JP2002030456A - Surface treating agent and surface treating method for magnesium or alloy thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface treating agent for magnesium or the alloy thereof easy in treatment because of its low toxicity and dangerousness and also capable of obtaining sufficient corrosion resistance and adhesive properties of a coating film. SOLUTION: This surface treating agent for magnesium or the alloy thereof contains (a) chlorine ions and/or nitric ions, (b) manganese ions and (c) phosphoric ions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treatment agent useful for imparting optimum corrosion resistance and coating film adhesion to the surface of magnesium or its alloy as a coating base, and a surface treatment method using the surface treatment agent. It is about.

2. Description of the Related Art Magnesium and its alloys are required to have a surface treatment for improving corrosion resistance. The treatment method varies greatly depending on the application. For example, anodic oxidation or the like may be used as a coating undercoat for a part requiring heavy rust prevention such as an automobile. As a general coating undercoating, hexavalent chromic acid is used. The chromating treatment used has been used. In recent years, the use of these hexavalent chromic acids has tended to be restricted from the viewpoint of environmental protection, and there has been an increasing demand for a coating base treatment instead of a chromate treatment. As an alternative to the chromate treatment, a treatment with an aqueous solution comprising phosphoric acid and a phosphate and a hexavalent manganese such as potassium permanganate is performed. However, in these methods, since the reduction reaction proceeds in a weakly acidic, neutral, or weakly alkaline solution in addition to high toxicity of manganese (7), the processing solution is very unstable, and There are problems such as difficulty in handling and management, such as opacity and generation of sludge.

[0002]

The object of the present invention is to provide a surface treating agent for magnesium or its alloy which is easy to handle, for example, has low toxicity and low danger, and provides sufficient corrosion resistance and coating film adhesion. With the goal. The present invention is capable of imparting sufficient corrosion resistance and coating film adhesion to the surface of magnesium or its alloys.
An object of the present invention is to provide a method for treating a coating film base.

SUMMARY OF THE INVENTION The present invention is based on the finding that the above-mentioned problems can be solved efficiently by combining chlorine ions and / or nitrate ions, manganese ions and phosphate ions on the surface of magnesium or its alloy. It was based on. That is, the present invention provides a surface treating agent for magnesium or an alloy thereof, comprising (a) a chloride ion and / or a nitrate ion, (b) a manganese ion and (c) a phosphate ion. The present invention also provides a method for anticorrosion and undercoat treatment of a surface of magnesium or an alloy thereof, which comprises applying the surface treating agent to the surface of magnesium or an alloy thereof.

[0003]

BEST MODE FOR CARRYING OUT THE INVENTION The surface treating agent for magnesium or its alloy according to the present invention contains (a) chloride ion and / or nitrate ion, (b) manganese ion and (c) phosphate ion. Here, examples of the chlorine ion and / or nitrate ion supply source include inorganic and organic compounds capable of supplying chloride ion, nitrate ion, or a mixture thereof in an aqueous solution. In addition, as a manganese ion supply source, in an aqueous solution,
Inorganic and organic compounds that can supply manganese ions. Of these, manganese nitrate, manganese chloride or a mixture thereof, which can simultaneously supply chlorine ions or nitrate ions and manganese ions, is preferred. Examples of the phosphate ion supply source include various compounds capable of supplying phosphate ions in an aqueous solution, particularly preferred are inorganic compounds, various phosphoric acids and salts thereof are preferable, and among them, ammonium hydrogen phosphate is preferable. .

[0004] The surface treating agent of the present invention may be in the form of powder, granules, or liquid.
(a) Chloride ion and / or nitrate ion 0.001-3m
ol / L, preferably 0.01 to 1 mol / L, (b) manganese ion 0.001 to 3 mol / L, preferably 0.01 to 1 mol / L and (c) phosphate ion 0.00
1-3 mol / L, preferably 0.01-1 mol / L
Is preferably contained. In particular, in the present invention, an aqueous solution having the above concentration is preferably used as a surface treatment agent. Further, manganese nitrate, manganese chloride or a mixture thereof is added in an amount of 0.001 to 3 mol / L, preferably 0.1 to 3 mol / L.
01 to 1 mol / L, ammonium hydrogen phosphate is added to 0.1 mol / L.
001 to 3 mol / L, preferably 0.01 to 1 mol
/ L is preferably used, and the pH is adjusted to 2 to 9, preferably 3 to 8, by adding phosphoric acid or aqueous ammonia. It is preferable to adjust the pH to this range, since a good undercoating treatment can be performed and excellent stability can be obtained. It is preferable to add a stabilizer to the surface treatment agent of the present invention in order to prevent manganese from being oxidized and precipitated by oxygen in the atmosphere.

