JP5537233B2 - Corrosion-resistant treatment method for aluminum heat exchanger - Google Patents

Description

  INDUSTRIAL APPLICABILITY The present invention is used for an aluminum heat exchanger (hereinafter also referred to as an NB heat exchanger) brazed with a flux by a Nocolok brazing method (hereinafter also referred to as an NB method), particularly an automobile air conditioner. The present invention relates to a corrosion-resistant treatment method for an aluminum material heat exchanger.

In heat exchangers used for air conditioners for automobiles, aluminum fins are usually held at a narrow interval in order to obtain as much heat exchange surface area as possible, and furthermore, aluminum tubes for supplying refrigerant to these fins are arranged in a complicated manner. It has a complicated structure. Moisture in the air adheres to the fin surface as condensed water when the air conditioner is operating, but on the fin surface with poor wettability, it becomes a substantially hemispherical water droplet or it exists in a bridge shape between the fins, making the exhaust smooth This hinders the flow and increases the draft resistance. Thus, if the wettability of the fin surface is poor, the heat exchange efficiency is lowered.
Furthermore, aluminum and its alloys constituting aluminum fins and aluminum tubes (hereinafter referred to as “aluminum fins”) are usually excellent in rust prevention, but if condensed water stays on the fin surface for a long time, Oxygen concentration cells are formed, or pollutants in the atmosphere are gradually adhered and concentrated to promote hydration and corrosion reactions. This corrosion product accumulates on the fin surface, impairs heat exchange characteristics, and becomes white fine powder and is discharged by a blower.

  Therefore, in order to improve these problems, for example, after washing the aluminum heat exchanger with an acid, it is immersed in a zirconium-based chemical conversion treatment solution and subjected to a zirconium chemical conversion treatment, and then modified polyvinyl alcohol, phosphorus compound salt, boron compound salt , Surface treatment methods for imparting good hydrophilicity and deodorizing properties to the aluminum surface by immersing in a hydrophilic treatment liquid mixed with a hydrophilic organic compound, a crosslinking agent, etc. have been proposed (Patent Documents). 1).

On the other hand, aluminum heat exchangers used in air conditioners for automobiles are made by assembling many aluminum fins and aluminum tubes, and then joining aluminum fins together or aluminum fins and aluminum tubes. Since a strong and dense oxide film is formed, joining by brazing or soldering other than the mechanical joining method cannot be easily performed. As a brazing method, the VB method (vacuum brazing) is used for brazing in vacuum. The method was mainly used.
However, in recent years, halogen-based fluxes have been developed as a means for effectively removing and destroying oxide films. Brazing is easy to manage, the furnace is inexpensive, and brazing costs are low. A flux brazing method represented by the NB method for brazing has come to be used.
This NB method is a method of assembling aluminum fins and the like and then brazing the aluminum fins and the like in nitrogen gas using a flux such as KAlF ₄ and K ₂ AlF ₅ . It has also been applied to fabrication.
However, the NB heat exchanger manufactured by this NB method has a non-uniform surface condition because flux unavoidably remains on the aluminum surface, and uniform surface treatment such as chemical conversion treatment and hydrophilization treatment cannot be performed. There is a problem peculiar to NB heat exchangers such as insufficient corrosion resistance and adhesion.

Therefore, until now, in the surface treatment of NB heat exchanger, (1) flux removal process, (2) chemical conversion treatment process (rust prevention process), (3) hydrophilization treatment process have been performed in order, There is a problem that halogen-based wastewater is generated in the removal process. In addition, the flux removal process is performed by etching with acid or alkali to improve the chemical conversion property, but since only the flux cannot be removed, there is a problem in that the aluminum fins are excessively etched and uniform chemical conversion treatment cannot be performed. .
Furthermore, a Cr ^{6 + -free} chemical conversion treatment is required due to safety issues to the human body, but in that case, the corrosion resistance is insufficient. Furthermore, reduction of the number of processes has been demanded.

  As a method of surface-treating the NB heat exchanger in order to cope with such problems, for example, the NB heat exchanger is immersed in a zirconium-based chemical conversion treatment solution and then subjected to zirconium chemical conversion treatment, and then modified with polyvinyl alcohol or polyoxyalkylene. A surface treatment method has been proposed in which a hydrophilic treatment is performed by immersing in a hydrophilic treatment liquid in which polyvinyl alcohol, an inorganic crosslinking agent, a guanidine compound, etc. are mixed to provide a deodorizing effect in addition to a good corrosion resistance and hydrophilic effect. (See Patent Document 2).

  On the other hand, a silicic acid of a metal selected from alkali metals and alkaline earth metals as a hydrophilizing agent capable of forming a film excellent in hydrophilicity and corrosion resistance and excellent in frosting prevention, especially for heat exchange fin materials of outdoor units Salt, preferably lithium silicate (a), polyvinyl alcohol (b), and acrylic resin (c) having a weight average molecular weight in the range of 3,000 to 300,000 and a resin acid number of 400 mg KOH / g or more Heat treatment fin material-containing hydrophilizing agent containing a heat exchanger, and further, this hydrophilizing agent is applied to the surface of the aluminum fin material and baked to form a film having a dry film thickness of 0.2 to 5 μm A method for hydrophilizing an aluminum fin material is disclosed (see Patent Document 3).

  On the other hand, it is known that a zirconium-vanadium chemical conversion treatment film having excellent corrosion resistance is formed by surface treatment of an aluminum material using a chemical conversion treatment solution containing zirconium ions and vanadium ions as a conventional non-chromate chemical conversion treatment solution. Yes. An aluminum alloy heat exchanger is disclosed in which a zirconium-vanadium chemical conversion film is formed on the surface using this non-chromate chemical conversion treatment technique and a hydrophilic film is further formed thereon (for example, Patent Documents). 4).

