Exterior component and method for manufacturing the same

Abstract

To provide an exterior member with excellent resistance to acids and alkalis and a manufacturing method thereof.SOLUTION: The exterior member comprises a metal material made of aluminum or aluminum alloy and an anodic oxide layer formed on the surface of the metal material. The anodic oxide layer has numerous micro-pores and a composite film layer made of metal hydroxide and metal oxide on the surface side of the micro-pores.SELECTED DRAWING: Figure 1

Description

[[Technical Field]]

[0001] The present invention relates to various exterior members using aluminum or an aluminum alloy as a raw material and a method for manufacturing the same, and particularly relates to exterior members requiring acid resistance and alkali resistance, such as automotive exterior members. [[Background Art]]

[0002] Conventionally, anodizing treatment has been performed for the purpose of rust prevention on various products using aluminum or an aluminum alloy as a raw material. This type of anodized film consists of a barrier layer with a thickness of about 10 to 20 nm and a porous layer formed with countless fine pores having an inner diameter of about 5 to 30 nm on the barrier layer.

[0003] Since the corrosion resistance is insufficient if the fine pores of the anodized film remain as they are, so-called sealing treatment is performed. As sealing treatment, boehmite treatment by hot water treatment at 90°C or higher, steam treatment or the like has insufficient corrosion resistance and may cause clouding on the surface. Therefore, a high-temperature sealing treatment method, in which nickel hydroxide is precipitated along with the boehmite formation of aluminum oxide in fine pores by performing treatment in relatively high-temperature hot water of 80°C or higher using a nickel acetate-based aqueous solution, and a method, in which nickel hydroxide and aluminum fluoride are compositely precipitated at a relatively low temperature from normal temperature to 40°C using a nickel fluoride-based aqueous solution, are known.

[0004] Patent Document 1 describes a sealed anodized film which comprises an anode region filled with at least one selected from among crystalline transition metal oxides, crystalline noble metal oxides, metalloid oxides, alkaline earth metal oxides and alkali metal oxides, and a sealing region containing at least one of the above, for the purpose of further improving steam resistance, alkali resistance and acid resistance. According to the specific content described in the examples of Patent Document 1, an anodized aluminum substrate is heat-treated at about 150°C to about 300°C for about 30 minutes to about 2 hours to be at least partially crystallized. However, there is a significant difference in thermal expansion coefficients between aluminum metal materials and inorganic materials such as anodized coatings. During heat treatment, countless cracks may form in the anodized coating, potentially reducing its acid and alkali resistance. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Special Publication No. 2013-528707 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] The present invention aims to provide an exterior component with excellent acid and alkali resistance, and a method for manufacturing the same. [Means for solving the problem]

[0007] The exterior member according to the present invention comprises a metal material made of aluminum or an aluminum alloy, and an anodic oxide layer formed on the surface of the metal material, wherein the anodic oxide layer has countless micropores, and the surface side of the micropores has a composite film layer of metal hydroxide and metal oxide. In this invention, as a pore-sealing treatment for an anodic oxide film, a composite film layer is formed by depositing metal hydroxide and metal oxide within micropores, thereby achieving both alkali resistance due to the metal hydroxide and acid resistance due to the metal oxide.

[0008] In an anodized film, the aluminum oxide formed during anodizing undergoes a hydration reaction to form boehmite (monohydrate) or byerlite (trihydrate). These hydrates may also be compounded with metal hydroxides and metal oxides.

[0009] Examples of metal hydroxides in this invention include nickel hydroxide, zirconium hydroxide, cobalt hydroxide, zinc hydroxide, and vanadium hydroxide. Examples of metal oxides include zirconium oxide and titanium oxide. In the present invention, it is preferable that the composite film layer contains at least nickel hydroxide and zirconium oxide or zirconium hydroxide.

[0010] In this invention, further compounding with a silicate or an acrylic organic material, which have high affinity for the metal oxide precipitated in the micropores, further improves acid and alkali resistance. Here, silicates refer to silicic acid compounds whose backbone consists of orthosilicate ions, pyrosilicate ions, etc. Furthermore, acrylic organic materials refer to resin components such as polyacrylic and copolymer, which penetrate the gaps in inorganic precipitates, improving acid and alkali resistance.

