JP2002322567A - Surface treatment method for casting and cast article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-cost surface treatment method for a casting, which causes no adverse effect on the human body, and a cast article which has excellent corrosion resistance. SOLUTION: A casting is subjected to the surface treatment of performing heating and pressurizing treatment in liquid at suitable temperature, under suitable pressure, for suitable time, so that a release agent and stain can be removed without performing pretreatment. Thus, a surface treated film containing a reaction product of metal and surface treatment solution under heating and pressurizing can uniformly be formed on the surface of the casing of a magnesium alloy and an aluminum alloy or the like to obtain the cast article having excellent corrosion resistance.

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 capable of performing a low-cost surface treatment such as cleaning and sealing of the surface of a casting to obtain a uniform surface, and a cast article having good corrosion resistance.

[0002]

2. Description of the Related Art Castings have innumerable pores on their surfaces and are easily corroded when exposed to atmospheric moisture or water. For this reason, castings are often used after being coated with a thick film. However, corrosion occurs before application such as high temperature and high humidity. In addition, the mold release agent used during the molding adheres to the surface of the casting and covers the hot water lines and cracks, so that the adhesion of the anticorrosion coating, which is the anticorrosion layer, is significantly impaired, and the corrosion is quickly prevented. This is a factor that occurs.

[0003] As a solution to these problems, conventionally, for example, (a) a pretreatment step of cleaning the surface of the casting by alkali degreasing, pickling, or blast polishing;
After a base treatment step of performing a chemical conversion treatment with chromate (chromate) or the like, (c) a coating step of applying an anticorrosive paint was performed. However, in the case of (a) blast polishing in the pretreatment step, in the case of a complicated molded article, it is difficult to clean deep recesses and the like, and treatment such as alkali degreasing and pickling causes corrosion due to contact with remaining water. easy. (B) In addition, the chromate treatment in the undercoat treatment process is urgently required to be reduced in terms of the effect on the human body, and there is still a problem in application, and there is no other effective chemical treatment method. That is the current situation.

In recent years, molded articles made of metal material castings such as lightweight alloys represented by magnesium alloys have been used in various fields as environmentally friendly materials, but the molded articles have particularly complicated shapes. Many. For this reason, conventional surface treatment methods such as pre-treatment and ground treatment do not provide sufficient effects on the adhesion and corrosion resistance of the anti-corrosion film as the anti-corrosion layer. Therefore, the appearance of a cast article having a surface treatment method suitable for these castings and an anticorrosive film having excellent corrosion resistance has been desired.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to meet the above-mentioned demands, and the inventions of claims 1 and 2 include a pretreatment step such as surface cleaning of a casting,
An object of the present invention is to provide a method for treating a surface of a casting, which is a low-cost alternative to the undercoating process and has no fear of affecting the human body.

It is an object of the present invention to provide a cast article having a surface treatment film having good adhesion to an anticorrosion layer and having corrosion resistance by itself.

[0007]

In order to solve the above-mentioned problems, the invention according to claim 1 of the present invention comprises subjecting a casting to a surface treatment by heating and pressurizing the casting in a liquid. It is characterized by.

According to the present invention, the release agent and the dirt attached to the surface of the casting, including those present in the inside of the hot water lines, pores, cracks, recesses, etc., are subjected to a proper temperature and pressure in a liquid. Appropriate time, by heating and pressurizing treatment, dissolves in the liquid or softens and is removed, and in the meantime, a surface treatment film containing a reaction product of the metal and the liquid of the casting is formed, and the surface of the casting is formed. It is formed so as to cover uniformly.

According to a second aspect of the present invention, in the surface treatment method for a casting according to the first aspect, the liquid comprises one or more of an aqueous solution of a phosphate, a silicate, a manganese compound or a zinc compound. It is a mixed liquid or water.

[0010] Since these liquids have a strong bonding force with the metal of the casting, they have good corrosion resistance and are easy to form a uniform surface treatment film.

