JPH0874026A - Method for surface-reforming metallic material - Google Patents

Abstract

PURPOSE: To form a dense Cr oxide-contg. coating layer excellent in adhesion by forming a film of specified composition on the surface of a metallic material and then heat-treating the film in a minute oxygen activity atmospher. CONSTITUTION: A film contg. >=25wt.% of >=1 kind among Cr hydroxide and the hydrous compds. and contg. >=0.1wt.% silane coupling agent is formed on the surface of a metallic material. The film is heat-treated in the reduced- pressure atmosphere of 10<-8> - -10<0> Torr or in the minute oxygen activity atmosphere as the oxygen activity corresponding to the former atmosphere to form a Cr oxide-contg. coating layer. When a steel material contg. >=0.1wt.% of at least one kind of element selected from the group consisting of groups IVa, Va and VIa elements is used as the metallic material, a dense coating layer contg. the carbides of the elements is formed. Consequently, a surface- coated metallic material highly resistant to the highly corrosive atmosphere contg. halogenous gases is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for modifying the surface of a metal material, and particularly to halogen gases such as hydrogen chloride gas, chlorine and hydrogen fluoride gas, which are highly corrosive and are used in semiconductor manufacturing equipment. The present invention also relates to a surface modification method for forming a coating showing excellent corrosion resistance on the surface of a metal material.

[0002]

2. Description of the Related Art In the recent semiconductor field, submicron accuracy is required for wiring intervals as the integration of devices becomes higher. Impurity fine particles and bacteria adhere to such devices. Even just doing this will cause a short circuit and cause product failure. Therefore, the gases and pure water used in the manufacture of semiconductors are required to have ultra-high purity,
In handling the gas, it is necessary not only to make the gas highly purified, but also to reduce the release of impure gas such as water and dust from the piping and the wall of the reaction chamber as much as possible.

Therefore, SUS316L is used as a gas pipe for semiconductor manufacturing equipment from the viewpoint of weldability and general corrosion resistance.
Austenitic stainless steels such as
The surface is smoothed to reduce the area of attachment / adsorption of impure gas and dust, and electrolytic polishing treatment is performed to suppress adsorption / desorption of impurity gas. Those in which an amorphous oxide film is formed by heating inside have been developed (Japanese Patent Laid-Open Nos. 64-87760 and 63-161145).

However, the stainless steel material which has been subjected to the surface treatment as described above exhibits excellent performance in a gas atmosphere having no corrosiveness such as oxygen and nitrogen, but is
When exposed to a highly corrosive halogen-based gas atmosphere such as hydrogen fluoride, the progress of corrosion is unavoidable, and the corrosion products become gas adsorption / desorption sites, making it difficult to maintain gas purity. Alternatively, corrosion products such as metal chlorides themselves become fine particles and cause pollution.

Corrosion of stainless steel in a dry halogen-based gas is said to be comparatively slight, but in reality, in most cases, a small amount of water coexists in these gases, so that it is considerably small. Corrosion is inevitable.
Therefore, it is conceivable to use a high Ni-based alloy (Hastelloy or the like) having a higher corrosion resistance than SUS316L, but these high Ni-based alloys are very expensive and cannot completely prevent corrosion. In addition, when paying attention to general steel materials, it is obvious that their corrosion resistance is significantly inferior to that of stainless steel and high Ni alloys.

[0006]

The present invention has been made in view of the above circumstances, and its purpose is not only stainless steel materials which are said to have relatively excellent corrosion resistance, It is intended to establish a surface modification method capable of giving various metal materials including general steel materials excellent corrosion resistance to withstand a highly corrosive gas atmosphere.

[0007]

The structure of the surface modification method according to the present invention, which has been able to solve the above-mentioned problems, is one in which at least one of a hydroxide of Cr and a hydrous compound is added to the surface of a metal material.
After forming a film containing not less than 0.1% by weight of a silane coupling agent and containing at least 0.1% by weight of a silane coupling agent, a micro oxygen activity atmosphere (preferably having an atmospheric composition of 10 ⁻⁸ to 10 ⁰ to
The essential point is to form a Cr oxide-containing coating layer by heat treatment in a reduced pressure atmosphere of rr or an oxygen activity atmosphere corresponding thereto.

Another surface modification method according to the present invention is IVa
A steel material containing 0.1% by weight or more of at least one element selected from the group consisting of Group III, Group Va, and Group VIa is used, and a hydroxide of Cr and a water-containing compound are formed on the surface thereof in the same manner as above. At least 5% by weight and at least 0.1% by weight of a silane coupling agent are formed, and then heat treatment is performed in a micro oxygen activity atmosphere to form a group IVa group together with a Cr oxide. , Va and VIa
The gist is to form a coating layer containing a carbide of at least one element selected from the group consisting of groups.

