KR101274978B1 - Method for surface treatment to manufacture aluminium material with high strength and black color - Google Patents

Abstract

The present invention relates to a surface treatment method of an aluminum material that can exhibit high strength and black coloring effect by performing plasma electrolytic oxidation on the surface of the aluminum material in an electrolyte solution containing manganese ions and molybdenum ions. The surface treatment method of the aluminum material according to the present invention can reduce the environmentally harmful substances generated in the anodizing process for coloring conventional aluminum, and by providing a black coloring effect and excellent mechanical properties to the aluminum material, the electrical and electronic component metal It can be applied to a wide range of fields requiring high strength and black coloring properties such as materials.

Description

TECHNICAL FOR SURFACE TREATMENT TO MANUFACTURE ALUMINIUM MATERIAL WITH HIGH STRENGTH AND BLACK COLOR}

The present invention relates to a surface treatment method of an aluminum material having high strength and black coloring effect. More specifically, the present invention relates to a surface treatment method of an aluminum material that can exhibit high strength and black coloring effect by performing plasma electrolytic oxidation on the surface of an aluminum material in an electrolyte solution containing an alkali of manganese ions and molybdenum ions.

Recently, with the development of the electronic component industry, much attention has been focused on the properties and development of lightweight materials in the field of materials engineering, and plastic materials and metal materials are used as electrical and electronic component materials. Plastic materials have the advantage of being easy to manufacture and light in a complicated shape and easy to implement a variety of colors by the addition of pigments.

On the other hand, metal materials have excellent wear resistance, are resistant to heat and sunlight, and are environmentally friendly. However, they are difficult to manufacture in a complicated shape, are heavy, and have a metallic luster, but have various disadvantages in implementing various colors.

Among these metal materials, aluminum has better workability at a higher temperature than steel and the like, and therefore, a shape member having various cross-sectional shapes can be obtained relatively easily by hot extrusion. In addition, aluminum is used in a wide range of fields such as building materials, vehicle parts, furniture, and the like by utilizing the excellent properties of the original aluminum, which is light in weight and easy in workability or excellent in corrosion resistance, and is particularly used as a material for building materials.

As a method for coloring such a metal material as aluminum, anodizing which forms a ceramic layer by immersing a metal in an anode in electrolyte solution is widely used for electrodeposition coating.

However, in the prior art, the anodizing process for forming a metal film requires an environment-friendly new surface treatment method because it uses an electrolyte in an acid atmosphere containing components harmful to humans such as sulfuric acid and chromic acid.

Plasma electrolytic oxidation treatment is a plating method that can solve the above-mentioned problems of anodizing. Plasma electrolytic oxidation is applicable not only to aluminum but also to magnesium, titanium, hafnium, and niobium, which is a rare metal. In addition, the plasma electrolytic oxidation treatment is an environmentally friendly surface treatment technique using an electrolyte in an alkaline atmosphere. At this time, the resulting film is dense, excellent in corrosion resistance and abrasion resistance, it is possible to improve the adhesion of the coating.

SUMMARY OF THE INVENTION An object of the present invention is to provide a surface treatment method of an aluminum material which can exhibit high strength and black coloring effect, which is an environmentally friendly improvement of a conventional aluminum anodizing process for improving the coloring effect and physical properties of an aluminum alloy.

In order to achieve the above object, the present invention provides a surface treatment method of an aluminum material through plasma electrolytic oxidation consisting of the following configuration.

A surface treatment method of an aluminum material by plasma electrolytic oxidation, the aluminum material surface treatment method of performing plasma electrolytic oxidation on a base material containing aluminum or an aluminum alloy in an alkaline electrolyte solution in which manganese and molybdate salts are dissolved.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a process flow chart schematically showing a surface treatment method of an aluminum material having strength and black coloring effect of the present invention and will be described in detail below.

First, a base material containing aluminum or an aluminum alloy is prepared as a base material for forming a film on the surface through plasma electrolytic oxidation (S1).

In one embodiment of the present invention, the aluminum alloy contains 5.1 to 6.1 wt% of zinc and 2.1 to 2.9 wt% of magnesium, and the balance may be aluminum.

Since the aluminum alloy material can control the current density according to the surface area, it is not limited by the size of the material. The aluminum alloy material can be washed, dried, and polished using sandpaper or the like for the prepared alloy specimen.

Next, an alkaline electrolyte solution for performing plasma electrolytic oxidation on a base metal including aluminum or an aluminum alloy is prepared (S2).

In the present invention, the electrolyte for performing plasma electrolytic oxidation on the base metal including aluminum or aluminum alloy is prepared so that manganese and molybdate are dissolved in the ionic state.

