JP2001192871A - Magnesium member and producing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that, though, for depositing a titania film on the surface of a substrate composed of an Mg alloy, ordinarily, a solution containing a photocatalytic semiconductor is applied on the surface of the substrate, and, next, sintering is executed at 300 to 500 deg.C in the air, by this method, the film has not been firmly deposited on the substrate. SOLUTION: The surface of a substrate composed of Mg or the alloy thereof is coated with an aqueous solution containing amorphous type titanium peroxide or the same and anatase type titanium oxide, drying is executed at <200 deg.C, and next, a corrosion protective film is deposited thereon.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnesium member having a transparent titania film formed on the surface of a substrate made of Mg or an alloy thereof, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, Mg (specific gravity = approximately 1.75) or an alloy containing the same (hereinafter collectively referred to as "Mg alloy") is lightweight and has excellent workability, strength and cosmetic properties. Its applications are wide-ranging, including accessories, medical equipment, building materials, aircraft, automotive parts, and information home appliances. Since this Mg alloy is chemically active and has a problem in corrosion resistance, it has been subjected to surface treatment such as chemical conversion treatment, anodic oxidation, painting, plating and the like. However, even the simplest chemical conversion treatment includes pretreatments such as solvent degreasing, mechanical degreasing, alkali degreasing, and pickling, and in the case of painting, for example, degreasing, washing,
Including basic steps such as chemical treatment (for example, chemical treatment), primer treatment, and finish coating, the surface treatment of the Mg alloy requires many man-hours and may account for 20 to 30% of the product cost. In the case of chemical conversion treatment, the dichromic acid method is usually adopted in consideration of cost and workability, but there is a problem in terms of environmental pollution. On the other hand, the increase in petrochemical products has caused a problem of complex contamination of harmful organic compounds inside and outside the living environment. Attention has been paid to utilizing oxidative decomposition by a photocatalytic semiconductor as a means for solving this. For example, it has been proposed that a photocatalytic semiconductor is supported on the surface of a base constituting an apparatus or a facility, and a harmful organic compound attached thereto is oxidatively decomposed by the photocatalytic semiconductor, and is being put to practical use. Therefore, in order to protect the surface of the Mg alloy substrate, a photocatalytic layer typified by a titania film is formed, and additionally, a function of decomposing organic compounds and inorganic gases by ultraviolet excitation of the titania film is added. Conceivable.

[0003]

However, when a titania film is simply formed on the surface of a substrate made of an Mg alloy, a small amount of Fe, Ni or Cu is contained in the substrate, so that the corrosion resistance is reduced. However, there is a problem that a sufficient anticorrosion effect cannot be obtained and that the adhesion between the titania film and the substrate is reduced. That is, in order to form a titania film on the surface of a substrate made of an Mg alloy, usually, a solution containing a photocatalytic semiconductor (for example, anatase type titanium oxide) is applied to the surface of the substrate, and then the adhesion with the substrate is increased and Although sintering is performed at a temperature of more than 300 ° C. to 500 ° C. or less in the air to enhance photocatalytic activity, the conventional method has a problem that a film cannot be formed firmly on the surface of the substrate.

Accordingly, an object of the present invention is to provide a magnesium member having improved corrosion resistance and excellent adhesion. Another object of the present invention is to provide a manufacturing method capable of obtaining a magnesium member having improved corrosion resistance and excellent adhesion at low cost.

[0005]

