JP2000328259A - Precoated fin material for heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a precoated fin material excellent in adhesion for a coating film, free from the generation of forming defects even in the case of being formed by using volatile pressing oil having low viscosity and moreover excellent in corrosion resistance in a precoated fin material for a heat exchanger in which a coating type chromate film has been formed on the surface of an Al alloy base material, and also, a hydrophilic coating film has been formed on the surface of the film. SOLUTION: The coating type chromate film contains 1 to 100 mg/m2 Cr and moreover contains Zr, P, F, O and H, in which, also, the weight ratio of Cr/Zr lies in the range of 0.5 to 5, the weight ratio of P/Cr to 0.1 to 1, the weight ratio of F/Cr to 0.04 to 2.5, and moreover, the weight ratio of Cr(III)/Cr(VI) in a chromium compd. is controlled to >=9.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy precoated fin material used for a heat exchanger of a room air conditioner or the like, and more particularly to a coating type chromate film formed on a surface of an aluminum alloy thin plate as a base material. The present invention relates to a pre-coated fin material having a hydrophilic film formed on a film.

[0002]

2. Description of the Related Art Aluminum alloy fins, which are lightweight and have excellent workability and heat conductivity, have been widely used for heat exchangers generally used in room air conditioners and car air conditioners. On the other hand, in recent years, for room air conditioners, car air conditioners, and the like, there has been a strong demand for compactness and energy saving, and accordingly, it has been strongly desired to further improve the heat exchange efficiency. As a structural measure of the heat exchanger to respond to such a demand, it is necessary to raise a louver or to reduce a distance between fins, that is, a distance between portions through which air as a heat medium substance flows. This has been done conventionally. However, when the fin interval is reduced as described above, it is necessary to increase the hydrophilicity of the fin surface. That is, if the hydrophilicity of the fin surface is insufficient, water droplets on the fin surface generated by dew condensation of moisture in the air during the cooling operation form a bridge between the fins, and the ventilation resistance against air passing between the fins is reduced. This increases the heat exchange efficiency, and conversely lowers the heat exchange efficiency. In addition, there is a disadvantage that water jumps out with the ventilation, and the water on the fin surface stays for a long time, and the corrosion of the fin material proceeds. There are also problems. On the other hand, if the hydrophilicity of the fin surface is good, the contact angle of water droplets generated by condensation on the fin surface with respect to the fin surface is reduced, so that the water droplets spread on the fin surface without forming a bridge between the fins and form a water film. Because it flows down quickly, the ventilation resistance does not increase, the water droplets rarely jump out to the outside due to the ventilation, and the residence time of water on the fin surface is also shortened, so that the progress of corrosion is avoided. As a result, the corrosion resistance can be improved.

[0003] Therefore, in order to improve the hydrophilicity of the fin surface, various hydrophilic treatments have been conventionally performed on the fin material surface. In this case, the surface of the aluminum alloy sheet, which is the base material of the fin material, is subjected to a chromate treatment or a bayite treatment as a base treatment to form a corrosion-resistant film (base film), and then a hydrophilic treatment is performed on the corrosion-resistant film. It is widely practiced to apply an inorganic paint such as water glass or colloidal silica or various organic paints and bake and dry to form a hydrophilic coating film.

By the way, when assembling a heat exchanger such as a room air conditioner using an aluminum alloy fin material, conventionally, a thin aluminum alloy sheet for fin is formed into a fin shape and then assembled, and then formation of a base corrosion-resistant film and hydrophilicity are improved. A method of forming a coating film, that is, a post-coating method, was generally used, but recently, from the viewpoint of improving productivity, the formation of a base corrosion-resistant film and a hydrophilic property on the surface of an aluminum alloy sheet for fins before forming are mainly performed. In many cases, a method in which a coating film is formed and then formed into a fin shape and assembled, that is, a precoat method, is applied. In the case of the latter pre-coat method, the fin material (that is, the pre-coated fin material) is required to have good moldability in a state where a base corrosion-resistant film or a hydrophilic film is formed.

On the other hand, recently, from the viewpoint of improving productivity and protecting the environment, a press oil having a low viscosity and a high volatility is used at the time of forming the fin material, and after press forming, degreasing with conventional trichloroethylene or an alkaline degreasing agent is performed. In many cases, only the heating and drying is performed without the step.

