JPH07163942A - Formation of corrosion-resistant fluororesin-coating film - Google Patents

Abstract

PURPOSE:To provide a method forming a fluororesin-coating film having excellent corrosion resistance on an aluminum or aluminum alloy forming body applied to a rice boiler, a rice warmer or the like. CONSTITUTION:This corrosion-resistant fluororesin-coating film is formed by anodic-oxidizing the aluminum or aluminum alloy forming body in an electrolyte mainly consisting of hydrazine to form an oxide film having 3-15mum thickness on the surface and forming the fluororesin-coating film thereon.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a corrosion-resistant fluororesin film, and more particularly to a molded product of aluminum or an aluminum alloy, such as rice cooker, rice cooker,
The present invention relates to a method for forming a fluororesin film having excellent corrosion resistance and excellent scratch resistance without applying a primer (undercoat) on the surface of copying machine rolls.

[0002]

2. Description of the Related Art Conventionally, among many methods for forming a fluororesin film on the surface of a seed metal, as a processing method without using a primer, generally as a pretreatment, aluminum or an aluminum alloy is treated with an inorganic acid or a salt, For example, etching is performed by immersing or electrolytically treating hydrochloric acid, salt, etc. alone or a mixture thereof to enhance the adhesion effect when fluororesin is applied to the roughened metal surface. There is known a method in which an etching surface formed on the surface of the metal to be treated is subjected to anodizing treatment with an acidic solution, and further, after anodizing treatment, treatment with chromic acid is performed. After these pretreatments, an aqueous dispersion of a fluororesin is applied to the metal surface by an appropriate method, and then heated at a temperature equal to or higher than the melting point of the material resin to melt the applied resin to form a desired fluororesin film. It has gained.

[0003]

However, in these conventional methods for forming a fluororesin film, a concave surface is formed by etching or an uneven surface is formed by blasting, and then anodic oxidation is performed. Generally, when anodic oxidation is performed with an acidic liquid, cracks are generated in the anodic oxide film when the fluororesin formed on the surface is baked. Further, in the case where the uneven surface is formed by blasting and then the acid anodic oxidation is performed thinly, the anchor effect is small and it is difficult to obtain good adhesion of the fluororesin. In the case where the uneven surface is formed by blasting and anodized in an alkaline solution, cracks do not occur due to baking during the formation of the fluororesin film, but the anchor effect is slightly insufficient as compared with the case where recesses are formed by etching. Weakness in adhesion and scratch test)
When forming the fluororesin film, it is necessary to perform firing in a vacuum furnace under conditions of about 1 Pa. This method is a method of performing two steps of etching and anodic oxidation only by anodic oxidation without etching, and the anodic oxide film is thick (15 to 17 μm).
It has the feature that even if it is a product, it does not generate cracks in the anodic oxide film due to heating during the baking of the fluororesin, and that it is possible to obtain a product with excellent corrosion resistance to the anodic oxidation of this method. In addition, it has the excellent feature that it can be fired in a normal furnace in the air and does not require a vacuum furnace.

[0004]

The present invention has taken the following technical means in order to solve the above problems and achieve the objects. That is,

1. Corrosion-resistant fluororesin film characterized in that an aluminum or aluminum alloy is anodized in an electrolytic solution containing hydrazine as a main component to form an oxide film with a thickness of 3 to 15 μm, and a fluorine resin film is directly formed on the surface of the oxide film. Forming method.

2. The fluororesin is PFA, FEP,
A single substance or a mixture of PTFE, or a fluororesin containing potassium titanate, SnO ₂ , C, ceramic powder and the like. The thickness of the fluororesin film is 5 to 50 μm. It consists of the contents.

[0007]

The present invention constructed as described above has the following actions.

1. When an aluminum or aluminum alloy molded body is anodized in an electrolytic solution containing hydrazine as a main component, the concave holes become large during the anodization due to the characteristics of hydrazine, and an oxide film is formed on the uneven surface. That is, it is possible to obtain the same operational effects as those obtained by the conventional blasting or etching treatment in one step.

