JPH0359753B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] This invention relates to a method for surface treatment of aluminum or aluminum alloy (hereinafter simply referred to as aluminum), particularly a surface treatment method for producing a composite film material in which a coating film is further provided on the surface of an anodized film. This relates to a processing method. [Technical background of the invention and its problems] Conventionally, aluminum having this kind of composite film has been treated by (a) anodizing film treatment, (b) hydration treatment by washing with hot water or sealing, and (c) draining and drying. Treatment, (d) painting treatment, and (e) baking drying treatment are performed in order to form an anodic oxide film and a paint film on the surface of aluminum, but generally aluminum composites produced by the above methods are Coatings are always accompanied by the problem of water spots and coating cracking. Before explaining this problem, let us briefly describe each treatment step of the conventional method. (a) The anodic oxide film treatment is generally carried out in a sulfuric acid aqueous solution or a solution containing various electrolytes for 20 to 30 minutes.
Perform DC anodic electrolysis for several 10 minutes. After electrolytic treatment, a dense aluminum oxide film with a thickness of several micrometers to several tens of micrometers and good corrosion resistance is formed on aluminum, and this film has approximately 100 to 200 Å pores.
Exists at a pitch of 400 Å. In the hydration treatment (b), in the case of hot water washing, water spots are prevented by a hydration reaction with the anodic oxide film, and various ions in the pores of the anodic oxide film are removed, and usually miscellaneous ions are removed. It is immersed for about 1 to 30 minutes in a small amount of ground water, pure water, or a liquid containing various hydration reaction accelerators at a temperature of 70°C or higher. The reaction also differs depending on the liquid composition; the higher the temperature and the longer the immersion time, the faster the reaction progresses and the more hydrates are produced. In addition, in the case of pore sealing treatment, the main purpose is to improve corrosion resistance by hydrating the anodic oxide film to the extent that the pores are closed with hydrates, and the treatment method is to A method of immersing in underground water or a solution heated to about 95℃ by adding various substances to it for 10 minutes or more, or 10 to several tens of minutes in a pressurized steam atmosphere of 1 to several atmospheres. There are various treatment methods, and the amount of hydration achieved by these treatments is greater than by washing with hot water. The draining and drying process (c) is not normally carried out when using water-soluble paints, but is mainly used to remove moisture from the surface of the material when painting with oil-based paints. In an atmosphere around ℃
Treat for about 10 to several tens of minutes, or dry by air drying. The purpose of the painting process (d) is to form a paint film on the top surface of the base film that has undergone the above-mentioned treatments, and is performed by dip painting using an acrylic thermosetting resin paint for TFS painting. Thickness of several μm to 10-odd μm can be achieved by methods such as electrodeposition coating using water-soluble acrylic thermosetting resin paint, or spray painting using polyurethane resin paint. Forms a coating film. The baking drying treatment (e) is for the purpose of curing the paint after painting, and is generally performed at a temperature of 120° C. or higher for 10 to several tens of minutes. Problems in the above-mentioned normal process are water spots and film cracks, but of these, "water spots" are caused by rain on the material after anodizing and hot water washing, or on the material after anodizing, hot water washing, and painting. This is a phenomenon in which traces of water droplets remain even after wiping off the water droplets, and if this occurs,
There is a problem that the color tone differs between the area where water spots occur and other areas, resulting in a poor appearance.Water spots are less likely to occur in materials that have undergone a hydration reaction, and there are almost no problems with materials that have undergone pore-sealing treatment. No. Furthermore, "film cracking" occurs when a material that has been subjected to hot water washing or pore sealing treatment after anodizing treatment is heated by baking paint, etc., and a difference in thermal expansion occurs between the aluminum and the anodized film, causing cracks in the anodized film. Referring to the phenomenon that occurs, this film cracking is more likely to occur as the hydration reaction progresses, the higher the heating temperature, the more likely it is to occur, and the thicker the anodic oxide film is, the more likely it is to occur. Next, Table 1 shows the relationship between water spots and film cracks that occur when treated using the conventional method.

[Purpose of the invention]