[0006]

As described above, in forming a pre-coated fin material in which a base corrosion-resistant film and a hydrophilic film are formed in advance on an aluminum alloy sheet,
Although good moldability is desired, it is desired that the moldability be further excellent, particularly when molding is performed using a low-viscosity volatile press oil. However, in the case of a conventional general precoated fin material, when molding is performed using a low-viscosity volatile press oil, molding defects such as buckling, cracking, and jumping at the collar portion often occur during molding. The fact is that the moldability was not good.

Conventional methods for improving the formability of precoated fin materials include, for example, JP-A-4-19828.
7, JP-A-5-31123, JP-B 1-2178
As described in JP-A No. 5 or JP-B-2-25692, studies have been made in the direction of improving the lubricity of the surface of the hydrophilic coating film. However, when a conventional pre-coated fin material is molded using a low-viscosity volatile press oil, the above-described molding defects occur during molding, even when the kinetic friction coefficient of the coating film surface is low and lubricity is good. It turns out that. As a result of various studies by the present inventors on this point, not only the lubricity of the coating film surface in the formability,
It was found that the adhesion between the coating film and the substrate had a great effect. That is, when molding using a low-viscosity volatile press oil, even if the dynamic friction coefficient of the coating film surface is low, if the adhesion between the coating film and the substrate is poor, the coating film peels from the substrate during molding. In addition, the base having poor lubricity (corrosion-resistant film or aluminum alloy thin plate surface) comes into direct contact with the molding die, and adhesion (so-called seizure) occurs. Was found to be more likely to occur.

Therefore, in order to improve the moldability of the precoated fin material and to reliably prevent the occurrence of molding defects such as buckling, cracking, and jumping even in molding using a low-viscosity volatile press oil, it is necessary to use a pre-coated fin material. It is necessary to improve the adhesion between the hydrophilic coating film and the base in the fin material. Further, if the adhesion of the hydrophilic coating film to the base is improved, the water resistance of the coating film is also improved, and as a result, it contributes to the improvement of corrosion resistance.

On the other hand, conventionally, as a measure for improving the adhesion of a hydrophilic coating film to a substrate, for example, as disclosed in JP-A-4-32583 and JP-A-4-32585, an undercoat corrosion-resistant film such as a chromate treatment is used. In order to improve the surface properties of the aluminum alloy sheet at a stage before forming the aluminum alloy sheet, the aluminum alloy sheet is subjected to alkali cleaning or etching. It is difficult to sufficiently improve the adhesion, and thus the above-described problem has occurred during molding using a low-viscosity volatile press oil.

That is, in a precoated fin material in which a base corrosion-resistant coating and a hydrophilic coating are formed on an aluminum alloy thin plate, even if the adhesion of the base corrosion-resistant coating to the surface of the aluminum alloy thin plate is good, the base corrosion-resistant coating itself is not formed. If it is not dense and its film strength is low, or if the adhesion of the hydrophilic coating to the underlying corrosion resistant film is poor,
In particular, the coating film was easily peeled off at the time of molding using a low-viscosity volatile press oil, so that the above-mentioned problem was likely to occur. Therefore, simply providing good adhesion of the base corrosion-resistant coating to the surface of the aluminum alloy sheet does not mean that the overall adhesion of the coating is good, and especially when molding using low-viscosity volatile press oil. It has been difficult to reliably and stably prevent the above-mentioned problems from occurring.

The present invention has been made in view of the above circumstances, and particularly, a precoat for a heat exchanger in which a coating type chromate film is formed as a base corrosion-resistant film, and a hydrophilic coating film is formed on the coating type chromate film. Regarding the fin material, by paying attention to the composition of the underlying coating type chromate film itself, and by appropriately adjusting the composition, the overall adhesion of the hydrophilic coating film is reliably and stably improved, and as a result, low viscosity An object of the present invention is to provide a precoated fin material for a heat exchanger, which exhibits excellent moldability stably even when molded using a volatile press oil of the above and is also excellent in corrosion resistance.