JP 2003-003282 A JP 2006-069197 A JP 2001-164175 A JP 2000-345362 A

According to the surface treatment method of the NB heat exchanger described in Patent Document 2, the NB heat exchanger is subjected to a rust prevention treatment with a zirconium-based compound and / or a titanium-based compound, and then a specific hydrophilic resin and an anti-rust treatment are performed. By hydrophilizing with the hydrophilizing agent composition containing a rust component, a deodorizing effect can be imparted in addition to a good corrosion resistance / hydrophilic effect. However, in this technique, vanadium ions are not contained in the chemical conversion treatment solution used for the rust prevention treatment.
Moreover, the hydrophilization treatment agent currently disclosed by the said cited reference 3 is with respect to the heat exchange fin material of an outdoor unit, and a hydrophilization treatment agent is given with respect to the aluminum plate before assembling an aluminum fin. Therefore, the above-mentioned problem peculiar to the hydrophilic treatment for the heat exchanger manufactured by the NB method does not exist.
On the other hand, in the technique described in Patent Document 4, the hydrophilization treatment liquid for forming the second protective layer contains substantially no phosphate compound and / or lithium ions. Moreover, although this technique is applied to an aluminum alloy heat exchanger, no mention is made that the aluminum alloy heat exchanger is an NB heat exchanger.

  The present invention has been made under such circumstances, and has excellent corrosion resistance and resistance to aluminum heat exchangers flux-brazed by the NB method, particularly aluminum heat exchangers used in automobile air conditioners. An object of the present invention is to provide a corrosion-resistant treatment method for a heat exchanger that can impart moisture resistance (blackening resistance) and can also impart good hydrophilicity and deodorization.

  As a result of intensive research to achieve the above object, the inventors of the present invention conducted chemical conversion treatment of an aluminum material heat exchanger flux-brazed by the NB method with a chemical conversion treatment solution having a specific composition and pH range. After the chemical conversion treatment film is formed, it is brought into contact with a hydrophilization treatment liquid having a specific composition, then dried and baked to form a hydrophilic treatment film on the surface thereof, and interaction with the chemical conversion treatment film. It was found that the purpose can be achieved. The present invention has been completed based on such findings.

That is, the present invention
[1] A corrosion-resistant treatment method for an aluminum heat exchanger flux brazed by a Nocolok brazing method,
(A) The aluminum material heat exchanger has a zirconium and / or titanium content of 10 to 10000 mass ppm, a vanadium content of 1 to 10000 mass ppm, and a [(zirconium + titanium) / vanadium] mass ratio of 0.1. A step of chemical conversion treatment with a chemical conversion treatment liquid having a pH of 1.5 to 7 and a chemical conversion treatment film to form a chemical conversion treatment film;
(B) The aluminum material heat exchanger on which the chemical conversion film is formed in the step (a) is selected from phosphoric acid, condensed phosphoric acid, phosphonic acid and derivatives thereof, and lithium ions while containing a hydrophilic resin And (c) a step of baking the aluminum material heat exchanger subjected to the contact treatment in the step (b) to form a hydrophilic coating on the surface thereof. ,
A corrosion-resistant treatment method for an aluminum heat exchanger, comprising:
[2] The corrosion resistance treatment method for an aluminum material heat exchanger according to [1], wherein the chemical conversion treatment liquid in the step (a) further contains 100 to 5000 mass ppm of aluminum ions and 1 to 100 mass ppm of free fluorine ions.
[3] In the chemical conversion coating in the step (a), the (Zr + Ti) coating amount is 1 to 200 mg / g, the V coating amount is 1 to 200 mg / m ² , and the [(Zr + Ti) / V] mass ratio is 0. The corrosion resistance treatment method for an aluminum heat exchanger according to [1] or [2], wherein the hydrophilized film amount in step (c) is 0.05 to 5.0 g / m ² .
[4] The corrosion resistance treatment method for an aluminum heat exchanger according to any one of [1] to [3], wherein the hydrophilic resin is polyvinyl alcohol having a saponification degree of 90% or more and / or modified polyvinyl alcohol.
[5] In the step (b), the hydrophilization treatment liquid further contains vanadium, and the vanadium concentration in the hydrophilization film after the baking treatment is 0.005 to 25% by mass in terms of metal. 4], the corrosion resistance treatment method for an aluminum heat exchanger according to any one of
Is to provide.

  According to the present invention, the aluminum material heat exchanger flux-brazed by the NB method, particularly the aluminum material heat exchanger surface used in an air conditioner for automobiles, using a specific chemical conversion treatment liquid and a hydrophilization treatment liquid, respectively. An anti-corrosion treatment method for an NB heat exchanger that forms a chemical conversion treatment film and a hydrophilization film, greatly improves corrosion resistance and moisture resistance (blackening resistance) by their interaction, and imparts good hydrophilicity and deodorization property. Can be provided.

The corrosion resistance treatment method for an aluminum heat exchanger according to the present invention (hereinafter sometimes simply abbreviated as a treatment method) is a corrosion resistance treatment method for an aluminum heat exchanger flux-brazed by the NB method,
(A) The aluminum material heat exchanger has a zirconium ion and / or titanium ion content of 10 to 10000 mass ppm, a vanadium ion content of 1 to 10000 mass ppm, [(zirconium ion + titanium ion) / vanadium ion]. A chemical conversion treatment with a chemical conversion treatment liquid having a mass ratio of 0.1 to 100 and pH 1.5 to 7 to form a chemical conversion treatment film;
(B) The aluminum material heat exchanger on which the chemical conversion film is formed in the step (a) is selected from phosphoric acid, condensed phosphoric acid, phosphonic acid and derivatives thereof, and lithium ions while containing a hydrophilic resin And (c) the aluminum material heat exchanger that has been contact-treated in the step (b) is dried and baked to form a hydrophilic film on the surface thereof. Forming,
It is characterized by including.
In addition, the metal (Li, Ti, Zr, V, Al) ion amount in the present invention refers to an amount of a compound having the metal expressed in terms of the metal ion.

