KR20020026889A - Corrosion inhibiting compositions for heat transfer fluids - Google Patents

Abstract

The present invention is directed to the corrosion of various metals by a heat transfer liquid composed of a combination of unsaturated monocarboxylic acid, saturated monocarboxylic or dicarboxylic acid, 1,3,5-triazine tricarboxylic derivative and azole compound derivative. It relates to a composition to inhibit. The composition especially inhibits cavitation corrosion.

Description

Corrosion Inhibition Composition for Heat Transfer Liquid {CORROSION INHIBITING COMPOSITIONS FOR HEAT TRANSFER FLUIDS}

Water and aqueous solutions are very widely used as coolants in circuits constructed of various metals, copper, steel, aluminum, cast iron and their alloys, which begin to corrode as soon as they reach corrosion conditions. There are a number of corrosion factors, such as the presence of ions, high temperatures, pressure, fluid flow (cavitation corrosion), coupling to the welding point, and very particular attention should be paid to cavitation corrosion.

The first consequence of corrosion is the loss of material from the walls of the circuit and its perforations. In addition, corrosion products are formed, the precipitates of which hinder heat transfer between the fluid and the walls of the circuit, result in overheating of the hot walls and are at high risk of malfunction of sensitive mechanical components.

Products used to lower the freezing point of water are factors that have a very serious effect on worsening the corrosiveness of the coolant. In particular, the use of brine, which is no longer satisfactory with respect to weld points and corrosiveness to aluminum, is almost forbidden. In the industrial world, alcohol-based organic antifreeze liquids such as methanol, ethanol, 2-propanol, glycerol, ethylene glycol, diethylene glycol, propylene glycol, ethylene glycol methyl, ethyl, propyl or butyl ether, and 1-methoxy-2-propanol Depends on Ethylene glycol is the most widely used antifreeze to date. However, to protect a cooling circuit filled with an aqueous solution with or without an organic antifreeze from corrosion, to develop a composition that inhibits corrosion in such a medium, and, if possible, an antifreeze composition that inhibits corrosion by itself. Problems such as formulating a drug still remain.

These compositions are subject to specific constraints with regard to environmental protection. It is prohibited or in some cases very inappropriate to include amines in combination with phosphates, nitrites, borates, molybdates, and nitrites, which have all been recommended in the prior art and some have been widely used. Phosphates precipitate upon contact with hard water and for this reason their concentration and activity decrease (depletion). By using certain additives, this can be overcome, but at the cost of increased environmental protection costs (JP-A-62205183). In addition, these phosphates are harmful to the environment (water eutrophication). Amines, when used in combination with nitrite, carry the risk of nitrosamine formation, a highly toxic substance. Release of liquids with addition of boron derivatives or molybdates is also harmful and requires treatment before returning to the environment. Thus, attention has turned to other organic corrosion inhibitors, and they have generated a number of documents and many patents. For example:

US Pat. No. 8,19,321, cited in US Pat. No. 4,759,864, discloses alkylbenzoic acid (or alkylbenzoate) and C ₈ -C ₁₂ monocarboxylic acid (as well as aminophosphonic acid derivatives as precipitation inhibitors and polyacrylic acids (polyacrylates) as stabilizers). Or carboxylates) and antiazoles based on combinations with triazoles;

- US 4,647,392 has a anti-freeze containing a C ₅ -C ₁₆ monocarboxylic acid (mono-carboxylate), C ₅ -C ₁₆ diacid (salts), and triazole derivatives is described;

US 4,657,689 describes antifreezes containing C ₅ -C ₁₆ carboxylic acids (carboxylates), C ₅ -C ₁₆ dicarboxylic acids (or salts), triazole derivatives and alkaline C ₁₀ -C ₂₀ sulfonates It is done;

US 4,588,513 describes antifreezes containing dicarboxylic acids (or salts), alkaline silicates and triazole derivatives;

US 2,832,742 describes corrosion inhibitors containing C ₇ -C ₁₈ carboxylic acids and p-tert-butylbenzoic acid;

US 4,759,864 describes antifreezes containing C ₆ -C ₁₂ acids or salts, alkaline derivatives of boron and triazole derivatives.

G.T. Hefter et al. [Organic Corrosion Inhibitor in Neutral Solutions], "Corrosion-53, No. 8, 1997, NACE International", pp. 657-667] discusses the problems of multimetal corrosion.

