JP3255606B2 - 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 Coatings on transportation vehicles such as railway cars, ships, motorcycles, and aircrafts and automobiles, and particularly coatings used on automobile bodies, are made by subjecting materials to phosphating and then electrochemically reacting. Cationic electrodeposition coating, and intermediate and top coating spray coating (2 coats 2 bake) have been 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 findings of the present inventors, a boehmite film was similarly provided on the surface of an Al alloy plate, and was subjected to cationic electrodeposition coating (hereinafter referred to as ED coating), intermediate coating, and top coating. It has been found that, in the Al alloy material coated with, the water resistance performance required for the use in a transport aircraft is significantly varied. 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 respect to the water resistance, Al alloy materials for transportation used for outer panels 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.

According to the findings of the present inventors, the ED coating deteriorates the boehmite coating itself at the angle, and conversely lowers the corrosion resistance of the surface of the Al alloy plate, and also reduces the rust resistance of the Al alloy coated plate. May be deteriorated.

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 can be significantly reduced.

[0013] Therefore, from the above points, it is first required that an Al alloy material for a transport machine such as an automobile 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 substitute for phosphate treatment + ED coating.
An 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.

[0015]

In order to achieve this object, the gist of the present invention is to provide an Al alloy material for a transport machine in which an Al hydrated oxide film and a paint film are provided on the surface of the Al alloy material. a is a natural potential of the hydrated oxide film of the Al is the chamber in a non-deaerated
Potential of an Al alloy material having an Al hydrated oxide film measured in a 0.5 M NaCl aqueous solution at room temperature is lower than that of an Al alloy material without an Al hydrated oxide film measured under the same conditions. , 10 mV or more.

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

The present inventors have repeatedly studied the boehmite film and found that Al ₂ O ₃ .XH ₂ O such as boehmite was used.
It has been found that the spontaneous potential of the Al hydrated oxide film represented by the formula has a significant effect on water resistance, yarn rust resistance, and corrosion resistance such as general corrosion. In other words, the lower the natural potential of the hydrated oxide film of Al, the higher the cathodic polarization, the better the corrosion resistance of the film, and the more the cathode reaction of the coating film is suppressed. It has been found that the electric current is reduced and the rust resistance is improved. In addition, even when moisture, seawater, or salt water penetrates the coating film, the natural potential difference is smaller, as the natural potential of the hydrated oxide film of Al is lower, as compared to the hydrated oxide film of Al.
It has been found that the water resistance is improved due to low compoundability and reactivity with permeated water, seawater, salt water, or the like.

Further, the natural potential of the hydrated oxide film of Al is preferably a metal compound contained in the film and having a potential lower than that of Al, more preferably an alkali such as Mg, Li or Ca. It has also been found that the inclusion of a metal compound of an element selected from a metal , an alkaline earth metal, and Si or Mn lowers the content, thereby improving the above-described yarn rust resistance and corrosion resistance.

The metal compound which is lower in potential than the Al natural potential is usually contained in the hydrated oxide film of Al only at the level of impurities or less. Therefore, the natural potential of the normally prepared hydrated oxide film of Al is the natural potential of the Al alloy material having the hydrated oxide film of Al measured in a 0.5 M NaCl aqueous solution (non-degassed, room temperature). Measured under the same conditions
It does not drop by 10 mV or more from the natural potential of the Al alloy material without the Al hydrated oxide film.

Therefore, in the present invention, the metal compound having a potential lower than the natural potential of Al is positively contained in the hydrated oxide film of Al, so that the Al compound having the hydrated oxide film of Al is provided. It is characterized by actively lowering the natural potential of the alloy material.

Further, according to the present invention, the method disclosed in
-70969, the ED coating, which is essentially provided, deteriorates the hydrated oxide film of Al itself, and on the contrary, deteriorates the rust resistance and water resistance of the Al alloy coated plate. I also found out. On the other hand, the composite coating of the present invention does not deteriorate even when this ED coating is used, and ensures excellent thread rust resistance and water resistance of the Al alloy coated plate.

