JP3410910B2 - Aluminum material for phosphate treatment and surface treatment method thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phosphating aluminum material for use as a body for automobiles, a housing for home electric appliances and the like which is coated and used. In the present specification, aluminum includes both pure aluminum and aluminum alloy.

[0002]

2. Description of the Related Art Conventionally, steel has been usually used for automobile bodies. As the steel materials for automobile bodies of this type, in addition to ordinary steel materials and high-tensile steel materials, surface-treated steel materials such as galvanized steel materials and alloyed galvanized steel materials are used. Among these, surface-treated steel materials such as galvanized steel materials and alloyed galvanized steel materials are excellent in corrosion resistance, and are therefore recommended especially for parts or vehicle models that require corrosion resistance.

By the way, in an automobile body assembly and manufacturing line using such a steel material, after the body steel material is formed into a predetermined shape by pressing or the like to form each body part, each body part is assembled and spotted. After welding, after degreasing the assembled body, a phosphate treatment, which is a type of chemical conversion treatment, is applied to improve the adhesion between steel and coating and corrosion resistance, and then the electrolysis is applied. It is common to carry out coating and ordinary spray painting.

On the other hand, recently, an aluminum material is often used for the body of an automobile mainly for the purpose of reducing the weight of the vehicle body for improving the fuel consumption of the automobile. In this case, it is still rare to make the entire body of the automobile aluminized, and it is usual to use a steel material and an aluminum material together. In order to assemble and manufacture an automobile body by using such a steel material and an aluminum material in combination, it is required to use the same line as in the case of only the steel material described above. That is, after assembling a body part made of molded steel material and a body part made of molded aluminum material to create a body, the whole body is degreased, then phosphated, and then electrodeposited. Painting and spray painting are performed. If you do this,
Even when the steel material and the aluminum material are used in combination, there is no need to newly establish another assembly and production line, and the continuity of the process is maintained, which is advantageous in terms of manufacturing cost. However, in this case, since the aluminum material is also subjected to the phosphate treatment at the same time as the steel material, the following problems occur.

That is, when the aluminum material is subjected to the phosphating treatment, a phosphating film is not uniformly and densely formed on the aluminum material, resulting in a problem that the corrosion resistance after coating is poor. Furthermore, the surface of the aluminum material is dissolved during the phosphate treatment, and Al ions are eluted in the treatment bath. Therefore, as described above, the phosphate is simultaneously applied to the steel material and the aluminum material that are integrated as an automobile body. During the treatment, aluminum ions eluted from the aluminum material form a passivation film of aluminum on the surface of the steel material, which also hinders the formation of a phosphate-treated film on the surface of the steel material. There is a problem that sufficient corrosion resistance and sufficient adhesion of the coating film cannot be obtained.

As one measure against such a problem, there is a method of adding a fluorine compound to a phosphate treatment bath to remove an oxide film on the surface of an aluminum material and form a phosphate treatment film uniformly. U.S. Pat. No. 3,619,300
Proposed in the issue. In this method, Al ions dissolved in the treatment bath are converted into elpasolite (K ₂ NaAl
Since the precipitate can be removed as F ₆ ), the above-mentioned problems can be solved. However, in the case of this proposed method, there are problems in terms of concentration control of the phosphate treatment bath, waste liquid treatment, equipment corrosion countermeasures, and the like.

As another countermeasure, Japanese Patent Laid-Open No. 61-15
In Japanese Patent No. 7693, there is proposed a method of performing zinc-based plating in advance before the phosphate treatment. This proposed method is based on the fact that a Zn plating layer or Zn
The alloy plating layer is formed with an adhesion amount of 1 g / m ² or more. By previously forming the zinc-based plating film in this way, it is possible to remove Al ions from the aluminum material during the subsequent phosphate treatment. Does not elute into the bath, so that even if the body made of both aluminum and steel is subjected to phosphating, a sufficient phosphating film can be formed on the steel, and It is said that a phosphate-treated film can be formed on the surface as well.

