JPH0141719B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to an electric nickel plating method, particularly to an improvement in a method of nickel plating an object having a shape with a deep recess. (Prior art) Electroplating can coat the surface of inexpensive metals with other metals to give them superior properties, and it is also useful for decoration because it can densely cover the surface of objects and reproduce precise shapes. It is used for a variety of purposes, including corrosion protection, surface hardening, electroforming, and more. In particular, electric nickel plating is a technology that is widely used due to the excellent properties of nickel.
However, when electric nickel plating is applied to an object that has a deep recess and a shaded area relative to the nickel anode, such as a C-shaped cross section such as lip groove steel, the current density in the shaded area is It is difficult to obtain good results because the coverage of the plating is low and the coverage of the area is poor. Therefore, a method is generally adopted in which an auxiliary anode is placed close to the shadowed area as described above to increase the current density in that area and improve the coverage of the plating. % of sulfur or phosphorus added, titanium or titanium whose surface is plated with platinum, and processed according to the object to be plated. However, all of these conventional auxiliary anodes have a high anode potential, poor conductivity, and poor anode current efficiency. In addition, especially when pure nickel is used, undissolved nickel grains are generated and dispersed in the plating solution, which causes the surface of the plated object to become hard and rough, causing cracks in the precipitated nickel. It causes When using nickel containing a trace amount of sulfur or phosphorus of 0.01 to 0.1%, the anode potential will be lower than when using pure nickel, but insoluble nickel particles will be dispersed and contained in the plating solution, Sulfur or phosphorus becomes an impurity in the plating solution, causing embrittlement of the deposited nickel, increased hardness, and increased electrodeposition stress. The auxiliary anode, which has titanium plated with platinum, is insoluble and has extremely high resistance on the electrode surface, causing oxidation stress and other side reactions at the anode. Decomposition of acid salts and sulfates occurs,
The precipitated nickel becomes brittle in the same way as in the case described above. Furthermore, its effectiveness as an auxiliary anode, which is its main purpose, is extremely low. In addition, on the inner surface of steel pipes, etc.
When performing nickel plating, it is done by inserting a nickel anode or the above-mentioned phosphorous-added nickel, titanium, titanium, etc. into the steel pipe, but when plating the inner surface of the tube, it is difficult to improve the current density because it is limited by the size of the anode. It took a long time to do the plating work because I couldn't plan it properly. (Problems to be Solved by the Invention) The present invention focuses on the above-mentioned drawbacks,
It is an object of the present invention to provide a nickel plating method that can uniformly, smoothly and efficiently apply nickel to an object to be plated, even on an object shaped like a square. (Means for Solving the Problem) Therefore, in order to achieve the above-mentioned object, the present inventor has made extensive research, and as a result, has developed an electric nickel plating method using sulfamic acid nickel plating, nickel sulfate salt plating, nickel plating using Watt's solution, etc. When cobalt is used as an auxiliary anode, the solubility of the cobalt auxiliary anode in the plating tank is extremely good, which means that the anode current efficiency is high, and the effect of increasing current density to low current density parts of the object to be plated is large. It has been found that the plated surface can be finished with a smooth or uniform gloss with less occurrence of sludge, and that it is possible to perform good nickel plating without causing embrittlement of the precipitated nickel.
It has also been found that as a special method of use, cobalt can be used as the main anode instead of as an auxiliary anode to provide good nickel plating as described above. This is because the standard redox potential of nickel and cobalt is Nickel Ni ² +2e ^- = Ni Eo = -0.250 Cobalt Co ²⁺ +2e ^- = Co Eo = -0.277, and cobalt is easier to ionize than nickel. It dissolves well in the plating tank, and the amount of cobalt dissolved is very small compared to the amount dissolved in the mainstay nickel anode, and this very small amount of cobalt forms an alloy in the plating tank of the object to be plated, resulting in high hardness. This is thought to be because it becomes nickel-metsuki. In addition, cobalt itself has the disadvantage of poor workability.
