Aluminum alloy substrate ultra-high phosphorus chemical nickel plating solution system and preparation method

Abstract

The application discloses a plating solution system for an ultrahigh-phosphorus chemical nickel plating layer, which comprises A agent, B agent and C agent, wherein the A agent comprises the following components: 250-350 g / L of nickel sulfate, 30-60 g / L of a complexing agent, 10-25 g / L of a buffer, 0.1-2 mg / L of a stabilizer, and the rest is deionized water; the B agent comprises the following components: 200-300 g / L of sodium hypophosphite, 5-15 g / L of an accelerator, 0.5-2 g / L of ammonia water, and the rest is deionized water; the C agent comprises the following components: 400-600 g / L of sodium hypophosphite, 10-25 g / L of an accelerator, 0.5-2 g / L of ammonia water, and the rest is deionized water; the A agent and the B agent are mixed at a volume ratio of 1:4-5, and then diluted by 3 times to form a working plating solution. During immersion plating, the aluminum alloy base material is first treated, then immersed into the working plating solution, and a chemical nickel plating reaction is carried out at 82-87 DEG C; and the A agent and the C agent are dynamically added during the nickel plating process; after the reaction is completed, the finished product is obtained through water washing and drying. Through the above manner, the content of phosphorus elements in the plating layer can be stably provided to be more than 12%, so that the use requirements of special working conditions are met.

Description

Technical Field

[0001] This invention relates to the field of metal surface treatment, and in particular to a method for preparing an ultra-high phosphorus chemical coating on the surface of an aluminum alloy substrate and the coating solution system thereof. Background Technology

[0002] Chemical nickel plating refers to the application of a nickel-phosphorus alloy coating to a metal surface using a specialized nickel plating agent. Due to the excellent wear resistance, good ductility and hardness of nickel-phosphorus alloy coatings, and especially their good weldability during heat treatment, they are widely used as a passivation and protective layer for various metal materials, particularly aluminum alloys. Traditional chemical nickel plating is generally classified into low-phosphorus, medium-phosphorus, and high-phosphorus types based on phosphorus content. In practice, while the hardness of chemical nickel plating decreases with increasing phosphorus content, it exhibits better performance stability in high-temperature and oxidizing environments, and better resistance to various strong corrosive media. Importantly, as the phosphorus content increases, the alloy becomes non-magnetic, making it more suitable for some special strong magnetic environments. Currently, the phosphorus content of commonly available high-phosphorus chemical nickel plating is generally around 11 wt%. However, in some special applications, especially in strong magnetic and high-heat environments, the phosphorus content needs to be >12 wt% to meet practical requirements due to the characteristics of nickel-phosphorus alloys. Platings with a phosphorus content greater than 12 wt% are considered ultra-high phosphorus platings, but currently, there are no stable ultra-high phosphorus plating products on the market. Summary of the Invention

[0003] The main technical problem solved by this invention is to provide a plating solution system and method for ultra-high phosphorus electroless nickel plating, which can effectively increase the phosphorus content in the plating and meet the requirements of aluminum alloy products in strong magnetic and high heat environments.

[0004] To solve the above-mentioned technical problems, one technical solution adopted by the present invention is: providing a plating solution system for ultra-high phosphorus electroless nickel plating, the plating solution system for ultra-high phosphorus electroless nickel plating comprising: agent A, agent B, and agent C, wherein agent A comprises the following components: nickel sulfate 250-350 g / L, complexing agent 30-60 g / L, buffer 10-25 g / L, stabilizer 0.1-2 mg / L, and the balance being deionized water; agent B comprises the following components: sodium hypophosphite 200-300 g / L, accelerator 5-15 g / L, ammonia 0.5-2 g / L, and the balance being deionized water; agent C comprises the following components: sodium hypophosphite 400-600 g / L, accelerator 10-25 g / L, and ammonia 0.5-2 g / L, and the balance being deionized water; g / L, ammonia water 0.5~2g / L, the balance is deionized water; the working plating solution of the ultra-high phosphorus electroless nickel plating layer is composed of agent A and agent B mixed at a volume ratio of 1:4~5 and then diluted 3 times with deionized water according to the volume ratio, and agent C is a supplement to the working plating solution.

