JP7387089B2 - Method for forming sulfur-resistant coating on refrigeration circuit equipment - Google Patents

Description

The present invention provides a refrigeration circuit that is exposed to an atmosphere containing sulfur components, and which has a two-layer coating of epoxy resin and polyurethane resin formed on the outer surfaces of related equipment and copper pipes in the refrigeration circuit equipment, including the welded parts. This invention relates to a method for forming a sulfuric coating.

As is generally known, the refrigeration circuit installed in a refrigerator consists of an evaporator, compressor, condenser, pressure reducer, etc. connected with copper piping to form a refrigerant circulation path. By evaporating the refrigerant, the inside of the refrigerator is cooled by the heat of vaporization of the refrigerant. In the evaporator, refrigerant flows through copper pipes, and the copper pipes are welded together. Further, the copper piping connected to the copper pipe of the evaporator is covered with a heat insulating tube in order to keep the temperature of the refrigerant flowing inside the evaporator at a low temperature (see Patent Documents 1 and 2).

Regarding corrosion on the copper surface, the surface of ordinary winding wire is coated with a baked-on layer of insulating paint such as polyester resin or polyurethane resin on the conductor such as copper wire to reduce the slippage between the wires. In order to provide a rectangular litz wire that prevents twisting from becoming untwisted during processing, a large number of insulated wire strands with a round cross section and a surface layer made of a material with a coefficient of static friction of 0.30 or more are twisted together. A method of forming into a rectangular cross-section has been proposed (see Patent Document 3).

In addition, as a method for treating copper surfaces, in order to provide a water-based conductive paint using copper powder, electrolytic copper powder that has undergone lipophilic surface treatment is mixed into a water-based emulsion paint in which polyurethane resin with an average particle size of 200 nm or less is dispersed. A dispersed water-based conductive paint has been proposed (see Patent Document 4).

A nonwoven fabric is provided on at least one side of a wet-laid nonwoven fabric containing an antibacterial and antifungal agent that is a copper salt of an organic compound containing at least one of a nitrogen-containing heterocycle and a sulfur atom, an organic fiber, and an adsorbent substance as essential components. The shoe insole is made by laminating, preferably a non-woven fabric, and applying a composition mainly composed of a urethane-based polymer compound to the surface. An antibacterial and fungicide composition containing an antibacterial and fungicide A and a water-insoluble polymer compound D in place of the fibrous material containing an antibacterial and fungicide in a wet nonwoven fabric, and having a weight ratio A/D of 0.05 to 5. It has been proposed that a shoe insole is made by coating or impregnating a wet-laid nonwoven fabric, or by coating or impregnating a nonwoven fabric to be bonded together (see Patent Document 5).

There are few methods to prevent corrosion resistance on copper surfaces and make them stable.There are methods to treat the surface with resin, or methods to create a special effect using a combination of resin and copper. No method has been proposed to cover it. In particular, in a refrigeration circuit in an atmosphere containing sulfur components, there is no sulfur-resistant refrigeration circuit in which a polyurethane coating is formed on the outer surface of the evaporator except for the welded part of the copper pipe with the copper pipe. do not have.

Japanese Patent Application Publication No. 2004-360069 Japanese Patent Application Publication No. 2007-255850 Japanese Patent Application Publication No. 8-36922 Japanese Patent Application Publication No. 6-346006 Japanese Patent Application Publication No. 2000-23711

In the above, the outer surface of the copper piping for the evaporator, compressor, condenser, pressure reducer, etc. is baked with a coating to prevent corrosion caused by corrosive gases generated from the food stored in the refrigerator. However, the baked coating film is not formed on the welded part of the copper pipe with the copper piping, and the copper pipe is exposed. This is because if a baked coating film is formed in advance, welding will be incomplete. Further, the end of the copper pipe protrudes from the heat insulating tube to be welded to the copper pipe of the evaporator, leaving the copper pipe exposed. The copper surface, which is sensitive to sulfur components, is often exposed. As a result, problems occur in refrigeration circuit equipment in areas where the smell of sulfur is felt.

Generally, it is possible to form a baking coating on the copper pipes and copper piping that connects each device after welding, but this method cannot be used because the heat insulating tubes will be altered by the heat from welding during baking. Therefore, in conventional refrigeration circuits, the welded portion between the copper pipe of the evaporator and the copper piping remains exposed. In this state, the chemical combination of metal components, copper components, and sulfur components contained in the hot spring source causes a corrosion phenomenon, leading to damage to pipes and causing malfunctions. In environments containing sulfur components, equipment that uses copper pipes frequently breaks down.

