JPH0925587A - Anticorrosive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve safety and to exhibit excellent anti corrosive performance to various metals by incorporating further a triazol compound in an anticorrosive consisting of phosphoric acid, molybdic acid, benzotriazol or the like. SOLUTION: The anticorrosive used for a cooling water line or a circulating water line is prepared by incorporating (1) at least one kind selected from phosphoric acid, polyphosphoric acid and the salts, (2) at least one kind selected from molybdic acid, tungstic acid, vanadic acid and the salts, (3) at least one kind selected from benzotriazol, tolyltriazol, 2-mercaptobenzothiazol and the salts and (4) at least one kind selected from a triazol compound expressed by formula I, a triazol compound expressed by formula II and the salts. In formulas 1 and II, each of X, Y and Z expresses hydrogen, a hydroxyl group, a nitro group, a lower alkyl group or a mercapto group.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a novel anticorrosive agent having excellent anticorrosion properties and useful for anticorrosion of various metals.
More specifically, the present invention relates to an anticorrosive agent which is highly safe to the environment and animals and humans, and is particularly useful for preventing corrosion of a water-cooled engine having parts made of aluminum-based materials such as aluminum and aluminum alloys.

[0002]

Conventionally, water-cooled engines for automobiles, ships, etc. have been made of, for example, copper, solder, brass,
Since various parts made of metals such as steel, cast iron, and aluminum-based materials are used together, their corrosion protection is an important issue. In particular, along with the recent demand for energy saving, weight reduction of vehicle bodies such as automobiles and then engine weight reduction have been promoted, and parts made of lightweight aluminum-based materials have been widely used, and aluminum-based materials and copper, solder, Contact corrosion with other metals such as brass and cast iron and corrosion of heat transfer surfaces made of aluminum-based materials (hereinafter referred to as "aluminum heat transfer surfaces") have become serious problems.

In order to solve such a problem, it has been practiced to add an anticorrosive agent such as a chromic acid type anticorrosive agent to the cooling water. However, although the chromic acid type anticorrosive is effective against various metals, it has a serious drawback that it is highly toxic and the used cooling water cannot be discarded as it is.

Further, amine type anticorrosives containing phosphoric acid, sodium nitrate, amines and the like have been proposed and widely used. The amine-based anticorrosive agent has excellent anticorrosion performance and is effective for a heat transfer surface made of aluminum, but has a drawback that it is less effective for contact corrosion between an aluminum material and copper, brass or the like. In addition, the amine-based anticorrosive agent is not sufficiently stable, and if it is used for a long time in cooling water, the active ingredient deteriorates or precipitates, which is not preferable.

Further, the present inventor has proposed an aluminum anticorrosive agent for heat transfer surfaces containing the following components (1) to (3) (Japanese Patent Publication No.
-40916).

(1) Phosphoric acid, polyphosphoric acid and salts thereof.

(2) Molybdic acid, tungstic acid, vanadic acid, their salts, and their heteropolyacid salts.

(3) Benzotriazole, tolyltriazole and their salts.

This anticorrosive is classified into a category different from the above-mentioned chromic acid-based or amine-based anticorrosives, and is highly safe for the environment and humans and animals, and moreover, for the corrosion protection of the heat transfer surface made of aluminum. It is effective, and no deterioration of active ingredients or formation of precipitates is observed due to long-term use, but due to recent improvements in engine performance and further weight reduction, the cooling system around the aluminum heat transfer surface has a higher temperature. In addition, since it is placed under high pressure conditions, there is a demand for an anticorrosive agent having better performance.
In reality, there is a demand for a safe anticorrosion agent that complies with the ASTM standard for aluminum heat transfer surface corrosion.

[0010]

As a result of intensive studies to solve the above problems, the present inventors have found that
When the anticorrosive agent proposed in JP-A-40916 is used in combination with a specific triazole compound, a remarkable synergistic effect is exhibited, the safety to the environment and humans and animals is very high, and it is extremely excellent against various metals. It has excellent anti-corrosion performance, and also conforms to the ASTM standard even for aluminum heat transfer surfaces that are placed under extremely high temperature and high pressure conditions, and is also excellent in that it can significantly prevent contact corrosion between aluminum materials and other metals. It has been found that the anticorrosive property is exhibited for a long period of time, and that even if it is used for a long period of time in cooling water, there is no deterioration of the active ingredient or formation of a precipitate. The present invention has been completed based on such findings.

