JPH0576554B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention is directed to the use of iron plating solutions and iron alloy plating solutions containing divalent iron ions (Fe ²⁺ ) as the main component (ions to be reduced and precipitated). Trivalent iron ion (Fe ³⁺ )
Relating to a method for removing impurities.

Prior Art and Problems to be Solved by the Invention Conventionally, iron plating or iron alloy plating has been used for various purposes. These iron plating and iron alloy plating reduce Fe ²⁺ in the plating solution to metallic iron,
The plating principle is to precipitate Fe ²⁺
is used as the plating metal source. However, Fe ²⁺ in the iron plating solution or iron alloy plating solution is oxidized to Fe ³⁺ by air oxidation, electrolytic oxidation, etc., and Fe ³⁺ accumulates in the plating solution. An increase in Fe ³⁺ in the plating solution or iron alloy plating solution causes problems such as deterioration of the physical properties of the plating film, and in the case of electroplating, decreases the current rate. In addition, Fe ³⁺ in such a solution causes precipitation due to the formation of hydroxide and precipitation due to the formation of sparingly soluble salts with other phosphorous acid, phosphoric acid, etc.

For this reason, iron plating liquid containing Fe ³⁺ as an impurity,
It is desirable to remove Fe ³⁺ in the iron alloy plating solution by reducing it to Fe ²⁺ .

Conventionally, methods for reducing Fe ³⁺ to Fe ²⁺ have been known, such as an electrolytic method and a metal powder addition method (for example, Japanese Patent Application Laid-Open Nos. 59-25991 and 59-45930).
In addition, ion exchange methods and solvent extraction methods are known as Fe ³⁺ removal methods.

However, these conventional methods require large and complicated equipment, expensive equipment costs, and are relatively troublesome to operate, so they are not simple.

The present invention was made in view of the above circumstances, and it is an object of the present invention to provide a method for removing trivalent iron ions from an iron or iron alloy plating solution, which is inexpensive in equipment cost and easy to operate.

Means and Effects for Solving the Problems That is, in order to achieve the above object, the present invention has two features:
A method for removing trivalent iron ions contained as impurities in an iron or iron alloy plating solution containing trivalent iron ions as a main component. A soluble metal made of an iron alloy or a metal alloyed with iron and an inert electrode are respectively immersed in the liquid, and the soluble metal and the inert electrode are connected directly or with a conductor to form a negative electrode. , a battery is formed using an inert electrode as a positive electrode, the soluble metal is oxidized and dissolved, and the trivalent iron ions in the plating solution are oxidized and dissolved.
Provided is a method for removing trivalent iron ions in an iron or iron alloy plating solution, which is characterized by reducing trivalent iron ions to valent iron ions.

The present invention will be explained in more detail below.

Fe ³⁺ in the iron or iron alloy plating solution according to the present invention
In the impurity removal method, a known composition containing F ²⁺ as a main component is used as the iron or iron alloy plating solution.

Contained in this plating solution according to the invention
The method for removing Fe ³⁺ is to reduce ^{Fe 3+} to Fe ^{2+ .}
As shown in FIGS. 1 to 3, a soluble ferrous metal, an iron alloy, or a metal alloyed with iron is used as a negative electrode in an iron or iron alloy plating solution 2 in a reduction tank 1. A metal 3 is immersed, an inert electrode 4 is immersed as a positive electrode, and these are connected by a conductor 5 to form a battery (Fig. 1), or in this case, an insulated conductor 5' is immersed in a plating solution 2. It is used in a state where the soluble metal 3 and the inert electrode 4 are connected to form a battery (Fig. 2), or the soluble metal 3 and the inert electrode 4 are directly contacted to form an electric ground. (Figure 3).

