KR100916479B1 - Electrolyte for electro-chemical machining of metal product - Google Patents

Abstract

An electrolytic solution for metal product electrolytic processing is proposed, which reduces defects of electrolytically processed products, extends electrolyte and electrode life, and improves processing efficiency. The electrolytic solution for metal product electrolytic processing of the present invention includes an inorganic salt in a solvent, and includes at least one of a complexing agent and a reducing agent.

Complexing agent, reducing agent, electrolytic processing

Description

Electrolyte for electro-chemical machining of metal product

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrolytic solution for metal product electrolytic processing, and more particularly, to an electrolytic solution for metal product electrolytic processing in which defects of the electrolytic processed product are reduced, the electrolyte and electrode life are extended, and processing efficiency is improved.

Electrolytic processing is a processing method using an electrochemical reaction of a conductive material. In electrolytic processing, a workpiece is processed in the shape of an electrode by immersing a workpiece having a specific shape and an electrode having a specific shape in an electrolytic solution, and using a workpiece as an anode and a cathode while maintaining a constant gap with current.

By using the electrolytic processing method, it is possible to process regardless of the hardness of the workpiece, and there is an advantage in that it can be processed into a complicated shape such as curved surface or inside hole processing. Recently, micro-machining has been made possible by using ultra-short pulses during electrolytic machining, for example, microgroove processing of fluid dynamic bearings.

During electrolytic processing, metal components elute because they act as anodes. The eluted metal component may form a metal hydroxide and precipitate in the form of sludge. This precipitation is precipitated on the surface of the workpiece and the surface of the electrode or the electrolytic processing bath, which is a major cause of defects in the electrolytic processing.

The composition of the electrolyte is an electrolyte for conducting electricity and contains only a single or complex inorganic salt. Therefore, when the metal component of the workpiece is eluted during electrolytic processing, precipitation of hydroxide form occurs in the electrolyte solution. For example, when the main component of the workpiece is iron, a large amount of precipitates of iron hydroxide such as Fe (OH) ₃ or Fe (OH) ₂ may be generated when the electrolytic processing proceeds.

Sludge-type precipitation distorts the shape of the workpiece or hinders the supply of electricity, which is a major cause of poor processing. Conventionally, a method of physically removing the precipitate by using a filter press or centrifugation has been used, but there is a problem that the electrolyte must be replaced when the precipitate increases by a certain level or more.

Therefore, during the electrolytic processing of metal products, it is required to reduce the metal precipitates deposited in the electrolyte solution to improve the quality of the workpiece and to develop an electrolyte solution that can increase the efficiency of the processing process.

The present invention is to solve the above-mentioned problems, an object of the present invention is to provide an electrolytic solution for electrolytic processing of metal products, the defect of the electrolytically processed product is reduced, the electrolyte and electrode life is extended, and the processing efficiency is improved.

Electrolytic solution for metal products electrolytic processing according to an aspect of the present invention for achieving the above object includes an inorganic salt in the solvent, at least one of a complexing agent and a reducing agent. The metal may be any of iron, copper, nickel, aluminum, tin, chromium, zinc and alloys thereof. The solvent may be water, among which pure water, so that the electrolyte solution may be an aqueous solution.

The inorganic salt is at least one selected from the group consisting of NaNO ₃ , NaCl, NaClO ₄ , Na ₂ SO ₄ , KNO ₃ , KCl, KClO ₄ , K ₂ SO ₄ , LiNO ₃ , LiCl, LiClO ₄ , and Li ₂ SO ₄ It is preferable. The concentration of the inorganic salt may be a concentration suitable for electrolytic processing is 100g / L to 500g / L based on the total volume of the electrolyte solution.

Complexing agents include citric acid, acetic acid, oxalic acid, fulvic acid, succinic acid, tartaric acid, lactic acid, and gluconic acid. acid), maleic acid (Maleic acid), malic acid (Malic acid) and salts thereof may be used.

In particular, the complexing agent may be acetic acid, specifically, selected from the group consisting of ethylenediaminetetraacetic acid, hydroxyethylethylenediaminetriacetic acid, and nitrilotriacetic acid. There may be at least one .

