JP2003239085A - Inorganic film clad copper or copper alloy member, method of forming inorganic film to surface of copper or copper alloy member, heat exchanger for hot-water supply device, and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method which is a method of forming inorganic films having an excellent corrosion resistance, oxidation resistance, wear resistance, and heat resistance on the surfaces of copper tubes or components, etc., of a heat exchanger for a hot-water supply device and forms the inorganic films having the high adhesion strength between base materials and the inorganic films and excellent durability. <P>SOLUTION: The surface of the copper tube is degreased and after the naturally oxidized film is removed therefrom, the oxidized film having a thickness of 10 to 1,000 nm and containing at least either of Cu<SB>2</SB>O and Cu(OH)<SB>2</SB>is formed on the surface of the copper tube by immersing the copper tube into aqueous alkaline solution. Next, a treating solution containing a polymer of metal alkoxide is applied on the oxidized film and is then subjected to heat treatment, by which an amorphous ceramic film is formed. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides an inorganic coating on the surface of a copper member for the purpose of improving the corrosion resistance, acid resistance and heat resistance of members made of copper or copper alloy (hereinafter collectively referred to as copper members). Forming method, an inorganic film-coated copper member having an inorganic film formed on at least a part of the surface by this method, and an inorganic film-coated copper or copper alloy heat exchanger having an inorganic film formed by the method (hereinafter, referred to generically) And a copper heat exchanger) and a method for manufacturing the same. More specifically, a copper heat exchanger used in a bath kettle, a water heater, an instantaneous water heater, etc., and a method for manufacturing the same, an inorganic film-coated copper member such as a heat transfer tube and a can body incorporated in the copper heat exchanger, and The present invention relates to a method for forming an inorganic film on the surface of an inorganic film-coated copper member.

[0002]

2. Description of the Related Art Generally, copper and copper alloy pipes (hereinafter collectively referred to as copper pipes) are excellent in corrosion resistance, toughness, spreadability, brazing property and the like. , Collectively referred to as water), that is, a pipe for building, a heat transfer pipe incorporated in a heat exchanger for a hot water heater, a heat transfer pipe incorporated in a water heat exchanger, and the like. The reason for this is that these pipes are required to have high corrosion resistance against water in a wide temperature range from low temperature to high temperature. In addition, since the heat exchanger itself is required to have corrosion resistance and heat resistance, a heat exchanger for a hot water heater for hot water is usually made of copper or fin components such as a can body and a fin material. It is formed of a copper alloy (hereinafter collectively referred to as copper).

However, even if the pipe is made of copper having high corrosion resistance as described above, a through hole is formed in a part of the pipe during use and water inside leaks out. Occasionally, an accident occurs that you cannot do it. Such accidents are often caused primarily by pitting corrosion. Pitting corrosion is corrosion in which a small portion of the inner surface of a copper pipe progresses in the thickness direction of the pipe to form point-like holes. Pitting corrosion is a stagnation of water flowing in the pipe such as a portion where precipitates or deposits are likely to stay when the water flow in the pipe stops, a portion where the flow velocity of the water flow slows, a joint portion and the vicinity of the joint portion. It is easy to occur in the department. At these sites, deposits tend to adhere to the inner surface of the pipe,
This is because an oxygen concentration battery or an ion concentration difference battery is formed at the attached portion, and pitting corrosion occurs under the deposit. Such pitting corrosion is caused by the pH of water flowing in the pipe (SO ₄ ²⁻ / H) even when the pipe is made of the same kind of copper.
The CO ₃ ⁻ ) ratio, the residual chlorine, the water quality of the soluble silicic acid, and the like differ in susceptibility to generation, and pitting corrosion of copper pipes has become a problem in Japan when cold water near room temperature is used.

Pitting corrosion can be prevented to some extent by administering a chemical to the water flowing in the pipe to make the water quality so that it does not easily occur. However, it is difficult to change the water quality in practice, and it is particularly difficult to target drinking water because the influence of the drug administration on the human body is concerned. Therefore, with respect to pitting corrosion, countermeasures are required from the viewpoint of the material forming the pipe.

In particular, in the bent portion and the joint portion of the copper pipe for water supply and hot water supply, dissolved gas dissolved in water is easily vaporized, and in the return pipe having low water pressure, the dissolved gas is vaporized due to the change in flow velocity. It is easy to make. When the dissolved gas is vaporized in this way and bubbles are generated in the water flow, a mechanical load is applied to the inner surface of the copper pipe due to friction between the bubbles and the inner surface of the copper pipe and impact caused by the destruction of the bubbles. As a result, the oxide film that naturally forms on the inner surface of the copper pipe and functions as a protective film for the copper pipe is partially peeled off, and erosion easily occurs on the inner surface of the copper pipe. As measures against this erosion, it is conceivable to reduce the curvature of the bent portion of the pipe and change the design of the pipe such as the number of bent portions, and to limit the flow velocity of water flowing in the pipe, but it is still difficult to realize. Many. For this reason, measures against the erosion are also required from the viewpoint of the material forming the pipe.

As a countermeasure against pitting corrosion from the viewpoint of material,
Conventionally, the following measures have been taken. Usually, when copper is cast, the cast copper ingot is drawn, and then annealed to form a copper tube, the drawn oil of the copper tube inevitably remains on the inner surface of the formed copper tube. In addition, the drawn oil is carbonized to form a carbon film on the inner surface of the copper pipe. The reason for this is
When a copper pipe is drawn using a drawing lubricating oil and then the copper pipe coil is annealed, most of the drawing oil remaining inside the pipe is decomposed and discharged outside the pipe, but this drawing oil is decomposed. Is insufficient or the decomposed drawn oil is not discharged to the outside of the pipe, and if annealing is completed and the drawn oil is re-condensed, lubricating oil remains inside the copper pipe or carbide is formed. This is because If water is passed through a copper pipe having a large amount of residual oil or residual coal, a local battery is likely to be formed and pitting corrosion is likely to occur. Therefore, as a first method for preventing corrosion of a copper pipe, there is a method of removing residual carbon and residual oil from the inside of the copper pipe. Hereinafter, this method is referred to as Conventional Example 1.

The residual carbon and the residual oil can be removed by heating the copper pipe in the air and burning the residual carbon and the residual oil, but the copper pipe is oxidized due to the heating, and this oxidation is controlled. Is difficult. Therefore,
For example, in the method for manufacturing a heat exchanger described in JP-A-5-126483, in order to prevent the carbon film from remaining, a copper pipe is heated during the process to burn the carbon film, and a small amount of residual carbon is also left. A technique for removing, for example, air or water by pressing together with the oxide generated during heating is disclosed. Further, in order to reduce the amount of residual coal, there is also a method of purging the inside of the copper pipe with an inert gas for annealing or sucking the gas inside.

A second method for preventing corrosion of copper pipes is to form a protective film on the inner surface of the pipe. For example, JP-A-6
JP-A-49620 discloses that the inner surface of a copper pipe is oxidized under appropriate conditions to reduce the amount of residual carbon in the pipe and forms an oxide film of CuO or / and Cu ₂ O (hereinafter referred to as a copper oxide film). A method is disclosed. Also, US Pat.
Japanese Patent Laid-Open No. 2000-242242 discloses a method of forming an Sn coating layer by performing Sn plating on the inner surface of a copper tube.

A third method is to improve the pitting corrosion resistance by alloying the copper forming the tube. As the corrosion-resistant copper alloy, a base material made of copper is used, and Mn, Sn, Al,
Ni, Mg, Zn, Si, Ti, Cr, Zr, Ag, A
One added with one or more elements selected from the group consisting of s and P has been developed. For example, the piping described in JP-A-6-184669 has Zr of 0.0
It is formed of a copper alloy containing 0.05 to 1 mass% of P, Sn, Ag, Ti or R (a rare earth element other than Y) in a small amount. This pipe has improved pitting corrosion resistance by containing Zr. This technology is the conventional example 2
And In addition, Kobe Steel Making Technique Vol. 38 No. Four
The copper tube described in (1988) is made of a Cu-Al-Sn-based alloy, and by adding a small amount of Al and Sn to Cu, it is possible to suppress an increase in the natural potential of the copper tube, and to remove phosphorus deoxidized copper. The pitting corrosion resistance can be improved as compared with a copper pipe made of. Hereinafter, this technique is referred to as Conventional Example 3.

