High-phosphorus chemical black nickel plating layer with excellent corrosion resistance on surface of steel and iron material and low-cost preparation method of high-phosphorus chemical black nickel plating layer

Abstract

The invention relates to the technical field of metal surface treatment processes, in particular to a high-phosphorus chemical black nickel plating layer with excellent corrosion resistance on the surface of a steel material and a low-cost preparation method of the high-phosphorus chemical black nickel plating layer. The method comprises the following steps: preparing a chemical nickel-plated phosphorus layer as an innermost layer of a plating layer by adopting a high-phosphorus chemical nickel-plating process; preparing an electro-coppering layer on the chemical nickel-phosphorus plating layer by using an alkaline copper plating solution to serve as a middle layer; a chemical nickel-plated phosphorus layer is prepared on the electrocoppering layer through a high-phosphorus chemical nickel-plating process and serves as the outermost layer; according to the method, the compact pulse copper layer is added in the chemical nickel plating process, the defects of the chemical nickel plating layer below the pulse copper layer can be covered to a great extent, so that some chemical nickel plating solutions which are long in period and have degraded performance can be used as the chemical nickel plating solution, the operation procedure is simple, and the material cost and the maintenance cost of production are reduced to a great extent.

Description

Technical Field

[0001] The present invention relates to the technical field of metal surface treatment processes, and particularly to a high-phosphorus electroless nickel black layer with excellent corrosion resistance on the surface of steel materials and a low-cost preparation method therefor. Background Art

[0002] The high-phosphorus electroless nickel layer is a coating with a non-crystalline structure and a relatively high phosphorus content (generally exceeding 10 wt.%). It has high hardness, wear resistance and corrosion resistance, and its mechanical properties can be further improved or new functions can be imparted through post-treatment, such as blackening treatment or heat treatment. The electroless nickel plating solution has a certain service life, calculated in cycles (i.e., when the amount of nickel ions replenished is equal to the amount of nickel ions contained in the initial plating solution, it is one cycle). As the service cycle extends, the performance of the plating solution gradually deteriorates, resulting in fluctuations in the phosphorus content and compactness of the coating. Therefore, high requirements for the coating performance often lead to a significant shortening of the available service life of the plating solution, increasing production and maintenance costs. In addition, the post-treatment method of the coating is also an important factor affecting its corrosion resistance and anti-discoloration ability. For the blackening treatment of electroless nickel coatings, the earliest method was to use a simple nitric acid corrosion method to form a large number of microporous networks on the surface, reducing the refraction of light to achieve a blackening effect. However, this treatment method makes the surface structure relatively loose, to a certain extent, destroying the integrity of the coating surface and resulting in a significant decrease in corrosion resistance and anti-discoloration performance. Later, various other blackening processes were developed, including various chemical oxidation methods or electrodeposition methods, etc., and the corrosion resistance of the coating was significantly improved. However, these process methods are more complicated in operation procedures and higher in material costs compared to the nitric acid corrosion method. Summary of the Invention

[0003] The present invention provides a high-phosphorus electroless nickel black layer with excellent corrosion resistance on the surface of steel materials and a low-cost preparation method therefor, overcoming the above-mentioned deficiencies of the prior art and effectively solving the problems of complex operation procedures and high material costs existing in the existing blackening treatment methods for electroless nickel coatings.

[0004] To solve the above problems, one of the technical solutions of the present invention is achieved by the following means: A low-cost preparation method for a high-phosphorus electroless nickel black layer with excellent corrosion resistance on the surface of steel materials, comprising the following steps: Adopt a high-phosphorus electroless nickel plating process to prepare an electroless nickel-phosphorus layer as the innermost layer of the coating; Use an alkaline copper plating solution on the electroless nickel-phosphorus layer to make an electroplated copper layer as the intermediate layer; Use a high-phosphorus electroless nickel plating process on the electroplated copper layer to prepare an electroless nickel-phosphorus layer as the outermost layer.