[0005] In a preferred embodiment of the present invention, the complexing agent is selected from sodium citrate, lactic acid, succinic acid, or any combination thereof in any proportion.

[0006] In a preferred embodiment of the present invention, the buffer is selected from sodium acetate, boric acid, or any combination thereof in any proportion.

[0007] In a preferred embodiment of the present invention, the accelerator is selected from sodium fluoride, sodium propionate, or a combination thereof, and the stabilizer is selected from lead salt, sodium thiosulfate, or any combination thereof in any proportion.

[0008] One technical solution adopted by the present invention is: providing a method for preparing an ultra-high phosphorus electroless nickel plating layer on an aluminum alloy substrate using a plating solution system for ultra-high phosphorus electroless nickel plating, characterized by comprising the following steps: Step 1: Perform pretreatment on the aluminum alloy substrate, which includes degreasing, alkaline etching, primary zinc plating, zinc stripping, and secondary zinc plating. Step 2: Immerse the pretreated aluminum alloy substrate in the initial working plating solution and perform a chemical nickel plating reaction at 82-87℃. Step 3: During the reaction, Agent A and Agent C are dynamically replenished according to the consumption of nickel ions and phosphite ions in the tank. Step 4: After the reaction is complete, remove the workpiece, wash it with water, and dry it to obtain an ultra-high phosphorus electroless nickel plating layer with a phosphorus content greater than 12 wt%.

[0009] In a preferred embodiment of the present invention, the nickel plating process in step 2 involves first heating the initial working plating solution to 87 degrees Celsius, then adjusting the pH value of the initial working plating solution to 4.5 ± 0.1, and then starting immersion plating of electroless nickel within the above pH range, while simultaneously slowly lowering the plating solution temperature to between 82°C and 85°C. The cooling rate of the working plating solution is ≤10 min / 1°C.

[0010] In a preferred embodiment of the present invention, the method for replenishing agents A and C in step 3 includes: online real-time monitoring of the nickel ion content in the working plating solution according to process requirements; dynamically replenishing agents A and C to the working plating solution in real time based on changes in the nickel ion concentration; during the replenishment process, monitoring the pH value and temperature of the working plating solution in real time to maintain it within the pH range of 4.5±0.1 and controlling the plating solution temperature to not exceed 82-87℃; after replenishment, controlling the plating solution temperature to slowly decrease to 82-85℃. Agents A and C are added simultaneously at a volume ratio of 1:1. During immersion plating, the controlled concentration of nickel ions in the working plating solution is Ni+≥5.5g / L.

[0011] The beneficial effects of this invention are: by further optimizing the existing high-phosphorus electroless nickel formulation and production process, the phosphorus content of the electroless nickel plating on the surface of aluminum alloy can be stably maintained at more than 14%. The resulting electroless nickel plating not only has excellent antimagnetic properties, but also stronger resistance to corrosion from strong acids and alkalis, and better performance stability in high-temperature and oxidizing environments, thus meeting the needs of use in special working environments with strong magnetic fields and high heat. Attached Figure Description

[0012] Figure 1 These are sample photographs corresponding to the three embodiments of this invention; Figure 2 This is the EDS composition analysis result of sample 1; Figure 3 This is the EDS spectrum of sample 1; Figure 4 This is the EDS composition analysis result of sample 2; Figure 5 This is the EDS spectrum of sample 2; Figure 6 This is the EDS composition analysis result of sample 3; Figure 7 This is the EDS spectrum of sample 3. Detailed Implementation

[0013] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0014] Please see Figures 1 to 7 The embodiments of the present invention include: Example 1 The plating solution system for the ultra-high phosphorus electroless nickel plating layer includes: Agent A, Agent B, and Agent C, wherein Agent A contains the following components: Nickel sulfate 250 g / L, succinic acid 30 g / L, sodium acetate 15 g / L, sodium thiosulfate 2 mg / L, balance deionized water; Agent B contains the following components: Sodium hypophosphite 200 g / L, sodium propionate 10 g / L, ammonia 1 g / L, the remainder is deionized water; Agent C contains the following components: Sodium hypophosphite 500 g / L, sodium propionate 15 g / L, ammonia 1 g / L, balance deionized water; The working plating solution for the ultra-high phosphorus electroless nickel plating layer is composed of agent A and agent B mixed uniformly at a volume ratio of 1:5, and then diluted 3 times with deionized water at a volume ratio. Agent C is a supplement to the working plating solution.

