JP6403198B2 - Manufacturing method of product made of magnesium or magnesium alloy - Google Patents

Description

  The present invention relates to a method for producing a product made of magnesium or a magnesium alloy, in which an anodized film is formed on the surface of a substrate made of magnesium or a magnesium alloy by anodizing the surface.

  Magnesium and magnesium alloy are the lightest among practical metals, and have good heat dissipation and electromagnetic wave sealing. Therefore, the demand is increasing in various industrial fields. However, since magnesium and magnesium alloys have an electrochemically low potential among practical metals and are easily corroded, surface treatment having corrosion resistance is necessary.

  An anodizing treatment method is known as a surface treatment method performed to improve the corrosion resistance of magnesium and magnesium alloys. Excellent corrosion resistance can be imparted by anodizing magnesium and magnesium alloys.

  So far, the inventors have included 0.1 to 1 mol / L of phosphate radicals, 0.2 to 5 mol / L of ammonia or ammonium ions, and magnesium or a magnesium alloy in an electrolyte solution having a pH of 9 to 13. A method for producing a product made of magnesium or a magnesium alloy having an anodic oxide film on its surface has been reported (Patent Document 1).

  The anodized film obtained by this method is excellent in corrosion resistance and is characterized by not containing heavy metal elements. For this reason, products made of magnesium or magnesium alloys obtained by this method are suitably used for electronic equipment casings, transportation machinery parts, and the like. In recent years, with the enhancement of functionality of electronic devices and transportation machines, products made of magnesium or magnesium alloys that are excellent not only in corrosion resistance but also in mechanical properties have been demanded.

JP 2008-231578 A

  The present invention has been made to solve the above-mentioned problems, and provides a method for producing a product comprising magnesium or a magnesium alloy having an anodized film excellent in corrosion resistance and excellent in mechanical properties. It is.

  The said subject is a base material which consists of magnesium or a magnesium alloy in the electrolyte solution which contains 0.1-1 mol / L of phosphate radicals, 0.2-5 mol / L of ammonia or ammonium ion, and pH is 8-14. The spark start voltage (Es [V]) and the final voltage (Ef [V]) are set so as to satisfy the following formulas (1) to (3), and an AC voltage or a pulse voltage is applied. Solved by providing a method for producing a product made of magnesium or a magnesium alloy, characterized in that an anodized film having a thickness of 2 μm or more and 30 μm or less is formed on the surface by anodizing the surface of the substrate. Is done.

50 ≦ Es ≦ 160 (1)
60 ≦ Ef ≦ 300 (2)
5 ≦ Ef−Es ≦ 200 (3)

  At this time, the anodic oxide film preferably contains 10 to 65% by mass of magnesium element, 10 to 60% by mass of oxygen element, and 10 to 50% by mass of phosphorus element.

  Further, the substrate made of magnesium or a magnesium alloy is immersed in the electrolytic solution as a working electrode, and the substrate made of magnesium or a magnesium alloy is also immersed as a counter electrode, and an AC voltage is applied between the working electrode and the counter electrode. Is preferably applied, and the surfaces of both the working electrode and the counter electrode are simultaneously anodized to form an anodized film.

  According to the present invention, a product made of magnesium or a magnesium alloy having an anodized film excellent in corrosion resistance and excellent in mechanical properties can be produced.

It is the figure which showed the dumbbell-shaped base material used by a tension test. 2 is a secondary electron image of the surface of a test piece in Example 1. FIG. 2 is a secondary electron image of a cross section of a test piece in Example 1. FIG. 2 is a secondary electron image of the surface of a test piece in Comparative Example 1. 2 is a secondary electron image of a cross section of a test piece in Comparative Example 1.

  The present invention relates to a method for producing a product made of magnesium or a magnesium alloy, in which a surface of a base material made of magnesium or a magnesium alloy is anodized to form an anodized film on the surface. In the production method of the present invention, when an AC voltage or pulse voltage is applied to anodize the surface of the substrate, the spark start voltage (Es [V]) and the final voltage (Ef [V]) are expressed by the following formula (1). It is very important to set so as to satisfy () to (3).

