Magnesium-aluminum alloy nickel plating material and preparation method thereof

Abstract

The invention belongs to the technical field of electroplating, and particularly relates to a magnesium-aluminum alloy nickel plating material and a preparation method thereof. The preparation method of the magnesium-aluminum alloy nickel plating material comprises the following steps: (1) pretreatment; (2) oil removal: the pretreated magnesium-aluminum alloy is subjected to oil removal; (3) first alkaline etching; (4) acid etching; (5) descaling for the first time; (6) secondary alkaline etching; (7) descaling for the second time; (8) zinc deposition; (9) alkaline chemical nickel plating; (10) carrying out acidic chemical nickel plating; (11) recycling; (12) secondary cleaning; and (13) drying is conducted, specifically, the magnesium-aluminum alloy is dried, and the magnesium-aluminum alloy nickel-plated material is obtained. The magnesium-aluminum alloy nickel plating material prepared through the method is high in plating layer binding force, excellent in weldability and high in heat resistance, impact resistance and salt spray resistance.

Description

Technical Field

[0001] This invention belongs to the field of electroplating technology, specifically relating to a magnesium-aluminum alloy nickel plating material and its preparation method. Background Technology

[0002] With the rapid development of modern electronics, communications, aerospace, and automotive industries, higher demands are being placed on lightweight, high-strength structural materials and their surface functionalization treatments. Magnesium-aluminum alloys, due to their low density, high specific strength, good thermal conductivity, and electromagnetic shielding properties, are widely used in portable electronic device housings, automotive parts, and aerospace structural components. However, magnesium-aluminum alloys are chemically reactive and readily oxidize and corrode in atmospheric environments, severely affecting their service life and reliability.

[0003] Electroplating, as a mature surface treatment process, can form a dense and uniform functional metallic coating on the surface of magnesium-aluminum alloys. Among these, nickel plating has become an important choice for magnesium-aluminum alloy surface treatment due to its excellent corrosion resistance, good electrical and thermal conductivity, and good compatibility with solderability. However, due to factors such as the presence of a natural oxide film on the surface of magnesium-aluminum alloys, a relatively negative electrode potential, and a large difference in the coefficient of thermal expansion between the alloy and the nickel layer, direct electroplating often results in poor coating adhesion and easy blistering and peeling, which seriously restricts its application in high-end manufacturing fields.

[0004] To improve coating adhesion, existing technologies typically employ multi-step pretreatment processes, including alkaline washing, acid washing, zinc or nickel immersion, and pre-plating, to activate the substrate surface and form a transition layer. While these methods improve coating adhesion to some extent, under high-temperature service or thermal cycling conditions, microcracks can easily form between the coating and the substrate due to accumulated thermal stress, affecting the material's heat resistance and impact resistance. CN105803431B describes a magnesium alloy electroless nickel plating solution, its preparation method, and the nickel plating method thereon. The nickel plating solution of this invention contains salicylaldehyde, which effectively reduces corrosion of the magnesium alloy zinc immersion layer in the electroless nickel plating solution, promotes a smooth reaction, and facilitates nickel deposition, thereby improving coating density and reducing pinholes and missed plating issues.

[0005] However, the existing nickel plating process cannot simultaneously achieve excellent solderability, heat resistance, and resistance to high and low temperature shocks, and cannot meet the comprehensive requirements of the next generation of lightweight high-performance devices for material surface functionalization. Summary of the Invention

[0006] The purpose of this invention is to provide a magnesium-aluminum alloy nickel-plated material and its preparation method.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a magnesium-aluminum alloy nickel-plated material includes the following steps: (1) Pretreatment: The surface of the magnesium-aluminum alloy is sandblasted; (2) Degreasing: The pretreated magnesium-aluminum alloy is degreased; (3) First alkaline etching; (4) Acid etching; (5) First descaling; (6) Second alkaline corrosion; (7) Second descaling; (8) Zinc precipitation: The magnesium-aluminum alloy after the second descaling is precipitated with zinc; (9) Alkaline electroless nickel plating: The magnesium-aluminum alloy after zinc immersion cleaning is placed in an alkaline nickel plating solution for plating; (10) Acidic electroless nickel plating: The magnesium-aluminum alloy after alkaline electroless nickel plating is placed in an acidic nickel plating solution and plated at a temperature of 80-85℃. The acidic nickel plating solution includes the following components: NiSO4, sodium hypophosphite, citric acid, L-lactic acid, sodium acetate trihydrate, ammonium hydrogen fluoride, thiourea, potassium iodide, compound surfactant and deionized water. (11) Recycling; (12) Second cleaning; (13) Drying: The magnesium-aluminum alloy is dried to obtain a magnesium-aluminum alloy nickel-plated material.

