KR20160060523A - Method of forming tantalum coating film and structure frame manufactured by the same - Google Patents

Abstract

Disclosed are a method for forming a tantalum coating film and a structural member manufactured by the same. According to the present invention, the method for forming a tantalum coating film includes: (a) a step of welding a tantalum wire and a base material; (b) a step of forming molten salt consisting of LiF, NaF, and K_2TaF_7, wherein the molten salt is to electroplate tantalum; (c) a step of inserting a platinum wire as a reference electrode and the tantalum wire and the base material as a work electrode, into the molten salt; and (d) a step of electrodepositing tantalum metal to the base material by applying a current to the base material. The method for forming a tantalum coating film is to solve a problem in which a coating film is not formed due to the formation of an oxide film (TaO_x) and mixed-melting of a welding unit in electroplating of the molten salt by using a double welding method and controlling a concentration of a coating raw material.

Description

TECHNICAL FIELD The present invention relates to a method for forming a tantalum-containing coating film,

More particularly, the present invention relates to a method of forming a tantalum-containing coating film, and more particularly, to a method of forming a tantalum-containing coating film using a molten salt electroplating (MSE) method and a multi-anode reactive alloy coating The present invention relates to a method of forming a tantalum-containing coating film, which can solve the problem that a metal film is not formed on a welded portion when forming a tantalum-type and tantalum-alloy coating film of a single kind by using the method of the present invention.

The electroplating technique based on molten salt is a technique for imparting specific physical properties required for use environment to the base metal. In particular, molten salt electroplating is being applied to the development of tantalum coating materials suitable for SI (Sulfur-Iodine) process environment, which is a hydrogen production process using atomic energy, which requires high corrosion resistance. Tantalum has a high corrosion resistance to sulfuric acid and iodic acid. It is easy to process and has a high melting point. It is widely regarded as a structural material of SI (Sulfur-Iodine) process, which is a hydrogen production process using nuclear power. Due to its high conductivity and processability It is used in semiconductor capacitor materials and various chemical industries.

Among the currently commercialized coating methods, a technique of forming a metal (tantalum) coating on a material by using a molten salt electroplating method is based on US Patent No. 6936155, and many researches and products are commercialized in VISHAY and TANTALINE.

Further, a study on a molten salt multiple anodic reaction alloy plating method (MARC) for the formation of a tantalum alloy coating film for stronger surface hardness and corrosion resistance than a pure single phase coating layer is filed in Korean Patent Laid-Open No. 10-2012-0128972.

However, the molten salt electroplating method and the multi-anode alloy coating method, which are disclosed in the above-described conventional techniques, have a problem that the coating film is not formed on the welded portion between the metal wire for applying electricity and the base metal, High pressure and high corrosiveness).

Corrosion of welds reduces the reliability of the base material in harsh environments. Particularly, safety is important for the materials used in SI (Sulfur-Iodine) process, which is a hydrogen production process using nuclear power. To solve this problem, there is a growing demand for a technique for forming a tantalum-containing coating film.

In order to solve the problems of the prior art as described above, the embodiments of the present invention solve the problems of the prior art as described above, in which the coating film is not formed due to the fusion of the welded portion and the formation of the oxide film (TaO _x ) during the molten salt electroplating through the double welding method and the adjustment of the coating material concentration And to provide a tantalum-containing coating film method capable of solving the above problems.

According to a preferred embodiment of the present invention, there is provided a method of manufacturing a tantalum wire, comprising: (a) welding a tantalum wire and a base material; (b) forming a molten salt composed of LiF, NaF, and K ₂ TaF ₇ , for electroplating the tantalum; (c) charging the tantalum wire and the base material into the molten salt using the platinum wire as the working electrode as the reference electrode; And (d) depositing a tantalum metal on the base material by applying an electric current to the base material.

The step of forming the molten salt may include the steps of weighing LiF and NaF so as to have a composition of 61 mol% LiF - 39 mol% NaF, followed by heat treatment; And it can include the addition of K ₂ TaF _7.

Re-welding the tantalum wire after polishing the welded portion of the electrodeposited tantalum material after the step of depositing the tantalum metal on the base material; Re-charging the re-welded base material into the molten salt; And a step of doubly electrodepositing the tantalum metal by applying an electric current to the re-charged base metal.

In the step of adding K ₂ TaF ₇ , 1 mol% K ₂ TaF ₇ may be added.

In the step of adding K ₂ TaF ₇ , 2 mol% K ₂ TaF ₇ may be added.

The electrodeposition step can be carried out under an argon atmosphere.

The electrodeposition temperature may be 800 ° C.

According to another aspect of the present invention, there is provided a tantalum-coated film structural material produced by the above-described method.

