JP3038249B2 - Anodizing treatment method for metal surface - Google Patents

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 a metal surface such as stainless steel or a copper alloy such as copper, brass or bronze.

[0002]

2. Description of the Related Art For example, alloy steel such as stainless steel locally heated by welding, fusing, or the like, or copper or an alloy thereof heated during brazing or left in air for a long time. Oxide (scale) is generated on the surface,
The gloss of the surface may be lost and the aesthetic appearance may be impaired, or corrosion may occur from the formation site of the oxide. An anodic dissolution treatment is performed as one of the methods for removing oxides generated on the surface of such a metal.

The above-mentioned anodic dissolution treatment may be applied instead of mechanical polishing, pickling, etc., for polishing or deburring a metal surface, and for example, also for etching treatment for producing a name plate or a nameplate. As the anodic dissolution treatment, an immersion method in which the metal to be treated connected to the anode was immersed in an electrolytic solution filled in a tank together with an electrode piece connected to the cathode to perform an electrolytic treatment, and the anode was connected to the anode. There is a brush method in which the surface of the metal to be treated is wiped while energizing the surface with a treatment brush connected to a cathode coated with a water-repellent material such as felt or sponge impregnated with an electrolytic solution.

The electrolytic solution used in the immersion method is an aqueous solution of one or more strong acids selected from sulfuric acid, hydrochloric acid, nitric acid, hydrofluoric acid, phosphoric acid and the like, while the brush method is an immersion method. Unlike the surface treatment workers, which are not specialists in surface treatment, for example, in the descaling method of alloy steel described in Japanese Patent Publication No. 1-27160, a safer and more sanitary sodium salt of phosphoric acid is used as an electrolyte. , Potassium salt, aqueous solution of ammonium salt alone or sulfuric acid,
By using a mixed aqueous solution of sodium, potassium and ammonium salts of nitric acid and hydrofluoric acid and a mixed aqueous solution of glycerin, special handling and equipment such as those used in the above immersion method are not required. An anodic dissolution treatment method is disclosed.

[0005]

In such an anodic melting treatment method, the finished state of the treated surface of the metal to be treated and the slowing of the treating speed are determined by the components of the electrolytic solution. In particular, in the brush method, it is required that there is little unevenness in finish near the periphery of the portion to be processed. However, in the invention described in Japanese Patent Publication No. 27160/1990, the immersion method is inferior in the processing speed as compared with the method in which a strong acid is used as an electrolytic solution, and may cause unevenness in the finish in the vicinity of the portion to be processed. It is pointed out. It is considered that such a drawback is caused by the use of orthophosphoric acid, which is inferior in reactivity to an aqueous solution of a strong acid such as sulfuric acid, hydrochloric acid, nitric acid, hydrofluoric acid, phosphoric acid, etc., as an electrolytic solution in the immersion method.

The present invention has been proposed in view of the above-mentioned conventional circumstances, and provides an anodic dissolving method for a metal surface which is easy to handle, has a beautiful finished state, and has a reduced processing time. The purpose is to do so.

[0007]

In order to achieve the above object, the present invention employs the following means. That is, in the anodic dissolution treatment method for the metal surface, an aqueous solution containing either or both of potassium phosphate and ammonium salt of pyrophosphoric acid, or an aqueous solution of polyphosphoric acid is used as an electrolytic solution. Either electrolytic treatment is performed, or electrolytic treatment is performed with a current in which an alternating current is superimposed on the direct current by connecting the treated metal to the anode of a direct current power supply.

[0008]

[Function] The polyphosphoric acid used in the above constitution is a general term for condensed phosphoric acid which is more reactive than orthophosphoric acid, and includes chain pyrophosphoric acid, triphosphoric acid, tetraphosphoric acid and cyclic condensed phosphoric acid. Refers to a substance containing trimetaphosphoric acid, tetrametaphosphoric acid, etc., and improves the reactivity at the time of electrolytic treatment by adopting such condensed phosphoric acid as a component of the electrolytic solution, so that the treatment time is beautiful and short. Can be performed.

The concentration of the aqueous solution containing either or both of the potassium salt and the ammonium salt of pyrophosphoric acid contained in the aqueous solution as the electrolytic solution is 10 to 50% by weight.
If the amount is less than 10% by weight, anodic dissolution cannot be performed within a desired treatment time, and if it exceeds 50% by weight, the solubility of the potassium and ammonium salts of pyrophosphoric acid reaches a saturated state. It cannot withstand use as a liquid. When an aqueous solution of polyphosphoric acid is used as the electrolyte, the concentration is preferably 10% by weight or more, and if the concentration is less than 10% by weight, anodic dissolution may not be performed within a desired processing time. Not preferred.

Further, when an aqueous solution containing either or both of the potassium salt and the ammonium salt of pyrophosphoric acid is used as the electrolytic solution, the pH is desirably 9.5 or less, and the pH is 9.5 or less. In the case of exceeding the above, the potassium and ammonium salts of pyrophosphoric acid are not preferable because they may precipitate as crystals in the electrolytic solution. In particular, a single solution of a potassium salt of pyrophosphoric acid has a pH of 10 due to hydrolysis.
In view of the strong alkaline property before and after, in addition to the above-mentioned tendency being remarkable, for example, in the brush method, in order to eliminate the need for complicated handling of such a strong alkaline solution, for example, phosphoric acid ( It is preferable to lower the pH by adding a pH adjuster such as condensed phosphoric acid.