50 ≦ Es ≦ 160 (1)
60 ≦ Ef ≦ 300 (2)
5 ≦ Ef−Es ≦ 200 (3)

  As proved in Examples and Comparative Examples described later, the anodized film obtained by applying an AC voltage or a pulse voltage so as to satisfy the above conditions is an anodized film obtained by applying a DC voltage. Compared to the film, it had excellent corrosion resistance. Moreover, the product which consists of obtained magnesium or magnesium alloy was excellent also in the mechanical characteristic. These were first demonstrated by the present inventors.

  The base material used in the present invention is not limited as long as it contains magnesium as a main component, and may be a metal made of magnesium alone or an alloy. Usually, a magnesium alloy is preferably used to impart formability, mechanical strength, ductility, and the like. Magnesium alloys include Mg-Al alloys, Mg-Al-Zn alloys, Mg-Al-Mn alloys, Mg-Al-Ca alloys, Mg-Al-Li alloys, Mg-Zn-Zr alloys. Mg-rare earth element alloy, Mg-Zn-rare earth element alloy and the like. Of these, Mg—Al—Zn based alloys and Mg—Al—Mn based alloys are preferably used from the viewpoint of balance between workability and mechanical properties. When importance is attached to flame retardancy and heat resistance, a magnesium alloy containing calcium, such as an Mg—Al—Ca alloy, can be used. When weight reduction is important, a magnesium alloy containing lithium such as an Mg—Al—Li alloy can be used.

  The form of the base material subjected to the anodizing treatment is not particularly limited. A molded product formed by a press molding method, a forging method, a thixo mold method, a die casting method, or the like can be used. Such a molded article may have dirt on the surface due to organic matter such as a mold release agent made of a silicone compound attached at the time of molding. Therefore, it is preferable to perform a degreasing treatment. As the liquid for degreasing, an aqueous solution containing a surfactant or a chelating agent is preferably used.

  After degreasing as necessary, it is preferable to immerse in an acidic aqueous solution and then immerse in an electrolytic solution to perform anodization. By dipping in an acidic aqueous solution, the surface of the substrate can be appropriately etched to remove an insufficiently formed oxide film and remaining organic matter. Although it does not specifically limit as acidic aqueous solution, Phosphoric acid aqueous solution has moderate acidity, and is suitable. When a phosphoric acid aqueous solution is used, magnesium phosphate may be formed on the surface simultaneously with etching. In addition, a degreasing treatment can be performed simultaneously by mixing a surfactant or a chelating agent with an acidic aqueous solution. When using a base material made of a magnesium alloy containing calcium or lithium, from the viewpoint of further improving the corrosion resistance of the anodized film, the base material is further treated with an aqueous solution containing hydrogen fluoride, and then immersed in an electrolytic solution. Then, it can be anodized.

  Moreover, since an insoluble component (smut) may adhere to the surface of the base material, the base material may be washed with an alkaline aqueous solution before the anodizing treatment. Thereby, it is possible to remove the smut adhering to the surface of the substrate. As the alkaline aqueous solution, an aqueous sodium hydroxide solution or an aqueous potassium hydroxide solution is preferably used. And the base material to which these pre-processing was performed is immersed in electrolyte solution, and is anodized.

  After each treatment step such as degreasing treatment, acidic aqueous solution treatment, alkaline aqueous solution treatment, washing and drying may be performed as necessary. In this way, a base material made of magnesium or a magnesium alloy that has been pretreated if necessary is immersed in the electrolytic solution.

  The electrolytic solution used in the present invention contains 0.1 to 1 mol / L of phosphate groups, 0.2 to 5 mol / L of ammonia or ammonium ions, and has a pH of 8 to 14.

  The electrolytic solution used in the present invention contains 0.1 to 1 mol / L of phosphate radical. The phosphate group here is one included in the electrolyte as free phosphoric acid, phosphate, hydrogen phosphate, or dihydrogen phosphate. In addition, in the case of polyphosphoric acid obtained by condensation of phosphoric acid or a salt thereof, it is assumed that the phosphoric acid radicals are contained by the number of phosphate radicals obtained by hydrolysis thereof. In the case of a salt, it may be a metal salt or a non-metallic salt such as an ammonium salt. The content of phosphate radicals is preferably 0.15 mol / L or more. Moreover, the content of phosphate groups is preferably 0.7 mol / L or less.

