CN108660450B - Surface treatment method for aluminum heat exchanger - Google Patents
Surface treatment method for aluminum heat exchanger Download PDFInfo
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- CN108660450B CN108660450B CN201810344019.6A CN201810344019A CN108660450B CN 108660450 B CN108660450 B CN 108660450B CN 201810344019 A CN201810344019 A CN 201810344019A CN 108660450 B CN108660450 B CN 108660450B
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Abstract
The invention provides a surface treatment method capable of endowing an aluminum heat exchanger with excellent corrosion resistance (white rust resistance) and moisture resistance (blackening resistance). The surface treatment method of the aluminum heat exchanger comprises the following steps: (a) forming a chemical conversion coating on a surface of the aluminum heat exchanger by subjecting the heat exchanger to a chemical conversion treatment with a chemical conversion treatment agent; (b) bringing the aluminum heat exchanger having the chemical conversion coating formed on the surface thereof in the step (a) into contact with a hydrophilizing agent containing a hydrophilic resin; and (c) forming a hydrophilic coating on the surface of the aluminum heat exchanger after the contact treatment in the step (b) by sintering; the chemical conversion treatment agent used in the step (a) contains at least one of zirconium and titanium, and has a total content of 5 to 5000 mass ppm, a content of 10 to 1000 mass ppm of vanadium, a content of 5 to 5000 mass ppm of a metal stabilizer, and a pH of 2 to 6.
Description
The patent application of the invention is a divisional application of an invention patent application with the international application number of PCT/JP2013/056547, the international application date of 2013, 3, month and 8, the application number of 201380012367.9 entering the China national stage and the name of a surface treatment method of an aluminum heat exchanger.
Technical Field
The present invention relates to a surface treatment method for an aluminum heat exchanger.
Background
In an aluminum heat exchanger used for an automobile air conditioner, from the viewpoint of improving heat exchange efficiency, a plurality of fins are arranged at a narrow interval while increasing the surface area as much as possible, and pipes for supplying a refrigerant are arranged in the fins in a complicated manner. In such a heat exchanger having a complicated structure, moisture in the air adheres to the surfaces of fins and tubes (hereinafter referred to as "fins and the like") as condensed water during air conditioning operation. However, when the wettability of the surface of the fin or the like is poor, the adhered condensed water forms a substantially hemispherical water droplet, and the condensed water exists between the fins in a bridge shape to increase the ventilation resistance, which results in a problem of hindering smooth flow of the exhaust gas and causing a decrease in heat exchange efficiency. In order to suppress this phenomenon, a hydrophilization treatment is generally performed on the surface of the fin or the like.
Aluminum and its alloy constituting fins and the like are materials which are originally excellent in rust resistance. However, if the condensed water stays on the surface of the fin or the like for a long time, the corrosion reaction proceeds by locally forming an oxygen concentration cell, and further, if the contaminant components in the atmosphere adhere and are concentrated, the corrosion reaction is promoted. The products generated by the corrosion reaction, such as white rust, have a problem that they are deposited on the surface of fins or the like to inhibit the heat exchange characteristics, and are discharged into the atmosphere by a blower.
Therefore, various techniques have been proposed to suppress the formation of white rust and improve corrosion resistance. For example, as a chemical conversion treatment agent for imparting good corrosion resistance to the surface of aluminum and its alloy materials, a chemical conversion treatment agent containing titanium complex fluoride ions, 5-valent vanadium compound ions, and zirconium complex fluoride ions is disclosed (see patent document 1).
Further, as a chemical conversion treatment agent for imparting excellent corrosion resistance to the surface of an aluminum heat exchanger, a chemical conversion treatment agent containing decavanadate ions and zirconium complex fluoride ions corresponding to 5-valent vanadium compound ions is disclosed (refer to patent document 2).
However, the aluminum heat exchanger used for the automobile air conditioner is manufactured by arranging and assembling a plurality of fins and the like as described above, and then joining them. In the case of joining, since a strong and dense oxide film is formed on the surface of aluminum, joining by brazing methods other than mechanical bonding is difficult, and a step such as brazing in vacuum is required.
In contrast, in recent years, as a method for effectively removing the oxide film on the surface, flux brazing using a halogen-based flux has been developed, and among these, a nanogold brazing method (hereinafter referred to as "NB method") in which flux brazing is performed in nitrogen is often used from the viewpoints of easy brazing management and low processing cost. In the NB method, a plurality of fins are arranged and assembled, and KAlF is used in a nitrogen atmosphere4And K2AlF5Brazing fins, etc.
However, in the aluminum heat exchanger manufactured by the NB method (hereinafter, referred to as "NB heat exchanger"), the flux inevitably remains on the surface of the fins and the like. Thus, the surface state (potential state or the like) of the fin or the like is not uniform, and as a result: there is a problem that a uniform chemical conversion coating and hydrophilic coating cannot be obtained by subsequent treatments and that good corrosion resistance and hydrophilicity cannot be obtained.
As a method for treating the surface of an NB heat exchanger, which is provided with excellent corrosion resistance and hydrophilicity and also with deodorization, which is an important characteristic for use in an automobile air conditioner, there is disclosed a technique in which the NB heat exchanger is immersed in a chemical conversion treatment agent containing at least 1 of zirconium complex fluoride ions and titanium complex fluoride ions to perform a chemical conversion treatment, and then immersed in a hydrophilization treatment agent containing polyvinyl alcohol, polyoxyalkylene-modified polyvinyl alcohol, an inorganic crosslinking agent, a guanidine compound, and the like to perform a hydrophilization treatment (see patent document 3).
As a surface treatment method capable of maintaining the hydrophilicity, high corrosion resistance, antibacterial properties, and odor resistance of the surface of an aluminum or aluminum alloy base material for a long period of time, there is disclosed a technique of sequentially performing a surface conditioning step of bringing the surface of the aluminum or aluminum alloy base material into a state suitable for forming a chemical conversion coating, a water washing step, a step of forming a 1 st protective layer composed of the chemical conversion coating on the surface of the aluminum or aluminum alloy base material, a water washing step, a step of coating the 1 st protective layer with an organic coating as a 2 nd protective layer, and a drying step (see patent document 4). In this technique, the 1 st protective layer is formed from a chemical conversion treatment liquid containing vanadium and at least 1 or more metals selected from titanium, zirconium, and hafnium; the aforementioned 2 nd protective layer is formed from a composition containing (1) a chitosan derivative and a solubilizer therefor, (2) a modified polyvinyl alcohol obtained by graft polymerization of a hydrophilic polymer onto a side chain of polyvinyl alcohol, and (3) a water-soluble crosslinking agent.
Further, as a technique for imparting excellent corrosion resistance to an aluminum-based metal material or the like, a technique related to a surface treatment agent containing a resin compound having a specific structure, a vanadium compound, and a specific metal compound as essential components is disclosed (see patent document 5). In this technique, the water-soluble organic compound having at least one functional group selected from a hydroxyl group, a carbonyl group, a carboxyl group, a phosphate group, a phosphonate group, a 1-3-stage amino group, and an amide group, for example, has ascorbic acid or the like, and thus not only can the vanadium compound be reduced, but also the stability of the vanadium compound can be significantly improved, and an excellent corrosion resistance-imparting effect can be maintained for a long period of time. Further, a uniform coating film can be formed, and the level of corrosion resistance can be improved.
Documents of the prior art
Patent document
Patent document 1 Japanese patent laid-open No. 2010-261058
Patent document 2 Japanese patent application laid-open No. 2004-510882
Patent document 3 Japanese patent laid-open No. 2006-69197
Patent document 4 Japanese patent laid-open publication No. 2011-
Patent document 5 Japanese patent laid-open No. 2001-181860
Disclosure of Invention
Technical problem to be solved by the invention
However, in recent years, it has become important to improve the corrosion resistance and the moisture resistance of aluminum heat exchangers for automobile air conditioners. Here, white rust is an index of corrosion resistance as described above, while black rust is an index of moisture resistance. White rust is a local corrosion phenomenon caused by corrosion factors such as oxygen, water, and chloride ions, while blackening is a general corrosion phenomenon caused by the presence of oxygen, water, and heat. Therefore, it is expected that an aluminum heat exchanger for an automobile air conditioner exposed to a high-temperature environment can improve corrosion resistance and also suppress blackening to improve moisture resistance.
