JP2003166098A - Composition for anodizing magnesium alloy and anodizing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composition for forming an anodic oxide film having superior corrosion resistance without using hazardous heavy metal salts, and to provide an anodizing method. <P>SOLUTION: The composition for anodizing a magnesium alloy includes a silicate compound, an aluminum compound, a surface conditioner, a base, and water. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a composition used for anodizing a magnesium alloy material and a method for surface treating a magnesium alloy material.

[0002]

2. Description of the Related Art Magnesium alloy is a relatively new metal material, and it is replaced by a plastic material that is difficult to recycle due to the enactment of the Recycling Law, and the weight of magnesium alloy is used to make housings for mobile phones and notebook personal computers. It is a material whose usage range is increasing as the material of the part.

Magnesium, which is the main component of the magnesium alloy, is a highly reactive metal belonging to the alkaline earth metals. Therefore, the magnesium alloy material is significantly inferior in corrosion resistance to other materials.

Therefore, conventionally, in order to improve the corrosion resistance of the magnesium alloy material, a heavy metal salt of hexavalent chromate, manganate or permanganate is used to form an anodized film. . However, anodic oxidation using these heavy metal salts causes pollution of wastewater by the heavy metal salts and is not preferable from the viewpoint of environmental protection.

JP-A-9-176894 discloses that an aqueous solution containing at least one kind of hydroxide, carbonate or bicarbonate of an alkali metal or an alkaline earth metal is added to an organic compound having a silicon oxide or a hydroxyl group. It has been proposed to use an electrolyte solution containing a film formation stabilizer, but an anodic oxide film having sufficient corrosion resistance has not been obtained.

[0006]

DISCLOSURE OF THE INVENTION The present invention provides a composition for anodizing treatment and an anodizing method capable of forming an anodized film having excellent corrosion resistance without using harmful heavy metal salts. With the goal.

[0007]

The present inventors can achieve the above object by using a composition containing a silicic acid compound, an aluminum compound, a surface conditioner, a base and water for anodizing treatment of a magnesium alloy. The present invention has been completed and the present invention has been completed.

That is, the present invention provides the invention according to the following items. Item 1. An anodizing composition for a magnesium alloy, which contains a silicic acid compound, an aluminum compound, a surface conditioner, a base and water. Item 2 The composition according to Item 1, further containing a thiocyanic acid compound. Item 3 0.01 to 10 mol of silicic acid compound per 1 L of water
(As an anhydride), aluminum compound 0.01 ~ 10mo
Item 1. The composition according to Item 1, which contains 0.01 to 10 mol of a surface conditioner and 0.1 to 10 mol of a base. Item 4 0.01 to 10 mol of silicic acid compound per 1 L of water
(As an anhydride), aluminum compound 0.01 ~ 10mo
Item 3. The composition according to Item 2, which contains 0.01 to 10 mol of a surface conditioner, 0.1 to 10 mol of a base, and 0.01 to 10 mol of a thiocyanic acid compound. Item 5 The composition according to Item 1 or 2, wherein the surface modifier is a glycol compound and the base is at least one kind of hydroxide, carbonate or bicarbonate of an alkali metal or an alkaline earth metal. object. Item 6 The silicic acid compound is at least one of sodium silicate and lithium silicate, and the aluminum compound is aluminum nitrate, aluminum phosphate, aluminum sulfate, aluminum chloride, aluminum silicate, sodium aluminate or potassium aluminate. At least one kind, the surface modifier is at least one kind of ethylene glycol, ethyl glycol, ethyl diglycol, ethyl triglycol, butyl glycol and butyl diglycol, and the base is sodium hydroxide, potassium hydroxide and water. Item 2. The composition according to Item 1, which is at least one kind of lithium oxide. Item 7 The silicic acid compound is at least one of sodium silicate and lithium silicate, and the aluminum compound is aluminum nitrate, aluminum phosphate, aluminum sulfate, aluminum chloride, aluminum silicate, sodium aluminate or potassium aluminate. At least one kind, the surface modifier is at least one kind of ethylene glycol, ethyl glycol, ethyl diglycol, ethyl triglycol, butyl glycol and butyl diglycol, and the base is sodium hydroxide, potassium hydroxide and water. Item 3. The composition according to Item 2, which is at least one kind of lithium oxide and the thiocyanate compound is at least one kind of potassium thiocyanate, sodium thiocyanate, calcium thiocyanate and ammonium thiocyanate. Item 8. A surface treatment method for a magnesium alloy, which comprises immersing the magnesium alloy in the composition according to Item 1 to perform anodizing treatment, and sealing the resulting anodized film. Item 9. The surface treatment method according to Item 8, wherein a polymer having a primary amino group in a side chain is used as a pore-sealing agent used for the pore-sealing treatment. Item 10. The surface treatment method according to Item 9, wherein a composition containing a polymer having a primary amino group in a side chain, an epoxy resin, and a silane coupling agent is used as the pore-sealing agent. Item 11 A magnesium alloy having an anodized film containing silicic acid and alumina, and at least one compound oxide of silicon and aluminum. Item 12 A molded product made of the magnesium alloy according to Item 11.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