Further, as a countermeasure from the viewpoint of the material for erosion, some techniques have been proposed as well as a countermeasure against pitting corrosion. For example, JP-A-8-120456 discloses a method of performing Sn plating on the inner surface of a copper tube. Further, JP-A-61-231131 discloses a technique for improving strength and corrosion resistance by alloying copper, and JP-A-9-242983 discloses a technique for coating an inner surface of a copper pipe with a resin. Has been done.

However, the first method described above, namely,
With the method for removing residual carbon and residual oil content as in Conventional Example 1, although the occurrence of pitting corrosion due to residual carbon and residual oil content can be suppressed, for example, when using well water, chlorine ions contained in this well water (Cl ^-), bicarbonate / sulfate ratio, can not be suppressed due to the direct corrosion factor corrosion solvents oxygen content and pH value, etc., is hard fundamental solution of pitting and潰食. Furthermore, in order to perform a method such as purging or suctioning an inert gas in the pipe, it is necessary to modify the annealing equipment, and it is necessary to lengthen the annealing time when removing residual carbon and residual oil from the long coil. Therefore, there is a problem that the productivity of the copper pipe is reduced.

Further, in the above-mentioned second method, that is, the method of forming the protective film on the inner surface of the tube, when the copper oxide film is formed as the protective film, the formed copper oxide film is brittle and the film thickness is However, since it is difficult to form a thick copper oxide film, the copper oxide film is easily consumed during use, and it is difficult to maintain sufficient corrosion resistance for a long time. Further, if the oxide film is partly peeled off, a local battery is formed in this peeled part, and the corrosion resistance is rather deteriorated.

Further, when the Sn coating layer is formed as a protective film, a plating treatment for forming the Sn coating layer is required. However, in order to perform plating inside a long copper tube, electroless plating is required. It is difficult to use other methods than plating. However, when plating is performed by the electroless plating method, defects such as pinholes are likely to occur in the plating film. In addition, if residual carbon, residual oil, oxides, etc. remain inside the copper pipe, the adhesion strength of the Sn plating decreases, and the plating film is likely to partially peel off. When the plating film is partly peeled off, a local battery is formed in this part and the corrosion resistance is rather deteriorated. Also,
For copper pipes used at high temperatures such as hot water supply copper pipes, S of Sn plating layer
There is a problem that n reacts with Cu forming the copper tube to change the Sn plating layer into a brittle intermetallic compound, so that the Sn plating layer easily peels off and the corrosion resistance decreases.

The third method, that is, the method of alloying copper described in Conventional Example 2 and Conventional Example 3 changes the natural electrode potential of copper due to alloying of copper, and the hardness of copper. Corrosion resistance is improved due to the hardened steel. However, alloying increases the deformation resistance and work hardening coefficient, so
There are problems that the number of times of annealing at the time of manufacturing increases and that it becomes difficult to manufacture a small-diameter pipe, and the manufacturing cost easily increases.

A method of coating the resin on the inner surface is also conceivable, but this method has a problem that the adhesiveness with the copper pipe is deteriorated due to the change of the resin with time. Further, there is a problem that the inner surface resin-coated copper pipe has low recyclability.

In order to solve the above-mentioned problems, the present inventors have proposed a method of coating the surface of a copper pipe with an amorphous inorganic ceramic to improve the corrosion resistance of the copper pipe without causing the above-mentioned problems. Developed, JP 2001-183089 A,
JP 2001-280890 A, JP 2001-2
It has been disclosed in JP-A-79474 and JP-A-2001-280891.

According to this method, it is possible to maintain good corrosion resistance such as pitting corrosion resistance and erosion resistance of the copper pipe for a long time over a wide temperature range from low temperature to high temperature regardless of the water quality which varies depending on the use environment. . In particular, in the coating anticorrosion method of copper or copper alloy, which has been a problem of peeling due to the difference in linear expansion coefficient with the coating material because the base material has an extremely large linear expansion coefficient,
By having an organic group in the molecular structure, it is possible to impart flexibility even though it is an inorganic material, and it is possible to provide a copper tube resistant to the above-mentioned various corrosions. Further, the heat exchanger for a water heater shows excellent corrosion resistance and acid resistance even in a severe environment in which the outer surface of the water passage portion is exposed to the strongly acidic condensed water.

The inorganic film such as amorphous ceramics is chemically stable to an aqueous fluid without reacting with water, an aqueous solution or the like. Further, since it has sufficient hardness, it is strong against friction with water. Therefore, when this inorganic film is formed on the surface of a copper pipe, for example, corrosion due to water flow in the copper pipe such as pitting and erosion, ant nest corrosion, ammonia, sulfurous acid gas, environmental factors such as hydrogen sulfide It has ideal characteristics for corrosion caused by condensed water containing these environmental factors and corrosion from the outer surface of the pipe, and has good corrosion resistance and acid resistance. Furthermore, it has excellent heat resistance. Furthermore, the copper pipe and the heat exchanger on which the inorganic film is formed are excellent in recyclability of the material as compared with the resin film, because the inorganic film is separated on the surface of the molten metal to become slag by remelting.

[0019]

However, the above-mentioned conventional techniques have the following problems. In the technology to prevent corrosion by forming an amorphous ceramics film on the copper tube and heat exchanger, the adhesion strength between the copper base material and the film is low depending on the manufacturing conditions, and the non-corrosion of the copper surface is The crystalline ceramic film may peel off and may not satisfy the desired function. That is, even if an inorganic coating is formed on the surface of a copper base material that has undergone a normal manufacturing process or on the surface of a copper base material that has been degreased and pickled, durability is inferior depending on the usage environment, and initial corrosion resistance, acid resistance and heat resistance There is a problem that the sex cannot be maintained.

As described above, when the adhesion between the copper surface and the amorphous ceramic film is insufficient, the film peels off. Therefore, even if the amorphous ceramic coating itself has excellent corrosion resistance, acid resistance, abrasion resistance, and heat resistance, the above-mentioned excellent characteristics cannot be maintained if the coating peels off. This problem is fatal in a copper tube and a heat exchanger used in a particularly severe environment, and it becomes impossible to maintain its characteristics and functions for a long period of time.

Further, in the above-mentioned conventional technique, the copper tube and the heat exchanger coated with the amorphous ceramics film are
It is manufactured through the steps of applying a liquid amorphous ceramics film-forming solution to the surface of a copper tube, etc., and heating the solution after application, but there are coating unevenness of the processing solution and a complicated shape on the outer surface of the heat exchanger. There may be a part where the coating is not formed after the coating is baked due to the uncoated portion of the part.
In this case as well, similarly to the case where the above-mentioned film is peeled off, it becomes a fatal defect for the copper tube and the heat exchanger.

That is, when the copper pipe and the heat exchanger are used in an acidic atmosphere or a high temperature atmosphere, oxidation corrosion is caused from a portion where the coating is not formed due to uneven coating and unpainted portion and a portion where the coating is lost due to peeling. Progresses,
The morphology of the surface changes. Therefore, the film starts to peel off from this portion. This vicious cycle is repeated to cause extensive corrosion and film peeling over a long period of time. In addition,
In Japanese Patent Laid-Open No. 2000-33327, when a treatment solution is applied to the surface of a copper pipe having a complicated shape to form an inorganic film, bubbles are generated on the surface of the copper pipe due to the surface shape of the copper pipe, and uneven coating occurs. In order to prevent the problem, a method is disclosed in which the treatment solution is ultrasonically vibrated and agitated, and further the pressure is reduced while the copper tube is immersed in the treatment solution. In addition, JP 2000
JP-A-336288 proposes a method of electrodeposition coating a film. However, neither method is realistic because the equipment cost increases significantly.

The present invention has been made in view of the above problems, and an inorganic coating excellent in corrosion resistance, acid resistance, wear resistance and heat resistance is applied to the surface of a copper pipe or a component of a heat exchanger for a water heater. In the method of forming on the above, a method of forming an inorganic film having high adhesion strength between the base material and the inorganic film and excellent durability, an inorganic film-coated copper or copper alloy member formed by this method, heat for a water heater An object of the present invention is to provide an exchanger and a manufacturing method thereof.

[0024]

Means for Solving the Problems Inorganic film coating according to the present invention
The copper-clad or copper alloy member is a member made of copper or a copper alloy,
By contacting this member with an alkaline aqueous solution,
It is formed on at least a part of the surface of the member and has a thickness of 10 to
1000 nm and Cu_TwoO and Cu (OH) _TwoOut of
An oxide film containing at least one and a shape on this oxide film
And an inorganic film formed.

