JP2003221684A - Method of surface treatment for magnesium and/or magnesium alloy, and magnesium and/or magnesium alloy product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of surface treatment for magnesium and/or a magnesium alloy, which comprises the use of a treating agent that is substantially free of a substance harmful to the environment or a human body, such as chromium and manganese, and simultaneously attains corrosion resistance low electric resistance of the resulting coating film. <P>SOLUTION: The method of surface treatment for magnesium and/or a magnesium alloy comprises treating magnesium and/or the magnesium alloy with an aqueous chemical treatment solution (A) containing 0.001 to 10 mass% of a carbonate compound. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treatment method for imparting high corrosion resistance and coating adhesion to members and products made of magnesium metal or magnesium alloy. Furthermore,
Automotive components that require high coating adhesion and corrosion resistance after painting, home appliances such as televisions and audio devices that require electrical conductivity in addition to the above performance, and magnesium alloys for electronic devices such as personal computers and mobile phones. The present invention relates to a surface treatment method that can be suitably used for a manufacturing member. Further, since the formed film does not contain elements harmful to the human body such as chromium and manganese, it is a promising future surface treatment for biomaterials made of magnesium metal.

[0002]

2. Description of the Related Art As a chemical conversion treatment technology for magnesium metal and magnesium alloy, it is disclosed in many patents, papers, technical books and the like. The most common of these is the chromate treatment. Chromate treatment has a wide range of applicable products and can impart excellent corrosion resistance and coating adhesion to magnesium products. However, the chemical conversion treatment bath and the chemical conversion film produced therefrom contain hexavalent chromium, which adversely affects the human body and the environment. Therefore, chemical conversion treatment technology that does not use chromium, so-called non-chromium chemical conversion treatment technology, has been developed.As a result, phosphorylation treatment, zirconium-based chemical conversion treatment, and manganese-based chemical conversion treatment have been developed, and some have been put to practical use. (See, for example, Patent Document 1 and Patent Document 2).

Phosphorylation can improve the corrosion resistance and coating adhesion of magnesium alloys to some extent, but it is often insufficient and its use is considerably limited. This is because when the phosphorylation treatment is performed, water-soluble MgHPO ₄ is formed in the chemical conversion film formed on the surface of the magnesium alloy, and thus it is difficult to form a film having sufficient corrosion resistance. In addition, treatment temperature and treatment time are long, and phosphoric acid is also a cause of environmental pollution such as soil eutrophication.

The zirconium-based chemical conversion treatment forms a hydroxide, oxide or phosphoric acid compound of zirconium on the surface of the magnesium alloy to impart corrosion resistance and coating adhesion to the magnesium alloy. However, as compared with the chromate treatment, the unpainted corrosion resistance may be slightly inferior and may not be sufficient depending on the application. Zirconium is also a rare element and is scarce in resources and expensive. Further, in order to stably exist in a solution, it is generally present as a fluorine complex ion, and it is difficult to avoid containing fluorine, which is not preferable in terms of environmental protection.

The manganese-based chemical conversion treatment has a performance comparable to that of the chromate treatment. Roughly classified, phosphoric acid type,
It is roughly classified into non-phosphoric acid type. Manganese chemical conversion treatment is currently the mainstream for magnesium alloy casings of notebook personal computers. However, although manganese is less strict than hexavalent chromium, it remains an emission control substance. In the future, stricter emission regulations will make their use more difficult.

When chemical conversion treatment without using a heavy metal is carried out in order to improve such a problem, it becomes difficult to satisfy well-balanced physical properties required for magnesium alloy products such as coating film adhesion, corrosion resistance and electric resistance. .
In particular, when it is used for information devices such as personal computers and mobile phone casings, the electrical resistance of the magnesium alloy surface must be kept at a low resistance value in terms of antistatic properties. It is not preferable that the chemical conversion treatment film formed on the surface has high electric resistance. Therefore, salt spray test 24
The corrosion occurrence rate over time is 5% or less, the electric resistance value of the film is about 0.2Ω or less, and the salt spray test 120
It is required to have both the electric resistance of the coating and the corrosion resistance so that the coating does not peel off with time.

Further, depending on the molding method of the magnesium alloy product, the metal surface is contaminated by the release agent,
Since it is difficult to remove this, it may be difficult to impart corrosion resistance and coating adhesion, but even in such cases, sufficient corrosion resistance and coating adhesion can be imparted to the metal surface. Is needed.

[0008]

As described above, the inclusion of substances that are harmful to the environment and the human body, such as hexavalent chromium, permanganate ions, and phosphate ions, and to achieve both film electrical resistance and corrosion resistance. There is a problem that there is a limit.
Therefore, an object of the present invention is to use a treatment agent which does not substantially contain substances such as chromium and manganese harmful to the environment and the human body,
Moreover, a surface treatment method for a magnesium metal and / or a magnesium alloy capable of forming a chemical conversion treatment film satisfying the requirements of high corrosion resistance, coating film adhesion, and high film electrical resistance, and such a surface treatment method. To provide a magnesium and / or magnesium alloy product treated by.

[0009]

[Patent Document 1] Japanese Unexamined Patent Publication No. 8-35073 (page 2)

[0010]

[Patent Document 2] JP-A-7-126858 (second
page)

[0011]

According to the present invention, 0.001 to 10% by mass of magnesium and / or magnesium alloy is used.
The method for surface treatment of magnesium and / or magnesium alloy is characterized in that it is treated with the chemical conversion treatment aqueous solution (A) containing the carbonate compound.