The composition of the present invention contains a silicic acid compound, an aluminum compound, a surface conditioner, a base and water.

Examples of the silicic acid compound include silicates such as sodium silicate and lithium silicate. The silicic acid compounds may be used alone or in combination of two or more.

Examples of the aluminum compound include aluminum nitrate, aluminum phosphate, aluminum sulfate, aluminum chloride, aluminum silicate, sodium aluminate, potassium aluminate and the like. The aluminum compounds may be used alone or in combination of two or more.

The surface conditioner may be any polar substance having an alcohol group, an ether group, etc. For example, a protic solvent such as alcohol can be preferably used. As the alcohol, specifically, glycol compounds such as ethylene glycol, ethyl glycol, ethyl diglycol, ethyl triglycol, butyl glycol and butyl diglycol can be preferably exemplified. As the surface conditioner, polyhydric alcohols are preferable, and among the exemplified compounds, ethylene glycol is more preferable.
These surface modifiers can be used alone or in combination of two or more. It is considered that the surface conditioner stabilizes the surface of the oxide film by relaxing the surface tension of the electrolytic solution (anodizing composition).

As the base, hydroxides, carbonates, bicarbonates and the like of alkali metals or alkaline earth metals are preferably used, and hydroxides are more preferable. Specific examples thereof include hydroxides of alkali metals such as sodium hydroxide, potassium hydroxide and lithium hydroxide. The base may be used alone or in combination of two or more.

The composition of the present invention may further contain a thiocyanate compound in addition to the above components. Addition of a thiocyanate compound improves the corrosion resistance, and
The adhesion of the coating film is also greatly improved.

Examples of thiocyanate compounds include alkali metal salts of thiocyanic acid such as potassium thiocyanate and sodium thiocyanate, thiocyanates such as alkaline earth metal salts of thiocyanic acid such as calcium thiocyanate; ammonium thiocyanate and the like. it can. The thiocyanic acid compounds can be used alone or in combination of two or more.

In the composition of the present invention, the blending amount of each component is not particularly limited as long as the intended effect of the present invention can be obtained, and can be appropriately set according to the type of each component. Normally, with respect to 1 L of water, a silicic acid compound of 0.01 to
About 10 mol (as an anhydride), especially about 0.02-5 mol (as an anhydride); about 0.01-10 mol of aluminum compound,
Especially about 0.02 to 5 mol, further about 0.04 to 5 mol; surface conditioning agent 0.01 to 10 mol, especially about 0.02 to 5 mol, further 0.3 to 5 mol
Amount: base 0.1 to 10 mol, preferably 0.2 to 10 mol.

When using, for example, No. 3 water glass as the silicic acid compound, the amount used may be set so as to be in the above-mentioned molar concentration range, and 1.2 to 1000 per 1 L of water.
It is preferably about g, particularly about 2.4 to 500 g.

When the thiocyanic acid compound is added, the amount of the thiocyanic acid compound added is usually 0.
It is preferable to add about 01 to 10 mol, particularly about 0.02 to 5 mol.

In addition to the above components, the composition of the present invention may contain acetylenic alcohol, a surfactant and the like.