In order to achieve the above object, according to a first aspect of the present invention, there is provided a substrate made of Mg or an alloy thereof, an amorphous titania film formed on the surface thereof, and a substrate formed on the surface of the titania film. Having an anticorrosion coating,
The technical means that was adopted. In the first invention, the anticorrosion coating is preferably a hardly decomposable organic polymer. In order to achieve the above object, in the second invention, a substrate made of Mg or an alloy thereof, and an anticorrosion coating mainly composed of amorphous titania and a hardly decomposable organic polymer formed on the surface thereof, The technical means that was adopted. In order to achieve the above object, in the third aspect, an aqueous solution containing amorphous titanium peroxide or an anatase type titanium oxide is applied to a surface of a substrate made of Mg or an alloy thereof at a temperature of less than 200 ° C. The technical means of drying and then forming an anticorrosion coating was employed. In order to achieve the above object, in the fourth aspect, an aqueous solution containing amorphous titanium peroxide or an anatase type titanium oxide is applied to the surface of a substrate made of Mg or an alloy thereof at a temperature of 200 ° C. or more. The technical means of heating and then forming an anticorrosion film was employed. According to the present invention, since an amorphous titania film and an anticorrosion coating or an anticorrosion coating mainly composed of amorphous titania and a hardly decomposable organic polymer are formed on the surface of the Mg base, magnesium having improved corrosion resistance and adhesion is provided. A member is obtained. Further, when the titania film has a photocatalytic function, dirt is decomposed by the oxidative decomposition action of the photocatalyst, and the surface of the magnesium member can be kept clean. In addition, when a decorative film is formed on the surface of these magnesium members, the adhesion between the surface and the decorative film can be improved.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a base according to one embodiment of the present invention. The base shown in FIG. 1 has an Mg substrate 1 and an amorphous titania film 2 formed on the surface thereof. Mg
The substrate 1 is made of, for example, Mg or Mg by die casting.
And an alloy containing various additive elements. As additional elements, Al (improvement of mechanical properties), Mn (improvement of corrosion resistance), Ag (improvement of heat resistance), Zn (improvement of corrosion resistance and strength), Zr (miniaturization of crystal grains), misch metal ( Improvement of mechanical properties), RE (rare earth element, improvement of mechanical properties) and the like. As a practical alloy, Mg-Al-
Zn-Mn (MC1 to MC5), Mg-Zn-Zr (MC6, MC7), Mg-Zn-Zr-RE (MC
8), Mg-Zr-RE-Ag (MC9) and the like. The titania film 2 is coated with an aqueous solution containing amorphous titanium peroxide (or may additionally contain anatase type titanium oxide) or a viscous aqueous solution by a spray method, a dipping method, a spin coating method, or the like. And dried at a temperature of less than 200 ° C. The thickness of the titania film is desirably in the range of 0.1 to 2 μm.
If the thickness of the titania film is less than 0.1 μm, a sufficient anticorrosion effect cannot be obtained, and if it is more than 2 μm, the film is easily peeled. A preferable range of the thickness of the titania film is 0.1 to 1 μm,
A more preferred range is from 0.1 to 0.2 μm. Amorphous titanium peroxide does not crystallize at a temperature of less than 200 ° C., and therefore, a uniform and flat transparent titania film having excellent adhesion to a substrate can be formed due to a strong fixing effect of a peroxo group. However, if the heating temperature is too low, the film formation time will be long, so it is desirable to heat at a temperature of 70 ° C. or higher. Amorphous titanium peroxide is
Since the composition does not include a ceramic-based composition and has good compatibility with metals, it has excellent adhesion and is unlikely to peel off even if the substrate bends or vibrates.

Next, as shown in FIG. 2, the surface of the titania film 2 formed on the substrate 1 is coated with (a) a high molecular organic polymer such as an acrylic, polyester, vinyl chloride or fluorine-based polymer. (B) an inorganic coating containing silica or a compound thereof or a siloxane cross-linked material; and (c) an anticorrosion coating 3 such as plating (Cu-Ni-Cr plating, electroless Ni plating). Thereby, a Mg member having a more advanced anticorrosion function can be obtained. Among the high molecular weight organic polymers of the above (A), a hardly decomposable organic polymer having a weight average molecular weight of several hundred thousand or more is desirable from the viewpoint of corrosion resistance. The coating can be formed by a known method such as a spray method, a dipping method, brush coating or electrostatic coating. The most economical of these methods may be used. Also, an aqueous solution (or viscous aqueous solution) containing amorphous titanium peroxide or anatase titanium oxide is sprayed on the surface of the Mg base,
Coating by dip coating, spin coating, etc., then drying at room temperature, and then heating at a temperature of 200 ° C or higher, the amorphous titanium peroxide is transferred to the anatase titanium oxide. Can be provided. However, if the heating temperature is too high,
Since the crystal structure of titanium oxide changes to a rutile type, 50
It is desirable to heat at a temperature of 0 ° C. or less. These M
The g member can be used, for example, for building hardware, fittings, interior and exterior materials, curtain walls, glasses, watches, accessories, and the like. In the present invention, the titania film of FIG. 1 may be formed of a mixture of amorphous titanium peroxide and a hardly decomposable organic polymer. This titania film has a high corrosion resistance, and is effective in reducing the production cost because the film formation and the resin coating are performed simultaneously.