The chemical conversion treatment aqueous solution (A) further contains a coating film adhesion promoter, and the coating film adhesion promoter is
It is preferably 0.01 to 1% by mass of a triazine thiol compound, a silane coupling agent, and one or more compounds selected from the group of polyallylamine.

The surface treatment method of magnesium and / or magnesium alloy further comprises a chemical conversion treatment solution containing magnesium and / or magnesium alloy treated with the chemical conversion treatment solution (A) containing a second coating film adhesion promoter ( The second coating film adhesion promoter is preferably at least one selected from the group consisting of triazine thiol compounds, silane coupling agents and polyallylamine.

The triazine thiol compound is 1,
3,5-triazine-2,4,6-trithiol, 2-
(Dibutylamino) -4,6-dimercapto-1,3
5-triazine and 2- (phenylamino) -4,
It is preferably at least one compound selected from the group consisting of 6-dimercapto-1,3,5-triazine.

The silane coupling agent is N- (6-
Aminohexyl) aminopropyltrimethoxysilane,
N- (6-aminohexyl) aminopropyltriethoxysilane, N- (6-aminohexyl) aminopropyltrichlorosilane, N- (2-aminoethyl) -3-aminopropyltriethoxysilane, N- (2-amino Ethyl) -3-aminopropyltrimethoxysilane, N-
(2-Aminoethyl) -3-aminopropyltrichlorosilane, 3-aminopropylethoxysilane, and 3
It is preferably at least one aminosilane compound selected from the group consisting of -aminopropylmethoxysilane.

It is preferable that the coating adhesion promoter is a triazine thiol compound and the second coating adhesion promoter is polyallylamine.

Before the above-mentioned surface treatment, it is preferable that degreasing, pickling and desmutting treatments are carried out to remove contaminants and uneven substances existing on the surface. The present invention is also a magnesium and / or magnesium alloy alloy product characterized by being treated by the above-mentioned magnesium and / or magnesium alloy surface treatment method. The present invention will be described in detail below.

The surface treatment method for magnesium and / or magnesium alloy of the present invention is a surface treatment method using a treating agent which does not substantially contain heavy metals. That is, conventional magnesium metal, chromium used in the surface treatment method of magnesium alloy, manganese, zirconium,
This is a method of surface treating magnesium metal or magnesium alloy using a treating agent which does not substantially contain a heavy metal compound such as titanium.

In the above surface treatment method for magnesium and / or magnesium alloy, the fact that the treatment agent does not substantially contain heavy metal means that no heavy metal ion is intentionally added, and the heavy metal functions in the treatment agent. It means that it is not included to the extent that it can be exerted.

The magnesium metal and magnesium alloy treated by the surface treatment method of magnesium and / or magnesium alloy of the present invention are magnesium metal and magnesium alloy produced by rolling, die casting method, thixomold method and the like. Magnesium metal is promising as a biomaterial, and it is considered that AZ31 alloy and 99.9% pure magnesium metal will be widely used in the future from the economical viewpoint. The present invention can also be used for magnesium alloys. The more preferably used alloy is AZ9.
1, AZ31, AM60, AM50, etc. here,
The notations AZ and AM represent the added metal element. A
Is aluminum, M is manganese, and Z is zinc. The numbers following these notations represent the addition concentrations of these additional elements, for example, in the case of AZ91, aluminum is 9% and zinc is 1%. When M is 0, it means that the content of Mn is less than 1%. Especially, aluminum such as AZ91 and AM60 is 5%.
It is preferably used for alloys containing the above.

When processing a magnesium metal or a magnesium alloy, mechanical oil or a release agent is used. In particular,
In the case of die-casting or thixomolding, the release agent is applied not only on the surface of the metal or alloy, but also inside the metal or alloy.
-30 μm, and sometimes it may remain inside. For this reason, the conventional surface treatment method has insufficient corrosion resistance after coating and coating film adhesion, but the surface treatment method of the present invention has sufficient corrosion resistance and coating film against such magnesium metal and magnesium alloy. Adhesiveness can be imparted.

The surface treatment method for magnesium and / or magnesium alloy of the present invention (hereinafter also referred to as surface treatment method) is a chemical conversion treatment containing 0.001 to 10% by mass of a carbonate compound for magnesium and / or magnesium alloy. It is treated with an aqueous solution (A).

The characteristic of the surface treatment method is that magnesium metal and / or magnesium alloy is treated with an aqueous solution containing carbonate ions or an aqueous solution containing carbonate ions and a coating film adhesion promoter. The important chemical point of the treatment method when the coating film adhesion promoter is not included is that the magnesium metal or magnesium alloy is a stable alkaline solution, for example, a 1% by mass K ₂ (CO ₃ ) solution. At a pH of about 11.5 (measured and confirmed), the reaction liquid is kept at a high temperature to promote the formation of an oxide film or a hydroxide film or a mixed film of both, and magnesium carbonate is produced by a reaction with carbonate ions. It is to let.

