly bonded initial zinc layer is quickly established on the surface; Step 5: Electroplating zinc: Electroplating the magnesium alloy to produce the initial zinc layer.

[0005] Furthermore, step 1 includes the following steps: Step 1.1: Use AZ31B magnesium alloy and sandpaper ranging from 400# to 800# to 1200# for polishing; Step 1.2: Rinse with anhydrous ethanol and dry.

[0006] Furthermore, step 2 includes the following steps: Step 2.1: Prepare an alkaline washing solution using 40-60 g / L NaOH and 5-15 g / L Na3PO4·12H2O; Step 2.2: Heat the alkaline cleaning solution to 60-80℃ and keep it at that temperature, then immerse the AZ31B magnesium alloy for 8-10 minutes; Step 2.3: Rinse with deionized water and dry.

[0007] Furthermore, step 3 includes the following steps: Step 3.1: Prepare an acid washing and activation solution using 20-40 g / L Na2MoO4 and 10-30 mL / L H3PO4; Step 3.2: Immerse AZ31B magnesium alloy at room temperature for 1~2 minutes, shaking constantly to prevent over-etching; Step 3.3: Rinse with deionized water and dry.

[0008] Furthermore, step 4 includes the following steps: Step 4.1: Prepare a pre-plating solution using 20-40 g / L ZnSO4 and 100-150 g / L Na4P2O7, and adjust the pH to 9.5-10.5 with 10-20 mL / L NH3·H2O; Step 4.2: The magnesium alloy is first energized and then immersed in the pre-plating solution, using J... c =3 A·dm -2 Electroplating of magnesium alloy for 15-30 seconds, followed by J... c =1 A·dm -2 Electroplating magnesium alloy for 1~2 minutes.

[0009] Furthermore, step 5 includes the following steps: Step 5.1: Use 20-40 g / L ZnSO4, 100-150 g / L Na4P2O7, 5-15 g / L KF, 0.5-1.5 g / L NH4F, 3-8 g / L NaCO3, and 2-4×10 -2 An electroplating solution was prepared by mixing 5-15 g / L sodium dodecyl sulfonate and 5-15 g / L sodium citrate, and the pH was adjusted to 9.5-10.5 with 10-20 mL / L NH3·H2O. Step 5.2: Using a zinc sheet as the anode, employ J... c=1-2 A·dm -2 Electroplating magnesium alloy at 50-60℃ for 30-45 minutes; Step 5.3: Wash with deionized water and dry.

[0010] Magnesium alloy coated parts obtained by the method of electroplating zinc onto magnesium alloy according to the present invention.

[0011] The corrosion current density of the magnesium alloy plated part is ≤2.421×10⁻⁶. -5 A / dm 2 The coating exhibits no peeling, blistering, or flaking, and demonstrates excellent adhesion.

[0012] Application of the magnesium alloy plated parts in highly corrosive environments.

[0013] Application of the magnesium alloy plated parts in welded parts.

[0014] The preferred magnesium alloy plated part is a circular sheet with a diameter of 29.5 mm and a thickness of 5 mm. That is, in this invention, the magnesium alloy substrate used for welding has dimensions d = 29.5 mm and a thickness of 5 mm; other magnesium alloys used for testing have dimensions of 5 × 10 × 20 mm. This invention's pre-plating followed by welding mainly solves the oxide layer problem in conventional welding with welding strips. This invention directly plating zinc onto the magnesium alloy and directly welding two pieces of magnesium alloy without the need for welding strips. Figure 7 According to the energy spectrum, oxygen is not concentrated in the weld seam, therefore the magnesium alloy plated parts of this invention have good weldability.

[0015] Compared with the prior art, the present invention has the following beneficial effects: In the prior art, magnesium alloys turn black and oxidize during welding, and zinc is easily oxidized and evaporated during welding. However, by using the method of the present invention, the weld (i.e. the joint) obtained after welding is silvery-white, which overcomes the influence of the oxide layer and thus improves the joint performance.

