JPH06220647A - Aluminums base stock for electrodeposition coating coated with zinc phosphate coating film and formation of zinc phosphate coating film on aluminums base stock - Google Patents

Abstract

PURPOSE:To form the coating film excellent in corrosion resistance in spite of the film formation on the aluminums base stock which differs in a reaction activity, that is, film forming property against a zinc phosphate treatment. CONSTITUTION:The ratio of the plane index [040]/[311] of the hopeite in a zinc phosphate coating film is <=3. In the forming method of the zinc phosphate coating film, the surface modifying agent containing coloidal titanium phosphate and at least one kind coloidall particles selected from among LaPO4, La2(CO3)3, Zn3(PO4)2, ZrO2, FePO4 and Al2O3 is used, and the zinc phosphate treating agent contains 0.1-2g/l zinc ion, 0.1-3g/l manganese ion and 5-40g/l phosphoric acid ion and also contains 0.05-3g/l fluorine compd. in which a simple fluoride contained is 0.2-0.5g/l in terms of HF and the mol. ratio of [complex fluoride]/[simple fluoride] is >=0.01.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an aluminum-based material for electrodeposition coating coated with a zinc phosphate coating and a method for forming a zinc phosphate coating on the aluminum-based material.
More specifically, it relates to an aluminum-based material having a zinc phosphate coating capable of forming a coating having excellent coating adhesion and corrosion resistance, and a method for forming a zinc phosphate coating of the aluminum-based material.

[0002]

2. Description of the Related Art In recent years, aluminum or aluminum alloy sheets have been used as a material for automobile bodies for weight reduction. Such an automobile body material has a coating film formed by electrodeposition coating such as cationic electrodeposition coating. In many cases, phosphoric acid is used as a pretreatment for electrodeposition coating in order to improve the adhesion and corrosion resistance of the coating film. A zinc phosphate coating treatment is performed to form a zinc coating. When an aluminum or aluminum alloy plate is adopted as an automobile body material, it is often combined with a cold-rolled steel plate or a galvanized steel plate, and such a steel plate and an aluminum-based material are treated at the same time with the same treatment liquid. It is desirable to form a zinc phosphate coating.

However, when such an aluminum-based material is treated with an acidic zinc phosphate coating solution for cold-rolled steel sheet or galvanized steel sheet, aluminum ions are eluted in the treatment solution, resulting in poor chemical conversion on the iron-based surface. There was a problem. In order to prevent such an increase in aluminum ions in the treatment liquid, a method of adding a fluoride to the treatment liquid and precipitating the aluminum ions as Na ₃ AlF ₆ (cryolite) or the like is disclosed in JP-A-57-70281. , JP-A-63-157879 and JP-A-64-684.
No. 81, etc. However, according to these methods, since Na ₃ AlF ₆ or the like adheres to the zinc phosphate coating or is mixed in the zinc phosphate coating,
There is a problem that the adhesion and corrosion resistance of the coating film deteriorate.

In order to solve such a problem, a method of using a zinc phosphate treatment liquid in which the concentrations of simple fluorides and complex fluorides in the zinc phosphate treatment liquid are adjusted to a predetermined range is disclosed in Japanese Patent Laid-Open No. 3-2980.
No. 191071.

[0005]

However, when a No. 6000 series aluminum alloy (Al-Mg-Si alloy) is used as the aluminum-based material, the zinc phosphate coating treatment solution of the above publication has a reaction activity with respect to the treatment solution. It was low, and it was necessary to increase the concentration of active fluorine in the treatment liquid.
However, a zinc phosphate coating formed by simply using a treatment liquid having an increased concentration of active fluorine has a problem of low coating corrosion resistance.

