JPH0344497A - Polychromatic surface treatment of aluminum material - Google Patents

Abstract

PURPOSE:To form a polychromatic coating film of a uniform thickness by coating an Al material by electrodeposition in two steps in polychromatic surface treatment and making voltage in the latter step lower than that in the former step. CONSTITUTION:An Al material is subjected to primary anodic oxidation and colored through a mask having a desired pattern. The Al material may be subjected to secondary anodic oxidation before the coloring. The mask is then removed and the Al material is coated by electrodeposition. In such polychromatic surface treatment, coating by electrodeposition is carried out in two steps by intercepting voltage once and voltage in the latter step is made lower than that in the former step by about 10-50V. Polychromatic surface treatment giving a coating film of a uniform thickness is carried out.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a multicolor surface treatment method for aluminum materials,
In more detail, 2 formed on the surface of aluminum material
The present invention relates to a surface treatment method for forming a uniform coating film on an anodic oxide film and/or a colored oxide film that has a color (pattern) greater than color.

[Conventional technology]

Conventionally, as a multicolor surface treatment method for aluminum materials that has two or more colors (patterns) and a uniform coating thickness, first, the surface of the aluminum material that has been anodized (or further colored) is treated. Apply a colored (for example, A color) or transparent coating, then mask the surface of the coating film into a desired pattern, then grind the coating film other than the masked areas, and then anodize the exposed non-masked areas. A method is known in which the surface of a film (or colored oxide film) is coated with a transparent or colored (for example, B color) coating, and then the masking is removed.

According to the above method, the color A of the coating film in the masked part
and the color B of the paint film in the non-masking area, or if one of the paint films is transparent, the silver color of the anodic oxide film (
Alternatively, a pattern is formed by the color of the colored oxide film) and the color of the other coating film (A or B).

[Invention! Issues to be resolved]

According to the conventional method, since the expensive paint is ground after masking and the grinding waste is discarded, there is a problem in that the manufacturing cost becomes high. In addition, workability is poor due to the grinding process involved, and furthermore, since it may not be possible to grind a shape with a complicated shape, there are naturally limitations on the pattern.

Therefore, it is an object of the present invention to avoid the above-mentioned drawbacks, to be applicable to shapes with relatively complex shapes, to have high productivity at a relatively low cost, and to provide two or more colors ( The object of the present invention is to provide a method that can perform multicolor surface treatment so that the pattern (pattern) is H and a uniform coating thickness can be formed.

[Means to solve the problem]

According to the present invention, in order to achieve the above object, an aluminum material is subjected to a first anodic oxidation treatment, then masked in a desired pattern, and then subjected to a coloring treatment, or a second anodization treatment is performed on the aluminum material. This is a multicolor surface treatment method for aluminum materials in which a coloring treatment is performed after the treatment, and then after the masking is removed, an electrodeposition coating treatment is performed. Provided is a method for multicolor surface treatment of aluminum material, which is characterized in that it is a step-by-step painting process and the voltage in the subsequent painting process is set lower than the voltage in the previous painting process.

Further, according to the present invention, after the aluminum material is subjected to the first anodizing treatment, the first coloring treatment is performed, and then the desired pattern is masked, and then the second anodizing treatment is performed. This is a multicolor surface treatment method for aluminum materials in which a second coloring treatment is applied after the coating is applied, and then the masking is removed and then an electrodeposition coating treatment is performed. Provided is a multicolor surface treatment method for aluminum material, which is a two-step painting process and is characterized in that the voltage in the subsequent painting process is set lower than the voltage in the previous painting process.

[Operation and mode of the invention]

As a result of intensive research in order to eliminate the drawbacks of the conventional methods, the present inventors conducted a first anodizing treatment (
Alternatively, after applying a further coloring treatment, masking in the desired pattern, then coloring after performing a second anodizing treatment, then removing the masking, and then electrodepositing with a clear paint. We have researched and developed a method that can create patterns using the color of the anodic oxide film (or the color of the colored oxide film) in the masked areas and the color of the colored oxide film in the non-masked areas.

According to this method, grinding waste of paint is not generated as in the conventional method, and it can also be applied to shapes with relatively rough shapes, and moreover, it can be applied to the surface of aluminum material at a relatively low cost and with good productivity. can be patterned.