Further, Japanese Patent Application Laid-Open No. 8-99256 proposes a method of preventing the amount of zinc phosphate film formed in a ground portion from decreasing with an Al—Mg alloy containing Cu.
That is, it is a method of grinding in the presence of one kind or two or more kinds of metals nobler than aluminum and oxides of those metals. By doing so, it is difficult to cause an electrochemical difference between the non-ground portion of the material where Cu is concentrated on the surface in the pickling treatment and the ground portion where it is not so that unevenness of the zinc phosphate film formation amount is prevented. Therefore, specifically, copper, copper oxide, or zinc oxide is used.

[0009]

Generally, a coated aluminum material is remarkably excellent in corrosion resistance unless the coating film has defects such as scratches and pinholes, but the coating film is damaged by flying stones while the automobile is running. If this occurs, corrosion of the aluminum of the base proceeds from the scratched portion, the coating film swells, and the appearance becomes poor. The appearance defect due to the blister of the coating film is affected not only by the corrosion resistance of the aluminum material of the base material itself but also by the uniformity and denseness of the phosphate-treated coating of the coating base. In particular, when a phosphate coating is formed using a zinc-based plating layer as a medium as proposed in JP-A-61-157693, it is necessary to form a uniform and dense zinc-based plating layer without pinholes. However, in the case of the above proposal, the adhesion of the zinc-based plating layer to the aluminum substrate is low,
It was difficult to reliably form a uniform and dense zinc-based plating layer without pinholes. In addition, the cost is naturally increased by plating. Furthermore, if the zinc-based plating layer remains after the phosphate film is formed, there is a potential difference with aluminum, which deteriorates the corrosion resistance. Further, in Japanese Patent Laid-Open No. 8-99256, it is intended to prevent unevenness in the amount of phosphate film formation between the non-ground portion and the ground portion, but to increase the amount of phosphate film formation and the coverage of the entire material. is not.

The present invention has been made in view of the above circumstances, and provides an aluminum material for phosphating in which a pretreatment for forming a dense and fine phosphating film on the surface of the aluminum material is devised. That is the purpose.

[0011]

Means for Solving the Problems The present inventors have considered that the reason why the aluminum material is poor in phosphating property as compared with the steel material is that the phosphating film used for "surface conditioning" before the usual phosphating process. It was considered that the titanium colloid, which is said to act as a nucleus for the formation, is less likely to adhere to the aluminum material than the steel material. In order to improve the phosphating property of aluminum materials, it is necessary to previously attach to the surface of the aluminum material a substance that becomes the nucleus of the phosphate film formation or a substance that promotes the adhesion of titanium colloid. The present invention has been found out.

[0012] Specifically, the invention according to claim 1 is 9
<Poorly soluble in alkali with pH ≦ 14, and 5 ≦ p
Particles having a maximum particle size of 0.0010 to 10 μm, which is a metal inorganic compound having poor solubility in water and having a H ≦ 9, are embedded in at least a part of the surface, and are measured at an arbitrary 100 μm ^2. An aluminum material for phosphating, characterized in that

According to the second aspect of the present invention, before the subsequent step of molding-alkali degreasing-phosphate treatment and subsequent steps, the aluminum material surface is hardly soluble in an alkali having a pH of 9 <pH≤14, and 5 A suspension containing 0.01 to 50 wt.% Of a metal inorganic compound having a poor solubility in water having a pH of ≤ pH ≤ 9 is adhered and then rubbed to at least partially embed the inorganic compound particles on the surface. A surface treatment method for a phosphate-treating aluminum material, characterized in that the surface treatment is performed.

