Metal surface composite coating process and metal surface composite coating component

Abstract

The invention relates to the technical field of material surface treatment, and discloses a metal surface composite coating process and a metal surface composite coating part. According to the metal surface composite coating process, the metal surface is subjected to the steps of pretreatment, nickel pre-plating, copper plating, ternary alloy plating, silver pre-plating, silver plating, nickel plating, nickel plating again, mask positioning, pretreatment again, local gold plating, post-treatment and the like, the appearance of a prepared metal surface composite coating part is qualified, the total coating thickness is 9.3-12 m, and the thickness of the metal surface composite coating is 0.5-1.5 mm. And the thickness of the eighth gold plating layer is 0.76-1.1 m, the binding force of the metal surface composite coating component reaches the 0-level or 1-level level, and after a corrosion resistance test, the surface is not corroded, so that the requirements of good binding force on the metal surface composite coating component, relatively high corrosion resistance in an extreme environment and the like in the application fields of electronics, aerospace and the like are met.

Description

Technical Field

[0001] This application relates to the field of material surface treatment technology, and in particular to a metal surface composite coating process and a metal surface composite coating component. Background Technology

[0002] In the field of metal surface treatment, coating technology has always been a key technology for improving the performance of metal products. With the continuous development of industry, the requirements for the quality and performance of metal products are increasing, especially in terms of corrosion resistance, adhesion, and adaptability to complex environments. The development of coating technology has brought enormous value to many industries, such as electronics and aerospace. High-quality coatings can significantly extend the service life of metal products and improve their stability in various harsh environments, thereby ensuring the normal operation of related equipment.

[0003] Currently, to improve corrosion resistance, multi-layer metallization is commonly used, forming a protective barrier by sequentially depositing different metal layers on a metal surface. To improve coating adhesion, the substrate undergoes simple degreasing and activation treatments to enhance the bond between the coating and the substrate. However, these traditional processes have certain limitations. Multi-layer metallized products often fail to meet protective performance requirements in complex environments.

[0004] However, existing technologies have significant drawbacks. Multi-layer metal-plated products lack sufficient corrosion resistance and struggle to pass Japanese mixed gas tests. Furthermore, the coating is prone to peeling, discoloration, and other problems, exhibiting poor adhesion. Traditional processes also lack adaptability to complex environments such as 5G base stations and aerospace applications. These issues severely impact the quality and lifespan of metal products, limiting their application in high-end fields. Summary of the Invention

[0005] To at least overcome one of the problems existing in the prior art, one objective of this application is to provide a localized gold plating process for metal surfaces. Through pretreatment, pre-plating with nickel, copper, and ternary alloys, the pretreatment effectively removes oil, providing a high-adhesion foundation for subsequent plating layers. The functional gradient design of the multi-layer plating, especially the precise control of the ternary alloy plating solution, forms a uniform and fine ternary alloy plating layer, resulting in strong adhesion between the metal surface plating layer and the metal substrate, and excellent corrosion resistance. A second objective of this application is to provide the aforementioned composite plating component on the metal surface.

[0006] Therefore, this application adopts the following technical solution: The first aspect of this application provides a composite coating process for a metal surface, comprising the following steps: S1. Pretreatment: After ultrasonic degreasing, cathodic electrolytic degreasing, and anodic electrolytic degreasing, the metal substrate undergoes activation treatment, polishing, and reactivation. S2, Pre-plating nickel: After washing with water, place in a pre-plating nickel solution to pre-plat nickel, forming the first nickel plating layer; S3, Copper plating: After washing with water, place in copper plating solution to plating copper, forming a second copper plating layer; S4. Ternary alloy plating: After washing with water, place in a ternary alloy plating solution to plating ternary alloy to form a third ternary alloy plating layer. S5. Pre-plating silver: After washing with water, place in a pre-plating silver solution to pre-plat silver, forming the fourth silver plating layer; S6, Silver plating: Plating silver in a silver plating solution at 17-23℃ to form the fifth silver plating layer; S7. Nickel plating: After washing with water, place in a nickel plating solution to plating nickel, forming the sixth nickel plating layer; S8. Re-plating nickel: After washing with water, place the plated in a re-plating nickel solution to form the seventh nickel plating layer, and then wash with water, slow pull water wash, and bake. S9. Mask positioning: Wrap the non-gold-plated area with 5 layers of mask material to expose the gold-plated area; S10. Further pretreatment: After ultrasonic degreasing with a degreasing agent, activate with an acidic solution. S11, Localized gold plating: After washing with water, gold is plated in a gold plating solution to form the eighth gold plating layer; S12. Post-processing: water washing, drying, mask removal, ultrasonic degreasing, water washing, activation, water washing again, gold protection, water washing again, slow pull water washing, baking, to obtain the composite coating component on the metal surface. In step S4, the ternary alloy plating solution comprises 12-18 g / L copper salt, 17-25 g / L tin salt, 2-4 g / L zinc salt, 45-55 g / L sodium cyanide, and 17-21 g / L potassium hydroxide, and the Baume degree of the ternary alloy plating solution is 10-15°Bé.

[0007] Preferably, in step S1, the concentration of the degreasing powder in the ultrasonic degreasing is 40-60 g / L, the Baume degree is 2-6°Bé, the temperature of the ultrasonic degreasing is 45-85℃, the ultrasonic frequency of the ultrasonic degreasing is 15-30 kHz, and the ultrasonic time of the ultrasonic degreasing is 5-10 min; the cathodic electrolytic degreasing is carried out at room temperature, the concentration of the degreasing powder in the cathodic electrolytic degreasing is 40-60 g / L, the Baume degree is 2-6°Bé, the current of the cathodic electrolytic degreasing is 80-150 A, and the time of the cathodic electrolytic degreasing is 1-3 min; the anodic electrolytic degreasing is carried out at room temperature, the concentration of the degreasing powder in the anodic electrolytic degreasing is 40-60 g / L, the Baume degree is 2-6°Bé, the current of the anodic electrolytic degreasing is 50-100 A, and the time of the anodic electrolytic degreasing is 1-2 min.