As an aluminum-based material, 500
Even in the case of using a No. 0 series aluminum alloy (Al-Mg alloy), on the surface to be processed which has been ground,
There is a problem that the coating conversion is low, and it is necessary to increase the concentration of active fluorine in the treatment liquid like the 6000 series alloy, and the zinc phosphate coating obtained has poor coating corrosion resistance. An object of the present invention is to solve such conventional problems and to form a coating film excellent in corrosion resistance even with aluminum-based materials having different reaction activities with respect to a zinc phosphate treatment liquid and different film conversion properties. An object of the present invention is to provide an aluminum-based material for electrodeposition coating having a zinc phosphate coating, and a method for forming a zinc phosphate coating of the aluminum-based material.

[0007]

DISCLOSURE OF THE INVENTION The inventors of the present invention have conducted extensive studies on an aluminum-based material coated with a zinc phosphate coating having high coating corrosion resistance for the purpose of solving the above conventional problems, and as a result, The inventors have found that an aluminum-based material coated with a zinc phosphate coating having a specific crystal structure exhibits excellent coating corrosion resistance, and completed the present invention.

That is, the aluminum-based material according to the present invention has a ratio of the surface index of the houpite in the zinc phosphate coating [04
[0] / [311] is 3 or less.

[0009] Hopite is one of the crystal structures of hydrous zinc phosphate, and the surface index [040] corresponds to α-hopite and the surface index [311] corresponds to β-hopite. That is, the present invention is characterized in that the ratio of α-hopite to β-hopite in the zinc phosphate coating is set to a predetermined value or less. The present invention was made based on the finding that the low coating corrosion resistance of conventional zinc phosphate coatings is attributed to α-hopite contained in a large amount in zinc phosphate coatings.

Since the present invention contains a large amount of β-hopite excellent in coating corrosion resistance, when it is coated on the aluminum-based material of the present invention, a coating film excellent in corrosion resistance can be obtained.

In the present invention, the ratio [040] / [311] of the face index of hopite (hereinafter simply referred to as "face index ratio") is determined by measuring the peak intensity of the corresponding face index by X-ray diffraction analysis. The surface index ratio can be obtained from the ratio of peak intensities.

In the present invention, the surface index ratio needs to be 3 or less, and more preferably 2 or less. When the surface index ratio exceeds 3, the effect of the present invention that the coating corrosion resistance is excellent cannot be sufficiently obtained. Further, in the present invention, the aluminum-based material includes aluminum and aluminum alloy.

In the present invention, the coating amount of the zinc phosphate coating is not particularly limited, but is 0.5 to 5 g / m.
It is preferably within the range of ² . Coating amount is 0.5g /
If it is less than m ² , the coating corrosion resistance may not be sufficiently exhibited, and if it exceeds 5 g / m ² , no particular effect is added and it may be unfavorable from the economical point of view. In addition, the coating adhesion may deteriorate.

In the present invention, the manganese content in the zinc phosphate coating is preferably 0.3% by weight or more. If the manganese content is less than 0.3% by weight, it may be difficult to control the surface index ratio in the coating to 3 or less, and the coating corrosion resistance may not be sufficiently improved. Further, the manganese content is preferably 9% by weight or less. Even if it exceeds 9% by weight,
It is economically disadvantageous because the special effect is not added.

The zinc phosphate coating preferably contains a nickel component in the range of 0.1 to 3% by weight. The nickel component has the effect of reducing the surface index ratio in the zinc phosphate coating, that is, increasing the β-hopite formation ratio, and can improve the coating corrosion resistance. When the nickel component is less than 0.1% by weight, such effects are reduced, and it may not be possible to sufficiently improve the coating corrosion resistance. If it exceeds 3% by weight, the content of manganese in the zinc phosphate coating tends to decrease,
The effect of improving the coating corrosion resistance may be reduced.

Further, in the present invention, the sodium content in the zinc phosphate coating is preferably less than 0.2% by weight. Such sodium component is cryolite (N
a ₃ AlF ₆ ) or elpasolite (K ₂ NaAlF
₆ ) Aluminum / fluorine compounds (hereinafter referred to as Al
It is contained in the form of (-F compound)), and such an Al-F compound is easily dissolved in an acid or an alkali. Therefore, when the zinc phosphate coating contains 0.2% by weight or more of a sodium component, it is coated. Corrosion resistance decreases. The sodium component in the zinc phosphate coating is more preferably less than 0.1% by weight.

