JP2012201889A - Electroplating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electroplating apparatus which hardly produces a knob-like or dendritic plated metal crystal on the surface of a metal belt and, moreover, and can perform electroplating treatment so as to secure high adhesiveness between a plating layer and the metal belt.SOLUTION: The electroplating apparatus 10 includes: an electrolyzer 2; a feeding mechanism 3 which causes the metal belt S to pass in the electrolyzer 2; a passage mechanism 5 which causes plating liquid to pass in the plate-passing direction (X3 direction) or the direction (X4 direction) reverse to the plate-passing direction of the metal belt S in the electrolyzer 2; and a pair of electrodes 1A, 1B arranged on positions which hold the metal belt S therebetween, wherein both of the pair of electrodes 1A, 1B have alternatively protruded parts 1b and recessed parts 1a on the positions corresponding to each other and in the plate passing direction, inter-electrode distances are shortened between the protrusion parts 1b, 1b of both electrodes, the inter-electrode distances are lengthened between the recessed parts 1a, 1a of both electrodes and the recessed parts 1a', 1a' having the longest length in the plate-passing direction are arranged on the input side end part into which the metal belt S enters.

Description

  The present invention relates to an electroplating apparatus applied when performing electroplating on the surface of a metal strip such as a steel strip.

  Surface treatment of a steel plate or the like is performed for various purposes such as rust prevention, corrosion prevention, and decoration, and the quality of the steel plate can be improved by the surface treatment, and the use can be diversified and broadened.

  There are a wide variety of surface treatment methods for steel plates, etc., but one of the treatment methods is a continuous surface treatment method using an electrolytic cell. Electroplated steel plates produced by this method can be applied to, for example, vehicle body members. Has been. In addition, although the metal used by plating is also various, Zn, Ni, Sn, Cr, Cu, etc. are used alone or from alloys such as Zn-Fe alloy, Zn-Ni alloy, Zn-Ni-Co alloy. The plating material to be electroplated on the surface of a steel plate or the like.

  The electrolytic cell types applied during the continuous electroplating include a horizontal electrolytic cell, a vertical electrolytic cell, and a curved electrolytic cell. For example, in a horizontal electrolytic cell, a metal band to be plated is passed between insoluble electrodes disposed in an electrolytic cell in which a plating solution is jetted in the horizontal direction, and the metal band is used as a cathode. Electroplating is performed on the surface of the metal strip in the process of passing the metal strip between the electrodes that are anodes.

  For example, in the horizontal electrolytic cell described above, there are a plurality of jet forms of the plating solution in the electrolytic cell, and the plating solution is jetted in the direction opposite to the plate passing direction of the metal strip passing between the electrodes. There are horizontal type one-side inflow type electrolytic cells and horizontal type central inflow type electrolytic cells in which a plating solution is jetted from the electrode center in two directions, ie, a plate passing direction and the opposite direction. Note that vertical type one-side inflow type electrolytic cells also exist in vertical type electrolytic cells.

  By the way, the electrode generally applied in the electrolytic cell for continuous electroplating has a planar shape in which a certain distance from the metal strip is maintained.

  Although the plating solution is electrolyzed at a constant current density between the above planar electrodes, for example, when the speed of passing the metal strip is relatively slow, the deposited plating metal crystals tend to be nodal or dendritic crystals. In this way, when the metal band-like or dendritic metal crystal is plated on the surface of the metal band, when the metal band is bent in a later process, along the interface of the node-like or dendritic metal crystal The present inventors have identified a problem that cracks are likely to occur and the plating quality is degraded.

  Here, turning to the conventional published technique, Patent Document 1 describes that an electrode having a concavo-convex portion on the surface and a continuous metal band using this electrode are provided for the purpose of significantly extending the life of the electrode. An electroplating method is disclosed.

  More specifically, a groove is provided on the discharge-side surface of the metal substrate, which is an electrode substrate, to form irregularities, and the coating is coated after increasing the actual surface area of the electrode surface. Unlike electrodes with a conventional structure where a metal plate is coated with a coating, the current load per electrode unit surface area when using the electrode can be reduced, and the same electrode can be used for a long time by reducing the consumption rate of the coating. It makes it possible.

  Although Patent Document 1 does not disclose any of the problems specified by the present inventors as described above, according to the present inventors, the surface of the electrode is made uneven as disclosed in Patent Document 1. The distance between the electrodes facing each other can be changed alternately (the distance between the electrodes between the convex portions facing each other is shortened, and the distance between the electrodes between the concave portions facing each other is increased). For example, the equipment cost is expensive. It is possible to change the electrolytic current density between one electrode by applying a direct current without applying a pulse current.