[Heat exchanger]
The heat exchanger used in the present invention is an aluminum material heat exchanger flux-brazed by the NB method. The flux inevitably remains on the surface of the heat exchanger.
Examples of the NB heat exchanger include an aluminum material heat exchanger used for an air conditioner of an automobile. In the present invention, the “aluminum material” refers to aluminum or an aluminum alloy.
The heat exchanger is joined by a known NB method in which fins and tubes made of aluminum are brazed in nitrogen gas.
The flux used in the NB method is not particularly limited as long as the flux includes a salt composed of lithium ions and an anion that forms a hardly soluble salt, and a normal halogen-based flux used in the NB method can be used. . Examples of the halogen-based flux include KAlF ₄ , K ₂ AlF ₅ , K ₃ AlF ₆ , CsAlF ₄ , Cs ₃ AlF ₆ and Cs ₂ AlF ₅ , and a mixture of two or more thereof.

[(A) Chemical conversion treatment step]
The process (a) in the treatment method of the present invention comprises the aluminum material heat exchanger flux-brazed by the above-described NB method, wherein the zirconium ion and / or titanium ion content is 10 to 10,000 ppm by mass in terms of metal, Chemical conversion treatment is performed using a chemical conversion treatment solution having a vanadium ion content of 1 to 10000 mass ppm in terms of metal, [(zirconium ion + titanium ion) / vanadium ion] mass ratio of 0.1 to 100, and pH of 1.5 to 7. And forming a chemical conversion film. Here, in this specification, the concentration of metal ions refers to a value in terms of metal unless otherwise specified.
In addition, before performing the said chemical conversion treatment process, you may acid-treat the to-be-processed NB heat exchanger as needed for the purpose of improving this chemical conversion effect further. There is no restriction | limiting in particular in an acid cleaning process condition, The well-known method currently used for the acid cleaning process of the aluminum material heat exchanger can be used.

The chemical conversion treatment solution containing zirconium ions and / or titanium ions and vanadium ions is obtained by dissolving a zirconium-based compound and / or titanium-based compound and a vanadium-based compound in water to obtain zirconium ions and / or titanium ions and vanadium ions. Is a solution containing as an active species. Zirconium compounds include zirconium compounds such as fluorozirconic acid and zirconium fluoride, and salts thereof such as lithium, sodium, potassium, and ammonium. A zirconium compound such as zirconium oxide may be dissolved with a fluoride such as hydrofluoric acid.
Titanium compounds include titanium compounds such as fluorotitanic acid and titanium fluoride, and salts thereof such as lithium, sodium, potassium, and ammonium, and these are dissolved in water to make titanium ions active species. Make chemical conversion solution. Further, a titanium compound such as titanium oxide may be dissolved with a fluoride such as hydrofluoric acid.

<Vanadium ion>
Vanadium ions have excellent film-forming properties due to self-healing effects. By using zirconium ions and / or titanium ions in combination with vanadium ions in the chemical conversion treatment solution, the vanadium film is formed together with the zirconium and / or titanium films. Form. Vanadium coexists with a zirconium film and / or a titanium film, so that the elution of vanadium becomes a very small amount. Further, even when vanadium is eluted, the eluted vanadium ion has an action as an oxidant, and oxidizes the aluminum material to passivate it to exert a corrosion resistance effect.

As the vanadium compound for supplying vanadium ions to the chemical conversion treatment liquid, a divalent to pentavalent vanadium compound can be used. Specifically, metavanadate, ammonium metavanadate, sodium metavanadate, vanadium pentoxide, vanadium oxytrichloride. Vanadyl sulfate, vanadium oxide, vanadium dioxide, vanadium oxyacetylacetonate, vanadium chloride and the like are preferable.
In the present invention, tetravalent and pentavalent vanadium compounds are more preferred, and specifically, metavanadate ammonium (pentavalent) and vanadyl sulfate (tetravalent) are more preferred.

  In the chemical conversion treatment liquid, from the viewpoint of significantly improving the corrosion resistance and moisture resistance (blackening resistance) of the corrosion-treated NB heat exchanger and imparting good hydrophilicity and chemical resistance to the heat exchanger. The zirconium ion and / or titanium ion content needs 10 to 10000 mass ppm, preferably 30 to 5000 mass ppm, more preferably 100 to 3000 mass ppm, and the vanadium ion content 1 to 10000 mass ppm. In short, it is preferably 3 to 5000 ppm by mass, more preferably 30 to 3000 ppm by mass. Further, the mass ratio of [(zirconium ion + titanium ion) / vanadium ion] needs to be 0.1 to 100, preferably 0.2 to 20, and more preferably 0.3 to 10.

The chemical conversion treatment solution needs to have a pH of 1.5 to 7. If this pH is 1.5 or more, a chemical conversion film can be formed without causing excessive etching by the chemical conversion treatment solution. If it is 7 or less, a sufficient amount of chemical conversion film can be obtained without being insufficiently etched. A preferred pH is 3-6. The pH can be adjusted with a general acid or alkali such as sulfuric acid, nitric acid, or ammonia.
In addition to the above-mentioned zirconium-based and / or titanium-based and vanadium-based compounds, this chemical conversion treatment liquid is made of manganese, zinc, cerium, trivalent chromium, magnesium, strontium, calcium, tin in order to improve rust prevention. , Anti-corrosion agents for metal ions such as copper, iron and silicon compounds, phosphorus compounds such as phosphonic acid, phosphoric acid and condensed phosphoric acid, phenol resins, polyacrylic acid, polyacrylic acid derivatives, guanidine and biguanidine compounds; Therefore, various silane coupling agents such as polyallylamine, aminosilane, and epoxysilane may be contained.

