Electrolytic polishing liquid for stainless steel

Abstract

To provide a neutral or alkaline electrolytic polishing liquid improved in an electrolytic polishing speed (weld scale removal speed).SOLUTION: The electrolytic polishing liquid for use in subjecting stainless steel to an electrolytic polishing treatment, satisfies the following condition: (1) a neutral salt of an acid other than phosphonic acid and aminocarboxylic acid, and a phosphonic acid compound or a salt thereof are contained therein, or (2) a neutral salt of an acid is contained therein, and the neutral salt of an acid contains a neutral salt of phytic acid.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an electropolishing solution for stainless steel. [Background technology]

[0002] When stainless steel is welded, an oxide scale (weld scale) called "weld burn" is generated at the welded area. This weld scale can cause various problems and must be removed. There are three known methods for removing weld scale: physical polishing, chemical polishing, and electrolytic polishing. Among them, electrolytic polishing, which has excellent performance for removing weld scale, is widely used. The electrolytic polishing method is a method for removing the weld scale on the stainless steel surface by connecting the stainless steel base material as the anode to the positive electrode, connecting the cathode to the negative electrode, and passing a current between the anode and cathode with an electrolytic polishing solution between them.

[0003] The electrolytic polishing liquid used in this electrolytic polishing method is roughly divided into an acidic electrolytic polishing liquid and a neutral or basic electrolytic polishing liquid. Of these, the acidic electrolytic polishing liquid has a faster processing speed (welding scale removal speed) than the neutral or basic electrolytic polishing liquid, so in recent years, various acidic electrolytic polishing liquids have been proposed, and in recent years, acidic electrolytic polishing liquids mainly composed of phosphoric acid have been widely used in the industrial world, and since the processing speed (welding scale removal speed) of the electrolytic polishing process is fast, the AC current method or the AC / DC superimposed current method is widely used. However, when this phosphoric acid is used as the acidic electrolytic polishing liquid and the electrolytic polishing process is performed by the AC current method or the AC / DC superimposed current method, insoluble iron phosphate is generated, and the surface treated part of the stainless steel becomes cloudy. Summary of the Invention [Problem to be solved by the invention]

[0004] On the other hand, it is possible to avoid this clouding by using a neutral or basic electrolytic polishing liquid, but conventional neutral or basic electrolytic polishing liquids have the problem that the processing speed of the electrolytic polishing process (weld scale removal speed) is slow.

[0005] The present invention is intended to solve such problems, and aims to provide an electrolytic polishing liquid that is neutral or basic yet has an improved processing speed (weld scale removal speed) of electrolytic polishing treatment. [Means for solving the problem]

[0006] The present inventors have conducted intensive research to achieve the above-mentioned object. As a result, they have found that an electropolishing solution that is neutral but has an excellent processing speed (weld scale removal speed) of electropolishing treatment can be obtained by containing a neutral salt of an acid other than phosphonic acid and aminocarboxylic acid and a phosphonic acid compound or its salt, or by containing a neutral salt of phytic acid and at least one neutral salt selected from the group consisting of tartaric acid, malic acid, gluconic acid, and citric acid as the neutral salt of the acid. Based on this finding, they have conducted further research and completed the present invention. That is, the present invention includes the following configurations.

[0007] Item 1. An electrolytic polishing solution for electrolytic polishing of stainless steel, a neutral salt of an acid other than a phosphonic acid or an aminocarboxylic acid; An electropolishing solution comprising a phosphonic acid compound or a salt thereof, and / or an aminocarboxylic acid compound or a salt thereof.

[0008] Item 2. The electropolishing solution according to Item 1, wherein the neutral salt of an acid is at least one neutral salt selected from the group consisting of phosphoric acid, phytic acid, tartaric acid, malic acid, gluconic acid, and citric acid.

[0009] Item 3. An electrolytic polishing solution for electrolytic polishing of stainless steel, Contains a neutral salt of an acid, The electropolishing solution, wherein the neutral salt of an acid contains a neutral salt of phytic acid.

[0010] Item 4. The electropolishing solution according to Item 3, further comprising at least one neutral salt selected from the group consisting of tartaric acid, malic acid, gluconic acid, and citric acid.

[0011] Item 5. The electropolishing liquid according to Item 3 or 4, further comprising a phosphonic acid compound or a salt thereof.

[0012] Item 6. The electropolishing solution according to claim 1, 2, or 5, wherein the content of the phosphonic acid compound or a salt thereof is 0.5 to 20.0 mass % relative to 100 mass % of the total amount of the electropolishing solution.

[0013] Item 7. The electropolishing liquid according to any one of Items 3 to 6, further comprising an aminocarboxylic acid compound and / or a salt thereof.

[0014] Item 8. The electropolishing solution according to Item 1 or 2, wherein the content of the aminocarboxylic acid compound and / or a salt thereof is 0.5 to 5.0 mass % relative to 100 mass % of the total amount of the electropolishing solution.

[0015] Item 9. The electropolishing solution according to Item 7, wherein the content of the aminocarboxylic acid compound and / or a salt thereof is 0.5 to 5.0 mass % based on 100 mass % of the total amount of the electropolishing solution.

[0016] Item 10. The electropolishing solution according to any one of Items 1 to 9, wherein the content of the neutral salt of the acid is 0.5 to 40.0 mass % relative to 100 mass % of the total amount of the electropolishing solution.

[0017] Item 11. The electropolishing liquid according to any one of Items 1 to 10, further comprising a sulfonic acid compound or a salt thereof.

[0018] Item 12. The electropolishing solution according to Item 11, wherein the content of the sulfonic acid compound or a salt thereof is 0.5 to 20.0 mass % relative to 100 mass % of the total amount of the electropolishing solution.

[0019] Item 13. The stainless steel electropolishing solution according to any one of Items 1 to 12, which is used for electropolishing stainless steel by an AC current method or an AC / DC superimposed current method.

[0020] Item 14. A method for electrolytic polishing of stainless steel, comprising electrolysis using the stainless steel electrolytic polishing solution according to any one of items 1 to 13.

