High-uniformity metal surface silver plating process and corrosion-resistant treatment method thereof

Abstract

The invention belongs to the technical field of metal surface treatment, and discloses a high-uniformity metal surface silver plating process and a corrosion-resistant treatment method thereof.The high-uniformity metal surface silver plating process comprises the following steps that firstly, pretreatment is conducted; step 2, activating treatment; step 3, pre-plating a bottom layer; step 4, electrosilvering; step 5, post-processing; according to the method, pre-plating of the bottom layer and electroplating of silver are combined, a layer of thin nickel or copper is pre-plated firstly, and then electroplating of silver is performed, so that the binding force and uniformity of the silver plating layer are effectively improved, and in the electroplating process, the mode of stirring and circulating the electroplating liquid is adopted, so that silver ions in the electroplating liquid are uniformly distributed, and the uniformity of the plating layer is improved; and a thin aluminum oxide protective film is deposited on the surface of the silver plating layer by adopting a chemical vapor deposition technology, so that the corrosion resistance of the silver plating layer is further improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal surface treatment, and particularly relates to a high-uniformity silver plating process for metal surfaces and its corrosion-resistant treatment method. Background Art

[0002] Existing silver plating processes have been widely used in metal surface treatment, but there are problems such as insufficient coating uniformity and poor corrosion resistance. Especially on complex-shaped or large-area metal parts, it is often difficult to ensure the uniformity of the coating. At the same time, the silver plating layer is prone to oxidation and discoloration in a specific environment, affecting aesthetics and service life. Therefore, it is particularly important to develop a silver plating process with high uniformity and corrosion resistance. Summary of the Invention

[0003] In view of the above situation, to overcome the defects of the existing technology, the present invention provides a high-uniformity silver plating process for metal surfaces and its corrosion-resistant treatment method, effectively solving the problems raised in the background art.

[0004] To achieve the above object, the present invention provides the following technical solution: A high-uniformity silver plating process for metal surfaces, comprising the following steps:

[0005] Step 1, pretreatment:

[0006] Thoroughly clean the metal surface to remove oil, oxides, and impurities. Adopt a combination of ultrasonic cleaning and chemical degreasing to ensure that the metal surface is clean and free of contaminants. Add an appropriate amount of cleaning agent to the ultrasonic cleaning tank, with a temperature of 40 - 60 °C and a cleaning time of 10 - 20 minutes. Subsequently, rinse thoroughly with deionized water and proceed to the next step;

[0007] Step 2, activation treatment:

[0008] Immerse the cleaned metal parts in a solution containing an activator to remove residual oxides and impurities on the surface, while increasing the surface roughness and improving the adhesion between the coating and the substrate, creating good conditions for electroplating;

[0009] Step 3, pre-plating the bottom layer:

[0010] To improve the adhesion and uniformity of the silver plating layer, first pre-plate a thin layer of nickel or copper on the metal surface. Adopt the electroplating method, using a nickel plate or copper plate as the anode, the metal part as the cathode, and the electroplating solution as Watts nickel plating solution or acidic copper plating solution. The current density is 1 - 5 A / dm 2 , and the electroplating time is 5 - 15 minutes;

[0011] Step 4, electroplating silver:

[0012] Take the pre-plated metal component as the cathode and a pure silver plate as the anode, place them in an electroplating bath, and use potassium silver cyanide electrolyte as the electroplating solution. The formula is: silver nitrate 20 - 50 g / L, potassium cyanide 50 - 150 g / L, pH value 9 - 11. During the electroplating process, the current density is 2 - 8 A / dm 2 , and the electroplating time is 30 - 90 minutes;

[0013] Step Five, post-treatment:

[0014] After electroplating is completed, take out the metal component, rinse it thoroughly with deionized water, and then carry out passivation treatment to improve the corrosion resistance of the silver plating layer. The passivation solution formula is: potassium dichromate 5 - 15 g / L, sulfuric acid 5 - 20 ml / L, temperature 20 - 25 °C, time 5 - 10 minutes; finally, carry out drying treatment to prevent the generation of water stains or rust stains.

[0015] Preferably, use chemical vapor deposition technology to deposit a thin layer of aluminum oxide protective film on the surface of the silver plating layer; the chemical vapor deposition treatment temperature is 300 - 500 °C, time 1 - 3 hours, and this aluminum oxide protective film can effectively isolate air and moisture and protect the silver plating layer from corrosion.

