JPS59208082A - Corrosion preventive method of metal of cooling water system - Google Patents

Abstract

PURPOSE:To prevent effectively corrosion of various metals of a cooling water system by adding a corrosion preventive agent contg. additive salts of benzotriazole and tert-butyl benzoic acid and amine, nitrite, benzoate, etc. in cooling water for an internal combustion engine. CONSTITUTION:A corrosion preventive agent contg. an additive salt (BT.SA) of benzotriazole and water soluble amine, an additive salt (TBA.SA) of tert- butyl benzoic acid and water soluble amine, nitrite and benzoate is added to cooling water for an internal combustion engine, by which corrosion prevention of almost all of many and diversified kinds of metals such as copper, brass, aluminum alloy, solder, steel, cast iron, etc. constituting the cooling water system is effected. The preferred amts. of said corrosion preventive agent components to be added to the cooling water are about 0.005-2.5%, more preferably about 0.05-1.0% BT.SA, about 0.01-2.5%, more preferably about 0.1-1.0% TBA.SA, about 0.03-1.5% nitrite and about 0.001-2.0% benzoate.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for preventing corrosion of metals in a cooling water system.

The cooling system of an internal combustion engine through which cooling water flows is made of metal materials such as aluminum casting, cast iron, steel, brass, solder, and copper, while the constituent materials of the internal combustion engine are mainly cast iron and aluminum alloy. Therefore, a rust preventive agent for a radiator is required to have sufficient anticorrosion properties against all of these various metal materials.

Conventionally, anticorrosion additives such as amines and phosphoric acid have been used, but they are ineffective unless amines and phosphoric acid are added at a high concentration of 5% (wt%) or more. Addition of such a high concentration promotes wear of mechanical seals in coolant pumps, etc., resulting in leakage of coolant water.

Another improvement method is to keep phosphoric acid at a low concentration (< 0.05% or higher) and use nitrite alone or a mixture with nitrate at 0.01% or higher; It is unfavorable in terms of handling and storage because NOx gas is generated.

In addition, as mentioned above, the main constituent materials of internal combustion engines are cast iron and aluminum alloy, and since the corrosivity of these materials by cooling water is different, it is necessary to use an anticorrosive agent that has the same anticorrosive effect against them. This creates the inconvenience of having to use different anticorrosive agents depending on the constituent materials. However, at present, there are almost no anticorrosive agents that simultaneously exhibit sufficient anticorrosion properties for all of the various metal materials that constitute such internal combustion engines.

In addition, the radiator part, which has a particularly thin and complex structure in the cooling system, is made of copper and brass, which have good thermal conductivity.
A sealed structure is formed by solder welding the connecting parts. That is, the solder serves as a sealant in the radiator portion, and if the solder corrodes and the radiator's sealing structure collapses, the cooling function of the internal combustion engine will be lost.

In view of the above-mentioned circumstances, the inventors of the present invention have conducted extensive research and have found that an addition salt of benzotriazole and a water-soluble amine, te
A method for preventing corrosion of metals in a cooling water system, which is characterized by adding an anticorrosive agent containing an addition salt of rt-butylbenzoic acid and a water-soluble amine, nitrite, and benzoate to cooling water for use between internal combustion lines, A grade Ili corrosion inhibitor that can sufficiently effectively protect the various metal materials that make up the internal combustion engine, eliminates the need to use different types of corrosion inhibitors depending on the main constituent materials of the internal combustion engine, and does not generate NOx gas. We have found that this is the case, and have completed the present invention.

That is, the present invention provides an addition salt of benzotriazole and a water-soluble amine (hereinafter referred to as BT-3A) and an addition salt of tert-butylbenzoic acid and a water-soluble amine (hereinafter referred to as TBΔ・SA).
By mixing nitrites and benzoates, it provides a corrosion inhibitor that has almost comprehensive corrosion protection against a wide variety of metals such as copper, brass, aluminum alloys, solder, steel, and cast iron. .

BT-8A used in the present invention is obtained by heating benzotriazole and a water-soluble amine to a low temperature and reacting it; for example, T.228 manufactured by Chiyoda Chemical Research Institute is used, may be used alone. However, its use as an addition salt increases the solubility of the benzotriazole. Examples of water-soluble amines include monoethanolamine, jetanolamine, triethanolamine, cyclohexylamine, and isopropylamine. B
T-8A has excellent corrosion resistance against copper, brass, and aluminum, and the amount added to cooling water is 0.005 to 2.5
%, preferably 0.05 to 1.0%. o, oo
If the amount is less than s%, the anticorrosion properties of copper, brass, aluminum castings, steel, and cast iron will be poor, while if it is added in excess of 2.5%, the cooling liquid phase will turn dark brown, reducing the commercial value and reducing corrosion protection. The effect is saturated and it is also uneconomical.

TBA-SA used in the present invention can be obtained by adding tert-butylbenzoic acid and a water-soluble amine to water or isopropyl alcohol in a molar ratio of i:1.1, and heating the mixture to 60 to 70°C. Alternatively, tert-butylbenzoic acid and a water-soluble amine may be directly mixed without using a solvent.

