Patent Application
20250011963
The present disclosure relates to various exterior members made of aluminum or aluminum alloys and to a method for producing the same, and in particular to exterior members that are required to be resistant to acid and alkali, such as exterior members for automobiles.
Anodizing has been used to prevent rust on various products made from materials such as aluminum or aluminum alloys. This type of anodic oxide film consists of a porous layer with countless micropores with inner diameters of approximately 5 to 30 nm formed on a barrier layer that has a thickness of approximately 10 to 20 nm.
Since the micropores in the anodized film do not have sufficient corrosion resistance as they are, the anodic oxide film is subjected to a so-called pore-sealing treatment.
As a pore-sealing treatment, when a boehmite treatment is carried out by hot water treatment or steam treatment at 90° C. or higher, there is a risk that the corrosion resistance is insufficient or that the surface becomes cloudy. For this reason, the following two methods and etc. are known. One method is a high-temperature pore-sealing treatment method in which nickel hydroxide is precipitated in the micropores in conjunction with the conversion of aluminum oxide to boehmite by treating with hot water at a relatively high temperature of 80° C. or higher using a nickel acetate-based aqueous solution. The other method is a method in which nickel hydroxide and aluminum fluoride are precipitated in combination at a relatively low temperature of room temperature to 40° C. using a nickel fluoride-based aqueous solution.
JP2013-528707A describes an anodized coating improving steam resistance and resistance to alkali and acid, the anodized coating includes an anode region filled with at least one of a crystalline transition metal oxide, a crystalline precious metal oxide, a semi-metal oxide, an alkaline earth metal oxide and an alkali metal oxide, and a pore-sealing region adjacent to at least a part of the anode region.
Specifically, according to an embodiment of JP2013-528707A, an anodized aluminum substrate is heat-treated at about 150° C. to about 300° C. for about 30 minutes to about 2 hours to at least partially crystallize the substrate.
However, there is a large difference in the thermal expansion coefficient between aluminum metal material and inorganic material such as anodized film, and there is a risk that countless cracks will occur in the anodized film during heat treatment, which may in turn cause a decrease in acid and alkali resistance.
The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. These are, of course, merely examples and are not intended to be limiting. In addition, the disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. Further, when a first element is described as being “connected” or “coupled” to a second element, such description includes embodiments in which the first and second elements are directly connected or coupled to each other, and also includes embodiments in which the first and second elements are indirectly connected or coupled to each other with one or more other intervening elements in between.
An object of the present disclosure is to provide an exterior member having excellent acid and alkali resistance and a method for producing the same.
In accordance with one of some embodiments, there is provided an exterior member comprising;
a metal material made of aluminum or an aluminum alloy;
As a result, in some embodiments, the pore-sealing treatment for the anodized film involves precipitating the metal hydroxide and the metal oxide within the fine pores to form the composite film layer, which makes it possible to achieve both the alkali resistance provided by the metal hydroxide and the acid resistance provided by the metal oxide.
In the anodized film, boehmite (monohydrate) or bayerite (trihydrate) is formed by the hydration of aluminum oxide formed during anodization, and these hydrates may be combined with metal hydroxide and metal oxide.
In the present disclosure, examples of metal hydroxides include nickel hydroxide, zirconium hydroxide, cobalt hydroxide, zinc hydroxide, vanadium hydroxide, and the like.
Examples of metal oxides include zirconium oxide and titanium oxide.
In accordance with one of some embodiments, the composite film layer may include nickel hydroxide and zirconium oxide or zirconium hydroxide.
In accordance with one of some embodiments, the composite film layer may further include silicate.
In accordance with one of some embodiments, the composite film layer may further include an acrylic organic substance.
As a result, in some embodiments, the acid resistance and alkali resistance are further improved, if one or both of the silicate and the acrylic organic substance, which have a high affinity with the metal oxide deposited in the fine pores, are further compounded.
Here, silicates refer to silicate compounds whose skeleton consists of orthosilicate ions, pyrosilicate ions, etc.
Furthermore, acrylic organic substances refer to resin components such as polyacrylics and copolyacrylics, which penetrate into the gaps in inorganic deposits and improve acid and alkali resistance.
In accordance with one of some embodiments, there is provided a method for producing an exterior member comprising: forming an anodized layer on a metal material made of aluminum or an aluminum alloy, the anodized layer including micropores; immersing the metal material having the anodized layer in an aqueous solution containing nickel fluoride and zircon hydrofluoric acid; and thereafter, immersing the metal material in an aqueous solution containing silicates.
Here, nickel fluoride precipitates as nickel hydroxide when deposited in the micropores, and zircon hydrofluoric acid precipitates as zirconium oxide or zirconium hydroxide when deposited in the micropores.
Nickel fluoride may be a tetrahydrate such as F2Ni·4H2O, and zircon hydrofluoric acid is also called hydrofluoric zirconate or hydrofluoric zirconic acid and is expressed as H2ZrF6.