In the present invention, an alkaline aqueous solution is brought into contact with the member to form an oxide film on the surface of the member, whereby the inorganic film is strongly bonded to oxygen or hydroxyl groups of the oxide film, so that the inorganic film and the member are separated from each other. The adhesion strength of can be improved. As a result, the durability of the inorganic film is improved, and excellent film adhesion is achieved in an environment where a mechanical load is applied by a high-speed water stream (water hammer) and in a severe environment where it is exposed to highly concentrated acidic water under a high heat cycle. The strength can be maintained. Further, by bringing the member into contact with the alkaline aqueous solution, the member and the oxide film have opposite polarities to the inorganic film. This strongly adheres the member and the oxide film to the inorganic film due to the electrodeposition effect. As a result, the wet spreadability is improved when forming the inorganic film, and the inorganic film can be formed without uneven coating. Therefore,
It is possible to prevent the occurrence of a portion where a film is not formed, and prevent a fatal decrease in life. Furthermore, since minute irregularities are formed on the surface of the oxide film,
Due to the anchor effect of the unevenness, the adhesion between the member and the oxide film and the inorganic film is further improved.

In the method for forming an inorganic film on the surface of a copper or copper alloy member according to the present invention, a member made of copper or a copper alloy is brought into contact with an alkaline aqueous solution so that at least a part of the surface of the member has a thickness of 10 to 1000 nm. And Cu ₂ O and Cu
The method is characterized by including a step of forming an oxide film containing at least one of (OH) ₂ and a step of forming an inorganic film on the oxide film.

The hot water heat exchanger according to the present invention is configured such that a can body made of copper or a copper alloy, a fin material made of copper or a copper alloy provided inside the can body, and the fin material are inserted. And a tube made of copper or a copper alloy connected to each other, and having a thickness of 10 to 1000 nm by contacting at least the inner surface of the can body and the outer surface of the tube with Cu ₂ O, An oxide film containing at least one of Cu (OH) ₂ is formed, and an inorganic film is formed on the oxide film.

A method of manufacturing a heat exchanger for hot water supply according to the present invention comprises a can body made of copper or a copper alloy, a fin material made of copper or a copper alloy provided inside the can body, and the fin material. A step of assembling a heat exchanger body having a tube made of copper or a copper alloy connected so as to be inserted, and contacting at least an inner surface of the can body and an outer surface of the tube with an alkaline aqueous solution; The outer surface has a thickness of 10 to 1000.
It has a step of forming an oxide film having a thickness of at least one of Cu ₂ O and Cu (OH) ₂ and a step of forming an inorganic film on the oxide film.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION As described above, the inorganic film formed on the surfaces of the copper pipes for water supply and hot water supply pipes and heat exchangers is used for a long time regardless of the difference in temperature, pipe flow velocity, external environment and water quality. Even if it does not peel off, it is necessary to maintain corrosion resistance, acid resistance, abrasion resistance, heat resistance and the like. Further, in the heat exchanger and the like, due to the harsh environment, if there is even a slight coating unevenness in the inorganic coating, that portion will be selectively eroded. Therefore, it is necessary that the coatability in the coating step of the inorganic coating treatment solution is good.

The inventors of the present invention have conducted diligent experimental research to solve the problems in forming an inorganic film on the surface of such a copper member, and as a result, performed a pretreatment on the surface of the copper member under appropriate conditions to obtain copper. By forming an oxide film containing at least one of Cu ₂ O and Cu (OH) _{2 on} the surface of the member and having a thickness of 10 to 1000 nm, and forming an inorganic film on the oxide film, the inorganic film is It has been found that it strongly binds to oxygen or a hydroxyl group of the oxide film, improves the coatability of the inorganic film coating material, and improves the adhesion strength between the copper member and the inorganic film.

Examples of the present invention will be specifically described below. In this embodiment, a pipe made of copper or a copper alloy (copper pipe) is used as a base material, and first, the surface of the copper pipe,
That is, the inner surface and the outer surface are degreased and washed to remove oil adhering to the surface. Next, the surface of this copper tube is washed with an acid to remove the oxide formed on the surface.
Then, the copper tube is immersed in an alkaline aqueous solution having a pH of 10 or more and an oxidizing agent at room temperature to contain at least one of Cu ₂ O and Cu (OH) _{2 on} the surface of the tube and has a thickness of 10 to 1000 nm. To form an oxide film.

Next, an inorganic film is formed on the oxide film. As the inorganic film, for example, a film having a Si—CH ₃ bond and a Si—O bond is formed. An alcohol is added to an alkoxide-based solution having a structure containing a Si—CH ₃ bond, a Si—O bond, and a hydroxyl group (—OH) at the end, represented by the following chemical formula 1, to give an appropriate concentration to prepare an inorganic film treatment solution. Then, this inorganic film treatment solution is applied to the surface of the copper substrate.

[0033]

[Chemical 1]

After that, the copper tube is heated to a temperature range of 50 to 600 ° C. in an inert gas or reducing gas atmosphere. As a result, the inorganic film treatment solution causes a dehydration condensation reaction, the oxygen of the hydroxyl group is cut off, and bonds with other oxygen or Si to form an amorphous ceramic film having a structure represented by the following chemical formula 2. . On the other hand, when the treatment solution undergoes a dehydration condensation reaction, unstable Cu ₂ O and / or Cu (OH) _{2 on} the outermost surface of the oxide film is also cut off from the bond in the film layer to form a surface of the oxide film. The coating solution and the coating solution come together to bond. Therefore, a structure having excellent adhesion strength between the oxide film and the formed inorganic film can be obtained. As described above, the treatment solution applied to the surface of the copper tube is subjected to heat treatment to form Si—CH ₃ bonds and S on the surface of the copper substrate.
A uniform amorphous inorganic film having an i-O bond is formed. Then, the copper tube is cooled to room temperature.

[0035]

[Chemical 2]

In this embodiment, Cu ₂ is formed on the surface of the copper tube.
By forming an oxide film containing O and / or Cu (OH) ₂ , when the inorganic film treatment solution is applied and heat-treated, the inorganic film becomes a copper substrate surface due to the dehydration condensation reaction of the inorganic film treatment solution. Of Cu ₂ O and / or Cu (OH) ₂ to improve the adhesion strength between the inorganic film and the copper substrate. Therefore, the formed inorganic film does not crack or come off.

Further, while metal oxides such as silica which form an inorganic film are usually “positively” charged, an oxide film made of copper oxide or cuprous oxide is pre-treated with an alkaline aqueous solution. , The copper base material and the oxide film are negatively charged, so that a simple electrodeposition coating state is formed between the copper base material and the oxide film and the inorganic film containing the metal oxide. . That is, Cu ₂ O and / or Cu on the copper surface
The oxide film containing (OH) ₂ has a polarity opposite to that of the treatment solution. Therefore, the inorganic coating treatment solution has excellent wettability and spreadability on the surface of the oxide coating, and even when coating on a surface having a complicated shape and structure, it has excellent coatability because it can prevent coating unevenness and unpainted residue. It is considered that this also contributes to the improvement of the adhesion strength between the copper base material and the inorganic film. Further, it is considered that the oxide film is formed on the surface of the copper base material to roughen the surface thereof, and the adhesion strength between the copper base material and the inorganic coating is improved by the anchor effect. That is, in this example, the adhesion between the copper base material and the inorganic coating is improved by (1) chemical bonding effect, (2) electrodeposition effect, and (3) anchor effect.

Even if an inorganic film is formed after the surface of the copper substrate is appropriately roughened by pretreating the copper substrate with an acidic aqueous solution, the adhesion strength between the copper substrate and the inorganic film is high. Does not improve much. Therefore, the improvement of the adhesion strength between the copper base material and the inorganic film by forming the oxide film is not only due to the anchor effect resulting from the shape of the oxide film,
It can be seen that it depends on the above-mentioned chemical bonding effect and electrodeposition effect.