  In this way, by changing the electrolytic current density between one electrode, a relatively high current density region is formed between the convex portions facing each other, and a dense metal crystal is deposited here, and between the concave portions facing each other. The present inventors have found that, by forming a relatively low current density region to precipitate and grow metal crystals and repeating these alternately, no node-like or dendritic metal crystals are likely to occur. .

  However, it has also been specified by the present inventors that the adhesiveness between the metal strip and the plating layer (plating film) is insufficient only by providing an uneven surface on the electrode surface.

JP-A-9-235698

  The present invention has been made in view of the above-described problems, and relates to an apparatus for performing electroplating on the surface of a metal strip. Nodular or dendritic plated metal crystals are hardly generated on the surface of the metal strip, and the plating layer and An object of the present invention is to provide an electroplating apparatus capable of electroplating a metal strip with high adhesion.

  In order to achieve the above object, an electroplating apparatus according to the present invention comprises an electrolytic cell, a feed mechanism for passing a metal band in the electrolytic cell, and a metal band passing direction in the electrolytic cell or in the opposite direction. An electroplating apparatus comprising a flow mechanism for flowing a plating solution and a pair of electrodes arranged at a position sandwiching a metal band, both of the pair of electrodes being at a corresponding position and in a plate passing direction. Protrusions and recesses are provided alternately, the distance between the electrodes is shortened between the projections of both electrodes, the distance between the electrodes is increased between both recesses, and the metal band of the electrode enters the electrode At the entrance end, a recess having the longest length in the plate passing direction is disposed among the plurality of recesses.

  In the electroplating apparatus of the present invention, a metal strip such as a steel plate forming a cathode is passed between a pair of electrodes forming an anode in an electrolytic cell in which a plating solution is accommodated, and electroplating is performed on the surface of the metal strip. It is a rubbing device. This apparatus may be a horizontal electrolytic cell, a vertical electrolytic cell, or a curved electrolytic cell. For example, in the case of a horizontal electrolytic cell, the direction opposite to the direction of the metal strip that passes between the electrodes. Either a horizontal type one-side inflow type electrolytic cell that jets the plating solution at the center, or a horizontal type one-side inflow type electrolytic cell that jets the plating solution from the center of the electrode in two directions, the plate passing direction and the opposite direction. There may be.

  Also, the plating metal to be electroplated is not limited in any way. For example, in addition to a single pure metal such as Zn, Ni, Sn, Cr, Cu, Zn—Fe alloy, Zn—Ni alloy, Zn An alloy such as a Ni—Co alloy may be used.

  The pair of electrodes constituting the electroplating apparatus is provided with alternating concave portions and convex portions, the inter-electrode distance is long between the corresponding concave portions, and the inter-electrode distance is short between the corresponding convex portions. Among the plurality of concave portions, the concave portion having the longest length in the sheet passing direction is arranged at the end of the entrance side where the metal band enters the electrode.

  Since the electrodes are provided with uneven portions alternately, it is possible to change the electrolytic current density between one electrode without passing a pulse current. In this case, a relatively high current density region is formed and a dense metal crystal is deposited here, and a relatively low current density region is formed between opposing concave portions having a long inter-electrode distance to slowly form a metal crystal. By depositing and growing and repeating these alternately, it is possible to suppress node-like or dendritic plated metal crystals.

  Furthermore, a concave portion is provided at the end of the entrance side where the metal band of the electrode enters the electrode, and the length of the concave portion in the plate passing direction is the longest compared to other concave portions, so that The current density at the initial stage of plating can be lowered, and this can suppress the deposition rate of the plating metal. For example, the length of the recess at the entry end can be adjusted to about twice the length of the other recess. Here, the plating solution jetted by the flow mechanism causes a vortex due to the stirring effect due to the unevenness between the electrodes, but the plating metal deposition rate at the initial stage of plating is suppressed and the plating solution on the surface of the metal band is sufficiently stirred. By bringing the stirred plating solution into contact with the metal strip, the adhesion between the metal strip and the plating layer formed by depositing the plating metal can be enhanced.

  If adhesion between the metal strip at the initial stage of plating and the plating layer is ensured, a plating layer having a desired thickness is formed by metal deposition in the process of passing the metal strip between the electrodes. Needless to say, the adhesion between one kind of plated metals is good.

Here, there are the following forms of unevenness on the electrode surface.
One of them is a form in which the length in the plate passing direction of the recesses and the projections other than the recess having the longest length in the plate passing direction is constant.

