JP2007231413A - Electrolytic solution to be used for electrolytic polishing method for stainless steel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolytic solution which is usable at AC, DC and AC/DC superposition in an electrolytic polishing method to the surface of stainless steel, and further improves corrosion resisting performance even in the case of not only austenitic stainless steel but also martensitic and ferritic stainless steel. <P>SOLUTION: The electrolytic solution to be used for an electrolytic polishing method for stainless steel is obtained by using the one obtained by adding one or more selected from triethanolamine, diethanolamine and monoethanolamine in ≥0.1 wt.% to acid acting so as to be non-oxidizable to stainless steel such as sulfuric acid, phosphoric acid, citric acid, tartaric acid, oxalic acid, malic acid, acetic acid, gluconic acid, glycolic acid and succinic acid in ≥0.1 wt.% as a base material, and blending the same with hydrofluoric acid or one or more salts selected from the ammonium salts, potassium salts and sodium salts of hydrofluoric acid in ≥0.01 wt.%. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a composition of an electrolytic solution used in electrolytic polishing of a stainless steel surface performed for burning off after welding of stainless steel.

  As a metal processing method, electrolytic processing is widely used in which a metal is processed by applying a direct current or an alternating voltage while being in contact with an electrolytic solution. In stainless steel, for example, the burnt portion after welding of stainless steel is subjected to surface polishing. As a method, an electrolytic polishing method by electrolytic processing is performed.

  In addition, there are a method of bringing a metal into contact with an electrolytic solution, a dipping method in which a metal (workpiece) to be polished is immersed in the electrolytic solution, and a simple method in which a natural or synthetic nonwoven fabric is placed between the electrode and the workpiece.

As an electrolytic solution that has been used up to now, regardless of alternating current, direct current, AC / DC superposition, and regardless of methods such as immersion, simple, etc., sulfuric acid, phosphoric acid, citric acid, tartaric acid, oxalic acid, malic acid, Acetic acid, gluconic acid, glycolic acid, succinic acid, hydrofluoric acid or their ammonium, potassium, sodium salts have been used as an electrolyte solution (for example, Patent Document 1, Patent Document 2).
Japanese Patent No. 3484525 JP 2003-82495 A

  However, in the case of using the above-described conventional electrolytic solution, there is a risk that corrosion such as pitting corrosion occurs after electrolysis, particularly in austenitic stainless steel.

  Further, as disclosed in Patent Document 1, a method has been devised in which a water-soluble fluoride is added to a sodium salt, ammonium salt, or potassium salt of a non-oxidizing acid to form a fluorinated passive film on the surface. However, there is a risk of increasing the overall corrosion when the salt spray test is performed on ferritic stainless steel using a aesthetic problem after processing.

  Therefore, the present invention has been accomplished by solving various problems in order to obtain an electrolytic solution that can solve the above problems more effectively with any steel type. is there.

  In order to solve the above problems, the present invention is applied to 0.1% by weight or more of stainless steel such as sulfuric acid, phosphoric acid, citric acid, tartaric acid, oxalic acid, malic acid, acetic acid, gluconic acid, glycolic acid, and succinic acid. On the other hand, a base material containing 0.01% by weight or more of triethanolamine, diethanolamine and monoethanolamine in an amount of 0.1% by weight or more added to a non-oxidizing acid is 0.01% by weight. An electrolytic solution for use in an electrolytic polishing method for stainless steel, characterized in that one or more of the above hydrofluoric acid or ammonium, potassium and sodium salts of hydrofluoric acid are blended.

  The electrolytic solution of the present invention can be used by alternating current, direct current, and AC / DC superposition in electrolytic polishing of stainless steel, and is economical because it can improve the corrosion resistance and the aesthetic appearance after processing in any stainless steel.

  (1) An aqueous solution in which 0.01% by weight sodium fluoride is added to 10% by weight sodium oxalate, and (2) 0.01% by weight fluoride in 10% by weight potassium oxalate. An aqueous solution containing sodium, (3) 0.01% of supersaturated water of ammonium oxalate (because a small amount of precipitation was caused by addition of 5% by weight because of its low solubility in water: 4.3% solubility at 20 ° C.) An aqueous solution containing 10% by weight of sodium fluoride and (4) an aqueous solution of 0.01% by weight of sodium fluoride added to 10% by weight of oxalic acid neutralized with triethanolamine are each soaked as an electrolyte. SUS304 (30 mm × 90 mm × 1.6 mm) which is an austenitic stainless steel and SUS430 (30 mm × 90 mm × 1. After applying an alternating current of pressing 20V in mm), I tried to compare the state of the surface.

