JP2003013253A - Aluminum-alloy structural material superior in adhesiveness to coating and method for evaluating adhesiveness to coating of aluminum-alloy structural material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an Al-alloy structural material provided with an Al hydrated oxide film superior in adhesiveness to a paint film, and a method for evaluating adhesiveness to a paint film of the Al-alloy structural material with the Al hydrated oxide film. SOLUTION: The Al-alloy structural material used after being phosphatised and painted has an aluminum hydrated oxide film on the surface of the structural material before the above treatment, of which the thickness is 1,500-10,000 angstrom (Å), and of which the contact angle of water droplet for indicating the wettability of the film surface is 20 degree or less. The adhesiveness to a paint film is evaluated by the contact angle, which indicates the wettability of the surface of the hydrated oxide film.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an aluminum alloy structural material excellent in coating film adhesion (hereinafter, simply referred to as aluminum).
It is referred to as Al) and a coating film adhesion evaluation method for aluminum alloy structural materials.

[0002]

2. Description of the Related Art In recent years, in response to global environmental problems caused by exhaust gas and the like, it has been pursued to improve fuel consumption by reducing the weight of vehicle bodies such as vehicles, ships, aircrafts, motorcycles and automobiles. As part of the weight reduction of this transport aircraft body,
The use of Al alloy materials (rolled sheets, extruded shapes, wrought Al alloy materials such as forged materials) for structural members such as frame materials is also increasing. Al alloy material has a specific gravity of about 1 / compared to steel materials.
It is as light as 3 and has a large weight saving effect.

Most of these Al alloy materials (Al alloy structural materials) for structural materials such as vehicle body of transport aircraft are not Al alloy materials alone, but
It is often used as a part of structural members together with the steel materials that have been used so far. In addition, the corrosion resistance of the Al alloy is utilized, and it is used without coating, but it is often used after being molded, bonded, or assembled for structural materials, and then painted.

Taking the manufacturing process of an automobile panel of automobile members as an example, a steel plate or an Al alloy plate is formed into a predetermined shape by press forming and then assembled together with other parts as an automobile body structural member. After that, it is completed as an automobile body by a coating base treatment with a phosphate treatment such as zinc phosphate and a coating treatment such as cationic electrodeposition coating. Among them, the panel outer panel located on the outer side of the automobile body has not only mechanical properties such as strength but also sharpness that affects the appearance of the automobile, thread rust resistance against surface scratches, coating adhesion, etc. Required.

However, when the Al alloy material and the steel material are subjected to the phosphate treatment, elution of Al ions from the surface of the Al alloy material becomes a problem. When the amount of Al ions eluted into the phosphate bath increases, a new problem arises in that the zinc phosphate treatment of the steel material is impaired.

Of course, accumulated Al from the zinc phosphate treatment bath
Ions should be removed, but the loss of zinc phosphate bath due to removal and the cost of processing equipment are large, resulting in cost increase from the automobile manufacturing line where energy saving and efficiency are strictly pursued Becomes

For this reason, the present inventors have previously proposed, as an Al alloy material that prevents the elution of Al during zinc phosphate treatment,
JP-A-2001-20080, JP-A-2001-20082, etc.,
We proposed an Al alloy material with a hydrated oxide film of Al provided on the surface in advance.

According to this hydrated oxide film of Al, when the Al alloy material is treated with zinc phosphate, the Al alloy material can be removed from the surface of the Al alloy material.
Elution of Al ions can be significantly suppressed.

[0009]

However, this Al alloy material provided with a hydrated oxide film of Al is basically an Al alloy material even when a hydrated oxide film of Al is provided under the same conditions. When the material is subjected to zinc phosphate treatment and coating treatment, there arises a problem that the adhesiveness of the coating film (coating film adhesiveness) varies.

In addition, as an Al alloy structural member for a vehicle body of a transportation machine, it usually takes several weeks to several months from the formation of the hydrated oxide film of Al to the treatment with zinc phosphate. Therefore, depending on the storage condition of the Al alloy material during this period, there is a possibility that the coating film adhesion may be reduced.

