JPH07138798A - Method and device for deciding life of noble metal-based insoluble electrode for electroplating - Google Patents

Abstract

PURPOSE:To decide the life of the noble metal-based insoluble electrode and to stabilize operation by determining voltage differences between the actual voltages of plating cells and the theoretical voltages of the plating cells. CONSTITUTION:The theoretical voltages of the plating cells are calculated from the actual voltage of the plating cells and the records of the electroplating operation, and the voltage differences between the actual voltages of the plating cells and the theoretical voltages of the plating cells are determined at all times. The degree of deterioration of the insoluble electrode is decided from these voltage differences. Practically, an alarm which emits an alarm when the voltage differences attain a specified value is installed. As a result, the deterioration conditions of the electrodes by each of the individual plating cells are continuously measured and, therefore, the adequate exchange of the electrodes by each of the plating cells is possible. The product quality is thus improved and the operation is stabilized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a titanium substrate coated with a noble metal-based coating or a noble metal oxide-based coating, which is used in a continuous electroplating process in which current density varies greatly in response to various operating conditions. The present invention relates to a method and apparatus for determining the life of a noble metal-based insoluble electrode.

[0002]

2. Description of the Related Art In a continuous electroplating process, a noble metal-based insoluble electrode having a titanium substrate coated with a noble metal-based or noble metal oxide-based {eg, iridium (Ir), Ir-Ox, Pt (platinum)} film is used. There is. Hereinafter, one example thereof, an electrode in which a titanium substrate is coated with an Ir-Ox film (hereinafter, referred to as
"Ir-Ox electrode"). Electrolysis technology that uses Ir-Ox electrodes is well established in the soda industry.
-It is easy to determine the life of the Ox electrode (determination of the degree of deterioration). Ir
-Ox electrode, as shown in Fig. 1, continues to flow current,
Abrasion occurs from the electrode surface, which increases the plating cell voltage (tray voltage). Then, when the amount of the residual Ir—Ox coating film falls below a certain ratio, the plating cell voltage rapidly increases. This time is the life of the electrode. Fig. 1 is a graph showing the relationship between the film consumption of the Ir-Ox electrode and the plating cell voltage. The film thickness of the Ir-Ox film is 10 g / m ² , and the current density is 120 A /.
It is constant at dm ² . In the soda process, since the production is performed in a static bath at a nearly constant current density, the amount of Ir-Ox coating consumed is directly proportional to the energization time. Therefore, the electrode life can be easily determined.

On the other hand, in a continuous electroplated steel sheet production line using an Ir-Ox electrode, the current density also changes as the charging steel sheet (steel strip) size and the operating line speed (steel sheet moving speed) change. It changes a lot. Taking a numerical value as an example, the change is 30 to 100 A / dm ² . FIG. 2 is a graph showing the relationship between the current density and the film consumption of the Ir—Ox electrode. In addition, FIG. 2 shows the data in the static bath of the zinc sulfate plating bath for pure zinc. As shown in FIG. 2, the change in current density and the film consumption of the Ir-Ox electrode have a relationship that the film consumption increases as the current density increases. Therefore, there is a problem that the life of the Ir-Ox electrode in continuous electroplating cannot be accurately determined by the energization time and the energization amount.

The plating cell voltage, which is a life determining factor, depends on the current density, the distance between the steel plate and the electrode (hereinafter referred to as "between electrodes"), the bath resistance in the plating tank (tray), and the like. Since the plating process line for electroplated steel plates is a continuous line and these factors change sequentially, the voltage rise also occurs due to factors other than the consumption of the Ir-Ox coating, and it is difficult to judge the life due to the voltage rise. Therefore, there has been no method of managing the electrodes without changing the electrodes as early as possible or affecting the line operation.

Continuous electroplated steel sheet manufacturing facility (line)
As described above, since it is impossible to judge the life of the Ir-Ox electrode by the energization time as described above, the life must be judged by measuring the amount of remaining Ir-Ox coating film. However, in order to measure the Ir-Ox coating amount of the electrode during the electroplating process, the operation must be interrupted, which is not realistic.
Also, there is no equipment that can easily measure the amount of Ir-Ox coating on the electrode. Therefore, according to the conventional test data, it was necessary to replace the electrodes long before the amount of electricity expected to reach the end of life was reached.

As a means for solving the above-mentioned problem of determining the life of a noble metal insoluble electrode for electroplating, JP-A-3-
In the 120397 publication, a device consisting of a measuring point switch, a potentiometer, a calculator and an alarm device is arranged, and the potential difference between the anode side branch point to the electrode and each electrode plate is continuously measured. A method and apparatus for identifying the life of a noble metal-based electrode for electroplating, which determines the degree of deterioration of the electrode plate from changes in the potential difference, have been disclosed (hereinafter referred to as "Prior Art 1").

[0007]

However, in the prior art 1, there is a problem that the device configuration is complicated and it is disadvantageous in terms of facility construction and economy.

Therefore, an object of the present invention is to accurately determine the electrode life without being influenced by various operating conditions and to construct a noble metal system for electroplating which can be constructed by a relatively simple apparatus. An object of the present invention is to provide a method and an apparatus for determining the life of an insoluble electrode.