The invention according to claim 3 is characterized in that magnesium, magnesium alloy, aluminum, aluminum alloy, iron
_, Iron alloy, copper, copper alloy, zinc, zinc alloy, tin or tin alloy, the surface of a casting formed by casting any one, a cast article having a surface-treated film, The surface treatment film contains a reaction product of the metal forming the casting and a surface treatment solution under heating and pressure, and the surface treatment solution is a phosphate, silicate, manganese compound, or an aqueous solution of a zinc compound. It is characterized by being a liquid or a water in which one or two or more kinds are mixed.

According to the present invention, when the surface treatment film containing the reaction product of the metal forming the casting and the surface treatment solution under heating and pressurization by itself has corrosion resistance and the anticorrosion film is provided. , Good adhesion to it.

According to a fourth aspect of the present invention, in the cast article according to the third aspect, an anticorrosion paint formed by dissolving a resin with an organic solvent or water is applied on the surface-treated film and cured to form an anticorrosion film. It is characterized by becoming.

According to the present invention, since the adhesion between the surface treatment film and the anticorrosion film is good, an anticorrosion composite film having extremely excellent corrosion resistance is formed.

The invention according to claim 5 is the invention according to claim 3 or 4.
The article of claim, wherein said casting comprises a magnesium alloy or an aluminum alloy.

According to the present invention, since the casting is made of a magnesium alloy or an aluminum alloy, a light-weight surface treatment film having excellent corrosion resistance and a corrosion-resistant composite film are formed.

[0017]

Embodiments of the present invention will be described with reference to the drawings. Drawing 1 is a mimetic diagram for explaining the surface treatment method of the cast and the cast article of the present invention. In FIG. 1, reference numeral 20 denotes a casting on which a surface treatment is performed and an anticorrosion film is applied, and FIG. 1A shows a casting 20 before the surface treatment is performed.
FIG. In FIG. 1B, reference numeral 1 denotes a cast article as an example of the embodiment of the present invention. The cast article 1 is obtained by subjecting a casting 20 to a surface treatment to form a surface treatment film 30. In FIG. 1C, reference numeral 10 denotes a cast article according to another embodiment, and the cast article 10 is formed by applying an anticorrosion paint on the surface treatment film 30 of the cast article 1 to form an anticorrosion coating 40. Is formed.

First, a method for surface treatment of a casting will be described. On the surface of the casting 20, in addition to the irregularities formed by the shape of the target article, small projections 21 such as burrs and hot water lines are formed.
And irregularities such as small recesses 22 such as pores and cracks are present. Also, although not shown, the residue of the release agent and the like may be present on the surface of the casting 20, the shadows of the projections 21, and the inside of the recesses 22. Is attached.

In the surface treatment method for a casting according to the present invention, the casting 20 is immersed in a liquid in a container such as an autoclave and subjected to heat and pressure treatment to dissolve the deposits such as the above-mentioned release agent residue. Or, it is softened and removed not only from the surface of the casting 20 but also from the shadow of the projection 21 and the inside of the recess 22. In addition, by appropriately selecting the liquid, a surface treatment film is formed between the metal of the casting and the liquid, thereby uniformly covering the surface of the casting. Conventionally, the surface treatment, which has been performed in two steps of a pretreatment step and a base treatment step (chemical conversion treatment step), is reduced to one step, thereby reducing costs and eliminating concerns about adverse effects on the human body.

The liquid used for the surface treatment may be water, but it is more effective if it is an aqueous solution of a solute having a strong bonding force with the metal of the casting. As the solute, one or a mixture of two or more of an aqueous solution of a phosphate, a silicate, a manganese compound or a zinc compound is preferable.

Phosphates are compounds such as alkali metal, ammonium and amine salts of metaphosphoric acid, pyrophosphoric acid, phosphoric acid, triphosphoric acid and tetraphosphoric acid, and silicates are metasilicic acid, orthosilicic acid, disilicic acid, Compounds such as alkali metal salts, ammonium salts, and amine salts of tetrasilicic acid. The manganese compound is a compound such as a salt with phosphoric acid, nitric acid, sulfuric acid and carbonic acid, and the zinc compound is a compound such as a salt with phosphoric acid, nitric acid, sulfuric acid and carbonic acid.