[0012]

Means for Solving the Problems The present inventors have paid attention to a chromate film, particularly a coating type chromate film, among various base corrosion-resistant films in a precoated fin material.
After conducting various studies on the relationship between the component composition of the coating type chromate film and the adhesion of the hydrophilic coating film, the coating type chromate film was converted to oxides, hydroxides, phosphates, fluorides of Cr, And a composite film composed of oxides, hydroxides, phosphates and fluorides of Zr and Zr, and the chromium compound in the film is mainly composed of a compound of trivalent chromium Cr (III), so that the coating is performed. The inventors have found that the adhesion of the film can be surely and stably improved, and have accomplished the present invention. In the present invention, the composition of the components contained in the coating, particularly the Cr content, the Cr / Zr ratio, the P / Cr
Ratio, F / Cr ratio, trivalent chromium Cr (III) / hexavalent chromium C
The r (VI) ratio was adjusted appropriately.

Specifically, the present invention relates to a precoated fin material for a heat exchanger in which a coating type chromate film is formed on the surface of an aluminum alloy substrate and a hydrophilic coating film is formed on the coating type chromate film. The coating type chromate film contains Cr in an amount of 1 to 100 mg / m ² and Zr, P, F, O, and H, respectively.
And the weight ratio of Cr / Zr is in the range of 0.5 to 5, P / C
The weight ratio of r is in the range of 0.1 to 1, the weight ratio of F / Cr is in the range of 0.04 to 2.5, and the weight ratio of Cr (III) / Cr (VI) in the chromium compound. Is set to 9 or more.

Further, the precoated fin material for a heat exchanger of the present invention will be described in detail.

The precoated fin material for a heat exchanger according to the present invention is basically formed by applying a coating type chromate solution onto an aluminum alloy base material as a coating type chromate treatment and performing heating for baking and drying. It is obtained by solidifying on an aluminum alloy substrate, applying a hydrophilic paint on the obtained coating type chromate film, and baking to form a hydrophilic coating film.

Here, a conventional general coating type chromate solution is used.
If used, transfer the coated chromate solution to aluminum
When applied on a gold substrate, the Al of the substrate is dissolved
Al ³⁺Ions are generated and Cr in the coating type chromate⁶⁺
The ions are reduced and the oxide of trivalent chromium Cr (III), water
Generates trivalent chromium Cr (III) compounds such as oxides and salts
Is done. However, if such a reaction does not proceed sufficiently
The compound of hexavalent chromium Cr (VI) also remains. In any case
However, the coating type chromate film mainly uses these Cr compounds.
And the state where the Cr compound is fixed as a film
Has become. In addition, conventional coating-type chromate treatment
Therefore, the reactions described above simply occur naturally.
Was only understood to be
Type and composition of coating type chromate film and adhesion of coating film
There wasn't enough consideration on the relationship with
Is the actual situation.

However, the present inventors have repeatedly conducted a study on the reaction of the coating type chromate liquid on the surface of the aluminum alloy substrate and the compounds formed thereby, and furthermore, the relationship between the composition of the coating type chromate film and the adhesion of the coating film. As a result of repeated experiments and studies, the reaction of the coating type chromate solution on the surface of the aluminum alloy substrate caused the oxides, hydroxides,
By forming phosphates, fluorides and oxides, hydroxides, phosphates and fluorides of Zr and forming a film with these composite compounds, coating film adhesion and corrosion resistance are greatly improved. I found that I got it. That is,
When the coating type chromate film is made of a single compound of Cr or Zr, it is difficult to obtain excellent coating adhesion and corrosion resistance. They have found that the adhesion and the corrosion resistance can be greatly improved. It is not yet clear why such a composite film of a Cr compound and a Zr compound can improve the adhesion and corrosion resistance of the coating film. It is presumed that the surface of the coating type chromate film is sometimes dissolved, the hydrophilic coating film and the coating type chromate film are integrated, and the adhesion of the coating film is enhanced.

Further, the present inventors have improved the water resistance and chemical resistance of the coating type chromate film by converting a part of the Cr compound and the Zr compound in the coating type chromate film into insoluble phosphates. Corrosion resistance and coating film adhesion,
In particular, it was found that the secondary coating adhesion (adhesion after immersion in water for a long time) was improved.

