JPH04311598A - Anodic dissolving processing method for metal surface - Google Patents

Abstract

PURPOSE:To offer an anodic dissolving processing method of a metal surface which makes a beautiful finishing with easy working and reduces processing time. CONSTITUTION:A electrolytic process is executed with a solution containing potassium salt and/on ammonium salt of pyrophosphoric acid or polyphosphoric acid aq. solution as an electrolytic solution by connecting a metal to be treated to an anodic electrode with direct current or by connecting the metal to be treated to the anodic electrode of direct power source with current which allows alternate current to superimpose the direct current.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for anodic dissolution treatment of the surface of metals such as stainless steel or copper alloys such as copper, brass, and bronze.

0002

[Prior Art] For example, alloy steel such as stainless steel that has been locally heated by welding, fusing, etc., copper and its alloys that have been heated during brazing, etc., or left in air for a long time. Oxide (scale) is generated on the surface,
The surface may lose its luster, impairing its appearance, or corrosion may occur at the locations where the oxide is generated. One method for removing oxides generated on the surface of such metals is anodic dissolution treatment.

[0003] Furthermore, the above-mentioned anodic dissolution treatment is sometimes applied in place of mechanical polishing, pickling, etc. for polishing and deburring metal surfaces, and even for etching treatment for producing name plates and nameplates. This anode dissolution treatment includes two methods: the immersion method, in which the metal to be treated connected to the anode is immersed in an electrolytic solution filled in a tank together with the electrode piece connected to the cathode; There is a brush method in which the surface of the metal to be treated is wiped while being energized with a treatment brush connected to a cathode covered with a water retentive material such as felt or sponge impregnated with an electrolytic solution.

The electrolytic solution used in the above immersion method is an aqueous solution of one or more strong acids selected from sulfuric acid, hydrochloric acid, nitric acid, hydrofluoric acid, phosphoric acid, etc., while the brush method uses the above immersion method. For example, in the descaling method for alloy steel described in Japanese Patent Publication No. 1-27160, the safer and more hygienic sodium salt of phosphoric acid is used as the electrolyte. , a single aqueous solution of potassium salt, ammonium salt, or sulfuric acid,
Adopting a mixed aqueous solution of sodium, potassium, and ammonium salts of nitric acid and hydrofluoric acid and a mixed aqueous solution of glycerin, there is no need for special consideration or equipment in handling or equipment as used in the above-mentioned immersion method. An anodic dissolution treatment method is disclosed.

[0005]

However, in such an anodic dissolution treatment method, the components of the electrolytic solution are important factors in determining the finished state of the treated surface of the metal to be treated and the slowness of the treatment speed. Particularly in the brush method, it is required that there is little unevenness in the finish near the periphery of the treated area. However, in the invention described in Japanese Patent Publication No. 1-27160, the processing speed is inferior to the method of processing using a strong acid as an electrolyte in the immersion method, and uneven finish may occur near the periphery of the treated area. It has been pointed out. These drawbacks are thought to be due to the use of orthophosphoric acid, which is less reactive than a strong acid alone aqueous solution such as sulfuric acid, hydrochloric acid, nitric acid, hydrofluoric acid, or phosphoric acid, as the electrolyte in the above-mentioned immersion method.

The present invention has been proposed in view of the above-mentioned conventional circumstances, and provides an anodic dissolution treatment method for metal surfaces that is easy to handle, provides a beautiful finish, and shortens treatment time. The purpose is to

[0007]

[Means for Solving the Problems] In order to achieve the above object, the present invention employs the following means. That is, in the anodic dissolution treatment method for metal surfaces, an aqueous solution containing either potassium salt of pyrophosphoric acid, ammonium salt, or both, or polyphosphoric acid aqueous solution is used as an electrolyte, and the metal to be treated is connected to the anode and subjected to direct current. The structure is such that electrolytic treatment is performed, or the metal to be treated is connected to the anode of a DC power source and electrolytic treatment is performed using a current in which alternating current is superimposed on the direct current.

