JPH01208499A - Electrode for electroplating - Google Patents

Abstract

PURPOSE:To make dissipation of generated gas easy and to enable plating at low voltage and also to prevent build-up unevenness of plating by making a steel sheet carried in a plating bath to a cathode and utilizing a specified perforated metallic anode and performing electroplating treatment. CONSTITUTION:A steel sheet 4 is continuously electroplated by making the steel sheet 4 transferred in an electroplating tank 1 to a cathode and utilizing the perforated metallic anodes 5, 6 having a coated layer consisting of activated electrode substance parallel thereto. The anodes 5, 6 are an electrode in which the base material is expanded metal and a coarse-hole network body consisting of metal such as Ti and Zr forming a passive film and has a coated layer of activated electrode substance incorporating metallic oxide of platinum group especially iridium oxida. Gaseous oxygen generated at a time of electrolysis is easily dissipated because the electrode is perforated by utilizing this electrode as the anodes 5, 6 and plating of the steel sheet 4 can be performed at low voltage and also current density is raised and therefore the carrying velocity of the steel sheet 4 is made high and productivity can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an electroplating electrode that is installed in a continuous electroplating facility and is used to plate the surface of a steel plate.

(Prior art) Currently, electroplating of steel sheets is carried out using zinc, tin, copper, nickel, chromium alone, alloys of these metals, or multilayer plating of these metals, and a large number of various types of anticorrosive and decorative steel sheets are produced. It is produced continuously. The electrodes that are used in this continuous electroplating facility and serve as anodes are comprised of a pair, and the steel plate that is the material to be treated is transported between the pair of electrodes at high speed.

A consumable N-electrode was once used as this electrode, but later an insoluble electrode whose main component was lead.

That is, a plate-like body in which the periphery of an iron core material is coated with metallic titanium and further homogeneously welded lead or a lead-tin alloy on the surface thereof has been used. The use of platinum-coated electrodes has been discouraged due to the fact that such flat plate electrodes, whose main component is lead, are subject to considerable wear and tear even though they are insoluble, and that melted materials may mix with the product, causing problems with product quality. were partially implemented. Although this electrode is effective as an insoluble electrode, it is economically problematic. In recent years, metal oxide-coated electrodes mainly made of platinum group metals have entered the stage of practical application because they are more efficient.

(Problems to be Solved by the Invention) However, conventional electrodes serving as anodes are all flat plate bodies with considerable weight. For example, a lead plate electrode has a width of approximately 100 mm.
The thickness of the lead alloy welded in a size of 0 mm, length 1800 mm, and thickness 30 mm is approximately 15 to 20 mm, and in the case of platinum-coated electrodes and metal oxide-coated electrodes such as platinum group metals, an insoluble titanium plate is attached to the iron plate. Platinum or an oxide thereof is attached to the surface of the electrode, and each electrode weighs about 300 to 60 kg. Such heavy objects are extremely difficult to handle.

In addition, in order to reduce power consumption, the gap between the poles is shortened as much as possible, so especially at high current densities, the gas generated between the poles is not well distributed, and the liquid pressure changes due to the increase in voltage and fluctuations in the gas generated. However, there is a risk that the steel plate shakes during transportation, causing significant fluctuations in the distance between the poles, and eventually causing a short circuit. At the same time, if the plating solution is not sufficiently replenished to the plating surface, this may be one of the causes of uneven plating deposition, and there are problems such as difficulty in increasing the speed of steel sheet processing and improving production capacity.

(Means for Solving the Problems) As a result of various studies, the present inventors have found that the above-mentioned problems can be solved by using a porous electrode as an electrode serving as an anode, and have completed the present invention.

The present invention is thus an electrode for continuous electroplating consisting of a porous metal anode having a coating layer of electrode active material, and a method for continuous electroplating of steel sheets using this electrode.