Further, F is added to the coating type chromate solution.
As a result, fluoride is contained in the coating type chromate film.
Being rare, on the aluminum alloy substrate
Between the coating type chromate liquid applied to the aluminum and aluminum
Chromatographic solution as described below.
Cr⁶⁺The ions are sufficiently reduced and Cr³⁺By ion
Compound, i.e., trivalent chromium Cr (III) compound
To significantly improve coating film adhesion and corrosion resistance
It was found that it could be improved. That is,
F in the solution is the coating type chromate
Dissolve the aluminum of the base material while applied to the alloy
Promote. At this time, Al → Al³⁺+ 3e^- Dissolution of
E generated by the reaction^-Is Cr in the coating type chromate solution
⁶⁺Cr ion ³⁺Contributes to the reduction to ions
r³⁺Ions produce chromium compounds of trivalent chromium Cr (III)
Chromium compound of trivalent chromium Cr (III)
Chromium conversion of hexavalent chromium Cr (VI)
It is much more dense than the film composed of the compound
The chromium compound of trivalent chromium Cr (III) is
Contributes to improved adhesion and corrosion resistance of chromate film
I do. In addition, Cr⁶⁺If the reduction of ions does not proceed enough
Hexavalent chromium Cr (VI) compound in coating type chromate film
Will remain in large quantities, but the hexavalent chromium Cr (VI)
Since compounds are generally water-soluble, hexavalent chromium
Pre-coated fins were exposed to water if Cr (VI) was high
Sometimes hexavalent chromium Cr (VI) elutes and causes environmental pollution.
You. Therefore, Cr in the coating type chromate film is trivalent
Desirably present as a compound of chromium Cr (III)
In order to do this, the addition of F
It is effective to increase the reactivity of aluminum with aluminum.

As described above, in order to improve the coating adhesion and corrosion resistance of the coating type chromate film, the film is formed of a Cr compound (oxide, hydroxide, phosphate, fluoride) and a Zr compound (oxide). , Hydroxide, phosphate, fluoride), and the addition of P is particularly effective in improving corrosion resistance and secondary coating adhesion through the improvement of water resistance and chemical resistance. Further, the addition of F is effective in improving the coating adhesion and corrosion resistance through densification of the coating by increasing the reactivity and promoting the formation of a compound of trivalent chromium Cr (III). Therefore, in the present invention, Zr, P, and F are essential as components of the coating type chromate film in addition to Cr. O and H are also indispensable in order to form a compound of Cr and a compound of Zr, especially an oxide and a hydroxide.
Therefore, O and H are also essential components of the coating type chromate film.

Further, the reason why the composition range of the coating type chromate film in the precoated fin material for a heat exchanger of the present invention will be described.

First, the amount of Cr in the coating type chromate film is in the range of 1 to 100 mg / m ^{2 in} terms of metal Cr. The Cr content is less than 1 mg / m ^2, not sufficient coating film adhesion, corrosion resistance is obtained, whereas 100 mg / m ²
If the ratio exceeds the above range, the film becomes brittle, for example, cracks are likely to be formed in the film, and the adhesion of the film decreases. Therefore, the amount of Cr needs to be in the range of 1 to 100 mg / m ² .

In addition, Cr / Zr in the coating type chromate film
Is in the range of 0.5 to 5 by weight. Cr / Z
If the r weight ratio is less than 0.5, the Cr compound in the coating will be excessive, while if the Cr / Zr weight ratio exceeds 5, Z in the coating will be excessive.
The r compound becomes excessive, and in any case, a significant improvement in coating film adhesion and corrosion resistance cannot be expected. Cr / Z
Only when a Cr compound or a Zr compound is contained so that the r weight ratio is in the range of 0.5 to 5, coating film adhesion,
It has been found from experiments by the present inventors that the corrosion resistance can be significantly improved.

Further, P / Cr in the coating type chromate film
The ratio must be in the range of 0.1 to 1 by weight.
When the P / Cr weight ratio is less than 0.1, the amounts of the formed chromium phosphate salt and zirconium phosphate salt are small, and the water resistance,
The effect of improving the chemical resistance cannot be obtained, which makes it difficult to improve the corrosion resistance and the coating film secondary adhesion. On the other hand, P
If the / Cr weight ratio exceeds 1, excessive phosphate remains in the coating, and P is eluted when the precoated fin is exposed to water, causing environmental pollution.