For this reason, the above-mentioned welded parts are corroded by corrosive gases in hot spring areas where there is a lot of sulfur-containing gas, so improvements in this respect have been desired. In particular, various equipment, copper pipes, piping, etc. are often damaged by sulfur compounds such as sulfur dioxide gas and hydrogen sulfide gas. This invention was completed based on the above-mentioned circumstances, and has improved corrosion resistance of the welded part between the copper pipe of the evaporator and the copper piping, and an epoxy resin that forms a dense film layer. The purpose of this study is to establish a method for forming a sulfur-resistant coating in a refrigeration circuit device that provides a refrigeration circuit coated with two layers of chemical-resistant polyurethane coating.

As a means to achieve the above object, the device of the present invention includes an evaporator, a compressor, a condenser, a pressure reducer, a compressor, a four-way valve, an evaporator, and a heat exchanger in copper piping or copper pipes. A refrigeration circuit comprising equipment for flowing refrigerant, in which a refrigerant circulation path is constructed by welding copper piping to both ends of the copper pipe connecting the equipment, and the outer surface of the copper piping is covered with a heat insulating tube, A baked coating is formed on the outer surface of the evaporator except for the welded part of the copper pipe with the copper pipe, and the outer surface of the welded part of the copper pipe on the equipment side with the copper pipe is heated at room temperature. An anti-corrosion coating is formed using a special hardening paint.

In an air conditioner refrigeration circuit, a refrigerant circulation path is provided with a compressor, a four-way valve, an evaporator, and a heat exchanger that allow refrigerant to flow through copper pipes, and copper piping is welded to both ends of the copper pipe that connects these devices. In addition, the outer surface of the copper pipe is connected to the outer surface of the compressor, four-way valve, evaporator, and heat exchanger and each device in a refrigeration system exposed to an atmosphere containing a sulfur component. The outer surface of the welded portion of the copper pipe to the copper piping is uniformly coated with an epoxy resin paint that cures at room temperature as an undercoat, and then a topcoat is applied on the epoxy resin coating with a polyurethane paint. A laminated coating film of polyurethane resin paint is formed, and the outer surface of the welded part between the surface of the equipment, the copper pipe connecting them, and the copper piping of the copper pipe is coated with an epoxy component and a polyurethane component with a thickness of 300 to 600 μm. This is a method for forming a sulfur-resistant coating film on a refrigeration circuit device, in which a sulfur-resistant coating film is formed on the anticorrosion coating film of a two-layer laminated film.

As an epoxy resin paint for undercoating, it is a modified epoxy resin paint consisting of bisphenol A and epichlorohydrin, and is a two-component paint that cures at room temperature and forms a resin layer with multiple epoxy groups in the molecule, mainly used on copper pipes. It is used as a 250-500 μm thick layer on the outside of equipment to provide rust prevention, corrosion protection, and chemical resistance for piping and electrical/electronic parts.It is a component with excellent density and adhesion. . It can be applied by brush or spray gun, but it is preferable to use both methods to maintain uniformity.

A curing agent for paints that have an isocyanate bond (-NH-CO-O-) that forms an isocyanate bond (-NH-CO-O-) between the acrylic polyol base material and urethane during curing as a polyurethane resin paint for top coating that provides chemical resistance. , a two-component type in which the base resin and a curing agent are mixed, and a one-component type in which the vehicle is an oil-modified polyurethane resin, a moisture-curing polyurethane resin, a block isocyanate-curing polyurethane resin, or a lacquer-type polyurethane resin. Coat the epoxy resin coating on the copper pipe in a layer thickness of 50-100 μm. A two-component type that mixes the base resin and a curing agent, and a one-component type that uses an oil-modified polyurethane resin, moisture-curing polyurethane resin, block isocyanate-curing polyurethane resin, or lacquer-type polyurethane resin as a vehicle. Apply to the pipe.

The drying method for applying the two-layer paint is to apply a film layer with a thickness of 50 to 500 μm in each application, and use a copper pipe in the equipment to ensure a uniformly coated surface with no pinholes. The parts were rapidly cured at room temperature to 70°C for 1 to 24 hours.