[0011] The present invention relates to a method for manufacturing an exterior component, characterized by comprising the steps of: forming an anodic oxide layer having countless micropores on the surface of a metal material made of aluminum or an aluminum alloy; reacting it with an aqueous solution containing nickel fluoride and zircon hydrofluoric acid; and reacting it with an aqueous solution containing a silicate. Here, nickel fluoride precipitates as nickel hydroxide when deposited in the micropores, and zirconhydrofluoric acid precipitates as zirconium oxide or zirconium hydroxide when deposited in the micropores. Nickel fluoride may also be in the form of a tetrahydrate such as F2Ni·4H2O, and zirconhydrofluoric acid is also called fluorizirconate or fluorizirconhydrofluoric acid and is represented as H2ZrF6. Furthermore, the aqueous solution may contain nickel acetate, potassium fluoride, surfactants, etc.

[0012] In the present invention, the aqueous solution containing the above-mentioned silicate may also contain an acrylic organic substance together with a surfactant. [Effects of the Invention]

[0013] The exterior member of the present invention has excellent acid resistance and alkali resistance because it is formed as a composite film layer of a metal hydroxide and a metal oxide for the sealing treatment of the anodized film thereof. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] [Figure 1] Evaluation results are shown. [Figure 2] A method for measuring the thickness of a composite film layer is shown. [Figure 3] Element mapping images are shown, where (a) shows Si, (b) shows Ni, and (c) shows Al. MODE FOR CARRYING OUT THE INVENTION

[0015] Test pieces were prepared and evaluated for alkali resistance and acid resistance, which will be described below. However, the present invention is not limited thereto. EXAMPLES

[0016] (1) Using a sulfuric acid aqueous solution with a concentration of 200 g / L on an aluminum plate at 20°C, current density 1 A / dm 2 , an electrolytic treatment was performed for 30 minutes to form an anodized film of approximately 9 µm, which was sufficiently washed with water. (2) Next, immersion treatment was performed at 75°C for 15 minutes in an aqueous solution comprising, by mass%, 0.55% nickel fluoride (tetrahydrate), 0.5% nickel acetate, 0.05% zirconhydrofluoric acid, 0.04% potassium fluoride, and 0.2% or less surfactant, followed by sufficient water washing. (3) Next, immersion was performed at approximately 95°C for 20 minutes in an aqueous solution containing about 0.1% silicate, about 0.1% acrylic organic substance, and 0.1 to 0.2% surfactant, followed by sufficient water washing. (4) Regarding the thickness of the composite film layer formed on the surface side of the anodized film, when the surface-treated portion is bent as shown in Figure 2, a fracture surface of the anodized film is exposed. Observation at 35,000 times magnification was performed using JSM-IT700HR manufactured by JEOL Ltd., and the thickness from the top surface to the position where columnar micropores of the anodized film can be confirmed was defined as the composite film layer. In Example 1, the thickness was approximately 300 nm. (5) shows TEM element mapping images of Si, Ni, and Al near the surface portion of the anodized film. From these facts, it can be seen that the composite film layer is formed of a portion filled in the micropores and a layer deposited on the surface thereof. [Examples]

[0017] In Example 2, the treatment time of the first stage shown in (2) in Example 1 was set to 10 minutes, and the treatment time of the second stage shown in (3) was set to 15 minutes. Others were prepared in the same manner as in Example 1. The thickness of the composite film layer was about 200 nm. Reference Example 1

[0018] In Reference Example 1, the first-stage treatment condition shown in (2) of Example 1 was set to 5 minutes, and the second-stage treatment condition shown in (3) was set to 10 minutes. Others were prepared in the same manner as in Example 1. The thickness of the composite film layer was about 100 nm. Comparative Example 1

[0019] In Comparative Example 1, after forming an anodized film in the same manner as (1) in Example 1, sealing treatment was performed at 90°C for 20 minutes using a 0.5% nickel acetate aqueous solution. Comparative Example 2

[0020] In Comparative Example 2, after forming an anodized film in the same manner as (1) in Example 1, a first-stage sealing treatment was performed at 30°C for 20 minutes using an about 3% nickel fluoride aqueous solution, and then steam pore sealing was performed for 20 minutes as the second stage.