[0016] Preferably, in Step One, the cleaning agent is one of alkaline cleaning agents or acidic cleaning agents.

[0017] Preferably, the alkaline cleaning agent is one of sodium hydroxide and sodium carbonate, and the acidic cleaning agent is one of sulfuric acid and hydrochloric acid.

[0018] Preferably, in Step Two, the specific formula of the activator is: copper sulfate 5 - 10 g / L, nickel sulfate 5 - 15 g / L, ammonium sulfate 10 - 30 g / L; the pH value of the activator solution is 2 - 4, temperature 20 - 40 °C, and the activation time is 5 - 15 minutes.

[0019] Preferably, in Step Four, while electroplating silver, stir and circulate the electroplating solution to ensure the uniform distribution of silver ions in the electroplating solution, thereby improving the uniformity of the plating layer.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] By combining pre-plating the bottom layer with electroplating silver, first pre-plating a thin layer of nickel or copper and then electroplating silver, the adhesion and uniformity of the silver plating layer are effectively improved. And during the electroplating process, by stirring and circulating the electroplating solution, the uniform distribution of silver ions in the electroplating solution is ensured, thereby improving the uniformity of the plating layer;

[0022] By using chemical vapor deposition technology to deposit a thin layer of aluminum oxide protective film on the surface of the silver plating layer, the corrosion resistance of the silver plating layer is further improved. Description of the Drawings

[0023] The accompanying drawings are used to provide a further understanding of the present invention, and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation to the present invention.

[0024] In the accompanying drawings:

[0025] Figure 1 It is a schematic flow chart of a silver plating process on a metal surface with high uniformity of the present invention. Specific embodiments

[0026] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0027] It is given by Figure 1 The present invention relates to a silver plating process on a metal surface with high uniformity, including the following steps:

[0028] Step 1, pretreatment:

[0029] Thoroughly clean the metal surface to remove oil, oxides and impurities. Adopt a combination of ultrasonic cleaning and chemical degreasing to ensure that the metal surface is clean and free of dirt. Add an appropriate amount of cleaning agent to the ultrasonic cleaning tank, with a temperature of 40 - 60 °C and a cleaning time of 10 - 20 minutes. Subsequently, rinse it thoroughly with deionized water and proceed to the next step;

[0030] Step 2, activation treatment:

[0031] Immerse the cleaned metal parts in a solution containing an activator to remove residual oxides and impurities on the surface, while increasing the surface roughness and improving the adhesion between the coating and the substrate, creating good conditions for electroplating;

[0032] Step 3, pre - plating the bottom layer:

[0033] To improve the adhesion and uniformity of the silver - plated layer, first pre - plate a thin layer of nickel or copper on the metal surface. Adopt the electroplating method, using a nickel plate or copper plate as the anode, the metal part as the cathode, and the electroplating solution as Watts nickel plating solution or acidic copper plating solution. The current density is 1 - 5 A / dm 2 , and the electroplating time is 5 - 15 minutes;

[0034] Step 4, electroplating silver:

[0035] Take the metal part with a pre-plated bottom layer as the cathode and a pure silver plate as the anode, place them in an electroplating bath, and use potassium silver cyanide electrolyte as the electroplating solution. The formula is: silver nitrate 20 - 50 g / L, potassium cyanide 50 - 150 g / L, pH value is 9 - 11. During the electroplating process, the current density is 2 - 8 A / dm 2 , and the electroplating time is 30 - 90 minutes;

[0036] Step Five, post-treatment:

[0037] After electroplating is completed, take out the metal part, rinse it thoroughly with deionized water, and then perform passivation treatment to improve the corrosion resistance of the silver plating layer. The formula of the passivation solution is: potassium dichromate 5 - 15 g / L, sulfuric acid 5 - 20 ml / L, temperature is 20 - 25 °C, time is 5 - 10 minutes; finally, perform drying treatment to prevent the generation of water stains or rust stains.

[0038] In this embodiment, a thin layer of alumina protective film is deposited on the surface of the silver plating layer by chemical vapor deposition technology; the chemical vapor deposition treatment temperature is 300 - 500 °C, time is 1 - 3 hours, and this alumina protective film can effectively isolate air and moisture and protect the silver plating layer from corrosion.

