JP6889447B2 - Titanium plating solution manufacturing method and titanium plating product manufacturing method - Google Patents

Description

The present invention relates to a method for producing a titanium plating solution and a method for producing a titanium plating product. This application claims priority based on Japanese Patent Application No. 2016-227050, which is a Japanese patent application filed on November 22, 2016. All the contents of the Japanese patent application are incorporated herein by reference.

Titanium is a metal having excellent corrosion resistance, heat resistance and specific strength. However, the high production cost of titanium and the difficulty of smelting and processing hinder its widespread use. Currently, as one of the methods for utilizing the characteristics such as high corrosion resistance and high strength of titanium and titanium alloys, a dry film forming method using CVD (Chemical Vapor Deposition) and PVD (Physical Vapor Deposition) has been partially industrialized. However, there is a problem that the dry film forming method cannot form a film on a substrate having a complicated shape. As a titanium film forming method capable of solving this problem, a method of electrodepositing titanium in a molten salt can be considered.

For example, Japanese Patent 2015-193899 (Patent Document 1), forming an alloy film of Fe and Ti on the surface of the Fe wire with a molten salt bath with the addition of _K 2 TiF ₆ or TiO ₂ to KF-KCl It is stated that it was done.

Japanese Unexamined Patent Publication No. 2015-193899

In the method for producing a titanium plating solution according to one aspect of the present invention, a titanium plating solution containing fluorine and titanium is measured by cyclic voltammetry under the following conditions, and the difference between the ^{natural potential and the Ti 3+} / Ti ^{4+ reaction potential is large.} This is a method for producing a titanium plating solution, in which titanium is added to the titanium plating solution so that the voltage becomes 0.75 V or higher.
<Conditions>
When the temperature of the titanium plating solution is 650 ° C or higher and 850 ° C or lower, glassy carbon is used as the working electrode, platinum is used as the pseudo reference electrode, and titanium is used as the counter electrode, the immersion potential of the working electrode is set as the lower limit potential, and 2V is further increased from there. As mentioned above, the potential scanning with respect to the working electrode is repeated at least 5 times at a scanning speed of 1 mV / sec or more and 500 mV / sec or less with respect to the upper limit potential which is a noble potential of 4 V or less.

FIG. 1 is a schematic view showing an image of the result of measuring a titanium plating solution by cyclic voltammetry. FIG. 2 is a schematic view showing an example of a state in which areas A to E are defined on the titanium-plated product in a method of measuring the average film thickness of the titanium-plated film in the titanium-plated product. FIG. 3 is a conceptual diagram showing an example of the field of view (i) when the area A of the titanium-plated product shown in FIG. 2 is observed with a scanning electron microscope. FIG. 4 is a conceptual diagram showing an example of a field of view (ii) when the area A of the titanium-plated product shown in FIG. 2 is observed with a scanning electron microscope. FIG. 5 is a conceptual diagram showing an example of a field of view (iii) when the area A of the titanium-plated product shown in FIG. 2 is observed with a scanning electron microscope. FIG. 6 shows the titanium plating solution No. 2 prepared in Example 4. It is a figure which shows the result of having measured 4 by cyclic voltammetry. FIG. 7 shows the titanium plating solution No. 1 prepared in Comparative Example 1. It is a figure which shows the result of having measured A by cyclic voltammetry.

[Issues to be solved by this disclosure]
As a result of examination by the present inventors, the method described in Patent Document 1 can electrodeposit an alloy film of Fe and Ti on the surface of the cathode used for molten salt electrolysis, but electrodeposits a metallic titanium film. I couldn't. That is, while the alloy film of Fe and Ti is stable in the molten salt bath, the metal Ti has been dissolved in the molten salt bath by the leveling reaction.

Therefore, the present inventors have repeated further studies ^{, and Ti 4+} is added to a titanium plating solution composed of a molten salt containing _{KF, KCl and K 2} TiF ₆ by a leveling reaction represented by the following formula (A) to Ti ^3+. It was found that it is effective to supply molten salt electrolysis after supplying an amount of titanium exceeding the minimum necessary amount.
Formula (A) 3Ti ⁴⁺ + Ti metal → 4Ti ³⁺ .

According to the above method, it is possible to form a smooth titanium plating film on the surface of the cathode used for molten salt electrolysis.

However, since it is not possible to confirm whether or not the leveling reaction has proceeded sufficiently by the above method alone, it is necessary to allow more time than necessary between supplying titanium to the titanium plating solution and performing molten salt electrolysis. was there. In addition, if oxygen is mixed into the titanium plating solution from the external environment for some reason, the titanium ions will be oxidized from trivalent to tetravalent, so whether or not the trivalent titanium ions are sufficiently present in the titanium plating solution. I don't understand.