As a result, the soluble metal in the negative electrode is oxidized into metal ions and dissolved in the plating solution as shown in the formula below, and Fe ³⁺ is converted to Fe ²⁺ in the positive electrode (inert electrode).
It will be reduced to

Negative electrode: M−ne→M ⁿ⁺ ...(1) Positive electrode: Fe ³⁺ +e→Fe ²⁺ ...(2) Overall: M+nFe ³⁺ →M ⁿ⁺ +nFe ²⁺ ...(3) (M in the formula is soluble In this case, when the soluble metal M is iron, Fe ⁰ (soluble metal) is oxidized to Fe ²⁺ and Fe ³⁺ is reduced to Fe ²⁺ as shown in the formula below.

Negative electrode: Fe ⁰ −2e→Fe ²⁺ ……(1′) Positive electrode: Fe ³⁺ +e→Fe ²⁺ ……(2′) Overall: Fe ⁰ +2Fe ³⁺ →3Fe ²⁺ ……(3′) This To further explain this point, as mentioned above,
A known method for reducing Fe ³⁺ is to add soluble metal powder, but this oxidizes the soluble metal (M) into metal ions (M ⁿ⁺ ) according to equation (3).
It is based on the reaction in which Fe ³⁺ is reduced to Fe ²⁺ while being dissolved in the plating solution. However, at the same time, this reaction occurs when the soluble metal (M) becomes a metal ion (M ⁿ⁺ ).
The consumption of acid (H ⁺ ) shown in formula (4) when oxidized to
This is accompanied by a hydrogen generation reaction, and the plating solution
Easily fluctuates PH.

M+nM ⁺ →M ⁿ⁺ +n/2H ⁺ ↑ ...(4) Here, in order to promote the reaction of formula (3), it is preferable that the surface area of the soluble metal is large, and for this reason, soluble metal powder is used. However, this also promotes the reaction of equation (4). The disadvantages of acid dissolution include an increase in metal ions and an accumulation of the acid used for neutralization. Suppression of the reaction expressed by equation (4) is strongly required for iron plating and maintenance or regeneration of iron plating solution, and for this purpose, it is necessary to reduce the surface area of the soluble metal. However, as long as powder is used, it is difficult to reduce the surface area, and in this case, if small pieces or the like are used instead of powder, the reaction rate of equation (3) will slow down.

In contrast, the present invention, as described above, immerses the above-mentioned soluble metal plate as a negative electrode in a plating solution,
Moreover, by forming a battery by immersing an inert electrode as a positive electrode, the reaction of formula (4) can be suppressed and the reaction of formula (3) can proceed advantageously. That is, the reaction of equation (3) is divided into equation (1), which is a dissolution reaction of soluble metal at the negative electrode, and reaction of equation (2), which is an electron supply at the positive electrode and a reduction reaction by the electrons.
Equation (4) is proportional to the surface area of the soluble metal, but equation (3) is rate-limited by equation (2), which is a cathode reaction.
In the conventional soluble metal powder addition method, reactions of equations (1) and (2) proceed simultaneously in the same metal, and therefore
It is difficult to control the reaction of equation (1) and reaction of equation (2). However, in the present invention, in addition to the soluble metal negative electrode, an inert electrode is used as the positive electrode to supply electrons, thereby allowing the reaction of formula (3) to proceed as a whole. Since the area of the negative electrode can be reduced and the area of the positive electrode can be increased,
It is capable of promoting the reaction of formula (3) while controlling the reaction of formula (4).

Here, as the negative electrode (soluble metal), iron metal, iron alloy, or metal alloyed with iron is used as described above, but as the inert electrode used as the positive electrode, a metal that simply transfers electrons is used. Preferably, materials that act as electrodes include, but are not limited to, gold, platinum, titanium, niobium, tantalum, zirconium, lead, stainless steel, carbon, graphite, carbon paste, glassy carbon, carbon fiber, and the like. I can do it.

In this case, the surface area ratio between the negative electrode and the positive electrode is selected appropriately, but from the viewpoint of controlling the reaction of formula (4) and favorably performing the reaction of formula (2), when the negative electrode is 1, the surface area ratio of the positive electrode is 1 or more. In particular, it is preferable to set the surface area ratio to 5 or more.

