JP5467374B2 - Apparatus for forming electroplating on shaft body, manufacturing method of shaft body having plating film, and plating solution for forming zinc-based plating film on shaft body - Google Patents

Description

The present invention relates to an apparatus for forming electroplating on a shaft body, a method for manufacturing a shaft body having a plating film, and a plating solution for forming a zinc-based plating film on the shaft body.
In the present invention, the shaft body refers to a member having a central axis and a substantially rotationally symmetric shape.

  When electroplating a workpiece made of a shaft body such as a cylinder rod, it is common practice to hang the workpiece on a rack and immerse it in the plating solution, and then feed the workpiece through the rack to form a plating film. ing.

  However, in the case of this suspension method, the thickness of the plating film in the circumferential direction of the workpiece is likely to vary, and if the management width of the thickness of the plating film is strict, defective products are generated.

  As means for suppressing variations in the thickness of the plating film on a workpiece made of such a shaft, for example, Patent Document 1 discloses a workpiece inlet and a workpiece outlet at both ends of a workpiece feeding direction of a plating tank into which a plating solution has been injected. In an electroplating machine for long workpieces with anode plates arranged on both sides of the workpiece passage passage in the plating tank, the drive is inclined with respect to the axis of the cylindrical or round bar workpiece on the workpiece inlet side of the plating tank A work drive mechanism having a shaft is arranged, and a drive roller that presses against the outer peripheral surface of the work is fixed to the drive shaft so that the work roller rotates and moves in the length direction by the rotation of the drive roller. An electroplating for long workpieces, in which a plating solution jet pipe is arranged in the tank, and a plurality of nozzle portions for spraying a jet of the plating solution onto the workpiece passing through the plating tank are provided on the jet pipe. Location is disclosed.

Japanese Patent No. 2716741

  However, in the apparatus disclosed in Patent Document 1, although the workpiece is rotated about the axis by the workpiece driving mechanism, the plating solution is supplied from one region in the circumferential direction of the workpiece in consideration of a moment of rotation. ing. For this reason, the state (flow direction, flow velocity, etc.) of the plating solution in contact with the workpiece is not uniform in the circumferential direction of the workpiece. Therefore, the apparatus disclosed in Patent Document 1 has a problem that the thickness uniformity of the plating film in the circumferential direction of the workpiece is low.

  In view of such a technical background, the present invention is excellent in the uniformity of the thickness of the plating film formed on the shaft, and is an apparatus for forming electroplating on the shaft, and the manufacture of the shaft having the plating film. It is an object to provide a plating solution for forming a zinc-based plating film on a method and a shaft.

The present invention provided to solve the above problems is as follows.
(1) An apparatus for forming an electroplating film on a shaft body, which includes a hollow portion including a portion where a plating film is to be formed on a shaft body which is a member to be plated and having both ends opened in the vertical direction. A tubular member having a tubular member, a support means provided above the opening at the upper end in the vertical direction of the hollow portion, and holding the shaft body in the hollow portion; from the opening at the lower end in the vertical direction of the hollow portion to the hollow A plating solution jet means for supplying a plating solution into the part, provided near the opening at the upper end in the vertical direction of the hollow part, and the plating solution supplied into the hollow part by the plating solution jet means can be discharged out of the tubular member A discharge structure for supplying the plating solution discharged from the tubular member through the discharge structure to the plating solution jet means, and the support means is a contact portion that can be electrically connected to the shaft body. Wherein the tubular member comprises an insoluble anode in the hollow portion, said support means rotating mechanism for enabling rotation about the axis of the shaft body while maintaining electrical connection between the shaft body at the contact portion the a, this rotation mechanism, the shaft member, the linear velocity of the surface of the shaft body Ru is possible to form the plating film while rotating such that the 10 mm / sec or more, on the shaft An apparatus for forming an electroplated film.

(2) An insoluble anode provided on the inner surface of the hollow tubular member having hollow portions having openings at both ends in the vertical direction, and a shaft body to be plated are held in the hollow portion of the tubular member. A method for forming a plating film on the shaft body by applying a voltage to a contact portion that is provided in the support means and enables electrical connection with the shaft body, A plating solution jet means for supplying a plating solution into the hollow portion from the opening at the lower end portion in the vertical direction, provided in the vicinity of the opening at the upper end portion in the vertical direction of the hollow portion, and supplied into the hollow portion by the plating solution jet means. A discharge structure that allows the plating solution to be discharged out of the tubular member, and a plating solution that is discharged from the tubular member through the discharge structure to the plating solution jet means, and is fed into the hollow portion by the circulating means. The Is it possible to continuously fed into the vapor plating, the provided on the support means, allowing rotation around the axis of the shaft body while maintaining electrical contact with the shaft body at the contact portion and the rotation mechanism, the shaft, the linear speed of the surface of said shaft body Ru is possible to form a plating film on the shaft on the body while rotating such that the 10 mm / sec or more, the plating film The manufacturing method of the shaft body which has.

(3) The plating solution is a zinc sulfate-based plating solution containing a water-soluble zinc-containing substance and polyethyleneimine, and the content of the water-soluble zinc-containing substance is 70 g / L or more and 100 g / L or less in terms of zinc. The polyethyleneimine has a weight average molecular weight of 1500 or more and 2500 or less, a content of 0.1 g / L or more and 10 g / L, and a pH of the plating solution of 1 or more and 2 or less. The production method according to (2) above , wherein electroplating is performed under conditions of a temperature of 30 ° C. or more and 50 ° C. or less and a current density of 20 A / dm ² or more and 100 A / dm ² or less.

(4) The plating solution further contains a water-soluble metal-containing material, the metal element contained in the water-soluble metal-containing material is one or more selected from the group consisting of iron, nickel, the (3 ) Described production method.