In the present invention, as shown in FIG. 3, an amorphous titanium peroxide aqueous solution (or a mixed sol or aqueous solution of an amorphous titanium peroxide aqueous solution and an anatase titanium oxide) is sprayed on the surface of the Mg substrate 1. , Dip coating, spin coating, etc.
By heating and drying at a temperature of not less than ° C., a titania film 2 ′ having a photocatalytic function can be formed. Also in this case, since the titanium aqueous solution contains amorphous titanium peroxide, the adhesion and spreadability of the titanium oxide sol solution is improved, so that it is easy to get wet, and it is possible to uniformly and widely form the optical touch functional layer on the surface of the substrate. it can. However, if the heating temperature is too high, the crystal structure of the titanium oxide changes to a rutile type. Therefore, it is desirable to heat at a temperature of 500 ° C. or lower.
In FIGS. 1 to 3, white circles are amorphous titanium oxide, and black circles are anatase titanium oxide. This Mg substrate can be used for, for example, medical and dental instruments, vehicles, aircraft, automobiles, electric appliances, tools, machine tools, and the like in addition to the above. Further, a decorative coating film made of an organic polymer resin or a decorative coating film formed by electrostatic coating may be formed on the surface of the substrate shown in FIGS.

The photocatalytic function is an anatase type titanium oxide
And other photocatalytic semiconductor metals on the substrate surface.
The excitation wavelength (TiO 2)₂In the case of 360-38
0nm or less), active radical species
Generate and purify by redox decomposition of organic compounds and inorganic gases
It has a function. This has an antifouling function
Mg members become possible. TiO as a photocatalytic semiconductor₂
Besides ZnO, SrTiO₃, CdS, CdO, Ca
P, InP, In₂O₃, CaAs, BaTiO₃, K
₂NbO₃, Fe ₂O₃, Ta₂O₅, WO₃, SnO
₂, Bi₂O₃, NiO, Cu₂O, SiC, Si
O₂, MoS₂, MoS₃, InPb, RuO₂, Ce
O₂and so on. Among them, titanium oxide TiO₂(you
Type) is inexpensive, has stable characteristics, and has no effect on the human body.
It is harmful and is the best photocatalyst. In particular, primary grains
TiO with a diameter of 8 to 20 nm₂Preferably contain particles
No.

The amorphous titanium peroxide sol used in the present invention has excellent spreadability even when the substrate is a metal, and is effective for applying the sol liquid widely and uniformly. For example, it can be adjusted as follows. it can. Titanium tetrachloride T
A 50% solution of iCl ₄ (Sumitomo Sitix Co., Ltd.) diluted 70 times with distilled water, and ammonium hydroxide N
25% solution of H ₄ OH (Takasugi Pharmaceutical Co., Ltd.) with distilled water
The mixture diluted 0-fold is mixed at a volume ratio of 7: 1 to perform a neutralization reaction. After the neutralization reaction, the pH is adjusted to 6.5 to 6.8, and after standing for a while, the supernatant is discarded. The remaining Ti (O
H) Add about 4 times the amount of distilled water to the amount of ₄ gel, stir well, and allow to stand. Check with silver nitrate, repeat washing with water until chloride ions in the supernatant are no longer detected, and finally discard the supernatant and leave only the gel. In some cases, dehydration treatment can be performed by centrifugation. This pale blue white Ti (O
H) _{4 In} 3,600 ml, 210 m of 35% hydrogen peroxide solution
l is added twice every 30 minutes and stirred at about 5 ° C. overnight to obtain about 2500 ml of amorphous titanium peroxide sol having a pH of 6.0 to 7.0. Since this titanium sol contains titanium peroxide having a peroxo group, it has a yellow transparent appearance. In addition, in the above steps, if the heat generation is not suppressed, a substance insoluble in water such as metatitanic acid may be precipitated. Therefore, it is preferable that all the steps be performed with the heat generation suppressed.

[0011]

[Experimental example] (Example 1) Mg substrate (MC2B, 100 mm ×
After polishing the surface of 150 mm × 1 mm) with sandpaper, an aqueous solution containing amorphous titanium peroxide and anatase titanium oxide (TK100 manufactured by TAO, concentration 1.7)
(0 wt%) was applied by a dip method (wet application amount 0.7 g / 100 cm ² ) and dried at room temperature. On the surface of the Mg substrate, alkyd resin 3% and saturated ester 2
Polyester resin containing 6% (weight average molecular weight: about 50
10,000) of an aqueous emulsion (trade name: Aqua F emulsion) by a dip method (coating amount 2 in a wet state).
g / 150 cm ² ) and air dried.