The tantalum coating film structural material may have a corrosion rate of 0.03 mm / year or less.

The examples are based on the problem that the coating is not electrodeposited on the welded part by using the multi-anode reaction alloy plating (MARC) method and the molten salt electroplating method (MSE), which is an economical technology capable of producing a super corrosion resistant structural material in a high corrosion environment, The problem of limited use can be solved. That is, in the embodiment, the double welding method and the improvement of the concentration of the coating target material can produce a highly corrosion-resistant tantalum-containing coating material free from corrosion in the welded portion, so that it can be applied even in a high corrosive environment.

1 is a schematic view of a double welding method according to an embodiment.
2 is a molten salt electroplating apparatus using the double welding method according to the embodiment.
3 is a state diagram of LiF-NaF for producing a molten salt used as an electrolyte according to an embodiment.
4 is a scanning electron micrograph of a welded portion of a tantalum-containing coating film produced according to Comparative Example 1 and Example 1. Fig.
5 is a cross-sectional scanning microscope photograph of a welded portion of a tantalum-containing coating film produced according to Example 2. Fig.
6 is a photograph of the tantalum-coated structural member after corrosion test.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The following drawings are provided by way of example so that those skilled in the art can fully understand the spirit of the present invention. Therefore, the present invention is not limited to the following drawings, but may be embodied in other forms, and the following drawings may be exaggerated in order to clarify the spirit of the present invention. Also, throughout the specification, like reference numerals designate like elements.

Hereinafter, the technical and scientific terms used herein will be understood by those skilled in the art without departing from the scope of the present invention. Descriptions of known functions and configurations that may be unnecessarily blurred may be omitted.

Examples are those in which a metal coating is not formed on a welded portion when a metal coating is formed using a molten salt electroplating (MSE) method or a multi-anode reactive alloy coating (MARC) method And how to solve the problem. The conventional molten salt-based tantalum electroplating technique has a problem in that a coating film is not formed due to a mixed portion (SUS316L-tantalum) and an oxide film (TaOx) due to a high current in a weld portion of a tantalum wire and a metal base material for applying electricity It is disadvantageous that the corrosion is concentrated on the welded part when exposed to the actual corrosion environment and is limited to the application of the corrosive environment.

In order to achieve the above-mentioned object, the embodiment of the present invention provides a method of manufacturing a coating material by a double welding method [Technique (I)] and a coating material of potassium heptafluorotantalate (hereinafter referred to as K ₂ TaF ₇ ) (Ⅱ)] is applied to solve the problem of non - forming of the coating film of welded part. The techniques (I) and (II) described above can be applied to a welded part using a multi-anode reaction alloy plating (MARC) method and a molten salt electroplating (MSE) method, which is an economical technology capable of producing a super corrosion- It is an effective method to solve the problems that are limited to the corrosive environment due to the non-electrodeposition problem.

The double welding method is a technique for solving the problem that the coating film is not electrodeposited on a welded portion when a metal wire for applying electricity to a base material is welded by electroplating based on a molten salt. In addition, the K ₂ TaF ₇ control technique as a coating material is a technique for forming a uniform coating film on a base material including welds by controlling the concentration of the coating material K ₂ TaF _{7 in} the molten salt.

1 is a schematic view of a double welding method according to an embodiment. Referring to FIG. 1 (a), the double welding method is a primary welding process in which a tantalum wire for applying electricity to a stainless steel plate is spot welded to a base metal. The tantalum wire may be used to apply electricity to the base material.

Thereafter, a primary tantalum coating film is formed as shown in Fig. 1 (b). 2 is a molten salt electroplating apparatus using the double welding method according to the embodiment. The primary tantalum coating film may be formed by first welding a tantalum wire for applying electricity to the base material, and then using the molten salt electroplating apparatus.

The step of forming the first tantalum-coated film comprises first preparing a molten salt for electroplating the tantalum. Thereafter, a tantalum room, which is a corrosion-resistant metal, and a base material are charged into the molten salt, and a current is applied to the base material to deposit the tantalum metal on the base material.

Next, referring to FIG. 1 (c), the welded portion of the electrodeposited tantalum material is secondarily welded to the tantalum wire by spot welding after polishing. Polishing improves uniformity and can be achieved using sandpaper. Thereafter, a secondary tantalum coating film is formed as shown in Fig. 1 (d). That is, the secondary welding base material is charged into the molten salt, and a current is applied to the base material to double-deposit the tantalum metal.

The K ₂ TaF ₇ control technique for coating material is to weld the tantalum wire for spot welding to the base metal to apply electricity to the base metal. Thereafter, a molten salt electroplating apparatus of FIG. 2 is used to form a tantalum-containing coating film. In the step of forming the tantalum-containing coating film, a molten salt for electroplating the tantalum room is prepared, the tantalum room, which is a corrosion-resistant metal, and the base material are charged into the molten salt, and the current is applied to the base material to electrodeposit the tantalum metal to the base material.