The F / Cr ratio in the coating type chromate film must be in the range of 0.04 to 2.5 by weight. If the F / Cr weight ratio in the coating is less than 0.04, the amount of F in the coating type chromate solution is too small, and the coating type chromate solution and the aluminum in a state where the coating type chromate solution is applied to the surface of the aluminum alloy base material. And the reduction of Cr ⁶⁺ ions to Cr ³⁺ ions does not proceed sufficiently, resulting in a large amount of hexavalent chromium Cr (VI) remaining in the coating. When the pre-coated fins are exposed to water, Cr (VI) elutes, causing environmental pollution.In addition, the amount of the trivalent chromium Cr (III) compound in the coating is insufficient, and the denseness of the coating is reduced. Cannot be improved, so that coating film adhesion and corrosion resistance cannot be sufficiently improved. On the other hand, if the F / Cr weight ratio in the coating exceeds 2.5, the amount of F becomes excessive and fluorides such as aluminum fluoride in the coating increase, and the denseness of the coating is lost.
On the contrary, the coating film adhesion and the corrosion resistance are reduced. Therefore, the amount of F in the film needs to be in the range of 0.04 to 2.5.

Further, trivalent chromium Cr (III) and hexavalent chromium Cr (V)
The ratio Cr (III) / Cr (VI) to I) needs to be 9 or more by weight. If the weight ratio of Cr (III) / Cr (VI) is less than 9, the amount of the water-soluble Cr (VI) compound in the film increases, and the Cr (VI) compound is exposed in a state where the precoated fin is exposed to water.
Elutes and causes environmental pollution, and C in the film
Since the amount of the r (III) compound is not sufficient, the denseness of the film cannot be sufficiently increased, and the adhesion and corrosion resistance of the film cannot be sufficiently improved.

The coating type chromate film contains, in addition to Cr, Zr, P, and F, O and H to form compounds such as chromium and Zr oxides and hydroxides. The amount of O and the amount of H are not particularly limited. However, in general, the amount of O is determined from the relationship between the amount of Cr and the weight ratio of Cr / Zr and the types of oxides and hydroxides to be generated. O / Cr weight ratio is about 0.5-3,
Further, it is desirable that the H content be contained such that the H / Cr weight ratio is about 0.05 to 0.25. However, these O amounts and H amounts exclude O and H contained in the resin component in the coating type chromate film.

In the coating type chromate film, the above-described Cr compound or Zr compound may be fixed as a film on the surface of the aluminum alloy base material, and a resin component may be included in order to improve moldability. The amount of the resin component in that case is not particularly limited, but generally, the resin / C
It is preferable that the r weight ratio be about 0.1 to 1.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION The aluminum alloy sheet used as a base material in the precoated fin material for a heat exchanger of the present invention is not particularly limited as long as it has been conventionally used as a fin material for a heat exchanger. Not something.
That is, JIS standard 1100 alloy, 1050 alloy,
Pure aluminum alloy such as 1N30 alloy or 20
Al-Cu alloys such as 17 alloy, 2024 alloy, and 3
Al-Mn alloys such as 003 alloy and 3004 alloy, 50
Al-Mg based alloys such as 52 alloy and 5083 alloy, and Al-Mg-Si based alloys such as 6061 alloy can be used. The shape of the aluminum alloy substrate is
In short, it is sufficient if the thickness is about 50 to 200 μm,
Either a sheet or a coil may be used.

In producing the precoated fin material for a heat exchanger of the present invention, the above-mentioned aluminum alloy base material (thin plate) is degreased, washed with water, dried and cooled, and then coated with a coating type chromate solution. The coating may be applied, and then heated for baking and drying to be solidified as a film on the substrate, and a hydrophilic coating film may be applied on the obtained coating type chromate film, followed by baking and drying.