The composition of the present invention can be prepared by dissolving predetermined amounts of components in water.

A magnesium alloy is immersed in the composition thus obtained and electrolysis (anodizing treatment) is performed to obtain an anodized film on the surface of the magnesium alloy.

The magnesium alloy to be anodized is, for example, Li: 5 to 16% by weight, Y, Zn, Al, Ag, M.
An alloy having a composition of at least one of n, Si, Ca, Zr and lanthanoid: 6% by weight or less and Mg: balance is included.

In the present invention, the magnesium alloy is usually subjected to anodic oxidation after being processed into a molded product having a desired shape by plastic working such as press working, die casting, thixomolding and the like.

The thickness of the anodic oxide coating is not particularly limited as long as it provides corrosion resistance suitable for the intended use, but is usually about 0.5 to 30 μm, preferably 1 to 20 μm. It is a degree. The conditions of the anodizing treatment can be appropriately set depending on the type and concentration of each component contained in the composition so that a desired film thickness can be obtained.

Specifically, the bath temperature is preferably about 20 to 90 ° C, more preferably about 30 to 80 ° C. The electrolysis time is usually about 2 to 40 minutes, preferably about 5 to 30 minutes. As a power supply for electrolysis, any power supply such as a DC power supply, an AC power supply, a PR power supply, and a pulse power supply can be used. Current density is 0.1-30A / dm ²
The degree is preferably about 0.5 to 20 A / dm ^{2 and} more preferable.

The film obtained by anodic oxidation usually has pores having openings, and corrosion easily occurs from the pores. Therefore, after the anodization is performed, usually, a sealing treatment for covering the pores is performed.

The pore-sealing treatment can be carried out using a pore-sealing agent which is usually used for sealing the anodized film. As the pore-sealing agent, for example, a polymer containing a primary amino group in its side chain (preferably a number average molecular weight of 3
Polymers of about 00 to 500,000 are preferably used. Examples of such a polymer include a graft polymer of polyethyleneimine and methacrylic acid. In addition to such polymers, the pore-sealing agent includes epoxy resins such as sorbitol polyglycidyl ether and glycerin polyglycidyl ether, vinyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, p-styryltrimethoxysilane, A silane coupling agent such as γ-methacryloxypropylmethyldiethoxysilane or γ-aminopropyltriethoxysilane may be added.

The conditions for the pore-sealing treatment can be appropriately set depending on the kind of the pore-sealing treatment agent. For example, after diluting with a solvent, the anodic oxide film is dipped in the solution to impregnate it with 20 to 20. The treatment may be performed at about 250 ° C. for about 30 seconds to 60 minutes.

The anodic oxide film thus obtained contains silicic acid and alumina, or a composite oxide of silicon and aluminum as a main component. A magnesium alloy or a molded body of a magnesium alloy having such an anodized film is also included in the present invention.

The molded product of the present invention can be further used for manufacturing a final product, for example, a mobile phone, PHS, P.
Mobile information terminals such as DA (Personal Digital Assistance); notebook computers; video equipment such as digital video and digital cameras; robots such as industrial robots and entertainment robots; information about CD players, MD players, portable cassette disks, portable DVDs, etc. The recording and / or reproducing apparatus can be used for a housing part of a game machine, an internal mechanical part (for example, an internal pickup of a game machine) and the like. The molded product can also be used for automobile parts, parts for the aerospace industry (casings for artificial satellites, support for paddles for solar cells, structural materials for space stations, etc.).

[0032]

According to the anodizing composition of the present invention,
It is possible to impart excellent corrosion resistance to a magnesium alloy. Further, according to the present invention, the anodic oxide film is formed without the step of using the treatment liquid containing the harmful substance (heavy metal salt). Therefore, the formed anodic oxide film does not contain harmful substances, and environmental pollution does not pose a problem during recycling, for example.