However, in the technique of patent document 1, since the object to be treated is not a heat exchanger, hydrophilization treatment is not performed. In addition, this technique has not been studied for moisture resistance at all, and is not a technique for improving moisture resistance.
In the technique of patent document 2, although the object to be processed is an aluminum heat exchanger, no study is made on moisture resistance. This technique is a technique focused on imparting good corrosion resistance, but is not a technique for improving moisture resistance.
The object to be treated by the technique of patent document 3 is an aluminum heat exchanger for automobile air conditioners, and is a technique for imparting not only good corrosion resistance and hydrophilicity but also good odor resistance, but is not a technique focusing on moisture resistance. Therefore, this technique has not been investigated for moisture resistance at all, and excellent moisture resistance cannot be obtained. Patent document 3 does not describe an embodiment in which a predetermined amount of vanadium ions is contained in a chemical conversion agent, and the evaluation time of corrosion resistance in patent document 3 is significantly shorter than that of the present invention, and the level thereof is lower than that of the present invention.
The subject of the technique of patent document 4 is a heat exchanger made of aluminum or aluminum alloy, and is a technique for imparting long-term hydrophilicity, high corrosion resistance, antibacterial properties, moisture resistance, and odor resistance, but the evaluation time of corrosion resistance in this technique is significantly shorter than that in the present invention. In addition, the evaluation temperature of the moisture resistance in this technique is also significantly lower than that of the present invention, and the level thereof is lower than that of the present invention.
In the technique of patent document 5, since the object to be treated is not a heat exchanger, hydrophilization treatment is not performed. In addition, this technique has not been studied for moisture resistance at all, and is not a technique for improving moisture resistance. This technique is a technique related to a coating-type surface treatment agent, and is not a technique related to a reaction-type chemical conversion treatment agent as in the present invention.
As described above, in the present situation, for an aluminum heat exchanger for an automobile air conditioner, a surface treatment method capable of imparting excellent corrosion resistance (white rust resistance) and moisture resistance (blackening resistance) has not been established yet.
The present invention has been made in view of the above circumstances, and an object thereof is to provide a surface treatment method capable of imparting excellent corrosion resistance (white rust resistance) and moisture resistance (blackening resistance) to an aluminum heat exchanger for an automobile air conditioner.
Technical scheme for solving technical problem
In order to achieve the above object, the present invention provides a surface treatment method of an aluminum heat exchanger, comprising: (a) forming a chemical conversion coating film on a surface of the aluminum heat exchanger with a chemical conversion treatment agent; (b) bringing the aluminum heat exchanger having the chemical conversion coating formed on the surface thereof in the step (a) into contact with a hydrophilization agent containing a hydrophilic resin; and (c) forming a hydrophilic coating on the surface of the aluminum heat exchanger after the contact treatment in the step (b) by sintering;
the chemical conversion treatment agent used in the step (a) contains 5 to 5000 mass ppm of at least one of zirconium and titanium in total, 10 to 1000 mass ppm of vanadium, 5 to 5000 mass ppm of a metal stabilizer, and has a pH of 2 to 6.
The metal stabilizer is preferably at least one selected from the group consisting of a reducing organic compound and an iminodiacetic acid derivative.
The chemical conversion coating formed in the step (a) has a total of 5 to 300mg/m of zirconium and titanium2The amount of vanadium is 1-150 mg/m2And the amount of the metal stabilizer is 0.5 to 200mg/m in terms of carbon2The amount of the hydrophilic coating film formed in the step (c) is preferably 0.05 to 5g/m2。
The chemical conversion coating formed in the step (a) preferably contains both zirconium and titanium.
The hydrophilizing agent used in the step (b) preferably further contains at least one of a guanidine compound represented by the following general formula (1) and a salt thereof:
[ solution 1]
In formula (1), Y represents-C (═ NH) - (CH)2)m-、-C(＝O)-NH-(CH2)m-or-C (═ S) -NH- (CH)2)m-; m represents an integer of 0 to 20, n represents a positive integer, and k represents 0 or 1; x represents hydrogen, amino, hydroxy, methyl, phenyl, chlorophenyl or tolyl; z represents hydrogen, amino, hydroxyl, methyl, phenyl, chlorophenyl, tolyl, or a polymer represented by the following general formula (2) and having a mass average molecular weight of 200 to 100 ten thousand;
[ solution 2]
In the formula (2), p represents a positive integer.
The guanidine compound and its salt are preferably a guanidine compound containing a biguanide structure represented by the following general formula (3):
[ solution 3]
The hydrophilizing agent used in the step (b) preferably further contains at least 1 selected from phosphoric acid, condensed phosphoric acid, phosphonic acid, derivatives thereof and lithium ions.
The hydrophilic resin in the hydrophilization treatment agent used in the step (b) preferably contains at least one of polyvinyl alcohol having a saponification degree of 90% or more and modified polyvinyl alcohol.
The aluminum heat exchanger is preferably an aluminum heat exchanger brazed with a flux by the nano-acryl brazing method.
ADVANTAGEOUS EFFECTS OF INVENTION
According to the present invention, a surface treatment method capable of imparting excellent corrosion resistance (white rust resistance) and moisture resistance (blackening resistance) to an aluminum heat exchanger for an automobile air conditioner can be provided.
Detailed Description
Hereinafter, embodiments of the present invention will be described in detail.
The surface treatment method of the present embodiment is a method of performing surface treatment of an aluminum heat exchanger. The surface treatment method of the present embodiment includes: (a) a chemical conversion treatment step; (b) a hydrophilization treatment step; (c) and (5) sintering.
In the following description, white rust resistance is described as corrosion resistance, and black discoloration resistance is described as moisture resistance.
[ Heat exchanger ]
The surface treatment method of the present embodiment is preferably applied to an aluminum heat exchanger as a treatment target, and is preferably used for an automobile air conditioner. Here, "aluminum" means that it is made of aluminum or an aluminum alloy (hereinafter simply referred to as "aluminum").
As described above, in the aluminum heat exchanger of the present embodiment, in order to increase the surface area as much as possible, a plurality of fins are arranged at narrow intervals, and tubes for supplying a refrigerant are arranged in the fins in a complicated manner, from the viewpoint of improving the heat exchange efficiency. Further, when these fins and the like are assembled and brazed using a flux in nitrogen, for example, the flux inevitably remains on the surfaces of the fins and the like. Therefore, the surface state (potential state, etc.) of the fins and the like becomes uneven, and it is difficult to obtain a uniform chemical conversion coating and hydrophilic coating with the conventional chemical conversion treatment agent.
As the flux, a halogen-based flux generally used in NB method can be used. As the halogen brazing flux, KAlF selected from the group consisting of4、K2AlF5、K3AlF6、CsAlF4、Cs3AlF6And Cs2AlF5At least 1 kind of (1).
[ (a) chemical conversion treatment Process ]
The chemical conversion treatment step (a) of the present embodiment is a step of forming a chemical conversion coating on the surface of a chemical conversion treatment agent for an aluminum heat exchanger, the chemical conversion treatment agent containing at least one of zirconium and titanium in a total amount of 5 to 5000 mass ppm, vanadium in a total amount of 10 to 1000 mass ppm, a metal stabilizer in a total amount of 5 to 5000 mass ppm, and a pH of 2 to 6.
Before the chemical conversion treatment, the aluminum heat exchanger may be subjected to an acid pickling treatment as necessary in order to further improve the chemical conversion treatment effect. The pickling conditions are not particularly limited, and conventionally used pickling conditions can be adopted as the pickling of the aluminum heat exchanger.
Here, in the chemical conversion treatment agent of the present embodiment, any of zirconium, titanium, and vanadium exists as various ions such as complex ions. Therefore, in the present specification, the contents of each of zirconium, titanium and vanadium refer to values in terms of metal elements of each ion.
