JPH0971894A - Method for electroplating steel strip - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method for electroplating a steel strip by which the progress of corrosion of the anode basket frequently used in electroplating is suppressed. SOLUTION: In the method for electroplating a steel strip using a basket anode, the plating current set according to a line speed is decreased by the equivalent to the electroless coating weight corresponding to the dipping time of the strip in a plating soln. and/or the plating soln. temp.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for electroplating a steel strip, and more particularly to a method for electroplating a steel strip using a basket type anode.

[0002]

2. Description of the Related Art Generally, in electroplating a steel strip,
In order to obtain a constant amount of plating for any line speed, a method of controlling the plating current according to the line speed (as an increasing function of the line speed) is adopted. A basket type is often used as the anode. As disclosed in Japanese Patent Laid-Open No. 62-4899, a basket-type anode is a basket-shaped power feeding portion (also referred to as a basket anode or an anode basket) made of a material having resistance to plating liquid such as titanium. Is filled with a soluble plating metal such as Ni in the form of fine-grained pellets,
It is immersed in a plating bath and electroplated by power supply. As the anode basket, as disclosed in Japanese Utility Model Laid-Open No. 63-7172, there is also known a detachable combination of a pellet storage member whose entire surface is coated with a corrosion-resistant electric insulating material and an electric current-carrying member. ing.

Although the anode basket is made in consideration of the corrosion resistance as described above, even if it is immersed in the plating solution for a long period of time, the corrosion progresses from the surface on the side facing the steel strip, so that the service life is extended. It has been decided to replace it with a new one. Since this hinders the improvement of plating efficiency, it has been desired to reduce the frequency of replacement (longer the replacement cycle).

[0004]

SUMMARY OF THE INVENTION In view of the above-mentioned problems of the prior art, the present invention provides a method for electroplating a steel strip capable of suppressing the progress of corrosion of an anode basket which is frequently used for electroplating. This is an issue.

[0005]

As a result of earnest studies, the present inventors set the plating current first according to the line speed,
The present invention has been completed based on the finding that corrosion of the anode basket can be suitably suppressed by resetting the set value in consideration of the immersion time and the plating solution temperature.

That is, the present invention relates to a method for electroplating a steel strip using a basket type anode, wherein the plating current set according to the line speed is further applied to the steel strip for immersion time and / or plating solution temperature. It is a method of electroplating a steel strip characterized by controlling according to, preferably, in the method of electroplating a steel strip using a basket type anode, the plating current further set according to the line speed The method for electroplating a steel strip is characterized in that the amount of the electroless plating adhered is reduced by an amount corresponding to the immersion time in the plating solution and / or the temperature of the plating solution.
And such control or reduction is achieved by coiling the steel strip and / or
Alternatively, it is most suitable to perform it during cutting work.

[0007]

According to the present invention, the plating current density can be reduced and the polarization can be weakened especially during low-speed operation, so that the progress of corrosion of the anode basket can be suppressed. Since the ratio of normal operation time to low speed operation time is about 15: 1, its corrosion inhibiting effect is large. Further, by setting the reduction rate of the plating current according to the amount corresponding to the plating adhesion amount by electroless plating, the plating adhesion amount can be made uniform and the plating unit can be reduced.

[0008]

EXAMPLE A conceptual diagram of a plating facility suitable for carrying out the present invention is shown in FIG. In FIG. 2, 1 is a conductor roll, 2
Is a basket type anode (basket anode or anode basket), 3 is a steel strip, 4 is a plating solution, and 5 is a plating tank. During the electroplating operation, a plating current is applied between the steel strip 3 supplied with a negative charge from the conductor roll 1 and serving as a cathode and the basket anode 2 supplied with a positive charge. In the anode basket 2, for example, Ni
Soluble plating metal such as For example standard Watts solution as a plating solution _{4 (NiSO 4 · 7H 2 O} : 250g / l, NiCl 6 · 6
_{H 2 O: 45g / l,} H 3 BO 3: composed of 30 g / l) can be used.

In carrying out the present invention, the dependency of the amount of electroless plating adhered on the steel strip 3 on the temperature of the plating solution and the immersion time is determined in advance. The electroless plating deposition amount refers to the plating deposition amount when a plating current is not applied. Specifically,
Electroless Ni obtained by Ni plating using standard Watt's solution
The graph of FIG. 3 shows the dependency of the amount of deposition on the plating solution temperature and immersion time. The immersion time is the line length in the plating solution 4 is L,
If the line speed is v, it is given by L / v. The plating solution temperature is measured at the management position provided in the plating tank 5.

