JP2007277682A - Electrolytic solution used for electrolytic polishing method on stainless steel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolytic solution that can be used in AC and DC and AC/DC superposition system in an electrolytic polishing method on a surface of stainless steel and that can improve corrosion resistance not only in austenitic stainless steel but martensitic and ferritic stainless steel. <P>SOLUTION: The electrolytic solution to be used for an electrolytic polishing on stainless steel is prepared by compounding one or more kinds in triethanolamine, diethanolamine and monoethanolamine of 0.1 wt.% or more into an aqueous solution of 0.1 wt.% or more comprising one or more kinds in a group consisting of sulfuric acid and acids which are non-oxidative on stainless steel such as phosphoric acid, citric acid, tartaric acid, oxalic acid, malic acid, acetic acid, gluconic acid, glycolic acid and succinic acid and a group consisting of salts of the above acids such as sodium, potassium and ammonium salts. <P>COPYRIGHT: (C)2008,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 not oxidized to 0.1% by weight or more of stainless steel such as phosphoric acid, citric acid, tartaric acid, oxalic acid, malic acid, acetic acid, gluconic acid, glycolic acid, and succinic acid. 0.1% by weight or more of triethanolamine or diethanolamine in one or two or more aqueous solutions of the group consisting of acid and sulfuric acid acting on the nature, and each salt group of these acids such as sodium, potassium and ammonium And an electrolytic solution used for an electrolytic polishing method of stainless steel containing one or more of monoethanolamine.

  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) 20 wt% sodium pyrophosphate aqueous solution, (2) 20 wt% potassium pyrophosphate aqueous solution, (3) 20 wt% pyrophosphoric acid neutralized with diethanolamine, It was impregnated as an electrolytic solution, pressed against SUS304 (30 mm × 90 mm × 1.6 mm), which is austenitic stainless steel, and an alternating current of 20 V was applied, and then the surface states were compared.

  In addition, after the comparison of the surface state, 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, and the weight loss after 24 hours was measured.

  (1) The reduction rate of the SUS304 specimen immersed in a 6% by weight ferric chloride aqueous solution after AC electrolytic treatment with a 20% by weight sodium pyrophosphate aqueous solution and (2) a 20% by weight potassium oxalate aqueous solution, respectively. 1.7% by weight and 1.9% by weight, but (3) only 1.4% of the test piece treated with 20% by weight of pyrophosphoric acid neutralized with diethanolamine as the electrolyte. It was.

  In addition, since similar results were obtained with monoethanolamine, triethanolamine and other acids, as described in claim 1, 0.1 wt% or more of phosphoric acid, citric acid, tartaric acid, oxalic acid, malic acid, Acetic acid, gluconic acid, glycolic acid, succinic acid, and the like, and non-oxidizing acid and sulfuric acid group of acids such as acetic acid, gluconic acid, glycolic acid, succinic acid, 0.1% by weight of triethanolamine, diethanolamine and monoethanolamine It was found that the pitting corrosion resistance was drastically improved by adding one or more kinds. The same tendency was found even when the base material was a salt of such acid, such as sodium, potassium or ammonium. If the amount of amine is increased, the effect is improved proportionally.

Claims (1)

  A group consisting of acids and sulfuric acid that act 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. One or two or more of triethanolamine, diethanolamine and monoethanolamine in an amount of 0.1% by weight or more in an aqueous solution of one or two or more of each salt group such as sodium, potassium and ammonium of these acids An electrolytic solution for use in an electrolytic polishing method for stainless steel, characterized in that