JPH0853773A - High corrosion resistant surface treated metallic material and its production - Google Patents

Abstract

PURPOSE:To give excellent corrosion resistance even under a high corrosive environment containing halogen gas or the like by forming a dense corrosion resistant coating containing a fixed quantity of Cr, O and P on the surface of an Fe based or Al based metallic material. CONSTITUTION:The corrosion resistant coating to be formed contains a Cr phosphate and a Cr oxide, and >=0.15% O, >=15% Cr and >=1% P constituting a phosphate, phosphite or hypophosphite by atomic are present in the coating. The base material metal of the coating is a Cr-containing steel or an iron or steel containing no Cr, and the coating is formed by bringing the surface into contact with a treating solution containing at least the phosphite and/or hypophosphite after electropolishing, drying and heating under and oxidizing atmosphere. In the case of using Al or Al alloy, the surface is brought into contact with a treating solution containing at least one kind of phosphoric acid, phosphite or hypophosphite and chromic acid and after being bried, heated under the oxidizing atmosphere.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is particularly useful in various applications such as automobiles, various vehicles, aircraft and other equipment and skins, chemical and vacuum equipment, and building materials. The present invention relates to a metal material having excellent corrosion resistance even in a highly corrosive environment containing a halogen-containing gas having strong properties, and a method for producing the same.

[0002]

2. Description of the Related Art For example, an Al alloy exhibits excellent corrosion resistance in normal atmosphere and can obtain an arbitrary strength by selecting an alloying element, so that it can be used for automobiles, various vehicles, aircrafts, building materials, etc. Has been widely used as.

However, even an Al alloy may cause pitting, intergranular corrosion, stress corrosion cracking, etc. when used in a highly corrosive environment such as on the sea or in seawater.
In a high-strength Al alloy such as a Zn-Mg-based alloy, stress corrosion cracking tends to occur more easily as the strength increases, and therefore a preventive measure is required. For this reason, alloy compositions and heat treatment conditions that are resistant to corrosion are selected according to individual use conditions.

Further, since the Al alloy has the characteristics that it has a large thermal conductivity, is lightweight, and is unlikely to cause heavy metal contamination or activation, the demand for it as a vacuum container or a vacuum equipment component material has increased in recent years. There is. However, when it is attempted to be put to practical use as a vacuum device part or the like, the corrosive damage that occurs in a portion exposed to a highly corrosive gas such as a halogen-based gas becomes a serious problem.

On the other hand, in the field of semiconductors in recent years, as the integration of elements has advanced, the wiring interval has been required to have an accuracy of submicron. In such an element, impure fine particles and bacteria are attached. Even just doing this will cause a short circuit and cause product failure. Therefore, the gas and pure water used in the production of semiconductors are required to have ultra-high purity, and in handling the gas, not only the gas is highly purified, but also water from the pipes, reaction chamber wall surface, etc. It is necessary to reduce the emission of impure gas, dust, etc. 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, even if the stainless steel material subjected to the surface treatment as described above exhibits excellent performance in a gas atmosphere having no corrosiveness such as oxygen and nitrogen, hydrogen chloride, chlorine, hydrogen fluoride, etc. When exposed to a highly corrosive halogen-based gas atmosphere, the progress of corrosion is unavoidable, and the corrosion products become gas adsorption / desorption sites, making it difficult to maintain gas purity, or metal chlorides. Corrosion products themselves, etc., become particulates 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.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and its purpose is to provide an Al alloy or a stainless steel material which is considered to have relatively excellent corrosion resistance. It aims to establish a technique capable of giving excellent corrosion resistance to various metal materials including general steel materials even in a highly corrosive gas atmosphere.

[0010]

The structure of the highly corrosion-resistant metal material according to the present invention, which has been capable of solving the above-mentioned problems, is such that a coating containing Cr phosphate and Cr oxide is formed on the surface of the metal material, In the coating, O is present at 15 atom% or more, Cr is present at 10 atom% or more, and P constituting the phosphate, phosphite or hypophosphite is present at 1 atom% or more. I have. In the above, various kinds of metal materials can be used as the coating base material, but when the metal material contains Cr as an alloy element (for example, Cr-containing steel or stainless steel), the metal base material When the coating layer can contain Cr by utilizing Cr contained therein, while the metal material does not contain Cr (for example, Al or Al alloy, Cr-free iron or steel, etc.) It is necessary to separately use Cr or a Cr-containing compound as a constituent material of the coating layer.