[0016] In existing technologies, magnesium oxide films easily reform after mechanical polishing. Ultrasonic treatment aims to address the oxide film problem through cavitation. Even without ultrasonic treatment, the oxide film remains. Conventional electroplating methods also suffer from oxide film effects. Conventional zinc electroplating involves a process of mechanical polishing, alkaline washing, acid washing, activation, zinc immersion, and zinc electroplating, with deionized water rinsing between each step. Acid washing removes the oxide layer from the magnesium alloy substrate, exposing the substrate. However, the magnesium alloy will still oxidize within a short time after acid washing. Activation forms a uniform, thin, and catalytically active temporary conversion film to prevent magnesium from undergoing rapid corrosion or re-oxidation upon entering the electroplating solution. In conventional zinc electroplating, acid washing and activation are usually separated into two steps, during which oxide films are still easily formed. Moreover, traditional zinc immersion is a displacement reaction, leaving zinc in a porous state. This invention, however, directly uses high current density pre-plating, which can rapidly cover a continuous metal layer before the displacement reaction occurs. Therefore, by using a one-step acid pickling activation, the generated conversion film enters the pre-plating solution after being energized, and at the same time, a current density 2-3 times larger than the main plating current density is applied. While the film layer is being removed, zinc is deposited on the substrate. This method can effectively reduce the problem of oxide film.

[0017] The present invention provides a method for electroplating zinc onto magnesium alloys, which has the following advantages: the process is simple and easy to implement, low in cost, requires no complex equipment, and is suitable for industrial mass production; through the synergistic control of pretreatment and impact current preplating, the coating is uniform, dense, and bright silver-white, with a strong bond to the substrate and is not prone to peeling or flaking; the obtained zinc coating has both excellent corrosion resistance and weldability, and can be directly used as a welding intermediate layer to optimize interface characteristics, effectively solving the problem of welding defects in magnesium alloys, and has broad application prospects.

[0018] This invention belongs to the field of magnesium alloy surface treatment technology, specifically disclosing a method for electroplating zinc onto AZ31B magnesium alloy. The method includes the following steps: 1. Substrate pretreatment: The AZ31B magnesium alloy is sanded, rinsed with anhydrous ethanol, and then dried; 2. Alkali washing: This increases the microscopic specific surface area of ​​the substrate and strengthens the mechanical bonding between the coating and the substrate; 3. Acid pickling activation: This forms a protective film on the surface of the magnesium alloy, preventing corrosion in the electroplating solution; 4. Pre-zinc plating: An impact current is used to quickly establish a uniform, dense, and strongly bonded initial zinc layer on the surface; 5. Electroplating zinc: The magnesium alloy with the initial zinc layer is electroplated. The zinc coating on the AZ31B magnesium alloy obtained by this invention is uniform, dense, and silvery-white, combining low cost and high practicality, with broad application prospects. Attached Figure Description

[0019] Figure 1 This is a flowchart of a method for electroplating zinc onto AZ31B magnesium alloy according to the present invention; Figure 2The polarization curves of magnesium alloy plated parts of Examples 1, 2, and 3 are shown in the example, with a saturated calomel electrode as the reference electrode, a platinum sheet as the auxiliary electrode, and a 3.5% NaCl solution as the corrosive medium. Figure 3 The image shows a SEM image of a magnesium alloy part plated with zinc using an AZ31B magnesium alloy electroplating method according to the present invention. The zinc on the magnesium alloy surface is uniform and dense. Figure 4 The XRD patterns of Examples 1, 2 and 3 are shown. In Examples 1 and 2, the (100) and (101) peaks are stronger and the zinc has no obvious orientation. In Example 3, the (002) basal plane peak intensity of the zinc coating is improved and the coating is more flat, dense and uniform. Figure 5 Schematic diagram of the cross-cut adhesion tester and high-temperature heat treatment furnace; Figure 6 A schematic diagram of the SPS sintering furnace of FCT in Germany; Figure 7 Example 2 uses SPS process (p=7 MPa, t) 保温 =10 min, T=340℃, t 加热 =7 min) Microstructure and energy spectrum of the joint weld. Detailed Implementation

[0020] The following description, in conjunction with the accompanying drawings and embodiments of the present invention, will further clarify the objectives, technical solutions, and advantages of the present invention. The specific embodiments described are merely illustrative and are not intended to limit the scope of the invention.

