JPH09235698A - Electrolytic surface-clad electrode and method for continuously electroplating metallic strip using the electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolytic surface-clad electrode with the service life remarkably prolonged and to furnish a method for continuously electroplating a metallic strip using the electrode. SOLUTION: An electrolytic surface-clad electrode having a rugged part consisting of at least one among a protrusion 3, a recess 4, and a groove 5 on the discharge surface 2 of an electrode 1, an electrolytic surface-clad electrode having a rugged part consisting of a pyrmidal protrusion 3 on the discharge surface 2 of the electrode 1 or an electrolytic surface-clad electrode having a rugged part with one surface in the longitudinal direction of the triangular prism 8 or square prism 9 placed on the discharge surface 2 of the electrode 1 is used, and a plating soln. is circulated between the electrode and the metallic strip opposed to the electrode at a flow velocity of 1.0m/sec to conduct plating.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode for electrolysis and an electroplating method using the same, and particularly to electrolysis used for electroplating equipment for metal strips such as steel strips or for electrolytic cleaning equipment for the metal strips. TECHNICAL FIELD The present invention relates to an electrode for surface coating and a continuous electroplating method for metal strips using the same.

[0002]

_2. Description of the Related Art Surface-coated electrodes in which a coating layer (hereinafter referred to as a coating) such as IrO ₂ is formed on the surface of a metal substrate such as Ti used in electroplating equipment, etc. Passivation of certain metal substrate surfaces is prevented. In this case, generally, as the life determining factor of the surface-coated electrode,
The adhesion between the coating and the substrate and the durability of the coating itself may be mentioned.

In order to improve these characteristics, Japanese Patent Laid-Open No.
63-235493 discloses a method of coating an underlayer (intermediate layer), and JP-A-6-200391 describes a method of coating an underlayer (intermediate layer) by electric discharge machining. Japanese Patent No. 3497 discloses a method of coating a coating agent by a sputtering method. All of these conventional techniques are based on the idea that coating components and coating methods or coating techniques such as coating an intermediate layer between the coating and the metal substrate can improve the adhesion and durability of the coating. is there.

However, in the case of these prior arts, the life of the surface-coated electrode is limited, and the required voltage during plating rises sharply as the time of use elapses, requiring replacement of the electrode.

[0005]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art and provides a surface-coated electrode for electrolysis capable of significantly extending the life of the electrode and a method for continuous electroplating of metal strips using the same. For the purpose of provision.

[0006]

A first aspect of the present invention is characterized by having an uneven portion composed of at least one of a projection 3, a depression 4 and a groove 5 on the electrode surface on the discharge surface side 2 of the electrode 1. Is a surface-coated electrode for electrolysis. A second aspect of the invention is a surface-coated electrode for electrolysis, which is characterized in that it has a concavo-convex portion consisting of triangular pyramidal protrusions 3 on the electrode surface on the discharge surface side 2 of electrode 1.

A third aspect of the invention is characterized in that an uneven portion having a shape in which one surface in the longitudinal direction of the triangular prism 8 or the quadrangular prism 9 is placed on the electrode surface on the discharge surface side 2 of the electrode 1 is characterized. Is a surface-coated electrode for electrolysis. In the first invention, the second invention, and the third invention, the ratio of the surface area of the discharge portion of the electrode 1 to the energization area S of the electrode 1 in the virtual surface 7 formed by the bottom portion 6 of the uneven portion. But preferably 1.
2 or more, more preferably 1.3 to 3.0, and even more preferably
It is preferably 1.3 or more and less than 2.0.

The first invention, the second invention, and the third invention
In the invention, the height or depth h of the uneven portion is preferably 0.5 to 3.0 mm, more preferably 0.5 mm or more,
It is preferably less than 2.0 mm. A fourth invention uses the surface-coated electrode for electrolysis according to any one of the first invention, the second invention, and the third invention, and between the electrode and a metal strip facing the electrode. In addition, the flow rate is 1.0 m / sec or more, and more preferably, the plating solution is circulated under the condition of 1.0 to 3.0 m / sec,
It is a continuous electroplating method for a metal strip, which is characterized by performing plating.