The concentration of each aqueous solution is 20%
The content is preferably not more than 10%, more preferably not more than 10% (% indicates% by weight, and the same applies hereinafter). 20%
However, the effect is saturated and there is no economic merit. Generally, if the concentration is too large, the residue of the surface treatment liquid adheres to the surface of the surface-treated casting, and the adhesion to the anticorrosion layer described later. And the stability may be impaired.

The heating and pressurizing conditions cannot be uniquely specified because they are related to the freezing point and boiling point of the surface treatment solution, but generally, the heating temperature is 40 ° C. to 250 ° C., preferably 100 ° C. to 180 ° C.
The pressure is 0.5 to 20 atm, preferably 1 to 10 atm, and the treatment time is 1 to 60 minutes, preferably 5 to 30 minutes, but may vary depending on the type of casting. If the treatment temperature is lower, the desired surface cannot be obtained due to a decrease in the reaction rate. Heating may be performed at 250 ° C. or higher, but depending on the type of the surface treatment liquid, deterioration progress is recognized, which is not economically preferable. Although the pressure may be set to 20 atm or more, the effect of the high-pressure treatment is saturated, and the same tendency is observed when the treatment time is set to 120 minutes or more. Some metal materials may be accompanied by a dimensional change. In addition, the surface treatment liquid is not limited to the above, and can be appropriately selected in consideration of the bonding force with the cast metal, the handleability, and the like. In addition, heating
The pressurizing means is not limited to an autoclave as long as it is suitable for the above-mentioned heating and pressurizing. Also, the metals of the castings subject to the present invention include iron, copper, aluminum, magnesium, zinc, tin, and alloys based on each of the foregoing metals.

The cast article 1 shown in FIG. 1 (b) obtained as described above has the surface of the casting 20 clean and clean, and combines the metal of the casting 20 with the surface treatment liquid. Since the force is strong, the surface treatment film 30 is formed not only on the surface of the casting 20 but also on the inside of the projections 21 and the depressions 22, and the surface becomes uniform. Moreover, the surface treatment film 30 has no adverse effect on the human body, has corrosion resistance by itself, and has good adhesion to the anticorrosion film described later.

Next, FIG.
A coating method for forming the anticorrosion film shown in FIG.
As the anticorrosion paint, one or more paints in which a resin is dissolved in an organic solvent or water are used. Examples of the resin material include epoxy, urethane, phenol, polyolefin, silicone, alkyd, acrylic, fluorine, melamine-based resins, and the rust preventive composition described in JP-A-2001-59194 by the inventor.

As the organic solvent, any organic solvent may be used as long as it can form a coating film on the surface of the casting by application of a curing agent at room temperature, heat treatment, or the like. Is preferably added.

The coating method includes, but is not particularly limited to, dipping, spraying, brushing, electrostatic coating, electrodeposition coating, and the like. The anticorrosion layer formed on the surface of the casting is cured by air drying or heat treatment, electron beam, UV, addition of a curing agent, and the like. Heat treatment time, paint concentration, and the like in these coating methods can be appropriately selected.

However, the concentration of the resin in the above-mentioned paint for forming the anticorrosion film is 0.1 or more, preferably 1 to 50%. If the concentration is less than 0.1%, the formed anticorrosive layer is thin,
A uniform anticorrosion film cannot be obtained. If the concentration exceeds 50%, the surface layer may become sticky in some cases.

FIG. 1 (b) By applying the anticorrosion paint on the cast article 1 as described above, the anticorrosion film 40 as shown in FIG. 1 (c) is formed, and the cast article 10 is obtained.
In the conventional method, the casting has a release agent attached to the surface,
Due to surface pores and the like unavoidable from the processing itself, even if these anticorrosion films were formed, adhesion with various anticorrosion films could not be obtained, but a uniform and clean surface treatment film was obtained by the aforementioned surface treatment, Since the adhesiveness with the anticorrosion film is excellent, an anticorrosion composite film 50 comprising the surface treatment film 30 and the anticorrosion film 40 having extremely excellent corrosion resistance is formed.

