JPH11269595A - Automotive magnesium-containing aluminum alloy treated sheet excellent in zinc phosphate treatability and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an Mg-contg. aluminum alloy treated sheet excellent in zinc phosphate treatability and suitable for use for coating application after zinc phosphate treatment of a substrate. SOLUTION: The surface of an Mg-contg. aluminum alloy sheet is treated with an aq. soln. contg. 0.5 to 10g/l Zn ions, 5.0 to 40g/l PO4 ions, 0.5 to 10g/l NO3 ions and >=200 ppm free fluorine, by which the surface is provided with a shapeless compd. contg. zinc and phosphorus by the weight ratio(zinc/ phosphorus) of 3.2 to 9.0 by 0.05 to 2.0 g/m<2> . The surface is preferably further provided with an oil layer of 0.1 to 1.8 g/m<2> as the upper layer.

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 for automobiles having a surface excellent in zinc phosphate treatment, and more particularly to an aluminum alloy containing Mg for use such as being coated after a base treatment by zinc phosphate treatment. It relates to an alloy-treated plate.

[0002]

2. Description of the Related Art In recent years, aluminum alloys are being used in automobile parts for the purpose of weight reduction. Aluminum materials for automobiles include aluminum alloys containing Mg, such as 5xxx, 6xxx, and 7xxx series aluminum alloys. Alloys are used. However, most automotive materials are steel plates, and aluminum alloys are treated with zinc phosphate, which is a coating base treatment, in a form integrated with the steel plates.

[0003] Aluminum alloys are inferior in zinc phosphate treatability due to their lower reactivity than steel sheets.
When zinc phosphate treatment is performed in contact with a steel sheet, the steel sheet becomes a cathode and the aluminum alloy becomes an anode, and a zinc phosphate film is formed on the steel sheet, but the zinc phosphate film is not easily deposited on the aluminum alloy. there were. Therefore, there is a need for a treatment bath, method and aluminum alloy sheet suitable for simultaneously treating the aluminum alloy and the steel sheet with phosphate.

[0004] However, as a method of improving the zinc phosphate treating property, a method of increasing the reactivity by adding a fluoride to a zinc phosphate treating bath has been proposed. Also,
As a method of improving the zinc phosphate treatability by treating aluminum, Japanese Patent Application Laid-Open No. 61-157693 discloses a method in which a Zn plating layer, a Zn-based alloy plating layer, or an Fe-based alloy plating layer is coated on an aluminum surface at 1 g / m 2. ^A method of providing ^two or more is disclosed. This technique aims to improve the zinc phosphate treatment property and also 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 alloy is set to 70 Å or less and the 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.

[0006]

However, the method for improving the zinc phosphate treatment bath is effective when the aluminum alloy is treated alone, but cannot be sufficiently effective when treated simultaneously with the steel sheet. Also, Japanese Patent Application Laid-Open No. 61-1576
In the case of Japanese Patent No. 93, in order to form a plating layer on an aluminum alloy on the surface, it is necessary to go through a complicated process in the case of displacement plating, and expensive equipment and electricity cost are required even in the case of electroplating. However, it is industrially undesirable in that the cost increases. Furthermore, if the Zn plating layer remains after the zinc phosphate treatment, blisters are likely to occur in the coating film, which is not preferable.

[0007] In the case of JP-A-5-70970 and JP-A-2-250944, a uniform surface can be formed by controlling the surface state, but an oxide film is formed on the surface. As compared with a steel sheet, the formation of a zinc phosphate film is inhibited, and sufficient zinc phosphatability cannot be obtained. An object of the present invention is to provide a low-cost Mg-containing aluminum alloy treated plate excellent in zinc phosphate treatability 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 inventors of the present invention have conducted intensive studies to solve these problems, and as a result, in order to achieve the above-mentioned object, the present invention provides a method of manufacturing a magnesium phosphate excellent in zinc phosphate treatment.
Containing aluminum alloy treated plate, Zn ion: 0.5 ~
10 g / l, PO ₄ ion: 5.0 to ₄₀ g / l, NO
By treating the surface of the Mg-containing aluminum alloy plate with an aqueous solution containing ₃ ions: 0.5 to 10 g / l and containing 200 ppm or more of free fluorine, zinc and phosphorus are added to the surface in a weight ratio (zinc / phosphorus). ) An amorphous compound contained in an amount of from 3.2 to 9.0 is contained in an amount of from 0.05 to 2.0 g / m ² .