  After comparison of the surface conditions, a test piece of SUS304 (30 mm × 90 mm × 1.6 mm), which is an austenitic stainless steel, was immersed in a 6% by weight ferric chloride aqueous solution to reduce the weight after 24 hours. A test piece of 30 mm × 90 mm × 1.6 mm) was sprayed with a 10% by weight sodium chloride aqueous solution, and the state after 24 hours was compared.

  (1) an aqueous solution in which 0.01% by weight sodium fluoride is added to 10% by weight sodium oxalate; (2) an aqueous solution in which 0.01% by weight sodium fluoride is added to 10% by weight potassium oxalate; (3) Although the SUS304 and SUS430 were electrolyzed with an aqueous solution obtained by adding 0.01% by weight of sodium fluoride to supersaturated water of ammonium oxalate, both the SUS304 and SUS430 had discolored the work surface, but (4) 10% by weight Only the one obtained by neutralizing oxalic acid with triethanolamine and adding 0.01% by weight of sodium fluoride could polish the workpiece cleanly regardless of the steel type.

  (1) an aqueous solution in which 0.01% by weight sodium fluoride is added to 10% by weight sodium oxalate; (2) an aqueous solution in which 0.01% by weight sodium fluoride is added to 10% by weight potassium oxalate; (3) Aqueous solution in which 0.01% by weight of sodium fluoride is added to supersaturated water of ammonium oxalate, (4) 0.01% of fluoride in 10% by weight of oxalic acid neutralized with triethanolamine The reduction rates of the SUS304 specimen immersed in a 6% by weight ferric chloride aqueous solution after AC electrolytic treatment with an aqueous solution containing sodium were (1) 1.5% by weight, (2) 1.7% by weight, respectively. (3) 2.5% by weight, but (4) an aqueous solution obtained by adding 0.01% sodium fluoride to 10% by weight of oxalic acid neutralized with triethanolamine was treated as an electrolyte. Shi It was only 1.3% in the test piece.

  (1) an aqueous solution in which 0.01% sodium fluoride is added to 10% by weight sodium oxalate; (2) an aqueous solution in which 0.01% sodium fluoride is added to 10% by weight potassium oxalate; (3) An aqueous solution obtained by adding 0.01% sodium fluoride to supersaturated water of ammonium oxalate; (4) 0.01% sodium fluoride obtained by neutralizing 10% by weight of oxalic acid with triethanolamine After AC electrolytic treatment with an aqueous solution added with sodium chloride, a sodium chloride aqueous solution was sprayed and the surface conditions after 24 hours were compared. The results were (1) 25%, (2) 26%, (3) 35% of the sample was discolored brown. (4) Test using an aqueous solution in which 0.01% by weight of sodium fluoride was added after neutralizing oxalic acid with triethanolamine as the electrolyte. Fee only discoloration was not fall below 10% of the total.

  In general, stainless steel with a fluorinated passive film produced a tendency to increase corrosion when a salt spray test was performed on ferritic stainless steel. did.

  In addition, since similar results were obtained with monoethanolamine, diethanolamine and other acids, as described in claim 1, 0.1% by weight or more of sulfuric acid, phosphoric acid, citric acid, tartaric acid, oxalic acid, malic acid, acetic acid The base material is a non-oxidizing acid such as gluconic acid, glycolic acid, or succinic acid, with one or more of triethanolamine, diethanolamine and monoethanolamine added in an amount of 0.1% by weight or more. In addition, 0.01% by weight or more of hydrofluoric acid or a mixture of one or more of ammonium, potassium and sodium salts of hydrofluoric acid is used as an electrolytic solution to obtain a stainless steel grade. It has been found that the anti-corrosion performance is dramatically improved and the aesthetics are improved at the same time. If the amount of each ethanolamine is increased, the effect is proportionally improved.

Claims (1)

  0.1% by weight or more of sulfuric acid, or acid that acts non-oxidatively on stainless steel such as phosphoric acid, citric acid, tartaric acid, oxalic acid, malic acid, acetic acid, gluconic acid, glycolic acid, succinic acid, etc. A base material containing one or more of at least 1% by weight of triethanolamine, diethanolamine and monoethanolamine is added, and 0.01% by weight or more of hydrofluoric acid or hydrofluoric acid An electrolytic solution for use in an electrolytic polishing method for stainless steel, characterized in that one or more of ammonium, potassium and sodium salts are blended.