The zinc phosphate coating forming method of the present invention is the same as that of the present invention.
Formed zinc phosphate coating of aluminum-based material for electrodeposition coating of
This is a method that can
The surface is titanium phosphate colloid and LaPO_Four, La₂(C
O₃)₃, Zn₃(PO_Four) ₂, ZrO₂, FePO_Four
And Al₂O₃At least one colloid selected from
With a surface conditioner containing hydrophilic particles and zinc ion.
0.1 to 2 g / liter, manganese ion 0.1 to 3
g / l, and phosphate ions 5-40 g / l
Fluorine compound is 0.05 to 3 g / liter
Therefore, among the fluorine compounds, simple fluorides have an HF conversion of 0.
2 to 0.5 g / liter, [complex fluoride] / [single
Pure Fluoride] (Molar ratio) 0.01 or more zinc phosphate
And a step of treating with a treatment liquid.
It

The zinc phosphate treatment liquid used in the present invention contains zinc ions in an amount of 0.1 to 2 g / liter. Zinc ion is 0.
If it is less than 1 g / liter, the coating property of the zinc phosphate coating becomes insufficient, the coating amount of the zinc phosphate coating decreases, and the effect of improving the coating corrosion resistance may not be sufficiently exhibited.
If the zinc ion content is more than 2 g / liter, the coating adhesion of the zinc phosphate coating may be reduced.

Manganese ions are contained in an amount of 0.1 to 3 g / liter. When the manganese ions are less than 0.1 g / liter, the manganese content in the zinc phosphate coating is 0.3% by weight.
If the ratio is less than 3, the surface index ratio may not be controlled to 3 or less. Further, even if the amount of manganese ions is more than 3 g / liter, no particular effect is added, which is economically disadvantageous.

Phosphate ions are contained in an amount of 5 to 40 g / liter. If the phosphate ions are less than 5 g / liter, the zinc phosphate coating film may have insufficient coverage. Again 40
Even if it exceeds g / liter, no special effect is added, which is economically disadvantageous.

The content of the fluorine compound is 0.05-3 g /
If it is less than 0.05 g / liter, the coverage of the zinc phosphate coating becomes insufficient, and the effect of improving the coating corrosion resistance may not be exhibited. Further, when the fluorine compound is contained in an amount of more than 3 g / liter, the above-mentioned Al / F compound is mixed in the zinc phosphate coating, and there is a possibility that the corrosion resistance is deteriorated.

Further, in the present invention, among the fluorine compounds in the zinc phosphate treatment liquid, the simple fluoride is 0.
It is contained in the range of 2 to 0.5 g / liter. If the content of the simple fluoride is less than 0.2 g / liter, the coating coverage may be insufficient for an aluminum-based material having a low reaction activity, that is, a coating conversion property. Also,
If the content of simple fluoride is more than 0.5 g / liter, the Al-F compound may be mixed in the zinc phosphate coating in an aluminum-based material having high reaction activity, that is, high film-forming property.

In the zinc phosphate treatment liquid of the present invention, [complex fluoride] / [simple fluoride] (molar ratio) is 0.01 or more. When this value is less than 0.01, the Al-F compound may be mixed in the zinc phosphate coating in the aluminum-based material having high reaction activity, that is, high coating conversion.

Examples of the simple fluoride in the present invention include HF, NaF, KF, NH ₄ F, NaHF ₂ and K.
HF ₂ , NF ₄ HF _{2 and the} like are used, and as the complex fluoride, for example, H ₂ SiF ₆ , HBF ₄ and their metal salts (for example, nickel salt, zinc salt) and the like are used.