For double welding and K ₂ TaF ₇ control technique as a coating material, the base material may be SUS 316L. The working electrode is a tantalum wire (SUS316L) and the reference electrode can be platinum (Pt) wire. In order to improve the uniformity, it is preferable to polish with sand paper # 1500. The electrodeposition atmosphere is preferably an argon (Ar) atmosphere in order to suppress the generation of an oxide film of the base material. Further, in order to maintain the state of K ₂ TaF ₇ in a liquid phase, electrodeposition is preferably performed at 800 ° C.

In the double welding method and the K ₂ TaF ₇ controlling technique as a coating material, the molten salt is referred to as lithium fluoride (hereinafter referred to as LiF), sodium fluoride (hereinafter referred to as NaF) .) And K ₂ TaF ₇ . At this time, an electrolyte having a composition of 61 wt% LiF-39 wt% NaF can be used. As a result, the electrolyte can be maintained in a low-temperature liquid phase, thereby reducing power consumption and increasing the diffusion rate. That is, a molten salt can be formed by adding K ₂ TaF ₇ as a coating material to a LiF-NaF electrolyte.

More specifically, the molten salt is prepared by weighing LiF and NaF so as to have a predetermined chemical composition (61 mol% LiF-39 mol% NaF), and then heat-treated at 100 DEG C for 24 hours to remove moisture present in the powder. After the heat treatment, heat treatment is performed again at a temperature of 350 ° C to remove crystal water.

3 is a state diagram of LiF-NaF for producing a molten salt used as an electrolyte according to an embodiment. In the molten salt electroplating apparatus fabricated as shown in FIG. 2, the heat-treated powder was subjected to heat treatment at a temperature of 649 ° C, which is a melting temperature of LiF-NaF in the state diagram of FIG. 3, to a predetermined mole percentage of K ₂ TaF ₇ Powder may be added. In the double welding method, molten salt can be prepared by adding about 1 mol% K ₂ TaF ₇ . In addition, the molten salt can be prepared by adding about 2 mol% K ₂ TaF ₇ to the coating material K ₂ TaF ₇ .

Hereinafter, the present invention will be described in more detail with reference to Experimental Examples. However, the following Experimental Examples are for illustrative purposes only and are not intended to limit the present invention. In other words, the embodiments of the present invention can be modified in various forms, and the scope of the present invention should not be construed to be limited by the experimental examples described below.

(Example 1)

Using the molten salt electroplating method using the double welding method On base metal  Tantalum Coating Film Formation

A molten salt containing 1 mol% K ₂ TaF ₇ as a raw material for coating the electrolyte (61 mol% LiF-39 mol% NaF) in a stainless steel plate and a tantalum wire for electricity application Was charged into a molten salt electroplating apparatus. At this time, SUS316L was used as the base material.

The working electrode (Tantalum wire-SUS316L) 5mA / cm 2 The current density was applied to perform electroplating for 8 hours to form an alloy film having a thickness of 20 mu m. The calculation of the thickness of the alloy film with time is given by the following equation (1).

After the first electroplating, the welds were re-polished and secondary welded to the area where the tantalum-coated film was formed. A second electrode of the welding operation (wire Tantalum-Tantalum-SUS316L) and then re-charged into the molten salt electroplating apparatus, 5mA / cm ² And electroplating was performed for 12 hours in order to form an alloy film having a thickness of 30 mu m by applying a current density. The calculation of the thickness of the alloy film with time is given by the following equation (1).

At this time, a platinum wire was used as a reference electrode, and sandpaper # 1500 was used for polishing. The electrodeposition was carried out in an argon atmosphere and at 800 占 폚.

[Formula (1)

(Where, s is the electrodeposition time required to form the coating layer, m is the required mass of the coating material to form the coating layer, g is the electrochemical equivalent of the electrodeposited material, A is the current applied to the electrode, a is the area (cm ² ) of the base material to be electrodeposited, D is the density of the electrodeposited material (g / cm ² ), n is the electron of the electrodeposited material, and M is the atomic weight of the electrodeposited material.

(Example 2)

Coating raw material K ₂ TaF ₇ Using the control technique of On base metal  Tantalum Coating Film Formation

The base metal and the tantalum wire were firstly welded to a molten salt electroplating apparatus containing a molten salt containing 2 mol% K ₂ TaF ₇ as a raw material for coating the electrolyte (61 mol% LiF-39 mol% NaF). At this time, SUS316L was used as the base material.

