EP1192296A1

EP1192296A1 - Corrosion inhibiting compositions for heat transfer fluids

Info

Publication number: EP1192296A1
Application number: EP00949557A
Authority: EP
Inventors: Emeryc Valot
Original assignee: Atofina SA
Current assignee: Arkema SA
Priority date: 1999-06-28
Filing date: 2000-06-23
Publication date: 2002-04-03
Also published as: CA2377776A1; FR2795432B1; PL352778A1; CN1371431A; FR2795432A1; CZ20014588A3; KR20020026889A; BR0011906A; MXPA01013315A; WO2001000902A1; AU6287700A

Abstract

The invention concerns compositions for inhibiting corrosion of various metals by heat transfer fluids consisting of a combination of an unsaturated monocarboxylic acid, a saturated monocarboxylic or dicarboxylic acid, a 1,3,5-triazine tricarboxylic derivative and an azole compound derivative. Said compositions inhibit corrosion by cavitation in particular.

Description

CORROSION INHIBITOR COMPOSITIONS FOR FLUIDS

HEAT TRANSFER

The field of the invention is that of aqueous liquids which can be used as heat transfer fluids for cooling circuits, for example the cooling circuits of internal combustion engines, the corrosivity of which must be remedied.

Water and aqueous solutions are very widely used as cooling fluids in circuits constructed of various metals, copper, steel, aluminum, cast iron and their alloys, which they attack as soon as corrosion conditions are found. There are many corrosion factors: presence of ions, high temperatures, pressure, flow of fluids (corrosion by cavitation), coupling to welds. Particular attention should be paid to the phenomena of cavitation corrosion. The first consequence of corrosion is the loss of material from the walls of the circuits and their perforation. Added to this is the formation of corrosion products, the deposits of which disturb the heat transfers between the fluid and the walls of the circuit, and cause overheating in the hot walls with significant risks of rupture of sensitive mechanical parts. The products used to lower the freezing point of water are a particularly aggravating factor in the corrosiveness of cooling fluids. Little by little, the use of saline brines was abandoned, the aggressiveness of which, in particular towards welds and aluminum, we never really found a satisfactory solution. The industry has rallied to organic antifreezes in the class of alcohols, methanol, ethanol, 2-propanol, glycerol, ethylene glycol, diethylene glycol, propylene glycol, methyl-, ethyl-, propyl-, butylether of ethylene glycol and 1 methoxy-2-propanol. Ethylene glycol is by far the most widely used antifreeze today. The problem remains posed, however, of protecting the cooling circuits supplied with aqueous fluids containing or not containing organic antifreezes against corrosion, of developing compositions which inhibit corrosion in such environments, and if possible formulating antifreeze compositions which themselves are inhibitors. corrosion. Particular constraints relating to the protection of the environment weigh on these compositions. It is prohibited or in any case strongly advised against bringing in phosphates, nitrites, borates, molybdates and amines associated with nitrites, which in the prior art had however been recommended and for some widely used. The phosphates precipitate in contact with hard water, and therefore their concentration and their activity decreases (depletion), which we can fight against, but at the cost of an increase in the cost of protection, by using certain additives (JP -A-62205183); these phosphates are also harmful to the environment (eutrophication of water). Amines when combined with nitrites generate the risk of formation of nitrosamines, highly toxic products. Releases of fluids containing boron derivatives or molybdates are also harmful and require treatment before being returned to the environment. We therefore turned resolutely to other organic inhibitors, which has given rise to numerous publications and numerous patents, including for example:

- US application No. 819,321, cited in US 4,759,864, relating to an antifreeze based on the association of an alkylbenzoic acid (or alkylbenzoate) with a C ₈ -Cι ₂ monocarboxylic acid (or carboxylate) and triazol, with an aminophosphonic acid derivative as a precipitation inhibitor and polyacrylic acid (polyacrylate) as a stabilizer;

- US 4,647,392 for an antifreeze with monocarboxylic acid (monocarboxylic boxylate) C ₅ -C ₁₆ dibasic acid (salt) C ₅ -Cι ₆ and derived from triazol;

- US 4,657,689 for an antifreeze comprising a C ₅ -Cι ₆ carboxylic acid (carboxylate), a C ₅ -C ₁₆ dicarboxylic acid (or salt), a triazol derivative and a C10-C20 alkali sulfonate;

- US 4,588,513 for antifreeze with dicarboxylic acid (or a salt), an alkali silicate and a triazol derivative;

- US 2,832,742 for an inhibitor comprising a C ₇ -C ₁₈ carboxylic acid and p-terbutylbenzoic acid; - US 4,759,864 for an antifreeze comprising a CQ-C- \ 2 acid or a salt, an alkaline derivative of boron and a derivative of triazol. The article by GT Hefter et al. "Organic Corrosion Inhibitor in Neutral Solutions" published in "Corrosion-Vol. 53, n ° 8, 1997, NACE International" pages 657-667, takes stock of the problems encountered in multi-metal corrosion.

