JPH0665787A - Al or al alloy sheet excellent in adhesiveness and corrosion resistance after coating - Google Patents

Abstract

PURPOSE:To produce an Al sheet excellent in adhesiveness and corrosion resistance after coating by forming a porous anodized film having a specified thickness on both sides of an Al sheet and forming an Fe-base plating material on the one side through the pores of the anodized film. CONSTITUTION:An Al or Al alloy sheet is anodized to form a porous alumite film having >=0.5mum thickness and having 60-98% porosity on both sides of the sheet. The one side is electroplated to form a Zn-base plating material, an Fe-base plating material or an Mn plating material through the pores of the film. As a result, the plating is not stripped off in press forming, etc., the corrosion resistance after coating is improved, and an Al or Al alloy sheet excellent in adhesiveness is obtained.

Description

Detailed Description of the Invention

[0001]

The present invention relates to an adhesive property obtained by forming a plated material having excellent corrosion resistance after coating on one surface of an Al or Al alloy plate and forming a film having excellent adhesiveness on the other surface. And an Al or Al alloy sheet having excellent corrosion resistance after painting.

[0002]

2. Description of the Related Art An Al or Al alloy plate (hereinafter also referred to as an Al alloy plate) is lightweight and has excellent corrosion resistance and designability, and therefore has been used in a wide range of fields such as home appliances and building materials. Further, recently, also in the field of automobiles and the like, Al alloy plates have come to be used for the purpose of weight reduction, and there is an increasing number of occasions where coating is applied to the front surface and an inner material is adhered to the back surface for use. However, since the surface of the Al alloy plate is covered with a strong oxide film, direct coating is not appropriate, and it is considered that pretreatment such as phosphate treatment or chromate treatment is necessary. Is very strong, the phosphate treatment or chromate treatment itself becomes insufficient, and therefore the coating film formed thereon does not show sufficient coating film adhesion, and peeling of the coating film easily occurs, or Has a problem that the corrosion resistance after painting is insufficient.

Therefore, the surface of the Al alloy plate is plated with Fe (Fe
It has been investigated to improve the phosphate treatment property and the chromate treatment property by forming an alloy plating (the same applies hereinafter), and thereby improvement of coating film adhesion has been achieved. However, in such a Fe-plated Al alloy plate, since the adhesion between the plating layer and the base is poor, the Fe plating is peeled off, for example, at the stage of press molding before coating.
The effect of forming the Fe plating layer has not been sufficiently exhibited. The same problem occurs when bending or the like is performed after painting.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and by forming a plating layer, the phosphate treatment property is enhanced and at the time of molding such as press molding. By increasing the adhesion of the plating layer so that problems such as plating peeling do not occur, excellent post-paint corrosion resistance is given to the Al alloy plate front side, and adhesion is improved by increasing the adhesiveness of the Al alloy plate back surface. The present invention intends to provide an Al alloy plate having excellent properties and excellent corrosion resistance after painting.

[0005]

The Al or Al alloy plate of the present invention which has been able to achieve the above object has an alumite film having a thickness of 0.5 μm or more on both surfaces thereof, and on any one surface thereof. Through the pores of the alumite film,
The gist is that a Zn-based plated material, a Fe-based plated material, or a Mn-based plated material is formed, and the alumite coating is preferably a porous alumite coating with a porosity of 60 to 98%. .

[0006]

The present inventors made the development of means for making the plating layer formed on the Al alloy plate adhere to the base as strongly as possible, and have studied various concrete means therefor.

As a result, excellent adhesion can be obtained by controlling the shape of the strong oxidative film formed on the surface of the Al alloy plate from both sides of the film thickness and the porosity. It was found that the plating adhesion was remarkably improved in the case of depositing and depositing on the outermost surface.

Further, in the present invention, since the plating material is formed so as to be deposited on the surface from inside the pores of the alumite coating, the plating layer is prevented from being peeled off by the anchor effect, and the phosphoric acid is formed by the plating layer. The salt processability was improved, the coating film adhesion was secured, and excellent post-coating corrosion resistance was exhibited.

The thickness of the alumite coating must be 0.5 μm or more. If this condition is not satisfied, the anchoring effect of the alumite coating on the plating material is insufficient and the effect of preventing plating peeling is insufficient. The upper limit of the thickness of the alumite coating is not particularly set, but if it is too thick, the alumite coating itself may crack due to internal stress, so it is desirable to keep it below 1.5 μm. A more preferable range is 0.5 to 1.0 μm.

Explaining the shape of the alumite coating for effectively exhibiting the above-mentioned effects, the porosity is 6
It is preferable to set it in the range of 0 to 98%, and if it is less than 60%, the anchor effect for Fe-based plating may not be sufficiently exhibited, and the adhesion of the plated material is insufficient and the effect of preventing plating peeling is not exhibited. There is. On the other hand, 98%
Above the range, the alumite coating tends to lack growth, and not only is the alumite coating thin, but the pore walls are thin, so the alumite coating itself lacks strength,
In addition, the holding force for the plating layer deposited / deposited from the inside of the pores is weakened, and it becomes difficult to effectively exhibit the plating peeling prevention effect during press molding. The more preferable porosity of the porous alumite coating is 70 to 95%. However, since the alumite coating has a function of enhancing the adhesiveness of the plating layer by itself, the effect of improving the adhesiveness to the plating layer is better than that without the underlayer even if it is out of the preferable porosity range. It is demonstrated by it.