Examples of the carbonate ion source include carbonate compounds such as lithium carbonate, sodium carbonate, potassium carbonate and calcium carbonate. solubility,
Considering the cost, it is preferable to use sodium carbonate or potassium carbonate. The concentration of the carbonate compound in this case is
It is 0.001 to 10% by mass, and it can be used in a bag having a solubility limit of the carbonate compound used. It is preferably 0.01 to 10% by mass, and more preferably 0.1 to 3% by mass. If it is less than 0.001% by mass, sufficient corrosion resistance and electric resistance of the film cannot be obtained.
Even if it exceeds 0% by mass, no further improvement of the effect is recognized, which is economically unfavorable.

The treatment method of magnesium and / or magnesium alloy with the above chemical conversion treatment solution (A) is not particularly limited, and the surface of the object to be treated and the chemical conversion treatment solution (A) may be treated by a known method such as spraying or dipping. It can be performed by contacting. The immersion method is preferable because it can be suitably used for processing personal computer housings, mobile phone housings, automobile members / parts, and other products having complicated shapes.

In the above-mentioned surface treatment method, the temperature of the chemical conversion treatment bath is not particularly limited, and may be 50 ° C. or higher, preferably 60 to 90 ° C., more preferably 80 to 90 ° C. . If the temperature is lower than 50 ° C., the formation of an oxide film is insufficient and good performance is not exhibited, which is not suitable. If the temperature exceeds 90 ° C., not only is there a lot of waste such as evaporation of the solution and securing of a heat source, but also no particular improvement in performance is observed, which is not preferable.

In the above surface treatment method, the treatment time is 1
It is preferably -5 minutes. If it is less than 1 minute, the oxide film is not sufficiently formed and good performance is not exhibited, which is not suitable. If it exceeds 5 minutes, it is not preferable because not only is there a lot of waste such as evaporation of the solution and securing of a heat source, but also no special improvement in performance is observed. More preferably, it is 3 to 5 minutes.

In the above surface treatment method, sufficient coating film adhesion can be obtained by treatment with the above carbonate compound alone.
When a coating film adhesion promoter is added, stronger coating film adhesion can be imparted to magnesium metal or magnesium alloy. In particular, when a release agent that is difficult to remove is used, or when the molten metal flow is poor and the structure is porous, it is possible to impart corrosion resistance and coating adhesion to poor quality magnesium castings.

As the coating film adhesion promoter used in the above surface treatment method, it is preferable to use a silane cup agent having an amino group at the terminal, a triazine thiol compound, or a polyallylamine.

Examples of the silane coupling agent include N- (6-aminohexyl) aminopropyltrimethoxysilane, N- (6-aminohexyl) aminopropyltriethoxysilane and N- (6-aminohexyl).
Aminopropyltrichlorosilane, N-aminoethyl)
-3-Aminopropyltriethoxysilane, N- (2-
Aminoethyl) -3-aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrichlorosilane, 3-aminopropylethoxysilane,
Mention may be made of aminosilane compounds such as 3-aminopropylmethoxysilane.

The above triazine thiol compound is a compound having both a triazine ring and a thiol group. In particular, thiol-substituted 1,3,5-triazine is preferable. Further, the triazine thiol compound may be one in which a part of the triazine ring is substituted with alkylamino. Examples of the triazine thiol compound, for example,
1,3,5-triazine-2,4,6 trithiol, 2
-(Dibutylamino) -4,6-dimercapto-1,
3,5-triazine, 2- (phenylamino) -4,6
-Dimercapto-1,3,5-triazine and the like can be mentioned.

The polyallylamine is represented by the following general formula (1)

[0033]

[Chemical 1]

It is a polymer represented by: In the general formula (1), the degree of polymerization n is preferably in the range of 10 as the lower limit and 1200 as the upper limit. When the degree of polymerization is too low, the effect of coating film adhesion may not be obtained, and when the degree of polymerization is too high, there is a problem that the bath stability is poor. As the polyallylamine, PAA series manufactured by Nitto Boseki (PAA-0
1, PAA-03, PAA-05, PAA-15, PA
Commercially available products such as A-15B, PAA-10C, PAA-H-10C) can be used.

The coating film adhesion promoter that can be used in the above surface treatment method is not limited to these, is stable in an alkaline atmosphere, has a functional group effective for coating film adhesion, Any organic molecule that can be adsorbed can be used. The concentration of the coating film adhesion promoter used is preferably 0.01 to 1% by mass, and less than 0.01% by mass unfavorably reduces the effect. On the other hand, even if it exceeds 1% by mass,
No increase in effect is observed, which is economically unfavorable. The concentration of carbonate in the treatment bath when the above coating film adhesion promoter is used is the same as in the case of the above carbonate treatment, and is 0.001
It can be used in an amount of from 10 to 10% by mass, preferably from 0.01 to 10% by mass, more preferably from 0.1 to 3% by mass. In addition, the temperature of the chemical conversion treatment bath when the above coating film adhesion promoter is used is 4
The temperature may be 0 ° C or higher, preferably 60 to 90 ° C, more preferably 60 to 80 ° C.

In the surface treatment method of magnesium and / or magnesium alloy of the present invention, first, as described above, 0.001 to 0.001 of magnesium and / or magnesium alloy is added.
Chemical conversion treatment aqueous solution (A) containing 10% by mass of carbonate compound
It is preferable that the treatment is performed with the chemical conversion treatment aqueous solution (B) containing the second coating film adhesion promoter after the treatment with.