[0008] Step S1 thoroughly removes grease, scale, and organic contaminants from the substrate surface through a triple process of ultrasonic degreasing, cathodic electrolysis, and anodic electrolysis, providing a high-adhesion foundation for subsequent coatings. Activation removes the surface passivation film, polishing further refines the surface microstructure, and reactivation ensures the exposure of fresh metal surfaces, forming an interlocking interface that significantly improves the mechanical bonding strength between the coating and the substrate.

[0009] Preferably, in step S2, the pre-plating nickel solution comprises 150-250 g / L nickel chloride and 200-250 mL / L hydrochloric acid, and the Baumé degree of the pre-plating nickel solution is 10-15°Bé. More preferably, in step S2, the pre-plating nickel solution comprises 180-210 g / L nickel chloride and 220-240 mL / L hydrochloric acid, and the Baumé degree of the pre-plating nickel solution is 12-15°Bé.

[0010] Preferably, in step S3, the copper plating solution comprises 40-60 g / L cuprous cyanide and 15-25 g / L sodium cyanide, the Baumé degree of the copper plating solution is 10-15°Bé, the temperature of the copper plating solution is 45-55°C, the copper plating current is 20-30 A, and the copper plating time is 5-8 min. More preferably, in step S3, the copper plating solution comprises 50-60 g / L cuprous cyanide and 20-25 g / L sodium cyanide, the Baumé degree of the copper plating solution is 13-15°Bé, the temperature of the copper plating solution is 48-55°C, the copper plating current is 25-30 A, and the copper plating time is 6-8 min.

[0011] Step S3, performed at 45-55℃, increases ion migration rate and cathodic polarization, promoting the rapid adsorption and arrangement of copper atoms on the substrate surface, forming a mirror-like second copper plating layer.

[0012] Preferably, in step S4, the temperature for plating the ternary alloy is 45-55°C, the current for plating the ternary alloy is 60-80A, and the plating time is 10-15 minutes.

[0013] In the ternary alloy plating bath of step S4, sodium cyanide acts as a ligand to stabilize copper, tin, and zinc ions and prevent hydrolysis and precipitation; potassium hydroxide adjusts the pH to promote the reduction of metal ions and form a uniform and fine alloy coating; a Baumé degree of 10-15°Bé ensures a moderate ion concentration, avoiding a rough coating due to high concentration or a slow deposition rate due to low concentration; a temperature of 45-55℃ promotes metal ion diffusion, reduces the viscosity of the plating bath, and increases the co-deposition rate of the ternary alloy while inhibiting tin hydrolysis; a high current density of 60-80A increases cathodic polarization, thereby refining the grains and improving the hardness and wear resistance of the coating.

[0014] Preferably, in step S5, the pre-plating silver solution comprises 1-3 g / L of potassium silver cyanide and 130-150 g / L of potassium cyanide, the Baumé degree of the pre-plating silver solution is 10-15°Bé, the temperature of the pre-plating silver solution is 20-25°C, the pre-plating current is 50-60 A, and the pre-plating time is 1-2 min. More preferably, in step S5, the pre-plating silver solution comprises 1-3 g / L of potassium silver cyanide and 130-140 g / L of potassium cyanide, the Baumé degree of the pre-plating silver solution is 11-15°Bé, the temperature of the pre-plating silver solution is 20-25°C, the pre-plating current is 55-60 A, and the pre-plating time is 1-2 min.

[0015] Low concentrations of potassium silver cyanide provide Ag + It forms a stable [Ag(CN)2]- complex ion with high concentrations of potassium cyanide, thereby reducing Ag + The reduction potential enables rapid flash plating; the low temperature (20-25℃) helps reduce the crystallization rate of silver, forming a fine and uniform fifth silver layer, providing a smooth substrate for subsequent plating layers; the high current density of 50-60A promotes Ag... + Instant reduction on the cathode surface increases the density of the coating.

[0016] Preferably, in step S6, the silver plating solution comprises 10-15 g / L potassium silver cyanide, 130-150 g / L potassium cyanide, and 5-10 g / L potassium hydroxide; the Baumé degree of the silver plating solution is 10-15°Bé; the silver plating current is 10-20 A; and the silver plating time is 15-25 min. More preferably, in step S6, the silver plating solution comprises 13-15 g / L potassium silver cyanide, 130-150 g / L potassium cyanide, and 5-10 g / L potassium hydroxide; the Baumé degree of the silver plating solution is 12-15°Bé; the silver plating current is 10-20 A; and the silver plating time is 18-25 min.

[0017] Step S6 uses potassium hydroxide to adjust the pH, inhibit the hydrolysis of potassium cyanide, stabilize the plating solution composition, and at the same time improve the cathode current efficiency and reduce the occurrence of hydrogen evolution side reactions; the low current density of 10-20A ensures uniform reduction of silver ions and avoids scorching of the plating layer caused by high current.

[0018] Preferably, in step S7, the nickel plating solution comprises 150-250 g / L nickel sulfate, 40-60 g / L nickel chloride, and 40-60 g / L boric acid; the Baumé degree of the nickel plating solution is 15-25°Bé; the pH value of the nickel plating solution is 4.0-4.8; the temperature of the nickel plating solution is 50-60°C; the nickel plating current is 20-40 A; and the silver plating time is 30-35 min.