Therefore, in order to ensure that the hydrated oxide film of Al exhibits the rust resistance and water resistance performance in the present invention, a coating film that does not involve an ED coating and does not involve an electrochemical reaction is applied. On the other hand, it is another advantage of the present invention that ED coating can be applied as a conventional coating as a base coating of a coating film that does not involve an electrochemical reaction.

As an option, when the ED coating is not performed, there is also an effect that the ED coating step can be omitted together with the phosphate treatment particularly from a coating line used for an automobile body.

[0024]

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, the Al alloy material 6 for a transport aircraft according to the present invention basically has an Al alloy material 1 on the surface of the Al alloy material 1.
Containing a metal compound that is more potential than the natural potential of Al, and hydrated oxide film 2 of Al that satisfies the potential condition in the present invention.
And a coating film 5 that does not involve an electrochemical reaction. The coating film 5 is, for example, a middle coat 3, a top coat,
The coating film without electrochemical reaction such as spray coating (4)
2 bake coats).

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 the 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 pseudo-boehmite in which the value of X is about 1.5 to 1.9 are generally referred to as boehmite films.

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. Also, a hydrated oxide film 2 of Al,
The distinction of the coating film 5 and the measurement of the film thickness can be performed by observing the fracture surface of the Al alloy material (for example, the fracture surface of the Al alloy material by bending at 180 °) at a magnification of 20,000 or more with the above-mentioned scanning electron microscope. . This magnification needs to be higher as the thickness of the hydrated oxide of Al becomes thinner. In addition, the hydrated oxide film 2 of Al can be identified by X-ray diffraction, and morphological observation can be performed by a transmission electron microscope.

Further, the metal compound in the hydrated oxide film 2 of Al that is lower in potential than the natural potential of Al was also measured by X-ray photoelectron analysis (XPS method) described in detail in Examples. By measuring the binding energy of each metal element (the XPS spectral intensity of each metal element), it is possible to identify and measure the content of Al in the hydrated oxide film of Al. Or
These measurements can also be made by X-ray diffraction.

Further, the thickness of the hydrated oxide film of Al in the present invention is preferably in the range of 100 to 30,000 °. Film thickness
If the thickness is less than 100 mm, the corrosion resistance including the rust resistance generally decreases, while if the thickness exceeds 30,000 mm, the adhesion of the hydrated oxide film of Al to the Al alloy material and the coating film is reduced. Drop,
On the contrary, the hydrated oxide film of Al and the peeling of the paint film occur,
There is a possibility that corrosion resistance including water resistance and yarn rust resistance is generally reduced.

Next, the natural potential (hereinafter simply referred to as potential) of the hydrated oxide film of Al in the present invention will be described. First, regarding the method of measuring the potential of the hydrated oxide film of Al, it is substantially difficult to directly measure the potential of the hydrated oxide film of Al itself, which is a thin film. On the other hand, measurable
The potential of the Al alloy material provided with the hydrated oxide film of Al
By taking the difference in potential from the Al alloy material without the hydrated oxide film, the potential of the Al hydrated oxide film itself can be measured accurately and with good reproducibility. Therefore,
In the present invention, the potential of the hydrated oxide film of Al is represented by the potential of the Al alloy material with and without the hydrated oxide film of Al.

The specific method of measuring the potential of the Al alloy material is as follows. Each of the Al alloy materials with and without the Al hydrated oxide film is used as a sample electrode, and has a potential of 1.0 mol (M) or less. It can be easily measured by using a potentiometer in a neutral or weakly alkaline electrolytic solution such as NaCl having a concentration of According to this potentiometer, it is possible to quantitatively measure the difference between the potentials of both electrodes, including which sample electrode has the higher potential. In the present invention, in order to give reproducibility to the measured potential value, the electrolysis condition which most affects the potential among the measurement conditions is defined as a non-degassed room temperature, 0.5 mol concentration NaCl electrolytic solution in the present invention. And specifies a potential measurement method.

In the present invention, the potential of the Al alloy material having the hydrated oxide film of Al measured as described above is lower by at least 10 mV than the potential of the Al alloy material having no hydrated oxide film of Al. (Hereinafter, this potential is simply referred to as the potential of the hydrated oxide film of Al).