By treatment with the chemical conversion treatment aqueous solution (A), a mixture film of magnesium compounds such as magnesium carbonate, magnesium hydroxide and magnesium oxide is formed on the metal surface, whereby corrosion resistance can be obtained and the above chemical conversion treatment is performed. Further treatment with the treatment aqueous solution (B) can further improve the corrosion resistance and coating adhesion. Further treatment with the chemical conversion treatment aqueous solution (B) forms an organic molecule adsorption layer comprising the coating film adhesion promoter and the second coating film adhesion promoter on the mixture film of the magnesium compound. It is presumed that the organic molecule adsorption layer further improves the corrosion resistance, and at the same time, improves the adhesion between the coating film and the magnesium metal or magnesium alloy surface. Further, since the mixture film of the magnesium compound is a very thin film at the molecular level, it is possible to impart corrosion resistance and coating adhesion without significantly impairing the conductivity of magnesium metal or magnesium alloy.

By further treating with the above-mentioned chemical conversion treatment solution (B), it is difficult to perform sufficient chemical conversion treatment only by treating with the above-mentioned chemical conversion treatment solution (A), for example, Sufficient chemical conversion treatment can be performed even on a particularly poor quality magnesium cast product to which the release agent is firmly attached.

When the chemical conversion treatment solution (B) is further treated, the pH of the chemical conversion treatment solution (A) is preferably 10 or more. By setting it within the above range,
A chemical conversion treatment reaction with a carbonate occurs efficiently, and an efficient chemical conversion treatment can be performed. The pH is more preferably 11 or higher. The upper limit of pH is not particularly limited, but is preferably 13 or less.

When the chemical conversion treatment solution (B) is further treated, the chemical conversion treatment solution (A) contains a basic compound as a pH adjuster in order to adjust the pH within the above range. May be. The basic compound is not particularly limited, and examples thereof include lithium hydroxide, sodium hydroxide, potassium hydroxide, and ammonia.

The second coating film adhesion promoter is preferably at least one selected from the group consisting of triazine thiol compounds, silane coupling agents and polyallylamine. The triazine compound, the silane coupling agent, and the polyallylamine that can be used as the second coating film adhesion promoter are not particularly limited. For example, the above-mentioned compounds that can be used as the coating film adhesion promoter can be used. Can be mentioned.

When a triazine thiol compound is used as the second coating film adhesion promoter, the content of the triazine thiol compound is in the range of 10 ppm as the lower limit and 10000 ppm as the upper limit with respect to the chemical conversion treatment solution (B). Is preferred. If it is less than 10 ppm, sufficient corrosion resistance may not be obtained, and if it exceeds 10,000 ppm, no further improvement of the effect is recognized, which is economically undesirable. The lower limit is more preferably 100 ppm, further preferably 500 ppm. More preferably, the upper limit is 5000 ppm,
More preferably, it is 2000 ppm.

When an aminosilane compound is used as the second coating film adhesion promoter, the lower limit of the content of the aminosilane compound to the chemical conversion treatment solution (B) is 10 pp.
m, and the upper limit is preferably 10,000 ppm. If it is less than 10 ppm, sufficient corrosion resistance may not be obtained, and if it exceeds 10,000 ppm, no further improvement of the effect is recognized, which is economically undesirable. The lower limit is more preferably 100 ppm, and 5
More preferably, it is 00 ppm. The upper limit is 5
000 ppm is more preferable, and 2000 pp
More preferably m.

When polyallylamine is used as the second coating film adhesion promoter, the content of the polyallylamine is at the lower limit of 50 ppm with respect to the chemical conversion treatment solution (B),
The upper limit is preferably 10,000 ppm.
If it is less than 50 ppm, sufficient corrosion resistance may not be obtained, and if it exceeds 10000 ppm, no further improvement of the effect is recognized, which is economically unfavorable. The lower limit is more preferably 100 ppm and is preferably 500
More preferably, it is ppm. The upper limit is 500
It is more preferably 0 ppm and even more preferably 3000 ppm.

The second coating film adhesion promoter may be the same compound as the above coating film adhesion promoter, but if they are different, the coating film adhesion promoting effect will be better. , And more preferable.

As a combination of the coating adhesion promoter and the second coating adhesion promoter, the coating adhesion promoter is a triazine thiol compound and the second coating adhesion promoter is an aminosilane compound or polyallylamine. A combination in which the coating adhesion promoter is an aminosilane compound and the second coating adhesion promoter is polyallylamine is preferable from the viewpoint of improving adhesion. Among these, a combination in which the coating adhesion promoter is a triazine thiol compound and the second coating adhesion promoter is polyallylamine is most preferable.

The treatment method with the chemical conversion treatment solution (B) is not particularly limited, and it can be carried out by bringing the object to be treated into contact with the chemical conversion treatment solution (B) by a known method such as spraying or dipping. In order to efficiently carry out the second chemical conversion treatment reaction, the temperature of the chemical conversion treatment aqueous solution (B) is preferably within the range of the lower limit of 40 ° C and the upper limit of 80 ° C.
If the temperature is lower than 40 ° C., the film formation will be insufficient and good performance will not be exhibited, such being unsuitable. Above 80 ° C,
It is not preferable because not only is there a lot of waste such as evaporation of the solution and securing of a heat source, but also no special improvement in performance is observed. More preferably, the lower limit is 50 ° C., and the upper limit is 60 ° C.