[0021] Item 15. A method for producing stainless steel, comprising electrolysis using the stainless steel electropolishing solution according to any one of items 1 to 13. Effect of the Invention

[0022] According to the present invention, it is possible to provide an electropolishing liquid that is neutral and yet has an excellent processing speed (weld scale removal speed) for electropolishing. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] In this specification, the term "containing" is a concept that encompasses all of "comprise," "consist essentially of," and "consist only of."

[0024] In this specification, when a numerical range is indicated as "A to B," it means A or more and B or less.

[0025] 1. Electropolishing solution (first aspect) The electropolishing liquid according to the first aspect of the present invention is an electropolishing liquid for electropolishing stainless steel, and contains a neutral salt of an acid other than phosphonic acid, a phosphonic acid compound or a salt thereof, and / or an aminocarboxylic acid compound or a salt thereof.

[0026] (1-1) Neutral salt of acid The neutral salts of acids other than phosphonic acid and aminocarboxylic acid are not particularly limited, but neutral salts of phosphoric acid, phytic acid, tartaric acid, malic acid, gluconic acid, citric acid, etc. can be used.

[0027] The neutral salt is not particularly limited, but examples thereof include alkali metal salts, alkaline earth metal salts, ammonium salts, etc., and specifically, examples thereof include potassium salts, sodium salts, magnesium salts, calcium salts, ammonium salts, etc. Among these, from the viewpoint of the processing speed of the electrolytic polishing treatment (weld scale removal speed), alkali metal salts are preferred, and potassium salts are more preferred.

[0028] Specific examples of neutral salts of acids other than phosphonic acid include potassium phosphate, sodium phosphate, potassium phytate, sodium phytate, potassium tartrate, sodium tartrate, potassium malate, sodium malate, potassium gluconate, sodium gluconate, potassium citrate, sodium citrate, etc. When a neutral salt of phosphoric acid is used, examples of the phosphoric acid include metaphosphoric acid, hypophosphorous acid, orthophosphoric acid, pyrophosphoric acid, trimetaphosphoric acid, triphosphoric acid, tetraphosphoric acid, hexaphosphoric acid, etc. These neutral salts of acids can be used alone or in combination of two or more.

[0029] Among them, from the viewpoint of the processing speed of the electrolytic polishing treatment (weld scale removal speed), it is preferable to contain a neutral salt of phytic acid (potassium phytate, sodium phytate, etc.) and a neutral salt of tartaric acid, malic acid, gluconic acid, citric acid, etc. (potassium tartrate, sodium tartrate, potassium malate, sodium malate, potassium gluconate, sodium gluconate, potassium citrate, sodium citrate, etc.). In this case, the content of the neutral salt of phytic acid (potassium phytate, sodium phytate, etc.) is preferably 5 to 20 parts by mass, more preferably 6 to 18 parts by mass, and even more preferably 7 to 15 parts by mass, relative to 100 parts by mass of the neutral salt of tartaric acid, malic acid, gluconic acid, citric acid, etc. (potassium tartrate, sodium tartrate, potassium malate, sodium malate, potassium gluconate, sodium gluconate, potassium citrate, sodium citrate, etc.).

[0030] The content of the neutral salt of the acid in the electropolishing solution of the present invention is not particularly limited, but from the viewpoint of the processing speed of the electropolishing treatment (weld scale removal speed), the total amount of the electropolishing solution of the present invention is preferably 0.5 to 40.0 mass%, more preferably 1.0 to 30.0 mass%, and even more preferably 3.0 to 20.0 mass%, taken as 100 mass%. In addition, when two or more kinds of neutral salts of the acid are used, it is preferable to adjust the total content to be within the above range.

[0031] (1-2) Phosphonic acid compound or its salt The phosphonic acid compound or its salt used in the present invention functions as a phosphonic acid-based chelating agent that captures metal ions, and when used in combination with the neutral salt of the above-mentioned acid, it is easy to further improve the processing speed of the electrolytic polishing process (weld scale removal speed).

[0032] Specific examples of the phosphonic acid compound or its salt include phosphonic acid compounds such as nitrilotris(methylene phosphonic acid), 1-hydroxyethylidene-1,1-diphosphonic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid, and ethylenediaminetetrakismethylenephosphonic acid, as well as salts thereof. Among these, from the viewpoint of the processing speed of the electrolytic polishing treatment (weld scale removal speed), nitrilotris(methylene phosphonic acid), 1-hydroxyethylidene-1,1-diphosphonic acid, and the like, and salts thereof are preferred.

[0033] Examples of the salts of these phosphonic acid compounds include alkali metal salts, alkaline earth metal salts, and ammonium salts, and more specifically, potassium salts, sodium salts, magnesium salts, calcium salts, and ammonium salts. Hydrates of these salts can also be used. Among these, from the viewpoint of the processing speed of the electrolytic polishing process (weld scale removal speed), alkali metal salts are preferred, and potassium salts are more preferred.

[0034] Specific examples of the phosphonic acid compound or a salt thereof include nitrilotris(methylene phosphonic acid), nitrilotris(methylene phosphonic acid) potassium salt, nitrilotris(methylene phosphonic acid) sodium salt, 1-hydroxyethylidene-1,1-diphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid potassium salt, 1-hydroxyethylidene-1,1-diphosphonic acid sodium salt, 2-phosphonobutane-1,2,4-tricarboxylic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid potassium salt, 2-phosphonobutane-1,2,4-tricarboxylic acid sodium salt, ethylenediaminetetrakismethylenephosphonic acid, ethylenediaminetetrakismethylenephosphonic acid potassium salt, ethylenediaminetetrakismethylenephosphonic acid sodium salt, and the like.

[0035] These phosphonic acid compounds or salts thereof can be used alone or in combination of two or more kinds.

