JPS63293200A - Electroplating method - Google Patents

Abstract

PURPOSE:To form plating layers of a uniform thickness on a traveling long-sized steel strip by dividing an insoluble anode in a plating cell to plural pieces in the longitudinal direction of the steel strip so that electric conditions can be adjusted at the time of subjecting said steel strip continuously to metal plating with an electroplating device having the insoluble anode. CONSTITUTION:The steel strip 1 is moved in an arrow direction by means of conductor rolls 2 and backup rolls 3 in a plating bath contg. a plating bath 6. The steel strip 1 as a negative pole and the insoluble anodes 20 disposed in above and below the steel strip 1 as the anode are energized by the rolls 2 and metal ions of Zn, etc., in the plating bath 6 are electrodeposited on the surfaces of the steel strip 1, by which the steel strip is galvanized. The insoluble anodes 20 provided in the traveling direction of the steel strip 1 are divided to A1-A3 and the voltages and currents thereof are made discretely controllable by an electric control device 21, by which the uniform control of the current density over the entire surface of the steel strip 1 is enabled and, therefore, the plating layers having no fluctuations in the thickness are formed on the steel strip 1.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an electroplating apparatus equipped with an insoluble electrode for electroplating a material to be plated, such as a strip-shaped steel plate, which runs continuously.

[Conventional technology]

1%i in the field of electroplating such as the steel industry.

Zinc is applied to plated materials such as steel strips that run continuously.

Electroplating of metals such as tin has been practiced for a long time. In this case, the soluble electrodes used in the plating bath require complicated work to insert and replace them, and the plating bath becomes larger. Electroplating using electrodes is becoming more common.

FIG. 4 is an explanatory diagram of a generally used electroplating apparatus equipped with an insoluble electrode (Japanese Patent Publication No. 55-2451
(See No. 7).

In the figure, the material to be plated 1 runs continuously in the direction of the arrow. The material to be plated 1 is negatively charged by the plating conductor roll 2, enters the plating bath 6, and undergoes an electrode reaction with the insoluble electrodes 4 provided above and below the material to be plated. Metals such as zinc are deposited on the surface.

After the material to be plated 1 has traveled through the plating bath 6, it is negatively charged by the conductor roll 2 for the next device and electroplated in the same manner in the next plating bath (not shown).

The process is repeated until a predetermined plating thickness is obtained, and finally, post-treatment such as washing with water is performed and the process is wound up on a Tensilan reel. 3 in Figure 0 is a backup roll.

The plating solution is discharged from the plating bath 6 through a drain pipe 7 to the tank 9, and is sent to the plating bath 6 through a pipe 11 by a circulation pump 10. A filter 8 is installed with a bypass provided in a drain pipe 7 from a plating bath 6 to a tank 9.

As mentioned above, in electroplating equipment, insoluble electrodes are used as anodes, so pb-based electrodes (Pb-
^,, pb-sb, etc.) are used. In order to narrow the electrode spacing, there is a method in which the plating solution 12 is jetted in the direction of the arrow from the nozzle 13 from the outlet side of the material to be plated 1 of the insoluble electrode 4 as shown in FIG. 5, or as shown in FIG. Another method is to blow the plating solution 12 from the center of the insoluble electrode 4 through the nozzle 13 at high speed in the direction of the arrow. In Figures 5 and 6.

The material to be plated 1 runs continuously in the direction of the large arrow.

First, it is negatively charged by the conductor roll 2 for plating, enters the plating bath 6, and undergoes an electrode reaction with the insoluble electrodes 4 provided above and below the material 1 to be plated, and then the surface of the material 1 to be plated is 3 in Figure 0 where metals such as zinc are deposited
is a back unroll.

7 shows the drainage pipe (``Current status and future trends of surface-treated steel plates'', 106th and 107th Nishiyama Memorial Technical Lectures, September 1960, pages 40-42).

In the above-mentioned electroplating equipment, the electric bridge spacing is generally 1
It is about 5 to 25 cranes, and the longitudinal length of the electrode is 1
Those less than 000 Tsuru are commonly used.

[Problem that the invention seeks to solve]

However, recent trends require further downsizing of ancillary equipment such as electroplating equipment and plating tanks, and for this reason, the spacing between electrodes must be further narrowed and the length of the electrodes in the longitudinal direction must be further reduced. Attempts are being made to lengthen it. However, there is a limit to the method of jetting the plating solution between the electrodes as described above, and if the limit is exceeded, the variation in current density in the longitudinal direction of the electrode becomes large, and as a result, the variation in the longitudinal direction of the material to be plated increases. Problems such as non-uniform adhesion occur. Particularly in the case of electroplating of zinc-iron alloys, zinc-nickel alloys, etc., large variations in current density will affect the composition, causing problems in product quality and appearance.

Table 1 shows the variations in current density in the longitudinal direction of the material to be plated, which are affected by the longitudinal length of the electrodes and the electrode spacing, and are calculated under certain conditions.

Table 1 <m Consideration) The numbers in the table are expressed as σ/=xtoo.

Here, i is the average value of the current density in the longitudinal direction of the plated material corresponding to the longitudinal length of the electrode, and σ is the standard deviation of the current density distribution in that case.

This table is an example, but when the electrode length is 1000fi, the electrode spacing is 15m+ or less, and when the electrode length is 1400m
It can be seen that when the electrode spacing is 25 squares or less, the variation in current density in the longitudinal direction of the material to be plated increases, which is a problem.

The present invention has been made to solve the above-mentioned problems, and even if the electrode spacing is made narrower and the length of the electrodes in the longitudinal direction is made longer, the current density in the longitudinal direction of the material to be plated remains unchanged. The purpose is to provide an electroplating device with small variations.