A specific control method of the plating current is, for example, a target value of Ni deposition amount of 0.08 g / m ² , a dipping time of the steel strip in a low speed operation at the time of coil welding of the steel strip 3 of 20 s, a plating solution temperature. As for the case of about 50 ° C., the maximum amount of electroless Ni deposited at this time is about 0.01 g / m ² with reference to FIG. 3, which is the target Ni deposit amount of 0.08 g / m ² . Since it corresponds to 12.5%, the setting value of the plating current at this time is reduced to a value obtained by subtracting 12.5% of the maximum value from the setting value of the plating current according to the line speed.

This will be described in more detail. FIG.
In the longitudinal direction of the steel strip 3 including the low speed portion in the above case.
It is a distribution diagram of the amount of Ni deposition and the amount of plating current reduction, (a) is
Conventional examples and (b) show invention examples. Shown in Figure 1 (a)
Thus, in the conventional example, low-speed plate passing during coil welding and cutting
At, plating current was reduced according to line speed
A value is set (this setting is the plating current in Fig. 1)
The zero point of the reduction amount, that is, the table as the basis of the control of the present invention.
Is the amount of Ni deposited in the low speed part in the longitudinal direction of the steel strip.
Is almost the target value (0.08g / m²) Electrolytic electrolytic Ni deposition amount
In addition, according to the electroless Ni adhesion tendency shown in Fig. 3, the immersion time
Electroless according to the extension of temperature (or increase in plating solution temperature)
Ni deposit (maximum 0.01 g / m ²Degree) is added
You. This added amount is originally an extra amount of adhesion to the target value.
Yes, as shown in the invention example of FIG. 1 (b), this extra adhesion
You can just cancel the amount (up to 12.5% against the target value)
Value (up to 12.5% reduction in plating current)
The control is performed so as to reduce

By controlling the plating current in this way, the current density between the steel strip 3 and the anode basket 2 is reduced, and the polarization of the anode basket 2 is weakened. As a result, corrosion is suppressed and the anode basket is correspondingly reduced. Two
Will last longer. According to FIG. 3, electroless
The Ni deposition amount increases monotonically as the plating solution temperature rises and the immersion time increases, but the increment is 50% of the plating solution temperature.
It is small below ℃, and suddenly increases when the plating solution temperature exceeds 50 ℃. This means that in the temperature range where the plating solution temperature exceeds 50 ° C, the amount of electroless Ni adhered is large, so there is the advantage that the amount of reduction in the plating current can be increased accordingly, but on the other hand, the dipping time and the plating solution It means that the amount of deposited electroless Ni is likely to fluctuate in response to slight changes in temperature. Therefore, unless special control accuracy improvement measures are taken, in the case of Ni plating, it is appropriate to set the plating solution temperature to 50 ° C. or less and control the plating current within that range.

FIG. 4 is a graph showing the replacement cycle of the anode basket before and after the present invention is carried out.
As shown in FIG. 4, the replacement cycle of the anode basket after carrying out the present invention is extended to 6 times as long as that before carrying out the present invention, which shows that the effect of the present invention is remarkable. Further, according to the plating current control method of the present invention, since the surplus electroless Ni deposition amount is canceled at the same time, it is also effective in terms of reducing the plating unit consumption and making the plating deposition amount uniform.

[0014]

According to the present invention, the conventional plating current set according to the line speed is further reduced by an amount corresponding to the amount of electroless plating adhered, which depends on the immersion time of the steel strip and the temperature of the plating solution. Since the control is performed, the progress of corrosion of the anode basket can be suppressed, the replacement cycle thereof can be greatly extended, and at the same time, the reduction of the plating unit and the uniformization of the coating adhesion amount are improved, which is a remarkable effect.

[Brief description of drawings]

FIG. 1 is a distribution diagram of a Ni deposition amount and a plating current reduction amount in a longitudinal direction of a steel strip including a low speed portion, (a) showing a conventional example and (b) showing an invention example.

FIG. 2 is a conceptual diagram of a plating facility suitable for implementing the present invention.

FIG. 3 is a graph showing the dependence of the amount of electroless Ni deposited on the plating solution temperature and immersion time.

FIG. 4 is a graph showing a replacement cycle of the anode basket.

[Explanation of symbols]

1 conductor roll 2 basket type anode (basket anode or anode basket) 3 steel strip 4 plating solution 5 plating tank

Claims (3)

[Claims] 1. In a method for electroplating a steel strip using a basket type anode, a plating current set according to a line speed is further controlled according to a dipping time of the steel strip in a plating solution and / or a plating solution temperature. A method for electroplating a steel strip, which comprises: 2. A method of electroplating a steel strip using a basket type anode, wherein the plating current set according to the line speed is further adjusted according to the immersion time of the steel strip in the plating solution and / or the temperature of the plating solution. A method for electroplating a steel strip, which is characterized by reducing the amount of electrolytic plating adhered. 3. The method of electroplating a steel strip according to claim 1, wherein the control of the plating current is performed during the coil connecting and / or cutting operation of the steel strip.