(Example 2) Mg substrate (MC2B, 100 mm
After polishing the surface of × 150 mm × 1 mm) with sandpaper, the same aqueous solution containing amorphous titanium peroxide and anatase type titanium oxide as in Example 1 (concentration 0.85 wt.
%) Was applied by a dip method (a coating amount in a wet state: 0.7 g / 100 cm ² ), and then dried at normal temperature. The above Mg
An aqueous emulsion of the same polyester resin as in Example 1 was applied to the surface of the substrate by a dipping method (wet coating amount: 8.6 g / 150 cm ² ) and air-dried.

(Example 3) Mg substrate (MC2B, 100 mm
After polishing the surface of (× 150 mm × 1 mm) with sandpaper, the same amorphous titanium peroxide and anatase type titanium oxide aqueous solution (concentration 1.70 wt%) as in Example 1 was applied by a dip method (wet coating amount 0). 0.7g
/ 100 cm ² ) and then at room temperature with ultraviolet light (0.3 mW / cm
² ) was irradiated for 3 days. An aqueous emulsion of the same polyester resin as in Example 1 was applied to the surface of the Mg substrate by a dip method (application amount in a wet state: 7.5 g / 150).
cm ² ) and air dried.

(Example 4) Mg substrate (MC2B, 100 mm
After polishing the surface of (× 150 mm × 1 mm) with sandpaper, the same aqueous solution (concentration: 0.85 wt) containing amorphous titanium oxide and anatase type titanium oxide as in Example 1 was used.
%) By a dip method (a coating amount in a wet state: 0.7 g / 100 cm ² ), and then, at room temperature, an ultraviolet ray (0.3 m
W / cm ² ) for 3 days. An aqueous emulsion of the same polyester resin as in Example 1 was applied to the surface of the Mg substrate by a dipping method (application amount in wet state: 6.8).
g / 150 cm ² ) and air dried.

(Evaluation) The above four types of Mg substrates were subjected to a salt spray test to evaluate corrosion resistance. Test conditions: Sprayed with 5% saline for 8 hours, left in air for 16 hours after lifting,
Again, 5% saline was sprayed for 8 hours. All of Examples 1 to 4 did not corrode and showed good corrosion resistance, and no peeling of the titania film was observed.

[0016]

According to the present invention, a specific titania film is provided on the surface of a substrate made of an Mg alloy, so that a Mg member having excellent cosmetic properties and high corrosion resistance can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a base according to an embodiment of the present invention.

FIG. 2 is a sectional view of a base according to another embodiment of the present invention.

FIG. 3 is a sectional view of a base according to another embodiment of the present invention.

[Explanation of symbols]

 1 Mg substrate, 2 titania film, 3 anticorrosion coating

Continued on the front page F-term (reference) 4G069 AA03 AA08 BA04A BA04B BA48A CA07 CA10 CD10 DA06 EA07 EB15Y EB18Y EC22X EC22Y ED04 FB23 FC07 4K022 AA02 BA15 BA22 BA33 DA06 DA09 EA01 EA02 EA04 4K062 AA01 BC02 BC08

Claims (5)

[Claims] 1. A magnesium member comprising a substrate made of Mg or an alloy thereof, an amorphous titania film formed on the surface thereof, and an anticorrosion film formed on the surface of the titania film. 2. The magnesium member according to claim 1, wherein the anticorrosion coating is a hardly decomposable organic polymer. 3. A magnesium member comprising: a substrate made of Mg or an alloy thereof; and an anticorrosion coating mainly formed of amorphous titania and a hardly decomposable organic polymer formed on the surface thereof. 4. An amorphous titanium peroxide or an aqueous solution containing the same and anatase titanium oxide is applied to the surface of a substrate made of Mg or an alloy thereof, dried at a temperature lower than 200 ° C., and then an anticorrosion film is formed. A method for producing a magnesium member, comprising: 5. A method for applying an aqueous solution containing amorphous titanium peroxide or an anatase type titanium oxide to a surface of a substrate made of Mg or an alloy thereof, heating the same at a temperature of 200 ° C. or more, and then forming an anticorrosion film A method for producing a magnesium member, comprising: