KR102621658B1 - A method of powder painting to prevent surface corrosion of a heat exchange pin tube coil and a heat exchange pin tube coil manufactured by the method - Google Patents

Abstract

The present invention relates to a powder coating method for preventing surface corrosion of a heat exchange fin tube coil and to a heat exchange fin tube coil manufactured by the method, such as in semiconductor, display, and secondary battery manufacturing plants, etc., where corrosive harmful gases are used. This is to prevent corrosion of heat exchange fins applied in environments exposed to moisture, etc., and to improve acid resistance, moisture resistance, and adhesion. This is to remove foreign substances on the coil surface before painting. Clean the surface with a high-temperature, high-pressure cleaner. Pretreatment process of degreasing and washing (S-1); Pre-drying and preheating process (S-2) to evaporate moisture inside the coil and increase the temperature of the coil surface to increase painting efficiency; Paint spraying process (S-3) in which epoxy-based powder coating is sprayed onto the coil; It relates to a powder coating method for preventing surface corrosion of a fin tube coil for heat exchange, which consists of a bake drying process (S-4) of drying the product on which paint spraying has been completed at high temperature in a drying furnace.

Description

Powder coating method to prevent surface corrosion of a heat exchange fin tube coil and a heat exchange fin tube coil manufactured by the method {A method of powder painting to prevent surface corrosion of a heat exchange pin tube coil and a heat exchange pin tube coil manufactured by the method}

The present invention relates to a powder coating method for preventing surface corrosion of a heat exchange fin tube coil and to a heat exchange fin tube coil manufactured by the method, such as in semiconductor, display, and secondary battery manufacturing plants, etc., where corrosive harmful gases are used. This is to prevent corrosion of heat exchange fins applied in environments exposed to moisture, etc., and to improve acid resistance, moisture resistance, and adhesion.

As a prior art regarding corrosion prevention of heat exchangers, Public Utility Model Publication No. 20-2017-0000892 (published on March 8, 2017) includes a plurality of heat conduction fins arranged at predetermined intervals, and a plurality of heat conduction fins penetrating the heat exchanger fins. heat transfer tubes, and a pair of tube plates disposed at both ends of the plurality of heat transfer tubes and having through-holes through which each heat transfer tube passes, wherein each tube plate is made of a corrosion-resistant material and is unpainted, and at least a portion of the above-described tube plates is provided. A technology related to a heat exchanger is disclosed, which is characterized in that the heat exchanger is in close contact with the heat transfer tube around the entire circumference of the through hole.

In addition, as a prior art regarding the coating of the outer surface of a fin-type heat exchanger, in Patent Publication No. 10-2010-0103940 (published on September 29, 2010), it consists of 10 to 30% by weight of acrylic and 70 to 90% by weight of ethylene. 30 to 60% by weight of acrylic group-addition carboxylated low-density polyethylene water-soluble resin with a solid content of 20 to 30% by weight in which the carboxyl group of the acrylic group is substituted with potassium and/or ammonium salt, and 13 to 25% by weight in a carbonate or ammonium salt solution. It consists of 5 to 20% by weight of titanium or zirconium complex solution dissolved in content, 5 to 20% by weight of inorganic binder, 2 to 10% by weight of zirconium oxide as a hydrophilic additive, and the balance is water, and the solid content is 10 to 10% based on the total weight of the composition. A technology related to a water-soluble coating composition for coating a heat exchanger of aluminum or aluminum alloy material containing 25% by weight is disclosed.

In addition, as a prior art regarding a surface treatment method to improve paint adhesion, Patent Publication No. 10-2005-0002057 (published on January 7, 2005) describes a first washing step to remove foreign substances from the metal surface. (S1), a surface adjustment step (S2) of making the metal surface into a state suitable for forming a zinc phosphate film, a zinc phosphate treatment step (S3) of applying a zinc phosphate film to the metal surface, and the zinc phosphate film treatment step (S3), A secondary washing step (S4) of washing the metal surface with water to stop the reaction of the film, a water drying step (S5) of drying the metal surface, and an amino silane solution diluted with water on the metal surface. Paint adhesion consisting of a silane treatment step (S6) to form a silane film, a powder coating step (S7) to paint the metal surface, and a paint drying step (S8) to dry the paint on the metal surface. Technology regarding surface treatment methods for improvement is disclosed,

In addition, as a prior art regarding Long Muzzle of Gun for Electrostatic Powder Coating}, in Publication Patent Publication No. 10-2017-0022358 (published on March 2, 2017), a long muzzle cap and , a holder fixed to the rear end of the long muzzle cap, a long sleeve inserted into the inside of the long muzzle cap, a short sleeve inserted into the front end of the long muzzle cap, and the long sleeve and short sleeve inside the long muzzle cap. A supporter fixed between, a short rod attached to and supported by the supporter, a diffuser attached to the short rod and the holder, passing between the long muzzle cap and the long sleeve, passing through the supporter, the short rod and the diffuser. A technology regarding a long muzzle of a powder electrostatic coating gun consisting of an electrode wire penetrating is disclosed.

Patent Document 1: Public Utility Model Publication No. 20-2017-0000892 (2017. 03. 08, published) Patent Document 2: Public Patent Publication No. 10-2010-0103940 (published on September 29, 2010) Patent Document 3: Public Patent Publication No. 10-2005-0002057 (published on January 7, 2005) Patent Document 4: Public Patent Publication No. 10-2017-0022358 (published on March 2, 2017)

Conventional coating methods commonly used to prevent corrosion of fin tube coils (hereinafter referred to as 'coils') for heat exchange include spraying directly on the coil using liquid paint and liquid paint. A method of dipping a coil in a submerged water tank is known.

The liquid paint generates a foul odor during operation, resulting in a very poor working environment, and there is a risk of water pollution due to the use of the liquid paint and a fire risk due to the use of solvents.

In addition, in order to increase the thickness of the paint film, it must be painted several times, and after painting, it must be naturally dried until the paint dries completely, which poses the problem of requiring a long working time.

In addition, when the fins of the fin tube coil are arranged at narrow intervals, the paint is not completely injected due to the surface tension of the liquid paint itself, resulting in an unpainted section, which may cause corrosion.

In addition, in a situation where environmental problems have emerged as a serious social issue and ESG management is being emphasized recently, the conventional painting method has the problem of causing environmental problems.

The purpose of the present invention is to prevent corrosion of heat exchange fins of heat exchangers applied in environments exposed to corrosive and harmful gases, moisture, etc., such as semiconductor, display, and secondary battery manufacturing plants, and to improve acid resistance, moisture resistance, and adhesion. It is for improvement.

In addition, the purpose of the present invention is to ensure that the paint can be stably attached to the entire fin even when painting a heat exchanger coil with a very small fin spacing.

In addition, the purpose of the present invention is to provide an environmentally friendly working environment by not using organic solvents, thereby reducing the risk of fire and not generating bad odors.

Additionally, the purpose of the present invention is to improve the coating quality by improving the adhesion of the coating film and making the thickness of the coating film uniform.

The present invention seeks to solve the above problems, [1] to remove foreign substances on the surface of the coil before painting, including a pre-treatment process (S-1) of degreasing and cleaning the surface with a high-temperature, high-pressure cleaner; Pre-drying and preheating process (S-2) to evaporate moisture inside the coil and increase the temperature of the coil surface to increase painting efficiency; Paint spraying process (S-3) in which epoxy-based powder coating is sprayed onto the coil; It relates to a powder coating method for preventing surface corrosion of a fin tube coil for heat exchange, which consists of a bake drying process (S-4) of drying the product on which paint spraying has been completed at high temperature in a drying furnace.

[2] In [1], the material of the coil is copper (Cu) for the tube, aluminum (Al) or copper (Cu) for the fin, and the specification of the coil is tube. It relates to a powder coating method for preventing surface corrosion of a heat exchange finned tube coil with a diameter of 1/2 inch and a fin pitch of 3.2mm (8FPI).

[3] In [1], the pretreatment process (S-1) is a heat exchange fin in which the surface is cleaned at a pressure of 100 bar to 150 bar and a temperature of 30°C to 140°C. This relates to a powder coating method to prevent surface corrosion of tube coils.

[4] In [1] above, the pre-drying and preheating process (S-2) maintains the temperature in the drying furnace at 100°C to 150°C, and the surface corrosion of the fin tube coil for heat exchange This relates to a powder coating method for prevention.

[5] In [1] above, the powder coating in the paint spraying process (S-3) contains 32 to 46% of pigment and 52 to 59% of epoxy resin, and the pigment includes a white pigment and an extender pigment. A powder coating method for preventing surface corrosion of a heat exchange fin tube coil, wherein the white pigment has a particle size of 0.5 micron to 1 micron, and the extender pigment has a particle size of 4 to 6 micron. It's about.

[6] In [5], the powder coating material is sprayed together with spray air by a spray coating electrostatic gun, and input air is supplied from an air supply device (not shown). ) is partially supplied to the pump through the manifold, and the sprayed air from the pump is mixed with the powder paint (Power) and supplied to the powder coating spray gun, and the manifold The injection pressure (Atomizing Air) that forms the vortex supplied from the fold is controlled by 5% to 15% (Atomizing Air Pressure) of the air pressure supplied from the air supply device, and the fluid that forms direct current supplied from the manifold Pressure (Flow-Rate Air) is controlled by 50% to 70% (Flow-Rate Air Pressure) of the air pressure supplied from the air supply device, and is a powder coating method to prevent surface corrosion of fin tube coils for heat exchange. It's about.

In addition, the present invention [7] according to [6], wherein the spray direction of the spray coating electrostatic gun is a method of spraying parallel to the fin direction and a method of spraying in a direction perpendicular to the fin direction. This relates to a powder coating method to prevent surface corrosion of fin tube coils.

[8] In the above [1], the bake drying process (S-4) is performed in a drying furnace, and the setting temperature of the drying furnace is maintained at 210°C to 220°C to maintain the surface temperature of the coil. It relates to a powder coating method for preventing surface corrosion of a fin tube coil for heat exchange, maintaining the temperature at 180°C to 200°C.

Additionally, the present invention [9] relates to a finned tube coil for heat exchange manufactured by the powder coating method of any one of [1] to [8] above.

The present invention consists of the above-mentioned structure, and prevents corrosion of the coil fins of a heat exchanger applied in environments exposed to corrosive harmful gases, moisture, etc., such as semiconductor, display, and secondary battery manufacturing plants, and provides acid resistance and resistance. Improves wetness and adhesion.

In addition, the present invention allows the paint to be stably attached to the entire fin even when painting a heat exchanger coil with a very small fin spacing.

Additionally, by not using organic solvents, the present invention reduces the risk of fire and does not generate bad odors, thereby providing an environmentally friendly working environment.

Additionally, the present invention can improve coating quality by improving the adhesion of the coating film and making the thickness of the coating film uniform.

In addition, in the present invention, an appropriate airflow is formed in the powder coating booth so that the paint easily penetrates between the fins of the coil and is attached electrostatically, so the paint does not flow or clump up, thereby increasing painting efficiency.

1 is a conceptual diagram showing a conventional coil manufacturing process.
Figure 2 is a conceptual diagram showing the painting process of the present invention.
Figure 3 is a photograph of a coil specimen of a heat exchanger to which the present invention is applied.
Figure 4 is a photograph showing the spraying process of the present invention.
Figure 5 is a photograph of coil fin specimens of Examples (1 to 3) and Comparative Examples (1 to 3) of the present invention.
Figure 6 is a photograph of a coil fin specimen after a neutral salt spray test for Examples (1 to 3) and Comparative Examples (1 to 3) of the present invention.
Figure 7 is a photograph of a coil pin specimen after CASS testing for Examples (1 to 3) and Comparative Examples (1 to 3) of the present invention.
Figure 8 is a photograph of a coil pin specimen after an acid resistance (hydrochloric acid) test for Examples (1 to 3) and Comparative Examples (1 to 3) of the present invention.
Figure 9 is a photograph of a coil pin specimen after an acid resistance (sulfuric acid) test for Examples (1 to 3) and Comparative Examples (1 to 3) of the present invention.
Figure 10 is a photograph of a coil pin specimen after moisture resistance test for Examples (1 to 3) and Comparative Examples (1 to 3) of the present invention.
Figure 11 is a photograph of a coil pin specimen after an adhesion test for Examples (1 to 3) of the present invention.
Figure 12 is a photograph of coil specimens of Example 4 (coil specimen to which Example 1 was applied) and Comparative Examples 4 to 6 (specimens to which Comparative Examples 1 to 3 were applied) of the present invention.
Figure 13 is a photograph after the CASS test of the coil specimens of Example 4 and Comparative Examples 4 to 6 of the present invention.
Figure 14 is a photograph after an acid resistance (hydrochloric acid) test on the coil specimens of Example 4 and Comparative Examples 4 to 6 of the present invention.
Figure 15 is a photograph of the performance test for Example 5 (coil to which Example 1 was applied) and Comparative Example 7 (coil to which Comparative Example 2 was applied) of the present invention.
Figure 16 is a performance comparison table between the invention of Example 5 and the invention of Comparative Example 7 according to Figure 15.
Figure 17 is a diagram showing an embodiment of an injection device used in the present invention.

The manufacturing process of the coil subject to painting in the present invention is, as shown in Figure 1, (1) coil frame NCT processing, (2) pin press processing, (3) copper tube processing, (4) assembly and dimensions. Confirmation, (5) copper tube expansion, (6) header, U band welding, (7) airtightness test and welding inspection, (8) coil high-pressure cleaning, and (9) coil air shower, the present invention includes the above. It relates to a powder coating method for preventing surface corrosion of coils manufactured through the same process.

However, of course, the present invention also includes a powder coating method for coils other than those manufactured by performing all of the above processes in the same order.

The present invention is to remove foreign substances from the coil surface before painting, and includes a pretreatment process (S-1) of degreasing and cleaning the surface with a high-temperature, high-pressure cleaner; Pre-drying and preheating process (S-2) to evaporate moisture inside the coil and increase the temperature of the coil surface to increase painting efficiency; Paint spraying process (S-3) in which epoxy-based powder coating is sprayed onto the coil; A powder coating method for preventing surface corrosion of a fin tube coil for heat exchange, which consists of a bake drying process (S-4) in which the product on which paint spraying has been completed is dried at a high temperature in a drying furnace. Below, each of the above processes is shown in the drawings. This will be explained in detail by looking at.

In the following examples and comparative examples of the present invention, the coil tube is made of copper (Cu), the fin is made of aluminum (Al) or copper (Cu), and the tube size is 1/2 inch, The pitch of the pin was set to 3.2mm (8FPI).

[Pretreatment process (S-1)]

The pretreatment process (S-1) of the present invention is degreasing and washing, as shown in (1) of FIG. 2, to remove foreign substances such as oil and dust on the coil surface before painting, using a high-temperature, high-pressure washer. Clean the surface with

The pretreatment process (S-1) is intended to prevent adverse effects on the adhesion of the coating film and to prevent appearance defects when there are foreign substances on the surface of the coil to be painted.

The pre-treatment process (S-1) is omitted when the painting process of the present invention is performed immediately after (8) coil high-pressure washing and (9) coil air showering in the coil manufacturing process shown in FIG. 1. can do.

The maximum pressure in the pre-treatment process (S-1) is set to 150 bar, preferably 120 bar, so that surface cleaning can be performed without damaging the coil.

Additionally, the temperature of the washing water can be adjusted in the temperature range of 30°C to 140°C. And the discharge amount is set in the range of 5 L/min to 15 L/min, and is preferably adjusted around 11 L/min.

[Pre-drying and preheating process (S-2)]

The pre-drying and preheating process (S-2) of the present invention evaporates moisture inside the coil and increases the temperature of the coil surface to increase painting efficiency.

In general, powder coatings have set curing conditions, and curing is generally preferably achieved when exposed to 180°C to 200°C for more than 10 minutes based on surface temperature.

Since the curing conditions are based on the surface temperature of the material (pin), in order for the material (pin) to be heated to the corresponding temperature, the ambient temperature inside the drying furnace must be raised higher than the curing condition temperature.

In the present invention, the temperature is set to 200°C or higher in the baking drying process (S-4) described below, so the drying temperature in the pre-drying and preheating process (S-2) of the present invention is 200°C to 220°C. It is desirable to do so.

As shown in (2) of Figure 2, when pre-drying and pre-heating are performed in an independent kiln, the temperature is maintained at 200°C for 10 minutes, and when pre-drying and pre-heating are performed on a conveyor, the temperature is around 215°C. is maintained for 10 minutes, and conveyor line work is performed with a transfer time of 2 M/min to 2.5 M/min.

Through the above process, moisture inside the coil can be removed, and oil and foreign substances that were not removed in the pretreatment process (S-1) can be removed.

[Paint spraying process (S-3)]

The powder coating (power) used in the present invention is an epoxy-based powder coating.

Conventional FBE coating (Fusion-bond epoxy powder coating) is an epoxy-based powder coating widely used to protect against corrosion of steel pipes used in pipe structures, concrete rebars, and various piping joints, valves, etc. At this time, FBE refers to an epoxy-based resin that is sprayed at a hot temperature (218℃ to 240℃) on the object to be coated.

The FBE heats the product to a high temperature and then instantly liquefies and attaches the paint, and is not suitable for coil coating of a heat exchanger. This is because, due to the nature of the heat exchanger, the heat cools down quickly and the paint does not melt on the coil surface, and the surface tension of the paint liquefied in the gap between the fins impedes airflow between the fins, making it difficult for the powder paint to adhere well to the heat exchanger fins. It won't happen.

In addition, EX4413-F103KCC (KCC), the powder paint for the FBE coating, is a paint for steel pipes that is painted after preheating the material to a high temperature, so even though adhesion is low, painting was possible by continuously piling the paint at a high temperature ( Material Safety Data Sheet (MSDS), KCC).

However, when applying the EX4413-F103KCC paint to a heat exchanger coil, when the paint penetrates into a narrow pin gap, an electrostatic repulsion phenomenon occurs in which paint particles with negative (-) charge repel each other, resulting in positive ( Adhesion is reduced due to the repulsive force generated with the material having a +) charge.

Compared to the conventional FBE (example F-103), the powder coating material of the present invention is characterized by reducing the particle size (particle diameter) of the pigment and increasing the specific gravity of the pigment.

Specifically, the pigment is composed of a white pigment and an extending pigment. In this case, the particle size diameter of the white pigment is 0.5 micron to 1 micron, and the particle size diameter of the extending pigment is 4 to 6 micron. At this time, the white pigment can be titanium dioxide. Additionally, adhesion is improved by setting the specific gravity of the powder to 1,660 ± 50 g/L.

Additionally, the powder coating is supposed to contain 32 to 46% of pigment and 52 to 59% of epoxy resin.

Additionally, it is preferable that the pigment in the powder coating material contains 50% or more of titanium dioxide.

In addition, the powder coating of the present invention further contains binders and additives in addition to the pigments.

The binder serves to keep the pigment particles together, attach the paint to the surface, and provide durability. It is composed of a resin or emulsifier and converts the powder paint into a liquid form to evenly spread the paint on the surface. It plays a distribution role.

Fillers are used to improve the physical properties of paint or reduce costs and control the concentration or texture of paint.

Defoamers or Antifoaming Agents control and eliminate foaming that may occur in paint mixtures. Foaming in the paint mixture can deteriorate the quality of the paint, so disperse and remove fine bubbles from the paint mixture to keep the surface smooth.

Since the present invention involves powder coating on a heat exchanger coil, the paint must be injected at narrow pin spacing, and therefore the residence time of the paint must be maximized so that the powder paint can remain between the fins as much as possible during work.

Therefore, it is desirable to limit the constant voltage applied to the powder coating to 30 to 50 kV in order to eliminate excessive electrostatic repulsion between the coatings.

The spray painting electrostatic gun used for spraying the powder coating in the present invention can be, for example, the Encore LT Manual powder spray from Nordson. In addition, depending on the type of object to be painted, the spray painting electrostatic gun can be used by changing the nozzle into two types: flat and radial. Preferably, the straight nozzle is used to paint narrow gaps between pins.

At this time, the powder coating spraying method includes spraying in a direction perpendicular to the pin as shown in FIG. 4(a) and in a direction perpendicular to the pin as shown in FIG. 4(b). It is advisable to use the spraying method in parallel to ensure that the paint penetrates evenly. Additionally, by spraying as described above, it can be confirmed that the paint passes through the rear of the coil during the painting process, as shown in FIG. 4(c). In other words, in order for the painted surface of the pin to come out smoothly, it is desirable to use the above two methods together.

In addition, as shown in FIG. 17, the input air supplied from the air supply device (not shown) of the injection device is partially supplied to the pump through the manifold, and the input air is supplied to the pump through the manifold. The spray air is mixed with the powder paint (Power) and supplied to the spray gun.

At this time, the injection pressure (Atomizing Air) that forms the vortex supplied from the manifold is controlled to 5% to 15% (Atomizing Air Pressure) of the air pressure supplied from the air supply device, and the direct current supplied from the manifold is controlled by The forming fluid pressure (Flow-Rate Air) is controlled to 50% to 70% (Flow-Rate Air Pressure) of the air pressure supplied from the air supply device, so that the powder coating is evenly mixed without clumping. Ensure that it is sprayed from the paint spray gun.

Additionally, the pressure of the air supplied from the pump is preferably 7 to 8 bar.

In addition, in the powder coating of the present invention, in addition to the above pigments, a silica-based post-additive can be added to the powder coating to increase fluidity, and a solid resin-type electrostatic additive can be further added to improve electrostatic arrival efficiency.

[Baking drying process (S-4)]

The bake drying process (S-4) of the present invention is to dry the product on which paint spraying has been completed in the paint spraying process (S-3) in a drying furnace maintaining a temperature of 180°C to 200°C. By going through this process, the powder coating is baked and hardened.

However, since the baking process is based on the surface temperature of the material (pin), the internal ambient temperature of the drying furnace needs to be higher than the curing condition temperature in order for the material to be heated to the corresponding temperature.

Therefore, when the material (fin) is thick, the setting temperature of the drying furnace can be maintained at 210°C to 220°C in order to set the surface temperature of the coil to 180°C to 200°C.

Below, the pins of the coils powder-coated through the above processes are compared between the example invention and the comparative example invention.

The coating conditions of the Example invention and the Comparative Example invention were the same as the Wagner Lab coating (50kV, 30%), and the specimen conditions of the pin were shown in FIG. 3 and were set to the same conditions as follows.

1) Copper pipe size: 1/2 inch (diameter 12.7mm)

2) Heat exchanger specimen specifications: 4Row, 4Pass (size 110mm

3) Number of pins: 30

4) Pin pitch: 3.3mm (8FPI)

Example inventions of the present invention were divided into Examples 1 to 3, and comparative inventions were divided into Comparative Examples 1 to 3 and pin tests were performed.

Example 1 is an invention in which the powder paint (MK23) of the present invention is coated on an Al-general fin, and Example 2 is an Al-resin coated fin that is coated with the powder paint (MK23) of the present invention, Example 3 The invention involves coating a Cu fin with the powder coating material (MK23) of the present invention.

Comparative Example 1 Invention to Comparative Example 3 The invention manufactured Al-general fin, Al-resin coated fin, and Cu fin without powder coating.

Test specimens of the inventions of Examples 1 to 3 and Comparative Examples 1 to 3 are shown in Figure 5.

(1) A neutral salt spray test was conducted on the inventions of Examples 1 to 3 and Comparative Examples 1 to 3. The test conditions are to spray neutral salt water prepared by dissolving salt concentration at 5% in distilled water at 25℃ onto the test piece for 240 hours under air conditions at 35℃ (Test standard: KS D 9502).

As can be seen in FIG. 6, Examples 1 to 3 and Comparative Example 2 were maintained in good condition, but discoloration occurred in all of the remaining Comparative Example inventions.

(2) A CASS test was conducted on the inventions of Examples 1 to 3 and Comparative Examples 1 to 3. The test conditions were: a solution containing 5% mass of salt, acetic acid, and cupric chloride in distilled water was maintained at 45°C and sprayed on the test piece, and the corrosion condition was checked after 48 hours (test standard: KS D 9502).

As can be seen in Figure 7, the inventions of Examples 1 to 3 were maintained in good condition, but the remaining inventions of Comparative Examples 1 to 3 all suffered corrosion or discoloration.

(3) The inventions of Examples 1 to 3 and Comparative Examples 1 to 3 were tested for acid resistance (hydrochloric acid). The test conditions were to place the specimen in a test beaker containing 5% hydrochloric acid, leave it for 48 hours, expose it to hydrochloric acid solution and hydrochloric acid vapor, and determine whether corrosion or reaction occurred.

As can be seen in Figure 8, the inventions of Examples 1 to 3 were maintained in good condition, but the remaining inventions of Comparative Examples 1 to 3 all suffered corrosion, discoloration, or reaction.

(4) The inventions of Examples 1 to 3 and Comparative Examples 1 to 3 were tested for acid resistance (sulfuric acid). The test conditions were to place the specimen in a test beaker containing 5% sulfuric acid, leave it for 48 hours, expose it to sulfuric acid solution and sulfuric acid vapor, and determine whether corrosion or reaction occurred.

As can be seen in Figure 9, the inventions of Examples 1 to 3 were maintained in good condition, but the remaining inventions of Comparative Examples 1 to 3 all suffered corrosion or discoloration.

(5) A moisture resistance test was conducted on the inventions of Examples 1 to 3 and Comparative Examples 1 to 3. The test conditions were to evaluate corrosion and resistance to rust and deterioration by exposing the test specimens to a constant temperature and humidity condition of 40 degrees Celsius and 95% relative humidity for 240 hours.

As can be seen in FIG. 10, the inventions of Examples 1 to 3 as well as the inventions of Comparative Examples 1 to 3 were all maintained in good condition.

(6) For the inventions of Examples 1 to 3 above, an adhesion test was conducted. Since the inventions of Comparative Examples 1 to 3 were not painted, they were excluded from the test. The test conditions were to scratch the surface of the painted/coated test piece in an

As can be seen in Figure 11, Examples 1 to 3 were all maintained in good condition.

As can be seen from the above tests, the pins of Examples 1 to 3 of the present invention are superior to those of Comparative Examples 1 to 3 in corrosion resistance, acid resistance, moisture resistance, etc.

Next, we compare the invention of an example of a coil specimen powder-coated through the above processes with the invention of a comparative example of a coil specimen manufactured by a different method.

As can be seen in Figure 12, the invention of Example 4 is an assembly of the pin of the invention of Example 1, the invention of Comparative Example 4 is an assembly of the pin of the invention of Comparative Example 1, and the invention of Comparative Example 5 is an assembly of the pin of the invention of Comparative Example 1. The fin of the invention was assembled, and the invention of Comparative Example 6 shows a heat exchanger coil assembled with the fin of the invention of Comparative Example 3.

All of the above heat exchanger specimens were made of 1/2 “Copper tube, 4Row

(7) The inventions of Example 4 and Comparative Examples 4 and 6 were tested for acid resistance (hydrochloric acid). The test conditions were to place the specimen in a test beaker containing 5% hydrochloric acid, leave it for 48 hours, expose it to hydrochloric acid solution and hydrochloric acid vapor, and determine whether corrosion or reaction occurred.

As can be seen in Figure 13, the invention of Example 4 did not cause a corrosion reaction or oxidation-reduction reaction by 5% hydrochloric acid, but the inventions of Comparative Examples 4 and 5 reacted with 5% hydrochloric acid and caused corrosion of the aluminum pin. It can be seen that a reaction occurs, hydrogen gas is generated, and the remaining aluminum fins are softened by hydrochloric acid vapor and easily broken. In the invention of Comparative Example 6, the surface of copper is oxidized by 5% hydrochloric acid, giving a blue-green color. A copper chloride film was formed.

(8) A CASS test was conducted on the inventions of Example 4 and Comparative Examples 4 and 6. The test conditions were a solution of 5% mass of salt, acetic acid, and cupric chloride added to distilled water, maintained at 45°C, sprayed on the test piece, and the condition was evaluated 48 hours later ((Test Standard: KS D 9502).

As can be seen in Figure 14, the invention of Example 4 did not cause corrosion or discoloration, but the invention of Comparative Example 4 and Comparative Example 5 corrodes the aluminum surface due to the reaction between salt and acetic acid and at the same time causes foreign matter to form on the surface of the pin. This was attached. This may cause static pressure loss in the coil or reduce thermal performance. In addition, in Comparative Example 6, the surface of copper was oxidized to form a bluish-green copper chloride film.

As can be seen from the above tests, it can be seen that the coil of Example 4 of the present invention has superior corrosion resistance, acid resistance, etc. compared to the inventions of Comparative Examples 4 to 6.

In addition, through the above processes, we compare the invention of Example 5, which is a coil to which the fins of Example 1 of the powder-coated coil are applied, and the invention of Comparative Example 7, which is a coil to which the fins of Comparative Example 2 are applied. However, the pin applied in the invention of Comparative Example 7 differs only in that it is coated with blue resin compared to the pin of Comparative Example 2 which was coated with resin in the same color.

(9) Figure 15 compares the pressure drop and cooling capacity between the coil of the invention of Comparative Example 7 and the coil of the invention of Example 5, and the test conditions are as follows (the test was divided into two cases based on wind volume).

1) Heat exchanger coil specifications: 4Row * 14Pass * 900EL (intake diameter 32A)

2) Pin pitch: 3.2mm (8FPI)

3) Air volume: case 1 - 48CMM / case 2 - 60CMM

4) Cold water flow rate and inlet temperature conditions: 50 LPM, 7℃

5) Air inlet conditions: dry bulb temperature 27℃, wet bulb temperature 19℃

As can be seen in Figure 16, as a result of the experiment, compared to the coil of the invention of Example 5, the cooling heat amount increased by 2.4%, and the pressure drop showed a change of less than 1% compared to the coil of the invention of Example 7.

In other words, it can be seen that powder coating did not have a negative effect of static pressure loss on the heat exchanger coil, and when powder coating was applied, the external surface area through which heat was transferred increased due to the effect of increasing the fin thickness, improving cooling capacity. You can see that

The above description is an illustrative description of the present invention, and the embodiments published in the specification are not intended to limit the technical idea of the present invention, but are for illustrative purposes, so those skilled in the art Various modifications and variations will be possible without departing from the technical idea of .

Therefore, the scope of protection of the present invention should be interpreted based on the matters stated in the claims, and technical matters within the equivalent scope thereof should also be interpreted as being included in the scope of rights of the present invention.

Claims (9)

To remove foreign substances on the coil surface before painting, a pretreatment process (S-1) of degreasing and cleaning the surface with a high-temperature, high-pressure cleaner;
Pre-drying and preheating process (S-2) to evaporate moisture inside the coil and increase the temperature of the coil surface to increase painting efficiency;
Paint spraying process (S-3) in which epoxy-based powder coating is sprayed onto the coil;
It consists of a bake drying process (S-4) in which the product on which paint spraying has been completed is dried at high temperature in a drying furnace,
The pre-drying and preheating process (S-2),
Maintain the temperature in the drying furnace at 100°C to 150°C,
The bake drying process (S-4),
This is done in a drying furnace, and the surface temperature of the coil is maintained at 180°C to 200°C by maintaining the setting temperature of the drying furnace at 210°C to 220°C,
The material of the coil is,
The tube is made of copper (Cu), and the fin is made of aluminum (Al) or copper (Cu).
The specifications of the coil are,
The tube diameter is 1/2 inch, the pin pitch is 3.2mm (8FPI),
The powder coating in the paint spraying process (S-3) contains 32 to 46% by weight of pigment, 52 to 59% by weight of epoxy resin, and other binders and additives,
The pigment is composed of a white pigment and an extending pigment. At this time, the particle size diameter of the white pigment is 0.5 micron to 1 micron, and the particle size diameter of the extending pigment is 4 to 6 micron,
Powder coating method to prevent surface corrosion of finned tube coils for heat exchange.
delete According to paragraph 1,
The pretreatment process (S-1) is,
Surface cleaning at a pressure of 100 bar to 150 bar and a temperature of 30°C to 140°C,
Powder coating method to prevent surface corrosion of finned tube coils for heat exchange.
delete delete According to paragraph 1,
The powder coating is sprayed with spray air by a spray paint electrostatic gun,
Input air supplied from an air supply device (not shown) is partially supplied to the pump through the manifold.
From the pump, the sprayed air is mixed with the powder paint (Power) and supplied to the powder coating spray gun.
The injection pressure (Atomizing Air), which forms a vortex supplied from the manifold, is controlled to 5% to 15% (Atomizing Air Pressure) of the air pressure supplied from the air supply device, and forms a direct current supplied from the manifold. The fluid pressure (Flow-Rate Air) is controlled by 50% to 70% (Flow-Rate Air Pressure) of the air pressure supplied from the air supply device.
Powder coating method to prevent surface corrosion of finned tube coils for heat exchange.
According to clause 6,
The spraying direction of the spray coating electrostatic gun combines a method of spraying parallel to the pin direction and a method of spraying in a direction perpendicular to the pin direction.
Powder coating method to prevent surface corrosion of finned tube coils for heat exchange.
delete A fin tube coil for heat exchange manufactured by the powder coating method of any one of claims 1, 3, 6, and 7.