JP3068690B2 - Surface treatment method for metallic materials with excellent paint adhesion - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating a metal material having excellent paint adhesion, and more particularly to a method for improving the adhesion of paint when coating a metal material. It is.

[0002]

2. Description of the Related Art In recent years, in many cases, metallic materials have been used by painting the surface in order to improve the corrosion resistance or coloring the surface from the viewpoint of diversification.

[0003] Generally, metal materials are used as a pretreatment for painting.
Phosphoric acid treatment or chromic acid treatment (chromate treatment) is usually performed after degreasing and pickling activation, but as a special case, a method using a silane coupling agent is known (Japanese Unexamined Patent Publication No. Sho 63 (1988)). -7877, JP-A-2-30599
No. 3).

[0004]

The above-mentioned Japanese Patent Application Laid-Open No. 2-305
No. 993 discloses that, although a metal material is subjected to anodic electrolysis at least once in an aqueous solution of a silane coupling agent, the adhesion of the paint is evaluated by the following water resistance test method. This is an excellent treatment method. However, it is necessary to have a certain performance in the following composite test method as a method for testing the adhesion of a paint placed in a corrosive environment.

Water resistance test method: 480 hours in hot water at 60 ° C.
After immersion, tape test (1 mm square cross-cut peeling method 10 m
(m × 10 mm = 100 squares), and evaluated by the state of peeling of the paint. Evaluation criteria ○: No peeling at all, △: Edges of squares are covered, ×: Squares peeled

[0006] Composite test method: A cross-cut is made in advance on a painted sample, and a salt spray (40 ° C., 20 hours), drying (65 ° C., 2 hours), and room temperature standing (2 hours) are defined as one cycle, and a cross-cut is performed every 10 cycles. The part is subjected to a peeling test using cellophane tape. Evaluation criteria When the paint was peeled off by 2 mm or more from the cross cut part, it was judged as unacceptable.

In the method disclosed in Japanese Patent Application Laid-Open No. Hei 2-305993, the composite test result of the treated material was 30 cycles, and the paint adhesion in the evaluation test was insufficient. In the case of painting on stainless steel, there is a use that utilizes the gloss of stainless steel, so that a treatment that does not change the gloss of stainless steel is required.

The present invention provides a surface treatment of a metal material that does not impair the gloss of the metal material and has excellent paint adhesion in a water resistance test and a composite test.

[0009]

According to the present invention, in a pretreatment for applying a paint to a metal material, the metal material is subjected to at least one anodic electrolysis treatment in an aqueous alkali solution, and then to a cathodic electrolysis treatment in a chromic acid aqueous solution. And a surface treatment method for a metal material having excellent paint adhesion by performing anodic electrolysis at least once in an aqueous solution of a silane coupling agent.

Here, as is well known, a silane coupling agent includes a reactive group chemically bonded to an inorganic material (a methoxy group, an ethoxy group, a silanol group, etc.) and a reactive group chemically bonded to an organic material (a vinyl group, an epoxy group, etc.). , A methacrylic group, an amino group, etc.), which are two kinds of different reactive groups, specifically, vinyltriethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxy Silane, γ-methacryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, and the like can be used, all of which have been widely used as treatment agents for improving the adhesiveness.

[0011]

EXAMPLES Next, the operation and effects of the present invention will be specifically described with reference to each experimental example and examples. In the following experiments, 0.4 mm thick × 70 mm wide × 1
In addition to using a bright-annealed finishing material of a SUS430 stainless steel cold-rolled steel plate having a length of 50 mm, coating was performed under the commercially available coating conditions and coating conditions shown in Table 1.

[0012]

[Table 1]

Experiment 1 First, in order to examine a good combination of treatments in the composite test, each treatment such as an alkali treatment, a chromic acid treatment, and a silane coupling agent treatment as shown in Table 2 and the respective electrolysis and immersion treatments were performed. Combination experiments were performed.