[0021] To better understand the purpose, structure, and function of this invention, the following detailed description of a method for electroplating zinc onto AZ31B magnesium alloy, in conjunction with the accompanying drawings, is provided.

[0022] Example 1: Step 1: Substrate pretreatment: The substrate type is AZ31B magnesium alloy, and the substrate size is 5 mm × 10 mm × 20 mm. The substrate is polished with 600#, 800# and 1200# sandpaper in sequence, rinsed with anhydrous ethanol and blown dry.

[0023] Step 2: Alkaline washing: Prepare an alkaline washing solution using 50 g / L NaOH and 10 g / L Na3PO4·12H2O. Heat the alkaline washing solution to 70℃ and keep it at that temperature, then immerse the AZ31B magnesium alloy for 8 minutes.

[0024] Step 3: Acid pickling and activation: Prepare an acid pickling and activation solution using 30 g / L Na2MoO4 and 20 mL / L H3PO4. Immerse the AZ31B magnesium alloy at room temperature for 2 min, shaking continuously to prevent over-etching. Then rinse with deionized water and dry.

[0025] Step 4: Pre-plating with zinc: A pre-plating solution was prepared using 30 g / L ZnSO4 and 120 g / L Na4P2O7, and the pH was adjusted to 10 with 15 mL / L NH3·H2O. The magnesium alloy was first energized and then immersed in the pre-plating solution, using J... c =1 A·dm -2 Electroplated magnesium alloy 90 s.

[0026] Step 5: Electroplating with zinc: using 30 g / L ZnSO4, 120 g / L Na4P2O7, 10 g / L KF, 1 g / L NH4F, 5 g / L NaCO3, 3×10 -2 An electroplating solution was prepared using 10 g / L sodium dodecyl sulfate and 10 g / L sodium citrate, and the pH was adjusted to 10 with 15 mL / L NH3·H2O. A zinc sheet was used as the anode, and J... c =1 A·dm -2 Magnesium alloy was electroplated at 50℃ for 30 min. After electroplating, it was rinsed with deionized water and dried.

[0027] Example 1 Technical Effect: Using 1 A / dm 2 A continuous initial zinc layer can be formed on the surface of AZ31B magnesium alloy after pre-plating with a constant current for 90 s. After electroplating, the coating has good adhesion to the substrate and no obvious peeling or flaking. However, due to the low current density and long pre-plating time, the cathodic polarization is weak and the zinc grain nucleation rate is slow. The surface finish of the coating is moderate, and the corrosion current density is lower than that of Example 3, therefore the corrosion resistance is lower than that of Example 3.

[0028] Example 2: Step 1: Substrate pretreatment: The substrate type is AZ31B magnesium alloy, and the substrate size is 5 mm × 10 mm × 20 mm. The substrate is polished with 600#, 800# and 1200# sandpaper in sequence, rinsed with anhydrous ethanol and dried.

[0029] Step 2: Alkaline washing: Prepare an alkaline washing solution using 50 g / L NaOH and 10 g / L Na3PO4·12H2O. Heat the alkaline washing solution to 70℃ and keep it at that temperature, then immerse the AZ31B magnesium alloy for 8 minutes.

[0030] Step 3: Acid pickling and activation: Prepare an acid pickling and activation solution using 30 g / L Na2MoO4 and 20 mL / L H3PO4. Immerse the AZ31B magnesium alloy at room temperature for 2 min, shaking continuously to prevent over-etching. Then rinse with deionized water and dry.

[0031] Step 4: Pre-plating with zinc: A pre-plating solution was prepared using 30 g / L ZnSO4 and 120 g / L Na4P2O7, and the pH was adjusted to 10 with 15 mL / L NH3·H2O. The magnesium alloy was first energized before entering the pre-plating solution, using 1.5 A / dm². 2 After 30 seconds of pre-plating with the impact current, the current is increased to 1 A / dm. 2 Pre-plating for 60 seconds.

