JP3214835B2 - Al alloy material for transport equipment with excellent water resistance and yarn rust resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an Al alloy material for transport equipment having excellent water resistance and rust resistance, and more particularly to an Al alloy material for transport equipment suitable for use in outer plates and various members of automobiles and the like. Things.

[0002]

2. Description of the Related Art A railway vehicle, a ship, a motorcycle, a transport machine such as an aircraft or an automobile, and particularly, a coating used for an automobile body is preferably prepared by subjecting a material to a phosphate treatment and then subjecting the material to a cationic reaction by an electrochemical reaction. Spray painting of coating, intermediate coating and top coating (2 coats 2 bake)
Has been commonly used.

[0003] This series of coatings has been conventionally used for steel sheets for automobile bodies,
In recent years, aluminum alloys have been used to reduce the weight of automobiles.
Sheets (hereinafter simply referred to as Al alloys) have been used, and steel sheets and Al alloy sheets are processed in the same series of coating lines.

[0004] However, these phosphate-treated Al alloy coated plates have a problem that they are inferior in rust resistance as compared with similarly coated steel plates. This thread rust is a rust extending in a thread form on the surface of the Al alloy coated plate,
In addition to hindering the appearance of the alloy-coated plate, it also degrades the corrosion resistance itself of the Al-coated plate.

[0005] Therefore, in order to improve the rust resistance of the Al alloy coated plate, a coating base treatment instead of this phosphate treatment is desired. For this reason, in the phosphate treatment,
Techniques of adding free F ions of about 150 to 500 ppm or chromate treatment after phosphate treatment have also been proposed.

However, these treatments for improving the rust resistance are necessary only for the Al alloy sheet, and are unnecessary treatments for the steel sheet. When processing is performed, differences in processing steps and conditions occur, which significantly impairs the processing efficiency of the coating line. In addition, when these processes are performed, F ions and Cr
There is also the problem of treating waste liquid containing ions. In addition,
It is difficult to improve the rust resistance of the Al alloy coated plate reliably and with good reproducibility by F ion and chromate treatment, and it is difficult to control bath conditions etc. I'm sorry.

[0007] For this reason, in Japanese Patent Application Laid-Open No. 05-70969, etc., a boehmite film made of a neutral or weakly alkaline bath is applied on the surface of an Al alloy plate as a base coat for coating instead of the above-mentioned phosphate treatment. An Al alloy coated plate for automobile outer panels excellent in thread rust resistance, having a thickness of 1.5 μm and forming a coating film thereon, has been proposed.

The publication discloses that a boehmite film formed in a neutral or weakly alkaline bath becomes a uniform and stable protective film on the Al surface and improves the corrosion resistance of the surface of the Al alloy plate. In addition, it is also effective as a base treatment for coating, and the fine pores generated in the boehmite film exhibit an anchoring effect with the interface of the subsequently formed coating film, improving the adhesion of the coating film Is described.

[0009]

However, according to the publication, according to the coating line of the automobile body,
After the boehmite film is provided on the surface of the Al alloy plate, cationic electrodeposition coating (hereinafter simply referred to as ED coating) is performed, and then intermediate coating and top coating are performed.

Therefore, according to the findings of the present inventors, as will be described later, the ED coating deteriorates the boehmite coating itself at the angle, and conversely reduces the corrosion resistance of the surface of the Al alloy plate, As a result of deteriorating the yarn rust resistance.

Further, according to the findings of the present inventors,
In the same way, the Al alloy plate surface is also provided with a boehmite film, ED coating, intermediate coating, and even top coating Al alloy material,
It has been found that a remarkable difference occurs in the water resistance required for use in a transport aircraft. That is, even if the boehmite film is provided on the surface of the Al alloy plate, the water resistance may be poor in some cases, and this has led to a decrease in the reliability of application to automobiles.

With regard to the water resistance, Al alloy materials for transportation used for outer plates and various members of automobiles and the like are required to have water resistance to water in use, especially seawater and salt water. Rather, the water resistance is more important than the rust resistance in that it greatly affects the increase in the service life of the Al alloy material for transport vehicles. This water resistance is important as a required characteristic particularly in an application used in a corrosive atmosphere such as seawater or salt water such as on the sea or on the seashore.

On the other hand, among the coatings used for the automobile body, ED coating as a coating base treatment after phosphate treatment occupies a large weight in the cost of coating. Therefore, this ED coating is omitted, and intermediate coating and top coating are spray-coated (2 coats 2 bake)
Even if a coating treatment such as that described above is performed, if excellent yarn rust resistance and water resistance can be exhibited, there is an advantage that the cost of the coating used for the automobile body is significantly reduced.

