RU2249634C2 - Corrosion-inhibiting compositions for liquid heat carriers - Google Patents

Abstract

FIELD: corrosion protection.

SUBSTANCE: invention relates to aqueous solutions appropriate as liquid heat carriers for cooling circuits, for instance for internal combustion engine cooling systems. Polymetallic corrosion-inhibiting organic composition contains (i) 5-15% at least one unsaturated C₁₀-C₁₈-monocarboxylic acid or one of the salts thereof with alkali metal, amine selected from group including ethylamine, diethylamine, and triethylamine, or alkanolamine selected from group including monoethanolamine, diethanolamine, triethanolamine, or methyldiethanolamine; (ii) 40-70% at least one saturated carboxylic acids selected from group including saturated C₅-C₁₆-monocarboxylic acids and saturated C₄-C₁₂-dicarboxylic acids or salts thereof with alkali metal, amine, or alkanolamine; (iii) 20-40% tricarboxylic derivative of 1,3,5-triazine; and (iv) 1-5% azole derivative. Aqueous polymetallic corrosion-inhibiting composition contains 10 to 60 wt % of above-indicated organic inhibiting composition. Polymetallic corrosion-inhibiting antifreeze contains 0.1 to 10 wt % of the above aqueous inhibiting composition and 90 to 99.9 wt % of the water-alcohol solution with freezing temperature below 0єC, wherein alcohol is selected from group including methanol, ethanol, 2-propanol, glycerol, ethylene glycol, diethylene glycol, propylene glycol, 1-methoxy-2-propanol, and ethylene glycol methyl, ethyl, propyl and butyl ethers. Method of inhibiting polymetallic corrosion caused by liquid heat carriers comprises adding 3-6%, preferably 3.8-5%, of the above-indicated organic inhibiting composition to liquid heat carriers.

EFFECT: enhanced protection of parts made from various metals, in particular against cavitation corrosion.

11 cl, 2 tbl, 2 ex

Description

The scope of the invention is aqueous liquids suitable for use as liquid coolants for cooling circuits, for example, for cooling systems of internal combustion engines, which need to be improved with regard to their corrosion.

Water and aqueous solutions are widely used as coolants in circuits made of various metals, copper, steel, aluminum, cast iron and their alloys, which are subjected to corrosive attack by coolants under the conditions favorable for corrosion. Corrosion factors are numerous: the presence of ions, elevated temperatures, pressure, fluid flow (cavitation corrosion), the appearance of pairs on welds. Particular attention should be paid to the phenomenon of cavitation corrosion.

The first consequence of corrosion is the loss of material by the walls of the contours and the formation of through holes. To this we can add the formation of corrosion products, deposits of which impede heat transfer between the liquid and the walls of the circuit and lead to overheating of the hot walls with a great risk of serious damage to mechanical parts.

Substances used to lower the freezing point of water represent a factor particularly conducive to the corrosiveness of the coolant. Little by little there is a rejection of the use of salt cooling mixtures, the aggressiveness of which, especially with regard to welds and aluminum, has still not been found a truly satisfactory solution. In industry, they resort to the use of organic antifreezes from the class of alcohols: methanol, ethanol, 2-propanol, glycerol, ethylene glycol, diethylene glycol, propylene glycol, methyl-, ethyl-, propyl- and butyl ether of ethylene glycol and 1-methoxy-2-propanol. Currently, ethylene glycol is the most widely used one. However, there remains the problem of corrosion protection of cooling circuits fed with aqueous fluids containing or not containing organic antifreeze, the development of corrosion inhibiting compositions in such environments, and, if possible, the preparation of frost-preventing compositions that themselves inhibit corrosion.

The composition is subject to specific restrictions due to environmental protection. It is forbidden or in any case highly recommended to introduce phosphates, nitrites, borates, molybdates and amines associated with nitrites into these compositions, which, however, have been recommended and widely used in some compositions in the prior art. Phosphates in contact with hard water precipitate and for this reason their concentration and their activity are reduced (depletion), which can be combated, but at the expense of increasing the cost of protection by using some additives (JP-A-62205183). These phosphates are also harmful to the environment (eutrophication of water). Amines, when combined with nitrites, pose a risk of the formation of nitrosamines - highly toxic compounds. The effluents of liquids with additives of boron derivatives or molybdates are also harmful and need to be treated before they are released into the environment. Thus, there was a decisive orientation towards other organic inhibitors, which was the reason for numerous publications and many patents, including, for example:

- US application No. 819321, cited in US patent No. 4759864 relating to antifreeze based on a combination of alkylbenzoic acid (or alkylbenzoate) with C ₈ -C ₁₂ monocarboxylic acid (or carboxylate) and triazole, with an aminophosphonic acid derivative as a precipitation inhibitor and polyacrylic acid (polyacrylate) as a stabilizer;

- US patent No. 4647392 relating to antifreeze containing C ₅ -C ₁₆ monocarboxylic acid (monocarboxylate), C ₅ -C ₁₆ dicarboxylic acid (or salt) and a triazole derivative;

- US patent No. 4657689 relating to antifreeze containing C ₅ -C ₁₆ carboxylic acid (carboxylate), C ₅ -C ₁₆ dicarboxylic acid (or salt), a triazole derivative and alkali metal sulfonate with 10-20 carbon atoms;

- US patent No. 4588513 relating to antifreeze with dicarboxylic acid (or salt), alkali metal silicate and triazole derivative;

- US patent No. 2832742 relating to an inhibitor containing C ₇ -C ₁₈ -carboxylic acid and p-tert-butylbenzoic acid;

- US patent No. 4759864 relating to antifreeze containing C ₆ -C ₁₂ acid or salt, alkaline boron derivative and triazole derivative.

Article G.T. Hefter et al. Organic Corrosion Inhibitor in Neutral Solutions, published in Corrosion - Vol. 53, n ° 8, 1997, NACE International, pp. 657-667, focuses on the problems encountered in polymetallic corrosion.

However, in any case, the aforementioned compositions leave to a satisfactory degree the problem of cavitation corrosion, which remains, in particular, a serious concern for designers of automobile engines. The compositions of the present invention provide a solution to this problem, which is practically expressed in accordance with the requirements of a test called “cavitation”, and at the same time with the requirements of traditional tests for evaluating the effectiveness of inhibition at elevated temperatures against various metals in liquid antifreeze. The “Cavitation” test CEC S-05X-95 is a test that evaluates the performance of an inhibitory composition effective against corrosion of steel and aluminum resulting from cavitation of a fluid, in particular antifreeze, circulating in the circuit at standard fluid flow rate, temperature and pressure. These tests are described in the examples.

The present invention is the invention of a method of inhibiting polymetallic corrosion caused by liquid coolants that contain or do not contain an organic compound that lowers the freezing point, which consists in introducing from these liquids from 3 to 6% of the mass. and preferably from 3.8 to 5% of the mass. organic inhibitor systems containing:

(I) 5-15% of the mass. at least one unsaturated monocarboxylic acid with 10-18 carbon atoms or one of its salts with an alkali metal, an amine selected from the group consisting of monoethylamine, diethylamine and triethylamine, or an alkanolamine from the group consisting of monoethanolamine, diethanolamine, triethanolamine and methyldiethanolamine;

(II) 40-70 wt.% Of at least one saturated carboxylic acid selected from the group consisting of saturated monocarboxylic acids with 5-16 carbon atoms and saturated dicarboxylic acids with 4-12 carbon atoms or salts of these acids with an alkali metal, amine or alkanolamine;

(III) 20-40% of the mass. tricarboxyl derivative of 1,3,5-triazine, corresponding to the formula:

in which R represents a carboxyalkyl group with 2-6 carbon atoms, or salts of this derivative with an alkali metal, amine or alkanolamine;

(IV) 1-5% of the mass. an azole derivative selected from the group consisting of:

(a) imidazoles of the formula

(b) benzimidazoles of the formula

(c) triazoles of the formula

или

or

or

(d) benzotriazoles of the formula

(e) tetrahydrobenzotriazole

(f) thiazoles of the formula

(g) benzothiazoles of the formula

(h) and alkali metal salts of these azole derivatives, in the formulas of which

R ₁ is a hydrogen atom or methyl,

R ₂ is a hydrogen atom or a mercapto group,

R ₃ is a hydrogen atom or a radical of the formula

in which R ₄ and R ₅ , identical or different, are 2-ethylhexyl or hydroxyalkyl, in particular an ethanol residue.

In one of the preferred forms of implementing the method of the invention, the mass ratio of components I and II, on the one hand, and III (I + II) / III is from 1.5 to 3 and preferably from 1.9 to 2.2.

