KR20170000199A

KR20170000199A - Surface treatment method and surface treatment of an aluminum-based substrate base

Info

Publication number: KR20170000199A
Application number: KR1020150089112A
Authority: KR
Inventors: 송미수
Original assignee: 송미수
Priority date: 2015-06-23
Filing date: 2015-06-23
Publication date: 2017-01-02

Abstract

A surface treatment method of an aluminum base material capable of forming a chemical conversion coating film and a hydrophilic coating film having excellent corrosion resistance, hydrophilicity and releasability with respect to an aluminum base material, and a surface treatment base material and a heat exchanger treated thereby.
(1) of forming a chemical conversion coating on the surface of an aluminum base material by a chemical conversion treatment with a chemical conversion agent composed of a fluorine- and zirconium-containing compound and / or a fluorine- and titanium-containing compound,
(2), wherein the chemical conversion reaction is an aluminum-based surface treatment method performed by an electrolytic treatment.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treatment method of an aluminum-

TECHNICAL FIELD [0001] The present invention relates to a surface treatment method, a surface treatment substrate, and a heat exchanger of an aluminum base material.

The heat exchanger is generally made of aluminum and has a complicated structure in which the fins for performing the heat exchange are held between the tubes at narrow intervals. When the heat exchanger is used for cooling, Condensed and attached to the surface as water droplets.

The attached water droplets are clogged at the pin gaps to increase the ventilation resistance to lower the heat exchange rate or to scatter in the room by the blower and cause an unpleasant odor. Water condensed during cooling

Thereby facilitating the discharge of minute particles.

In addition, condensed water droplets cause corrosion of aluminum or an aluminum alloy, so that the surface of the fin is oxidized in the form of white powder

There is also a problem of attaching aluminum. For this reason, the surface of aluminum or an aluminum alloy is generally subjected to surface treatment for the purpose of improving properties such as corrosion resistance.

As a kind of such a surface treatment, surface treatment by a chemical treatment agent containing a zirconium compound and a titanium compound is known. Such a surface treatment method is performed by an electroless reaction, The elution reaction and the reaction in which the hydrogen ions are reduced and the hydrogen is generated cause the pH rise in the vicinity of the surface of the object to be treated so that the fluorine of the zirconium complex ion and the titanium complex ion is displaced by the hydroxide ion, An insoluble zirconium salt film composed of a hydroxide or oxide of zirconium precipitates on the surface of the metal.

In the electroless reaction of the zirconium conversion treating agent and the titanylation treating agent, it is difficult to cause a uniform reaction on the entire surface of the object to be processed. Therefore, it is difficult to form a sufficiently dense and uniform film, And the corrosion resistance is deteriorated or the adhesion after painting is lowered. In addition, since the reactivity is low, it is also necessary to raise the reaction temperature. In addition, there is a problem that it is necessary to perform the acid washing step.

Therefore, in the surface treatment of aluminum metal, it is required to achieve a higher level of corrosion resistance by forming a chemical conversion coating film obtained by electroless reaction using a zirconium chemical conversion treatment agent and a titanium chemical conversion treatment agent with good properties Therefore, a surface treatment method capable of forming a more uniform and dense chemical film is required.

Also, as a metal surface treatment method, there is known a surface treatment method by an electrolytic reaction. In addition, sludge is generated by reaction with metal ions during the phosphate treatment, and the aluminum alloy has insufficient corrosion resistance particularly for zirconium treatment. However, there is a problem in that the conversion treatment using a phosphate compound gives a load to the environment due to eutrophication. Moreover, these have not been developed for the purpose of improving corrosion resistance and hydrophilicity of an aluminum fin of a heat exchanger .

Furthermore, as a surface treatment for aluminum, a method is known in which a chemical conversion coating is formed by chemical conversion treatment and then a hydrophilic coating is formed

However, they are a method of forming a chemical conversion film by performing chemical conversion treatment by electroless treatment. For this reason, it is desired to form a more uniform and dense chemical film.

Therefore, development of a surface treatment method capable of imparting superior corrosion resistance to the aluminum or aluminum alloy used in the fin or the like of a heat exchanger, while maintaining excellent hydrophilicity and antifouling property is desired.

In view of the above, it is an object of the present invention to provide an aluminum base surface treatment method capable of forming a chemical conversion coating film and a hydrophilic coating film having excellent corrosion resistance, hydrophilicity and releasability, and a surface treatment base material and a heat exchanger treated thereby The purpose is to do.

The present invention relates to a method for producing a hydrophilic coating film, comprising the steps of (1) forming a chemical conversion coating on the surface of an aluminum base material by a chemical conversion treatment with a chemical conversion agent composed of fluorine and a zirconium-containing compound and / of

(2), wherein the chemical conversion treatment is carried out by an electrolytic treatment. The aluminum-based surface treatment method according to claim 1,

Since the surface treatment method of the aluminum base material of the present invention has the above-described constitution, the corrosion resistance can be improved as compared with the case of performing the electroless treatment. In addition, since the hydrophilic coating is formed, not only excellent hydrophilicity and defoaming property but also corrosion resistance can be further improved. In addition, it is a method in which the load on the environment is small and the occurrence of sludge is suppressed.

Therefore, the present invention can be suitably applied to an aluminum base material such as a heat exchanger, an automobile evaporator and the like.

The chemical conversion treatment agent preferably has a concentration of fluorine and a zirconium-containing compound of 10 to 1000 ppm in terms of zirconium metal, an effective fluorine ion concentration of 0.1 to 1000 ppm, and a pH of 1 to 6.

The chemical conversion treatment agent preferably has a concentration of fluorine and titanium-containing compounds of 10 to 100,000 ppm in terms of titanium metal, an effective fluorine ion concentration of 0.1 to 1,000 ppm, and a pH of 1 to 6.

The electrolytic treatment is preferably a cathode electrolysis treatment under the condition of a voltage of 0.1 to 40 V and a current density of 0.01 to 300 A / dm 2.

Preferably, the chemical conversion coating formed by the step (1) has an amount of zirconium in the chemical conversion coating of 1 to 1000 mg / m 2, and the hydrophilic coating formed by the step (2) has a hydrophilic coating amount of 0.01 to 10 g / Do.

The present invention is a surface treatment substrate characterized by having a chemical conversion coating and a hydrophilic coating obtained by the surface treatment method of the aluminum base.

The present invention is also a heat exchanger characterized by having a chemical conversion coating and a hydrophilic coating obtained by a surface treatment method of an aluminum base.

Hereinafter, the present invention will be described in detail.

A method for surface treatment of an aluminum base material according to the present invention is a method comprising a step (1) of forming a chemical film by an electrolytic treatment and a step (2) of forming a hydrophilic film using a hydrophilic agent, And a hydrophilic film and a hydrophilic film are formed on the surface of the substrate.

In the surface treatment method of the aluminum base material, since a dense chemical film can be formed on the surface of the aluminum base material by performing the step (1), the corrosion resistance of the aluminum base material can be greatly improved. In addition, by carrying out step (2)

(1), the corrosion resistance of the material can be greatly improved, so that the corrosion resistance of the corrosion-resistant material such as aluminum hydroxide And as a result, the cause of dust odor can be eliminated. Therefore, it is presumed that it is possible to further improve the embrittlement property by performing both the steps (1) and (2). Therefore, by using the surface treatment method of the aluminum base material, it is possible to obtain a surface-treated aluminum base material having both excellent corrosion resistance, hydrophilicity and flame retardancy. It can be suitably applied to heat exchangers, evaporators for automobiles, room air conditioners, and the like.

In the electroless treatment, it is necessary to carry out the degreasing step or the etching step for the purpose of improving the chemical conversion property or forming a uniform chemical conversion film. However, in the case of the electrolytic treatment such as the surface treatment method of the aluminum- And the conditions of the degreasing step and the etching step can be alleviated or omitted because the coating film can be made compact as described above. The electrolytic treatment step can also be carried out in a manner that facilitates the bath management of the chemical conversion treatment bath Furthermore, since the deodorizing performance can be greatly improved, it is possible to make the hydrophilic coating thinner and to simplify the formation of the hydrophilic coating.