The chemical conversion treatment agent of the present embodiment contains vanadium ions and at least one of zirconium ions and titanium ions, and is obtained by dissolving a vanadium compound and at least one of a zirconium-based compound and a titanium-based compound in water. That is, the chemical conversion treatment agent of the present embodiment is a solution containing vanadium ions and at least one of zirconium ions and titanium ions as active species (hereinafter, referred to as "reactive species"). The chemical conversion treatment agent according to the present embodiment preferably contains zirconium ions, titanium ions, and vanadium ions as active species.
Zirconium ions are changed by a chemical conversion reaction, and thereby zirconium precipitates mainly composed of zirconium oxide are precipitated on the surface of aluminum. Examples of the zirconium-based compound as a source of the zirconium ion include, in addition to zirconium compounds such as fluorozirconic acid and zirconium fluoride, lithium salts, sodium salts, potassium salts, and ammonium salts thereof. Further, a zirconium compound such as zirconia may be dissolved with a fluoride such as hydrofluoric acid and then used. These zirconium compounds have an etching effect on the surface of aluminum due to the fluorine contained therein.
Titanium ions change by a chemical conversion reaction, and thereby titanium precipitates mainly composed of titanium oxide are precipitated on the surface of aluminum. Since the precipitation pH of titanium ions is lower than that of zirconium ions, the precipitation of zirconium precipitates and vanadium precipitates described later can be promoted in addition to the titanium ion precipitates themselves being likely to precipitate, and as a result, the amount of the chemical conversion coating mainly formed of these precipitates can be increased. In particular, in the case where the aluminum heat exchanger is a flux-brazed aluminum heat exchanger, titanium ions are likely to precipitate and precipitate titanium precipitates in the vicinity of the flux remaining on the surface of the aluminum heat exchanger.
The titanium compound as a titanium ion supply source may, for example, be a titanium compound such as fluorotitanic acid or titanium fluoride, or a lithium salt, a sodium salt, a potassium salt or an ammonium salt thereof. In addition, a titanium compound such as titanium oxide may be dissolved with a fluoride such as hydrofluoric acid and then used. These titanium compounds contain fluorine as in the case of the zirconium compounds described above, and thus have an etching effect on the surface of aluminum. Also, the etching effect is higher than that of the above zirconium-based compound.
In the present embodiment, the chemical conversion treatment agent contains vanadium ions and at least one of zirconium ions and titanium ions, thereby forming a chemical conversion coating film containing vanadium and at least one of zirconium and titanium. The vanadium ions have a property of precipitating at a lower pH than the titanium ions, whereby vanadium precipitates composed mainly of vanadium oxide precipitate on the surface of aluminum. More specifically, vanadium ions are converted into vanadium oxide by a reduction reaction, and thereby vanadium precipitates are precipitated on the surface of aluminum.
Unlike zirconium precipitates and titanium precipitates, which have the property of entirely coating the aluminum surface except for a part thereof, vanadium precipitates have the property of being easily precipitated on segregated substances on the aluminum surface, which are difficult to form zirconium precipitates and titanium precipitates. Thus, if the chemical conversion treatment agent of the present embodiment is used, a dense chemical conversion coating having high covering properties can be formed mainly of zirconium precipitates, titanium precipitates, and vanadium precipitates, as compared with a conventional chemical conversion treatment agent containing no vanadium ion.
The vanadium precipitates exhibit a self-healing effect in the same manner as a conventional chromium film by coexisting with zirconium ions and titanium ions, and have excellent film-forming properties. That is, a small amount of vanadium ions are appropriately eluted from the vanadium precipitate, and the eluted vanadium ions are automatically repaired by oxidizing and passivating the surface of aluminum, thereby maintaining good corrosion resistance. On the other hand, when vanadium ions do not coexist with zirconium ions and titanium ions, precipitation of vanadium precipitates is difficult, and even if vanadium precipitates are precipitated, a large amount of vanadium ions are eluted from the precipitates, and the self-healing effect as described above cannot be obtained.
In the present embodiment, it is preferable that the chemical conversion treatment agent contains zirconium ions, titanium ions, and vanadium ions to form a chemical conversion coating film containing zirconium, titanium, and vanadium. By using an activating treatment agent containing zirconium ions, titanium ions and vanadium ions as active species, particularly in the case of an aluminum heat exchanger brazed by using a flux, a denser chemical conversion coating having high covering properties can be formed even in the vicinity of the flux.
As the vanadium compound, a vanadium compound having a valence of 2 to 5 can be used. Specifically, the catalyst may include metavanadate, ammonium metavanadate, sodium metavanadate, vanadium pentoxide, vanadium oxytrichloride, vanadyl sulfate, vanadyl nitrate, vanadyl phosphate, vanadium oxide, vanadium dioxide, vanadyl acetylacetonate, vanadium chloride, and the like. These vanadium compounds do not contain fluorine, and therefore do not have an etching effect on the surface of aluminum.
In this embodiment, a vanadium compound having a valence of 4 or 5 is preferably used, and specifically, vanadyl sulfate (valence of 4) and ammonium metavanadate (valence of 5) are preferably used.
As described above, in the chemical conversion treatment agent of the present embodiment, the total content of zirconium ions and titanium ions is 5 to 5000 mass ppm in terms of metal, and the content of vanadium ions is 10 to 1000 mass ppm in terms of metal. By satisfying the above conditions, the corrosion resistance and moisture resistance of the aluminum heat exchanger can be greatly improved and excellent hydrophilicity and odor resistance can be obtained by a synergistic effect by combining the above conditions with hydrophilization treatment described later.
In addition, from the viewpoint of further improving the above effect, the sum of the contents of zirconium ion and titanium ion is preferably 5 to 3000 mass ppm in terms of metal, the content of zirconium is preferably 5 to 3000 mass ppm, the content of titanium is preferably 5 to 500 mass ppm, and the content of vanadium is preferably 10 to 500 mass ppm.
The chemical conversion treatment agent of the present embodiment contains a metal stabilizer that stabilizes each metal ion composed of zirconium ion, titanium ion, and vanadium ion. The metal stabilizer used in the present embodiment forms a complex by chelating and binding zirconium ions, vanadium ions, and titanium ions in the chemical conversion agent. Thereby, each metal ion composed of a zirconium ion, a vanadium ion, and a titanium ion is stabilized in the chemical conversion agent.
As described above, each metal ion composed of a zirconium ion, a titanium ion, and a vanadium ion has an inherent precipitation pH. Therefore, in the case of the conventional chemical conversion treatment agent, the pH of the interface increases with the etching reaction on the surface of the treatment material, and the metal ions are sequentially precipitated from the side having a lower precipitation pH, thereby forming a chemical conversion coating.
In contrast, in the case of the chemical conversion treatment agent of the present embodiment, each metal ion forms a complex and is stabilized by the action of the metal stabilizer, and therefore the precipitation pH rises. Therefore, at a pH higher than the precipitation pH inherent to each metal ion, each metal ion precipitates simultaneously as a complex. Specifically, at a pH higher than the precipitation pH at which the zirconium ion having the highest precipitation pH is precipitated, the respective metal ions are simultaneously precipitated as a complex. This enables the formation of a more uniform chemical conversion coating than in the prior art, and the precipitation of the chemical conversion coating as a complex increases the particle size of the precipitate, resulting in a higher coating rate than in the prior art. Therefore, corrosion resistance, particularly moisture resistance, superior to those of the conventional ones can be obtained.
From the viewpoint of sufficiently exhibiting the effects of the above metal stabilizer, the chemical conversion treatment agent of the present embodiment preferably contains zirconium, vanadium, and titanium at the same time.
In the chemical conversion treatment agent of the present embodiment, the metal ions in which the respective metal ions are complexed by the action of the metal stabilizer and the metal ions which are not complexed and exist in the state of the metal ions coexist.
Here, in the case of the conventional chemical conversion treatment agent, each metal ion is precipitated on a defect portion of the surface of the aluminum-based metal material, and then the same metal is precipitated on a portion of the metal after precipitation. Therefore, the film is not uniformly formed, and the film is defective.