In the case of salts of organic acids, mass percentages are given for the acid part of the salt.

Of the saturated C ₅ -C ₁₆ monocarboxylic acids, C ₅ -C ₁₀ acids are preferred, in particular n-hexanoic, heptanoic, n-octanoic and nonanoic acids.

Of aliphatic dicarboxylic acids with saturated C ₄ -C ₁₂ chains, C ₄ -C ₁₀ acids are preferred, in particular suberinic, azelaic and sebacic acids.

Of the unsaturated C ₁₀ -C ₂₂ monocarboxylic acids, undecylenic acid is preferred.

If saturated monocarboxylic and dicarboxylic acids are used together, it is advisable to combine them in a mass ratio of diacid / mono acid from 0.1: 1 to 10: 1 and, more preferably, from 0.6: 1 to 5: 1.

A preferred tricarboxyl derivative of 1,3,5-triazine is a compound of the formula

or its salt with triethanolamine.

The inhibitory system of the invention can be used in aqueous fluids with or without antifreeze for cooling circuits and, in particular, for cooling systems of internal combustion engines.

This system can be used by directly introducing various components of the inhibitory system into a liquid carrier. It is more convenient to use mother liquors, which are aqueous solutions containing from 10 to 60% of the mass. an inhibitory system consisting of the above-described components I, II, III and IV, the pH of which is adjusted by neutralizing, for example, sodium hydroxide, in order to dissolve the entire amount of the components, for which the pH of the liquid carrier should be in the range from 7 to 9 and preferably from 7.5 to 8.5.

These aqueous mother liquors are compositions of the invention. If you want to simultaneously protect the circuits from corrosion and freezing, it is preferable to use inhibitory antifreezes (which are also the subject of the present invention) containing:

- from 0.1 to 10% of the mass. the inhibitory composition described above;

- from 90 to 99.9% of the mass. water-alcohol solution with a freezing temperature below 0 ° C, mainly from -10 to -40 ° C, and the alcohol belongs to the group comprising methanol, ethanol, 2-propanol, glycerin, ethylene glycol, diethylene glycol, propylene glycol, 1-methoxy -2-propanol, methyl-, ethyl-, propyl- and butyl ethers of ethylene glycol. Ethylene glycol is preferred.

The inhibitor system of the invention provides protection against polymetallic corrosion under conditions of cavitation corrosion (high temperature, high pressure), especially effective in a less aggressive environment.

The inhibitor system according to the invention can be widely used for environments, in particular, the type of ferrous iron, cast iron, monovalent copper and aluminum. Mention may be made of surface treatment, metalworking, etching during dyeing, and lubrication.

Examples

The following examples will help to better understand the invention. They provide the results of tests commonly practiced in the automotive industry, which will be recalled below:

a) Glass corrosion test (ASTM D 1384: “Corrosion test for Engine Coolants in Glassware”), which monitors the mass changes of various metals (copper, welds, brass, steel, gray iron and cast aluminum alloys) after holding for 336 hours (15 days) at 88 ° C in corrosive water with the addition of antifreeze.

b) Hot plate test (ASTM D 4340: "Corrosion of cast aluminum alloys in Engine Coolants under Heat-rejecting Conditions"), by which the mass changes of a piston-simulating cast aluminum alloy sample heated at 135 ° C for 168 are monitored hour (7 days) and experiencing a pressure of 193 kPa, in a corrosive solution (0.165 g / l NaCl) with 25% antifreeze.

c) Cavitation test (СЕС С-05Х-95), which measures the changes in the mass of the test bodies, which are discs of gray cast iron and aluminum, which are exposed to a circulating stream of a corrosive solution in accordance with ASTM D 1384 (148 mg / l Na ₂ SO ₄ , 165 mg / L NaCl, 138 mg / L NaHCO ₃ ) under test conditions leading to local variations in velocity and pressure, as well as temperature gradients, the nature of which causes the occurrence of cavitation and corrosion phenomena. The test temperature is 115 ° C, a fluid flow rate of 300 l / h, a pressure of 150 kPa. The test duration is 72 hours.

Three types of inhibitors are involved in the trials:

i) conventional mineral compositions based on nitrites, borax or sodium molybdate,

ii) organic or mixed compositions containing sebacic acid used in the prior art,

iii) compositions of the invention.

