JPH04356694A - Heat exchanger aluminum fin material and manufacture thereof - Google Patents

Abstract

PURPOSE:To establish the development of a heat exchange aluminum material having excellent coated film bonding property and workability, and having corrosion resistance. CONSTITUTION:A fin material is roughened over its surface. Thereafter, there is performed an AC electrolytic treatment where the amount of electricity exceeds 80C/dm at 4-50A/dm current density in an alkali aqueous solution at 35-80 deg.C bath temperature. Hereby, an oxide film of 500-5000Angstrom thickness is formed. Thus, a porous oxide film having a branching structure and having a greater pore size is formed, and hence a fin material excellent in a film bonding property upon processing. Further, a processing method permits high current density electrolysis, and hence there are ensured degrease cleaning and production of a porous oxide film in the sam tank with a single treatment and further a fluid disposing treatment is facilitated.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum fin material used for heat exchanger fins used in condensers, evaporators, etc. of household, commercial, and car air conditioners.

[0002] After painting and baking an inorganic film such as resin or water glass on aluminum or aluminum alloy material, fin material is formed by drawing or ironing, degreasing and cleaning (removal of press oil), and assembly (copper pipe insertion). , tube expansion)
When used as a heat exchanger fin, it has excellent adhesion between the aluminum or aluminum alloy material and the coating, has high corrosion resistance and chemical resistance (solvent resistance, alkali chemical resistance), and is highly productive (short and short). The present invention provides an aluminum fin material for heat exchangers (time-processed, inexpensive) and a method for manufacturing the same.

0003

[Prior Art] Aluminum fin materials are used in heat exchangers such as evaporators and condensers for air conditioners and coolers, whether for home or commercial use, because they have excellent workability and heat dissipation, and are lightweight and have good corrosion resistance. ing. In recent years, in order to miniaturize heat exchangers, save energy, and increase thermal efficiency, fin materials have been processed into complex shapes, and the surface area per unit weight has been increased, and moisture in the air has been transferred to the fin surface during cooling operation. To prevent dew condensation and the resulting increase in ventilation resistance, aluminum fin surfaces are treated to make them hydrophilic (resin coating, etc.), and to further improve corrosion resistance, coating with a corrosion-resistant paint film is performed. is being carried out.

[0004] These painting treatments include post-coating, in which the molded material is painted, and pre-coating, in which the painted aluminum plate is molded after being painted before the molding process. It goes without saying that it is extremely difficult to apply a pre-coat coating at the board stage.

[0005] The precoat material is assembled by molding a coated aluminum plate, and the coating film on the aluminum plate must be able to withstand the molding process. Molding generally involves the following steps for forming fins. Forming (drawing or ironing) → Cutting → Copper pipe insertion → Copper pipe expansion → Degreasing → Drying → Manufacturing The forming performed here is performed by drawing or ironing, but it belongs to deep drawing or harsh forming. Normally, the processing rate (plate thickness reduction rate) of fin materials is 50% or more. Therefore, if the adhesion between the aluminum plate and the coating film is insufficient, the coating film may crack or peel. Under such conditions, white rust and pitting corrosion are likely to occur in defective areas of the coating due to condensation during cooling operation of the heat exchanger, and electrolytic corrosion is also likely to occur due to direct contact with copper pipes.

Furthermore, since press oil is used in heat exchanger molding, degreasing and cleaning is required after molding. Degreasing is usually done by immersion in an aqueous solution of an organic solvent such as 1,1,1-trichloroethane or 1,1,2-trichloroethylene, an alkaline degreaser such as an alkali silicate, a nonionic or anionic activator, and/or steam. Bath cleaning is being carried out. At this time, if the adhesion between the aluminum plate and the paint film is insufficient, the degreaser will enter the adhesive surface between the aluminum plate and the paint film, causing defects such as blistering and peeling, and the degreaser will remain in the final product. This causes inconveniences such as the generation of strange odors.

On the other hand, while the heat exchanger is in use, dust, oil floating in the air, dirt, etc. adhere to it over time.
This can lead to clogging, the growth of bacteria and mold, and a decrease in heat exchange performance. Therefore, the fin surface may be washed with an alkaline detergent several times a year. In this case, too, if the adhesion between the aluminum surface and the paint film is poor, the cleaning solution will spread to the interface between the aluminum and the paint film and react with the adhesive defects, causing dissolution, corrosion, blistering, and paint peeling (such defects occurs regardless of post-coat or pre-coat).