The concentration of the complexing agent is preferably 0.5 g / L to 20 g / L based on the volume of the total electrolyte.

The reducing agent may use at least one of L-ascorbic acid, D-isoascorbic acid and salts thereof, the concentration of which is 0.5 g / y based on the total volume of the electrolyte. It is preferable that it is L-20g / L.

The electrolytic solution for metal products electrolytic processing according to an embodiment of the present invention preferably further includes at least one of a corrosion inhibitor, a surfactant, a viscosity regulator, and a pH regulator for improving physical properties.

Electrolyte solution for electrolytic processing of metal products according to an embodiment of the present invention may have a pH range of pH 2 to pH 7.

In electrolytic processing in the electrolytic solution for metal products electrolytic processing according to the present invention it is possible to suppress the generation of metal precipitates. Therefore, deposition of deposits on the electrode or the workpiece during electrolytic processing can be suppressed, thereby preventing processing defects and improving processing efficiency.

In addition, the lifespan of the electrolytic solution to be used is increased, thereby reducing the cost of the electrolytic process, and eliminating additional metal precipitates, thereby eliminating time loss, thereby improving productivity.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described in detail. However, embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below. Embodiments of the present invention are provided to more fully describe the present invention to those skilled in the art.

Electrolyte solution for metal products electrolytic processing according to an aspect of the present invention comprises an inorganic salt in the solvent, at least one of a complexing agent and a reducing agent.

The electrolyte is prepared by dissolving an inorganic salt in water. Inorganic salts that may be used in the electrolyte are NaNO ₃ , NaCl, NaClO ₄ , Na ₂ SO ₄ , KNO ₃ , KCl, KClO ₄ , K ₂ SO ₄ , LiNO ₃ , LiCl, LiClO ₄ , and Li ₂ SO ₄ It is preferably at least one selected from. The concentration of the inorganic salt may be a concentration suitable for electrolytic processing is 100g / L to 500g / L based on the total volume of the electrolyte solution.

As a solvent used for the electrolyte solution of this invention, water can be used. The electrolyte solution becomes an aqueous solution. It is preferable to use pure water from which salt was removed.

The metal product may be any metal product that can be processed through electrolytic processing. The metal can be, for example, any one of iron, copper, nickel, aluminum, tin, chromium, zinc and alloys thereof.

Hereinafter, the precipitation of the metal eluted during electrolytic processing of metal products will be described with iron as an example. Iron-containing products are eluted from the surface of the product during electrolytic processing and flow into the electrolyte. Iron in the electrolyte is converted to hydroxide as follows.

Fe ^-> Fe ⁺⁺ + 2e -

Fe ⁺⁺ + 2OH ^-- > Fe (OH) ₂

4Fe (OH) ₂ + 2H ₂ O + O _2- > 4Fe (OH) ₃

In Scheme 1, iron in the metal product is eluted with divalent ions. Iron present in the electrolyte are react with the hydroxide ions present in the electrolyte, as in Scheme 2 to form an Fe (OH) _2, Fe (OH) ₂ is converted back to Fe (OH) ₃ in the form of hydroxide. The converted hydroxide precipitates in sludge form. Therefore, the electrolytic solution according to an embodiment of the present invention includes at least one of a complexing agent and a reducing agent in order to suppress or remove the metal hydroxide precipitated in the form of sludge.

The complexing agent forms a chemically stable chelate compound with the metal. Therefore, the metal is present in the electrolyte in a stable form in an ionic state to suppress precipitation.

As the complexing agent, any complexing agent capable of complexing a metal and having no significant effect on electrolytic processing can be used. For example, the complexing agent includes citric acid, acetic acid, oxalic acid, fulvic acid, succinic acid, tartaric acid, lactic acid, At least one of gluconic acid, maleic acid, maleic acid, and salts thereof may be used.

In particular, the complexing agent may be acetic acid, in particular at least one selected from the group consisting of ethylenediaminetetraacetic acid, hydroxyethylethylenediaminetriacetic acid, and nitrilotriacetic acid. Can be.