Therefore, in view of the above problems, it is an object of the present invention to provide a method for monitoring the concentration ratio ^{of Ti 3+} and Ti ^{4+ in} the titanium plating solution and producing a titanium plating solution having a sufficiently high concentration of ^{Ti 3+.} And.

[Effect of the present disclosure]
According to the above invention, it is possible to provide a method of monitoring the concentration ratio ^{of Ti 3+} and Ti ^{4+ in} a titanium plating solution and producing a titanium plating solution having a sufficiently high concentration of ^{Ti 3+.}

[Explanation of Embodiments of the Present Invention]
First, embodiments of the present invention will be listed and described.

(1) In the method for producing a titanium plating solution according to one aspect of the present invention, a titanium plating solution containing fluorine and titanium is measured by cyclic voltammetry under the following conditions, and the natural potential and Ti ³⁺ / Ti ⁴⁺ reaction potential are used. This is a method for producing a titanium plating solution, in which titanium is added to the titanium plating solution so that the difference between the two is 0.75 V or more.
<Conditions>
When the temperature of the titanium plating solution is 650 ° C or higher and 850 ° C or lower, glassy carbon is used as the working electrode, platinum is used as the pseudo reference electrode, and titanium is used as the counter electrode, the immersion potential of the working electrode is set as the lower limit potential, and 2V is further increased from there. As mentioned above, the potential scanning with respect to the working electrode is repeated at least 5 times at a scanning speed of 1 mV / sec or more and 500 mV / sec or less with respect to the upper limit potential which is a noble potential of 4 V or less.

According to the aspect of the invention described in (1) above, it is provided a method of monitoring the concentration ratio ^{of Ti 3+} and Ti ^{4+ in} the titanium plating solution and producing a titanium plating solution having a sufficiently high concentration of ^{Ti 3+.} Can be done.

(2) In the method for producing the titanium plating solution according to (1) above, it is preferable that the titanium plating solution is obtained by dissolving titanium in a molten salt of potassium fluoride and potassium chloride.

(3) Production method (1) or titanium plating solution according to the above (2), said titanium plating solution, in which K ₂ TiF ₆ to a molten salt of potassium fluoride and potassium chloride were dissolved Is preferable.

According to the aspect of the invention described in (2) or (3) above, it is possible to provide a titanium plating solution that can maintain a liquid state at a lower temperature than a titanium plating solution in which titanium is dissolved in potassium fluoride.

(4) In the method for producing a titanium plating solution according to (3) above, _{the content of K 2} TiF ₆ in the titanium plating solution is preferably 0.1 mol% or more.

According to the aspect of the invention described in (4) above, it is possible to provide a titanium plating solution capable of stably performing titanium plating.

(5) In the method for producing a titanium plating solution according to any one of (2) to (4) above, the mixing ratio of potassium fluoride and potassium chloride is 10:90 to 90 in molar ratio. It is preferably 10.

According to the aspect of the invention described in (5) above, it is possible to provide a titanium plating solution capable of obtaining a smooth titanium plating film.

(6) In the method for producing a titanium plating solution according to any one of (1) to (5) above, it is preferable that the titanium added to the titanium plating solution is sponge titanium.

According to the aspect of the invention described in (6) above, it is possible to facilitate the progress of the titanium leveling reaction in the titanium plating solution.

The sponge titanium refers to a porous titanium metal having a porosity of 1% or more. Here, the porosity (%) of titanium sponge is calculated by 100- (volume calculated from mass) / (apparent volume) × 100.

(7) In the method for producing a titanium-plated product according to one aspect of the present invention, titanium is electrolyzed on the surface of the cathode by providing a cathode and an anode in a titanium plating solution containing fluorine and titanium and performing molten salt electrolysis. A method for producing a titanium plating product having an electrolytic step of analysis, wherein the titanium plating solution is titanium obtained by the method for producing a titanium plating solution according to any one of (1) to (6) above. This is a method for manufacturing a titanium-plated product, which is a plating solution.

According to the aspect of the invention described in (7) above, it is possible to provide a method for producing a titanium-plated product capable of producing a titanium-plated product having a smooth titanium-plated film on the surface.