The chemical conversion treatment liquid may further contain 50 to 5000 mass ppm of aluminum ions and 1 to 100 mass ppm of free fluorine ions.
Aluminum ions are also eluted from the base material into the chemical conversion treatment solution. Apart from the elution from the base material, the chemical conversion treatment reaction can be promoted by positively adding aluminum ions. Moreover, by setting the free fluorine ions higher than the composition of the conventional zirconium or titanium chemical conversion treatment liquid, the mass ratio of (zirconium ions + titanium ions) / vanadium ions decreases, and a chemical conversion treatment film with better corrosion resistance is formed. be able to. A dense chemical conversion film is formed only with zirconium ions or titanium ions, but the film may not have sufficient coverage. In addition, zirconium ions and titanium ions do not coexist and vanadium ions alone are difficult to precipitate, and even if a film is formed, the film is likely to be eluted.
Zirconium and / or titanium-vanadium films are dense and have high coverage, and vanadium elutes moderately and exhibits a self-healing effect.
The preferable content of aluminum ions is 100 to 3000 ppm by mass, and more preferably 200 to 2000 ppm by mass. Moreover, preferable content of a free fluorine ion is 5-80 mass ppm, More preferably, it is 15-50 mass ppm. Examples of the supply source of aluminum ions include aluminum nitrate, aluminum sulfate, aluminum fluoride, aluminum oxide, alum, aluminum silicate, aluminate such as sodium aluminate, and fluoroaluminum salt such as sodium fluoroaluminate. Hydrofluoric acid, ammonium hydrofluoride, zirconium hydrofluoric acid, titanium hydrofluoric acid and the like as hydrofluoric acid and its salts; sodium fluoride, zirconium fluoride, titanium fluoride Metal fluorides such as ammonium fluoride and the like.

The method of chemical conversion treatment in the present invention is not particularly limited, and may be any of a spray method, an immersion method, and the like. The temperature of the chemical conversion treatment liquid is preferably 50 to 70 ° C, more preferably 55 to 65 ° C. Further, the chemical conversion treatment time is preferably 20 to 900 seconds, and more preferably 30 to 600 seconds. It is because the chemical conversion film which has rust prevention property can be formed if it is the temperature of the process liquid of this range, and processing time.
In this way, the NB heat exchanger is subjected to a chemical conversion treatment, and in the chemical conversion treatment film formed on the surface, the (Zr + Ti) film amount and the V film amount are respectively 1 to 200 mg / g, preferably 5 to 150 mg / g. m ² , more preferably in the range of 20 to 100 mg / m ² , and the [(Zr + Ti) / V] mass ratio of 0.1 to 100, preferably 0.1 to 10, more preferably 0. It can be in the range of 2-5.

[(B) Hydrophilization treatment step]
In the treatment method of the present invention, the step (b) includes the aluminum material heat exchanger on which the chemical conversion film is formed in the step (a) described above, including a hydrophilic resin, phosphoric acid, condensed phosphoric acid, phosphonic acid and It is a hydrophilization treatment step for contacting with a hydrophilization treatment liquid containing at least one selected from those derivatives and lithium ions.

(Hydrophilic treatment liquid)
The hydrophilization treatment liquid contains a hydrophilic resin in an aqueous solvent and an aqueous solution containing at least one selected from phosphoric acid, condensed phosphoric acid, phosphonic acid and derivatives thereof, and lithium ions as a phosphorus compound. Or it is an aqueous dispersion.
In addition, the said hydrophilic treatment liquid can contain a vanadium ion further.

<Hydrophilic resin>
The hydrophilic resin is not particularly limited, but is preferably 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 in the molecule. The hydrophilic resin preferably forms a film having a contact angle with water droplets of 40 degrees or less. Since such a film exhibits good hydrophilicity, sufficient hydrophilicity can be imparted to an object to be processed by applying a hydrophilic treatment liquid containing the hydrophilic resin. Examples of the hydrophilic resin include polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylic acid, polystyrene sulfonic acid, polyacrylamide, carboxymethyl cellulose, chitosan, polyethylene oxide, water-soluble nylon, and a copolymer of monomers forming these polymers. An acrylic polymer having a polyoxyethylene chain such as 2-methoxypolyethyleneglycol methacrylate / 2-hydroxylethyl acrylate copolymer is preferred. These may be used individually by 1 type, and may be used in combination of 2 or more types.

These hydrophilic resins have excellent hydrophilicity and water resistance, have no odor of their own, and are difficult to adsorb odorous substances. Therefore, the hydrophilic treatment liquid containing the hydrophilic resin is hydrophilic and It has excellent deodorizing properties, and the resulting hydrophilized film does not easily deteriorate even when exposed to water droplets or running water, so it is contained as desired, and it contains inorganic substances such as silica that emit dust odors and unpleasant odors of adsorbents. Since the residual monomer component is difficult to be exposed, it is prevented that the agent to be treated itself scatters and emits a dust odor.
The hydrophilic resin preferably has a number average molecular weight in the range of 1,000 to 1,000,000. When the number average molecular weight is 1000 or more, the film-forming property, hydrophilicity and other film properties are good. On the other hand, when the number-average molecular weight is 1 million or less, the viscosity of the hydrophilized liquid does not become too high, and the workability And film properties are improved. A more preferred number average molecular weight is in the range of 10,000 to 200,000.
In addition, the said number average molecular weight is the value of standard polystyrene conversion measured by the gel permeation chromatography method (GPC method).

The hydrophilic resin is more preferably polyvinyl alcohol because it is excellent in terms of preventing odor and imparting hydrophilicity, and in particular, polyvinyl alcohol and / or modified polyvinyl alcohol having a saponification degree of 90% or more. Particularly preferred. When the saponification degree is less than 90%, the hydrophilicity may be inferior. The saponification degree is more preferably 95% or more.
As said modified polyvinyl alcohol, 0.01-20% in a pendant group is following General formula (1).