[0036] The content of the phosphonic acid compound or its salt in the electropolishing solution of the present invention is not particularly limited, but from the viewpoint of the processing speed of the electropolishing treatment (weld scale removal speed), the total amount of the electropolishing solution of the present invention is preferably 0.5 to 20.0 mass%, more preferably 3.0 to 18.0 mass%, and even more preferably 7.0 to 15.0 mass%, based on 100 mass% of the total amount of the electropolishing solution of the present invention. In addition, when two or more kinds of phosphonic acid compounds or their salts are used, it is preferable to adjust the total content to be within the above range.

[0037] (1-3) Aminocarboxylic acid compound or its salt The aminocarboxylic acid compound and / or its salt that can be used in the present invention can further improve the processing speed of the electrolytic polishing process (weld scale removal speed) by using it in combination with the neutral salt of the above-mentioned acid. This aminocarboxylic acid compound and / or its salt can continue to improve the processing speed of the electrolytic polishing process (weld scale removal speed) without deteriorating over time in the solution.

[0038] Specific examples of the aminocarboxylic acid compound and / or its salt include aminocarboxylic acid compounds such as ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), hydroxyethylethylenediaminetriacetic acid (HEDTA), 1,3-propanediaminetetraacetic acid (PDTA), triethylenetetraminehexaacetic acid (TTHA), 1,3-diamino-2-propanoltetraacetic acid (DPTA-OH), hydroxyethyliminodiacetic acid (HIDA), and nitrilotriacetic acid (NTA), and their salts. Among these, from the viewpoint of the processing speed of the electrolytic polishing process (weld scale removal speed), ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), hydroxyethylethylenediaminetriacetic acid (HEDTA), and their salts are preferred, and ethylenediaminetetraacetic acid (EDTA) and its salts are more preferred.

[0039] Examples of the salts of these aminocarboxylic acid compounds include alkali metal salts, alkaline earth metal salts, and ammonium salts, and more specifically, potassium salts, sodium salts, magnesium salts, calcium salts, and ammonium salts. Hydrates of these compounds can also be used. Among these, from the viewpoint of the processing speed of the electrolytic polishing process (weld scale removal speed), alkali metal salts are preferred, and potassium salts are more preferred.

[0040] Specific examples of the aminocarboxylic acid compound or a salt thereof include ethylenediaminetetraacetic acid (EDTA), potassium ethylenediaminetetraacetic acid, sodium ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid (DTPA), potassium diethylenetriaminepentaacetic acid, potassium diethylenetriaminepentaacetic acid, hydroxyethylethylenediaminetriacetic acid (HEDTA), potassium hydroxyethylethylenediaminetriacetic acid, sodium hydroxyethylethylenediaminetriacetic acid, 1,3-propanediaminetetraacetic acid (PDTA), potassium 1,3-propanediaminetetraacetic acid, and 1,3-propanediaminetetraacetic acid. Examples of the diaminetetraacetic acid include sodium diaminetetraacetic acid (TTHA), potassium triethylenetetramine hexaacetic acid, sodium triethylenetetramine hexaacetic acid, 1,3-diamino-2-propanol tetraacetic acid (DPTA-OH), potassium 1,3-diamino-2-propanol tetraacetic acid, sodium 1,3-diamino-2-propanol tetraacetic acid, hydroxyethyliminodiacetic acid (HIDA), potassium hydroxyethyliminodiacetic acid, sodium hydroxyethyliminodiacetic acid, nitrilotriacetic acid (NTA), potassium nitrilotriacetic acid, and sodium nitrilotriacetic acid.

[0041] These aminocarboxylic acid compounds or salts thereof can be used alone or in combination of two or more kinds.

[0042] The content of the aminocarboxylic acid compound or its salt in the electropolishing solution of the present invention is not particularly limited, but from the viewpoint of the processing speed of the electropolishing treatment (weld scale removal speed), the total amount of the electropolishing solution of the present invention is preferably 0.5 to 5.0 mass%, more preferably 0.6 to 4.0 mass%, and even more preferably 0.7 to 3.0 mass%, taken as 100 mass%. In addition, when two or more kinds of aminocarboxylic acid compounds or their salts are used, it is preferable to adjust the total content to be within the above range.

[0043] (1-4) Sulfonic acid compound or its salt The sulfonic acid compound or a salt thereof that can be used in the present invention tends to further increase the processing speed (weld scale removal speed) of the electrolytic polishing treatment by using it in combination with the neutral salt of the above-mentioned acid.

[0044] Specific examples of the sulfonic acid compound include methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid (1-propanesulfonic acid, 2-propanesulfonic acid, etc.), vinylsulfonic acid, benzenesulfonic acid, toluenesulfonic acid (o-toluenesulfonic acid, m-toluenesulfonic acid, p-toluenesulfonic acid, etc.), phenolsulfonic acid (o-phenolsulfonic acid, m-phenolsulfonic acid, p-phenolsulfonic acid, etc.), nitrobenzenesulfonic acid (o-nitrobenzenesulfonic acid, m-nitrobenzenesulfonic acid, p-nitrobenzenesulfonic acid, etc.), bis(3-sulfopropyl)disulfide, and salts thereof. Among these, from the viewpoint of the processing speed of the electrolytic polishing process (weld scale removal speed), methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid (1-propanesulfonic acid, 2-propanesulfonic acid, etc.), benzenesulfonic acid, toluenesulfonic acid (o-toluenesulfonic acid, m-toluenesulfonic acid, p-toluenesulfonic acid, etc.), phenolsulfonic acid (o-phenolsulfonic acid, m-phenolsulfonic acid, p-phenolsulfonic acid, etc.), nitrobenzenesulfonic acid (o-nitrobenzenesulfonic acid, m-nitrobenzenesulfonic acid, p-nitrobenzenesulfonic acid, etc.), bis(3-sulfopropyl)disulfide, and the like, and salts thereof are preferred, and methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid (1-propanesulfonic acid, 2-propanesulfonic acid, etc.), toluenesulfonic acid (o-toluenesulfonic acid, m-toluenesulfonic acid, p-toluenesulfonic acid, etc.), nitrobenzenesulfonic acid (o-nitrobenzenesulfonic acid, m-nitrobenzenesulfonic acid, p-nitrobenzenesulfonic acid, etc.), bis(3-sulfopropyl)disulfide, and the like, and salts thereof are more preferred.