[0039] In step one of this embodiment, the cleaning agent is one of an alkaline cleaning agent or an acidic cleaning agent.

[0040] The alkaline cleaning agent in this embodiment is one of sodium hydroxide and sodium carbonate, and the acidic cleaning agent is one of sulfuric acid and hydrochloric acid.

[0041] In step two of this embodiment, the specific formula of the activator is: copper sulfate 5 - 10 g / L, nickel sulfate 5 - 15 g / L, ammonium sulfate 10 - 30 g / L; the pH value of the activator solution is 2 - 4, temperature is 20 - 40 °C, and the activation time is 5 - 15 minutes.

[0042] In step four of this embodiment, while electroplating silver, the electroplating solution is stirred and circulated to ensure the uniform distribution of silver ions in the electroplating solution, thereby improving the uniformity of the plating layer.

[0043] Example 1:

[0044] The present invention relates to a silver plating process for a metal surface with high uniformity, including the following steps:

[0045] Step One, pre-treatment:

[0046] Thoroughly clean the metal surface to remove oil stains, oxides, and impurities. Adopt a combination of ultrasonic cleaning and chemical degreasing to ensure that the metal surface is clean and free of dirt. Add an appropriate amount of cleaning agent to the ultrasonic cleaning tank, the temperature is 40 °C, the cleaning time is 10 minutes. Subsequently, rinse it thoroughly with deionized water and proceed to the next step;

[0047] Step 2, Activation Treatment:

[0048] Immerse the cleaned metal parts in a solution containing an activator to remove residual oxides and impurities on the surface, while increasing the surface roughness and improving the adhesion between the plating layer and the substrate, creating good conditions for electroplating;

[0049] Step 3, Pre-plating the Bottom Layer:

[0050] To improve the adhesion and uniformity of the silver plating layer, first pre-plate a thin layer of nickel or copper on the metal surface. Using the electroplating method, with a nickel plate or copper plate as the anode, the metal parts as the cathode, and the electroplating solution being Watts nickel plating solution or acidic copper plating solution, the current density is 1 A / dm 2 , and the electroplating time is 5 minutes;

[0051] Step 4, Silver Electroplating:

[0052] Place the metal parts with the pre-plated bottom layer as the cathode and a pure silver plate as the anode in the electroplating bath. The electroplating solution uses potassium silver cyanide electrolyte, and the formula is: silver nitrate 20 g / L, potassium cyanide 50 g / L, pH value is 9. During the electroplating process, the current density is 2 A / dm 2 , and the electroplating time is 30 minutes;

[0053] Step 5, Post-treatment:

[0054] After electroplating is completed, take out the metal parts, rinse them thoroughly with deionized water, and then carry out passivation treatment to improve the corrosion resistance of the silver plating layer. The passivation solution formula is: potassium dichromate 5 g / L, sulfuric acid 5 ml / L, temperature is 20 °C, time is 5 minutes; finally, carry out drying treatment to prevent the generation of water stains or rust stains.

[0055] In this embodiment, a thin layer of alumina protective film is deposited on the surface of the silver plating layer by chemical vapor deposition technology; the chemical vapor deposition treatment temperature is 300 °C, and the time is 1 hour. This alumina protective film can effectively isolate air and moisture and protect the silver plating layer from corrosion.

[0056] In step 1 of this embodiment, the cleaning agent is one of an alkaline cleaning agent or an acidic cleaning agent.

[0057] The alkaline cleaning agent in this embodiment is one of sodium hydroxide and sodium carbonate, and the acidic cleaning agent is one of sulfuric acid and hydrochloric acid.

[0058] In step 2 of this embodiment, the specific formula of the activator is: copper sulfate 5 g / L, nickel sulfate 5 g / L, ammonium sulfate 10 g / L; the pH value of the activator solution is 2, the temperature is 20 °C, and the activation time is 5 minutes.

[0059] In step four of this embodiment, while electroplating silver, the electroplating solution is stirred and circulated to ensure the uniform distribution of silver ions in the electroplating solution, thereby improving the uniformity of the coating.