In the surface treatment method of magnesium and / or magnesium alloy of the present invention, in order to perform the treatment more efficiently, degreasing, pickling, and
It is more preferable to perform the desmutting process. For example, when the release agent remains not only on the surface of the object to be treated but also inside the object to be treated, it is necessary to remove the machine oil and the releasing agent from the surface of the object to be treated. As described above, when treating a magnesium metal or a magnesium alloy that is heavily contaminated with machine oil or a mold release agent, the release agent removal step differs slightly depending on the degree of contamination of the object to be treated. However, degreasing → washing with water → acid etching → washing with water → desmutting → washing with water are generally performed.

In the above degreasing step, an aqueous solution of an alkaline degreasing agent containing a surfactant is generally used. This step is performed for the purpose of removing the mechanical oil and the release agent loosely attached to the surface. The degreasing agent used is not particularly limited. When the degree of contamination is small, this degreasing may be sufficient, but in most cases it is insufficient, and acid etching is generally performed.

The purpose of the above acid etching step is to provide a non-uniform oxide layer on the surface of the metal or alloy, mechanical oil adhering to the surface of the object to be treated, metal, or a release agent that has penetrated into the interior of the alloy. It is to remove it by melting the alloy. If these are not removed sufficiently, there is a possibility that sufficient corrosion resistance and coating film adhesion cannot be imparted. Further, although it is not necessary to completely remove the release agent, if the release agent is extremely insufficiently removed, this may also adversely affect the corrosion resistance and the coating film adhesion. This step is indispensable and important especially when the release agent is heavily contaminated.

As the acid used in the above acid etching step, in addition to inorganic acids such as phosphoric acid, sulfuric acid and nitric acid, oxalic acid and
Organic acids such as acetic acid can be used. The acid concentration in the acid etching solution is preferably 0.1 to 5 g / l, more preferably 0.1.
It is 3-1 g / l. When it is less than 0.1 g / l, the pH is increased by dissolution of magnesium, and the frequency of solution exchange is increased, which is not preferable. When it exceeds 5 g / l, magnesium metal and magnesium alloy are remarkably dissolved, resulting in vigorous hydrogen generation. Therefore, it may undesirably damage the surface of the metal or alloy. If carboxylic acid or phosphoric acid is used at a concentration of more than 5 g / l, oxalate or phosphate may be deposited on the surface and sufficient release agent may not be removed. Although some of these acids are effective when used alone, such as oxalic acid and nitric acid, it is generally preferable to use them as a mixed acid of two or more kinds. For example, sulfuric acid and nitric acid, phosphoric acid and hydrosilicofluoric acid can be preferably used.

In the desmutting process, KOH and NaOH are used.
Although an aqueous solution containing the alkaline compound as a main component can be preferably used, the present invention is not limited thereto. It is carried out for the purpose of removing products adhering to the surface by acid etching, removing aluminum that is biased on the surfaces of metals and alloys, and removing the release agent adhering to the vicinity of the aluminum.

The magnesium metal or magnesium alloy product treated by the above surface treatment method can be suitably used for a casing of a mobile phone, a personal computer, a lid material and the like.
Such a magnesium alloy product is also one aspect of the present invention.

The surface treatment method of magnesium and / or magnesium alloy of the present invention is to treat magnesium and / or magnesium alloy with a chemical conversion treatment aqueous solution (A) containing 0.001 to 10 mass% of a carbonate compound. Therefore, a film made of a mixture of magnesium compounds can be formed on the surface of magnesium and / or magnesium alloy, and excellent corrosion resistance, coating adhesion and conductivity can be imparted. Further, when the chemical conversion treatment aqueous solution (A) further contains a coating film adhesion promoter, the corrosion resistance and the coating film adhesion can be further improved.

In the case where the above-mentioned surface treatment method is a treatment by the chemical conversion treatment aqueous solution (B) containing the second coating film adhesion promoter, a film made of a mixture of magnesium compounds is formed, and The water-soluble organic molecule adsorption layer can be formed. Therefore, higher corrosion resistance can be imparted by the mixture film of the above-mentioned magnesium compound, and further corrosion resistance can be further improved by the water-soluble organic molecule adsorption layer, and high coating film adhesion can be imparted. As a result, it is possible to sufficiently perform the chemical conversion treatment even on poor quality magnesium metal or magnesium alloy, which is difficult to sufficiently perform the chemical conversion treatment with the chemical conversion treatment aqueous solution (A). Further, since the formed mixture film of magnesium compounds is a very thin film at the molecular level, the electric resistance value of the surface of the treated magnesium metal or magnesium alloy does not become too high. That is, even with the method of performing the chemical conversion treatment with the chemical conversion treatment aqueous solution (B), more excellent corrosion resistance, coating film adhesion and conductivity can be imparted.

[0056]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to these examples. In the examples, "parts" means "parts by mass" unless otherwise specified.