That is, the present invention provides (1) at least one selected from the group consisting of phosphoric acid, polyphosphoric acid and salts thereof.
At least one selected from the group consisting of species, (2) molybdic acid, tungstic acid, vanadic acid, salts thereof and heteropolyacid salts thereof, (3) benzotriazole, tolyltriazole, 2-mercaptobenzothiazole and their At least one selected from the group consisting of salts, and (4) general formula

[0012]

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[In the formula, X and Y are the same or different and each represents a hydrogen atom, a hydroxyl group, a nitro group, a lower alkyl group or a mercapto group. ] A triazole compound represented by the general formula

[0014]

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[In the formula, Z represents a hydrogen atom, a hydroxyl group, a nitro group, a lower alkyl group or a mercapto group. ] It is related to the anticorrosive containing at least 1 sort (s) selected from the group which consists of the triazole compound represented by these, and those salts.

According to the present invention, the aluminum heat transfer surface is very safe for the environment and humans and animals, exhibits extremely excellent anticorrosion performance against various metals, and is exposed to extremely high temperature and high pressure conditions. Also provides an excellent anticorrosion property conforming to the ASTM standard for a long period of time, and further provides an anticorrosion agent that does not deteriorate the active ingredient or form a precipitate even when used for a long time in cooling water. .

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION In the above general formulas (I) and (II), examples of the lower alkyl group represented by X, Y and Z include, for example, methyl group, ethyl group, n-propyl group, i.
so-propyl group, n-butyl group, sec-butyl group,
A linear or branched alkyl group having about 1 to 4 carbon atoms such as a tert-butyl group can be mentioned, and among these, a methyl group, an ethyl group and the like are preferable.

In the anticorrosive agent of the present invention, the above-mentioned compounds (1) to (4) are used as active ingredients.

The component (1) is at least one selected from the group consisting of phosphoric acid, polyphosphoric acid and salts thereof. More specifically, for example, orthophosphoric acid, pyrophosphoric acid,
Tripolyphosphoric acid, trimetaphosphoric acid, tetrametaphosphoric acid,
Hexametaphosphoric acid etc. can be mentioned. Examples of these salts include alkali metal salts such as sodium salts and potassium salts, ethanolamine salts such as triethanolamine salts and isopropanolamine salts. Among these, sodium salt of orthophosphoric acid,
Preference is given to potassium salt, triethanolamine salt and the like. The concentration of the component (1) in the anticorrosive agent of the present invention is not particularly limited and can be appropriately selected from a wide range, but in consideration of prevention of contact corrosion between cast iron and aluminum-based material, economical efficiency, etc., it is usually 500 to About 30,000 ppm, preferably 5
It may be about 00 to 10000 ppm.

The component (2) is at least one selected from the group consisting of molybdic acid, tungstic acid, vanadic acid, salts thereof and heteropolyacid salts thereof.
Examples of the molybdate include alkali metal salts such as potassium salt and sodium salt. Examples of the heteropoly acid of molybdic acid include phosphomolybdic acid, silicomolybdic acid, boromolybdic acid, and the like, and examples of these salts include alkali metal salts such as sodium salt and potassium salt. Examples of tungstates include alkali metal salts such as sodium salts and potassium salts. Examples of the heteropoly acid of tungstic acid include silicotungstic acid, borotungstic acid, phosphotungstic acid and the like, and examples of the salt thereof include alkali metal salts such as sodium salt and potassium salt. Vanadic acid includes orthovanadic acid and metavanadic acid, and examples of the salt thereof include alkali metal salts such as sodium salt and potassium salt. Examples of the heteropolyacid of vanadic acid include silicovanadic acid, borovanadic acid, phosphovanadic acid, and the like, and examples of these salts include alkali metal salts such as sodium salt and potassium salt. Among these, sodium molybdate, sodium tungstate, etc. are preferable. The concentration of the component (2) in the anticorrosive agent of the present invention is not particularly limited and can be appropriately selected from a wide range. However, the anticorrosion effect on steel, cast iron, etc. when the concentration is low, the aluminum material when the concentration is high and other Considering the frequency of contact corrosion with metal, etc., it is usually about 50 to 5000 ppm, preferably about 500 to 2000 ppm.

The component (3) is at least one selected from the group consisting of benzotriazole, tolyltriazole, 2-mercaptobenzothiazole and salts thereof. Examples of the salt include alkali metal salts such as sodium salt and potassium salt. The component of (3) is 2
It is preferable to use one or more kinds in combination. The concentration of the component (3) in the anticorrosive agent of the present invention is not particularly limited and can be appropriately selected from a wide range, but the anticorrosive effect on copper and brass when the concentration is low, the COD in the drainage when the concentration is high, etc. Considering this, usually about 5 to 5000 ppm, preferably 100 to
It may be about 2000 ppm.