Here, in applying a coating type chromate solution to an aluminum alloy base material to form a coating type chromate film which is a corrosion resistant film, a rolled oil-containing aluminum oxide film produced by rolling or annealing and It is necessary to remove the hydroxide film in the degreasing step. The degreasing step is not particularly limited, but may include one or more alkali compounds such as a hydroxide compound, a phosphoric acid compound, a carbonate compound and a silicate compound as an alkali inhibitor, and may be an aluminum alloy base. It is appropriate to use a degreasing agent containing a surfactant having an HLB of about 11 to 15 for removing and dispersing oil on the surface of the material.

Thus, an oxide film containing a rolling oil,
The means for applying the coating type chromate solution to the surface of the aluminum alloy substrate from which the hydroxide film has been removed is not particularly limited, and may be generally applied by a roll coater or spray. In addition, it is preferable that the temperature (liquid temperature) of the coating type chromate liquid at the time of coating be in the range of 10 to 45 ° C.

After the application type chromate solution is applied to the surface of the aluminum alloy base material, heating for baking and drying is performed. The time from the application until the start of heating is 0.5 seconds or more and 60 seconds or less. Is preferred. The heating for baking and drying is performed at 40 to 300 ° C., preferably 150 to 300 ° C.
A few seconds to a few minutes, preferably 5 seconds to 3 minutes
The condition may be 0 seconds.

As described above, the coating type chromate film formed on the surface of the aluminum alloy base material contains 1 to 100 mg / m ^{2 of} Cr, and
r, P, F, O, H, respectively, and Cr / Zr
Weight ratio is in the range of 0.5 to 5, P / Cr weight ratio is 0.1
, A F / Cr weight ratio in the range of 0.04 to 2.5, and a Cr compound (oxide, hydroxide) having a Cr (III) / Cr (VI) weight ratio of 9 or more. , Phosphates, fluorides) and Zr compounds (oxides, hydroxides, phosphates,
(Fluoride), and these compounds are fixed as a film by a resin. As described above, the coating type chromate liquid to be applied is also Cr, Z
It is necessary to contain r, P, F, O, and H.

Here, Cr in the coating type chromate solution
Hexavalent chromic acid (CrO _Three), P source
Phosphoric acid, hydrofluoric acid as the F source, and hydrofluoric acid as the Zr source.
It is preferable to use one containing Zr acid
In this state, most of the Cr in the liquid is Cr⁶⁺Because
Add an organic reducing agent such as³⁺Exist
It is desirable to keep it. In coating type chromate
Cr³⁺/ (Cr³⁺+ Cr⁶⁺) Is greater than 0.5
For example, the Cr (III) / C
The r (VI) weight ratio can be secured to 9 or more. Note that
Regarding the component ratio of each element in the cloth type chromate liquid,
A ratio similar to the weight ratio of each component in the coating already described
And the concentration can be adjusted according to the characteristics of the coating equipment.
It may be determined appropriately according to the above. In addition, application type chrome
The coating solution fixes the coating on the substrate and improves the moldability.
The weight ratio of resin / Cr is about 0.1 to 1
It is usually contained so that it becomes
Polyacrylic acid, polyacrylate, polyacrylic
Use of acrylic resin with excellent corrosion resistance such as amide
preferable.

As the base coating material for the hydrophilic coating film formed on the coating type chromate film, any of an organic polymer coating material and an inorganic coating material may be used as long as it has hydrophilicity. Examples of the organic polymer paint base material used for the hydrophilic coating film include polyvinyl alcohol, a cellulose resin such as carboxymethyl cellulose, acrylamide, acrylic acid, an acrylic resin mainly containing an acrylate ester, and an epoxy resin. It is suitable and may be a homopolymer thereof, a mixture of two or more thereof, or a copolymer thereof. These resins may be of a self-crosslinking type, if necessary, hexabutylol melamine, a melamine compound such as hexabutylol methyl melamine, a compound containing an epoxy group, urea to which a butyrol group is added, or A curing agent such as a compound having an isocyanate group may be added. On the other hand, the inorganic paint used for the hydrophilic coating film may be an inorganic paint mainly composed of water glass, colloidal silica, or the like, or may be a mixed paint of acrylic resin or polyvinyl alcohol. Further, a metal cross-linking agent such as zirconate may be added.