[0032] Step 5: Electroplating with zinc: using 30 g / L ZnSO4, 120 g / L Na4P2O7, 10 g / L KF, 1 g / L NH4F, 5 g / L NaCO3, 3×10 -2 An electroplating solution was prepared using 10 g / L sodium dodecyl sulfonate and 10 g / L sodium citrate, and the pH was adjusted to 10 with 15 mL / L NH3·H2O. A zinc sheet was used as the anode, and J... c =1 A·dm -2 Magnesium alloy was electroplated at 50℃ for 30 min. After electroplating, it was rinsed with deionized water and dried.

[0033] Example 2 Technical Effect: Using 1.5 A / dm 2 After 30 seconds of pre-plating with the impact current, the current is increased to 1 A / dm. 2 After 60 seconds of pre-plating, a continuous initial zinc layer can be formed on the surface of the AZ31B magnesium alloy. The coating has good adhesion to the substrate and no obvious peeling or flaking. However, the cathodic polarization is still weak, and the zinc grain nucleation rate is slow. The surface finish of the coating is moderate, and the corrosion current density is between that of Example 1 and Example 3. Therefore, the corrosion resistance is between that of Example 1 and Example 3.

[0034] Example 3: like Figure 1 As shown, a method for electroplating zinc onto a magnesium alloy includes the following steps: Step 1: Substrate pretreatment: The substrate type is AZ31B magnesium alloy, and the substrate size is 5 mm × 10 mm × 20 mm. The substrate is polished with 600#, 800# and 1200# sandpaper in sequence, rinsed with anhydrous ethanol and dried.

[0035] Step 2: Alkaline washing: Prepare an alkaline washing solution using 50 g / L NaOH and 10 g / L Na3PO4·12H2O. Heat the alkaline washing solution to 70℃ and keep it at that temperature, then immerse the AZ31B magnesium alloy for 8 minutes.

[0036] Step 3: Acid pickling and activation: Prepare an acid pickling and activation solution using 30 g / L Na2MoO4 and 20 mL / L H3PO4. Immerse the AZ31B magnesium alloy at room temperature for 2 min, shaking continuously to prevent over-etching. Then rinse with deionized water and dry.

[0037] Step 4: Pre-plating with zinc: A pre-plating solution was prepared using 30 g / L ZnSO4 and 120 g / L Na4P2O7, and the pH was adjusted to 10 with 15 mL / L NH3·H2O. The magnesium alloy was first energized and then immersed in the pre-plating solution, using J... c =3 A·dm -2 Electroplating of magnesium alloy for 30 seconds, followed by J... c =1 A·dm -2 Electroplating magnesium alloy for 1 minute.

[0038] Step 5: Electroplating with zinc: using 30 g / L ZnSO4, 120 g / L Na4P2O7, 10 g / L KF, 1 g / L NH4F, 5 g / L NaCO3, 3×10 -2 An electroplating solution was prepared using 10 g / L sodium dodecyl sulfonate and 10 g / L sodium citrate, and the pH was adjusted to 10 with 15 mL / L NH3·H2O. A zinc sheet was used as the anode, and J... c =1 A·dm -2 Magnesium alloy was electroplated at 50℃ for 30 min. After electroplating, it was rinsed with deionized water and dried.

[0039] Example 3 Technical Effect: Using 3 A / dm 2 After 30 seconds of pre-plating with the impact current, the current is increased to 1 A / dm. 2 The segmented process of pre-plating for 60 seconds, with its short-term high-current strong polarization, promotes rapid and uniform nucleation of zinc atoms, while subsequent low current ensures orderly grain growth. For example... Figure 3 As shown, Figure 3 The image shows a SEM image of a magnesium alloy part plated using an AZ31B magnesium alloy electroplating zinc method described in this example. The zinc on the magnesium alloy surface is uniform in size and dense. XRD results indicate that the diffraction peak intensity of the (002) crystal plane of the coating is enhanced. Figure 4 As shown. (002) is an atomic close-packed plane with the lowest surface energy. Growing this plane parallel to the substrate surface means that the coating expands in the most stable way, easily forming a flat, smooth, and low-porosity dense coating. The resulting zinc coating is uniform and dense, bright silver-white, firmly bonded to the substrate, without roughness or blackening defects, and has excellent corrosion resistance. Spark Plasma Sintering (SPS) technology is used. Figure 6(A schematic diagram of the SPS sintering furnace of FCT, Germany) was used for welding, with p=7 MPa and t 保温 =10 min, T=340℃, t 加热 Welding parameters were set for 7 minutes to obtain the microstructure and energy spectrum of the joint weld, such as... Figure 7 As shown, the joint has no obvious delamination and there are no obvious oxide inclusions at the interface with the substrate, so the coating has good solderability.