[0008] In order to eliminate such inconveniences and to improve the adhesion between the aluminum plate and the coating film, the following surface treatment for the coating base of the aluminum plate has been conventionally carried out. For example, Japanese Patent Publication No. 60-13428 (Japanese Patent Publication No. 5
No. 7-19381) or JP-A No. 59-215564, the aluminum surface is anodized in a solution such as sulfuric acid, oxalic acid, or phosphoric acid. The anodic oxide film formed in such an acidic solution is dense and certainly has high corrosion resistance, and if no sealing treatment is performed, an anchoring effect can be expected due to the diffusion and solidification of the resin into the pores. , paint film adhesion is improved.

[0009] However, the anodic oxide film formed in such an acidic solution is dense and hard, and is prone to cracking when subjected to severe forming such as deep drawing or ironing.
This may cause corrosion and peeling of the paint film. In addition, to satisfy corrosion resistance, a film thickness of several μ or more is required, and to achieve this film thickness, a long processing time of several minutes to several tens of minutes is required.
It has the disadvantage of low productivity. Furthermore, there are many problems, such as high drug prices, leading to increased costs.

Furthermore, in JP-A-59-211578 and JP-A-58-48676, the aluminum surface is treated with demineralized water or a basic aqueous solution with a pH of 9 to 12 to form a hydrated oxide film on the aluminum surface. It has been proposed to form a boehmite film. This hydrated oxide film has needle-like crystals, and when the resin penetrates into the gaps between the crystals, it exerts an anchoring effect and improves coating adhesion.

However, even with this method, in order to obtain a film with sufficient corrosion resistance, a thick boehmite film is required, and a processing time of several minutes to several tens of minutes is required, resulting in poor productivity. In addition, since the film is thick and hard, severe forming processes such as deep drawing and ironing can cause cracks, leading to corrosion and peeling of the paint film.

[0012] Also, Japanese Patent Publication No. 53-48177, Japanese Patent Publication No. 53-48177,
No. 4-2945 proposes treating the surface of an aluminum plate with an aqueous alkali silicate solution or an alkali silicate solution to which one or more organic silicate compounds are added. In this case, corrosion resistance is improved by covering the aluminum surface with a silicate compound, but since the silicate compound formed is brittle, it cracks and peels during the forming process, becoming a starting point for corrosion and a cause of paint peeling. Therefore, it is extremely difficult to use as a precoat.

Furthermore, in Japanese Patent Publication No. 60-13429,
Aluminum is immersed in an acid treatment solution (chromic acid, chromate, dichromate, chromic acid/phosphoric acid, titanate, tannic acid-titanate) for about a few seconds to 20 minutes. This treatment improves corrosion resistance by forming a corrosion-resistant film of chromic acid, chromium phosphate, etc. on the aluminum surface, but even in this case, if severe forming with an ironing rate of 50% or more is performed, the film may crack. , becoming a starting point for corrosion and causing paint film peeling.

[0014] Furthermore, when using chemically formed chromate, washing with water is required after the chemical conversion treatment, which generates a large amount of wastewater containing chromium, which requires wastewater treatment equipment with a large capacity and requires a large amount of cost. It is disadvantageous in terms of pollution, safety, and cost, as it requires careful handling.

[0015]

[Problems to be Solved by the Invention] The purpose of the present invention is to develop an aluminum fin material for pre-coating with high productivity. To obtain a coating base that does not cause defects such as cracking or peeling in the painted coating even after the above ironing process and maintains high corrosion resistance even after processing and forming.■
To obtain a coating base that has high adhesion between the base and the paint film and does not cause blistering or peeling of the paint film even after degreasing and cleaning after press molding. To obtain a coating base that does not cause paint peeling, blistering, corrosion, etc. even when washed or immersed; ■ To obtain a coating base that requires short processing time and has high productivity; ■ To have low toxicity and safety. ■ Obtaining a method for manufacturing a paint base that is expensive and low pollution in terms of waste liquid treatment, etc.; ■ Obtaining a low-cost method for manufacturing a paint base that uses low chemical costs;
The present invention was completed by conducting research with the following goals in mind.