In contrast, in the case of the chemical conversion treatment agent of the present embodiment, as the pH of the interface increases, first, the metal ions that are not complexed precipitate sequentially at their own precipitation pH, and coat the defective portions of the surface of the aluminum-based metal material. Then, the complex formed by the action of the metal stabilizer precipitates at a higher pH, and a chemical conversion coating can be uniformly formed.
Thus, the chemical conversion treatment agent of the present embodiment is greatly different from conventional chemical conversion treatment agents in that the coating formation step of the chemical conversion coating is performed in two stages.
The technique of patent document 5 is a technique in which ascorbic acid or the like is contained in a coating-type surface treatment agent, not a reactive chemical conversion treatment agent. Therefore, the technique of patent document 5 is greatly different from the present embodiment in that the effects peculiar to the reactive chemical conversion treatment agent are not exhibited, and the peculiar effects are stabilization of each metal ion and an increase in precipitation pH due to formation of a complex with a metal stabilizer such as ascorbic acid, and homogenization of the chemical conversion coating and improvement of the coating rate due to simultaneous precipitation of each metal ion as a complex.
The metal stabilizer used in the present embodiment is preferably at least one selected from the group consisting of a reducing organic compound and an iminodiacetic acid derivative.
The organic compound having reducibility is preferably at least one selected from the group consisting of ascorbic acid, oxalic acid, aluminum lake (Japanese: アルミニウムレーキ), anthocyanin, polyphenol, aspartic acid, sorbitol, citric acid, and sodium gluconate. These organic compounds having reducing properties can be stabilized by reducing vanadium, which is easily changeable in valence number.
Examples of the aluminum lake include "edible blue aluminum lake No. 1 (japanese: edible cyan No. 1 アルミニウムレーキ)", "edible red aluminum lake No. 2 (japanese: edible red No. 2 アルミニウムレーキ)", and "edible yellow aluminum lake No. 4 (japanese: edible yellow No. 4 アルミニウムレーキ)" manufactured by trionyuan FFI corporation (trinitrogen エフ, エフ, アイ).
Examples of the anthocyanins include "アルベリー L" (registered trademark), "テクノカラーレッド ADK" and "マイスレッド a" manufactured by mitsubishi chemical food corporation (mitsubishi chemical フーズ).
The polyphenol may be pyrogallol, catechin, tannin or the like, and examples thereof include "パンシル FG-70", "パンシル F G-60" manufactured by Riliss science industries, Inc. (, リリース Co., Ltd.), and "PL-6757", "PL-4012" manufactured by Rong chemical industries, Inc. (Eiken Co., Ltd.).
Further, as the iminodiacetic acid derivative, iminodiacetic acid and tetrasodium iminodisuccinate are preferably exemplified.
As tetrasodium iminodisuccinate, "BaypureCX-100" manufactured by Langshan corporation (ランクセス Co., Ltd.) can be used, for example.
Among the above-listed compounds, ascorbic acid, anthocyanins, and polyphenols are preferably used from the viewpoint of corrosion resistance, moisture resistance, and safety.
In the present embodiment, two or more metal stabilizers may be used simultaneously. Specifically, for example, two or more kinds of organic compounds having reducing property may be used at the same time, one kind of organic compound having reducing property and one kind of iminodiacetic acid derivative may be used at the same time, or two or more kinds of iminodiacetic acid derivatives may be used at the same time.
In the present embodiment, the content of the metal stabilizer is 5 to 5000 ppm by mass. The content of the metal stabilizer in the present specification means the total amount of two or more metal stabilizers used together. When the content of the metal stabilizer is within this range, the effects of the metal stabilizer can be exhibited surely. Preferably 10 to 2000 ppm by mass, and within this range, the effect of the metal stabilizer can be further improved.
As described above, the chemical conversion treatment agent of the present embodiment has a pH of 2 to 6, preferably 3 to 5. When the pH is 2 or more, a chemical conversion coating can be formed without causing excessive etching by the chemical conversion treatment agent, and excellent corrosion resistance and moisture resistance can be obtained. When the pH is 6 or less, a sufficient amount of chemical conversion coating can be formed without causing insufficient etching, and excellent corrosion resistance and moisture resistance can be obtained. The pH of the chemical conversion treatment agent can be adjusted by using a common acid or base such as sulfuric acid, nitric acid, or ammonia.
The chemical conversion treatment agent of the present embodiment may contain metal ions such as manganese, zinc, cerium, chromium (3-valent), molybdenum, magnesium, strontium, calcium, tin, copper, iron, and silicon compounds for the purpose of improving rust prevention; phosphorus compounds such as phosphonic acid, phosphoric acid and condensed phosphoric acid; and various rust inhibitors such as various silane coupling agents including aminosilane and epoxysilane.
The chemical conversion treatment agent of the present embodiment may contain 50 to 5000 ppm by mass of aluminum ions and 1 to 100 ppm by mass of free fluorine ions.
Although aluminum ions are eluted from the aluminum to be treated into the chemical conversion treatment agent, the chemical conversion treatment reaction can be promoted by positively adding additional aluminum ions. Further, if the concentration of free fluorine ions is set higher than that in the conventional case, a chemical conversion coating film having more excellent corrosion resistance can be formed.
From the viewpoint of further improving the above effect, the content of aluminum ions is more preferably 100 to 3000 mass ppm, and still more preferably 200 to 2000 mass ppm. Similarly, the content of free fluoride ion is more preferably 5 to 80 mass ppm, and still more preferably 15 to 50 mass ppm.
Examples of the source of the aluminum ions include aluminates such as aluminum nitrate, aluminum sulfate, aluminum fluoride, alumina, alum, aluminum silicate and sodium aluminate, and fluoroaluminates such as sodium fluoroaluminate.
The supply source of the free fluorine ions may, for example, be hydrofluoric acid, ammonium bifluoride, zirconium hydrofluoric acid, titanium hydrofluoric acid or the like, or a salt thereof; metal fluorides such as sodium fluoride, zirconium fluoride and titanium fluoride; ammonium fluoride, and the like. When zirconium fluoride, titanium fluoride, or the like is used as a supply source of the free fluorine ions, these compounds serve as supply sources of zirconium ions and titanium ions.
The chemical conversion treatment method of the present embodiment is not particularly limited, and any of a spraying method, an immersion method, and the like may be used. The temperature of the chemical conversion treatment agent is preferably 45-70 ℃, and more preferably 50-65 ℃. The time for the chemical conversion treatment is preferably 20 to 900 seconds, more preferably 30 to 600 seconds. By satisfying these conditions, a chemical conversion coating film having excellent corrosion resistance and moisture resistance can be formed.
As described above, in the chemical conversion coating film of the present embodiment formed on the surface of the aluminum heat exchanger, the total amount of zirconium and titanium is preferably 5 to 300mg/m2The amount of vanadium is preferably 1 to 150mg/m2The amount of the metal stabilizer is preferably 0.5 to 200mg/m in terms of carbon2. By satisfying these conditions, more excellent corrosion resistance can be obtainedCorrosion and moisture resistance. The ratio of the amount of zirconium to the amount of titanium may vary depending on the surface state of the aluminum heat exchanger to be treated, particularly the amount of segregation, etc., but the total amount thereof may be within the above range.
The amount of zirconium, the amount of titanium, and the amount of vanadium in the chemical conversion coating film can be calculated from the measurement result of a fluorescence X-ray analysis device "XRF-1700" (manufactured by shimadzu corporation) by laminating fins under the condition of 10mm × 10mm or more.
The amount of the metal stabilizer in the chemical conversion coating can be calculated as the amount of organic carbon in the chemical conversion coating (i.e., calculated as carbon conversion) from the measurement results of a TOC apparatus "TOC-VCS" (manufactured by shimadzu corporation). However, when the various rust inhibitors listed above are included for the purpose of improving rust inhibition, the amount of C derived from the metal stabilizer can be calculated by subtracting the amount of C calculated from the measured values of the amount of Si, the amount of P, the amount of N, and the like contained in the various rust inhibitors from the amount of C measured by the TOC apparatus.
