JPH11117077A - Magnesium-containing aluminum alloy-treated sheet excellent in filiform errosion resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To impart excellent filiform erosion resistance to a sheet and to improve its formability and phosphating treatability by forming a specified amt. of coating film composed of a phosphate hydrate contg. specified ratios of zinc and phosphous on the surface of an Mg-contg. aluminum alloy sheet. SOLUTION: The coating film to be formed on the surface of an alloy sheet is composed of a phosphate hydrate contg., by weight, 33.5 to 42.7% Zn and 13.5 to 13.8% P, and its coating weight is regulated to 0.05 to 2.0 g/m<2> . Furthermore, in this coating film, one or more kinds of metals selected from Ni, Mn, Co and Fe are preferably incorporated by 0.05 to 8.0 wt.% in total. Moreover, as the coating film forming method, liminations are not particularly placed, but, for economically forming it in a short time, the means for bringing the alloy sheet into contact with aq. soln. contg. each ion of zinc, phosphoric acid and nitric acid and furthermore contg. at least one or more kinds of metallic ions selected from each ion of fluorides, complex fluorides and nitrous acid and peroxide is preferably adopted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy material having a surface excellent in thread rust resistance, and more particularly, to an application in which coating is performed after a base treatment by zinc phosphate treatment, for example, suitable for an automobile panel. And a Mg-containing aluminum alloy treated plate.

[0002]

2. Description of the Related Art In recent years, aluminum alloys have been used in automobile parts for the purpose of weight reduction. As aluminum materials for automobiles, aluminum alloys such as 5000 series, 6000 series and 7000 series aluminum alloys containing Mg are used. Alloys are used. However, for applications requiring thread rust resistance, such as panel materials for automobiles, a coating base treatment such as chromate chromate has been required. In this regard, zinc phosphate treatment, which is a conventional material treatment for steel sheets, is used for the surface treatment of ordinary automobile coating lines, and when this surface treatment is applied to an aluminum alloy, the zinc phosphate treatment property is sufficient. No sufficient performance was obtained in terms of yarn rust resistance. Further, there is a problem that the aluminum alloy plate itself is a material having poor formability as compared with a steel plate.

[0003] For this purpose, as a method for improving the zinc phosphate treating property, Japanese Patent Application Laid-Open No. 61-157693 discloses a method in which 1 g of a Zn plating layer, a Zn-based alloy plating layer, or an Fe-based alloy plating layer is coated on the surface of aluminum. / M ² or more. This technique aims to improve the zinc phosphate treatment property and to prevent elution of aluminum ions into the zinc phosphate bath.

In Japanese Patent Application Laid-Open No. 5-70970, the thickness of an oxide layer formed on the surface of an Al—Mg-based alloy is set to 70 Å or less and M
It is disclosed that the g concentration is reduced to 20 atomic% or less.
Alternatively, JP-A-2-250944 discloses that a heat treatment is performed after the surface layer of the Mg-containing Al alloy plate is once removed.
A material having an oxide film thickness of 50 to 150 angstroms and an Mg / Al ratio adjusted to a specific range of 0.6 to 5 and having excellent zinc phosphate treatment properties is disclosed.

[0005]

However, in the case of Japanese Patent Application Laid-Open No. 157,693 / 1986, in order to form a plating layer on an aluminum alloy on the surface, a complicated process must be performed in the case of displacement plating. In the case of electroplating, expensive equipment and electricity are required, and the cost is increased. Furthermore, if the Zn plating layer remains after the zinc phosphate treatment, blisters are easily generated in the coating film, which is not preferable.

In the case of JP-A-5-70970 and JP-A-2-250944, a uniform surface can be formed by controlling the surface condition, but the surface has an oxide film. As compared with a steel sheet, the formation of a zinc phosphate film is hindered, and sufficient chemical conversion treatment properties cannot be obtained. In the case of the chromate chromate treatment of the prior art, the thread rust resistance is improved, but a special treatment facility is required, and the treatment cost including wastewater treatment is increased.

An object of the present invention is to provide a low-cost Mg-containing aluminum alloy treated plate excellent in thread rust resistance by solving the above-mentioned problems of the prior art on the surface of the Mg-containing aluminum alloy.

[0008]

Means for Solving the Problems The present inventors have conducted intensive studies in order to solve these problems, and as a result, in order to achieve the above-mentioned objects, the present invention provides a Mg-containing aluminum alloy having excellent rust resistance. The alloy-treated plate is characterized in that a surface of a Mg-containing aluminum alloy plate has a specific weight coating containing zinc and phosphorus in a specific weight ratio.