The above [complex fluoride] / [simple fluoride]
In (molar ratio), [simple fluoride] is the number of moles in terms of HF. Thus, for example, in the case of HF becomes 1 mol HF, a 2 mol in the case of NaHF ₂ NaHF _2. For [complex fluoride], the number of moles of the compound,
For example, H ₂ SiF ₆ makes 1 mol, and HBF ₄ makes 1 mol.

Further, in the present invention, when the zinc phosphate treatment liquid is used for the treatment of the zinc phosphate coating on the iron-based material as well as the aluminum-based material, the nitrite ion, the organic nitro compound, and the peroxide are further added. It is preferable to contain a film formation accelerator selected from the group consisting of hydrogen. The content of nitrite ion is 0.01-0.5g
/ L, the organic nitro compound is preferably 0.05 to 5 g / L, and hydrogen peroxide is preferably 0.5 to 10 g / L as H ₂ O ₂ . If the amount of the film formation accelerator selected from the group consisting of nitrite ion, organic nitro compound, and hydrogen peroxide is less than these ranges, the coverage with iron-based materials may be insufficient. . On the other hand, when the content is more than these ranges, the coating crystals on the surface of the iron-based material become too fine, the coating amount may decrease, and the corrosion resistance may deteriorate.

The zinc phosphate treatment liquid of the present invention preferably contains nickel ions in an amount of 0.1 to 4 g / liter. If it is less than 0.1 g / liter, the effect of lowering the surface index ratio in the coating film may be reduced, and the effect of improving coating corrosion resistance may be reduced. On the other hand, if it is contained in an amount of more than 4 g / liter, the nickel component in the zinc phosphate coating will increase, and as a result, the manganese content will decrease, and the effect of improving coating corrosion resistance may decrease.

The treatment temperature with the zinc phosphate treatment liquid in the present invention is preferably 20 to 70 ° C., more preferably 3
It is 5-60 degreeC. If the temperature is lower than this temperature range, the chemical conversion of the coating film may be deteriorated and the treatment may be required for a long time.
On the other hand, if the temperature is higher than this temperature range, the treatment solution may be unbalanced due to the decomposition of the film formation accelerator and the precipitation of the treatment solution.

The treatment time of the zinc phosphate treatment is preferably 15 seconds or longer, more preferably 30 to 120 seconds. If the treatment time is less than 15 seconds, a film having desired crystals may not be sufficiently formed. When treating an object having a complicated shape such as an automobile body, it is practically preferable to combine the immersion treatment and the spray treatment. In this case, for example, 15 seconds or more, preferably 30 to
Immersion treatment for 120 seconds, then 2 seconds, preferably 5
Spray for 45 seconds. In order to wash off the sludge attached during the dipping treatment, it is preferable that the spraying treatment be performed for as long as possible.

As described above, the zinc phosphate treatment in the present invention can be carried out by dipping treatment, spraying treatment or a combination thereof.

In the present invention, the surface conditioner used in the pretreatment of the zinc phosphate coating forming treatment is a titanium phosphate colloid and LaPO ₄ , La ₂ (CO ₃ ) ₃ , Zn ₃ (P
O ₄ ) ₂ , ZrO ₂ , FePO ₄ and Al ₂ O ₃ are included in the colloidal particles. By incorporating the above colloidal particles into a titanium phosphate colloid that has been conventionally used as a component of a surface conditioner, the surface index ratio in the zinc phosphate coating can be reduced, and the zinc phosphate having a surface index ratio of 3 or less can be obtained. A coating can be formed.

The titanium phosphate colloid has a Ti content of 0.0
It is preferably contained in an amount of 01 to 0.1 g / liter.
If it is less than 0.001 g / liter, the crystals may be coarsened and the coverage of the zinc phosphate coating may be deteriorated, so that the corrosion resistance may not be improved. On the other hand, if it exceeds 0.1 g / liter, no particular effect is added, which is economically disadvantageous.