[0005] The thickness of the innermost electroless nickel-phosphorus layer accounts for 50% - 80% of the total thickness, and the allowable range of its phosphorus content is 8 - 12 wt.%; the thickness of the intermediate electroplated copper layer accounts for 10% - 25%; the thickness of the outermost electroless nickel-phosphorus layer accounts for 10% - 25%, and the allowable range of its phosphorus content is 10 - 12 wt.%.

[0006] The preparation raw materials of the above high-phosphorus electroless nickel plating process include nickel sulfate, sodium hypophosphite, sodium citrate, malic acid, succinic acid, lactic acid, propionic acid, MoO 3 , adjust the pH value of the solution to 4.8, the temperature to 90 °C, and use the plating solution of the second cycle to prepare the electroless nickel-phosphorus layer.

[0007] The preparation raw materials of the above alkaline copper plating solution include copper sulfate, HEDP, sodium tartrate, K 2 CO 3 , adjust the pH value of the solution to 8.5.

[0008] When electroplating the electroplated copper layer in the middle layer, a pulse electroplating process is adopted. The pulse peak current density is controlled at 2 - 4 times the maximum current density allowed under the conditions of this copper plating process in direct current electroplating, the duty cycle is 20% - 30%, and the average current density shall not be higher than the maximum current density allowed under the conditions of direct current electroplating; a complexing agent is added to the plating solution, and the dosage of the complexing agent is 0.8 - 1 times the lower limit in the process specification; the pH value of the electroplating solution is taken as the lower limit value in the process specification.

[0009] The second technical solution of the present invention is realized in the following way: a high-phosphorus electroless nickel black layer with excellent corrosion resistance on the surface of a steel material, which is prepared by using a low-cost preparation method of a high-phosphorus electroless nickel black layer with excellent corrosion resistance on the surface of a steel material. Its high-phosphorus electroless nickel black layer is composed of an electroless nickel-phosphorus layer, an electroplated copper layer, and an electroless nickel-phosphorus layer from the inside to the outside.

[0010] The thickness of the innermost electroless nickel-phosphorus layer accounts for 50% - 80% of the total thickness, and the allowable range of its phosphorus content is 8 - 12 wt.%; the thickness of the intermediate electroplated copper layer accounts for 10% - 25%; the thickness of the outermost electroless nickel-phosphorus layer accounts for 10% - 25%, and the allowable range of its phosphorus content is 10 - 12 wt.%.

[0011] By adding a dense pulse copper layer in electroless nickel plating in the present invention, the deficiencies of the underlying electroless nickel layer can be covered to a great extent. Therefore, some electroless nickel plating solutions with long cycles and degraded performance can be used for the electroless nickel plating solution. The operation process is simple, and the material cost and maintenance cost of production are reduced to a great extent. Specific embodiments

[0012] The present invention is not limited by the following embodiments, and specific implementation manners can be determined according to the technical solution of the present invention and actual situations.

[0013] Embodiment 1: An embodiment of the present invention discloses a low-cost preparation method for a high-phosphorus electroless nickel blackening layer with excellent corrosion resistance on the surface of a steel material, including the following steps: Adopt a high-phosphorus electroless nickel plating process to prepare an electroless nickel-phosphorus layer as the innermost layer of the coating; Use an alkaline copper plating solution to make an electroplated copper layer on the electroless nickel-phosphorus layer as the intermediate layer; Use a high-phosphorus electroless nickel plating process to prepare an electroless nickel-phosphorus layer on the electroplated copper layer as the outermost layer.

[0014] Among them, the thickness of the innermost electroless nickel-phosphorus layer accounts for 50% - 80% of the total thickness, and the allowable range of its phosphorus content is 8 - 12 wt.%; the thickness of the intermediate electroplated copper layer accounts for 10% - 25%; the thickness of the outermost electroless nickel-phosphorus layer accounts for 10% - 25%, and the allowable range of its phosphorus content is 10 - 12 wt.%.

