JPH05104674A - Surface-treated metallic material excellent in corrosion resistance and formability - Google Patents

Abstract

PURPOSE:To provide a surface-treated metallic material excellent in corrosion resistance which has good surface-lubricating property and formability. CONSTITUTION:While the plated layer of Zn or Fe with coated weight of at least 0.1g/m<2> is formed on the surface of metallic material, at least 20% of the surface of the plated layer is covered with the organic film of cellulose.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-treated metal material having improved corrosion resistance and press formability, which is useful as an outer plate material for vehicles such as automobiles and household electric appliances, a construction material and the like. ..

[0002]

2. Description of the Related Art Steel materials, Al alloy materials and the like are widely used in a wide range of fields such as outer plate materials for automobiles and household electric appliances and construction materials. In most cases, these metal materials are processed into various shapes according to their applications by press molding or the like. Therefore, the metal materials are required to have excellent moldability and corrosion resistance from the viewpoint of improving durability. Is also an important required property.

[0003]

Among the metal materials, Al or Al alloy materials are attracting attention for their light weight, and the demand for them has been rapidly increasing recently for the purpose of reducing fuel consumption and exhaust gas by reducing the weight of the vehicle body. However, there is a problem that the press formability is inferior to that of cold rolled steel. Moreover, since the Al alloy material has a stable passivation film made of an oxide formed on the surface, it has poor chemical conversion treatment properties such as phosphate treatment, which is performed as a pre-painting treatment, so that satisfactory post-painting corrosion resistance can be obtained. It is hard to be caught.

On the other hand, in the case of steel materials, the chemical conversion treatability has been improved by the development of various surface treatment methods, the corrosion resistance after coating has been considerably improved, and the press formability has also been improved.
The demands of consumers are unceasing, and further improvements in moldability and corrosion resistance are required to improve productivity and quality of final products.

The present invention has been made by paying attention to the above circumstances, and its purpose is to form various metal materials such as Al or Al alloys and steel materials by press forming and the like. In addition to improving the corrosion resistance, it aims to establish a technology that can further improve the corrosion resistance.

[0006]

The constitution of the surface-treated metal material according to the present invention, which was able to solve the above-mentioned problems, is such that a Zn-based or Fe-based plated layer of 0.1 g / m ² or more is formed on the surface of the metal material. And the surface of the plating layer is covered with a cellulose-based organic film in an amount of 20% or more. The organic film in the present invention is applied to a metal material before molding for the purpose of improving moldability, primary rust prevention, etc., and is generally applied as a final top coat paint after molding. It is different from the organic paint of.

[0007]

The present inventors examined factors affecting various metal materials on formability from various angles. as a result,
It was confirmed that a metal material that is poorly press-molded has a poor surface lubrication retention ability under high surface pressure, which is a major cause of insufficient formability. Therefore, in order to improve the formability, it is desired to modify the surface layer portion such that the surface layer retains the lubricity even under a high surface pressure, like a work material.

Further, in order to impart a high corrosion resistance to a metal material, it is not enough to simply coat the surface of the metal material with a plating film as in the conventional example, and a substance formed on the surface of the metal material in a corrosive environment (corrosion reaction product It has been found that it is extremely important to stably retain the above) as a protective film as it is on the surface of the metal material.

Therefore, based on such knowledge, as a result of further research on an inexpensive surface treatment method capable of improving the formability and corrosion resistance more effectively, as a result, Zn
If a system-based or Fe-based plating layer is formed and the surface of the plating layer is coated with a cellulose-based organic film,
It was found that a high level of lubricity is maintained even under high surface pressure and excellent formability is secured. Moreover, the corrosion product generated by the corrosion reaction of the Zn-based or Fe-based plated layer is stably held by the organic film, and as a result, the dense protective film is stably held on the substrate surface, and the corrosion resistance is remarkable. To be enhanced.

That is, the cellulosic organic film formed on the surface of the plating layer has a network structure peculiar to the organic polymer, and the hydroxide which is a corrosion reaction product of the Zn or Fe plating layer on the lower side thereof It has the function of holding oxides stably. Therefore, the metal base material is covered with the protective film when the dense corrosion reaction product is generated. Moreover, since the Zn-based or Fe-based plated layer becomes a dense hydroxide-based corrosion product having a smaller electric conductivity in a humid atmosphere, the corrosion reaction is stopped at this point, and the corrosion resistance is remarkably enhanced. ..

Further, when the metal base material is Al or an Al alloy, the surface thereof is covered with the stable passivation film as described above, and the chemical conversion treatment performed as a pretreatment for coating is lacking. However, if the Zn-based or Fe-based plated layer is formed as described above, the chemical conversion treatment property is enhanced, and the chemical conversion treatment film generated by the chemical conversion treatment is stably retained by the cellulose organic coating, and as a result, the surface Adhesion with the coating film applied to is improved and the corrosion resistance after coating is also significantly improved.

