JP2003027284A - Surface treatment method of aluminum material and surface treated aluminum material - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To eliminate rolling traces and extrusion traces at the time of forming a material, and to enhance uniformity and reproducibility in surface gloss and color tone.
Provided is a surface treatment method for an aluminum material, which can impart a controlled surface gloss and color tone over a wide range. SOLUTION: A surface treatment method for an aluminum material made of aluminum or an aluminum alloy, the first step of forming an anodized film on the surface of the aluminum material by anodizing in an aqueous solution containing a polybasic acid and / or a salt thereof. And a second step of performing anodic electrolysis in an aqueous solution containing a monobasic acid and / or a salt thereof.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uniformly controls the metallic luster of the surface of an aluminum material such as an extruded material or a rolled material made of aluminum or an aluminum alloy to obtain a uniform and calm surface state without unevenness in the finished appearance. The present invention relates to a surface treatment method for an aluminum material for producing the surface-treated aluminum material, and a surface-treated aluminum material produced by this method.

[0002]

2. Description of the Related Art Aluminum materials are lightweight, have excellent corrosion resistance, durability, workability, surface treatment, etc., and also have appropriate strength, so that they are used as exterior materials, interior materials, surface layer materials, etc. It is widely used in an extremely large number of fields, including casing materials for materials and electrical equipment.

The surface gloss of such an aluminum material is adjusted by a method such as a satin finish or a blast treatment for the purpose of improving the harmony with the surrounding environment and the design according to the purpose of use. Alternatively, a surface treatment for coloring by an electrolytic coloring treatment, a coating treatment or the like is performed.

Specific examples of this type of surface treatment include, for example, Fe, Mn, Zr, Si, Cr, Mg, Zn and Cu.
A method of obtaining an aluminum material having a white color tone by anodizing after adjusting the addition amount of alloy components such as, and adjusting the surface color tone to white by roughening treatment (JP-A-3-47,937), heat treatment And a method for obtaining an aluminum material having a crystal pattern by coarsening the crystal grains by performing an etching treatment (Japanese Patent Laid-Open No. 3-257,177), applying a plastic deformation after performing a complete softening annealing treatment, and then performing a heat treatment. A method of coarsening crystal grains to obtain an aluminum material having a crystal pattern (JP-A-5-70,906), extruding an Al-Mg-Si alloy containing a Fe component and a Cu component in a predetermined ratio,
Then, a method for obtaining an aluminum material having a crystal pattern by etching (Japanese Patent Laid-Open No. 6-336682) has been proposed.

However, in such a conventional surface treatment, the range of surface gloss given to the surface of the aluminum material is narrow, the color tone varies depending on the observation angle, and the appearance after the treatment is different. Since it cannot be controlled, it lacks uniformity and reproducibility in surface gloss and color tone.
Especially in the field of building materials, etc., a wide variety of surface luster and color tones required with the diversification of tastes, especially without feeling gritty to the touch, but with a slight metallic luster and a gritty feeling to the eyes There is a problem that it is not possible to deal with the surface gloss and color tone that have

[0006]

Therefore, as a result of intensive studies to solve such problems, the present inventors have found that anodizing treatment in an aqueous solution containing a polybasic acid and / or a salt thereof is carried out. , Anode electrolysis treatment in an aqueous solution containing monobasic acid and / or its salt has excellent uniformity and reproducibility in surface gloss and color tone, and has a wide range of controlled surface gloss and color tone. The present invention has been completed based on the finding that it is possible to impart a gentle gritty feeling) and, at the same time, to eliminate rolling marks, extrusion marks, and the like.

Therefore, the object of the present invention is to eliminate the rolling marks, extrusion marks, etc. at the time of forming the material, and to provide uniform and reproducible surface gloss and color tone, and control surface gloss and color tone over a wide range. An object of the present invention is to provide a surface treatment method for an aluminum material capable of imparting

[0008]

That is, the present invention is a surface treatment method for an aluminum material made of aluminum or an aluminum alloy, which comprises subjecting the aluminum material to anodization in an aqueous solution containing a polybasic acid and / or a salt thereof. First step of forming an anodized film on the surface, and monobasic acid and /
Or a second step of performing anode electrolysis in an aqueous solution containing a salt thereof, which is a surface treatment method for an aluminum material.