That is, the gist of the present invention is as follows. (1) Zn: 33.5 to 42.7% by weight and P: 1 on one or both sides of a Mg-containing aluminum alloy plate
Mg-containing aluminum excellent in filiform rust resistance, characterized in that a coating composed of phosphate hydrate containing 3.5 to 13.8% by weight has 0.05 to 2.0 g / m ² per one surface. Alloy treated plate. (2) One or more metals selected from Ni, Mn, Co, and Fe are contained in the coating in an amount of 0.05 to 8.0% by weight in total.
The Mg-containing aluminum alloy treated plate excellent in thread rust resistance according to the above (1), further comprising: (3) An automotive panel material using the Mg-containing aluminum alloy-treated plate according to (1) or (2).

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, when the weight% of zinc in a film exceeds 42.7% by weight, the film is easily broken in press molding, which is not preferable. Also, 3
If it is less than 3.5% by weight, the coating properties after the subsequent zinc phosphate treatment are good, but the properties are saturated, which is disadvantageous in terms of production cost, which is not preferred.

The coating of the present invention is composed of a phosphate hydrate. In order to obtain sufficient formability, its crystal structure is represented by the composition of Zn ₃ (PO ₄ ) ₂ .2H ₂ O. Is considered to be the most effective. In order for this phosphate hydrate to be the main component, the phosphorus content is 13.5 to 13.8.
It must be weight percent. In the present invention, the Mg
Ni, Mn,
One or more metals selected from Co and Fe
Preferably, it is contained in an amount of at least% by weight. In particular, 1.0
More preferably, it is contained in an amount of at least 8.0% by weight. When the content is 0.05% by weight or more, the film is less likely to be broken during press molding, which is preferable. on the other hand,
If it exceeds 8.0% by weight, the coating properties after the subsequent zinc phosphate treatment are good, but the properties are saturated, which is disadvantageous in production cost.

In the present invention, it is considered that one or more metals selected from Ni, Mn, Co and Fe are present in the coating in a form in which zinc and phosphorus compounds are substituted for zinc. In the present invention, Ca, Mg is contained in the treatment film.
And the like may be substituted with zinc.

The amount of the phosphate hydrate coating on the Mg-containing aluminum alloy-treated plate of the present invention is 0.05 to 2.0 g.
/ M ² is preferred. Unfavorable in the deposition amount is less than 0.05 g / m ^2, a filiform rust resistance is unsatisfactory, since the filiform rust resistance exceeds 2.0 g / m ² is produced economically disadvantageous to saturate . The method for forming a film formed on the surface of the Mg-containing aluminum alloy plate in the present invention is not particularly limited, and a coating method such as a vapor deposition method or a thermal spraying method is used, using a Mg-containing aluminum alloy plate as a substrate and a metal phosphate on the surface. Can be used, but it is economically unfavorable because of the equipment cost. As a method of forming in a short time with an economical facility, at least one or more selected from fluoride ions, complex fluoride ions, nitrite ions, and peroxides containing zinc ions, phosphate ions, and nitrate ions By contacting with an aqueous solution containing metal ions. When the Mg-containing aluminum alloy-treated coating contains one or more metals selected from Ni, Mn, Co and Fe, the aqueous solution is selected from Ni ions, Mn ions, Co ions and Fe ions. The film can be formed by contact with an aqueous solution to which one or more metal ions have been added.

As a method of manufacturing the treated plate of the present invention in a short time, the aqueous solution is maintained at a temperature of 30 to 90 ° C. Preferably, the surface is treated. If the temperature of the aqueous solution is lower than 30 ° C., the rate of film formation is extremely slow. On the other hand, if the temperature exceeds 90 ° C., the effect of the present invention cannot be obtained, and both are not economical.

The pretreatment method is not particularly limited. For example, a titanium colloid aqueous solution prepared by using titanium oxide, titanium sulfate, titanium phosphate or the like alone or in any combination, or a nickel colloid solution such as nickel nitrate or nickel sulfate is used. Nickel ions or cobalt ions such as cobalt nitrate and cobalt sulfate are brought into contact with an aqueous solution prepared alone or in any combination.

In the present invention, the rust resistance of the Mg-containing aluminum alloy treated plate having the above-mentioned coating is markedly improved as compared with the Mg-containing aluminum alloy plate without such a coating. The reason why the Mg-containing aluminum alloy-treated plate of the present invention improves the thread rust resistance and coating film adhesion is that zinc phosphate treatment, which greatly affects the yarn rust resistance and coating film adhesion, was improved. It is considered to be caused. That is, where the zinc-containing aluminum alloy sheet does not form a sufficient zinc phosphate film under the normal zinc phosphate treatment conditions, the Mg-containing aluminum alloy sheet is subjected to a treatment having a film containing zinc and phosphorus. It is thought that it supplements.