[0021] Using test pieces produced in Examples 1 and 2, Reference Example 1, and Comparative Examples 1 and 2, alkali resistance and acid resistance tests were carried out as described below. <Alkali Resistance Test Method> Immerse in a sodium hydroxide aqueous solution of pH 12.5 at normal temperature for 10 minutes, then wash and dry. Gloss before and after the test was measured with an IG-410 gloss meter manufactured by HORIBA, and the gloss retention rate was calculated by the following formula (1). Gloss retention rate (%) = Gloss after test / Gloss before test × 100 ···(1) <Acid resistance test method> Add one drop of pH 4 sulfuric acid solution to the test piece, let it dry, and then add another drop to the same spot, repeating the process. Wipe the dripping area with a paper towel dampened with water, and measure the number of drops required until it turns white.

[0022] The evaluation results are shown in the table in Figure 1. Examples 1 and 2 both exhibit superior alkali and acid resistance compared to Comparative Examples 1 and 2. When applying this invention to automotive exterior parts, the targets were a gloss retention rate of 80% or more and acid resistance of 200 cycles or more. Although Reference Example 1 also exhibits superior acid resistance compared to Comparative Examples 1 and 2, demonstrating the effectiveness of the present invention, when the composite film thickness is thin, at the 100 nm level, its alkali and acid resistance is inferior to that of Examples 1 and 2. Therefore, it is preferable that the composite film thickness be 200 nm or more.

[0023] <Comparison with conventional technology> Based on the test specimen of Example 1 of the present invention and paragraph (0051) of Patent Document 1, the applicant prepared a test specimen and conducted an immersion test in a pH 0.8 sulfuric acid aqueous solution for 24 hours. In Example 1 of this application, the reduction in film thickness was less than 5%, whereas in the follow-up sample of Patent Document 1, the reduction was approximately 20%. From this, it is presumed that the exterior component according to the present invention has superior acid resistance compared to the conventional technology.

[0024] In this embodiment, the processing conditions are not limited to those of Examples 1 and 2. For example, the purpose of the first-stage processing solution is to precipitate nickel hydroxide and zirconium oxide or zirconium hydroxide in the micropores, and the composition is preferably within the following range in mass%. (1) Nickel fluoride: 0.30~1.00% (2) Zircon hydrofluoric acid: 0.02~0.05% (3) Potassium fluoride: 0.05% or less The second stage treatment solution preferably contains 0.05-0.20% silicate, 0.05-0.20% acrylic organic matter, and 0.20% or less surfactant.

Claims

1. The material comprises a metal material made of aluminum or an aluminum alloy, and an anodized layer formed on the surface of the metal material. The anodic oxide layer has countless micropores, and the surface side of the micropores has a composite film layer of metal hydroxide and metal oxide. The composite film layer comprises at least nickel hydroxide and zirconium oxide or zirconium hydroxide. An exterior component characterized in that the thickness of the composite film layer is 200 nm or more.

2. The exterior member according to claim 1, characterized in that the composite film layer further contains silicate.

3. The exterior member according to claim 2, characterized in that the composite film layer further contains an acrylic organic substance.

4. The steps include forming an anodic oxide layer having countless micropores on the surface of a metal material made of aluminum or an aluminum alloy, The step of reacting with an aqueous solution containing nickel fluoride: 0.30 to 1.00% by mass and zircon hydrofluoric acid: 0.02 to 0.05% by mass, A method for manufacturing an exterior component, comprising the step of reacting with an aqueous solution containing 0.05 to 0.20% by mass of silicate, characterized in that the thickness of the composite film layer formed on the surface side of the anodic oxide layer is 200 nm or more.

5. The method for producing an exterior component according to claim 4, characterized in that the aqueous solution containing the silicate contains 0.05 to 0.20% by mass of an acrylic organic substance.

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