Since an anticorrosive coating is formed on the welded parts of the compressor, four-way valve, evaporator, heat exchanger, and the copper pipes that connect them, the corrosion resistance of these welded parts is improved. Since the above-mentioned anticorrosive coating film of 300 to 600 μm epoxy resin-urethane resin coating film is formed from a room-temperature curing paint, a baking process is not necessary, and deterioration of the heat-insulating tube due to heat can be prevented. In addition, the epoxy resin-urethane resin coating provides rust resistance and durability against corrosive gases containing sulfur, making it possible to operate refrigeration circuit equipment such as air conditioners for long periods of time.

By forming a dense and uniform epoxy resin-urethane resin coating with a thickness of 300 to 600 μm, the paint is evenly applied to the entire outer surface of the welded part between the copper pipe of the evaporator and the copper pipe. As a result, there is no uneven paint film, no pinholes, and the surface of copper piping and equipment is protected from sulfur components, so there is no corrosion of the piping, and there is no failure for a long time. It is also laminated on the outer surface of the welded parts that connect pipes and equipment so that they overlap in the thickness direction of the coating, which brings about the effect of epoxy resin-urethane resin coating. In particular, we were able to efficiently cover the outer surface of the welded area with a film that is rust-proof, impact-resistant, weather-resistant, and durable. It has become a durable refrigeration circuit device.

Schematic configuration diagram of refrigeration circuit device A: Indoor unit B: Outdoor unit State diagram of an example of an actual device in a refrigeration circuit device A: Top view B: Front view Process diagram of a method for forming a sulfur-resistant coating film on a refrigeration circuit device in schematic painting of a refrigeration circuit device Diagram of painted copper pipes in refrigeration circuit equipment A: Diagram of coated pipes B: Cross-sectional view of coated pipes A photograph showing the state of the coating film of a refrigeration circuit device, showing an enlarged cross-sectional state of the copper pipe, epoxy resin layer, and urethane resin layer measured by an electron beam microanalyzer (EPMA). A photograph of an enlarged EPMA measurement between the epoxy resin layer and the urethane resin layer showing the state of the coating film of the refrigeration circuit equipment. A photograph of an enlarged EPMA measurement on an epoxy resin layer showing the state of the coating film of a refrigeration circuit device A photograph of an enlarged EPMA measurement on a urethane resin layer showing the condition of the coating film of a refrigeration circuit device

DESCRIPTION OF THE PREFERRED EMBODIMENTS The refrigeration circuit according to the present invention will be described with reference to the drawings of an embodiment in which the refrigeration circuit is applied to a refrigerator. The refrigeration circuit according to this embodiment is installed in a refrigerator to cool the air inside the refrigerator. As shown in FIG. 1, the refrigeration circuit includes a compressor that compresses refrigerant, a condenser that condenses the refrigerant compressed by the compressor, and a pressure reducer that reduces or expands the refrigerant condensed by the condenser. A refrigerant circulation path is formed by connecting an evaporator, which lowers the ambient temperature by evaporating the refrigerant that has been depressurized with a pressure reducer, with copper piping.

In the operation of forming a sulfur-resistant coating on refrigeration circuit equipment such as air conditioners, as shown in Figure 3, as an acceptance inspection, visual inspection is performed to check for deformation, scratches, and rust inside the equipment, and then preparations are made before painting. Then, remove the outer panel and each part. Next, mask parts that are difficult to remove from the device. First, as a base coat, a two-component epoxy resin paint was sprayed to a film thickness of about 150 to 400 μm. Equipment coated with two-component epoxy resin paint is dried at 20-70°C for 2-24 hours. The device coated with the dried epoxy resin paint was then spray-painted with acrylic urethane resin paint to a thickness of 30 to 100 μm. This two-layer film coating device is further dried at 20 to 70°C for 2 to 24 hours. After drying, visually inspect the parts and piping to confirm the uniformity of the paint film, mask the entire equipment, install each part, piping, etc., then fit the outer panel, and check for deformation, scratches, and rust. A visual completion inspection will be conducted to complete the device. The method is shown in Table 1.