(8) In the method for producing a titanium-plated product according to (7) above, the titanium plating solution used in the electrolysis step is measured by cyclic voltammetry under the following conditions, and the natural potential and Ti ³⁺ / Ti ⁴⁺ reaction potential are measured. It is preferable to control so that the difference from the above is 0.75 V or more.
<Conditions>
When the temperature of the titanium plating solution is 650 ° C or higher and 850 ° C or lower, glassy carbon is used as the working electrode, platinum is used as the pseudo reference electrode, and titanium is used as the counter electrode, the immersion potential of the working electrode is set as the lower limit potential, and 2V is further applied from there. Above, the potential scanning is repeated at least 5 times with respect to the working electrode at a scanning speed of 1 mV / sec or more and 500 mV / sec or less with respect to the upper limit potential which is a noble potential of 4 V or less.

According to the aspect of the invention described in (8) above, a method for producing a titanium-plated product capable of continuously and stably producing a titanium-plated product having a smooth titanium-plated film on the surface is provided. be able to.

[Details of Embodiments of the present invention]
Specific examples of the method for producing the titanium plating solution and the method for producing the titanium plating product according to the embodiment of the present invention will be described in more detail below. It should be noted that the present invention is not limited to these examples, and is indicated by the scope of claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of claims.

<Manufacturing method of titanium plating solution>
In the method for producing a titanium plating solution according to the embodiment of the present invention, first, a titanium plating solution containing fluorine and titanium is prepared. Then, the titanium plating solution is measured by cyclic voltammetry (hereinafter sometimes abbreviated as "CV") so that ^{the difference between the natural potential and the Ti 3+} / Ti ⁴⁺ reaction potential is 0.75V or more. Titanium may be added to the titanium plating solution to dissolve it.

The CV may be measured in a non-oxidizing atmosphere that does not form a compound with titanium. For example, it may be carried out in an atmosphere of an inert gas such as argon gas. Further, the CV may be measured at a temperature of 650 ° C. or higher and 850 ° C. or lower so that the titanium plating solution can maintain a liquid state, and a voltage scanning speed of 1 mV / sec or higher and 500 mV / sec or lower. The temperature of the titanium plating solution is more preferably 650 ° C. or higher and 800 ° C. or lower, and further preferably 650 ° C. or higher and 750 ° C. or lower, from the viewpoint of suppressing a decrease in the conductivity of the titanium plating solution. From the viewpoint of shortening the measurement time and improving the measurement accuracy, the scanning speed of the potential scanning is more preferably 50 mV / sec or more and 300 mV / sec or less, and further preferably 100 mV / sec or more and 200 mV / sec or less. preferable.

For the working electrode, for example, graphite, glassy carbon or the like can be used.
For the reference electrode, for example, platinum, Ni, or the like can be used.

For the counter electrode, for example, titanium, glassy carbon, graphite or the like can be used.

In the measurement of CV, the immersion potential of the working electrode is set as the lower limit potential, and the potential scanning is repeated at least 5 times with the upper limit potential which is a noble potential of 2 V or more and 4 V or less.

FIG. 1 shows an image of the result of CV measurement of the titanium plating solution. In FIG. 1, the vertical axis represents the current value (mA) and the horizontal axis represents the potential (V) of the reference electrode.

The natural potential 1 refers to the voltage difference between the working electrode and the reference electrode when no current is flowing.

Further, the Ti ³⁺ / Ti ⁴⁺ reaction potentials are the peak potential 2 caused by the oxidation of ^{Ti 3+} to Ti ⁴⁺ and the peak potential 3 caused by the reduction of ^{Ti 4+} to Ti ^3+. It shall mean the potential in the middle of. The potential potential 2 of the peak caused by the oxidation of Ti ³⁺ to Ti ⁴⁺ means an average value measured by repeating potential scanning at least 5 times with respect to the working electrode. Similarly, ^{the peak potential 3 caused by the reduction of Ti 4+} to Ti ³⁺ means an average value measured by repeating potential scanning at least 5 times with respect to the working electrode.

In the titanium plating solution in which the difference between the natural potential 1 and Ti ³⁺ / Ti ⁴⁺ reaction potential 4 is 0.75 V or more, the concentration ^{of Ti 3+} in the titanium plating solution becomes much higher than the concentration of ^{Ti 4+.} There is. Therefore, by performing molten salt electrolysis using a titanium plating solution having a difference between the natural potential 1 and Ti ³⁺ / Ti ^{4 +} reaction potential 4 of 0.75 V or more, titanium having a silvery white color and high smoothness is formed on the surface of the cathode. A plating film can be formed. On the other hand, when molten salt electrolysis is performed using a titanium plating solution in which the difference between the natural potential 1 and Ti ³⁺ / Ti ^{4 +} reaction potential 4 is less than 0.75 V, a titanium plating film may be formed on the cathode surface. Can not. From the viewpoint of forming a smooth titanium plating film, ^{the difference between the natural potential 1 and the Ti 3+} / Ti ^{4 +} reaction potential 4 is more preferably 1.0 V or more, and further preferably 1.1 V or more. ..