[0045] Examples of the salts of these sulfonic acid compounds include alkali metal salts, alkaline earth metal salts, and ammonium salts, and more specifically, potassium salts, sodium salts, magnesium salts, calcium salts, and ammonium salts. Hydrates of these salts can also be used. Among these, from the viewpoint of the processing speed of the electrolytic polishing process (weld scale removal speed), alkali metal salts are preferred, and potassium salts are more preferred.

[0046] Specific examples of the sulfonic acid compound or a salt thereof include methanesulfonic acid, potassium methanesulfonate, sodium methanesulfonate, ethanesulfonic acid, potassium ethanesulfonate, sodium ethanesulfonate, propanesulfonic acid (e.g., 1-propanesulfonic acid, 2-propanesulfonic acid), potassium propanesulfonate (e.g., potassium 1-propanesulfonate, potassium 2-propanesulfonate), sodium propanesulfonate (e.g., sodium 1-propanesulfonate, sodium 2-propanesulfonate), vinyl sulfonate, acid, potassium vinyl sulfonate, sodium vinyl sulfonate, benzenesulfonic acid, potassium benzenesulfonate, sodium benzenesulfonate, toluenesulfonic acid (o-toluenesulfonic acid, m-toluenesulfonic acid, p-toluenesulfonic acid, etc.), potassium toluenesulfonate (potassium o-toluenesulfonate, potassium m-toluenesulfonate, potassium p-toluenesulfonate, etc.), sodium toluenesulfonate (sodium o-toluenesulfonate, sodium m-toluenesulfonate, p-toluenesulfonate, etc.), sodium phenolsulfonate, etc.), phenolsulfonic acid (o-phenolsulfonic acid, m-phenolsulfonic acid, p-phenolsulfonic acid, etc.), potassium phenolsulfonate (o-phenolsulfonic acid, m-phenolsulfonic acid, p-phenolsulfonic acid, etc.), sodium phenolsulfonate (o-phenolsulfonic acid, m-phenolsulfonic acid, p-phenolsulfonic acid, etc.), nitrobenzenesulfonic acid (o-nitrobenzenesulfonic acid, m-nitrobenzenesulfonic acid, p-nitrobenzenesulfonic acid, etc.), potassium nitrobenzenesulfonate (o-nitrobenzenesulfonic acid, m-nitrobenzenesulfonic acid, p-nitrobenzenesulfonic acid, etc.), sodium nitrobenzenesulfonate (o-nitrobenzenesulfonic acid, m-nitrobenzenesulfonic acid, p-nitrobenzenesulfonic acid, etc.), bis(3-sulfopropyl) disulfide, 3,3'-dithiobis(propane-1-sodium sulfonate), and the like.

[0047] These sulfonic acids or salts thereof can be used alone or in combination of two or more.

[0048] The content of the sulfonic acid compound or its salt in the electropolishing solution of the present invention is not particularly limited, but from the viewpoint of the processing speed of the electropolishing treatment (weld scale removal speed), the total amount of the electropolishing solution of the present invention is preferably 0.5 to 20.0 mass%, more preferably 3.0 to 18.0 mass%, and even more preferably 7.0 to 15.0 mass%, based on 100 mass% of the total amount of the electropolishing solution of the present invention. In addition, when two or more kinds of sulfonic acid compounds or their salts are used, it is preferable to adjust the total content to be within the above range.

[0049] (1-5) Electrolytic polishing liquid The electropolishing solution of the present invention can contain various components other than the neutral salt of an acid other than the above-mentioned phosphonic acid and aminocarboxylic acid, a phosphonic acid compound or a salt thereof, and, if necessary, an aminocarboxylic acid compound or a salt thereof, and, if necessary, a sulfonic acid compound or a salt thereof.

[0050] The electropolishing solution of the present invention may also contain a gelling agent. By including a gelling agent, the electropolishing solution of the present invention may be given a suitable viscosity, and a paste-like electropolishing solution may be obtained. This is useful when dripping during electropolishing is to be avoided, for example, when a stainless steel base material is welded at a site where it is installed vertically and welding burns are to be removed. From this viewpoint, when a gelling agent is included in the electropolishing solution of the present invention, the content is preferably 0.01 to 1 mass%, more preferably 0.02 to 0.5 mass%. Such gelling agents are not particularly limited, and may include one or more of chemically modified cellulose derivatives such as hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, and carboxymethyl cellulose, and polysaccharides such as xanthan gum, guar gum, carrageenan, tamarind gum, locust bean gum, and pectin.

[0051] The electropolishing solution of the present invention may also contain diethylene glycol. By containing diethylene glycol, it is possible to further improve the processing speed. From this viewpoint, when the electropolishing solution of the present invention contains diethylene glycol, the content is preferably 0.01 to 1 mass %, more preferably 0.02 to 0.5 mass %.

[0052] The electrolytic polishing solution of the present invention is preferably an aqueous solution from the viewpoint of increasing the processing speed when removing weld scale by electrolytic polishing. The amount of water used is preferably adjusted so that the content of each component in the electrolytic polishing solution of the present invention is within the above range. As a result, the electrolytic polishing solution of the present invention can be made neutral, for example, pH 6.0 to 8.0, preferably 6.5 to 7.5, and unlike acidic electrolytic polishing solutions, it is a neutral electrolytic polishing solution that does not become cloudy, but can particularly effectively remove weld scale.

[0053] 2. Electropolishing solution (second embodiment) An electropolishing liquid according to a second aspect of the present invention is an electropolishing liquid for electropolishing stainless steel, which contains a neutral salt of an acid, and the neutral salt of the acid contains a neutral salt of phytic acid.

[0054] (2-1) Neutral salt of acid Neutral salts of acids include the neutral salt of phytic acid.

[0055] The neutral salt is not particularly limited, but examples thereof include alkali metal salts, alkaline earth metal salts, ammonium salts, etc., and specifically includes potassium salts, sodium salts, magnesium salts, calcium salts, ammonium salts, etc. Among them, from the viewpoint of the processing speed of the electrolytic polishing treatment (weld scale removal speed), alkali metal salts are preferred, and potassium salts are more preferred.