However, according to this method, the degree of coloring of the masked area and the non-masked area is usually different, that is, there are light colored areas and dark colored areas, which causes the paint film to be damaged during the electrophoretic coating process (electrodeposition coating). It has been found that there are areas where it is easy to adhere and areas where it is difficult to adhere, resulting in uneven coating film thickness.

Therefore, in the present invention, the voltage is temporarily cut off in the middle of the electrodeposition coating process, resulting in a two-stage coating process, and the voltage in the subsequent coating process is set lower than the voltage in the previous coating process. It has been found that a uniform coating thickness can be obtained by performing the electrodeposition coating treatment in this manner.

Although it cannot be said that the effects of the treatment method of the present invention have been completely elucidated yet, it can be estimated as follows based on certain evidence (experimental results).

Here, for convenience of explanation, we will explain: 1st anodic oxidation treatment - masking - (2nd anodization treatment -) coloring treatment - masking removal →
Considering the series of processes called electrodeposition coating, before electrodeposition coating, only an anodic oxide film exists on the masking part of the aluminum surface because no coloring treatment is applied, and therefore the anodic oxide film hardens. It has a silver color (light color). On the other hand, the non-masking area is colored, for example, electrolytically colored, and metals, metal salts, etc. are deposited within the micropores of the anodic oxide film, and the area is colored, for example, light bronze (darker than silver). Ru. When electrodeposition is applied to aluminum (O) that has such light-colored areas and dark-colored areas after masking is removed, as mentioned above, a coating film is attached to the light-colored areas.
<, there is a tendency that it tends to stick to dark colored areas. The reason for this is that an anodic oxide film (light bronze color) in which genus a and metal salts, etc. are precipitated and attached within the micropores is better than an anodized film (silver color) in which metal salts, etc. are not precipitated or attached. This is thought to be because the conductivity is better than that of . In other words, the anodic oxide film (light bronze color) in which metals, metal salts, etc. are precipitated and adhered within the micropores, is composed of a microporous layer and a barrier layer that is a low antibody for electricity. Precipitation・
Since the attached metal is a good conductor, current can easily flow through it, making it easier for a paint film to form when applying the 713 coating.

On the other hand, a normal anodic oxide film (silver color) is composed of a microporous layer and a barrier layer that has a low resistance to electricity, so it has poorer electrical conductivity than the colored oxide film mentioned above, and therefore, it is difficult to coat during electrodeposition. This is thought to be due to the fact that it becomes difficult to adhere, and as a result, variations in coating film thickness occur between light-colored areas and dark-colored areas (or masked areas and non-masked areas).

As a result of intensive research into the above-mentioned problems, the present inventors focused on the fact that the coating film formed by electrocoating is also an electrical resistor4, and divided the electrocoating process into two stages.
It has been discovered that the above problem can be solved by forming a coating film in advance in the previous step to create a difference in coating thickness, that is, a difference in electrical resistance, between light and dark colored areas, and then lowering the voltage and performing further electrodeposition coating. I found it.

In other words, as mentioned above, the anodic oxide film (light bronze color) in which metals, metal salts, etc. are precipitated and attached within the micropores is a QTs conductor, so current flows easily, and it is concentrated during the previous electrodeposition coating process. A coating film is formed over time, and there is a difference in coating thickness between it and a normal anodic oxide film (silver color). At the same time, a paint concentration gradient occurs between the light color area (silver color) and the dark color area (light bronze color) at the paint film interface, but the paint concentration is then made uniform by cutting off the current. . In other words, the solid content (negative charge) of the paint was attracted to the aluminum material to be treated, but when the current was cut off, this attraction disappeared, and on the other hand, the paint was refluxed by the pump, so the dark colored parts The paint will not be concentrated and will be uniform. After that, when electricity is applied at a voltage lower than the voltage of the previous electrodeposition coating process, the current flows preferentially to the light-colored areas (silver color) where the coating thickness is thinner, that is, the electrical resistance is low, and a coating film is formed. Therefore, it is thought that the coating film thickness can be made uniform. In this case, if the voltage of the subsequent electrodeposition coating treatment is higher than the voltage of the previous electrodeposition coating treatment, the difference in coating film thickness between the light-colored area and the dark-colored area will be growing. This is because the high voltage in the subsequent electrodeposition coating process overcomes the effect of the electrical resistance difference due to the difference in coating film thickness, and the tendency of the difference in coating film thickness caused by the previous electrodeposition coating process is maintained. Seem.