2. The oxide film on the uneven surface due to anodic oxidation has a shape different from that of the conventional alumite film, so that the oxide film is not cracked by heating the fluororesin.

3. The recesses formed by anodic oxidation are larger than the conventional holes, and the fluororesin film formed on the surface of the recesses adheres and is fixed so that scratches are less likely to occur.

4. Fluorine resin containing potassium titanate, carbon, SnO _{2 and the} like has non-adhesiveness and antistatic effect due to its conductivity, and is suitable for rolls such as copy and facsimile. Suitable.

[0012]

Embodiments of the present invention will be described.

Example 1 Aluminum alloy 3004 was degreased according to a conventional method,

NH ₂ NH ₂ 0.2 mol / liter NH ₁ F 0.2 mol / liter CH ₃ COONH ₄ 0.05 mol / liter

Anodization was performed under stirring at 2 A / dm ² for 30 minutes. The anodized film obtained by this is 7 to 10
was μm. In this case, the 3004 alloy is colored in amber.

A PFA dispersion liquid of 10 to 25 μm is formed on this surface.
(Dry coating thickness) It was applied and baked at 400 ° C for 30 minutes in the atmosphere. The anodized film did not cause cracks, and the fluororesin coating film had no cracks, and a smooth surface was obtained.

Results of Cerotape Test after Cross-cut 10
It was 0/100, and it showed good fixing property in a scratch test with a cut. This test piece is saline 5
%, No abnormality was observed even after 800 hours under the condition of 70 ° C.

Example 2.1001 An aluminum plate was

NH ₄ NH ₄ 0.1 mol / liter NH ₄ F 0.1 mol / liter (NH ₄ ) ₂ CO ₃ 0.1 mol / liter H ₂ NCH ₂ COOH 0.1 mol / liter

The solution was anodized at 20 ° C. and a constant voltage of 80 V. The final current density value at this time is 0.31A.30
The anode thickness was 14 μm.

PFA was attached to the surface to a thickness of 22 μm and treated in the same manner as in Example 1. This product had good adhesion and test results.

A mixture of electrically conductive substances (potassium titanate, SnO ₂ , carbon, ceramic powder) in the fluororesin in the range of 3 to 7% by weight through the same steps as described above is non-adhesive. The effect was recognized in the property and antistatic.

In this invention, it was confirmed that the baking of the fluororesin can be carried out in a furnace in the air. Further, in order to obtain a fluororesin film having a high density, the purpose can be achieved by baking in a vacuum furnace of about 1 Pascal.

[0024]

The present invention having the above-described structure has the following excellent effects.

1. Since it is possible to form a deep etching with a large recess and an oxide film in one process, there is an effect that a blast treatment is unnecessary and a fluororesin film having excellent corrosion resistance can be formed.

2. Since the etching and the oxide film are formed at the same time, there is an effect that the concave portion of the anodic oxide film becomes large and deep, and this has an effect of enhancing the adhesiveness of the upper fluororesin film as compared with the blast treatment.

3. Due to the good adhesion of the fluororesin film, there is an effect that scratches between the oxide film and the fluororesin film are unlikely to occur, which also has an effect of improving the corrosion resistance.

4. A mixture of potassium titanate, carbon, tin oxide, etc., in a fluororesin is used in a copying machine or a roll for a facsimile machine, and it has a non-adhesive property and an antistatic effect.

Claims (3)

[Claims] 1. A molded body made of aluminum or an aluminum alloy is anodized in an electrolytic solution containing hydrazine as a main component to form an oxide film having a thickness of 3 to 15 μm, and a fluorine resin film is directly formed on the surface thereof. A method for forming a corrosion-resistant fluororesin film, which is characterized in that 2. The fluorine resin is PFA, FEP, PT
FE is a single substance or a mixture, and the film thickness is 5 to 50.
The method for forming a corrosion-resistant fluororesin film according to claim 1, wherein the thickness is μm. 3. The method for forming a corrosion-resistant fluororesin film according to claim 1, wherein the fluororesin contains any one of potassium titanate, stannous oxide, carbon, ceramic powder and the like.