[0056] Among the neutral salts of acids, specific examples of the neutral salt of phytic acid include potassium phytate, sodium phytate, etc. These neutral salts of phytic acid can be used alone or in combination of two or more.

[0057] In the neutral salt of an acid, in addition to the neutral salt of phytic acid, at least one neutral salt selected from the group consisting of tartaric acid, malic acid, gluconic acid, and citric acid may be included. Specific examples of the at least one neutral salt selected from the group consisting of tartaric acid, malic acid, gluconic acid, and citric acid include potassium tartrate, sodium tartrate, potassium malate, sodium malate, potassium gluconate, sodium gluconate, potassium citrate, and sodium citrate. These neutral salts of acids may be used alone or in combination of two or more.

[0058] In particular, from the viewpoint of the processing speed of the electrolytic polishing treatment (weld scale removal speed), the content of the neutral salt of phytic acid (potassium phytate, sodium phytate, etc.) is preferably 5 to 20 parts by mass, more preferably 6 to 18 parts by mass, and even more preferably 7 to 15 parts by mass, per 100 parts by mass of the neutral salt of tartaric acid, malic acid, gluconic acid, citric acid, etc. (potassium tartrate, sodium tartrate, potassium malate, sodium malate, potassium gluconate, sodium gluconate, potassium citrate, sodium citrate, etc.).

[0059] The content of the neutral salt of the acid in the electropolishing solution of the present invention is not particularly limited, but from the viewpoint of the processing speed of the electropolishing treatment (weld scale removal speed), the total amount of the electropolishing solution of the present invention is taken as 100 mass%, and it is preferably 0.5 to 40.0 mass%, more preferably 1.0 to 30.0 mass%, and even more preferably 3.0 to 20.0 mass%. The content of the neutral salt of the acid is preferably adjusted so that the total content of the neutral salt of phytic acid and at least one neutral salt selected from the group consisting of tartaric acid, malic acid, gluconic acid, and citric acid is within the above range.

[0060] (2-2) Phosphonic acid compound or its salt The phosphonic acid compound or its salt that can be used in the present invention functions as a phosphonic acid-based chelating agent that captures metal ions, and when used in combination with the neutral salt of the above-mentioned acid, it is easy to further improve the processing speed of the electrolytic polishing process (weld scale removal speed).

[0061] Specific examples of the phosphonic acid compound or its salt include phosphonic acid compounds such as nitrilotris(methylene phosphonic acid), 1-hydroxyethylidene-1,1-diphosphonic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid, and ethylenediaminetetrakismethylenephosphonic acid, as well as salts thereof. Among these, from the viewpoint of the processing speed of the electrolytic polishing treatment (weld scale removal speed), nitrilotris(methylene phosphonic acid), 1-hydroxyethylidene-1,1-diphosphonic acid, and the like, and salts thereof are preferred.

[0062] Examples of the salts of these phosphonic acid compounds include alkali metal salts, alkaline earth metal salts, and ammonium salts, and more specifically, potassium salts, sodium salts, magnesium salts, calcium salts, and ammonium salts. Hydrates of these salts can also be used. Among these, from the viewpoint of the processing speed of the electrolytic polishing process (weld scale removal speed), alkali metal salts are preferred, and potassium salts are more preferred.

[0063] Specific examples of the phosphonic acid compound or a salt thereof include nitrilotris(methylene phosphonic acid), nitrilotris(methylene phosphonic acid) potassium salt, nitrilotris(methylene phosphonic acid) sodium salt, 1-hydroxyethylidene-1,1-diphosphonic acid, 1-hydroxyethylidene-1,1-diphosphonic acid potassium salt, 1-hydroxyethylidene-1,1-diphosphonic acid sodium salt, 2-phosphonobutane-1,2,4-tricarboxylic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid potassium salt, 2-phosphonobutane-1,2,4-tricarboxylic acid sodium salt, ethylenediaminetetrakismethylenephosphonic acid, ethylenediaminetetrakismethylenephosphonic acid potassium salt, ethylenediaminetetrakismethylenephosphonic acid sodium salt, and the like.

[0064] These phosphonic acid compounds or salts thereof can be used alone or in combination of two or more kinds.

[0065] The content of the phosphonic acid compound or its salt in the electropolishing solution of the present invention is not particularly limited, but from the viewpoint of the processing speed of the electropolishing treatment (weld scale removal speed), the total amount of the electropolishing solution of the present invention is preferably 0.5 to 20.0 mass%, more preferably 3.0 to 18.0 mass%, and even more preferably 7.0 to 15.0 mass%, based on 100 mass% of the total amount of the electropolishing solution of the present invention. In addition, when two or more kinds of phosphonic acid compounds or their salts are used, it is preferable to adjust the total content to be within the above range.

[0066] (2-3) Aminocarboxylic acid compound or its salt The aminocarboxylic acid compound and / or its salt that can be used in the present invention can further improve the processing speed of the electrolytic polishing process (weld scale removal speed) by using it in combination with the neutral salt of the above-mentioned acid. This aminocarboxylic acid compound and / or its salt can continue to improve the processing speed of the electrolytic polishing process (weld scale removal speed) without deteriorating over time in the solution.

[0067] Specific examples of the aminocarboxylic acid compound and / or its salt include aminocarboxylic acid compounds such as ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), hydroxyethylethylenediaminetriacetic acid (HEDTA), 1,3-propanediaminetetraacetic acid (PDTA), triethylenetetraminehexaacetic acid (TTHA), 1,3-diamino-2-propanoltetraacetic acid (DPTA-OH), hydroxyethyliminodiacetic acid (HIDA), and nitrilotriacetic acid (NTA), and their salts. Among these, from the viewpoint of the processing speed of the electrolytic polishing process (weld scale removal speed), ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), hydroxyethylethylenediaminetriacetic acid (HEDTA), and their salts are preferred, and ethylenediaminetetraacetic acid (EDTA) and its salts are more preferred.