Further, these hydrophilic coating film forming paints include:
Polyoxyethylene alkylphenyl ether, polyoxyethylene alkyl ether, sorbitan fatty acid ester, polyoxyethylene-added sorbitan fatty acid ester, sucrose fatty acid ester, polyoxyethylene polyoxypropylene block copolymer, polyoxyethylene lanolin alcohol ether, polyoxy Nonionic surfactants such as ethylene alkylamine ethers, anionic surfactants such as dialkyl sulfosuccinates, alkyl sulfonates, alkyl phosphates, polyoxyethylene alkyl phosphates, and cations such as alkyl trimethyl ammonium chloride It may contain a surfactant.

The amount of the applied hydrophilic coating, the drying temperature and the drying time cannot be specified by the characteristics of the coating for forming the hydrophilic coating, the characteristics of the drying oven, and the like. In the case of a product, the coating amount is 0.1 to 5 g
/ M ² , preferably 0.2 to 1.5 g / m ² , and the heating and drying temperature is 140 to 300 ° C., preferably 150 to 250 ° C. in the case of the thermosetting type, and the heating and drying time is 5 to 60 seconds, preferably 10 to 30 seconds. The coating amount is 0.1 g / m ²
If it is less than 3, hydrophilicity tends to be insufficient, and 5 g / m ²
If the ratio exceeds the above, the hydrophilicity is not improved, and only the cost is increased. On the other hand, in the case of an inorganic hydrophilic coating film such as a water glass type or a colloidal silica type, the amount of Si is 20 to 400 mg / m 2.
² , preferably in the range of 50 to 300 mg / m ² .
If it is less than 50 mg / m ² , sufficient hydrophilicity cannot be obtained, and if it exceeds 400 mg / m ² , not only does the hydrophilicity not improve any more, but also the precipitated silicon compound becomes powdery and the coating film adhesion becomes poor. This causes problems such as the coating film being easily peeled off in press molding or the like.

[0039]

EXAMPLES Example 1 A 0.1 mm thick aluminum alloy thin plate (J
IS 1100 alloy H24 material) and prepare an alkaline degreasing agent containing a surfactant on its thin plate (Nippon Paint Co., Ltd.)
(Trade name: Surf Cleaner 330) with a 1% aqueous solution at 60 ° C by spray degreasing (spray pressure = 2 kgf /
cm ² , spray time = 10 seconds), followed by washing and drying. Thereafter, a coating type chromate solution containing chromic acid, phosphoric acid, hydrofluoric acid, and fluorinated zirconium acid and having various composition ratios was applied, and heated and baked at 150 ° C. for 15 seconds to form a film as shown in Table 1. A coating type chromate film having the composition was prepared. Water glass-based paint (Nippon Paint Co., Ltd.) is applied as a hydrophilic paint on this coating type chromate film.
(Trade name: SAT131) at 200 ° C.
After baking for ² seconds, a hydrophilic coating film having a Si content of 200 mg / m ² was formed to obtain a precoated fin material.

With respect to the obtained precoated fin material, adhesion of the coating film, corrosion resistance, and elution of Cr and P were examined as follows.

Film adhesion: 3/16 inφ steel ball, load 1
00gf, rubbing the same part of the coating film surface without lubrication,
The number of times until coating film peeling was examined. The evaluation criteria are as follows. ◎: No peeling even after sliding 15 times ○: Peeling after 10 to less than 15 times △: Peeling after 5 to less than 10 times ×: Peeling after 1 to less than 5 times

Corrosion resistance: salt spray test (SST) of 100
Performed for 0 hours and evaluated as follows. ：: Corrosion area rate less than 0.25% △: Corrosion area rate 0.25% or more and less than 2.5% ×: Corrosion area rate 2.5% or more

Cr elution, P elution: Precoated fin
3 m ² was immersed in 200 ml of pure water for 72 hours, and the amounts of Cr and P in the liquid were measured by ICP and evaluated as follows. ◎: 0.1 ppm or less ○: 0.1 ppm or more and less than 0.3 ppm Δ: 0.3 ppm or more and less than 0.7 ppm ×: 0.7 ppm or more

The evaluation results are shown in Table 1.