In the method of the present invention, a battery may be formed by immersing a soluble metal and an inert electrode in a plating solution as described above, and the embodiment thereof is not particularly limited. For example, a battery may be formed directly in a plating tank, but as shown in FIGS.
A reduction tank 1 is installed separately from the tank 1, and both tanks 1 and 6
A plating liquid delivery pipe 7 and a plating liquid return pipe 8 are used to connect the plating liquid (Fe ³⁺ -containing solution) 2 to both tanks 1 and 1, respectively. It is also possible to perform the glazing while reducing Fe ³⁺ to Fe ²⁺ while circulating for 6 hours. Although not shown, necessary plating equipment such as an anode plate is installed in the plating tank.

EXAMPLES Next, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to the following Examples.

Example 1 Using an apparatus as shown in FIG. 4, changes in Fe ³⁺ concentration were investigated using an iron plating solution having the following composition.

Iron plating liquid composition FeSo ₄・7H ₂ O 250g/ (NH ₄ ) ₂ SO ₄ 100 〃 PH 2.1 Iron is used as the soluble metal for the negative electrode of the reduction tank, and porous carbon is used as the inert positive electrode. A plate was used, and an ammeter was inserted into the conductor (conductor wire) connecting these two poles.

As a result, the Fe ³⁺ concentration immediately after the iron plating liquid preparation bath was
250mg/, and the initial current value due to the formation of a battery between the soluble metal (iron) and the inert electrode (carbon plate) was approximately 0.05A/, but the current value gradually decreased and the current decreased after being left overnight. The value decreased to 0.01 A/, and the Fe ³⁺ concentration decreased to 93 mg/. Furthermore,
Although it was left in this state for a week, there was almost no change in the concentration of Fe ³⁺ , and the method of the present invention suppressed the increase in Fe ³⁺ ,
It was observed that Fe ³⁺ was maintained at a low concentration.

For comparison, the same iron plating (Fe ³⁺ concentration 250
mg/) was left for one week, but the Fe ³⁺
The concentration was 600mg/.

Example 2 Using the apparatus shown in FIG. 5 and using the same iron plating solution as in Example 1, changes in Fe ³⁺ concentration were investigated.

In this case, a carbon plate with drilled through holes is used as the inert electrode for the positive electrode of the reduction tank, and iron bolts and nuts are used as the soluble metal for the negative electrode. A battery was formed by inserting a bolt and tightening a nut.

As a result, the Fe ³⁺ concentration immediately after the iron plating liquid preparation bath was
The Fe 3+ concentration was 250 mg/, but after standing overnight, the Fe ³⁺ concentration decreased to 71 mg/. Furthermore, when the sample was left in this state for one week, there was almost no change in the concentration of Fe ³⁺ , confirming that the method of the present invention suppresses the increase in Fe ³⁺ and maintains Fe ³⁺ at a low concentration.

For comparison, the same iron plating solution (Fe ³⁺ concentration
250mg/) was left for a week, but in that case
The Fe ³⁺ concentration was 550 mg/.

Effects of the Invention As explained above, according to the present invention, impurities can be removed by simply immersing a soluble metal and an inert electrode in an iron or iron alloy plating solution to form a battery.
Since Fe ³⁺ can be removed, equipment costs are low;
This is something that can be implemented very easily.

[Brief explanation of the drawing]

1 to 5 are schematic diagrams each showing an example of an apparatus used for carrying out the present invention. 1... Reduction tank, 2... Iron or iron alloy plating liquid,
3...Soluble metal, 4...Inert electrode, 5,5'
……conductor.

Claims (1)

[Claims] 1. A method for removing trivalent iron ions contained as impurities in an iron or iron alloy plating solution containing divalent iron ions as a main component. Immersing a soluble metal made of iron metal, an iron alloy, or a metal alloyed with iron and an inert electrode in a dipping solution, and
The soluble metal and the inert electrode are connected directly or through a conductor to form a battery with the soluble metal as the negative electrode and the inert electrode as the positive electrode, and the soluble metal is oxidized and dissolved, and the trivalent metal in the plating solution is 1. A method for removing trivalent iron ions from an iron or iron alloy plating solution, the method comprising reducing iron ions to divalent iron ions.