[Means for solving problems]

The present invention provides an electrode plating apparatus equipped with an insoluble electrode for electroplating a continuously traveling material to be plated, in which the insoluble electrode constitutes an electrode divided in the longitudinal direction of the traveling material to be plated, and the divided electrodes The electroplating apparatus is characterized in that it is equipped with an independent electric control device.

[For production]

According to the electroplating apparatus of the present invention, the insoluble electrode provided in the apparatus is composed of electrodes divided in the longitudinal direction of the traveling material to be plated, and each of the divided electrodes is provided with an independent electric control device. .

The material to be plated faces the insoluble electrode as it travels from a negatively charged position on the conductor roll, and even if the resistance due to the covering material itself increases until it passes through it, the divided electrodes that make up the insoluble electrode Corresponding current control,
By controlling the voltage, it is possible to reduce the variation in current density in the longitudinal direction of the plated material.

〔Example〕

Examples will be described below with reference to FIGS. 1 to 3.

As shown in FIG. 1, the material to be plated 1, which is continuously traveling in the direction of the large arrow, is negatively charged by the conductor roll 2 and enters the plating bath 6 where it is coated with one-part electrode Al.

It faces an insoluble electrode 20 composed of AI+A3, and metal is deposited there by an electrode reaction and electroplated.

Then, it leaves the plating bathtub 6 and travels to the next plating bathtub (not shown). In this case, the divided electrodes A, AlA3 are provided with an electrical control device 21 that can electrically control them independently. FIG. 2 shows that the electric control device in FIG. 1 is a voltage control device, thereby dividing the divided electrode AI.

This is an explanatory diagram showing the distribution of potential and current density in the longitudinal direction of the plated material when the current density is adjusted by voltage control of Am and A3 respectively.In Figure 0, regarding the anode potential, the solid line indicates the anode potential when the electrode according to the invention was used. In the case, 9 divided electrodes A,, A
It operates by switching the voltage stepwise in Am.
Moreover, the chain double-dashed line shows the case where conventional electrodes are used, and the operation is performed at a constant potential.

As is clear from this figure, when the electroplating apparatus according to the present invention is used, the variation in current density in the longitudinal direction of the material to be plated is reduced, as shown by the solid line. On the other hand, 2
When an electroplating apparatus using a conventional electrode shown by a dotted chain line is used, there is a large variation.

Note that the broken lines in the vertical axis direction indicate the range in the longitudinal direction of the plated material corresponding to the length direction of the divided electrodes A+, At, and As.

FIG. 3 shows the current density in the longitudinal direction of the plated material when the electric control device in FIG. 1 is a current control device, and the current density is adjusted by controlling the divided electrodes At, Am, and As. It is an explanatory diagram showing distribution. As in FIG. 2, the solid line shows the current density distribution in the longitudinal direction of the plated material according to the present invention, and the two-dot chain line shows the current density distribution in the conventional case.

As is clear from this figure, when the electroplating apparatus according to the present invention is used, the variation in current density in the longitudinal direction of the material to be plated is reduced.

Next, an experimental example will be shown regarding the relationship between the number of divided electrodes and the variation in current density in the longitudinal direction of the material to be plated when current is controlled using the electroplating apparatus of the present invention as shown in FIG.

[Experiment example]

0.7 x 1200 Tsuru strip steel plate is galvanized.

(Conditions) ■Material of insoluble electrode: PB-based bridge ■Longitudinal length of unnecessary electrode: 1000 m ■Current (per single side)
12500A ■ Electrode spacing 10 dragons ■ Number of electrode divisions 2 or 3 divisions.

5 divisions, 10 divisions For comparison, an undivided electrode was used.

(Experimental results) (Remarks) j: X5in+ Xa+ax indicates the average value of the current density in the longitudinal direction of the plated material, II small value, Il large value, σ represents the distribution of current density in that case as standard deviation thing.

The experimental results show that increasing the number of divided electrodes reduces the variation in current density in the longitudinal direction of the plated material. It goes without saying that similar results can be obtained even if voltage control is performed instead of current control.

In the experimental example, an electrode with a length of 1000 m was used.

For more electrodes, if the number of divided electrical bridges is set accordingly, it is possible to similarly operate with less variation in current density in the longitudinal direction of the material to be plated.

〔Effect of the invention〕

According to the electroplating apparatus of the present invention, the insoluble electrode is composed of electrodes divided in the longitudinal direction of the material to be plated.

Since an independent electric control device is provided for each of the divided electrodes, the current density in the longitudinal direction of the plated material can be reduced even if the electrode spacing is narrowed to about 1Ofi and the longitudinal length of the insoluble electrode is over 1000Ofi. Variations can be reduced and the amount of plating deposited can be made uniform.

Furthermore, it is an invention of equivalent value that it is possible to obtain a plating film of zinc-iron alloy or the like with a uniform composition.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of an electroplating apparatus showing an embodiment of the present invention, Figure 2 is an explanatory diagram showing the distribution of potential and current density when the apparatus of the present invention is used, and Figure 3 is an illustration of the distribution of potential and current density when the apparatus of the present invention is used. FIG. 4 is an illustration of a conventional electroplating apparatus, and FIGS. 5 and 6 are illustrations of a conventional electroplating apparatus. 20... Insoluble electrode, 21... Electric control device.

Claims (1)

[Claims] In an electroplating device equipped with an insoluble electrode that electroplates a continuously moving material to be plated, the insoluble electrode is composed of electrodes divided in the longitudinal direction of the material to be plated, and each of these divided electrodes has an independent An electroplating device characterized by being equipped with an electric control device.