FR2489355A1 - Sodium sebacate as corrosion inhibitor - for glycol antifreeze and heat transfer liq. - Google Patents

Abstract

Antifreeze or heat-transfer liq. based on monoethylene or monopropylene glycols contains sodium sebacate (I) as corrosion inhibitor. Opt. (I) is used in conjunction with other usual additives esp. Na metasilicate; K2HPO4; tolutriazole or 1,2,3-benzotriazole. Pref. (I) is at least 0.2 (esp. 1-3) wt.% on the liq. and the other additives are pref. less than 1%. (I) is compatible with other standard additives; satisfies legislative requirements regarding hygiene and provides efficient protection for all metals generally used in cooling systems.

Description

 The present invention relates to a corrosion inhibitor intended to be added to an antifreeze or heat transfer fluid, based on monoethylene glycol or monopropylene glycol, in order to effectively protect against corrosion the metals with which such a fluid is brought into contact.

 In the cooling circuits of motor vehicles, ethyl alcohol was originally used as an antigen. This product was then abandoned in favor of monoethylene glycol, which has the advantage of not evaporating like the made ethyl alcohol and thus provides constant protection against frost. These solutions of monoethylene glycol-ean in a proportion of 20 to 50%, depending on the desired protection temperature, have the disadvantage, if they are used as such, between corrosives vis-à-vis the metals of which The components of the cooling circuit of the vehicle are constituted. Also, corrosion inhibitors have been introduced into these solutions whose role is to passivate the antifreeze solution with respect to each of these metals.

These corrosion inhibitors are specific to each metal and their range has widened as the evolution of the engines themselves,
If thirty years ago, the elements of the cooling circuits consisted mainly of cast iron, steel, copper and brass, involving the use, as inhibitors, of sodium borate (for ferrous metals) and triethanolamine (for the copper and brass), the appearance of aluminum cylinder heads must have necessitated the addition of active inhibitor products to light metals. A whole set of inhibitors then appeared, in particular benzoates, nitrites and nitrates. , benzotriazoleset to lutriazoles phosphoric acids, amines, the resulting complex inhibition formulas giving more or less good results, characterized by standardized corrosion measurements (in general A, STM), However, a large number of these currently used inhibition formulas are now being questioned because of the prohibition by the legislation on the hygiene and the environment of nitrites. ites and nitrates of sodium and amines.

In addition, sodium borate, the use of which was widespread in all the inhibition formulas, is detrimental to light alloys of aluminum whose use is increasing in vehicle engines and in heat exchange circuits of fixed, solar or refrigerated installations.

 The aim of the invention is to provide a corrosion inhibitor which does not have the drawbacks of the additives mentioned above and which can be used in combination with other components in order to provide effective protection for the common metals constituting the elements of the reaction circuits. cooling or heat exchange.

 The corrosion inhibitor according to the invention, in antifreeze or heat transfer fluids based on monoethylene glycol or monopropylene glycol, is sodium sebacate (EaOOC- (C ~ 8-COONa) in proportions of at least 0.2% by weight antifreeze or heat-transfer liquid, preferably between 1 and 3%.

Preferably, sodium sebaeate is combined with other known additives, in proportions of less than 1%, such as salts of metals or of metalloSdes, for example sodium metasilicate, or dipotassium phosphate, or organic products such as tolutriazole or 1,2,3-benzothiazole,
By way of nonlimiting examples, two formulas of antifreeze liquids based on monoethylene glycol are indicated below.

Example I
The following composition is prepared by mixing
monoethylene glycol 94.8

<tb> sebacate <SEP> of <SEP> sodium <SEP> 3 <SEP>><SEP><SEP> inhibitors
<tb> tolutriazole <SEP> 0.15 <SEP><<SEP><SEP> from
<tb> Metasilicate <SEP> of <SEP> Sodium <SEP> 0.5 <SEP> 5 <SEP><SEP> Corrosion
<tb> water (for constitution of the mixture 2
inhibitors) 100
This mixture is supplemented with distilled water at a rate of 33% by volume of mixture to 67% by volume of water.

 This proportion of 33 was chosen because of the conventional freezing point that it allows to obtain (-180C) retained for most anti-freezing fluids.

 the liquid obtained has been tested according to the corrosion test, in the presence of metals, described in the ASEM-D 138 X method, but with the use of distilled water, more aggressive than that described in ASEM and with metals adapted to the uses automotive engines and heat transfer fluid systems.

 In 33% solution, the pH of the liquid was 8.10 before testing.

Corrosion results were as follows
Metals Mass variation in m / cm2
AMI lightweight aluminum alloy - 0.03
Light aluminum alloy AS10b - 0,02
Cast iron F18 + 0.02
C35 steel - 0.01
Brass UZ33 - 0,03
Copper Cu / d - 0.06
Solder (Sn 33% Pb 67%) - 0.03
After testing, the pH of the solution is 8-3
Example II
The following solution is prepared: mass%
i en masse
monoethylene glycol 96.30

<tb> sebacate <SEP> of <SEP> sodium <SEP> 1.50
<tb> I <SEP>, 2,3-benzotriazole <SEP> 0.10 <SEP> inhibitors
<tb> metasilicate <SEP> of <SEP> sodium <SEP> 0.06 <SEP> from
<tb> phosphate <SEP> of <SEP> potash <SEP> dipotassium <SEP> 0.04 <SEP> corrosion
<Tb>
water (for constitution of the mixture 2
inhibitors) 100
As in Example I, a solution is obtained in distilled water at a rate of 33% of the mixture to 67% by volume of water and is subjected to the corrosion test identified with that of test NO 1.

 the pH of the 33% solution is 7.6 before the test.

The corrosion results for the different metals are as follows
Metals Mass variation in mg / cm2
AM1 lightweight aluminum alloy - 0.03
ASlOb lightweight aluminum alloy - 0.08
FT18 + 0.03
Steel C35 + 0.01
Brass UZ33 - 0,03
Copper Cu / d - 0.05
Solder (Sn 33% Pb 675s) - 0,07
After testing, the pH of the solution is 7.45.

 This second test shows that by halving the sodium sebacate content, compared to that of model I, we still obtain very satisfactory results compared to the requirements of the usual standards and the car manufacturers.

 Given that the physicochemical properties of the monopropylene glycol are close to those of monoethylene glycol, tests of liquids based on the first compound give similar results to those based on the second.

Claims (7)

REVENDI CATI ONS  1. Corrosion inhibitor for antifreeze or heat transfer liquid based on monoethylene glycol or monopropylene glycol, characterized in that it comprises sodium sebacate.  2o corrosion inhibitor according to claim 1, wherein the sodium sebacate is associated with other customary additives.  3. Corrosion inhibitor according to claim 2, wherein the additives associated with sodium sebacate are selected from metal or metal salts and organic compounds.  4. Corrosion inhibitor according to claim 3, wherein the additives associated with sodium sebacate are selected from sodium metasilicate and dipotassium phosphate.  5. Corrosion inhibitor according to claim 3, wherein the additives associated with sodium sebacate are selected from tolutriazole and 1,2,3-benzotriazole.  6. Antifreeze or heat-transfer liquid, characterized in that it contains a corrosion inhibitor according to one of claims 1 to 5.  An antifreeze or heat transfer fluid as claimed in claim 6, wherein the sodium sebacate is in a proportion greater than 0% by weight of the liquid.  8. antifreeze or heat transfer liquid according to claim 7, wherein the sodium sebacate is in a proportion of between t and 3% by weight of the liquid.  Antifreeze or heat transfer fluid according to one of claims 7 or 8, wherein the additives associated with sodium sebacate are in a proportion of less than 1%.