[0030]

The present invention will be described in more detail with reference to the following examples. The test substrate for evaluation used in the examples was a magnesium alloy ASTM standard product AZ91D (Al: 8.5 to 9.5).
%, Zn: 0.45 to 0.9%, Mn: 0.17% or more, balance Mg), and aluminum alloy JIS standard ADC12 (Cu: 1.5 to 3.5
%, Si: 9.6 to 12.0%, Mg: 0.3% or less, Zn: 1.0% or less, N
i: 0.5% or less, Fe: 1.3% or less, Mn: 0.3% or less, Ni: 0.5
%, Si: 0.3% or less, with the balance Al) not having been pretreated with an acid, alkali, organic solvent or the like.

All the heating and pressurizing treatments were performed using an autoclave, and the test piece was immersed in one or more kinds of aqueous solutions of a phosphate, silicate, manganese compound, or zinc compound or in water, and heated and pressed. . The formation of the anticorrosion composite film was performed by immersing all of the test pieces that had been subjected to the above surface treatment in an anticorrosion paint in which a resin was dissolved in an organic solvent or water at room temperature for 3 seconds. The test piece subjected to the immersion treatment was left at room temperature or heat-treated to obtain a durability test piece of the anticorrosion film. JIS Z 2371 “Salt spray test method”
The time during which white rust occurs on the surface of the test piece was visually measured.

In the examples, the following materials were used. Potassium pyrophosphate was used as the phosphate. Sodium metasilicate and potassium orthosilicate were used as silicates. Manganese dihydrogen phosphate was used as the manganese compound. Zinc nitrate was used as a zinc compound. Organopolysiloxane resin ES-1002T (Shin-Etsu Chemical Co., Ltd., trade name) as a resin (paint) used for forming an anticorrosion film, silane coupling agent X-12-817H as a curing agent (Shin-Etsu Chemical Co., Ltd.) Product name), acrylic resin U-double C-3600
(Nippon Shokubai Co., Ltd., trade name) Methyl ethyl ketone (hereinafter referred to as MEK) was used for dissolution and dispersion of the above materials. Bisphenol A type epoxy resin Epiletz 3520WY55 (Japan Epoxy Resin Co., Ltd., trade name) as a resin, polyamideamine type curing agent EpiCure 8536MY60 (Japan Epoxy Resin Co., Ltd., trade name) as a curing agent, silane-modified epoxy resin ADEKA RESIN EM-0477
(Asahi Denka Kogyo Co., Ltd., trade name), and water was used for dissolution and dispersion of the above materials. The preparation and evaluation of the test pieces are as described below.

Examples 1 to 16 Magnesium alloy ASTM standard product AZ91D (3 × 25 × 50) was used with an aqueous solution of potassium pyrophosphate, sodium metasilicate, potassium orthosilicate, manganese dihydrogen phosphate, or zinc nitrate or water, respectively. , Using an autoclave,
Heat and pressurize, wash with water and dry with warm air.Evaluate the durability of the obtained test specimens according to JIS Z 2371 "Salt Spray Test Method" and visually observe the time until white rust occurs. Was measured. The evaluation was classified into five stages according to the criteria shown in Table 1. Those with less than 24 hours corresponding to "x" are those that may cause a problem practically, and those with 24 hours or more are considered to be at least practically no problem, and the time until the occurrence of white rust is considered. The longer is the more durable.

[0034]

[Table 1]

Table 2 shows the surface treatment liquids (treating agents and concentrations), surface treatment conditions (heating and pressure treatment conditions) of Examples 1 to 16, and the results of the determination based on the criteria shown in Table 1.

[0036]

[Table 2]

In Table 2, "Temperature / Pressure / Time" in the column of heat treatment conditions indicates the heating temperature and pressure of the surface treatment (heat and pressure treatment) and the time of heat and pressure. The treating agent is water or phosphate, silicate,
An aqueous solution of a manganese compound and a zinc compound is shown (the same applies hereinafter).