[0016]

[Means for Solving the Problems] The present invention roughens the surface of aluminum or aluminum alloy material so that the center line average roughness (Ra) becomes 0.5 to 5 μm, and further provides an alkaline solution to the surface. The present invention provides an aluminum fin material for a heat exchanger, characterized in that an oxide film with a thickness of 500 to 5000 Å is formed by alternating current electrolysis treatment in an aqueous solution.

[0017] Moreover, this aluminum material for heat exchanger is
The aluminum or aluminum alloy material is roughened so that the center line average roughness (Ra) becomes 0.5 to 5 μm, and then the current density is 4 in an alkaline aqueous solution with a pH of 9 to 13 and a bath temperature of 35 to 85°C. The obtained aluminum fin material is obtained by a method for producing an aluminum fin material for a heat exchanger, which is characterized by performing an AC electrolytic treatment at ~50 A/dm2 for a time such that the amount of electricity exceeds 80 C/dm2. Provided is an aluminum fin material for a heat exchanger in which a corrosion-resistant film or a hydrophilic film is provided on an oxide film, or a corrosion-resistant film is first provided and a hydrophilic film is provided thereon.

In the present invention, the surface roughening treatment can be performed by mechanical or electrochemical means. As the mechanical means, methods such as rolling using a roughened roll (transferring the roughness of the roll surface), shot blasting, air blasting, liquid honing, brush graining, etc. can be adopted. Among these, the air blasting method using 200 to 300 mesh alundum as the abrasive material is particularly convenient and preferred for obtaining a uniform uneven shape.

Electrochemical means include alternating current or direct current anodic electrolysis in an inorganic acid such as nitric acid, hydrochloric acid, sulfuric acid or sulfamic acid, an organic acid such as sulfonic acid, or a mixture thereof. Such surface roughening provides unevenness with a center line average roughness (Ra) of 0.5 to 5 μm. If the surface roughness is less than 0.5 μm, the unevenness is small and there is simply little difference from a normal rolled aluminum plate, and the improvement in coating film adhesion due to the shape effect is not sufficient. Moreover, if the surface roughness exceeds 5 μm, the formation of thin parts of the coating film during coating is unavoidable, resulting in insufficient corrosion resistance and hydrophilicity. The aluminum material thus roughened is then subjected to alkaline alternating current electrolysis treatment to form an oxide film.

The oxide film obtained by alkaline alternating current electrolysis according to the present invention has a large pore diameter (about 200 Å in diameter, about 50 Å for a normal sulfuric acid anodic oxide film) and has a large number of branched structures. Therefore, when organic substances such as paint resin or inorganic substances such as water glass are applied, these substances easily penetrate into the pores, resulting in a high anchoring effect and strong adhesion between the coating film and the aluminum plate. is obtained. Further, a barrier type film layer is formed under the porous layer, and when coated with a resin or the like, synergistically high corrosion resistance can be obtained.

[0021] In the present invention, the thickness of the oxide film is 500~
As a result of being as thin as 5000 Å, having a branched pore structure, and having fine irregularities on the surface, the oxide film is highly flexible and has a narrowing of 50% or more.
Even after the above ironing process, etc., no cracks or peeling occurred in the oxide film, and as a result, the resin applied to the surface,
Cracks and peeling will not occur in inorganic coatings, etc. However, when the film thickness is less than 500 Å, the pore length is short;
A sufficient anchor effect cannot be obtained, resulting in poor adhesion. In addition, if the thickness exceeds 5000 Å, the adhesion of the coating will be 5000 Å.
Not only is there no particular improvement compared to the case of Å, but the flexibility of the oxide film decreases as the film becomes thicker, making it more likely to cause cracks during molding, which is wasteful.

[0022] As the alkali source for the alkaline aqueous solution,
Although not particularly limited, those containing phosphates such as sodium phosphate, potassium phosphate, sodium pyrophosphate, potassium pyrophosphate, and phosphoric acid + sodium hydroxide are preferred. In the case of a liquid containing phosphate, the pore diameter tends to be large, so particularly high adhesion can be obtained. In addition, an aqueous solution of an alkali or alkaline earth carbonate such as sodium carbonate, an alkali or alkaline earth hydroxide such as sodium hydroxide, or a mixture of two or more of these may be used.

[0023] Furthermore, a surfactant may be included in order to improve the liquid wettability with the aluminum surface and the degreasing property. The pH of the electrolyte is 9 to 13, preferably pH 10 to
It is 12.

[0024] If the pH is less than 9, the degreasing property is poor, and the rolling oil on the surface of the aluminum plate and the oxide film formed during rolling cannot be dissolved and removed. In addition, the bath voltage increases and uneven electrolysis (burning) is likely to occur, increasing equipment costs. pH is 13
If it exceeds this value, the solubility of the formed oxide film will be too strong, making it impossible to form a porous film with excellent adhesion.

[0025] The bath temperature is in the range of 35 to 85°C, preferably 6
A range of 0 to 80°C is preferable. If the bath temperature is less than 35°C, the degreasing and cleaning effects will be insufficient and the treatment will take a long time. On the other hand, if the bath temperature exceeds 85°C, the solubility is too strong, making it difficult to obtain an anodic oxide film of the required thickness, and a porous film with excellent adhesion cannot be formed.

[0026] The current density during AC electrolysis is 4 to 50 A/dm.
2, preferably 5 to 30 A/dm2. If the current density is less than 4 A/dm2, the amount of bubbles generated during electrolysis will be insufficient, the surface cleaning effect will be poor, and the formation of a porous oxide film with excellent adhesion will be insufficient, which is undesirable. If the current density exceeds 50A/dm2, the electrolytic voltage will become too high.
Production problems such as electrical leakage are likely to occur, uneven electrolysis (burning) due to reaction heat is likely to occur, and equipment costs are high. The amount of electricity (total amount of electricity) must exceed 80 c/dm2. If the amount of electricity is less than 80 c/dm2, the porous oxide film will be thin, the adhesion to the coating film formed thereon will be insufficient, and the degreasing and cleaning effects will also be poor.

Looking more closely, it is preferable that the amount of electricity when the polarity is positive (referred to as the amount of electricity at the anode) exceeds 40 c/dm2. Anode electricity amount is 40c/dm2
Below this, the growth of the porous oxide film will be insufficient and the cleaning action will not be sufficient. The amount of electricity when the polarity is negative (referred to as the amount of cathode electricity) is preferably 40 c/dm2 or more. If the amount of electricity at the cathode is less than 40 c/dm2, the cleaning action will be insufficient. The current waveform may be an alternating current waveform, such as a sine wave alternating current, a rectangular wave, a trapezoidal wave, a triangular wave, etc., and the amount of electricity at the anode and the amount of electricity at the cathode may be different. The electrolysis time may be set based on the relationship between the required amount of electricity and the current density. If the current density is high, the process can be done in a short time.

For aluminum alloys such as 5182, which have a thick natural oxide film, it is recommended to remove the natural oxide film with an acidic solution before electrolytic treatment, which will extend the life of the electrolyte and reduce the porosity caused by electrolysis. This is effective because it increases the uniformity in the formation of a sexual film. Cleaning treatment before electrolysis may be performed as necessary. For example, if a very large amount of rolling oil is present, cleaning with a solvent such as trichloroethane or immersion cleaning with an alkaline solution such as an aqueous solution of caustic soda is effective.

Corrosion-resistant organic paints used in the present invention include polyacrylic acid, polymethacrylic acid, polyacrylic acid derivatives, polymethacrylic acid derivatives, urethane resins, urethane resin derivatives, epoxy resins, epoxy resin derivatives,
The paint may contain polyamide, polyamide derivatives, etc., or a copolymer or mixture of two or more of these, and may further contain SiO2, silicate, zirconium salt, chromium, etc.

For example, acrylic copolymer melamine resin as disclosed in JP-A-61-101798, acrylic resin as disclosed in JP-A-1-174438, and acrylic resin as disclosed in JP-A-63-168473. Examples include mixtures of hexavalent chromium and polyacrylamide. The coating thickness is preferably 5 g/m2 or less. If it exceeds 5 g/m2, thermal conductivity decreases, which is not preferable. The baking temperature may be appropriately selected depending on the paint to be applied, but is usually selected from a range of 80 to 320°C. Baking time can be selected appropriately depending on the paint, but considering productivity,
It is preferable to select a paint that lasts approximately 300 seconds. The coating method may be dipping, roll coater, or the like.

In the present invention, it is preferable to form a hydrophilic film on the oxide film in order to improve thermal efficiency. The hydrophilic film to be used is one of silicates, polyacrylic acid derivatives, polyamide derivatives, cellulose derivatives, polyvinyl alcohol and polyvinyl alcohol derivatives, etc., or a copolymer or mixture of two or more of these. It may also contain one or more surfactants such as polyoxyethylene derivatives, sorbitan derivatives, sucrose fatty acid esters, sulfuric acid esters, sulfonic acid esters, and phosphoric acid esters.

For example, polyacrylic acid, polymethacrylic acid, or a mixture thereof having a degree of polymerization in the range of 1,000 to 10,000, as disclosed in JP-A-1-201487; JP-A-61-8598; styrene-maleic acid copolymer, polyacrylamide, butylene-maleic acid copolymer, polyacrylic acid, or one or more water-soluble organic polymers and silicate salts as disclosed in . Mixture of compounds; Japanese Patent Publication No. 53-481
SiO2/M2O(M
= Li, Na, K, Ca, etc.) ratio is 1 or more; polyvinyl alcohol, polyamide resin, urea resin mixture as disclosed in JP-A-1-299877; JP-A-61-101798 Examples include cellulose derivatives.

[0033] As a surfactant, JP-A-64-612
39, the molecular weight of the hydrophobic group is 4.
00 or less phosphate ester surfactant; JP-A-63-
HLB value 8-20 as disclosed in 304067
There are nonionic surfactants, etc.

[0034] The thickness of the hydrophilic film is preferably 0.1 to 5 g/m2. If it is less than 0.1g/m2, hydrophilicity is insufficient, and 5g/m2
/m2 is not preferable because thermal conductivity decreases.

[0035] The baking temperature may be appropriately selected depending on the coating material to be applied, but it is usually selected from the range of 150 to 300°C. If the temperature is less than 150°C, baking tends to be insufficient, while if it exceeds 300°C, the hydrophilic groups are destroyed, resulting in a decrease in hydrophilicity. The baking time may be appropriately selected depending on the coating material, but it is preferable to select a baking time in the range of about 5 to 300 seconds in consideration of productivity. The amount of surfactant added is preferably about 0 to 50%, preferably about 0 to 20%, based on the resin solid content. If it exceeds 50%, curing of the paint will be hindered. The coating method may be dipping, roll coater, or the like.

Further, the above-mentioned corrosion-resistant coating and hydrophilic coating may contain one or more of a fungicide, a preservative, and a deodorizing agent. As a fungicide, JP-A-58-10207
TBZ, 2-(2-frill) as exemplified in 3.
-3-(5-nitro-2-furyl)-acrylic acid amide, 5,6-tetrachloroisophthalonitrile, N-dimethyl-N'-phenol-(N'fluorodichloromethylthio)-acrylic acid sulfamide, etc. . Examples of preservatives include benzoic acid or its salts, sorbic acid or its salts, and salicylic acid or its salts, as exemplified in JP-A-62-129695. Examples of deodorants include sodium peroxide, calcium peroxide, and benyl peroxide as exemplified in JP-A-61-129694. The amount of each added is preferably 50% or less, and if it exceeds 50%, film formation will be hindered, which is inappropriate.

[0037]

[Function] The present invention roughens the surface of the aluminum material to give it an unevenness of 0.5 to 5 μm in terms of center line average roughness (Ra), and then electrolytically treats the aluminum material using alternating current in an alkaline solution. This relates to an aluminum fin material in which the surface of the material is degreased and washed, and a porous oxide film with excellent paint film adhesion is formed, and its manufacturing method. The present invention provides a fin material having corrosion resistance. The operation of the present invention will be explained below.

(2) Since the surface is roughened, the surface roughness increases the surface area and improves the adhesion of the coating.

(2) The alkaline solution itself has degreasing properties. Furthermore, since electrolytic treatment using an alternating current waveform is performed at the same time, a stronger cleaning effect is exerted. That is, since oxygen gas is generated during the anode reaction, organic substances such as rolling oil adhering to the aluminum surface are oxidized and removed, resulting in strong degreasing and cleaning properties. Further, during cathode cleaning, hydrogen bubbles are generated, and the expansion of the bubbles acts as a mechanical cleaning action, making it difficult for smut to adhere, which is the case in normal degreasing, and thus exhibiting a strong cleaning action. The synergistic effect of each of the above functions produces a strong degreasing and cleaning effect, and removes rolling oil, smut, etc. from the aluminum plate surface that adversely affects paint film adhesion in a short time, and at the same time provides a clean and uniform surface with porous pores. oxidized film is formed.

[0040] Normal anodization is often carried out at a temperature below 35°C, and sulfuric acid anodization is often carried out at a temperature below 20°C. On the other hand, this method performs alternating current electrolysis at a high temperature of 35 to 85° C., which enables electrolysis at a high current density and causes a high-speed chemical reaction. That is, since the electrolyte temperature is high, the liquid resistance is low, and the current density can be set to a high value, so the oxide film formation rate is high. The oxide film formed by alternating current in an alkaline solution is much more difficult to etch than the oxide film formed by anodic oxidation by direct current electrolysis in a general acidic aqueous solution because of the greater etching properties of this electrolyte. It is porous and has a large pore diameter, and because it uses AC electrolysis, it has a branched structure.

On the other hand, in direct current electrolysis in a general acidic bath, the bath voltage increases rapidly over time, making it difficult to conduct electrolysis at the high current density necessary for high-speed processing. Furthermore, since the oxide film does not have a branched structure, the film lacks flexibility compared to an oxide film from an alkaline bath.

On the other hand, when an acidic aqueous solution is used, the barrier type oxide film tends to become thicker, and when processing at a high current density for a short time, a voltage five times or more is required as compared to an alkaline aqueous solution. In addition, if a high voltage is forcibly applied in such a liquid, an uneven reaction called "burning" (dissolution due to heat generation due to concentration of current due to uneven electrical resistance) is likely to occur. Not only does it spoil the appearance, but the adhesion of the paint film is also poor, and there are many safety problems such as the generation of sparks. Further, the acidic aqueous solution usually has an acid concentration of 10% or more and a pH of 1 to 2 or less, which is disadvantageous in terms of waste liquid treatment and chemical solution handling.

[0043] As described above, the oxide film formed by subjecting a pre-roughened aluminum material to AC electrolytic treatment in an alkaline aqueous solution has a clean surface and is extremely porous and has a branched structure. , because the adhesion with the paint film is significantly improved and it is highly flexible,
Even when subjected to severe drawing or ironing such as % or more, no cracking or peeling of the paint film occurs, so strong paint film adhesion can be maintained even after processing.

Furthermore, since degreasing and cleaning and the formation of a porous oxide film are carried out simultaneously in the same tank through the same electrolytic treatment, and the electrolytic time is short, the working time is shorter than before, and productivity is improved. , equipment costs are also low. Furthermore, unlike chemical conversion treatment, it does not use substances harmful to the human body, such as a chromium aqueous solution, which is a great advantage in terms of operation and maintenance.

[0045]

[Example] Test method ■ Solvent resistance test A test piece was placed in 1,1,1-trichloroethane at 74°C for 30 minutes.
After being immersed for a minute, it was dried at room temperature for 1 hour. The appearance of this test piece was observed and a goban adhesion test was conducted. For the grid adhesion test, cellophane tape (25 mm width, manufactured by Sekisui) was pasted on 10 x 10 squares cut at 1 mm intervals, then peeled off, and the number of squares with remaining paint film was counted.

(2) Alkali cleaner resistance test The test piece was washed with trichloroethane and dried according to the method (2). Next, after immersing in aluminum fin cleaner (manufactured by Seiwa Kogyo: Aluminum Fin Cleaner W 5 times diluted solution, pH = 12 to 13) for 10 minutes (room temperature), one cycle was 15 minutes of washing under running water, and a total of 10 cycles were performed. Appearance observation and goblin adhesion test were conducted using method (2).

■ Formability test The coated test piece was formed into fins with a fin pitch of 25 mm and a collar height of 2 mm using a fin press machine (manufactured by Hidaka Seiki), and the state of coating film adhesion on the fin surface and the inner and outer surfaces of the collar was evaluated by SE.
M observed. A coating film adhesion area of 100% was evaluated as ◎, 80% or more of less than 100% was evaluated as △, 50% or more of less than 80% was evaluated as ▽, and less than 50% was evaluated as ×.

■ Corrosion Resistance Test After passing a 9.8 mm diameter copper pipe through the fins formed in ■, the copper pipe was expanded to create a model heat exchanger. After degreasing and cleaning this model heat exchanger using method ■,
T test (35°C, NaCl concentration = 5%, 2000h, J
IS-Z 2371-1988) and evaluated based on the corrosion area.

(Example 1, Comparative Example 1) JIS A12
00-H24 (0.115mmt) with morundum (#
240) as an abrasive material (air pressure = 3
kilogram/cm2), measurement length = 2.5mm
, a roughened aluminum plate with Ra=2.5 μm was obtained.

Next, alkaline alternating current electrolysis (sine wave, 2% sodium pyrophosphate aqueous solution, frequency 50 Hz, pH adjusted with NaOH) was performed under the conditions shown in Table 1. After washing with water and drying, an acrylic resin (manufactured by Shinto Toyo Co., Ltd.: Esbia AL-50B) was applied to each surface-treated board (coating amount = 1 g/m2), and the test pieces were baked at 290°C. The results are shown in Table 1.

[0051]

(Example 2) JIS A1200-H2
4 (0.115 mmt), an aluminum plate was air blasted under the conditions shown in Table 2, and the measured length = 2.5
A roughened aluminum plate with Ra=0.6 to 4.8 μm was obtained.

Next, alkaline alternating current electrolysis (sine wave, 2% sodium pyrophosphate aqueous solution, frequency 50Hz, NaOH
After washing with water and drying, a mixture of acrylic resin and SiO2 (manufactured by Nippon Paint Co., Ltd.: Surf Alcoat 131) was applied to each surface-treated board (coating amount = 0.3 g/m).
2), baked at 250°C and used as a test piece. Table 2 shows the results.
Shown below.

(Comparative Example 2) JIS A1200-H2
4 (0.115 mmt), an aluminum plate was air blasted under the conditions shown in Table 2, and the measured length = 2.5
Roughened aluminum plates with Ra = 0.3, 5.5 and 10 μm were obtained.

Next, alkaline AC electrolysis (sine wave, 2% sodium pyrophosphate aqueous solution, frequency 50Hz, NaOH
After washing with water and drying, a mixture of acrylic resin and SiO2 (Surf Al Coat 131, manufactured by Nippon Paint Co., Ltd.) was applied to each surface-treated board (coating amount = 0.3 g/m).
2), baked at 250°C and used as a test piece. Table 2 shows the results.
Shown below.

[0056]

(Example 3) JIS A1200-H2
4 (0.115mmt) was air blasted using Morundum (#240) as an abrasive (air pressure = 3Kg/cm).
2), measurement length = 2.5mm, Ra = 2.5μ
A roughened aluminum plate of m was obtained.

Next, alkaline alternating current electrolysis was carried out under the conditions shown in Table 3. After washing with water and drying, each surface-treated board was coated with a cellulose resin (Solidite WH-10 manufactured by Mitsui Toatsu Co., Ltd.), a surfactant (phosphoric acid ester type) in an amount of 3% based on the solid content of the resin, and a melamine curing agent (Mitsui Toatsu Co., Ltd.: Solidite WH-10). A mixture containing 30% Cymel 272 (manufactured by Tensha Co., Ltd.) based on the resin solid content was applied (coating amount = 1 g/m2) and baked at 220°C to prepare a test piece. The results are shown in Table 3.

(Comparative Example 3) JIS A1200-H2
4 (0.115mmt) was air blasted using Morundum (#240) as an abrasive (air pressure = 3Kg/cm).
2), measurement length = 2.5mm, Ra = 2.5μ
A roughened aluminum plate of m was obtained.

Next, caustic etching (etching amount 4μ)
→Desmut (20wt% - nitric acid, room temperature) treated sample and phosphoric acid chromate treatment (chromium adhesion amount = 30mg/
Two types of samples were prepared. For this sample, a cellulose resin (Solidite WH-10 manufactured by Mitsui Toatsu Co., Ltd.) was mixed with a surfactant (phosphate ester type) at a ratio of 3% to the solid content of the resin.
% and melamine curing agent (manufactured by Mitsui Toatsu Co., Ltd.: Cymel 272
) was added at 30% based on the resin solid content.
Amount of coating film = 1 g/m2) was baked at 220°C to obtain a test piece. The results are shown in Table 3.

[0061]

(Example 4) JIS A1200-H2
4 (0.115mmt ) using Morundum (#240) as an abrasive and air blasting (air pressure = 3Kg/cm).
2), measurement length = 2.5mm, Ra = 2.5μ
A roughened aluminum plate was obtained.

Next, alkaline alternating current electrolysis was carried out under the conditions shown in Table 3. After washing with water and drying, each surface treated board has Cr3+,C
r6+, SiO2 and an acrylic resin mixture (NRC-300 manufactured by Nippon Paint Co., Ltd.) was applied (film thickness = 1μ),
After drying at 100°C, a mixture of a hydrophilic acrylic resin (Mitsui Toatsu Co., Ltd.: XCE-1847) and a surfactant (Daiichi Kogyo Seiyaku Co., Ltd.: Neugen ET120) was coated (coating amount: 1 g/m2). and baked at 270℃. The results are shown in Table 4.

(Comparative Example 4) JIS A1200-H2
4 (0.115mmt ) using Morundum (#240) as an abrasive and air blasting (air pressure = 3Kg/cm).
2), measurement length = 2.5mm, Ra = 2.5μ
A roughened aluminum plate was obtained.

After cleaning with solvent (methyl ethyl ketone, room temperature immersion) and drying, each surface treated plate was coated with Cr3+, Cr6+, S.
iO2 and acrylic resin mixture (Nippon Paint Co., Ltd. N
RC-300) (coating film thickness = 1μ), dried at 100°C, and further coated with hydrophilic acrylic resin (Mitsui Toatsu: XCE-1847) and surfactant (Daiichi Kogyo Seiyaku: XCE-1847).
Apply a mixture of Neugen ET120 (coating amount: 1 g/m
2) and baked at 270°C. The results are shown in Table 4.

[0066]

[0067]

Effects of the Invention The present invention is an aluminum fin material on which an oxide film is formed by roughening treatment and AC electrolysis in an alkaline aqueous solution, and in order to manufacture this fin material, the center line average roughness (Ra) It has been found that after roughening the surface to a thickness of 0.5 to 5 μm, it is necessary to perform an AC electrolytic treatment using a specific aqueous solution, electrolysis temperature, current density, and quantity of electricity.

[0068] In addition to increasing the surface area by roughening the surface and improving the adhesion of the coating film by the anchor effect, this treatment method has a strong cleaning effect by AC electrolytic treatment with an aqueous alkaline solution, and has a branched structure and a porous structure. The pore diameter is large due to
The present invention also provides an aluminum fin material that has excellent coating film adhesion due to the formation of a relatively flexible oxide film.

Furthermore, since this manufacturing method uses high-temperature alternating current electrolysis with low liquid resistance, the necessary oxide film can be formed in a short time at high current density, and the degreasing process and oxide film forming process are performed in the same process. Because it can be done simultaneously, equipment costs are low, and since no harmful substances such as chromium are used, it is extremely advantageous in waste liquid treatment and handling of chemical solutions.

Claims (5)

[Claims] Claim 1: The surface of aluminum or aluminum alloy material is roughened so that the center line average roughness (Ra) becomes 0.5 to 5 μm, and the surface is further subjected to AC electrolysis treatment in an alkaline aqueous solution. An aluminum fin material for a heat exchanger, characterized in that an oxide film with a film thickness of 500 to 5000 Å is formed. 2. After roughening the aluminum or aluminum alloy material so that the center line average roughness (Ra) is 0.5 to 5 μm, the surface is subjected to AC electrolysis treatment in an alkaline aqueous solution to reduce the film thickness. An aluminum fin material for a heat exchanger, characterized by forming an oxide film of 500 to 5000 Å and further providing a corrosion-resistant film. 3. After roughening the aluminum or aluminum alloy material so that the center line average roughness (Ra) is 0.5 to 5 μm, the surface is subjected to AC electrolysis treatment in an alkaline aqueous solution to increase the film thickness. An aluminum fin material for a heat exchanger, characterized in that an oxide film of 500 to 5000 Å is formed and a hydrophilic film is further provided. 4. After roughening the aluminum or aluminum alloy material so that the center line average roughness (Ra) is 0.5 to 5 μm, the surface is subjected to AC electrolysis treatment in an alkaline aqueous solution to reduce the film thickness. An aluminum fin material for a heat exchanger, characterized in that an oxide film of 500 to 5000 Å is formed, a corrosion-resistant film is provided thereon, and a hydrophilic film is further provided on the surface. 5. The aluminum or aluminum alloy material is subjected to surface roughening treatment so that the center line average roughness (Ra) becomes 0.5 to 5 μm, and further the pH is 9 to 13 and the bath temperature is 35 to 5 μm.
Current density 4-50A/d in alkaline aqueous solution at 85℃
1. A method for producing an aluminum fin material for a heat exchanger, characterized in that AC electrolytic treatment is performed for a time such that the amount of electricity exceeds 80 C/dm2.