The above colloidal particles are preferably contained in an amount of 0.001 to 0.1 g / liter as Me (metal). When Me is less than 0.001 g / liter, it may be difficult to stably control the surface index ratio in the zinc phosphate coating to 3 or less. Even if Me exceeds 0.1 g / liter, no special effect is added, which is economically disadvantageous.

The phosphate group in the surface conditioning agent is preferably 0.05 to 1.5 g / liter as PO ₄ . If it is less than 0.05 g / liter, the crystals may be coarsened, the coverage of the zinc phosphate coating may be deteriorated, and the corrosion resistance may not be improved. Moreover, even if 1.5 g / liter is added,
It is economically disadvantageous because no special effect is added.

The pH of the surface conditioner is preferably in the range of 8.0 to 9.5. When the pH is less than 8.0, the coverage of the zinc phosphate coating deteriorates with time, and the crystals tend to coarsen with time. Even if the pH exceeds 9.5, no particular effect is observed, and the amount of alkali replenished for maintaining the pH is large, which is economically disadvantageous.

As the method of treatment with the surface conditioner, it is possible to apply dipping treatment, spraying treatment, a combination of these treatments, and the like, as in the treatment with the zinc phosphate treatment solution described above. The processing temperature is preferably room temperature to 60 ° C. If it is lower than this temperature range, the effect of adjusting the surface may be insufficient.

On the other hand, if the temperature is higher than this range, the effect of adjusting the surface becomes excessive, and especially when a zinc phosphate-treated film is formed on an iron-based material, the film crystals formed on the surface become too fine, and the film amount is increased. There is a possibility that the corrosion resistance will deteriorate and the corrosion resistance will deteriorate.

The treatment time is preferably in the range of 15 seconds to 5 minutes, and when it is less than 15 seconds, it is difficult to sufficiently obtain the effect of the treatment of the surface conditioner, and it exceeds 5 minutes. However, it is economically disadvantageous because no special effect is added.

[0039]

EXAMPLE FIG. 1 shows a case where a zinc phosphate coating is formed under various conditions to change the surface index ratio in the zinc phosphate coating, and cationic type electrodeposition coating is applied to an aluminum-based material having the zinc phosphate coating. It is a figure which shows the result of having measured the coating film swell width at the time of carrying out the dry-wet compound corrosion test on the obtained coated plate, and shows the relationship between the surface index ratio and the coating film swell width. In this experimental example, a 5000-series aluminum alloy material was used as the aluminum-based material, and the zinc phosphate film forming treatment was performed on the aluminum alloy material in the following procedure.

Degreasing → Washing → Treatment with surface conditioning agent → Treatment with zinc phosphate treatment liquid → Washing → Washing with pure water → Drying

In FIG. 1, in Experimental Example A, Ni and Mn were used.
A zinc phosphate coating is formed using a zinc phosphate treatment liquid that does not contain Further, B forms a coating film with a zinc phosphate treatment liquid containing Mn, and C forms a coating film with a zinc phosphate treatment liquid containing Ni and Mn. As is clear from the comparison of A, B and C, Mn,
Further, it can be seen that the inclusion of Mn and Ni tends to form a zinc phosphate coating having a lower surface index ratio.

In each of Experimental Examples A, B and C, a surface conditioner containing titanium phosphate colloid as a surface conditioner for pretreatment (trade name: Surffine 5N-8: 0.01 g / liter at a concentration of 0.1 g / liter) was used. Liter, PO ₄ 0.5g /
Liter content: manufactured by Nippon Paint Co., Ltd. is used. Experimental Examples A ₁ , B ₁ , and C ₁ were pretreated with a surface conditioning agent containing colloidal particles such as LaPO ₄ described above instead of the conventional surface conditioning agent, as shown in FIG. As shown in, the surface index ratio of the zinc phosphate coating can be further lowered by using such a surface modifier.