However, in any case, these compositions leave the problem of cavitation corrosion, which remains a major concern in particular of automobile engine manufacturers, unsatisfactory. The compositions of the present invention provide an answer to this problem which is practically expressed in their compliance with the requirements of the so-called "cavitation" test at the same time as those of the conventional tests for evaluating the hot inhibitory efficacy vis-à-vis - screws of different metals in an antifreeze liquid. The CEC C-05X-95 "cavitation" test is one which provides an evaluation of the performance of an inhibiting composition with regard to the corrosion of steel and aluminum by cavitation of a possibly antifreeze fluid. circulating in a loop under standardized conditions of flow, temperature and pressure. These tests are described in the examples.

The present invention is that of a method for inhibiting multimetal corrosion by heat transfer fluids, whether or not these fluids contain an organic compound lowering the freezing point, which consists in introducing into said fluids 3 to 6% by weight , and preferably 3.8 to 5%, of an organic inhibitor system consisting of:

(I) 5 to 15% by weight of at least one monocarboxylic acid unsaturated with 10-18 carbon atoms or of an alkali metal salt thereof, of amine from the group of monoethylamine, diethylamine, triethylamine or alkanolamine from the monoethanolamine group, diethanolamine, triethanolamine or methyldiethanolamine;

(II) 40 to 70% by weight of at least one saturated carboxylic acid taken from the group comprising saturated monocarboxylic acids with 5-16 carbon atoms and saturated dicarboxylic acids with 4-12 carbon atoms, or a salt thereof alkali or amine or alkanolamine metal of these acids; - (III) 20 to 40% by weight of a tricarboxylic derivative of 1,3,5-triazine corresponding to the formula: NHR. -NOT. NHR

N., N

NHR

in which R is a carboxyalkyl group with 2-6 carbon atoms, or an alkali metal or amine or alkanolamine salt of this derivative - (IV) 1 to 5% by weight of an azole derivative taken from the group made up of:

(a) imidazoles of formula:

(b) the benzimidazoles of formula

(c) the triazoles of formula

(d) the benzotriazoles of formula

(e) tetrahydrobenzotriazole

(f) the thiazoles of formula

(g) the benzothiazoles of formula

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

R _T 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 formula

with R ₄ and R ₅ , identical or different, representing a 2-ethylhexyl or hydroxyalkyl radical, in particular an ethanol residue.

In a preferred embodiment of the process of the invention, the weight ratio of the constituents I and II (l / ll) will be between 5 and 15 and, preferably, between 8 and 12, and the weight ratio of the constituents I and II on the one hand and III (I + ll / lll) will be between 1.5 and 3 and, preferably, between 1.9 and 2.2.

For the salts of organic acids, the weight percentages are reduced to the acid fraction of the salt concerned. Among the saturated C ₅ -C ₆ monocarboxylic acids, C ₅ -C ₁₀ acids are preferred, in particular n-hexanoic acid, heptanoic acid, n-octanoic acid and nonanoic acid;

Among the aliphatic dicarboxylic acids with saturated C ₄ -C ₁₂ chains, C ₄ -Cι ₀ acids are preferred, in particular suberic acid, azelaic acid and sebacic acid.

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

When a saturated monocarboxylic acid and a saturated dicarboxylic acid 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 .

The preferred 1,3,5 triazine tricarboxylic derivative is the compound of formula:

RN = 80584-91 -4 or its triethanolamine salt.

The inhibitor system according to the invention can be used in aqueous fluids with or without antifreeze for cooling circuits and in particular for cooling circuits of internal combustion engines. It can be implemented by introducing the various components of the inhibitor system directly into the transfer fluid. It is more convenient to use stock solutions which are aqueous solutions comprising from 10 to 60% by weight of the inhibitor system constituted by the components (I), (II), (III) and (IV) as described more high, and whose pH will be adjusted by neutralization, for example with sodium hydroxide in order to dissolve all of the components and so that the pH of the transfer fluid will be in the range 7-9, preferably 7.5- 8.5. These aqueous stock solutions are compositions of the invention. If it is desired to obtain both protection of the circuits against corrosion and freezing, use will be made of inhibiting anti-freeze compositions, also objects of the present invention, consisting of: 0.1 to 10% by weight of the composition inhibitor described above;

90 to 99.9% by weight of a hydroalcoholic solution having a freezing point below 0 ° C, preferably between -10 and - 40 ° C, the alcohol being taken from the group consisting of methanol, l ethanol, 2-propanol, glycerol, ethylene glycol, diethylene glycol, propylene glycol, 1-methoxy-2-propanol, methyl-, ethyl-, propyl-, butyl ethers of ethylene glycol. Ethylene glycol is preferred.

