WO2012111739A1

WO2012111739A1 - Surface treatment method for metal member and metal member obtained by same

Info

Publication number: WO2012111739A1
Application number: PCT/JP2012/053635
Authority: WO
Inventors: 新吉田; 新村　仁; 生杉浦
Original assignee: アイシン軽金属株式会社; アイシン精機株式会社
Priority date: 2011-02-18
Filing date: 2012-02-16
Publication date: 2012-08-23
Also published as: JPWO2012111739A1; EP2677068A4; JP5878133B2; EP2677068A1; CN103392030A; US20130319868A1; CN103392030B

Abstract

[Problem] The purpose of the present invention is to provide a surface treatment method for a metal member which, while maintaining the metal texture of the surface of a metal member, improves surface characteristics of the metal member. Also provided is a metal member thus obtained. [Solution] The surface of an anodic oxide coating formed on a metal surface prior to sealing is brought into contact with a fluorine-based polymer solution, after which steam sealing is performed. Thus, the metal member obtained is characterized by having a fluorine-based polymer layer with a thickness of 100 nm or less, and a composite sealing treatment layer formed contiguously under the fluorine-based polymer layer and in which fluorine-based polymer has been filled into the pores of the anodic oxide coating.

Description

Surface treatment method for metal member and metal member obtained thereby

The present invention relates to a surface treatment method for an anodizable metal member and a metal member having improved surface characteristics.

A metal member made of aluminum and its alloy, magnesium and its alloy, titanium and its alloy, etc. is widely subjected to an anodic oxide film treatment for the purpose of improving corrosion resistance, improving design and the like.
However, the anodic oxide film alone may have insufficient corrosion resistance for long-term use.
There is also a problem that dirt easily adheres.
Furthermore, when there is a coloring step such as secondary electrolytic coloring after the anodizing treatment, there is a problem that the discoloration is large due to insufficient corrosion resistance of the anodized film.
As a countermeasure for this, in the field of aluminum building materials and the like, a clear coating by anion electrodeposition coating or the like is performed after anodizing treatment.
However, clear coating has a thick film thickness of 10 to 20 μm, so that the texture specific to the metal surface is impaired.
Therefore, in the field of decorative parts such as decorative trims in automobile parts, the texture of the metal surface is regarded as important and cannot be handled by conventional clear coating.
Therefore, a transparent fluororesin coating has been proposed that can ensure corrosion resistance with a thinner coating film than conventional acrylic clear coating and urethane clear coating.
Patent Document 1 discloses a technique for forming a PTFE (polytetrafluoroethylene) coating layer on the surface of an alumite film, which is intended to prevent wax rim bars.
However, according to the publication, the thickness of the coating layer of PTFE is 3 μm, so that a coating-like texture appears on the surface, and the primer coating or the enlarged pores of the anodized film Since it is described that the processing is necessary, the process is complicated and the processing cost becomes high.
Patent Document 2 discloses a process of immersing the amorphous fluororesin in a solution containing a hydrophilic amorphous fluororesin for the purpose of allowing the amorphous fluororesin to enter the pores of the anodized film, but it is not sufficient in quality alone. Preliminary heat treatment is performed, and a fluororesin layer must be polymerized and laminated thereon by heating at 200 ° C. for 30 minutes.
Therefore, the coating layer disclosed in the publication is also thick and has a coating-like texture, and when heated to a high temperature of 200 ° C., there is a problem that the anodized film is crisp.

Japanese Laid-Open Patent Publication No. 2006-257552 Japanese Unexamined Patent Publication No. 2006-126680

An object of the present invention is to provide a surface treatment method having improved surface characteristics while maintaining the metal texture of the surface of the metal member, and a metal member obtained thereby.

The surface-treated metal member according to the present invention is made of fluorine having a thickness of 100 nm or less by subjecting the surface of the anodized film formed on the metal surface to the surface of the anodized film before contact with the fluorine polymer solution and then subjecting the surface to a water vapor sealing treatment. It is characterized by having a system polymer layer and a composite sealing treatment layer continuously formed thereunder, in which a fluorine-based polymer has entered the pores of the anodized film.
The present invention includes those having an electrolytic coloring step after the formation of the anodized film, as long as the fluoropolymer solution is brought into contact before the sealing treatment and the water vapor sealing treatment is performed.

As a surface treatment of such a metal member, a step of forming a porous anodic oxide film on the metal surface, and a step of bringing the anodic oxide film into contact with a fluoropolymer solution in an unsealed or semi-sealed state; And a step of performing a water vapor sealing process thereafter.
Also in this case, an electrolytic coloring step may be provided between the step of forming the anodized film and the step of contacting with the fluoropolymer solution.