In another experimental example shown in FIG. 1 in which the surface index ratio is 3 or more, a zinc phosphate treatment liquid modified with various metals such as Co, Cu, Mg, and Ca is used, and a conventional titanium phosphate colloid-containing surface preparation is performed. It is an example of an experiment pretreated with an agent. Other experimental examples in which the surface index ratio is 3 or less are those treated with a zinc phosphate treatment liquid containing these various metals, and the surface conditioner containing the above-mentioned colloidal particles such as LaPO ₄ as a surface conditioner is used. A zinc phosphate coating is formed after pretreatment with the zinc phosphate coating. As is clear from FIG. 1, by incorporating colloidal particles such as LaPO ₄ as a surface conditioner, a zinc phosphate coating having a small surface index ratio can be formed.

On the aluminum-based material coated with the zinc phosphate coating formed as described above, a commercially available cationic electrodeposition coating was used as an undercoat so that the dry film thickness was 30 μm. Further, a commercially available melamine alkyd coating was used as the intermediate coating and the top coating so that the dry film thickness was 30 μm (intermediate coating) and 40 μm (top coating), and the coating corrosion resistance of the obtained coating film was evaluated.

The coating corrosion resistance was determined by a dry-wet composite test. Make a cross damage to the coating film with a cutter knife, and use a salt spray (5%, 35 ° C x 2 minutes) → dry (60 ° C, 58 minutes) → wet (95% RH, 50 ° C, 3 hours) cycle corrosive environment For 200 cycles, the maximum blistering width (mm) of the coating film from the scratch was measured and evaluated.

As is apparent from FIG. 1, in the aluminum-based material having the zinc phosphate coating having a surface index ratio of 3 or less, the blister width of the coating is remarkably small and the coating corrosion resistance is excellent. Next, the zinc phosphate coating forming method of the present invention will be described in detail with reference to specific examples.

As the aluminum-based material to be treated, a 5000-series aluminum-magnesium alloy was used and treated and coated according to the following steps (Examples 1 to 6 and Comparative Examples 1 to 5). (1) Degreasing → (2) Washing → (3) Surface adjustment → (4) Chemical conversion → (5) Washing → (6) Pure water washing → (7) Drying → (8) Painting Table 1 shows the surface conditioning agents. The composition shown was used.

[0048]

[Table 1]

(A) Surface conditioner Surffine 5N-8 (titanium phosphate colloid former) manufactured by Nippon Paint Co., Ltd. 0.1
Ti 0.01 g / liter, PO at g / liter concentration
₄ Contains 0.5 g / liter.

(B) A solution obtained by adding a lanthanum nitrate solution to the primary sodium phosphate solution, washing the precipitated product (lanthanum phosphate), and drying. (C) Reagent Zn ₃ (PO ₄₎ using ₂ · 4H ₂ O. (D) Product name “Zirconia sol NZS” manufactured by Nissan Chemical Industries, Ltd.
-20A "(e) Product name" Alumina sol 200 "manufactured by Nissan Chemical Industries, Ltd. As the zinc phosphate treatment liquid, one having the composition shown in Table 2 was used.

[0051]

[Table 2]

Each step will be described below. (1) Degreasing An alkaline degreasing agent (“Surf Cleaner SD250” manufactured by Nippon Paint Co., Ltd.) was used at a concentration of 2% by weight, and immersion treatment was performed at 40 ° C. for 2 minutes.

(2) Washing with water Using tap water, a spray washing treatment by water pressure was performed. (3) Surface Adjustment Using the surface adjusting agents shown in Table 1 above, immersion treatment was carried out at room temperature for 15 seconds, and treatment with the surface adjusting agents was performed.

(4) Chemical conversion Using a zinc phosphate treatment solution having the composition shown in Table 2 above, 4
Immersion treatment was performed at 0 ° C. for 2 minutes to form a zinc phosphate coating. (5) Washing with water Using tap water, washing was performed at room temperature for 15 seconds.