  When the electrolytic solution contains a phosphate group, phosphorus element is included in the anodized film. Moreover, unnecessary elution of the substrate can be prevented by making the electrolytic solution alkaline. Since this electrolytic solution does not substantially contain heavy metal elements, drainage management is easy, and the obtained anodic oxide film is also preferable because it does not contain heavy metals. In addition, an aqueous solution containing elemental fluorine is often difficult to treat with waste water, but the electrolytic solution used in the present invention does not contain elemental fluorine, which is preferable from this viewpoint.

  The electrolytic solution used in the present invention contains ammonia or ammonium ions in a total amount of 0.2 to 5 mol / L. As a result, the pH of the electrolytic solution is maintained at an appropriate alkalinity. The content of ammonia or ammonium ions is preferably 0.5 mol / L or more. Moreover, it is 3 mol / L or less suitably.

  The pH of the electrolyte used in the present invention is 8-14. The pH of the electrolytic solution is preferably 10 or more. Moreover, it is 12 or less suitably.

  And a base material is immersed in the said electrolyte solution, an alternating voltage or a pulse voltage is applied by making this into a working electrode, and the surface of a base material is anodized. Here, since the alternating voltage is a voltage that periodically changes between plus and minus, when the working electrode is an anode (cathode), the counter electrode is a cathode (anode). When an AC voltage is applied to anodize the surface of the substrate, the surface of the substrate is anodized when the working electrode is an anode. The counter electrode material is not particularly limited, and for example, a stainless material can be preferably used.

  From the viewpoint of productivity, the base material made of magnesium or a magnesium alloy is immersed in the electrolytic solution as a working electrode, and the base material made of magnesium or a magnesium alloy is also immersed as a counter electrode, between the working electrode and the counter electrode. It is preferable to apply an AC voltage and simultaneously anodize the surfaces of both the working electrode and the counter electrode to form an anodized film. This makes it possible to obtain twice the productivity with the same amount of power. In this case, both the working electrode and the counter electrode play the same role.

  The AC power source used in the present invention is not particularly limited, and examples thereof include a known single-phase AC power source and a three-phase AC power source. The frequency is not particularly limited, but is usually 50 Hz or 60 Hz.

  The pulse power source used in the present invention is not particularly limited, and a known pulse power source can be used. The duty ratio is not particularly limited, but is usually 0.1 to 0.9. The frequency is not particularly limited, but is usually 50 Hz or 60 Hz.

The spark start voltage (Es [V]) is set so as to satisfy the following formula (1). When the spark start voltage (Es [V]) is less than 50 V, the film thickness becomes thin and there is a possibility that excellent corrosion resistance cannot be obtained. In addition, an anodized film with a spark due to dielectric breakdown cannot be formed, and the corrosion resistance of the film may be inferior. The spark start voltage (Es [V]) is preferably 60 V or more, more preferably 70 V or more, and further preferably 80 V or more. On the other hand, if the spark start voltage (Es [V]) exceeds 160 V, it may not be possible to obtain a product made of magnesium or a magnesium alloy having excellent mechanical properties. The spark start voltage (Es [V]) is preferably 150 V or less, and more preferably 140 V or less. The spark start voltage (Es [V]) in the present specification is an applied voltage when spark (light emission) is visually confirmed on the surface of the substrate.
50 ≦ Es ≦ 160 (1)

The final voltage (Ef [V]) is set so as to satisfy the following formula (2). When the final voltage (Ef [V]) is less than 60 V, an anodized film having a desired thickness cannot be formed. The final voltage (Ef [V]) is preferably 70 V or higher, more preferably 80 V or higher, and further preferably 90 V or higher. On the other hand, if the final voltage (Ef [V]) exceeds 300 V, it may not be possible to obtain a product made of magnesium or a magnesium alloy having excellent mechanical properties. The final voltage (Ef [V]) is preferably 250 V or less, and more preferably 220 V or less.
60 ≦ Ef ≦ 300 (2)