The present invention has a composite sealing treatment layer formed by water vapor sealing in a state in which a fluorine-based polymer has entered the pores of the anodized film from the viewpoint of emphasizing the metal texture of the metal surface. There is a feature, and the thickness of the fluorine-based polymer layer continuously formed thereon may be thin.
In order not to cause a coating-like texture to appear on the surface of the anodized film, the thickness of the fluoropolymer layer may be 100 nm or less, and preferably 10 nm or less.

The metal member applied to the present invention is a material that can form a porous anodic oxide film, and mainly includes aluminum, magnesium, titanium, and alloys thereof.
Further, the type of the anodized film is not particularly limited as long as it is porous, and the anodized film is anodized using a known electrolyte such as sulfuric acid or organic acid.
In the present invention, the term “before sealing treatment” means that before the sealing treatment with water vapor, including those washed with water after anodizing, those washed with hot water, and those half-sealed with hot water at 60 to 90 ° C. included.
Also included are those that are washed with water after anodization, electrolytically colored, and then washed with water and hot water.
Here, electrolytic coloring is before sealing treatment, and after the formation of the anodized film, DC electrolysis, AC electrolysis treatment, etc. are performed in an aqueous solution containing various metal ions such as nickel ions and tin ions, and metal ions are introduced into the pores. It means to precipitate.
In the present invention, the water vapor sealing treatment refers to a sealing treatment using normal pressure or pressurized water vapor.

The fluoropolymer used in the present invention is a fluoropolymer having a molecular weight that can be dissolved in a solvent to form a solution.
For example, polytetrafluoroethylene, copolymers of polytetrafluoroethylene such as ethylene-tetrafluoroethylene copolymer, polyvinyl fluoride and copolymers thereof, polyvinylidene fluoride and copolymers thereof, polychlorotrifluoroethylene and The copolymer etc. are mentioned as an example.
In addition, a fluoropolymer having a perfluoroalkyl group imparted with water repellency and oil repellency and improved antifouling property is also effective.
For example, polyperfluoroalkyl (meth) acrylate, poly 2- (perfluoroalkyl) ethyl (meth) acrylate, tetrafluoroethylene-perfluoroalkyl vinyl ether, polyperfluoroalkyl vinyl, poly 2- (perfluoroalkylethyl vinyl), etc. Is given as an example.
Here, the perfluoroalkyl group is preferably represented by CnF ₂ n + 1 (n = 1 to an integer of 1 to 6).

The solvent used in the present invention may be an organic solvent such as ketones such as acetone, MEK and MIBK, ethyl acetate, butyl acetate, diethyl ether, dioxane, ethanol, isopropyl alcohol, etc., but a fluorine-based polymer having high affinity with the fluorine-based polymer. Solvents are preferred.
In addition, fluorine-based solvents do not require special exhaust and explosion-proof equipment.
Examples of the fluorine-based solvent include perfluorocarbon, hydrofluorocarbon, hydrochlorofluorocarbon, hydrofluoroether, perfluoropolyether, hydrofluoropolyether and the like.
Further, in the present invention, contacting with the fluoropolymer solution means that any means such as dipping, spraying, brushing, etc. can be selected.

The surface-treated metal member according to the present invention has a composite sealing treatment layer in which a fluoropolymer has entered into the pores of the anodized film, so that it has excellent adhesion and is continuously formed on the fluoropolymer. Since the layer is as thin as 100 nm or less, a conventional film-like texture does not appear.
As a result, it has excellent long-term corrosion resistance, and the water- and oil-repellent properties of the fluorine-based polymer make it difficult to get dirt and can be easily cleaned simply by wiping.
In addition, in the case of electrolytic coloring, discoloration of the colored color tone can be suppressed by improving the corrosion resistance of the anodized film.

The preparation conditions of the test sample are shown. The evaluation result of a test sample is shown. An SEM image is shown. The component analysis result of a film cross section is shown. The evaluation result of the test sample colored secondary electrolytically is shown. The photograph after the test of a secondary electrolytic coloring film is shown.

Hereinafter, although the manufacture example of the metal member which concerns on this invention is demonstrated concretely, it is not limited to this.