[0060] Example 2:

[0061] The present invention relates to a silver plating process for a metal surface with high uniformity, comprising the following steps:

[0062] Step one, pretreatment:

[0063] The metal surface is thoroughly cleaned to remove oil, oxides, and impurities. The ultrasonic cleaning and chemical degreasing are combined to ensure that the metal surface is clean and free of contaminants. An appropriate amount of cleaning agent is added to the ultrasonic cleaning tank, the temperature is 60 °C, and the cleaning time is 20 minutes. Subsequently, it is rinsed thoroughly with deionized water and proceeds to the next step;

[0064] Step two, activation treatment:

[0065] The cleaned metal parts are immersed in a solution containing an activator to remove residual oxides and impurities on the surface, while increasing the surface roughness and improving the adhesion between the coating and the substrate, creating good conditions for electroplating;

[0066] Step three, preplating the bottom layer:

[0067] To improve the adhesion and uniformity of the silver plating layer, a thin layer of nickel or copper is first preplated on the metal surface. The electroplating method is used, with a nickel plate or copper plate as the anode, the metal parts as the cathode, and the electroplating solution being Watts nickel plating solution or acidic copper plating solution. The current density is 5 A / dm 2 , and the electroplating time is 15 minutes;

[0068] Step four, electroplating silver:

[0069] The metal parts with the preplated bottom layer are used as the cathode, and a pure silver plate is used as the anode. They are placed in the electroplating tank. The electroplating solution uses potassium silver cyanide electrolyte, and the formula is: silver nitrate 50 g / L, potassium cyanide 150 g / L, pH value is 11. During the electroplating process, the current density is 8 A / dm 2 , and the electroplating time is 90 minutes;

[0070] Step five, post-treatment:

[0071] After electroplating is completed, the metal parts are taken out, rinsed thoroughly with deionized water, and then passivated to improve the corrosion resistance of the silver plating layer. The passivation solution formula is: potassium dichromate 15 g / L, sulfuric acid 20 ml / L, temperature is 25 °C, time is 10 minutes; finally, drying treatment is carried out to prevent the generation of water stains or rust stains.

[0072] In this embodiment, a thin alumina protective film is deposited on the silver-plated layer by using chemical vapor deposition technology; the chemical vapor deposition treatment temperature is 500 °C and the time is 3 hours. This alumina protective film can effectively isolate air and moisture and protect the silver-plated layer from corrosion.

[0073] In step one of this embodiment, the cleaning agent is one of an alkaline cleaning agent or an acidic cleaning agent.

[0074] The alkaline cleaning agent in this embodiment is one of sodium hydroxide and sodium carbonate, and the acidic cleaning agent is one of sulfuric acid and hydrochloric acid.

[0075] In step two of this embodiment, the specific formula of the activator is: 10 g / L of copper sulfate, 15 g / L of nickel sulfate, and 30 g / L of ammonium sulfate; the pH value of the activator solution is 4, the temperature is 40 °C, and the activation time is 15 minutes.

[0076] In step four of this embodiment, during electroplating silver, the methods of stirring and circulating the electroplating solution are adopted to ensure the uniform distribution of silver ions in the electroplating solution, thereby improving the uniformity of the coating.

[0077] Example 3:

[0078] The present invention relates to a silver plating process with high uniformity on the metal surface, including the following steps:

[0079] Step one, pretreatment:

[0080] The metal surface is thoroughly cleaned to remove oil, oxides, and impurities. The method of combining ultrasonic cleaning and chemical degreasing is adopted to ensure that the metal surface is clean and free of dirt. An appropriate amount of cleaning agent is added to the ultrasonic cleaning tank, the temperature is 50 °C, and the cleaning time is 15 minutes. Subsequently, it is rinsed clean with deionized water and enters the next step;

[0081] Step two, activation treatment:

[0082] The cleaned metal parts are immersed in a solution containing an activator to remove residual oxides and impurities on the surface, increase the surface roughness at the same time, improve the bonding force between the coating and the substrate, and create good conditions for electroplating;

[0083] Step three, pre-plating the bottom layer:

[0084] To improve the bonding force and uniformity of the silver-plated layer, a thin layer of nickel or copper is pre-plated on the metal surface first. The electroplating method is used, with a nickel plate or copper plate as the anode, the metal parts as the cathode, the electroplating solution being Watts nickel plating solution or acidic copper plating solution, and the current density being 3 A / dm 2 , and the electroplating time is 10 minutes;

[0085] Step four, electroplating silver:

[0086] Take the pre-plated bottom metal part as the cathode and a pure silver plate as the anode, place them in the electroplating bath, and use potassium silver cyanide electrolyte as the electroplating solution. The formula is: silver nitrate 35 g / L, potassium cyanide 100 g / L, pH value is 10. During the electroplating process, the current density is 5 A / dm 2 , and the electroplating time is 60 minutes;

[0087] Step Five, post-treatment:

[0088] After electroplating is completed, take out the metal part, rinse it thoroughly with deionized water, and then carry out passivation treatment to improve the corrosion resistance of the silver plating layer. The formula of the passivation solution is: potassium dichromate 10 g / L, sulfuric acid 12.5 ml / L, temperature is 22.5 °C, and time is 7.5 minutes; finally, carry out drying treatment to prevent the generation of water stains or rust stains.

[0089] In this embodiment, a thin alumina protective film is deposited on the surface of the silver plating layer by chemical vapor deposition technology; the chemical vapor deposition treatment temperature is 400 °C and the time is 2 hours. This alumina protective film can effectively isolate air and moisture and protect the silver plating layer from corrosion.

[0090] In step one of this embodiment, the cleaning agent is one of an alkaline cleaning agent or an acidic cleaning agent.

[0091] The alkaline cleaning agent in this embodiment is one of sodium hydroxide and sodium carbonate, and the acidic cleaning agent is one of sulfuric acid and hydrochloric acid.

[0092] In step two of this embodiment, the specific formula of the activator is: copper sulfate 7.5 g / L, nickel sulfate 10 g / L, ammonium sulfate 20 g / L; the pH value of the activator solution is 3, the temperature is 30 °C, and the activation time is 10 minutes.

[0093] In step four of this embodiment, while electroplating silver, the electroplating solution is stirred and circulated to ensure the uniform distribution of silver ions in the electroplating solution, thereby improving the uniformity of the plating layer.

[0094] Example 4:

[0095] The present invention relates to a silver plating process for metal surfaces with high uniformity, including the following steps:

[0096] Step One, pre-treatment:

[0097] Thoroughly clean the metal surface to remove oil stains, oxides, and impurities. Adopt a combination of ultrasonic cleaning and chemical degreasing to ensure that the metal surface is clean and free of dirt. Add an appropriate amount of cleaning agent to the ultrasonic cleaning tank, the temperature is 45 °C, the cleaning time is 12 minutes, and then rinse it thoroughly with deionized water and proceed to the next step;

[0098] Step Two, activation treatment:

[0099] Immerse the cleaned metal parts in a solution containing an activator to remove residual oxides and impurities on the surface, while increasing the surface roughness and improving the adhesion between the coating and the substrate, creating good conditions for electroplating;

[0100] Step 3, pre-plating the bottom layer:

[0101] To improve the adhesion and uniformity of the silver coating, first pre-plate a thin layer of nickel or copper on the metal surface. Using the electroplating method, with a nickel plate or copper plate as the anode, the metal part as the cathode, and the electroplating solution being Watts nickel plating solution or acidic copper plating solution, the current density is 2 A / dm 2 , and the electroplating time is 7 minutes;

[0102] Step 4, electroplating silver:

[0103] Place the metal part with the pre-plated bottom layer as the cathode and a pure silver plate as the anode in the electroplating tank. The electroplating solution uses potassium silver cyanide electrolyte, and the formula is: silver nitrate 30 g / L, potassium cyanide 70 g / L, pH value is 10. During the electroplating process, the current density is 4 A / dm 2 , and the electroplating time is 40 minutes;

[0104] Step 5, post-treatment:

[0105] After electroplating is completed, take out the metal parts, rinse them thoroughly with deionized water, and then perform passivation treatment to improve the corrosion resistance of the silver coating. The passivation solution formula is: potassium dichromate 8 g / L, sulfuric acid 10 ml / L, temperature is 22 °C, time is 7 minutes; finally, perform drying treatment to prevent the generation of water stains or rust stains.

[0106] In this embodiment, a thin layer of alumina protective film is deposited on the surface of the silver coating by chemical vapor deposition technology; the chemical vapor deposition treatment temperature is 350 °C, and the time is 1.5 hours. This alumina protective film can effectively isolate air and moisture and protect the silver coating from corrosion.

[0107] In step 1 of this embodiment, the cleaning agent is one of an alkaline cleaning agent or an acidic cleaning agent.