  The other is a form in which the lengths in the plate passing direction of both the concave portion and the convex portion are gradually shortened from the entrance end portion to the exit end portion of the electrode.

  The other is a form in which only the length of the recess in the plate passing direction is gradually shortened from the entrance end to the exit end of the electrode.

  Moreover, when the length between the metal plate passing position between the electrodes and the concave portion is L, the protruding length of the convex portion with respect to the concave portion toward the metal band is in the range of L / 6 to L / 3. It is preferable.

  According to the present inventors, when the protruding length of the convex portion with respect to the concave portion to the metal band side is smaller than L / 6, the current density change in the electrode is too small and the plating solution stirring effect or nodal shape It has been identified that the dendritic plated metal crystal suppressive effect is small. On the other hand, when the protrusion length is larger than L / 3, it has been specified that the distance between the convex portions facing each other becomes too small and the risk of contact between the electrodes increases. The lower limit is specified.

  Furthermore, when the length between the plate passing position of the metal strip between the electrodes and the recess is L, it is preferable that both the length in the plate passing direction of the recess and the projection is in the range of 2L to 10L. .

  According to the present inventors, if the lengths of the concave and convex portions in the plate passing direction are both less than 2L, the current density change is too small, and the concave and convex portions in the plate passing direction length are both less than 10L. If it is large, it has been specified that the effect of the concavo-convex electrode is reduced because the time for the sprayed plating solution to stay within a certain current density becomes too long. It is a thing.

  As can be understood from the above description, according to the electroplating apparatus of the present invention, the pair of electrodes constituting the electroplating apparatus are provided with recesses and protrusions alternately, and the distance between the electrodes is long between the corresponding recesses. Electrode current density can be changed between one electrode without passing a pulse current due to the short inter-electrode distance between the convex portions, and thus, between the opposing convex portions having a short inter-electrode distance. In this case, a relatively high current density region is formed and a dense metal crystal is deposited here, and a relatively low current density region is formed between opposing concave portions having a long inter-electrode distance to slowly form a metal crystal. By depositing and growing and repeating these alternately, it is possible to suppress node-like or dendritic plated metal crystals. Furthermore, at the end of the entrance side where the metal band of the electrode enters the electrode, a recess having the longest length in the plate-passing direction is disposed among the plurality of recesses. The current density can be lowered, and this suppresses the deposition rate of the plating metal and sufficiently stirs the plating solution on the surface of the metal band. By bringing this stirred plating solution into contact with the metal band, the metal The adhesion between the band and the plating layer formed by depositing the plating metal can be enhanced.

It is a schematic diagram of one embodiment of the electroplating apparatus of the present invention. (A) is the current density distribution map in the electrode which comprises the electroplating apparatus of this invention, (b) is the current density distribution map in the electrode which comprises the conventional electroplating apparatus. It is the figure which simulated the flow of the plating solution which flows between electrodes. (A), (b) is a schematic diagram of other embodiment of an electrode.

  Embodiments of the electroplating apparatus of the present invention will be described below with reference to the drawings. The illustrated electroplating apparatus includes a horizontal type one-side inflow type electrolytic cell, but in addition to this, a horizontal type central inflow type electrolytic cell, a vertical electrolytic cell, a curved electrolytic cell, etc. Of course, it may be.

  FIG. 1 is a schematic view of an embodiment of an electroplating apparatus of the present invention. The illustrated electroplating apparatus 10 includes an electrolytic cell 2, a feed mechanism 3 for passing the metal band S in the electrolytic cell 2, and a direction opposite to the plate direction (X3 direction) of the metal band S in the electrolytic cell 2. It is mainly composed of a flow mechanism 5 for jetting the plating solution M in the (X4 direction), a pair of electrodes 1A and 1B arranged at positions sandwiching the metal band S, and a DC power source 4. In the figure, the end where the metal strip S enters the electrodes 1A and 1B is the entry side, and the end where the electroplated metal strip S exits the electrodes 1A and 1B is the exit side.

  The feed roller constituting the feed mechanism 3 is an electrode roller (the upper roller rotates in the X1 direction and the lower roller rotates in the X2 direction), and the cathode of the DC power source 4 communicates with the metal, and is in contact with the feed mechanism 3 The band S serves as a cathode, and the metal cations for plating are electroplated on the surface of the metal band S.