The surface of an extruded profile (T5 material) produced by extrusion using JIS A6063 alloy was pretreated by buffing and chemical polishing.
Next, an anodized film having a thickness of 10 μm was formed on the metal surface by anodizing using an electrolytic solution of 15% sulfuric acid under conditions of a current density of 1 A / dm ² and a bath temperature of 20 ° C.
Example 1 was washed with water after forming the anodized film, and Example 2 was subjected to semi-sealing treatment (washing) at 80 ° C. for 10 minutes using pure water after forming the anodized film. Both were then dipped into a solution (Noda Screen Co., Ltd., trade name: OPC-800) in which a fluoropolymer was dissolved in a fluorosolvent and pulled up.
While Examples 1 and 2 were dipped into the fluoropolymer solution and pulled up, Example 3 sprayed this solution onto the surface.
Although the thickness of the fluoropolymer adhering to the surface of the treated product pulled up after dipping cannot be measured, it was estimated to be about 10 nm level.
In Examples 1 to 3, the sealing process was performed for 20 minutes using steam at 150 ° C.
The water vapor sealing treatment condition may be normal pressure, but the sealing time is relatively long. Therefore, it is preferable to carry out the sealing treatment for 10 to 30 minutes using water vapor pressurized to 130 to 180 ° C. .
For comparison, in Comparative Example 1, boiling water was sealed at 100 ° C. for 20 minutes using pure water after the formation of the anodized film.
In Comparative Example 2, a primer for a fluororesin was applied after the sealing treatment of Comparative Example 1, and then dipped into the fluoropolymer solution and dried.
Comparative Example 3 was the same as Example 2 up to the step of dipping into a fluoropolymer solution, and then dried without a water vapor sealing treatment.
In Comparative Example 4, after the formation of the anodized film, the same process as in Example 2 was carried out until dipping into the fluorine-based polymer solution, and then boiling water was sealed with pure water at 100 ° C. for 20 minutes.
The samples obtained in Examples 1 to 3 and Comparative Examples 1 to 4 were visually evaluated for appearance, and then a 200 Hr salt spray test was performed based on JIS Z 2371 to measure the color difference before and after the test (color). Color difference meter: CR-400 manufactured by KONICA MINOLTA).
The table of FIG. 1 shows the test sample preparation conditions, and FIG. 2 shows the evaluation results.
In the table of FIG. 1, DIP means dipping.
As a result, any of the test samples of Examples 1 to 3 maintained the texture of the metal surface as it was, and no surface change was observed before and after the salt spray test.
On the other hand, the surface of Comparative Example 1 was slightly whitened, and Comparative Example 2 was observed after the primer, and the texture was inferior.
Since Comparative Example 3 was not dipped into a fluorine-based polymer solution and then steam sealed, whitening (discoloration) was observed in the salt spray test.
In Comparative Example 4, boiling water sealing was carried out after dipping in a fluoropolymer solution, and the surface was slightly whitened.
From this, it became clear that dipping or spraying the fluorine-based polymer solution to the fluorine-based polymer solution is insufficient and the subsequent water vapor sealing treatment is effective.

Next, the cross section of the test sample according to Example 2 was observed with an SEM and the components were subjected to semi-quantitative analysis.
The results are shown in the photograph of FIG. 3 and the table of FIG.
JSM-7000FZ made by JEOL was used for the scanning electron microscope, and EX-2300 × BU made by JEOL was used for semi-quantitative analysis of the components.
FIG. 3 shows an SEM photograph.
FIG. 4 shows component analysis values for the surface, the upper section and the lower section of FIG.
As a result, the thickness of the fluoropolymer layer on the surface was so thin that the thickness could not be measured. However, since fluorine was deposited on the upper part of the cross section of the anodized film, fluorine also entered the pores of the anodized film. It was confirmed that a composite sealing layer was formed.
In order to confirm the influence due to the presence or absence of electrolytic coloring, the same as in Example 1 except that, after forming an anodized film as Example 4, it was washed with water, subjected to secondary electrolytic coloring of a mixed bath system of nickel and tin, and colored black. A similar salt spray test was performed using the treated specimens.
Further, as Comparative Example 5, the same boiling water sealing treatment as in Comparative Example 1 was performed without contacting the fluoropolymer solution after the secondary electrolytic coloring.
The measurement results of the color difference before and after this test are shown in FIG.
Moreover, the photograph after the test of Example 4 and Comparative Example 5 is shown in FIG.
As a result, it was possible to improve the corrosion resistance while maintaining the metal texture on the surface by forming a fluorine-based polymer layer in the secondary electrolytically colored anodic oxide film and subjecting it to water vapor sealing treatment.

The present invention is a surface treatment method suitable for a metal member capable of forming a porous anodic oxide film, and can be applied to many fields such as automobile parts as long as it is a field using such a metal member.

Claims

The surface of the anodized film formed on the metal surface before the sealing treatment is contacted with the fluorine-based polymer solution and then subjected to the water-vapor sealing treatment, so that the fluorine-based polymer layer having a thickness of 100 nm or less is continuously formed thereunder. A surface-treated metal member, comprising: a composite sealing treatment layer formed by fluorinated polymer infiltrating into the pores of the anodized film.
The surface-treated metal member according to claim 1, wherein the anodized film before the sealing treatment is electrolytically colored after the anodizing treatment.
Forming a porous anodized film on the metal surface;
Contacting the anodic oxide film with a fluoropolymer solution in an unsealed or semi-sealed state;
And a step of performing a water vapor sealing process thereafter.
4. The surface treatment method for a metal member according to claim 3, further comprising a step of electrolytically coloring between the step of forming the porous anodic oxide film and the step of contacting with the fluoropolymer solution.