[0008] Preferably, the acidic nickel plating solution comprises the following components: NiSO4 20-25 g / L, sodium hypophosphite 15-20 g / L, citric acid 20-25 g / L, L-lactic acid 8-12 g / L, sodium acetate trihydrate 12-15 g / L, ammonium bifluoride 1.5-2.5 g / L, thiourea 0.8-1.2 mg / L, potassium iodide 0.08-0.12 mg / L, compound surfactant 0.5-1.0 g / L, and the balance being deionized water.

[0009] The plating solution of this invention precisely combines a compound surfactant, a corrosion inhibitor ammonium bifluoride, complexing agents citric acid and L-lactic acid, a buffer sodium acetate trihydrate, and a stabilizer thiourea and potassium iodide. These components work synergistically to significantly improve the interfacial bonding between the coating and the substrate, greatly enhancing the adhesion of the coating. At the same time, it also possesses excellent weldability, heat resistance, and impact resistance, meeting the stringent application requirements of magnesium-aluminum alloys in high-end equipment fields.

[0010] Preferably, the compound surfactant includes surfactant C. 12 -APEO-12, Octylphenol polyoxyethylene ether (OP-10), Alkylphenol polyoxyethylene ether TX-10.

[0011] Preferably, the surfactant C 12 The preparation method of APEO-12 includes the following steps: (1) Transfer the dried dodecylphenol into a high-pressure reactor and add a catalyst; (2) Under a nitrogen atmosphere, start stirring in the reactor, raise the temperature to 110-130℃, control the pressure inside the reactor at 0.2-0.4MPa, introduce 720g of ethylene oxide into the reactor, and continue to react at 110-130℃ and 0.2-0.4MPa for 4-6 hours. (3) After the reaction is complete, cool the temperature to 60-70℃, add phosphoric acid to the reactor to neutralize and adjust the pH to 6.5-7.5, let it stand, filter to remove the generated potassium phosphate, and obtain surfactant C. 12 -APEO-12.

[0012] Preferably, the molar ratio of dodecylphenol to ethylene oxide is 1:(12-13).

[0013] In existing technologies, the compound surfactants used in plating solutions mainly employ alcohol polymers as dispersants or common compound surfactants. However, the nickel plating effect is not ideal, especially for magnesium alloy nickel plating materials where the heat resistance cannot be effectively improved. The nickel plating temperature of 80-85℃ in this invention places higher demands on the compound surfactant. This invention utilizes surfactant C... 12 APEO-12, when combined with two other common compound surfactants, can significantly improve the heat resistance of nickel-plated magnesium alloy materials. Analysis shows that the active hydrogen of the phenolic hydroxyl group in the dodecylphenol molecule undergoes a nucleophilic addition reaction with ethylene oxide. Under alkaline conditions, the ethylene oxide molecule undergoes ring-opening and connects to the dodecylphenol via ether bonds, forming a hydrophilic polyoxyethylene ether chain. The final product is a nonionic structure of hydrophobic dodecylphenol-hydrophilic polyoxyethylene ether chain, possessing both the high-temperature stability of a long hydrophobic chain and the water solubility of a suitable-length hydrophilic chain.

[0014] The three compound surfactants achieve synergistic effects through structural complementarity, precisely adapting to the 80-85℃ acidic nickel plating process, ultimately improving the overall performance of the coating. 12 -APEO-12 of C 12 Long hydrophobic chains enhance intermolecular hydrophobic interactions, and when combined with EO hydrophilic chains, they raise the system's cloud point, enabling better dispersion at 80-85℃ and resolving the turbidity issue in high-temperature plating solutions. Meanwhile, OP-10 exhibits strong wettability but weak high-temperature stability, while TX-10 balances wettability with moderate stability. 12 APEO-12 exhibits excellent high-temperature stability. The combination of these three components can form a gradient hydrophobic chain and a combination that matches the EO number. The surface tension of the compound system is increased, which can quickly wet the surface of magnesium-aluminum alloys, avoiding defects such as incomplete plating and pinholes caused by insufficient wettability, ensuring full coverage of the coating, and improving the heat resistance of the coating.