Manganese ions in the alkaline electrolyte may form a film containing manganese oxide together with aluminum oxide on the surface of the aluminum material by plasma electrolytic oxidation, thereby exhibiting a black coloring effect.

In addition, molybdenum ions in the alkaline electrolyte may form molybdenum oxide together with manganese oxide on the surface of the aluminum material by plasma electrolytic oxidation, thereby making the black color darker and improving the surface roughness.

Manganese salts include _{KMnO 4, (MnHPO 4) 2} .25H 2 O, MnS 2 O 6, MnSO 4 · H ₂ O, etc. may be used, the concentration of the manganese salt is preferably contained in the alkaline electrolyte solution is 0.005 ~ 0.04 M Do.

As the molybdate, (NH ₄ ) ₆ Mo ₇ O ₂₄ , MoBr _{3 ,} MoCl _{3 ,} MoCl _{5 ,} MoO ₂ Cl _{2 ,} MoF _6, etc. may be used. The concentration of molybdate in the alkaline electrolyte is 0.001 to 0.02 M This is preferred.

In addition, it is more preferable that the manganese salt and molybdate salt contained in the alkaline electrolyte are contained in a 5: 2 to 2: 1 molar ratio in terms of vivid black coloring effect and surface roughness improvement.

In the present invention, the alkaline electrolyte may be prepared by further adding hydroxide salts, silicates and phosphates to a solvent such as distilled water, and preferably prepared to have a pH of 11.5 or more.

In one embodiment of the present invention, as the hydroxide salt, potassium hydroxide, sodium hydroxide and the like can be used, and the hydroxide salt in the alkaline electrolyte is used to adjust the pH of the electrolyte in the range of 0.08 to 0.2 M.

 As the silicate, sodium silicate, potassium silicate and the like can be used, and the concentration of the silicate is preferably 0.01 to 0.07 M.

Potassium pyrophosphate, potassium diphosphate, potassium triphosphate and the like can be used as the phosphate, and the concentration of phosphate is preferably 0.002 to 0.006 M.

In one embodiment of the present invention, the alkaline electrolyte solution may be prepared further comprising tungstate.

Tungsten ions contained in the alkaline electrolyte may form tungsten oxide on the surface of the aluminum material by plasma electrolytic oxidation, thereby improving mechanical strength.

In addition, as tungstate, Na ₂ WO ₄ , WCl ₄ , WCl ₆ , WOCl ₄ , H ₂ WO ₄ Etc. may be used but is not specific to these. It is preferable that tungstic acid salt is contained in alkaline electrolyte solution at the density | concentration of 0.01-0.02 M.

Finally, plasma electrolytic oxidation is performed on the base material including aluminum or an aluminum alloy prepared in the alkaline electrolyte (S3).

In one embodiment of the present invention, plasma electrolytic oxidation may be performed by placing a base material containing aluminum or an aluminum alloy in the alkaline electrolyte at the anode and placing stainless steel at the cathode, and then applying a voltage.

 After the plasma electrolytic oxidation process, a film including manganese oxide and molybdenum oxide is formed on the surface of the base material including aluminum or aluminum alloy.

In the present invention, when the surface treatment by plasma electrolytic oxidation, the temperature of the electrolyte is more preferably maintained at room temperature, and when performed at a high temperature, the homogeneity of the aluminum oxide may be reduced.

The surface treatment step by plasma electrolytic oxidation may be performed for 100 to 1800 seconds under a current density condition of 100 to 300 mA / cm ² . However, in the surface treatment step by plasma electrolytic oxidation, the applied power, power source type and current density may be adjusted by those skilled in the art depending on the conditions.

According to the above conditions, when the aluminum alloy is placed on the anode in the alkaline electrolyte and the stainless steel is installed on the cathode, and surface treatment is performed on the aluminum alloy by applying alternating current or direct current, hydrogen gas is generated on the surface of the stainless steel as the cathode. On the surface of the aluminum alloy serving as the anode, oxygen gas is generated and an oxidation reaction of the metal occurs to form a film containing aluminum oxide, manganese oxide, and molybdenum oxide.

In addition, the present invention provides an aluminum material having a film containing manganese oxide, molybdenum oxide and aluminum oxide on the surface of the base material by performing surface treatment by plasma electrolytic oxidation on the base material containing aluminum or an aluminum alloy.

In one embodiment of the present invention, the film formed on the surface of the aluminum material may further include tungsten oxide or silicon oxide together with manganese oxide, molybdenum oxide and aluminum oxide.

The present invention provides a method capable of forming a film containing manganese oxide, molybdenum oxide and aluminum oxide on the surface of an aluminum material by performing a surface treatment by plasma electrolytic oxidation using an alkaline electrolyte solution. Accordingly, it is possible to reduce environmentally harmful substances generated in the anodizing process for coloring the conventional aluminum material and to impart black coloring effect and excellent mechanical properties to the aluminum material. Therefore, the aluminum material surface-treated according to the present invention can be applied to a wide range of fields that require high strength and black coloring properties such as electrical and electronic component metal materials.

1 is a process flow chart schematically showing a method for surface treatment of an aluminum material having high strength and black coloring effect of the present invention.
2 is a photograph taken with a digital camera of the surface of the aluminum alloy surface treated according to Examples 1 to 3 of the present invention.
3 is a microstructure photograph of the surface of the aluminum alloy surface-treated with a coating according to Example 1 of the present invention.
4 is a microstructure photograph of the surface of the aluminum alloy surface-treated with a coating according to Example 2 of the present invention.
Figure 5 is a microstructure photograph of the surface of the aluminum alloy surface-treated with a coating according to Example 3 of the present invention.
Figure 6 is a photograph taken after the ultrasonic vibration test for the aluminum alloy surface treatment according to Examples 1 to 3 of the present invention.
Figure 7 is a graph showing the results measured using a three-dimensional shape measuring device for the surface of the aluminum alloy surface treated according to Examples 1 to 3 of the present invention.

Hereinafter, the surface treatment method of the aluminum material having high strength and black coloring effect according to the present invention will be described in detail.

The aluminum alloy Al7075 was cut into thin plates 30 mm long, 50 mm long, and 20 mm thick, and then ground evenly with SiC paper # 1000, washed with acetone, and dried to prepare aluminum alloy specimens. It was.

The aluminum alloy can be prepared in various compositions in consideration of the application field and the like. In addition, aluminum alloy materials having various sizes and shapes can be prepared according to plasma electrolytic oxidation surface treatment conditions.

0.085 M KOH, 0.065 M Na ₂ SiO ₃ , 0.0025 M K ₄ P ₂ O ₇ , 0.0055 M KMnO ₄ , 0.015 M Na ₂ MoO _4, and 0.015 M Na ₂ WO ₄ were mixed in distilled water. After stirring to prepare an alkaline electrolyte.

After maintaining the alkaline electrolyte prepared as described above to 20 to 30 ℃, the aluminum alloy specimen in the alkaline electrolyte solution is placed on the positive electrode and stainless steel is installed on the negative electrode and applied AC power through the equipment of 20 kW 150 mA / The plasma electrolytic oxidation treatment was performed for 600 seconds at a current density condition of cm ² to form a film on the surface of the aluminum alloy.

As described above, the surface of the aluminum alloy surface treated with a digital camera was photographed in FIG. 2 (a), and a microstructure photograph of the aluminum alloy surface was photographed in FIG. 3. In addition, the surface of the specimen after the ultrasonic vibration test of 40 kHz for 1 minute, 3 minutes, 5 minutes for the film of the aluminum alloy surface formed in Example 1 was shown in Figure 6 (a).

0.15 M KOH, 0.015 M Na ₂ SiO ₃ , 0.0055 M K ₄ P ₂ O ₇ , 0.035 M KMnO ₄ And 0.015 M Na ₂ MoO ₄ was mixed with distilled water, and then the surface treatment was performed in the same manner as in Example 1 except that the alkaline electrolyte prepared by stirring was used to form a film on the surface of the aluminum alloy. The surface of the aluminum alloy surface treated as described above was photographed with a digital camera, and is shown in FIG. 2 (b). In addition, the surface of the specimen after the ultrasonic vibration test at 40 kHz for 1 minute, 3 minutes, 5 minutes for the film on the surface of the aluminum alloy formed in Example 2 was shown in Figure 6 (b).

0.085 M KOH, 0.065 M Na ₂ SiO ₃ , 0.0055 M K ₄ P ₂ O ₇ , 0.035 M KMnO ₄ And 0.0015 M of (NH ₄ ) ₆ Mo ₇ O ₂₄ was mixed with distilled water, followed by a surface treatment in the same manner as in Example 1 except that the alkaline electrolyte prepared by stirring was used to form a film on the surface of the aluminum alloy. The surface of the aluminum alloy surface treated as described above was photographed with a digital camera, and is shown in FIG. 2 (c). In addition, the aluminum alloy oxide layer prepared in Example 1 was photographed after the ultrasonic vibration test of 40 kHz for 1 minute, 3 minutes, 5 minutes and the surface of the specimen is shown in Figure 6 (c).

As a result of observing the surface of the aluminum alloy surface treated in Examples 1 to 3 with reference to Figure 2, it showed a dark color in the order of Example 3, Example 2, Example 1.

3 to 5 in which microstructure photographs of the surface of the aluminum alloy surface treated in Examples 1 to 3 are taken. Referring to FIG. In contrast, it can be seen that an oxide having a relatively larger pore is formed on the porous oxide. In Example 2, the coating of the aluminum alloy formed by the surface treatment showed a surface texture similar to that of the general plasma electrolytic oxidation treatment, but it can be seen that new oxide was formed in or around the pores. The film of the aluminum alloy formed by surface treatment in Example 3 has a small number of pores, unlike the film of the aluminum alloy formed by surface treatment in Examples 1 to 2, and it can be seen that the oxide covers the pores.

Referring to Figure 6 taken after the ultrasonic vibration test for the surface-treated aluminum alloy according to Examples 1 to 3, the aluminum alloy surface-treated according to the present invention when comparing the surface state after the surface treatment and the surface state after the ultrasonic test It turns out that the oxide in a film did not peel, and it turns out that the oxide is firmly formed in the aluminum alloy surface.

Surface Roughness Measurement for Aluminum Alloys

Surface roughness measured by a three-dimensional shape measuring device for the surface of the aluminum alloy prepared in Examples 1 to 3 is shown in Table 1, and the graph showing the measurement results are shown in Figures 7 (a), (b) and ( c).

Average roughness
(Ra) 10 points average roughness
(Rz) Maximum vertical distance
(Rt) Maximum Mountain Height (Rq) Max roughness
(Rmax) Example 1 4.02 19.36 23.93 5.36 22.91 Example 2 1.34 4.9 5.9 1.54 5.9 Example 3 1.56 6.99 8.65 1.94 6.63

Referring to Table 1 and FIG. 7, the surface roughness of the aluminum alloy surface treated in Examples 2 and 3 shows a low value, and the scale shown in the upper right corner of the graphs of FIGS. 7B and 7C. It can be seen that the surface of the aluminum alloys prepared in Examples 2 and 3 is smoother than the surface of the aluminum alloy surface treated in Example 1, as shown in the low values as shown in Table 1.

As mentioned above, although this invention is demonstrated about preferable embodiment, this invention is not limited to the specific embodiment mentioned above, The person of ordinary skill in the art to which this invention belongs is variously-modified without departing from the technical idea. You can do it. Therefore, the scope of the present invention should be construed as defined by the appended claims rather than the specific embodiments.

Claims (16)

delete delete delete delete As a surface treatment method of the aluminum material by plasma electrolytic oxidation,
A surface treatment method of an aluminum material which performs plasma electrolytic oxidation on a base material containing aluminum or an aluminum alloy in an alkaline electrolyte in which manganese salt, molybdate salt and tungstate salt are dissolved.
delete The method according to claim 5,
The manganese salt is _{KMnO 4, (MnHPO 4) 2} .25H 2 O, MnS 2 O 6 , and MnSO ₄ · surface treated aluminum material is selected from the group consisting of H ₂ O.
The method according to claim 5,
The molybdate is (NH ₄ ) ₆ Mo ₇ O ₂₄ , MoBr _{3 ,} MoCl _{3 ,} MoCl _{5 ,} MoO ₂ Cl ₂ And MoF ₆ The surface treatment method of the aluminum material.
The method according to claim 5,
Manganese salt is contained in the alkaline electrolyte solution 0.005 ~ 0.04 M, molybdate salt is contained in 0.001 ~ 0.02 M surface treatment method.
The method according to claim 5,
The manganese salt and molybdate salt in the alkaline electrolyte solution is contained in a 5: 2 to 2: 1 molar ratio, the surface treatment method of the aluminum material.
The method according to claim 5,
The tungstate salt is a surface treatment method of aluminum material selected from the group consisting of Na ₂ WO ₄ , WCl ₄ , WCl ₆ , WOCl ₄ and H ₂ WO ₄ .
The method according to claim 5,
A tungsten salt is 0.01 to 0.02 M in the alkaline electrolytic solution surface treatment method.
The method according to claim 5,
The alkaline electrolytic solution is a surface treatment method of an aluminum material containing hydroxide salts, silicates and phosphates.
The method according to claim 5,
The said alkaline electrolyte solution has the surface treatment method of the aluminum material whose pH is 11.5 or more.
The method according to claim 13,
And a hydroxide concentration of 0.08 to 0.2 M, a silicate concentration of 0.01 to 0.07 M, and a concentration of phosphate of 0.002 to 0.006 M in the alkaline electrolyte.
The method according to claim 5,
The plasma electrolytic oxidation is carried out for 100 to 1800 seconds under a current density of 100 to 300 mA / cm ² surface treatment method of the aluminum material.

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