(6) Washing with pure water Using ion-exchanged water, immersion treatment was performed for 15 seconds at room temperature. (7) Drying It was dried with hot air of 100 ° C. for 10 minutes.

(8) Painting Cationic electrodeposition paint "Power Top U" manufactured by Nippon Paint Co., Ltd.
-1000 "was used to perform cationic electrodeposition coating (film thickness: 30 μm) according to a conventional method, and a melamine alkyd-based intermediate top coating composition manufactured by Nippon Paint Co., Ltd. was applied on the intermediate coating according to a conventional method. (Thickness 30 μm and 40 μm).

With respect to the zinc phosphate-coated plates and coated plates of Examples 1 to 6 and Comparative Examples 1 to 5 obtained as described above, coating properties and coating quality were evaluated as follows. Coating characteristics-Coating amount (g / m ² ) After pre-weighing a treated plate of a certain area, ² in 1 + 1 nitric acid solution
The zinc phosphate coating was dissolved by immersing it at 0 ° C. for 1 minute, and the coating was weighed after the dissolution to determine the coating amount.

Ni, Mn, Na (%) In the above measurement of the coating amount, the amount of each metal ion in the solution dissolved in the nitric acid solution was determined by atomic absorption spectrometry, and the content of each metal ion was determined from the coating amount. I asked. -Face index ratio The peak intensity ratio of each crystal face of [040] and [311] in the zinc phosphate coating of the zinc phosphate coating-treated plate was measured by the X-ray diffraction method to obtain the surface index ratio.

Coating quality-Fast rust resistance (984 hours) After leaving for 24 hours in a standard state, constant temperature and humidity (50 ° C, 8 hours)
The cycle of 0% RH, 240 hours) and 5% NaCl (immersion for 1 second) was repeated 4 times, and the thread rust was observed from the part where the cross scratch had been made beforehand with the cutter knife, and the maximum thread rust length was measured. evaluated.

Coating film blistering resistance (200 cycles) After the coating film was cross-scratched with a cutter knife, the following cycle was repeated 200 cycles to observe the blistering of the coating film from the cross-scratched part. The maximum blistering width was measured and evaluated.

Salt spray test (JIS K 2371) 2
Leave for minutes → Hot air (60 ℃ × 58 minutes) → Constant temperature and humidity (50
(° C, 95% RH, 3 hours) Table 3 shows the results of the coating properties and coating quality obtained as described above.

[0062]

[Table 3]

Comparative Example 1 is an example in which a surface conditioner containing only titanium phosphate colloid was used as the surface conditioner,
Comparative Example 2 is an example in which the zinc phosphate treatment liquid does not contain simple fluoride, Comparative Example 3 is an example in which the zinc phosphate treatment liquid contains 0.5 g / liter or more of simple fluoride, and Comparative Example 4 is This is an example in which manganese ions are not contained in the zinc phosphate treatment liquid, and Comparative Example 5 is an example in which the complex phosphate is not contained in the zinc phosphate treatment liquid.

As is clear from Table 3, in Examples 1 to 6 according to the present invention, the surface index ratios are all 3 or less, and the yarn rust resistance and the coating film blistering resistance are excellent. In the above-mentioned embodiment, the No. 5000 series aluminum alloy material is used as the object to be treated, but the present invention is not limited to this and can be applied to other aluminum alloys and aluminum. It can be applied to an aluminum-based material that is combined with a cold-rolled steel sheet or a galvanized steel sheet and composited, such as a body material.

[0065]

The aluminum-based material for electrodeposition coating according to the present invention has a zinc phosphate coating having a face index ratio of 3 or less of hopite, so that it has better corrosion resistance than conventional zinc phosphate coatings. It can be an aluminum-based material.

The method for forming a zinc phosphate film of the present invention is a method capable of forming a zinc phosphate film having a facet index ratio of 3 or less, and by following the method of the present invention,
A zinc phosphate coating having a surface index ratio of hopite of 3 or less can be formed on the surface of an aluminum-based material, and an aluminum-based material having excellent coating corrosion resistance can be obtained.