[0015] Preferably, the compound surfactant comprises surfactant C in a mass ratio of 1:(1.2-1.4):(0.3-0.5). 12-APEO-12, Octylphenol polyoxyethylene ether (OP-10), Alkylphenol polyoxyethylene ether TX-10.

[0016] When surfactant C 12 A specific blend of APEO-12, octylphenol polyoxyethylene ether (OP-10), and alkylphenol polyoxyethylene ether (TX-10) can improve the temperature shock resistance of nickel plating materials. Analysis shows that the combination of these three surfactants promotes structural synergy, ensures plating solution stability, optimizes wettability, results in a dense and uniform coating, reduces stress concentration, and enhances temperature shock resistance. Simultaneously, the blend reduces the surface tension of the plating solution, decreases pinholes / missing plating spots, improves solder wettability, forms a uniform solder film, and optimizes solderability and salt spray resistance.

[0017] Preferably, white fused alumina and glass beads are mixed in a mass ratio of (1-2):(1-2) and sandblasted under a pressure of 0.2 MPa.

[0018] Preferably, the pretreated magnesium-aluminum alloy is degreased: the concentration of degreasing agent in the degreasing tank is 50-55 mL / L, the temperature is controlled at 50-60℃, and the treatment time is 5-7 min.

[0019] Preferably, the first alkaline etching uses an alkaline etchant with a concentration of 200-220 mL / L, at a temperature of 50-60℃, and for a treatment time of 60-70 seconds.

[0020] Preferably, the alkaline nickel plating solution comprises the following components: NiCO3 4-6 g / L, pH value 8.0-8.2, and the balance being deionized water.

[0021] This invention provides a magnesium-aluminum alloy nickel-plated material prepared by the aforementioned method.

[0022] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows: 1. The plating solution of the present invention precisely combines a compound surfactant, a corrosion inhibitor ammonium fluoride, a complexing agent citric acid and L-lactic acid, a buffer sodium acetate trihydrate, and a stabilizer thiourea and potassium iodide to work synergistically. Under the synergistic effect of each component, the interfacial bonding state between the coating and the substrate is significantly improved, the adhesion of the coating is greatly enhanced, and it also has excellent weldability, heat resistance and impact resistance, meeting the stringent application requirements of magnesium-aluminum alloys in the field of high-end equipment.

[0023] 2. This invention utilizes surfactant C 12 When APEO-12 is combined with two other common compound surfactants, it can improve the adaptability to electroplating temperature and significantly improve the heat resistance and salt spray resistance of the material.

[0024] 3. When surfactant C 12- APEO-12, octylphenol polyoxyethylene ether (OP-10), and alkylphenol polyoxyethylene ether TX-10, when combined in a specific ratio, can improve the temperature shock resistance of nickel-plated materials. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the magnesium-aluminum alloy nickel-plated material prepared in Example 1 before the adhesion test. The left image shows the front, and the right image shows the back.

[0026] Figure 2 This is a schematic diagram showing the adhesion test results of the nickel-plated magnesium-aluminum alloy material prepared in Example 1. The left image shows the front side, and the right image shows the back side.

[0027] Figure 3 This is a schematic diagram of the magnesium-aluminum alloy nickel-plated material prepared in Example 1 before the solderability test. The left image shows the front side, and the right image shows the back side.

[0028] Figure 4 This is a schematic diagram showing the weldability test results of the nickel-plated magnesium-aluminum alloy material prepared in Example 1. The left image shows the front side, and the right image shows the back side.

[0029] Figure 5 This is a schematic diagram of the magnesium-aluminum alloy nickel-plated material prepared in Example 1 before the heat resistance test. The left image shows the front, and the right image shows the back.

[0030] Figure 6 This is a schematic diagram showing the heat resistance test results of the nickel-plated magnesium-aluminum alloy material prepared in Example 1. The left image shows the front side, and the right image shows the back side.

[0031] Figure 7 This is a schematic diagram of the impact resistance test of the nickel-plated magnesium-aluminum alloy material prepared in Example 1. The left image shows the front, and the right image shows the back.