(5) Using the apparatus described in (1) above , electroplating is performed on the shaft body under the conditions of a plating temperature of 30 ° C. or higher and 50 ° C. or lower and a current density of 20 A / dm ² or higher and 100 A / dm ² or lower. A plating solution for forming a zinc-based plating film, wherein the plating solution is a zinc sulfate-based plating solution containing a water-soluble zinc-containing substance and polyethyleneimine, and the content of the water-soluble zinc-containing substance is It is 70 g / L or more and 100 g / L or less in terms of zinc, and the polyethyleneimine has a weight average molecular weight of 1500 or more and 2500 or less, and its content is 0.1 g / L or more and 10 g / L, and the plating solution The plating solution for forming a zinc-based plating film on the shaft body is characterized in that the pH of the shaft is 1 or more and 2 or less.

(6) The plating solution further contains a water-soluble metal-containing substance, and the metal element contained in the water-soluble metal-containing substance is one or more selected from the group consisting of iron and nickel, (5 ) The plating solution described.

  According to said invention, since the flow state of the plating solution in the circumferential direction of the workpiece | work which consists of a shaft body becomes uniform, the plating film formed on the workpiece | work is excellent in the uniformity of the thickness of the circumferential direction.

It is the top view (a) which shows notionally a specific example of the plating apparatus which concerns on this embodiment, and sectional drawing (b) in the AA cross section of a top view. It is sectional drawing which shows the specific shape and dimension of the shaft-shaped workpiece | work used in the Example.

A plating apparatus according to an embodiment of the present invention will be described below.
In the plating apparatus according to this embodiment, the central axis of a shaft body (hereinafter also referred to as “shaft workpiece”) that is a member to be plated is set to a substantially vertical direction, and the plating solution is directed substantially vertically upward in the hollow portion. It arrange | positions in the flowing tubular member, and in one preferable aspect, it is for performing a plating (electrolysis), rotating a shaft-shaped workpiece, and forming a plating film on a shaft-shaped workpiece.

  The plating apparatus according to the present embodiment includes a tubular member having a substantially tubular shape, and the tubular member has a hollow portion whose both ends are open in the vertical direction. A portion where the plating film of the shaft-like workpiece is to be formed is included in the hollow portion. An insoluble anode is provided in the hollow portion. In a preferred embodiment, the insoluble anode forms at least a part of the inner surface of the hollow portion, and in a more preferred embodiment, all of the portion of the inner surface of the hollow portion of the tubular member facing the axial workpiece is formed from the insoluble anode. Become. The material of the insoluble anode is not particularly limited. Generally used titanium-platinum clad, iridium oxide, etc. may be used.

  Above the opening on the upper side in the vertical direction of the hollow portion of the tubular member, support means for realizing the holding of the shaft-like workpiece in the hollow portion is provided. The support means includes a contact portion that can be electrically connected to the shaft-like workpiece. The shaft-like workpiece can be electrically connected to an external power source through this contact portion to form a cathode in the plating solution.

  Although the specific configuration of the support means is arbitrary, it is preferable that the shaft-like workpiece is rotatable around the axis as described below. In a preferred aspect, the support means has a rotation mechanism that enables rotation around the axis of the shaft-like workpiece while maintaining electrical connection with the shaft-like workpiece at the contact portion. It is possible to form a plating film on the shaft-like workpiece while rotating. If the specific example of such a structure is shown, the center axis | shaft of a shaft-shaped workpiece and the rotation axis of a motor will correspond in the perpendicular direction uppermost part of a shaft-shaped workpiece using the clip connected with the rotating shaft of the motor. The current from an external power source is guided to the shaft-like workpiece by a power supply brush that is gripped by the motor and contacts the central axis of the motor.

  The plating apparatus according to the present embodiment includes plating solution jet means for supplying a plating solution into the hollow portion from the opening on the lower side in the vertical direction of the hollow portion of the tubular member. In one example, the plating solution jet means includes a pump and a discharge port for the plating solution from the pump that is disposed on the lower side in the vertical direction of the hollow portion of the tubular member and whose opening faces the upper side in the vertical direction. By this plating solution jet means, the plating solution flows vertically upward in the hollow portion of the tubular member. For this reason, the circumferential flow state of the shaft-like workpiece disposed in the hollow portion is almost uniform, and the variation of the plating film thickness is suppressed based on the variation of the plating solution flow state in the circumferential direction. Is done. In addition, air bubbles generated on the surface of the shaft-like workpiece due to the deposition of the plating metal can be smoothly detached from the shaft-like workpiece by the flow of the vertically upward plating solution. Occurrence is suppressed.

  In a preferred embodiment of the plating apparatus according to the present embodiment, the inner surface of the hollow portion of the tubular member is made of an insoluble anode, and the axial workpiece rotates around the axis during plating. For this reason, the fluctuation | variation in the circumferential direction of the flow state of a plating solution is further suppressed.

  Moreover, the fluctuation | variation of the circumferential direction of the axial workpiece | work of the electric field which an insoluble anode and the axial workpiece | work as a cathode produce is also suppressed. The central axis of the insoluble anode on the inner surface of the hollow portion of the tubular member and the central axis of the shaft-like workpiece coincide with each other in the design of the plating apparatus, but in reality, errors during processing or assembly of the plating apparatus (on the apparatus) The center axis of the insoluble anode and the center axis of the shaft-shaped workpiece do not exactly match due to the mounting error when mounting the shaft-shaped workpiece to the plating apparatus. When plating is performed without rotating the shaft-shaped workpiece, the deviation between the central axes causes variation in the electric field distribution in the circumferential direction of the shaft-shaped workpiece, and the plating metal is concentrated in a portion where the electric field is strong. That is, when the shaft-like workpiece is not rotated, a slight variation in the thickness of the circumferential plating film may be caused by an inevitable slight error on the apparatus and / or when the workpiece is attached. By performing plating while rotating the shaft-like workpiece, such a deviation of the central axis is leveled, and thus the variation in the thickness of the plating film in the circumferential direction is particularly suppressed.