The difference between the final voltage (Ef [V]) and the spark start voltage (Es [V]) is set so as to satisfy the following expression (3). When the difference between the final voltage (Ef [V]) and the spark start voltage (Es [V]) is less than 5 V, an anodized film having a desired thickness cannot be formed. The difference between the final voltage (Ef [V]) and the spark start voltage (Es [V]) is preferably 10 V or more, and more preferably 20 V or more. On the other hand, if the difference between the final voltage (Ef [V]) and the spark start voltage (Es [V]) exceeds 200 V, a product made of magnesium or a magnesium alloy having excellent mechanical properties may not be obtained. . The difference between the final voltage (Ef [V]) and the spark start voltage (Es [V]) is preferably 150 V or less, more preferably 100 V or less, and even more preferably 80 V or less.
5 ≦ Ef−Es ≦ 200 (3)

Current density is usually 0.1 to 10 A / dm ^2. Preferably it is 0.2 A / dm ² or more. Further, it is preferably 6 A / dm ² or less. The energization time is usually 10 to 1000 seconds. Preferably it is 20 seconds or more. Moreover, it is 500 seconds or less suitably.

  Along with the oxidation reaction, oxygen gas is generated from the surface of the anode, so that impurities adhering to the surface of the substrate during the anodizing treatment are easily removed. On the other hand, hydrogen gas twice the amount of oxygen gas is generated from the surface of the cathode. When an AC voltage is applied to anodize the surface of the substrate, the working electrode periodically becomes an anode or a cathode, so that oxygen gas and hydrogen gas are alternately generated from the surface of the substrate. Therefore, when an alternating voltage is applied and the surface of the base material is anodized, impurities attached to the surface of the base material are more easily removed. The temperature of the electrolytic solution during energization is usually 5 to 70 ° C. It is preferably 10 ° C or higher. Moreover, it is 50 degrees C or less suitably.

  After the energization is completed, the electrolyte attached to the surface of the anodized film is removed by washing the base material. In washing, not only water but also an acidic aqueous solution may be used. As the acidic aqueous solution, nitric acid aqueous solution, hydrochloric acid aqueous solution, sulfuric acid aqueous solution and the like can be used. After washing, drying is performed to obtain a product made of magnesium or a magnesium alloy having an anodized film on the surface.

  The thickness of the anodized film formed on the surface of the substrate is 2 μm or more and 30 μm or less. When the film thickness is less than 2 μm, a product made of magnesium or a magnesium alloy having excellent corrosion resistance cannot be obtained. In addition, a product made of magnesium or a magnesium alloy having excellent mechanical properties cannot be obtained. The thickness of the anodized film is preferably 4 μm or more, and more preferably 6 μm or more. On the other hand, the thicker the anodic oxide film, the better the corrosion resistance. However, if it is too thick, the surface roughness may increase and the production cost may increase. The thickness of the anodized film is preferably 25 μm or less, and more preferably 20 μm or less.

  The chemical composition of the anodic oxide film obtained in the present invention is not particularly limited, but the anodic oxide film is 10 to 65% by mass of magnesium element, 10 to 60% by mass of oxygen element, and 10 to 50% of phosphorus element. It is preferable to contain by mass%. That is, it is preferable that the base material which consists of magnesium or a magnesium alloy contains the oxidized magnesium which is a product as a result of anodizing.

  The content of magnesium element is more preferably 15% by mass or more. Moreover, it is 45 mass% or less more suitably. The content of oxygen element is more preferably 20% by mass or more. Moreover, it is 55 mass% or less more suitably. The content of phosphorus element is more preferably 15% by mass or more. Moreover, it is 45 mass% or less more suitably. A film having excellent corrosion resistance can be obtained by containing an appropriate amount of phosphorus element.

  It is also suitable to contain 0-10 mass% of aluminum elements. It is also preferable to contain 0-5% by mass of zinc element. You may contain 0-5 mass% of calcium elements. Moreover, you may contain 0-20 mass% of lithium elements. The anodized film of the present invention may contain elements other than those described above as long as the effects of the present invention are not impaired. However, it is preferred that substantially no heavy metals, particularly chromium elements, are contained except those originally contained in the substrate. The content of elements other than magnesium element, oxygen element and phosphorus element is usually 30% by mass or less, preferably 20% by mass or less, and more preferably 10% by mass or less.