[0009]

According to the method of the present invention, a plating cell actual voltage and an electric voltage are used for determining the life of a precious metal insoluble electrode for continuous electroplating in which a titanium substrate is coated with a precious metal coating or a precious metal oxide coating. It is characterized in that the plating cell theoretical voltage is calculated from the plating operation record, the voltage difference between the plating cell record voltage and the plating cell theoretical voltage is always obtained, and the deterioration degree of the insoluble electrode is determined from this voltage difference. . The apparatus of the present invention, a calculator for calculating the plating cell theoretical voltage from the plating cell actual voltage and the electroplating operation record, constantly compares the plating cell theoretical voltage and the plating cell actual voltage obtained from the calculator, the plating cell theoretical voltage And an alarm device that issues an alarm when the difference between the plating cell actual voltage and a predetermined value reaches a certain value.

As mentioned above, the life of the Ir-Ox electrode is
x Determined by the amount of film remaining. Ir over time
-Ox coating wears and the plating cell voltage (plating tank voltage) rises as the life approaches, and the theoretical value of the plating cell calculated according to the operating conditions and the actual voltage of the plating cell are continuously calculated. By comparing and monitoring and eliminating the error of the actual voltage value due to the operating condition, it is possible to judge the electrode life by the voltage difference between the two.

The present invention will be described in detail below. First, each influential factor for obtaining the theoretical voltage of the plating cell and the change with time of those electrodes will be described by taking an electrogalvanizing process as an example. FIG. 3 is a schematic sectional view showing the structure of a continuous galvanizing bath. In FIG. 3, 1 is an Ir-Ox electrode, 2 is a conductor roll, 3 is a rectifier, and 4 is a plating solution. The theoretical plating cell voltage when performing electroplating with the cell structure as shown in FIG. 3 is calculated as follows. The voltage calculation method for each resistor is shown in (1) to (5) below. (1) Circuit resistance Rectifier → Electrode CDR → Rectifier Busbar + CDR contact + CDR + brush contact (2) Electrode resistance Titanium (Ti) material resistance × current + substrate and electrode contact resistance ×
Current (3) Ir-Ox Oxygen overvoltage: 3V (4) Plating bath resistance Voltage = Conductivity x Gap x Current density (5) Plate resistance Voltage = Plate resistance (R) x Current where plate resistance R = R ₁ × R ₂ / R ₁ + R ₂ R ₁ = plate resistance × l ₁ / plate thickness × plate width R ₂ = plate resistance × l ₂ / plate thickness × plate width Sum of the voltages shown in (1) to (5) above Is the plating cell theoretical voltage. These can be obtained by knowing the charged steel plate size, the gap, the current density, and the current.

Next, Table 1 shows the degree of influence of the above voltage changes (1) to (5) due to electrode deterioration. As shown in Table 1, the plating cell theoretical voltage can be obtained by knowing the charged steel plate size, the gap, the current density, and the current.

[0013]

[Table 1]

The voltage increase due to electrode wear (deterioration) in (3) and (4) above occurs due to the following reasons. Shown in (3) above
Ir-Ox: Because the oxygen overvoltage rises. Plating bath resistance shown in (4) above: As the deterioration of the electrode due to surface wear progresses, the discharge area decreases. Since a certain amount of current flows, the discharge current density increases, so the plating bath resistance also increases, thus increasing the voltage.

Next, the variation in the actual voltage of the plating cell will be described. In addition to voltage increase due to electrode deterioration,
In some cases, "theoretical voltage ≠ actual voltage". This is caused by the fluctuation of the gap (difference from the gap value used for the theoretical voltage calculation) due to the influence of the jet flow and the plate shape, which causes the variation of the voltage. FIG. 4 is a graph showing variations in voltage when the electrodes are normal, and the distance between the set electrodes is 15 mm. As shown in FIG. 4, the variation in voltage correlates with the current density. According to our research, for example, the conductivity 115
It has been found that the maximum inter-electrode variation is ± 1.5 mm in the electrogalvanizing equipment with a plating bath of ms. From this, the maximum variation of the plating cell voltage can be found at ± 0.013 of the theoretical voltage. That is, even when the electrodes are normal, a maximum error of 1.3% occurs between the actual voltage and the theoretical voltage.

Next, the change over time and the change in voltage will be described. As you can see from the data shown in Figure 2 above,
As the life of Ir-Ox electrodes approaches, the difference between the theoretical voltage of the plating cell and the actual voltage increases. From the above data,
The influence of electrode deterioration is ± 1.3%, but the variation exceeding this is due to electrode deterioration.

FIG. 5 is a graph showing the relationship between the energization time and the plating cell voltage. The operating conditions are: current density: 30 to 10
0 A / dm ² , maximum current 25,000 A, maximum voltage: 30 V, Ir-Ox
Electrode film thickness: about 50 g / m ² . Based on the actual continuous electrogalvanizing operation data (actual line data), the difference between the actual voltage and the theoretical voltage exceeds 2% until the Ir-Ox electrode reaches its life (overvoltage occurs at the maximum current) ,
As shown in FIG. 5, it can be seen that the energization time is at least 300 hours.