  Furthermore, when the shaft-like workpiece is provided with a screw portion having a rotation center axis in the direction along the center axis, the thread valley portion is only in the direction in which the plating solution flows along the center axis of the shaft-like workpiece. The bubbles generated in the film are difficult to be detached, and the plating thickness of the thread valley portion tends to be thin. Therefore, by rotating the shaft-shaped workpiece and applying a circumferential component of the shaft-shaped workpiece in the plating solution flow direction, bubbles generated in the screw valley portion are easily detached, and the plating thickness of the screw valley portion is reduced. Can be increased. That is, when the shaft-like workpiece includes a screw portion having a rotation center axis in the direction along the center axis, the occurrence of plating defects in the screw portion is suppressed by rotating the shaft-like workpiece, which is particularly preferable. .

  In the vicinity of the opening on the upper side in the vertical direction of the hollow portion of the tubular member, a discharge structure is provided that allows the plating solution supplied into the hollow portion by the plating solution jet means to be discharged out of the tubular member. The specific configuration of the discharge structure is arbitrary as long as the plating solution can be discharged out of the tubular member as described above. An example of such a structure is an overflow structure.

  The plating apparatus according to this embodiment includes a circulating unit that supplies the plating solution discharged from the tubular member through the discharge structure to the plating solution jet unit. The specific configuration of the reflux means is arbitrary. As a specific example, there may be mentioned means comprising a cushion tank that receives the plating solution from the discharge structure, and a pipe that connects the plating solution in the cushion tank to the pump of the plating solution jet means.

  Here, when the flow rate or flow rate of the plating solution supplied by the plating solution jet means is large, there is a possibility that a part of the plating solution from the hollow portion of the tubular member will be close to the member constituting the support means. There is. Some members constituting the supporting means may include those that cannot corrode and perform the initial function when they come into contact with the plating solution (for example, a power supply brush). Therefore, the support means may include a shielding member for stably suppressing the plating solution supplied by the plating jet means from coming into contact with a member constituting the support means.

A specific example of the plating apparatus according to the present embodiment will be described in detail with reference to the drawings.
FIG. 1 is a top view (a) conceptually showing a specific example of the plating apparatus according to the present embodiment, and a sectional view (b) taken along the line AA of the top view.

  In the plating apparatus 100 according to this example, the shaft-shaped workpiece 8 is a shaft body whose rough shape is a hexagonal bolt shape. The top of the tubular member 7 is made of titanium having a cylindrical shape with both ends open, and the entire inner side surface 6 of the tubular member 7 functions as an insoluble anode. It is arranged to protrude. Here, the shaft-like workpiece 8 is inserted so as to penetrate the through-hole of the donut-shaped support member 1 having a through-hole substantially on a flat plate, and the lower side of the top of the shaft-like workpiece 8 and the penetration of the shaft-like workpiece 8 are inserted. The shaft-like workpiece 8 is supported by the support member 1 by coming into contact with the opening edge of the hole.

  Above the top of the shaft-shaped workpiece 8, a contact pressure lid 3 to which the contact portion 2 and the rotating electrode 4 above it are attached is provided. Contact pressurization is performed so that the contact pressurization lid 3 is urged in a direction in which the contact pressurization lid 3 approaches the support member 1 while maintaining contact between the contact portion 2 and the top of the shaft-shaped workpiece 8. The lid 3 is fixed to the support member 1. By doing in this way, it is suppressed that a plating solution enters into the top part side of the shaft-shaped workpiece 8 from the contact part of the shaft-shaped workpiece 8 and the supporting member 1. Therefore, in this example, the support means includes the support member 1 that also functions as a shielding member, the contact portion, the contact pressure lid 3, and the rotating electrode 4.

  Here, the arrangement relationship of each member will be described. The central axis of the tubular member 7, the central axis of the shaft-like workpiece 8, and the central axis of the rotary electrode 4 are arranged so as to substantially overlap. Therefore, when the rotating mechanism 5 is driven to rotate the contact pressure lid 3, the shaft-like workpiece 8 rotates with the rotation, and even if the shaft-like workpiece 8 rotates in this way, the insoluble anode and the shaft-like workpiece are rotated. The distance to 8 does not change. In other words, the electric field generated by the shaft-shaped workpiece 8 that forms the insoluble anode and the cathode does not vary depending on the rotation of the shaft-shaped workpiece 8.

  The plating solution supplied into the hollow portion of the tubular member 7 by the plating solution jet means (pump) from the lower opening of the tubular member 7 is discharged from the discharge structure 9 having an overflow structure, and the discharged plating solution is the cushion tank 10. To the plating solution jet means (pump). Thus, the plating solution flow in the hollow portion of the tubular member 7 is maintained. The capacity of the cushion tank 10 is arbitrary. It is set appropriately in consideration of the flow rate of the plating solution and the temperature range of the plating solution to be managed. As a standard, the volume of the tubular member 7 is 10 to 100 times, preferably 20 to 50 times.

  The higher the flow rate of the plating solution in the hollow portion of the tubular member 7, the thinner the diffusion layer on the surface of the shaft-like workpiece 8, making it easier to perform high-speed plating. Further, since hydrogen generated in the shaft-like workpiece 8 is easily detached from the surface of the shaft-like workpiece 8, the possibility of occurrence of pinholes is reduced.