[0019] Preferably, in step S8, the nickel plating solution comprises 250-300 g / L nickel sulfate, 40-60 g / L nickel chloride, and 40-60 g / L boric acid; the Baumé degree of the nickel plating solution is 15-25°Bé; the pH value of the nickel plating solution is 1.5-2.5; the temperature of the nickel plating solution is 50-60°C; the nickel plating current is 20-30 A; and the silver plating time is 20-25 min.

[0020] In step S7, nickel sulfate provides Ni. 2+ Nickel chloride provides Cl - The anode is activated, and boric acid is used as a buffer to maintain pH stability, ensuring coating uniformity and forming the sixth nickel plating layer. Step S8: Ni under acidic conditions. 2+ The reduction rate accelerates, forming the seventh nickel plating layer. The sixth nickel plating layer relieves the interfacial stress between the seventh nickel plating layer and the fifth silver plating layer, preventing plating peeling.

[0021] In step S9, the mask material is selected from at least one of polytetrafluoroethylene film and high-temperature resistant tape, and the area of ​​the non-gold-plated area is 1.8-2.3 times the area of ​​the gold-plated area.

[0022] Preferably, in step S10, the degreasing agent is selected from degreasing powder with a concentration of 45-58 g / L and a Baume degree of 2-6°Bé, the degreasing temperature is 46-55℃, the ultrasonic frequency of the degreasing is 40 kHz, and the ultrasonic time of the degreasing is 1-2 min; the acidic solution is a 15-20% by mass sulfuric acid solution.

[0023] Preferably, in step S11, the gold ion concentration of the gold plating solution is 1-2 g / L, the cobalt ion concentration of the gold plating solution is 0.3-0.5 g / L, the additive concentration of the gold plating solution is 20-40 mL / L, the equilibrium salt concentration of the gold plating solution is 20-40 g / L, the Baume degree of the electroplating solution is 8-12°Bé, the pH value of the electroplating solution is 3.8-5.0, the temperature of the electroplating solution is 35-45℃, the gold plating current is 8-9 A, and the gold plating time is 30-40 min.

[0024] In step S11, 35-45℃ and 8-12°Bé Baume help balance the ion diffusion rate and solution viscosity; the weak acidity of pH 3.8-5.0 promotes the reduction of gold ions while inhibiting the hydrolysis of cobalt, ensuring the uniformity of the eighth gold plating layer.

[0025] Preferably, in step S12, the concentration of the gold protective agent in the bath is 3%, the baking temperature is 90-110℃, and the baking time is 5-10 minutes.

[0026] In this application's technical solution, step S1, pretreatment, involves degreasing, activation, and polishing of the metal substrate to remove surface impurities and oxide layers, improving the adhesion between the plating layer and the substrate. In step S2, pre-plating nickel, the first nickel layer serves as the bottom layer, forming a metallurgical bond between the nickel and the metal substrate, enhancing the adhesion between subsequent plating layers and the substrate. Step S3, copper plating, reduces overall contact resistance and improves the conductivity and solderability of the plating layer. Step S4, ternary alloy plating, improves the hardness, corrosion resistance, and wear resistance of the plating layer. In step S5, pre-plating silver, the fourth silver layer quickly covers the surface of the third ternary alloy layer, preventing its oxidation in air. Step S6, silver plating, imparts good conductivity to the plating layer. Steps S7 and S8, nickel plating and re-plating nickel, enhance the corrosion resistance and wear resistance of the plating layer. Step S9, mask positioning, enables gold plating in designated areas. Step S11, localized gold plating, improves the performance of specific areas of the component. Step S12, post-treatment, further cleans and protects the plating layer, resulting in a metal surface composite plating component with good adhesion and strong corrosion resistance.

[0027] The second aspect of this application provides a metal surface composite plating component manufactured according to the metal surface composite plating process described in the first aspect of this application, wherein the metal surface composite plating component is composed of a metal substrate, a first nickel plating layer, a second copper plating layer, a third ternary alloy plating layer, a fourth silver plating layer, a fifth silver plating layer, a sixth nickel plating layer, a seventh nickel plating layer, and an eighth gold plating layer stacked sequentially, wherein the total plating thickness is 9.3-12 μm, and the thickness of the eighth gold plating layer is 0.76-1.1 μm.

[0028] The multi-layer composite coating on the metal surface of this application forms a gradient hardness structure, which can effectively resist the impact and wear of external forces. Among them, the third ternary alloy layer gives the coating good hardness, corrosion resistance and wear resistance. The fourth and fifth silver layers provide preliminary protection for the metal substrate through their own passivation effect. The sixth and seventh nickel layers isolate the metal substrate from the external environment. In addition, by precisely controlling the area and thickness of the eighth gold layer, it is possible to meet the requirements of good adhesion of composite coating components on metal surfaces and strong corrosion resistance in extreme environments in electronic, aerospace and other application fields while saving costs.

[0029] Compared with the prior art, this application has at least the following beneficial effects: 1) In step S4, a ternary alloy is plated. Sodium cyanide is used as a coordinating agent to uniformly deposit copper, tin and zinc ions on the second copper plating layer. At the same time, the high current density increases the cathodic polarization effect, promotes further grain refinement, and thus improves the adhesion and overall hardness of the plating layer.

[0030] 2) In step S5, the pre-plating of silver uses a combination of low-concentration potassium silver cyanide and high-concentration potassium cyanide to allow the fourth silver plating layer to quickly cover the surface of the third ternary alloy plating layer, achieving rapid flash plating and preventing oxidation of the surface of the third ternary alloy plating layer; in step S6, the silver plating utilizes a low temperature of 17-23℃ to reduce the crystallization rate of silver, so as to form a fine and uniform fifth silver plating layer, providing a flat and dense substrate for subsequent plating layers.