[0040] The magnesium alloy plating obtained in this example has a corrosion current density of 2.421 × 10⁻⁶. -5 A / dm 2 The coating exhibits no peeling, blistering, or flaking, and demonstrates excellent adhesion.

[0041] In this example, the magnesium alloy plated part is used as a welding strip in the welded part, and the joint obtained after welding the welding strip is silvery white.

[0042] Example 4: The only difference between Example 4 and Example 3 is that Example 4 uses 4 A / dm. 2 After a 20-second pre-plating period with the impact current, the current is increased to 1 A / dm. 2 A segmented process with a pre-plating time of 60 seconds.

[0043] This example uses 4 A / dm 2 Excessive inrush current results in poor adhesion of the pre-plated substrate, leading to peeling during subsequent electroplating. In this example, the inrush current was approximately four times the main plating current, which is too high and causes severe hydrogen evolution. This demonstrates that an excessively high pre-plating inrush current cannot yield a satisfactory coating.

[0044] The coating performance of Examples 1, 2, and 3 was evaluated using the following method.

[0045] (1) The corrosion resistance of the coating was evaluated using an electrochemical workstation, GAMRY INTERFACE 1010, to perform electrochemical Tafel tests on Examples 1, 2, and 3. A saturated calomel electrode was used as the reference electrode, a platinum sheet as the counter electrode, and the corrosive medium was a 3.5% NaCl solution with a pH of 7.0. Figure 2 As shown, the corrosion current density of Examples 1, 2, and 3 gradually decreases, and the corrosion current density of Example 3 is about half that of Example 1, thus the corrosion resistance is significantly improved.

[0046] (2) The coating adhesion was evaluated using the cross-cut test and thermal shock test as recommended by the national standard QB / T 3821-1999. Figure 5This diagram illustrates the cross-cut adhesion test tool and high-temperature heat treatment furnace. For the cross-cut test, a cross-cut tool is used to make two cuts, one horizontal and one vertical, on the surface of the plated sample. Sufficient pressure must be applied during the cuts to allow the blade to penetrate the plating and reach the base metal. Afterward, the cut area is gently brushed with a soft brush to remove debris. Test tape is then completely applied to the cut surface, and a stable pulling force perpendicular to the plating surface is applied before quickly removing the tape. The extent of plating detachment within the cut area is observed. For the thermal shock test, the obtained plating sample is placed in a high-temperature heat treatment furnace and heated to 180°C. It is then held at this temperature for 1 hour, removed, and immediately immersed in room temperature (18-25°C) water. After 5 minutes, it is removed and dried, and the plating is observed for blistering, wrinkles, peeling, or other defects.

[0047] Table 1. Coating adhesion assessment

[0048] Example 5: like Figure 1 As shown, a method for electroplating zinc onto a magnesium alloy includes the following steps: Step 1: Substrate pretreatment: The substrate type is AZ31B magnesium alloy, and the substrate size is 5 mm × 10 mm × 20 mm. The substrate is polished with 600#, 800# and 1200# sandpaper in sequence, rinsed with anhydrous ethanol and dried.

[0049] Step 2: Alkaline washing: Prepare an alkaline washing solution using 40 g / L NaOH and 5 g / L Na3PO4·12H2O. Heat the alkaline washing solution to 60℃ and keep it at that temperature, then immerse the AZ31B magnesium alloy for 10 min.

[0050] Step 3: Acid pickling and activation: Prepare an acid pickling and activation solution using 20 g / L Na2MoO4 and 10 mL / L H3PO4. Immerse the AZ31B magnesium alloy at room temperature for 1 min, shaking continuously to prevent over-etching. Then rinse with deionized water and dry.