If the difference between the natural potential 1 and the Ti ³⁺ / Ti ^{4+ reaction potential 4 is known, the concentration of Ti 3+ and} the concentration of Ti ^{4+ in} the titanium plating solution can be used by using the Nernst equation represented by the following equation (B). The ratio of can be calculated.

Equation (B) E = E ₀ − (RT / zF) ln (a _{Ti3 +} / a _{Ti4 +} )
E: Electrode potential
E ₀ : Standard electrode potential
R: Gas constant
T: Absolute temperature
z: Number of moving electrons
F: Faraday constant
a: Activity.

^{However, when calculating the ratio of the concentration of Ti 3+ to} the concentration of Ti ⁴⁺ from the Nernst equation, the electrode potential E in the equation (B) is the ^{reaction in which Ti 3+} is oxidized to Ti ⁴⁺ and the Ti ⁴⁺ is reduced. It is assumed that the reaction that becomes ^{Ti 3+ has a dominant effect.} The ratio of activity of the ^{Ti 4+} active amount of ^{Ti 3+ (Ti 3+} activity / ^{Ti 4+} activity) is the same as the ratio of the density of the density and ^{Ti 4+} of ^{Ti 3+ (Ti 3+} concentration / ^{Ti 4+} concentration) Suppose there is.

The titanium plating solution before measurement by CV may be a molten salt containing fluorine and titanium. For example, molten salt or dissolving the _K 2 TiF ₆ to KF-KCl molten salt and dissolving the _K 2 TiF ₆ to LiF-KCl, the molten salt was dissolved _K 2 TiF ₆ to NaF-KCl etc. Can be used. The titanium compound to be dissolved in the molten salt is not limited to _{K 2} TiF _{6, and may be TiCl 4} or the like. It is preferable to use a molten salt dissolving the _K 2 TiF ₆ to KF-KCl Of these. Molten salt dissolving the K ₂ TiF ₆ to KF-KCl is titanium plating solution capable of obtaining a smooth titanium plating film.

When KF-KCl is used as a molten salt, the mixing ratio of KF and KCl is preferably 10:90 to 90:10 in terms of molar ratio. When the content ratio of KF in KF-KCl is 10 mol% or more, a smooth titanium plating film can be electrodeposited on the surface of the cathode. Further, when the content ratio of KF in KF-KCl is 90 mol% or less, the melting point can be lowered as compared with the molten salt of KF alone. From these viewpoints, the mixing ratio of KF and KCl is more preferably 20:80 to 80:20 and further preferably 40:60 to 60:40 in terms of molar ratio.

^{When the difference between the natural potential 1 and Ti 3+} / Ti ^{4 +} reaction potential 4 is less than 0.75V when the titanium plating solution composed of the above molten salt is measured by CV, titanium is added to the titanium plating solution. , The difference between the natural potential 1 and Ti ³⁺ / Ti ^{4 +} reaction potential 4 may be 0.75 V or more.

The shape of titanium added to the titanium plating solution is not particularly limited, but it is preferable to use sponge titanium, titanium powder as fine as possible, or the like. The higher the porosity of titanium sponge, the larger the specific surface area, so it is easier to dissolve it in a molten salt bath. Therefore, it is more preferable to use sponge titanium having a porosity of 20% or more, and it is further preferable to use sponge titanium having a porosity of 40% or more. By using sponge titanium having a high porosity, it is possible to facilitate the progress of the leveling reaction in the titanium plating solution.

By performing molten salt electrolysis using the titanium plating solution obtained by the method for producing a titanium plating solution according to the embodiment of the present invention, a titanium plating product having a smooth titanium plating film having a small film thickness distribution on the surface is produced. be able to.

<Manufacturing method of titanium-plated products>
In the method for producing a titanium-plated product according to an embodiment of the present invention, a cathode and an anode are provided in the titanium-plated solution obtained by the above-mentioned method for producing a titanium-plated solution according to the embodiment of the present invention, and molten salt electrolysis is performed. It has an electrolysis step of electrodepositing titanium on the surface of the cathode.

(Cathode)
In the electrolysis process, a titanium plating film is formed on the surface of the cathode. Therefore, as the cathode, a material having a purpose of forming a titanium plating film on the surface may be used. For example, a metal, a conductive sintered body, and the like can be mentioned. Specifically, nickel, iron, SUS304, molybdenum, tungsten, copper, carbon and the like can be preferably used.