The working electrode (Tantalum wire-SUS316L) 5mA / cm 2 The current density was applied to perform electroplating for 20 hours to form an alloy film having a thickness of 50 mu m. At this time, a platinum wire was used as the reference electrode, and electrodeposition was performed in an argon atmosphere and at 800 ° C.

(Comparative Example 1)

The base metal and the tantalum wire were spot-welded and charged into a molten salt electroplating apparatus containing molten salt containing 1 mol% K ₂ TaF ₇ as a raw material for coating the electrolyte (61 mol% LiF-39 mol% NaF). At this time, SUS316L was used as the base material.

The working electrode (Tantalum wire-SUS316L) 5mA / cm 2 The current density was applied to perform electroplating for 20 hours to form an alloy film having a thickness of 50 mu m. At this time, platinum wire was used as a reference electrode in the same manner as in Examples 1 and 2, and electrodeposition was performed in an argon atmosphere and at 800 占 폚.

(Results According to Examples 1 and 2)

4 is a scanning electron micrograph of the welded portion of the tantalum-containing coating film according to Comparative Example 1 and Example 1, and Fig. 5 is a cross-sectional scanning micrograph of the welded portion of the tantalum-containing coating film according to Example 2. 4 (a) is a scanning electron micrograph of a welded portion of a tantalum-containing coating film and a tantalum wire formed by the double welding method, and FIG. 4 (b) FIG. 5 is a cross-sectional scanning micrograph of a welded portion of a tantalum-coated coating film by controlling the concentration of K ₂ TaF _{7 as} a coating material.

FIG. 6 is a photograph of a corrosion test of a tantalum-coated structural member manufactured through double welding and control of K ₂ TaF _{7 as} a coating material. 6 (a) is a tantalum-coated structural member using the double welding method according to Example 1, and FIG. 6 (b) is a tantalum-coated structural member manufactured through the control of K ₂ TaF ₇ as a coating material according to Example 2. FIG. 6 (c) is a coated structural member manufactured through the conventional molten salt electroplating method according to Comparative Example 1. [FIG.

The structural materials according to Examples 1, 2 and Comparative Example 1 and a corrosion test in an atmosphere of hydroiodic acid (HI) in a 150 C autoclave were conducted for 100 hours to obtain a structural member as shown in FIG. As a result of the corrosion test, corrosion rate measurement results as shown in Table 1 were obtained.

The corrosion resistance of the coated structural material prepared by the double welding method and the control method of the coating material K ₂ TaF ₇ was 0.021 mm / year and 0.026 mm / year, respectively, whereas the structural material according to Comparative Example 1 was severely corroded And 13.187mm / year, respectively. That is, it is confirmed that the tantalum-coated structural member according to the embodiment has a tantalum-coated film of 50 탆 and can have a corrosion resistance of 0.03 mm / year or less.

Example 1 Example 2 Comparative Example 1 Weight of before corrosion test (g) 11.078 13.175 15.219 Weight of after corrosion test (g) 11.051 13.143 12.157 Corrosion rate (mm / year) 0.021 0.026 0.0085

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. You will know that it is possible. Further, it is to be understood that the scope of the present invention is defined by the appended claims. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be defined by the claims.

Claims (9)

(a) welding a tantalum wire and a base material;
(b) forming a molten salt composed of LiF, NaF, and K ₂ TaF ₇ , for electroplating the tantalum;
(c) charging the tantalum wire and the base material into the molten salt using the platinum wire as the working electrode as the reference electrode; And
(d) depositing a tantalum metal on the base material by applying current to the base material. The method according to claim 1,
Wherein forming the molten salt comprises:
LiF and NaF are weighed to have a composition of 61 mol% LiF - 39 mol% NaF and then heat-treated; And
K _{2 < /} RTI > TaF < RTI ID = 0.0 > _{7. &} Lt; / RTI > 3. The method of claim 2,
After the step of depositing the tantalum metal on the base material,
Re-welding the tantalum wire after polishing the welded portion of the electrodeposited tantalum material;
Re-charging the re-welded base material into the molten salt; And
Applying a current to the re-charged base metal to double-deposit the tantalum metal. The method of claim 3,
The step of adding K ₂ TaF _{7 is performed} by adding 1 mol% K ₂ TaF ₇ to the tantalum film. 3. The method of claim 2,
Wherein the step of adding K ₂ TaF ₇ comprises adding 2 mol% K ₂ TaF ₇ to the tantalum film. The method according to claim 1,
Wherein the electrodeposition step is performed under an argon atmosphere. The method according to claim 1,
Wherein the electrodeposition temperature is 800 占 폚. A tantalum coating film structural material produced by the process according to any one of claims 1 to 7. 9. The method of claim 8,
Tantalum-coated structural material with a corrosion rate of less than 0.03 mm / year.

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