[0009]

As described above, in the present invention, Cr is formed on the surface of the metal material.
After forming a film containing 5% by weight or more of one or more of the hydroxides and hydrous compounds of 1) and 0.1% by weight or more of a silane coupling agent, by heat treatment in a micro oxygen activity atmosphere. , Which form a very dense and corrosion resistant Cr oxide-containing coating and to which the above-mentioned method is applied, are metal materials of group IVa, group Va and group VIa.
When the same treatment as above is carried out using a steel material containing 0.1% by weight or more of at least one element selected from the group consisting of group a, the coating layer diffuses and transfers from the metal material to group IVa. It is possible to obtain a surface-treated steel material having a further improved corrosion resistance by forming a denser coating layer containing a carbide of at least one element selected from the group consisting of the group consisting of Al, Va and VIa.

By the way, it is well known that Cr oxide has an excellent corrosion resistance as a surface coating, and has been used so far for improving the corrosion resistance of metal materials, for example, as a chromate treatment. However, conventional Cr oxide coatings generally have the drawback of lacking compactness, and as a single coating, they do not always have satisfactory corrosion resistance. Therefore, attempts have been made to densify the Cr oxide coating and improve the corrosion resistance by devising the film forming conditions and the like, but the expected effect has not been obtained.

Under these circumstances, the inventors of the present invention have conducted earnest research in anticipation of the development of an effective method capable of densifying a Cr oxide coating. As a result, as described above, on the surface of the metal material, 1
If a method is adopted in which a film containing 5% by weight or more of seeds and 5% by weight or more and 0.1% by weight or more of a silane coupling agent is formed and then heat-treated in a micro oxygen activity atmosphere, a Cr compound is obtained. It was confirmed that the coating was extremely dense and exhibited significantly superior corrosion resistance compared to conventional chromate coating and the like.

The reason why the density of the Cr oxide-based coating is significantly increased by adopting the above method has not been theoretically elucidated, but as described above, a predetermined amount of Cr or more is used.
When a Cr oxide-based coating is formed by heat-treating a film in which a hydroxide or a hydrous compound and a silane coupling agent coexist in an oxidizing atmosphere, a Cr hydroxide or a Cr-based hydrous compound and a silane coupling agent are formed. This is considered to be because the reaction with the agent causes the film to be densified into a network, and the Cr-based oxide coating formed by subsequent further thermal oxidation is also dense and free of pinhole defects.

In order to effectively develop such a densification effect of the coating, at least 5% of Cr hydroxide or Cr-containing hydrous compound is contained in the coating for forming Cr-based oxide coating (that is, the coating before heat oxidation treatment). % Or more, more preferably 2
It is necessary to contain the silane coupling agent in an amount of 0 to 90% by weight and a silane coupling agent in an amount of 0.1% by weight or more, and preferably 0.5 to 5% by weight. The formation of the above-described network that occurs during the heat treatment becomes insufficient, and the finally formed Cr
The system oxide coating cannot be made sufficiently dense.

Specific examples of the Cr-containing hydrous compound contained in the above include Cr oxide hydrate, Cr carbonate hydrate, Cr phosphate hydrate, and the like. Besides being usable, two or more kinds can be used in combination, if necessary.

The type of the silane coupling agent is not limited at all, but preferred examples are γ- (2-
Aminoethyl) aminopropyltrimethoxysilane, γ
-(2-aminoethyl) aminopropylmethyldimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane,
γ-anilinopropyltrimethoxysilane, vinyltrimethoxysilane, dimethyldichlorosilane, γ-mercaptopropyltrimethoxysilane, methyltrimethoxysilane, γ-chloropropyltrimethoxysilane, methyltrichlorosilane, trimethylchlorosilane and the like can be mentioned. The molecular weights of these silane coupling agents are not particularly limited, but those of 100 to 300 are particularly preferable.

Other components constituting the above-mentioned film are chromic acid or a salt thereof which is the main component of the Cr-based oxide coating (ammonium chromate salt, sodium chromate salt, potassium chromate salt, ammonium dichromate, Potassium dichromate, sodium dichromate, etc.).