The main object of the present invention is to eliminate the various problems associated with the conventional treatments mentioned above and to establish a new method for surface treatment of aluminum that does not cause water spots or film cracks. [Structure of the Invention] The present invention was developed to achieve the above-mentioned object, and consists of applying a hydration treatment by hot water washing or sealing to aluminum or an aluminum alloy after forming an anodized film, and After the primary drying process, a normal painting process is performed, followed by a secondary drying process for the purpose of baking the paint.In the first surface treatment process, the heating during the primary drying process This process is characterized by processing at a temperature higher than the heating temperature during the secondary drying process. As mentioned above, the aluminum surface treatment method according to the present invention is basically the same as the conventional process order when comparing all the steps, but in order to prevent water spots and film cracking, the aluminum surface treatment method after the anodized film has been formed is After hydration treatment by hot water washing or pore sealing, in the first drying process, the object to be treated is heated at a higher temperature than the subsequent heating temperature during baking and drying of the coating film. In the painting method using paint, the base film is originally subjected to a high-temperature drying process in a low-temperature drying process that only removes moisture, and then the painting process and baking drying process of the paint film are performed. Even if cracks occur in the film during the treatment process, the paint will soak into the cracked parts of the film in the next painting process and fill the cracks. Since the treatment is carried out at a heating temperature lower than the above temperature, there is no risk of cracks occurring in the paint film at this point, and the paint film after the second drying process will have no cracks that occurred during the initial drying process. A coating film that is always smooth and has a beautiful appearance is obtained without any appearance of the coating. [Examples of the Invention] Hereinafter, typical examples of the present invention and comparative examples thereof will be listed below, and the embodiments and effects of the surface treatment method according to the present invention will be specifically explained. However, the present invention does not necessarily cover these examples. The present invention is not limited only to the embodiments. Example 1 70×200×1.8t aluminum extrusion (6063S
−T ₅ ) after normal pretreatment, bath temperature 20℃,
Anodic electrolysis treatment was carried out for 42 minutes at a current density of 1 A/dm ² using a lead plate as a counter electrode in a 150 g/sulfuric acid bath to form an anodic oxide film with a thickness of 15 μm on the surface. Next, a hydration process is performed by washing in hot water for about 10 minutes at a temperature of 90℃, followed by a drying process for 20 minutes at a temperature of 230℃, and then a coating film is applied using an acrylic thermosetting resin paint for TFS. Dip coating was performed to a thickness of 7 μm. Finally, the coating film was baked and dried at a heating temperature of 200℃ for 30 minutes, and the resulting sample was
The performance was shown in Table 2. Example 2 70×200×1.8t aluminum extrusion forming (6063S
−T ₅ ) after normal pretreatment, bath temperature 20℃,
Anodic electrolytic treatment was performed for 28 minutes at a current density of 1 A/dm ² using a lead plate as the counter electrode in a 150 g/sulfuric acid bath.
A 10 μm thick anodic oxide film was formed on the surface. Next, a steam sealing process was performed for 20 minutes at a steam pressure of 4 kg/ ^cm2 , followed by a draining and drying process for 20 minutes at a temperature of 230°C, and then a coating film was applied using an acrylic thermosetting resin paint for TFS. Dip coating was performed to a thickness of 7 μm. Finally, the coating film was baked and dried at a heating temperature of 200℃ for 30 minutes, and the resulting sample was
The test results showed the performance shown in Table 2. Example 3 70×200×1.8t aluminum extrusion (6063S
−T ₅ ) after normal pretreatment, bath temperature 20℃,
Anodic electrolytic treatment was performed for 42 minutes at a current density of 1 A/dm ² using a lead plate as the counter electrode in a 150 g sulfuric acid bath.
A 15 μm thick anodic oxide film was formed on the surface. Next, seal the hole at a temperature of 100℃ for 30 minutes (Sealing
(Manufactured by Hanami Chemical Co., Ltd.) treatment at a temperature of 150℃ for 20
After drying for a few minutes, spray painting was performed using a polyurethane paint to a film thickness of about 7 μm. Finally, the coating film was baked and dried at a heating temperature of 120°C for 10 minutes, and the resulting sample was
The performance was shown in Table 2. Comparative example 1 70×200×1.8t aluminum extrusion (6063S
−T ₅ ) to a thickness of 15 μm by the same treatment as in Example 1.
An anodic oxide film was formed. Next, a hydration treatment was performed by washing in hot water for about 10 minutes at a temperature of 80℃, followed by a draining and drying treatment for 20 minutes at a temperature of 100℃, followed by a painting treatment and a baking drying treatment of the coating film in the same manner as in Example 1. (200°C, 30 minutes), the obtained sample showed the performance as shown in Table 2. Comparative Example 2 70×200×1.8t aluminum extrusion (6063S
−T ₅ ) to a thickness of 10 μm by the same treatment as in Example 2.
Anodized film is formed, and then steam pressure is 4Kg/
After applying steam sealing treatment at cm ² for 20 minutes, draining and drying treatment was performed at room temperature, and dip painting was performed using an acrylic thermosetting resin paint for TFS to a coating thickness of 7 μm. Finally, the coating film was baked and dried at a temperature of 200°C for 30 minutes, and the resulting sample exhibited the performance as shown in Table 2 as a result of the test. Comparative Example 3 70×200×1.8t aluminum extrusion (6063S
−T ₅ ) to a thickness of 15 μm by the same treatment as in Example 3.
An anodic oxide film was formed. Next, seal the hole at a temperature of 100℃ for 30 minutes (Sealing X)
After treatment and drying at a temperature of 100°C for 10 minutes, the same painting process as in Example 3 and baking drying process of the coating film (120°C, 10 minutes) were performed. The samples obtained showed the performance as shown in Table 2.

【table】

[Table] Performance test method in Table 2
According to JISH 8602 (composite coating of anodic oxidation coating on aluminum and aluminum alloys).
[Effects of the Invention] As described above, if the method of the present invention is applied to the production of a composite film material in which an anodic oxide film and a paint film are formed on the surface of aluminum, the primary drying process performed before the painting process can be By setting the heating temperature during the treatment higher than the heating temperature during the secondary drying treatment (baking drying of the paint film), the problems of water spots and film cracking that accompany this type of surface treatment can be completely eliminated. This problem can be solved all at once, and a composite film can be formed on the aluminum surface that always has a smooth, beautiful appearance and excellent durability.

Claims (1)

[Claims] 1 After the anodic oxide film has been formed, the aluminum or aluminum alloy is subjected to a hydration treatment by hot water washing or sealing, followed by a primary drying treatment, and then a painting treatment for the purpose of baking the paint. Second
In a series of surface treatment steps for performing a secondary drying treatment, the heating temperature during the primary drying treatment is higher than the heating temperature during the secondary drying treatment. Surface treatment method.