JP2005068555A - Metallic material and surface treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metallic material which is excellent in adhesion to a coating film and in colorability while retaining metallic gloss inherent in its base material; and a surface treatment method for forming an anode oxidation film structure which is excellent in adhesion to a coating film and in colorability while retaining metallic gloss inherent in its base material. <P>SOLUTION: A 0.5 mm-thick rolled magnesium alloy AZ31B is subjected to a surface treatment with an acid, then immersed in an electrolytic solution containing sodium silicate+diethylene glycol in a concentration of 0.1±0.05 mol/L as a film formation stabilizer, and subjected to electrolysis under electrolytic conditions of a liquid temperature of 65±2°C, a current density of 2.0±0.5 A/dm<SP>2</SP>, and a voltage of 4-8 V. The magnesium alloy after the electrolysis has an anodic oxidation film consisting of a surface layer and a barrier layer. In the surface layer, micropores having an average pore size of about 500 nm and a pore length of 8-10 μm are present in a pore density of about 1,000,000/mm<SP>2</SP>, and the light reflectance of the surface layer is 60% or higher. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a metal material having a novel oxide film structure and a surface treatment method for magnesium or an alloy thereof, and more particularly, a metal material having metallic luster, good smooth surface, corrosion resistance, wear resistance, and metal on the surface. The present invention relates to a surface treatment method for forming a high-quality film by anodic oxidation that provides color, good smooth surface, corrosion resistance, and wear resistance.

  Magnesium or magnesium alloy materials are the lightest among practical metal materials, have good machinability, have a high strength / density ratio, and have good castability in die casting, so that they can be used in computers, audio products, communication equipment, aircraft, automobile materials, etc. Widely used in cases, structures, various parts, etc.

  However, magnesium or a magnesium alloy is oxidized in the atmosphere and a thin oxide film is formed on the surface, so that it is difficult to paint and the adhesion of the film is also poor. Moreover, corrosion resistance, abrasion resistance, etc. are low. Therefore, under the present circumstances, it is common to perform coating after the chemical conversion treatment is applied to the surface of the same metal, but the dimensional accuracy is reduced by coating, and the coating film must be peeled off when discarded or reused. And so on.

  On the other hand, it is also known that a film made of magnesium oxide or hydroxide is formed by anodic oxidation instead of chemical conversion, followed by coating. In this case, the anodic oxidation treatment is performed using heavy metal salts such as hexavalent chromate, manganate, permanganate, and phosphate. The anodized film formed by this method has many irregular holes and cracks with a large diameter of about 3 to 30 μm generated by spark discharge, and the surface of the film is not glossy. Furthermore, anodic oxidation using these heavy metal salts causes waste water contamination by heavy metal salts, which is not preferable from the viewpoint of environmental protection.

  Regarding the anodizing treatment without using a heavy metal salt, the present inventor uses an electrolytic solution obtained by adding a film-forming stabilizer to an aqueous solution containing an alkali metal or alkaline earth metal hydroxide, carbonate or bicarbonate. A method of electrolytic treatment has been proposed (see, for example, Patent Document 1).

JP-A-9-176894

  However, the oxide film obtained by the method described in Patent Document 1 has no risk of contamination of industrial wastewater by heavy metal salts, and the surface roughness and pore size of the oxide film are also compared with the conventional method using chromates. Although improved, there is still room for improvement in light reflectance (metallic luster), smoothness, corrosion resistance, coating film adhesion, and the like.

  Therefore, the present invention has been proposed in view of such conventional circumstances, and a metal material having good coating film adhesion and colorability while retaining the original metallic luster of the substrate, and the original metal of the substrate. An object of the present invention is to provide a surface treatment method for forming an anodized film structure having good coating film adhesion and colorability while leaving gloss.

  In order to achieve the above object, the present inventor performed anodizing treatment by changing electrolytic conditions such as electrolytic treatment voltage and electrolytic solution composition. As a result, it was found that by electrolyzing under specific conditions, an anodic oxide film having good coating film adhesion and colorability was formed while retaining the original metallic luster of the substrate.