[0015] Example 2 The plating solution system for the ultra-high phosphorus electroless nickel plating layer includes: Agent A, Agent B, and Agent C, wherein Agent A contains the following components: Nickel sulfate 350 g / L, sodium citrate 50 g / L, sodium acetate 25 g / L, sodium thiosulfate 2 mg / L, balance deionized water; Agent B contains the following components: Sodium hypophosphite 250 g / L, sodium propionate 15 g / L, ammonia 1 g / L, balance deionized water; Agent C contains the following components: Sodium hypophosphite 550 g / L, sodium propionate 15 g / L, ammonia 1 g / L, balance deionized water; The working plating solution for the ultra-high phosphorus electroless nickel plating layer is composed of agent A and agent B mixed uniformly at a volume ratio of 1:5, and then diluted 3 times with deionized water at a volume ratio. Agent C is a supplement to the working plating solution.

[0016] Example 3 The plating solution system for the ultra-high phosphorus electroless nickel plating layer includes: Agent A, Agent B, and Agent C, wherein Agent A contains the following components: Nickel sulfate 300 g / L, heat-resistant DL-lactic acid 60 g / L, boric acid 10 g / L, sodium thiosulfate 2 mg / L, balance deionized water; Agent B contains the following components: Sodium hypophosphite 300 g / L, sodium fluoride 5 g / L, ammonia 1 g / L, balance deionized water; Agent C contains the following components: Sodium hypophosphite 500 g / L, sodium propionate 10 g / L, ammonia 1 g / L, balance deionized water; The working plating solution for the ultra-high phosphorus electroless nickel plating layer is composed of agent A and agent B mixed uniformly at a volume ratio of 1:4, and then diluted 3 times with deionized water at a volume ratio. Agent C is a supplement to the working plating solution.

[0017] The working plating solutions were prepared according to Examples 1-3 above, and then ultra-high phosphorus electroless nickel plating layers were prepared on aluminum alloy samples according to the following steps: Step 1: The aluminum alloy sample is subjected to degreasing, alkaline etching, first zinc plating, zinc stripping, and second zinc plating in sequence. Step 2: Immerse the pretreated aluminum alloy sample in the pre-prepared initial working plating solution and perform electroless nickel plating at 82-87℃. During the nickel plating process, first heat the initial working plating solution to 87℃, then adjust the pH value of the initial working plating solution to 4.5±0.1, and then start electroless nickel plating within the above pH range. While immersing, slowly reduce the temperature of the plating solution to between 82℃ and 85℃. The cooling rate of the working plating solution is ≤10min / 1℃. The control of temperature and pH value here is the key node of this process route. If not controlled properly, the phosphorus content in the coating is prone to large fluctuations. Step 3: During the reaction process, the nickel ion content in the working plating solution is monitored online in real time using an ESNICON NS-06 online plating solution detector. Agent A and Agent C are added dynamically and in real time according to the consumption of nickel ions in the tank. When adding, Agent A and Agent C are added simultaneously at a volume ratio of 1:1. The nickel ion content (Ni+) in the working plating solution is controlled to be ≥5.5 g / L. During the addition process, the pH value and temperature of the working plating solution are monitored in real time to maintain it within the pH range of 4.5±0.1 and to control the plating solution temperature to not exceed 82-87℃. After the addition is completed, the plating solution temperature is slowly reduced to between 82 and 85℃. Step 4: After the reaction is complete, remove the workpiece, wash it with water, and dry it to obtain an ultra-high phosphorus electroless nickel plating layer.

[0018] The above embodiment 1 corresponds to Figure 1 Sample 1, corresponding to the above Example 2 Figure 1 Sample 2, corresponding to the above Example 3 Figure 1 The P element detection results for sample 3, and samples 1, 2, and 3 above are as follows: The test results above show that, based on the above formula and combined with the process control of the present invention, the phosphorus content in the coating can be stably increased by more than 14%, thereby meeting the needs of special working environments.