Furthermore, the inorganic film formed as described above is (1) dense and impermeable to water, (2) hard and hard to wear due to abrasion with water (water or aqueous solution),
(3) The surface is smooth and does not disturb the flow of water, precipitation of insoluble matter contained in water is unlikely to occur, (4) Does not react with water, has water repellency, corrodes even if it is in water for a long time. (5) Because it is insulating, it does not easily precipitate ions that are dissolved in water. (6) It is stable over a wide temperature range from low to high temperatures, and is stable to water or environmental temperatures. Since it has many excellent properties such as maintaining stable corrosion resistance without depending on it, it is most suitable for giving corrosion resistance such as pitting corrosion resistance and erosion resistance to copper tube and heat exchanger, and acid resistance. .
Further, for example, when the copper tube or heat exchanger on which the inorganic film is formed is charged into the melting furnace as it is, the inorganic film is separated from copper in the melting process and floats on the surface of the molten metal to form slag, which is easy. Can be collected. It is possible to regenerate as copper by refining (degassing, pulling out) the molten copper after removing the slag and then casting. Therefore, the inorganic film-coated copper pipe of this example is also excellent in recyclability.

In the present invention, copper (copper or copper alloy) means oxygen-free copper, phosphorous deoxidized copper, tough pitch copper, Cu.
-Fe-P alloy, Cu-Mn-P alloy, Cu-Ni-S
The i alloy, the Cu-Sn-P alloy, the Cu-Zn alloy, and the like can be applied to all the other alloys so-called copper alloys. Further, from the viewpoint of adhesion strength between the copper base material surface and the inorganic coating, prevention of swelling at the interface between the copper base material surface and the inorganic coating, and the like, the amount of oxygen contained in the copper base material is 30 p.
It is desirable that the amount of hydrogen is pm or less and the amount of hydrogen is less than 2 ppm.

As the shape of the copper tube, there are a smooth tube mainly used for piping, an inner grooved tube mainly used as a heat transfer tube for a heat exchanger, a low fin tube, a corrugated tube and the like. It can be applied to copper pipes of any shape. Further, like a low fin tube, Kobe Steel top cloth and Kobe steel end cloth, it has a complicated shape such that the effective heat transfer area is increased by complexly plastically processing the surface of the heat transfer tube. Even on the surface of the heat transfer tube, it is possible to eliminate the unevenness of the film and improve the adhesion strength.

Further, the alkaline aqueous solution may be one that is usually used for a cleaning solution or the like, and may be an aqueous solution of an inorganic compound such as sodium hydroxide, potassium hydroxide or ammonium hydroxide, or an organic compound such as tetramethylammonium hydroxide or choline. It is also possible to use an aqueous solution.

Further, the oxidizing agent added to the alkaline aqueous solution includes dissolved air, oxygen, peroxide, hypochlorite, chlorite, perchlorate, persulfate, peroxosulfate and peroxodioxide. There are sulfates, permanganates, chromic acid, and soluble metal ions belonging to Group 3B (Group IIIB), Group 4B (Group IVB) and Group 5B (Group VB). Any material that acts as an oxidizing agent for the surface of copper or copper alloy can be applied.

The concentration of the oxidizing agent in the alkaline aqueous solution is appropriately selected depending on the etching speed and the surface oxidizing ability depending on the type of oxidizing agent, the temperature of the treatment solution, etc., but the concentration is usually 40 to 300 g / It is in the liter range. For example, in the case of hydrogen peroxide, the concentration is preferably 40 to 200 g / liter, and the concentration is 50 to 90 g if the treatment capacity is improved in consideration of productivity in order to obtain a specified oxide film thickness. / Liter is more preferable. Further, if necessary, by raising the temperature of the treatment solution to about 90 ° C., more excellent treatment capacity can be obtained. However, if the treatment is performed at a high temperature, it becomes difficult to obtain a uniform oxide film, the risk to the operator is increased, and the cost is increased. It is preferable to carry out the treatment with a hydrogen oxide concentration of 40 g / liter or less.

In the present invention, the inorganic film formed on the surface of a member such as a copper tube or a heat exchanger is the above-mentioned Si--CH ₃
The film is not limited to an amorphous ceramic film having a bond and a Si—O bond, and may be any inorganic film that generally deposits an amorphous ceramic solid phase from a liquid phase by a sol-gel method,
Further, it may be a polycrystalline film, a porous film or the like. Even when such an inorganic film is formed, the adhesion strength with the substrate can be improved by forming the above-mentioned oxide film. Therefore, even when an inorganic film is formed for the purpose of accelerating the heat transfer of the heat transfer tube, it contributes to the improvement of the adhesion strength and the reliability in terms of durability can be improved.

In addition, the inorganic film treatment solution contains the Si--CH ₃ bond, the Si--O bond and the hydroxyl group (--O) shown in this embodiment.
In addition to the alkoxide-based solution containing H), for example, Si
O ₂ , ZrO ₂ , Al ₂ O ₃ , TiO _{2 and the} like as a main component, a metal alkoxide-based polymer to which an inorganic filler, metal fine particles, whiskers and the like are appropriately added, to a suitable concentration with water and / or alcohol. It is also possible to use a diluted inorganic coating solution. Furthermore, the inorganic film treatment solution may be a hybrid polymer obtained by synthesizing an organic component in a metal alkoxide-based polymer, and a silane coupling material mainly used for the purpose of improving the adhesion between the inorganic material and the polymer is used. It may be contained. Even if these inorganic film treatment solutions are used, the same effect as that of this embodiment can be obtained.

The present invention is also useful for improving the adhesion strength of the inorganic hydrophilic film formed for the purpose of improving the wettability and spreadability of the dropped refrigerant in the heat transfer tube for the absorption refrigerator evaporator.

In this embodiment, an example of applying the inorganic coating treatment solution to the surface of the copper pipe has been shown. However, a copper pipe having an oxide coating formed on the surface of the copper pipe is dipped in this inorganic coating treatment solution or An inorganic coating treatment solution was sprayed onto the copper pipe, the inorganic coating treatment solution was sealed in a copper pipe and then drained, or the inorganic coating treatment solution was impregnated when the length of the copper pipe was short. The sponge ball may be passed through a copper tube to adhere the inorganic coating treatment solution to the surface of the copper tube.

The inorganic coating may be a single layer or two layers, that is, a primer layer may be formed as a lower layer coating and then an upper layer coating may be coated.
In order to improve the adhesiveness of the inorganic film, the adhesiveness with the upper layer is good, and there is a chemical affinity for the base copper and copper alloy, such as the thermal expansion coefficient and thermal conductivity. It is preferable to form a primer layer having a physical and thermal physical property close to that of the upper layer film, and more preferably having a large elasticity so as to follow the deformation of the base material as the lower layer.

The copper pipe having at least one of the inner surface and the outer surface coated with an inorganic film by the method of the present embodiment is a heat transfer tube incorporated in a heat exchanger for a water heater, a water supply hot water supply, an air conditioner heating construction, etc. Piping, room air conditioner in-flight piping,
In addition, it can be suitably used for in-machine piping of refrigerators and freezers of prefabricated type and showcase type. In the present invention, in view of the intended use of the copper tube, of the inner surface and the outer surface of the copper tube, select the surface to which functions such as corrosion resistance and hydrophilicity are to be imparted, and by the above-mentioned inorganic film forming method, The inorganic film can be formed. That is, the inorganic film may be formed on only one of the inner surface and the outer surface of the copper tube, or may be formed on both surfaces.

Further, in the heat exchanger for a water heater constituted by the copper fin material, the copper can body and the copper pipe by the inorganic film forming method as described above, the inorganic film is formed on at least the inside of the can body and the outer surface of the copper pipe. Can be formed. This makes it possible to manufacture a heat exchanger having excellent corrosion resistance against corrosion due to strongly acidic condensed water that is inevitably generated during operation. As described above, the heat exchanger in which at least a part of the surface is coated with the inorganic film can be suitably used for a heat exchanger for a water heater, a heat exchanger using water, and the like.

The reasons for limiting the numerical values which are the constituent features of the present invention will be described below.

Thickness of oxide film: 10 to 1000 nm When the thickness of the oxide film is less than 10 nm, the chemical composition of the oxide film becomes unstable and it is effective for chemically bonding the oxide film to the inorganic film. Film thickness becomes insufficient.
Further, if the thickness of the oxide film exceeds 1000 nm, it becomes extremely difficult to maintain the denseness of the oxide film, so that the oxide film may become brittle. When the strength of the oxide film decreases due to the oxide film becoming brittle, when the inorganic film is formed on this oxide film, the adhesion strength between the copper base material and the inorganic film cannot be maintained due to the destruction of the oxide film. . Therefore, the thickness of the oxide film is 10 to 1000n.
It must be m.

