JP2006137996A - Liquid coolant composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid coolant composition having corrosion-protective properties for both aluminum and magnesium. <P>SOLUTION: The liquid coolant composition mainly includes a melting-point-lowering agent selected from the group consisting of an glycol and an alcohol; in addition, (a) a corrosion inhibitor selected from fluorides; and (b) 2-ethylhexylphosphoric acid or a salt thereof. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a coolant composition that is added to cooling water of an internal combustion engine such as an automobile, and particularly relates to a coolant composition that is excellent in metal corrosion resistance.

  Conventionally, a cooling liquid mainly composed of a melting point depressant such as alcohols or glycols is added to the cooling water of an automobile engine to prevent freezing in winter. However, alcohols and glycols are not only rust-proof, but also oxidized when they come into contact with oxygen during circulation at high temperatures, and the resulting oxide promotes corrosion of the metals that make up the cooling water flow path. There is.

  Therefore, the coolant generally includes phosphate, borate, carbonate, sulfate, nitrate, molybdate, benzoate, silicate, benzotriazole, sodium salt of mercaptobenzothiazole, tolyltriazole, A rust inhibitor selected from ethanolamine salts and the like is added and mixed in a predetermined amount with cooling water to prevent corrosion of the metal during use.

  Since various metals such as cast iron, steel, and copper alloys are used for the cooling system of an internal combustion engine such as an automobile engine, it is required to prevent corrosion in the coolant regardless of the type of metal. . However, with the frequent use of aluminum parts for the purpose of resource saving and energy saving, it has become clear that the conventional cooling liquid has insufficient anticorrosion properties against aluminum-based metals.

  For example, borates have excellent anticorrosion properties for cast iron materials, but corrosive properties for aluminum-based metal materials. Triethanolamine phosphate has anticorrosive properties against both iron-based metals and aluminum-based metals. However, it can react with nitrite to produce toxic nitrosamines. In addition, the amine salt has a problem that the anticorrosion property against iron is rapidly lowered due to deterioration.

  Furthermore, there is a movement to consider adopting magnesium alloy parts in the cooling system for resource and energy saving purposes. However, magnesium has the lowest standard potential among practical metals and has low corrosion resistance, and it is necessary to consider corrosion resistance for practical use. In order to improve the corrosion resistance, in addition to improving the corrosion resistance of the magnesium alloy itself, it may be achieved by the cooling water used in the cooling system, but magnesium cannot be prevented by conventional coolant additives. .

Therefore, the following Patent Document 1, as a coolant which can anticorrosion magnesium, a) alkyl benzoate is selected from C ₅ -C ₁₅ monobasic acid and a C ₅ -C ₁₅ dibasic acids or salts thereof Disclosed is a corrosion inhibitor composition comprising 0.1 to 15% by weight of one or more inhibitors and b) 0.005 to 5% by weight of fluoride and / or fluorocarboxylic acid or salt thereof. Yes.

  However, fluoride has a high anticorrosion property against magnesium, but has a problem of adversely affecting aluminum alloys.

JP-T-2002-527619

That is, fluoride has an adverse effect on aluminum, and in the coolant composition using alkylbenzoic acid, C _{5 to} C ₁₅ monobasic acid, or C _{5 to} C ₁₅ dibasic acid disclosed in Patent Document 1 above. However, the adverse effect of fluoride is suppressed, but the problem is that the aluminum anticorrosion property is weak.

  This invention is made | formed in view of such a situation, and it aims at providing the cooling fluid composition which has aluminum corrosion resistance and magnesium corrosion resistance.

  The present inventors have found that the above problems can be solved by using a fluoride and a specific compound in combination as a corrosion inhibitor, and have reached the present invention.

  That is, the coolant composition of the present invention is a coolant composition mainly composed of a melting point depressant selected from the group consisting of glycols and alcohols, and (a) a corrosion inhibitor selected from fluorides. And (b) 2-ethylhexyl phosphoric acid or a salt thereof.

  As the fluoride, a water-soluble fluoride is preferable, and specifically, one or more selected from sodium fluoride, potassium fluoride and ammonium fluoride are preferably exemplified.

  In the cooling liquid composition of the present invention, the addition amount of fluoride and 2-ethylhexyl phosphoric acid or a salt thereof is appropriately selected from a range that exhibits the effect. For example, it is preferable to contain 0.01 to 2% by weight of fluoride in terms of elemental fluorine per 100% by weight of the composition, and 0.05 to 2% of 2-ethylhexyl phosphoric acid or a salt thereof per 100% by weight of the composition. It is preferable to contain 5% by weight.