The component (4) is at least one selected from the group consisting of the triazole compound represented by the general formula (I), the triazole compound represented by the general formula (II), and salts thereof.
Is a seed. Although these triazole compounds have been effective against various metals from the past, they are slightly inferior in corrosion resistance to benzotriazole and the like, and have an additive effect even when simply used in combination with benzotriazole and the like. I could only get it. Specific examples of the triazole compound represented by the general formula (I) include 1,2,4-triazole, 3-mercapto-1,2,4-triazole,
3-hydroxy-1,2,4-triazole, 3,5-
Dihydroxy-1,2,4-triazole, 3-methyl-1,2,4-triazole, 1-methyl-1,2,4
-Triazole, 1-methyl-3-mercapto-1,
2,4-triazole etc. can be mentioned. Specific examples of the triazole compound represented by the general formula (II) include 1,2,3-triazole, 4-methyl-1,
2,3-triazole etc. can be mentioned. Examples of these salts include alkali metal salts such as sodium salts and potassium salts. Among these, 1,
2,3-triazole, 1,2,4-triazole, 3
-Hydroxy-1,2,4-triazole, 3-mercapto-1,2,4-triazole, 3,5-dihydroxy-1,2,4-triazole and salts thereof are preferable, and 1,2,3- Triazole, 1,2,4-triazole, 3-hydroxy-1,2,4-triazole and salts thereof are particularly preferable. The concentration of the component (4) in the anticorrosive agent of the present invention is not particularly limited and can be appropriately selected from a wide range.
About 50,000 ppm, preferably 1000-1000
It may be about 0 ppm.

In the anticorrosive agent of the present invention, other conventionally known anticorrosive ingredients may be used in combination with the active ingredients (1) to (4) as long as the effect thereof is not impaired. Examples of the anticorrosive component include carboxylic acids such as aliphatic carboxylic acids and aromatic carboxylic acids and salts thereof (for example, alkali metal salts), nitrates such as sodium nitrate and potassium nitrate, amines and the like. When used together, the metal species for which the anticorrosive agent of the present invention is effective is further increased.

Furthermore, in the anticorrosive agent of the present invention, in addition to the active ingredients of (1) to (4) above, ethylene glycol, diethylene glycol, triethylene glycol,
Glycols such as propylene glycol, dipropylene glycol and tripropylene glycol, glycol ether and the like may be contained. By including these, the anticorrosive agent of the present invention can be used as a heat medium in various cooling systems or as an additive to the heat medium. Moreover, since ethylene glycol is contained among glycols in particular, the anticorrosive agent of the present invention can be used as an antifreeze liquid for the purpose of preventing freezing and anticorrosion of the coolant for a water-cooled engine. When the engine has an aluminum heat transfer surface,
Particularly useful.

In the anticorrosive agent of the present invention, in order to further exert its performance, and particularly to effectively prevent the corrosion of the aluminum heat transfer surface, its pH is 6 to 8, preferably 6.
It is better to adjust the range of 5 to 7.5. As the pH adjuster, known ones commonly used in this field can be used, for example, hydroxides such as sodium hydroxide and potassium hydroxide,
Examples thereof include amines such as triethanolamine and isopropanolamine.

The anticorrosive agent of the present invention is usually prepared by adding the above-mentioned (1) to water.
It is manufactured by adding the components (4) to (4) and, if necessary, other components and dissolving them. The water used here is not particularly limited, and specific examples thereof include tap water, ground water, distilled water, ion-exchanged water, activated carbon-treated water, etc., but distilled water containing few trace components, ion-exchanged water. , Activated carbon treated water and the like are preferable.

The anticorrosive agent of the present invention may be used by selecting an appropriate active ingredient concentration depending on the place of application and the intended use. If a specific example is given, the component of said (1): 500-30000p.
pm, component (2): 50 to 5000 ppm,
Component (3): about 5 to 5000 ppm, and component (4): 100 to 50,000 ppm (preferably 1000).
.About.15000 ppm), and if necessary, a standard concentration of the anticorrosive agent of the present invention containing 5 to 95% by weight of ethylene glycol is added to the cooling water of the water-cooled engine,
The added amount may be about 25 to 60% by weight with respect to the total amount of cooling water. Further, the anticorrosive agent of the present invention containing the above-mentioned components (1) to (4) and, if necessary, other components in a high concentration may be produced, and appropriately diluted in each use scene to be used in an appropriate concentration. .

The anticorrosive agent of the present invention is, for example, copper, solder,
It is effective for various metals such as brass, steel, cast iron, aluminum-based materials and zinc.