In Claims 3 and 4, titanium oxide, magnesium oxide, tungsten oxide, niobium oxide, aluminum oxide, zinc oxide, cuprous oxide are used as the inorganic compounds of the metals used in Claims 1 and 2. , Cupric oxide, ferric oxide, molybdenum oxide, magnesium hydroxide, nickel hydroxide, magnesium carbonate, calcium carbonate, zinc phosphate, magnesium oxalate, barium titanate, sodium metavanadate, ferric sulfate, calcium silicate , Magnesium hydrogen phosphate, and ammonium tungstate.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The aluminum material for this use usually undergoes a post process of molding-alkali degreasing-phosphate treatment after being delivered from the aluminum material manufacturer to the user. Therefore, if the metal inorganic compound adhering to the surface is dissolved by the alkaline degreasing treatment, it does not act as a nucleus for forming a phosphate film, and does not act as an effect for promoting the adhesion of the titanium colloid for surface adjustment. Therefore, the metal inorganic compound used in the present invention needs to be hardly soluble in alkali having 9 <pH ≦ 14. Further, when dissolved in water having a pH of 5 ≦ pH ≦ 9 and ionized, it is considered to act as particles of the inorganic compound of the metal, which is a nucleus for forming a phosphate film,
Alternatively, it does not promote the adhesion of titanium colloid. Therefore, the metal inorganic compound used in the present invention has a pH of 5 ≦ pH.
It is also necessary to show poor solubility in water of ≦ 9.

Examples of the inorganic compound of a metal having such characteristics are titanium oxide, magnesium oxide, tungsten oxide, niobium oxide, aluminum oxide, zinc oxide, copper oxide, ferric oxide, molybdenum oxide, magnesium hydroxide, water. Nickel oxide, magnesium carbonate, calcium carbonate, zinc phosphate, magnesium oxalate, barium titanate, sodium metavanadate, ferric sulfate, calcium silicate, magnesium hydrogen phosphate, ammonium tungstate, and the like. The selected one may be used, or two or more may be mixed and used.

The particle size distribution of the inorganic compound of the metal used may be over a wide range, but the particle size is 0.001.
Since particles of 0 to 10 μm are considered to exhibit the above effect, at least the inorganic compound of the metal existing in a state of being partially embedded in the surface of the aluminum material has a maximum particle size of 0.0
The particle size is 010 to 10 μm. Particle size is 0.0010μ
When it is less than m, it does not act as a nucleus for forming a phosphate film or promoting adhesion of titanium colloid. When particles having a particle size of more than 10 μm are present in a state of being partially embedded in the surface of the aluminum material, a phosphate film is formed around the particles and the particles become granular, which deteriorates the adhesion of the phosphate film and causes a decrease in the adhesiveness after coating. Poor adhesion and appearance after painting. For the same reason as above, the particle size of the metal inorganic compound is preferably 0.0050 to 5 μm, more preferably 0.0100 to 3 μm. The coverage of the particles of the inorganic compound of the metal is 20 to 80% when measured at an arbitrary 100 μm ² . If it is less than 20%, the nucleus for forming a phosphate film or the promotion of adhesion of titanium colloid is small and the sufficient effect is not exhibited. On the other hand, when the coverage of the particles of the inorganic compound of the metal exceeds 80%, the particles become continuous and become large lumps, which is a site for nucleation of phosphate film formation or promotion of adhesion of titanium colloid. The number becomes too small and inhibits the formation of a phosphate film.

