JPH057472B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention provides a method for electroplating metal strips.
The present invention relates to a method for detecting plated metal adhering to a conductor roll.

[Prior Art] Horizontal electroplating equipment has advantages over vertical electroplating equipment, such as lower voltage loss and the need for lower strength conductor rolls and support rolls. It is widely used for tsuki, etc. FIG. 3 is a schematic diagram of a horizontal electroplating device commonly used for galvanizing steel strips. A plurality of electrolytic cells 16 are sequentially arranged in the horizontal electroplating apparatus, and each electrolytic cell 16 has a pair of anode electrodes 14 corresponding to the upper and lower sides of the material to be plated (in this case, a steel strip) 1 to be transferred. is installed. Here, since two series of a pair of anode electrodes 14 are sequentially installed, the distance for transporting the material 1 to be plated in the electrolytic cell 16 becomes long, which causes the material 1 to be plated to fluctuate or loosen. A support roll 18 is installed. A conductor roll 2 and a back-up roll 4 are installed near the entrance and exit side of the steel strip in each tank, where the steel strip is negatively charged.
Electrode reaction is carried out in the plating solution 3 to galvanize the surface of the steel strip. In this case, a dam roll 17 is used to prevent the plating liquid from flowing out of the tank together with the steel strip and to maintain the level of the plating liquid at a constant level. However, this type of horizontal electroplating equipment is generally large, with 10 to 15 electrolytic cells, such as 6 m (length) x 2.5 m (width) x 1.0 m (depth), arranged in sequence. has been done. Correspondingly, a large amount of plating liquid is required, so the plating liquid storage tank, piping, etc. become large-sized, and in addition, a large amount of cost is required for heating the plating liquid. In addition, the distance between the center axis of the conductor roll and the anode electrode is long, for example, 1 m, due to the fact that a dam roll is installed between them. Therefore, the voltage due to the resistance of the plated material itself The loss is huge. Therefore, in recent years, horizontal electroplating equipment
While taking advantage of this, attempts are being made to make the equipment more compact by switching from soluble electrodes to insoluble electrodes, and to shorten the distance between the conductor roll and anode electrode without using dam rolls. It is being said. When a dam roll is not used, the conductor roll generally comes into direct contact (including immersion) with the plating solution.

In an electroplating device with such a structure,
During plating work, plating metal adheres to the conductor roll. If the plating metal adheres to the conductor roll, the electrical contact between the conductor roll and the plated metal strip becomes incomplete, partially blocking current flow and making uniform plating impossible. Furthermore, the plating metal adhering to the conductor roll peels off onto the plated metal strip and gets caught between the conductor roll and the plated metal strip, causing scratches on the surface of the plated metal strip. This results in a product defect. Since the occurrence of such product defects is a problem that must be avoided at all costs, it is necessary to prevent or remove the plating metal from adhering to the conductor roll. Conventionally, the following method has been used for this purpose. FIG. 4 shows the method according to Japanese Patent Application Laid-Open No. 60-967981. A reverse electrolytic electrode 13 is attached between the conductor roll 2 and the plating anode 14 in the vicinity of the conductor roll 2, and a reverse electrolytic voltage is applied from the power source 11 to electrolytically peel off the plating metal adhering to the conductor roll 2. be. In FIG. 5, the abrasive material 15 is pressed against the rotating conductor roll 2 to mechanically remove the stuck metal attached to the conductor roll 2.

[Problems to be Solved by the Invention] In the method using reverse electrolysis described above, electrolysis is performed between the conductor roll and the reverse electrolysis electrode installed in close proximity to the conductor roll. If the plated metal is not attached to the entire surface, the plated metal can be removed without causing any problems, but if a part of the conductor roll surface is exposed, performing reverse electrolysis will cause the metal on the roll body of the conductor roll to become electrolyzed. Then, the metal ions are mixed into the plating solution as impurity metal ions, and the rolls are further electrolytically eroded.
There is a problem that the roll life is shortened. In addition, in the case of mechanically removing the plating metal adhering to the conductor roll by pressing an abrasive material, since the adhering plating metal is mechanically scraped off, the plating metal powder is mixed with the plating liquid. If the metal strip gets mixed in with the metal strip, it will cause scratches on the surface of the coated metal strip, resulting in product defects. Also, in areas where part of the conductor roll surface is exposed,
There is a problem in that the surface of the conductor roll is scratched and the life of the roll is shortened. Visual observation determines whether the metal is adhered to the conductor roll over the entire surface without any gaps. As can be seen from the above, when removing the stuck metal attached to the conductor roll, there are problems due to incomplete electrical contact between the conductor roll and the covered metal strip if the timing of removal is delayed. Alternatively, problems may occur due to peeling off of the stuck metal attached to the conductor roll, or if removal is performed too early or for a long period of time, problems may arise due to electrolysis or polishing of the exposed conductor roll. happens. Therefore, when removing the stuck metal adhering to the conductor roll, it is important to accurately judge when to start and end the removal. However, in the conventional method, the state of adhesion of plating metal to the conductor roll is determined by visual observation, so it is not possible to accurately determine when to start and end the removal of plating metal. There is a problem in that the attached metal cannot be removed effectively.

This invention was made in view of the above circumstances, and in order to effectively remove the stuck metal attached to the conductor roll, it is possible to accurately determine the start and end point of removal of the stuck metal on the conductor roll. The purpose is to provide a removal method.