When the adhesion of the coating film is lowered, problems occur such that the corrosion resistance of the Al alloy structural member is lowered and the coating film is peeled off. In the structural member application intended by the present invention, this problem is not merely an aesthetic problem, but in a severe saltwater corrosive environment such as seawater, the thickness of the Al alloy structural member decreases due to corrosion, and the strength and durability of the structural member are reduced. It causes a problem of deterioration of sex.

Further, conventionally, there is no method for evaluating the coating adhesion of the Al hydrated oxide coating itself before the phosphate treatment and the cationic electrodeposition coating treatment. Therefore, at present,
In order to evaluate the coating adhesion of Al hydrated oxide coating, a phosphate treatment and a coating treatment are actually performed, and after further dipping in ion-exchanged water for 10 days, a cross-cut tape peeling test is performed. In the process, it is the actual situation that an evaluation means that requires a long time is used.

In view of these problems of the prior art, an object of the present invention is to provide an Al alloy structural material provided with a hydrated oxide film of Al having improved coating adhesion and a hydrated oxide film of Al. Was
An object of the present invention is to provide a method for evaluating the coating film adhesion of an Al alloy structural material.

[0014]

In order to achieve this object, the subject matter of claim 1 of the aluminum alloy structural material of the present invention is an aluminum alloy structural material used after being subjected to a phosphate treatment and a coating treatment. The hydrated oxide film of aluminum is preliminarily provided on the surface of the structural material before the treatment, and the hydrated oxide film of aluminum has a thickness of
It is 1500 to 10000 angstroms (Å), and the contact angle of water droplets showing the wettability of the coating surface is 20 ° or less.

Further, the gist of the coating film adhesion evaluation method for an aluminum alloy structural material according to claim 2 of the present invention is that the aluminum alloy structural material provided with a hydrated oxide film of aluminum on the surface is treated with phosphate and coating. Is a method of previously evaluating the adhesion of the coating film, which is to evaluate the adhesion of the coating film by the contact angle of a water droplet showing the wettability of the surface of the hydrated oxide film of aluminum.

The coating adhesion of the Al alloy material is affected by the cleanliness and roughness of the surface of the Al alloy material, and the cleanliness is evaluated by the contact angle of water droplets showing the wettability of the surface of the Al alloy material. That is, JP-A-2001-49458 and JP-A-9-1334.
It is known from Japanese Patent Publication No. 93 and the like.

Among these, in Japanese Patent Laid-Open No. 2001-49458, an Al which is formed into a lid shape after painting, particularly a lid material for a beverage can.
It discloses that the alloy material is grounded with a commercially available chromium-based, titanium-based, or zirconium-based chemical conversion treatment agent, and then acrylic, urethane-based, ester-based, ethylene-based, or epoxy-based resin coating is performed. . Then, at the time of this coating, the cleanliness of the Al alloy material surface is set to 30 ° or less at the contact angle of water droplets showing wettability, and polar groups such as active OH groups are increased on the Al alloy material surface, The gist is to promote the chemical bonding of the film and improve the adhesion of the coating film during the molding process.

On the other hand, the present invention is for a structural material such as a panel material for a transportation machine which is not disclosed in Japanese Patent Laid-Open No. 2001-49458, which is used after being subjected to phosphate treatment and painting after molding, joining or assembling. The difference is that the target is an Al alloy material. In JP 2001-49458 A, the surface is usually
In contrast to Al alloy material that is an Al oxide film, in the present invention, when subjected to coating treatment, water droplets showing the wettability of a hydrated oxide film of Al having a different composition from Al oxide. The difference is that the point is to control the contact angle of 20 ° or less.

As will be described later, the Al hydrated oxide film in the present invention is an Al hydrated oxide film formed by the hydration reaction of the Al oxide, unlike the above-mentioned normal Al oxide film. is there. Depending on the generation conditions, the normal Al oxide film may also
Some polar groups such as OH groups are also included. However, most of the composition is a film composed of Al oxide. On the other hand, most of the hydrated oxide film of Al in the present invention is OH.
It is a hydrated oxide of Al having polar groups such as groups, and the film composition is completely different.