Next, the relationship between the potential of the hydrated oxide film of Al and the corrosion resistance will be described below. 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, by lowering the potential of the hydrated oxide film of Al by 10 mV or more, the cathodic polarization of the hydrated oxide film is increased, and the corrosion resistance of the hydrated oxide film itself is improved, and By suppressing the cathode reaction, the anode current at the tip of the rust of the coating film is reduced, and the rust resistance is improved.

The deterioration of water resistance is caused by the reaction of the dense lower layer film 4 of the Al hydrated oxide film 2 with moisture. On the other hand, the potential of the hydrated oxide film of Al
By lowering it by 100 mV or more, even when moisture, seawater, or salt water penetrates the paint film, the hydrated oxide film of Al is not compatible with the permeated water, sea water, salt water, etc. And water resistance can be improved.

On the other hand, the potential difference of the hydrated oxide film of Al is 10 mV
If it is less than the above, the function of improving the water resistance and the yarn rust resistance is insufficient or lost, and other corrosion resistance such as overall corrosion resistance also decreases. That is, in the boehmite film of JP-A-05-070969, a metal compound that is more potential than Al is
Normally, it is contained only below the level of impurities, and the potential of the produced boehmite film is the same as the potential of the Al alloy material having the boehmite film measured in a 0.5 M NaCl aqueous solution (non-degassed, room temperature). The potential does not drop by 10 mV or more from the measured potential of the Al alloy material without the boehmite film.

The means for lowering the potential of the hydrated oxide film of Al in the present invention is a metal compound which is more potential than Al,
More preferably, it can be achieved by positively including a metal compound of an element selected from alkali metals such as Mg, Li and Ca, alkaline earth metals and Si and Mn in a hydrated oxide film of Al. It is. In addition, lowering the potential of the hydrated oxide film of Al is also possible by controlling the type and morphology of the hydrated oxide film of Al, the structure such as the crystal structure and the degree of crystallinity, etc. However, the control itself and reproducibility are difficult, and it is simplest to add a metal compound that is more potential than Al, and the control itself and reproducibility are good. Therefore,
The hydrated oxide film of Al in the present invention is a film substantially composed of only the hydrated oxide of Al except for the impurities contained inevitably, and a composite or a composite with each of the metal compounds or each of the metal compounds. It refers to the film of the hydrated oxide of mixed Al.

In the present invention, the metal compound which is more potential than Al is a metal compound of an element selected from alkali metals such as Mg, Li and Ca, alkaline earth metals, and Si and Mn. Is done. However, considering that it does not impair the film properties such as corrosion resistance and adhesion due to being contained in the film and the ease of inclusion in the hydrated oxide film of Al, Mg, L
It is preferable to use metal salts of alkali metals and alkaline earth metals such as i and Ca, for example, sulfates, carbonates and hydroxides. And among these, especially Mg, Li, Ca
However, the effect of forming a hydrated oxide film of Al having a low potential is great. When using these compounds of Mg, Li, Ca, usually,
A hydrated oxide film of Al that is formed only in high-temperature neutral or weakly alkaline baths exceeding 50 ° C or high-temperature steam or high-pressure water exceeding 100 ° C, and at relatively low-temperature neutral temperatures such as room temperature below 50 ° C Alternatively, it also has an effect that it can be formed by a weak alkaline bath.

The metal compound Al which is more electric potential than Al
The amount of Al introduced into the hydrated oxide film is an amount that can lower the potential of the Al hydrated oxide film by 10 mV or more, and the potential level determined by the potential lowering characteristics of the metal compound and the required corrosion resistance differs. It is generally difficult to specify. But said
Based on the case of Mg, Li, and Ca, the potential of the hydrated oxide film of Al can be reduced by 10 mV or more.The amount of metal introduced into the film is the total of metal compounds that are more potential than Al and in the film. Is preferably at least 1 at% or more. The term “at%” of the metal compound referred to in the present invention refers to at% converted to a metal element such as Mg, Li, and Ca measured by the X-ray photoelectron analysis (XPS method).

