JPH0557239A - Aluminum surface treated plate superior in spot weldability and electrodeposition coating property - Google Patents

Abstract

PURPOSE:To improve the spot weldability and the electrodeposition coating property by eliminating an adverse effect on a phosphation treatment of a steel plate by providing a chemical conversion coating layer on an Al or Al alloy plate surface and forming a film layer consisting of an organic resin incorporating an electrically conductive material on it. CONSTITUTION:On the surface of Al or an Al alloy plate, a chemical conversion coating layer to increase an adhesive strength with an organic resin formed on it and a corrosion resistance is provided. A film layer consisting of the organic resin incorporating electrically conductive material powder having <=5X10<10>OMEGAcm of the electric specific resistance is formed on it. By combining the Al surface treated plate with a steel plate member, elution of Cr ions and Zr ions is prevented after a phosphation treatment, when it is subjected to a phosphation treatment according to the treating process of a steel plate, and the effect of a chromate film is kept on the later coating and also elution of Al ions is prevented, and the spot weldability of the plate and the electrodeposition coating property are also improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum surface-treated plate which is excellent in spot weldability and electrodeposition paintability, and more particularly to an aluminum surface-treated plate suitable as an automobile body panel material.

[0002]

2. Description of the Related Art Recently, studies are being made on the use of aluminum for automobile body panels. Some have already been put to practical use, and future development is expected as a major field of application of aluminum materials. The material performance required for automobile body panels is that they have excellent press formability, spot weldability, paint corrosion resistance, and paint appearance. The surface treatment process that satisfies the above performance has been established. However, the fact is that the surface treatment of aluminum plates for body panels has not been sufficiently studied.

For example, in JP-A-61-96074, an aluminum plate is chromated and then combined with a steel plate,
Degreasing the combined product → Surface preparation → Phosphate treatment →
A procedure has been proposed in which the treatment is performed according to the steel plate treatment process consisting of electrodeposition coating → intermediate coating → top coating.However, in this method, chromium ions are eluted from the chromate coating into the phosphate treatment liquid, and the phosphate coating on the steel sheet There is a problem that it adversely affects the formation.

Further, an aluminum / iron simultaneous treatment method has been proposed, in which a steel sheet member is assembled to a press-formed aluminum alloy body panel and then the steel sheet is directly treated in the treatment step of the steel sheet without chromate treatment. However, according to this treatment method, aluminum ions are eluted in the phosphating solution to increase the aluminum ions in the solution, which tends to inhibit the formation of the phosphate film on the aluminum alloy plate and the steel plate. There is.

[0005]

DISCLOSURE OF THE INVENTION The present invention aims to provide an aluminum surface treated plate which can solve the above-mentioned conventional problems during treatment and has a surface texture excellent in spot weldability and electrodeposition coating property. To aim.

[0006]

An aluminum surface-treated plate excellent in spot weldability and electrodeposition paintability according to the present invention for achieving the above object is provided with a chemical conversion treatment layer on the surface of an aluminum or aluminum alloy plate, A structural feature is that a film layer made of an organic resin containing a conductive substance is formed on the chemical conversion treatment layer.

In the present invention, the chemical conversion treatment layer provided on the surface of the aluminum or aluminum alloy plate is for increasing the adhesion with the organic resin formed thereon and the corrosion resistance, and is a reactive or coating type chromic acid. It is formed as a layer such as a chromate film, a chromate phosphate film, a non-chromium type chemical conversion film.

The coating layer formed on the chemical conversion treatment layer is preferably made of an organic resin containing a powder of a conductive substance having an electric resistivity of 5 × 10 ¹⁰ Ωcm or less. Examples of such conductive substances include metals such as zinc and nickel, metal salts such as strontium chromate and zinc chromate, iron phosphide, tungsten disulfide, and graphite. Of these, tungsten disulfide and graphite are also useful for improving the press formability of plate materials. As an organic resin,
For example, epoxy resin, epoxy ester resin, acrylic resin, oil-free alkyd resin, urethane resin,
Alternatively, a resin obtained by mixing two or more of these resins is used.

[0009]

In the case of a chromate film, when an aluminum surface-treated plate having two coating layers formed according to the present invention is assembled with a steel plate member and a phosphate treatment is carried out according to the treatment process of the steel plate, the organic resin film layer on the surface serves as a barrier. Prevents chromium ions and, in the case of non-chromium type conversion coatings, zirconium ions from eluting into the phosphating solution, and maintains the effect of the chromate coating on subsequent coating. Moreover, the two coating layers completely prevent the elution of aluminum ions. Furthermore, since the organic resin film layer contains a conductive substance, the spot welding property and the electrodeposition coating property of the plate material are improved.