In the surface treatment method of an aluminum base material of the present invention, a step of electrolytically treating the surface of an aluminum base material by a chemical conversion treatment agent composed of a fluorine- and zirconium-containing compound and / or a fluorine- and titanium- (Step (1)). When the reaction is carried out by an electrolytic treatment, the film becomes denser and more uniform than the chemical conversion film by the electroless treatment. A chemical conversion coating excellent in corrosion resistance is formed.

When the electrolytic reaction is carried out with a chemical conversion agent composed of a fluorine- and zirconium-containing compound and / or a fluorine- and a titanium-containing compound, a corrosion-resistant chemical film having a very excellent corrosion resistance can be obtained. By electrolysis reaction of a phosphate- Corrosion resistance superior to that of the obtained chemical conversion film can be obtained.

The fluorine and zirconium-containing compound is not particularly limited, and examples thereof include fluorozirconic acid or its lithium, sodium, potassium, ammonium salt, zirconium fluoride and the like. It may also be one obtained by dissolving a zirconium compound such as zirconium oxide in a fluoride aqueous solution such as hydrofluoric acid.

The fluorine- and titanium-containing compound is not particularly limited, and examples thereof include alkali metal fluorotitanate, fluorotitanate such as (NH4) 2TiF6; Soluble fluorozirconate such as fluorotitanate acid such as H 2 TiF 6; And titanium fluoride. It may also be one obtained by dissolving a titanium compound such as titanium oxide in a fluoride aqueous solution such as hydrofluoric acid.

In addition to the above zirconium fluoride and titanium fluoride, the fluorine concentration may be adjusted by using hydrofluoric acid, ammonium fluoride, ammonium fluoride, sodium fluoride, sodium hydrofluoride, or the like in combination.

The fluorine and zirconium-containing compounds are preferably compounded in the above-mentioned chemical conversion agent in a range of a lower limit of 10 ppm and an upper limit of 10000 ppm in terms of zirconium metal. If it is less than 10 ppm, the zirconium compound does not sufficiently precipitate on the surface of the metal, so that the corrosion resistance may not be improved. , And the upper limit is more preferably 3000 ppm.

The fluorine- and titanium-containing compound is preferably compounded in the above-mentioned chemical conversion agent in a range of a lower limit of 10 ppm and an upper limit of 100000 ppm in terms of titanium metal. If it is less than 10 ppm, the titanium compound does not sufficiently precipitate on the metal surface, and therefore corrosion resistance may not be improved. And the upper limit is more preferably 3000 ppm.

When the chemical conversion agent contains fluorine and a zirconium-containing compound and a fluorine-containing compound, it is preferable that the total amount of zirconium and titanium is within the above range in terms of metal.

When the electrolytic reaction is carried out by a chemical conversion treatment agent composed of a fluorine- and zirconium-containing compound, a corrosion-resistant chemical film having excellent corrosion resistance is obtained.

For example, when a chemical conversion coating is formed by electrolytically treating a zinc phosphate treatment agent, crystals of zinc phosphate in the coating are reduced. Therefore, the coating film formed by the electrolytic treatment of the zinc phosphate treatment agent becomes a crystalline zinc phosphate coating densely formed by small crystals.

On the other hand, in the case of forming a chemical conversion film by electrolytic treatment of the chemical conversion treatment agent in the present invention, the formed film is not a crystalline film but an amorphous film. Therefore, it is presumed that when the electrolytic treatment is carried out using the chemical conversion treatment agent, the crystal in the formed film is not reduced, and the amorphous film which is not porous is uniformly coated. Therefore, the electrolytic treatment of the phosphatizing agent and the electrolytic treatment of the treating agent of the fluorine and zirconium-containing compound are greatly different from each other.