Specifically, the anticorrosive agent of the present invention can be used in substantially all fields to which the anticorrosive agent has been conventionally applied. However, it is used for cooling a cooling water system of a water-cooled engine, a chemical factory, a thermal power plant, etc. It can be preferably applied to a water system, a cogeneration system, a floor heating system, a circulating water system of a cooling system, and the like, and is particularly preferably applied to a water-cooled engine in which parts made of an aluminum material (in particular, an aluminum heat transfer surface) are incorporated.

[0030]

The present invention will be specifically described below with reference to examples and comparative examples.

Example 1 Distilled water was mixed with ethylene glycol and orthophosphoric acid (H ₃ PO).
₄ ), sodium molybdate (Na ₂ MoO ₄ ), benzotriazole, and the triazole compounds described in Table 1 were dissolved at the concentrations shown in Table 1, respectively. 1-5 were produced. In Table 1, the concentration of ethylene glycol is% by weight and the other components are shown in ppm.

The anticorrosive agent consisting of ethylene glycol, orthophosphoric acid, sodium molybdate and benzotriazole was proposed by the present inventor in Japanese Patent Publication No. 1-40916, to which a triazole compound was added. Is the anticorrosive agent of the present invention.

[0033]

[Table 1]

Comparative Example 1 No. 1 of Example 1 was used except that the triazole compound was not included.
An anticorrosive agent was produced in the same manner as in 1.

Comparative Example 2 No. 1 of Example 1 was used except that orthophosphoric acid was not included. An anticorrosive agent was produced in the same manner as in 1. Comparative Example 3 No. 1 of Example 1 was replaced with the benzoic acid instead of the triazole compound. An anticorrosive agent was produced in the same manner as in 1. still,
The concentration of benzoic acid is 5000 ppm.

Test Example 1 An aluminum casting heat transfer surface corrosion test was conducted based on JIS K 2234-1944. The test piece was made of aluminum casting JIS H 5202 AC2B and had a diameter of 6 mm.
The one having a thickness of 5 mm and a thickness of 13 mm was used. The anticorrosive agent was diluted 4-fold with distilled water to prepare a 25 vol% aqueous solution.

The test is carried out at a temperature of 135 ° C. and 1.5 kg.
/ V / cm ² of pressure, test piece and 25v for 7 days
After contacting with an ol% aqueous solution, the change in mass of the test piece was determined and the appearance was observed. Table 2 shows the results.

The change in mass of the test piece was obtained from the following calculation formula.

Mass change of test piece = (W'-W) / S Here, W is the mass (mg) of the test piece before the test, W'is the mass (mg) of the test piece after the test, and S is the test. The total surface area (cm ² ) of the previous test piece is shown.

The aluminum casting heat transfer surface corrosion test specified in JIS K 2234-1944 is ASTM D 43.
40, and the prescribed corrosion amount of the aluminum test piece in ASTM is -1.0 mg / cm ² or less (A
STM D 3306).

[0041]

[Table 2]

From Table 2, it can be seen that the anticorrosive agent described in Japanese Patent Publication No. 1-40916 and a specific triazole compound act synergistically to remarkably improve the corrosion prevention effect on the heat transfer surface made of aluminum. . In addition, the anticorrosive agent of the present invention is ASTM
It turns out that it complies with the standard.

Further, the aluminum heat transfer surface corrosion test of the present invention is
Examination of Japanese Patent Publication No. 1-40916 (110 ± 5 ° C. × 2
Note that it was performed under much more severe conditions than (0 hours).

Claims (2)

[Claims] 1. A method comprising: (1) at least one selected from the group consisting of phosphoric acid, polyphosphoric acid and salts thereof, and (2) molybdic acid, tungstic acid, vanadic acid, salts thereof and heteropolyacid salts thereof. At least one selected from the group, (3) at least one selected from the group consisting of benzotriazole, tolyltriazole, 2-mercaptobenzothiazole and salts thereof, and (4)
General formula [In the formula, X and Y are the same or different and each represents a hydrogen atom, a hydroxyl group, a nitro group, a lower alkyl group or a mercapto group. ] A triazole compound represented by the following general formula: [In the formula, Z represents a hydrogen atom, a hydroxyl group, a nitro group, a lower alkyl group or a mercapto group. ] The anticorrosive containing at least 1 sort (s) selected from the group which consists of the triazole compound represented by these, and those salts. 2. The component (1) is added in an amount of 500 to 30,000 pp.
m, 50 to 5000 ppm of the component (2), 5 to 5000 ppm of the component (3), and 100 to 5000 of the component (4).
The anticorrosive according to claim 1, containing 0 ppm.