In the present invention, according to the suggestion of Japanese Patent Laid-Open No. 2001-49458, the hydrated oxide of Al, which should have improved the adhesion of the coating film by increasing the polar groups such as OH groups. An attempt is made to solve the problem of the peeling property of the coating film (when subjected to the phosphate treatment and the coating treatment) in the coating film. Therefore, as a result, although the point of controlling the contact angle of water droplets showing the wettability of the film to a certain value or less is common, the present invention and JP 2001-494A
The technical idea and the 58 gazette differ greatly with the effect.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION (Hydrated oxide film of Al) In the present invention, a hydrated oxide film of Al means the general formula: Al
A film of hydrated oxide of Al, which is represented by ₂ O ₃ · XH ₂ O and is formed by a hydration reaction of an oxide of Al. The hydrated oxide of Al in the present invention is not particularly limited to the type, morphology, crystal structure, crystallinity, etc. of the hydrated oxide depending on the degree of hydration (value of X). However, among the hydrated oxides of Al, those of pseudo-boehmite having the X value of about 1.5 to 1.9 are generally referred to as boehmite coatings.

Then, the identification of these film structures is performed by observing the incident angle of 75 in addition to the morphological observation by the scanning electron microscope.
This can be done by FTIR (Fourier Transform Infrared Spectrophotometer) analysis using parallel polarized light of degrees. That is, by FTIR,
3000 to 3700 when the absorbance of the hydroxyl group spectrum is displayed
cm ^-1 (Kaiser) AlO found in the vicinity ← → absorption spectrum due to stretching vibration of H, and 1000~1050cm are found in the vicinity of ^-1 Al ← → absorption spectrum due to stretching vibrations of OH,
Furthermore, the presence or absence of the hydrated oxide film of Al of the present invention was confirmed by confirming the existence of one or more of the absorption spectra due to the stretching vibration of OAl ← → O observed near 800 to 600 cm ^-1 . It can be distinguished from the Al oxide film.

Further, the distinction between the hydrated oxide film of Al and the coating film and the measurement of the film thickness are carried out by using the scanning type as described above for the fracture surface of the Al alloy material (for example, the fracture surface due to 180 ° bending of the Al alloy material). It can be observed by 20,000 times or more with an electron microscope. In addition,
This magnification, as the film thickness of the hydrated oxide of Al becomes thinner,
Higher magnification is required. In addition, the hydrated oxide film of Al can be identified by X-ray diffraction, and morphological observation can be performed by a transmission electron microscope.

(Film Thickness of Hydrated Oxide Film of Al) Further, the film thickness of the hydrated oxide film of Al in the present invention is 1500 to 10000 angstrom (Å). If the film thickness is less than 1500Å, the absolute amount of the film thickness is insufficient, and when the Al alloy material is treated with zinc phosphate, the elution of Al ions from the Al alloy material surface cannot be significantly suppressed.

On the other hand, when the film thickness exceeds 10,000 Å, the adhesion of the hydrated oxide film of Al to the Al alloy material is rather lowered,
The coating film peelability cannot be improved.

(Method for Producing Al Hydrated Oxide Film) The Al hydrated oxide film in the present invention is formed after forming and welding joining an Al alloy material to a structural member such as a transport machine, or before these. In advance, at the stage of Al alloy material, at least before the phosphate treatment.

The hydrated oxide film of Al is produced by using an Al alloy material or
The Al alloy structural member surface is pre-treated by degreasing or washing with an organic solvent or alkaline solution, and then directly contacted with high temperature water or steam, or the Al alloy material surface is treated with Al.
After forming the oxide layer of the above, a method of converting into a hydrated oxide film of Al by a hydration reaction, further, after forming a hydrated oxide film of these Al, a method of adjusting the hydration amount by heating, etc. Is appropriately selected.

The water or water used to form the hydrated oxide film of Al is a neutral or weakly alkaline bath, more specifically, tap water, pure water, or an aqueous solution of triethanolamine or ammonia. Is used.

At this time, the higher the temperature for forming the hydrated oxide film of Al (contact temperature of water and water) is, and the longer it is, the denser the hydrated oxide film of Al becomes, and the above-mentioned film peeling occurs. It is possible to improve the sex.