Example 1 A magnesium alloy AZ91D test plate manufactured by Thixomolding and having a plate thickness of 2 mm was degreased, washed with water under the following conditions.
After acid etching, washing with water, desmutting, washing with water, chemical conversion treatment, washing with water, and drying, powder coating was performed. Washing with water
The tap water shower was used, and all other steps were processed by the dip method. Drying with an electric dryer at 100 ℃, 20
I went for a minute. (A) Degreasing treatment liquid: 1 mass% Magdyne SF100 cleaner (manufactured by Nippon Paint Co., Ltd.) Treatment temperature: 50 ° C. Treatment time: 2 minutes (B) Acid etching treatment liquid: 1 vol% Magdyne SF400 acid etching (manufactured by Nippon Paint Co., Ltd.) Treatment Temperature: 50 ° C. Treatment time: 10 minutes (C) Desmutting treatment liquid: 5 vol% Magdine SF300 Alkaline etching treatment temperature: 60 ° C. Treatment time: 5 minutes (D) Chemical conversion treatment liquid: 1% by mass potassium carbonate aqueous solution pH: 11 .5 Treatment temperature: 80 ° C. Treatment time: 5 minutes Using the obtained test plate, the unpainted corrosion resistance was measured by the following method.
The electrical resistance of the chemical conversion coating, the corrosion resistance after coating, and the coating adhesion were evaluated and the results are shown in Table 1.

[0058]Unpainted corrosion resistance Salt spray test: 5% saline solution was sprayed on the test piece at 35 ° C.,
Occupancy of the corroded portion after 48 hours was visually evaluated.Chemical film electrical resistance Surface resistance measuring device EP-T360 (manufactured by KEYENCE CORPORATION)
Using the 2-probe method, measure 9 points on the chemical conversion film, and
The average value of the 7 points excluding the value and the minimum value is the electrical resistance value.
It wasCorrosion resistance after painting Magdyne PD-E (epoxy powder coating, Japanese
(Paint Co., Ltd.) to a dry film thickness of 40 μm
Then, the coated plate was prepared by baking at 160 ° C. for 20 minutes.
Put a cross cut to the base with a metal cutter in this
Subjected to salt spray test, cross cut after 120 hours
The peeling width of the coating film when pressure-sensitive adhesive tape is peeled off
evaluated.Coating adhesion (1) 120-hour salt spray test of powder coated test plates
After that, put a grid on the test plate taken out at 1 mm intervals.
100 pieces were made, and an adhesive tape was attached and peeled off. Remaining
The number of crosses was measured and evaluated. (2) Powder coated test plate in hot water at 50 ℃ for 120 hours
Soak. After that, the test plate was taken out and a 1 mm-spaced board
100 eyes were made, and an adhesive tape was attached and peeled off.
The number of remaining grids was measured and evaluated.

Example 2 A test plate was prepared in the same manner as in Example 1 except that the chemical conversion treatment agent in Example 1 was changed to a 0.1 mass% potassium carbonate aqueous solution. Further, in place of the thixomolding-made magnesium alloy AZ91D test plate having a plate thickness of 2 mm, a die-cast magnesium alloy AZ91D test plate having a plate thickness of 1 mm, which is an alloy having poor coating adhesion and corrosion resistance, was used, except that the test example 1 was used. A test plate was prepared in the same manner as in. Then, each was evaluated in the same manner as in Example 1, and the obtained results are shown in Table 1.

Example 3 A test plate was prepared in the same manner as in Example 1 except that the treatment temperature in Example 1 was changed to 60 ° C. Then Example 1
Evaluation was carried out in the same manner as above, and the obtained results are shown in Table 1.

Example 4 A test plate was prepared in the same manner as in Example 1 except that the chemical conversion treatment agent in Example 1 was changed to a saturated calcium carbonate aqueous solution (concentration: 0.0014% by mass). Then, the evaluation was performed in the same manner as in Example 1, and the obtained results are shown in Table 1.

Example 5 A test plate was prepared in the same manner as in Example 1 except that the chemical conversion treatment agent in Example 1 was changed to a 5 mass% potassium carbonate aqueous solution. Then, the evaluation was performed in the same manner as in Example 1, and the obtained results are shown in Table 1.

Example 6 A die cast magnesium alloy AZ91D test plate having a plate thickness of 1 mm, which is an alloy having poor coating film adhesion and corrosion resistance, was immersed in a chemical conversion treatment bath shown below to prepare a test plate. Then, the results obtained by evaluation as in Example 1 are shown in Table 1. The conditions other than the steps and the chemical conversion treatment were the same as in Example 1. (A) Chemical conversion treatment: Aqueous solution of 1% by mass of K ₂ CO ₃ and 0.1% of 1,3,5-triazine-2,4,6 trithiol pH: 11.5 Treatment temperature: 80 ° C. Treatment time: 2 Minute

Example 7 A test plate was produced in the same manner as in Example 6 except that the concentration of triazinethiol in the chemical conversion treatment bath in Example 6 was changed to 1% by mass. Then, evaluation is performed in the same manner as in Example 1,
The obtained results are shown in Table 1.

Example 8 A test plate was prepared in the same manner as in Example 6 except that the concentration of triazinethiol in the chemical conversion treatment bath in Example 6 was changed to 0.01%. Then, the results obtained by evaluating in the same manner as in Example 1 are shown in Table 1.

Example 9 A test plate was prepared in the same manner as in Example 6 except that the temperature of the chemical conversion treatment bath in Example 6 was changed to 60 ° C. Then, the results obtained by evaluating in the same manner as in Example 1 are shown in Table 1.

Example 10 The chemical conversion treatment bath in Example 6 was changed to 1% by mass K ₂ CO ₃ and 0.1% by mass N- (2-aminoethyl) -3-aminopropyltrimethoxysilane aqueous solution. ,
A test plate was prepared in the same manner as in Example 6. Then, the results obtained by evaluating in the same manner as in Example 1 are shown in Table 1.