In the case of surface treatment of an aluminum base material, aluminum ions are generally accumulated in the equilibrium bath composition. In this case, since accumulation of aluminum of 500 ppm or more in the electroless treatment inhibits the chemical reactivity, On the other hand, since the electrolytic treatment film is formed in a relatively small amount of aluminum ion etching (the film conversion efficiency is good) and the influence on the accumulated aluminum ions is small, It becomes unnecessary.

It is preferable that the chemical treatment agent has an effective fluorine ion concentration within a range of a lower limit of 0.1 ppm and an upper limit of 10000 ppm. The effective fluorine ion concentration is HF or F - which does not form a complex with an aluminum ion, a zirconium ion, If the effective fluorine ion concentration is less than 0.1 ppm, there is a problem that sufficient etching prevention of the aluminum surface does not proceed. Therefore, when the effective fluorine ion concentration is more than 10,000 ppm, there is a problem that rust prevention performance can not be obtained due to excessive etching. It is more preferable that the lower limit is 0.5 ppm, and the upper limit is more preferably 100 ppm.

It is preferable that the pH of the chemical conversion agent is in the range of the lower limit of 1 and the upper limit of 6. If the pH is less than 1, the precipitation of the zirconium compound and the titanium compound becomes difficult, so that a sufficient coating amount can not be obtained and the corrosion resistance may be lowered. If the pH exceeds 6, a sufficient amount of coating can not be obtained, which is not preferable. The lower limit is preferably 2, and the upper limit is more preferably 5.

In addition to the above components, the chemical conversion agent may be a metal ion such as titanium, manganese, silicon, zinc, cerium, iron, molybdenum, vanadium, trivalent chromium, or magnesium; Other rust inhibitors such as tannic acid, imidazoles, triazines, triazoles, guanines, hydrazines, biguanides, phenolic resins, silane coupling agents, colloidal silicas, amines and phosphoric acid; Surfactants; Chelating agents; And the like.

In the step (1) of the surface treatment method of the aluminum base material of the present invention, the electrolytic treatment may be electrolysis at either the cathode or the anode. In any case, the electrolytic treatment can be performed by a known method,

It is preferable that the cathode electrolysis treatment is an electrolysis treatment by using an object to be treated.

The cathode electrolysis treatment preferably has a lower voltage of 0.1 V and an upper limit of 40 V. If the voltage is lower than 0.1 V, the amount of the film is decreased and the corrosion resistance is lowered. If the voltage is higher than 40 V, Saturated and energetically unfavorable

The lower limit is more preferably 1 V, and the upper limit is more preferably 30 V. In the cathode electrolysis treatment, the current is lowered to a lower limit of 0. 1 A / dm 2 and an upper limit of 30 A / dm 2 If it is less than 0.1 A / dm < 2 >, the amount of the coating film is decreased and corrosion resistance may be lowered. When it exceeds 30 A / dm < 2 >, the effect of increasing the amount of coating is saturated,

The lower limit is more preferably 0.2 A / dm 2, and the upper limit is more preferably 10 A / dm 2.

The treatment time of the cathode electrolytic treatment is preferably 3 seconds at the lower limit and 180 seconds at the upper limit. If it is less than 3 seconds, the film is less likely to be formed and the corrosion resistance is poor and control of the electrolysis treatment is difficult. If it exceeds,

There is a fear that the increase effect becomes saturated and it becomes energetically unfavorable.

The treatment temperature of the cathode electrolysis treatment is preferably 10 deg. C lower limit and 70 deg. C upper limit. If the temperature is lower than 10 ° C, the film is less likely to be formed and the corrosion resistance is deteriorated, and the electrolysis treatment may be difficult to control.

There is a fear that the energy becomes disadvantageous.

In the electrolytic treatment, the electrode used as the opposite electrode is not particularly limited as long as it is an electrode that does not dissolve in the chemical conversion treatment agent. Examples of the electrode include stainless steel, platinum-plated titanium, niobium-plated titanium, carbon, iron, .

It is preferable that the chemical conversion coating formed by the step (1) has a coating amount of zirconium within a range of a lower limit of 1 mg / m 2 and an upper limit of 1000 mg / m 2. If it is less than 1 mg / m 2, corrosion resistance may not be sufficient. / M < 2 >

The lower limit is more preferably 10 mg / m 2, and the upper limit is more preferably 100 mg / m 2.