The thickness and composition of the oxide film on the copper substrate are preferably controlled in the oxide film treatment step, and the natural oxide film originally present on the surface of the copper substrate is degreased / degreased.
It is desirable to be removed in advance by the pickling process.

The method for measuring the thickness of the oxide film will be described below. There are two types of oxides of copper, cupric oxide (CuO) and cuprous oxide (Cu ₂ O). The valences of copper are divalent (Cu ²⁺ ) and monovalent (Cu ⁺ ), respectively. Is. Further, in the case of a copper alloy, an oxide of an alloy element may be formed in addition to the oxide of copper. The film thickness of such an oxide film can be measured by an electrochemical method (cathode reduction method). Actual oxide film is CuO, Cu
₂ O, Cu (OH) ₂ , oxides of additional elements, and the like are mixed, but in the present invention, the film thickness when they are all considered to be Cu ₂ O is defined as the oxide film thickness. The thickness of the oxide film is T (nm) and the molecular weight is M (Cu ₂ O: 143.
1 (g)), the current density is i (mA / cm ² ), the time required for the reduction of the oxide film is t (sec), the number of electrons for the reduction of one molecule of the product is n (Cu ₂ O: 2), Assuming that the density of the product is ρ (Cu ₂ O: 6.04 (g / cm ³ )) and the Faraday number is F (96500 (C / mol)), the thickness T of the oxide film is calculated by the following mathematical formula 1. be able to.
In the present invention, the film thickness of the oxide film is measured by this electrochemical method.

[0056]

[Equation 1]

In the electrochemical method described above, it is possible to measure the film thickness of the oxide film when all the components of the oxide film are assumed to be Cu ₂ O, but the composition of the oxide film,
For example, it is not possible to measure the content of Cu (OH) ₂ . The composition of the oxide film is measured by X-ray electron spectroscopy (X-Ra
y Photoelectron Spectroscopy: XPS method, also called ESCA). The oxide film on the surface of the copper substrate to be measured is irradiated with X-rays, and the kinetic energy of photoelectrons emitted from the oxide film by the photoelectric effect is measured. This kinetic energy is the difference between the energy of incident X-rays and the binding energy of electrons in the oxide film.
The binding energy of an electron is chemically shifted depending on the binding state of the atom, and if the binding state of the atom is different, the binding energy of the electron is different.Therefore, the binding state of the atom can be investigated by detecting the kinetic energy spectrum of photoelectrons. You can For example, the hydroxide and oxide of copper can be specified by measuring the narrow-range photoelectron spectrum of the Cu ₂ p ₃ orbital, which is the spectrum derived from the hydroxide and copper oxide of copper. Specifically, Cu (OH) ₂ , CuO,
The spectral peaks of the Cu ₂ p ₃ binding energy corresponding to Cu ₂ O are Cu (OH) ₂ : 935, 1 eV,
Since CuO: 933.7 eV and Cu ₂ O: 932 eV are typically expressed, Cu (OH) ₂ , CuO and Cu ₂ O can be detected by detecting these peaks. However, since these spectral peaks change somewhat depending on the measurement equipment and measurement conditions,
It is preferable to make appropriate corrections using standard values attached to the measuring device. Further, the surface of the oxide film is sputtered by an ion sputtering device equipped in the XPS measuring device, and the above-mentioned copper hydroxide and Cu derived from the oxide are used.
_{By 2} p ₃ binding energy measure the sputtering time until no longer detected, it is possible to measure the film thickness of the oxide film. As described above, the film thickness and composition of the oxide film by the XPS method, that is, Cu (OH) ₂ , Cu
The contents of O and Cu ₂ O can be measured simultaneously. Therefore, when the film thickness of the oxide film is measured, in addition to the electrochemical method described above, the measurement by the XPS method is performed if necessary, and the measurement result of the XPS method can be used as a reference value.

PH value of alkaline aqueous solution : 10 or more When the pH value of the aqueous solution is in the alkaline range, the higher the pH value is, the more accelerated the elution of copper and the oxidation of copper ions eluted on the copper surface are. If the pH value of the aqueous solution is less than 10, the reaction rate will be slow even if the temperature of the aqueous solution is increased, or copper for forming an oxide film will hardly elute, and the productivity will be reduced.

Further, according to this treatment method, the addition of an oxidizing agent to the alkaline aqueous solution can promote the formation of a cuprous oxide film on the copper surface of the eluted copper ions. Even in this case, when the pH value is less than 10, the elution of copper is suppressed and it becomes impossible to form a desired cuprous oxide film. Therefore, the pH value of the alkaline aqueous solution is preferably 10 or more.

Furthermore, as described above, in contrast to the fact that the metal oxides such as SiO ₂ which are the main components of the inorganic coating are usually charged “positively”, copper and copper which have been pretreated with an alkaline aqueous solution are used. Since the alloy base material and the copper oxide and cuprous oxide are negatively charged, a simple electrodeposition coating effect can be obtained by applying an inorganic metal oxide on the surface thereof. Therefore, the pH value of the alkaline aqueous solution for pretreatment is preferably 10 or more.

Temperature of alkaline aqueous solution: normal temperature or 90 ° C.
In the present invention, a desired oxide film treatment can be performed even at room temperature by using an alkaline aqueous solution having a pH value of 10 or more. In addition, alkaline aqueous solution at 90 ℃
By performing an oxidation treatment by heating in the following temperature range,
The processing speed can be increased and the productivity can be improved. However, if the temperature of the alkaline aqueous solution exceeds 90 ° C., not only the concentration of the aqueous solution becomes difficult to control due to severe evaporation from the surface of the water, but also local heating during processing may cause bumping. Safety considerations are required. Therefore, it is preferable that the alkaline aqueous solution is heated at room temperature or 90 ° C. or lower.

Further, even when the alkaline aqueous solution is used at room temperature, it is desirable to control the temperature of the alkaline aqueous solution so as to suppress the temperature change due to factors such as seasons. When the alkaline aqueous solution is used at room temperature, if the water temperature is 10 ° C. or higher, the oxide film can be sufficiently formed by the treatment for 1 hour or longer. The processing time is more preferably 3 hours or more.

On the other hand, when the alkaline aqueous solution is heated to a temperature of 90 ° C. or lower, if the treatment time is too long, the oxide film becomes thicker than necessary. Usually, the oxide film formed on the surface of the copper substrate is easy to form a laminated structure of granular oxides, and if the film thickness becomes too thick, it becomes difficult to form a dense oxide film, and The quality of the film becomes brittle. If the treatment time is too long, the film thickness of the oxide film becomes unnecessarily large, making it difficult to form a dense oxide film, resulting in a porous brittle film. Further, the average diameter of the granular oxide becomes too large, and the effect of improving the coatability due to the capillary phenomenon is lost. Thus, if the treatment time is too long, many of the excellent features of the oxide film of the present invention will be lost. Therefore,
When the alkaline aqueous solution is heated to 90 ° C. or lower, the time required for the treatment is preferably 10 to 1200 seconds,
More preferably, it is 100 to 600 seconds.

Heating atmosphere for forming an inorganic film: inert
In a gas atmosphere or a reducing gas atmosphere, if the film baking treatment is performed in the atmosphere, not in an inert gas atmosphere, the heating temperature becomes high (150 ° C. or higher) or low temperature (less than 150 ° C.) performs long-time heating. As a result, an oxide is formed on the surface of the copper substrate when the inorganic film is cured, and the inorganic film cannot adhere to the copper substrate, or even if it adheres, the oxide layer becomes thick and extremely brittle. Therefore, the adhesion strength of the inorganic film is reduced. Therefore, the heat treatment for forming the inorganic film is preferably performed in an inert gas or reducing gas atmosphere.

Heating temperature for forming an inorganic film: 50 to
600 ° C The heating temperature for forming an inorganic film, that is, the film baking temperature is 5
When the temperature is lower than 0 ° C., the dehydration condensation reaction required for curing the treatment solution is not promoted and the firing step requires a lot of time, which is not practical. On the other hand, the film firing temperature is 600 ° C
When it exceeds, the dehydration condensation reaction is accelerated more than necessary, and the volume of the inorganic film is reduced by dehydration,
The residual stress inside the coating becomes extremely large. As a result, defects such as cracks tend to occur in the coating film at last. Therefore, the film firing temperature is preferably 50 to 600 ° C.,
Since the influence of the high temperature side factor is great, it is more preferable that the temperature is 100 to 300 ° C.