[0014] Therefore, from the above points, it is first required that the Al alloy material for vehicles such as automobiles has both the rust resistance and the water resistance as an Al alloy coated plate. Furthermore, even if the ED coating is omitted, the Al alloy material for transporting vehicles such as automobiles can be replaced with an Al alloy coated plate having both rust resistance and water resistance, or a phosphate treatment + ED coating. There is a demand for an Al alloy coated plate having both rust resistance and water resistance. Nevertheless, the fact is that there has never been such an Al alloy coated plate or a coating base treatment that can be substituted for phosphate treatment + ED coating.

The present invention has been made in view of such circumstances, and has as its object to solve the problems of the conventional Al alloy material for transport equipment, and to replace phosphate treatment + ED coating. Another object of the present invention is to provide an Al alloy material for a transport machine, which has been subjected to a coating base treatment excellent in both rust resistance and water resistance.

[0016]

In order to achieve this object, the gist of the present invention is to provide a hydrated oxide film of Al on the surface of an Al alloy material, and further a coating except for a cationic electrodeposition coating on the surface. A transporting Al alloy material provided with a coating, wherein the hydrated oxide coating of Al comprises a plate-shaped upper layer coating and a granular lower layer coating, and the granular lower layer coating has a thickness of 50%. It shall be ~ 3000Å.

According to the gist of the present invention,
Solving the problem of the boehmite film, while having both the rust resistance and water resistance, the phosphate treatment and
It is possible to provide an Al alloy material for a transport machine which has been subjected to a coating base treatment that can be used instead of the ED coating.

As a result of repeated studies on the boehmite film, the present inventors have found that among the hydrated oxide films such as boehmite, basically, a plate-like upper film and a granular lower film are used. The hydrated oxide film of Al consisting of a layer structure contributes to the rust resistance and water resistance.The plate-like upper film contributes to the rust resistance, and the thickness of the granular lower film increases the water resistance. Was found to affect sex.

That is, the film thickness of the granular lower layer film in the two-layer structure, particularly the film thickness of the granular lower layer film, greatly changes depending on the preparation conditions of the Al hydrated oxide film, thereby greatly affecting the water resistance of the film. Receiving, and when the film thickness of this lower layer film is increased, the water resistance is deteriorated. Conversely, when the film thickness of the lower layer film is suppressed to 3000 mm or less, together with the plate-shaped upper layer film, water resistance and It has been found that it has an excellent effect on yarn rust resistance.

Furthermore, in the above-mentioned Japanese Patent Application Laid-Open No. 05-70969, the ED coating (cationic electrodeposition coating) which is essentially provided deteriorates the hydrated oxide film itself of Al, and We also found that the result was that the rust resistance and water resistance of the alloy coated plate were degraded. Then, in order to exhibit the rust resistance and water resistance performance of the hydrated oxide film of Al, without applying ED coating, directly on the hydrated oxide film of Al
We also found that it was necessary to apply a double coating of a middle coat and a top coat by non-ED coating.

That is, in the ED coating, an Al alloy material is used as a cathode, a DC voltage is applied between the anode and the anode, and a paint component ionized into positive ions is electrophoresed to form a coating film on the surface of the Al alloy material. How to Therefore, when the Al alloy material becomes a cathode, hydrogen is generated on the surface of the Al alloy material, and as a result, the pH of the surface of the Al alloy material is extremely increased.
The oxide film on the alloy material surface is destroyed, the phosphate film is destroyed, the adhesion of the coating film is reduced, and even after coating, the alkali component remains on the Al alloy material surface and penetrates the coating film during use Even after coating, because the surface of the Al alloy material is attacked by the reaction with the moisture
Deterioration of corrosion resistance such as thread rust resistance of Al alloy material.

Therefore, in the present invention, since the ED coating is not applied on the hydrated oxide film of Al, it is possible to omit the ED coating step as well as the phosphate treatment particularly from a coating line used for an automobile body. It also has In addition,
The coating film other than the cationic electrodeposition coating in the present invention means a coating selected from electrostatic coating, anion electrodeposition coating and spray coating, roll coater coating, and dip coating. And, as will be described later, ED coating in which a coating film is formed by a cathode electrode reaction is excluded from the scope of the invention.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, FIG. 1 schematically shows a basic structure of a hydrated oxide film of Al and a coating film of an Al alloy material for a transport aircraft according to the present invention. In FIG. 1, a transport aircraft Al alloy material 8 according to the present invention basically has an Al alloy material 1 on the surface thereof.
A hydrated oxide film 2 and a paint film 5 not involving an electrochemical reaction are provided. Al hydrated oxide film 2
It is composed of a (rough plate-shaped) relatively coarse upper film 3 and a granular relatively dense lower film 4. And the coating film 5
For example, it is composed of a coating film (2 coats 2 bake) which does not involve an electrochemical reaction such as spray coating of the intermediate coat 6 and the top coat 7.