The inhibitory constituents of all test compositions were dissolved in ethylene glycol. The pH of the concentrated solution was adjusted to 7 to 8 with sodium hydroxide. The reserve alkalinity (RF) of these compounds, expressed in milliliters of 0.1 N hydrochloric acid, is determined in accordance with ASTM D 1121-93. These concentrated solutions are antifreezes. Coolants are prepared by diluting to 50% with deionized water. The test solution consists of a corrosive solution to which coolant is added in an amount of 33% by volume if ASTM D 1384 is used, 25% by volume for ASTM D

4340 and 20% by volume for the standard CEC-0, 5X-95.

To prepare the compositions shown in the examples, the following were used:

- as monocarboxylic acid type I heptanoic (C ₇ ) acid,

- as monocarboxylic acid type II undecylenic acid (C _{11: 1} ),

- as a tricarboxyl derivative of triazine, the compound IRGACOR® L190, marketed by CIBA (L190; RN = 80584-91-4),

- as a triazole derivative tolyltriazole.

Example 1

The following compositions are prepared (in% by weight relative to the composition in ethylene glycol; compositions V9 and V10 are preferred compositions for the invention; compositions V2, V3 and V6 are not in accordance with the invention):

Composition Component V2 V3 V6 V8 V9 V10 C ₇ - 3 3 2 2,5 2,5 C _{11: 1} - - - 0.2 0.3 0.3 L190 2 - 1 1 1 1,5 Tolyltriazole 0.1 0.2 0.2 0.1 0.1 0.1

The results of various tests according to the following standards are given in table 1.

- Test ASTM D 1384 (corrosion in glass production),

the test is positive if weight loss is below 5 mg on copper, 5 mg on brass, 5 mg on weld, 2.5 mg on steel, 4 mg on cast iron and 10 mg on aluminum.

- Test ASTM D 4340 (hot plate), the test is positive if the weight loss is below 1 mg / cm ² for 1 week.

- The CEC S-05X-95 test is considered satisfactory if the mass change is from -50 to +10 mg for aluminum and from -10 to +5 mg for cast iron.

Table 1 Composition Test Technical Requirements V2 V3 V6 V8 V9 V10 ASTM D 1384 Copper 5 mg -2.1 -0.1 -0.2 -0.4 -0.4 -0.2 Brass 5 mg -2.0 -0.1 -0.7 -0.5 -0.5 -0.4 The seam 5 mg -6.0 -4.0 -9.3 -44.4 -5.0 -5.0 Steel -2 mg -3.5 -2.0 -1/0 -0.2 -0.2 -0.1 Gray cast iron 4 mg -4.7 -2.8 -1/0 -0.5 -0.5 -0.4 Foundry Al Alloy 10 mg -9.0 -8.0 -1/5 -0.3 -0.4 -0.3 ASTM D 4340 Foundry Al Alloy -1 mg / cm ² / week. -2/5 -1/1 -0.2 -0.4 -0.3 -0.1 SEC S-05X-95 Foundry Al Alloy -50 +10 mg -275 -240 -140 -55 -49.2 -45.0 Gray cast iron -10 +5 mg +65 -14 +12 +8 +0.9 +0.5

From the table it follows that all tests are positive only for systems with four inhibitory components and only for the claimed compositions. In particular, one can see how difficult the cavitation test is.

Example 2 (comparative): Suitable compositions

Organic (O) and organo-mineral (M) compositions were used with dibasic acids (adipic H ₂ C ₆ and sebacic H ₂ C ₁₀ ), octanoic acid, sodium molybdate, sodium nitrite and tolyltriazole contained (in wt%):

Composition Component O1 O2 O3 M1 Octanoic acid (Ca) 2 - - - H ₂ C ₆ - 1 H ₂ C ₁₀ 1,5 3,5 4.25 4,5 Sodium Molybdate - - - 0.25 Sodium nitrite - - - 0.25 Tolyltriazole 0.1 0.1 0.25 0.1

The test results are given in table 2 below.

Of all the above compositions known from the prior art, only a purely mineral composition has all tests positive, but it contains prohibited or very non-recommended components. It is also seen that the O3 composition has valuable performance characteristics, with the exception, however, of ASTM D 1384 test for gray cast iron, where weight gain is observed (instead of its loss). This mass gain is contraindicated due to possible contouring.