[0032] Figure 8 This is a schematic diagram showing the impact resistance test results of the nickel-plated magnesium-aluminum alloy material prepared in Example 1. The left image shows the front side, and the right image shows the back side.

[0033] Figures 9-12 The image shows the salt spray resistance test report of the nickel-plated magnesium-aluminum alloy material prepared in Example 1. The left image is the front side, and the right image is the back side.

[0034] Figure 13 The image shows the salt spray resistance test results of the nickel-plated magnesium-aluminum alloy material prepared in Example 1.

[0035] Figure 14 Salt spray resistance test image of the nickel-plated magnesium-aluminum alloy material prepared for Comparative Example 1.

[0036] Figure 15 Salt spray resistance test image of the nickel-plated magnesium-aluminum alloy material prepared for Comparative Example 2.

[0037] Figure 16 Salt spray resistance test image of the nickel-plated magnesium-aluminum alloy material prepared in Comparative Example 3.

[0038] Figure 17 Salt spray resistance test image of the nickel-plated magnesium-aluminum alloy material prepared in Comparative Example 4.

[0039] Figure 18 Salt spray resistance test image of the nickel-plated magnesium-aluminum alloy material prepared in Comparative Example 5.

[0040] Figure 19 Salt spray resistance test image of the nickel-plated magnesium-aluminum alloy material prepared in Comparative Example 6.

[0041] Figure 20 Salt spray resistance test results for the nickel-plated magnesium-aluminum alloy material prepared in Comparative Example 7. Detailed Implementation

[0042] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] All raw materials used in the following embodiments of the present invention are commercially available products: Degreasing agent, Dongguan Haoquan Chemical Co., Ltd., model: HQ-126, main component: NaOH.

[0044] Alkaline etchant, Guangdong Bigley Technology Co., Ltd., model BC-20, main component NaOH.

[0045] Acid etching agent, Foshan Jianghe Environmental Protection Chemical Co., Ltd., model JH-L-02B, main component HNO3.

[0046] Descaling agent: 20wt% hydrofluoric acid aqueous solution. Zinc precipitation agent, Guangdong Bigley Technology Co., Ltd., model BC-22.

[0047] Surfactant C 12 The preparation method of APEO-12 includes the following steps: (1) Dry 1000g of dodecylphenol at 85℃ and -0.08MPa vacuum for 1.5h. Transfer the dried dodecylphenol to a high-pressure reactor and add 5g of catalyst KOH. (2) Under a nitrogen atmosphere, start the stirring speed of the reactor at 60 r / min, raise the temperature to 120℃, control the pressure inside the reactor to stabilize at 0.3 MPa, and introduce 720 g of ethylene oxide. The introduction rate is controlled by the mass flow controller at 110 g / h. After the introduction is completed, continue to keep the reaction at 120℃ and 0.3 MPa for 5 h. During this period, monitor the pressure and temperature inside the reactor in real time. If the pressure drops by more than 0.05 MPa, add a small amount of nitrogen to maintain the pressure stability. (3) After the reaction is complete, the temperature is lowered to 65°C, phosphoric acid is added to the reactor to neutralize and adjust the pH to 7.0. After standing, the generated potassium phosphate is removed by filtration to obtain surfactant C. 12 -APEO-12.

[0048] Example 1 This embodiment provides a magnesium-aluminum alloy nickel-plated material, the preparation method of which includes the following steps: (1) Pretreatment: The surface of the magnesium-aluminum alloy was sandblasted under a pressure of 0.2MPa after mixing 180-mesh white corundum and 220-mesh glass beads in a mass ratio of 1:1. (2) Degreasing: The pretreated magnesium-aluminum alloy is placed in the degreasing tank. The degreasing agent is prepared with deionized water to a concentration of 50 mL / L in the degreasing tank. The temperature is controlled at 50℃ and the treatment time is 5 min. The degreased magnesium-aluminum alloy is then transferred to the water washing tank for three cleanings. Each cleaning requires shaking up and down 6 times to ensure that there is no residual degreasing agent on the surface of the magnesium-aluminum alloy. (3) First alkaline etching: The cleaned magnesium-aluminum alloy is placed in the alkaline etching tank. The alkaline etching agent is prepared with deionized water to a concentration of 200 mL / L, the temperature is 50℃, and the treatment time is 60 s. Then it is transferred to the water washing tank for three cleanings. Each cleaning requires shaking up and down 6 times to ensure that there is no residual alkaline etching agent on the surface of the magnesium-aluminum alloy.