The inhibitor system according to the invention provides protection against multimetal corrosion under cavitation corrosion conditions (high temperature, high pressure), a fortiori under milder aggressiveness conditions.

The inhibitor system of the invention can be used in wide ranges of applications, using media of ferrous iron, cast iron, copper copper and aluminum in particular. We can cite surface treatment, metalworking, paint stripping, lubrication.

EXAMPLES

The following examples will better understand the invention. They call on the results of tests regularly carried out in the automobile industry which we recall here: - a) The corrosion test in glassware (ASTM D 1384: "Corrosion test for

Engine Coolants in Glassware "), which tracks the weight variations of different metals (copper, solder, brass, steel, cast steel, cast aluminum) after immersion for 336 hours (15 days) at 88 ° C in corrosive water with antifreeze added; - b) Hot plate test (ASTM D 4340: "Corrosion of cast aluminum alloys in Engine Coolants under Heat-rejecting Conditions"), by which follows the variations in weight of a cast aluminum sample simulating a piston, heated to 135 ° C, for 168 hours (7 days) and subjected to a pressure of 193 kPa in a corrosive solution (0.165 g / l of NaCl ) containing 25% antifreeze; - c) Cavitation test (CEC C-05X-95), by which we measure the mass variation of test bodies made up of cast iron and aluminum discs subjected to the action of flow in loop of a corrosive solution according to ASTM D 1384 (Na ₂ S0 ₄ : 148 mg / l, NaCI: 165 mg / l, NaHC0 _3: 138 mg / l) under test conditions generating differences in speed and pressure local and temperature likely to induce cavitation and corrosion. The test temperature is 115 ° C, the fluid flow rate of 300 l / h, the pressure of 150 kPa. The duration of the test is 72 hours.

The tests take into account three types of inhibitors: i) conventional mineral compositions based on nitrites, borax or sodium molybdate, ii) organic or mixed compositions of the prior art comprising sebacic acid, iii ) compositions according to the invention.

For all test compositions, the inhibitor components were dissolved in ethylene glycol. The pH of the concentrated solution was adjusted between 7 and 8 by adding sodium hydroxide. The alkaline reserve (RA) of these compositions, expressed in milliliters of 0.1N hydrochloric acid is determined according to standard ASTM D 1121-93. These concentrated solutions constitute antifreezes. Coolants are obtained by dilution to 50% with deionized water. The test solution consists of a corrosive solution to which this coolant has been added, at a rate of 33% by volume if the ASTM D 1384 standard is applied, 25% by volume for the ASTM D 4340 standard. , 20% by volume for the CEC C-05X-95 standard.

To prepare the exemplified compositions, the following were used: - as monocarboxylic acid of type (I) heptanoic acid (C ₇ ), - as type (II) monocarboxylic acid undecylenic acid

(C _{11 1} ),

- as triicarboxylic derivative of triazine, the compound IRGACOR ^® L190 marketed by CIBA (L190; RN = 80584-91-4), - as triazole derivative, tolyltriazole (TTZ)

EXAMPLE 1:

The following compositions were produced, in% by weight relative to the composition in ethylene glycol, compositions V9 and V10 being preferred compositions according to the invention; the compositions V ₂ , V ₃ and V ₆ emerging from the invention.

The results of the various tests according to the standards referred to below are given in Table 1.

For ASTM D1384 - corrosion in glassware - the test is passed if the weight loss is less than 5 mg on copper, 5 mg on brass, 5 mg on welding, 2.5 mg on steel, 4 mg on cast iron and 10 mg on aluminum.

The ASTM D4340 hot plate test is passed if the weight loss is less than 1 mg / cm / week.

The CEC C-05X-95 test is considered accepted if the weight variation is between -50 and +10 mg for aluminum and between -10 and +5 mg for cast iron. TABLE 1

It can be observed that all of the tests pass the only systems with four inhibitor components and within the limits of the claimed compositions. We see in particular the difficulty in passing the cavitation test.

EXAMPLE 2 (comparative): compositions of the prior art

These are organic (O) or organic-mineral (M) compositions, with diacids (adipic (H ₂ C ₆ ) and sebacic (H ₂ Cι ₀ )), octanoic acid (C ₈ ), sodium molybdate (Molyb.) , sodium nitrite (Nitrite) and tolyltriazole (TTZ) containing (in% by weight):

The results of the tests are given in Table 2 below.