The method of making particles of the inorganic compound of the metal partially embedded in the surface of the aluminum material to have a coverage of 20 to 80% by measuring at an arbitrary 100 μm ² is as follows. First, a suspension of an inorganic compound of these metals is attached. This is done by spraying the suspension on an aluminum material or by immersing the aluminum material in the suspension. By using the suspension to adhere to the plate surface, it can be evenly adhered. If the particles of the inorganic compound of the metal are rubbed on the surface of the aluminum material as a powder without using a suspension, not only cannot the particles be uniformly attached, but also the surface of the aluminum plate is scratched. The particle size distribution of the metal inorganic compound used as described above may extend over a wide range, but particles having a particle size of 0.0010 to 10 μm are considered to exhibit the above-mentioned action, and therefore the maximum particle size of 0.0
It is preferable to suspend the inorganic compound particles having a size of 01 to 10 μm. After that, the inorganic compound particles are at least partially embedded by rubbing them in a state where they are not completely dried. By rubbing in a state where it is not completely dried, scratches are less likely to occur on the surface of the board as compared with rubbing in a state where it is completely dried. In this specification,
“Rubbing” refers to an operation of mechanically rubbing to embed the particles on the surface of the aluminum material. Specific examples include brushing using a brush roll, light pressure reduction using a rubber roll or sponge, and buff polishing using a polishing cloth. However, since deep scratches on the surface of the aluminum plate may cause breakage during molding, the depth of traces remaining after rubbing is preferably less than 10 μm. This "adhesion-rubbing treatment" may be performed at any step after the final thickness (cold rolling) at the time of manufacturing an aluminum material, and after the inorganic compound of the metal is adhered, distortion correction (leveler), hot water washing, heat treatment , Cutting, etc. may be used. However, when the aluminum degreasing process and the alkaline degreasing process of strong etching are performed later, the aluminum base is dissolved and the inorganic compound of the partially embedded metal is removed, and the action as a phosphate film formation nucleus or the surface conditioning The action of promoting the adhesion of titanium colloid does not work. Therefore, when there is pickling and alkaline degreasing treatment, it is preferable to carry out "adhesion-rubbing treatment" thereafter.

The suspension used contains an inorganic compound of a metal.
It is contained at a concentration of 01% to 50%. If the concentration of the inorganic compound is less than 0.01%, the particle coverage is low, and the effect as a phosphate film forming nucleus or the effect of promoting the adhesion of titanium colloid is not achieved. If the concentration exceeds 50%, not only the cost increases but also the particle coverage becomes too high. Therefore, 0.01% ~
The concentration is 50%, but 0.1% to 10% is more preferable for the same reason.

The aluminum plate subjected to the treatment of the present invention may be subjected to a phosphate treatment such as zinc phosphate treatment according to a conventional method after the molding-alkali degreasing step. The amount of phosphate film deposited is 0.5-3 g
/ M ² is preferred. In this case, the "surface adjustment" with titanium colloid prior to the usual phosphate treatment is not necessary, but may be performed. Whether treated with "surface conditioning" or not, the treated aluminum material of the present invention has many nucleation points of phosphate through promoting adhesion of titanium colloid or directly. Therefore, a uniform film is formed with a phosphate film crystal size of 8 μm or less, and excellent coating film adhesion is obtained when the film is subsequently applied for practical use. If a long time is likely to elapse before the phosphate treatment is applied, immediately after the treatment of the present invention, a rust preventive oil having a viscosity of 1 to 4 C.ST at 40 ° C. is 0.1 to 4 C.ST.
By applying 2 g / m ² , the surface deterioration of the aluminum plate can be prevented.

The component composition of the aluminum material which is the base material of the aluminum material for phosphating of the present invention is not particularly limited as long as it is subjected to phosphating and used for coating. In addition to aluminum, various aluminum alloys can be used. Particularly in the case of automobile body applications, which are the main targets of the present invention, Al-M
g-based alloy (JIS 5000 series alloy), Al-Mg-
The Si-based alloy (JIS 6000 series alloy) is most suitable.
The method for manufacturing the base aluminum material itself is not particularly limited, and may be the required final material thickness through ordinary manufacturing processes such as casting, heating, hot rolling, cold rolling, and annealing.

[0022]

EXAMPLES Table 1 shows the chemical composition of the aluminum alloy used in the present invention.

[0023]

[Table 1]

Often used for automobile bodies 5
5182 as a representative of 000 series alloys and 6000 series alloys
And 6101 were used. For both alloys, the amount of Cu used was particularly small within the standard range. This is because if the amount of Cu is large, the phosphating property is improved as a whole, and the phosphating property difference is less likely to occur. On the surface of a 1.0 mm thick aluminum plate having the composition shown in Table 1, the particles of the inorganic compound of the metal shown in Table 2 were immersed in pure water at room temperature and immersed in a suspension liquid,
After rubbing with a nylon brush on the surface of the aluminum alloy having the above composition, it was washed with water and dried to obtain a test piece. This test piece was post-treated with alkaline degreasing (FC-L4460: 43 ° C × 2min PH = 10.5, manufactured by Nippon Perkazing Co., Ltd.) → washing → surface conditioning
(PL-4040: Made in Japan-Karizing room temperature x 30 sec) → Zinc phosphate (PB-L3020: Made in Japan-Karizing 43 ° C x 60 sec) → Washed →
Phosphate treatment was performed in the drying step. As a comparative example, a test piece labeled as a conventional method was also prepared in which the treatment of embedding metal inorganic compound particles was not performed. The maximum particle diameter and the particle coverage of the inorganic compound were mainly measured by EPMA, and SIMS was used for particles of less than 0.1 μm which cannot be measured by this.

[0025]

[Table 2]

Regarding this test piece, first, a phosphate film coverage and a phosphate film crystal size, and a test piece subjected to cation electrodeposition coating (coating thickness 20 μm) after the phosphate treatment. For, the properties of the coating film and the adhesion of the coating film were investigated. Phosphate film coverage The higher the film coverage, the better the finish of the film without the occurrence of citron skin on the surface of the film after electrodeposition coating. In the present invention, S
The film coverage was visually evaluated by EM (× 300) observation. If the coverage is 90% or more, the performance of the coating film surface after painting is satisfactory. ⊚ If the coverage is 80 to 89%, the performance of the coating film surface after coating is practically sufficient. ○ If the coverage is 60 to 79%, the performance of the coating film surface after coating is usable. Δ When the coverage is 59% or less, the performance of the coating film surface after coating cannot be used. × Phosphate film crystal size The smaller the film crystal size, the higher the film coverage and the better the coating property and corrosion resistance. The larger the film crystal size, the lower the coating ratio and the lower the coating property and corrosion resistance.
In the present invention, the average particle size was measured by SEM (× 1500) observation. If it is 6 μm or less, it is satisfactory. ⊚ A thickness of 7 to 8 μm is practically sufficient. ○ If it is 9 to 12 μm, it can be used. Δ If it is 13 μm or more, it cannot be used. × Properties of Electrodeposition Coating Film In the invention of the present application, the surface roughness of the electrodeposition coating film and the state of occurrence of granular spots were visually determined. ◎ There is no citron skin or spots. ○ Yuzu skin is weak, and no spots occur. △ No spots were found on the yuzu skin. × There are spots in the yuzu skin. In the invention of the present application, the number of remaining coating films was evaluated by immersing the coating film in pure water at 40 ° C. for 240 hours and then peeling off the cross-cut tape. 100 (no peeling) is perfect. ⊚ A value of 98 to 99 is practically sufficient. ○ If it is 95 to 97, it can be used. If it is Δ94 or less, it cannot be used. ×

The results are shown in Table 2. Those within the scope of the present application are evaluated as "satisfactory" or "practically sufficient" in all of the phosphate film coating rate, phosphate film crystal size, electrodeposition coating film property, and electrodeposition coating film adhesion. , The average particle size of ferric oxide is 2
If it is too large as 0 μm, the surface properties of the electrodeposition coating film and the adhesion of the electrodeposition coating film are poor, and if the concentration of nickel oxide in the suspension is as high as 60%, the particle coverage becomes too high. If the zinc phosphate coating has a large crystal size and the zinc phosphate coating has a low coverage, and the zinc phosphate concentration in the suspension is as low as 0.001%, the particle coverage is too low, resulting in The crystal size of the zinc oxide film is large, the coverage of the zinc phosphate film is low, and the surface property of the electrodeposition coating film and the Poor adhesion and poor phosphate film coverage and film crystal size. Although not shown in the table, a high level of phosphate film coverage was also shown in the ground portion where grinding after molding was carried out by a usual method. Although all of the above are the results when there is no prior pickling treatment, according to the present invention a good phosphate film can be obtained without prior pickling treatment, resulting in good coating properties. And coating film adhesion can be obtained.