In order to effectively bring out the above-mentioned effects, the deposition amount of the Zn-based or Fe-based plated layer must be set to 0.1 g / m ² or more, as will be made clear in the examples below.
If it is less than this value, it becomes difficult for a dense corrosion product to be formed on the entire surface of the metal substrate, and pinhole defects are likely to occur,
Corrosion resistance becomes insufficient. Moreover, when it is applied to an Al or Al alloy substrate, the chemical conversion treatability becomes insufficient, and the adhesion of the coating film after chemical conversion treatment and the corrosion resistance after coating cannot be sufficiently improved. A more preferable adhesion amount of the Zn-based or Fe-based plated layer is 1 g / m ² or more. There is no particular upper limit to the coating amount of the plating layer, but an excessively large coating amount is not only economically wasteful but also may cause a decrease in the adhesion of the plating layer. / m ² or less, more preferably 50 g / m ² or less.

Further, in order to effectively exhibit the above-mentioned effects of the cellulose-based organic film, the coverage of the film must be 20% or more, and if the coverage is less than that, the effect of improving the moldability cannot be sufficiently exhibited. Not only is the retention effect of the corrosion products insufficient, it becomes difficult to obtain satisfactory corrosion resistance. In order to secure excellent moldability and corrosion resistance, the coverage of the cellulose-based organic film is more preferably 5
It is 0% or more.

The Zn-based or Fe-based plating may be Zn or Fe alone plating, Zn-Fe alloy plating containing Zn and Fe in various ratios, or Zn, Fe, Ni, Cr, Mn, Co, etc. Metals or non-metals such as B and P, as well as SiO ₂ , Al ₂ O ₃ and Al (OH) ₃
It includes various composite platings including the above, and these can be appropriately selected and determined according to the required characteristics of the plating layer. The plating method is also not particularly limited, and wet plating methods such as chemical plating, displacement plating, electroless plating and electroplating, dry plating methods such as vapor deposition plating, CVD method and ion plating method, or a combination thereof can be used. It is possible.

Examples of the cellulose-based organic film include acetyl cellulose, cellulose propionate, cellulose butyrate, and nitrocellulose. Of these, the most common is acetyl cellulose. The method for forming the organic film is not particularly limited, and the P method such as the dipping method, the roll coating method, the spray coating method, or the vapor deposition method is used.
The VD method or the like can be appropriately adopted.

The most common metal materials to which the present invention is applied are steel materials and Al or Al alloys as described above, but the materials are not limited to these, and C
The present invention can be applied to metals such as u, Ni, Sn, and Mg, or alloys thereof, and the shape thereof is also applicable to wire rods, rods, pipes, and the like in addition to the most general plate material.

[0017]

EXAMPLES The constitution and effects of the present invention will be specifically described below with reference to examples, but the present invention is not limited to the examples below. Steel plates (aluminum killed steel) and Al alloy plates (Al-Mg) as metal substrates
System) is used to form a Zn-based or Fe-based plating as shown in Table 1, and then an acetylcellulose-based organic film is formed thereon by a dipping method. The press formability and corrosion resistance were evaluated by the method. The results are shown in Table 1.

<Press Formability> Evaluation was made by the maximum drawing load by the Erichsen cylindrical deep drawing test. ○ Excellent: Cold rolled steel sheet or less △ Good: Equivalent to cold rolled steel sheet × Inferior: Cold rolled steel sheet or more <Corrosion resistance> Evaluated by the red rust occurrence time by a salt spray test.

[0019]

[Table 1]

From Table 1, the following can be considered. N
Examples 1 to 7 are examples satisfying all the requirements of the present invention, and both press moldability and corrosion resistance are good. On the other hand, Nos. 8 to 15 are comparative examples lacking any of the prescribed requirements of the present invention, and as described below, either press moldability or corrosion resistance is insufficient.

No. 8, 13, 15: The press-formability is particularly poor because the coverage of the cellulosic organic film is insufficient. No.9: Both the press moldability and the corrosion resistance are poor because the cellulose-based organic film is not formed. No.10: Neither the plating layer nor the cellulose-based organic film was formed, and both press moldability and corrosion resistance were very poor. No.11: Corrosion resistance is poor due to insufficient adhesion of the plating layer. No.12,14: Polyolefin-based organic film other than cellulose is formed, but press formability is poor due to lack of surface lubricity.

[0022]

The present invention is constituted as described above, and a Zn-based or Fe-based plated layer is formed on the surface of a metal substrate so as to have a predetermined adhesion amount or more, and the surface is coated with a cellulose-based organic material. By coating with a film at a predetermined coverage, it is possible to provide a surface-treated metal material having excellent formability and corrosion resistance.

Claims (1)

[Claims] 1. A Zn- or Fe-based plating layer of 0.1 g / m ² or more is formed on the surface of a metal material, and the surface of the plating layer is covered with a cellulose-based organic film in an amount of 20% or more. A surface-treated metal material with excellent corrosion resistance and moldability.