[0010]

EXAMPLES Examples of the present invention will be described below in comparison with comparative examples.

Examples 1 to 9 and Comparative Examples 1 to 3 A5182 alloy plates (thickness 1 mm) were prepared, immersed in a 10% sulfuric acid solution at 50 ° C. for 2 minutes for pretreatment, washed with water and dried. Each sample was subjected to a chemical conversion treatment under the following conditions, and an organic resin containing a conductive substance was applied to the layer surface to form a coating layer.

Chemical conversion treatment: (1) Reactive chromate treatment Chromate chromate treatment agent (manufactured by Nippon Paint Co., Ltd.,
It was immersed in a 0.1% solution of "Alsurf 1000"] at a temperature of 40 ° C. By changing the dipping time, the amount of chromium in the chromate coating was changed within the range of 10 to 30 mg / m ² . (2) Coating-type chromate treatment A coating-type chromate treatment agent [Nippon Paint Co., Ltd., "Surfcoat NRC-5000"] was diluted with water and coated with a bar coater to a predetermined amount of chromium, then 180 ° C And dried for 1 minute. (3) Non-chromium type chemical conversion treatment A non-chromium chemical conversion treatment agent comprising a composition of polyacrylic acid (average degree of polymerization: 500) and zircon hydrofluoric acid in a weight ratio of 1: 1 [Nippon Paint Co., Ltd., "Surf The coat "] was diluted with water, a predetermined amount was applied with a percoder, and dried at 180 ° C for 1 minute.

Application of organic resin: The organic resin shown in Table 1 was used. The conductive substance was made into a powder form and dispersed in an organic resin at a predetermined ratio to obtain a primer composition. Each primer composition was applied to a chemical conversion treated sample with a bar coder and baked at 180 ° C. for 1 minute. The details of the test conditions are shown in Table 2.

[0014]

[Table 1] Table Note: (1) Asahi Denka Kogyo Co., Ltd. (2) Dainippon Ink and Chemicals Co., Ltd. (3) Sumitomo Bayer Urethane Co., Ltd.

[0015]

[Table 2]

A spot welding test and an electrodeposition coating test were conducted on the sample on which the chemical conversion treatment layer and the organic resin film layer were formed. Spot welding uses a three-phase low frequency spot welding machine, electrode chromium copper alloy, welding current 2.2kA
The energization time was 0.083 seconds and the welding pressure was 300 kgf. The electrodeposition coating was performed by a conventional cationic electrodeposition coating. The test results are shown in Table 3.

The judgment of the spot weldability shown in Table 3 is based on the following criteria. ○: Shear strength of 250 kgf / spot or more with little electrode wear △: Shear strength of 170 to 250 kgf / spot with normal electrode wear ×: Shear strength of less than 170 kgf / spot with severe electrode wear Also, electrodeposition coating To determine the sex, the appearance was visually inspected and displayed according to the following criteria. ◯: Yuzu haze and no clettering Δ: Yuzu haze and little cletering x: Unpaintable

[0018]

[Table 3]

From the results shown in Table 3, each of the aluminum surface-treated plates according to the examples of the present invention exhibits excellent spot weldability and electrodeposition coatability. On the other hand, when the organic resin film layer did not contain a conductive substance, the spot weldability and the electrodeposition coatability were poor, and some electrodes could not be electrodeposited.

[0020]

As described above, the aluminum surface-treated plate according to the present invention does not elute chromium ions and aluminum ions into the zinc phosphate bath and does not adversely affect the zinc phosphate treatment of the steel sheet. It has excellent spot weldability and electrodeposition coating properties, and is extremely suitable as an automobile body panel material.

Claims (2)

[Claims] 1. A spot-weldability and an electrodeposition coatability obtained by providing a chemical conversion treatment layer on the surface of an aluminum or aluminum alloy plate, and forming a coating layer made of an organic resin containing a conductive substance on the chemical conversion treatment layer. Excellent aluminum surface treatment plate. 2. The conductive material has an electric resistivity of 5 × 10 ¹⁰ Ωcm.
The aluminum surface-treated plate excellent in spot weldability and electrodeposition coating property according to claim 1, which is the following powder substance.