[0028]

EFFECT OF THE INVENTION In the aluminum material for phosphating according to the present invention, as a base of the phosphating film, the aluminum material surface is hardly soluble in alkali of 9 <pH ≦ 14 and 5 ≦ pH. Since particles having a particle diameter of 0.001 to 10 μm of a metal inorganic compound having a poor solubility in water of ≦ 9 are present in a state of being at least partially embedded, the particles are attached with a surface-adjusted titanium colloid. The phosphating property is improved by the action as a phosphite film-forming nucleus through the accelerating action or directly. The improvement of the phosphate treatment property, in turn, improves the coatability to obtain a good coating film, and improves the coating film adhesion after coating. Therefore, it became possible to obtain excellent corrosion resistance after painting. Further, even if alkaline degreasing is performed between the treatment of the present invention and the phosphate treatment, this effect is maintained unless the conditions are such that the aluminum base is dissolved. Therefore, the phosphating aluminum material of the present invention is most suitable for applications such as automobile bodies to which coating is applied.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI C25D 5/30 C25D 5/30 (56) References JP-A-6-25866 (JP, A) JP-A-2-19475 (JP , A) JP 4-2882 (JP, A) JP 63-162881 (JP, A) JP 60-39171 (JP, A) JP 63-76883 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) C23C 22/00-22/86 C23C 24/02 C25D 5/30

Claims (4)

(57) [Claims] 1. The surface of an aluminum material has 9 <pH ≦ 14.
Maximum particle size 0.0010 of the inorganic compound of the metal, which is hardly soluble in the alkali and is hardly soluble in the water of 5 ≦ pH ≦ 9
Particles with a size of 10 μm are embedded in at least a part of the surface, and the area coverage is ² when measured at an arbitrary 100 μm 2.
An aluminum material for phosphating, characterized by being present in an amount of 0 to 80%. 2. Before the molding-alkali degreasing-phosphate treatment and subsequent subsequent steps, 9 <pH≤
0.01 to 50 w of a metal inorganic compound which is hardly soluble in alkali of 14 and hardly soluble in water of 5 ≦ pH ≦ 9
A surface treatment of an aluminum material for phosphating, characterized in that the inorganic compound particles are at least partially embedded in the surface by adhering a suspension containing t. Method. 3. The metal inorganic compound is titanium oxide, magnesium oxide, tungsten oxide, niobium oxide, aluminum oxide, zinc oxide, cuprous oxide, cupric oxide, ferric oxide, molybdenum oxide, magnesium hydroxide. , Nickel hydroxide, magnesium carbonate, calcium carbonate, zinc phosphate, magnesium oxalate, barium titanate, sodium metavanadate, ferric sulfate, calcium silicate, magnesium hydrogen phosphate, ammonium tungstate or one or two selected from The aluminum material for phosphate treatment according to claim 1, wherein the aluminum material is at least one kind. 4. The inorganic compound of metal is titanium oxide, magnesium oxide, tungsten oxide, niobium oxide, aluminum oxide, zinc oxide, cuprous oxide, cupric oxide, ferric oxide, molybdenum oxide, magnesium hydroxide. , Nickel hydroxide, magnesium carbonate, calcium carbonate, zinc phosphate, magnesium oxalate, barium titanate, sodium metavanadate, ferric sulfate, calcium silicate, magnesium hydrogen phosphate, ammonium tungstate or one or two selected from The method for surface treatment of an aluminum material for phosphate treatment according to claim 2, wherein the surface treatment method is at least one kind.