On the other hand, when the voltage of the subsequent electrodeposition coating treatment is lower than the voltage of the previous electrodeposition coating treatment, as in the method of the present invention, the difference in electrical resistance due to the difference in coating film thickness acts effectively, resulting in the above-mentioned effect. It is thought that uniformity of coating film thickness can be achieved through this process.

From the above point of view, in order to make the difference in coating film thickness, that is, the difference in electrical resistance caused by the previous electrodeposition coating treatment, effectively work in the subsequent electrodeposition coating treatment, the current application time of the previous electrodeposition coating treatment must be 30 It is preferable to set it as 60 seconds. If the energization time is too short, no effective coating film thickness difference, that is, no electrical resistance difference will occur, and conversely, if the energization time is not long, the coating thickness difference will be too large, and this will be compensated for in the subsequent electrodeposition coating process. This is not desirable because it makes it difficult to do so. Similarly, in order to make effective use of the difference in coating film thickness, that is, the difference in electrical resistance, it is desirable to lower the voltage of the subsequent electrodeposition coating process by 10 to 50 V compared to the voltage of the previous electrodeposition coating process.

The above description of the operation was made regarding the first method of the present invention, but the second method of the present invention, that is, primary anodizing treatment-1
The operation is exactly the same in a method including a series of steps: secondary coloring treatment, masking, secondary anodizing treatment, secondary coloring treatment, masking removal, and electrodeposition coating. Suna wachi,
In the second method of the present invention, both the masking area and the non-masking area are composed of a colored anodic oxide film, but the degree of precipitation and adhesion of metal salts etc. in the primary coloring treatment process and the secondary coloring treatment process may vary. If there is a difference in shading due to the difference, in other words, if there is a difference in electrical conductivity between the colored anodic oxide film on the masked area and the non-masked area, the coating film will be weak in the electrodeposition coating after masking is removed, based on the principle described above. To avoid variations in thickness, the voltage in the electrodeposition coating process is interrupted midway through the process to create a two-stage coating process, and the voltage in the subsequent coating process is set lower than the voltage in the previous coating process. , it is possible to eliminate variations in film thickness and obtain a uniform coating film thickness.

Depending on the color, there are colors that are easy to adhere to, and colors that are difficult to adhere to, and when it comes to bronze, light colors are less likely to adhere.
Dark colors tend to stick, but in any case, uneven coating thickness can be corrected by performing the electrodeposition coating process as described above.

If it is not known in advance whether the colored oxide film is more likely to adhere to the masked area or the non-masked area, first perform a series of treatments such as anodizing, coloring, and electrodeposition using the usual method. All you have to do is try this and determine the total coating thickness. Further, the method of the present invention can be applied to all treatment methods including the series of steps described above, and can also be applied to a multicolor surface treatment method in which masking treatment is performed in multiple stages and patterns of three or more colors are applied. It should be clear from the explanation of the action.

The method for multicolor surface treatment of aluminum material according to the present invention will be outlined below.

First, the aluminum material is degreased, washed with water, etched, washed with water,
After performing appropriate pretreatment such as neutralization, a well-known anodic oxidation treatment is performed to form an anodic oxide film. That is, electrolytes containing well-known inorganic acids and/or organic acids, such as sulfuric acid, chromic acid, phosphoric acid, etc., mixed acids thereof, oxalic acid, malonic acid, etc., or mixed acids of these or with inorganic acids, etc. The aluminum material is anodized in an electrolyte using direct current, alternating current, or a similar current waveform.

The applied voltage, application time, etc. for the anodic oxidation treatment are sufficient as usual.

Next, the anodized aluminum material is washed with water as necessary, and sealed or semi-sealed by known means such as washing with pure water, boiling water, chemical sealing, and pressurized steam. After that, masking is performed using a masking film, masking paint, etc. (first method of the present invention), or after coloring treatment, the hole is sealed or semi-sealed and masked (second method of the present invention). ).

After that, after performing pre-treatments such as degreasing, etching, and neutralization again, a secondary coloring treatment is performed, or a secondary anodizing treatment is performed to promote coloring, and then a secondary coloring treatment is performed after washing with water. administer.