[0045]

[Table 1]

Example 2 After forming a coating type chromate film in the same manner as in Example 1, an organic paint (manufactured by Nippon Paint Co., Ltd., trade name: SAT240) was applied as a hydrophilic paint film. ° C
For 20 seconds to form a hydrophilic coating film having a coating amount of 1.0 g / m ² , thereby obtaining a precoated fin material.

Example 1 for each precoated fin material
In the same manner as described above, the coating film adhesion, corrosion resistance, and elution of Cr and P were examined. The results are also shown in Table 2.

[0048]

[Table 2]

As shown in Tables 1 and 2, Example 1-1 in which the composition of the coating type chromate film was within the scope of the present invention.
Each of the precoated fin materials of Examples 1 to 2 to 14 and Examples 2-1 to 2-14 shows good coating adhesion and excellent corrosion resistance, and has a high C content when exposed to water.
It was confirmed that there was little r elution and P elution, and there was no risk of environmental pollution.

On the other hand, Comparative Examples 1-1 and 2-1 are examples in which the Cr / Zr weight ratio in the coating type chromate film was less than 0.5. In these cases, the adhesion of the coating film and the corrosion resistance were poor. Both were inferior. Comparative Examples 1-2 and 2-2 are examples in which the P / Cr weight ratio in the coating type chromate film was less than 0.04. In these cases, the film adhesion was slightly inferior and the corrosion resistance was poor. Was inferior. And again, Comparative Example 1-3,
2-3 is an example in which the weight ratio of P / Cr in the coating was more than 1. In these cases, although the coating film adhesion and corrosion resistance were relatively good, it was found that P elution was large. Further, in Comparative Examples 1-4 and 2-4, the F / Cr weight ratio in the coating was 0.3.
In this case, the weight ratio of Cr (III) / Cr (VI) is less than 9, but in these cases, the corrosion resistance is slightly inferior, and
It was found that r elution was large. Comparative Examples 1-5 and 2-
No. 5 does not contain F in the film and has a Cr (III) / Cr (V
I) Although the weight ratio was extremely small, it was found that in these cases, the coating film adhesion was inferior, the corrosion resistance was slightly inferior, and the Cr elution was large. Comparative Examples 1-6
2-6 is an example in which the F / Cr ratio in the coating is higher than 2.5, and in these cases, it was also found that the coating adhesion was poor.

[0051]

As is clear from the above-mentioned embodiments, the precoated fin material for heat exchanger of the present invention has a coating type chromate film formed on the surface of a base material made of an aluminum alloy, and the coating type chromate film is formed on the coating type chromate film. As a pre-coated fin material for a heat exchanger with a hydrophilic coating film formed, the composition of the coating type chromate film is appropriately set, and the coating type chromate film is converted to a chromium compound, particularly an oxide of Cr (III), The adhesion of the coating film significantly more than before by forming a coating comprising a substance, a phosphate, a fluoride and a zirconium compound, particularly an oxide, hydroxide, phosphate, or fluoride of Zr. It is possible to remove the coating film during molding of the pre-coated fin material,
In particular, even when molding using low-viscosity volatile press oil, molding can be performed stably to good quality without forming defects such as buckling, cracking, and jumping due to the collar part, and corrosion resistance. Is also significantly better.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Nobuyoshi Sasaki 1-2-1 Kinshi, Sumida-ku, Tokyo Sky Aluminum Co., Ltd. F-term (reference) 4K026 AA09 BA06 BA12 BB02 BB06 BB08 CA16 CA18 CA19 CA21 CA26 CA28 CA39 DA02 DA15 DA16 EB08

Claims (1)

[Claims] 1. A pre-coated fin material for a heat exchanger in which a coating type chromate film is formed on the surface of an aluminum alloy substrate and a hydrophilic coating film is formed on the coating type chromate film, wherein the coating type chromate film is , Cr in an amount of 1 to 100 mg /
as well as m ² containing, Zr, P, F, O, H and containing respectively, and in the range of 0.5 to 5 weight ratio of Cr / Zr, a 0.1 to 1 weight ratio of P / Cr Within range, F / Cr
Characterized in that the weight ratio of Cr (III) / Cr (VI) in the chromium compound is 9 or more. Pre-coated fin material for exchangers.