If the shape of the object to be plated is complex, it is difficult to process it so that it matches the object to be plated, but it has relatively good workability.
A lump of nickel, titanium, iron, or other metal that does not have a negative effect on the plating solution, etc. is processed in advance to match the object to be plated, and the surface of the metal lump is plated with a thick layer of cobalt, and the metal lump is used as an auxiliary anode. By using it, the above-mentioned drawbacks are eliminated. That is, one aspect of the present invention is to apply cobalt plating to the surface of a metal lump that has been formed in advance so that it can be approached to a low current density part of the object to be plated, and to apply cobalt plating to the surface of the metal lump that has been formed in advance so as to be close to the low current density part of the object to be plated. The cobalt plating metal lump and the object to be plated are immersed in a nickel plating tank filled with a nickel electrolyte, and the nickel electrode is similarly immersed in the nickel plating tank, and the nickel electrode and cobalt plating metal lump are connected to the anode of a DC power supply. The nickel plating method is characterized by connecting the object to be plated to the cathode and applying electricity.
Cobalt plating is applied to the surface of a metal lump that has been formed in advance so that it can be approached to the desired part of the object to be plated, and the cobalt-plated metal lump and the object to be plated are immersed closely in a nickel plating tank filled with a nickel electrolyte. This is a nickel plating method characterized by connecting the cobalt plating metal block to the anode of a DC power source and the object to be plated to the cathode and applying electricity. (Example) Specific examples of the present invention will be further described below. Example 1 FIG. 1 shows an application of the method of the present invention to electroforming, in which a cobalt nickel metal ingot is used as an auxiliary anode. Reference numeral 1 in FIG. 1 is an electroforming mother mold whose surface is electrically conductive and has a concave cross section. When a plating coating is formed over the entire surface of the mother mold, usually when an auxiliary anode is not used, the recessed portion 2 of the electroforming mother mold shadows the nickel electrode 3, resulting in a low current density. 4 in the figure is a cobalt-plated metal ingot, which is the main feature of the present invention, and as shown in Fig. 2, the titanium ingot has been preformed, degreased, and washed so as to be close to the low current density part 2 of the depression of the electroforming mold. 5 to liquid 6 having the composition shown in Table 1.
The cobalt electrode 8 and the cobalt electrode 8 were immersed in a cobalt plating bath filled with (cobalt sulfamate solution), the cobalt electrode 8 was connected to the anode of the DC power supply 9, and the titanium lump 5 was connected to the other cathode, and the current density was 0.5 to 5 A/dm ^{2 .} A cobalt plating 10 with a thickness of 3 to 5 mm is applied to the surface of the titanium block 5 by applying electricity.

[Table] Table 2 shows the electroforming master mold 1 and nickel electrode 3 described above.
It is immersed in a nickel plating tank 12 filled with a nickel plating solution 11 (sulfur amic acid nickel solution) having a composition of
5 to 20 mm to the current density part 2 of the depression of the electroforming mother mold 1.
The anode of the DC power supply 13 is connected to the cobalt-plated metal block 4 via a power supply 15 whose surface is insulated, and the anode of the power supply 14 is connected to the nickel electrode 3.

[Table] In addition, the cathodes of both power supplies are placed on the electroforming mother mold 1 and the power supply body 16.
Connect using. And each 1~6A/
To obtain a uniform and sufficient thickness of nickel coating even on the low current density portion of the recess of the electroforming mold 1 without causing embrittlement of the precipitated nickel by applying current at a current density of dm ² and precipitating nickel appropriately. Can be done. Incidentally, better results can be obtained if the plating liquid 11 is slightly stirred during the plating operation. Example 2 The present invention uses a cobalt-plated metal lump as an anode for the nickel plating method.As in the example, the nickel anode can be used as the main anode, and the metal lump of the invention can be used as the auxiliary anode. Although this is preferred, in special cases it is also possible to use the cobalt-plated metal block of the present invention as the main anode, as shown in the following embodiments. An example of application of the present invention to plating the inner surface of a steel pipe is shown below. FIG. 3 shows an application of the nickel plating method according to the present invention to nickel plating the inner surface of a steel pipe. In the figure, 15 indicates an inner diameter of φ50~
It is a φ500 steel pipe. 16 is 1/8 of the inner diameter of steel pipe 15
Example 1 A titanium round bar 17 with an outer diameter of ~3/4
This is a cobalt-plated metal lump having a cobalt-plated tank 18 coated on its surface by the method shown in FIG.