In any case, however, these compositions do not provide a satisfactory solution to the cavitation corrosion problem, which remains a major problem, especially for manufacturers of automotive engines. The composition of the present invention provides an answer to this problem, which is expressed in practice to meet the requirements of the so-called "cavitation" test for various metals in antifreeze and at the same time the requirements of the standard test to evaluate the corrosion inhibitory effect under high temperature conditions. . The CEC C-05X-95 "cavitation" test is to provide a performance assessment of corrosion inhibiting formulations regarding corrosion of steel and aluminum by cavitation of a floatable liquid circulated under standard flow rate, temperature and pressure conditions. These tests are described in the Examples.

The field of the invention relates to an aqueous liquid which can be used as a heat transfer liquid for a cooling circuit, for example for a cooling circuit of an internal combustion engine, whose corrosiveness must be overcome.

The present invention provides a method for inhibiting multimetal corrosion by a heat transfer liquid containing or not freeing an organic compound that lowers the freezing point, wherein the organic corrosion inhibitor system composed of 3 to 6% by weight, preferably 3.8 to 5% by weight The method consists in introducing into the heat transfer solution as follows:

(I) at least one unsaturated monocarboxylic acid having 10 to 18 carbon atoms, or one of its alkali metal salts, one of its amine salts, wherein the amines are from the group of monoethylamine, diethylamine or triethylamine ), Or one of the alkanolamine salts, wherein the alkanolamine originates from the group of monoethanolamine, diethanolamine, triethanolamine or methyldiethanolamine);

(II) at least one saturated carboxylic acid selected from the group comprising saturated monocarboxylic acids having 5 to 16 carbon atoms and saturated dicarboxylic acids having 4 to 12 carbon atoms, or alkali metals or amines or alkanols of these acids 40 to 70 weight percent of amine salts;

(III) 20 to 40% by weight of tricarboxyl derivatives of 1,3,5-triazines corresponding to the following formula or alkali metal or amine or alkanolamine salts of these derivatives:

[Wherein R is a carboxyalkyl group having 2 to 6 carbon atoms];

(IV) 1 to 5% by weight of azole derivatives 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 general formula;

(e) tetrahydrobenzotriazole;

(f) thiazoles of the formula:

(g) benzothiazoles of the formula:

(h) and alkali metal salts of these azole derivatives represented by:

R ₁ is a hydrogen atom or a methyl radical,

R ₂ is a hydrogen atom or a mercapto radical,

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

[Wherein R ₄ and R ₅ are the same or different and represent a 2-ethylhexyl or hydroxyalkyl radical, in particular an ethanol residue].

In a preferred form of using the process of the invention, the weight ratio (I / II) of components (I) and (II) is in the range of 5 to 15, preferably 8 to 12, on the other hand of components (I) and ( II), the weight ratio (I + II / III) between the other component (III) ranges from 1.5 to 3, preferably from 1.9 to 2.2.

Regarding salts of organic acids, the weight percentages for the acid fractions of these salts were calculated.

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

Among the aliphatic dicarboxylic acids containing saturated C ₄ -C ₁₂ chains, preferred are C ₄ -C ₁₀ acids, in particular suberic acid, azelaic acid and sebacic acid.

Among the unsaturated C ₁₀ -C ₂₂ monocarboxylic acids, undecylenic acid is preferable.

When saturated monocarboxylic acids and saturated dicarboxylic acids are used together, it is advantageous to combine them in a diacid / monoacid mass ratio of 0.1: 1 to 10: 1, preferably 0.6: 1 to 5: 1.

Preferred tricarboxylic derivatives of 1,3,5-triazine are compounds of the formula:

RN = 80584-91-4

Or triethanolamine salts thereof.

The corrosion inhibitor system according to the invention can be used for cooling circuits, in particular for cooling circuits of internal combustion engines, as aqueous liquids, with or without antifreeze. It can be used by introducing different components of the corrosion inhibitor system directly into the delivery liquid. It is more convenient to use a mother liquor, which is an aqueous solution containing 10 to 60% by weight of a corrosion inhibitor system consisting of components (I), (II), (III) and (IV) as described above, dissolving all components. The pH is adjusted by neutralizing, for example, with caustic soda, in such a way that the pH of the delivery liquid is in the range of 7 to 9, preferably 7.5 to 8.6. These aqueous mother liquors are the compositions of the present invention. If it is desired to simultaneously protect the circuit from corrosion and freezing, a corrosion inhibiting antifreeze composition, which is also the subject of the present invention, is used instead:

0.1 to 10% by weight of said corrosion inhibiting composition;

90 to 99.9% by weight of an aqueous / alcoholic solution having a freezing point below 0 ° C., preferably −10 to −40 ° C. Alcohols include methanol, ethanol, 2-propanol, glycerol, ethylene glycol, diethylene glycol, propylene glycol, 1-methoxy-2-propanol, ethylene glycol methylether, ethylene glycol ethyl ether, ethylene glycol propyl ether and ethylene glycol butyl ether It is selected from the group consisting of. Ethylene glycol is preferred.