[0049] (4) Acid etching: The cleaned magnesium-aluminum alloy is placed in an acid etching tank for acid etching treatment. The acid etching agent is prepared with water to a concentration of 200 mL / L, at room temperature, and the treatment time is 10 seconds. Then it is transferred to a water washing tank for three cleanings. Each cleaning requires shaking up and down 6 times to remove residual acid etching agent from the surface of the magnesium-aluminum alloy.

[0050] (5) First descaling: Place the acid-etched magnesium-aluminum alloy into the descaling tank, prepare the descaling agent with water to a concentration of 200 mL / L, temperature 30℃, and treatment time 50 s; transfer it to the water washing tank for three cleanings, and shake it up and down 6 times in each cleaning to remove the residual descaling agent on the surface of the magnesium-aluminum alloy.

[0051] (6) Second alkaline etching: The cleaned magnesium-aluminum alloy is placed in the alkaline etching tank, and the alkaline etching agent is prepared with water to a concentration of 200mL / L, the temperature is 60℃, and the treatment time is 60s; it is then transferred to the water washing tank for three cleanings. Each cleaning requires shaking up and down 6 times to ensure that there is no residual alkaline etching agent on the surface of the magnesium-aluminum alloy.

[0052] (7) Second descaling: Place the acid-etched magnesium-aluminum alloy into the descaling tank, prepare the descaling agent with deionized water to a concentration of 200 mL / L, temperature 30℃, treatment time 50 s; transfer to the water washing tank for three cleanings, each cleaning requires shaking up and down 6 times to remove residual descaling agent from the surface of the magnesium-aluminum alloy.

[0053] (8) Zinc precipitation: Place the cleaned magnesium-aluminum alloy into the zinc precipitation tank, prepare the zinc precipitation agent with deionized water to a concentration of 500 mL / L, temperature 60℃, treatment time 3 min; transfer to the water washing tank for three cleanings, each cleaning requires shaking up and down 6 times to remove residual zinc precipitation agent on the surface of the magnesium-aluminum alloy.

[0054] (9) Alkaline electroless nickel plating: After zinc plating, the magnesium-aluminum alloy is placed in an alkaline nickel plating bath. The alkaline nickel plating solution includes the following components: NiCO3 concentration 5g / L, pH value adjusted to 8.2 using 50% ammonia water, and the remainder is deionized water. The temperature is 88℃, and a film is formed with a thickness of 10μm. The alloy is then transferred to a water rinsing tank for three cleaning cycles. Each cleaning cycle requires the alloy to be shaken up and down 6 times to remove any residual alkaline electroless nickel plating solution from the surface of the magnesium-aluminum alloy.

[0055] (10) Acidic electroless nickel plating: The magnesium-aluminum alloy treated with alkaline electroless nickel plating is placed in an electroless nickel plating bath. The acidic nickel plating solution includes the following components: NiSO4 22 g / L, sodium hypophosphite 17 g / L, citric acid 22 g / L, L-lactic acid 10 g / L, sodium acetate trihydrate 13 g / L, ammonium bifluoride 1.9 g / L, thiourea 0.9 mg / L, potassium iodide 0.11 mg / L, compound surfactant 0.7 g / L, and the balance being deionized water. The compound surfactant includes surfactant C in a mass ratio of 1:1.3:0.4. 12 -APEO-12, octylphenol polyoxyethylene ether (OP-10, Jiangsu Haian Petrochemical Plant), alkylphenol polyoxyethylene ether TX-10 (Shandong Jinshengtai Chemical Co., Ltd.); coating was carried out at 83℃ with a coating thickness of 10μm.