The aqueous solution containing nickel fluoride and zircon hydrofluoric acid may also contain nickel acetate, potassium fluoride, a surfactant, and the like.
The aqueous solution containing the silicate may contain an acrylic organic substance together with a surfactant.
The exterior member in the present disclosure has excellent acid resistance and alkali resistance due to the use of a composite film layer of a metal hydroxide and a metal oxide as a sealing treatment for the anodized film.
Exemplary embodiments are described below. Note that the following exemplary embodiments do not in any way limit the scope of the content defined by the claims laid out herein. Note also that all of the elements described in the present embodiment should not necessarily be taken as essential elements
Test pieces were prepared and the alkali resistance and acid resistance were evaluated, which will be described below, but the present disclosure is not limited thereto.
The composite film layer was observed under 35,000× magnification with JSM-IT700HR manufactured by JEOL Ltd., and was defined to have a thickness from the top surface to a point where columnar micropores of the anodic oxide film was observed.
In Example 1, the thickness was about 300 nm.
From these, it is clear that the composite film layer is formed of a portion filled in the micropores and a layer deposited on the surface thereof.
In Example 2, the first-stage processing time given in (2) of Example 1 was changed to 10 minutes, and the second-stage processing time given in (3) was changed to 15 minutes.
A composite film layer was prepared in the same manner as in Example 1 except for the above.
The thickness of the composite film layer was about 200 nm.
In Reference Example 1, the first stage treatment conditions shown in (2) of Example 1 were changed to 5 minutes, and the second stage treatment conditions shown in (3) were changed to 10 minutes.
The rest of the process was the same as in Example 1.
The thickness of the composite film layer was approximately 100 nm.
In Comparative Example 1, similar to Example 1 (1), an anodized film was formed, and then a sealing treatment was performed at 90° C. for 20 minutes using a 0.5% aqueous solution of nickel acetate.
In Comparative Example 2, an anodized film was formed in the same manner as in Example 1 (1), and then a first-stage sealing treatment was performed using an approximately 3% aqueous solution of nickel fluoride at 30° C. for 20 minutes, followed by a second-stage steam sealing for 20 minutes.
The test pieces produced in Examples 1 and 2, Reference Example 1, and Comparative Examples 1 and 2 were used to carry out alkali resistance and acid resistance tests as described below.
The test pieces are immersed in a pH 12.5 sodium hydroxide solution at room temperature for 10 minutes, then washed and dried.
The gloss before and after the test was measured using a HORIBA IG-410 gloss meter, and the gloss retention was calculated using the following formula (1).
A drop of a pH 4 sulfuric acid solution is dropped onto the test piece, and after drying, another drop is dropped onto the same spot, and this is repeated.
The dropped area is then wiped off with a damp paper towel, and the number of drops is counted until the area turns white.
The evaluation results are shown in the table in
Both Examples 1 and 2 have better alkali resistance and acid resistance than Comparative Examples 1 and 2.
When attempting to apply the present disclosure to exterior parts of an automobile, the targets are a gloss retention of 80% or more and acid resistance of 200 cycles or more.
Reference Example 1 also had better acid resistance than Comparative Examples 1 and 2, and the effects of the present disclosure were evident. However, when the composite film thickness was as thin as 100 nm, as in Reference Example 1, the alkali resistance and acid resistance were inferior to Examples 1 and 2, so it is preferable for the composite film thickness to be 200 nm or more.
<Comparison with the Prior Art>
Based on the test piece of Example 1 in this disclosure and paragraph (0051) of JP2013-528707A, the applicant produced test pieces and performed an immersion test in a sulfuric acid aqueous solution with a pH of 0.8 for 24 hours.
In Example 1 of the present disclosure, the reduction rate of the thickness of the coating was less than 5%, while the retest sample of JP2013-528707A was reduced by approximately 20%.
From this, it is presumed that the exterior member according to the present disclosure has better acid resistance than the prior art.
In this example, 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 in the following range in mass %:
The second stage treatment liquid preferably contains 0.05-0.20% silicate, 0.05-0.20% acrylic organic matter, and 0.20% or less surfactant.
Exterior components made from the aluminum alloy of the present disclosure have excellent resistance to both acids and alkalis, and can be used for a variety of exterior parts, including automotive exterior components.
Although only some embodiments of the present disclosure have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the embodiments without materially departing from the novel teachings and advantages of this disclosure. Accordingly, all such modifications are intended to be included within scope of this disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-051449 | Mar 2022 | JP | national |
This application is a continuation of International Patent Application No. PCT/JP2022/040426, having an international filing date of Oct. 28, 2022, which designated the United States, the entirety of which is incorporated herein by reference. Japanese Patent Application No. 2022-051449 filed on Mar. 28, 2022 is also incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2022/040426 | Oct 2022 | WO |
| Child | 18888351 | US |