It is preferable that the chemical conversion coating formed by the step (1) has a coating amount of titanium within the range of the lower limit of 1 mg / m 2 and the upper limit of 1000 mg / m 2. When the coating film is less than 1 mg / m 2, the corrosion resistance may not be sufficient. / M < 2 >

In the case where the step (1) is carried out with a chemical conversion treatment agent composed of a fluorine- and zirconium-containing compound and a fluorine- and titanium-containing compound, the chemical conversion coating film formed by the step (1) has a total amount of zirconium and titanium, ㎡, upper limit 1000

Mg / m < 2 >. If less than 1 mg / m < 2 >, the corrosion resistance may not be sufficient. If it exceeds 1000 mg / m 2, no further effect is obtained, which is economically disadvantageous. The lower limit is more preferably 10 mg / m 2, and the upper limit is more preferably 100 mg / m 2.

In the method for surface treatment of an aluminum base material of the present invention, a step of forming a hydrophilic film on a chemical conversion film formed after forming the chemical conversion film by the above step (1) is carried out (step (2)). Not only the excellent corrosion resistance is imparted by the chemical conversion film formed in the step (1) but also the hydrophilic film and the water repellent property are imparted to the aluminum base material by forming the hydrophilic film in the step (2) It is also possible to do.

The hydrophilic treatment agent to be used in the step (2) is not particularly limited, and can be formed using a conventionally known hydrophilic treatment agent capable of forming a hydrophilic coating. Particularly, a post coat treatment, When it is used for treatment, it preferably contains a water-soluble or water-dispersible hydrophilic resin having a hydroxyl group, a carboxyl group, an amide group, an amino group, a sulfonic acid group and / or an ether group.

Examples of the hydrophilic resin include polyvinyl alcohol, polyvinylpyrrolidone, polyacrylic acid, polystyrenesulfonic acid, polyacrylamide, carboxymethylcellulose, polyethylene oxide, water-soluble nylon, a copolymer of monomers forming these polymers

, An acrylic polymer having a polyoxyethylene ring such as 2-methoxypolyethylene glycol methacrylate / 2-hydroxyethyl acrylate copolymer, a crosslinking agent comprising N-methylol acrylamide, copolymerization of methoxypolyethylene glycol monomethacrylate The hydrophilic treatment agent is preferably a hydrophilic treatment agent containing polyvinyl alcohol from the viewpoint of excellent hydrophilic property of the formed hydrophilic coating.

These hydrophilic resins have excellent hydrophilicity and water resistance, and have no odor of their own and are less likely to adsorb odorous substances. Therefore, the hydrophilic treatment agent containing the hydrophilic resin is excellent in hydrophilicity and defoaming property, and the obtained hydrophilic coating film has water droplets

Since it is difficult to deteriorate even when exposed to running water, it is difficult to expose an inorganic substance such as silica or other residual monomer components which is contained in the desired amount and which gives off an unpleasant smell of the substance or the adsorbed substance itself. It can prevent bad breathing or corrosion.

The hydrophilic resin preferably has a number average molecular weight in the range of the lower limit of 1,000 and the upper limit of 1,000,000. If it is less than 1000, the film-forming property is poor and the hydrophilic property and other physical properties of the film are inferior. When it exceeds 1000000, The workability and physical properties of the film are inferior. The lower limit is more preferably 10000, and the upper limit is more preferably 200000.

It is preferable that the hydrophilic resin has a solid content concentration in the hydrophilic treatment agent within a range of 0.01% by weight lower limit and 30% by weight upper limit. If it is less than 0.1% by weight, sufficient film formability and hydrophilicity can not be obtained. If it exceeds 30% by weight, the resultant hydrophilic treatment agent tends to flocculate and the workability and film properties are poor. , And the upper limit is more preferably 20% by weight.