  However, when the flow rate of the plating solution becomes excessively fast, turbulent flow is likely to occur in the plating solution in the vicinity of the surface of the shaft-shaped workpiece 8, particularly the portion where the shaft diameter changes. When the turbulent flow occurs, the deposition state of the plating in that portion becomes unstable, and the possibility that the quality of the obtained plating film is deteriorated increases.

  The preferable range of the flow rate of the plating solution that does not substantially generate turbulent flow is the inner diameter of the hollow portion of the tubular member 7 (turbulent flow is likely to occur when the inner diameter is small), the shaft diameter of the shaft-like workpiece 8 (hollow portion). Turbulent flow is likely to occur when the difference between the inner diameter of the workpiece and the inner diameter of the shaft is small), the degree of axial diameter change of the shaft-like workpiece 8 (turbulent flow is likely to occur if there is a sudden step), plating solution Composition (when the content is high, viscosity is likely to increase, and turbulence is likely to occur at this time), plating solution temperature (when temperature is low, viscosity is likely to increase, and turbulence is likely to occur at this time), etc. Should be set as appropriate.

  In addition, when the metal ion concentration in the plating solution is low, the plating solution flow rate may tend to decrease as the plating solution flow rate increases to some extent. It may be preferable to set an upper limit.

  The rotational speed of the shaft-like workpiece 8 is not particularly limited. If the linear velocity on the surface of the shaft-like workpiece is about 10 mm / second or more, the effect of suppressing the variation in the circumferential direction of the thickness of the plating film can be stably obtained. The linear velocity on the surface of the shaft-like workpiece is more preferably 20 mm / second or more, and particularly preferably 30 mm / second or more. Although depending on the composition of the plating solution and the like, it may be preferable to set it to 50 mm / second or more. The upper limit of the rotational speed of the shaft workpiece 8 is not definitely defined. If it becomes too fast, the vector sum with the plating solution flow rate will increase, increasing the possibility of turbulence, and the mechanism for increasing the number of rotations will become larger and the energy required for rotation will increase. It may be set as appropriate in consideration.

As an example, when the inner diameter of the tubular member 7 is 50 mm and the shaft diameter of the shaft-shaped workpiece is 18 mm, the flow rate of the plating solution is in the range of 0.10 m / second to 1.5 m / second, and the plating solution is described later. In the case of a plating solution having a suitable composition, the range is from 0.10 m / second to 1.0 m / second, and the linear velocity due to rotation of the shaft-shaped workpiece 8 is from 10 mm / second to 200 mm / second, When the plating solution is a plating solution having a suitable composition to be described later, an axial workpiece having a shaft diameter change (constriction, protrusion, tap, etc.) of several mm can be obtained if the plating solution is in the range of 10 mm / second to 30 mm / second. Even when plating is performed under high electrolysis conditions of 20 A / dm ² or more and 100 A / dm ² or less with respect to 8, a plating film with stable quality can be obtained.

Hereinafter, a plating solution suitable for performing a plating process using the plating apparatus 100 according to the present embodiment (hereinafter also referred to as “the present plating solution”) will be described.
The present plating solution is a zinc sulfate-based plating solution containing a water-soluble zinc-containing substance and polyethyleneimine and having a pH of 1 or more and 2 or less. Here, the zinc-based plating solution is a generic term for a zinc plating solution that is a plating solution for forming a zinc plating film and a zinc alloy plating solution that is a plating solution for forming a zinc alloy plating film. When this plating solution is a zinc alloy plating solution, it may further contain a water-soluble metal-containing substance. Specific examples of the metal element contained in the water-soluble metal-containing material include one or more selected from the group consisting of iron and nickel.

(Water-soluble zinc-containing substance)
The plating solution contains a water-soluble zinc-containing substance. In the present specification, the water-soluble zinc-containing substance is a source of zinc deposited as a zinc-based plating film, and is one or more selected from the group consisting of zinc cations and water-soluble substances containing the same. Refers to the ingredients.

  Examples of the raw material for supplying the water-soluble zinc-containing material to the plating bath (also referred to as “zinc source” in the present invention) include zinc sulfate, zinc oxide, and zinc chloride. Among these, zinc sulfate is preferable as a zinc source. This plating solution does not contain chloride-containing substances such as chloride ions or substances containing the same from the viewpoint of reducing the possibility that the stability of the plating solution is lowered or the film quality of the plating film is lowered. Is preferred.

The zinc equivalent content of the water-soluble zinc-containing substance in the plating solution is preferably 70 g / L or more and 100 g / L or less. When the zinc equivalent content of the water-soluble zinc-containing substance is less than 70 g / L, even if the plating apparatus 100 according to this embodiment is used, a high current density, specifically about 20 A / dm ² or more, is good. It is difficult to stably form a plating film having a good appearance. On the other hand, when the zinc equivalent content of the water-soluble zinc-containing substance in the present plating solution is over 100 g / L, the viscosity of the plating solution increases, and it is difficult to stably form a plating film with a good appearance. It becomes. From the viewpoint of enabling more stable formation of a plating film with high productivity and good appearance, the zinc equivalent content of the water-soluble zinc-containing substance of the present plating solution is 75 g / L or more and 95 g / L or less. It is preferable. Considering the viewpoint of alleviating the load on the wastewater treatment and the good throwing power, the zinc equivalent content of the water-soluble zinc-containing substance of the plating solution is preferably 75 g / L or more and 90 g / L or less.

(Water-soluble metal-containing substance)
When this plating solution is a zinc alloy plating solution, it contains a water-soluble metal-containing substance. In the present specification, the water-soluble metal-containing substance is a source of metals other than zinc contained in the zinc alloy plating film, and is selected from the group consisting of metal element cations and water-soluble substances containing the metal element cations. It refers to one or more components. Examples of the metal element contained in the water-soluble metal-containing material include iron and nickel. In a preferred example, the metal element contained in the metal-containing material is selected from the group consisting of iron and nickel.