  The hardness of the anodized film obtained by the production method of the present invention is preferably 110 or more, more preferably 120 or more in terms of Vickers hardness. On the other hand, the upper limit of Vickers hardness is usually 300 or less. The anodized film obtained by the production method of the present invention has a higher Vickers hardness and a smaller surface roughness (Ra) than an anodized film obtained by applying a DC voltage.

  As described above, according to the manufacturing method of the present invention, it is possible to manufacture a product made of magnesium or a magnesium alloy having an anodized film excellent in corrosion resistance and excellent in mechanical properties. As a reason why a product made of magnesium or a magnesium alloy obtained by a manufacturing method that satisfies the conditions defined in the present invention has such characteristics, the following is presumed.

  When a base material is immersed in the above-described electrolyte and the surface of the base material is anodized, a large number of holes that are thought to be derived from sparks during energization are often formed on the surface. Also in this-application Example and the comparative example, many holes considered to originate from the spark during energization were confirmed (see FIGS. 2 and 4). Here, when both FIG. 2 and FIG. 4 are compared, it can be seen that the pores are finer in the anodic oxide film formed by applying an alternating voltage. For this reason, the inventors have determined that the spark voltage (Es [V]) and the final voltage (Ef [V]) when an AC voltage is applied are lower than those when a DC voltage is applied. It is considered that the application of an alternating voltage rather than the application is due to the uniform dispersion of fine sparks. And, it is considered that the formation of a dense anodic oxide film on the surface of the substrate has an effect on the improvement of the mechanical properties.

  In addition, according to the manufacturing method of the present invention, an anodic oxide film having the same film thickness can be obtained with a lower applied voltage as compared with a method in which a DC voltage is applied and anodized. In addition, the processing time can be greatly shortened. Therefore, the significance of adopting the production method of the present invention is great from the viewpoint of energy consumption and cost.

  The production method of the present invention is a method for forming an anodized film by applying an alternating voltage or a pulse voltage to anodize the surface of a substrate. Since the alternating voltage is a voltage that periodically changes between plus and minus, there is no distinction between an anode and a cathode in a pair of electrodes. The inventors of the present invention focused on this point and attempted an anodic oxidation treatment by connecting a base material to both of the pair of electrodes. As described in Example 4 of the present specification, a base material made of a magnesium alloy is connected to both of a pair of electrodes, and an anodic oxidation is performed by applying an alternating voltage under the above conditions using the above electrolytic solution. Tried to process. As a result, an anodized film was formed on the surface of either substrate.

  In addition, the present inventors tried to perform anodizing treatment by connecting a base material made of aluminum to both of a pair of electrodes and applying an alternating voltage under the above conditions using the above electrolytic solution. As a result, an anodized film could not be formed on the surfaces of both substrates. For this reason, the present inventors have the property that the anodized film formed by anodizing treatment allows current to flow only in one direction because aluminum is a valve (valve) metal. I guess that is because.

  Furthermore, the inventors connected a base material made of a magnesium alloy to both of the pair of electrodes, and applied an AC voltage according to a known formulation called the Dow 17 method to perform anodization. As a result, an anodized film could not be formed on the surfaces of both substrates.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail using an Example, this invention is not limited to these. The test method in this example was performed according to the following method.

(1) Surface observation Using X-ray microanalyzer “JXA-8500FS” manufactured by JEOL Ltd., the surface of the test piece was photographed to obtain a secondary electron image.

(2) Film thickness measurement of anodized film The test piece was cut into a size of 5 mm × 10 mm, embedded in an epoxy resin, and then the cut surface was polished to obtain a mirror surface. From the cross-sectional direction of the sample, an electron micrograph was taken using an X-ray microanalyzer “JXA-8500FS” manufactured by JEOL Ltd., and the film thickness was measured. And the composition analysis was performed from the cross-sectional direction of the membrane | film | coat using the said X-ray microanalyzer.

(3) Measurement of hardness of film Vickers hardness was measured at a load of 0.1 N using a micro Vickers hardness tester “HM-114” manufactured by Mitutoyo Corporation.