For example, although it varies depending on the chemical composition of the Al alloy material and the treatment liquid for the hydrated oxide film of Al, at the treatment temperature of less than 70 ° C. or the short-time treatment within 10 minutes, the hydrated oxide film of Al is formed. Could not be densified, and the thickness of the hydrated oxide film of Al should be 15
Can't do more than 00Å.

However, as treated water, tap water, oil content,
And other metal ions and impurities, etc. are included in the treated water. Will be included. Then, in such a case, other metal ions or impurities are mixed in the hydrated oxide film of Al, and the contact angle of water droplets showing the wettability of the hydrated oxide film of Al in the present invention is 20. There is a high possibility that the temperature cannot be reduced below

According to the findings of the present inventors, as described above, even if the basic conditions such as the treatment conditions and the film thickness for the hydrated oxide film formation of Al are satisfied, the Al alloy material is The difference in coating film adhesion after zinc oxide treatment and coating treatment is mainly due to the inclusion of other metal ions and impurities in the hydrated oxide film of Al.

Therefore, in the present invention, treated water such as pure water containing as little other metal ions and impurities as possible is used,
A film composed only of Al hydrated oxide of Al ₂ O ₃ · XH ₂ O can reduce the contact angle of water droplets, which shows the wettability of the hydrated oxide film of Al, to 20 ° or less. It is preferable in that the film adhesion can be improved.

Here, when the treated water containing calcium carbonate is used, it is possible to prevent mixing of Al with the hydrated oxide film of the above-mentioned other metal ions and impurities including the calcium carbonate itself, The contact angle of water droplets showing the wettability of the hydrated oxide film of Al in the present invention can be easily set to 20 ° or less.
Therefore, it is preferable to use treated water containing calcium carbonate or aluminum hydroxide for the production of the hydrated oxide film of Al.

It should be noted that quantitatively grasping the amount of other metal ions and impurities or the amount (purity) of Al hydrated oxide in the Al hydrated oxide film is inefficient even by selecting the analysis method. Yes, not realistic. Further, even if strict control is performed during the production of the hydrated oxide film of Al, the coating film adhesion may be lowered depending on the storage conditions until the zinc phosphate treatment, as described above.

Therefore, according to the present invention, phosphoric acid does not depend on various causes that deteriorate the coating adhesion of the hydrated oxide film of Al, or even if the history of the Al alloy structural material is unknown. Immediately before the zinc treatment, it is also possible to collectively evaluate the coating film adhesion of the Al alloy structural material.

Further, as described above, so far, actually,
It was the actual situation that after the phosphate treatment and coating treatment, the coating adhesion of the Al alloy structural material provided with the hydrated oxide film of Al was evaluated. The significance of the coating adhesion evaluation method for the hydrated oxide coating of the present invention is significant.

The evaluation method of the coating film adhesion of the Al alloy structural material provided with the hydrated oxide film of Al and the Al alloy structural material provided with the hydrated oxide film of Al of the present invention is applicable. It is a phosphate treatment and a coating treatment as a coating base treatment. More specifically, it is widely used for the automobile panel and the like,
Directly apply coating base treatment by phosphate treatment such as zinc phosphate and coating treatment such as cationic electrodeposition coating. However, the evaluation of coating adhesion at the contact angle of water droplets, which shows the wettability of Al hydrated oxide film, was performed when the conditions of zinc phosphate treatment were significantly different, or when zinc phosphate was used with other phosphates or fluorine. It is also applicable to the case where additives such as the above are included, or the case of a phosphate treatment other than zinc phosphate. The relationship or tendency between the contact angle of water droplets showing the wettability of the hydrated oxide film of Al and the adhesion of the coating film is common to these phosphate treatments. This point is the same when the means and conditions of the coating treatment are different.

(Al alloy material to be applied) Next, the Al alloy material to be applied in the present invention is a component such as 3000 series, 5000 series, 6000 series, 7000 series, etc., which is included in the standards specified by AA to JIS. A standard Al alloy can be used as appropriate. But this
The present invention is applicable to all Al alloy materials other than the AA to JIS standards that satisfy the required characteristics for use as structural members.