The air conditioner refrigeration circuit shown in Figures 1 and 2 is equipped with a compressor, a four-way valve, an evaporator, and a heat exchanger that allow refrigerant to flow through copper pipes, and the copper pipes at both ends connecting these devices are equipped with a compressor, a four-way valve, an evaporator and a heat exchanger. Copper pipes are welded to form a refrigerant circulation path, and the outer surface of the copper pipes is coated in a refrigeration system exposed to an atmosphere containing sulfur as shown in the above painting process and according to the process chart in Figure 3. , coat the outer surfaces of the compressor, four-way valve, evaporator, and heat exchanger, the copper pipes connecting each device, and the welded portions of the copper pipes with the copper pipes with an undercoat that is a room-temperature curing paint. The outer surface is uniformly coated with epoxy resin paint, and a laminated coating film of polyurethane resin paint is formed on the epoxy resin paint film, and the surface of the equipment and the copper pipe connecting them are formed. A refrigeration circuit device with a sulfur-resistant coating film is formed by forming an anticorrosive coating of a two-layer laminated film of epoxy and polyurethane components with a thickness of 300 μm on the outer surface of the welded portion of the copper pipe with the copper piping. Anti-corrosion measures were taken.

The undercoat shown in Figure 3 is used as an epoxy resin paint for rust prevention, corrosion prevention, and chemical resistance for piping and electrical/electronic parts, and is a component of bisphenol A that has excellent density and adhesion. The film was formed by spray painting with a two-component modified epoxy resin paint consisting of and epichlorohydrin. This coating film is a two-component paint that cures at room temperature and forms a resin layer having a plurality of epoxy groups in the molecule, and is made of copper pipes as a main component and has a film thickness of about 250 μm on the outer surface of the device. Drying was performed at 30°C for 1 hour.

In the top coat shown in Figure 3, as a polyurethane resin paint in the top coat that provides chemical resistance, an isocyanate bond that forms an isocyanate bond (-NH-CO-O-) between the main base material of acrylic polyol and urethane during curing is used. There are two types of curing agents for paints: two-component types that mix the main agent and curing agent, and one-component types that use oil-modified polyurethane resins, moisture-curing polyurethane resins, block isocyanate-curing polyurethane resins, and lacquer-type polyurethane resins as vehicles. A liquid selected from the following was applied to a copper pipe in a layer of 50 μm thick on an epoxy resin coating. The coating was applied by spraying with a spray gun. The coating film was dried at 30° C. for 4 hours.

The drying method for applying the two-layer paint is to apply a film layer with a thickness of 350 μm in each application, and to dry the copper pipes and parts in the equipment with a uniformly coated surface with no pinholes. In contrast, rapid curing was performed at 30°C for 1 to 4 hours. As an epoxy resin paint, it is a resin with multiple epoxy groups in the molecule, and is a modified epoxy resin paint consisting of bisphenol A and epichlorohydrin.It is a two-component paint that hardens at room temperature, and is used to protect the inside and outside of pipes, as well as electrical and electronic parts. This component has excellent water resistance, chemical resistance, and adhesion. This can be done by spray gun application, but uniformity was maintained.

A polyurethane resin paint that has urethane bonds that generate urethane bonds during curing, including two-component types that mix the base agent and curing agent, oil-modified polyurethane resins, moisture-curing polyurethane resins, block isocyanate-curing polyurethane resins, and lacquers. A one-component type using a polyurethane resin as a vehicle, and a selected one from these is applied to the copper pipe in liquid form. The coating is dried by coating it on a copper pipe at 30° C. for 1 hour or more to a thickness of 350 μm, and by applying multiple coats to avoid pinholes, it is cured in this state. The method of applying the room-temperature curing paint is shown in Figure 4. Furthermore, when we observed the cross-section and surface conditions measured using an electron beam microanalyzer (EPMA), we found that the results shown in Figures 5, 6, 7, and 8. It was coated evenly.
Air conditioner refrigeration circuits located in hot spring areas with a sulfur component atmosphere that are not coated with a two-layer anti-corrosion coating consisting of epoxy and polyurethane components on the outer surface will be unable to operate due to pinholes in the copper piping within six months. However, with the equipment coated with the anticorrosive coating of the two-layer laminated film, no problems occurred even after two years or more.