That is, the gist of the present invention is as follows. (1) The weight ratio of zinc to phosphorus on the surface (zinc / phosphorus) 3.2
0.05 to 2.0 g of the amorphous compound contained in an amount of from 0.05 to 9.0
/ M ^{2, which is} a magnesium-containing aluminum alloy treated plate for automobiles excellent in zinc phosphate treatability. (2) 0.1-1.8 g /
(2) The magnesium-containing aluminum alloy-treated plate for automobiles according to the above (1), which has an oil layer of m ² and has excellent zinc phosphate treatability. (3) Zn ion: 0.5 to 10 g / l, PO ₄ ion: 5.0 to 40 g / l, NO ₃ ion: 0.5 to 10 g / l, an aqueous solution containing 200 ppm or more of free fluorine, M
The method for producing a magnesium-containing aluminum alloy treated sheet for automobiles excellent in zinc phosphate treatment according to the above (1) or (2), wherein the surface of the g-containing aluminum alloy sheet is treated.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the amorphous compound containing zinc and phosphorus formed on an Mg-containing aluminum alloy plate is defined as a zinc phosphate film usually formed on an aluminum alloy, such as hopite (Zn ₃ (PO _4)). ) ₂ · 4H ₂ O)
[The weight ratio of zinc and phosphorus in Hopite is 3.17. ]
Rather, it refers to a non-stoichiometric compound containing zinc, phosphorus, oxygen, Ni, Fe, etc. added to the plating bath as needed, and having the form shown in FIG.

The weight ratio of zinc to phosphorus (zinc / phosphorus) is 3.
If it is less than 2, the reactivity of the zinc phosphate treatment is low and it is difficult to perform the treatment in a short time. If it exceeds 9.0, the effect of the treatment in a short time is saturated, and wasteful chemicals are consumed. Be disadvantaged. Preferably, the weight ratio of zinc to phosphorus is between 5.0 and 5.0.
8.0. The amount of the amorphous compound in the Mg-containing aluminum alloy-treated plate of the present invention is 0.05 to 2.0 g / m ² . In its coating weight is less than 0.05 g / m ^2, is insufficient zinc phosphate treatment properties, be attached exceed 2.0 g / m ^2, only it is saturated moldability and zinc phosphate treatment properties This is disadvantageous in manufacturing cost.

In the present invention, the amorphous compound of the Mg-containing aluminum alloy-treated plate contains Ni, Mn, C
It is preferable to contain at least 0.05% by weight of one or more metals selected from o, Ca, Mg, and Fe. By containing these metals, the coating film adhesion after the zinc phosphate treatment and the coating treatment is improved. There is no particular upper limit,
Since the characteristics are saturated, the production cost is disadvantageous.

In order to produce the Mg-treated aluminum alloy-treated plate of the present invention having excellent zinc phosphate treatability, Zn ions: 0.5 to 10 g / l, PO ₄ ions;
0 g / l, NO ₃ ion: 0.5 to 10 g / l and Mg in an aqueous solution containing 200 ppm or more of free fluorine.
An amorphous compound containing zinc and phosphorus at a weight ratio (zinc / phosphorus) of 3.2 to 9.0 is formed on the surface of the Mg-containing aluminum alloy plate by immersing the aluminum-containing plate. .