Comparative Examples 1 to 16 Magnesium alloy ASTM standard product AZ91D (3 × 25 × 50) was subjected to surface treatment in an autoclave under the conditions of a surface treatment solution shown in Table 3 and heat and pressure treatments. Table 3 also shows the results of the determination. Examples 1 to 16 all had a time to white rust generation (hereinafter referred to as “durable time”) of 24 hours or more, and there was no practical problem, whereas Comparative Examples 1 to 16 all had a durable time of 24 hours. And there is a practical problem. It is considered that the reason is that in the case of the comparative example, one of the heating temperature, the pressure, and the heating and pressurizing time is insufficient. As for the surface treatment liquid, the one treated in an aqueous solution of sodium metasilicate, potassium orthosilicate, potassium pyrophosphate and manganese dihydrogen phosphate has a longer durability time than the one treated in an aqueous solution of water or zinc nitrate. Is long.

[0039]

[Table 3]

Examples 17 to 32 Aluminum alloy JIS standard ADC12 (3 × 25 × 50) was subjected to a surface treatment in an autoclave under the conditions of a surface treatment solution shown in Table 4 and heat and pressure treatment. Table 4 also shows the results of the determination.

[0041]

[Table 4]

Comparative Examples 17 to 32 Aluminum alloy JIS standard ADC12 (3 × 25 × 50) was subjected to surface treatment in an autoclave under the conditions of a surface treatment solution shown in Table 5 and heat and pressure treatments. Table 5 also shows the determination results. Example 1
Nos. 7 to 32 all have a durability time of 24 hours or more, which is within the range of practical use.
All 32 have a durable time of less than 24 hours, and thus have a practical problem. The reason is considered to be that any one of the heating temperature, the pressure, and the heating and pressurizing time is insufficient. In the surface treatment liquid of the embodiment, the difference from the case of the magnesium alloy is that the treatment in an aqueous zinc nitrate solution has the longest durability time, and water, sodium metasilicate, potassium orthosilicate, potassium pyrophosphate, and manganese dihydrogen phosphate are used. Those subjected to surface treatment in an aqueous solution have a shorter durability time.

[0043]

[Table 5]

Examples 33 to 64 Magnesium alloy ASTM standard product AZ91D (3 × 25 × 50) was prepared as shown in Table 6.
After the surface treatment was performed in an autoclave under the conditions of a surface treatment solution and heating and pressure treatment shown in (1), an anticorrosion paint was applied to form an anticorrosion film. The results of the determination are also shown in Tables 6 to 9. Naturally, the durability time is longer than that of the examples 1 to 16 before the anticorrosion film is provided.

[0045]

[Table 6]

[0046]

[Table 7]

[0047]

[Table 8]

[0048]

[Table 9]

Comparative Examples 33 to 36 Table 1 shows magnesium alloy ASTM standard product AZ91D (3 × 25 × 50).
As shown in Fig. 0, the surface was treated in an autoclave under the conditions of a surface treatment solution and heat and pressure treatment, and then an anticorrosion paint was applied to form an anticorrosion film. Table 10 also shows the determination results. The reason why the durable time is less than 24 hours even when the anticorrosion coating is applied is considered to be due to insufficient one of the heating temperature, the pressure, and the heating / pressing time of the surface treatment.

[0050]

[Table 10]

Example 65-80 Aluminum alloy JIS standard ADC12 (3 × 25 × 50)
And, after surface treatment in an autoclave under the conditions of a surface treatment solution and heating and pressure treatment shown in Table 12, an anticorrosion paint was applied to form an anticorrosion film. Table 11 shows the results of the determination.
And Table 12. Naturally, the durability time is longer than that of the examples 17 to 32 before the anticorrosion film is provided.

[0052]

[Table 11]

[0053]

[Table 12]

Comparative Examples 37 to 40 Aluminum alloy JIS standard ADC12 (3 × 25 × 50)
After the surface treatment was performed in an autoclave under the conditions of a surface treatment solution and heating and pressure treatment shown in (1), an anticorrosion paint was applied to form an anticorrosion film. Table 13 also shows the determination results. The reason why the durable time is less than 24 hours even when the anticorrosion film is applied is considered to be due to insufficient heating temperature, pressure or heating and pressurizing time of the surface treatment.