[0031] 3) The sixth nickel plating layer formed in step S7 relieves the interfacial stress between the seventh nickel plating layer and the fifth silver plating layer, effectively preventing the plating layer from peeling off.

[0032] 4) This application uses a multi-step pretreatment method, combined with functional gradient coating design and precise control of key process parameters, to make the resulting metal surface composite coating parts have strong adhesion, reaching level 0 or 1, and excellent corrosion resistance. After undergoing a gas corrosion test under harsh conditions, there is no corrosion on the surface. Detailed Implementation

[0033] The following detailed description of the contents of this application is provided through specific embodiments, comparative examples, and tables, but is not limited to all the arguments and data.

[0034] The metal substrate used in the embodiments and comparative examples of this application is copper. The additives in the gold plating solution are gold additives from Shih Hsin Chemical Co., Ltd. The balancing salt is a balancing salt from Shih Hsin Chemical Co., Ltd. The gold protectant is a gold protectant from Shih Hsin Chemical Co., Ltd.

[0035] It is particularly important to emphasize that, unless otherwise specified, the raw materials, reagents or devices used in this application can be obtained from conventional commercial sources.

[0036] According to the metal surface composite coating process of this application, the specific embodiments and comparative examples are as follows: Example 1: A composite coating process for a metal surface specifically includes the following steps: S1. Pretreatment: The copper material is ultrasonically degreased in a degreasing tank with a degreasing powder concentration of 45 g / L and a Baume degree of 2-6°Bé. The temperature is adjusted to 55℃, the ultrasonic frequency to 28 kHz, and the ultrasonic time to 7 min. Next, the copper material is subjected to cathodic electrolytic degreasing at room temperature with a degreasing powder concentration of 50 g / L, a Baume degree of 2-6°Bé, a current of 100 A, and a time of 2 min. Then, the copper material is subjected to anodic electrolytic degreasing at room temperature with a degreasing powder concentration of 50 g / L, a Baume degree of 2-6°Bé, a current of 70 A, and a time of 2 min. After washing with water, it is activated with a 30% (w / w) sulfuric acid solution for 25 s, washed with water, polished with a 30 g / L chromic anhydride and 2 mL / L sulfuric acid solution for 2 min, washed with water, and then activated with a 30% (w / w) hydrochloric acid solution for 30 s. S2. Pre-plating nickel: After washing with water, place the copper material in a pre-plating nickel solution containing 200g / L nickel chloride, 230g / L hydrochloric acid, and 10-15°Bé Baume to form the first nickel plating layer. S3. Copper plating: After washing with water, place the copper plating solution at 50°C in a copper plating solution containing 48g / L cuprous cyanide, 20g / L sodium cyanide, and 10-15°Bé Baume, set the current to 20A, and electroplate for 8 minutes to form a second copper plating layer. S4. Ternary alloy plating: After washing with water, place the plating solution at 50°C in a ternary alloy plating solution containing 12g / L copper salt, 18g / L tin salt, 2g / L zinc salt, 45g / L sodium cyanide, 17g / L potassium hydroxide, and 10-15°Bé Baume. Set the current to 60A and electroplate for 15 minutes to form the third ternary alloy layer. S5. Pre-plating silver: After washing with water, place the sample in a pre-plating silver solution with 1g / L potassium silver cyanide, 130g / L potassium cyanide, and 10-15°Bé Baume degree at 20°C. Set the current to 50A and electroplat for 2 minutes to form the fourth silver plating layer. S6. Silver plating: At 17℃, place the sample in a silver plating solution containing 10g / L potassium silver cyanide, 130g / L potassium cyanide, 5g / L potassium hydroxide, and 10-15°Bé Baume, set the current to 10A, and electroplat for 15 minutes to form the fifth silver plating layer. S7. Nickel plating: After washing with water, place the product in a nickel plating solution containing 150g / L nickel sulfate, 45g / L nickel chloride, 50g / L boric acid, 15-25°Bé Baume degree, and 4.0-4.3 pH value at 50℃, set the current to 35A, and electroplat for 32 minutes to form the sixth nickel plating layer. S8. Re-plating with nickel: After rinsing with water, place the plating solution at 50°C in a nickel plating solution containing 250g / L nickel sulfate, 45g / L nickel chloride, 50g / L boric acid, 15-25°Bé Baume, and 1.5-1.8 pH. Set the current to 25A and electroplat for 20 minutes to form the seventh nickel plating layer. Then rinse with water, followed by slow pulling and rinsing at 50°C with a conductivity of <30μS / cm, and then baking at 80°C for 8 minutes. S9. Mask positioning: Wrap 5 layers of high-temperature resistant tape over the non-gold-plated area to expose the gold-plated area. The area of ​​the non-gold-plated area is twice the area of ​​the gold-plated area. S10. Pretreatment: At 50℃, use a degreasing powder with a concentration of 55g / L and a Baume degree of 2-6°Bé for ultrasonic degreasing. The ultrasonic frequency for ultrasonic degreasing is 40kHz and the ultrasonic time is 2min; wash with water; activate with 15% sulfuric acid solution for 2min. S11, Localized gold plating: After rinsing with water, place the sample in a gold plating solution at 45℃ containing 1.5g / L gold ions, 0.3g / L cobalt ions, 25mL / L additives, 25g / L balanced salt, 8-12°Bé Baume degree, and 4.0-4.2 pH value. Set the current to 8.5A and electroplat for 35 minutes to form the eighth gold plating layer. S12. Post-treatment: Water washing; drying; after removing the high-temperature resistant tape, ultrasonic degreasing is performed in a degreasing tank at 50℃ with a degreasing powder concentration of 45g / L and a Baume degree of 2-6°Bé. The ultrasonic frequency is adjusted to 25kHz and the ultrasonic time is 5min; water washing; activation in 3% oxalic acid solution for 25s; water washing again; gold protection in a 3% gold protectant solution at 60℃ for 30s; water washing again; slow-pull water washing at 50℃ with a water conductivity of <30μS / cm; baking at 100℃ for 10min to obtain the metal surface composite coating part.