As described above, the hydrophilic resin is more preferably polyvinyl alcohol, particularly preferably polyvinyl alcohol having a degree of saponification of 90% or more. If the saponification degree is less than 90%, the hydrophilicity may be poor. The degree of saponification is more preferably 95% or more. The polyvinyl alcohol may be partially modified.

These hydrophilic resins may be used alone or in combination of two or more. In this case, it is preferable that the saponification degree is a mixture of 90% or more of polyvinyl alcohol and other hydrophilic resins. Other hydrophilic resins may be hydrophilic

The resin is not particularly limited, but an additive resin or an additive compound made of a film having surface hydrophilicity by a hydrophilic functional group of the resin, or a film having a surface shape of an oxide or resin particle such as silica and having a hydrophilic property is preferable In the case of a mixture, the polyvinyl alcohol having a degree of saponification of 90% or more is preferably contained in an amount of 20% by weight or less as a solid content based on the total amount of the hydrophilic resin. The lower limit is preferably 40% by weight

The solvent of the hydrophilic treatment agent is not particularly limited, but it is preferable to use water as a main component from the viewpoint of waste liquid treatment and the like. The solvent is not particularly limited as long as it is generally used in paints and can be uniformly mixed with water. Examples of the solvent include alcohols , Ketones, esters, ethers, etc. The amount of the solvent to be used is preferably within a range of 0.01% by weight as the lower limit and 5% by weight as the upper limit with respect to the hydrophilic treatment agent.

The hydrophilic treatment agent may further contain other additives. The other additives are not particularly limited and include, for example, a hardening agent, a dispersant, a rust preventive additive, a pigment, a silane coupling agent, an antibacterial agent, a surfactant, Deodorant and the like.

The curing agent is not particularly limited and includes, for example, melamine resin, block isocyanate compound, epoxy compound, oxazoline compound, and carboymide compound.

The dispersion agent is not particularly limited, and examples thereof include surfactants and dispersion resins.

The rust preventive additive is not particularly limited and examples thereof include tannic acid, imidazole compound, triazine compound, triazole compound, guanine compound, hydrazine compound and zirconium compound. Among them, The zirconium compound is not particularly limited, and examples thereof include alkali metal fluorozirconates such as K 2 ZrF 6; (NH 4) 2 ZrF 6; Soluble fluorozirconates such as fluorozirconate acids such as H 2 ZrF 6 and the like; Zirconium fluoride; Zirconium oxide, and the like.

Examples of the pigment include titanium oxide (TiO 2), zinc oxide (ZnO), zirconium oxide (ZrO 2), calcium carbonate (CaCO 3), barium sulfate (BaSO 4), alumina (Al 2 O 3) , Carbon black, iron oxide (Fe 2 O 3, Fe 3 O 4), and various coloring pigments such as aluminum oxide (Al 2 O 3) inorganic pigments and organic pigments.

The incorporation of the silane coupling agent is preferable in that the affinity between the organic resin and the pigment can be improved and the adhesiveness and the like can be improved.

Examples of the silane coupling agent include, but are not limited to, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltri Ethoxysilane, N- [2- (vinylbenzylamino)

Ethyl] -3-aminopropyltrimethoxysilane, and the like.

The antimicrobial agent is not particularly limited, and for example, conventionally known antimicrobial agents such as 2- (4-thiazonyl) -benzimidazole and zinc pyrithione can be used.

The hydrophilic coating formed by the step (2) preferably has a hydrophilic coating amount of 0.01 g / m < 2 > and an upper limit of 10 g / m & If it is more than 10 g / m < 2 >, it is economically disadvantageous because no further effect is obtained. The lower limit is more preferably 0.1 g / m < 2 & Is more preferably 1 g / m < 2 >.

The material to be treated to which the aluminum-based surface treatment method of the present invention can be applied is applicable to all substrates containing aluminum metal generally used. For example, aluminum alloys of 5000 series, aluminum alloys of 6000 series, 1000

Aluminum alloy, aluminum silicon alloy, aluminum manganese alloy, and the like, and includes those molded in a heat exchanger such as an air conditioner such as a tube, a fin and a hollow plate.