Further, the Al alloy material according to the present invention can be rolled by a conventional method or extruded by a conventional method.
It is manufactured as a plate or profile (a profile whose cross-sectional shape is essentially the same at any position along its length, such as a hollow cross section). That is, the molten aluminum alloy melt-adjusted within the component specification range is cast by appropriately selecting a normal melting casting method. Then, this aluminum alloy ingot is subjected to homogenizing heat treatment, and hot rolling-cold rolling-tempering treatment (annealing, solution treatment and quenching treatment, age hardening treatment, etc.), extrusion processing-tempering treatment, hot working Forging-
By tempering treatment or a combination of these, plate material,
An Al alloy material having a desired cross-sectional shape, such as a shaped material or a forged material.

[0041]

EXAMPLES Next, examples of the present invention will be described. Hollow extruded profile with cross section mouth shape extruded under conditions suitable for each alloy composition from A to D shown in Table 1.
(Height 70 mm, width 50 mm, wall thickness 2 mm) were prepared.

A sample material was sampled from this Al alloy shaped material, and a cleaning process accompanied by etching of the sample material (selectively including electrolytic degreasing) was performed. Then, a hydrated oxide film of Al was formed under the conditions of various treated waters (using pure water or tap water), treatment temperature, treatment time, and additives (to treated water) shown in Table 2. At this time, a comparative example in which the treated water contained various impurities was also prepared by simulating that the treated water was sequentially contaminated due to mass production of the film forming treatment. In all the invention examples in Table 2, pure water was used as the treated water. For 8 only, 1% of calcium carbonate was added to treated water obtained by mixing pure water with 0.5% oil as an impurity. The thickness (Å) of these Al hydrated oxide films was determined under the above-mentioned measurement conditions. The results are shown in Table 2.

Next, the test materials provided with the hydrated oxide film of Al were stored under various conditions shown in Table 2, and then the test materials were tested.
(Al hydrated oxide film) The contact angle of water droplets showing the wettability of the surface was measured. The results are also shown in Table 2. As shown in Fig. 1, the contact angle is such that when the water droplet 1 is placed (attached) on the surface of the specimen 2 placed horizontally, the surface of the droplet 1 is the specimen 2 (hydration of Al). (Oxide film) When the tangent 3 was drawn from the point of contact with the surface, the angle θ1 formed by the tangent 3 and the surface of the test material 2 was measured and used as the contact angle.

Further, the test material provided with the hydrated oxide film of Al was immersed in a colloidal dispersion containing 0.1% titanium phosphate at room temperature for 20 seconds, and the surface of the test material was treated with phosphorus. Titanium acid was adsorption coated. Immediately thereafter, a zinc phosphate treatment was carried out by immersing in a zinc phosphate bath containing 150 ppm of free fluorine suitable for a steel plate for 2 minutes under the same conditions in each example. Then, the total Al amount (mg) in the zinc phosphate bath increased by the zinc phosphate treatment of each test material was measured by an atomic absorption method, and the elution amount of Al from each test material (mg / m ² ) Was converted to (/ m ² ) per unit area of the test material. And
◯ when the amount of eluted aluminum is less than 70 mg / m ^{2, the} amount of eluted aluminum is 70 mg / m ^2.
2 or more and less than 120 mg / m ² △, Al elution amount is 120 mg / m ²
The above cases were evaluated as x. The results are shown in Table 3.

Further, an epoxy resin-based coating film was further provided on the test material provided with the zinc phosphate coating by cationic electrodeposition coating (coating baking treatment 170 ° C. × 20 minutes).

Test pieces were taken from these test materials provided with a coating film, and a coating film adhesion (peelability) test was conducted. 40 tests
The film was dipped in ion-exchanged water at ℃ for 10 days, and the coating film after dipping was subjected to a 10 mm square cross-cut tape peeling test with a width of 2 mm. It was evaluated by the number of peeled squares out of 100 squares. These results are also shown in Table 3.