[0068] Examples of the salts of these aminocarboxylic acid compounds include alkali metal salts, alkaline earth metal salts, and ammonium salts, and more specifically, potassium salts, sodium salts, magnesium salts, calcium salts, and ammonium salts. Hydrates of these compounds can also be used. Among these, from the viewpoint of the processing speed of the electrolytic polishing process (weld scale removal speed), alkali metal salts are preferred, and potassium salts are more preferred.

[0069] Specific examples of the aminocarboxylic acid compound or a salt thereof include ethylenediaminetetraacetic acid (EDTA), potassium ethylenediaminetetraacetic acid, sodium ethylenediaminetetraacetic acid, diethylenetriaminepentaacetic acid (DTPA), potassium diethylenetriaminepentaacetic acid, potassium diethylenetriaminepentaacetic acid, hydroxyethylethylenediaminetriacetic acid (HEDTA), potassium hydroxyethylethylenediaminetriacetic acid, sodium hydroxyethylethylenediaminetriacetic acid, 1,3-propanediaminetetraacetic acid (PDTA), potassium 1,3-propanediaminetetraacetic acid, and 1,3-propanediaminetetraacetic acid. Examples of the diaminetetraacetic acid include sodium diaminetetraacetic acid (TTHA), potassium triethylenetetramine hexaacetic acid, sodium triethylenetetramine hexaacetic acid, 1,3-diamino-2-propanol tetraacetic acid (DPTA-OH), potassium 1,3-diamino-2-propanol tetraacetic acid, sodium 1,3-diamino-2-propanol tetraacetic acid, hydroxyethyliminodiacetic acid (HIDA), potassium hydroxyethyliminodiacetic acid, sodium hydroxyethyliminodiacetic acid, nitrilotriacetic acid (NTA), potassium nitrilotriacetic acid, and sodium nitrilotriacetic acid.

[0070] These aminocarboxylic acid compounds or salts thereof can be used alone or in combination of two or more kinds.

[0071] The content of the aminocarboxylic acid compound or its salt in the electropolishing solution of the present invention is not particularly limited, but from the viewpoint of the processing speed of the electropolishing treatment (weld scale removal speed), the total amount of the electropolishing solution of the present invention is preferably 0.5 to 5.0 mass%, more preferably 0.6 to 4.0 mass%, and even more preferably 0.7 to 3.0 mass%, taken as 100 mass%. In addition, when two or more kinds of aminocarboxylic acid compounds or their salts are used, it is preferable to adjust the total content to be within the above range.

[0072] (2-4) Sulfonic acid compound or its salt The sulfonic acid compound or a salt thereof that can be used in the present invention tends to further increase the processing speed (weld scale removal speed) of the electrolytic polishing treatment by using it in combination with the neutral salt of the above-mentioned acid.

[0073] Specific examples of the sulfonic acid compound include methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, vinylsulfonic acid, benzenesulfonic acid, toluenesulfonic acid (o-toluenesulfonic acid, m-toluenesulfonic acid, p-toluenesulfonic acid, etc.), phenolsulfonic acid (o-phenolsulfonic acid, m-phenolsulfonic acid, p-phenolsulfonic acid, etc.), nitrobenzenesulfonic acid (o-nitrobenzenesulfonic acid, m-nitrobenzenesulfonic acid, p-nitrobenzenesulfonic acid, etc.), bis(3-sulfopropyl)disulfide, and salts thereof. Among these, from the viewpoint of the processing speed of the electrolytic polishing process (weld scale removal speed), methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid (1-propanesulfonic acid, 2-propanesulfonic acid, etc.), benzenesulfonic acid, toluenesulfonic acid (o-toluenesulfonic acid, m-toluenesulfonic acid, p-toluenesulfonic acid, etc.), phenolsulfonic acid (o-phenolsulfonic acid, m-phenolsulfonic acid, p-phenolsulfonic acid, etc.), nitrobenzenesulfonic acid (o-nitrobenzenesulfonic acid, m-nitrobenzenesulfonic acid, p-nitrobenzenesulfonic acid, etc.), bis(3-sulfopropyl)disulfide, and the like, and salts thereof are preferred, and methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid (1-propanesulfonic acid, 2-propanesulfonic acid, etc.), toluenesulfonic acid (o-toluenesulfonic acid, m-toluenesulfonic acid, p-toluenesulfonic acid, etc.), nitrobenzenesulfonic acid (o-nitrobenzenesulfonic acid, m-nitrobenzenesulfonic acid, p-nitrobenzenesulfonic acid, etc.), bis(3-sulfopropyl)disulfide, and the like, and salts thereof are more preferred.

[0074] Examples of the salts of these sulfonic acid compounds include alkali metal salts, alkaline earth metal salts, and ammonium salts, and more specifically, potassium salts, sodium salts, magnesium salts, calcium salts, and ammonium salts. Hydrates of these salts can also be used. Among these, from the viewpoint of the processing speed of the electrolytic polishing process (weld scale removal speed), alkali metal salts are preferred, and potassium salts are more preferred.