The present invention has been completed based on such knowledge, and has a base material made of magnesium or a magnesium alloy, an average pore diameter of 5 nm to 1000 nm, a length of 1 μm to 50 μm, and a ratio of the length to the pore diameter of 1 or more. An anodized film comprising a surface layer having a fine pore density of 10,000 or more per 1 mm ² and a substantially non-porous barrier layer at the bottom of the surface layer is provided. In particular, the surface layer preferably has a fine pore density of 100,000 or more per 1 mm ² .

  Here, the light reflectance of the surface layer of the metal material according to the present invention is set to 60% or more when the reflectance is measured at a measurement angle of 85 °.

Further, the present invention provides magnesium or a magnesium alloy in an electrolytic aqueous solution containing at least one salt selected from hydroxides, carbonates, bicarbonates, silicates, and silicofluorides of alkali or alkaline earth metals. Is electrolyzed without spark discharge at a current density of 0.7 to 5 A / dm ² and a voltage of ² to 40 V, and the surface has an average pore diameter of 5 nm to 1000 nm and a length of 1 μm to 50 μm. An anodized film having a surface layer in which fine pores having a pore size ratio of 1 or more exist at a density of 10,000 or more per 1 mm ² and a substantially non-porous barrier layer at the bottom of the surface layer is formed. .

The anodized film in the present invention has elongated micropores having a length / pore diameter ratio, so-called aspect ratio of 1 or more, preferably 10 or more, and these extend from the surface layer toward the barrier layer. Substantially covers the entire coating at a density of at least 10,000 per mm ² .

  The thickness of the surface layer is suitably 3 to 50 μm. When the film thickness is 3 μm or less, sufficient corrosion resistance is difficult to obtain, and when it exceeds 50 μm, it is difficult to obtain a sufficient metallic luster. Furthermore, the anodized film has a surface layer having micropores and a very thin, substantially non-porous barrier layer following the surface layer.

The anodized film is formed mainly of magnesium oxide (MgO) and magnesium hydroxide (Mg (OH) ₂ ), and the composition is 0.1 to 40% for the former and 60 to 99 for the latter. It is composed of 5%. In addition, manganese, titanium, molybdenum, silicon, tungsten, zirconium, vanadium, chromium, cobalt, palladium, phosphorus, sulfur, bromine, fluorine, iodine, boron, carbon, nitrogen, or a compound thereof in the range of 0 to 30% Furthermore, the organic compound contains a chain or cyclic hydrocarbon having a hydroxyl group, an aldehyde group, a carbonyl group, or an amino group. The barrier layer in this anodic oxide film is mainly formed of hydroxide.

In order to form such an oxide film, magnesium or a magnesium alloy is added with one or more of alkali, alkaline earth metal hydroxide, carbonate, bicarbonate, silicate or fluorosilicate 0.2- Spark discharge at a current density of 0.7 to 5 A / dm ² and a voltage of ² to 40 V in an electrolytic aqueous solution containing 7 mol / L, preferably 0.01 to 5 mol / L of a film-forming stabilizer. Anodizing without accumulating.

As the electrolytic aqueous solution used in the surface treatment method according to the present invention, alkali or alkaline earth metal hydroxide, carbonate, bicarbonate, silicate or fluorosilicate can be used. Specific examples include hydroxides such as NaOH, KOH, Ba (OH) ₂ , carbonates such as Na ₂ CO ₃ , K ₂ CO ₃ , CaCO ₃ , and MgCO ₃ , NaHCO ₃ , KHCO ₃ , and Ca (HCO _{3). 2} ) Bicarbonates such as ₂ are listed, and an aqueous solution containing one or more of these is used. In addition, a film-forming stabilizer is added to the electrolyte for the purpose of improving the life of the solution, alone or in combination.

  As conditions for anodizing the magnesium or magnesium alloy material in the electrolytic solution prepared as described above, the electrolytic bath temperature is 30 to 90 ° C., particularly preferably 50 to 80 ° C., and a pH of 9 or higher is weak to strong. It may be basic, and it is preferable to pre-treat magnesium or a magnesium alloy with an acid before the electrolytic treatment.

