JPS5919197B2 - Single-sided electroplating method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for electroplating one side of a metal strip.

Conventional methods for electroplating one side of a metal strip include insulating the side that does not require plating with paint or adhesive tape and then plating in an electrolyte, or in which the electrolyte surface contacts only one side of the metal strip. There is a method of plating the contact surface between the metal strip and the electrolyte while keeping the water level of the electrolyte constant.

However, the former method has disadvantages such as not only the paint and adhesive tape being relatively expensive, but also the work of covering and peeling these materials is required, which is time-consuming. It is difficult to maintain the electrolyte at a constant water level, and stable one-sided plating cannot be obtained because the electrolyte partially circulates around the non-plated surface of the metal strip.Furthermore, it is difficult to maintain the electrolyte at a constant water level. Another disadvantage is that it is not suitable for high-speed plating because the electrolyte cannot be stirred strongly.

In addition, in Japanese Patent Publication No. 48-31454, an air curtain was created using air from an air jet pipe installed around the top surface of the metal strip to prevent the plating solution from flowing into and coming into contact with the top surface of the metal strip. A single-sided plating method for completely single-sided metal plates has also been disclosed, but when attempting to perform single-sided plating of metal using this method, an electrolytic solution with a specific gravity of about 1.1 to 1.2 is used as an electrolytic solution with a specific gravity much lower than that. The pressure of the injected air must be very high because it must be removed by
As a result, the air becomes bubbles and becomes entangled in the electrolyte, and the electrolyte on the plating side also contains a large amount of air bubbles, which increases the liquid resistance and not only requires a high plating voltage but also a high current. Because it has to be plated with density 6
There was a drawback that no discoloration occurred, and the top surface of the metal strip was oxidized by the air jetted, resulting in a significant deterioration in the quality of the unplated surface. The present invention solves this problem by injecting the electrolyte onto the top surface of the metal strip that is shallowly immersed horizontally in the electrolyte and passing through, thereby removing the electrolyte present on the top surface of the metal strip into the electrolytic cell. By pushing the metal strip toward both walls, applying electricity with the top surface of the metal strip slightly covered with electrolyte, and plating only the bottom surface of the metal strip, there is no need to insulate the unplated surface, reducing costs. To provide a single-sided electroplating method that is inexpensive and capable of continuously and stably performing high-speed single-sided plating without increasing the number of work steps.

More specifically, the present invention involves shallowly immersing a metal strip in an electrolytic solution in a horizontal electrolytic tower and passing the strip continuously horizontally.
The electrolytic solution is continuously sprayed from above in the longitudinal direction of the metal strip onto the upper surface near both ends of the metal strip, and the electrolytic solution on the upper surface of the metal strip is pushed toward both side walls of the electrolytic cell, and the ↓ side of the metal strip is A single-side electroplating method characterized by continuously plating only the bottom surface of the metal strip facing the anode while preventing the top surface of the metal strip from being plated by keeping the metal strip slightly covered with an electrolyte. It is.

In general, when electroplating one side of a metal strip, the current that flows around to the non-plated side is smaller as the distance between the electrodes is shorter.
It is said that the longer the electrode width is, the closer the side wall and rear wall of the electrolytic cell are to the electrode, the less the electrolytic cell side wall and rear wall are.

However, when performing continuous single-sided plating by passing a metal strip continuously through a horizontal electrolytic cell, it is important to consider the possibility of contact with the counter electrode due to deflection of the metal strip, or contact with the side wall of the electrolytic cell due to meandering of the metal strip. There is an inherent limit to how close the metal strip can be to the counter electrode or the side wall of the electrolytic cell. Furthermore, in order to perform complete one-sided plating, it is extremely effective to lower the electrolyte level and bring it as close to the metal strip surface as possible.

In view of the above points, the method of the present invention involves injecting electrolytic solution in a band shape in the longitudinal direction of the metal strip onto the top surface near both ends of a metal strip that has been shallowly immersed in electrolytic solution, thereby transferring the electrolytic solution on the top surface of the metal strip into an electrolytic bath. By pushing the electrolyte toward both side walls of the metal strip and removing the electrolyte on the top surface of the metal strip, it is possible to prevent current from flowing around to the top surface of the metal strip and prevent oxidation of the top surface of the metal strip. It is used to plate the target metal.

Hereinafter, the single-sided electroplating method according to the present invention will be explained in detail with reference to the drawings. FIG. 1 is a side view showing one embodiment of the apparatus used for carrying out the method of the present invention, and FIG.
-A' line cross-sectional enlarged view.

In the drawing, 1 is an electrolytic solution storage tank, 2 is a horizontal electrolytic tank installed above the electrolytic solution storage tank 1, and the electrolytic solution overflowing from this electrolytic tank 2 flows down into the electrolytic solution storage tank 1. The electrolyte level in the electrolytic cell 2 is 1 point from the metal strip.
It has a height of 0 to 40 ut.