[0033]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Test Example 1 (Anodic oxidation of Li-based Mg alloy) After degreasing and etching the test piece of lithium-based magnesium alloy (LW91) shown below, anodization was performed using the composition shown in Table 1 below. It was Specimen: Li: 9% by weight, Y: 1% by weight, Mg: 90% by weight, magnesium alloy degreasing: 5% NaOH, 60 ° C, 3 minutes Ultrasonic degreasing etching: 5% phosphoric acid, 60 ° C, 20 seconds Immersion treatment Anodizing condition: Constant current electrolysis method, Electrolysis device: HA by Hokuto Denko
Type 310 used 60 ° C, 4A / dm ² , 20 minutes anodic oxidation

[0035]

[Table 1]

[0036]

[Table 2]

In Table 1 and the table below, "water glass" is 3
No. water glass (sodium silicate) is shown. In addition, in Table 1 and the table described later, “LSS-75” represents lithium silicate.

The thickness of the anodized oxide film of the obtained test piece was measured. In addition, after the oxide film was sealed, a salt spray test was carried out for those with and without the cut of 30 mm in length to evaluate their corrosion resistance. Film thickness measurement: Made by Fisher Instruments Inc .:
Isoscope MP30 type sealing treatment: Polyment NK-380 manufactured by Nippon Shokubai Co., Ltd.
(Polyethyleneimine and methacrylic acid polymer)
After being diluted 2-fold with butanone, the anodized test piece was dipped and baked at 60 ° C. for 10 minutes. Salt spray test conditions (SST test): 5% NaCl, 35 ± 1 ℃, 24
Table 2 shows the results of using the SASS tester manufactured by Suga Test Instruments Co., Ltd. with the CASS90 model.

[0039]

[Table 3]

The anodic oxide coatings of the examples all showed excellent corrosion resistance with no rust spots and no widening of the cut width.

Test Example 2 (Anodic Oxidation of AZ31B Alloy) Specimens of magnesium alloy (AZ31B) shown below were degreased and etched, and then anodized using the compositions shown in Table 3 below. Specimen: AZ31B magnesium alloy (Al: 3% by weight, Zn: 1% by weight, Mg: 96% by weight) Degreasing: 5% NaOH, 60 ℃, 3 minutes ultrasonic degreasing etching: 5% phosphoric acid, 60 ℃ , 20 seconds immersion treatment Smut removal: 10% sodium hydroxide, 60 ° C, 5 minutes immersion treatment Anodizing condition: constant current electrolysis method, electrolysis device: Hokuto Denko HA
Type 310 used 60 ° C, 4A / dm ² , 20 minutes anodic oxidation

[0042]

[Table 4]

The film thickness of the anodized oxide film of the obtained test piece was measured. In addition, after the oxide film was sealed, a salt spray test was carried out for those with and without the cut of 30 mm in length to evaluate their corrosion resistance. Film thickness measurement: Made by Fisher Instruments Inc .:
Isoscope MP30 type sealing treatment: Polyment NK-380 manufactured by Nippon Shokubai Co., Ltd.
(Polyethyleneimine and methacrylic acid polymer)
After being diluted 2-fold with butanone, the anodized test piece was dipped and baked at 60 ° C. for 10 minutes. Salt spray test conditions (SST test): 5% NaCl, 35 ± 1 ℃, 120
Table 4 shows the results of using the time SST test apparatus: CASS90 type manufactured by Suga Test Instruments Co., Ltd.

[0044]

[Table 5]

The anodic oxide coatings of the examples all showed excellent corrosion resistance with no rust spots and no widening of the cut width.

Test Example 3 (Anodic Oxidation of Li-based Mg Alloy) In order to evaluate the change in the concentration of each component and the effect on the obtained anodic oxide film, the concentrations of lithium silicate, aluminum nitrate and ethylene glycol are shown in Tables 5 to 7, respectively. Using the composition changed as shown, a lithium-based magnesium alloy (LW91) test piece shown below was degreased and etched, and then anodized. Specimen: Li: 9% by weight, Y: 1% by weight, Mg: 90% by weight, magnesium alloy degreasing: 5% NaOH, 60 ° C, 3 minutes Ultrasonic degreasing etching: 5% phosphoric acid, 60 ° C, 20 seconds Immersion treatment Anodizing condition: Constant current electrolysis method, Electrolysis device: HA by Hokuto Denko
Type 310 used 60 ° C, 4A / dm ² , 20 minutes anodic oxidation