The raw material for supplying the water-soluble metal-containing substance to the plating bath (also referred to as “metal source” in the present invention) may be appropriately selected according to the type of metal element contained in the water-soluble metal-containing substance. For example, when the metal element contained in the water-soluble metal-containing material is iron, that is, when the zinc alloy plating bath contains the water-soluble iron-containing material, Fe ₂ (SO ₄ ) ₃ · 7H ₂ O, FeSO ₄ · 7H ₂ O, Fe (OH) ₃ , FeCl ₃ · 6H ₂ O, FeCl ₂ · 4H ₂ O and the like are exemplified as iron sources. When the metal element contained in the water-soluble metal-containing material is nickel, that is, when the zinc alloy plating bath contains a water-soluble nickel-containing material, NiSO ₄ .6H ₂ O, NiCl ₂ .6H ₂ O, Ni (OH) ₂ or the like is exemplified as the nickel source.

  The metal equivalent content of the water-soluble metal-containing substance in the zinc-based plating bath according to the present embodiment is appropriately set according to the intended composition of the zinc alloy plating. When the zinc-based plating bath contains a water-soluble iron-containing substance, it is exemplified that the content in terms of iron of the water-soluble iron-containing substance is about 0.8 g / L or more and 2 g / L or less. In the case where the zinc-based plating bath contains a water-soluble nickel-containing substance, the nickel-converted content of the water-soluble nickel-containing substance is exemplified to be about 10 g / L or more and 17 g / L or less.

(Polyethyleneimine)
Since the plating apparatus 100 according to this embodiment includes an insoluble anode, electrolysis of components contained in the plating solution tends to occur at the anode. From the viewpoint of exhibiting excellent characteristics even in such a chemically active environment, the present plating solution contains polyethyleneimine as an organic additive.

The weight average molecular weight of polyethyleneimine contained in the plating solution is 1500 or more and 2500 or less. When the weight average molecular weight is less than 1500, specifically 1000, for example, foreign matter is adsorbed to the shaft body (shaft workpiece 8) which is a non-plated member under the condition of high current density (for example, about 50 A / dm ² or more). (Hereinafter, this phenomenon is also referred to as “foreign matter adsorption”), the deposition state of the plating becomes unstable, and an oxide of the plating metal is deposited (hereinafter, this phenomenon is also referred to as “abnormal precipitation”). ) And the appearance of the plating film deteriorates. On the other hand, when the weight average molecular weight of polyethyleneimine is 2500 or more, specifically, for example, 3000, the above-described foreign matter adsorption and abnormal precipitation occur due to relatively low current density (for example, about 30 A / dm ² ). The appearance of the film deteriorates.

  The content of polyethyleneimine in the plating solution is 0.1 g / L or more and 10 g / L. When the content is less than 0.1 g / L, it is difficult to obtain the effect of containing polyethyleneimine, and the appearance of the plating film is deteriorated. On the other hand, even if the content of polyethyleneimine exceeds 10 g / L, it is difficult to obtain an effect commensurate with the content (for example, improvement in plating deposition rate), which is not preferable from an economical viewpoint. Moreover, the gloss of the obtained plating film may become excessively high, and it may not be possible to confirm the presence or absence of plating film formation, or the wastewater treatment load may increase.

(PH)
The pH of the plating solution is 1 or more and 2 or less. When the pH is excessively low, dissolution of the plated metal proceeds simultaneously with the deposition of the plating, so that the apparent deposition rate of the plating film is reduced and it is difficult to perform high-speed plating. On the other hand, when the pH is excessively high, the deposition state at a high current density, particularly about 80 A / dm ² or more becomes unstable, and the appearance of the plating film deteriorates. From the viewpoint of more stably forming a plating film having a good appearance without reducing the deposition rate of the plating film, the pH of the present plating solution is preferably 1.0 or more and 2.0 or less, and 1.5 ± 0.3 is more preferable, and 1.5 ± 0.2 is particularly preferable.

  When the plating solution is a zinc alloy plating solution, the plating solution contains a complexing agent such as a chelating agent for stabilizing the metal ions related to the alloy metal. In this case, plating can be performed. That is, since the present plating solution has a pH of 1 or more and 2 or less, even if the present plating solution is a zinc alloy plating solution, the composition of the plating solution is simplified (specifically, constituent components of the plating solution). (Reducing the number) has been achieved. As described above, since the plating apparatus 100 according to the present embodiment employs an insoluble anode, the components contained in the plating solution are easily electrolyzed. From the viewpoint of reducing the possibility that the substance generated by this electrolysis will adversely affect the plating characteristics (appearance, etc.), it is preferable that the present plating solution has a simple composition, that is, has a small number of contained components.

  In addition, what is necessary is just to perform adjustment of pH of this plating solution using a well-known acid and an alkali. As described above, since it is preferable to simplify the composition of the plating solution, it is preferable to use sulfuric acid as the acid.

(Other ingredients)
As described above, since the plating apparatus 100 according to the present embodiment employs an insoluble anode, the components contained in the plating solution are easily electrolyzed. Therefore, it is preferable that the present plating solution reduce the number of components other than the above components as much as possible. For example, it is preferable that the zinc source or the metal source is a sulfate, and the type of metal ion counter anion contained in the plating solution is only a sulfate ion. In addition, this plating solution may contain an antioxidant, an antifoaming agent, an organic additive other than polyethyleneimine, and a complexing agent in the case of a zinc alloy plating solution, but its content should be small. Is preferable, and it is more preferable not to contain these components. As the number of components contained in the plating solution is reduced as described above, the load of the waste solution treatment is also reduced. Therefore, the treatment cost including the waste solution treatment is reduced by reducing the number of components contained in the plating solution. be able to.