[0056] (11) Recycling: The magnesium-aluminum alloy after acidic chemical nickel treatment is placed in the recycling tank, and the original liquid level in the recycling tank is maintained. Specifically, after the product is taken out of the chemical nickel tank, it is cleaned in the first pure water tank. The nickel ion concentration in this tank is not negligible and cannot be regarded as a direct discharge material. It must be recycled and uniformly treated to meet the discharge standards. This step is a routine operation in this field. (12) Second cleaning: The recycled magnesium-aluminum alloy is transferred into a water washing tank for two cleanings. Each cleaning is performed by shaking the alloy up and down 6 times to ensure that there is no plating residue on the surface of the magnesium-aluminum alloy. (13) Drying: Use clean compressed air to dry the magnesium-aluminum alloy, paying special attention to the hole area to prevent water accumulation; remove the dried magnesium-aluminum alloy from the hanger and gently wipe the surface of the magnesium-aluminum alloy with a towel and cotton cloth to prevent water residue; put the wiped magnesium-aluminum alloy into the oven and dry it according to the set temperature and time, temperature 200℃, processing time 20min, to obtain magnesium-aluminum alloy nickel plating material.

[0057] Example 2 The difference between this embodiment and Embodiment 1 is that the acidic nickel plating solution comprises the following components: NiSO4 21 g / L, sodium hypophosphite 18 g / L, citric acid 25 g / L, L-lactic acid 12 g / L, sodium acetate trihydrate 12 g / L, ammonium bifluoride 1.5 g / L, thiourea 0.8 mg / L, potassium iodide 0.08 mg / L, a compound surfactant 1.0 g / L, and the balance being deionized water. The compound surfactant comprises surfactant C in a mass ratio of 1:1.2:0.5. 12 -APEO-12, Octylphenol polyoxyethylene ether (OP-10), Alkylphenol polyoxyethylene ether TX-10.

[0058] Comparative Example 1 The difference between this comparative example and Example 1 is that dodecylphenol is replaced with nonylphenol.

[0059] Comparative Example 2 The difference between this comparative example and Example 1 is that 720g of ethylene oxide was replaced with 480g of ethylene oxide.

[0060] Comparative Example 3 The difference between this comparative example and Example 1 is that the compound surfactant is replaced with polyethylene glycol 6000.

[0061] Comparative Example 4 The difference between this comparative example and Example 1 is that surfactant C is used. 12 - APEO-12 is replaced with fatty alcohol polyoxyethylene ether (AEO-9).

[0062] Comparative Example 5 The difference between this comparative example and Example 1 is that surfactant C is used. 12 -APEO-12 is replaced with sodium dodecylbenzenesulfonate.

[0063] Comparative Example 6 The difference between this comparative example and Example 1 is that the compound surfactant includes surfactant C in a mass ratio of 1:1:1. 12-APEO-12, octylphenol polyoxyethylene ether (OP-10), alkylphenol polyoxyethylene ether TX-10.

[0064] Comparative Example 7 The difference between this comparative example and Example 1 is as follows: The operation of step (10) in Example 1 of the electroless nickel plating solution for magnesium alloy, its preparation method and nickel plating method in CN105803431B was carried out on the electroless nickel plating solution for magnesium alloy in Example 1. The remaining operation steps are the same as those in Example 1.

[0065] Performance Test The nickel-plated materials of magnesium-aluminum alloy in Examples 1-2 and Comparative Examples 1-7 were subjected to performance tests.

[0066] 1. Adhesion test: A thermal shock test was carried out on the nickel-plated materials of magnesium-aluminum alloy to observe the adhesion of the coating. It was carried out according to the thermal shock test in Section 2.4 of "QJ479 Test Method for Adhesive Strength of Metal Coatings". The specimen was placed in a constant temperature oven and heated to 220 °C, kept warm for 1 hour, then quickly cooled in normal temperature water, and visual inspection was carried out after taking out. It is required that the coating should not peel, blister, crack or flake, and is recorded as qualified. If at least one of the phenomena appears, it is recorded as unqualified.

[0067] 2. Solderability test: A solderability test was carried out on the nickel-plated materials of magnesium-aluminum alloy. It was carried out according to the requirements of Method 2003.1 in "GJB548B-2005 Test Methods and Procedures for Microelectronic Devices". Meeting the requirements that the solder and the coating have good wetting, forming a uniform and smooth solder film and the solder film has no fracture is recorded as qualified.

[0068] 3. Heat resistance test: A heat resistance test was carried out on the nickel-plated materials of magnesium-aluminum alloy. According to the requirements of Section 5.8.6 of "NJCY-AG-05-2025 Electroless Nickel Plating Process Specification for Magnesium-Aluminum Alloy", the specimen was placed on a hot stage or in an oven and heated to 350 °C, kept warm for 30 minutes, and then visual inspection was carried out after taking out. It is required that the coating should not peel, blister or flake and is recorded as qualified. If at least one of the phenomena appears, it is recorded as unqualified.