  In addition to fluoride and 2-ethylhexyl phosphoric acid or a salt thereof, the coolant composition of the present invention can further contain conventionally known additives as appropriate. Specifically, corrosion selected from nitrates, triazoles, thiazoles, phosphoric acid and its alkali metal salts, molybdates, aliphatic carboxylic acids and their alkali metal salts, and aromatic carboxylic acids and their alkali metal salts An inhibitor is contained.

  The coolant composition of the present invention, in which fluoride and 2-ethylhexyl phosphoric acid or a salt thereof are added together, has both aluminum corrosion resistance and magnesium corrosion resistance. Lightweight materials such as aluminum alloys and magnesium alloys are used for engine and cooling. When used in an automobile or the like used in the system, a coolant composition having both aluminum corrosion resistance and magnesium corrosion resistance is obtained.

  The melting point depressant, which is the main component of the coolant composition of the present invention, is conventionally known. As alcohols and glycols that are melting point depressants, methanol, ethanol, 2-propanol, monoethylene glycol, propylene glycol, and the like can be used alone or in admixture of two or more.

  As the fluoride added to the coolant composition of the present invention, a water-soluble fluoride is preferable. Specific examples include hydrogen fluoride, fluorocarboxylic acid, alkali metal salts, ammonium salts, and soluble amine salts thereof. Among these, sodium fluoride, potassium fluoride and ammonium fluoride are preferably exemplified from the viewpoint of workability and anticorrosive effect.

  The fluoride compounding amount is less than 0.01% by weight of fluoride, but the effect of adding fluoride is recognized, but the weight loss of aluminum alloy and magnesium alloy is large. Since a saturation phenomenon is observed, the blending amount of fluoride is preferably 0.01 to 2% by weight.

  If the amount of 2-ethylhexyl phosphoric acid or a salt thereof is less than 0.05% by weight, the corrosion resistance to aluminum alloy, cast iron, or steel is insufficient, and if it exceeds 5% by weight, the saturation effect is reduced and the cost increases. Therefore, the amount of 2-ethylhexyl phosphoric acid or a salt thereof is desirably 0.05 to 5% by weight.

  The cooling liquid composition of the present invention further includes 0.01% by weight of nitrate, 0.05 to 1.0% by weight of triazoles, 0.01 to 1.0% by weight of thiazoles, and other phosphoric acid. And one or more corrosion inhibitors selected from alkali metal salts, molybdates, aliphatic carboxylic acids and alkali metal salts thereof, and aromatic carboxylic acids and alkali metal salts thereof. Thereby, corrosion resistance improves further. Nitrate suppresses pitting corrosion of aluminum, and triazoles and thiazoles are effective in preventing copper corrosion. Each of these may be added alone, but it is more preferable to include all of these three types. Examples of nitrates include sodium nitrate and potassium nitrate, and examples of triazoles include benzotriazole and tolyltriazole. Examples of thiazoles include benzothiazole and mercaptobenzothiazole sodium.

  Furthermore, it is desirable that the coolant composition of the present invention does not contain amine salts, borates, and nitrites.

  The coolant composition of the present invention is usually used by mixing 20 to 60% by volume in cooling water. Therefore, each component to be added to the cooling liquid composition of the present invention needs to be completely dissolved in cooling water at least when used, and a component that is difficult to dissolve is desirably blended as an easily soluble alkali metal salt. Examples of the alkali metal salt include Na salt and K salt. Further, from the viewpoint of storage stability and handleability, it is desirable that each component is completely dissolved in the stock solution state of the cooling liquid composition. Therefore, it is preferable that sodium hydroxide, potassium hydroxide and the like are further added to the cooling water composition of the present invention to improve the solubility and to adjust the pH optimally.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. In the following, “%” means “% by weight” unless otherwise specified.

(Example 1 and Comparative Examples 1 to 4)
The coolant compositions of Example 1 and Comparative Example 1 were prepared with the blending amounts shown in Table 1 below. Here, the example (Example 1) which adds together fluoride and 2-ethylhexyl phosphoric acid or a salt thereof, and the case where fluoride and 2-ethylhexyl phosphoric acid or a salt thereof are added alone (Comparative Examples 1 to 3). Indicated. Here, AZ91D is a magnesium alloy, and AC2A is an aluminum alloy.