Further, a method for producing a hydrated oxide film of Al according to the present invention will be described. Preparation of the hydrated oxide film of Al in the present invention, after forming and welding-joining the Al alloy material for a transport machine, before degreasing or cleaning the Al alloy surface of the formed material with an organic solvent or an alkaline solution. After performing the treatment, a method of directly contacting 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 converting it to a hydrated oxide film of Al by a hydration reaction, Furthermore, a method of adjusting the hydration amount by heating after providing the hydrated oxide film of Al may be appropriately selected. But,
As described above, when a compound of Mg, Li, and Ca is used, 50 ° C.
With a relatively low temperature neutral or weak alkaline bath, such as room temperature, and a relatively short processing time, low potential Al
It is possible to form a hydrated oxide film, and the effect of reducing the cost of the treatment step and improving the efficiency is great.

The water used for producing the hydrated oxide film of Al is a neutral or weak alkaline bath, more specifically, tap water, pure water, or an aqueous solution of triethanolamine or ammonia. Is used. Therefore,
As described above, a metal compound that is more potential than Al is usually included in the hydrated oxide film of Al only at the level of impurities or less, and therefore, the potential of the normal hydrated oxide film of Al is reduced. Does not drop by more than 10 mV.

For this reason, in the present invention, a metal compound which is more potential than Al is positively contained in water or water used for producing this hydrated oxide film of Al, so that Al The potential of the Al alloy material having the hydrated oxide film is intentionally lowered. However, even if these metallic compounds that are more potential than Al are intentionally not included in the hydrated oxide film of Al, depending on the method of forming the hydrated oxide film of Al, the metal compound is necessarily higher than Al. May also contain metal compounds that are potentially lower in potential,
Even in such a case, the potential condition in the present invention may be satisfied, and such a case is also included in the scope of the present invention.

The method of introducing a metal compound having a potential lower than that of Al into the hydrated oxide film of Al is used for forming the hydrated oxide film of Al on the surface of the Al alloy material. If these compounds are added and dissolved in the above-mentioned high-temperature water, steam or an aqueous solution for forming an Al oxide layer on the surface of an Al alloy, they can be introduced. Therefore, the ease of dissolution in an aqueous solution is a measure of the ease of including a metal compound, which is more electric potential than Al, in the hydrated oxide film of Al.

When the hydrated oxide film of Al is formed on the surface of the Al alloy material, the hydrated oxide film is not formed at the stage of the plate material or the mold material.
As a material for a transport machine, it is preferable to form a hydrated oxide film of Al on the surface of the Al alloy of the formed material after forming and welding-joining the Al alloy material for the transport machine. This is because when the hydrated oxide film of Al is provided at the material stage, the hydrated oxide film of Al may be peeled or damaged in the next forming or welding joint stage.

Further, in the present invention, the non-cationic electrodeposition coating, that is, the electrostatic coating, the anion electrodeposition coating, and the ED coating are not applied to the Al alloy molded material provided with the hydrated oxide film of Al. It is preferable to perform a coating selected from spray coating, roll coater coating, and dip coating that does not involve an electrochemical reaction. That is, in the ED coating as in the prior art, the Al alloy material is used as a cathode, a DC voltage is applied between the anode and the anode, and the paint component ionized into positive ions is electrophoresed.
This is a method of forming a coating film on the surface of an Al alloy material. 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 rises extremely, and as a result, the oxide film on the surface of the Al alloy material is destroyed. The phosphate film is destroyed, and the adhesion of the coating film is reduced.Alkali component remains on the surface of the Al alloy material even after painting, and Al reacts with the moisture permeating the coating film during use.
The corrosion resistance such as the thread rust resistance of the Al alloy material is deteriorated even after the coating, for example, because the alloy material surface is attacked. In addition, there is no cost reduction effect by omitting the ED coating. However, when it is necessary to apply the ED coating because the ED coating cannot be omitted due to transportation machine production or a coating line, the ED coating may be applied.

It is known that an Al hydrated oxide film is provided with a composite basic salt film containing Mg, Na and the like. That is, for example, the surface technology Vol. 40, No. 5, 1989, pp. 81-86 discloses the effect of a pitting corrosion inhibitor containing magnesium sulfate and sodium hydrogen carbonate on an Al alloy. According to this document, when an Al alloy is subjected to boiling conversion treatment with an aqueous solution containing magnesium sulfate or sodium hydrogen carbonate, A
It is disclosed that a composite basic salt film containing l, Mg and sulfate is formed, and that this film has an effect of suppressing pitting corrosion of a heat exchanger made of an Al alloy.