[Means for solving the problem] When performing electroplating by bringing a part of the conductor roll into contact with the plating liquid, a reference plate for measuring the electric potential of the conductor roll is placed in the vicinity of the conductor roll in the plating liquid. This is a method for detecting metal deposited on a conductor roll, in which an electrode is installed, the potential difference between the conductor roll and a reference electrode is continuously measured, and plated metal deposited on the conductor roll is detected from changes in the measured value of the potential difference.

[Function] The method of the present invention continuously measures the potential difference between the conductor roll and the reference electrode during electroplating, and since the surface potential changes when plating metal adheres to the surface of the conductor roll, Detects attached metal.

[Embodiments of the Invention] Next, the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram of an apparatus for carrying out the method of the present invention. The reference electrode 6 for potential measurement of the conductor roll is installed so as to be immersed in the conductor roll 3, and the insulating cover 5 covers the periphery of the reference electrode 6 for potential measurement except for the side facing the conductor roll 2.
is provided. The potential difference between the conductor roll 2 and the potential measurement reference electrode 6, that is, the potential of the conductor roll is detected by the potential difference measuring device 7 (hereinafter referred to as potential). When no plating metal is attached to the conductor roll, it indicates the potential of the main body of the conductor roll, and as the plating metal begins to adhere to the conductor roll, the potential approaches the deposition potential of the plating metal, and the entire surface of the conductor roll When the plating metal is further deposited, the potential suddenly shifts to the less base direction and reaches the deposition potential of the plating metal, and does not change any further. It was found that this was the point at which the plating metal adhered to the entire surface of the conductor roll. Since the potential difference recording device 8 shows changes in potential, it is possible to easily determine when the plating metal has adhered to the entire surface of the conductor roll. Examples of the present invention will be specifically described below.

(Example) The conductor roll body was made of an Fe-Cr-Ni alloy material, and the reference electrode was a silver-silver chloride electrode. The potential of the conductor roll was measured by the potentiometric measuring device 7, and at the same time, the state of adhesion of the plated metal to the conductor roll was observed. The plating conditions are as follows. Plating liquid composition: Zinc sulfate: 400g/
, sodium sulfate: 70 g/, magnesium sulfate: 60 g/, PH: 1.5, temperature: 50°C, current density 100 A/dm ² and 70 A/dm ² , respectively.
60A/ ^dm2 , 50A/ ^dm2 . The running speed of the coated metal strip is 120 m/min. The plating work continued for 48 hours. Figure 2 shows the change in the conductor roll surface potential depending on the plating time. The current density is 100A/dm ² and 70A/dm 2 respectively.
When plating work is performed at dm ² and 60 A/dm ² , the potential suddenly shifts to a less noble direction after 5, 10, and 20 hours, respectively, and becomes the Zn deposition potential, which does not change thereafter. Ta. At this time, plating metal was adhered to the entire surface of the conductor roll. Also Zn
After reaching the deposition potential of , Zn adhering to the conductor roll was observed to peel off after a while. Zn peeling occurred in a shorter time at higher current densities. Furthermore
When plating was carried out at 50 A/dm ² , the surface potential gradually shifted to a less noble direction, but the change gradually became gentler and eventually it never reached the Zn deposition potential. At this time, no plating metal adhered to the entire surface of the conductor roll. Furthermore, no peeling of Zn from the conductor roll surface was observed. The electric potential suddenly shifts to the base direction,
The point at which the Zn deposition potential reaches and no longer changes is the point at which plating metal has adhered to the entire surface of the conductor roll, and the position difference recording device 8 shows the situation where the potential is gradually changing. The point at which the bright metal has adhered can be easily determined.

In this example, zinc plating was performed using a sulfuric acid bath, but even if the composition of the plating bath is changed, similar results can be obtained by measuring the potential of the metal adhering to the conductor roll surface accordingly.

[Effects of the Invention] According to the method of the present invention, adhesion of plating metal to the conductor roll can be detected by continuously measuring changes in the potential difference between the conductor roll and the reference electrode during electroplating. To accurately determine when to start and end when removing metal adhered to a conductor roll. Therefore, it is an excellent invention that allows the removal of plated metal from the conductor roll in a timely manner.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the apparatus used in the method of the present invention, FIG. 2 is a diagram showing the relationship between plating time and conductor roll potential according to an embodiment of the present invention, and FIG. 3 is a diagram of a conventional horizontal type A schematic diagram of an electrogalvanizing apparatus, FIGS. 4 and 5 show a schematic diagram of a conventional apparatus for removing deposited metal from conductor rolls. DESCRIPTION OF SYMBOLS 1...Plated metal strip, 2...Conductor roll, 3...Plating liquid, 4...Backup roll, 5...Insulating cover, 6...Reference electrode for potential measurement, 7...Potential difference measuring device , 8...Potentiometric recording device, 14...Plated electrode, 16...Electrolytic cell.

Claims (1)

[Claims] 1. When electroplating is performed by bringing a part of the conductor roll into contact with the plating liquid, a reference electrode for measuring the potential of the conductor roll is installed in the plating liquid in the vicinity of the conductor roll, and the conductor roll and A method for detecting metal deposited on a conductor roll, comprising continuously measuring a potential difference between the electrode and a reference electrode, and detecting plated metal deposited on the conductor roll based on a change in the measured value of the potential difference.