JPH07173684A - Surface treatment of metallic aluminum material - Google Patents

Abstract

PURPOSE:To form an anodic oxide film enhanced in surface hardness and excellent in wear resistance by chemically or electrochemically forming a film on a metallic aluminum material and anodizing the obtained film. CONSTITUTION:A metallic aluminum material with the surface cleaned, as required, by buffing, etc., is dipped in a chemical processing agent or cathodized in an electrolyte to form the film of the metal oxide, etc., on the material surface. The film-coated material is anodized with aq. sulfuric acid, oxalic acid, etc., as an electrolyte to form an anodized aluminum film on the film.

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 an anodized film on the surface of a metallic aluminum material, and more particularly to a method for forming an anodized film having excellent wear resistance and high surface hardness.

[0002]

2. Description of the Prior Art Metallic aluminum materials are lightweight, have excellent mechanical strength, and have a unique metallic luster on the surface.
Since it can be finished in various colors and gloss, it is used in various fields such as building board materials, building sashes, vehicle chassis materials, vehicle parts materials, machine parts materials and other household appliances materials. It is a material. However, when the aluminum metal material is used in the above-mentioned various fields, it is not only oxidized and rusted to lose its luster unless it is subjected to an appropriate surface treatment, but also the corrosion reaches the material body and the machine. The physical strength is deteriorated. In fact, products using metallic aluminum materials are
Surface treatment is carried out at the material stage or the product stage to prevent surface oxidation and rusting. There are many methods for such surface treatment, and electrochemical methods include, for example,
Examples thereof include anodic oxidation, electroplating, electrolytic color development, and other non-electrochemical methods include chemical treatment, coating, metallikon, and the like.

Recently, for the purpose of weight saving and energy saving, more and more various structures and products are required to be lighter. For example, it is a characteristic item required in various fields such as weight reduction of motor shafts and weight reduction of fire protection equipment for high-rise buildings. Therefore, metallic aluminum materials are becoming more and more important. When a metal aluminum material is used for a motor shaft for the purpose of weight reduction, surface treatment of the material is required not only to prevent surface oxidation and rusting but also to improve surface abrasion resistance. Conventionally, as an excellent surface treatment to prevent surface oxidation and rusting of metallic aluminum materials, electrochemically performed anodization treatment of the material surface has been widely used, but at present, abrasion resistance of anodized film Is not at a sufficiently satisfactory level, and further improvement is required.

The present inventors have conducted diligent research to form a film chemically or electrochemically on the surface of a metal aluminum material in advance, and then carry out anodizing treatment using the metal aluminum material having the film as an anode. As a result, they have found that the wear resistance of the anodized surface of the metallic aluminum material is significantly improved, and have reached the present invention.

[0005]

An object of the present invention is to solve the drawbacks of the conventional surface anodizing method for metallic aluminum materials, and to provide an anodized film having high surface hardness and excellent abrasion resistance. It is to provide a method of forming.

[0006]

The above object can be achieved by the method for surface treating a metallic aluminum material according to the present invention.
That is, 1) A surface treatment method for metallic aluminum, which comprises chemically treating the surface of a metallic aluminum material and then performing anodizing treatment on the coating. Or
2) A surface treatment method for a metal aluminum material, which comprises electrochemically subjecting the surface of the metal aluminum material to a film treatment, and then performing anodizing treatment on the film.

The structure of the present invention comprises three processes. These processes will be described for the case where the metallic aluminum material is in the form of a plate. The technical idea of the treatment method of the present invention does not change even if the metallic aluminum material is in the form of a plate, a block or other complicated product state. The surface treatment method of the metal aluminum plate of the present invention is as follows. First, the process (1) performs surface buffing, degreasing treatment, degreasing treatment and etching pretreatment if necessary, and then process (2-1) immersing the metal aluminum plate in a chemical treatment agent, Form a film chemically on the surface. Alternatively, in the process (2-2), electrolytic treatment is performed using the electrolytic apparatus shown in FIG. The metal aluminum plate 2 is used as a cathode in most cases, and a platinum plate 3 is used as a counter electrode. After the above-mentioned treatment, the metal aluminum plate is anodized according to the usual process (3). The process (2-
In the electrolysis apparatus of FIG. 1 used in 2), 1 is an electrolytic cell,
2 is a metal aluminum plate, 3 is a platinum plate used as a counter electrode, 4 is an ammeter, 5 is a rectifier, 6 is a voltmeter, and 7 is a power supply. The above series of processing of the metallic aluminum material is the essence of the processing method of the present invention.