In the fourth invention, more preferably, the plating solution is a sulfuric acid acidic plating solution, and further preferably the pH is 1.0 to 2.0. In addition, in the said 1st invention, 2nd invention, 3rd invention, the uneven | corrugated | grooved part shows the state which a surface has unevenness, ie, the state which is not flat, as above-mentioned, 1st invention,
In the present invention, the shape of the bumps is not limited.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The present invention relates to a surface-coated electrode for electrolysis (hereinafter referred to as an electrode) that is preferably used for electroplating equipment for metal strips such as steel strips or for electrolytic cleaning equipment for the metal strips, and continuous electroplating for metal strips using the same. Regarding the method.

The electrodes in the present invention include Ti, Ta, N
An electrode in which a platinum group metal such as Ir, Pt or Ru or an oxide thereof such as IrO ₂ is coated on the surface of a conductive substrate such as b, Zr, Hf, V 2, Mo, W or an alloy thereof is preferably exemplified. It In this case, an intermediate layer may be provided between these films and the conductive substrate for the purpose of further improving the adhesion and durability of the films.

The continuous electroplating method for metal strips of the present invention is preferably applied to Zn strips, Ni platings, Zn-Ni alloy platings, Sn platings, Fe platings, Cr platings and the like for metal strips such as steel strips (strips). However, the type of metal strip and the plating metal are not limited. As the plating bath, a plating bath containing a sulfuric acid aqueous solution as a mother liquor is more preferable, and a pH of 1.0 to 2.0 is more preferable.

When the pH is less than 1.0, the plating adhesion of the obtained metal strip is deteriorated, and the current efficiency at the time of plating is deteriorated. When the pH is more than 2.0, the plating burns and the like are not preferable. In addition, as the plating tank in this case, a horizontal tank (horizontal cell), a vertical tank, a closed horizontal tank (jet cell),
The format is not limited, such as radial cell.

FIGS. 1 (a) and 2 (a)-(d) show an example of the electrode of the present invention, and FIG. 3 shows a conventional flat plate type electrode in perspective view. Further, FIGS. 1 (b), 2 (e), and (f) show the concavo-convex portion A of the electrode according to the present invention, along with the dimensions of the concavo-convex portion, in a sectional view and a perspective view, respectively. In addition, in FIG. 1, FIG. 2, and FIG. 3, the arrow F indicates the flow direction of the plating solution with respect to the electrodes in the examples described later.

FIG. 1 shows a pyramid (triangular pyramid) on the electrode surface.
It is an electrode having a large number of mold-shaped convex portions (hereinafter referred to as a pyramid-type electrode). FIGS. 2 (a) and 2 (b) show an electrode (hereinafter referred to as a slit A type electrode) having a large number of convex portions in which one surface in the longitudinal direction of a triangular prism is placed on the upper surface of a flat plate on the electrode surface. 2 (c) and 2 (d), an electrode having a large number of convex portions in which one surface in the longitudinal direction of a quadrangular prism having a square cross section is placed on the upper surface of a flat plate (hereinafter referred to as slit B-type electrode Note).

Table 1 collectively shows the electrodes according to the present invention, the ratio of the discharge area of the electrodes to the discharge area of the flat plate type electrode, and the height or depth h of the irregularities on the electrode surface.

[0017]

[Table 1]

As described above, all the conventional methods are
The idea is to improve the adhesion of the coating and the durability of the coating by a coating technique such as coating components, coating method of the coating, or coating an intermediate layer between the coating and the metal substrate. The present invention is different from such an idea in that the surface of the metal base on the side to be coated is made into a specific three-dimensional shape by a method such as machining to reduce the current load per unit area of the coating, This is intended to extend the service life.

That is, in the present invention, in order to achieve a long service life of the electrolysis electrode used as a plating electrode or the like, the discharge side surface (discharge surface) of the metal base body which is the electrode base body is machined or the like. By providing irregularities such as grooves,
The coating was coated after increasing the actual surface area of the electrode surface. As a result, unlike the conventional method in which a flat plate, which is a metal substrate, is coated with a film, the current load per electrode surface area when using an electrode is reduced, the wear rate of the film is reduced, and the same electrode can be used for a long time. It was

Further, in the present invention, regarding the surface shape of the metal substrate and the flow rate of the plating solution, the optimum shape and the optimum flow rate of the plating solution were tested by taking into consideration the bubble escape property of oxygen gas generated from the electrode surface during electrolysis. Sought by. That is, when irregularities are provided on the surface of the electrode substrate by machining or the like, there is a risk that the degassing of oxygen gas generated from the electrode surface will deteriorate and the electrolysis voltage will increase.
The optimum shape of the electrode surface and the optimum flow rate of the plating solution during electroplating were found.