(Plating conditions)
In forming a zinc-based plating film by electroplating using the present plating solution, the current density is preferably set to 20 A / dm ² or more and 100 A / dm ² or less. When the current density is less than 20 A / dm ² , even when the plating apparatus 100 according to the present embodiment is used, the deposition rate does not increase and it is difficult to improve productivity. On the other hand, when the current density exceeds 100 A / dm ² , a plating film having an excellent appearance can be stably formed even if the molecular weight or content of polyethyleneimine or the pH is adjusted as described above. It becomes difficult to form.

  Moreover, when forming a zinc-type plating film by electroplating using this plating solution, it is preferable that the temperature of a plating solution shall be 30 degreeC or more and 50 degrees C or less. When the temperature of the plating solution is less than 30 ° C., the current density dependence of the residual stress of the obtained plating film becomes remarkable, and when the current density increases, a stronger tensile stress tends to remain in the plating film. From the viewpoint of more stably lowering the current density dependence of the residual stress of the plating film and facilitating obtaining a plating film with little characteristic change in a wide current density range, the temperature of the plating solution is set to 35 ° C. or higher. It is preferable. On the other hand, when the plating solution temperature exceeds 50 ° C., it is required that the members constituting the plating apparatus 100 according to the present embodiment have heat resistance, and the equipment load increases. The residual stress of the plating film is preferably a slight amount of compressive stress from the viewpoint of increasing the film strength. When it is particularly desired to obtain such a plating film, the plating temperature is preferably 40 ° C. ± 5 ° C.

  When this plating solution is used, the conditions for the flow rate of the plating solution and the rotation condition of the shaft-like workpiece (hereinafter referred to as “operating conditions”) in the plating apparatus 100 according to this embodiment can be relaxed. By relaxing these operating conditions, turbulent flow is less likely to occur in the plating solution in the vicinity of the surface of the shaft-like workpiece, so that the phenomenon that the deposition state of plating becomes unstable is less likely to occur. Therefore, when the operating conditions are relaxed, the quality of the plating film formed on the shaft-like workpiece is not easily lowered.

  In addition, by reducing the operating conditions, the initial cost and the running cost of the plating process are reduced as described below. First, since it is not necessary to particularly increase the specifications of components (pump, motor, etc.) constituting the plating apparatus 100, the manufacturing cost of the apparatus can be suppressed. Secondly, since the power required for operating the apparatus is reduced with the relaxation of the operating conditions, the cost required for forming the plating film on the shaft-like workpiece is also reduced. Third, the durability of the device is improved by reducing the operating conditions.

(Characteristics of plating film)
When electroplating is performed using the plating apparatus 100 and the present plating solution according to the present embodiment under the above-described preferable conditions, a semi-gloss plating film can be obtained in a wide current density range. When the plating film is semi-glossy, it is preferable because it can be easily confirmed visually that the plating film is formed on the member to be plated having gloss. Further, as described above, the absolute value of the residual stress of the plating film can be reduced by setting the plating temperature within an appropriate range. When the absolute value of the residual stress is large, particularly when a strong tensile stress remains, the plating film is easily peeled off or stress corrosion of the plating film is likely to occur.

  The result of plating the shaft-like workpiece 8 using the plating apparatus 100 described above is shown below.

Example 1
A shaft-like workpiece (effective treatment area 1.22 dm ² ) having the shape shown in FIG. 2 was held inside the tubular member made entirely of titanium and having a diameter of 50 mm and a wetted part of 300 mm in length using a support member. At this time, the shaft-like workpiece was disposed so that the range A (length: 200 mm) in FIG. 2 was opposed to the insoluble anode on the inner surface of the tubular member.

The plating tank was filled with 15 L of plating solution, and the solution temperature was maintained at 45 ° C. The composition of the plating solution was as follows.
Zinc content of water-soluble zinc-containing material: 100 g / L (zinc source: zinc sulfate)
Ammonium sulfate: 30 g / L
Polyethyleneimine (molecular weight 7000): 0.5 g / L
Solvent: water pH: 2.5

  The plating solution in the plating tank is jetted into the tubular member from the discharge port arranged below the lower end of the opening tubular member by using a pump to generate a plating solution flow of 1 m / second inside the tubular member. It was. The plating solution flow spouted from the opening at the upper end of the tubular member collides with the supporting member that also serves as a shielding member, and the gap provided between the supporting member and the upper end of the tubular member serves as a discharge structure toward the outer surface of the tubular member. And was stored in a cushion tank (capacity 15 L) arranged to include this outer surface. The plating solution in the cushion tank was allowed to flow out from the drain provided on the lower surface of the cushion tank to the plating tank. In this way, the plating solution was circulated through the path of the plating tank, pump, discharge port, tubular member, discharge structure, cushion tank, and plating tank. The temperature of the plating solution during the circulation was controlled at 45 ° C.

  The shaft-like work is rotated at 180 rpm (the maximum linear velocity at the portion in contact with the plating solution is 170 mm / s) by the rotation mechanism provided above the support member, and the shaft-like work is rotated through the rotation electrode provided above the support member. A voltage can be applied to the workpiece.

In this state, the plating process was performed for 30 seconds by setting the current between the cathode made of the axial workpiece and the anode made of the tubular member so that the current density at the cathode was 60 A / dm ² .

The shaft-like workpiece after the completion of the plating treatment was taken out, and the plating thickness at the body portion, the constricted portion, and the thread and valley of the threaded portion was measured. Moreover, about the trunk | drum part and the constriction part, the plating thickness was measured in the circumferential direction, and the ratio ((maximum plating thickness-minimum plating thickness) / average plating thickness) of the variation width of the plating thickness to the average plating thickness was obtained.
Table 1 shows the measurement results regarding the obtained plating thickness.