[0066]

EXAMPLES The effects of the examples of the present invention will be specifically described below in comparison with comparative examples that depart from the scope of the claims.

First Test Example In this test example, a copper tube and a copper plate were used as the base material. The copper pipe was subjected to a running water test, and the copper plate was subjected to a cross-cut test and an acid water corrosion test. The test level of each test was set to 20 and the copper tube and copper plate as the base material were prepared so that the N number was 2 for each test.

FIG. 1 is a side view showing a copper tube used in this test example. For copper tubes, JIS H3300 C12
20 is a phosphorous deoxidized copper pipe according to 20, and has an outer diameter of 15.88 m.
m, thickness 0.6 mm, length 400 mm, and tempered O material phosphorous deoxidized copper pipe was used. This copper tube is cast → rolled →
The pipe was manufactured by the steps of drawing, winding, straightening, and annealing. Next, the copper tube was bent for a running water test.
Bending of the copper pipe was performed using a hand bending bender for piping. As shown in FIG. 1, the shape of the copper tube 20 after bending is L with one bent portion formed at the center in the longitudinal direction.
B-shaped with a bend radius of 57.15 mm and a bend angle of 9
The distance from the intersection of the tube axes passing through both ends to each tube end is 212.26 mm.

JIS H3100 C122 is used for the copper plate.
The phosphorous deoxidized copper plate described in No. 0, having a plate width of 23 mm, a length of 100 mm, a plate thickness of 0.3 mm, and a temper of O material was used. A strip having a width of 120 mm was manufactured by the steps of casting-rolling-winding-annealing.

Next, the inner and outer surfaces of the copper tube and the surface of the copper plate were pretreated by the following method to form an oxide film, and then an amorphous ceramic film was formed. The pretreatment of the surface of the base material (copper tube and copper plate) is a degreasing process (alkali degreasing) for the base material surface → a water washing process (neutralization).
→ Chemical polishing process → Oxide film treatment process → Water washing process (neutralization)
Went through. The chemical polishing was performed by immersing the test material in an aqueous solution in which a hydrogen peroxide solution having a concentration of 3% was added to a sulfuric acid aqueous solution having a concentration of 75% to remove the natural oxide film on the surface of the base material.

Next, the base material (copper tube and copper plate) was immersed in an alkaline aqueous solution to form an oxide film. As the alkaline aqueous solution, a treatment solution prepared by adding 15 g of sodium hydroxide to 1 liter of ion-exchanged water was used. Sodium perchlorate (NaClO ₄ ) was added to the alkaline aqueous solution as an oxidizing agent. The pH value of this alkaline aqueous solution was adjusted to 12, but for comparison, a treatment solution was also prepared in which an appropriate amount of HCl was added to adjust the pH to 5 and 9. The temperature of these alkaline treatment solutions is from room temperature to 90 ° C,
The substrate was dipped. At this time, the immersion time was adjusted so that the film thickness of the oxide film was 10 to 1000 nm.

Next, an amorphous ceramics film, which is an inorganic film, was formed on the oxide film. Amorphous ceramic film is formed by applying an inorganic film treatment solution on each surface,
The heating was performed at a predetermined temperature to form an amorphous ceramics film. As a treatment solution, a stock solution of Ceramica G1-50 manufactured by Nittetsu Institute was used. The treatment solution was filled in a poly container having a volume of 30 liters, and the pretreated substrate was immersed in the treatment solution, and the immersed state was maintained for 5 minutes. Then, the base material was pulled up and air blown with a dryer. This air blowing is performed to remove the excessively attached processing solution and form an amorphous ceramics film uniformly in the subsequent step. Then, the substrate having the treatment solution attached thereto was placed in a drying oven having a temperature of 50 ° C., and the substrate was held in the drying oven for 5 minutes to be dried.

Next, the dried base material was placed in a vacuum electric furnace, and after vacuuming, the inside of the drying furnace was replaced with nitrogen gas having a purity of 99.99%, and the temperature inside the furnace was raised to 200.degree. The test piece was heated. As a result, the treatment solution was dehydrated and condensed, and an amorphous ceramics film was formed on the surface of the base material. The temperature raising and lowering conditions of the test material were such that the temperature rising rate from 30 ° C. to 200 ° C. was 60 ° C./min, and the holding time at the temperature of 200 ° C. was 3
0 minutes, the temperature decrease rate from 200 ℃ to 30 ℃ is 30 ℃
/ Min.

Thereafter, for the copper tube, in order to obtain a test material having a uniform film, 20 mm was cut from each end of the tube, and the test material was collected from the rest. Also, for copper plates, in order to obtain a test material with a uniform coating, about 20 m from both ends of the strip
The portion m was cut off, and the test material was cut out from the portion having the remaining width of 80 mm. In this way, it was possible to obtain the test material in which the oxide film was formed on the surface of the base material and the amorphous ceramics film was formed thereon. The amorphous ceramic film thus obtained had a film thickness of 0.8 to 1.20 μm, which was almost constant.

Next, each evaluation method of the test material manufactured as described above will be described. The evaluation of the adhesion strength between the amorphous ceramics film and the substrate is performed according to JIS K5400.
The test was performed by the "cross-cut tape method (8.5.2.)".
Hereinafter, a method of evaluating the adhesion strength of the film by the cross-cut tape method will be described. The test material used was the above-mentioned phosphor-deoxidized copper plate as a base material on which an amorphous ceramics film was formed. The distance between the grids is 1 mm,
The number of squares was 100. After the test, the evaluation points of 10 points were evaluated as “◯”, 9 points and 8 points were evaluated as “Δ”, and the other points were evaluated as “x”.

Next, the running water test method will be described. This running water test is a test for evaluating the peel resistance and erosion resistance of the inorganic film. As described above, after forming an oxide film on a copper tube which was previously bent, an amorphous ceramics film was formed to obtain a test material. Further, for comparison, a copper tube that was similarly bent and was not formed with an amorphous ceramic film was also prepared. The temperature of the test material is 25 ° C
The following aqueous solution of was circulated at a flow rate of 4.0 m / sec for 6 months. The aqueous solution had a pH of 6.5 and a chloride ion (Cl ⁻ ) concentration of 1000 ppm. Chloride ion was added with sodium chloride and pH was adjusted with sulfuric acid.

After the test, the copper tube was half-cut and the inner surface of the copper tube was observed to determine whether patina was generated. In addition, the cross section of the part where the patina or discoloration occurred in the test material was observed with an optical microscope to measure the corrosion depth, and the occurrence of erosion was confirmed. Thereby, the peel resistance of the film was evaluated. When the corrosion depth was 0.02 mm or more, it was determined that erosion had occurred, and the evaluation was "x". The case where patina was generated but the corrosion depth was less than 0.02 mm was marked with “Δ”, and the case where neither patina nor discoloration was found was marked with “◯”.

Next, the acid water corrosion test will be described.
This acidic water corrosion test is a test for evaluating the acid resistance of the test material by evaluating the presence or absence of pinholes. The pinhole means an uncoated portion of the coating material caused by uneven coating. As the test material, the test material having the above-mentioned phosphorous deoxidized copper plate as a base material was used. Ion-exchanged water 50 for test water
The pH value of nitric acid (HNO ₃ ) was 2.5 in 0 ml.
It was added until it was used. Test water and test materials are immersed in a sealed bottle with a volume of 1 liter and sealed.
It was kept for 168 hours (1 week) in a warmed atmosphere.
When pinholes are present in the inorganic film, acidic water permeates through the pinholes to form a crystalline corrosion product between the film and the surface of the material, causing the film to peel off. Since the corrosion product exhibits a unique discoloration (purple color), the presence or absence of pinholes can be easily determined by checking the presence or absence of discoloration. The evaluation confirmed the existence of pinholes, and
The case where the film was peeled off was marked with "x", the case where a pinhole was confirmed but no further film peeling was marked with "△", and the case where there was no pinhole was marked with "○".

The thickness of the oxide film was measured by the cathode reduction method described above. In addition, the thickness of the amorphous ceramic film is S
About 5,000 to 200 by EM (scanning electron microscope)
It was measured by observing at a magnification of 00 times. It was confirmed by the above-described ceramic film forming method that the film thickness of each part of the amorphous ceramic film was uniform at about 1.0 μm.