[Wherein, n represents an integer of ¹ to 500, R ¹ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and R ² represents a hydrogen atom or a methyl group. Polyoxyalkylene-modified polyvinyl alcohol which is a polyoxyalkylene ether group represented by the following formula can be used.
In the polyoxyalkylene-modified polyvinyl alcohol, the polyoxyalkylene-modified group is preferably 0.1 to 5% in the pendant group, and the polyoxyalkylene group has a polymerization degree n of preferably 3 to 30.
The polyoxyalkylene-modified polyvinyl alcohol plays a particularly role of imparting hydrophilicity in the hydrophilization solution because of the hydrophilicity of the polyoxyalkylene group.

  The hydrophilic resin is preferably 10 to 99% by mass, more preferably 30 to 95% by mass in the solid content of the hydrophilizing agent of the present invention.

<Phosphorus compounds>
When the hydrophilic treatment agent contains a phosphorus compound, a hydrophilic film containing the phosphorus compound is formed on the surface of the aluminum substrate by the hydrophilic treatment agent. As a result, even if aluminum is eluted from the aluminum substrate, the phosphorus compound in the hydrophilized film reacts with the eluted aluminum to form aluminum phosphate, thereby suppressing further aluminum elution over a long period of time. be able to.
When the hydrophilization treatment liquid contains vanadium ions, the vanadium ions have an action as an oxidant, and it is considered that the aluminum material is oxidized and passivated to exert a corrosion resistance effect. As the phosphorus compound, phosphoric acid, condensed phosphoric acid, phosphonic acid and derivatives thereof are used. Specifically, phosphoric acid, polyphosphoric acid, tripolyphosphoric acid, metaphosphoric acid, ultraphosphoric acid, phytic acid, phosphinic acid, hydroxyethylidene diphosphonic acid, nitrilotris (methylenephosphonic acid), phosphonobutanetricarboxylic acid, ethylenediaminetetra (methylene Phosphonic acid), tetrakis (hydroxymethyl) phosphonium salt, acrylic phosphone copolymer and the like can be used.
These phosphorus compounds may be used alone or in combination of two or more. Moreover, although the content of the phosphorus compound in the hydrophilization treatment liquid depends on the type, the concentration of the phosphorus compound in the total solid content of the hydrophilization treatment agent is preferably 0 from the viewpoint of obtaining the effect of the phosphorus compound. 0.05 to 25% by mass, and more preferably 0.1 to 10% by mass.

<Vanadium ion>
The hydrophilic treatment liquid may contain vanadium ions together with the hydrophilic resin described above. The action of this vanadium ion is as described above.
As the vanadium ion source, it is desirable to use the vanadium compound shown in the chemical conversion treatment step (a), preferably a tetravalent and pentavalent vanadium compound.
When the said hydrophilization process liquid contains a vanadium ion, it is preferable that the vanadium density | concentration in the said hydrophilization film | membrane is 0.005-25 mass%, and it is more preferable that it is 0.05-2 mass%.
Vanadium has an action as an oxidant, and is considered to passivate by oxidizing the aluminum substrate and exhibiting a corrosion resistance effect. In addition, since vanadium incorporated into the hydrophilized film continues to have the same effect, excellent corrosion resistance can be obtained over a long period of time even when aluminum ions are eluted from the aluminum base material over time.

<Lithium ion>
The hydrophilic treatment liquid may contain lithium ions together with the hydrophilic resin described above. The lithium ion source is not particularly limited as long as it is a lithium compound capable of forming lithium ions in the hydrophilization treatment solution. For example, lithium hydroxide, lithium sulfate, lithium carbonate, lithium nitrate, lithium acetate, citric acid Lithium, lithium lactate, lithium phosphate, lithium oxalate, lithium silicate, lithium metasilicate, or the like can be used. Among these, lithium hydroxide, lithium sulfate, and lithium carbonate are preferably used because they have little influence on odor. A lithium ion source may be used individually by 1 type, and may be used in combination of 2 or more type.
In the present invention, using the hydrophilization treatment liquid containing lithium ions in this way, the aluminum material heat exchanger flux-brazed by the NB method having the chemical conversion coating is surface-treated, and the chemical conversion coating is hydrophilic. By forming the chemical film, the corrosion resistance can be greatly improved.

Inferring the above-mentioned mechanism for greatly improving the corrosion resistance, flux residue and hydrophilicity can be obtained by utilizing an ion exchange reaction between alkali metal ions such as potassium ions in the flux, particularly halogen-based fluxes, and lithium ions from the hydrophilized film. A slightly soluble film is formed at the interface with the chemical film.
As the ion exchange reaction, for example, a reaction represented by the following formula (2) is conceivable.
K _x AlF _y + xLi ⁺ → Li _x AlF _y + xK ⁺ (2)
(Where x and y are x = 1, y = 4, x = 2, y = 5 or x = 3, y = 6)

The flux residue is mainly a composite compound of potassium fluoride or cesium fluoride and aluminum fluoride, and the present invention is obtained by performing surface treatment with the hydrophilization treatment solution containing lithium ions, and the like with potassium ions in the flux residue. By the ion exchange reaction with lithium ions from the hydrophilized film, a layer containing a hardly soluble lithium salt is formed at least at the interface between the flux residue and the hydrophilized film, thereby improving the rust prevention (corrosion resistance) of the flux residue. be able to.
Further, since the lithium in the hydrophilized film remains for a long time, the above effect can be maintained for a long time.

When the hydrophilization treatment liquid contains lithium ions, the lithium ions are adsorbed on the flux and suppress the aluminum elution from the aluminum material as shown by the mechanism described above, thereby exhibiting a rust prevention effect.
The metal equivalent concentration of lithium in the solid content of the hydrophilization treatment liquid is preferably 0.01 to 25% by mass, more preferably 0.05 to 5% by mass.

