JPH03243798A - Supplying method for iron ion in electroplating iron-based alloy - Google Patents

Abstract

PURPOSE:To always stabilize the concn. of Fe ion in plating liquid at constant value by circulating the plating liquid in the specified conditions through a dissolving tank of Fe chips for replenishing Fe ions contained in the plating liquid in an Fe-based plating device equipped with an insoluble anode. CONSTITUTION:In order to replenish reduction of Fe<2+> ion in plating liquid M in an Fe-based plating device equipped with an insoluble anode, this plating liquid M whose Fe<2+> ions are reduced is supplied from an inlet 12 in the lower part of a dissolving tank 1 packed with Fe chips T and raised at the relative velocity of at least >=3 m/min through the Fe chip layer T. The Fe chips are dissolved and the concn. of Fe<2+> is raised to the specified % and this plating liquid is circulated and supplied to the plating tank. In this case, the relation of b/a <=3 is held between the diameter (a) of the Fe chip layer in the Fe chip packing tank 1 and height (b). Further, the concn. of Fe<3+> of the plating liquid in the inlet 12 is regulated to >=5 g/l. Thereby Fe chips T are rapidly dissolved into plating liquid. The Fe chips pulverized by dissolution are discharged from the dissolving tank 1 by rotation of a screw rod 8. Thereby passage of plating liquid supplied from the inlet 12 is enhanced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for supplying iron ions in iron-based alloy electroplating, and more specifically, to a method for stabilizing the amount of iron chips dissolved in an iron packed bed in an iron chip melting chamber. The present invention relates to a method of supplying iron ions to an iron-based alloy electroplating tank by dissolving Fe'+ with priority given to reduction.

[Prior Art] Generally, in electroplating using an insoluble anode, the metal to be plated is dissolved in the plating solution in order to supply the metal ions that decrease as the plating progresses to the plating solution. It's coming.

However, in iron-based alloy electroplating using an insoluble anode, Fe" ions are oxidized by Fe needle bioions at the anode, and when the concentration of Fe" ions increases, the plating current efficiency decreases and the appearance of the plating surface deteriorates. Problems such as this arise. Therefore, when Fe''+ ions are supplied to the plating tank, it is necessary to ionize Pe'30 ions in the plating solution at the same time.

The dissolution reaction of metallic iron by the plating solution includes two reactions: a hydrogen generation dissolution reaction and an Fe3+ ion reduction dissolution reaction, and these two reactions coexist.

In addition, when comparing electrochemically the hydrogen generation dissolution reaction and the Fe3+ ion reduction and dissolution reaction of metallic iron, it is found that the Fe3 ion reduction and dissolution reaction is usually more likely to occur than the redox potential which is the driving force of the reaction. Recognize.

In fact, if a certain amount of Fe'+ ions exist,
Since the Fe5f ion reduction and dissolution reaction takes precedence, Fe'→
The ion reduction efficiency is 90% or more, and the amount of iron dissolved is large and stable. This Fe′+ ion reduction efficiency is the ratio of the Fe 3 size ion reduction and dissolution reaction to the iron dissolution reaction.

However, when the Fe3+ ion concentration becomes low, there is a problem that the amount of dissolved iron and the Fe3+ ion reduction efficiency decrease. In other words, when the iron chips are dissolved by pressurizing the plating solution from one side of the iron dissolution tank, a reduction and dissolution reaction of Fe3+ ions occurs, so the Fe3+ ion concentration in the plating solution increases from the inlet side to the outlet side of the iron dissolution tank. It gradually decreases over time.

Furthermore, if the iron chips in the iron melting tank are melted continuously over a long period of time, the iron chips may be unevenly melted due to the uneven flow of the plating solution flowing through the iron packed bed, and the Fe" ion reduction efficiency may be reduced. A problem arises in that the amount of dissolution decreases.The cause of this uneven flow of the plating solution flowing through the iron packed bed is that it gets between the iron chips that have become finer due to melting or the iron chips that have a larger shape, resulting in uneven voids. This is thought to be due to the formation of

When iron chips in an iron melting tank are melted for a long time, the Fe3" ion reduction efficiency and amount of iron dissolution decreases. In addition to the uneven flow of the plating solution, hydrogen gas generated by the dissolution reaction of the iron chips is also a cause. It adheres to the iron chip surface and F
This is thought to inhibit the diffusion of e3+ ions to the surface of the iron chip.