[0019] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A plating solution system for ultra-high phosphorus electroless nickel plating, characterized in that, The plating solution system for the ultra-high phosphorus electroless nickel plating layer includes: agent A, agent B, and agent C, wherein... Agent A contains the following components: Nickel sulfate 250-350 g / L, complexing agent 30-60 g / L, buffer 10-25 g / L, stabilizer 0.1-2 mg / L, balance deionized water; Agent B contains the following components: Sodium hypophosphite 200-300 g / L, accelerator 5-15 g / L, ammonia 0.5-2 g / L, balance deionized water; Agent C contains the following components: Sodium hypophosphite 400-600 g / L, accelerator 10-25 g / L, ammonia 0.5-2 g / L, balance deionized water; The working plating solution for the ultra-high phosphorus electroless nickel plating layer is composed of agent A and agent B mixed evenly at a volume ratio of 1:4~5, and then diluted 3 times with deionized water according to the volume ratio. Agent C is a supplement to the working plating solution.

2. The plating solution system for ultra-high phosphorus electroless nickel plating according to claim 1, characterized in that, The complexing agent is selected from sodium citrate, lactic acid, succinic acid, or any combination thereof in any proportion.

3. The plating solution system for ultra-high phosphorus electroless nickel plating according to claim 1, characterized in that, The buffer is selected from sodium acetate, boric acid, or any combination thereof in any proportion.

4. The plating solution system for ultra-high phosphorus electroless nickel plating according to claim 1, characterized in that, The accelerator is selected from sodium fluoride, sodium propionate, or a combination thereof; the stabilizer is selected from lead salt, sodium thiosulfate, or any combination thereof in any proportion.

5. A method for preparing an ultra-high phosphorus electroless nickel plating layer on an aluminum alloy substrate using a plating solution system for ultra-high phosphorus electroless nickel plating as described in any one of claims 1 to 4, characterized in that... Includes the following steps: Step 1: Perform pretreatment on the aluminum alloy substrate, which includes degreasing, alkaline etching, primary zinc plating, zinc stripping, and secondary zinc plating. Step 2: Immerse the pretreated aluminum alloy substrate in the initial working plating solution and perform a chemical nickel plating reaction at 82-87℃. Step 3: During the reaction, Agent A and Agent C are dynamically replenished according to the consumption of nickel ions and phosphite ions in the tank. Step 4: After the reaction is complete, remove the workpiece, wash it with water, and dry it to obtain an ultra-high phosphorus electroless nickel plating layer with a phosphorus content greater than 12 wt%.

6. The method for preparing an ultra-high phosphorus electroless nickel plating layer on an aluminum alloy substrate using the plating solution system according to claim 5, characterized in that, The nickel plating process in step 2 involves first heating the initial working plating solution to 87 degrees Celsius, then adjusting the pH value of the initial working plating solution to 4.5±0.1, and then starting the immersion plating of chemical nickel within the above pH range, while slowly lowering the plating solution temperature to between 82°C and 85°C during the immersion plating process.

7. The method for preparing an ultra-high phosphorus electroless nickel plating layer on an aluminum alloy substrate using the plating solution system according to claim 6, characterized in that, The cooling rate of the working plating solution is ≤10 min / 1℃.

8. The method for preparing an ultra-high phosphorus electroless nickel plating layer on an aluminum alloy substrate using the plating solution system according to claim 5, characterized in that, The method for adding agents A and C in step 3 includes: real-time online detection of the nickel ion content in the working plating solution according to process requirements; dynamic addition of agents A and C to the working plating solution based on changes in nickel ion content; real-time monitoring of the pH and temperature of the working plating solution during the addition process to maintain it within the pH range of 4.5±0.1 and control the plating solution temperature to not exceed 82-87℃; and slow reduction of the plating solution temperature to 82-85℃ after the addition is completed.

9. The method for preparing an ultra-high phosphorus electroless nickel plating layer on an aluminum alloy substrate using the plating solution system according to claim 8, characterized in that, When replenishing, Agent A and Agent C are added simultaneously at a volume ratio of 1:

1.

10. The method for preparing an ultra-high phosphorus electroless nickel plating layer on an aluminum alloy substrate using the plating solution system according to claim 8, characterized in that, During immersion plating, the concentration of nickel ions in the working plating solution is controlled to be Ni+≥5.5g / L.

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