  As described above, vanadium and phosphorus compounds that suppress aluminum elution on the surface of the aluminum base material and lithium that suppresses flux elution in the flux portion are used in combination to complement each other in the corrosion resistance treatment of the NB evaporator. Therefore, excellent corrosion resistance and moisture resistance can be obtained.

<Crosslinking agent>
The hydrophilic treatment liquid may contain a crosslinking agent as necessary for the purpose of improving the water resistance of the hydrophilic coating formed using the hydrophilic treatment liquid.
As the crosslinking agent, an inorganic crosslinking agent or an organic crosslinking agent that reacts with a hydroxyl group of polyvinyl alcohol or modified polyvinyl alcohol can be used.
Examples of the inorganic crosslinking agent include silica compounds such as silicon dioxide, zirconium compounds such as zircon ammonium fluoride and zircon ammonium carbonate, metal chelate compounds such as titanium chelate, metal salts such as Ca, Al, Mg, Fe and Zn. It is done.
On the other hand, examples of the organic crosslinking agent include melamine resin, phenol resin, epoxy compound, blocked isocyanate compound, oxazoline compound, carbodiimide compound and the like.
These crosslinking agents may be used individually by 1 type, and may be used in combination of 2 or more types.
Moreover, when containing a crosslinking agent, 0.1-50 mass% is preferable in the solid content of a hydrophilic treatment agent, and 0.5-30 mass% is more preferable.

<Other optional components>
In the hydrophilization treatment liquid, as other optional components, a dispersant, a rust preventive additive, a pigment, a silane coupling agent, an antibacterial agent (preservative), a surfactant, a lubricant, a deodorant, as necessary. An agent or the like can be appropriately contained.
It does not specifically limit as said dispersing agent, Surfactant, a dispersion resin, etc. can be mentioned.

The antirust additive is not particularly limited, and examples thereof include tannic acid, imidazole compound, triazine compound, triazole compound, guanidine compound, hydrazine compound, zirconium compound and the like. Among these, a zirconium compound is preferable because rust prevention can be effectively imparted. The zirconium compound is not particularly limited, and examples thereof include alkali metal fluorozirconates such as K ₂ ZrF ₆ ; soluble fluorozirconates such as fluorozirconates such as (NH ₄ ) ₂ ZrF ₆ ; and H ₂ ZrF ₆ . Fluorozirconic acid 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), calcium carbonate (CaCO ₃ ), barium sulfate (BaSO ₄ ), alumina (Al ₂ O ₃ ), kaolin clay, carbon Examples thereof include inorganic pigments such as black, iron oxide (Fe ₂ O ₃ , Fe ₃ O ₄ ), aluminum oxide (Al ₂ O ₃ ), and various colored pigments such as organic pigments.

The inclusion of a silane coupling agent is preferred in that the affinity between the hydrophilic resin and the pigment is improved, and adhesion and the like can be improved.
The silane coupling agent is not particularly limited. For example, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, N -[2- (vinylbenzylamino) ethyl] -3-aminopropyltrimethoxysilane and the like can be mentioned. The silane coupling agent may be a condensate or a polymer.
The antibacterial agent (preservative) is not particularly limited, and conventionally known antibacterial agents such as 2- (4-thiazolyl) benzimidazole, zinc pyrithione, and benzisothiazoline can be used.
When these optional components are contained, the total amount is preferably 0.01 to 50% by mass, and more preferably 0.1 to 30% by mass in the solid content of the hydrophilic treatment agent.

<Solvent>
The solvent for the hydrophilic treatment liquid is not particularly limited, but an aqueous solvent mainly composed of water is preferable from the viewpoint of waste liquid treatment. Further, a solvent may be used in combination in order to improve the film forming property and form a more uniform and smooth film. The solvent is not particularly limited as long as it is generally used for paints and can be uniformly mixed with water, and examples thereof include alcohol-based, ketone-based, ester-based and ether-based organic solvents. it can. As for the usage-amount of the said solvent, it is preferable that this solvent content in the said hydrophilization processing liquid is 0.01-5 mass%.
The hydrophilic treatment liquid may be adjusted in pH in order to improve the stability as the treatment liquid. Adjustment of pH can be performed with common acids and alkalis, such as a sulfuric acid, nitric acid, and ammonia.

<Concentration of each component in hydrophilization solution>
The total solid content concentration in the hydrophilization treatment liquid is usually 1 to 11% by mass, preferably 2 to 5% by mass, from the viewpoints of workability, uniformity and thickness of the hydrophilized film to be formed, and economic efficiency. It is.

(Hydrophilic treatment)
In the present invention, the hydrophilization treatment is performed by bringing the aluminum material heat exchanger (object to be treated) on which the chemical conversion treatment film has been formed in the step (a) described above into contact with the hydrophilization treatment liquid.
It is preferable that the material to be treated is subjected to a water-washing treatment using a conventionally known method for the chemical conversion treatment of the aluminum material heat exchanger before the hydrophilic treatment.
Examples of the method for bringing the object to be treated into contact with the hydrophilization treatment liquid include an immersion method, a spray method, a coating method, and the like, but the aluminum material heat exchanger of the object to be processed has a complicated shape, and thus the immersion method. Is preferred. When the immersion method is adopted, the immersion treatment is usually performed at room temperature for about 10 seconds. The film amount of the formed hydrophilic film can be controlled by controlling the wet amount by air blow.