The corrosion inhibitor system according to the invention provides protection against multimetal corrosion under cavitation corrosion conditions (high temperature, high pressure), more particularly under milder conditions of corrosion.

The corrosion inhibitor system according to the invention can be used in a wide range of fields involving various metals, in particular ferrous iron, cast iron, primary copper and aluminum. These areas include surface treatment, metalworking, paint removal, lubrication and the like.

The following examples will make the present invention better understood. The results of tests performed regularly in the automotive industry are needed, which are re-described below:

a) Corrosion test in glassware (ASTM standard D 1384: "Corrosion test for engine coolant in glassware"). It is possible to monitor the change in the weight of various metals (copper, solder, brass, steel, cast iron, cast aluminum) after immersion in an anticorrosive aqueous medium added with antifreeze at 88 ° C. for 336 hours (15 days);

b) Hot plate test (ASTM standard D 4340: "Corrosion under exothermic conditions of cast aluminum alloys in engine coolant"). Piston simulation samples made of cast aluminum were heated in a corrosive solution (0.165 g / L NaCl) containing 25% antifreeze at 135 ° C. for 168 hours (7 days) and treated at a pressure of 193 kPa to change the weight change. Monitor;

c) cavitation test (CEC standard C-05X-95). Specimens consisting of discs made of cast iron and cast aluminum were subjected to corrosive solutions (Na ₂ SO ₄₎ according to ASTM standard D 1384, under test conditions that would induce cavitation and corrosion phenomena, which would differ in local speed and local pressure and temperature. : 148 mg / l, NaCl: 165 mg / l, NaHCO ₃ : 138 mg / l), affected by the action of the circulating flow, and the change in mass is measured. The test temperature is 115 ° C., the flow rate of the liquid is 300 L / h and the pressure is 150 kPa. The duration of the test is 72 hours.

The test covers three types of corrosion inhibitors:

i) conventional inorganic compositions based on nitrite, borax or sodium molybdate,

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

iii) a composition according to the invention.

For all test compositions, the corrosion inhibitor component was dissolved in ethylene glycol. The pH of the concentrated solution is adjusted to 7 to 8 by adding sodium hydroxide. According to ASTM standard D 1121-93, the alkaline reserve (AR) of these compositions, expressed in milliliters of 0.1N hydrochloric acid, is measured. These concentrated solutions constitute an antifreeze. Dilution with 50% with deionized water gives a coolant. The test solution is added with the coolant at a rate of 33% by volume when ASTM Standard D 1384 is applied, 25% by volume for ASTM Standard D 4340, or 20% by CEC Standard C-05X-95. It consists of a caustic solution added at a rate of%.

In preparing the compositions given in the Examples, the following were used:

Heptanoic acid (C7) as monocarboxylic acid of type (I),

Undecylenic acid (C11: 1) as monocarboxylic acid of type (II),

The compound Irgacor sold by Ciba, as a tricarboxylic derivative of triazine L190 (L190; RN = 80584-91-4),

Tolyltriazole (TTZ) as a triazole derivative.

Example 1

The following compositions were prepared in weight percent of the composition in ethylene glycol, with compositions V9 and V10 being preferred compositions according to the invention; Compositions V2, V3 and V6 are outside the scope of this invention:

Table 1 shows the results of various tests according to the criteria associated with the following.

-ASTM D1384 (corrosion in glassware), weight loss less than 5 mg for copper, less than 5 mg for brass, less than 5 mg for solder, less than 2.5 mg for steel, 4 mg for cast iron Less than 10 mg for aluminum and pass the test successfully.

If the weight loss is less than 1 mg / cm 2 / week, pass the ASTM D4340 test (hot plate).

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

It can be seen that only systems that contain four corrosion inhibitor components and which contain these components within the limits of the compositions claimed herein pass all tests. In particular, it shows how difficult it is to pass the cavitation test.

Example 2 (Comparative Example): Composition of the Prior Art

These include diacids (adipic acid (H ₂ C ₆ ) and sebacic acid (H ₂ C ₁₀ )), octanoic acid (C ₈ ), sodium molybdate (molybdate), sodium nitrite (nitrite) and tolyltriazole ( Organic (O) or organic / inorganic (I) compositions containing TTZ) in the following composition (in weight percent):

The test results are shown in Table 2 below:

In all of these formulations according to the prior art, only the composition which is totally inorganic passes all tests, but contains prohibited or very inappropriate ingredients. It can also be observed that composition O3 produces good results, with the exception of the ASTM standard D4340 test, where the weight of cast iron increases (instead of decreasing). This weight increase is a testament to the possibility of blockage of the circuit.