[0015] Among them, the preparation raw materials of the high-phosphorus electroless nickel plating process include nickel sulfate, sodium hypophosphite, sodium citrate, malic acid, succinic acid, lactic acid, propionic acid, MoO 3 , adjust the pH value of the solution to 4.8, the temperature to 90 °C, and use the plating solution of the second cycle to prepare the electroless nickel-phosphorus layer.

[0016] In the inner electroless phosphorus layer, the allowable service life (calculated by cycle) of the plating solution can be extended to 1.5 - 2 times the life of the corresponding electroless nickel under normal operating conditions, thereby greatly reducing the production material cost and maintenance cost.

[0017] In the outer electroless phosphorus layer, the allowable service life (calculated by cycle) of the plating solution can be appropriately extended with reference to the allowable service life of the corresponding electroless nickel under normal operating conditions. Specifically, the acidic plating solution can be extended by 1 - 2 cycles, and the alkaline plating solution can be extended by 1 cycle, thereby further reducing the material and maintenance costs.

[0018] Among them, the preparation raw materials of the alkaline copper plating solution include copper sulfate, HEDP, sodium tartrate, K 2 CO 3 , adjust the pH value of the solution to 8.5, the pulse peak current density to 4 A / dm 2 , and the duty cycle to 20%.

[0019] Among them, when electroplating the copper electroplating layer in the middle layer, a pulse electroplating process is adopted. The pulse peak current density is controlled at 2 to 4 times the maximum current density allowed under direct current electroplating conditions for this copper plating process, the duty cycle is 20 to 30%, and the average current density shall not be higher than the maximum current density allowed under direct current electroplating conditions; a complexing agent is added to the plating solution, and the dosage of the complexing agent is 0.8 to 1 times the lower limit in the process specification; the pH value of the electroplating solution is taken as the lower limit value in the process specification.

[0020] Example 2: The embodiment of the present invention discloses a high-phosphorus electroless nickel black coating with excellent corrosion resistance on the surface of a steel material, which is prepared by using a low-cost preparation method for a high-phosphorus electroless nickel black coating with excellent corrosion resistance on the surface of a steel material. The high-phosphorus electroless nickel black coating is composed of an electroless nickel-phosphorus layer, a copper electroplating layer, and an electroless nickel-phosphorus layer from the inside to the outside.

[0021] Among them, the thickness of the innermost electroless nickel-phosphorus layer accounts for 50% to 80% of the total thickness, and the allowable range of its phosphorus content is 8 to 12 wt.%; the thickness of the middle copper electroplating layer accounts for 10% to 25%; the thickness of the outermost electroless nickel-phosphorus layer accounts for 10% to 25%, and the allowable range of its phosphorus content is 10 - 12 wt.%.

[0022] Example 3: The embodiment of the present invention discloses the effect of a pulse electroplated copper layer on the corrosion resistance of the coating.

[0023] Among them, a conventional high-phosphorus electroless nickel plating process is adopted, and its formula and process conditions are as follows: Nickel sulfate 25 g / L, sodium hypophosphite 36 g / L, sodium citrate 14 g / L, malic acid 15 g / L, succinic acid 5 g / L, lactic acid 15 mL / L, propionic acid 5 mL / L, MoO 3 5 mg / L, pH value 4.8, temperature 90 °C. The plating solution used is the plating solution of the second cycle, that is, the plating solution in the period of optimal performance state.

[0024] The formula and process conditions of the copper plating solution used are as follows: Copper sulfate 60 g / L, HEDP 180 g / L, sodium tartrate 5 g / L, K 2 CO 3 60 g / L, pH value 8.5, pulse peak current density 4 A / dm 2 , duty cycle 20%.