The base material used as the cathode may have at least a conductive surface. By using a material that alloys with titanium as the cathode, a titanium alloy layer can be formed on the cathode side of the titanium plating film. Further, in the case of forming a high-purity titanium plating film without forming a titanium alloy layer, a material that does not alloy with titanium in the titanium plating solution may be used as the cathode.

(anode)
The anode is not particularly limited as long as it is a conductive material, and for example, glassy carbon, titanium, or the like can be used. From the viewpoint of stably and continuously producing a titanium plating film, it is preferable to use titanium as an anode.

(Other conditions)
The atmosphere for performing molten salt electrolysis may be a non-oxidizing atmosphere that does not form a compound with titanium or a vacuum. For example, the molten salt electrolysis may be performed in a state where the glove box is filled with an inert gas such as argon gas or circulated.

The current density for performing molten salt electrolysis is not particularly limited, but may be, for example, 10 mA / cm ² or more and 500 mA / cm ² or less. By setting the current density to 10 mA / cm ² or more, a titanium plating film can be stably formed on the surface of the cathode. Further, by setting the current density to 500 mA / cm ² or less, the diffusion of titanium ions in the titanium plating solution does not become rate-determining, and it is possible to suppress blackening of the formed titanium plating film. From these viewpoints, the current density, 50 mA / cm ² or more, more preferably, to 250 mA / cm ² or less, 100 mA / cm ² or more and more preferably be 200 mA / cm ² or less.

In the electrolysis step, the temperature of the titanium plating solution is preferably 650 ° C. or higher and 850 ° C. or lower. By setting the temperature of the titanium plating solution to 650 ° C. or higher, the titanium plating solution can be kept in a liquid state and molten salt electrolysis can be stably performed. Further, by setting the temperature of the titanium plating solution to 850 ° C. or lower, it is possible to prevent the components of the titanium plating solution from evaporating and the titanium plating solution from becoming unstable. From these viewpoints, the temperature of the titanium plating solution is more preferably 650 ° C. or higher and 750 ° C. or lower, and further preferably 650 ° C. or higher and 700 ° C. or lower.

The time for performing the molten salt electrolysis is not particularly limited, and the time may be sufficient for the target titanium plating film to be sufficiently formed on the surface of the cathode.

(CV measurement in electrolysis process)
In the electrolysis step, it is preferable to measure the titanium plating solution periodically or irregularly by cyclic voltammetry ^{and control the difference between the natural potential and the Ti 3+} / Ti ⁴⁺ reaction potential to be 0.75 V or more.

If oxygen or water is mixed into the titanium plating solution from the external environment during the electrolysis process for some reason, the titanium ions will be oxidized from trivalent to tetravalent, making it impossible to form a smooth titanium plating film. It ends up. When an electrode other than the titanium electrode is used as the anode, the concentration of titanium ions in the titanium plating solution changes at any time.

Even in these cases, the titanium plating solution is measured by CV regularly or irregularly and controlled so that the difference between ^{the natural potential and the Ti 3+} / Ti ^{4+ reaction potential is 0.75V or more.} A stable and continuously smooth titanium plating film can be formed on the surface of the surface.

The conditions for CV measurement are the same as the conditions for CV measurement in the method for producing a titanium plating solution according to the embodiment of the present invention described above. ^{If the difference between the natural potential and the Ti 3+} / Ti ⁴⁺ reaction potential is less than 0.75V when the titanium plating solution is CV-measured, for example, titanium sponge titanium or the like is used until it becomes 0.75V or more. It may be added to the plating solution to dissolve it.

According to the method for manufacturing a titanium-plated product according to the embodiment of the present invention, it is possible to manufacture a titanium-plated product having a smooth titanium-plated film having a small film thickness distribution on the surface. A smooth titanium plating film with a small film thickness distribution means that all of the maximum and minimum thicknesses of the titanium plating film measured at any five points of the titanium plating product are within ± 50% of the average film thickness of the titanium plating film. It shall be said that it is in.

The average film thickness of the titanium plating film is measured as follows. The outline of the method for measuring the average film thickness is shown in FIG.

First, a titanium-plated product having a titanium-plated film on its surface is arbitrarily divided into areas without bias, and five measurement points (areas A to E) are selected. Then, the cross section of the titanium plating film in each area is observed with a scanning electron microscope (SEM). The SEM magnification is set so that the entire thickness direction of the titanium plating film can be confirmed and the thickness direction can be seen as large as possible within one field of view. Then, the maximum thickness and the minimum thickness of the titanium plating film are measured at three points in each area by changing the field of view, and the average is called the average film thickness of the titanium plating film.