In the surface treatment method of the aluminum base material of the present invention, it is preferable that the surface of the aluminum base material is subjected to a degreasing treatment and a degreasing water cleaning treatment before the electrolytic treatment in the step (1).

The degreasing treatment is carried out to remove oil and contamination adhering to the surface of the substrate, and the immersion treatment is usually carried out at a temperature of 30 to 55 DEG C for several minutes by a degreasing agent such as an unmanned and non-nitrogen degreasing cleaning liquid. , It is also possible to perform the preliminary degreasing treatment before the degreasing treatment.

The degreasing water washing treatment is carried out by spraying one or more times with a large amount of washing water to rinse the degreasing agent after the degreasing treatment. After the electrolytic treatment, the water washing treatment may be performed.

The present invention is also a surface treatment base material having a chemical conversion coating film and a hydrophilic coating film obtained by applying the surface treatment method of an aluminum base material to an aluminum base material. The surface treatment base material of the present invention further comprises a cation electrodeposition coating, Etc. The coating that can be applied to the surface treatment base material of the present invention is not particularly limited and includes a cation electrodeposition coating and a powder coating. The electrodeposition coating is not particularly limited, and it is possible to apply conventionally known cationic electrodeposition coatings composed of an aminated epoxy resin, an aminated acrylic resin, a sulfonated epoxy resin or the like. Aluminum Applicable to heat exchangers and automobile evaporators It is preferred. By applying to a heat exchanger, an automobile evaporator

The treated material obtained is excellent in corrosion resistance, hydrophilicity and flame retardancy, and thus can be suitably used.

The method for surface treatment of an aluminum base material of the present invention comprises the steps of (1) forming a chemical film by electrolytic treatment of a chemical agent composed of fluorine and a zirconium-containing compound and / or a fluorine- and titanium-containing compound, (2) for forming a hydrophilic coating film is applied to an aluminum base material. Thus, a surface treatment base material having excellent corrosion resistance, hydrophilicity and flammability can be obtained.

The present invention forms a coating film by electrolytic treatment, and therefore, it is possible to form a coating film densely, and it is possible to remarkably improve the corrosion resistance even in the same coating amount as compared with the case where a coating film is formed by electroless treatment, that

It is possible to form a film on the surface.

Claims

A step (1) of forming a chemical conversion coating on the surface of an aluminum base material by a chemical conversion treatment with a chemical conversion agent composed of a fluorine- and zirconium-containing compound and a fluorine- and a titanium-containing compound, and a step of forming a hydrophilic coating 2), characterized in that the above-described chemical treatment reaction is carried out by an electrolytic treatment.

Wherein the concentration of the fluorine and the zirconium-containing compound in terms of zirconium metal is from 10 to 1,000 ppm, the effective fluorine ion concentration is from 0.1 to 10,000 ppm, and the pH is from 1 to 6, (2).

The chemical conversion treatment agent according to claim 1, wherein the chemical conversion treatment agent is one selected from the group consisting of an aluminum-based compound having a concentration of fluorine and a titanium-containing compound of 10 to 1000 ppm in terms of titanium metal, an effective fluorine ion concentration of 0.1 to 100 ppm, (2).

The electrolytic treatment method according to any one of claims 1 to 3, wherein the electrolytic treatment is a cathode electrolysis treatment under a condition of a voltage of 0.1 to 40 V and a current density of 0.01 to 30 A / dm 2 Surface treatment method.

The method according to any one of claims 1 to 4, wherein the chemical conversion coating formed by the step (1) has a zirconium content of 1 to 1000 mg / m 2 in the chemical conversion coating film and the hydrophilic coating film formed by the step (2) To 0.01 g / m < 2 >.

A surface treatment substrate characterized by having a chemical conversion coating film and a hydrophilic coating film obtained by the surface treatment method of an aluminum base material according to any one of claims 1 to 5.

A heat exchanger characterized by having a chemical conversion coating and a hydrophilic coating obtained by a surface treatment method of an aluminum base according to any one of claims 1 to 5.