  Using the cooling liquid composition, a metal corrosion test at the time of contacting a magnesium alloy and an aluminum alloy was performed by an AZ91D-AC2A contact corrosion test. The test was conducted at 90 ° C. × 300 h with 50 vol% JIS water dilution based on the JISK2234 metal corrosion test. Further, a 170 ° C. aluminum heat transfer surface test was performed at a dilution of 45 vol. 1% ion-exchanged water and 170 ° C. × 168 h. Furthermore, the passive current density of the AC2A aluminum alloy was measured by diluting 50% JIS mixed water, liquid temperature: 88 ° C., sweep rate: 20 mV / min, and aeration: nitrogen. The results are shown in Table 1.

[Test 1: Metal corrosion test when contacting magnesium alloy and aluminum alloy]
From the results in Table 1, in Example 1, the combined use of fluoride and 2-ethylhexyl phosphoric acid makes the weight loss value of the magnesium alloy smaller than those of Comparative Example 1 and Comparative Example 3 containing only one of them, thus preventing corrosion of the magnesium alloy. Improved. Moreover, it turns out that Example 1 has a magnesium alloy anticorrosive property equivalent to the comparative example 2 which uses the double amount stool of a fluoride.

[Test 2: Anticorrosion test of aluminum alloy at high temperature]
From the results shown in Table 1, in Example 1, the weight loss of the aluminum heat transfer surface is reduced and the corrosion resistance of the aluminum alloy is improved as compared with Comparative Example 2 containing twice the amount of fluoride. Moreover, it turns out that Example 1 has an aluminum alloy anticorrosive property equivalent to that of Comparative Example 1 which does not contain 2 monoethylhexyl phosphoric acid.

[Test 3: Measurement of immobile bear current density of aluminum alloy]
From the results of Table 1, in Example 1, by using fluoride and 2-ethylhexyl phosphoric acid in combination, the passive current density is reduced compared to Comparative Example 1 and Comparative Example 3 containing only one, and magnesium alloy corrosion resistance Has improved. Moreover, Example 1 is a passive current density equivalent to the comparative example 2 which uses 2 times the amount of fluoride, and it turns out that it has magnesium alloy corrosion resistance.

  From the above results, the coolant of the present invention can maintain the corrosion resistance of the magnesium alloy even when the fluoride is reduced by using fluoride and 2-ethylhexyl phosphoric acid together. Aluminum alloy corrosion resistance is improved.

(Examples 2 to 12)
The coolant compositions of Examples 2 to 12 were prepared with the blending amounts shown in Table 2 below, and the blending amounts were examined. In Table 2, ← indicates the same on the left, and ← in Example 2 indicates the same as in Example 1.

  From the results of Table 2, when F is 0.008% by weight, the magnesium anticorrosive effect of F is recognized, but the weight loss is large. It is understood that 0.01 to 2% by weight is desirable. Moreover, if at least one of 2-ethylhexyl phosphoric acid and its salt is less than 0.05% by weight, the corrosion resistance to the magnesium alloy is insufficient, and if it exceeds 5% by weight, the effect is saturated and the cost increases. It can be seen that the blending amount of 2-ethylhexylphosphoric acid is preferably 0.05 to 5% by weight.

  By adding fluoride and 2-ethylhexyl phosphoric acid and salts thereof to the cooling liquid composition, a cooling liquid composition having both aluminum corrosion resistance and magnesium corrosion resistance can be obtained as compared with the case where each is used alone. It was. With this coolant composition, it has become possible to promote weight reduction of automobiles and the like.

Claims (5)

  A coolant composition comprising as a main component a melting point depressant selected from the group consisting of glycols and alcohols, (a) a corrosion inhibitor selected from fluorides, and (b) 2-ethylhexyl phosphoric acid Or the cooling liquid composition characterized by containing the salt.   2. The coolant composition according to claim 1, wherein the fluoride is contained in an amount of 0.01 to 2% by weight in terms of elemental fluorine per 100% by weight of the composition.   The coolant composition according to claim 1 or 2, wherein the fluoride is one or more selected from sodium fluoride, potassium fluoride, and ammonium fluoride.   The coolant composition according to any one of claims 1 to 3, wherein the 2-ethylhexyl phosphoric acid or a salt thereof is contained in an amount of 0.05 to 5% by weight per 100% by weight of the composition.   Further, at least one selected from nitrates, triazoles, thiazoles, phosphoric acid and alkali metal salts thereof, molybdates, aliphatic carboxylic acids and alkali metal salts thereof, and aromatic carboxylic acids and alkali metal salts thereof. The coolant composition according to any one of claims 1 to 4, wherein a corrosion inhibitor is contained.