[(C) Hydrophilized film forming step]
This hydrophilic film forming step is a step of drying and baking the aluminum material heat exchanger that has been contact-treated in the above-described step (b) to form a hydrophilic film on the surface thereof.
In the present invention, the object to be treated is baked by heating so that the temperature of the object itself becomes 130 to 150 ° C. to form a hydrophilic film. The baking time is preferably 2 to 120 minutes. The coating amount of the hydrophilic coating is preferably in the range of 0.1 to 5.0 g / m ² . If the coating amount is less than 0.1 g / m ² , the corrosion resistance and moisture resistance will be insufficient. On the other hand, if it exceeds 5.0 g / m ² , the effect of improving the corrosion resistance and moisture resistance will not be exhibited for the amount, Rather, it is economically disadvantageous. The coating amount is more preferably 0.1 to 3.0 g / m ² , and still more preferably 0.2 to 2.0 g / m ² .
In addition, the hydrophilic film preferably contains at least one selected from phosphoric acid, condensed phosphoric acid, phosphonic acid, derivatives thereof and lithium in a proportion of 0.05 to 25% by mass, More preferably, it is contained at a ratio of -10% by mass.

The anticorrosion treatment method of the NB heat exchanger of the present invention is a heat exchanger in which aluminum fins and tubes are joined and assembled by flux brazing by the NB method as a heat exchanger that is an object to be processed. The present invention is applied to a heat exchanger used in an automobile air conditioner.
According to the corrosion-resistant treatment method for an aluminum heat exchanger of the present invention, a chemical conversion film having the above-described properties is first formed on the surface of the NB heat exchanger, and then the hydrophilic property having the above-described properties is formed on the chemical conversion film. By forming the chemical film, the corrosion resistance and moisture resistance (blackening resistance) of the NB heat exchanger can be greatly improved by the interaction between the two films, and the hydrophilicity and deodorizing property of the NB heat exchanger are good. Can be granted.

EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in more detail, this invention is not limited only to these Examples. In the examples, “%”, “parts” and “ppm” mean “% by mass”, “parts by mass” and “ppm by mass” unless otherwise specified.
In addition, the physical property evaluation shown below was performed about the test heat exchanger by which the chemical conversion treatment and the hydrophilization treatment liquid obtained in each case were used.

(1) Corrosion resistance Based on JIS Z 2371, 5 mass% salt solution was sprayed at 35 degreeC, and the white rust generation | occurrence | production area after 2000 hours was evaluated visually by the following evaluation criteria.
10: No white rust generation 9: White rust was observed, but white rust generation area was less than 10% 8: White rust generation area was 10% or more and less than 20% 7: 20% or more but less than 30% 6: Same as 30 % To less than 40% 5: 40% to less than 50% 4: 50% to less than 60% 3: 60% to less than 70% 2: 70% to less than 80% 1: 80% to less than 90%

(2) Moisture resistance (blackening resistance)
Perform a moisture resistance test (500 hours) in an atmosphere with a temperature of 55 ° C. and a humidity of 98% or more, and determine the rust generation area of the blackened portion or the whitened and whitened rust according to the above (1) Evaluation criteria for corrosion resistance And visually evaluated.

(2) Hydrophilicity After contacting the test heat exchanger with running water for 72 hours, the contact angle with water droplets was measured. The smaller the contact angle, the higher the hydrophilicity. The contact angle was measured using an automatic contact angle meter “CA-Z” (manufactured by Kyowa Interface Chemical Co., Ltd.).
The hydrophilicity preferably has a contact angle of 40 ° or less.

(3) Odor After the test heat exchanger was brought into contact with running tap water for 72 hours, the smell was smelled and evaluated in 6 stages. The odor is preferably 1.5 or less.
0: Odorless 1: Slightly smell 2: Smelly smell 3: Obvious smell 4: Strong smell 5: Very strong smell

<Production of test heat exchanger>
As the heat exchanger, an aluminum heat exchanger for automobiles brazed with a flux of KAlF ₄ and K ₃ AlF ₆ was used. The flux amount of this heat exchanger was 50 mg / m ² (fin surface) as K.
This heat exchanger was subjected to acid cleaning by immersion for 20 seconds at 40 ° C. in an acid bath containing 5% sulfuric acid and 0.5% flux of KAlF ₄ and K ₃ AlF _6. Then, a chemical conversion treatment was performed, followed by a hydrophilization treatment and a baking treatment under the following conditions to produce a test heat exchanger.
(I) Chemical conversion treatment The heat exchanger was subjected to chemical conversion treatment by immersing it in a chemical conversion solution bath at 50 ° C for 60 seconds.
(B) Hydrophilization treatment and baking treatment The heat exchanger after the chemical conversion treatment of (b) above was washed with hot water at 50 ° C. for 30 seconds, and then immersed in a hydrophilic treatment solution bath at room temperature for 10 seconds. The amount of wet film is controlled to a predetermined value by air blowing. Next, in a drying furnace, the heat exchanger itself was heated and baked so that the temperature of the heat exchanger itself was maintained at 140 ° C. for 5 minutes, thereby producing a test heat exchanger.

Example 1
(1) Preparation of chemical conversion treatment solution Preparation of chemical conversion treatment solution containing 500 ppm of zirconium ion equivalent, 500 ppm of ammonium metavanadate in terms of vanadium ion, 200 ppm of aluminum ion equivalent, 10 ppm of free fluorine ions and pH of 4. did.
(2) Preparation of hydrophilization treatment liquid The solid content of the hydrophilization treatment liquid includes 50% polyvinyl alcohol, 25% ethylene oxide-modified polyvinyl alcohol, 5% condensed phosphoric acid, and 20% silica. Each component was blended, and ion-exchanged water was added thereto to prepare a hydrophilic treatment solution having a concentration of about 2%.
(3) Production of test heat exchanger After the chemical conversion treatment obtained in the above (1) and the chemical conversion treatment of (a) above, using the hydrophilic treatment liquid obtained in the above (2), The hydrophilization process and baking process of (b) were performed, a test heat exchanger was produced, and physical properties were evaluated.
Table 1 shows the content of each component in the chemical conversion treatment liquid and the hydrophilization treatment liquid and the evaluation results of the physical properties.
Chemical conversion coating amount in the test heat exchanger, zirconium coating: 30 mg / m ^2, the vanadium film: A 15 mg / m ^2, hydrophilic coating amount was 0.2 g / m ^2.
In addition, the film quantity of each component in a chemical conversion treatment film was measured in accordance with the method shown below. That is, the fin portions were bonded so as to be 10 mm × 10 mm or more, and quantified with a fluorescent X-ray analyzer (XRF-1700, manufactured by Shimadzu Corporation).
Moreover, the coating amount of the hydrophilic coating is a measured value of a TOC apparatus (TOC-VCSH manufactured by Shimadzu Corporation) using a conversion coefficient calculated from the relationship between the hydrophilic coating amount of the standard coating sample and the amount of organic carbon contained therein. Calculated from