[0055]

[Table 13]

[0056]

As is apparent from the above description, according to the first aspect of the present invention, the release agent adhered to the surface of the casting by heating and pressurizing the casting in a liquid. Stain is removed by dissolving or softening in liquid, including those present in the interior of hot water lines, pores, cracks, recesses, etc., and includes the reaction product between the metal of the casting and the liquid. The surface treatment film is formed so as to uniformly cover the surface of the casting, does not require a pretreatment step, is low in cost, and does not need to worry about the influence on the human body.

According to the second aspect of the present invention, in addition to the effects of the first aspect, the aqueous solution or water of the phosphate, silicate, manganese compound or zinc compound is capable of binding to the metal of the casting. , It is easy to form a more uniform surface treatment film with good corrosion resistance.

According to the third aspect of the present invention, a metal such as magnesium, magnesium alloy, aluminum, aluminum alloy, iron _, iron alloy, copper, copper alloy, zinc, zinc alloy, tin or tin alloy which forms a casting is formed. And an aqueous solution of a phosphate, silicate, manganese compound, or zinc compound
When a surface treatment film containing a reaction product under heating and pressurization with a surface treatment solution such as a liquid or a mixture of two or more types of water under heat and pressure has corrosion resistance by itself and a corrosion protection film is provided. , Good adhesion to it.

According to the fourth aspect of the present invention, in addition to the effects of the third aspect of the present invention, a surface treatment film and an anticorrosion paint obtained by dissolving a resin in an organic solvent or water are applied and cured. Since the adhesion to the film is good, an anticorrosion composite film having extremely excellent corrosion resistance is formed.

According to the invention set forth in claim 5, in addition to the effects of the invention set forth in claim 3 or 4, since the casting is made of a magnesium alloy or an aluminum alloy, a lightweight and excellent surface treatment film and corrosion prevention are provided. Since a composite film is formed, it is suitable for molded articles having a lightweight and complicated shape.

[Brief description of the drawings]

FIG. 1 is a schematic view for explaining a surface treatment method of a casting and a cast article according to the present invention.

[Description of Signs] 1 Casting article 10 Casting article 20 Casting 21 Convex part 22 Concave part 30 Surface treatment film 40 Corrosion protection film 50 Corrosion protection composite film

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B32B 15/08 B32B 15/08 A 15/20 15/20 C23C 22/12 C23C 22/12 22/18 22 / 18 22/73 22/73 Z 26/00 26/00 K 28/00 28/00 Z F term (reference) 4D075 BB73X BB75X BB76X CA33 DB08 EC02 4F100 AA03B AA04B AB02A AB08A AB09A AB10A AB17A AB18A AB21A AB31A AK51 AK53 AT00BA02 BA03 BA07 BA10A BA10B BA10C CA14C CC01C EJ17 EJ42 EJ68 GB90 4K026 AA02 AA06 AA07 AA09 AA10 AA21 BA03 BA04 BA05 BB08 CA16 CA23 CA27 CA32 DA03 DA13 DA14 EB08 4K044 AA02 AA06 AB10 BA17 BA21 BB03

Claims (5)

[Claims] 1. A method for treating the surface of a casting, wherein the surface of the casting is treated by heating and pressurizing the casting in a liquid. 2. The method according to claim 1, wherein the liquid is a liquid obtained by mixing one or more of aqueous solutions of phosphates, silicates, manganese compounds or zinc compounds, or water. A surface treatment method for a casting, characterized in that: 3. The surface of a casting formed by casting any one of magnesium, magnesium alloy, aluminum, aluminum alloy, iron _, iron alloy, copper, copper alloy, zinc, zinc alloy, tin or tin alloy. A cast article having a surface treatment film formed thereon, wherein the surface treatment film contains a reaction product of a metal forming the casting and a surface treatment solution under heat and pressure, and the surface treatment solution is A cast article, characterized in that it is a liquid or a mixture of one or more of aqueous solutions of phosphates, silicates, manganese compounds or zinc compounds. 4. The cast article according to claim 3, wherein an anticorrosive paint formed by dissolving a resin with an organic solvent or water is applied and cured on the surface treatment film to form an anticorrosive film. A featured cast article. 5. The cast article according to claim 3, wherein the cast is made of a magnesium alloy or an aluminum alloy.