Comparative Example 1 20% of the commercially available manganese phosphate treating agent Magdyne SF572 (manufactured by Nippon Paint Co.) was used for the chemical conversion treatment in Example 1.
A test plate was prepared in the same manner as in Example 1 except that an aqueous solution was used and immersion treatment was performed at 50 ° C. for 2 minutes. Then, the evaluation was performed in the same manner as in Example 1, and the obtained results are shown in Table 1.

COMPARATIVE EXAMPLE 2 The chemical conversion treatment in Example 1 was carried out except that a 5% aqueous solution of a commercially available zircon phosphate treating agent Alsurf 440 (manufactured by Nippon Paint Co., Ltd.) was used and dipping treatment was carried out at 50 ° C. for 2 minutes. A test plate was prepared in the same manner as in Example 1. Then, the evaluation was performed in the same manner as in Example 1, and the obtained results are shown in Table 1.

Comparative Example 3 In place of the chemical conversion treatment in Example 1, ion-exchanged water was added to 80
A test plate was prepared in the same manner as in Example 1 except that the immersion treatment was changed to 2 ° C. for 2 minutes. Then, the evaluation was performed in the same manner as in Example 1, and the obtained results are shown in Table 1.

Comparative Example 4 A test plate was prepared in the same manner as in Example 1 except that the chemical conversion treatment agent in Example 1 was changed to a 1 mass% potassium hydroxide aqueous solution. Then, the evaluation was performed in the same manner as in Example 1, and the obtained results are shown in Table 1.

Comparative Example 5 A test plate was prepared in the same manner as in Example 6 except that potassium hydroxide was used instead of potassium carbonate in the chemical conversion treatment bath. Then, evaluation was carried out in the same manner as in Example 1, and the obtained results are shown in Table 1.

[0073]

[Table 1]

From the above results, the magnesium and / or magnesium alloy surface treatment method of the present invention showed excellent corrosion resistance, coating adhesion and conductivity to the magnesium alloy substrate. When a 0.1 mass% potassium carbonate aqueous solution was used as the treatment agent (Example 2), compared with the treatment performance for a magnesium alloy AZ91D test plate manufactured by Thixomolding having a plate thickness of 2 mm,
Die-cast magnesium alloy AZ91 with a plate thickness of 1 mm
Although the processing performance for the D test plate was slightly inferior,
It was revealed that the treatment performance was improved by further adding the triazine thiol compound and the aminosilane compound to the treating agent (Examples 6 to 10).

Example 11 A casing for a personal computer obtained by a thixomolding magnesium alloy test plate (a test plate which is more contaminated than the test plate used in Example 6 and is difficult to be subjected to chemical conversion treatment) is shown below. Degreasing, washing with water, acid etching,
Washing with water, desmutting, washing with water, first chemical conversion treatment, washing with water, second
After performing the chemical conversion treatment, washing with water, and drying, the powder coating process (process example 1) was performed. Washing with water was performed with a tap water shower, and all other steps were treated with a dip method.
Drying was performed at 100 ° C. for 20 minutes with an electric dryer. In addition,
The above-mentioned housing for personal computers used as an object to be treated had a high degree of release agent contamination and was difficult to remove, and it was difficult to impart corrosion resistance and coating film adhesion. (A) Degreasing The same procedure as in Example 1 was performed. (B) Acid etching The same procedure as in Example 1 was performed. (C) Desmutting The same procedure as in Example 1 was carried out. (D) First chemical conversion treatment liquid: 1 mass% potassium carbonate, 100 ppm 1,3
Aqueous solution of 5-triazine-2,4,6-thiol pH: 11.5 Treatment temperature: 80 ° C. Treatment time: 2 minutes (E) Second chemical conversion treatment liquid: 2000 ppm Polyallylamine (manufactured by Nitto Boseki, PAA-) 5, n = 87.7) Aqueous solution treatment temperature: 60 ° C. Treatment time: 2 minutes Using the obtained test plate, unpainted corrosion resistance was measured by the following method.
The electrical resistance of the chemical conversion coating, the corrosion resistance after coating, and the coating adhesion were evaluated and the results are shown in Table 2.

[0076]Unpainted corrosion resistance Salt spray test: 5% saline solution was applied to the test piece continuously at 35 ° C for 8 hours.
Continuation spraying and subsequent corrosion resistance by rating number method
evaluated.Chemical film electrical resistance Evaluation was carried out in the same manner as in Example 1.Corrosion resistance after painting Evaluation was carried out in the same manner as in Example 1.Coating adhesion (1) Powder by the same method as the above-mentioned test method for corrosion resistance after coating
The painted test plate is subjected to a salt spray test for 72 hours, after which
Make 100 grids at 1mm intervals on the removed test plate.
Then, an adhesive tape was attached and peeled off. The remaining cross
Was measured and evaluated. (2) Powder by the same method as the above-mentioned test method for corrosion resistance after coating
Immerse the coated test plate in ion-exchanged water at 50 ° C for 72 hours
To do. After that, add a grid of 1mm intervals to the test plate taken out.
100 pieces were made, and an adhesive tape was attached and peeled off. Remaining
The number of crosses was measured and evaluated.