TABLE 2

Only of all these formulas according to the prior art, the all-mineral composition passes all of the tests, but with prohibited or strongly discouraged components. We can also observe that composition 03 has interesting performances except however in the test ASTM D 1384 for cast iron where it causes weight gain (instead of loss). This weight gain is a contraindication for a potential blockage of the circuits.

It is well known to those skilled in the art that certain additional additives can be incorporated into this type of formulation to provide specific properties. Among the most common products are defoamers, sequestering agents and dyes.

Among the commercial anti-foaming agents, the following products are particularly suitable for the claimed composition: - Wacker SE47 (surfactant on silicone base)

- BASF Pluronic PE6100 (non-ionic surfactant)

- Ultra MS 455-3A (mixture of a silicone surfactant and a non-ionic OP-OE)

The use dose of these products is generally between 0.01 and 0.03% by weight relative to the total of the formulation of stock solutions.

Among the sequestrants, a product well suited to the formulations is 1 - hydroxyethane-1, 1 diphosphonic acid and in particular the commercial product

DEQUEST 2010 from SOLUTIA. This product may exhibit a certain activity with respect to corrosion tests which may require an adjustment of the overall composition according to the invention.

Claims

1. A method for inhibiting multimetal corrosion by heat transfer fluids, whether or not these fluids contain an organic compound lowering the freezing point, which consists in introducing into said fluids 3 to

6% by weight, and preferably 3.8 to 5%, of an organic inhibitor system consisting of:

(I) 5 to 15% by weight of at least one monocarboxylic acid unsaturated with 10-18 carbon atoms or of one of its alkali metal salts, of amine from the group of monoethylamine, diethylamine, tnethylamine or alkanolamine from the monoethanolamine group, diethanolamine, triethanolamine or methyldiethanolamine;

(II) 40 to 70% by weight of at least one saturated carboxylic acid taken from the group comprising saturated monocarboxylic acids with 5-16 carbon atoms and saturated dicarboxylic acids with 4-12 carbon atoms, or a salt thereof alkali or amine or alkanolamine metal of these acids;

(III) 20 to 40%) by weight of a tricarboxylic derivative of 1,3,5-triazine corresponding to the formula

wherein R is a carboxyalkyl group with 2-6 carbon atoms, or an alkali metal or amine or alkanolamine salt of this derivative

(IV) 1 to 5% by weight of an azole derivative taken from the group consisting of: (h) imidazoles of formula:

(i) the benzimidazoles of formula

(j) the triazoles of formula

(k) the benzotriazoles of formula

(I) tetrahydrobenzotriazole (m) thiazoles of formula

(n) the benzothiazoles of formula

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

R 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 formula

2. Method according to claim 1, characterized in that the weight ratio l / ll is between 5 and 15, and preferably between 8 and 12, and the weight ratio I + ll / lll is between 1, 5 and 3 and preferably between 1, 9 and 2.2.

3. Method according to one of claims 1 or 2, in which the system of organic inhibitors consists of:

6 to 8% by weight of the constituent (I); 55 to 65% by weight of the constituent (II); - 25 to 35% by weight of the constituent (III);

2 to 3% of the constituent (IV).

4. Method according to one of claims 1 to 3, wherein the saturated carboxylic acid is n-hexanoic acid, heptanoic acid, n-octanoic acid or nonanoic acid.

5. Method according to one of claims 1 to 3, wherein the dicarboxylic acid is suberic acid, azelaic acid or sebacic acid.

6. Method according to one of claims 1 to 3, characterized in that the unsaturated monocarboxylic acid is undecylenic acid.

7. Method according to one of claims 1 to 3, in which the tricarboxylic derivative of 1,3,5 triazine is the compound of formula:

8. A multimetal corrosion inhibitor composition consisting of an aqueous solution titrating from 10 to 60%> by weight of an inhibitor system as described in claims 1 to 5.

9. Multi-metal corrosion inhibitor antifreeze composition comprising:

0.1 to 10% by weight of the inhibitor composition according to claim 8;

90 to 99.9% by weight of a hydroalcoholic solution having a freezing point below 0 ° C, preferably between -10 and -40 ° C, the alcohol being taken from the group consisting of methanol, l ethanol, 2-propanol, glycerol, ethylene glycol, diethylene glycol, propylene glycol, 1-methoxy-2-propanol, methyl-, ethyl-, propyl-, butyl ethers of ethylene glycol.

10. An inhibitory antifreeze composition according to claim 7, the alcohol of which is ethylene glycol.