[ (b) hydrophilization treatment Process ]
The hydrophilization treatment step (b) of the present embodiment is a step of bringing the aluminum heat exchanger having the chemical conversion coating formed on the surface thereof in the chemical conversion treatment step (a) into contact with a hydrophilization treatment agent containing a hydrophilic resin.
The hydrophilizing agent of the present embodiment is an aqueous solution or aqueous dispersion containing a hydrophilic resin in an aqueous solvent. The hydrophilizing agent of the present embodiment is preferably an aqueous solution or aqueous dispersion containing, in addition to the hydrophilic resin, at least one of the guanidine compound represented by the following general formula (1) and a salt thereof.
The hydrophilic resin of the present embodiment is not particularly limited, but is preferably a water-soluble or water-dispersible hydrophilic resin containing at least any one of a hydroxyl group, a carboxyl group, an amide group, an amino group, a sulfonic acid group, and an ether group in the molecule. From the viewpoint of obtaining good hydrophilicity, the hydrophilic resin of the present embodiment is preferably a hydrophilic resin capable of forming a hydrophilic film having a contact angle with water droplets of 40 ° or less.
Specific examples of the hydrophilic resin include acrylic polymers having a polyoxyethylene chain such as polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylic acid, sodium polyvinyl sulfonate, polystyrene sulfonic acid, polyacrylamide, carboxymethyl cellulose, chitosan, polyethylene oxide, water-soluble nylon, copolymers of monomers forming these polymers, and 2-methoxypolyethylene glycol methacrylate/2-hydroxyethyl acrylate copolymers. These may be used alone or in combination of 2 or more.
The hydrophilic resin has excellent hydrophilicity and water resistance, and has the characteristics of no odor and difficult odor adsorption. Therefore, if a hydrophilizing agent containing the hydrophilic resin is used, the resulting hydrophilized film is excellent in hydrophilicity and odor resistance and is not easily deteriorated even when exposed to water droplets or running water. Further, when the hydrophilic coating is used, an inorganic substance such as silica having odor and a residual monomer component having an odor substance adsorbed thereon are not easily exposed, and therefore, excellent odor-preventing property can be obtained.
The hydrophilic resin of the present embodiment preferably has a number average molecular weight in the range of 1000 to 100 ten thousand. When the number average molecular weight is 1000 or more, the coating properties such as hydrophilicity, odor resistance and film formability are good. When the number average molecular weight is 100 ten thousand or less, the viscosity of the hydrophilizing agent is not excessively high, and the workability and the coating physical properties are good. More preferably, the number average molecular weight is in the range of 1 to 20 ten thousand. The number average molecular weight and the weight average molecular weight in the present specification are values in terms of standard polystyrene measured by gel permeation chromatography (GPC method).
Among the above-mentioned hydrophilic resins, polyvinyl alcohols are preferable from the viewpoint of excellent hydrophilicity and odor resistance, and among them, polyvinyl alcohols and modified polyvinyl alcohols having a saponification degree of 90% or more are particularly preferable. By using at least one of these compounds, excellent hydrophilicity and deodorizing property can be obtained. More preferably, the degree of saponification is 95% or more.
The modified polyvinyl alcohol may, for example, be a polyoxyalkylene-modified polyvinyl alcohol having 0.01 to 20% of its pendant groups as a polyoxyalkylene ether group represented by the following general formula (4).
[ solution 4]
[ in the formula (4), n represents an integer of 1 to 500, R1R represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms2Represents a hydrogen atom or a methyl group]。
In the polyoxyalkylene-modified polyvinyl alcohol, the polyoxyalkylene-modified group preferably accounts for 0.1 to 5% of the side group, and the degree of polymerization n of the polyoxyalkylene-modified group is preferably 3 to 30. By satisfying these conditions, good hydrophilicity can be obtained from the hydrophilicity of the polyoxyalkylene modifying group. The polyoxyalkylene-modified polyvinyl alcohol may, for example, be an ethylene oxide-modified polyvinyl alcohol.
In the present embodiment, the content of the hydrophilic resin in the hydrophilizing agent is not particularly limited, but is preferably 10 to 99% by mass, more preferably 30 to 95% by mass, of the solid content of the hydrophilizing agent. This can provide excellent hydrophilicity and odor resistance.
The guanidine compound preferably contained in the hydrophilization treatment agent of the present embodiment is represented by the following general formula (1). Since the guanidine compound contains a large amount of nitrogen, it has a characteristic of good adhesion to a chemical conversion coating containing vanadium and at least one of zirconium and titanium, and a characteristic of being easily adsorbed on the surface of aluminum via a thin chemical conversion coating having a thickness of about 0.1 μm. Therefore, by blending a guanidine compound in the hydrophilizing agent, the aluminum or aluminum alloy substrate can be coated with the chemical conversion coating and the hydrophilizing coating, and the occurrence of blackening can be suppressed. That is, the hydrophilization agent of the present embodiment can provide excellent corrosion resistance and excellent moisture resistance by blending the guanidine compound.
In a preferred aspect of the present embodiment, for example, the aluminum heat exchanger brazed with the flux is subjected to a chemical conversion treatment with a chemical conversion treatment agent containing vanadium and at least one of zirconium and titanium, and then subjected to a two-stage rust prevention treatment by a treatment with a hydrophilization treatment agent containing a hydrophilic resin and at least one of a guanidine compound and a salt thereof, whereby a sufficient rust prevention effect can be provided to the entire surface of the aluminum heat exchanger even in a state where the flux is partially left.
Further, in the case where the chemical conversion coating contains zirconium, titanium and vanadium together, and the hydrophilized coating contains a guanidine compound, it is more preferable because the chemical conversion coating and the hydrophilized coating have particularly good adhesion, and the effect of remarkably improving the moisture resistance is exhibited on the entire surface of the aluminum or aluminum alloy substrate including the vicinity of the flux.
[ solution 5]
[ in formula (1), Y represents-C (═ NH) - (CH)2)m-、-C(＝O)-NH-(CH2)m-or-C (═ S) -NH- (CH)2)m-; m represents an integer of 0 to 20, n represents a positive integer, and k represents 0 or 1; x represents hydrogen, amino, hydroxy, methyl, phenyl, chlorophenyl or tolyl; z represents hydrogen, amino, hydroxyl, methyl, phenyl, chlorophenyl, tolyl, or a polymer represented by the following general formula (2) and having a mass average molecular weight of 200 to 100 ten thousand]。
[ solution 6]
[ in the formula (2), p represents a positive integer ].
Examples of the guanidine compound include guanidine, aminoguanidine, guanylthiourea, 1, 3-diphenylguanidine, 1, 3-di-o-tolylguanidine, 1-o-tolylbiguanide, polyhexamethylene biguanide, polypentamethylene biguanide, polypentaethylene biguanide, polyvinyl biguanide and polyallylguanidine.
Examples of the salt of the guanidine compound include organic acid salts such as phosphate, hydrochloride, sulfate, acetate and gluconate salts of the guanidine compound. The total amount of the salt of the guanidine compound is preferably in the range of 0.01 to 100 in terms of a molar ratio to the total amount of the guanidine compound and the salt thereof. Good corrosion resistance and moisture resistance are thereby obtained.
The number average molecular weight of the guanidine compound or the salt thereof is preferably within a range of 59 to 100 ten thousand. As shown by the above general formula (1), the guanidine compound has a molecular weight of at least 59, and a number average molecular weight of 100 ten thousand or less, and can be dissolved in water, and if it is within this range, good corrosion resistance and moisture resistance can be obtained. From the viewpoint of further improving the effect, the lower limit value of the number average molecular weight is more preferably 300, and still more preferably 500. On the other hand, the upper limit value is more preferably 10 ten thousand, and still more preferably 2 ten thousand.
Among the guanidine compounds represented by the general formulae (1) and (2) and the salts thereof, preferred are guanidine compounds having a biguanide structure represented by the general formula (3) below in the molecule and the salts thereof, because the guanidine compounds and the salts thereof have excellent corrosion resistance and moisture resistance.
[ solution 7]
Examples of the guanidine compound having a biguanide structure and a salt thereof include polyhexamethylene biguanide, 1-o-tolylbiguanide, chlorhexidine gluconate, and a salt thereof. These may be used alone or in combination of 2 or more.