[0008]

[Function] The metal aluminum material is processed (2-
When chemically or electrochemically treated by 1) and (2-2), a film is formed on the surface of the material in many cases,
Thereby the material is colored. When the colored metal aluminum material having such a surface coating is immersed in an acidic electrolytic solution and subjected to an anodic electrolytic treatment by energizing, an alumite coating grows over the coating. As the alumite coating grows, the color of the deposited coating fades. This is because the colored film is covered with the alumite film. At that time, although the mechanism has not been sufficiently clarified, it has been confirmed that the hardness of the alumite coating on the surface of the metallic aluminum material increases as the coloring density decreases, and the abrasion resistance is improved by an abrasion test. Even when coloring is not seen on the material surface chemically by the surface treatment or the cathodic electrolytic treatment as described above, when the anodized film is continuously grown and the alumite film is grown, the alumite film on the surface of the material is formed. The hardness increases.

Usually, when chemically treating a surface of a metal aluminum material, the surface is cleaned by buffing or chemical etching in advance, but it is not an essential treatment. Also,
The metallic aluminum material may be electrochemically cleaned by cathodic electrolysis in an electrolytic degreasing solution. The metallic aluminum materials targeted by the present invention include, in addition to pure metallic aluminum, aluminum-copper, aluminum-zinc, aluminum-magnesium, aluminum-silicon, aluminum-copper-
Aluminum and aluminum alloy materials such as aluminum-nickel alloys are also included.

As an example of chemically surface-treating the metallic aluminum material, there may be mentioned a treatment example of a chemical film described on pages 864 to 873 of Aluminum Handbook (Light Metal Association, Asakura Shoten, 1965 edition). For example, MBV method, EW method, LW method, Allock method, Ji
The rotka method and the like can be mentioned. By the above method, chromium oxide, molybdenum oxide, on the surface of the metallic aluminum material,
A chemical film of copper oxide, cobalt oxide, zinc oxide, silicon oxide or the like can be formed.

As a specific method of subjecting the metallic aluminum material to cathodic electrolysis, for example, an electrolytic apparatus having a structure as shown in FIG. 1 is used to form a film of a metal oxide such as a molybdenum compound or a chromium compound in an electrolytic cell. When an electrolytic solution containing a heavy metal compound to be formed is added and electrolysis is performed using a metal aluminum material (having a pH value of 3 to 8) as a cathode, an oxide film of those metals is formed on the surface of the sample. In the present invention, the electrolyte is a salt such as a water-soluble molybdenum compound or a chromium compound for adjusting the electric conductivity of the electrolyte and an acid, an alkali or a salt for adjusting the pH value, and other stabilizers or colors. Preparations have been added.

Examples of salts for controlling electric conductivity include sulfate, nitrate, hydrochloride, oxalate, phosphate,
Various ion-conducting salts such as sulfite and nitrite can be mentioned, but the salt is not particularly limited as long as it has electric conductivity. Also, two or more of these may be mixed and used. Examples of acids, alkalis and salts for adjusting the pH value include inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid, oxalic acid, phosphoric acid, boric acid, metaboric acid, succinic acid, sulfosuccinic acid, tartaric acid and citric acid. Acids and organic acids, caustic soda, caustic potash, sodium carbonate, borax, sodium thiocyanate, ammonia, etc. for alkalis, and ammonium chloride for salts,
Glauber's salt, salt, sodium phosphate, potassium phosphate and the like can be mentioned, but combinations showing a buffering action are also used. Therefore, if many additives are used and they are water-soluble, they are not particularly limited. The electrolytic current may be any of direct current, alternating current, and AC / DC superimposed flow, but AC / DC superimposed flow is preferable. There are various AC / DC superposed flows, but those with superposed sine wave alternating current,
A rectangular wave with a direct current superimposed and a bias applied to either the yin or the yang is appropriately used.

In the process (2-1) and the process (2-2), the metal whose surface is formed by chemically surface-treating the aluminum metal material or by electrochemically performing cathodic electrolysis on the material. The aluminum material is washed with water and, if necessary, subjected to a pore-sealing treatment, and an alumite-forming treatment is carried out in the usual manner using the metal aluminum material as an anode.
The electrolytic current may be DC, AC, or AC / DC superposed flow, but the thickness of the alumite coating is adjusted by adjusting the waveform, current density, voltage and electrolysis time.

In the alumite formation treatment, the electrolytic solution is an aqueous solution of 5 to 30% sulfuric acid, oxalic acid, phosphoric acid, a mixed solution of sulfuric acid and oxalic acid, a mixed solution of sulfuric acid and an organic acid such as sulfosuccinic acid. Is used. An electrode made of aluminum, carbon, stainless steel or the like is used for the counter electrode. Generally, the electrolytic voltage is 10 as the condition of the alumite treatment.
˜80 V, and the electrolytic current density is 0.5 to 5 A / dm ² . The temperature during the electrolytic treatment is adjusted between 5 ° C and 25 ° C. The surface hardness of the alumite coating is Vickers hardness (Hv), and the abrasion resistance is represented by the number of masatsu (DS / μm) required to wear 1 μm.