[Problems to be Solved by the Invention] The present invention is based on the inventor's extensive research in view of the various problems encountered when supplying iron ions to the plating tank during the conventional iron-based alloy electroplating described above. As a result of repeated studies, we determined the ratio between the diameter and height of the iron chip dissolution layer,
In addition, by setting the Fe3+ ion concentration of the plating solution on the side where the iron chips are melted and the relative flow rate between the iron chips and the plating solution to be above a certain value, the iron chips in the iron chip dissolution layer can be dissolved. The amount is stabilized, and Fe
'We have developed an iron ion supply method for iron-based alloy electroplating that can give priority to ion reduction.

Means for Solving Problem E] The method for supplying iron ions in iron-based alloy electroplating according to the present invention includes: (1) In iron-based alloy electroplating, filling a plating bath with iron chips to supply iron ions; When melting iron chips by pressurizing plating solution from below into the iron chip dissolving tank, the diameter a of the cylindrical soft iron chip packed bed in the iron chip dissolving tank is
The relationship between (mm) and height b (IIIll) is b /
a≦3, the p e3 + concentration in the plating solution on the inlet side of the iron chip dissolution tank is 5 g/l or more, and the relative flow rate between the iron chips in the iron chip dissolution tank and the plating solution press-fitted is 3 m
The first invention provides a method for supplying iron ions in electroplating of iron-based alloys, characterized in that the iron ions are supplied to the plating bath in order to supply iron ions to the plating bath in electroplating of iron-based alloys. When melting iron chips by pressurizing plating solution from below into a filled iron chip dissolving tank, the diameter a of the cylindrical soft iron chip filling bed in the iron chip dissolving tank is
(mm) and height b (mm) satisfies b/a≦3, and the Fe content in the plating solution at the entrance side of the iron chip dissolution tank is
3+ concentration is 5 g/l or more, the relative flow velocity between the iron chips in the iron chip dissolving tank and the plating solution press-in is 3 m/min or more, and while the iron chips are melting in the iron chip dissolving tank, from the bottom of the iron chip dissolving tank This invention consists of two inventions, the second invention being a method for supplying iron ions in iron-based alloy electroplating, which is characterized by removing iron chips and moving an iron chip packed bed.

The method for supplying iron ions in iron-based alloy electroplating according to the present invention will be described in detail below.

When supplying iron ions to an iron-based alloy electroplating tank, the iron chip dissolution tank is filled with iron chips, and the plating solution is pumped from the bottom of the dissolution tank and passed through the iron chip filling layer. The iron chips are melted and sent to a plating tank.

In this case, the iron dissolution reaction is P e+ 2 Fe"-+ 3 Fe" (F e3
+Reduction and dissolution reaction)Fe+H''-+Pe'' +Ht (Hydrogen generation and dissolution reaction).

Since the Fe'+ ion reduction and dissolution reaction occurs preferentially, the amount of iron chip dissolution largely depends on the Fe3+ ion concentration.

FIG. 1 shows the relationship between the Fe3+ ion concentration at the entrance side of the iron chip dissolution tank and the amount of iron chips dissolved, and the higher the Fe'+ ion concentration, the greater the amount of iron chips dissolved.

Therefore, it is clear from FIG. 1 that in order to increase the amount of iron chips dissolved, the Fe3+ ion concentration at the entrance side of the iron chip dissolution tank must be 5 g/l or more. In FIG. 1, the amount of iron chips filled is 500 kg, and the relative flow velocity between the iron chips and the plating solution is 10 m/l1in.