As an example, FIG. 2 shows a schematic view of a titanium-plated product 21 having a titanium-plated film on the surface of a substantially square base material, when the four corners are areas A to D and the central portion is area E. Further, FIG. 3 shows a conceptual diagram of the field of view (i) when the area A of the titanium-plated product 21 shown in FIG. 2 is observed by SEM. Similarly, FIG. 4 shows a conceptual diagram of the field of view (iii) of area A, and FIG. 5 shows a conceptual diagram of the field of view (iii) of area A.

In the field of view (i) to the field of view (iii) when the area A of the titanium-plated product 21 is observed by SEM, the thickness at which the titanium-plated film 23 is maximum (maximum thickness A (i), maximum thickness A (ii), maximum). The thickness A (iii)) and the thickness at which the titanium plating film 23 is minimized (minimum thickness a (i), minimum thickness a (ii), minimum thickness a (iii)) are measured. The thickness of the titanium plating film 23 means the length of the titanium plating film 23 extending in the vertical direction from the base material 22. When a titanium alloy layer made of titanium and a base metal is formed between the titanium plating film 23 and the base material 22, the thickness of the titanium plating film 23 is the titanium extending in the direction perpendicular to the base material 22. It shall mean the total length of the alloy layer and the titanium plating film. As a result, the maximum thickness A (i) to the maximum thickness A (iii) and the minimum thickness a (i) to the minimum thickness a (iii) of the three visual fields in the area A are determined. For areas B, C, D, and E, the maximum and minimum thicknesses of the titanium plating film in the three visual fields are measured in the same manner as in area A.

The average of the maximum thickness A (i) to the maximum thickness E (iii) and the minimum thickness a (i) to the minimum thickness e (iii) of the titanium plating film measured as described above is the average thickness of the titanium plating film. That is.

Hereinafter, the present invention will be described in more detail based on Examples, but these Examples are examples, and the method for producing a titanium plating solution and the method for producing a titanium-plated product of the present invention are limited thereto. is not it. The scope of the present invention is indicated by the description of the claims and includes all modifications within the meaning and scope equivalent to the description of the claims.

(Example 1)
-Manufacturing of titanium plating solution-
KCl and mixing ratio of 55: 45 next in a molar ratio of _KF, so that the concentration of K 2 TiF ₆ is 0.1 mol% KCl, a mixture of KF and _K 2 TiF ₆ was heated to 650 ° C., titanium plating A liquid was prepared.

The CV measurement was performed at a voltage scanning speed of 200 mV / sec in an atmosphere in which argon gas was circulated while the obtained titanium plating solution was heated to 650 ° C. A graphite rod having a diameter of 3 mm was used as the working electrode, a platinum wire having a diameter of 1 mm was used as the reference electrode, and a titanium rod having a diameter of 3 mm was used as the counter electrode. The potential scan for the working electrode was repeated 5 times.

As a result of CV measurement, the difference between the natural potential of the titanium plating solution and the Ti ³⁺ / Ti ⁴⁺ reaction potential was 0.65V.

Therefore, 0.3 mg of sponge titanium was added per 1 g of the titanium plating solution and sufficiently dissolved. As the titanium sponge, one having a porosity of 50% was used.

As a result of CV measurement of the titanium plating solution again under the same conditions ^{, the difference between the natural potential and the Ti 3+} / Ti ⁴⁺ reaction potential was 0.75V. This titanium plating solution is referred to as titanium plating solution No. It was set to 1.

-Manufacturing of titanium-plated products-
Titanium plating solution No. A cathode and an anode were provided in No. 1, and molten salt electrolysis was performed for 40 minutes.

Molten salt electrolysis was performed in a glove box with an argon flow atmosphere. A 0.5 cm × 2.5 cm × 0.1 mm Ni plate was used as the cathode, and a titanium rod was used as the anode. A platinum wire was used as the pseudo reference electrode. The current density was set to 25 mA / cm ² . The potential of the pseudo-reference electrode ^{was calibrated with the potential of metallic potassium (K +} / K potential) electrochemically deposited on the platinum wire.

As a result, titanium was electrodeposited on the surface of the Ni plate of the cathode, and a titanium-plated product having a titanium-plated film on the surface could be obtained.

The titanium-plated product was washed with water after the molten salt electrolysis step. The salt adhering to the surface of the titanium-plated product had excellent solubility in water and could be easily removed. By the above operation, the titanium plating product No. which has a titanium plating film on the surface. I got 1.