In the present invention, the hydrated oxide film of Al is represented by the general formula: Al ₂ O ₃ .XH ₂ O, and the hydrated oxide of Al formed by the hydration reaction of Al oxide. Say the film. The hydrated oxide of Al in the present invention refers to the degree of hydration (X
Is not particularly limited to the type, form, crystal structure, crystallinity, and the like of the hydrated oxide. Just Al
Among the hydrated oxides, those having a pseudo-boehmite in which the value of X is about 1.5 to 1.9 are generally referred to as boehmite films.

FIGS. 2 (a) and 2 (b) show cross-sectional structures of the hydrated oxide film of Al according to the present invention. 2 (a) and 2 (b) are those prepared according to the examples described later, and show a hydrated oxide film 2 of Al.
The cross section of the Al alloy material 1 provided with (the fracture surface of the Al alloy material obtained by bending the Al alloy material by 180 °) was observed with a scanning electron microscope at a magnification of 50,000. From FIGS. 2 (a) and 2 (b), the hydrated oxide film 2 of Al is composed of a plate-like relatively coarse upper film 3 and a granular relatively dense lower film 4 as described above. You can see that it is.

Further, according to our detailed analysis,
Among the hydrated oxide films of Al, the plate-like relatively coarse upper film 3 is a film rich in hydration in which X of Al ₂ O ₃ .XH ₂ O is 2 or more. As shown in FIGS. 1 and 2, the plate-like hydrated oxide 9 of Al is a coarse (porous) layer having a relatively large number of spaces or gaps in which plate-like crystals are alternately overlapped. . On the other hand, the lower layer coating 4 has a relatively dense layer in which X of Al ₂ O ₃ .XH ₂ O is about 1, and as shown in FIG. 1 and FIG. It is.

The identification of these film structures can be performed by infrared spectroscopy (FT-IR) in addition to the morphological observation by the scanning electron microscope. That is, FT-IR
The absorption spectrum due to the stretching vibration of AlO ← → H observed near 3000-3700 cm ^-1 and 1000-1050 cm ^-1
Absorption spectrum due to stretching vibration of Al ← → OH observed in the vicinity, and OAl ← → O observed in the vicinity of 800 to 600 cm ^-1
The presence of the Al hydrated oxide film of the present invention is confirmed by observing any one or more of the absorption spectra due to the stretching vibration of the present invention. The distinction between the plate-like upper film 3 and the granular lower film 4 and the film thickness are based on the fracture surface of the Al alloy material.
(For example, a fracture surface of an Al alloy material by bending at 180 °) can be observed by a scanning electron microscope at a magnification of 20,000 or more. This magnification needs to be higher as the thickness of the hydrated oxide of Al becomes thinner. In addition, identification is possible by X-ray diffraction, and morphological observation is possible by a transmission electron microscope.

The hydrated oxide film of Al in the present invention means not only a film composed of pure Al hydrated oxide of Al ₂ O ₃ .XH ₂ O, but also a hydrated oxide of Al. As long as it is mainly composed of a material film, it may be a mixture, that is, a material containing an impurity element which may possibly be mixed in or form an Al hydrated oxide film. However, the allowable amount is in a range that does not impair the properties such as corrosion resistance and adhesion of the hydrated oxide film of Al.

The structure itself of the hydrated oxide film of Al composed of the upper film and the lower film is known. That is, 110-114 of Metal Surface Technology Vol. 37, No. 3, 1986
Page or Metal Surface Technology Vol. 24, No. 12, 1973, No. 70
According to the production conditions of the hydrated oxide film of Al, for example, pages 0 to 705, etc. The above-mentioned document discloses that the inner layer is rich in monohydrate and a dense outer layer is rich in hydroxide.