As the stabilizer, an organic carboxylic acid is preferable, and among them, dicarboxylic acids such as oxalic acid and malonic acid, lactic acid, tartaric acid, citric acid, oxy or ketocarboxylic acid are preferable. In addition, ethylenediamine, diethylenetriamine, triethylenetetraamine , Pyridinecarboxylic acid,
Amines such as pyridinedicarboxylic acid and the like, and aminopolycarboxylic acids such as EDTA, iminodiacetic acid, mercaptoethyliminodiacetic acid, trans cyclohexane 1,2 diaminetetraacetic acid and the like are preferable. The amount of the stabilizer to be added is preferably 1/1 to 1 / 10,000, more preferably 1/10 to 1/1000 in terms of molar ratio to manganese in the treatment liquid. Among magnesium and its alloys to be subjected to the surface treatment agent of the present invention, magnesium alloys include metals that form alloys with magnesium, for example, AL and M
n, Zn, Th, Re, Zr, Si, Cu, Ni, F
alloys with e, Y, Ag, and Li. Here, the content of magnesium in the alloy is preferably 80% by mass (hereinafter abbreviated as%) or more, and preferably 80 to 9%.
It is better to be 9.9%.

[0006] The shape of magnesium and its alloy may be any shape such as a die-casting agent, a casting, an injection molding agent and the like. Prior to applying the surface treatment agent of the present invention, any pretreatment can be performed on magnesium and its alloys, but higher by performing the pretreatment specified in Japanese Patent Application No. 8-0518659 or Japanese Patent Application No. 2000-000641. The effect is chosen. Since an alkaline aqueous solution is used in these pretreatment methods, it is preferable to sufficiently wash with water when performing the treatment of the present invention. In the present invention, the surface treating agent of the present invention is applied to magnesium and its alloy surface by any means after or without such pretreatment. Preferably, magnesium or its alloy is immersed in the aqueous surface treating agent of the present invention. Specifically, as a condition of the coating base treatment, the temperature of the treatment liquid is preferably 0 to 90 ° C., more preferably 1 to 90 ° C.
The temperature is preferably from 0 to 60 ° C and the treatment time is preferably from 1 second to 30 minutes, more preferably from 30 seconds to 5 minutes. It is preferable that the processing liquid is stirred by a pump or bubbling, or the processed product is moved. The magnesium or alloy that has been subjected to the undercoating process is sufficiently washed with water, dried, and then coated with, for example, epoxy or acrylic resin.

[0007]

According to the present invention, it is possible to provide a surface treating agent which is excellent in stability, excellent in adhesion of a coating film, and excellent in corrosion resistance without requiring a highly toxic and dangerous chemical. In addition, the surface treatment method using this surface treatment agent is easy in process and does not require equipment such as exhaust, and the surface of the obtained magnesium or its alloy is excellent in adhesion and corrosion resistance of the coating film because the surface of the undercoating treatment is excellent. It is most suitable as a paint base for the housing of portable electronic devices such as notebook computers and mobile phones. Next, the present invention will be described with reference to examples.

[0008]

EXAMPLES Example 1 Manganese nitrate 15 g / L, manganese chloride 10 g / L, ammonium dihydrogen phosphate 12 g / L, EDTA 1 g / L
Is added to an aqueous solution containing
5 to obtain a coating base treatment liquid. 0.1 mol / L for chloride ions and 0.1 mol / L for nitrate ions in the processing solution,
Manganese ion is 0.1 mol / L, phosphate ion is 0.1 mol / L.
1 mol / L. Magnesium die-cast material (AZ91D) that has been previously degreased and activated with a metal cleaning agent PN-36 and a magnesium alloy activator Mg-733 (both manufactured by Dipsol Co., Ltd .; the same applies hereinafter).
Was immersed in the above treatment solution at a bath temperature of 30 ° C. for 1 minute.