(Example 2)
-Manufacturing of titanium plating solution-
In Example 1, the titanium plating solution No. 1 was the same as in Example 1 except that the amount of titanium sponge added to the titanium plating solution after the CV measurement was 0.5 mg per 1 g of the titanium plating solution. 2 was prepared. Titanium plating solution No. after adding titanium sponge. As a result of CV measurement of No. 2 under the same conditions as in Example 1 ^{, the difference between the natural potential and the Ti 3+} / Ti ⁴⁺ reaction potential was 0.85 V.

-Manufacturing of titanium-plated products-
In Example 1, the titanium plating solution No. Instead of 1, titanium plating solution No. Titanium-plated product No. 2 was used in the same manner as in Example 1 except that 2. I got 2.

(Example 3)
-Manufacturing of titanium plating solution-
In Example 1, the titanium plating solution No. 1 was the same as in Example 1 except that the amount of sponge titanium added to the titanium plating solution after CV measurement was 1 mg per 1 g of the titanium plating solution. 3 was prepared. Titanium plating solution No. after adding titanium sponge. As a result of CV measurement of No. 3 under the same conditions as in Example 1 ^{, the difference between the natural potential and the Ti 3+} / Ti ⁴⁺ reaction potential was 1.00V.

-Manufacturing of titanium-plated products-
In Example 1, the titanium plating solution No. Instead of 1, titanium plating solution No. Titanium-plated product No. 3 was used in the same manner as in Example 1 except that No. 3 was used. I got 3.

(Example 4)
-Manufacturing of titanium plating solution-
In Example 1, the titanium plating solution No. 1 was the same as in Example 1 except that the amount of titanium sponge added to the titanium plating solution after the CV measurement was 1.2 mg per 1 g of the titanium plating solution. 4 was prepared. Titanium plating solution No. after adding titanium sponge. As a result of CV measurement of No. 4 under the same conditions as in Example 1 ^{, the difference between the natural potential and the Ti 3+} / Ti ⁴⁺ reaction potential was 1.10 V.

FIG. 6 shows the titanium plating solution No. 4 represents the result of CV measurement (result of the fifth potential scan). In FIG. 6, the vertical axis represents the current value (mA) and the horizontal axis represents the potential (V) of the reference electrode.

-Manufacturing of titanium-plated products-
In Example 1, the titanium plating solution No. Instead of 1, titanium plating solution No. Titanium-plated product No. 4 was used in the same manner as in Example 1 except that No. 4 was used. I got 4.

(Comparative Example 1)
-Manufacturing of titanium plating solution-
In Example 1, the titanium plating solution No. 1 was the same as in Example 1 except that sponge titanium was not added to the titanium plating solution after the CV measurement. A was prepared. Titanium plating solution No. As a result of CV measurement of A under the same conditions as in Example 1 ^{, the difference between the natural potential and the Ti 3+} / Ti ⁴⁺ reaction potential was 0.67V. FIG. 7 shows the titanium plating solution No. The result of CV measurement of A (the result of the fifth potential scan) is shown. In FIG. 7, the vertical axis represents the current value (mA) and the horizontal axis represents the potential (V) of the reference electrode.

-Manufacturing of titanium-plated products-
In Example 1, the titanium plating solution No. Instead of 1, titanium plating solution No. Titanium-plated product No. 1 was used in the same manner as in Example 1 except that A was used. I got A.

(Comparative Example 2)
-Manufacturing of titanium plating solution-
In Example 1, the titanium plating solution No. 1 was the same as in Example 1 except that the amount of titanium sponge added to the titanium plating solution after the CV measurement was 0.2 mg per 1 g of the titanium plating solution. B was prepared. Titanium plating solution No. after adding titanium sponge. As a result of CV measurement of B under the same conditions as in Example 1 ^{, the difference between the natural potential and the Ti 3+} / Ti ⁴⁺ reaction potential was 0.70 V.

-Manufacturing of titanium-plated products-
In Example 1, the titanium plating solution No. Instead of 1, titanium plating solution No. Titanium-plated product No. 1 was used in the same manner as in Example 1 except that B was used. I got B.

<Evaluation>
Titanium plating solution No. obtained by Examples 1 to 4, Comparative Example 1 and Comparative Example 2. 1-No. 4. Titanium plating solution No. A, No. The ratio of the Ti ³⁺ concentration to the Ti ^{4+ concentration in B (Ti 3+} concentration / Ti ⁴⁺ concentration) was calculated based on the Nernst equation. The results are shown in Table 1.

Further, the titanium-plated product No. 1 obtained in Examples 1 to 4, Comparative Example 1 and Comparative Example 2 were obtained. 1-No. 4. Titanium plated product No. A, No. The state of the surface of the titanium plating film of B was visually observed. The results are shown in Table 1.

The current efficiency of the cathode in the electrolysis steps of Examples 1 to 4, Comparative Example 1 and Comparative Example 2 was calculated based on the following formula (C). The results are shown in Table 1.
Equation (C) Current efficiency (%) = (actual plating amount) / (theoretical plating amount) x 100

As shown in Table 1, ^{the difference between the natural potential and the Ti 3+} / Ti ⁴⁺ reaction potential is 0.75 V or more. 1-No. When molten salt electrolysis was performed using No. 4, the surface condition of the titanium plating film was silver foil color and smooth, and the titanium plating product No. 1-No. I was able to get 4. In particular, the titanium plating solution No. 1 in which the difference between the natural potential and the Ti ³⁺ / Ti ^{4+ reaction potential is 1.00 V or more.} 3, No. When 4 was used, the current efficiency of the cathode could be 90% or more.

On the other hand, the difference between the natural potential and the Ti ³⁺ / Ti ⁴⁺ reaction potential is less than 0.75 V. A, No. When molten salt electrolysis was performed using B, the titanium plating film could not be formed well on the cathode surface, and the black film was electrodeposited.

1 Natural potential, 2 Peak potential due to oxidation of ^{Ti 3+} to Ti ^{4+ , 3 Peak potential due to reduction of Ti 4+} to Ti ³⁺ , 4 Ti ³⁺ / Ti ⁴⁺ reaction potential, A Any area on titanium plated product, B Any area on titanium plated product, C Any area on titanium plated product, D Any area on titanium plated product, E Any area on titanium plated product, 21 Titanium plating products, 22 base materials, 23 titanium plating films, 61 natural potentials, 64 Ti ³⁺ / Ti ⁴⁺ reaction potentials, 71 natural potentials, 74 Ti ³⁺ / Ti ⁴⁺ reaction potentials.

Claims (8)

A titanium plating solution containing fluorine and titanium was measured by cyclic voltammetry under the following conditions.
A method for producing a titanium plating solution, in which titanium is added to the titanium plating solution so that the difference between the natural potential and the Ti ³⁺ / Ti ^{4+ reaction potential is 0.75 V or more.}
<Conditions>
When the temperature of the titanium plating solution is 650 ° C or higher and 850 ° C or lower, glassy carbon is used as the working electrode, platinum is used as the pseudo reference electrode, and titanium is used as the counter electrode, the immersion potential of the working electrode is set as the lower limit potential, and 2V is further increased from there. Above, potential scanning is repeated at least 5 times with respect to the working electrode at a scanning speed of 1 mV / sec or more and 500 mV / sec or less with respect to the upper limit potential which is a noble potential of 4 V or less. The method for producing a titanium plating solution according to claim 1, wherein the titanium plating solution is obtained by dissolving titanium in a molten salt of potassium fluoride and potassium chloride. The titanium plating solution is obtained by dissolving the K ₂ TiF ₆ to a molten salt of potassium fluoride and potassium chloride, producing a titanium plating solution according to claim 1 or claim 2. The method for producing a titanium plating solution according to claim 3 _{, wherein the content of K 2} TiF ₆ in the titanium plating solution is 0.1 mol% or more. The method for producing a titanium plating solution according to any one of claims 2 to 4, wherein the mixing ratio of potassium fluoride and potassium chloride is 10:90 to 90:10 in terms of molar ratio. The method for producing a titanium plating solution according to any one of claims 1 to 5, wherein the titanium added to the titanium plating solution is titanium sponge. A method for producing a titanium-plated product, which comprises an electrolysis step of electrodepositing titanium on the surface of the cathode by providing a cathode and an anode in a titanium plating solution containing fluorine and titanium and performing molten salt electrolysis.
A method for producing a titanium plating product, wherein the titanium plating solution is a titanium plating solution obtained by the method for producing a titanium plating solution according to any one of claims 1 to 6. 7. The titanium plating solution used in the electrolysis step is measured by cyclic voltammetry under the following conditions, ^{and the difference between the natural potential and the Ti 3+} / Ti ⁴⁺ reaction potential is controlled to be 0.75 V or more. A method for manufacturing a titanium-plated product according to.
<Conditions>
When the temperature of the titanium plating solution is 650 ° C or higher and 850 ° C or lower, glassy carbon is used as the working electrode, platinum is used as the pseudo reference electrode, and titanium is used as the counter electrode, the immersion potential of the working electrode is set as the lower limit potential, and 2V is further increased from there. As mentioned above, the potential scanning with respect to the working electrode is repeated at least 5 times at a scanning speed of 1 mV / sec or more and 500 mV / sec or less with respect to the upper limit potential which is a noble potential of 4 V or less.

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