Table 1 shows the conditions for forming an oxide film and the test results of each of the above tests in this test example. In the examples and comparative examples described below, regardless of whether the test material is a copper tube or a copper plate, the pretreatment process shown in Table 1 and the above-mentioned amorphous ceramics film formation treatment process were performed. It is a thing. The "room temperature" shown in Tables 1 and 2 is room temperature, and is about 15 to 25 ° C.

[0081]

[Table 1]

No. 1 shown in Table 1 1 to 12 are embodiments of the present invention. Example No. In each of Nos. 1 to 12, since the oxide film had a thickness of 10 to 1000 nm, the adhesion strength between the copper base material and the amorphous ceramics film was high, and all evaluation items were “Δ” or more. there were. In particular, Example No. In Nos. 2 to 12, since the oxide film had a sufficiently large thickness of 24 nm or more, all evaluation items were “◯”.

On the other hand, No. 1 shown in Table 1 was used. 13 to 20 are comparative examples. Comparative Example No. In No. 13, since the oxide film thickness was 1100 nm, which was beyond the specified range, the oxide film became brittle and a strong adhesion strength could not be obtained. Therefore, the evaluation results of the cross cut test, the running water test, and the acid corrosion test were all “x”.

Comparative Example No. In Nos. 14 to 19, the oxide film had a thickness of less than 10 nm, which was thinner than the specified range. As a result of SEM observation of the surface of the base material, the irregularities formed by the oxide of copper were unclear. For this reason, a sufficient anchoring effect with the ceramic film cannot be obtained, and the chemical bond between the oxide film and the ceramic film is insufficient, so that a strong adhesion strength cannot be maintained.

Further, in Comparative Example No. No. 20 is the one in which the ceramic film is formed on the natural oxide film formed on the surface of the copper base material without performing the treatment with the alkaline aqueous solution. Since this natural oxide film has a thin film thickness of 3.0 nm and is not treated with an alkaline aqueous solution, all of the adhesion effect, the electrodeposition effect and the anchor effect due to the chemical bond with the ceramic film are insufficient. However, sufficient adhesion strength of the ceramic film could not be obtained.

Second Test Example In this test example, the performance of the heat exchanger was tested. FIG. 2 is a perspective view showing a heat exchanger for a water heater evaluated in this test example, and FIG. 3 is a view showing a heat exchange section in the heat exchanger shown in FIG. As shown in FIG. 2 and FIG. 3, the heat exchanger to be tested in this test example is a body 1 made of a phosphorus deoxidized copper plate (JIS H3100 C1220), and a phosphorus deoxidized copper plate provided inside the body 1 ( J
A plurality of fins 3 made of IS H3100 C1220) and a phosphorus deoxidized copper pipe (JIS H3300 C1) which is spirally wound around the outer peripheral surface of the body 1 and brazed.
220) and a phosphorus deoxidized copper pipe (JIS H3) connected to the body winding pipe 2 and brazed to the fins 3
And a fin tube 4 made of 300 C1220).
The fin tubes 4 are connected to each other outside the body 1 by the U bend tube 1
The water inlet pipe 5 is connected to the inlet side of the body winding pipe 2, and the hot water outlet pipe 9 is connected to the outlet side of the fin pipe 4. As a result, the water inlet pipe 5, the fin pipe 4, the U bend pipe 18, and the hot water outlet pipe 9 form a single pipe. The ends of the water inlet pipe 5 and the hot water outlet pipe 9 that are not connected to the fin pipe 4 are pipe ends 17. The heat exchange section 6 is composed of the fins 3 and the fin tubes 4, and the fin tubes 4 are arranged in multiple stages in the upper part of the heat exchange section 6. A burner 7 is arranged below the heat exchange section 6 and the body 1. Further, a can body is formed by the body 1 and the body winding tube 2.

The brazing material for brazing the fins 3 and the fin tubes 4 is phosphor copper braze (JIS Z3264 BCuP-
2) was used. The brazing method is arranged in multiple stages 7
The fin-shaped tube 4 is penetrated through the fin-tube through-holes (not shown) of the six fins 3, and a rod-shaped phosphor copper brazing filler is inserted along the fin-shaped tube 4 to fix the heat-exchanger. Was placed in a vacuum furnace, and after evacuation, the inside of the furnace was replaced with nitrogen gas having a purity of 99.99%, the temperature inside the furnace was raised to 850 ° C, and the heat exchanger was heated to 700 to 800 ° C. The heating was performed to a certain degree and the temperature was maintained for 10 minutes. Cooling was performed by furnace cooling in the same atmosphere.

Joining portion 15 other than the heat exchanger 6 shown in FIG.
The joining of Nos. 16 and 16 was performed by hand brazing with an acetylene burner after bringing the tubes into contact with each other after completing the brazing in the heat exchange section 6. It should be noted that N ₂ gas having a purity of 99.99% was filled and vented into the tube for brazing so that the inside of the tube was not oxidized during the brazing operation of the heat exchange part 6 and other parts. Twenty such heat exchangers were produced.

After the completion of all the brazing operations, the outer surface of the body 1 and the inner surface of the entire length of the body including the body winding tube 2, the fin tube 4, the water inlet pipe 5 and the hot water outlet pipe 9 and all of the water inlet pipe 5 and the hot water outlet pipe 9 are excluded. The outer surface of the portion was subjected to a ceramic film forming treatment. The oxide film forming treatment on the inner surface of the copper pipe was performed by introducing the above-mentioned alkaline treatment solution into the pipe by a chemical pump. The flow rate of the alkaline processing liquid to the inner surface of the copper tube was set to about 5.0 liters / minute. The oxide film forming treatment on the outer surface of the copper pipe was performed by immersing the heat exchanger in the alkali treatment solution. Table 2 shows the oxide film forming conditions at this time.

After the oxide film was formed under the conditions shown in Table 2 as described above, the ceramic film was formed. First, a vessel having a volume of 30 liters was filled with the coating treatment solution to immerse the heat exchanger 6, and at the same time, the coating treatment solution was injected into the pipe, both ends 17 of the pipe were sealed with a silicon stopper, and held for 1 minute. After the pulling, compressor air was blown to the outer surface of the heat exchanger 6 to remove the excess coating solution. Also,
The coating solution in the tube was drained and the residual liquid was discharged by air blow. After that, the heat exchanger 6 was held in a drying oven kept at 65 ° C. for 5 minutes to be dried. Next, the inside of the tube was replaced with N ₂ gas having a purity of 99.99% so that the atmosphere remaining in the tube did not oxidize the copper tube base material, and a prescribed heat treatment was performed.

After that, the hot-water supply heat exchangers thus produced were each incorporated into a hot-water supply device, and an operation test was conducted. Kerosene was used as the fuel for the heat exchanger. Pilot operation by repeating hot water supply and stoppage was continuously performed for one week on these heat exchangers. FIG. 4 is a diagram showing a hot water supply / stop cycle pattern in this pilot operation.

After the pilot operation was completed, the heat exchanger including the water supply pipe 5 and the hot water supply pipe 9 was taken out from each water heater, and the sulfur dioxide test described in JIS H8502 was conducted. The sulfur dioxide test was carried out by keeping in an environment of a temperature of 40 ° C. and a humidity of 90% for 96 hours. The method of determining the degree of corrosion is to visually observe the appearance of the heat exchanger after the test and evaluate the degree of occurrence of discoloration due to oxidation and patina,
A sample was taken from this discolored portion and the degree of peeling of the coating and the degree of defects were evaluated. The judgment is “○” when there is no discolored part in the heat exchanger, “△” when partial oxidation or discoloration due to film pinholes and cracks is observed, and severe oxidation over a wide area due to film peeling. -When the occurrence of patina was recognized, it was marked as "x".

In the heat exchanger of this test example, oxidation discoloration at the bottom of the heat exchange section and black discoloration (soot) due to soot emitted from kerosene fuel occurred at the end of pilot operation. The discoloration generated after the sulfur dioxide test was not included in the target and was evaluated. Table 2 shows the test results of the sulfur dioxide test.

[0094]

[Table 2]

No. shown in Table 2 21 to 32 are embodiments of the present invention. Example No. In Nos. 21 to 32, the thickness of the oxide film was in the range of 10 to 1000 nm, and therefore no discoloration spot was observed over a wide area. In particular, Example No. In Nos. 22 to 32, since the oxide film had a sufficiently large thickness of 24 nm or more, no discoloration due to oxidation or patina was observed at all. In addition, Example No. In Nos. 21 to 32, the copper pipe was halved over the entire length and the state of the inner surface of the copper pipe was observed, but it was confirmed that no damage due to pilot operation was observed. In this way, the example No. 21 to 3
The heat exchanger of No. 2 had excellent corrosion resistance and heat resistance.