[0075] Specific examples of the sulfonic acid compound or a salt thereof include methanesulfonic acid, potassium methanesulfonate, sodium methanesulfonate, ethanesulfonic acid, potassium ethanesulfonate, sodium ethanesulfonate, propanesulfonic acid (e.g., 1-propanesulfonic acid, 2-propanesulfonic acid), potassium propanesulfonate (e.g., potassium 1-propanesulfonate, potassium 2-propanesulfonate), sodium propanesulfonate (e.g., sodium 1-propanesulfonate, sodium 2-propanesulfonate), vinyl sulfonate, acid, potassium vinyl sulfonate, sodium vinyl sulfonate, benzenesulfonic acid, potassium benzenesulfonate, sodium benzenesulfonate, toluenesulfonic acid (o-toluenesulfonic acid, m-toluenesulfonic acid, p-toluenesulfonic acid, etc.), potassium toluenesulfonate (potassium o-toluenesulfonate, potassium m-toluenesulfonate, potassium p-toluenesulfonate, etc.), sodium toluenesulfonate (sodium o-toluenesulfonate, sodium m-toluenesulfonate, p-toluenesulfonate, etc.), sodium phenolsulfonate, etc.), phenolsulfonic acid (o-phenolsulfonic acid, m-phenolsulfonic acid, p-phenolsulfonic acid, etc.), potassium phenolsulfonate (o-phenolsulfonic acid, m-phenolsulfonic acid, p-phenolsulfonic acid, etc.), sodium phenolsulfonate (o-phenolsulfonic acid, m-phenolsulfonic acid, p-phenolsulfonic acid, etc.), nitrobenzenesulfonic acid (o-nitrobenzenesulfonic acid, m-nitrobenzenesulfonic acid, p-nitrobenzenesulfonic acid, etc.), potassium nitrobenzenesulfonate (o-nitrobenzenesulfonic acid, m-nitrobenzenesulfonic acid, p-nitrobenzenesulfonic acid, etc.), sodium nitrobenzenesulfonate (o-nitrobenzenesulfonic acid, m-nitrobenzenesulfonic acid, p-nitrobenzenesulfonic acid, etc.), bis(3-sulfopropyl) disulfide, 3,3'-dithiobis(propane-1-sodium sulfonate), and the like.

[0076] These sulfonic acids or salts thereof can be used alone or in combination of two or more.

[0077] The content of the sulfonic acid compound or its salt in the electropolishing solution of the present invention is not particularly limited, but from the viewpoint of the processing speed of the electropolishing treatment (weld scale removal speed), the total amount of the electropolishing solution of the present invention is preferably 0.5 to 20.0 mass%, more preferably 3.0 to 18.0 mass%, and even more preferably 7.0 to 15.0 mass%, based on 100 mass% of the total amount of the electropolishing solution of the present invention. In addition, when two or more kinds of sulfonic acid compounds or their salts are used, it is preferable to adjust the total content to be within the above range.

[0078] (2-5) Electrolytic polishing liquid The electropolishing solution of the present invention may contain various components in addition to the neutral salts of the above-mentioned acids, and, if necessary, a phosphonic acid compound or a salt thereof, if necessary, an aminocarboxylic acid compound or a salt thereof, and, if necessary, a sulfonic acid compound or a salt thereof.

[0079] The electropolishing solution of the present invention may also contain a gelling agent. By including a gelling agent, the electropolishing solution of the present invention may be given a suitable viscosity, and a paste-like electropolishing solution may be obtained. This is useful when dripping during electropolishing is to be avoided, for example, when a stainless steel base material is welded at a site where it is installed vertically and welding burns are to be removed. From this viewpoint, when a gelling agent is included in the electropolishing solution of the present invention, the content is preferably 0.01 to 1 mass%, more preferably 0.02 to 0.5 mass%. Such gelling agents are not particularly limited, and may include one or more of chemically modified cellulose derivatives such as hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, and carboxymethyl cellulose, and polysaccharides such as xanthan gum, guar gum, carrageenan, tamarind gum, locust bean gum, and pectin.

[0080] The electropolishing solution of the present invention may also contain diethylene glycol. By containing diethylene glycol, it is possible to further improve the processing speed. From this viewpoint, when the electropolishing solution of the present invention contains diethylene glycol, the content is preferably 0.01 to 1 mass %, more preferably 0.02 to 0.5 mass %.

[0081] The electrolytic polishing solution of the present invention is preferably an aqueous solution from the viewpoint of increasing the processing speed when removing weld scale by electrolytic polishing. The amount of water used is preferably adjusted so that the content of each component in the electrolytic polishing solution of the present invention is within the above range. As a result, the electrolytic polishing solution of the present invention can be made neutral, for example, pH 6.0 to 8.0, preferably 6.5 to 7.5, and unlike acidic electrolytic polishing solutions, it is a neutral electrolytic polishing solution that does not become cloudy, but can particularly effectively remove weld scale.

[0082] 3.Electrolytic polishing process The electrolytic polishing solution of the present invention is preferably used to remove weld scale from the surface of stainless steel. In this case, unlike acidic electrolytic polishing solutions, it is a neutral electrolytic polishing solution that does not cause clouding, and can improve the processing speed during electrolytic polishing.

[0083] When the electropolishing solution of the present invention is used to remove weld scale from the surface of stainless steel, the electropolishing treatment can be carried out by an AC current method or an AC / DC superimposed current method.

[0084] In this case, the electrolytic polishing solution of the present invention can be used in the AC current method or the AC / DC superimposed current method under the same conditions as in the conventional method, except that the electrolytic polishing solution of the present invention is used. For example, when the AC / DC superimposed current method is adopted, the stainless steel base material can be connected to the anode side of the AC current or the AC / DC superimposed current obtained by superimposing an AC current on a DC current, and electrolytic treatment can be performed using the electrolytic polishing solution of the present invention. In this case, the electrolytic polishing solution of the present invention can be used as an electrolyte in electrolysis by impregnating or brushing a cloth or felt having good retention of the electrolytic polishing solution and pressing it against the stainless steel base material, which is the anode. Note that an electrolytic polishing solution containing a neutral salt of phytic acid and at least one neutral salt selected from the group consisting of tartaric acid, malic acid, gluconic acid, and citric acid as the neutral salt of an acid is particularly suitable for applying electrolytic polishing by brushing. As a result, dissolution occurs at the anode, and the welding scale is dissolved from the surface of the stainless steel base material, which is the anode, and the welding scale is removed. It is preferable to select the most suitable current method and conditions depending on the purpose of the surface treatment of the stainless steel, the specifications of the electrolytic treatment solution, the material of the base material to be surface-treated, the type of surface treatment of the base material, etc. Note that various conditions such as current and voltage during electrolytic polishing treatment using the AC current method or AC / DC superimposed current method can be adjusted according to standard methods. For example, it is preferable to adjust the output voltage in the range of 10 to 70 V and to pass a current of 5 to 90 A. EXAMPLES

[0085] EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but it goes without saying that the present invention is not limited to these examples.