(Example 2)
Except for changing the plating solution in Example 1 to the following composition, the same operation as in Example 1 was performed on the shaft-shaped workpiece, and the plating thickness of the obtained shaft-shaped workpiece was measured.
Zinc content of water-soluble zinc-containing substances: 100 g / L (zinc source: zinc chloride)
YUKEN INDUSTRY CO., LTD. METASU MZ-996A1: 60ml / L
Solvent: Water Table 1 shows the measurement results regarding the obtained plating thickness.

( Comparative Example 1 )
Except that the shaft-shaped workpiece was not rotated in Example 1, the same operation as in Example 1 was performed on the shaft-shaped workpiece, and the plating thickness of the obtained shaft-shaped workpiece was measured.
Table 1 shows the measurement results regarding the obtained plating thickness.

Example 4
Except that the shaft-shaped workpiece was not rotated in Example 1, the same operation as in Example 1 was performed on the shaft-shaped workpiece, and the plating thickness of the obtained shaft-shaped workpiece was measured.
Table 1 shows the measurement results regarding the obtained plating thickness.

(Example 5)
A shaft-like workpiece (effective treatment area 1.22 dm ² ) having the shape shown in FIG. 2 was held inside the tubular member made entirely of titanium and having a diameter of 50 mm and a wetted part of 300 mm in length using a support member. At this time, the shaft-like workpiece was disposed so that the range A (length: 200 mm) in FIG. 2 was opposed to the insoluble anode on the inner surface of the tubular member.

The plating tank was filled with 15 L of plating solution, and the solution temperature was maintained at 40 ° C. The composition of the plating solution was as follows.
Zinc content of water-soluble zinc-containing substances: 85 g / L (zinc source: zinc sulfate)
Polyethyleneimine (molecular weight 2000): 1 g / L
Solvent: water pH: 1.5

  The plating solution in the plating tank is jetted into the tubular member from the discharge port arranged below the lower end of the opening tubular member using a pump, and a plating solution flow of 0.13 m / sec is made inside the tubular member. Generated. The plating solution flow spouted from the opening at the upper end of the tubular member collides with the supporting member that also serves as a shielding member, and the gap provided between the supporting member and the upper end of the tubular member serves as a discharge structure toward the outer surface of the tubular member. And was stored in a cushion tank (capacity 15 L) arranged to include this outer surface. The plating solution in the cushion tank was allowed to flow out from the drain provided on the lower surface of the cushion tank to the plating tank. In this way, the plating solution was circulated through the path of the plating tank, pump, discharge port, tubular member, discharge structure, cushion tank, and plating tank. The temperature of the plating solution during the circulation was controlled at 40 ° C.

  The shaft-like workpiece is rotated at 20 rpm (the maximum linear velocity at the portion in contact with the plating solution is 20 mm / s) by the rotation mechanism provided above the support member, and the shaft-like work is rotated through the rotation electrode provided above the support member. A voltage can be applied to the workpiece.

In this state, the plating process was performed for 30 seconds by setting the current between the cathode made of the axial workpiece and the anode made of the tubular member so that the current density at the cathode was 60 A / dm ² .
Thereafter, the plating thickness was measured in the same manner as in Example 1. Table 1 shows the measurement results regarding the obtained plating thickness.

(Example 6)
Based on the plating solution prepared in Example 5, plating solutions 6-1 to 6-8 having different molecular weight (weight average molecular weight) and pH of polyethyleneimine were prepared. The plating solution 6-1 had the same composition as the plating solution prepared in Example 5.
A liquid circulation type hull cell tester (manufactured by Yamamoto Metal Tester Co., Ltd .: Smart Hull Cell B-53-SM) having a stirrer rotation speed of 500 rpm was prepared. Titanium-platinum clad as an anode having a length of 64 mm, a width of 64 mm, and a thickness of 1 mm, and a member to be plated (cathode) of 67 mm, a width of 100 mm, and a thickness of 0.2 mm at predetermined positions in the plating tank of this tester As a copper plate. Each of the plating solutions 6-1 to 6-8 was placed in the plating tank until the liquid level reached a predetermined height. The anode and cathode were connected to a plating power source, and electroplating was performed under the following conditions to obtain a zinc-based plated member having a zinc plating film.
Current: 20A
Energizing time: 10 seconds Plating bath temperature: 40 ° C
In the above current, the current density of the cathode scope ranged from 100A / dm ² of 10A / dm ^2.

In the obtained zinc-based plated member, the deposition state of the plating film at a position where the current density was 100 A / dm ² was observed. Moreover, the deposition state of the plating film was observed at a position where the current density decreased by 10 A / dm ² from that position (current density at the final evaluation position: 10 A / dm ² ). The observation results were evaluated according to the following criteria.
1: Abnormal precipitation or adhesion of foreign matter was not observed, and the plating film had a good appearance 2: Abnormal precipitation or adhesion of foreign matter was not observed, but the plating film was excessively glossy, confirming the formation of the plating film Hard to resist 3: Abnormal precipitation and adhesion of foreign matter were observed, and the appearance of the plating film was poor.

(Example 7)
For each of the plating solutions 6-1 to 6-4 prepared in Example 6, FeSO ₄ · 7H ₂ O is formed so that the iron equivalent content of the water-soluble iron-containing substance is 1.3 g / L. Plating solutions 7-1 to 7-4 to which an iron source was further added were prepared.
Using these plating solutions 7-1 to 7-4, electroplating was performed in the same manner as in Example 6 to obtain a zinc-based plated member having a zinc-iron alloy plating film.
Evaluation similar to Example 6 was performed with respect to this zinc-based plating member. The evaluation results are shown in Table 3.