However, this known example is not intended for an Al alloy material for a transport machine on the premise of coating as in the present invention. It is intended for Al alloy materials for heat exchangers made of Al alloy which are used only by providing an object coating. Further, this known example is intended for the pitting corrosion resistance of an Al alloy material for an Al alloy heat exchanger used without being coated, and
It is not intended to improve the two properties of water resistance and rust resistance of Al alloy materials for transport aircraft provided with a hydrated oxide film and a paint film.

As a result, in these documents, the effect of improving the pitting corrosion of the composite basic salt film containing Mg, Na, etc. is merely analyzed by measuring the corrosion potential of the film. In contrast, in the present invention, when further having a coating film, two characteristics of water resistance and yarn rust resistance, and Al
Of the hydrated oxide film of the present invention. Therefore, the configuration of the present invention cannot be obtained without knowledge of this mechanism.

Next, the Al alloy to be applied 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 the Al alloy material 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,
5086, 5456, JIS 6061, 6N01, 6063, 6151, JIS 7001,
7N01, 7003, 7050, 7072, 7075, etc. are preferred. In particular, these Al alloys, for example, for vehicles such as vehicles and aircraft, O material is a normal tempering treatment, solution treatment material,
Any of the H116 materials has a tensile strength of 200 N / mm ² or more and a proof stress of 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 manufactured as a plate or a mold material by rolling, extrusion, 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). Next, this aluminum alloy ingot is subjected to a homogenizing heat treatment, and a hot rolled and cold rolled steel sheet is added by rough annealing or intermediate annealing as necessary, or is subjected to a tempering treatment, or is extruded to a tempering treatment. Shaped product.
In addition, a molding process such as forging may be performed to obtain a product shape.

[0050]

Embodiment 1 Next, an embodiment of the present invention will be described. JIS 51
82,6022 Al alloy sheet compositions standards, in Al alloy type material of the composition of JIS 6063 standard, with tensile strength 200 N / mm ² or more and Strength
After forming an Al alloy material having 90 N / mm ² or more into each automobile member, a test piece having a size of 70 × 150 mm is cut out from the formed material, and a bath temperature of 70 ° C. × 1 minute is used with a commercially available weak alkaline degreasing solution. After performing the degreasing pretreatment, it was washed with tap water and ion-exchanged water. Then, under the conditions shown in Table 1, Mg, Li, C
The test piece was treated with an aqueous solution containing a sulfate, carbonate, hydroxide, or the like of an element selected from a, etc., and an Al hydrated oxide film having a predetermined potential was provided on the Al alloy surface. Table 1
And the same No. in Table 2 correspond to each other.
Although only the invention example No. 23 shown in FIG. 13 is subjected to the same treatment as the invention example No. 10 in Table 1, the only difference is that the test piece includes a welded portion.

The hydrated oxide film of Al was subjected to the FT-IR method.
As a result of identification, 3000-3700cm^-1AlO observed near ←
→ H absorption spectrum due to stretching vibration, and 1050-11
00cm ^-1Absorption by stretching vibration of Al ← → OH observed near
The spectrum shows that the hydrated oxide skin of Al
The presence of the film was confirmed. In addition, the surface of the Al alloy specimen was broken.
50000 times (150,000 times for thin film thickness)
Observation with a scanning electron microscope (SEM) and hydration of Al according to the present invention
Confirm that the oxide film is a vertical plate-like film
At the same time, the hydrated oxide film of Al was measured.

The element selected from Mg, Li and Ca is
The existence of these elements in the hydrated oxide film was confirmed by the XPS method, and the contents were measured. Table 2 shows the elements and amounts contained in these films and the film thickness. The form of these elements in the hydrated oxide film of Al is unknown, but is presumed to be present in the form of a composite oxide or hydroxide with Al.