[0014] The concentration of zinc ions in the processing solution is 0.5
If the amount is less than g / l, it is difficult to perform the treatment in a short time, and if it exceeds 10 g / l, the treatment can be performed in a short time, but wasteful chemicals are consumed, which is economically disadvantageous. In addition, PO ₄
When the amount of ions is less than 5.0 g / l, it is difficult to perform the treatment in a short time. When the amount exceeds 40 g / l, the treatment can be performed in a short time, but wasteful chemicals are consumed, which is economically disadvantageous. On the other hand, if the NO ₃ ion is less than 0.5 g / l, it is difficult to perform the treatment in a short time, and if it exceeds 10 g / l, the effect of the treatment in a short time is saturated and wasteful chemicals are consumed. Economically disadvantaged. In addition, free fluorine is 200
If it is less than ppm, the reactivity of the Mg-containing aluminum alloy plate is low, and it is difficult to perform the treatment in a short time. Although there is no particular upper limit, the characteristics are saturated, which is disadvantageous in manufacturing cost. Conventionally, up to about 1000 ppm is used. Also,
When producing an amorphous compound containing at least one metal selected from Ni, Mn, Co, Ca, Mg, and Fe, Ni solution, Mn ion, Co ion, Ca ion, Mg An aqueous solution containing at least one metal ion selected from ions and Fe ions may be used. After the Mg-containing aluminum alloy is treated, the treated surface is treated with 0.1%.
It is preferable to form an oil layer of 1 to 1.8 g / m ² .
By forming the oil layer, deterioration over time due to oxidation of the surface or the like can be prevented, and a brittle oxide is not generated. The formation of brittle oxides is one of the main causes of difficult workability in press working and the like, which is a problem in aluminum alloys. By protecting the surface with an appropriate oil layer,
The workability of the aluminum alloy of the present invention can be greatly improved. The amount of oil applied to the oil layer is 0.1 to 1.8 g /
An oil layer of m ² is preferable. If the amount of applied oil is less than 0.1 g / m ² , the effect of suppressing the formation of oxides is not sufficient, and
If it exceeds 8 g / m ² , the effect may be saturated and economic disadvantage may be caused, and at the same time, an excessive oil layer may cause dust and the like to adhere to the surface and cause surface defects. The type of oil to be applied is not particularly limited, but the viscosity at 40 ° C. is preferably 1.0 to 10.0 mm ² / s in consideration of the degreasing property.

As a method for manufacturing the Mg-containing aluminum alloy treated sheet of the present invention in a short time, the above aqueous solution is maintained at a temperature of 40 to 90 ° C. after performing a pre-treatment before the treatment. Preferably, the surface is treated. If the temperature of the aqueous solution is lower than 40 ° C., the film formation rate 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. In addition, when a treatment with the above aqueous solution is performed, by adding a cathodic electrolytic treatment, the reactivity is improved, and a Mg-containing aluminum alloy treated plate can be manufactured in a short time. The electrolysis treatment conditions are as follows.
It is preferable to carry out at a current density of 1 to 25 A / dm ² .
If the concentration is less than 0.1 A / dm ² , the effect is not sufficient, and 25 A
If it exceeds / dm ² , the electrolysis efficiency may decrease, which may be economically disadvantageous. Furthermore, if anodization is performed before performing cathodic electrolysis, adhesion is improved.

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 an arbitrary 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 zinc phosphate treatability of the Mg-containing aluminum alloy treated plate having the above-mentioned amorphous compound is improved as compared with the Mg-containing aluminum alloy plate without such amorphous compound. There are features,
In particular, the effect is remarkable when the zinc-containing aluminum alloy plate is subjected to the simultaneous zinc phosphate treatment in contact with the steel plate.

The reason why the zinc phosphate treatability is improved in the present invention is that the presence of an amorphous compound of zinc and phosphorus on the Mg-containing aluminum alloy-treated plate causes the cathode point and the nucleus during zinc phosphate treatment. It is considered that the formation of zinc phosphate promotes the generation of zinc phosphate phosphate crystals. In addition, the Mg-containing aluminum alloy-treated plate of the present invention has a low coefficient of friction during processing due to the presence of an amorphous compound of zinc and phosphorus on the Mg-containing aluminum alloy plate, particularly without lubrication. Since it has self-lubricating properties, it has high moldability. Also, when lubricating oil is applied, the oil retention is good, so that the formability is better than that of a normal Mg-containing aluminum alloy plate. Further, the Mg-containing aluminum alloy-treated plate of the present invention has an increased contact resistance and improved weldability due to the amorphous compound.

[0019]

Examples of the present invention will be described below. As a material,
A6009 alloy (Al-Mg-Si based) and A5182
Rolled plate of alloy (Al-Mg) (1mmx300mmx
300 mm). A6009 alloy and A5
182 alloy rolled plate, Zn ions: 0.1 to 10 g /
l, PO ₄ ions: 1.0 to 40 g / l, NO ₃ ions: 0.1 to 10 g / l, and free fluorine
0.1 to 3 g / l of nickel ion and 0.1 to 0.1 g of manganese ion in an aqueous solution containing 0 to 1000 ppm.
~ 2 g / l, cobalt ion 0.1-2 g / l, iron ion 0.1-1 g / l, nitrite ion 0.1-1 g
/ L, inorganic peroxide and / or hydrogen peroxide from 0.01 to
Immersed in an aqueous solution of 70 ° C. to which 1 g / l was appropriately added,
An aluminum alloy-treated plate was prepared.