4 (a), (b-1) and (c) are perspective views for explaining the surface shapes of the pyramid type electrode, the slit A type electrode and the slit B type electrode according to the present invention, respectively. The figure is shown. 4 (b-2) is a cross-sectional view of the slit A-type electrode for showing the height or depth h of the uneven portion of the slit A-type electrode.

In FIG. 4, 1 is an electrode, 2 is a discharge surface side,
3 is a protrusion, 4 is a depression, 5 is a groove, 6 is a bottom of an uneven portion including at least one of the protrusion 3, the depression 4, and the groove 5, and 7 is a virtual surface formed by the bottom 6 of the uneven portion. , 8 is a triangular prism, and 9 is a quadrangular prism. Further, S represents the energization area of the electrode 1 on the virtual surface 7, that is, the area of the portion surrounded by the straight lines l ₁ , l ₂ , l ₃ and l ₄ (dotted line portion) on the virtual surface 7 in FIG. Indicates the height of the uneven portion from the bottom portion 6, that is, the depth of the bottom portion 6 from the apex of the uneven portion.

In the electrolysis electrode of the present invention, the ratio of the surface area of the discharge portion of the electrode 1 to the energized area S of the electrode 1 on the virtual surface 7 formed by the bottom portion 6 of the uneven portion is preferably 1.2 or more, It is more preferably 1.3 to 3.0, still more preferably 1.3 or more and less than 2.0.
When it is less than 1.2, the effect of extending the electrode life due to an increase in the actual surface area of the electrode becomes small, and when it is more than 3.0, the degassing property of oxygen gas generated from the electrode surface becomes poor and the required electrolysis voltage becomes high.

In the present invention, the bottom portion 6 of the uneven portion is
Is not limited to the plane shown in FIG. 4, and also includes a curved bottom depending on the shape of the discharge surface of the metal base of the electrode. Further, in the present invention, the surface area of the discharge part of the electrode 1 is the geometric surface area of the discharge surface of the electrode, for example,
In the case of the pyramid-type electrode of FIG. 4 (a), the total value of the outer surface area of the protrusion 3 which is a triangular pyramid and the outer surface area of the bottom portion 6 which is the base of the uneven portion, that is, the total outer surface where the electrode is discharged. Indicates the surface area.

Further, for example, in the case of an electrode having a curved discharge surface, which is used in a radial cell, which is one type of plating cell for electroplating of steel strip, the current-carrying area S and the surface area of the discharge part are as described above. Defined similarly. Further, in the electrode of the present invention, h, which is the height or depth of the uneven portion, is preferably 0.5 to 3.0 mm,
More preferably, it is in the range of 0.5 mm or more and less than 2.0 mm.

When it is less than 0.5 mm, the effect of extending the electrode life is reduced due to the increase of the actual surface area of the electrode, and when it is more than 3.0 mm, the degassing of oxygen gas generated from the electrode surface is deteriorated and the required electrolysis voltage is required. Becomes higher. In the present invention, the height or depth of the uneven portion refers to the distance from the vertex of the convex portion to the intersection of the perpendicular line drawn to the virtual surface and the virtual surface and the vertex of the convex portion. If the shape is irregular,
The average value in the entire virtual surface is shown.

Further, when the flow path of the plating solution between the electrode (anode) according to the present invention and the both electrodes of the metal band (cathode) to be plated such as a steel plate during electroplating is defined as the gap between the electrodes, the plating within the gap is defined. The liquid flow rate is preferably 1.0 m / sec or more, more preferably 1.0 to 3.0 m / sec. If it is less than 1.0 m / sec, the required electrolysis voltage becomes high, and conversely, if the plating solution flow rate is increased to more than 3.0 m / sec, the effect of lowering the electrolysis voltage saturates, and the power consumption of the pump for liquid transfer, etc. Grows larger.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments. (Example 1) First, using electrodes having various surface shapes, the influence of the surface shape and the plating solution flow velocity in the interelectrode (hereinafter referred to as interelectrode flow velocity) on the electrolysis voltage was examined.