It is well known to those skilled in the art to mix certain auxiliary additives in this type of formulation to provide certain properties. Among the most standard products are antifoams, metal ion sequestrants and colorants.

Among commercial antifoaming agents, the following products are particularly suitable for the compositions claimed herein:

Wacker SE 47 (silicone based surfactant)

-Pluronic PE6100 (nonionic surfactant) sold by BASF

Ultra MS 455-3A (a mixture of one silicone surfactant and one nonionic OP-OE).

These products are generally used at a ratio of 0.01 to 0.03% by weight of the mother liquor formulation.

Among the metal ion sequestrants, suitable products for the formulation include 1-hydroxyethane-1,1 diphosphonic acid, especially the commercially available DEQUEST 2010 from SOLUTIA. This product can exhibit to some extent the activity which can adjust the general composition of this invention with respect to a corrosion test.

Claims (10)

As a method of suppressing corrosion of multimetals by a heat transfer liquid, The heat transfer liquid contains or does not contain an organic compound that lowers the freezing point, Wherein the heat transfer solution is introduced with an organic corrosion inhibitor system comprised of 3 to 6% by weight, preferably 3.8 to 5% by weight: (I) at least one unsaturated monocarboxylic acid having 10 to 18 carbon atoms or one of its alkali metal salts, one of its amine salts, wherein the amine is selected from the group of monoethylamine, diethylamine or triethylamine Or alkanolamine salts thereof, wherein the alkanolamine is selected from the group of monoethanolamine, diethanolamine, triethanolamine or methyldiethanolamine); (II) at least one saturated carboxylic acid selected from the group comprising saturated monocarboxylic acids having 5 to 16 carbon atoms and saturated dicarboxylic acids having 4 to 12 carbon atoms, or alkali metal or amine or alkanolamine salts of these acids Or from 40 to 70% by weight of an alkali metal or amine or alkanolamine salt of this derivative; (III) 20 to 40% by weight of a tricarboxyl derivative of 1,3,5-triazine, or an alkali metal or amine or alkanolamine salt of the derivative [Wherein R is a carboxyalkyl group having 2 to 6 carbon atoms]; (IV) 1 to 5 weight percent of azole derivatives 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 general formula; (e) tetrahydrobenzotriazole; (f) thiazoles of the formula: (g) benzothiazoles of the formula: And (h) alkali metal salts of these azole derivatives represented by R ₁ is a hydrogen atom or a methyl radical, R ₂ is a hydrogen atom or a mercapto radical, R ₃ is a hydrogen atom or a radical of the formula: [Wherein R ₄ and R ₅ are the same or different and represent a 2-ethylhexyl or hydroxyalkyl radical, in particular an ethanol residue]. The method according to claim 1, wherein the weight ratio (I / II) of components (I) and (II) is in the range of 5 to 15, preferably 8 to 12, The range of the weight ratio (I + II / III) between component (I) and (II) on one hand and component (III) on the other is in the range of 1.5 to 3, preferably 1.9 to 2.2. The method of claim 1 or 2, wherein the organic corrosion inhibitor system consists of: 6 to 8% by weight of component (I); 55 to 65% by weight of component (II) 25 to 35% by weight of component (III); And 2-3% by weight of component (IV). 4. The method of any one of claims 1 to 3, wherein the saturated carboxylic acid is n-hexanoic acid, heptanoic acid, n-octanoic acid or nonanoic acid. The method according to any one of claims 1 to 3, wherein the dicarboxylic acid is suberic acid, azelaic acid or sebacic acid. The method according to any one of claims 1 to 3, wherein the unsaturated monocarboxylic acid is undecylenic acid. The method according to any one of claims 1 to 3, wherein the tricarboxylic derivative of 1,3,5-triazine is a compound of the formula: A multimetal corrosion inhibiting composition, consisting of an aqueous solution containing from 10 to 60% by weight of the corrosion inhibitor system according to claim 1. Multimetal corrosion inhibiting antifreeze composition comprising: 0.1 to 10% by weight of the corrosion inhibiting composition of claim 8; Freezing point below 0 ° C., preferably −10 to −40 ° C. and the alcohol is methanol, ethanol, 2-propanol, glycerol, ethylene glycol, diethylene glycol, propylene glycol, 1-methoxy-2-propanol, ethylene 90-99.9% by weight aqueous / alcoholic solution, selected from the group consisting of glycol methyl ether, ethylene glycol ethyl ether, ethylene glycol propyl ether and ethylene glycol butyl ether. The corrosion inhibiting antifreeze composition of claim 9, wherein the alcohol is ethylene glycol.