[0025] For comparison, two Q235 steel sheets with dimensions of 20 mm × 20 mm × 2 mm were taken. After being polished with 800# sandpaper, degreased, and pickled and activated, one of them was directly subjected to 1-hour coating deposition in the above electroless nickel plating solution. The other one was first deposited in the above plating solution for 40 minutes, the surface was washed with deionized water, then electroplated with the above pulse copper plating process for 15 minutes, the surface was washed with deionized water, and then deposited in the above electroless nickel plating solution for 10 minutes. Finally, the above two test pieces were immersed in a 20% concentration of nitric acid solution at 50 °C for 15 seconds for blackening treatment.

[0026] The corrosion resistance of the two test pieces was tested under neutral salt spray conditions, and the surface state of the test pieces was checked every 1 hour. The results showed that local areas on the surface of the directly electroless nickel-plated test piece began to show red rust after 16 hours, while the test piece containing the pulse copper layer did not show local red rust until 40 hours.

[0027] Example 4: The present invention example discloses the effect of the pulse electroplated copper layer on extending the service life of the electroless nickel plating solution.

[0028] Among them, a conventional high-phosphorus electroless nickel plating process was adopted, and its formula and process conditions are as follows: Nickel sulfate 25 g / L, sodium hypophosphite 36 g / L, sodium citrate 14 g / L, malic acid 15 g / L, succinic acid 5 g / L, lactic acid 15 mL / L, propionic acid 5 mL / L, MoO 3 5 mg / L, pH value 4.8, temperature 90 °C. The plating solution used was the plating solution of the second cycle, that is, the plating solution in the optimal performance state, and the plating solution of the sixth cycle, that is, the plating solution whose performance had significantly deteriorated.

[0029] The formula and process conditions of the copper plating solution used are as follows: Copper sulfate 60 g / L, HEDP 180 g / L, sodium tartrate 5 g / L, K 2 CO 3 60 g / L, pH value 8.5, pulse peak current density 4 A / dm 2 , duty cycle 20%.

[0030] For comparison, two Q235 steel sheets with dimensions of 20 mm × 20 mm × 2 mm were taken. After being polished with 800# sandpaper, degreased, and pickled and activated, one of them was deposited in the electroless nickel plating solution in the second cycle for 40 minutes. After the surface was washed with deionized water, it was electroplated with the above pulse copper plating process for 15 minutes. After the surface was washed with deionized water, it was deposited in the electroless nickel plating solution in the second cycle for another 10 minutes. The other one was first deposited in the plating solution in the sixth cycle for 40 minutes. After the surface was washed with deionized water, without pulse copper plating, it was directly deposited in the plating solution in the second cycle for 20 minutes. Finally, the above two test pieces were immersed in a 20% concentration nitric acid solution at 50 °C for 15 seconds for blackening treatment.

[0031] The corrosion resistance of the two test pieces was tested under neutral salt spray conditions, and the surface state of the test pieces was checked every 1 hour. The results showed that local areas on the surface of the test piece without the pulse copper plating layer began to show red rust after 9 hours, while local red rust on the surface of the test piece without the pulse copper layer appeared after 32 hours.

[0032] The above results indicate that after the surface of the coating is blackened with 20% concentration nitric acid at 50 °C for 15 seconds, it still has excellent corrosion resistance and can maintain no rust for at least 24 hours under neutral salt spray conditions. In the electroless nickel plating of the present invention, a dense pulse copper layer is added. Even if the phosphorus content and compactness in the electroless nickel plating layer below the copper layer are somewhat lacking, it will not have an obvious impact on the corrosion resistance of the coating, and can largely cover up the deficiencies of the electroless nickel plating layer below it. Moreover, due to the presence of the pulse electroplated copper layer, the phosphorus content and compactness in the surface electroless nickel plating layer can be appropriately relaxed. Therefore, some electroless nickel plating solutions with a relatively long service life and degraded performance can be used, which greatly reduces the material cost and maintenance cost of production.