The concentration of the complexing agent depends on the concentration of metal ions in the electrolyte during electrolytic processing. In general, the concentration of the complexing agent is preferably included at least 0.5 g / L in order to fully express the function in the electrolyte. In addition, in order not to significantly affect the physical properties of the electrolyte solution, it is preferably included in 20g / L or less. That is, the complexing agent is preferably 0.5 g / L to 20 g / L based on the volume of the total electrolyte solution.

The electrolyte solution of the present invention may include a reducing agent. The reducing agent reduces the metal in the metal hydroxide to produce a metal hydroxide of a higher solubility form. Therefore, it is possible to maintain the metal precipitated state in the electrolyte solution.

Take iron hydroxide as an example, in the case of Fe (OH) ₃ is produced at a pH above 2 to produce a wide range of pH, while Fe (OH) ₂ is produced in a range of pH 7 to pH 9. I.e., Fe (OH) ₃ than Fe (OH) ₂ is more preferable and that is generated in the electrolytic solution, and thus, Fe (OH) ₃ is relatively large Fe (OH) a solubility -Fe ^{3+ ₂} -Fe ₂ ⁺ Reduction of this can suppress precipitation.

Reducing agents that can be used in the present invention may be used as long as the reducing agent can reduce the metal and does not significantly affect the electrolytic processing. For example, the reducing agent may use at least one of L-ascorbic acid, D-isoascorbic acid and salts thereof.

The concentration of the reducing agent also depends on the concentration of metal ions in the electrolyte during electrolytic processing. In general, the concentration of the reducing agent is preferably included 0.5 g / L or more in order to fully express the function in the electrolyte. In addition, the reducing agent is preferably included in 20g / L or less in order not to significantly affect the physical properties of the electrolyte solution. That is, the reducing agent is preferably 0.5 g / L to 20 g / L based on the volume of the total electrolyte solution.

The electrolytic solution for metal products electrolytic processing according to an embodiment of the present invention preferably further includes at least one of a corrosion inhibitor, a surfactant, a viscosity regulator, and a pH regulator for improving physical properties. Corrosion inhibitors are additives for inhibiting corrosion of the electrode. Surfactants, viscosity modifiers, pH adjusters are physical property additives for improving the processing properties of the electrolyte.

Electrolyte solution for electrolytic processing of metal products according to an embodiment of the present invention may have a pH range of pH 2 to pH 7. As described above, for example, iron hydroxide, Fe (OH) _{3 having} a higher oxidation number is produced at pH 2 or higher, and Fe (OH) ₂ reduced to have a lower oxidation number is in the range of pH 7 to pH 9. Is generated. Therefore, since Fe (OH) ₂ reduced by the reducing agent is generated in the range of pH 7 to pH 9, by adjusting the pH range of the electrolyte solution to pH 2 to pH 7, it is possible to further suppress the precipitation of Fe (OH) ₂ . .

EXAMPLE

In the following examples, electrolytically processed electrolyte solutions were prepared according to one embodiment of the present invention, and metal ions (iron ions) were added to calculate the removal rate in order to confirm the effect of removing metal precipitates from these electrolyte solutions.

First, in order to prepare an electrolyte, sodium nitrate (NaNO ₃ ) was dissolved as an inorganic salt in pure water as a solvent to prepare an aqueous solution of 150 g / L sodium nitrate. A certain amount of ferric nitrate (Fe (NO ₃ ) ₃ .12H ₂ O) is added without processing the metal product to include a certain concentration of iron ions in the electrolyte. The electrolyte is adjusted to neutral pH using 0.1 M sodium hydroxide (NaOH) solution. As a result, an ocher-colored precipitate that can be seen with the naked eye was confirmed.

It was observed whether the precipitate was removed by adding a certain amount of an additive that can act as a complexing agent and a reducing agent in the electrolyte, and the iron concentration change was measured by using ICP-AES (inductively coupled plasma atomic emission spectrometer). The complexing agents used in the experiments were EDTA, NTA, citric acid and HEDTA, and L-ascorbic acid and D-ascorbic acid were used as reducing agents.