[0051] Step 4: Pre-plating with zinc: A pre-plating solution was prepared using 20 g / L ZnSO4 and 100 g / L Na4P2O7, and the pH was adjusted to 9.5 with 10 mL / L NH3·H2O. The magnesium alloy was first energized and then immersed in the pre-plating solution, using J... c =3 A·dm -2 Electroplating magnesium alloy for 15 seconds, followed by J... c =1 A·dm -2 Electroplating magnesium alloy for 2 minutes.

[0052] Step 5: Electroplating with zinc: using 20 g / L ZnSO4, 100 g / L Na4P2O7, 5 g / L KF, 0.5 g / L NH4F, 3 g / L NaCO3, and 2×10 -2 An electroplating solution was prepared using 5 g / L sodium dodecyl sulfate and 5 g / L sodium citrate, and the pH was adjusted to 9.5 with 10 mL / L NH3·H2O. A zinc sheet was used as the anode, and J... c =2 A·dm -2 Magnesium alloy was electroplated at 60℃ for 45 min. After electroplating, the sample was rinsed with deionized water and dried.

[0053] The magnesium alloy plating obtained in this example has a corrosion current density of 2.357 × 10⁻⁶. -5 A / dm 2 The coating exhibits no peeling, blistering, or flaking, and demonstrates excellent adhesion.

[0054] This example demonstrates the application of magnesium alloy plated parts as welding strips in welded parts. The joint obtained after welding the welding strips is silvery-white and exhibits excellent mechanical properties.

[0055] Example 6: like Figure 1 As shown, a method for electroplating zinc onto a magnesium alloy includes the following steps: Step 1: Substrate pretreatment: The substrate type is AZ31B magnesium alloy, and the substrate size is 5 mm × 10 mm × 20 mm. The substrate is polished with 600#, 800# and 1200# sandpaper in sequence, rinsed with anhydrous ethanol and dried.

[0056] Step 2: Alkaline washing: Prepare an alkaline washing solution using 60 g / L NaOH and 15 g / L Na3PO4·12H2O. Heat the alkaline washing solution to 80℃ and keep it at that temperature, then immerse the AZ31B magnesium alloy for 9 minutes.

[0057] Step 3: Pickling and Activation: Prepare a pickling and activation solution using 40 g / L Na2MoO4 and 30 mL / L H3PO4. Immerse the AZ31B magnesium alloy at room temperature for 1.5 min, shaking constantly to prevent over-etching. Then rinse with deionized water and dry.

[0058] Step 4: Pre-plating with zinc: A pre-plating solution was prepared using 40 g / L ZnSO4 and 150 g / L Na4P2O7, and the pH was adjusted to 10.5 with 20 mL / L NH3·H2O. The magnesium alloy was first energized and then immersed in the pre-plating solution, using J... c =3 A·dm -2 Electroplating of magnesium alloy for 20 seconds, followed by J... c =1 A·dm -2Electroplating magnesium alloy for 1.5 min.

[0059] Step 5: Electroplating with zinc: using 40 g / L ZnSO4, 150 g / L Na4P2O7, 15 g / L KF, 1.5 g / L NH4F, 8 g / L NaCO3, and 4×10 -2 An electroplating solution was prepared using 15 g / L sodium dodecyl sulfonate and 15 g / L sodium citrate, and the pH was adjusted to 10.5 with 20 mL / L NH3·H2O. A zinc sheet was used as the anode, and J... c =1.5 A·dm -2 Magnesium alloy was electroplated at 55℃ for 35 min. After electroplating, the sample was rinsed with deionized water and dried.

[0060] The magnesium alloy plating obtained in this example has a corrosion current density of 2.391 × 10⁻⁶. -5 A / dm 2 The coating exhibits no peeling, blistering, or flaking, and demonstrates excellent adhesion.

[0061] This example demonstrates the application of magnesium alloy plated parts as welding strips in welded parts. The joint obtained after welding the welding strips is silvery-white and exhibits excellent mechanical properties.