[0037] Example 2: A composite coating process for a metal surface is the same as in Example 1, except that step S4 of Example 2, which involves plating a ternary alloy, is performed under the following conditions: after washing with water, the metal is placed in a ternary alloy plating solution containing 15 g / L copper salt, 20 g / L tin salt, 3 g / L zinc salt, 48 g / L sodium cyanide, 20 g / L potassium hydroxide, and 10-15°Bé Baume, at 50°C. The current is set to 70 A, and the plating is performed for 10 minutes to form a third ternary alloy layer.

[0038] Example 3: A composite coating process for a metal surface is the same as in Example 1, except that step S4 of Example 3, which involves plating a ternary alloy, is performed under the following conditions: after washing with water, the metal is placed in a ternary alloy plating solution containing 18 g / L copper salt, 25 g / L tin salt, 4 g / L zinc salt, 55 g / L sodium cyanide, 21 g / L potassium hydroxide, and 10-15°Bé Baume, at 45°C. The current is set to 80 A, and the plating is performed for 12 minutes to form a third ternary alloy layer.

[0039] Example 4: A composite coating process for a metal surface specifically includes the following steps: S1. Pretreatment: The copper material is ultrasonically degreased in a degreasing tank with a degreasing powder concentration of 50 g / L and a Baume degree of 2-6°Bé. The temperature is adjusted to 65℃, the ultrasonic frequency is 20 kHz, and the ultrasonic time is 8 min. Next, the copper material is subjected to cathodic electrolytic degreasing at room temperature with a degreasing powder concentration of 40 g / L, a Baume degree of 2-6°Bé, a current of 80 A, and a time of 3 min. Then, the copper material is subjected to anodic electrolytic degreasing at room temperature with a degreasing powder concentration of 40 g / L, a Baume degree of 2-6°Bé, a current of 60 A, and a time of 2 min. After washing with water, it is activated with a 30% (w / w) sulfuric acid solution for 25 s, washed with water, polished with a 30 g / L chromic anhydride and 2 mL / L sulfuric acid solution for 2 min, washed with water, and then activated with a 30% (w / w) hydrochloric acid solution for 30 s. S2. Pre-plating nickel: After washing with water, place the copper material in a pre-plating nickel solution containing 200g / L nickel chloride, 210g / L hydrochloric acid, and 10-15°Bé Baume to form the first nickel plating layer. S3. Copper plating: After washing with water, place the copper plating solution at 45°C with 55g / L cuprous cyanide, 22g / L sodium cyanide, and 10-15°Bé Baume, set the current to 25A, and electroplate for 6 minutes to form the second copper plating layer. S4. Ternary alloy plating: After washing with water, place the plating solution at 48°C in a ternary alloy plating solution containing 16g / L copper salt, 20g / L tin salt, 3g / L zinc salt, 50g / L sodium cyanide, 20g / L potassium hydroxide, and 10-15°Bé Baume. Set the current to 70A and electroplate for 10 minutes to form the third ternary alloy layer. S5. Pre-plating silver: After washing with water, place the sample in a pre-plating silver solution with 2g / L potassium silver cyanide, 140g / L potassium cyanide, and 10-15°Bé Baume at 22°C. Set the current to 52A and electroplat for 2 minutes to form the fourth silver plating layer. S6. Silver plating: At 20℃, place the sample in a silver plating solution containing 12g / L potassium silver cyanide, 140g / L potassium cyanide, 8g / L potassium hydroxide, and 10-15°Bé Baume, set the current to 15A, and electroplat for 18 minutes to form the fifth silver plating layer. S7. Nickel plating: After washing with water, place the product in a nickel plating solution containing 180g / L nickel sulfate, 50g / L nickel chloride, 55g / L boric acid, 15-25°Bé Baume degree, and 4.0-4.2 pH value at 55℃, set the current to 25A, and electroplat for 35 minutes to form the sixth nickel plating layer. S8. Re-plating with nickel: After rinsing with water, place the plating solution at 55°C in a nickel plating solution containing 280g / L nickel sulfate, 50g / L nickel chloride, 55g / L boric acid, 15-25°Bé Baume, and 1.5-1.6 pH. Set the current to 20A and electroplat for 22 minutes to form the seventh nickel plating layer. Then rinse with water, followed by slow pulling and rinsing at 50°C with a conductivity of <30μS / cm, and then baking at 80°C for 8 minutes. S9. Mask positioning: Wrap 5 layers of high-temperature resistant tape over the non-gold-plated area to expose the gold-plated area. The area of ​​the non-gold-plated area is twice the area of ​​the gold-plated area. S10. Pretreatment: At 55℃, use a degreasing powder with a concentration of 45g / L and a Baume degree of 2-6°Bé for ultrasonic degreasing. The ultrasonic frequency for ultrasonic degreasing is 40kHz and the ultrasonic time is 2min; wash with water; activate with 18% sulfuric acid solution for 2min. S11. Spot gold plating: After rinsing with water, place the sample in a gold plating solution containing 1.5 g / L gold ions, 0.4 g / L cobalt ions, 30 mL / L additives, 30 g / L balancing salt, 8-12° Bé Baume, and 4.0-4.1 pH at 40°C. Set the current to 9 A and electroplat for 30 minutes to form the eighth gold plating layer. S12. Post-treatment: Water washing; drying; after removing the high-temperature resistant tape, ultrasonic degreasing is performed in a degreasing tank at 50℃ with a degreasing powder concentration of 45g / L and a Baume degree of 2-6°Bé. The ultrasonic frequency is adjusted to 25kHz and the ultrasonic time is 5min; water washing; activation in 3% oxalic acid solution for 25s; water washing again; gold protection in a 3% gold protectant solution at 60℃ for 30s; water washing again; slow-pull water washing at 50℃ with a water conductivity of <30μS / cm; baking at 90℃ for 10min to obtain the metal surface composite coating part.