The present invention also provides a surface treatment method for an aluminum material, which comprises, after the electrolytic treatment of the second step, performing the alkaline treatment of dipping in an alkaline aqueous solution as the third step.

In the present invention, the polybasic acid and / or salt thereof used in the anodizing treatment in the first step for forming an anodized film on the surface of the aluminum material is
Examples thereof include polybasic acids such as boric acid, phosphoric acid, sulfuric acid, oxalic acid and tartaric acid, and salts thereof such as ammonium, sodium (Na) and potassium (K). These can be used alone, or as a mixed acid obtained by mixing two or more kinds and a salt thereof.

The aqueous solution containing such a polybasic acid and / or its salt is, for example, a neutral bath such as sodium tetraborate-boric acid bath, ammonium borate bath or ammonium phosphate bath, or sulfuric acid. Acid baths such as phosphoric acid, oxalic acid and tartaric acid can be used. When a neutral bath is used, the anodized film formed forms a barrier type film. The thickness is preferably in the range of 0.01 to 1 μm, and when an acidic bath is used, the formed anodic oxide film forms a porous film, so the film thickness is practically 0.01 to 1 μm. The range is preferably 10 μm. If the film thickness of this anodic oxide film is insufficient, the uniformity of the unevenness is reduced, and conversely, if the film is thicker than necessary, no improvement in the effect is observed, and it is not economical in terms of time and power.

The treatment conditions in the first step of anodic oxidation treatment differ depending on whether a neutral bath or an acidic bath is used, how thick the anodic oxide film to be formed is to be designed, and the like. , For example, in the case of a neutral bath,
Bath concentration 1 to 300 g / liter, pH 4 to 10, bath temperature 0 to 80 ° C., constant current (current density) 1 to 100 A / m ² ,
Final voltage 10-1000V (preferably 10-500)
V), and in the case of an acidic bath, a bath concentration of 1 to 30
0 g / liter, bath temperature 0 to 50 ° C., constant current (current density) 5 to 300 A / m ² or constant voltage 5 to 150 V, time 5 to 3600 seconds.

In the present invention, the electrolytic treatment of the second step, which is carried out after the anodizing treatment, is carried out by anodic electrolysis in an aqueous solution containing a monobasic acid and its salt. As the acid and its salt, hydrochloric acid,
Examples thereof include monobasic acids such as nitric acid, acetic acid, and perchloric acid, and their sodium salts, potassium salts, ammonium salts, etc., preferably hydrochloric acid, nitric acid, sodium chloride (NaCl), potassium chloride (KCl), ammonium chloride (NH 2). ₄ Cl), sodium nitrate (NaNO ₃ ), potassium nitrate (KNO ₃ ), ammonium nitrate (NH ₄ NO ₃ ), and the like. These monobasic acids and salts thereof may be used alone, or as a mixed acid obtained by mixing two or more kinds and salts thereof. By this electrolytic treatment, the anodized film formed on the surface of the aluminum material by the anodizing treatment is destroyed, and extremely fine irregularities are formed on the surface of the aluminum material.

The treatment conditions in the electrolytic treatment of the second step are usually 1 to 500 g / liter, preferably 10 to 200 g / liter, though they vary depending on the type of the monobasic acid and its salt used. Using liquid,
The liquid temperature is in the range of 10 to 60 ° C., preferably 20 to 50 ° C., and the current density is 0.1 to 3 A with the aluminum material as the anode.
/ Dm ² , preferably 0.5 to 2.5 A / dm ² direct current,
2 to 30 for commercial AC, rectangular wave AC, pulse waveform, etc.
Anode electrolysis is performed by energizing for 0 seconds, preferably 3 to 180 seconds.