(4) Measurement of surface roughness Surface shape measurement was performed with a non-contact type three-dimensional structural analysis microscope “Zygo New View 5000” to obtain arithmetic average roughness (Ra).

(5) Tensile test A tensile test was performed using "3382 floor-standing test system" manufactured by Instron. The strain rate was 5 mm / min. As a test piece, what performed the below-mentioned [pretreatment 1], [pretreatment 2], and [film-forming treatment] with respect to the base material shape | molded in the dumbbell shape was used.

(6) Measurement of friction coefficient The friction coefficient of the anodized film was measured. The measurement apparatus and measurement conditions are as follows.
・ Measuring device: Reciprocating sliding friction and wear tester manufactured by Shinko Engineering Co., Ltd. ・ Test ball: SUJ2 (HV810) with a diameter of 10 mm
・ Rotating radius: 4mm
・ Load 0.49N
・ Repetition frequency: 2Hz
・ Cycle: 7200
・ Temperature: 295 ± 1K
・ Relative humidity: 60 ± 1%

(7) Salt spray test The salt spray test was done with respect to the test piece based on JISZ2371. Then, the time until the rating number reached 9.0 was measured. The longer this time, the better the corrosion resistance of the film.

Example 1
[Base material]
ASTM No. consisting of 90% magnesium, 9% aluminum and 1% zinc by weight An alloy plate having dimensions of 170 mm × 50 mm × 2 mm cast from a AZ91D magnesium alloy and cast by a hot chamber method was used as a base material. This substrate had a Vickers hardness of 85 HV and a surface roughness (Ra) of 0.38 μm. For the tensile test, ASTM No. A base material was also prepared in which an alloy plate die cast by a hot chamber method using a AZ91D magnesium alloy as a raw material was formed into a dumbbell shape as shown in FIG. 1 using an NC milling machine. The base material had a tensile strength of 233 MPa and a strain (elongation at break) of 6.0%.

  Then, after performing [Pretreatment 1] and [Pretreatment 2] described below on each of the above-mentioned base materials, [Film forming treatment] was performed.

[Pretreatment 1]
As pretreatment 1, the substrate was immersed in an acidic aqueous solution 65 ° C. containing 0.25 mol / L phosphoric acid and a trace amount of surfactant for 60 seconds and washed with ion-exchanged water.

[Pretreatment 2]
As pretreatment 2, the substrate was immersed in a 3.8 mol / L 80 ° C. sodium hydroxide aqueous solution for 60 seconds and washed with ion-exchanged water.

[Film formation]
After the pretreatments 1 and 2, film formation was performed under the following conditions. An aqueous solution of phosphoric acid and aqueous ammonia were mixed to prepare an electrolyte solution containing 0.25 mol / L of phosphate groups and 1.5 mol / L of ammonia or ammonium ions in the total amount, and kept at 15 ° C. The pH of this electrolytic solution was 10.5. An anodizing treatment was performed by immersing the base material subjected to the above pretreatment in this as a working electrode. As a counter electrode at this time, a SUS316L plate having a surface area four times that of the working electrode was used. An AC constant current power supply (frequency: 60 Hz) was used, and current was applied for 140 seconds so that the current density on the surface of the working electrode was 1.5 A / dm ² . The occurrence of spark (light emission) on the surface of the substrate was visually confirmed 3 seconds after the start of energization. The applied voltage when the generation of sparks started was 125V. And after energization was completed, it was washed with ion-exchanged water and dried to obtain a test piece. The final voltage was 190V.

  FIG. 2 shows a secondary electron image on the surface of the test piece of Example 1, and FIG. 3 shows a cross-sectional secondary electron image. Existence of a large number of pores that were thought to be derived from sparks during energization was confirmed on the surface of the anodized film. The film thickness of the obtained anodized film was about 10 μm. The film thickness referred to here is an average distance from the surface of the thick part to the alloy surface of the base material in the film having local film thickness unevenness due to a large number of holes (described below). The film thickness is also the same). The film had a Vickers hardness of 142 HV and a surface roughness (Ra) of 0.79 μm. The obtained anodized film was composed of 26.1 at% (27.6 mass%) of magnesium element, 40.3 at% (27.9 mass%) of oxygen element, and 29.7 at% (39.9 mass%) of phosphorus element. %) And aluminum element 3.9 at% (4.6 mass%). The tensile strength in the tensile test was 293 MPa, and the strain (elongation at break) was 8.1%.