As is clear from Tables 2 and 3, Invention Example No. 1
In Nos. 9 to 9, the hydrated oxide film thickness of Al is 1500 to 10000Å, and the amount of Al eluted in the zinc phosphate treatment is smaller than that in the comparative example. The invention example No. Nos. 1 to 9 have a contact angle of water droplets of 20 ° or less indicating the wettability of the coating surface, and are excellent in coating film adhesion as compared with Comparative Examples. Inventive Example No. 1 treated with treated water obtained by mixing pure water with 0.5% oil as an impurity. 8
For the wettability of the coating surface, Comparative Example No.
As in 12, there are disadvantages. However, by adding calcium carbonate to the treated water, the wettability of the coating surface and the coating adhesion are excellent, and even if the treated water becomes dirty, it is generated.
The effect of adding calcium carbonate, which secures the wettability of the Al hydrated oxide film surface, can be seen.

On the other hand, although the Al hydrate oxide film formation treatment was performed with pure water, the comparative example No. 1 having a low treatment temperature was used. 10 is the wettability of the film surface, the contact angle of water droplets is 20 ° or less,
The hydrated oxide film thickness of Al is less than the lower limit of 1500Å, and the amount of Al eluted in zinc phosphate treatment is large. In addition, Comparative Example No. treated with tap water containing about 10 ppm of silicate as an elution impurity. 11 also shows that the contact angle of water droplets showing the wettability of the film surface is
Although it is 20 ° or less, the film thickness is less than the lower limit of 1500Å, and the amount of Al eluted in the zinc phosphate treatment is large.

Comparative Example No. treated with treated water in which pure water contained about 0.5% of oil. No. 12 satisfies the hydrated oxide film thickness of Al, and the elution amount of Al in the zinc phosphate treatment is small, but the contact angle exceeds 20 ° and the coating film adhesion is low. Comparative example No. treated with treated water containing 0.5% iron sulfate as an impurity in pure water. 13 also satisfies the hydrated oxide film thickness of Al, and the elution amount of Al in the zinc phosphate treatment is small, but the contact angle exceeds 20 ° and the coating film adhesion is low.

Comparative Example No. 1 in which the hydrated oxide film of Al was formed with pure water was used. Although Nos. 14 and 15 satisfy the Al hydrated oxide film thickness and the elution amount of Al in zinc phosphate treatment is small, the Al hydrated oxide film deteriorates due to poor storage conditions and the contact angle is 20. Exceeding °, adhesion of coating film is low.

The results of these Examples support the critical significance of the conditions of the present invention.

[0052]

[Table 1]

[0053]

[Table 2]

[0054]

[Table 3]

[0055]

EFFECTS OF THE INVENTION According to the present invention, coating of an Al alloy structural material having a hydrated oxide film of Al with improved coating adhesion and an Al alloy structural material having a hydrated oxide film of Al is applied. It is possible to provide a method for evaluating film adhesion. Therefore, the industrial value is great in that the Al alloy material can be expanded to applications such as structural materials.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a contact angle defined by the present invention.

[Explanation of symbols]

1: water droplet, 2: sample material, 3: tangent line, θ1: angle between tangent line 3 and sample material 2 surface,

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G01N 13/00 G01N 13/00 F term (reference) 4D075 BB67X BB75Z CA13 CA33 CA35 DA06 DA10 DA23 DB07 DC08 DC11 EB33 4K026 AA09 BA08 BB06 CA16 EA08 EB04

Claims (2)

[Claims] 1. An aluminum alloy structural material used after being subjected to a phosphate treatment and a coating treatment, wherein a hydrated oxide film of aluminum is previously provided on the surface of the structural material before the treatment, and the aluminum alloy structural material is used. Aluminum with excellent coating adhesion characterized by a hydrated oxide film thickness of 1500 to 10000 angstroms (Å) and a contact angle of water droplets showing wettability of the film surface of 20 ° or less. Alloy structural material. 2. A method of preliminarily evaluating coating film adhesion when an aluminum alloy structural material having a hydrated oxide film of aluminum provided on its surface is subjected to a phosphate treatment and a coating treatment, the method comprising: A coating film adhesion evaluation method for an aluminum alloy structural material, characterized in that the coating film adhesion property is evaluated by the contact angle of water droplets showing the wettability of the Japanese oxide film surface.