It is well known to those skilled in the art that some additional additives may be added to the composition of the type mentioned above to add specific properties. Among the most common additives are anti-foaming agents, complexones and dyes.

Of the commercial anti-foaming agents, the following products are particularly suitable for the claimed composition:

- Wacker SE47 (silicone based surfactant)

- Pluronic PE6100 from BASF (nonionic surfactant)

- Ultra MS 455-3A (a mixture of silicone surfactant with non-ionic surfactant OR-OE).

The applied dose of these products is usually in the range from 0.01 to 0.03% of the total weight of the composition consisting of mother solutions.

Of the complexones, it is best suited for 1-hydroxyethane-1,1-diphosphonic acid formulations and, in particular, the commercial product DEQUEST 2010 from SOLUTIA. This product may have some activity in corrosion tests, which may require some adjustment of the entire composition of the invention.

Claims (11)

1. Organic composition that inhibits polymetallic corrosion, containing (I) 5-15 wt.% At least one unsaturated monocarboxylic acid with 10-18 carbon atoms or one of its salts with an alkali metal, an amine selected from the group comprising monoethylamine, diethylamine and triethylamine, or alkanolamine from the group including monoethanolamine, diethanolamine, triethanolamine or methyldiethanolamine; (II) 40-70 wt.% Of at least one saturated carboxylic acid from the group consisting of saturated monocarboxylic acids with 5-16 carbon atoms and saturated dicarboxylic acids with 4-12 carbon atoms or salts of these acids with an alkali metal, amine or alkanolamine ; (III) 20-40 wt.% Tricarboxyl derivative of 1,3,5-triazine, corresponding to the formula

in which R represents a carboxyalkyl group with 2-6 carbon atoms, or salts of this derivative with an alkali metal, amine or alkanolamine; (IV) 1-5 wt.% Derived azole selected from the group consisting of (a) imidazoles of the formula

(b) benzimidazoles of the formula

[c) triazoles of the formula

or

(d) benzotriazoles of the formula

(e) tetrahydrobenzotriazole (f) thiazoles of the formula

(g) benzothiazoles of the formula

(h) and alkali metal salts of these azole derivatives, in the formulas of which R ₁ is a hydrogen atom or methyl, R ₂ is a hydrogen atom or a mercapto group, R ₃ is a hydrogen atom or a radical of the formula

in which R4 and R5, identical or different, are 2-ethylhexyl or hydroxyalkyl, in particular an ethanol residue. 2. The composition according to claim 1, in which the mass ratio (I + II) / III is from 1.5 to 3 and preferably from 1.9 to 2.2. 3. The composition according to claim 1 or 2, containing 6-8 wt.% Component I, 55-65 wt.% Component II, 25-35 wt.% Component III and 2-3 wt.% Component IV. 4. The composition according to any one of claims 1 to 3, in which the saturated carboxylic acid is n-hexanoic acid, heptanoic acid, n-octanoic acid or nonanoic acid. 5. The composition according to any one of claims 1 to 3, in which the dicarboxylic acid is suberic acid, azelaic acid or sebacic acid. 6. The composition according to any one of claims 1 to 3, in which the unsaturated monocarboxylic acid is undecylenic acid. 7. The composition according to any one of claims 1 to 3, in which the tricarboxyl derivative of 1,3,5-triazine is a compound of the formula

8. Aqueous polymetallic corrosion inhibiting composition comprising from 10 to 60 wt.% Of the organic inhibiting composition according to any one of claims 1 to 7. 9. Inhibiting polymetallic corrosion antifreeze containing from 0.1 to 10 wt.% The inhibitory composition of claim 8; from 90 to 99.9 wt.% water-alcohol solution with a freezing point below 0 ° C, mainly from -10 to -40 ° C, and the alcohol belongs to the group consisting of methanol, ethanol, 2-propanol, glycerol, ethylene glycol , diethylene glycol, propylene glycol, 1-methoxy-2-propanol, methyl, ethyl, propyl and butyl ethers of ethylene glycol. 10. The inhibitory antifreeze according to claim 9, in which the alcohol is ethylene glycol. 11. A method of inhibiting polymetallic corrosion caused by liquid coolants, whether or not containing an organic compound, lowering the freezing temperature, comprising introducing into the heat-transfer fluids 3-6 wt.%, Preferably 3.8-5 wt.%, The organic inhibitory composition according to any one of paragraphs 1-7.