[0008]

[Function] The polyphosphoric acid used in the above configuration is a general term for condensed phosphoric acids that are more reactive than orthophosphoric acid, and includes chain pyrophosphoric acid, triphosphoric acid, tetraphosphoric acid, and cyclic condensed phosphoric acid. Refers to a substance that includes certain trimetaphosphoric acid, tetrametaphosphoric acid, etc. By using such condensed phosphoric acid as a component of the electrolytic solution, the reactivity during electrolytic treatment is improved, resulting in beautiful and short treatment time. Processing can be done with .

[0009] The concentration of the aqueous solution containing either potassium salt or ammonium salt of pyrophosphoric acid, or both, contained in the aqueous solution as the electrolytic solution is 10 to 50% by weight.
If it is less than 10% by weight, anodic dissolution cannot be carried out within the desired treatment time, and if it exceeds 50% by weight, the solubility of the potassium salt and ammonium salt of pyrophosphoric acid will reach a saturated state, so electrolysis will not be possible. Unable to withstand use as a liquid. Furthermore, when a polyphosphoric acid aqueous solution is used as the electrolytic solution, it is desirable that its concentration be 10% by weight or more; if the concentration is less than 10% by weight, there is a risk that anodic dissolution may not be possible within the desired processing time. Undesirable.

Furthermore, when an aqueous solution containing either the potassium salt, the ammonium salt, or both of the above-mentioned pyrophosphoric acid is used as an electrolytic solution, it is desirable that the pH is 9.5 or less; If it exceeds this amount, the above-mentioned potassium salt and ammonium salt of pyrophosphoric acid may precipitate as crystals in the electrolytic solution, which is not preferable. In particular, a single solution of potassium salt of pyrophosphoric acid has a pH of 10 due to hydrolysis.
In addition to the fact that the above-mentioned tendency is remarkable because of the strong alkalinity of the before and after, in the brush method, for example, phosphoric acid ( It is desirable to lower the pH by adding a pH adjuster such as (not necessarily condensed phosphoric acid).

Note that the present invention does not preclude the addition of various substances for improving the finished state of the area treated by the anodic dissolution treatment. When performing anodic dissolution treatment using such an electrolyte, only direct current may be applied, but especially when performing scale removal treatment on stainless steel, it is necessary to keep the stainless steel in a high potential state for a long period of time. It is known that this causes the surface to passivate and takes a long time to process. Therefore, an alternating current with a maximum voltage slightly higher than the direct current is superimposed on the direct current to temporarily create a negative potential and the anode is dissolved. Accelerating the processing can also be done.

0012

[Example] Hereinafter, an example to which the present invention is applied will be described and its effects will be verified. =Example 1= A brass sample with a brazed portion connected to the anode is immersed in an electrolytic solution in which phosphoric acid is added to an aqueous solution consisting of 100 g/l of potassium pyrophosphate and the pH is adjusted to 9.0. Then, anodic dissolution treatment was performed using direct current at a current density of 6 A/dm2. A brass sample with an extremely beautiful surface was obtained in a processing time of about 60 seconds.

On the other hand, as a control group, sodium sulfate 1
When anodic dissolution treatment was performed under the same treatment conditions as above using an aqueous solution of 0.00 g/l as the electrolyte, clear roughness of the substrate was observed. =Example 2= Phosphoric acid was added to an aqueous solution consisting of 350 g/l of potassium pyrophosphate, and a SUS304 stainless steel having a welded part connected to the anode was immersed in an electrolytic solution whose pH was adjusted to 8.0. Anodic dissolution treatment was performed using direct current at a current density of /dm2. The welding burn was removed very beautifully in a processing time of about 60 seconds.