[0014]

[Table 2]

After the above-described treatment, the surface of the
0 was coated to a thickness of 20μ and baked, and the test material was evaluated for paint adhesion. Table 3 shows the results.

[0016]

[Table 3]

From the results shown in Table 3, the combination without alkali treatment and the combination with alkali immersion had a maximum of 30 cycles in the composite test. On the other hand, a combination of the alkaline electrolytic treatment, the chromic acid electrolytic treatment, and the silane coupling agent electrolytic treatment provided 70 cycles, which proved that the combination was the best. Therefore, this combination will be discussed below.

Experiment 2 In order to examine the conditions of the alkaline electrolysis treatment, those obtained by changing the concentration, temperature, current density, polarity and time of the alkali treatment solution were subjected to the chromic acid electrolysis treatment and the silane coupling agent electrolysis treatment of Experiment 1. , And evaluated in the same manner as in Experiment 1. Table 4 shows the results.

[0019]

[Table 4]

From the results shown in Table 4, among the alkaline electrolysis treatments, the chromic acid electrolysis treatment and the silane coupling agent electrolysis treatment, the conditions of the alkali electrolysis treatment with good adhesion were as follows: concentration: 3% or more, 6% or less ( Temperature: 50 ° C or more and 70 ° C or less (economically disadvantageous if 70 ° C or more) Current density: 5 mA / cm ² or more, 50 mA / cm ² or less Polarity: − + or + The alternating polarity of-is particularly good, and only + is good. Time: 10 seconds or more and 60 seconds or less (60 seconds or more is economically disadvantageous).

Experiment 3 As an alkaline electrolysis treatment, an electrolytic treatment was performed in a 4% aqueous solution of caustic soda (60 ° C.) at an alternating current of 10 mA / cm ² -10 seconds + 10 seconds. The treatment was performed by changing the chromic acid concentration, the temperature, the current density, and the time, and then the electrolytic treatment of the silane coupling agent of Experiment 1 was performed. Table 5 shows the results.

[0022]

[Table 5]

From the results shown in Table 5, the conditions of the chromic acid electrolytic treatment having good adhesion are as follows: concentration: 1% or more and 10% or less (10% or more is economically disadvantageous) Temperature: normal temperature (20 ° C.) or more, 50% ℃ or less (50 ℃
Above environment deteriorates) current density: 5 mA / cm ² or more, 30 mA / cm ² or less (30 mA / cm ² or more, the color change) between time: 5 seconds, 30 seconds or less (or 30 seconds uneconomical ).

Experiment 4 The conditions for the alkaline electrolysis were the same as those in Experiment 3, and the chromic acid electrolysis was carried out in a 5% aqueous solution of chromic acid (20 ° C.).
After electrolytic treatment at 0 mA / cm ² , -10 seconds, the concentration of the silane coupling agent solution, current density, and time were changed in order to examine the conditions of the silane coupling agent electrolytic treatment. The coating was performed in the same manner as described above and evaluated. Table 6 shows the results.

[0025]

[Table 6]

From the results in Table 6, the conditions for the electrolytic treatment of the silane coupling agent having good adhesion are as follows: concentration: 0.1% or more and 5% or less (5% or more is economically disadvantageous) Current density: 0.01 mA / or polar long cm ² or more: -: may be at least 2 seconds + + (+ may if once) during time

Experiment 5 In order to examine the adhesion depending on the type of the silane coupling agent and the type of the coating material, the silane coupling agent was subjected to the same conditions as in the experiment 1 under the alkaline electrolytic treatment, the chromic acid electrolytic treatment, and the silane coupling agent electrolytic treatment. Electrolytic treatment with 1% γ-glycidoxypropyltrimethoxysilane and γ-methacryloxypropyltrimethoxysilane dissolved in a 0.05% aqueous acetic acid solution as a ring agent
G80, Origin Plate Z, Amirac No. 100
0, Magiclon no. 1000 was applied and each adhesiveness was evaluated. Table 7 shows the results.