Example 2 Manganese nitrate 30 g / L, ammonium dihydrogen phosphate 1
Phosphoric acid was added to an aqueous solution consisting of 2 g / L and 1 g / L of EDTA to adjust the pH to 3.5 to obtain a coating base treatment liquid. In the treatment solution, nitrate ion is 0.2 mol / L, manganese ion is 0.1 mol / L, and phosphate ion is 0.1 mol / L.
L. A magnesium die-cast material (AZ91D) that had been degreased and activated with a metal cleaning agent PN-36 and a magnesium alloy activator Mg-733 in advance was immersed in the above treatment solution at a bath temperature of 30 ° C for 1 minute. Example 3 Manganese chloride 20 g / L, ammonium dihydrogen phosphate 1
Phosphoric acid was added to an aqueous solution consisting of 2 g / L and 1 g / L of EDTA to adjust the pH to 3.5 to obtain a coating base treatment liquid. In the treatment liquid, chloride ion is 0.2 mol / L, manganese ion is 0.1 mol / L, and phosphate ion is 0.1 mol / L.
L. A magnesium die-cast material (AZ91D) that had been degreased and activated with a metal cleaning agent PN-36 and a magnesium alloy activator Mg-733 in advance was immersed in the above treatment solution at a bath temperature of 30 ° C for 1 minute.

Example 4 Manganese nitrate 15 g / L, manganese chloride 10 g / L, diammonium hydrogen phosphate 12 g / L, citric acid 50 mg
/ L of an aqueous solution consisting of
To obtain a coating base treatment liquid. In the treatment liquid, chloride ions are 0.1 mol / L, nitrate ions are 0.1 mol / L, manganese ions are 0.1 mol / L, and phosphate ions are 0.1 mol / L.
Mol / L. Magnesium die-casting material (AZ91D) that has been degreased and activated with metal detergent PN-36 and magnesium alloy activator Mg-733 in advance.
Was immersed in the above treatment solution at a bath temperature of 30 ° C. for 1 minute. Example 5 Manganese nitrate 15 g / L, manganese chloride 10 g / L, diammonium hydrogen phosphate 12 g / L, tartaric acid 40 mg / L
Phosphoric acid was added to the aqueous solution consisting of L to adjust the pH to 3.5, thereby obtaining a coating base treatment liquid. Pre-metal cleaning agent PN
-36, a magnesium die-cast material (AZ91D) that had been degreased and activated with a magnesium alloy activator Mg-733, was immersed in the above treatment solution at a bath temperature of 30 ° C for 1 minute.

Example 6 Manganese nitrate 15 g / L, manganese chloride 10 g / L, diammonium hydrogen phosphate 12 g / L, tartaric acid 40 mg / L
Phosphoric acid was added to the aqueous solution composed of L to adjust the pH to 7.0 to obtain a coating base treatment liquid. In the treatment liquid, chlorine ions are 0.1 mol / L, nitrate ions are 0.1 mol / L, manganese ions are 0.1 mol / L, and phosphate ions are 0.1 mol / L. Magnesium die-casting material (AZ91D) that has been degreased and activated with metal detergent PN-36 and magnesium alloy activator Mg-733 in advance.
Was immersed in the above treatment solution at a bath temperature of 30 ° C. for 1 minute. Example 7 In an aqueous solution composed of 15 g / L of manganese nitrate, 10 g / L of manganese chloride, and 12 g / L of ammonium dihydrogen phosphate,
Phosphoric acid was added to adjust the pH to 3.5 to obtain a coating base treatment liquid. 0.1 mol / L of chloride ion in the processing solution,
Nitrate ion is 0.1 mol / L, manganese ion is 0.1 mol / L
Mol / L, phosphate ion is 0.1 mol / L. Metal cleaning agent PN-36, activator for magnesium alloy M
The magnesium die-cast material (AZ91D), which had been degreased and activated by g-733, was immersed in the above treatment solution at a bath temperature of 30 ° C. for 1 minute.

Comparative Example 1 Phosphoric acid was added to an aqueous solution composed of 20 g / L of potassium permanganate and 100 g / L of ammonium dihydrogen phosphate.
H was adjusted to 3.5 to give a coating base treatment liquid. The manganese ion and the phosphate ion in the treatment liquid are 0.1 mol / L and 0.8 mol / L, respectively. Metal cleaning agent PN-36 in advance,
Degreasing with magnesium alloy activator Mg-733,
Activated magnesium die cast material (AZ9
1D) was immersed in the above treatment solution at a bath temperature of 30 ° C. for 1 minute. Comparative Example 2 Manganese sulfate 30 g / L, ammonium dihydrogen phosphate 1
Phosphoric acid was added to an aqueous solution consisting of 2 g / L and 1 g / L of EDTA to adjust the pH to 3.5 to obtain a coating base treatment liquid. The manganese ion and the phosphate ion in the treatment liquid are 0.2 mol / L and 0.1 mol / L, respectively. Cleaning agent PN-36 for metal and activator Mg-733 for magnesium alloy in advance
The magnesium die-cast material (AZ91D), which had been degreased and activated by the above, was immersed in the above-mentioned treatment solution for 1 minute at a bath temperature of 30 ° C.