After that, wash with water, seal or semi-fill as necessary. ) After making the holes, remove the masking and apply electrodeposition coating. The electrodeposition coating process is carried out in two stages as described above, and is usually carried out in 8 stages.
The current is preferably applied at 0 to 250 V for 30 to 60 seconds, and then the current is once interrupted and maintained for about 30 to 60 seconds. After that, electricity is applied again at a voltage lower than the above voltage. As mentioned above, the voltage drop range is preferably 10-50V.

Next, washing with water and baking drying are performed to obtain an aluminum product.

As for the coloring processing, the method of immersing aluminum material in the solution containing dye or pigments, inorganic metal salt, for example, nickel, cobalt, chrome, copper, magnesium, etc.
Inorganic acid salts such as nitrates, sulfates, phosphates, hydrochlorides, chromates, oxalates of metals such as iron, cadmium, titanium, manganese, molybdenum, calcium, vanadium, tin, lead, zinc etc. Electrolytic coloring method that involves alternating current electrolysis or direct current cathodic electrolysis in an electrolytic solution containing organic acid salts such as acetate and tartrate, and forming an anodic oxide film in an electrolytic solution containing organic acids such as sulfamic acid and oxalic acid. An electrolytic coloring method that simultaneously colors the material can be applied.

In the method of the present invention, except for performing the electrodeposition coating treatment in two stages as described above, all other treatment steps may be carried out as usual.

The aluminum material treated by the method of the present invention is pure aluminum or pure aluminum containing one or more metals such as silicon, magnesium, copper, nickel, zinc, chromium, lead, bismuth, iron, titanium, and manganese. It is an alloy.

[Example of large application]

Hereinafter, the present invention will be specifically explained by showing Examples and Comparative Examples.

Example 1 An extruded aluminum profile A-60633 that had been degreased, etched, and neutralized by a conventional method was immersed in a 15% sulfuric acid aqueous solution to serve as an anode, and a direct current was applied at 13 V for 30 minutes between it and an aluminum cathode provided as a counter electrode. After energizing for minutes, set the final voltage to 3
, 5V and energized for 3 minutes, about 12μ on the surface.
A primary anodic oxide film of m was produced. This was washed with water and hot water with pure water (semi-sealed) to obtain a silver material.

Mask part of it with masking material, degrease it again,
Etching, neutralization, and secondary anodic oxidation using direct current for 13 minutes.
Vx was applied for 30 minutes to obtain an anodic oxide film of about 12 μm. It was washed with water, and then electrolytically colored in a nickel bath using carbon as a counter electrode and energized at 9 V for 3 minutes with alternating current to give mild bronze. After washing it with water and hot water, removing the masking material, it was immersed in a 10% water-soluble electrodeposition paint (thermosetting acrylic paint) and placed between it and a stainless steel plate provided as a counter electrode. A DC voltage of 130V was applied and the current was applied for 30 seconds, then the current was cut off and the current was held for 60 seconds.A DC voltage of 100V was again applied between the counter electrode and the current was applied for 3 minutes.After washing with water, The liquid was drained and baked at 180° C. for 40 minutes to obtain a composite film.

When the coating thickness of the silver part and mild bronze part of the obtained product was measured using a permascope, the difference in coating thickness was 1μ.
It was m.

Comparative Example 1 The treatment was carried out in the same manner as in Example 1, except that the electrodeposition was applied at 130V for 3 minutes, and no current interruption or voltage change was performed. Shita.

As a result, the difference in coating film thickness between the silver part and the mild bronze part was 3 μm.

Example 2 The same process as in Example 1 was carried out, except that the electrolytic coloring was performed by applying an AC current for 9 VxJ minutes to obtain dark bronze. As a result, the difference in film thickness between the silver part and the dark bronze part was 3.0 μm.

Example 3 In Example 2, the ID coating was applied by first applying a DC voltage of 130V and applying the current for 30 seconds, then cutting off the current and holding it for 60 seconds, and then applying a DC voltage of 120V again. The treatment was carried out in exactly the same manner as in Example 2, except that electricity was applied for 3 minutes. As a result, the difference in coating film thickness between the silver part and the dark bronze part was 3.5 μm.

Comparative Example 2 The same process as in Example 2 was carried out, except that the electrodeposition was applied at 130 V for 3 minutes, and no current interruption or voltage change was performed.

As a result, the difference in film thickness between the silver part and the dark bronze part was 4.5 μm.