  The plating solution M that is jetted in the direction opposite to the plate passing direction of the metal strip S in the electrolytic cell 2 includes a single pure metal such as Zn, Ni, Sn, Cr, or Cu, a Zn—Fe alloy, or Zn—Ni. An alloy such as an alloy or a Zn—Ni—Co alloy is used.

  The pair of electrodes 1A and 1B shown in the figure are provided with convex portions 1b and concave portions 1a alternately at corresponding positions and in the plate passing direction (X3 direction), and between the convex portions 1b and 1b of both electrodes 1A and 1B. The distance between the electrodes is shortened, and the distance between the electrodes is increased between the concave portions 1a and 1a.

  In addition, a recess 1a ′ having the longest length in the plate-passing direction among the plurality of recesses is disposed at the end of the electrode 1A, 1B where the metal band S enters (the plate-passing direction here). Length s1> the length s2 of other recesses 1a in the plate passing direction. In addition, this plate | board passing direction length s1 is adjusted to the range of about 1.5 to 3 times the plate passing direction length s2.

  In the illustrated electrodes 1A and 1B, the lengths of the concave portions 1a and the convex portions 1b other than the concave portion 1a 'at the entrance end are the same length s1.

  When the electrodes 1A and 1B are energized from the DC power source 4, as shown in FIG. 2A, a relatively high current density region is formed between the convex portions 1b and 1b with respect to the average current density, and the concave portions 1a and 1a. A relatively low current density region is formed between them, and a current having a different current density is applied in a current-carrying manner such as a pulse current in spite of power supply from a DC power source. Furthermore, this current density distribution exhibits a current density distribution in which the pulsed current density decreases from the input side and the output side of the electrode toward the center. In the electrode of the conventional structure shown in FIG. 2b (the electrode surface is flat), a pulse-shaped current density distribution does not occur, and a quadratic curve in which the current density decreases from the entrance side and the exit side of the electrode toward the center. Present.

  When the metal strip S is passed between the electrodes 1A and 1B exhibiting such a pulsed current density distribution (X3 direction) and the plating solution is jetted in the direction opposite to the passing direction (X4 direction), FIG. As shown in Fig. 4, the plating solution swells in the process of passing through the concave portion 1a and the convex portion 1b on the electrode surface (X4 'direction), and plating is performed by the undulation in the concave portion 1a' at the longest entrance side. The solution is agitated (X4 ″ direction). By this agitation, a plating solution that is consumed by precipitation (plating) on the surface of the metal strip and the metal ion concentration in the plating solution near the reduced metal strip surface is made uniform is obtained. It contacts the surface of the metal strip S, thereby increasing the adhesion between the metal plate and the plating layer.

  As shown in the figure, the electrodes 1A and 1B are provided with corresponding recesses 1a and 1a ′ and protrusions 1b alternately, so that the electrolysis current density can be increased between the electrodes 1A and 1B without applying a pulse current. By this, a relatively high current density region is formed between the convex portions 1b and 1b facing each other with a short distance between the electrodes, and a dense metal crystal is deposited here. By forming a relatively low current density region between the long opposing recesses 1a and 1a (and between the recesses 1a 'and 1a'), the metal crystals are slowly precipitated and grown, and these are repeated alternately. Nodular or dendritic plated metal crystals can be suppressed. This is because it takes a long time for the metal strip S to pass through the electrolytic cell 2 when electrolysis is carried out at a low speed of about 1 to 10 m / min. In such a case, the precipitation of the nodular or dendritic plated metal crystals is remarkable, so that the effect of the apparatus of the present invention is extremely great when electroplating while passing a metal strip at a low speed.

  Further, by providing a recess 1a ′ having the longest length in the plate passing direction at the end of the electrodes 1A and 1B on the entrance side of the metal band S, the current at the initial stage of plating on the surface of the metal band S as shown in FIG. The density can be lowered, and this can suppress the deposition rate of the plating metal, and the plating solution on the surface of the metal strip S is sufficiently stirred as described above. By making it contact with S, the adhesiveness between the metal belt | band | zone S and the plating layer in which a plating metal precipitates and grows can be improved.

  Here, when the length between the plate position of the metal band S between the electrodes and the concave portion 1a is L, the protruding length h of the convex portion 1b toward the concave portion 1a toward the metal band is L / 6 ~. It should be in the range of L / 3.

  If the protrusion length h of the protrusion 1b to the metal band S side with respect to the recess 1a is smaller than L / 6, the change in the current density in the electrodes 1A and 1B is too small, and the stirring effect of the plating solution, nodal shape and dendrites It has been specified that there is little effect of suppressing the shape of the plated metal crystal. On the other hand, it is specified that when the protrusion length h is larger than L / 3, the distance between the convex portions 1b and 1b facing each other becomes too small and the risk of contact increases.