And as shown in Figure 3, cobalt plated metal block 1
6 is immersed in the plating rod 20 filled with the plating liquid 19 having the composition shown in Table 2 so as to be located in the center of the steel pipe, and the anode of the DC power supply 21 is connected to the cobalt plating metal block, and the cathode of the DC power supply is connected to the steel pipe. Connect to 15,
Nickel plating can be favorably deposited on the inner surface of the steel pipe 15 by applying current at a current density of 1 to 6 A/dm ² . (Effects) By using cobalt as an auxiliary anode for nickel plating, the present invention has higher anode current efficiency than conventional anodes, and has a large effect of improving current density in low current areas of the object to be plated. It has the effect of reducing the occurrence of sludge, making it possible to finish the plated surface with a smooth or uniform gloss, and making it possible to perform nickel plating without causing embrittlement of the precipitated nickel.It also has the effect of being able to perform nickel plating according to the shape of the low current area of the object to be plated. By selecting a metal with relatively good workability, processing it in advance, applying cobalt plating to the workpiece, and using it as an auxiliary anode, it is possible to eliminate the possibility of using it as an auxiliary anode, where cobalt has poor workability. This has the effect of making it easier to work by avoiding the serious drawbacks that occur when nickel plating occurs, and the current density is low when using the normal nickel plating method on the inner shaded area of objects with a C-shaped cross section, resulting in poor plating. There is an effect that good nickel plating can be applied to the inside of the parts and tubular objects as well as other parts. In addition, by using a metal block coated with cobalt plating as the main anode, it is possible to plate areas where it is impossible to insert an anode with a sufficient surface area for the area to be plated, in a sufficient amount of time and in a short time. I can do the work.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram when the nickel plating method of the present invention is applied to electroforming, Fig. 2 is an explanatory diagram when applying cobalt plating to a preformed metal lump, and Fig. 3 is an explanatory diagram when applying the nickel plating method of the present invention to electroforming. This is an application of the Nickel plating method described above to plating the inner surface of steel pipes. 1... Electroforming mother mold (object to be plated), 2... Low current part, 3... Nickel electrode, 4, 16... Cobalt plating metal lump, 11, 19... Electrolyte, 12,
20...Nickelmetsuki tank, 13, 14, 21...
...DC power supply, 15... Steel pipe (object to be plated).

Claims (1)

[Scope of Claims] 1 Cobalt plating is applied to the surface of a metal lump formed in advance so that it can be brought close to a low current density area of the object to be plated, and the cobalt plated metal lump is brought close to the low current density area of the object to be plated. In this state, the cobalt plating metal lump and the object to be plated are immersed in a nickel plating tank filled with nickel electrolyte, and the nickel electrode is similarly immersed in the nickel plating tank, and the nickel electrode and the cobalt plating metal are connected to the anode of the DC power supply. The nickel plating method is characterized by connecting the mass to the cathode to the object to be plated and applying electricity. 2 Cobalt plating is applied to the surface of the formed metal lump in advance so that it can be approached to the desired part of the object to be plated, and the cobalt-plated metal lump and the object to be plated are placed in a nickel plating tank filled with nickel electrolyte. The nickel plating method is characterized by immersing them in close proximity, connecting the cobalt plating metal block to the anode of a DC power supply, and the object to be plated to the cathode, and applying electricity.