In the present invention, the addition of various substances for improving the finished state of the treated portion by the anodic dissolution treatment is not hindered at all. When performing anodic dissolution treatment using such an electrolytic solution, only a direct current may be applied, but particularly when performing scale removal treatment of stainless steel, the stainless steel is kept in a high potential state for a long time. Then, it is known that the surface is passivated and a long processing time is required. The direct current is superimposed on the direct current with an alternating current having a maximum voltage slightly higher than the direct current, and temporarily becomes a negative potential to dissolve the anode. Processing can also be facilitated.

[0012]

Embodiments of the present invention will be described below to verify the effects. = Example 1 = A brass sample with a brazed part connected to the anode was immersed in an electrolytic solution adjusted to pH 9.0 by adding phosphoric acid to an aqueous solution composed of potassium pyrophosphate 100 g / l. Then, an anodic dissolution treatment was performed with a direct current having a current density of 6 A / dm ² . A brass sample having a very beautiful surface was obtained with a treatment time of about 60 seconds.

On the other hand, sodium sulfate 1
When the anodic dissolution treatment was performed under the same treatment conditions as above using an aqueous solution of 00 g / l as an electrolyte, a clear roughening of the substrate was observed. = Example 2 = SUS304 stainless steel having a welded part connected to the anode was immersed in an electrolytic solution adjusted to pH 8.0 by adding phosphoric acid to an aqueous solution containing 350 g / l of potassium pyrophosphate, and subjected to 200 A The anodic dissolution treatment was performed with a direct current having a current density of / dm ² . In about 60 seconds, the burn was successfully removed.

On the other hand, sodium sulfate 2
When the anodic dissolution treatment was carried out under the same treatment conditions as above using an aqueous solution of 00 g / l as an electrolytic solution, it took a long time to remove the scale, and a clear roughening was observed. Example 3 Ammonia water was added to an aqueous solution containing 340 g / l of pyrophosphoric acid, and an ammonium pyrophosphate solution whose pH was adjusted to 3.5 was used as an electrolytic solution to impregnate a felt covering the electrode surface. Thereafter, while the electrode was connected to the cathode, a copper plate turned brown by natural standing was connected to the anode, and an anode dissolution treatment was performed by a brush method in which a DC current of 6 V was applied. With a processing time of about 60 seconds, a copper plate having a very beautiful finish and a restored gloss was obtained.

= Example 4 = Phosphoric acid was added to an aqueous solution consisting of 350 g / l of potassium pyrophosphate, and fine scratches were made with an emery paper connected to the anode in an electrolytic solution adjusted to pH 4.5. The brass pieces were immersed and subjected to anodic dissolution treatment with a direct current having a current density of 10 A / dm ² . A brass piece having a very beautiful luster was obtained in a processing time of about 30 seconds.

Example 5 Phosphoric acid was added to an aqueous solution composed of 400 g / l of potassium pyrophosphate, and an aqueous solution whose pH was adjusted to 7.5 was used as an electrolytic solution to impregnate a felt covering the electrode surface. Thereafter, while the electrode is connected to the cathode, the SU
S304 stainless steel was connected to the anode, a DC current of 25 V was applied, and a maximum voltage of 30 V was applied to the DC current.
When the anodic dissolution treatment was performed by a brush method in which an alternating current of V and a frequency of 60 Hz was superimposed and the electrolytic treatment was performed, welding scorch could be removed very beautifully in a treatment time of about 20 seconds.

On the other hand, as a control, ammonium sulfate 20
When the same treatment as above was performed using an aqueous solution of 0 g / l as an electrolytic solution, a strong irritating smell due to ammonia was generated in the treatment process, not only it took a long time to remove the scale, but also a clear roughening was observed. 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. Thereafter, while the electrode was connected to the cathode, SUS304 stainless steel having a welded portion was connected to the anode, and a current of 25 V was applied with a direct current to perform anodic dissolution treatment by a brush method in which electrolytic treatment was performed. In about 60 seconds, the welding burn was removed very beautifully.

On the other hand, approximately 2 parts by volume of orthophosphoric acid and 2 parts by volume of water are used as electrolytes to obtain the same finished state as described above.
It took twice as long, and in the same processing time of 60 seconds, unevenness in removal of oxide (scale) was clearly observed, resulting in an insufficiently polished state.

[0019]

As described above, according to the present invention, it is possible to obtain a metal in a better finished state in a shorter time and in a shorter time than in the conventionally known anodic dissolution treatment method, and special consideration is given to handling and equipment. Aqueous solution containing either potassium salt or ammonium salt of pyrophosphoric acid, or both, or polyphosphoric acid aqueous solution is used as electrolyte, so anodic dissolution method of metal surface regardless of dipping method or brush method As widely applicable.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Keigo Obata 402 Shirahama-cho, Himeji-shi Marui Plating Industry Co., Ltd. (58) Field surveyed (Int. Cl. ⁷ , DB name) C25F 1/04, 3/02

Claims (3)

(57) [Claims] 1. A method for anodic dissolution treatment of a metal surface,
One of potassium salt and ammonium salt of pyrophosphoric acid,
Alternatively, an aqueous solution containing both or an aqueous solution of polyphosphoric acid is used as an electrolytic solution, and the metal to be treated is connected to the anode to perform electrolytic treatment with a direct current, or the metal to be treated is connected to the anode of a DC power supply and the direct current is applied to the direct current. Anodic dissolution treatment method for a metal surface, wherein an electrolytic treatment is carried out with a current superimposed. 2. The concentration of an aqueous solution containing either or both of a potassium salt and an ammonium salt of pyrophosphoric acid as the electrolytic solution is adjusted to 10 to 50% by weight, and the pH of the aqueous solution is adjusted to 9.5 or less. The method for anodic dissolution treatment of a metal surface according to claim 1. 3. The method according to claim 1, wherein the concentration of the aqueous solution of polyphosphoric acid as the electrolytic solution is 10% by weight or more.