Magnesium and magnesium alloys having an anodic oxide film according to the present invention, the average pore diameter 5 nm to 1000 nm, the presence ratio of length to pore diameter is 1 or more micropores in 1 mm ² per 10,000 or more density length 1μm~50μm And an anodized film consisting of a substantially non-porous barrier layer at the bottom of the surface layer, and when the light reflectance of the surface layer is measured at a measurement angle of 85 °, the reflectance is 60. When it is at least%, good metallic luster is expressed. Moreover, it has favorable coating-film adhesiveness and coloring property.

Moreover, according to the surface treatment method of magnesium and magnesium alloy according to the present invention, at least one selected from alkali, alkaline earth metal hydroxide, carbonate, bicarbonate, silicate, and silicofluoride. By immersing magnesium or a magnesium alloy in an aqueous electrolytic solution containing the salt of, and electrolyzing it without a spark discharge at a current density of 0.7 to 5 A / dm ² and a voltage of ² to 40 V, an average pore diameter is formed on the surface. 5 nm to 1000 nm, a length of 1 μm to 50 μm, a ratio of length to hole diameter of 1 or more micropores present at a density of 10,000 or more per 1 mm ² and the bottom of the surface layer are substantially non-porous An anodized film having a barrier layer can be formed. This anodized film exhibits a good metallic luster. Moreover, it has favorable coating-film adhesiveness and coloring property.

As shown in FIG. 1, the metal material 1 according to the present invention includes a base material 2 made of magnesium or a magnesium alloy, fine pores having an average pore diameter of 5 nm to 1000 nm, a length of 1 μm to 50 μm, and a ratio of length to pore diameter of 1 or more. 3 is provided with an anodized film 6 comprising a surface layer 4 present at a density of 10,000 or more per 1 mm ² and a substantially non-porous barrier layer 5 at the bottom of the surface layer 4. In particular, in the surface layer 4, it is preferable that the fine holes 3 exist at a density of 100,000 or more per 1 mm ² .

In order to form the oxide film 6 having the micropores 3 having a specific structure on such a surface, magnesium or a magnesium alloy is alkali or alkaline earth metal hydroxide, carbonate, bicarbonate, silicate or silica fluoride. Current density of 0.7 to 5 A in an electrolytic aqueous solution containing at least one kind of salt in the range of 0.2 to 7 mol / L, preferably 0.01 to 5 mol / L of a film-forming stabilizer. / Dm ² , a voltage of ² to 40 V, and achieved by anodizing without spark discharge. The current used is preferably a direct current or a current obtained by rectifying an alternating current.

  A characteristic point here is that an oxide film of 1 μm or more is formed while forming magnesium oxide while anodizing under conditions that do not cause spark discharge at a voltage of 2 to 40 V, particularly preferably 4 to 10 V. It is.

  In the conventional electrolytic treatment, spark discharge occurred because the electrolytic treatment was performed at a voltage of 50 V or higher, particularly usually 90 V or higher, and as a result, an oxide film having irregularly large pores of 3 to 30 μm or more was formed. The film surface had low light reflectance and no gloss.

  When electrolytic treatment is performed under the conditions of the present invention, spark discharge does not occur, the average pore diameter of the micropores 3 formed in the surface layer 4 is substantially covered with the micropores 3 of 1 μm or less, and most of them are 700 nm or less, Further, many of these fine holes 3 are formed substantially vertically from the surface layer 4 toward the barrier layer 5 while maintaining the diameter of the holes, or with some width. For this reason, it is possible to form the oxide film 6 having a gloss that is substantially the same as that of a metal material and having good corrosion resistance, smoothness, and wear resistance.

Alkaline earth metal hydroxides, carbonates, bicarbonates, silicates or fluorosilicates can be used in the electrolytic aqueous solution used in this surface treatment method. Specific examples include hydroxides such as NaOH, KOH, Ba (OH) ₂ , carbonates such as Na ₂ CO ₃ , K ₂ CO ₃ , CaCO ₃ , and MgCO ₃ , NaHCO ₃ , KHCO ₃ , and Ca (HCO _{3). 2} ) Bicarbonates such as ₂ are listed, and an aqueous solution containing one or more of these is used. The concentration of the alkaline solution is preferably 0.2-7 mol / L. If the amount is 0.2 mol or less, unevenness is likely to occur in the formed oxide film, and if it is 7 mol or more, powdering occurs, resulting in a non-glossy gray to gray-black color, and the desired oxide film cannot be obtained.

In the present invention, a film-forming stabilizer is added to the electrolytic solution for the purpose of improving the life of the solution. As the film formation stabilizer, inorganic compounds and organic compounds can be used. Specifically, minerals such as NaNO ₃ , CaNO ₃ , MgNO ₃ , Na ₂ SO ₄ , K ₂ SO ₄ , CaSO ₄ , and MgSO ₄ are used. Acid salts, fluorides such as KF, NH ₄ F, silicic acid compounds such as Na ₂ SiO ₃ , Na ₄ SiO ₄ , K ₂ SiO ₂ Na ₂ SiF ₆ , MgSiF ₆ , silica fluorides such as (NH ₄ ) ₂ SiF ₆ And (CH ₂ OH) ₂ , (CH ₂ CH ₂ OH) O, (CH ₂ OH) ₂ CHOH and other alcohols, (COOH) ₂ , (CH ₂ CH ₂ COOH) ₂ , [CH (OH) COOH] ₂ , C ₆ H ₄ (OHCOOH), C ₆ H ₅ COOH, C ₆ H ₄ (COOH) _{2 and} other carboxylic acids, C ₆ H ₄ (SO ₃ H · COO H) and organic compounds having a sulfone group such as C ₆ H ₃ (COOH · OH · SO ₃ H) can be used.

  These film formation stabilizers may be used alone or in combination. In particular, liquid management becomes easy when an inorganic compound and an organic compound are used in combination. The amount of the film formation stabilizer added is preferably in the range of 0.01 to 5 mol / L in the electrolytic solution. If it is 0.01 mol / L or less, the stability of the liquid is insufficient, and if it exceeds 5 mol / L, phenomena such as so-called fogging, unevenness, and smut occur in the formed film.

  As conditions for anodizing the magnesium or magnesium alloy material in the electrolytic solution prepared as described above, the electrolytic bath temperature is 30 to 90 ° C., particularly preferably 50 to 80 ° C., and a pH of 9 or higher is weak to strong. Basic.

  In addition, it is preferable to pre-process with magnesium with respect to magnesium or a magnesium alloy before performing an electrolytic treatment. Examples of the acid used for the pretreatment include mineral acids such as sulfuric acid, nitric acid, phosphoric acid and chromic acid, monovalent or polyvalent aliphatic carboxylic acids such as formic acid, oxalic acid and benzoic acid, aromatic carboxylic acids, sulfonic acids, and One or more acids selected from these salts can be used.

As described above, the anodic oxide film 6 formed using the method of the present invention is formed mainly of magnesium oxide (MgO) and magnesium hydroxide (Mg (OH) ₂ ), and the composition is the former. In the range of 0.1 to 40% and the latter in the range of 60 to 99.5%. In addition, manganese, titanium, molybdenum, silicon, tungsten, zirconium, vanadium, chromium, cobalt, palladium, phosphorus, sulfur, bromine, fluorine, iodine, boron, carbon, nitrogen, or these in the range of 0 to 30% The compound further contains a chain or cyclic hydrocarbon having a hydroxyl group, an aldehyde group, a carbonyl group, or an amino group as an organic compound. The barrier layer 5 in the anodic oxide film 6 is mainly formed of hydroxide.

The anodic oxide film 6 formed by the method of the present invention has a length / hole diameter ratio, that is, a so-called aspect ratio of 1 or more, and is 1 mm ² by the elongated micropores 3 formed from the surface layer 4 toward the barrier layer 5. It is covered with a density of at least 10,000 per unit. Therefore, substantially the entire surface of the oxide film 6 is covered with the fine holes 3. Here, “substantially” means that it accounts for about 80% or more of the entire film. When the proportion of the fine pores 3 is 80% or less, the gloss of the oxide film 6 is lowered and does not meet the object of the present invention. Here, the aspect ratio is preferably 10 or more.

The thickness _{D 1} of the surface layer 4 is suitably 3 to 50 [mu] m. When the thickness D ₁ is at 3μm or less difficult sufficient corrosion resistance can be obtained and it becomes difficult enough metallic luster obtained exceeds 50 [mu] m. Further, as shown in FIG. 1, the anodic oxide film 6 has a surface layer 4 having micropores 3 and a very thin substantially non-porous barrier layer 5 following the surface layer 4. The barrier layer 5 may have ultra-fine pores with a pore diameter of about 5 nm or less that are almost impossible to measure.

  Further, when the light reflectivity was measured by setting the light reflectivity when the diamond cut surface was measured at a measurement angle of 85 ° as 100%, the original light reflectivity of the base material before anodizing treatment, for example, a magnesium alloy was 84%. On the other hand, the anodized film 6 according to the present invention has a light reflectivity of 60% at a minimum, and the light reflectivity is 68% as the average pore diameter of the micropores 3 decreases to 500 nm and 50 nm. To 87%. In particular, when the average pore diameter is about 50 nm, a remarkable effect is achieved in that the gloss is superior to that of the base material 2. Thus, the anodized film 2 according to the present invention has a gloss equivalent to or close to the metal gloss of magnesium itself or the magnesium alloy itself.

  Therefore, the metal material 1 according to the present invention is sufficiently practical as it is without performing various treatments for imparting gloss to the surface by subjecting the base material 2 to an anodizing treatment by the method of the present invention after the forming process. Can be used.

  Moreover, since the oxide film 5 formed by the surface treatment according to the method of the present invention has good coating film adhesion and colorability, it can be immersed in a dye / pigment-containing bath or electrolyzed as necessary. You may color by coloring. In this case, clear coloring can be performed while sufficiently maintaining the metallic luster inherent in the substrate 2.

  In the metal material 1 according to the present invention, the sealing layer 7 is provided on the surface layer 4. The sealing layer 7 prevents foreign substances such as moisture from entering the micropores 3 formed in the surface layer 4 and further improves the corrosion resistance of the metal material 1 on which the surface layer 4 is formed. Is provided.

  The sealing layer 7 is formed by applying a transparent synthetic resin paint on the surface layer 4 or immersing the metal material 1 in a coating liquid containing such a paint.

  The sealing layer 7 is formed by immersing the metal material 1 in a silicate liquid containing an inorganic material. The sealing layer 7 obtained here is formed as a light-transmitting film that can be seen through the oxide film layer 4.

  Examples to which the present invention is applied will be described in detail below.

Anodizing treatment , Example 1
As a material to be treated, a rolled material of magnesium alloy AZ31B having a thickness of 0.5 mm was used, and after an acid surface treatment, an anodic electrolytic oxidation treatment was performed. 0.1 ± 0.05 mol / L of sodium silicate + diethylene glycol as a film formation stabilizer was added to 2 ± 0.5 mol / L of potassium hydroxide to obtain an electrolytic solution. It was immersed for 30 minutes under electrolytic conditions of a liquid temperature of 65 ± 2 ° C., a current density of 2.0 ± 0.5 A / dm ² , and a voltage of 4 to 8 V, and after lifting, it was sealed by a known method. By this treatment, an anodized film having a thickness of 10 μm was obtained.

The average pore diameter of the micropores formed in the surface layer of the anodized film in Example 1 was about 500 nm as measured with a laser microscope, the length of the pores was 8 to 10 μm when observed with a cross section with an optical microscope, and the micropore density was about 100. It was found to be 10,000 pieces / mm ² . Therefore, the aspect ratio (ratio of the average length of micropores to the pore diameter) was 16 to 20 (8 to 10 μm / 0.5 μm).

Comparative example 1
The same magnesium alloy as in Example 1 was treated by MX-11 treatment (HAE treatment), which is representative of spark discharge type anodization defined in JIS-H8651. By this treatment, a metal surface having fine pores with an average pore diameter of 5000 nm or more and a film thickness of about 50 μm was obtained.

Comparative example 2
The same magnesium alloy as in Example 1 was treated by MX-6 treatment defined by JIS. By this treatment, a metal surface having fine pores with an average pore diameter of 5000 nm or less was obtained.

The reflectance on the surface of the film is the reflectance of the metal surface when the light reflectance when the diamond cut surface is measured at a measurement angle of 85 ° is taken as 100%. The original reflectance of the material to be processed was 84%.

Example 1
The reflectance of the metal surface obtained by this treatment was 68%.

Comparative example 1
The reflectance of this metal surface was measured and found to be 8%, which was almost no gloss compared to the metal surface based on the treatment of this example.

Comparative example 2
The reflectivity of this metal surface was about 50%, but the gloss was inferior compared to the metal surface based on the treatment of this example.

Dyeability Colorability Evaluation Subsequently, the dyeability of the magnesium alloys subjected to the three types of surface treatments of Example 1, Comparative Example 1, and Comparative Example 2 was compared and examined.

  Each of the three types of surface-treated magnesium alloys was immersed in an aqueous solution containing Sanodal Yellow (Sanodal Yellow, manufactured by SANDOZ) 3GL dye at a concentration of 1 g / L at 70 ± 2 ° C. for 30 minutes. After pulling up, after performing a sealing treatment by a known method, the dyeability was evaluated.

  The magnesium alloy subjected to the surface treatment of Example 1 was dyed in a clear and uniform gold color while leaving the metallic luster inherent in the magnesium alloy itself. On the other hand, the HAE-treated magnesium alloy (Comparative Example 1) has no luster and the HAE-treated alloy has a dark brown color. In the same dyeing method as in Example 1, the color of the dye itself is changed. Coloring was impossible. Further, the magnesium alloy treated with MX-6 (Comparative Example 2) has a reflectivity of about 50%, and thus some metallic luster is observed, but like the magnesium alloy of Comparative Example 2, the alloy after MX-6 treatment As a result, the dyeing method similar to that in Example 1 cannot be colored in the color of the dye itself, and uneven dyeing occurs, making vivid dyeing that can withstand practical use impossible.

The reflectance change reflectance due to the oxide film thickness indicates the metal surface light reflectance when the light reflectance when the diamond cut surface is measured at a measurement angle of 85 ° is defined as 100%. The original reflectance of the material to be processed was 84%.

  Magnesium alloys having different oxide film thicknesses were manufactured by changing the electrolytic treatment time by using the same materials and electrolytic conditions as those in Example 1 and changing the electrolytic treatment time. When the coating thickness is reduced, the electrolytic treatment time is shortened, and when the coating thickness is increased, the thickness is increased, so that the oxide coating thickness becomes 3 μm (Example 2), 5 μm (Example 3), 10 μm (the above-described example). 1), 15 μm (Example 4) and 20 μm (Example 5) magnesium alloys were produced. When the average pore diameter of the film micropores of each of these magnesium alloys was measured with a laser microscope, all were about 500 nm.

  When the reflectance of each magnesium alloy surface was measured, Example 1 was 68% as described above, Example 2 was 85%, Example 3 was 75%, Example 4 was 62%, and Example 5 was 60%. %Met.

  On the other hand, also in the HAE treatment shown as Comparative Example 1, magnesium alloys having oxide film thicknesses of about 5 μm and about 50 μm (Comparative Example 1) were manufactured, and the reflectance was measured. As a result, the reflectance was 15% when the oxide film thickness was 5 μm, and 8% when the thickness was about 50 μm.

Change in reflectivity by fine pore diameter Under the same electrolysis conditions as in Example 1, the same material to be treated was used to adjust the electrolysis time to produce a magnesium alloy with an oxide film thickness of 5 μm. At this time, magnesium alloys having different fine pore average pore diameters were produced by changing the potassium hydroxide concentration in the electrolytic solution and adjusting the electrolysis conditions. Magnesium alloys having an average pore diameter of 100 nm (Example 6), 500 nm (Example 7), and 1000 nm (Example 8) were prepared. When the reflectance of each of these magnesium alloy surfaces was measured, the reflectance of Example 6 was 95%, Example 7 was 75%, and Example 8 was 65%.