The precipitate removal rate was calculated by comparing the iron concentration added to the initial reference electrolyte with the iron concentration dissolved in the electrolyte rather than precipitation. That is, when the iron concentration of the supernatant separated from the precipitate was measured by centrifuging the reference electrolyte in which the initial precipitate was formed, most of the iron was precipitated in the form of a hydrate, and almost no iron was detected in the electrolyte supernatant separated from the precipitate.

On the other hand, when a complexing agent or a reducing agent for removing the precipitate is added to the reference electrolyte, the iron component contained in the precipitate is dissolved in the electrolyte, and the precipitate is removed, and the iron concentration of the electrolyte is increased. The precipitation removal rate of the electrolyte was calculated by comparing the iron concentration added to the initial electrolyte and the iron concentration of the electrolyte after the additive was added. Precipitation removal rates according to the type and amount of the complexing agent and the reducing agent added are shown in Tables 1 to 3 below.

Example Complexing agent Concentration (g / L) Iron concentration (mg / L) Precipitation Removal Rate (%) Amount Measurand Example 1 EDTA One 808 156 19 Example 2 EDTA 3 808 594 74 Example 3 EDTA 5 808 748 93 Example 4 EDTA 7 808 762 94 Example 5 HEDTA One 808 126 16 Example 6 HEDTA 3 808 460 57 Example 7 HEDTA 5 808 701 87 Example 8 HEDTA 7 808 732 91 Example 9 NTA One 808 170 21 Example 10 NTA 3 808 711 88 Example 11 NTA 5 808 754 93 Example 12 NTA 7 808 754 93 Example 13 Citric acid One 808 196 24 Example 14 Citric acid 3 808 662 82 Example 15 Citric acid 5 808 772 95 Example 16 Citric acid 7 808 753 93

In Examples 1 to 16, EDTA, HEDTA, NTA, and citric acid were included in the range of 1 g / L to 7 g / L as complexing agents in the electrolyte solution, respectively.

Referring to Table 1, when the electrolyte solution contains a complexing agent as in Examples 1 to 16, it was confirmed that iron was removed. Higher concentrations of complexing agents resulted in higher precipitation removal rates.

Example reducing agent Concentration (g / L) Iron concentration (mg / L) Precipitation Removal Rate (%) Amount Measurand Example 17 L-ascorbic acid One 808 364 45 Example 18 L-ascorbic acid 3 808 682 84 Example 19 L-ascorbic acid 5 808 690 85 Example 20 L-ascorbic acid 7 808 766 95 Example 21 D-ascorbic acid One 808 155 19 Example 22 D-ascorbic acid 3 808 630 78 Example 23 D-ascorbic acid 5 808 764 95 Example 24 D-ascorbic acid 7 808 776 96

In Examples 17 to 24, L-ascorbic acid and D-ascorbic acid were included in the electrolyte as a reducing agent in the range of 1 g / L to 7 g / L, respectively.

Referring to Table 2, as in Examples 17 to 24, when the electrolyte solution contains a reducing agent, iron was removed, and the higher the concentration of the reducing agent, the higher the precipitation removal rate.

Example Complexing agent reducing agent Concentration (g / L) Iron concentration (mg / L) Precipitation Removal Rate (%) Amount Measurand Example 25 NTA One 882 789 89 L-ascorbic acid One Example 26 NTA One 882 818 93 L-ascorbic acid 3 Example 27 NTA One 882 816 93 L-ascorbic acid 5 Example 28 NTA 3 882 835 95 L-ascorbic acid One Example 29 NTA 3 882 853 97 L-ascorbic acid 3 Example 30 NTA 3 882 860 98 L-ascorbic acid 5 Example 31 NTA 5 882 826 94 L-ascorbic acid One Example 32 NTA 5 882 839 95 L-ascorbic acid 3 Example 33 NTA 5 882 832 94 L-ascorbic acid 5

In the electrolyte solutions of Examples 25 to 33, NTA as a complexing agent and L-ascorbic acid as a reducing agent were contained at different concentrations.