The method for forming a film containing the above-mentioned Cr hydroxide or Cr-based hydrous compound and a silane coupling agent is not particularly limited, and any of wet method, electrolytic method, sol-gel method, vacuum deposition method and the like can be applied. However, if it is exemplified as a more general method, about 0.1 to 5 g / liter of a silane coupling agent is added to a Cr-containing aqueous solution containing Cr hydroxide and a Cr-based hydrous compound together with chromic acid and the like, Immerse a metal substrate in this solution as a cathode to obtain a current density of 0.1 to 100 A / d
After electrolyzing at about m ² , a method of forming a film by heating to 80 to ²⁰⁰ ° C. Chromate, Cr hydroxide, Cr hydrous compound, and silane coupling agent are added to silica sol. A sol is prepared by quantitative addition, and the sol is adhered to the surface of the metal substrate by a dipping method or an arbitrary coating method.
A method of heating and drying at about 0 ° C, a predetermined amount of a silane coupling agent is mixed with an aqueous solution of Cr containing Cr hydroxide and a Cr-containing hydrous compound together with chromic acid, and the solution is applied to the surface of a metal substrate and dried. And the like.

After forming the film in this way, it is
Oxygen activity atmosphere, preferably 10 ^-8-10⁰ tor
r, more preferably 10^-6-10^-2atmospheric composition of torr
Under reduced pressure atmosphere or corresponding oxygen activity atmosphere
Is heat-treated to form a Cr oxide-containing coating layer. this
The heating atmosphere at that time was defined as a micro oxygen activity atmosphere.
By moderately controlling the oxidation rate during heating
This is for promoting the densification of the coating, for example, in an atmospheric atmosphere.
Heat treatment in an atmosphere of oxygen or higher oxygen activity
When done, the densification of the coating is low due to the oxidation rate being too fast.
This is because it is likely to cause a drop or a pinhole defect. Addition
The heat treatment temperature is also not particularly limited, but it can be adjusted by an appropriate oxidation rate.
Especially preferred for forming a dense Cr-based oxide coating
In the range of 400 to 600 ° C, the heat treatment time is
About 10 minutes to 2 hours is sufficient. Shaped by this method
The Cr-based compound-based coating that is formed is a
It is a very precise product with no defect and is very thin.
Even though it has excellent corrosion resistance, it is too thin.
If it does, the satisfactory surface coating effect cannot be achieved.
Therefore, preferably about 0.005 μm or more, more preferably
It is desirable that the thickness is about 0.05 μm or more.

As described above, in the present invention, a film containing a predetermined amount of Cr hydroxide and / or a Cr-based hydrous compound and a silane coupling agent is formed on the surface of a metal material, and then the film is formed in a micro-oxidizing atmosphere. It is characterized in that it enhances corrosion resistance by heat treatment to form a dense film without pinhole defects, etc., so there is no limitation on the type of metal material to be coated.
At least one element selected from the group consisting of Group VI, Group Va and Group VIa, for example Ti, Zr, V, Nb, M
When a metal material containing 0.1% by weight or more of o, W, etc. is used, these elements diffuse and move toward the base material in the heat treatment step to form a metal carbide at the interface with the Cr-based oxide layer and Cr. It is preferable because the denseness of the system coating can be further enhanced, and the adhesion between the Cr system coating and the substrate can be enhanced, and the corrosion resistance can be further enhanced by the combination thereof. However, in order to effectively exhibit such effects, the heat treatment temperature is 600 to 105, which is slightly higher than that in the above case.
It is necessary to set the temperature to about 0 ° C., and if the temperature is lower than this, diffusion transfer of the above-mentioned elements and formation of carbide are difficult to proceed, and the effect of improving compactness and adhesiveness cannot be effectively exhibited. Therefore, as a metal substrate, Group IVa, Group Va and Group VIa
When using a metal containing at least about 0.1% by weight of at least one element selected from the group consisting of the group,
It is desired that the heat treatment temperature after film formation is set in the range of 600 to 1050 ° C. and the conditions are set so that the above-mentioned effects can be effectively exhibited.

The type of metal material to which the present invention is applied is not particularly limited, and various alloy steels including general steel materials and stainless steels, and various non-ferrous metals such as Al, Mg and Ni and their alloys are also available. The present invention can be applied to all alloys, and regarding the shape thereof, it can be applied to not only the most general plate materials and pipe materials, but also all wire materials, rod materials, various shaped materials, and the like.

[0021]

EXAMPLES Hereinafter, the constitution and effects of the present invention will be described in more detail with reference to examples. However, the present invention is not limited by the following examples, and conforms to the gist of the preceding and the following. It is also possible to carry out appropriate modifications within the range to be obtained, and all of them are included in the technical scope of the present invention.

Example 1 Stainless steel (SUS316), low alloy steel (Fe-3%)
Cr) or an Al alloy (6061) is used to form a film on the surface of a plate material by the following wet method, and then heat treatment is performed at a predetermined temperature and a vacuum degree for 60 minutes to form a surface coating. The surface coating forming material was examined for corrosion resistance by the following method. The results are shown in Table 1.