As the electrode active material in the coating layer of the metal anode, a material containing one or more metal oxides selected from platinum group metals, i.e., iridium, rhodium, palladium, ruthenium, and osmium, is suitable; In particular, iridium oxide or iridium oxide containing titanium, tantalum, etc. is preferable. Examples of the base material of the metal anode include metals that form passive films such as titanium, zirconium, tantalum, niobium, tungsten, molybdenum, and antimony, and metals such as silver, with titanium being preferred from a practical standpoint.

The shape of the porous metal anode is arbitrary, and as schematically shown in Fig. 1, it can be expanded metal (a), punched metal (b), coarse pore network (C), cTh, or cylindrical body (d).
) etc., but - Expanded metal is used for boat fishing. The eye size of this electrode is the maximum opening of 1 to 2
It is about 0 mm.

FIGS. 2 and 3 are schematic diagrams of a vertical electroplating apparatus and a horizontal electroplating apparatus in which the electrode of the present invention is used. As shown in Fig. 2, the vertical electroplating apparatus consists of conductor rolls (2>(2>) and electroplating tank ( 1
) and the conductor roll (2) and each of the conductor rolls (2) and the zinc roll (3
) a pair of vertical anodes (5) (5) arranged parallel to the steel plate (4) serving as the cathode, with the steel plate (4) moving in the electroplating tank (1) between them. It consists of (6) and (6). The steel plate (4) moves downward and then upward in the electroplating tank (1) in which a plating bath is contained and flowing, and a pair of anodes (5)'(5> and (6) (
6) is continuously electroplated during the passage. In the device shown in Figure 2, by using the electrodes of the present invention for the anodes (5) and (6), the oxygen gas generated during electrolysis is absorbed by the 81111 plate (4) and the anode (5) or (
6), it escapes not only between the electrodes but also on the back side thereof, and the amount of gas remaining between the electrodes can be significantly reduced, and at the same time, the plating solution can be sufficiently replenished.

As shown in Fig. 3, the horizontal electroplating apparatus has a pair of upper and lower dam rolls (8a>(8a> and (8b) (8b )
A pair of horizontal anodes (5a>(5b) are placed parallel to the steel plate (4) that will serve as the cathode, with the steel plate (4) moving in the electroplating tank (7) in between. and (6a) (
6bL! : It consists of. The steel plate (4) moves in an electroplating tank (7) in which a plating bath is contained and flowing;
Electroplating is performed continuously while passing through a pair of anodes (5a) (5b) and (6a>(6b)).

In the device shown in Fig. 3, by using the anodes of the present invention as the upper anodes (5a) and (6a), the oxygen gas generated during electrolysis escapes to the back side because the electrodes are porous, and the remaining gas between the electrodes The amount of plating solution can be significantly reduced, and at the same time, the plating solution can be sufficiently replenished. Note that it is preferable to use porous anodes for the lower anodes (5b) and (6b) from the perspective of replenishing the plating solution.

(Function) As described above, since the electrode of the present invention is porous, the generated gas that tends to stay between the electrodes can easily escape and cause a voltage drop. Furthermore, since the discharge surface of the porous metal anode 2, for example, an expanded metal, is entirely edge-shaped, the edge current concentrated around it is reduced compared to a conventional metal anode, resulting in a better current distribution. In addition, by using a porous anode, the entire cut surface acts as an electrode surface, and gas handling is good, so compared to conventional anodes, the influence of erosion due to liquid-gas flow is reduced, and the electrode has a long lifespan. The long term will be extended.

Example 1 Acrylic experimental tank (200 mm, 4 sides) shown in Figure 4.

Height: 200 mm> Zinc electroplating of a steel plate was performed using (9). Length 150mm, width 15mm, thickness 2m
A sample piece of a titanium plate with a diameter of 2 mm, and a sample piece of expanded metal with an opening of 2 mm made by processing a titanium plate with the same large serrations were prepared. 75m from one end in the length direction of these two types of specimens
An iridium oxide coating tank (10) was applied to the surface up to m to serve as an anode (11), a steel plate of the same size was used as a cathode (12), a plating solution (13) of the following composition was added, and electrolysis was performed under the following conditions. Ta.