[0069] 4. Impact resistance test: "QJ455 Technical Conditions for Nickel Coatings", test temperature: -190 °C to +150 °C, each test piece was temperature-controlled at its respective temperature control point; temperature tolerance: high end: +5 °C, low end: -5 °C; number of cycles: 50 times; heating rate: 20 °C / min, cooling rate: 100 °C / min. Visual inspection was carried out after taking out. It is required that the surface nickel-plated appearance film layer is uniform, continuous and complete. If there is no scratch, abrasion or corrosion on the film layer surface, it is recorded as qualified. If at least one of the phenomena appears, it is recorded as unqualified.

[0070] The performance test results are shown in Table 1 and Figure 1-12 .

[0071] Table 1 Performance Test Results

[0072] From Table 1 and Figure 1-20 It can be seen that the magnesium-aluminum alloy nickel plating materials of Examples 1-2 have strong coating adhesion, excellent weldability, and strong heat resistance, impact resistance, and salt spray resistance. Their overall performance is superior to that of plating solutions using existing technologies.

[0073] In Comparative Example 1, the hydrophobic chain of nonylphenol is 3 carbon atoms shorter than that of dodecylphenol, resulting in a product cloud point below 80°C. When coated at the coating temperature of Example 1, the coating solution is slightly turbid, the coating crystals are uneven and the density is reduced. During thermal shock, high temperature and high and low temperature cycling, the stress concentration at the interface between the coating and the substrate causes peeling and flaking, failure of impact resistance and poor salt spray resistance.

[0074] In Comparative Example 2, the decrease in the EO molar ratio led to C 12 - The shortened hydrophilic chain of APEO-8 reduces its water solubility and high-temperature dispersibility, making it prone to precipitation at the coating temperature of Example 1, resulting in slight turbidity in the coating solution; the increased porosity of the coating allows oxidizing gases to easily penetrate at high temperatures, causing the coating to peel during heat resistance testing; at the same time, the porosity weakens the physical bonding force between the coating and the substrate, making it prone to breakage during thermal shock and high and low temperature cycling, resulting in poor bonding strength, impact resistance, and salt spray resistance.

[0075] In Comparative Example 3, the compound surfactant was replaced with polyethylene glycol 6000, which resulted in poor wettability, uneven local thickness of the coating, stress concentration points, and easy cracking under thermal shock and high and low temperature cycling. At high temperatures, polyethylene glycol is easily oxidized, which leads to a decrease in the interfacial bonding force between the coating and the substrate, failure of heat resistance, and poor salt spray resistance.

[0076] Comparative Example 4, C 12 - APEO-12 was replaced with AEO-9. The structural synergy between AEO-9 and OP-10 / TX-10 is insufficient. The complex system has a low cloud point, which is close to the cloud point when coated at the coating temperature of Example 1, resulting in decreased stability of the coating solution. The coating has coarse crystals and insufficient density. It peels due to the difference in thermal expansion coefficients during thermal shock. It is prone to microcracks during high and low temperature cycling, resulting in failure of impact resistance. It affects the bonding between the coating and the substrate, has unqualified heat resistance, and poor salt spray resistance.

[0077] Comparative Example 5, C 12 When APEO-12 is replaced with sodium dodecylbenzenesulfonate and compounded with OP-10 / TX-10, it is easy to form local ion aggregation, which leads to a decrease in the stability of the plating solution; trace amounts of SDBS remain on the coating surface, affecting the uniform deposition of Ni²+, and causing pinholes and local porosity in the coating; during thermal shock, high temperature and high and low temperature cycling, the porosity becomes a stress concentration point, causing peeling, cracking and poor salt spray resistance.

[0078] In Comparative Example 6, the change in the compounding ratio failed to effectively raise the cloud point of the system, resulting in slight turbidity of the plating solution when plating at the coating temperature of Example 1. The excessively high proportion of OP-10 / TX-10 led to uneven surface tension of the coating, with some areas exhibiting excessive wettability and others insufficient wettability, resulting in increased coating thickness deviation. During thermal shock and high / low temperature cycling, the uneven thickness areas cracked due to stress differences, leading to failure of adhesion and impact resistance. At high temperatures, the coating thickness deviation areas were prone to oxidation and peeling, resulting in unsatisfactory heat resistance and poor salt spray resistance.