TBA-SA has particularly excellent anticorrosion properties against solder, but it also acts effectively against other metals as a result of its synergistic action with BT-SA and benzoate.

The amount added is 0.01 to 2.5%, preferably 0.1 to 2.5%.
It is 1.0%. If it is less than 0.01%, corrosion resistance against solder will be poor and synergistic effects with other components cannot be expected. On the other hand, if it is added in excess of 2.0%, the cooling water will foam and the anticorrosion effect will become saturated, making it uneconomical.

The nitrite used in the present invention is preferably a sulfur to lithium salt, but a potassium salt is also suitably used.

Its anticorrosion properties are superior to steel and cast iron, and the amount added to cooling water is 0.03 to 1.5%.

If it is less than 0.03%, the anticorrosion properties for steel and cast iron will decrease, and if it is added in excess of 1.5%, no improvement in the anticorrosion effect will be observed.

The benzoate used in the present invention is preferably a sodium salt, but a potassium salt is also suitably used. Benzoate alone has excellent corrosion resistance against solder, but TBA -
The effect is further improved by using it in combination with SA. Furthermore, by using benzoate, the amount of expensive TBA-8A added can be suppressed.

The amount added is 0.001 to 2.0%, but o, ooi
If the amount of the anticorrosive agent is less than 2.0%, the anticorrosion property of the solder is poor, and even if it is added in an amount exceeding 2.0%, no improvement in the anticorrosion effect is observed.

As described above, the anticorrosive agent used in the present invention can be applied to various types of products including solder by combining TBA-8 with nitrite, which has an excellent anticorrosion effect on solder as well as copper, brass, and aluminum castings. It has a comprehensive anti-corrosion effect on metal materials.

Borate salts and nitrate salts may also be added to the anticorrosive agents used in the present invention.

The borate is preferably a sodium salt, and the ta of the anticorrosive solution is
Shock effect reduces pH fluctuations. The amount added is 0.001 to 0.7%; if it is less than o, ooi%, the buffering effect of the anticorrosive solution will be poor, while if it exceeds 0.7%, the anticorrosion properties of cast iron will be particularly impaired. At the same time, the buffering effect becomes saturated.

Further, the nitrate is preferably a sodium salt, but a potassium salt is also suitably used, and the amount added is 0.001 to 0.5%. If the content is less than 0.001%, the anticorrosive property for aluminum castings will not be exhibited, while if it exceeds 0.5%, it will have an adverse effect on steel and cast iron.

Furthermore, since nitrates have excellent anticorrosion properties for aluminum castings and are inexpensive, it is possible to reduce the addition of BT-3A and TBA-SA when it comes to preventing corrosion of aluminum castings, thereby reducing the cost of anticorrosion treatment. can.

As described above, the method of the present invention can be particularly effectively applied to internal combustion engines and their cooling systems, especially radiators, but it can also be applied to cooling systems in chemical factories and thermal power plants, heating and cooling systems in buildings, etc. can also be effectively applied.

Furthermore, the method of the present invention can be applied without any problems to cooling systems that already contain antifreeze agents such as ethylene glycol.

The present invention will be described below based on Examples, but the present invention is not limited to these Examples.

Examples 1 to 13 1 g of sodium sulfate 148II, 765 mo of sodium chloride 13 and 1 mol of sodium hydrogen carbonate in 112 distilled water
Dissolve 38mQ, then add the amount shown in Table 1 (unit: %)
A test solution was prepared by adding an anticorrosion component according to the following.

Take 750 m of the test liquid thus obtained into a tall beaker and use it as a test piece for aluminum castings A specified in JIS H5202.
C2A, cast iron is Fe12 specified in JIS G 5501,
Steel is 5pcc-1 specified in JIS G 3141. Brass is 02680P specified in JIS H3100.

Solder is H30A specified in JIS Z 3282
For copper, use C1oop specified in JIS H3100, and the following JIS K 2408 (198
The anticorrosion effect of the method of the present invention was evaluated according to 1).

The results are shown in Table 2.

Comparative Examples 1 to 14 Test solutions were prepared in the same manner as in Examples 1 to 13 according to the anticorrosive components and their addition amounts shown in Table 3, and their anticorrosion effects were evaluated.

However, in Comparative Examples 9 to 14, commercial products A to F were used, respectively.
The degree of the conventional corrosion protection effect was shown using

The results are shown in Table 4.

Procedural amendment (spontaneous) June 29, 1988 1 Indication of case 1988 Patent application No. 82384 2 Name of invention Corrosion prevention method for metals in cooling water systems 3 Person making amendment Relationship to case Patent applicant 5 amendment (1) Contents of amendment in column 6 of "Detailed Description of the Invention" of the specification (1) The fourth face metal body on page 14 of the specification is amended as follows.

Claims (1)

[Claims] Addition salt of benzotriazole and water-soluble amine, ter
A method for preventing corrosion of metals in a cooling water system, which comprises adding an anticorrosive agent containing an addition salt of t-butylbenzoic acid and a water-soluble amine, nitrite, and benzoate to cooling water for an internal combustion engine.