The X-ray photoelectron analysis (XPS method) of the content of the metal compound element, which is lower in potential than the natural potential of Al selected from Mg, Li, Ca, etc., in the hydrated oxide film of Al. ) Was measured by cutting an Al alloy material with a hydrated oxide film of Al (before painting) into a 6 mm × 6 mm specimen at 5 points at 30-second intervals from the top of the film in the thickness direction of the film. Irradiation was performed, and the XPS spectrum of each element was measured each time. Then, at% of the total sum of each element introduced into the film was determined from the value obtained by correcting the XPS spectrum intensity of each element for sensitivity.

At% of the total sum of the elements introduced in this film is:
Obtained by dividing the sum of the XPS spectral intensities of each element introduced in the film after sensitivity correction by the sum of the XPS spectral intensities of each element introduced in the film and other elements contained in the film after sensitivity correction. . The other elements contained in the coating in large amounts are Al, O, which is the main component of the coating, and Si, Mn, which have a high content of the Al alloy component elements that may be substantially mixed into the coating from the Al alloy material. Be, Na, K, Ba and the like. Therefore, elements other than these elements which are or are likely to be included in the film are selected according to the Al alloy material and the film processing conditions. In this regard, in this example, in this embodiment, at% of the total sum of the elements introduced into the film = (Sum of XPS spectral intensities after sensitivity correction of each element introduced into the film such as Mg, Li, and Ca) / (A
l, O, Be, Na, K, Ba, Si, Mn, etc.
At% of the total sum of each element introduced into the film was determined by the sum of the XPS spectrum intensity + the sum of the XPS spectrum intensity after sensitivity correction of each of the introduced elements of Mg, Li and Ca. Then, the average content of at% of the total sum of the elements introduced in the five points of the coating in the thickness direction of each coating was determined.

Further, the potential of the Al hydrated oxide film of each test piece was measured by a potentiometer in a 0.5 M NaCl aqueous solution (non-degassed, room temperature). The potential of the material was determined by comparison (difference) with the potential of an Al alloy material having no Al hydrated oxide film measured under the same conditions. Table 2 shows the results.

Then, this Al hydrated oxide film was provided.
As shown in Table 2, a two-coat two-bake coating film was further provided on the surface of the Al alloy test piece by a spray coating method. More specifically, a 30-μm-thick polyester melamine-based coating film is provided as an intermediate coating, baked at 140 ° C for 20 minutes, and a 30-μm-thick polyester melamine-based coating film is further provided as a top coating. And baked at 140 ° C. for 20 minutes. In addition, Nos. 18 and 19 of the invention examples were coated with ED and then provided with 2 coats and 2 bake coats by the spray coating method, and No. 21 and 23 of the invention examples were coated with 2 coats by the roll coat method. 2 Bake coating was provided.

For comparison, a hydrated oxide film of Al containing a metal compound having a potential lower than that of Al in the hydrated oxide film of Al but out of the potential range of the present invention was provided.
Two coats and two bake coats were provided by spray coating.
Al alloy test pieces (Nos. 11 to 13 and 22), which do not contain a metal compound that is lower in potential than Al, deviate from the potential range of the present invention
A comparative example (No. 14) in which a two-coat two-bake coating film was provided by the spray coating method on an Al alloy test piece provided with an Al hydrated oxide film, a metal compound having a potential lower than that of Al Comparative Example in which the surface of the Al alloy test piece provided with a hydrated oxide film of Al which is not included in the potential range of the present invention was subjected to ED coating, and then provided with the 2 coat 2 bake coating film by the spray coating method ( No. 15), a comparative example in which, after the ED coating was performed on the surface of an Al alloy test piece provided with a phosphate treatment film by the conventional method, a two-coat two-bake coating film was provided by the spray coating method (No. 15).
16, 17) were also prepared and analyzed in the same manner as in the inventive examples except for these conditions.

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.
Was immersed in ion-exchanged water for 10 days, and then subjected to a JIS 1 mm width cross cut tape peeling test 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
-10, 18-21, and 23, the potential of the hydrated oxide film of Al on the surface of the Al alloy material satisfies the requirements of the present invention, and a coating film by non-ED coating that does not involve an electrochemical reaction is provided. Therefore, it is excellent in both water resistance and yarn rust resistance. Moreover, as shown in Table 2, Invention Examples Nos. 1 to 10 containing Mg, Li, and Ca
Can be processed at a low temperature of 50 ° C without being treated with a high-temperature processing solution.
Can be formed. In addition, Invention Example No. 1
Although Nos. 8 and 19 have both water resistance and yarn rust resistance because they are ED-coated, they are inferior to the above-described invention examples in which only a non-ED coating film is used.