On the other hand, No. 1 shown in Table 2 was used. 33 to 40 are comparative examples. Comparative Example No. In No. 33, the oxide film thickness was 1100 nm, which was beyond the specified range, so that the oxide film became brittle and a strong adhesion strength could not be obtained. Therefore, as a result of performing the sulfur dioxide test on the heat exchanger, the film peeled off, and intense oxidation and patina formation were observed over a wide area.

Comparative Example No. In Nos. 34 to 39, the thickness of the oxide film was less than 10 nm, which was less than the specified range. Therefore, in the heat exchanger after the sulfur dioxide test, generation of oxidation and patina was observed. In addition, Comparative Example No. 34 to 39
The areas where a large amount of patina was observed were concentrated in the gap forming portion between the fins 3 and the fin tubes 4 where dew condensation water is likely to stay and in the vicinity thereof, and in the gap forming portion between the body 1 and the body winding tube 2.

Further, in Comparative Example No. 40 is the one in which the ceramic film is formed on the natural oxide film formed on the surface of each member constituting the heat exchanger without the treatment with the alkaline aqueous solution. This natural oxide film has a thickness of 3.
Since it is as thin as 0 nm and is not treated with an alkaline aqueous solution, all of the adhesion effect, the electrodeposition effect and the anchor effect due to the chemical bond with the ceramic film are insufficient, and sufficient adhesion strength of the ceramic film is obtained. I couldn't do it. Therefore, in Comparative Example No. In the heat exchanger of No. 40, the ceramic film was peeled off, and intense oxidation and patina generation were observed over a wide area.

[0099]

As described in detail above, according to the present invention,
To form an inorganic film with high adhesion strength without uneven coating, excellent corrosion resistance, heat resistance, acid resistance, and durability on the surface of copper or copper alloy members such as components of heat exchangers for water heaters. You can

[Brief description of drawings]

FIG. 1 is a side view showing a copper tube used in a first test example.

FIG. 2 is a perspective view showing a heat exchanger for a water heater evaluated in a second test example.

FIG. 3 is a diagram showing a heat exchange section in the heat exchanger shown in FIG.

FIG. 4 is a diagram showing a hot water supply / stop cycle pattern in a pilot operation.

[Explanation of symbols]

1; torso 2; Body tube 3; Fin 4; Fin tube 5; Water pipe 6; Heat exchange section 7; Burner 9; Hot water pipe 15, 16; joints 17; pipe end 18; U bend tube 20; Copper tube

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) B32B 9/00 B32B 9/00 A 15/04 15/04 Z C23C 22/63 C23C 22/63 26/00 26/00 C F24H 9/00 F24H 9/00 A F28F 19/02 501 F28F 19/02 501D 21/08 21/08 E (72) Inventor Saiki 65 Hirazawa, Hadano City, Kanagawa Prefecture Kobe Steel Works, Hadano Factory F term (reference) 3L036 AA01 4D075 AA01 AB01 BB26Z BB65X BB76Y BB77Y BB92Y BB93Y BB93Z CA02 CA13 CA18 CA33 CA44 DA15 DA19 DA20 DB06 DC16 EA06 EA07 EA12 EB43 EB47 4F100 AA00C AA17B AB17A AB31A AD00C AH08C AK79C BA03 BA07 BA10A BA10C DA11 EH112 EH462 EJ422 EJ482 EJ642 GB48 GB51 JA12C JA20B JB01 JB02 JJ03 JK06 JK09 JK11 JL00 YY00B 4K026 AA06 BA08 BB08 CA15 CA18 CA22 CA33 CA34 CA35 DA03 EA08 EB02 EB07 4K044 AA06 AB03 BA12 BA13 CA14 BB03 BB17 BC02 CA44 CA15 CA16 CA15 CA15 CA15

Claims (16)

[Claims] 1. A member made of copper or a copper alloy, and an alkaline aqueous solution are brought into contact with the member to form at least a part of the surface of the member and have a thickness of 10 to 1000.
An inorganic film-coated copper or copper alloy member having an oxide film having a wavelength of at least 1 nm and containing at least one of Cu ₂ O and Cu (OH) ₂ , and an inorganic film formed on the oxide film. 2. The inorganic film-coated copper or copper alloy member according to claim 1, wherein the member is a tube. 3. The inorganic film-coated copper or copper alloy member according to claim 1, wherein the inorganic film is formed of amorphous ceramics. 4. A member made of copper or a copper alloy is contacted with an alkaline aqueous solution, and at least a part of the surface of the member has a thickness of 10 to 1000 nm and Cu ₂ O and Cu (O ₂
H) a step of forming an oxide film containing at least one of ₂ , and a step of forming an inorganic film on the oxide film,
A method for forming an inorganic film on the surface of a copper or copper alloy member, which comprises: 5. The method for forming an inorganic film on the surface of a copper or copper alloy member according to claim 4, wherein the member is a tube. 6. The step of forming the oxide film comprises a step of degreasing and cleaning the member to remove oil adhering to the surface of the member before the step of contacting the member with an alkaline aqueous solution, A step of cleaning the member with an acid to remove the natural oxide film formed on the surface of the member;
The method for forming an inorganic film on the surface of a copper or copper alloy member according to claim 4 or 5, further comprising: 7. The alkaline aqueous solution is at room temperature,
Alternatively, the method of forming an inorganic film on the surface of a copper or copper alloy member according to any one of claims 4 to 6, wherein the method is heated to a temperature of 90 ° C or lower, and has a pH of 10 or higher. . 8. The method for forming an inorganic film on the surface of a copper or copper alloy member according to claim 4, wherein the alkaline aqueous solution contains an oxidizing agent. 9. The oxidizing agent is dissolved air, oxygen, peroxide, hypochlorite, chlorite, perchlorate, persulfate,
Selected from the group consisting of peroxosulfates, peroxodisulfates, permanganates, chromic acid, soluble metal ions belonging to Group 3B, soluble metal ions belonging to Group 4B and soluble metal ions belonging to Group 5B. The method for forming an inorganic film on the surface of a copper or copper alloy member according to claim 8, wherein the method is a single substance or a mixture of two or more substances. 10. The method for forming an inorganic film on the surface of a copper or copper alloy member according to claim 4, wherein the inorganic film is formed of amorphous ceramics. 11. The step of forming the inorganic coating is an inorganic coating treatment solution containing a polymer of a metal alkoxide, diluted with at least one of water and alcohol, and causing a dehydration condensation reaction on heating, on the surface of the member. A step of adhering and a step of dehydrating and condensing the inorganic coating treatment solution by heating in an inert gas or reducing gas atmosphere to a temperature range of 50 to 600 ° C. to form an inorganic coating on the surface of the member. The method for forming an inorganic film on the surface of a copper or copper alloy member according to any one of claims 4 to 10, characterized by comprising. 12. The copper or copper alloy member surface according to claim 11, wherein the step of adhering the inorganic film treatment solution to the surface of the member is performed by a coating method, a spray method or a dipping method. Method for forming inorganic film. 13. A can body made of copper or copper alloy, a fin material made of copper or copper alloy provided inside the can body, and made of copper or copper alloy connected so as to pass through the fin material. of has a tube, a is from 10 to 1000nm thick by contacting the alkaline aqueous solution to the outer surface of the inner surface and the tube of at least the can body Cu 2 _O and Cu (OH)
_A heat exchanger for hot water supply, wherein an oxide film containing at least one of the _two is formed, and an inorganic film is formed on the oxide film. 14. The hot water heat exchanger according to claim 13, wherein the inorganic coating is formed of amorphous ceramics. 15. A can body made of copper or a copper alloy, a fin material made of copper or a copper alloy provided inside the can body, and a copper body or a copper alloy connected so as to pass through the fin material. Assembling the heat exchanger main body having the tube and the inner surface of the can and the outer surface of the tube are brought into contact with an alkaline aqueous solution so that the inner surface and the outer surface have a thickness of 10
To 1000 nm and forming an oxide film containing at least one of Cu ₂ O and Cu (OH) ₂ .
And a step of forming an inorganic coating on the oxide coating, the method for manufacturing a heat exchanger for hot water supply. 16. The method for manufacturing a heat exchanger for hot water supply according to claim 15, wherein the inorganic coating is formed of amorphous ceramics.