Next, as a result of investigating the dissolution conditions that affect the Fe 3 + ion reduction efficiency, it was found that the Fe" ion concentration has a large influence. In other words, when the P e" ion concentration decreases, the hydrogen generation dissolution reaction increases. In particular, when the plating solution passes through an iron chip packed bed, the Fe3 reduction efficiency becomes low.
Since the Fe3+ ion reduction and dissolution reaction occurs, the Fe3+ ion concentration gradually decreases from the inlet side to the outlet side of the iron chip packed bed. Therefore, the Fe3+ ion reduction efficiency at the outlet side of the iron chip packed bed becomes considerably low, and the total Fe3+ ion reduction efficiency from the inlet side to the outlet side decreases. In this case, it is thought that such a tendency becomes more remarkable as the iron chip filling layer becomes higher.

Figure 2 shows the height of the iron chip packed bed/diameter of the iron packed bed and F e
It shows the relationship with 3Y-on reduction efficiency, and when the ratio of height of iron chip packed bed/diameter of iron chip packed bed exceeds 3, F
The e3+ ion reduction efficiency is significantly reduced. Therefore, Fe
It is clear from FIG. 2 that in order to increase the 3+ ion reduction efficiency, the ratio of the height of the iron chip packed bed/the diameter of the iron chip packed bed must be 3 or less. In Figure 2, the Fe3+ ion concentration at the entrance side of the iron chip melting tank is 8.
g/l, and the diameter of the iron chip packed bed is 400mmφ.

Furthermore, the relative flow rate of the plating solution for dissolving the iron chips in the iron chip dissolution tank is: 3+
/ll1n or more, and if it is less than 3ffl/win, the hydrogen gas generated by the iron dissolution reaction remains attached to the surface of the iron chip and does not desorb, which inhibits the diffusion of Fe3+ ions to the surface of the iron chip. As a result, both Fe'+ ion reduction efficiency and iron chip dissolution amount become low.

An apparatus for carrying out the method for supplying iron ions in iron-based alloy electroplating according to the present invention will be explained with reference to FIG.

Iron chips T are transferred from iron chip hopper 2 to iron chip melting tank L.
Fill it. Next, a plating solution M for dissolving the iron chips T is forced into the plating solution M supply port 12 using a pump (not shown), and is discharged from the plating solution M overflow port It for circulation use. dissolve.

Further, the screw rod 8 is rotated by the electric motor 7 and the speed reducer 6, and the iron chips which have been melted and made into fine particles are extracted from the lower part of the iron chip melting tank 1 by the screw and received in the sludge bag 9.

In this way, by extracting the iron chips from the lower part of the iron chip dissolving tank, the iron chip packed bed is moved downward.

Therefore, fine iron chips are removed by melting,
Since the iron chip particle size in the cross section in the iron chip packed bed becomes uniform, there is no uneven flow of the plating solution press-ined to dissolve the iron chips. Furthermore, since the iron chip moves, hydrogen gas adhering to the iron chip is easily desorbed.

Therefore, the amount of dissolved iron chips is stabilized, and the reduction efficiency of Fe3+ ions can be improved. Note that the iron-based alloy electroplating solution is a sulfuric acid bath, p) (is O ~ 3, bath temperature 4
The temperature shall be 0 to 80°C.

The shape of the iron chip may be granular, plate-like, linear, block-like, etc., and the size is not particularly limited, but from the viewpoint of easily obtaining the relative flow rate between the plating solution and the iron chip, the diameter is l
It is desirable to have a diameter of 110 l.
It is desirable that the diameter be less than l1φ.

[Example] An example of iron ion supply direction in iron-based alloy electroplating according to the present invention will be described.

Example: Iron chip melting tank cylinder with a diameter of 400 mm contained an average particle size of 3a.
Filled with 450 to 600 kg of iron chips of + m, relative flow rate of plating liquid for dissolving iron chips and iron chips of 3 m, /+
The plating solution was circulated at a rate of 6 m/min, 10 m/win.