In these treated plates, the amorphous compound was dissolved in concentrated nitric acid, and the elements were quantified by atomic absorption analysis. As is clear from Table 1, all of the examples of the present invention were within the scope of the present invention. A6009 alloy and A5182 alloy treated plate (1 mm x 70 mm x 150 m
m) and the untreated plate, which is in a state of being electrically connected to a single or zinc-nickel alloy plated steel plate with a stainless steel bar,
Zinc phosphate treatment (including alkali degreasing and surface adjustment) and cationic electrodeposition coating (thickness 2
0 μm), intermediate coating (film thickness 35 μm) and top coating (film thickness 35 μm).

The zinc phosphate treatment property was determined by observing the surface of the zinc phosphate film formed on each plate after the zinc phosphate treatment with a scanning electron microscope and examining the deposition state. Evaluation,
：: Crystal precipitation on the entire surface, △: Partial material surface, X: Material surface 50% or more. Table 1 shows the evaluation results.
Shown in The rust resistance was evaluated by cross-cutting the coating film subjected to cationic electrodeposition coating with an NT cutter and then evaluating the rust resistance. The rust resistance is evaluated by salt spray (5% NaCl aqueous solution, 35 ° C, 24 hours) → wet test (50 ° C x 85% R)
H, 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:
The swollen width was 1 mm or more and less than 3 mm, and X: the swollen width was 3 mm or more.

Coating 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. In the evaluation, ○: no cross-cut peeling, Δ: cross-cut peel area less than 5%, x: cross-cut peel area 5% or more. In addition, a 100 mm spherical head overhang tool was used on a treated plate of A6009 alloy and A5182 alloy having a size of 1.0 mm × 30 mm × 300 mm and a length of 200 mm.
After lubricating oil was applied to a test piece having a width of 125 to 140 mm and a molding speed of 10 mm / min. And 10 tons of BHF to determine the break forming height (LDH0) and evaluate workability. Evaluation: ◎: LDH0 value improved by 30% or more over untreated material, ：: LDH0 value improved by 20% or more over untreated material, Δ: 10% or more improved over untreated material,
X: Equal to or less than the untreated material. Furthermore,
As an evaluation of weldability, a test piece under the same conditions was subjected to a continuous hitting test as an electrode, using a tip C type of 4.5 mmφ, a pressure of 200 kgf, a power-on time of 10 cycles, and a power-on condition using an appropriate welding current. . The evaluation was evaluated as ○: improved by 20% or more than the untreated material, Δ: improved by 10% or more than the untreated material, ×: equivalent to or less than the untreated material.

As is clear from Table 1, the results of the present invention examples were all zinc phosphate treatability, thread rust resistance, coating adhesion,
Good results were obtained for both workability and weldability.

[0024]

[Table 1]

[0025]

The Mg-containing aluminum alloy sheet of the present invention can solve the problem of zinc phosphate treatability, which has been a problem in the past. In this case, it has excellent zinc phosphate treatment properties even when it is simultaneously treated with zinc phosphate in contact with a steel sheet. Therefore, the use site of the Mg-containing aluminum alloy sheet is greatly expanded because there is no restriction on the use site due to the zinc phosphate treatment property, and it can be said that the invention is of extremely high industrial value.

[Brief description of the drawings]

FIG. 1 is a scanning electron micrograph of a nonstoichiometric compound containing zinc and phosphoric acid of the present invention deposited on the surface of an Mg-containing aluminum alloy.

Claims (3)

[Claims] 1. An amorphous compound containing zinc and phosphorus in a weight ratio (zinc / phosphorus) of 3.2 to 9.0 on the surface is 0.05%.
Mg-containing aluminum alloy treated sheet for automobiles having excellent zinc phosphate treatment properties characterized by having to 2.0 g / m ^2. 2. The method according to claim 1, further comprising:
Mg-containing aluminum alloy treated sheet for automobiles having excellent zinc phosphate treatment of claim 1, characterized in that it comprises an oil layer of 1.8 g / m ^2. 3. An aqueous solution containing Zn ions: 0.5 to 10 g / l, PO ₄ ions: 5.0 to 40 g / l, NO ₃ ions: 0.5 to 10 g / l, and free fluorine of 200 ppm or more. , M
3. The method of claim 1, wherein the surface of the g-containing aluminum alloy plate is treated. 4. The method of claim 1, wherein the surface of the g-containing aluminum alloy plate is treated with zinc phosphate.