[0040] Example 5: A composite coating process for a metal surface specifically includes the following steps: S1. Pretreatment: The copper material is ultrasonically degreased in a degreasing tank with a degreasing powder concentration of 60 g / L and a Baume degree of 2-6°Bé. The temperature is adjusted to 85℃, the ultrasonic frequency is 30 kHz, and the ultrasonic time is 5 min. Next, the copper material is subjected to cathodic electrolytic degreasing at room temperature with a degreasing powder concentration of 60 g / L, a Baume degree of 2-6°Bé, a current of 120 A, and a time of 2 min. Then, the copper material is subjected to anodic electrolytic degreasing at room temperature with a degreasing powder concentration of 60 g / L, a Baume degree of 2-6°Bé, a current of 90 A, and a time of 1 min. After rinsing with water, it is activated with a 30% (w / w) sulfuric acid solution for 25 s, rinsed with water, polished with a 30 g / L chromic anhydride and 2 mL / L sulfuric acid solution for 2 min, rinsed with water, and then activated with a 30% (w / w) hydrochloric acid solution for 30 s. S2. Pre-plating nickel: After washing with water, place the copper material in a pre-plating nickel solution containing 250g / L nickel chloride, 240g / L hydrochloric acid, and 10-15°Bé Baume to form the first nickel plating layer. S3. Copper plating: After washing with water, place the copper plating solution at 55℃ with 60g / L cuprous cyanide, 25g / L sodium cyanide, and 10-15°Bé Baume, set the current to 30A, and electroplate for 5 minutes to form a second copper plating layer. S4. Ternary alloy plating: After washing with water, place the plating solution at 52°C in a ternary alloy plating solution containing 18g / L copper salt, 25g / L tin salt, 4g / L zinc salt, 55g / L sodium cyanide, 21g / L potassium hydroxide, and 10-15°Bé Baume. Set the current to 80A and electroplate for 12 minutes to form the third ternary alloy layer. S5. Pre-plating silver: After washing with water, place the sample in a pre-plating silver solution containing 3g / L potassium silver cyanide, 150g / L potassium cyanide, and 10-15°Bé Baume at 25°C. Set the current to 60A and electroplat for 1.5 minutes to form the fourth silver plating layer. S6. Silver plating: At 23℃, place the sample in a silver plating solution containing 15g / L potassium silver cyanide, 150g / L potassium cyanide, 9g / L potassium hydroxide, and 10-15°Bé Baume, set the current to 18A, and electroplat for 20 minutes to form the fifth silver plating layer. S7. Nickel plating: After washing with water, place the product in a nickel plating solution containing 220 g / L nickel sulfate, 60 g / L nickel chloride, 60 g / L boric acid, 15-25° Bé Baume, and 4.0-4.1 pH at 60°C. Set the current to 35 A and electroplat for 32 minutes to form the sixth nickel plating layer. S8. Re-plating with nickel: After rinsing with water, place the plating solution at 60°C in a nickel plating solution containing 300g / L nickel sulfate, 55g / L nickel chloride, 55g / L boric acid, 15-25°Bé Baume, and 1.5-1.6 pH value. Set the current to 25A and electroplat for 20 minutes to form the seventh nickel plating layer. Then rinse with water, and then perform slow pull-rinse with water at 50°C and conductivity <30μS / cm. Finally, bake at 80°C for 8 minutes. S9. Mask positioning: Wrap 5 layers of high-temperature resistant tape over the non-gold-plated area to expose the gold-plated area. The area of ​​the non-gold-plated area is twice the area of ​​the gold-plated area. S10. Pretreatment: At 55℃, use a degreasing powder with a concentration of 50g / L and a Baume degree of 2-6°Bé for ultrasonic degreasing. The ultrasonic frequency for ultrasonic degreasing is 40kHz and the ultrasonic time is 2min. Wash with water. Activate with 20% sulfuric acid solution for 2min. S11. Local gold plating: After rinsing with water, place the sample in a gold plating solution at 45°C containing 2g / L gold ions, 0.5g / L cobalt ions, 35mL / L additives, 35g / L balanced salt, 8-12°Bé Baume degree, and 4.0-4.1 pH value. Set the current to 9A and electroplat for 30 minutes to form the eighth gold plating layer. S12. Post-treatment: Water washing; drying; after removing the high-temperature resistant tape, ultrasonic degreasing is performed in a degreasing tank at 50℃ with a degreasing powder concentration of 45g / L and a Baume degree of 2-6°Bé. The ultrasonic frequency is adjusted to 25kHz and the ultrasonic time is 5min; water washing; activation in 3% oxalic acid solution for 25s; water washing again; gold protection in a 3% gold protectant solution at 60℃ for 30s; water washing again; slow-pull water washing at 50℃ with a water conductivity of <30μS / cm; baking at 110℃ for 5min to obtain the metal surface composite coating part.

[0041] Example 6: A composite coating process for a metal surface is the same as in Example 1, except that the temperature of the silver plating solution in step S6 of Example 6 is 20°C.

[0042] Example 7: A composite coating process for a metal surface is the same as in Example 1, except that the temperature of the silver plating solution in step S6 of Example 6 is 23°C.