[0033] Furthermore, during the blackening treatment, nitric acid blackening treatment with low cost and certain damage to the coating integrity can be adopted, instead of other chemical oxidation or electrodeposition blackening methods with complex processes, and the good corrosion resistance of the coating can still be ensured, thus further reducing the cost.

Claims

1. A low-cost preparation method for a high-phosphorus chemically plated black nickel layer having excellent corrosion resistance on the surface of a steel material, characterized in that: The following steps are involved: A high-phosphorus chemical nickel plating process is used to prepare a chemical nickel-phosphorus layer as the innermost layer of the plating layer; An electroplated copper layer is prepared as an intermediate layer using an alkaline copper plating solution on the chemically plated nickel-phosphorus layer; A chemical nickel-phosphorus layer is prepared as the outermost layer on the electroplated copper layer using a high-phosphorus chemical nickel plating process.

2. The low-cost preparation method of the high-phosphorus chemically plated black nickel layer having excellent corrosion resistance on the surface of the steel material according to claim 1, characterized in that: The thickness of the innermost chemical nickel-phosphorus layer accounts for 50% to 80% of the total thickness, and its phosphorus content is allowed to range from 8 to 12 wt.%; the thickness of the middle electroplated copper layer accounts for 10% to 25%; the thickness of the outermost chemical nickel-phosphorus layer accounts for 10% to 25%, and its phosphorus content is allowed to range from 10-12 wt.%.

3. The low-cost preparation method of the high-phosphorus chemically plated black nickel layer having excellent corrosion resistance on the surface of the steel material according to claim 1, characterized in that: The raw materials for preparing the high-phosphorus chemical nickel plating process include nickel sulfate, sodium hypophosphite, sodium citrate, malic acid, succinic acid, lactic acid, propionic acid, and MoO3. The pH value of the solution is adjusted to 4.8 and the temperature is 90°C. The second cycle of plating solution is used to prepare the chemical nickel-phosphorus layer.

4. The low-cost preparation method of the high-phosphorus chemically plated black nickel layer having excellent corrosion resistance on the surface of the steel material according to claim 1, characterized in that: The raw materials for preparing the alkaline copper plating solution include copper sulfate, HEDP, sodium tartrate and K2CO3, and the pH value of the solution is adjusted to 8.

5.

5. The low-cost preparation method of the high-phosphorus chemically plated black nickel layer having excellent corrosion resistance on the surface of the steel material according to claim 1, characterized in that: When electroplating the middle copper layer, a pulse electroplating process is adopted, and the pulse peak current density is controlled at 2~4 times the maximum current density allowed by this copper plating process under DC electroplating conditions, the duty cycle is 20~30%, and the average current density shall not be higher than the maximum current density allowed under DC electroplating conditions; a complexing agent is added to the plating solution, and the amount of the complexing agent is 0.8~1 times the lower limit of the process specification; the pH value of the electroplating solution takes the lower limit value in the process specification.

6. A high-phosphorus chemically plated black nickel layer having excellent corrosion resistance on the surface of a steel material, characterized in that: The high-phosphorus chemically plated black nickel layer having excellent corrosion resistance on the surface of a steel material is prepared by a low-cost preparation method according to any one of claims 1 to 5, wherein the high-phosphorus chemically plated black nickel layer is composed of a chemically plated nickel-phosphorus layer, an electroplated copper layer and a chemically plated nickel-phosphorus layer from the inside to the outside.

7. The high-phosphorus chemically plated black nickel layer having excellent corrosion resistance on the surface of the steel material according to claim 6, characterized in that: The thickness of the innermost chemical nickel-phosphorus layer accounts for 50%~80% of the total thickness, and its phosphorus content is allowed to range from 8% to 12wt.%; the thickness of the middle layer electroplated copper layer accounts for 10%~25%; the thickness of the outermost chemical nickel-phosphorus layer accounts for 10%~25%, and its phosphorus content is allowed to range from 10-12wt.%.