(Wet Film Forming Method) Each metal plate is added to an aqueous solution containing chromic acid and Cr hydroxide or a Cr-based hydrous compound (chromium carbonate, chromium oxide, chromium phosphate) and a silane coupling agent. It is immersed as a cathode, electrolyzed at a current density of 50 A / dm ² for 1 minute, washed with water and dried at 120 ° C., and a silane coupling agent-containing Cr is added.
A compound film was formed.

(Corrosion Resistance Test Method) Gas Corrosion Test: Each surface-coated metal material was evaluated by the corrosion state when exposed to a 5% chlorine-argon mixed gas at 300 ° C. for 15 hours. ◯: No corrosion occurred Δ: Corrosion occurred area ratio less than 5% ×: Corrosion occurred area ratio over 5% Aqueous solution corrosion test: Anodic polarization was performed in a 5% NaCl aqueous solution at 45 ° C., and evaluated by the presence or absence of pitting corrosion . ○: No pitting corrosion occurred △: Pitting corrosion occurred in some samples ×: Pitting corrosion occurred in all samples

[0025]

[Table 1]

As is clear from Table 1, all the examples (Nos. 1 to 7) satisfying the specified requirements of the present invention have excellent corrosion resistance, while the silane coupling agent. Satisfactory corrosion resistance was not obtained in Comparative Examples (Nos. 8, 9, and 10) in which No. was not used, and the corrosion resistance of Comparative Example (No. 11) in which the amount of the silane coupling agent used was insufficient was poor. I understand.

Example 2 Using SUS316 as a basic composition, Ti, Nb,
Using steel sheets with various contents such as Mo as the base material,
A silane coupling agent-containing film was formed on the surface by the same method as used in Example 1, and then heat-treated at a predetermined temperature and a vacuum degree to form a corrosion-resistant coating. The corrosion resistance of each of the obtained surface coating materials was examined by the following method. The results are shown in Tables 2-5.

(Corrosion Resistance Test Method) Gas Corrosion Test: Each surface-coated metal material was evaluated by the corrosion state when exposed to a 5% chlorine-argon mixed gas at 350 ° C. for 15 hours. ◎: No corrosion at all ○: Almost no corrosion Δ: Corrosion occurrence area ratio less than 5% ×: Corrosion occurrence area ratio over 5% Aqueous solution corrosion test: Anodic polarization is performed in a 3% NaCl aqueous solution at 50 ° C. to cause pitting corrosion It was evaluated by the presence or absence of. ◎: No pitting corrosion ○: Almost no pitting corrosion △: Pitting corrosion occurred in some samples ×: Pitting corrosion occurred in all samples

[0029]

[Table 2]

[0030]

[Table 3]

[0031]

[Table 4]

[0032]

[Table 5]

As is clear from Tables 2 to 5, in the case where the metal carbide is formed at the interface between the coating and the substrate by satisfying the specified requirements of the present invention and adopting an appropriate heat treatment temperature, Excellent corrosion resistance is obtained. However, the corrosion resistance of the comparative example in which the silane coupling agent was not used in the film forming step is very poor. Even if a suitable amount of the silane coupling agent is blended, the reference example in which the heat treatment temperature is less than 600 ° C. does not exhibit the effect of improving the corrosion resistance due to the formation of carbides, and thus is slightly inferior in corrosion resistance to the examples. However, it can be seen that it has much more excellent corrosion resistance than the comparative example.

[0034]

The present invention is constituted as described above, and after forming a film containing an appropriate amount of a hydroxide or compound of Cr and a silane coupling agent on the surface of a metal material, a minute oxygen activity is formed. By forming the Cr oxide-containing coating layer by heat treatment in an atmosphere, the coating can be made extremely dense and excellent in adhesiveness, and in a highly corrosive atmosphere containing a halogen-based gas. It has become possible to provide a surface-coated metal material having excellent corrosion resistance.

Claims (3)

[Claims] 1. After forming a coating film containing 5% by weight or more of one or more of a hydroxide or a compound of Cr on the surface of a metal material and 0.1% by weight or more of a silane coupling agent, A surface modification method for a metal material, comprising forming a Cr oxide-containing coating layer by performing heat treatment in a micro oxygen activity atmosphere. 2. The micro oxygen activity atmosphere is 10 ⁻⁸ to 10 ^0.
The surface modification method according to claim 1, wherein a reduced pressure atmosphere of torr or an oxygen activity atmosphere corresponding thereto is used. 3. A steel material containing 0.1% by weight or more of at least one element selected from the group consisting of Group IVa, Group Va and Group VIa is used, and heat treatment is carried out in a micro oxygen activity atmosphere. , Cr oxides together with IVa, Va and
3. A coating layer containing a carbide of at least one element selected from the group consisting of VIa group.
The surface modification method described in 1.