The total content of the guanidine compounds and salts thereof is preferably 1 to 40% by mass based on the solid content of the hydrophilization treatment agent. Thereby, excellent corrosion resistance and moisture resistance can be obtained. From the viewpoint of further improving the effect, the content is more preferably 5 to 30% by mass.
The hydrophilization treatment agent of the present embodiment preferably further contains at least 1 selected from phosphoric acid, condensed phosphoric acid, phosphonic acid and derivatives thereof, and lithium ions.
The hydrophilizing agent of the present embodiment can form a hydrophilized film containing a phosphorus compound such as phosphoric acid, condensed phosphoric acid, phosphonic acid, or a derivative thereof on the aluminum surface by containing the phosphorus compound. Thus, even when aluminum is eluted from the surface of aluminum, the eluted aluminum reacts with the phosphorus compound in the hydrophilic coating to form aluminum phosphate, which is insolubilized, and further elution of aluminum can be continuously suppressed for a long period of time, thereby obtaining excellent corrosion resistance and moisture resistance.
Examples of the phosphorus-based compound include phosphoric acid, polyphosphoric acid, tripolyphosphoric acid, metaphosphoric acid, superphosphoric acid, phytic acid, phosphonic acid, hydroxyethylenediphosphonic acid, aminotri (methylenephosphonic acid), butanetricarboxylic acid phosphate (hereinafter referred to as "PBTC"), ethylenediamine tetrakis (methylenephosphonic acid), and tetrakis (hydroxymethyl)
Salts, acrylic phosphonic acid copolymers, and the like. These may be used alone or in combination of 2 or more.
The content of the phosphorus-based compound is preferably 0.05 to 25% by mass based on the solid content of the hydrophilization treatment agent. Thereby, excellent corrosion resistance and moisture resistance can be obtained. From the viewpoint of further improving the effect, the content is more preferably 0.1 to 10% by mass.
Further, the hydrophilization treatment agent of the present embodiment contains lithium ions, and thus excellent corrosion resistance and moisture resistance can be obtained by the following mechanism.
That is, particularly in the case of an aluminum heat exchanger after brazing using a flux, alkali metal ions such as potassium ions in a halogen-based flux remaining on the surface of the aluminum heat exchanger and lithium ions derived from the hydrophilic coating undergo an ion exchange reaction represented by, for example, the following formula (5), thereby forming a hardly soluble coating at the interface between the flux residue and the hydrophilic coating. The thus formed film, which is hardly soluble, suppresses elution of aluminum from the surface of aluminum, resulting in excellent corrosion resistance and moisture resistance. Further, since lithium ions are continuously left in the hydrophilic coating film for a long period of time, the above-described effects can be continuously maintained for a long period of time.
[ solution 8]
KxAlFy+xLi+→LixAlFy+xK+…(5)
[ in the above formula (5), the combination of x and y is: x is 1, y is 4, x is 2, y is 5 or x is 3, y is 6 ].
The lithium ion source is not particularly limited as long as it is a lithium compound capable of generating lithium ions in the hydrophilization treatment agent, and examples thereof include lithium hydroxide, lithium sulfate, lithium carbonate, lithium nitrate, lithium acetate, lithium citrate, lithium lactate, lithium phosphate, lithium oxalate, lithium silicate, and lithium metasilicate. Among them, lithium hydroxide, lithium sulfate, and lithium carbonate are preferable from the viewpoint of less influence on the odor. These may be used alone or in combination of 2 or more.
The content of lithium ions is preferably 0.01 to 25% by mass in terms of metal, based on the solid content of the hydrophilizing agent. Thereby, excellent corrosion resistance and moisture resistance can be obtained. From the viewpoint of further improving the effect, the content is more preferably 0.05 to 5% by mass.
The hydrophilizing agent of the present embodiment may contain a crosslinking agent as needed from the viewpoint of improving the water resistance of the hydrophilized film. As the crosslinking agent, an inorganic crosslinking agent and an organic crosslinking agent which react with hydroxyl groups of polyvinyl alcohol and modified polyvinyl alcohol can be used.
Examples of the inorganic crosslinking agent include silica compounds such as silica, zirconium compounds such as ammonium zirconium fluoride and ammonium zirconium carbonate, metal chelate compounds such as titanium chelate compounds, and metal salts such as Ca, Al, Mg, Fe, and Zn. These inorganic crosslinking agents have an effect of improving water resistance, forming fine irregularities on the surface of the hydrophilic coating film, and reducing the contact angle of water.
Examples of the organic crosslinking agent include melamine resins, phenol resins, epoxy compounds, blocked isocyanate compounds, and the like,
Oxazoline compounds, carbodiimide compounds, and the like. These may be used alone or in combination of 2 or more.
The content of the crosslinking agent is preferably 0.1 to 50% by mass based on the solid content of the hydrophilizing agent. Thereby, excellent water resistance can be obtained. From the viewpoint of further improving the effect, the content is more preferably 0.5 to 30% by mass.
The hydrophilization treatment agent of the present embodiment may contain, as optional components, a dispersant, a rust inhibitor, a pigment, a silane coupling agent, an antibacterial agent (antiseptic agent), a lubricant, a deodorant, and the like.
The dispersant is not particularly limited, and examples thereof include various surfactants and dispersion resins.
The rust inhibitor is not particularly limited, and examples thereof include tannic acid, imidazole compounds, triazine compounds, triazole compounds, hydrazine compounds, and zirconium compounds. Among them, a zirconium compound is preferable from the viewpoint of obtaining excellent corrosion resistance and moisture resistance. The zirconium compound is not particularly limited, and may, for example, be K2ZrF6Alkali metal fluorozirconates, (NH)4)2ZrF6Soluble fluorozirconates such as isofluorozirconates, H2ZrF6And fluorozirconic acid, zirconium fluoride, zirconium oxide, and the like.
The pigment is not particularly limited, and examples thereof include titanium oxide, zinc oxide, zirconium oxide, calcium carbonate, barium sulfate, alumina, kaolin, carbon black, and iron oxide (Fe)2O3、Fe3O4Etc.) and the like, and further, various coloring pigments such as organic pigments and the like can be exemplified.
The silane coupling agent can improve the affinity between the hydrophilic resin and the pigment and improve the adhesion between the hydrophilic resin and the pigment. The silane coupling agent is not particularly limited, and examples thereof include γ -aminopropyltrimethoxysilane, γ -aminopropyltriethoxysilane, γ -glycidoxypropyltrimethoxysilane, γ -methacryloxypropyltriethoxysilane, and N- [2- (vinylbenzylamino) ethyl ] -3-aminopropyltrimethoxysilane. The silane coupling agent may be a polycondensate or a polymer.
The antibacterial agent (antiseptic) is not particularly limited, and examples thereof include 2- (4-thiazolyl) benzimidazole, zinc pyrithione (Japanese: ジンクピリチオン), benzisothiazoline, and the like.
The content of the optional component is preferably 0.01 to 50% by mass in total based on the solid content of the hydrophilizing agent. This makes it possible to exert the respective effects without inhibiting the effects of the hydrophilizing agent. From the viewpoint of further improving each effect, 0.1 to 30% by mass is more preferable.
The solvent as the hydrophilizing agent is not particularly limited, but an aqueous solvent mainly containing water is preferred from the viewpoint of waste liquid treatment and the like. In addition, an organic solvent may be used together with the solvent from the viewpoint of improving film formability and forming a more uniform and smooth film. The organic solvent is not particularly limited as long as it is a solvent that can be uniformly mixed with water, which is generally used for paints and the like, and examples thereof include organic solvents such as alcohols, ketones, esters, and ethers. The content of these organic solvents is preferably 0.01 to 5% by mass of the hydrophilization treatment agent.
In addition, the hydrophilization treatment agent of the present embodiment may contain a pH adjuster from the viewpoint of improving stability. Examples of the pH adjuster include common acids and bases such as sulfuric acid, nitric acid, and ammonia.