Comparative Example 3 In Example 2, the electrodeposition coating was first applied with a DC voltage of 130 V and energized for 30 seconds, then the current was cut off and the electrodeposition was applied for 6 seconds.
After holding for 0 seconds, the voltage was increased to 140 V and the process was carried out in the same manner as in Example 2, except that the voltage was turned on for 3 minutes. As a result, the difference in film thickness between the silver part and the dark bronze part was 5.
．． It was 0 μm.

Example 4 An extruded aluminum profile A-6063S that had been degreased, etched, and neutralized by a conventional method was immersed in a 15% sulfuric acid aqueous solution to serve as an anode, and a DC current was applied at 13 V for 300 min between it and an aluminum cathode provided as a counter electrode. Electricity was applied for a minute to form a primary anodic oxide film of approximately 12 μm on the surface. This is washed with water, then electrolytically colored by using carbon as the counter electrode in a nickel bath and energized at 9V for 1 minute and 30 seconds to create a light bronze color, then washed with water, then washed with pure water (semi-sealed). It was made into a light bronze material. Part of it was masked with masking material, and then degreased, etched, and neutralized again.
Secondary anodic oxidation was carried out using direct current at 13V for 30 minutes to obtain an anodic oxide film of about 12 μm. Wash it with water, then use carbon as the counter electrode in a nickel bath, and heat it with alternating current for 9 seconds.
Electricity was applied for 3 minutes to perform electrolytic coloring, resulting in mild bronze. After washing it with water and hot water, removing the masking material, it was immersed in a 10% water-soluble electrocoating paint (heat-transformable acrylic paint), and then it was placed between a stainless steel plate and a counter electrode. A DC voltage of 130V was applied to the electrode and the current was applied for 30 seconds, then the current was cut off and the current was held for 60 seconds.A DC voltage of 100V was then applied between the electrode and the opposite electrode and the current was applied for 3 minutes.After washing with water, After draining the liquid, baking was performed at 180° C. for 40 minutes to obtain a composite film.

When the coating thickness of the light bronze portion and the mild bronze portion of the obtained product was measured using a permascope, the difference in coating thickness was 0.5 to 1.0 μm.

Comparative Example 4 The same process as in Example 4 was carried out, except that the electrodeposition was applied at 130 V for 3 minutes, and no current interruption or voltage change was performed.

As a result, the difference in coating film thickness between the light bronze part and the mild bronze part was 2 to 2.5 μm.

〔Effect of the invention〕

As described above, according to the present invention, in a method for multicolor surface treatment of aluminum materials using masking, the voltage of the electrodeposition coating treatment is once cut off midway through, resulting in a two-stage painting treatment, and the subsequent painting By setting the voltage in the treatment lower than the voltage in the previous painting process, the difference in film thickness, that is, the electrical resistance difference, between the light-colored areas and dark-colored areas that occurred in the previous painting process can be effectively used in the subsequent painting process. By acting, it is possible to eliminate variations in the coating film thickness and to make the coating film thickness uniform. In addition, by making the coating thickness uniform in this way, paint costs are reduced, and
The advantages are that the coating performance is improved and the defective rate is reduced.

In addition, unlike the conventional method, the expensive paint grinding process is not necessary, and the process can be performed using a normal processing line, so productivity is improved and production costs can be reduced compared to the conventional method.

Claims (2)

[Claims] (1) After performing a first anodic oxidation treatment on the aluminum material, it is masked in a desired pattern, and then a coloring treatment is performed, or a coloring treatment is performed after a second anodic oxidation treatment, This is a multicolor surface treatment method for aluminum materials in which the masking is then removed and then an electrodeposition coating treatment is performed.
In the above-mentioned electrodeposition coating process, the voltage is once cut off midway through, resulting in a two-step coating process, and the voltage in the subsequent coating process is set lower than the voltage in the previous coating process. Color surface treatment method. (2) After performing the first anodization treatment on the aluminum material, the first coloring treatment is performed, then the desired pattern is masked, and then the second anodization treatment is performed,
This is a multicolor surface treatment method for aluminum materials in which a secondary coloring process is applied, then masking is removed, and then an electrodeposition coating process is performed. A multicolor surface treatment method for aluminum material, characterized in that the voltage in the subsequent painting process is set lower than the voltage in the previous painting process.