  Similarly, when the length between the plate passing position of the metal band S and the concave portion 1a is L, the concave plate 1a, 1a ′ and the convex portion 1b are both in the plate passing direction length of 2L to 10L. It is good to be.

  If the lengths of the concave portions 1a, 1a ′ and the convex portions 1b are both less than 2L, the current density change is too small, and the lengths of the concave portions 1a, 1a ′ and the convex portions 1b are both 10L. This is because the effect of the concavo-convex electrode is reduced because the time during which the sprayed plating solution stays within the constant current density becomes too long.

  In addition, in electroplating, when the current density exceeds a certain value, a normal plating layer with a metallic luster cannot be obtained. For example, in zinc plating, black so-called “burning” occurs, and the current density increases. Current efficiency may be reduced. Here, the following general formula is valid for the limit current density: Dk.

  Here, F is the Faraday constant, D is the diffusion coefficient of metal ions (values specific to ions), C is the metal ion concentration in the electrolyte solution (which is limited by the concentration of various components in the electrolyte solution, for example, the solubility and composition of the drug And δ is the thickness of the diffusion layer (which can be reduced by stirring the electrolyte).

  Between the convex parts 1b and 1b, since the flow rate of the plating solution is increased, no burns occur even if Dk is high.

  Moreover, although the flow rate of a plating solution becomes slow between recessed part 1a, 1a, since Dk also becomes low, a burn does not arise similarly. As described above, even when the electrodes 1A and 1B constituting the apparatus 10 of the present invention are applied, the problem of plating burn cannot occur.

(Other embodiments of electrode)
4a and 4b are schematic views showing other embodiments of electrodes.
The electrode 1A ′, 1B ′ shown in FIG. 4a has a configuration in which the concave portion 1a ′ having the longest length in the plate passing direction is arranged at the end of the entrance side into which the metal band S enters, in the embodiment shown in FIG. However, the other recesses and projections are gradually shortened in the threading direction from the input end to the output end.

  Also, the electrodes 1A "and 1B" shown in FIG. 4b have a configuration in which the recess 1a 'having the longest length in the plate passing direction is arranged at the end of the entrance side where the metal band S enters, as shown in FIGS. However, only the length of the recess in the plate passing direction is gradually shortened from the entrance end of the electrode toward the exit end.

  Even if it is an electrode of any form, the adhesiveness between the metal belt | band | zone S and the plating layer in which a plating metal precipitates can be improved.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and there are design changes and the like without departing from the gist of the present invention. They are also included in the present invention.

  1A, 1A ′, 1A ″, 1B, 1B ′, 1B ″... Electrode, 1a ′... Concave portion at the entrance end, 1a... Concave portion, 1b. 4 ... DC power supply, 5 ... Distribution mechanism, 10 ... Electroplating device, S ... Metal strip, M ... Plating solution

Claims (6)

An electrolytic cell, a feed mechanism for passing a metal band in the electrolytic cell, a flow mechanism for flowing a plating solution in the direction of the metal band in the electrolytic cell or in the opposite direction, and a position sandwiching the metal band An electroplating apparatus comprising a pair of electrodes provided,
Each of the pair of electrodes is provided with convex portions and concave portions alternately at corresponding positions and in the plate passing direction, the distance between the convex portions of both electrodes is shortened, and the distance between the two electrodes is long. And
An electroplating apparatus in which a recess having the longest length in the sheet passing direction is arranged among a plurality of recesses at an entrance end where the metal band of the electrode enters the electrode.   2. The electroplating apparatus according to claim 1, wherein the lengths of the recesses and the protrusions other than the recess having the longest length in the plate passing direction are constant.   2. The electroplating apparatus according to claim 1, wherein the length in the plate passing direction of both the concave portion and the convex portion is gradually shortened from the entrance end to the exit end of the electrode.   2. The electroplating apparatus according to claim 1, wherein only the length of the recess in the plate passing direction is gradually shortened from the entrance end to the exit end of the electrode.   When the length between the metal plate passing position between the electrodes and the recess is L, the protrusion length of the protrusion with respect to the recess toward the metal band is in the range of L / 6 to L / 3. The electroplating apparatus in any one of Claims 1-4.   The length in the plate passing direction between the concave portion and the convex portion is in the range of 2L to 10L, where L is the length between the metal plate passing position between the electrodes and the concave portion. The electroplating apparatus in any one of.

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