3 and 3' are supply pumps that speed up the electrolyte in the electrolyte storage tank 1 to the electrolytic tank 2; 4 is a metal strip that is plated on one side;
Dam rolls 5 and 5' are respectively provided on the inlet and outlet sides of the metal strip 4 that passes through the electrolytic cell 2, and 6 is a dam roll that contacts the metal strip 4 that has passed through the electrolytic cell 2 and connects the metal strip 4 to the cathode. conductor roll,
7 is an anode provided in the electrolytic cell 2 facing the lower surface of the metal strip 4 passing through the electrolytic cell 2; 8 is a supply pump 3;
' is an electrolytic solution supply pipe that is connected to the electrolytic solution storage tank 1 and supplies the electrolytic solution in the electrolytic solution storage tank 1 into the electrolytic tank 2, and also powerfully stirs the electrolytic solution in the electrolytic tank 2. is inserted into the electrolytic cell 2.

Reference numeral 9 designates an electrolyte injection tube connected to the supply pump 3 and for injecting the electrolyte in the electrolyte storage tank 1 onto the upper surface of the metal strip 4 passing through the electrolyzer 4W2; The metal strips 4 are provided with pipes running parallel to each other in the longitudinal direction, and have injection holes drilled at appropriate intervals on the upper surface near both ends of the metal strip 4 to spray the electrolyte in a band shape. The slits may be arranged in parallel with a gap, or may be continuous slits with a minute gap as in the embodiment described later.

The method of the present invention uses such an apparatus to apply electroplating to one side of the metal strip 4.
The metal strip 4 is passed through the electrolytic cell 2 through the dam roll 5 on the inlet side so that it is horizontally and shallowly immersed in the electrolyte, and after passing through the dam roll 5' on the outlet side, it is brought into contact with the conductor roll 6 and becomes the cathode. The supply pump 3 sends electrolyte to the upper surface of the metal strip 4 in the electrolytic cell 2, and the electrolyte is injected from the electrolyte injection pipe 9. At the same time, the supply pump 3' sends the electrolyte to the upper surface of the metal strip 4. Then, an electrolytic solution is supplied into the electrolytic cell 2 from the electrolytic solution supply pipe 8, and the electrolytic solution is strongly stirred to perform high-speed plating.

When the electrolyte is injected onto the upper surface of the metal strip 4 from the electrolyte injection tube 9, the metal strip 4 is injected from above onto the upper surface near both ends of the metal strip 4, as shown in FIG.
When sprayed in a strip in the longitudinal direction, the electrolytic solution present on the top surface of the metal strip 4 is pushed to both side walls of the electrolytic cell 2, leaving the top surface of the metal strip 4 slightly covered with the electrolytic solution. Become. In this way, when electricity is applied with the top surface of the metal strip 4 slightly covered with the electrolyte, the current flowing around the top surface of the metal strip 4 is negligible, but the top surface of the metal strip 4 is Since it is slightly covered with the electrolyte, it will not be oxidized and its quality will deteriorate, and only the lower surface of the metal strip 4 facing the anode 7 is plated with the target metal, and the upper surface is not plated. The electrolytic solution used when electroplating one side by the method of the present invention is a zinc sulfate electrolytic solution or a zinc sulfate electrolytic solution.
The less uniformly electrodepositable the plating metal is, such as a copper sulfate electrolyte, the more suitable it is for single-sided electroplating, and the more it meets the purpose of the present invention.

As described above, in the method of the present invention, an electrolytic solution is injected onto the upper surface of the metal strip 4 to perform single-sided electroplating. However, the injection of this electrolyte onto the metal strip 4 will be explained in more detail.

The electrolytic solution sprayed onto the top surface of the metal strip 4 uses its spraying force to push the electrolytic solution on the top surface of the metal strip 4 toward both side walls of the electrolytic cell 2. It is preferable to spray the electrolyte from the center of the upper surface of the metal strip 4 at an acute angle to the perpendicular toward the end surface of the metal strip 4, and the amount of electrolyte sprayed is such that the upper surface of the metal strip 4 is slightly covered with the electrolyte. For the purpose of achieving a stable state, a range of 50 to 400 t/min per meter of injection pipe is preferable.

If it is less than 50 t/min per meter of injection tube, the injection force will become too weak and the electrolyte on the top of the metal strip 4 will be transferred to the electrolytic tank 2.
Since the metal strip 4 cannot be sufficiently pushed toward both side walls, the metal is undesirably deposited on the upper surface of the metal strip 4.
If it exceeds 400 t/min per meter of injection tube, the injection force will increase, but the upper surface of the metal strip 4 will be relatively thickly covered with the injection liquid, which is not preferable because metal will be deposited on the upper surface of the metal strip. In addition, when injecting the electrolyte, it is preferable to inject the electrolyte in a thin strip shape in order to increase the injection force. In order to sufficiently push the electrolytic solution present on the upper surface, especially the electrolytic solution present near both ends of the upper surface of the metal strip 4, to both side walls of the electrolytic cell 2, from each side end of the metal strip 4 toward the center, Preferably, the distance is 100vt. If it is less than 4011, the electrolytic solution that has fallen onto the top surface of the metal strip 4 will forcefully rush into the electrolytic solution between both ends of the metal strip 4 and the side wall of the electrolytic cell 2, and air will be mixed into the electrolytic solution, resulting in burnt spots. This is not preferable as it may cause

Moreover, if the number of cycles exceeds 100, the electrolytic solution on the upper surface of the metal strip 4 cannot be sufficiently pushed toward both side walls of the electrolytic cell 2, which is not preferable.