[0028]

[Table 7]

From the results in Table 7, the silane coupling agent was
Since the compatibility with the paint differs depending on the type, it is understood that the silane coupling agent may be appropriately selected and used depending on the type of the paint.

The test materials used in Experiments 1 to 5 were SU
S430 is a cold-rolled stainless steel sheet, but the material is not limited to this, and it can be applied to any metal material regardless of whether it is a ferrous or non-ferrous material such as ordinary steel, special steel, stainless steel, and plated products. .

EXAMPLE As a test material, a bright annealed SUS430 stainless steel cold-rolled steel sheet having a thickness of 0.4 mm and a width of 250 mm was used, and a 10% aqueous solution of caustic soda (60 ° C.) was used.
Alkaline electrolytic treatment with alternating polarity of mA / cm ² , +10 seconds-10 seconds, washing with water, and then chromic acid electrolytic treatment of 10 mA / cm ² -10 seconds (20 ° C.) in a 5% aqueous solution of chromic acid and washing with water After that, 0.3% in a 2% aqueous solution of N-β (aminoethyl) γ-aminopropyltrimethoxysilane
After subjecting the silane coupling agent to electrolytic treatment at an alternating polarity of mA / cm ² , −3 seconds + 3 seconds, washing with water, and further keeping the coil at 90 ° C.
Dried at 8 ° C for 8 hours.

This was coated and baked to a thickness of 20 μm with a urethane PG80 and an origin plate Z, and the adhesion was evaluated. Table 8 shows the results. In addition, as a comparative example, untreated, only alkaline electrolytic treatment, alkaline electrolytic treatment + chromic acid electrolytic treatment, alkaline electrolytic treatment + silane coupling agent electrolytic treatment are also described.

[0033]

[Table 8]

[0034]

As described above, according to the present invention, a metal material is subjected to anodic electrolysis at least once in an aqueous alkali solution, then to a cathodic electrolysis in a chromic acid aqueous solution, and then at least once to an aqueous silane coupling agent solution. By performing the anodic electrolytic treatment, an adhesiveness of 60 cycles or more of the composite test, which could not be achieved by the electrolytic treatment according to the related art, is obtained, and a treatment method excellent in paint adhesion together with the water resistance test can be obtained.

Further, those treated in the present invention show little change in color tone before and after the treatment, and can be used for applications utilizing the luster of metal materials. Furthermore, the present invention can be applied to a coil or a processed product as long as it is a metal material, and is industrially advantageous.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuki Ito 1-1-1, Shin-Kashigishi, Itabashi-ku, Tokyo Inside Takasago Iron Works Co., Ltd. (72) Yoshio Kimura 1-1-1, Shin-Kashigishi, Itabashi-ku, Tokyo Inside Takasago Iron Works Co., Ltd. (72) Inventor Toru Tanaka 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Co., Ltd. 72) Inventor Hiroaki Nakamura 2-1-1 Asahi-cho, Kariya-shi, Aichi, Japan Aisin Seiki Co., Ltd. (72) Inventor Toshimitsu Kobayashi 2-1-1, Asahi-cho, Kariya-shi, Aichi Aisin Seiki Co., Ltd. (56) References JP-A-56-25998 (JP, A) JP-A-63-130796 (JP, A) JP-A-2-305993 (JP, A) JP-A-52-145348 (JP, A) Hei 3-243796 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C25D 13/20 C25D 11/34 301 C25D 11/38 302

Claims (1)

(57) [Claims] In a pretreatment for applying a paint to the surface of a metal material, the metal material is subjected to anodic electrolysis at least once in an aqueous alkali solution, then to a cathodic electrolysis in a chromic acid aqueous solution, and then to a silane coupling agent aqueous solution. A surface treatment method for a metal material having excellent paint adhesion, wherein the method comprises subjecting the material to anodic electrolysis at least once.