[0043] Comparative Example 1: A composite coating process for a metal surface is the same as in Example 1, except that step S4, the ternary alloy plating operation, is omitted in Comparative Example 1.

[0044] Comparative Example 2: A composite coating process for a metal surface is the same as in Example 1, except that step S6, silver plating, is not performed in Comparative Example 2.

[0045] Comparative Example 3: A composite coating process for a metal surface is the same as in Example 1, except that the temperature of the silver plating solution in step S6 of Comparative Example 3 is 30°C.

[0046] Material performance testing: The metal surface composite coating components obtained in Examples 1-7 and Comparative Examples 1-3 were subjected to various performance tests. The test methods are as follows: Appearance: The product surface was observed under a microscope. The product was considered qualified if there were no scratches, exposed substrate, whitening, yellowing, pitting, dirt, watermarks, or blistering.

[0047] Coating thickness: The coating thickness was measured using a Fischer thickness gauge from Germany.

[0048] Coating adhesion: According to GB / T 9286 standard, the coating adhesion of non-gold-plated areas and gold-plated areas are tested separately. The test results are divided into 6 levels, from 0 to 5. The smaller the number, the higher the level and the stronger the coating adhesion.

[0049] Corrosion resistance: Place the product in a gas corrosion test chamber with a temperature of 30℃, a humidity of 70%, and a concentration of 10ppb Cl2, 10ppb H2S, 125ppb NO2, and 100ppb SO2. Observe the corrosion of the product surface after 12 days.

[0050] The test performance of the metal surface composite coating components of Examples 1-7 and Comparative Examples 1-3 is shown in Table 1 below: Table 1. Performance test results of Examples 1-7 and Comparative Examples 1-3 The metal surface composite coating components in Examples 1-7 involve pretreatment of the metal substrate, pre-plating with nickel, copper plating, ternary alloy plating, pre-plating with silver, silver plating, nickel plating, re-plating with nickel, mask positioning, re-pretreatment, local gold plating, and post-treatment. In particular, in step S4, ternary alloy plating, sodium cyanide is used as a coordinating agent to uniformly deposit copper, tin, and zinc ions onto the second copper plating layer. Simultaneously, high current density promotes further grain refinement, thereby improving the adhesion of the coating. Step S6, silver plating, utilizes… The low temperature conditions of 17-23℃ reduce the crystallization rate of silver, allowing it to form a fine and uniform fifth silver plating layer, providing a flat and dense substrate for subsequent plating layers. The resulting metal surface composite plating parts have a qualified appearance, with a total plating thickness of 9.3-12μm and an eighth gold plating layer thickness of 0.76-1.1μm. The bonding strength of the metal surface composite plating parts reaches level 0 or 1, with strong adhesion between the plating layer and the metal substrate. After rigorous corrosion resistance testing, no corrosion is observed on the surface.

[0051] Compared with Example 1, Comparative Example 1 did not include step S4, the ternary alloy plating operation, while other process conditions were the same as in Example 1. The results showed that Comparative Example 1 had slight blistering on its surface, and the adhesion of the plating in the gold-plated area and the plating in the non-gold-plated area was grade 1 and grade 2, respectively. After corrosion resistance testing, blistering was observed on the surface of both the gold-plated area and the non-gold-plated area. This indicates that in step S4, the ternary alloy plating, using sodium cyanide as a coordinating agent, resulted in a dense and strong third ternary alloy layer with copper, tin, and zinc ions, which directly affected the adhesion and corrosion resistance of subsequent plating layers to the metal substrate.

[0052] Compared with Example 1, Comparative Example 2 did not include the silver plating operation in step S6, but the other process conditions were the same as in Example 1. The results showed that Comparative Example 2 was visually acceptable, and the adhesion of the plating in both the gold-plated and non-gold-plated areas was Grade 1. After the corrosion resistance test, blistering occurred on the surface of both the gold-plated and non-gold-plated areas, indicating that although there was a pre-plating silver plating in step S5 before silver plating in step S6, the pre-plating silver alone was not enough to ensure that the composite coating on the metal surface passed the corrosion resistance test. The silver plating in step S6 made the silver plating layer more delicate and dense, which helped to enhance the corrosion resistance of the composite coating on the metal surface.

[0053] Compared with Example 1, the temperature of the silver plating solution in step S6 of Comparative Example 3 was 30°C, and other process conditions were the same as in Example 1. The results showed that Comparative Example 3 was qualified in appearance. The adhesion of the gold-plated area and the non-gold-plated area were grade 0 and grade 1, respectively. After corrosion resistance testing, slight blistering was observed on the surface of both the gold-plated area and the non-gold-plated area. This indicates that the increase in the temperature of the silver plating solution in step S6 may have increased the cathode overpotential, which disrupted the balance between the formation rate of the crystal nucleus and the crystal growth rate, resulting in coarser grains in the fifth silver plating layer. Therefore, defects appeared in the bonding or surface structure between the plating layers, which in turn affected the overall corrosion resistance of the plating layer.

[0054] Obviously, the above embodiments of this application are merely examples for clearly illustrating this application, and are not intended to limit the implementation of this application. For those skilled in the art, other variations or modifications can be made based on the above description. Any obvious variations or modifications derived from the technical solutions of this application are still within the protection scope of this application.