Plating solution composition FeS OF2 HtO: 350g/lZn5
O-・7HtO: I Og/IH1SO,:
10g/l pe”: 6g/l, 8
g/l, 10 g/l Bath temperature 60°C In Examples No. 1 to No. 004, the iron chip packed bed is fixed, and in Example Nos. 5 to 8, the iron chips are extracted from the bottom of the iron chip packed bed. (Iron ion supply direction in iron-based alloy electroplating according to the present invention.)

In Examples No. 9 to No. 12, the iron chip filling layer is fixed, and in Example No. 13, the iron chips are extracted from the lower part of the iron chip filling layer (comparative examples).

Table 1 shows the dissolution conditions and results.

Fe3 reduction efficiency and iron chip dissolution amount were determined by collecting the plating solution at the entrance and exit of the iron chip dissolution tank, and measuring the Fe' concentration and H,SO
, was calculated from the amount of variation in concentration using the following formula.

Fe3 + reduction efficiency = (△F e” (+nol/ 1)
)/(△Fe”(mol/I)+2 x△)(ts
o4 (mol/l))X 100(%) Iron dissolution amount = (△
Fe" (kg/Hr))/(2x Fe" reduction efficiency) x 100 (kg/Hr) [Effects of the invention] As explained in detail above, iron ions in the iron-based alloy electroplating according to the present invention Since the supply method is the above-mentioned horizontal throttling, when supplying iron ions to the plating tank for iron-based alloy electroplating, the amount of iron chips dissolved in the iron chip dissolution tank can always be stabilized, and Fe' + It has the excellent effect of being able to significantly improve the reduction efficiency and also being able to operate stably over a long period of time.

[Brief explanation of drawings]

Figure 1 shows the relationship between the Fe3+ ion concentration on the user side of the iron chip dissolution tank and the amount of iron chip dissolution, and Figure 2 shows the relationship between the height of the iron chip packed bed/diameter of the iron chip packed bed and p e3 + A diagram showing the relationship with ion reduction efficiency, and FIG. 3 is a diagram showing an example of an apparatus for carrying out the iron ion supply method in iron-based alloy electroplating according to the present invention. Summer ~ iron chip melting tank, 2 ~ iron chip hopper 3 ~ valve, 4 ~ gas vent hole, 5 ~ nitrogen/air supply hole, 6 ~ speed reducer, 7 ~ electric motor, 8 ~ screw rod, 9 ~ sludge receiving bag, XO ~ Perforated plate, 11 ~ Overflow, 12
Plating solution supply port.

Claims (2)

[Claims] (1) In iron-based alloy electroplating, when dissolving iron chips by pressurizing the plating solution from below into the iron chip dissolving tank filled with iron chips in order to supply iron ions to the plating tank, the iron chip dissolving tank is used. The diameter a of the cylindrical iron chip packed bed inside (
The relationship between the height b (mm) and the height b (mm) satisfies b/a≦3, and the Fe^3^ in the plating solution on the entrance side of the iron chip dissolution tank
+ A method for supplying iron ions in iron-based alloy electroplating, characterized in that the concentration is 5 g/l or more, and the relative flow velocity between the iron chips in the iron chip dissolving tank and the plating solution press-in is 3 m/min or more. (2) In iron-based alloy electroplating, when dissolving iron chips by pressurizing the plating solution from below into the iron chip dissolving tank filled with iron chips in order to supply iron ions to the plating tank, the iron chip dissolving tank is used. The diameter a of the cylindrical iron chip packed bed inside (
The relationship between the height b (mm) and the height b (mm) satisfies b/a≦3, and the Fe^3^ in the plating solution on the entrance side of the iron chip dissolution tank
+ The concentration is 5 g/l or more, the relative flow velocity between the iron chips in the iron chip dissolving tank and the plating solution press-in is 3 m/min or more, and while the iron chips are melting in the iron chip dissolving tank, from the bottom of the iron chip dissolving tank A method for supplying iron ions in iron-based alloy electroplating, characterized by extracting iron chips and moving an iron chip packed layer.