The method of the present invention will be further explained below with reference to Examples.

Example 1 ZnS04・7H20: 200g/T,. MgSO4・
7H20: 10g/T,. In an electrolytic cell containing an electrolytic solution with a composition of Na2sO4: 10 g/t and a pH of 3.4, an electrode distance of 20n1 and a current density of 10
Under electrolytic conditions of A/Dm2 and bath temperature of 40℃, thickness 0.6m7
! A steel strip with a width of L1 of 914 m1 was passed through, and electrolytic solution was injected onto the upper surface of the steel strip strip under the following conditions from the electrolytic solution storage tank in which the electrolytic solution was stored, to perform single-sided electroplating to a plating thickness of 5 μm. did.

As a result, the top surface of the steel strip is slightly covered with electrolyte, and there is no zinc electrodeposition on the top surface of the steel strip.
It was possible to galvanize only one side.

Example 2 zns04●7H20: 300g/T,. MgsO47
H2O: 12g/T,. In an electrolytic cell containing an electrolytic solution with a composition of Na2SO4: 12 g/t and a pH of 2.8, an electrode distance of 20111 and a current density of 20 A were applied.
/Dm2, under electrolytic conditions of bath temperature 50°C, thickness 0.611,
A steel strip having a width of 914 nm was passed through the steel strip, and an electrolytic solution was sprayed onto the upper surface of the steel strip under the following conditions from an electrolytic solution storage tank in which the electrolytic solution was stored, to perform single-sided electroplating to a plating thickness of 30 μm. .

As a result, the top surface of the steel strip is slightly covered with electrolyte, and there is no zinc electrodeposition on the top surface of the steel strip.
It was possible to galvanize only one side.

As detailed above, the single-sided electroplating method according to the present invention injects an electrolytic solution onto the top surface of a metal strip passing through an electrolytic bath, pushes the electrolytic solution on the top surface of the metal strip toward both side walls of the electrolytic barrel, and The top surface of the strip is slightly covered with electrolyte to prevent plating on the top surface of the metal strip, while plating is continuously applied only to the bottom surface of the metal strip that passes opposite to the anode. To perform continuous and stable high-speed single-sided plating without the need to insulate the non-plated surface as in conventional methods, and without the need for adjustment such as contacting only one side of the metal strip with an electrolyte. It also has the advantage that the equipment used for carrying out the method of the invention is simple, the method is extremely economical, and the single-sided plated metal obtained is of excellent quality. When applied to steel strips, etc., a single-sided electroplated steel strip with an excellent base for painting is obtained, and can be used for automobile parts,
It can be used for a wide range of purposes, including electrical appliances, household goods, furniture and building materials, and has great industrial value.

[Brief explanation of the drawing]

FIG. 1 is a side view showing one embodiment of an apparatus used to carry out the method of the present invention, and FIG. 2 is an enlarged cross-sectional view taken along line A-A' in FIG. 1... Electrolyte storage tank, 2... Electrolytic tank,
3, 3'...Feed pump, 4...Metal strip, 515', 0.1 dam roll, 6. ．． ．． ．．
．． ．． Conductor roll, 7... Anode, 8...
... Electrolyte supply pipe, 9... Electrolyte injection pipe.

Claims (1)

[Claims] 1. A metal strip is immersed shallowly in an electrolytic solution in a horizontal electrolytic cell and passed through it continuously horizontally, and electrolysis is applied from above in the longitudinal direction of the metal strip to the top surface near both ends of the metal strip. The electrolytic solution on the top surface of the metal strip is pushed to both sides of the electrolytic tank by continuously spraying the solution, and the top surface of the metal strip is slightly covered with the electrolytic solution, and the top surface of the metal strip is plated. A single-sided electroplating method characterized by continuously applying plating only to the lower surface of the metal strip facing the anode while preventing the electroplating from occurring. 2. The single-sided electroplating method according to claim 1, wherein the electrolytic solution is sprayed from the center of the upper surface of the metal strip toward the end surface of the metal strip at an acute spray angle with respect to the perpendicular line. 3. The single-sided electroplating method according to claim 1 or 2, wherein the injection amount of the electrolytic solution is 50 to 400 liters per meter of injection tube. 4 The position at which the electrolyte is dropped onto the top surface of the metal strip is 40 to 40 degrees from both ends of the metal strip toward the center.
Claims 1 to 3 that are a distance of 100 mm
The single-sided electroplating method described in any of the preceding paragraphs.