The hydrophilizing agent of the present embodiment has a solid content concentration of preferably 1 to 11% by mass, more preferably 2 to 5% by mass, from the viewpoints of workability, uniformity and thickness of the formed hydrophilized film, and economy.
In the hydrophilization treatment step (b) of the present embodiment, the aluminum heat exchanger after the chemical conversion treatment in the chemical conversion step (a) is preferably subjected to a water washing treatment by a conventionally known method before the hydrophilization treatment.
Further, as a method of bringing the hydrophilization agent having the above-mentioned components into contact with the aluminum heat exchanger having the chemical conversion coating formed on the surface thereof, there are a dipping method, a spraying method, a coating method and the like, and among them, the dipping method is preferable in view of the complicated structure of the aluminum heat exchanger. The immersion time is preferably about 10 seconds at room temperature. After the immersion, the amount of the wet coating film is adjusted by blowing air, whereby the amount of the hydrophilic coating film can be controlled.
[ (c) sintering Process ]
The sintering step (c) of the present embodiment is a step of forming a hydrophilic coating on the surface of the aluminum heat exchanger subjected to the hydrophilization treatment in the hydrophilization treatment step (b) by performing a sintering treatment.
The sintering temperature is preferably set to be 140-160 ℃, and the sintering time is preferably 2-120 minutes. Thus, a hydrophilic coating can be reliably formed.
The amount of the hydrophilic coating formed in the sintering step (c) of the present embodiment is preferably 0.05 to 5g/m2. When the amount of the hydrophilic coating is within this range, excellent corrosion resistance and moisture resistance are obtained, and excellent water resistance and odor resistance are obtained. The amount of the hydrophilic coating can be calculated from the measurement result of the TOC apparatus "TOC-VCS" (manufactured by shimadzu corporation) using a conversion coefficient calculated from the relationship between the amount of the hydrophilic coating of the standard coating sample and the amount of the organic carbon contained therein.
The present invention is not limited to the above-described embodiments, and modifications, improvements, and the like are also included within the scope of the present invention.
Examples
The present invention will be described in further detail below with reference to examples, but the present invention is not limited thereto. Unless otherwise specified, parts,% and ppm are by mass.
< examples 1 to 38 and comparative examples 1 to 6>
[ preparation of chemical conversion treating agent ]
According to a conventionally known production method, the chemical conversion treatment agent was prepared by blending and mixing the components according to the conditions shown in tables 1 to 3 with respect to the contents of zirconium, titanium, vanadium and the metal stabilizer and the pH. In addition, fluorozirconic acid was used as a supply source of zirconium, fluorotitanic acid was used as a supply source of titanium, and vanadyl sulfate was used as a supply source of vanadium. The concentrations in tables 1 to 3 can be calculated from the ratios.
[ preparation of hydrophilizing treatment agent ]
According to a conventionally known production method, hydrophilic treatment agents having a solid content of 2.5% were prepared by blending and mixing hydrophilic resins, guanidine compounds represented by the general formula (1), phosphorus compounds, lithium ions and additives under the conditions shown in tables 1 to 3, and using water as a solvent. However, in example 13 alone, a hydrophilization treatment agent having a solid content of 5% was obtained.
[ production of test Heat exchanger ]
In examples 1 to 33 and comparative examples 1 to 6, KAlF by the Narco brazing method was used as a heat exchanger4And K3AlF6An aluminum heat exchanger (NB heat exchanger) for an automobile air conditioner, wherein the brazing flux is brazed. In examples 34 to 38, an aluminum heat exchanger (VB heat exchanger) for an automobile air conditioner brazed by vacuum brazing was used. The brazing flux amount on the fin surface of the NB heat exchanger was 50mg/m in terms of potassium2。
For these heat exchangers, the process was carried out in a reactor containing 1% sulfuric acid, 0.4% KAlF4And K3AlF6The flux was immersed in an acid bath at 40 ℃ for 20 seconds to perform acid cleaning.
After acid cleaning, the heat exchanger was immersed in the chemical conversion treatment agent prepared as described above at 50 ℃ for 60 seconds to perform chemical conversion treatment.
After the chemical conversion treatment, the heat exchanger was washed with water for 30 seconds, and then immersed in the hydrophilization treatment agent prepared as described above at room temperature for 10 seconds. After the immersion, the amount of the wet skin was adjusted by blowing air.
Next, a heat exchanger for test was produced by performing a sintering treatment in a drying furnace at a sintering temperature at which the temperature of the heat exchanger itself reached 150 ℃ for 5 minutes.
< evaluation >
The heat exchangers for test prepared in the examples and comparative examples were subjected to the following physical property evaluations.
[ Corrosion resistance (white rust resistance) ]
The heat exchangers for testing prepared in the examples and comparative examples were evaluated for corrosion resistance (white rust resistance) according to JIS Z2371. Specifically, the heat exchangers for test prepared in each of examples and comparative examples were sprayed with 5% saline solution at 35 ℃ and then the areas of white rust-forming portions after 2000 hours had elapsed were evaluated by visual observation according to the following evaluation criteria. The evaluation was performed by two persons, and the corrosion resistance was evaluated based on the average of the evaluations by two persons.
(evaluation criteria)
10: no white rust is generated.
9: white rust was found, but the area of the white rust-formed portion was less than 10%.
8: the area of the white rust-forming portion is 10% or more and less than 20%.
7: the area of the white rust-forming portion is 20% or more and less than 30%.
6: the area of the white rust-forming portion is 30% or more and less than 40%.
5: the area of the white rust-forming portion is 40% or more and less than 50%.
4: the area of the white rust-forming portion is 50% or more and less than 60%.
3: the area of the white rust-forming portion is 60% or more and less than 70%.
2: the area of the white rust-forming portion is 70% or more and less than 80%.
1: the area of the white rust-forming portion is 80% or more and less than 90%.
[ resistance to moisture (resistance to blackening) ]
The heat exchangers for test prepared in the examples and comparative examples were subjected to a moisture resistance test at a temperature of 70 ℃ and a humidity of 98% or more for 3000 hours. The area of the blackening portion after the evaluation test was visually observed based on the above-mentioned corrosion resistance evaluation criteria. The evaluation subjects were two persons, and the moisture resistance was evaluated based on the average value of the evaluation of the two persons.
[ hydrophilicity ]
The test heat exchangers prepared in the examples and comparative examples were allowed to contact flowing water for 72 hours, and then the contact angle with a water droplet was measured. The contact angle was measured by using an automatic contact angle meter "CA-Z" (manufactured by kyowa interfacial chemical co., ltd.). Hydrophilicity was higher as the contact angle was smaller, and hydrophilicity was evaluated to be good when the contact angle was 40 ° or less.
[ smell ]
The test heat exchangers prepared in the examples and comparative examples were allowed to contact running water for 72 hours, and then their odor was evaluated according to the following evaluation criteria. The evaluators were two persons, and the odor was evaluated based on the average of the evaluations of the two persons. Odor was 1.5 or less, and odor-resistance was evaluated to be good.
(evaluation criteria)
0: has no odor.
1: only a slight smell was felt.
2: the smell is easily felt.
3: a noticeable odor was felt.
4: a strong smell was felt.
5: a very strong smell was felt.
[ amount of coating film ]
The amounts of zirconium, titanium and vanadium in the chemical conversion coatings formed on the surfaces of the test heat exchangers prepared in the examples and comparative examples were calculated from the measurement results of a fluorescent X-ray device "XRF-1700" (manufactured by shimadzu corporation) by bonding fins under the condition of 10mm × 10mm or more.
The amount of the metal stabilizer in the chemical conversion coating can be calculated as the amount of organic carbon in the chemical conversion coating (i.e., calculated as carbon conversion) from the measurement results of a TOC apparatus "TOC-VCS" (manufactured by shimadzu corporation).
The coating amount of the hydrophilic coating formed on the surface of the test heat exchanger prepared in each of examples and comparative examples was calculated from the measurement result of the TOC apparatus "TOC-VCS" (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.
The compositions of the chemical conversion treatment device and the hydrophilizing treatment agent prepared in each of examples and comparative examples, and the evaluation results of the heat exchangers for testing prepared in each of examples and comparative examples are shown in tables 1 to 3.