Examples 12 to 15 Using the chemical conversion treatment aqueous solution (A) and the chemical conversion treatment aqueous solution (B) having the formulations shown in Table 2, under the conditions shown in Table 2, as in Example 11, the surface of the magnesium alloy was used. Processed.
The results are shown in Table 2. In addition, Examples 12 to 14 are not the process example 1 in Example 11, but degreasing, water washing, acid etching, water washing, first chemical conversion treatment, water washing, second chemical conversion treatment,
After washing with water and drying, the powder coating process (process example 2) was performed. In addition, Example 15 was treated in the same manner as in Example 6.

[0078]

[Table 2]

As is clear from the results shown in Table 2, the magnesium alloy treated by the surface treatment method of magnesium and / or magnesium alloy of the present invention (further, the method of treatment with the second chemical conversion treatment liquid) has corrosion resistance, The coating film was excellent in adhesiveness and conductivity. When an aqueous solution of 1 mass% potassium carbonate and 100 ppm 1,3,5-triazine-2,4,6-trithiol was used as a treatment agent (Example 15), a die-cast magnesium alloy AZ91D test plate with a plate thickness of 1 mm was used. The treatment performance for the magnesium alloy test plate manufactured by Thixomolding (the test plate used in Example 6 is more contaminated than the test plate used in Example 6 and the chemical conversion treatment is difficult) is slightly inferior to that of Further, it was revealed that the treatment performance was improved by treating with the chemical conversion treatment aqueous solution (B) containing polyallylamine (Example 11).

[0080]

The surface treatment method of magnesium and / or magnesium alloy of the present invention is applied to magnesium metal and magnesium alloy with corrosion resistance equal to or higher than that of manganese phosphate treatment without using harmful substances such as chromium and manganese. It is possible to impart film adhesion and to achieve compatibility with film electrical resistance. As a result, it is possible to significantly reduce environmental protection and the influence on the human body. Moreover, since existing chromate treatment equipment and manganese-based chemical conversion treatment equipment can be used as they are, there is no need for new equipment investment. Also, in the case of treatment by the immersion method,
It can be suitably used for processing mobile phone housings, automobile parts / parts, and other products having complicated shapes.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Katsuyoshi Yamazoe             4-1, 15 Minami-Shinagawa, Shinagawa-ku, Tokyo Japan             Within Paint Co., Ltd. (72) Inventor Kiyotada Yasuhara             4-1, 15 Minami-Shinagawa, Shinagawa-ku, Tokyo Japan             Within Paint Co., Ltd. F term (reference) 4K026 AA01 BB06 BB08 CA15 CA18                       DA03 DA06 DA13 EA06 EA08

Claims (8)

[Claims] 1. A method for surface treatment of magnesium and / or magnesium alloy, which comprises treating magnesium and / or magnesium alloy with a chemical conversion treatment aqueous solution (A) containing 0.001 to 10 mass% of a carbonate compound. 2. The chemical conversion treatment aqueous solution (A) further contains a coating film adhesion promoter, and the coating film adhesion promoter is
The surface treatment method for magnesium and / or magnesium alloy according to claim 1, wherein the surface treatment method is at least one compound selected from the group consisting of 0.01 to 1% by mass of a triazine thiol compound, a silane coupling agent and a polyallylamine. 3. Further, the magnesium and / or magnesium alloy treated with the chemical conversion treatment aqueous solution (A) is treated with the chemical conversion treatment aqueous solution (B) containing a second coating film adhesion promoter. The coating adhesion promoter of
At least one selected from the group consisting of triazine thiol compounds, silane coupling agents, and polyallylamine
The surface treatment method of magnesium and / or magnesium alloy according to claim 1 or 2. 4. The triazine thiol compound is 1,3
5-triazine-2,4,6-trithiol, 2- (dibutylamino) -4,6-dimercapto-1,3,5-
Triazine and 2- (phenylamino) -4,6-
The surface treatment method for magnesium and / or magnesium alloy according to claim 2 or 3, which is at least one compound selected from the group consisting of dimercapto-1,3,5-triazine. 5. The silane coupling agent is N- (6-aminohexyl) aminopropyltrimethoxysilane, N
-(6-aminohexyl) aminopropyltriethoxysilane, N- (6-aminohexyl) aminopropyltrichlorosilane, N- (2-aminoethyl) -3-aminopropyltriethoxysilane, N- (2-aminoethyl) ) -3-Aminopropyltrimethoxysilane, N-
(2-Aminoethyl) -3-aminopropyltrichlorosilane, 3-aminopropylethoxysilane, and 3
-At least one aminosilane compound selected from the group consisting of -aminopropylmethoxysilane,
3. The surface treatment method for magnesium and / or magnesium alloy according to 3 or 4. 6. The surface treatment of magnesium and / or magnesium alloy according to claim 3, 4 or 5, wherein the coating adhesion promoter is a triazine thiol compound and the second coating adhesion promoter is polyallylamine. Method. 7. Before the surface treatment, degreasing, pickling,
Desmutting treatment is carried out to remove contaminants and irregularities existing on the surface.
Or the surface treatment method for magnesium and / or magnesium alloy according to item 6. 8. A magnesium and / or magnesium alloy alloy product treated by the surface treatment method of magnesium and / or magnesium alloy according to claim 1, 2, 3, 4, 5, 6 or 7.