Examples 2 to 22 and Comparative Examples 1 to 5
(1) Preparation of chemical conversion liquid The chemical conversion liquid was prepared like Example 1 (1) so that the density | concentration and pH of each component in a chemical conversion liquid might become the value shown in Table 1-3.
(2) Preparation of hydrophilization treatment liquid Hydrophilization treatment liquid in the same manner as in Example 1 (2) so that the solid content of each component of the hydrophilization treatment liquid has the values shown in Tables 1 to 3. Was prepared.
(3) Production of test heat exchanger A test heat exchanger was produced in the same manner as in Example 1 (3), and physical properties were evaluated.
Tables 1 to 3 show the evaluation results of the physical properties of the test heat exchanger, and the film amounts and hydrophilized film amounts of the respective components in the chemical conversion film.

[note]
(1) In the chemical conversion treatment, Zr (concentration: ppm) is a zirconium ion equivalent concentration, Ti (concentration: ppm) is a titanium ion equivalent concentration, ammonium vanadate (concentration: ppm) is a vanadium ion equivalent concentration, vanadyl sulfate (concentration: ppm) represents vanadium ion equivalent concentration, and Al (concentration: ppm) represents aluminum ion equivalent concentration.
(2) The ratio of each component in the hydrophilization treatment (solid content%) represents the content of each component in the solid content of the hydrophilization treatment liquid.
(3) PBTC: Phosphonobutanetricarboxylic acid (4) Polyvinyl alcohol: [degree of saponification: 99%, number average molecular weight: 60000]
(5) Ethylene oxide modified polyvinyl alcohol: [degree of saponification: 99%, number average molecular weight: 20000], polyoxyethylene group content (ratio of polyvinyl alcohol to all pendant groups): 3%
(6) Carboxymethylcellulose: [Number average molecular weight: 10,000]
(7) Sodium polyvinyl sulfonate: [number average molecular weight: 20000]
(8) Polyacrylic acid: [Number average molecular weight: 20000]
(9) Silica (anhydrous silica): [average primary particle diameter: 10 nm], inorganic crosslinking agent (10) phenol resin: [resol type phenol, number average molecular weight 300], organic crosslinking agent

  As can be seen from the physical property evaluation results of Examples and Comparative Examples in Tables 1 to 3, the chemical conversion treatment liquid and the hydrophilization treatment liquid in the present invention are used to form a chemical conversion treatment film and a hydrophilization film. The flux heat brazed aluminum material heat exchanger has extremely excellent corrosion resistance that can withstand a severe salt spray test of 2000 hours, and also has excellent moisture resistance (blackening resistance).

  The corrosion resistance treatment method for an aluminum material heat exchanger according to the present invention is a heat exchanger in which fins and tubes of an aluminum material are joined and assembled by flux brazing according to the NB method as a heat exchanger that is a workpiece. In particular, it is applied to a heat exchanger used in an air conditioner of an automobile, and can impart extremely excellent corrosion resistance and moisture resistance (blackening resistance) to the NB heat exchanger, and also has good hydrophilicity and deodorization. Sex can be imparted.

Claims (5)

A corrosion-resistant treatment method for an aluminum heat exchanger flux brazed by a Nocolok brazing method,
(A) The aluminum material heat exchanger has a zirconium and / or titanium content of 10 to 10000 mass ppm, a vanadium content of 1 to 10000 mass ppm, and a [(zirconium + titanium) / vanadium] mass ratio of 0.1. A step of chemical conversion treatment with a chemical conversion treatment liquid having a pH of 1.5 to 7 and a chemical conversion treatment film to form a chemical conversion treatment film;
(B) The aluminum material heat exchanger on which the chemical conversion film is formed in the step (a) is selected from phosphoric acid, condensed phosphoric acid, phosphonic acid and derivatives thereof, and lithium ions while containing a hydrophilic resin And (c) a step of baking the aluminum material heat exchanger subjected to the contact treatment in the step (b) to form a hydrophilic coating on the surface thereof. ,
A corrosion-resistant treatment method for an aluminum heat exchanger, comprising:   The corrosion-resistant treatment method for an aluminum material heat exchanger according to claim 1, wherein the chemical conversion treatment liquid in the step (a) further contains 100 to 5000 mass ppm of aluminum ions and 1 to 100 mass ppm of free fluorine ions. In the chemical conversion coating in the step (a), the (Zr + Ti) coating amount is 1 to 200 mg / g, the V coating amount is 1 to 200 mg / m ² , and the [(Zr + Ti) / V] mass ratio is 0.1 to 200 mg / g ^2. The corrosion resistance treatment method for an aluminum material heat exchanger according to claim 1, wherein the hydrophilized film amount in step (c) is 0.05 to 5.0 g / m ² .   The method for corrosion treatment of an aluminum heat exchanger according to any one of claims 1 to 3, wherein the hydrophilic resin is polyvinyl alcohol and / or modified polyvinyl alcohol having a saponification degree of 90% or more.   In the step (b), the hydrophilization liquid further contains vanadium, and the vanadium concentration in the hydrophilized film after the baking treatment is 0.005 to 25% by mass in terms of metal. The corrosion-resistant processing method of the aluminum material heat exchanger as described in 2.