On the other hand, as a control group, sodium sulfate 2
When anodic dissolution treatment was performed under the same treatment conditions as above using an aqueous solution of 0.00 g/l as the electrolyte, it took a long time to remove the scale, and clear roughness of the substrate was observed. =Example 3=Aqueous ammonia was added to an aqueous solution consisting of 340 g/l of pyrophosphoric acid, and an ammonium pyrophosphate solution whose pH was adjusted to 3.5 was used as an electrolyte to impregnate the felt covering the electrode surface. Thereafter, the electrode was connected to the cathode, and a copper plate, which had turned brown due to natural standing, was connected to the anode, and anodic dissolution treatment was performed using a brush method in which a direct current of 6 V was applied. A copper plate with an extremely beautiful finish and restored luster was obtained in a processing time of about 60 seconds.

=Example 4= Phosphoric acid was added to an aqueous solution consisting of 350 g/l of potassium pyrophosphate, and fine scratches were made in the electrolytic solution whose pH was adjusted to 4.5 using emery paper connected to the anode. A brass piece was immersed and subjected to an anodic melting treatment with direct current at a current density of 10 A/dm2. A brass piece that had regained its beautiful luster was obtained in about 30 seconds of processing time.

=Example 5= Phosphoric acid was added to an aqueous solution consisting of 400 g/l of potassium pyrophosphate and the pH was adjusted to 7.5.The aqueous solution was used as an electrolyte and was impregnated into felt covering the electrode surface. After this, while connecting the electrode to the cathode, the S
US304 stainless steel was connected to the anode, a DC current with a voltage of 25 V was applied, and an AC current with a maximum voltage of 30 V and a frequency of 60 Hz was superimposed on the DC current to perform an anode melting process using the brush method. ,
The welding burn was removed very beautifully in about 20 seconds.

On the other hand, as a control group, ammonium sulfate 20
When the same treatment as above was carried out using a 0 g/l aqueous solution as the electrolyte, a strong pungent odor from ammonia was generated during the treatment process, and not only did it take a long time to remove the scale, but clear roughness of the substrate was observed. It was done. =Example 6= A mixed solution consisting of 4 parts by volume of polyphosphoric acid and 10 parts by volume of water,
The felt covering the electrode surface was impregnated. After this, while connecting the electrode to the cathode, the SUS3
When 04 stainless steel was connected to the anode and anodic dissolution treatment was carried out using a brush method in which a direct current of 25 V was applied for electrolytic treatment, welding burns were removed very beautifully in a treatment time of about 60 seconds.

On the other hand, approximately 2 parts by volume of orthophosphoric acid and 2 parts by volume of water were used as an electrolyte to obtain the same finished state as above.
It takes twice as long, and with the same 60 second processing time, the oxide (
Uneven removal of scale) was clearly observed, resulting in insufficient polishing.

[0019]

As described above, according to the present invention, it is possible to obtain metal in a better finished state in a shorter time than with conventionally known anodic melting treatment methods, and special consideration is given to handling and equipment. Since the electrolyte is an aqueous solution containing potassium salt, ammonium salt, or both of pyrophosphoric acid, or an aqueous polyphosphoric acid solution, it is suitable for anodic dissolution treatment of metal surfaces regardless of the immersion method or brush method. It can be widely applied as

Claims (3)

[Claims] Claim 1: In a method for anodic dissolution treatment of a metal surface, an aqueous solution containing either a potassium salt of pyrophosphoric acid, an ammonium salt, or both, or an aqueous polyphosphoric acid solution is used as an electrolyte, and the metal to be treated is connected to an anode. A method for anodic dissolution treatment of a metal surface, characterized in that the metal to be treated is electrolytically treated with a direct current, or the metal to be treated is connected to the anode of a direct current power source and the electrolytic treatment is performed with a current obtained by superimposing alternating current on the direct current. [Claim 2] The concentration of the aqueous solution containing either a potassium salt or an ammonium salt of pyrophosphoric acid, or both, as the electrolytic solution is 10 to 50% by weight, and the pH of the aqueous solution is 9.5 or less. The method for anodic dissolution treatment of a metal surface according to claim 1. 3. The anodic dissolution treatment method for a metal surface according to claim 1, wherein the concentration of the polyphosphoric acid aqueous solution as the electrolytic solution is 10% by weight or more.