That is, when the metal material is a metal material containing Cr such as stainless steel, the Cr-containing metal material is electrolytically polished and then contacted with a treatment liquid containing at least phosphorous acid and / or hypophosphorous acid. By allowing it to dry, the Cr in the metal is eluted into the treatment liquid in this treatment step, and then deposited on the surface of the substrate as chromium phosphate,
Alternatively, a highly corrosion-resistant coating satisfying the requirements of the above-mentioned composition is formed by diffusing and transferring Cr to the surface film side, thereby containing Cr in the coating, or by heat treatment in an oxidizing gas atmosphere after that, if necessary. can do.

When the metal material is a metal material not containing Cr such as Al or Al alloy, and iron or general steel material, after the Cr-free metal material is polished if necessary,
By contacting (immersing or coating) a treatment liquid containing at least one of phosphoric acid, phosphorous acid or hypophosphorous acid and chromic acid, drying, and then heat treatment in an oxidizing atmosphere, the above component composition is obtained. A coating layer having a satisfactory high corrosion resistance is formed, and as a result, a highly corrosion resistant metal material that meets the above-mentioned object of the present invention can be obtained.

[0013]

As described above, in the present invention, O (15 atomic% or more) and Cr (10 atomic% or more) are present on the surface of the metal material, and P (composing phosphate, phosphite or hypophosphite) is formed. Hereinafter, a phosphate composition P) may be present in an amount of 1 atomic% or more to form a coating layer having excellent corrosion resistance, which results in excellent corrosion resistance even in a highly corrosive gas atmosphere such as a halogen-based gas. It is the one that can be obtained. That is,
The specific component composition of the coating layer and a typical method for forming the coating layer will be clarified later. However, the coating layer has a phosphate constituent P of 1 atom% or more, O (oxygen) of 15 atom% or more, and Cr of 1 atom% or more.
A coating having a content of 0 atomic% or more is a protective film which is extremely dense and has a high coating effect, and by coating the surface with the protective film, the corrosion resistance of all kinds of metal base materials can be dramatically improved. . In addition, in the present invention, regarding P among the components constituting the corrosion-resistant coating layer, only P constituting phosphate, phosphite, or hypophosphite is specified, but this depends on the method of forming the coating. Is to exclude those P components that may be mixed in as atomic P or P-containing intermetallic compounds.

In the above, the composition of the coating layer is determined by X-ray photoelectron spectroscopy (ESCA), and as will be apparent from the examples described later, the phosphate composition P is 1 atomic% or more, O (oxygen) is 15 atomic% or more,
If Cr does not meet any of the requirements of 10 atomic% or more,
The densification of the coating by the combination of Cr phosphate and Cr oxide and the excellent surface protection effect are not effectively exhibited, and the excellent corrosion resistance intended by the present invention cannot be obtained. A more preferable composition of the coating layer in the present invention is such that the phosphate constituent P is 5 to 10 atom%, O is 35 to 65 atom%, and Cr is
Is in the range of 15 to 30 atomic%, and elements other than the above are not particularly limited. For example, depending on the type of metal base material or the method of forming the coating layer, Fe, Al, Mg, N may be present in the coating layer.
A small amount of i, Mn, Ti, Nb, and other phosphates, oxides, etc. may be mixed in, but as long as the P, O, and Cr contents satisfy the specified requirements, the coating layer May contain a small amount of these other phosphates and oxides.

In the present invention, as described above, the specified amount of P, O,
By coating the surface of the metal material with a coating layer containing Cr (hereinafter sometimes referred to as Cr / P / O composite coating layer),
Because it has a characteristic that corrosion resistance is enhanced,
The thickness of the coating layer itself is not particularly limited, but in order to more reliably exhibit the corrosion resistance improving effect by a complete surface coating without pinhole defects, it is preferable that the thickness is 50 Å or more, more preferably 100 Å or more. desired.

The method of forming the Cr / P / O composite coating having the above-mentioned composition depends on the type of metal material used. That is, when a metal material not containing Cr such as Al, Al alloy, iron, or general Cr-free steel material is used as the metal material, the metal material is polished if necessary, and then phosphoric acid, phosphorous acid or A method of immersing in a solution containing at least one kind of hypophosphorous acid and chromic acid, or applying the solution and then performing heat treatment in an oxidizing gas atmosphere is adopted. By properly adjusting the concentrations of phosphorous acid and chromic acid and controlling the heat treatment conditions well, it is possible to easily form a Cr / P / O composite coating layer that satisfies the requirements for the component composition. In order to efficiently deposit chromium phosphate on the metal substrate in the above dipping or coating step, it is preferable to use at least one of phosphorous acid and hypophosphorous acid having a reducing property together with chromic acid and phosphoric acid.