As to the alumite coating, other conditions are not limited as long as they satisfy the above conditions regarding the porosity and the film thickness. In order to form such an alumite film, an anodizing treatment method in an aqueous solution of an inorganic acid such as phosphoric acid, oxalic acid, sulfuric acid or chromic acid is recommended.

The present invention may be applied to any one of Zn-based, Fe-based or Mn-based plating, such as pure Zn, pure Fe, pure Mn.
Or Zn-Fe, Zn-Mn, Fe-Mn alloy,
If necessary, other alloy elements such as Ni, Mg, Cr, M
A small amount of n, Si, P, B, etc., or Si
It is also possible to improve the plating characteristics by mixing ceramics such as O ₂ , Al ₂ O ₃ and Al (OH) ₃ . It is preferable to use Fe-based plating. For example, Fe deposited by using an electroplating method becomes very fine, and the pore filling effect of the porous alumite coating is excellent, and the anchoring effect is strongly exerted. The Rukoto. Further, Fe that is deposited through the holes to the surface of the alumite coating is likely to become fine and dense, and the effect of imparting lubricity becomes more remarkable.

One of the purposes of forming a plating layer in the present invention is to improve the phosphate treatment property which is carried out as a pretreatment for coating so that a uniform phosphate film as a coating base is formed on the surface of an Al-based alloy plate. However, if the plated material such as Fe or Zn remains after the phosphate treatment, it may become a source of corrosion and deteriorate the corrosion resistance after coating.
Therefore, with respect to the plating layer formed according to the present invention, it is preferable to control the coating weight to about 10 g / m ² or less so that all of it can be converted into a phosphate film in the subsequent phosphate treatment step.

Further, the present invention does not limit the lower limit of the coating amount, but in the present invention, it is necessary to deposit on the surface after being deposited in the pores in the porous alumite coating. Yes, 0.5g / m ² or more is desirable. The plating means is not particularly limited, but electroplating is recommended from the viewpoint of depositing so as to fill the pores of the alumite coating.

[0015]

EXAMPLES Next, examples will be given showing examples of the constitution and the effect of the present invention. However, the present invention is not limited to these examples, and changes and modifications can be made without departing from the spirit of the preceding and the following. All are included in the technical scope of the present invention. Al
After cleaning the plate, each was subjected to anodizing treatment to form a porous alumite coating shown in Table 1. Then, the plating shown in Table 1 was formed on only one surface by electroplating to obtain a test piece.

For the adhesion test, an epoxy adhesive was used, and the surface on which the plating layer was not formed and the aluminum base plate were adhered with an overlap margin of 10 mm, and a tensile shear strength test was conducted. It was evaluated by. The results are shown in Table 1. ◎: Adhesive strength of 210 Kgf / cm ² or more ○: Adhesive strength of 190 Kgf / cm ² or more and less than 210 Kgf / cm ² ×: Adhesive strength of less than 190 Kgf / cm ²

On the other hand, the test piece was subjected to a phosphate treatment, and an alkyd melamine-based paint or an epoxy-based paint was applied to the surface on which the plating layer was formed so that the dry film thickness was about 20 μm to obtain a coated Al plate. It was After putting a cross-cut reaching the Al substrate, a salt spray test was performed for 840 hours, and the swelling width (maximum value on both sides / 2) of the coating film from the cross-cut portion was measured and evaluated according to the following criteria. The results are also shown in Table 1. ◎: Coating swelling width less than 0.5 mm ○: Coating swelling width 0.5 mm or more and less than 3.0 mm ×: Coating swelling width 3.0 mm or more

[0018]

[Table 1]

No. Examples 1 to 6 are all examples satisfying the conditions of the present invention, and are excellent in both adhesiveness and corrosion resistance after coating. However, No. No. 5 has a low porosity of the alumite coating, and No. 5 No. 6 had a high porosity, so the evaluation was only marked with a circle. On the other hand, No. No. 7 is a comparative example in the case where the alumite coating is thin, the adhesion was poor, and the corrosion resistance after coating was insufficient. No. Since No. 8 had a low porosity, it had poor adhesion and poor corrosion resistance after painting.

[0020]

EFFECTS OF THE INVENTION Since the present invention is constructed as described above, it is possible to obtain an Al alloy plate which is free from plating peeling during press molding, has very good corrosion resistance after coating, and has excellent adhesiveness. It is now possible to provide.

Claims (2)

[Claims] 1. A film having a film thickness on both sides of an Al or Al alloy plate.
An adhesive characterized by having an alumite coating of 0.5 μm or more, and forming a Zn-based plating material, a Fe-based plating material, or a Mn-based plating material on one side through the pores of the alumite coating. Al or Al alloy plate with excellent heat resistance and corrosion resistance after painting. 2. An Al or Al alloy plate excellent in adhesiveness and corrosion resistance after coating according to claim 1, wherein the alumite coating is a porous alumite coating having a porosity of 60 to 98%.