In these documents, these two layers of Al
Corrosion resistance of hydrated oxide coatings (CAS test and salt spray test)
Is superior to a boehmite film. However, these documents do not first cover the Al alloy material for transport vehicles on the premise of coating as in the present invention, but apply an anodic oxide film of Al or a hydrated oxide film of Al on the surface. It is intended for an Al alloy material that is basically used naked just by providing it. Then, the water resistance and the rust resistance of the Al alloy material for transport aircraft provided with the hydrated oxide film of Al and the coating film
It is not intended to improve the three characteristics.

As a result, these documents merely recognize that the corrosion resistance of the two-layer hydrated oxide Al film itself is due to the formation of two layers or an increase in the film thickness. On the other hand, in the present invention, as described below, in the case of having a coating film, two layers of Al for two properties of water resistance and yarn rust resistance.
This is a result of the finding that the function or effect of each film (layer) of the hydrated oxide film is completely different. Therefore, without knowledge of this mechanism, the constitution of the present invention cannot be obtained, and the corrosion resistance of the above-mentioned document, which is used only by providing a hydrated oxide film of Al, means that the transport machine The mechanism of corrosion protection is completely different in relation to the type of coating film and the upper layer.

Next, the reason why the hydrated oxide film of Al in the present invention is excellent in water resistance and yarn rust resistance will be described. First, the thread rust itself is in the corroded portion at the tip of the coating film 5, and the corrosion of the coating film 5 progresses as the pH extremely decreases to about 1 or less. In contrast,
Among such hydrated oxide films of Al, the plate-like upper layer film 3 has a neutralizing effect of increasing the pH under such a strongly acidic environment, and has an effect of suppressing the corrosion reaction of the coating film 5. is there. Therefore, the effect of improving the rust resistance of the Al alloy material for a transport device according to the present invention is mainly exhibited by the plate-like coarse (porous) upper layer coating 3.

In order to exhibit the effect of improving the yarn rust resistance, the upper layer coating 3 of the hydrated oxide film of Al in the present invention is required.
It is preferable that the thickness of the film is 50 ° or more. If the thickness of the plate-like rough upper layer film 3 is smaller than this, the cathode polarization cannot be sufficiently increased, and the corrosion resistance decreases. Further, there is a possibility that a neutralizing effect of increasing the pH in a strongly acidic environment cannot be obtained. On the other hand, if the thickness is too large, the adhesion to the paint film may be reduced, and a phenomenon such as peeling of the paint film may occur.
The upper limit of the film thickness is preferably 5000 ° or less.

Further, the deterioration of water resistance is caused by the problem of Al in the present invention.
Of the hydrated oxide films, the lower film 4 reacts with moisture.
It is caused by That is, the granular underlayer film is Al_TwoO_Three
・ XH _TwoO is about 1 and X is 2 or more
Room to react with moisture, that is, X
There is room for it. Therefore, during the use of painted Al alloy material
Deterioration of paint film over time and external factors such as chipping
Seawater and salt through these
Water penetrates the paint film and contacts the base material, the Al alloy material.
When touched, the hydrated upper coating with X 2 or more
Although it does not react with water, the lower layer film actively reacts with water.
As a result, the volume of the film itself increases. As a result, the paint film
Al alloy material surface which is the base material, such as blistering and peeling
Between Al and the hydrated oxide film of Al, with the hydrated oxide film of Al
Deterioration of adhesion at the interface with the paint film and the film itself
To degrade water resistance. This is especially true of the sea
It becomes remarkable in water and salt water atmosphere and environment, etc.
Under the environment, the larger the thickness of the undercoat, the more
You.

The deterioration of the water resistance due to the film thickness of the lower layer film greatly changes when the film thickness reaches 3000 °, and the water resistance is improved by suppressing the film thickness to 3000 ° or less. On the other hand, the lower layer coating has a poorly soluble function to prevent the dissolution of Al hydrated oxide film by acid or alkali, etc., and improves general corrosion resistance such as general corrosion of Al hydrated oxide film Let it. In order to exhibit this effect, it is necessary that the thickness of the lower layer film be 50 mm or more.

On the other hand, the water resistance of this underlayer coating is
The finer the particle size of the granular crystals constituting the lower layer coating (hereinafter, simply referred to as the particle size of the lower layer coating), the better. In other words, the smaller the particle size of the lower layer film, the more the deterioration of the water resistance is suppressed. In order to exhibit this effect, the particle size of the underlayer coating must be
It is preferably 40 nm or less.