The solution composition and heating temperature conditions at this time are not particularly limited, but if shown as preferable conditions, the preferred chromic acid concentration of the treatment solution is 2 to 20% by weight, more preferably 5 to 15% by weight, and phosphoric acid. The concentration is 20 to 80% by weight, more preferably 50 to 70% by weight, phosphorous acid and / or
Alternatively, the concentration of hypophosphorous acid is in the range of 1 to 10% by weight, more preferably 2 to 5% by weight, and a predetermined amount of this solution is attached to the surface of the metal material by the dipping method or the coating method. When the dipping method is adopted, the amount of the adhering substance can be adjusted by the leaning time after the dipping, wiping, roll squeezing, etc., and in some cases, the amount of the adhering substance can be adjusted by repeating the dipping and drying twice or more. When the application method is adopted, a spray method, a wiping method, a roll method or a method using a brush or a sponge brush is adopted to adjust the solution concentration and the application amount, and in some cases, the application and the drying are repeated twice or more. The amount of adhesion is adjusted accordingly.

Thereafter, when this is heat-treated in an oxidizing gas atmosphere, for example, in the atmosphere or a reduced pressure atmosphere, a Cr / P / composite film having a high density and excellent corrosion resistance is formed. The preferable heating temperature at this time is preferably set in consideration of the heat resistant temperature of the metal material, for example, 130 to 200 ° C., and more preferably 145 to 155 ° C. for Al or Al alloy.
In the range of 400 to 650 ° C., more preferably 450 to 550 ° C. for general steel materials, and the heating time is 30 minutes or more, more preferably 1 to 2 hours. It is to be noted that the heating is performed in the air atmosphere or under reduced pressure as described above, but it is particularly preferable in order to form a more dense coating layer by appropriately controlling the oxidation rate by applying an appropriate oxidizing atmosphere. is given, 10 ^-3 ~10 ⁰ torr at atmospheric composition
It is a reduced pressure atmosphere.

In the above, the method of forming the Cr / P / O composite coating on the surface of the metal material containing no Cr is shown. However, the metal material contains Cr such as stainless steel or chrome steel. In this case, Cr in the metal material can be used to contain Cr in the surface coating. As a specific method therefor, a Cr-containing metal material is subjected to anodic electrolytic polishing in a solution containing phosphoric acid, phosphorous acid or hypophosphorous acid to elute Cr in the electrolytic solution, and then the electrolytic current is stopped. A method of precipitating chromium phosphate on the metal surface by immersing and holding it in the above state is mentioned. At this time, if phosphorous acid or hypophosphorous acid is allowed to coexist in the immersion liquid after electropolishing, the reduction action further promotes the precipitation of chromium phosphate on the surface of the metal substrate, and immersion for a short time is sufficient. A thick corrosion resistant coating can be formed.

The chromium phosphate-based coating formed by this dipping treatment is quite dense in itself, and a coating having high corrosion resistance can be obtained by simply drying it as it is, and thereafter, in the same oxidizing atmosphere as above. When heat-treated in (1), the coating contains a proper amount of chromium oxide and chromium phosphate, and further has excellent corrosion resistance.

As described above, the present invention has a great feature in enhancing the corrosion resistance by coating the surface of the metal material with the corrosion resistant coating containing specific atomic% of P, O and Cr. The method for forming such a corrosion resistant coating is disclosed, and the metal material to be coated in the present invention is not limited at all, including the inclusion or non-inclusion of Cr, and can be applied to all kinds of metal materials. However, when a corrosion-resistant coating as described above is formed using a Cr-free metal material, the treatment liquid for forming the coating is phosphoric acid, as described above,
It is necessary to use a solution containing chromic acid together with phosphorous acid or hypophosphorous acid. On the other hand, when a metal material containing Cr is used, Cr contained in the metal material is effectively used as a Cr source. The Cr-containing coating can be formed by using a solution containing phosphoric acid, phosphorous acid, or hypophosphorous acid as the treatment liquid for forming the coating as described above.

From this viewpoint, C used in the present invention
As the r-free metal material, general steel materials and various alloy steel materials, which are themselves insufficient in corrosion resistance, pure Al, various Al alloys (for example, Al-Si-based, Al-Mg-based, Al-Mn-based, Al-
Zn-Mg system, Al-Mg-Si system, Al-Cu-Mg
Etc.) and the like, and the most common Cr-containing metal material is a stainless steel material, but of course it is not limited to this, and Cr steel such as Cr
It can be applied to all of various alloy steel materials containing. Further, the shape of the metal material is not limited at all, and it can be applied to not only the most general plate materials and pipe materials, but also wire rods, bar materials, various deformed materials, and the like.