[0086] In the examples, the following reagents were used: Potassium orthophosphate: Fujifilm Wako Pure Chemical Industries, Ltd. (10% by weight aqueous solution) Potassium pyrophosphate: Fujifilm Wako Pure Chemical Industries, Ltd. (10% by weight aqueous solution) Potassium phytate: Fujifilm Wako Pure Chemical Industries, Ltd. (10% by weight aqueous solution) Potassium tartrate: Fujifilm Wako Pure Chemical Industries, Ltd. (10% by weight aqueous solution) Potassium malate: Fujifilm Wako Pure Chemical Industries, Ltd. (10% by weight aqueous solution) Potassium gluconate: Fujifilm Wako Pure Chemical Industries, Ltd. (10% by weight aqueous solution) Potassium citrate: Fujifilm Wako Pure Chemical Industries, Ltd. (10% by weight aqueous solution) 1-Hydroxyethylidene-1,1-diphosphonic acid (Chilest PH-210): manufactured by Chelest Co., Ltd. Ethylenediaminetetraacetic acid (EDTA; Chelest 3K-50): manufactured by Chelest Co., Ltd. Potassium p-toluenesulfonate: An aqueous solution (10% by mass) of p-toluenesulfonic acid monohydrate manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. was neutralized with potassium hydroxide to a pH of 7.0. 3,3'-Dithiobis(sodium propane-1-sulfonate) (SPS): manufactured by Asahi Chemical Industry Co., Ltd. (30% by mass aqueous solution).

[0087] The stainless steel plate used for the speed test was SUS-304 (50mm x 100mm x 1.6mm; 2B material) with a bead created by welding. The welding conditions were initial current 20A, welding current 60A, crater current 20A, gas flow rate 6L / min, and speed approximately 1000m / m / min.

[0088] The above-mentioned stainless steel plate was subjected to electrolytic polishing treatment by alternating current (AC) using the electrolytic polishing solution shown in Tables 1 to 4. Specifically, the above-mentioned stainless steel plate was connected to one pole of a power source, and the other pole was an electrode made of the same material as the above-mentioned stainless steel plate, wrapped in a nonwoven fabric made of synthetic fiber, and the nonwoven fabric was soaked with the electrolytic polishing solution (pH is about 7.0) shown in Tables 1 to 3 and slid. The above-mentioned stainless steel plate was also connected to one pole of a power source, and the other pole was an electrode made of the same material as the above-mentioned stainless steel plate, wrapped in a nonwoven fabric brushed with the electrolytic polishing solution (pH is about 7.0) shown in Tables 1 to 3 and slid. At this time, the voltage was 35.4 V and the current was 6 A. The results of the treatment speed of the electrolytic polishing treatment (weld scale removal speed) are shown in Tables 1 to 4.

[0089] [Table 1]

[0090] [Table 2]

[0091] [Table 3]

[0092] [Table 4]

[0093] As described above, in all the examples, it was shown that the treatment speed is improved while being neutral by containing a neutral salt of an acid other than phosphonic acid and aminocarboxylic acid and a phosphonic acid compound or its salt, or by containing a neutral salt of phytic acid and at least one neutral salt selected from the group consisting of tartaric acid, malic acid, gluconic acid and citric acid as the neutral salt of the acid. Note that, although only the results in the alternating current method (AC) are shown above, the results of the treatment speed being improved were also obtained when the AC-DC superimposed current method was used.

Claims

1. An electrolytic polishing solution for electrolytic polishing of stainless steel, a neutral salt of an acid other than a phosphonic acid or an aminocarboxylic acid; An electropolishing solution comprising a phosphonic acid compound or a salt thereof, and / or an aminocarboxylic acid compound or a salt thereof.

2. 2. The electropolishing solution according to claim 1, wherein the neutral salt of an acid is at least one neutral salt selected from the group consisting of phosphoric acid, phytic acid, tartaric acid, malic acid, gluconic acid, and citric acid.

3. An electrolytic polishing solution for electrolytic polishing of stainless steel, Contains a neutral salt of an acid, The electropolishing solution, wherein the neutral salt of an acid contains a neutral salt of phytic acid.

4. The electropolishing solution according to claim 3, further comprising at least one neutral salt selected from the group consisting of tartaric acid, malic acid, gluconic acid and citric acid.

5. The electropolishing solution according to claim 3 , further comprising a phosphonic acid compound or a salt thereof.

6. The electropolishing solution according to claim 1, 2 or 5, wherein the content of the phosphonic acid compound or a salt thereof is 0.5 to 20.0 mass% based on the total amount of the electropolishing solution being 100 mass%.

7. The electropolishing liquid according to any one of claims 3 to 5, further comprising an aminocarboxylic acid compound and / or a salt thereof.

8. The electropolishing solution according to claim 1 or 2, wherein the content of the aminocarboxylic acid compound and / or its salt is 0.5 to 5.0 mass% based on the total amount of the electropolishing solution being 100 mass%.

9. The electropolishing solution according to claim 7, wherein the content of the aminocarboxylic acid compound and / or its salt is 0.5 to 5.0 mass% based on the total amount of the electropolishing solution being 100 mass%.

10. The electropolishing solution according to any one of claims 1 to 5, wherein the content of the neutral salt of the acid is 0.5 to 40 mass% based on the total amount of the electropolishing solution being 100 mass%.

11. The electropolishing solution according to any one of claims 1 to 5, further comprising a sulfonic acid compound or a salt thereof.

12. The electropolishing solution according to claim 11, wherein the content of the sulfonic acid compound or a salt thereof is 0.5 to 20.0 mass% based on the total amount of the electropolishing solution being 100 mass%.

13. The stainless steel electropolishing solution according to any one of claims 1 to 5, which is used for electropolishing stainless steel by an AC current method or an AC / DC superimposed current method.

14. A method for electrolytic polishing of stainless steel, comprising electrolyzing the stainless steel electrolytic polishing solution according to any one of claims 1 to 5.

15. A method for producing stainless steel, comprising electrolysis using the stainless steel electropolishing solution according to any one of claims 1 to 5.

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