In this embodiment, the above-mentioned FIGS. 1 and 2 are used.
The pyramid type electrode, the slit A type electrode, the slit B type electrode according to the present invention, and the flat plate type electrode of FIG. 3 for comparison were used. That is, an experiment was conducted using an electrode in which an IrO ₂ film was coated on the surface of a substrate made of Ti having various surface shapes shown in FIGS. 1, 2, and 3.

Further, in order to examine the bubble escape property of oxygen gas generated during electrolysis, in the case of a slit type electrode, an electrode having a groove cut at right angles to the flow direction F of the plating solution (FIG. 2 (a),
(c)) and electrodes having grooves cut in parallel to the flow direction F of the plating solution (Figs. 2 (b) and 2 (d)), two types of electrodes each were tested. The experimental apparatus used in this example is shown in FIG.

In FIG. 7, reference numeral 21 is a plating solution flow path 22, an anode.
A horizontal cell that is a model of a horizontal cell type plating tank composed of 23 and a cathode 24, 25 is a thyristor rectifier with constant current control, 26 is a circulating tank, 27 is a plating solution, 28 is a plating solution temperature raising device. , 29 is a plating solution cooling device, 30 is a flow meter, T
Is a thermocouple, P is a pump, and V is a valve. In this example, the test pieces of electrodes having various surface shapes described above were prepared using the experimental apparatus of FIG. 7 and the model plating solution described below.
It was attached to the anode 23, a constant current was passed between the anode 23 and the cathode 24, the inter-electrode flow velocity was changed, and the electrolytic voltage was measured under the following conditions.

Model plating solution: Na ₂ SO ₄ = 150 g / l, pH = 1.
2 to 1.3, liquid temperature = 60 ° C. Current density: 150 A / dm ² Distance between electrodes: 10 mm FIG. 5 shows the result of an experiment conducted using the test electrode described above. As shown in Fig. 5, in the case of the slit B type electrode with the groove depth of the electrode increased to 2.0 mm, it is compared with the pyramid type electrode and the slit A type electrode in which the electrode groove depth is as small as 0.7 mm even if the plating solution flow rate is increased. Then, it was found that the electrolytic voltage increases when a predetermined current is applied and the groove depth of the electrode is increased, resulting in poor bubble removal.

That is, in the present invention, it is more preferable to limit the groove depth of the electrode to less than 2.0 mm in order to reduce the electrolytic voltage in the steady state. Further, as shown in FIG. 5, the inter-electrode flow velocity is preferably 1.0 m / sec or more, and when it is increased to 3.0 m / sec or more, the effect of lowering the electrolytic voltage in a steady state is saturated. I understood.

Example 2 Using the horizontal cell type continuous electroplating apparatus shown in FIG. 8, the test electrodes (pyramid type electrode, slit A type electrode) according to the present invention shown in FIGS. 1 and 2 were used.
And the operation experiment was conducted under the following conditions using the conventional flat plate type electrode shown in FIG. 8 (a) is a side view of the plating apparatus, and FIG. 8 (b) is a partial side view of the plating cell on the lower anode side to which the test electrode is attached.

Further, in FIG. 8, 40 is a plating cell and 41
In the present embodiment, is an anode to which a test electrode is attached, 42 is a steel strip, 43 is a plating solution, 44 is a conductor roll, 45 is a backup roll, 46 is a bus bar, and 47 is a traveling direction of the steel strip. [Metal substrate of test electrode, coating] Metal substrate: Ti, coating: IrO ₂ [Material to be plated] Cold rolled steel sheet after alkaline degreasing and sulfuric acid pickling [Plating bath] Components containing plating solution: NiS0 ₄ , ZnSO ₄ , Na ₂ S0 ₄ Plating solution pH: 1.4 (Sulfate acidity) Velocity of plating solution in the interelectrode: 1.0 m / sec or more Figure 6 shows the time course of the voltage rise rate with respect to the required voltage at the start of the experiment.