According to the method of the present invention, a zinc phosphate coating having excellent coating corrosion resistance can be formed not only on the surface of the aluminum-based material but also on the iron-based surface and the zinc-based surface. By treating with the same treatment liquid at the same time as the plated steel sheet, it is possible to obtain a material such as an automobile body having excellent coating corrosion resistance.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the surface index ratio of hopite in a zinc phosphate coating and the blistering property of the coating.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tamotsu Nakata 19-17 Ikedanaka-cho, Neyagawa City, Osaka Prefecture Japan Paint Co., Ltd.

Claims (8)

[Claims] 1. An aluminum-based material for electrodeposition coating, which is coated with a zinc phosphate coating, wherein the surface index ratio of the houpite in the zinc phosphate coating [04]
0] / [311] is 3 or less, an aluminum-based material for electrodeposition coating. 2. The coating amount of the zinc phosphate coating is 0.5-5.
The aluminum-based material for electrodeposition coating according to claim 1, which is g / m ² . 3. The aluminum for electrodeposition coating according to claim 1, wherein the manganese content in the zinc phosphate coating film is 0.3% by weight or more and the sodium content is less than 0.2% by weight. System material. 4. The zinc phosphate coating is titanium phosphate colloid.
Do and LaPO_Four, La₂(CO₃)₃, Zn₃(PO
_Four)₂, ZrO₂, FePO_FourAnd Al₂O ₃Choose from
Surface preparation comprising at least one colloidal particle
The film according to claim 1, which is a film formed after the treatment with the agent.
The aluminum-based material for electrodeposition coating according to any one of items. 5. The zinc phosphate coating is zinc ion 0.1.
˜2 g / liter, manganese ion 0.1 to 3 g / liter, and phosphate ion 5 to 40 g / liter, the fluorine compound is 0.05 to 3 g / liter, and the simple fluoride in the fluorine compound is HF conversion. 0.2-0.5
A coating film formed by treatment with a zinc phosphate treatment liquid having a g / liter and a [complex fluoride] / [simple fluoride] (molar ratio) of 0.01 or more.
The aluminum-based material for electrodeposition coating according to any one of 4 above. 6. A pie joint on the surface of an aluminum-based material
The ratio [040] / [311] of the surface index of g is 3 or less
A method for forming a zinc phosphate coating, comprising: a titanium phosphate colloid;_Four, La₂(CO₃)
₃, Zn₃(PO_Four) ₂, ZrO₂, FePO_FourAnd A
l₂O₃At least one colloidal particle selected from
The surface of the aluminum-based material with a surface conditioner containing
Treatment process, zinc ion 0.1-2g / l, manganese ion
0.1-3 g / liter, and phosphate ion 5-40 g /
Liters, fluorine compound 0.05 ~ 3g / liter
Tolu, and simple fluorides of fluorine compounds are converted to HF.
The total is 0.2 to 0.5 g / liter, and [complex fluoride
Substance] / [simple fluoride] (molar ratio) is 0.01 or more
And a step of treating with a zinc phosphate treatment liquid.
Film forming method. 7. The surface conditioner comprises 0.001 to 0.1 g / liter of titanium phosphate colloid as Ti, 0.05 to 1.5 g / liter of phosphate radical as PO ₄ , and colloidal particles of Me (metal). 0.001 to 0.1 g /
7. It contains liter and has a pH of 8.0 to 9.5.
The method for forming a zinc phosphate film according to item 1. 8. The zinc phosphate treatment solution comprises 0.01 to 0.5 g / liter of nitrite ion, and an organic nitro compound of 0.1 to 0.5 g / liter.
05-5g / l, and hydrogen peroxide 0.5-10g
The method for forming a zinc phosphate coating according to claim 6 or 7, containing at least one selected from the group consisting of 1 / liter.