[0108] The alkaline cleaning agent in this embodiment is one of sodium hydroxide and sodium carbonate, and the acidic cleaning agent is one of sulfuric acid and hydrochloric acid.

[0109] In step 2 of this embodiment, the specific formula of the activator is: copper sulfate 6 g / L, nickel sulfate 7 g / L, ammonium sulfate 15 g / L; the pH value of the activator solution is 3, the temperature is 25 °C, and the activation time is 7 minutes.

[0110] In step 4 of this embodiment, during electroplating silver, the electroplating solution is stirred and circulated to ensure the uniform distribution of silver ions in the electroplating solution, thereby improving the uniformity of the coating.

[0111] It should be noted that, in this document, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variation thereof is intended to cover non-exclusive inclusion, such that a process, method, article or device comprising a series of elements not only includes those elements but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device.

[0112] Although embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A silver plating process for a metal surface with high uniformity, characterized in that, It includes the following steps: Step 1, pretreatment: Thoroughly clean the metal surface to remove oil, oxides and impurities. Adopt a combination of ultrasonic cleaning and chemical degreasing to ensure that the metal surface is clean and free of contaminants. Add an appropriate amount of cleaning agent to the ultrasonic cleaning tank, with a temperature of 40 - 60°C and a cleaning time of 10 - 20 minutes. Subsequently, rinse it thoroughly with deionized water and proceed to the next step; Step 2, activation treatment: Immerse the cleaned metal parts in a solution containing an activator to remove residual oxides and impurities on the surface, increase the surface roughness at the same time, improve the adhesion between the coating and the substrate, and create good conditions for electroplating; Step 3, pre - plating the bottom layer: To improve the adhesion and uniformity of the silver plating layer, a thin layer of nickel or copper is first pre-plated on the metal surface by electroplating. Using a nickel plate or copper plate as the anode, the metal component as the cathode, and the electroplating solution as Watts nickel plating solution or acidic copper plating solution, the current density is 1 - 5 A / dm 2 , and the electroplating time is 5 - 15 minutes; Step 4, electroplating silver: Take the pre-plated bottom metal part as the cathode and a pure silver plate as the anode, place them in an electroplating bath, and use potassium silver cyanide electrolyte as the electroplating solution. The formula is: silver nitrate 20 - 50 g / L, potassium cyanide 50 - 150 g / L, pH value is 9 - 11. During the electroplating process, the current density is 2 - 8 A / dm 2 , and the electroplating time is 30 - 90 minutes; Step 5, post - treatment: After electroplating is completed, take out the metal parts, rinse them thoroughly with deionized water, and then carry out passivation treatment to improve the corrosion resistance of the silver coating. The passivation solution formula is: potassium dichromate 5 - 15 g / L, sulfuric acid 5 - 20 ml / L, temperature 20 - 25°C, time 5 - 10 minutes; Finally, carry out drying treatment to prevent the generation of water stains or rust stains.

2. The corrosion-resistant treatment method for a high-uniformity silver-plating process on a metal surface according to claim 1, characterized in that, Adopt chemical vapor deposition technology to deposit a thin alumina protective film on the surface of the silver coating; the chemical vapor deposition treatment temperature is 300 - 500°C and the time is 1 - 3 hours. This alumina protective film can effectively isolate air and moisture and protect the silver coating from corrosion.

3. A silver plating process for a metal surface with high uniformity according to claim 1, characterized in that, In the said Step 1, the cleaning agent is one of alkaline cleaning agents or acidic cleaning agents.

4. A silver plating process for a metal surface with high uniformity according to claim 3, characterized in that, The said alkaline cleaning agent is one of sodium hydroxide and sodium carbonate, and the acidic cleaning agent is one of sulfuric acid and hydrochloric acid.

5. A silver plating process for a metal surface with high uniformity according to claim 1, characterized in that, In the said Step 2, the specific formula of the activator is: copper sulfate 5 - 10 g / L, nickel sulfate 5 - 15 g / L, ammonium sulfate 10 - 30 g / L; the pH value of the activator solution is 2 - 4, the temperature is 20 - 40°C, and the activation time is 5 - 15 minutes.

6. A silver plating process for a metal surface with high uniformity according to claim 1, characterized in that, In the said Step 4, during electroplating silver, stir and circulate the electroplating solution to ensure the uniform distribution of silver ions in the electroplating solution, thereby improving the uniformity of the coating.

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