Plating solution composition Na2 SOa 100g/,
1! znso4-7H20300 (II/, 1!pHi
, o ~ 1.2 Distance between electrodes: 5 mm Electrolysis temperature: 55 to 60'C Current density: 808/dm2 The plating solution was circulated by a pump, and the concentration of the solution was adjusted by occasionally adding a high concentration plating solution. .

In addition, the cathode was periodically scraped to prevent the distance between the electrodes from becoming too small due to deposits. The results are shown in Table 1. Moreover, the relationship between current density and sliding voltage is shown in FIG.

No. 1 Front anode gas generation Only on the opposite side Double-sided anode
18.2! ;l 11. Oq Example 2 Using the same apparatus as in Example 1, tin plating of a steel plate was carried out under the same conditions except that the plating solution composition was changed to the following.

Plating solution composition Na2SO4100g/NSnSO
440! l]/j pHO, 8 to 1.0 Distance between electrodes 7 mm Current density 40 A/dm2 The results are shown in Table 2.

As shown in Table 2, the electrode of the present invention allows galvanizing or tin plating of a steel plate at a lower voltage than when using a conventional electrode.

(Effects of the Invention) By performing continuous plating treatment on the surface of a steel plate using the porous anode of the present invention, the following effects are produced compared to the case where a conventional flat plate anode is used.

i) The electrode itself is lighter and easier to handle.

11) The generated gas can be easily dissipated, which is effective in reducing the voltage, and the life of the electrode can be extended.

1! i) By facilitating the dissipation of generated gas, the plating solution is sufficiently supplied to the cathode surface, which is effective in preventing the causes of uneven plating 2 and improving the quality, and increasing the current density. The conveyance speed of steel plates is increased and productivity is improved.

iv) Conventionally, it was necessary to increase the flow rate of the plating solution in order to prevent the generated gas from stagnation, but according to the present invention, the gas can easily dissipate, so this is no longer necessary and power costs can be reduced. be.

■) By facilitating the dissipation of generated gas, fluctuations in liquid pressure are almost eliminated, and the fluctuation of the steel plate during electrolysis is reduced.
It can help prevent anode and cathode short circuits.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the shape of the porous part of the porous metal anode of the present invention, and FIGS. 2 and 3 are diagrams of a vertical electroplating device and a horizontal electroplating device in which the electrode of the present invention is used. It is a schematic diagram. Further, FIG. 4 is a schematic diagram of the experimental apparatus used in the example, and FIG. 5 is a graph showing the relationship between voltage and current density in Example 1. (1) Vertical electroplating tank (2) Conductor roll (3) Zinc roll (4) Steel plate (5
>(6)...Porous anode (7)...Horizontal electroplating tank (8)...Dam roll

Claims (7)

[Claims] (1) An electrode for continuous electroplating consisting of a porous metal anode with a coating layer of electrode active material. (2) The electrode according to claim 1, wherein the porous metal anode has an expanded metal, punched metal, net shape, or screen shape. (3) The electrode according to claim 1 or 2, wherein the electrode active material contains an oxide of a platinum group metal. (4) The electrode according to claim 3, wherein the platinum group metal oxide is one or more metal oxides selected from iridium, rhodium, palladium, ruthenium, and osmium. (5) The electrode according to claim 3, wherein the platinum group metal oxide is iridium oxide. (6) The base material of the metal anode is titanium, zirconium, tantalum, niobium, tungsten, molybdenum, antimony,
The electrode according to any one of claims 1 to 5, which is a metal selected from silver. (7) A method for continuous electroplating of steel sheets, characterized in that a porous metal anode having a coating layer of an electrode active material is used, and electrolysis of the plating bath is carried out using the steel sheet conveyed into the plating bath as a cathode.