[ Table 1]
[ Table 2]
[ Table 3]
The details of each component in tables 1 to 3 are as follows.
(1) In the chemical conversion treatment agent, the Zr concentration represents the zirconium content (metal element equivalent concentration of each ion) in the chemical conversion treatment agent, the Ti concentration represents the titanium content (metal element equivalent concentration of each ion) in the chemical conversion treatment agent, and the V concentration represents the vanadium content (metal element equivalent concentration of each ion) in the chemical conversion treatment agent.
(2) The concentration of the metal stabilizer in the chemical conversion treatment agent is the content of the metal stabilizer relative to the chemical conversion treatment agent.
(3) The metal stabilizer アルベリー L is anthocyanin.
(4) The metal stabilizer パンシル FG-70 is catechin.
(5) The metal stabilizer PL-6757 is polyphenol.
(6) The metal stabilizer Baypore CX-100 is tetrasodium iminodisuccinate.
(7) The% solids of each component in the hydrophilizing agent indicates the content of each component relative to the solids of the hydrophilizing agent.
(8) The polyvinyl alcohol had a degree of saponification of 99% and a number average molecular weight of 60000.
(9) The ethylene oxide-modified polyvinyl alcohol had a degree of saponification of 99%, a number average molecular weight of 20000, and a polyoxyethylene group content (ratio to the total pendant groups of the polyvinyl alcohol) of 3%.
(10) The number average molecular weight of carboxymethyl cellulose was 10000.
(11) The number average molecular weight of the sodium polyvinylsulfonate is 20000.
(12) The number average molecular weight of polyacrylic acid is 20000.
(13) The weight average molecular weight of chitosan was 430000. In addition, chitosan needs to be dissolved with citric acid, so in the case of using chitosan, citric acid is also included.
(14) The condensed phosphoric acid is tripolyphosphoric acid.
(15) PBTC represents butane phosphate tricarboxylic acid.
(16) The phenolic resin is an organic cross-linking agent consisting of resol type phenolic, and the number average molecular weight of the phenolic resin is 300.
As shown in tables 1 to 3, it is understood that each of examples 1 to 38 is excellent in corrosion resistance and moisture resistance as compared with comparative examples 1 to 5, and that hydrophilicity and odor (odor resistance) are not inferior to those of comparative example 6 in addition to excellent moisture resistance. From this result, it was confirmed that: the chemical conversion treatment agent for NB heat exchangers and VB heat exchangers is subjected to chemical conversion treatment to form a chemical conversion coating, and then the chemical conversion coating is brought into contact with a hydrophilizing treatment agent containing a hydrophilic resin and sintered to form the hydrophilizing coating, thereby obtaining corrosion resistance and moisture resistance superior to those of the conventional methods, wherein the chemical conversion treatment agent contains 5 to 5000 mass ppm in total of at least one of zirconium and titanium, contains 10 to 1000 mass ppm of vanadium, contains 5 to 5000 mass ppm of a metal stabilizer, and has a pH of 2 to 6.
Possibility of industrial utilization
The surface treatment method of the present invention can be suitably used for surface treatment of an aluminum heat exchanger for an automobile because it can impart excellent corrosion resistance and moisture resistance to a heat exchanger in which a brazing flux remains on the surface of fins or the like.
Claims (6)
1. A method for treating a surface of an aluminum heat exchanger after brazing with a flux, comprising:
(a) forming a chemical conversion coating on a surface of the aluminum heat exchanger with a chemical conversion treatment agent by using either a spraying method or a dipping method;
(b) bringing the aluminum heat exchanger having the chemical conversion coating formed on the surface thereof in the step (a) into contact with a hydrophilization agent containing a hydrophilic resin; and
(c) forming a hydrophilic coating on the surface of the aluminum heat exchanger after the contact treatment in the step (b) by sintering;
the chemical conversion treatment agent used in the step (a) contains 5 to 3000 ppm by mass of zirconium, 5 to 500 ppm by mass of titanium, 10 to 500 ppm by mass of vanadium, 5 to 5000 ppm by mass of a metal stabilizer, and has a pH of 2 to 6; the metal stabilizer is at least one selected from ascorbic acid, oxalic acid, anthocyanin, polyphenol, iminodiacetic acid and tetrasodium iminodisuccinate;
the supply source of the zirconium is fluorozirconic acid,
the supply source of the titanium is fluotitanic acid,
the supply source of the vanadium is vanadyl sulfate,
the hydrophilizing agent used in the step (b) further contains at least one of 1-o-tolylbiguanide and polyhexamethylene biguanide.
2. The method for treating the surface of an aluminum heat exchanger according to claim 1, wherein the total amount of zirconium and titanium in the chemical conversion coating formed in the step (a) is 5 to 300mg/m2The amount of vanadium is 1-150 mg/m2And the amount of the metal stabilizer is 0.5 to 200mg/m in terms of carbon2，
The amount of the hydrophilic coating formed in the step (c) is 0.05 to 5g/m2。
3. The method of surface treatment of an aluminum heat exchanger as recited in claim 1 or 2, wherein the chemical conversion coating formed in the step (a) contains both zirconium and titanium.
4. The method of treating the surface of an aluminum heat exchanger according to claim 1 or 2, wherein the hydrophilization agent used in the step (b) further contains at least one selected from the group consisting of phosphoric acid, condensed phosphoric acid, phosphonic acid and derivatives thereof, and lithium ions.
5. The method of treating the surface of an aluminum heat exchanger according to claim 1 or 2, wherein the hydrophilic resin in the hydrophilization agent used in the step (b) contains at least one of polyvinyl alcohol having a saponification degree of 90% or more and modified polyvinyl alcohol.
6. The surface treatment method of an aluminum heat exchanger according to claim 1 or 2, wherein the aluminum heat exchanger is an aluminum heat exchanger brazed by a nano-gram brazing method.
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| CN1730725A (en) * | 2004-08-06 | 2006-02-08 | 日本油漆株式会社 | Surface treatment method for flux-brazed aluminum-made heat exchanger |
| JP2011214105A (en) * | 2010-03-31 | 2011-10-27 | Nippon Paint Co Ltd | Anti-corrosion treatment method for heat exchanger made of aluminum material |
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|---|---|---|---|---|
| AU2003221348A1 (en) * | 2002-03-12 | 2003-09-22 | Nippon Soda Co., Ltd. | Method for preparing chemical adsorption film and solution for preparing chemical adsorption film for use therein |
| JP2005002370A (en) * | 2003-06-09 | 2005-01-06 | Nippon Paint Co Ltd | Surface treatment method for aluminum-based substrate, and surface-treated substrate |
| JP2005008975A (en) * | 2003-06-20 | 2005-01-13 | Nippon Paint Co Ltd | Metal surface treatment method, surface-treated aluminum based metal and pretreatment method to hydrophilic treatment |
| WO2005078372A1 (en) * | 2004-02-12 | 2005-08-25 | Showa Denko K.K. | Heat exchanger and method for manufacturing the same |
| WO2008029925A1 (en) * | 2006-09-08 | 2008-03-13 | Nippon Paint Co., Ltd. | Method of treating surface of metal base, metallic material treated by the surface treatment method, and method of coating the metallic material |
| CN102575357B (en) * | 2009-07-02 | 2015-08-12 | 日本帕卡濑精株式会社 | Do not contain the metallic surface chemical conversion treatment solution of chromium and fluorine, metal surface treating method and metal surface coating method |
-
2013
- 2013-03-08 CN CN201810344019.6A patent/CN108660450B/en active Active
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002030460A (en) * | 2000-05-11 | 2002-01-31 | Nippon Parkerizing Co Ltd | Metallic surface treating agent, metallic surface treating method and surface treated metallic material |
| CN1730725A (en) * | 2004-08-06 | 2006-02-08 | 日本油漆株式会社 | Surface treatment method for flux-brazed aluminum-made heat exchanger |
| JP2011214105A (en) * | 2010-03-31 | 2011-10-27 | Nippon Paint Co Ltd | Anti-corrosion treatment method for heat exchanger made of aluminum material |
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