[0062] It should be understood that, in order to simplify this disclosure and aid in understanding one or more of the various aspects of the invention, features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof in the above description of exemplary embodiments of the invention. However, this method of disclosure should not be interpreted as reflecting an intention that the claimed invention requires more features than expressly recited in each claim. Rather, as reflected in the claims, inventive aspects lie in fewer than all the features of the foregoingly disclosed embodiments. Therefore, the claims, following the detailed description, are hereby expressly incorporated into that detailed description, wherein each claim itself is a separate embodiment of the invention.

[0063] Although the invention has been described with reference to a limited number of embodiments, those skilled in the art will understand from the foregoing description that other embodiments are conceivable within the scope of the invention described herein. Furthermore, it should be noted that the language used in this specification has been chosen primarily for readability and edibility purposes, and not for the purpose of interpreting or limiting the subject matter of the invention. Therefore, many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the appended claims. The disclosure of the invention is illustrative and not restrictive, and the scope of the invention is defined by the appended claims.

[0064] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for electroplating zinc onto magnesium alloys, characterized in that: Includes the following steps: Step 1: Matrix pretreatment; Step 2: Alkali washing; Step 3: Acid washing and activation; Step 4: Pre-galvanizing; Step 5: Electroplating with zinc.

2. The method according to claim 1, characterized in that: In step 1, the matrix includes AZ31B magnesium alloy.

3. The method according to claim 1, characterized in that: In step 1, the substrate is sanded with sandpaper, rinsed with anhydrous ethanol, and then dried. Step 1.1: AZ31B magnesium alloy, sanded with sandpaper from 400# to 800# to 1200#; Step 1.2: Rinse with anhydrous ethanol and dry.

4. The method according to claim 3, characterized in that: Step 2 includes the following steps: Step 2.1: Prepare an alkaline washing solution using 40-60 g / L NaOH and 5-15 g / L Na3PO4·12H2O; Step 2.2: Heat the alkaline cleaning solution to 60-80℃ and keep it at that temperature, then immerse the AZ31B magnesium alloy for 8-10 minutes; Step 2.3: Rinse with deionized water and dry.

5. The method according to claim 4, characterized in that: Step 3 includes the following steps: Step 3.1: Prepare an acid washing and activation solution using 20-40 g / L Na2MoO4 and 10-30 mL / L H3PO4; Step 3.2: Immerse the AZ31B magnesium alloy at room temperature for 1-2 minutes, shaking it constantly to prevent over-etching; Step 3.3: Rinse with deionized water and dry.

6. The method according to claim 5, characterized in that: Step 4 includes the following steps: Step 4.1: Prepare a pre-plating solution using 20-40 g / L ZnSO4 and 100-150 g / L Na4P2O7, and adjust the pH to 9.5-10.5 with 10-20 mL / L NH3·H2O; Step 4.2: The magnesium alloy is first energized and then immersed in the pre-plating solution, using J... c =3 A·dm -2 Electroplating of magnesium alloy for 15-30 seconds, followed by J... c =1 A·dm -2 Electroplating magnesium alloy for 1~2 minutes.

7. The method according to claim 6, characterized in that: Step 5 includes the following steps: Step 5.1: Use 20-40 g / L ZnSO4, 100-150 g / L Na4P2O7, 5-15 g / L KF, 0.5-1.5 g / L NH4F, 3-8 g / L NaCO3, and 2-4×10 -2 An electroplating solution was prepared by mixing 5-15 g / L sodium dodecyl sulfonate and 5-15 g / L sodium citrate, and the pH was adjusted to 9.5-10.5 with 10-20 mL / L NH3·H2O. Step 5.2: Using a zinc sheet as the anode, employ J... c =1-2 A·dm -2 Electroplating magnesium alloy at 50-60℃ for 30-45 minutes; Step 5.3: Wash with deionized water and dry.

8. The magnesium alloy plated part obtained by the method according to any one of claims 1 to 7, characterized in that: The corrosion current density of magnesium alloy plated parts is ≤2.421×10⁻⁶. -5 A / dm 2 The coating exhibits no peeling, blistering, or flaking, and demonstrates excellent adhesion.

9. The application of the magnesium alloy plated part as a welding sheet in welded parts according to claim 8, characterized in that: The joint obtained after welding the welding plates is silvery-white.

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