The total thickness (total film thickness) of the hydrated oxide film of Al composed of the upper film and the lower film is 100%.
Preferably it is ~ 6000 °. If the total film thickness is less than 100 mm, the corrosion resistance including the rust resistance generally decreases, while if the total film thickness exceeds 6000 mm, the hydrated oxide film of Al
Adhesion with Al alloy material and coating film is reduced,
The hydrated oxide film and the coating film of the above may easily peel off, and the corrosion resistance including water resistance and yarn rust resistance may be generally reduced. In particular, from the viewpoint of chipping resistance, such as peeling of the coating film starting from scratches due to collisions with the coating film such as pebbles during the running of vehicles such as automobiles, it is preferable that the film thickness is thin, the total film thickness is 4000 Å or less More preferably,

Next, a method for producing a hydrated oxide film of Al in the present invention comprising an upper film and a lower film will be described. First, after the Al alloy material is formed and welded and joined for a transport machine, an appropriate pretreatment for degrease or washing the Al alloy surface of the formed material with an organic solvent, an alkaline solution or an acidic solution is performed. Among these pretreatments, when pretreatment with an aqueous nitric acid solution, the effect of improving the denseness of the hydrated oxide film of Al formed in a later step, suppressing the penetration of moisture, and further improving the water resistance. Have.

Then, after this pretreatment, a method of directly contacting with high-temperature water or steam, or a method of forming an Al oxide layer on the Al alloy surface of the molding material and then performing a hydration reaction to form a hydrated oxide film of Al. Method, further, after providing these hydrated oxide film of Al, a method of adjusting the amount of hydration by heating,
Alternatively, the method of the present invention is appropriately selected by, for example, a method of contacting with a high-temperature neutral or weakly alkaline bath (pure water, tap water, an aqueous solution of triethanolamine or ammonia) as described in JP-A-05-70969 or the like. 2 layers of hydrated oxide film of Al are prepared.

However, even if the main conditions such as the conditions for forming the hydrated oxide film of Al are the same, the two-layered hydrated oxide film of Al of the present invention is not always required. That is, for example,
Even if the main conditions for producing the hydrated oxide film of Al are the same, the surface condition of the Al alloy material, or the pretreatment conditions for producing the hydrated oxide film, If the detailed conditions during production are different, the two-layer hydrated oxide film of Al of the present invention may not be formed. In fact,
In Japanese Patent Application Laid-Open No. 05-70969, the resulting film is a hydrated oxide film consisting of only one layer of boehmite despite contact with a high-temperature neutral or weakly alkaline bath. Therefore, the specific conditions for producing the hydrated oxide film of Al, including the surface condition of the Al alloy material and the pretreatment conditions, are described in the present invention.
It is necessary to appropriately select conditions under which two hydrated oxide films of Al are obtained, depending on individual cases.

Further, when the hydrated oxide film of Al is provided at the material stage, the hydrated oxide film of Al may be peeled or damaged at the next forming or welding joint stage. After forming and welding joining Al alloy material for transport aircraft,
It is preferable to provide a hydrated oxide film of Al on the Al alloy surface of the molding material.

Then, on the molded material provided with the hydrated oxide film of Al of the present invention, the Al alloy surface is applied in a neutral or acidic range without being in an alkaline range. Specifically, coating by non-cationic electrodeposition coating selected from electrostatic coating, anion electrodeposition coating and spray coating, roll coater coating, and dip coating is selectively performed. As in the prior art, the molding material provided with the hydrated oxide film of Al, the cation electrodeposition coating, when subjected to coating by an electrochemical reaction using an Al alloy as a cathode, as described above,
The generated alkaline substance causes a phenomenon that the hydrated oxide film is partially damaged, and on the contrary, the rust resistance is remarkably deteriorated and the water resistance is also deteriorated. Also, ED
By applying the coating, the advantage that the ED coating of the present invention can be omitted is also lost.

Next, the target Al alloy in the present invention is:
Al alloys of JIS 5000 series, JIS 6000 series, and JIS 7000 series component standards are preferable. However, even Al alloys other than the JIS standard that satisfy the required characteristics for use in transport aircraft are all applicable to the present invention.

However, since the Al alloy material applied to the present invention is a material for transportation equipment, it is preferable that it has mechanical properties such as tensile strength and proof stress, workability, and weldability as basic characteristics. . In particular, depending on the application, it is necessary to ensure high tensile strength and proof stress. In this regard, among these Al alloys, JIS 5052, 5652, 5154, 5254, 5454, 5083, 508
6, 5456, JIS 6061, 6N01, 6063, 6151, JIS 7001, 7N0
1, 7003, 7050, 7072, 7075, etc. are preferred. In particular, these Al alloys are, for example, for transportation equipment such as vehicles and airplanes, for example, O material, solution treatment material, H1
In either tensile strength of 16 material at 200 N / mm ² or more and Strength
90 N / mm ² or more. It also has good plastic workability, formability and weldability, and has excellent uniform corrosion resistance even when used without painting, satisfying the basic characteristics.