As in Example 1, the air conditioner refrigeration circuit is equipped with a compressor, a four-way valve, an evaporator, and a heat exchanger that allow refrigerant to flow through copper pipes, and copper piping is installed at both ends of the copper pipe that connects these devices. Welding is performed to form a refrigerant circulation path, and the outer surface of the copper pipe is coated with the compressor as shown in the above painting process and in accordance with the process chart of FIG. The outer surfaces of the equipment, the four-way valve, the evaporator, and the heat exchanger, the copper pipes that connect each equipment, and the welded parts of the copper pipes to the copper pipes are coated with epoxy undercoat, which is a room-temperature curing paint. The outer surface is uniformly coated with a resin paint, and a laminated film of polyurethane resin paint is formed on the epoxy resin paint film with a top coat of polyurethane paint, and the copper pipe connecting the surface of the equipment and the copper pipe is formed. An anti-corrosion coating of a two-layer laminated film of epoxy and polyurethane components with a thickness of approximately 290 μm is formed on the outer surface of the welded part with the copper piping. Measures against rust were taken.

The undercoat shown in Figure 3 is used as an epoxy resin paint for rust prevention, corrosion prevention, and chemical resistance for piping and electrical/electronic parts, and is a component of bisphenol A that has excellent density and adhesion. The film was formed by spray painting with a two-component modified epoxy resin paint consisting of and epichlorohydrin. This coating film is a two-component paint that cures at room temperature and forms a resin layer having a plurality of epoxy groups in the molecule, and is made of copper pipes as a main component and has a film thickness of about 200 μm on the outer surface of the device. Drying was performed at room temperature for 2 hours.

In the top coat shown in Figure 3, as a polyurethane resin paint in the top coat that provides chemical resistance, an isocyanate bond that forms an isocyanate bond (-NH-CO-O-) between the main base material of acrylic polyol and urethane during curing is used. There are two types of curing agents for paints: two-component types that mix the main agent and curing agent, and one-component types that use oil-modified polyurethane resins, moisture-curing polyurethane resins, block isocyanate-curing polyurethane resins, and lacquer-type polyurethane resins as vehicles. A liquid selected from the following was applied to a copper pipe in a layer with a thickness of 40 μm on an epoxy resin coating. The coating was applied by spraying with a spray gun. The coating film was dried at room temperature for 5 hours.

The drying method for applying the two-layer paint is to apply a film layer with a thickness of 350 μm in each application, and to dry the copper pipes and parts in the equipment with a uniformly coated surface with no pinholes. In contrast, rapid curing was performed at 30°C for 1 to 4 hours. As an epoxy resin paint, it is a resin with multiple epoxy groups in the molecule, and is a modified epoxy resin paint consisting of bisphenol A and epichlorohydrin.It is a two-component paint that hardens at room temperature, and is used to protect the inside and outside of pipes, as well as electrical and electronic parts. This component has excellent water resistance, chemical resistance, and adhesion. This can be done by spray gun application, but uniformity was maintained.

A polyurethane resin paint that has urethane bonds that generate urethane bonds during curing, including two-component types that mix the base agent and curing agent, oil-modified polyurethane resins, moisture-curing polyurethane resins, block isocyanate-curing polyurethane resins, and lacquers. A one-component type using a polyurethane resin as a vehicle, and a selected one from these is applied to the copper pipe in liquid form. The coating material is dried by coating it on a copper pipe at room temperature for 1 to 5 hours to a thickness of 240 μm, applying multiple coatings to avoid pinholes, and curing in this state. The method of applying the room-temperature curing paint is shown in Figure 4.Furthermore, when we observed changes in the surface and cross-sectional conditions using an electron beam microanalyzer (EPMA), we found Figures 5, 6, 7, and 8. It looked like this and was evenly coated.
Air conditioner refrigeration circuits located in hot spring areas with a sulfur component atmosphere that are not coated with a two-layer anti-corrosion coating consisting of epoxy and polyurethane components on the outer surface will be unable to operate due to pinholes in the copper piping within six months. However, with the equipment coated with the anticorrosive coating of the two-layer laminated film, no problems occurred even after two years or more.

Gas leak test using corrosive gas First, a source of hydrogen sulfide gas, which is a corrosive gas, was prepared. The source of hydrogen sulfide gas is to pour 100 g of water into a 500 ml beaker, dissolve 24 g of sodium sulfide in this water, and dissolve 5.44 g of potassium dihydrogen phosphate in the aqueous solution in which the sodium sulfide is completely dissolved. It was prepared by
Under the above conditions, the refrigeration circuit device was operated for cooling, and the period until the welded part between the copper pipe of the evaporator and the copper pipe was corroded by sulfur-containing corrosive gas, a hole opened, and gas began to leak was investigated. The beaker, which is the source of both corrosive gases, was replaced with a freshly prepared one every approximately 200 hours of operation. Further, the concentration of corrosive gas in the refrigeration circuit device was approximately 5 ppm of hydrogen sulfide during the cooling operation.
Gas leakage from the evaporator was visually confirmed by filling nitrogen gas at a gas pressure of 1 MPa inside the evaporator and copper piping coated with a gas leak check liquid. Note that the cooling operation of the refrigerator was to be stopped when gas leakage was confirmed in the evaporator.

Test results using corrosive gases No gas leakage was observed from the welds between the copper pipes of the evaporator refrigeration circuit equipment treated by the method of the present application, and the test was stable even after 90 days after the start of cooling operation. On the other hand, gas leakage was observed in the refrigeration circuit device without general treatment on the 30th day after the start of cooling operation. In this way, by forming an anticorrosive coating on the welded portion between the copper pipe and the copper piping of the refrigeration circuit, the corrosion resistance of the welded portion can be improved.

1... Sulfur-resistant refrigeration circuit 20 Accumulator 2... Two-layer coating 21 Oil separator 3... Piping 22 Electronic expansion valve 4... Copper pipe 23 Closing valve 5... Urethane coating 24 Refrigerant regulator 6... Epoxy coating 25 Fin 7 ...undercoating 26 liquid receiver 8...top coating 27 four-way switching valve 9 refrigerant circulation path 28 check valve 10 compressor, 29 strainer 11 condenser, 30 service port 12 pressure reducer,
13 Two-way valve 14 Four-way valve 15 Evaporator 16 Heat exchanger 17 Fan 18 Solenoid valve 19 Motor

Claims (4)

In an air conditioner refrigeration circuit, a refrigerant circulation path is provided with a compressor, a four-way valve, an evaporator, and a heat exchanger that allow refrigerant to flow through copper pipes, and copper piping is welded to both ends of the copper pipe that connects these devices. In addition, the outer surface of the copper pipe is connected to the outer surface of the compressor, four-way valve, evaporator, and heat exchanger and each device in a refrigeration system exposed to an atmosphere containing a sulfur component. The outer surface of the welded portion of the copper pipe to the copper piping is uniformly coated with an epoxy resin paint that cures at room temperature as an undercoat, and then a topcoat is applied on the epoxy resin coating with a polyurethane paint. A laminated coating film of polyurethane resin paint is formed, and the outer surface of the welded part between the surface of the equipment, the copper pipe connecting them, and the copper piping of the copper pipe is coated with an epoxy component and a polyurethane component with a thickness of 300 to 600 μm. A method for forming a sulfur-resistant coating film for a refrigeration circuit device, characterized in that the anticorrosion coating film is formed of a two-layer laminated film. As an epoxy resin paint for undercoating, it is a modified epoxy resin paint consisting of bisphenol A and epichlorohydrin, and is a two-component paint that cures at room temperature and forms a resin layer with multiple epoxy groups in the molecule, mainly used on copper pipes. It is used as a 250-500 μm thick layer on the outside of equipment to provide rust prevention, corrosion protection, and chemical resistance for piping and electrical/electronic parts.It is a component with excellent density and adhesion. A method for forming a sulfur-resistant coating film on a refrigeration circuit device according to claim 1. A curing agent for paints that have an isocyanate bond (-NH-CO-O-) that forms an isocyanate bond (-NH-CO-O-) between the acrylic polyol base material and urethane during curing as a polyurethane resin paint for top coating that provides chemical resistance. , a two-component type in which the base resin and a curing agent are mixed, and a one-component type in which the vehicle is an oil-modified polyurethane resin, a moisture-curing polyurethane resin, a block isocyanate-curing polyurethane resin, or a lacquer-type polyurethane resin. The method for forming a sulfur-resistant coating film for a refrigeration circuit device according to claim 1, characterized in that the epoxy resin coating film is coated on a copper pipe in a layer thickness of 50 to 100 μm. The drying method for applying the two-layer paint is to apply a film layer with a thickness of 50 to 500 μm in each application, and use a copper pipe in the equipment to ensure a uniformly coated surface with no pinholes. and a sulfur-resistant coating film for a refrigeration circuit device according to any one of claims 1 to 3, characterized in that the parts are rapidly cured at room temperature to 70°C for 1 to 24 hours, respectively. Method of formation.