Comparative Example 3 An aqueous solution consisting of 30 g / L of ammonium sulfate, 120 g / L of ammonium dihydrogen phosphate, and 15 ml / L of 30% aqueous ammonia was prepared and used as a coating base treatment liquid. Cleaning agent for metal PN-36, activator for magnesium alloy Mg
A magnesium die-cast material (AZ91D), which has been degreased and activated by -733, is immersed in the above treatment solution at a bath temperature of 25 ° C. for 2 minutes, and then immersed in a 120 g / L aqueous sodium hydroxide solution at 80 ° C. for 1 minute. Sum processing was performed.

The properties of the surface-treated magnesium die-cast material (AZ91D) were evaluated as follows. Evaluation Test 1 Corrosion Resistance Test A salt water spray test (24 hours) specified in JISZ2317 was performed on each magnesium die-cast material that had been subjected to the pretreatments of Examples 1 to 5 and Comparative Examples 1 to 3, and was subjected to salt water spray according to the following criteria. The corrosion resistance was evaluated. Salt spray test evaluation ◎: The total corrosion area is 0 to 0.5% or less of the area of the test piece. ：: The total corrosion area is 0.5 to 1% or less of the area of the test piece. Δ: The total corrosion area is 1 to 5% or less of the area of the test piece. ×: The total corrosion area is 5% or more of the area of the test piece.

Evaluation Test 2 Paint Adhesion Test Each of the magnesium die-cast materials which had been subjected to the pretreatment of Examples 1 to 5 and Comparative Examples 1 to 3 was coated (undercoat: epoxy / polyester resin system, 160 ° C., 20 minutes) Baking, overcoat: acrylic resin, baking at 160 ° C for 20 minutes) J
Adhesion by crosscut tape method specified in ISK5400 The adhesion was confirmed according to the following criteria. Crosscut tape method test evaluation A : Each cut is thin and smooth, and there is no peeling at the intersection of the cut and each square. ：: There was slight peeling at the intersection of cuts, and there was no peeling at each square, and the area of the defect was 5% of the total square.
Within. Δ: Both sides of the cut were peeled off from the intersection, and the area of the defective portion was 5 to 15% of the entire square. ×: The width of the peeling due to the cut is wide, and the area of the defective portion is 15% or more of the entire square.

Evaluation Test 3 Treatment Solution Stability Test A 10-fold concentrated solution of the base treatment solution used in Examples 1 to 5 and Comparative Examples 1 to 3 was prepared, placed in a beaker, and left without covering for 20 days. Then, the appearance was observed. Further, the same solution was diluted 10-fold, and evaluation tests 1 and 2 were performed to confirm the presence or absence of a change in performance. ：: No change is observed in the appearance of the treatment liquid, the corrosion resistance, and the adhesion test results. Δ: Discoloration or precipitation was observed in the treatment liquid, but no change was observed in the corrosion resistance and adhesion test results. ×: No change was observed in the appearance of the treatment liquid, but the corrosion resistance and
Deterioration was observed in any of the results of the adhesion test. Alternatively, discoloration or precipitation was observed in the treatment liquid, and deterioration was observed in any of the corrosion resistance and adhesion test results.

The results are summarized in Table 1.

[Table 1] Table-1 Mn / carboxylic acid Corrosion resistance Coating film adhesion Treatment liquid stability Example 1 1 / 0.03 ◎ ◎ ○ Example 2 1 / 0.03 ◎ ○ ○ Example 3 1 / 0.03 ○ ◎ Example 4 1 / 0.002 ◎ ◎ ○ Example 5 1 / 0.003 ◎ ◎ ○ Example 6 1 / 0.003 ◎ ○ ○ Example 7-◎ ◎ △ Comparative example 1-△ ○ × Comparative example 2 1 / 0.02 × △ ○ Comparative example 3-× △ ○

Claims (5)

[Claims] (1) chlorine ion and / or nitrate ion,
A surface treating agent for magnesium or an alloy thereof containing (b) manganese ions and (c) phosphate ions. 2. Manganese chloride and / or manganese nitrate,
And a phosphoric acid compound. A surface treating agent for magnesium or an alloy thereof. 3. The surface treatment agent according to claim 1, wherein the surface treatment agent is in the form of an aqueous solution, and has a pH of 2 to 9. 4. The surface treating agent according to claim 1, further comprising an organic carboxylic acid or a salt thereof. 5. A method for anti-corrosion and undercoat treatment of magnesium or its alloy surface, comprising applying the surface treating agent according to claim 1 to the surface of magnesium or its alloy.