Further, in the present invention, following the electrolytic treatment of the second step, an alkaline treatment of immersing in an alkaline aqueous solution may be performed as a third step. Regarding the treatment conditions in the alkali treatment of the third step, the free alkali concentration is 20 to 100 g / liter, preferably 40 to 70 g / liter, and the treatment temperature is 30 to 70.
℃, preferably 40 ~ 60 ℃, pH value is 1
3 or more, and further, the processing time is 3 to 20 minutes, preferably 5 to 15 minutes. If the free alkali concentration is less than 20 g / liter, the treatment temperature is less than 30 ° C., or the pH value is less than 13, the dissolution rate is slow and the productivity is lowered in any case. On the contrary, the free alkali concentration exceeds 100 g / liter,
Alternatively, if the treatment temperature is higher than 70 ° C., the dissolution rate becomes too fast and it becomes difficult to control, the surface becomes gentle, and it becomes difficult to obtain a desired surface state. Further, the treatment time also varies depending on conditions such as free alkali concentration, treatment temperature, and pH value, but it is difficult to obtain the desired unevenness because uniform dissolution does not proceed in short-time immersion that does not reach 3 minutes, In a long-time immersion exceeding 20 minutes, uniform dissolution progresses excessively and concavities and convexities become conspicuous on the contrary, and dissolution loss of aluminum becomes large, which is not preferable.

Here, in the method of the present invention, a hydrochloric acid immersion treatment of immersing in a hydrochloric acid aqueous solution may be performed between the electrolytic treatment of the second step and the alkaline treatment of the third step. This hydrochloric acid immersion treatment is performed by immersing the aluminum material in an aqueous hydrochloric acid solution. Regarding the treatment conditions of this hydrochloric acid immersion treatment, the hydrochloric acid concentration is 10 to 200 g / liter, preferably 30 to 150 g / liter, and the treatment temperature is 20 to 50 ° C., preferably 25 to 40 ° C.
Furthermore, the processing time is 20 minutes or less, preferably 3 to
15 minutes. The hydrochloric acid immersion treatment with this hydrochloric acid aqueous solution
When the concentration of hydrochloric acid is 10 g / liter or higher and the treatment temperature is 20 ° C. or higher, on the contrary, when the concentration of hydrochloric acid is higher than 200 g / liter or the treatment temperature is higher than 50 ° C., the chemical dissolution reaction becomes violent and the fine particles become fine. It becomes difficult to control the unevenness, and if the treatment time exceeds 20 minutes, uniform dissolution will proceed excessively and the unevenness will not be noticeable,
The dissolution loss of aluminum also becomes large, which is not preferable.

Further, in this hydrochloric acid dipping treatment, in the hydrochloric acid aqueous solution used, Fe ions, Ni ions, Cu ions, SO ₄ ions, NO ₃ ions, PO ₄ ions are added in order to facilitate control of fine irregularities. One or more ions selected from the ions may be added, and specifically, for example, they are added in the form of, for example, sulfate, nitrate, chloride, phosphate, and oxalic acid. The organic acid may be added, and the addition amount is usually 0 to 5 g / liter, preferably 0 to 1
It is in the range of g / liter.

If necessary, after the alkali treatment in the third step, smut removal treatment, anodization treatment, coloring treatment by dyeing or electrolytic deposition of metal, or sealing treatment may be carried out. Chromate treatment may be performed instead of the treatment. These anodizing treatment, coloring treatment, sealing treatment, and chromate treatment can be carried out by conventionally known methods.

Further, in the present invention, prior to the anodizing treatment of the first step, as a pretreatment of the aluminum material,
Degreasing treatment and / or alkali etching treatment may be performed. Further, after the alkali etching treatment, a smut removing treatment may be performed if necessary. The degreasing treatment, the alkali etching treatment and the smut removing treatment can also be carried out by a conventionally known method.

According to the present invention, an anodized film having a predetermined thickness is formed on the surface of an aluminum material by the above anodizing treatment, and then the anodized film is destroyed by electrolytic treatment to destroy the aluminum material substrate. The surface of this aluminum material can be made to have irregularities of uniform, fine and uniform size without being affected by the metallographic structure of, and the size of the irregularities at this time varies depending on the processing conditions. The diameter [width of the opening of the valley read from the sectional curve] obtained by measurement (JIS B0601: 1994) is 0.1.
To 200 μm, and its depth (maximum height Ry of the sectional curve) is 5 to 75 μm.

Further, when the hydrochloric acid immersion treatment is performed subsequent to the electrolytic treatment after the anodizing treatment, the base material of the aluminum material reacts with hydrochloric acid only at the holes formed by the film destruction of the electrolytic treatment to form an etch pit. Can be formed,
When the alkali treatment is performed after that, the unevenness can be uniformly present without being affected by the metal structure of the base material of the aluminum material.

[0022]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be specifically described below based on Examples.

[Example 1] As a pretreatment, a JIS A6063 aluminum alloy extruded profile was immersed in an aqueous sodium hydroxide solution having a concentration of 50 g / liter and a bath temperature of 50 ° C for 5 minutes, and the surface of the aluminum alloy extruded profile was The natural oxide film was removed.

Next, the pretreated aluminum alloy extruded profile is anodized in an aqueous solution of ammonium borate having a concentration of 50 g / liter under the conditions of a bath temperature of 30 ° C., a current density of 10 A / m ² and a final voltage of 80 V ( The first step), followed by anodic electrolysis in a hydrochloric acid aqueous solution having a concentration of 100 g / liter under conditions of a bath temperature of 20 ° C., a current density of 100 A / m ² , and a treatment time of 120 seconds to form a large number of fine pits (second step). Step), and further immersing in a sodium hydroxide aqueous solution having a concentration of 50 g / liter under conditions of a bath temperature of 50 ° C. and a treatment time of 10 minutes to further expand the pits formed by the hydrochloric acid immersion treatment (third step), A surface-treated aluminum alloy extruded profile was obtained.

The glossiness and surface roughness (Ra) of the obtained surface-treated aluminum alloy extruded profile were measured at 10 points by changing the measurement position in the sample, and the average value and the maximum and minimum values were measured. I asked for the difference. The surface-treated aluminum alloy extruded profile of Example 1 has no variation in its glossiness and surface roughness, and has no rough feel to the touch.
There was no metallic luster and it had a rough and uniform appearance that was easy on the eyes. In addition, extrusion marks disappeared, there were no surface defects (strain marks, streaks, etc.), and the surface quality was stable. The results are shown in Table 1.

[Examples 2 to 5] In the anodizing treatment in the first step, as shown in Table 1, a treatment bath having a concentration of 100 was used.
Aluminum alloy in the same manner as in Example 1 except that g / liter phosphoric acid aqueous solution, concentration 150 g / liter sulfuric acid aqueous solution, concentration 40 g / liter aqueous oxalic acid solution, or concentration 10 g / liter tartaric acid aqueous solution was used. An extruded profile was obtained.

The glossiness and surface roughness (Ra) of the obtained surface-treated aluminum alloy extruded profile were measured in the same manner as in Example 1, and the average value and the difference between the maximum value and the minimum value were determined. . Similar to Example 1, the surface-treated aluminum alloy extruded profiles of Examples 2 to 5 had no unevenness in gloss and surface roughness, and had a uniform appearance without extrusion marks or surface defects. The results are shown in Table 1.

[Embodiment 6] The treatment time in the electrolytic treatment of the second step was 60 seconds, and the concentration was 10 after the second step.
Example 1 above except that the pits formed in the second step were enlarged (hydrochloric acid dipping treatment) by immersing in a 0 g / liter hydrochloric acid aqueous solution at a bath temperature of 30 ° C. and a treatment time of 120 seconds.
An aluminum alloy extruded profile was obtained in the same manner as in.

The glossiness and surface roughness (Ra) of the obtained surface-treated aluminum alloy extruded profile were measured in the same manner as in Example 1, and the average value and the difference between the maximum value and the minimum value were determined. . Similar to Example 1, the surface-treated aluminum alloy extruded profiles of Examples 2 to 5 had no unevenness in gloss and surface roughness, and had a uniform appearance without extrusion marks or surface defects. The results are shown in Table 1.