Further, the Al alloy material according to the present invention is produced as a plate or a mold by rolling, extruding, forging, casting or the like by a conventional method. That is, the molten aluminum alloy melt-adjusted within the component specification range is cast by appropriately selecting a normal melting casting method such as a continuous casting rolling method and a semi-continuous casting method (DC casting method). Subsequently, the aluminum alloy ingot is subjected to a homogenizing heat treatment, and is subjected to a tempering treatment such as hot rolling and cold rolling-T6 or the like where rough annealing or intermediate annealing is added as necessary, or a sheet material product, or extrusion-T6 It becomes a shape material product by tempering treatment. In addition, a forming process such as hot forging may be performed to obtain a product shape.

[0046]

Embodiment 1 Next, an embodiment of the present invention will be described. JIS 51
82,6016 Al alloy sheet compositions standards, in Al alloy type material of the composition of JIS 6063 standard, a tensile strength 200 N / mm ² or more and Strength 9
The Al alloy material having a 0N / mm ² or more, each formed into automotive parts, from the molding material, cut the size of the test piece of 70 × 150 mm, after pretreatment Al alloy specimen surface, shown in Table 1 Under the conditions, a hydrated oxide film of Al having a film thickness shown in Table 2 was provided. In Tables 1 and 2, for Invention Example No. 9, the test piece cut from the molded material included a welded portion.

Before providing the hydrated oxide film of Al,
The conditions of the pretreatment method of the alloy test piece were as follows. Inventive Examples Nos. 1 to 7 were first subjected to a degreasing treatment at 70 ° C. for 1 minute using a commercially available weak alkaline degreasing solution. Thereafter, Invention Examples Nos. 1 to 3 were immersed in 30% nitric acid at 40 ° C. for 2 minutes, washed with water, and then oxidized at 80 ° C. for 1 minute in the air. Inventive Examples Nos. 4 and 5 were immersed in 15% nitric acid at 40 ° C. for 10 seconds, washed with water, and then oxidized at 150 ° C. for 3.5 minutes in the air. Further, for Invention Examples Nos. 6 and 7, the degreased state was left as it was. In addition, for Invention Examples Nos. 8 and 9, 40 ° C.
Pretreatment by immersion in 15% nitric acid for 30 seconds. Comparative Example N
With respect to o.10 to 16, degreasing was performed using a commercially available weak alkaline degreasing solution at a bath temperature of 70 ° C. for 1 minute in the same manner as in Invention Examples Nos. 1 to 7. In addition, Comparative Examples Nos. 17 and 18 were degreased, and then invented.
The same pre-processing as Nos. 1-3 was performed.

After performing these pretreatments, the hydration reaction treatment shown in Table 1 was performed.
As a result of identification by the FT-IR method, absorption spectrum due to stretching vibration of AlO ← → H observed near 3000 to 3700 cm ⁻¹ ,
And 1000~1050cm absorption spectrum by stretching vibration for allowed Al ← → OH around ^-1, further 800 ～600Cm ^-1 observed is OAl ← → the O stretching at least one of the absorption spectrum due to the vibration of is observed in the vicinity of As a result, the existence of a hydrated oxide film of Al was confirmed. Furthermore, the morphological identification of the upper layer coating 3 and the lower layer coating 4 and the measurement of the film thickness were performed by multiplying the fracture surface of the Al alloy specimen by 180,000 bending by 50,000 times.
(150,000 times for thin film) Scanning electron microscope (SE)
M). As a result, A according to the present invention
As shown in FIGS. 2 (a) and 2 (b) showing a cross-sectional structural diagram of the hydrated oxide film of l, the hydrated oxide film of Al according to the present invention has a plate-shaped relatively rough upper film, It was confirmed that the film was composed of a granular and relatively dense lower layer film.

On the surface of the Al alloy test piece provided with the hydrated oxide film of Al, a two-coat two-bake coating film was further provided by a spray coating method without involving an electrochemical reaction. In the case of Invention Example No. 9 only, two coats and two bake coats were provided by roll coater coating. 2 Coat 2 As a bake coating, more specifically, as a middle coating, a polyester melamine-based coating film with a thickness of 30 μm is provided, baked at 140 ° C. for 20 minutes, and as a top coating, a 30 μm thick coating is applied. A polyester melamine-based coating film was provided and baked at 140 ° C. for 20 minutes.