[0015]

EXAMPLES The present invention will be described below with reference to examples.
However, it goes without saying that the following examples are intended to deepen the understanding of the present invention and are not intended to limit the present invention. Example 1 1. Zinc plating with double zincate [Example of the above process (1)] An aluminum plate (A1100) was washed with diluted NaOH,
It is dipped in the following plating solution for 30 seconds at room temperature for galvanizing. Caustic soda 120 g / l Zinc oxide 20 g / l Ferric chloride (water-containing) 2 g / l Rochelle salt 50 g / l Sodium nitrate 1 g / l After immersion, rinse with water and immerse in 1: 1 HNO ₃ solution for 10 seconds to remove zinc plating To do. Repeat this process once more. A small amount of galvanized layer with good adhesion remains on the aluminum plate.

2. Precipitation of Molybdenum Oxide [Example of Process (2-2) Above] 1. The double zincate-treated aluminum plate of No. ² is immersed in the following treatment solution and subjected to cathodic electrolysis at a DC current density of 2.3 V and 0.02 A / dm ² . (60 ° C., pH 4 to 5) A cathode electrolytic film is deposited on the aluminum plate of the cathode. As the amount of film increases, the color of the film goes through purple → yellow → red → green → orange, turns brown after 2 minutes, and finally becomes black. The film is thin (1 μm) and soft (Hv 100 or less). Ammonium molybdate 20 g / liter Magnesium sulfate 80 g / liter 3. Alumite film formation [Example of the above-mentioned process (3)] 2. After washing the aluminum plate having the molybdenum oxide cathodic electrolytic coating of No. 1 with water, anodizing treatment was performed at 20 ° C for 30 minutes at a current density of 3 A / dm ^{2 using} a 10% sulfuric acid aqueous solution as an electrolytic solution. The final anodized film (alumite film) has a thickness of 30 μm, hardness of Hv450, wear resistance D
The S / μm was 400.

Comparative Example 1 [Example omitting the above-mentioned process (2-1) or process (2-2)] An aluminum plate (A1100) galvanized by double zincate or a cleaned aluminum plate was used as described above. Immediately after washing with water without performing electrolytic deposition treatment of molybdenum oxide, anodizing treatment was immediately performed at 20 ° C. with a 10% sulfuric acid aqueous solution as an electrolytic solution at a current density of 3 A / dm ² for 30 minutes. The hardness of the final anodized film is Hv
The abrasion resistance DS / μm was 300 and the abrasion resistance DS / μm was 200.

Example 2 [Example of processes leading from (2-2) to (3) above] Under the same conditions as in Example 1 for the aluminum plate (A1100) galvanized by the double zincate. A molybdenum oxide cathodic electrolytic film is formed and washed with water, and a mixed aqueous solution of sulfosuccinic acid 70 g / liter and 6 g / liter sulfuric acid is used as an electrolytic solution at 3 A / dm ^2.
Anodizing treatment was performed for 30 minutes at the current density of. The final anodized film (alumite film) had a film thickness of 25 μm, a hardness of Hv600, and an abrasion resistance DS / μm of 450.

Example 3 [Example of the process from (2-1) to (3) above] For an aluminum plate (A1100), sodium carbonate 2 was used.
%, An aqueous solution containing 1% of sodium chromate was used to form a chromium oxide film by the MBV method at 90 ° C. for 5 minutes. After washing the aluminum plate having the chromium oxide chemical conversion coating by the MBV method with water, anodizing treatment was performed at 20 ° C. with a 10% sulfuric acid aqueous solution as an electrolytic solution at a current density of 3 A / dm ² for 30 minutes. The final anodic oxide film (alumite film) has a thickness of 30 μm, hardness of Hv400, wear resistance DS
/ Μm was 300.

[0020]

INDUSTRIAL APPLICABILITY A metallic aluminum material is produced by the surface treatment method of the present invention in which an anodizing treatment is performed on a metallic aluminum material having a surface coating made of a heavy metal oxide or a silicon oxide by chemical treatment or cathodic electrolytic treatment in advance. It is possible to obtain a metal aluminum plate which is excellent in surface hardness and abrasion resistance as compared with the conventional anodized metal aluminum material by forming an alumite coating on the aluminum plate.

[Brief description of drawings]

FIG. 1 is an explanatory view of an electrolytic treatment apparatus used for producing a metal surface coating of the present invention.

[Explanation of symbols]

 1 Electrolyzer 2 Metal Aluminum Plate 3 Platinum Plate 4 Ammeter 5 Rectifier 6 Voltmeter 7 Power Supply

Claims (2)

[Claims] 1. A method for surface treatment of a metallic aluminum material, which comprises chemically treating the surface of the metallic aluminum material and then performing anodizing treatment on the coating. 2. A method for treating a surface of a metallic aluminum material, which comprises electrochemically subjecting the surface of the metallic aluminum material to a coating treatment, and then performing anodizing treatment on the coating.