(Example 8)
A nickel source composed of NiSO ₄ .6H ₂ O so that the iron equivalent content of the water-soluble nickel-containing substance is 15 g / L for each of the plating solutions 6-1 to 6-4 prepared in Example 6. Were further added to the plating solutions 8-1 to 8-4.
Using these plating solutions 8-1 to 8-4, electroplating was performed in the same manner as in Example 6 to obtain a zinc-based plated member having a zinc-nickel alloy plating film.
Evaluation similar to Example 6 was performed with respect to this zinc-based plating member. The evaluation results are shown in Table 4.

Example 9
Using the plating solution prepared in Example 5, electroplating was performed while changing the plating conditions as follows, and the measurement surface (8 × 25 mm) of a plating film stress measuring apparatus (manufactured by Yamamoto Kakin Tester Co., Ltd .: Plate Laboratory ST) A galvanized film was formed on a copper plate with a square strain gauge.
Plating temperature: 20 ° C, 30 ° C, 35 ° C, 40 ° C, 45 ° C, 50 ° C
Current density: 10A / dm ² from 50A / dm ² to 10A / dm ² per Plating time: 15 seconds plating solution stirring at: stirrer rotation speed 500rpm
Table 5 shows the results of measuring the residual stress of the plating film on the measurement surface. In Table 5, a positive value was shown when the residual stress of the plating film was a tensile stress, and a negative value was shown when it was a compressive stress.

Claims (6)

A device for forming an electroplating film on a shaft body (except for a device for pulse plating),
A tubular member having a hollow portion including a portion where a plating film is to be formed in the shaft body which is a member to be plated and having both ends opened in the vertical direction;
A support means provided above the opening of the vertical upper end of the hollow portion to hold the shaft body in the hollow portion;
A plating solution jet means for supplying a plating solution into the hollow portion from the opening at the lower end in the vertical direction of the hollow portion;
A discharge structure that is provided in the vicinity of the opening at the upper end in the vertical direction of the hollow portion and that allows the plating solution supplied into the hollow portion by the plating solution jetting means to be discharged out of the tubular member, and the tubular through the discharge structure A circulating means for supplying the plating solution discharged from the member to the plating solution jet means;
The support means includes a contact portion that can be electrically connected to the shaft body, and the tubular member includes an insoluble anode in a hollow portion thereof .
The support means includes a rotation mechanism that enables rotation around the axis of the shaft body while maintaining electrical connection with the shaft body at the contact portion, and the rotation mechanism allows the shaft body to be linear speed of the surface of the shaft body Ru is possible to form the plating film while rotating such that the 10 mm / sec or more, an apparatus for forming an electroplated coating on the shaft. An insoluble anode provided on the inner surface of the hollow tubular member having hollow portions having openings at both ends in the vertical direction, and a supporting means for holding the shaft body to be plated in the hollow portion of the tubular member. A method of forming a plating film on the shaft body by applying a voltage between the shaft portion and a contact portion that enables electrical connection with the shaft body (excluding a method of pulse plating). And
A plating solution jet means for supplying a plating solution into the hollow portion from the opening at the lower end in the vertical direction of the hollow portion, and the hollow by the plating solution jet means provided in the vicinity of the opening at the upper end portion in the vertical direction of the hollow portion. The discharge structure that allows the plating solution supplied in the section to be discharged out of the tubular member, and the circulating means that supplies the plating solution discharged from the tubular member through the discharge structure to the plating solution jet means, the hollow It is possible to continuously supply the plating solution into the part during electroplating ,
The shaft body is provided on the surface of the shaft body by a rotation mechanism provided on the support means and capable of rotating around the axis of the shaft body while maintaining an electrical contact with the shaft body at the contact portion. the linear velocity of Ru is possible to form a plating film on the shaft on the body while rotating such that the 10 mm / sec or more,
A manufacturing method of a shaft having a plating film. The plating solution is a zinc sulfate-based plating solution containing a water-soluble zinc-containing substance and polyethyleneimine,
The content of the water-soluble zinc-containing substance is 70 g / L or more and 100 g / L or less in terms of zinc,
The polyethyleneimine has a weight average molecular weight of 1500 or more and 2500 or less, and its content is 0.1 g / L or more and 10 g / L,
The plating solution has a pH of 1 or more and 2 or less,
Plating temperature is 30 ° C. or higher 50 ° C. or less, and a current density of 20A / dm ² or more 100A / dm electroplating ² under the following conditions takes place, a manufacturing method of claim 2. The plating solution further contains a water-soluble metal-containing substance,
The manufacturing method according to claim 3 , wherein the metal element contained in the water-soluble metal-containing material is one or more selected from the group consisting of iron and nickel. A zinc-based plating film is formed on the shaft body by performing electroplating using the apparatus according to claim 1 under the conditions of a plating temperature of 30 ° C. or more and 50 ° C. or less and a current density of 20 A / dm ² or more and 100 A / dm ² or less. A plating solution for forming
The plating solution is a zinc sulfate-based plating solution containing a water-soluble zinc-containing substance and polyethyleneimine,
The content of the water-soluble zinc-containing substance is 70 g / L or more and 100 g / L or less in terms of zinc,
The polyethyleneimine has a weight average molecular weight of 1500 or more and 2500 or less, and its content is 0.1 g / L or more and 10 g / L,
The plating solution has a pH of 1 or more and 2 or less. The plating solution further contains a water-soluble metal-containing substance,
The plating solution according to claim 5 , wherein the metal element contained in the water-soluble metal-containing material is one or more selected from the group consisting of iron and nickel.

Images