As shown in FIG. 6, when the test electrode of the present invention in which the actual surface area of the electrode is increased is used, the usable time until the start of the voltage rise due to the deterioration of the electrode is higher than that of the conventional flat plate type electrode. It has been possible to obtain a good result that it is possible to greatly extend the life of the electrode. As shown in the above examples, in the present invention, the actual surface area of the electrode is increased and the current load per unit coating area of the electrode is reduced by a method of machining the discharge surface side of the plating electrode. planned.

As a result, the usable time of the electrode was greatly extended and the life of the electrode could be extended. Also,
With regard to the problem of electrolytic voltage at steady state due to the quality of bubble removal, the groove depth provided by a method such as machining is more preferably less than 2.0 mm, and the plating solution flow velocity between the electrodes is 1.0 m / m. It became possible to solve it by setting it to sec or more.

[0038]

According to the present invention, the usable time of the surface-coated electrode for electrolysis can be significantly extended and the life of the electrode can be extended. Furthermore, by regulating the flow velocity of the plating solution in the gap between electrodes, it has become possible to reduce the electrolysis voltage in the steady state.

[Brief description of drawings]

FIG. 1 is a perspective view (a) showing an electrode according to the present invention and an enlarged sectional view (b) of a main part showing a height of a convex portion of the electrode.

FIG. 2 is a perspective view showing an electrode according to the present invention (a), (b),
(c), (d) and an enlarged perspective view (e), (f) of the main part showing the height of the convex portion of the electrode.

FIG. 3 is a perspective view showing a conventional electrode.

FIG. 4 is perspective views (a), (b-1) and (C) for explaining the surface shape of the electrode according to the present invention, and a slit A-type electrode.
It is sectional drawing (b-2) of (b-1).

FIG. 5 is a graph showing a relationship between a plating solution flow velocity in an interelectrode and an electrolytic voltage in an experiment using a test electrode according to the present invention.

FIG. 6 is a graph showing the time course of the voltage increase rate in an experiment using the test electrode according to the present invention.

FIG. 7 is a side view showing an electrolysis test apparatus used in Examples.

FIG. 8 is a side view of the continuous electroplating apparatus used in the examples.
(a) and a partial side view (b).

[Explanation of symbols]

 1 Electrode 2 Discharge surface side 3 Protrusion 4 Depression 5 Groove 6 Bottom of uneven part 7 Virtual surface 8 Triangular prism 9 Square prism 21 Horizontal cell 22 Plating liquid flow path 23 Anode 24 Cathode 25 Thyristor rectifier 26 Circulating tank 27 Plating liquid 28 Plating Liquid temperature raising device 29 Plating liquid cooling device 40 Plating cell 41 Anode 42 Steel strip 43 Plating liquid 44 Conductor roll h Height or depth of irregularities S Current-carrying area T Thermocouple

Claims (7)

[Claims] 1. A surface-coated electrode for electrolysis, which has an uneven portion composed of at least one of a protrusion, a depression, and a groove on the electrode surface on the discharge surface side of the electrode. 2. A surface-coated electrode for electrolysis, comprising an uneven portion formed of triangular pyramidal protrusions on the electrode surface on the discharge surface side of the electrode. 3. A surface-coated electrode for electrolysis, comprising an uneven portion having a shape in which one surface in the longitudinal direction of a triangular prism or a quadrangular prism is placed on the electrode surface on the discharge surface side of the electrode. 4. The electrolysis according to claim 1, wherein the ratio of the surface area of the discharge portion of the electrode to the current-carrying area of the electrode on the virtual surface formed at the bottom of the uneven portion is 1.2 or more. Surface-coated electrode for. 5. The height or depth of the uneven portion is 0.5 to
The surface-coated electrode for electrolysis according to claim 1, which has a size of 3.0 mm. 6. The surface-coated electrode for electrolysis according to any one of claims 1 to 5, wherein a flow velocity is 1.0 m / sec or more between a metal strip and the electrode facing each other. A continuous electroplating method for a metal strip, which is characterized in that a plating solution is circulated under the conditions to perform plating. 7. The continuous electroplating method for a metal strip according to claim 6, wherein the plating solution is a sulfuric acid acidic plating solution.