Claims

1. A composite coating process for a metal surface, characterized in that, Includes the following steps: S1. Pretreatment: After ultrasonic degreasing, cathodic electrolytic degreasing, and anodic electrolytic degreasing, the metal substrate undergoes activation treatment, polishing, and reactivation. S2, Pre-plating nickel: After washing with water, place in a pre-plating nickel solution to pre-plat nickel, forming the first nickel plating layer; S3, Copper plating: After washing with water, place in copper plating solution to plating copper, forming a second copper plating layer; S4. Ternary alloy plating: After washing with water, place in a ternary alloy plating solution to plating ternary alloy to form a third ternary alloy plating layer. S5. Pre-plating silver: After washing with water, place in a pre-plating silver solution to pre-plat silver, forming the fourth silver plating layer; S6, Silver plating: Plating silver in a silver plating solution at 17-23℃ to form the fifth silver plating layer; S7. Nickel plating: After washing with water, place in a nickel plating solution to plating nickel, forming the sixth nickel plating layer; S8. Re-plating nickel: After washing with water, place the plated in a re-plating nickel solution to form the seventh nickel plating layer, and then wash with water, slow pull water wash, and bake. S9. Mask positioning: Wrap the non-gold-plated area with 5 layers of mask material to expose the gold-plated area; S10. Further pretreatment: After ultrasonic degreasing with a degreasing agent, activate with an acidic solution. S11, Localized gold plating: After washing with water, gold is plated in a gold plating solution to form the eighth gold plating layer; S12. Post-processing: water washing, drying, mask removal, ultrasonic degreasing, water washing, activation, water washing again, gold protection, water washing again, slow pull water washing, baking, to obtain the composite coating component on the metal surface. In step S4, the ternary alloy plating solution comprises 12-18 g / L copper salt, 17-25 g / L tin salt, 2-4 g / L zinc salt, 45-55 g / L sodium cyanide, and 17-21 g / L potassium hydroxide, and the Baume degree of the ternary alloy plating solution is 10-15°Bé.

2. The metal surface composite coating process according to claim 1, characterized in that, In step S2, the pre-plating nickel solution includes 150-250 g / L of nickel chloride and 200-250 mL / L of hydrochloric acid, and the Baumé degree of the pre-plating nickel solution is 10-15°Bé.

3. The metal surface composite coating process according to claim 1, characterized in that, In step S3, the copper plating solution includes 40-60 g / L of cuprous cyanide and 15-25 g / L of sodium cyanide. The Baumé degree of the copper plating solution is 10-15°Bé, the temperature of the copper plating solution is 45-55°C, the copper plating current is 20-30 A, and the copper plating time is 5-8 min.

4. The metal surface composite coating process according to claim 1, characterized in that, In step S4, the temperature for plating the ternary alloy is 45-55℃, the current for plating the ternary alloy is 60-80A, and the plating time is 10-15min.

5. The metal surface composite coating process according to claim 1, characterized in that, In step S5, the pre-plating silver solution includes 1-3 g / L of potassium silver cyanide and 130-150 g / L of potassium cyanide. The Baumé degree of the pre-plating silver solution is 10-15°Bé. The temperature of the pre-plating silver solution is 20-25°C. The current for pre-plating silver is 50-60A. The pre-plating time is 1-2 min.

6. The metal surface composite coating process according to claim 1, characterized in that, In step S6, the silver plating solution includes 10-15 g / L of potassium silver cyanide, 130-150 g / L of potassium cyanide, and 5-10 g / L of potassium hydroxide. The Baumé degree of the silver plating solution is 10-15°Bé. The silver plating current is 10-20 A. The silver plating time is 15-25 min.

7. The metal surface composite coating process according to claim 1, characterized in that, In step S7, the nickel plating solution comprises 150-250 g / L nickel sulfate, 40-60 g / L nickel chloride, and 40-60 g / L boric acid. The Baumé degree of the nickel plating solution is 15-25°Bé, the pH value of the nickel plating solution is 4.0-4.8, the temperature of the nickel plating solution is 50-60°C, the nickel plating current is 20-40 A, and the silver plating time is 30-35 min. Preferably, in step S8, the nickel plating solution comprises 250-300 g / L nickel sulfate, 40-60 g / L nickel chloride, and 40-60 g / L boric acid; the Baumé degree of the nickel plating solution is 15-25°Bé; the pH value of the nickel plating solution is 1.5-2.5; the temperature of the nickel plating solution is 50-60°C; the nickel plating current is 20-30 A; and the silver plating time is 20-25 min.

8. The metal surface composite coating process according to claim 1, characterized in that, In step S10, the degreasing agent is selected from degreasing powder with a concentration of 45-58 g / L and a Baume degree of 2-6°Bé, the degreasing temperature is 46-55℃, the ultrasonic frequency of the degreasing is 40 kHz, and the ultrasonic time of the degreasing is 1-2 min; the acidic solution is a 15-20% mass fraction sulfuric acid solution.

9. The metal surface composite coating process according to claim 1, characterized in that, In step S11, the gold ion concentration of the gold plating solution is 1-2 g / L, the cobalt ion concentration of the gold plating solution is 0.3-0.5 g / L, the additive concentration of the gold plating solution is 20-40 mL / L, the equilibrium salt concentration of the gold plating solution is 20-40 g / L, the Baume degree of the electroplating solution is 8-12°Bé, the pH value of the electroplating solution is 3.8-5.0, the temperature of the electroplating solution is 35-45℃, the gold plating current is 8-9 A, and the gold plating time is 30-40 min.

10. A component with a composite coating on a metal surface, characterized in that, The composite coating component is manufactured by the process described in any one of claims 1-9, and the composite coating component on the metal surface is composed of a metal substrate, a first nickel plating layer, a second copper plating layer, a third ternary alloy plating layer, a fourth silver plating layer, a fifth silver plating layer, a sixth nickel plating layer, a seventh nickel plating layer, and an eighth gold plating layer stacked sequentially, wherein the total coating thickness is 9.3-12µm, and the thickness of the eighth gold plating layer is 0.76-1.1µm.

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