On the other hand, the surface of the Al alloy test piece provided with the hydrated oxide film of Al out of the electric potential range of the present invention,
Comparative Example N with a non-ED coating film after coating
o.15, and without providing a hydrated oxide film of Al of the present invention,
Comparative Examples No. 16 and 17 in which after ED coating was applied to the surface of a phosphate-treated Al alloy specimen, a non-ED coating film was provided.
Although the rust resistance is moderate, the water resistance is remarkably inferior to the examples of the present invention. Further, Comparative Example N provided with a hydrated oxide film of Al deviating from the potential range of the present invention.
The aluminum alloy materials of o.11 to 14 and 22 are also inferior in both water resistance and yarn rust resistance or both water resistance and yarn rust resistance as compared with the examples of the present invention.

Therefore, the above facts support the critical significance of the potential of the hydrated oxide film of Al of the present invention, which is excellent in both water resistance and yarn rust resistance. Also, ED
Even without coating, non-ED coating is better than ED coating in water resistance and thread rust resistance.

[0063]

[Table 1]

[0064]

[Table 2]

[0065]

According to the present invention, it is possible to provide an Al alloy material for a transport machine which is excellent in both water resistance and yarn rust resistance, which can be substituted for phosphate treatment + ED coating. Therefore, Al
This has great industrial value in that the function of the 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.

[Explanation of symbols]

1: Al alloy material, 2: Al hydrated oxide film, 3: Middle coat, 4: Top coat, 5: Paint film, 6: Al alloy material for transport,

Claims (10)

(57) [Claims] Claims: 1. An Al alloy material for a transport machine, wherein an Al hydrated oxide film and a paint film are provided on an Al alloy material surface,
The natural potential of the Al hydrated oxide film is non-degassed at room temperature.
Measured under the same conditions as the spontaneous potential of an Al alloy material with a hydrated oxide film of Al measured in 0.5M NaCl aqueous solution
An aluminum alloy material for transport equipment that is excellent in water resistance and yarn rust resistance, characterized in that the natural potential of the aluminum alloy material without an aluminum hydrated oxide film is lower by at least 10 mV. 2. The hydrated oxide film of Al according to claim 1, wherein the metal compound has a potential lower than the spontaneous potential of Al in a total amount and an average content in the film of 1 at% or more. Al alloy material for transport aircraft with excellent water resistance and thread rust resistance. 3. The method according to claim 1, wherein the metal compound having a potential lower than the natural potential of Al is an alkali metal , an alkaline earth metal ,
2. A metal compound of an element selected from i and Mn.
Or for transport equipment excellent in water resistance and yarn rust resistance described in 2.
Al alloy material. 4. The water-resistant material according to claim 1, wherein the metal compound having a potential lower than the natural potential of Al is a metal compound of an element selected from Mg, Li, and Ca. Al alloy material for transport aircraft with excellent resistance and yarn rust resistance. 5. An Al hydrated oxide film containing a metal compound of an element selected from the group consisting of Mg, Li, and Ca is formed by coating an Al alloy material in a neutral or weakly alkaline bath of less than 50 ° C. containing these metal compounds. 5. A film formed by processing.
An aluminum alloy material for transport aircraft excellent in water resistance and yarn rust resistance described in 1. 6. The film thickness of the hydrated oxide film of Al is 100 to 100.
The Al alloy material for a transporting machine according to any one of claims 1 to 5, wherein the Al alloy material has excellent water resistance and yarn rust resistance. 7. 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. 8. The water resistance and thread 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. 9. The aluminum alloy material is provided with a hydrated oxide film and a paint film of Al 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. 10. The vehicle according to claim 1, wherein the transporter is for an automobile.
10. The Al alloy material for a transport machine, which is excellent in water resistance and yarn rust resistance according to any one of the above items 9 to 9.