[0047]

[Table 6]

[0048]

[Table 7]

[0049]

[Table 8]

The film thickness of the anodized oxide film of the obtained test piece was measured. In addition, after the oxide film was sealed, a salt spray test was carried out for those with and without the cut of 30 mm in length to evaluate their corrosion resistance. Film thickness measurement: Made by Fisher Instruments Inc .:
Isoscope MP30 type sealing treatment: Polyment NK-380 manufactured by Nippon Shokubai Co., Ltd.
(Polyethyleneimine and methacrylic acid polymer)
After being diluted 2-fold with butanone, the anodized test piece was dipped and baked at 60 ° C. for 10 minutes. Salt spray test conditions (SST test): 5% NaCl, 35 ± 1 ℃, 24
Time SST test device: Suga Test Instruments Co., Ltd. CASS90 type use results are shown in Table 8.

[0051]

[Table 9]

In Table 8, "EG" means ethylene glycol.

Test Example 4 (Anodic oxidation of Li-based Mg alloy) In order to evaluate the influence of the bath temperature during the anodizing treatment on the obtained film, a lithium-based magnesium alloy (LW9
After degreasing and etching the test piece of 1), anodization was performed under the conditions shown in Table 9 below. Specimen: Li: 9% by weight, Y: 1% by weight, Mg: 90% by weight, magnesium alloy degreasing: 5% NaOH, 60 ° C, 3 minutes Ultrasonic degreasing etching: 5% phosphoric acid, 60 ° C, 20 seconds Immersion treatment Anodizing condition: Constant current electrolysis method, Electrolysis device: HA by Hokuto Denko
Type 310 used 40, 50, 60 or 70 ℃, 4A / dm ² , 20 minutes anodic oxidation

[0054]

[Table 10]

The film thickness of the anodized oxide film of the obtained test piece was measured. In addition, after the oxide film was sealed, a salt spray test was carried out for those with and without the cut of 30 mm in length to evaluate their corrosion resistance. Film thickness measurement: Made by Fisher Instruments Inc .:
Isoscope MP30 type sealing treatment: Polyment NK-380 manufactured by Nippon Shokubai Co., Ltd.
(Polyethyleneimine and methacrylic acid polymer)
After being diluted 2-fold with butanone, the anodized test piece was dipped and baked at 60 ° C. for 10 minutes. Salt spray test conditions (SST test): 5% NaCl, 35 ± 1 ℃, 24
Table 10 shows the results of using the time SST test apparatus: CASGA 90 manufactured by Suga Test Instruments Co., Ltd.

[0056]

[Table 11]

Test Example 5 (Anodic oxidation of Li-based Mg alloy) In order to evaluate the effect of the current density during the anodizing treatment on the thickness of the film obtained, a lithium-based magnesium alloy (LW91) test piece was degreased. -After etching, anodization was performed using the compositions shown in Table 11 below. Specimen: Li: 9% by weight, Y: 1% by weight, Mg: 90% by weight, magnesium alloy degreasing: 5% NaOH, 60 ° C, 3 minutes Ultrasonic degreasing etching: 5% phosphoric acid, 60 ° C, 20 seconds Immersion treatment Anodizing condition: Constant current electrolysis method, Electrolysis device: HA by Hokuto Denko
Type 310 used 60 ° C, 1, 2, 3 or 4A / dm ² , anodizing for 20 minutes

[0058]

[Table 12]

Film thickness measurement: manufactured by Fisher Instruments Inc .: Isoscope MP30 type The results are shown in FIG.

Test Example 6 (Anodic oxidation of Li-based Mg alloy) In order to evaluate the influence of the anodizing time on the thickness of the obtained film, a lithium-based magnesium alloy (LW91)
After degreasing and etching the test piece of 1 above, anodization was performed using the compositions shown in Table 12 below. Specimen: Li: 9% by weight, Y: 1% by weight, Mg: 90% by weight, magnesium alloy degreasing: 5% NaOH, 60 ° C, 3 minutes Ultrasonic degreasing etching: 5% phosphoric acid, 60 ° C, 20 seconds Immersion treatment Anodizing condition: Constant current electrolysis method, Electrolysis device: HA by Hokuto Denko
Type 310 used 60 ° C, 4A / dm ² , anodizing for 5, 10 or 20 minutes

[0061]

[Table 13]

Film thickness measurement: manufactured by Fisher Instruments Inc .: Isoscope MP30 type The results are shown in FIG.