[0023]

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 An Al alloy plate (A60 was used as a typical metal material containing no Cr.
61) was used and immersed in the treatment liquid shown in Table 1, and then heat-treated in an atmosphere gas having an atmospheric composition to produce Cr.
A P / O composite coating was formed, the composition of the coating was clarified by X-ray photoelectron spectroscopy, and the corrosion resistance of each was investigated by the following method. (Corrosion resistance test method) Evaluated by a corrosion test when immersed in a 3% NaCl aqueous solution at 30 ° C. ○: No pitting corrosion caused by anodic polarization ×: No pitting corrosion caused by anodic polarization

The results are shown in Tables 1 and 2. In Examples (Nos. 1 to 8) in which the component composition of the surface coating layer satisfies the specified requirements of the present invention, excellent corrosion resistance was obtained. On the other hand, a comparative example (No.
In Nos. 9 to 12), satisfactory corrosion resistance was not obtained in any case.

[0026]

[Table 1]

[0027]

[Table 2]

Example 2 As a typical metal material containing Cr, stainless steel (S
US316L) and low alloy steel (Cr content: 3% by weight) are used, and each is subjected to an anodic electrolytic treatment under the conditions shown in Table 3 and then subjected to an immersion treatment in an electrolytic treatment liquid. For No. 3, a heat resistant coating was formed on the surface by heat treatment in an oxidizing atmosphere. With respect to each of the obtained coating forming materials, the composition of each coating was clarified by X-ray spectroscopic analysis and the corrosion resistance was examined in the same manner as in Example 1.

The results are collectively shown in Table 3. The corrosion resistance of each of the coating layers (Nos. 1 to 6) having a coating composition having the composition satisfying the requirements of the present invention was very excellent. On the other hand, the corrosion resistance of the comparative examples (Nos. 7 to 10) in which the coating composition deviates from the specified requirements of the present invention is poor.

[0030]

[Table 3]

[0031]

EFFECT OF THE INVENTION The present invention is constituted as described above, and the surface of the metal material is a coating mainly composed of chromium oxide / chromium phosphate having a specified content of P, O and Cr and having a high surface protection effect. It has become possible to provide a coated metal material having excellent corrosion resistance by forming the.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koji Wada 1-5-5 Takatsukadai, Nishi-ku, Kobe-shi, Hyogo Pref., Kobe Steel Co., Ltd. (72) Haruo Tomari, Nishi-ku, Kobe-shi, Hyogo Takatsukadai 1-5-5 Kobe Steel Co., Ltd. Kobe Research Institute

Claims (8)

[Claims] 1. A coating containing Cr phosphate and Cr oxide is formed on the surface of a metal material, and O in the coating is 15 atomic%.
As described above, Cr is present in an amount of 10 atomic% or more, and phosphate,
A metal material with high corrosion resistance, characterized in that P constituting phosphite or hypophosphite is present in an amount of 1 atomic% or more. 2. The highly corrosion-resistant surface-treated metal material according to claim 1, wherein the metal material is Cr-containing steel. 3. The highly corrosion-resistant surface-treated metal material according to claim 1, wherein the metal material is iron or steel containing no Cr. 4. The highly corrosion-resistant surface-treated metal material according to claim 1, wherein the metal material is Al or an Al alloy. 5. The method according to claim 1, wherein Cr-containing steel is used as the metal material, and the steel is electropolished and then brought into contact with a treatment liquid containing at least phosphorous acid and / or hypophosphorous acid and then dried. A method for producing a highly corrosion-resistant surface-treated metal material, which comprises forming a coating of 6. A Cr-containing steel is used as a metal material, which is electrolytically polished, brought into contact with a treatment liquid containing at least phosphorous acid and / or hypophosphorous acid, dried, and then heat-treated in an oxidizing atmosphere. The coating according to claim 1 is formed by doing so, and a method for producing a highly-corrosion-resistant surface-treated metal material. 7. Iron or steel which does not contain Cr is used as a metal material, which is polished, brought into contact with a treatment liquid containing phosphorous acid and / or hypophosphorous acid and chromic acid, and then dried and then oxidized. A method for producing a highly-corrosion-resistant surface-treated metal material, comprising forming the coating according to claim 1 by performing heat treatment in a corrosive atmosphere. 8. An Al or Al alloy is used as a metal material, and this is contacted with a treatment liquid containing at least one of phosphoric acid, phosphorous acid or hypophosphorous acid and chromic acid without polishing or polishing treatment. A method for producing a highly-corrosion-resistant surface-treated metal material, comprising forming the coating according to claim 1 by drying, then heat-treating in an oxidizing atmosphere.