At this point of ± 2%, if it is judged that the electrode life is near, there is a margin of 300 hours remaining (2 weeks based on operation) until the life, and it is necessary to take measures such as electrode replacement during the life. Can be taken. Therefore, it is assumed that {(actual voltage-theoretical voltage) / theoretical voltage} × 100 = voltage variation ... By monitoring this value from the above equation, the electrode life is close when the voltage variation exceeds 2%. By installing a device capable of making a judgment and determining the replacement timing in accordance with the operation cycle, it becomes possible to prolong the life of each electrode and execute the electrode replacement at an appropriate cycle.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described based on the embodiments shown in the drawings. The life of the Ir-Ox electrode was evaluated on the electrogalvanizing production line for steel plates using a continuous electrogalvanizing apparatus having 15 plating tanks. FIG. 6 is a flowchart of a control procedure for obtaining the plating cell theoretical voltage, and FIG. 7 is a front view of the screen of the electrode life determining device. According to the control method shown in FIG. 6, the plating cell theoretical voltage values of the plating tanks Nos. 1 to 15 are calculated. In FIG. 7, A is a display panel that displays the actual voltage of each plating cell of the 15 plating tanks of this line, B is a display panel that displays the theoretical voltage value of the plating cell of each plating tank, and C is the theoretical voltage and the actual voltage. And D is a lamp of an alarm device that issues an alarm when the variation of C exceeds ± 2%.

By installing the device shown in FIG. 7 in the operator's cab and allowing the operator to constantly monitor the display panels A to C and the lamp D, it is possible to grasp the electrode state, predict the service life, and determine the replacement time. It's easy.

Regarding the average life and replacement frequency of the electrodes,
Investigation and comparison were performed before introducing the determination device (comparative example) and after introducing the determination device (example of the present invention). The survey was conducted for one year each before and after the introduction of the equipment. The results are shown in Table 2.

[0022]

[Table 2]

As shown in Table 2, in the comparative example, the number of times n of electrode replacement was 61 times, and the average current-carrying time until each replacement was 2,418 hours (h), and there were 6 sudden replacements. It was In the example, the number of times n of electrode replacement was 26 times, and the average current-carrying time up to each replacement was 2,892 hours (h), and there was no sudden replacement. As described above, according to the embodiment of the present invention in which the determination device is introduced, it is possible to use the electrode more efficiently than before the introduction of the determination device (comparative example), the average life of the electrode is increased by 474 hours, and further, sudden It can be seen that the major electrode replacement has been resolved.

[0024]

As described above, according to the present invention, in determining the life of the noble metal insoluble electrode for continuous electroplating, the deterioration state of the electrode for each individual plating cell (plating tank) is continuously measured. Therefore, it is possible to accurately identify the life of each electrode, which makes it possible to appropriately replace the electrode for each plating cell, avoid quality problems due to the use of a deteriorated electrode, and at the same time, waste the electrode. Trouble due to consumption and sudden replacement can be avoided, which can greatly contribute to improvement of product quality, resource saving, and stable operation, thus providing industrially useful effects.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the film consumption of Ir-Ox electrodes and the plating cell voltage.

FIG. 2 is a graph showing the relationship between the current density and the film consumption of Ir—Ox electrodes.

FIG. 3 is a schematic sectional view showing the structure of a continuous electrogalvanizing bath.

FIG. 4 is a graph showing variations in voltage when the electrodes are normal.

FIG. 5 is a graph showing the relationship between energization time and plating cell voltage.

FIG. 6 is a flowchart of a control procedure for obtaining a plating cell theoretical voltage.

FIG. 7 is a front view of a screen of the electrode life determining device.

[Explanation of symbols]

 1 Ir-Ox electrode 2 Conductor roll 3 Rectifier 4 Plating liquid A Plating cell actual voltage display panel B Plating cell theoretical voltage display panel C Display panel showing the variation between theoretical voltage and actual voltage D Alarm lamp

Claims (2)

[Claims] 1. When determining the life of a precious metal-based insoluble electrode for continuous electroplating in which a titanium base material is coated with a precious metal-based coating or a precious metal oxide-based coating, a theoretical plating cell voltage is calculated from the actual plating cell voltage and the electroplating operation result, A method for determining the life of a noble metal-based electrode for electroplating, characterized in that the voltage difference between the actual voltage of the plating cell and the theoretical voltage of the plating cell is always obtained, and the degree of deterioration of the insoluble electrode is determined from this voltage difference. 2. A calculator for calculating a plating cell theoretical voltage from the plating cell actual voltage and an electroplating operation result, and the plating cell theoretical voltage and the plating cell actual voltage obtained from the calculator are constantly compared to obtain the plating cell theoretical voltage. An apparatus for determining the life of a precious metal-based insoluble electrode for electroplating, which comprises an alarm that issues an alarm when the difference from the actual voltage of the plating cell reaches a certain value.