[Brief description of drawings]

FIG. 1 is a diagram showing the results of Test Example 5.

FIG. 2 is a diagram showing the results of Test Example 6;

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Toshiyuki Takahashi             2-15-21 Mitsuyachu, Yodogawa-ku, Osaka-shi, Osaka             Issue Kasatani Co., Ltd. (72) Inventor Kino Gogo             2-15-21 Mitsuyachu, Yodogawa-ku, Osaka-shi, Osaka             Issue Kasatani Co., Ltd. (72) Inventor Kenki Matsumura             4-10-28, Seijaku, Settsu-shi, Osaka MIRIO             N Kagaku Co., Ltd.

Claims (12)

[Claims] 1. An anodizing composition for a magnesium alloy, which contains a silicic acid compound, an aluminum compound, a surface conditioner, a base and water. 2. The composition according to claim 1, further comprising a thiocyanate compound. 3. A silicic acid compound is added in an amount of 0.01 to 1 L of water.
10 mol (as anhydrous), 0.01-1 aluminum compound
The composition according to claim 1, which contains 0 mol, 0.01 to 10 mol of a surface modifier, and 0.1 to 10 mol of a base. 4. A silicic acid compound is added in an amount of 0.01 to 1 liter of water.
10 mol (as anhydrous), 0.01-1 aluminum compound
0 mol, 0.01 to 10 mol of surface conditioner, 0.1 to 10 mol of base,
The composition according to claim 2, which contains 0.01 to 10 mol of a thiocyanic acid compound. 5. The surface conditioner is a glycol compound,
Hydroxide whose base is an alkali metal or alkaline earth metal,
The composition according to claim 1, which is at least one kind of carbonate and bicarbonate. 6. The silicic acid compound is at least one of sodium silicate and lithium silicate, and the aluminum compound is aluminum nitrate, aluminum phosphate, aluminum sulfate, aluminum chloride, aluminum silicate, sodium aluminate and alumina. At least one kind of potassium acid, the surface modifier is at least one kind of ethylene glycol, ethyl glycol, ethyl diglycol, ethyl triglycol, butyl glycol and butyl diglycol, and the base is sodium hydroxide, hydroxide. At least one of potassium and lithium hydroxide
The composition of claim 1, wherein the composition is a seed. 7. The silicic acid compound is at least one of sodium silicate and lithium silicate, and the aluminum compound is aluminum nitrate, aluminum phosphate, aluminum sulfate, aluminum chloride, aluminum silicate, sodium aluminate and alumina. At least one kind of potassium acid, the surface modifier is at least one kind of ethylene glycol, ethyl glycol, ethyl diglycol, ethyl triglycol, butyl glycol and butyl diglycol, and the base is sodium hydroxide, hydroxide. At least one of potassium and lithium hydroxide
The composition according to claim 2, wherein the thiocyanate compound is at least one of potassium thiocyanate, sodium thiocyanate, calcium thiocyanate and ammonium thiocyanate. 8. A method for surface treatment of a magnesium alloy, which comprises immersing the magnesium alloy in the composition according to claim 1 for anodic oxidation treatment, and sealing the resulting anodic oxide film. . 9. The surface treatment method according to claim 8, wherein a polymer having a side chain containing a primary amino group is used as the pore-sealing agent used for the pore-sealing treatment. 10. The surface according to claim 9, wherein a composition containing a polymer having a primary amino group in a side chain, an epoxy resin and a silane coupling agent is used as a pore-sealing agent. Processing method. 11. A magnesium alloy having an anodic oxide coating containing silicic acid and alumina, and at least one compound oxide of silicon and aluminum. 12. A molded body made of the magnesium alloy according to claim 11.