[0079] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles 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 preparing a magnesium-aluminum alloy nickel-plated material, characterized in that, Includes the following steps: (1) Pretreatment: The surface of the magnesium-aluminum alloy is sandblasted; (2) Degreasing; (3) First alkaline etching; (4) Acid etching; (5) First descaling; (6) Second alkaline corrosion; (7) Second descaling; (8) Zinc precipitation: The magnesium-aluminum alloy after the second descaling is precipitated with zinc; (9) Alkaline electroless nickel plating: The magnesium-aluminum alloy after zinc immersion cleaning is placed in an alkaline nickel plating solution for plating; (10) Acidic electroless nickel plating: The magnesium-aluminum alloy after alkaline electroless nickel plating is placed in an acidic nickel plating solution and plated at a temperature of 80-85℃. The acidic nickel plating solution includes the following components: NiSO4, sodium hypophosphite, citric acid, L-lactic acid, sodium acetate trihydrate, ammonium hydrogen fluoride, thiourea, potassium iodide, compound surfactant and deionized water. (11) Recycling; (12) Second cleaning; (13) Drying: The magnesium-aluminum alloy after the second cleaning is dried to obtain the magnesium-aluminum alloy nickel-plated material.

2. The method for preparing the magnesium-aluminum alloy nickel-plated material according to claim 1, characterized in that, The acidic nickel plating solution comprises the following components: NiSO4 20-25 g / L, sodium hypophosphite 15-20 g / L, citric acid 20-25 g / L, L-lactic acid 8-12 g / L, sodium acetate trihydrate 12-15 g / L, ammonium bifluoride 1.5-2.5 g / L, thiourea 0.8-1.2 mg / L, potassium iodide 0.08-0.12 mg / L, compound surfactant 0.5-1.0 g / L, and the balance being deionized water.

3. The method for preparing magnesium-aluminum alloy nickel-plated material according to claim 2, characterized in that, The compound surfactant includes surfactant C. 12 -APEO-12, octylphenol polyoxyethylene ether and alkylphenol polyoxyethylene ether.

4. The method for preparing the magnesium-aluminum alloy nickel-plated material according to claim 3, characterized in that, The compound surfactant comprises surfactant C in a mass ratio of 1:(1.2-1.4):(0.3-0.5). 12 -APEO-12, octylphenol polyoxyethylene ether and alkylphenol polyoxyethylene ether.

5. The method for preparing the magnesium-aluminum alloy nickel-plated material according to claim 4, characterized in that, The surfactant C 12 The preparation method of APEO-12 includes the following steps: (1) Transfer the dried dodecylphenol into the reactor and add the catalyst; (2) Under a nitrogen atmosphere, start stirring in the reactor, raise the temperature to 110-130℃, introduce ethylene oxide into the reactor, and continue to react at 110-130℃ and 0.2-0.4MPa for 4-6 hours; (3) After the reaction is complete, the temperature is lowered, phosphoric acid is added to the reactor to neutralize and adjust the pH to 6.5-7.

5. After standing, the mixture is filtered to obtain surfactant C. 12 -APEO-12.

6. The method for preparing the magnesium-aluminum alloy nickel-plated material according to claim 5, characterized in that, The molar ratio of dodecylphenol to ethylene oxide is 1:(12-13).

7. The method for preparing magnesium-aluminum alloy nickel-plated material according to claim 1, characterized in that, White corundum and glass beads were mixed in a mass ratio of (1-2):(1-2) and sandblasted under a pressure of 0.2-0.3 MPa.

8. The method for preparing magnesium-aluminum alloy nickel-plated material according to claim 1, characterized in that, The temperature for the first alkaline etching is 50-60℃, and the treatment time is 60-70 seconds.

9. The method for preparing the magnesium-aluminum alloy nickel-plated material according to claim 1, characterized in that, The alkaline nickel plating solution consists of the following components: NiCO3 4-6 g / L, pH value 8.0-8.2, and the balance is deionized water.

10. A magnesium-aluminum alloy nickel-plated material prepared by the preparation method according to any one of claims 1-9.

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