Example 2
Anodizing treatment was performed in the same manner as in Example 1 except that the treatment time, spark start voltage (Es [V]) and final voltage (Ef [V]) were changed as shown in Table 1. The test piece was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 3
Anodization was performed in the same manner as in Example 1 except that the AC power source was changed to a pulse power source (frequency: 60 Hz, duty ratio: 0.5). The test piece was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Example 4
Anodizing treatment was performed in the same manner as in Example 1 except that the counter SUS316L plate was changed to a base material made of the same magnesium alloy as used in Example 1. As a result, both the base material connected to the working electrode and the base material connected to the counter electrode had an anodic oxide film formed on their surfaces. All the anodized films had the same thickness and properties as the film obtained in Example 1. Therefore, twice the productivity could be obtained by supplying the same amount of power.

Comparative Example 1
Anodizing treatment was performed in the same manner as in Example 1 except that the AC power source was changed to a DC power source, and the processing time, spark start voltage (Es [V]) and final voltage (Ef [V]) were changed as shown in Table 1. Went. The test piece was evaluated in the same manner as in Example 1. The results are shown in Table 1. 4 shows a secondary electron image of the surface of the test piece of Comparative Example 1, and FIG. 5 shows a secondary electron image of the cross section. Existence of a large number of pores that were thought to be derived from sparks during energization was confirmed on the surface of the anodized film. At this time, the diameter of the hole existing on the surface was larger than the diameter of the hole in Example 1. The film thickness of the obtained anodized film was about 10 μm. The Vickers hardness of the film was 106 HV and the surface roughness (Ra) was 1.17 μm. The obtained anodic oxide film had a magnesium element content of 20.1 at% (23.0 mass%), an oxygen element of 54.7 at% (41.1 mass%), and a phosphorus element of 22.0 at% (32.0 mass%). %) And an aluminum element of 3.2 at% (4.0 mass%). The tensile strength in the tensile test was 236 MPa, and the strain (elongation at break) was 5.8%.

Comparative Example 2
Anodization was performed in the same manner as in Comparative Example 1 except that the treatment time, the spark start voltage (Es [V]) and the final voltage (Ef [V]) were changed as shown in Table 1. The test piece was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 3
Anodizing treatment was performed in the same manner as in Example 1 except that the treatment time, spark start voltage (Es [V]) and final voltage (Ef [V]) were changed as shown in Table 1. The test piece was evaluated in the same manner as in Example 1. The results are shown in Table 1.

Claims (3)

A base material made of magnesium or a magnesium alloy is immersed in an electrolyte solution containing 0.1 to 1 mol / L of phosphate radicals, 0.2 to 5 mol / L of ammonia or ammonium ions, and having a pH of 8 to 14, The spark start voltage (Es [V]) and the final voltage (Ef [V]) are set so as to satisfy the following formulas (1) to (3), and an AC voltage or a pulse voltage is applied to the substrate. A method for producing a product made of magnesium or a magnesium alloy, wherein an anodized film having a thickness of 2 μm to 30 μm is formed on the surface by anodizing the surface.
50 ≦ Es ≦ 160 (1)
60 ≦ Ef ≦ 300 (2)
5 ≦ Ef−Es ≦ 200 (3)   The manufacturing method of the product which consists of magnesium or a magnesium alloy of Claim 1 in which the said anodic oxide film contains 10-65 mass% of magnesium elements, 10-60 mass% of oxygen elements, and 10-50 mass% of phosphorus elements. .   A substrate made of magnesium or a magnesium alloy is immersed in the electrolytic solution as a working electrode, and a substrate made of magnesium or a magnesium alloy is also immersed as a counter electrode, and an AC voltage is applied between the working electrode and the counter electrode. And the manufacturing method of the product which consists of magnesium or a magnesium alloy of Claim 1 or 2 which forms the anodized film by anodizing the surface of the base material of both a working electrode and a counter electrode simultaneously.