Further, the improvement of the formability of the Mg-containing aluminum alloy-treated plate of the present invention is attributable to the fact that the Mg-containing aluminum alloy plate is subjected to a treatment having a film containing zinc and phosphorus, whereby the friction coefficient is reduced. It is considered that the moldability was improved. Hereinafter, examples of the present invention will be described.

[0018]

EXAMPLE As a material, A6009 alloy (Al-Mg-
A rolled plate (1 × 300 × 300 mm) of an Si-based) and A5182 alloy (Al—Mg-based) was prepared. A60 above
The rolled sheets of the alloy No. 09 and the alloy A5182 were mixed with phosphate ions (PO ₄ ^{2 −} ) in an amount of 5 to 30 g / l and nitrate ions (NO ₃
^- ) 1 to 10 g / l, fluorine ion 0.5 to 5 g / l
1 to the aqueous solution containing zinc ions in an amount of 0.5 to 1
0 g / l, nickel ion 0.1-3 g / l, manganese ion 0.1-2 g / l, cobalt ion 0.1
To 2 g / l, iron ions 0.1 to 1 g / l nitrite ions 0.1 to 1 g / l, and inorganic peroxides and / or hydrogen peroxide 0.01 to 1 g / l were appropriately added. 30-90
The aluminum-treated plate containing Mg was immersed in an aqueous solution at ℃. The coatings of these treated plates were dissolved in concentrated nitric acid, the elements were quantified by atomic absorption analysis, and the coating compositions were measured.
As is evident from Table 1, the coatings of the examples of the present invention were within the stipulated range of the present invention in both the amount of coating and the components.

Plates of A6009 alloy and A5182 alloy (1 × 70 × 150 m
m), zinc phosphate treatment (including degreasing and surface conditioning), cationic electrodeposition coating (film thickness: 20 μm), intermediate coating (film thickness: 35 μm), and top coating (film thickness: 35 μm) similar to those for automotive panel materials ). Zinc phosphate treatment: The surface of the zinc phosphate film formed on the zinc phosphate treated plate was observed with a scanning electron microscope to examine the state of deposition. The evaluation was evaluated as follows: ：: crystal precipitation on the entire surface, Δ: partial material surface, ×: material surface 50% or more. Table 1 shows the evaluation results.

[0020] Yarn rust resistance: After a cross cut was made with a NT cutter on a coating film subjected to cationic electrodeposition coating, the evaluation was made of the yarn rust resistance. The rust resistance is determined by salt spray (5% aqueous NaCl solution, 35 ° C, 24 hours) → wet test (50 ° C x 85%
RH, 120 hr) as one cycle, five cycles were performed, and the evaluation was made based on the maximum swelling width of the coating film from the cross cut portion. Evaluation: ○: swollen width less than 1 mm,
Δ: swelling width 1 mm or more and less than 3 mm, X: swelling width 3 mm or more.

Coating film adhesion: A sample coated with a top coat was immersed in distilled water at 40 ° C. for 10 days, and then immediately coated with NT.
Cuts were made with a cutter so that 100 squares of 1 mm square were formed, and the state of the squares remaining after tape peeling was observed. The evaluation was evaluated as follows: な し: no cross-cut peeling, Δ: cross-cut peel area less than 5%, ×: cross-cut peel area 5% or more.

Formability: The treated material is 200 mm long × 125 to 140 mm long using a 100φ ball-overhang tool.
molding speed 1 after lubricating the lubricating oil
0 mm / min. , And 10 tons of BHF to determine a break forming height (LDH0) and evaluate it. Evaluation: ○: LDH
0 30 mm or more, Δ: LDH0 20 mm or more and 30 m
m, ×: LDH0 20 mm or less.

As is apparent from Table 1, the results of the present invention were all excellent in zinc phosphate treatment property, yarn rust resistance, coating film adhesion and moldability.

[0024]

[Table 1]

[0025]

According to the present invention, the problem of the rust resistance of the Mg-containing aluminum alloy, which has conventionally been a problem, can be solved. Therefore, it can be said that the invention has an extremely high industrial value.

Claims (3)

[Claims] The present invention relates to a Mg-containing aluminum alloy plate on one or both sides of which: Zn: 33.5 to 42.7% by weight;
P: a coating composed of phosphate hydrate containing 13.5 to 13.8% by weight was coated at 0.05 to 2.0 g /
Mg-containing aluminum alloy treated sheet having excellent filiform rust resistance, characterized in that it comprises m ^2. 2. Ni, Mn, Co, Fe in the coating.
At least one metal selected from the group consisting of 0.05-8.
The Mg-containing aluminum alloy treated plate excellent in thread rust resistance according to claim 1, further containing 0% by weight. 3. An automotive panel material using the Mg-containing aluminum alloy-treated plate according to claim 1 or 2.