[Comparative Example 1] As a pretreatment, a concentration of 50 g /
After dipping for 5 minutes in a sodium hydroxide aqueous solution having a bath temperature of 50 ° C. for 5 minutes to remove the natural oxide film on the surface of this aluminum alloy extruded profile, a hydrochloric acid aqueous solution having a concentration of 55 g / liter, a bath temperature of 35 ° C., and a treatment time Immersion was carried out for 5 minutes, and then in a sodium hydroxide aqueous solution having a concentration of 50 g / liter under conditions of a bath temperature of 50 ° C. and a treatment time of 10 minutes to obtain a surface-treated aluminum alloy extruded profile.

The glossiness and surface roughness (Ra) of the obtained surface-treated aluminum alloy extruded profile were measured in the same manner as in Example 1 above, and the average value and the difference between the maximum value and the minimum value were determined. It was The surface-treated aluminum alloy extruded profile of Comparative Example 1 had an uneven distribution of irregularities, and had extrusion marks remaining, resulting in an uneven surface state. The results are shown in Table 1.

[0032]

[Table 1]

[0033]

According to the surface treatment method of an aluminum material of the present invention, rolling marks and extrusion marks at the time of forming a material disappear, and the surface gloss and color tone are highly uniform and reproducible.
It is possible to impart a controlled surface gloss and color tone over a wide range.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yumiko Tsukamoto             1-34-1 Kambara, Kambara Town, Anbara District, Shizuoka Prefecture, Japan             Light Metal Co., Ltd. Group Technology Center (72) Inventor Takeshi Ebihara             1-34-1 Kambara, Kambara Town, Anbara District, Shizuoka Prefecture, Japan             Light Metal Co., Ltd. Group Technology Center (72) Inventor Mikio Asakura             11-11 Osaki, Shinagawa-ku, Tokyo             Within the corporation (72) Inventor Takashi Iriya             11-11 Osaki, Shinagawa-ku, Tokyo             Within the corporation

Claims (9)

[Claims] 1. A surface treatment method for an aluminum material made of aluminum or an aluminum alloy, which comprises anodizing in an aqueous solution containing a polybasic acid and / or a salt thereof to form an anodized film on the surface of the aluminum material. A surface treatment method for an aluminum material, comprising: a step; and a second step of performing anodic electrolysis in an aqueous solution containing a monobasic acid and / or a salt thereof. 2. The surface treatment method for an aluminum material according to claim 1, wherein after the electrolytic treatment of the second step, an alkali treatment of immersing in an alkaline aqueous solution is performed as the third step. 3. The polybasic acid used for the anodizing treatment in the first step is one kind or a mixed acid of two or more kinds selected from boric acid, phosphoric acid, sulfuric acid, oxalic acid and tartaric acid. 2. The surface treatment method for an aluminum material according to 2. 4. The surface treatment method for an aluminum material according to claim 1, wherein the film thickness of the anodized film formed by the anodizing treatment in the first step is 0.01 to 10 μm. 5. The monobasic acid used in the electrolytic treatment in the second step is one kind or a mixed acid of two or more kinds selected from hydrochloric acid, nitric acid, acetic acid, and perchloric acid. The surface treatment method for an aluminum material according to. 6. The treatment conditions in the electrolytic treatment of the second step are current density of 0.1 to 3 A / dm ² and treatment time of 2 to 3.
It is 00 seconds, The surface treatment method of the aluminum material in any one of Claims 1-5. 7. The surface treatment method for an aluminum material according to claim 2, wherein the treatment conditions in the alkali treatment of the third step are a free alkali concentration of 20 to 100 g / liter and a treatment temperature of 30 to 70 ° C. . 8. The surface treatment method for an aluminum material according to claim 1, wherein a degreasing treatment and / or an alkali etching treatment is carried out as a pretreatment prior to the anodizing treatment in the first step. 9. A surface-treated aluminum material produced by the method according to claim 1.