For comparison, it deviates from the scope of the present invention
Al hydrated oxide film was provided, and two coats and two bake paint films were provided by a spray coating method without electrochemical reaction.
Al alloy test pieces (No. 13 to 16), cation electrodeposition coating on the surface of Al alloy test pieces subjected to phosphate treatment and Cr rinse treatment or Zr rinse treatment without providing a hydrated oxide film of Al After that, a comparative example (No. 10 to 12) in which a two-coat two-bake coating film was provided by the spray coating method, and within the scope of the present invention.
Comparative examples (Nos. 17 and 18) in which two coats and two bake coatings were provided by spray coating after the cationic electrodeposition coating was applied to the surface of the Al alloy test piece provided with the hydrated oxide coating of Al were also prepared. .

Then, the coated test pieces of the invention examples and the comparative examples were subjected to a rust resistance evaluation test and a water resistance evaluation test under the same conditions. Table 2 also shows the results of these evaluations.
The rust resistance evaluation test was performed by cutting a painted test piece with a 7 cm cross cut, immersing it in a 3% HCl aqueous solution at 35 ° C for 2 minutes, and then in a constant temperature and humidity atmosphere of 40 ° C and 85% RH. After standing for 1500 hours, the maximum length L (the distance in the vertical direction from the cross cut) of the generated thread rust was measured. And, for comparison, the maximum length L of the thread rust generated on the conventional test piece which was subjected to phosphate treatment and ED coating film on the Al alloy test piece, and further the same intermediate coating and top coating was set to 1, And ○: L ≦ 0.5, 0.5: 0.5 <L ≦ 1, and ×: 1 <L.

Further, in the water resistance evaluation test, the test piece was heated at 40 ° C.
After 10 days of immersion in ion-exchanged water, a 1 mm width cross cut tape peeling test was performed to measure the residual ratio of the coating film. Then, those in which 100% of the coating film remained were evaluated as ◎, those in which 90% or more remained, and those in which 90% or less were evaluated as x.

As is clear from the results in Table 2, Invention Example No. 1
Nos. 9 to 9 are excellent in both water resistance and yarn rust resistance because the hydrated oxide film of Al on the surface of the Al alloy material satisfies the requirements of the present invention and is provided with a non-ED coating film. ing. In particular, Invention Example No. 9 was excellent in both water resistance and yarn rust resistance including the welded portion and the weld heat affected zone.

In contrast, Comparative Example Nos. 10 to 10 in which the surface of a phosphate-treated Al alloy test piece was subjected to cationic electrodeposition coating without providing a hydrated oxide film of Al and then a coating film was provided. 12
Has moderate rust resistance, but remarkably poor water resistance. In addition, Comparative Examples Nos. 17 and 18 in which the coating film was provided after the cationic electrodeposition coating was provided on the surface of the Al alloy test piece provided with the hydrated oxide film of Al within the scope of the present invention, the yarn rust resistance and the water resistance. Both sexes are significantly inferior. Further, among the comparative examples in which the hydrated oxide film of Al was provided outside the scope of the present invention, the Al alloy materials of Comparative Examples Nos. 13 and 14 in which the thickness of the lower layer film was too thin were inferior in both water resistance and yarn rust resistance. ing. Further, the Al alloy materials of Comparative Examples Nos. 15 and 16 in which the thickness of the lower layer film is too thick are excellent in yarn rust resistance, but are extremely poor in water resistance.

Therefore, from the above facts, the critical significance of the limitation of the hydrated oxide film and the film thickness of Al of the present invention, and the hydration of Al, in order to achieve both excellent water resistance and yarn rust resistance. The significance of providing a coating film other than the cationic electrodeposition coating on the oxide film is supported. In addition, it can be used instead of phosphate treatment + ED coating, and the effect of excellent water resistance and thread rust resistance as an Al alloy material for transport even without ED coating is supported.

Further, the particle diameters of the underlayer coatings of Invention Examples Nos. 1 to 9 were measured, and the relationship between the particle diameters and the evaluation results of the rust resistance and the water resistance was rearranged. Shown in As is clear from the results in Table 3, the invention examples Nos. 1 to 4 and 7 to 9 in which the particle size of the lower layer film of the hydrated oxide film of Al is smaller than 40 nm are invention examples No. 5 and 40 nm or more. It is superior to both 6 in water resistance and yarn rust resistance. Of course, although the other factors mentioned above also affect the result, the particle size of the lower layer film of the hydrated oxide film of Al of 40 nm or less is excellent in both water resistance and yarn rust resistance. It can be said that the superiority of the preferred condition of the present invention with respect to the particle size of the underlayer film is obtained.