When the complexing agent and the reducing agent were added together to the electrolyte solution as in Examples 25 to 33, a precipitation removal rate of 89% or more was calculated. In particular, in Example 25, NTA and L-ascorbic acid were added 1 g / L, respectively, and showed a high precipitation removal rate of 89% even though a relatively small amount was added.

Referring to Table 1 and Table 2, when the electrolyte solution contains a complexing agent as in Examples 1 to 16 and when the electrolyte solution contains a reducing agent as in Examples 17 to 24, iron precipitates were removed, respectively. The higher the concentration of complexing agent and reducing agent, the higher the precipitation removal rate.

Therefore, when any one of the complexing agent and the reducing agent is included in the electrolytic solution for metalworking, it was confirmed that precipitation of the metal ions eluted, such as iron, is possible with high efficiency. In particular, in each of the experimental results, in order to remove 90% or more of the precipitation, it was possible when the complexing agent or the reducing agent included 5g / L or more.

When the complexing agent and the reducing agent are added together to the electrolyte solution as in Examples 25 to 33, even when the amount of the complexing agent and the reducing agent is used alone as in Examples 1 to 24, A level of precipitation removal rate could be obtained.

In the present embodiment, the example of iron was performed and the results were confirmed. However, even in the case of a product other than iron, for example, a metal such as copper, nickel, aluminum, tin, chromium, or zinc, and an alloy thereof. In terms of the action of the complexing agent and the reducing agent on the metal, metal precipitates may be removed similarly to iron products.

The present invention should not be limited by the above-described embodiments, but should be construed by the appended claims. In addition, it will be apparent to those skilled in the art that various forms of substitution, modification, and alteration are possible within the scope of the present invention without departing from the technical spirit of the present invention.

Claims (12)

An inorganic salt in the solvent, at least one of a complexing agent and a reducing agent, The complexing agent is citric acid (Acetic acid), acetic acid (Acetic acid), oxalic acid (Oxalic acid), Fulvic acid (Fulvic acid), Succinic acid (Succinic acid), tartaric acid (Tartaric acid), lactic acid (glucoic acid) ( One or more selected from the group consisting of Gluconic acid, Maleic acid, Malic acid, and salts thereof, The reducing agent is at least one selected from the group consisting of L-ascorbic acid (L-ascorbic acid), D-isoascorbic acid (D-isoascorbic acid) and salts thereof. The method of claim 1, Wherein the metal is iron, copper, nickel, aluminum, tin, chromium, zinc and any one of these alloys, the electrolytic solution for metal products electrolytic processing. The method of claim 1, Electrolyte solution for electrolytic processing of metal products, characterized in that the solvent is pure water. The method of claim 1, The inorganic salt is at least one selected from the group consisting of NaNO ₃ , NaCl, NaClO ₄ , Na ₂ SO ₄ , KNO ₃ , KCl, KClO ₄ , K ₂ SO ₄ , LiNO ₃ , LiCl, LiClO ₄ , and Li ₂ SO ₄ Electrolyte solution for electrolytic processing of metal products, characterized in that the. The method of claim 1, The concentration of the inorganic salt is an electrolytic solution for metal product electrolytic processing, characterized in that from 100g / L to 500g / L based on the volume of the total electrolyte solution. delete The method of claim 1, The acetic acid Electrolyte solution for electrolytic processing of metal products, characterized in that at least one selected from the group consisting of ethylenediaminetetraacetic acid (Ethylenediaminetetraacetic acid), hydroxyethylethylenediaminetriacetic acid, and nitrilotriacetic acid. The method of claim 1, The concentration of the complexing agent is an electrolytic solution for metal product electrolytic processing, characterized in that 0.5 to 20 g / L based on the volume of the total electrolyte. delete The method of claim 1, The concentration of the reducing agent is an electrolytic solution for metal products electrolytic processing, characterized in that 0.5 to 20 g / L based on the total volume of the electrolyte. The method of claim 1, Electrolytic solution for a metal product electrolytic processing, characterized in that it further comprises at least one of a corrosion inhibitor, a surfactant, a viscosity regulator, a pH regulator. The method of claim 1, Electrolyte solution for electrolytic processing of metal products, characterized in that the pH range is pH 2 to pH 7.