  For comparison, a magnesium alloy with an average pore diameter changed also in the HAE treatment and MX-6 treatment was manufactured. However, these reflectances were 55% and 15%, and the metallic luster was almost lost, and the dyeability was also good. It was bad.

Results As described above, according to the surface treatment method of this example, the coating film adhesion and the colorability are good, and a clear coloring can be achieved with a metallic luster after the oxide film.

  Magnesium and its alloys used in the present invention can be used in a wide range of applications, including pure magnesium, magnesium-aluminum, magnesium-aluminum-zinc, magnesium-aluminum-silicon, and magnesium- Magnesium alloys such as zirconium-rare earth-silver, magnesium-zinc-zirconium, magnesium-zinc, magnesium-rare earth-zirconium, magnesium-aluminum-rare earth, magnesium-yttrium-rare earth, magnesium-calcium-zinc Can be used. The surface treatment method of the present invention can be widely applied to the surface treatment of housing cases and molded members made of these metal materials.

It is a schematic diagram explaining the cross section of the anodic oxide film formed by the surface treatment shown as a specific example of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Metal material 1, 2 Base material, 3 Micropore, 4 Surface layer, 5 Barrier layer, 6 Anodized film

Claims (10)

A substrate made of magnesium or a magnesium alloy;
A surface layer having an average pore diameter of 5 nm to 1000 nm, a length of 1 μm to 50 μm, and a ratio of the length to the hole diameter of 1 or more, and having a density of 10,000 or more per 1 mm ² ;
A metal material comprising an anodized film formed at the bottom of the surface layer and comprising a substantially non-porous barrier layer.   The metal material according to claim 1, wherein the light reflectance of the surface layer is 60% or more when the reflectance is measured at a measurement angle of 85 °. ^2. The metal material according to claim 1, wherein the fine pores are present in the surface layer at a density of 100,000 or more per 1 mm ² .   The metal material according to claim 1, wherein the surface layer contains magnesium oxide.   The surface layer is composed of 60 to 99.9% magnesium hydroxide and 0.1 to 40% magnesium oxide. In addition, manganese, titanium, molybdenum, silicon, tungsten, zirconium, vanadium, chromium, cobalt, palladium, phosphorus , Sulfur, bromine, fluorine, iodine, boron, carbon, nitrogen, or a compound thereof, or a linear or cyclic hydrocarbon having a hydroxyl group, an aldehyde group, a carbonyl group, or an amino group as an organic compound The metal material according to claim 1.   The metal material according to claim 1, wherein the surface layer has a thickness of 3 to 50 μm.   The metal material according to claim 1, wherein the surface layer is electrolytically colored. Magnesium or a magnesium alloy is immersed in an electrolytic aqueous solution containing at least one salt selected from alkali, alkaline earth metal hydroxide, carbonate, bicarbonate, silicate, silicofluoride, By electrolysis without spark discharge at a current density of 0.7 to 5 A / dm ² and a voltage of ² to 40 V, the average pore diameter on the surface is 5 nm to 1000 nm, the length is 1 μm to 50 μm, and the ratio of length to pore diameter is 1 or more. Forming an anodic oxide film having a surface layer having a density of 10,000 or more per 1 mm ² and a substantially non-porous barrier layer at the bottom of the surface layer Processing method. The surface treatment method according to claim 8, wherein the magnesium or the magnesium alloy is pretreated with an acid in advance. The electrolytic aqueous solution is an inorganic compound containing an alkali or alkaline earth metal hydroxide, carbonate, bicarbonate, silicate, silicofluoride, (CH ₂ OH) ₂ , (CH ₂ CH ₂ OH) O. , (CH ₂ OH) ₂ CHOH containing alcohols, (COOH) ₂ , (CH ₂ CH ₂ COOH) ₂ , [CH (OH) COOH] ₂ , C ₆ H ₄ (OHCOOH), C ₆ H ₅ COOH, At least one of carboxylic acids containing C ₆ H ₄ (COOH) ₂ , C ₆ H ₄ (SO ₃ H · COOH), and organic compounds having a sulfone group containing C ₆ H ₃ (COOH · OH · SO ₃ H) The surface treatment method according to claim 8, further comprising:

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