The particle size of the lower layer film was measured by measuring the cross section of the Al alloy material provided with the Al hydrated oxide film of Invention Examples No. 1 to 9 (the film obtained by bending the Al alloy material by 180 ° bending). (Fracture surface) was observed by using a scanning electron microscope at a magnification of 50,000 times.

[0058]

[Table 1]

[0059]

[Table 2]

[0060]

[Table 3]

[0061]

According to the present invention, it is possible to provide an Al alloy material for a transport machine which can be used instead of phosphating and ED coating, and which has both excellent rust resistance and water resistance without applying ED coating. can do. Therefore, it has a great industrial value in that the function of the Al alloy material can be improved and its use can be expanded.

[Brief description of the drawings]

FIG. 1 is an explanatory view schematically showing a basic structure of a hydrated oxide film of Al and a coating film of an Al alloy material for a transport aircraft according to the present invention.

FIG. 2 is a cross-sectional structural view of a hydrated oxide film of Al according to the present invention.

[Explanation of symbols]

1: Al alloy material, 2: Al hydrated oxide film, 3: Upper layer film, 4:
Lower layer coating, 5: Paint coating, 6: Intermediate coating, 7: Top coating, 8: Al alloy material for transport, 9: Plate-like hydrated oxide of Al, 10: Granular Al
Hydrated oxide of

Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI C23C 22/77 C23C 22/77 C25D 13/00 C25D 13/00 J (72) Inventor Kikuo Toyose 1-8-2 Marunouchi, Chiyoda-ku, Tokyo No. Shinko Alcoa Transport Equipment Co., Ltd. Tokyo Head Office In-house (56) References JP-A-62-180096 (JP, A) JP-A-4-3588083 (JP, A) JP-A-61-222630 (JP, A) JP JP-A-5-68939 (JP, A) JP-A-5-115839 (JP, A) JP-A-11-256395 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23C 22 / 00-22/86 B05D 3/10 B05D 7/14 101 C25D 13/00

Claims (9)

(57) [Claims] 1. An Al alloy material for a transport machine, wherein an Al hydrated oxide film is provided on the surface of an Al alloy material, and a coating film other than a cationic electrodeposition coating is further provided on the Al alloy material. The hydrated oxide film is composed of a plate-shaped upper film and a granular lower film, and the film thickness of the granular lower film is 50 to 3000 mm, and is excellent in water resistance and yarn rust resistance. Al for transport aircraft
Alloy material. 2. The Al alloy material for transport equipment according to claim 1, wherein the particle size of the granular crystals of the lower layer coating is 40 nm or less. 3. The film thickness of the hydrated oxide film of Al is 100 to 100.
The aluminum alloy material for transport equipment according to claim 1 or 2, wherein the aluminum alloy material has a water resistance and yarn rust resistance of 6000 °. 4. The water-resistant coating according to claim 1, wherein the coating film is a coating film selected from electrostatic coating, anion electrodeposition coating and spray coating, roll coater coating, and dip coating. Al alloy material for transport aircraft with excellent resistance and yarn rust resistance. 5. The water resistance according to claim 1, wherein the surface of the Al alloy material is treated with a nitric acid aqueous solution before the Al hydrated oxide film is provided. Al alloy material for transport equipment with excellent thread rust resistance. 6. The water resistance and yarn rust resistance according to claim 1, wherein the Al alloy material has a tensile strength of 200 N / mm ² or more and a proof stress of 90 N / mm ² or more. Al alloy material for transport aircraft. 7. The aluminum alloy material according to claim 1, wherein the aluminum hydrated oxide film and the paint film are formed after being formed and welded and joined for a transport machine. An aluminum alloy material for transport aircraft excellent in water resistance and yarn rust resistance described in 1. 8. The Al alloy material for transport equipment according to claim 1, wherein the transport equipment is for automobiles. 9. A hydrated oxide film of Al is provided on the surface of an Al alloy, and the hydrated oxide film of Al comprises a plate-like upper film and a granular lower film, wherein the granular lower film is a film. 50 thick
An aluminum alloy material with a thickness of up to 3000 mm, which is coated with the exception of cationic electrodeposition coating and has excellent water resistance and thread rust resistance for use in transport equipment.