WO2018095975A1 - Use of a lipid of triacylated mannosylerythritol as a corrosion inhibitor - Google Patents

Abstract

The invention relates to the use of a triacylated mannosylerythritol lipid as a corrosion inhibitor, to compositions comprising a triacylated mannosylerythritol lipid, and to methods implementing a triacylated mannosylerythritol lipid.

Description

 USE OF A TRI-ACYL MANNOSYLERYTHRITOL LIPID AS A CORROSION INHIBITOR

The present invention relates to a novel corrosion inhibitor, to compositions comprising it, as well as processes using this inhibitor.

 According to the present application, the term "corrosion inhibitor" refers to any compound aimed at preventing or slowing down a corrosion phenomenon.

 Corrosion is generally defined as a physico-chemical interaction between a metal and its environment, leading in particular to a modification, and more particularly to a degradation, of said metal or its properties.

 The problems related to corrosion concern many industrial fields, such as the field of lubricants, the field of coatings, or the oil field. Indeed, it is common to introduce a corrosion inhibitor in lubricants, coatings or petroleum products and or derivatives thereof, so as to protect the metals with which these products are intended to be in contact.

 Many corrosion inhibitors have been developed. In particular, research has recently focused on the development of environmentally friendly corrosion inhibitors.

 For example, application US 2015/0299556 discloses including the use of sophorolipids and / or mannosylerythritol lipids to inhibit corrosion due to the presence of strong acids or salts. In particular, the mannosylerythritol lipids described herein are di-acylated.

 However, there is still a need for environmentally friendly compounds with high corrosion inhibiting power.

 The work of the inventor has made it possible to demonstrate that a specific biodegradable compound has a high corrosion inhibiting power.

 The invention thus relates to the use of a tri-acylated mannosylerythritol lipid as a corrosion inhibitor.

By tri-acylated mannosylerythritol lipid (or tri-acylated MEL) is denoted more particularly a molecule having the following general formula (I):

 in which :

R ¹ and R ² , which are identical or different, represent an acyl group comprising an unsaturated or saturated acyclic carbon chain,

R ³ and R ⁴ , which are identical or different, represent an acetyl group or a hydrogen atom, and

- R ⁵ represents an acyl group comprising an unsaturated or saturated acyclic carbon chain.

 Preferably, each carbon chain of the acyl groups is linear. In particular, the carbon chain comprises only carbon and hydrogen atoms, optionally substituted by a hydroxyl (OH) function.

The acyl groups at R ¹ and R ² preferably comprise a carbon chain containing from 8 to 24 carbon atoms. More preferentially, the acyl groups at R ¹ and R ² are saturated and comprise a carbon chain comprising from 8 to 16 carbon atoms.

Advantageously, the acyl group at R ⁵ comprises a carbon chain comprising from 8 to 24 carbon atoms.

 It should be noted that in the context of the present application, and unless otherwise stated, the ranges of values indicated are inclusive.

 Two stereoisomers of the tri-acylated MEL of formula (I) are known and represented in formulas (II) and (III) below:

CH ₂ OR ⁵

H OH

OR ⁴

in which R ¹ , R ² , R ³ , R ⁴ and R ⁵ are identical to those indicated in formula

(!) ^■

 Advantageously, a tri-acylated MEL is a molecule of formula (II).

 The formulas (I), (II) and (III) above may represent different molecules, each molecule therefore being a tri-acylated MEL. By "tri-acylated MELs" is meant at least two molecules of formulas (I) different in their substitution (acyl groups, acetyl groups and / or hydrogen atoms) or by their stereoisomerism, more particularly, at least two molecules. different formulas (II).

There exist di-acylated MELs such as those described in application US 2015/0299556, which differ from "tri-acylated MELs" according to the nature of the substituent present at R ⁵ .

The use of the terminology "di-acylated MELs" and "tri-acylated MELs" is usual. It is for example used in the patent EP 2,055,314. It will be noted that according to this terminology, the acetyl groups that may be present at R ³ and R ⁴ are not counted in the acyl groups.

 By di-acylated MEL is thus denoted a molecule of formula (I), (II) or (III) in which:

R ¹ and R ² , which are identical or different, represent an acyl group comprising an unsaturated or saturated acyclic carbon chain,

R ³ and R ⁴ , which are identical or different, represent an acetyl group or a hydrogen atom, and

- R ⁵ represents a hydrogen atom.

Moreover, di-acylated and tri-acylated MELs are generally classified into four classes of molecules, denoted from A to D, according to their degree of acetylation at R ³ and R ⁴ . Whether di-acylated or tri-acylated, the MEL-A class comprises molecules of formula (I), more particularly of formula (II) and / or (III), having two acetyl groups at R ³ and R ⁴ . The class of MELs-B and the class of MELs-C contain molecules of formula (I), more particularly, of formula (II) and / or (III), having a single acetyl group at R ⁴ and R ³ respectively. Finally, the class of MELs-D comprises molecules of formula (I), more particularly, of formula (II) or (III), having no acetyl group (R ³ = R ⁴ = H).

 In addition to their degree of acetylation, tri-acylated MELs can vary in their structure, due to the nature of the acyl groups that make up their hydrophobic part. This variation is generally a function of the process used to obtain the tri-acylated MELs.

 Advantageously, according to the invention, tri-acylated MELs are used as a corrosion inhibitor.

 The tri-acylated MEL (s) can be obtained by conventional production methods using the cultivation of fungi, and more particularly yeasts.

 Advantageously, the tri-acylated MEL (s) is (are) obtained by a process for producing tri-acylated MEL (s), comprising the following steps:

 Step 1: the conversion of a carbon substrate such as a vegetable oil (rapeseed) with a yeast strain to obtain di-acylated MELs;

 Step 2: the recovery of MEL (s) di-acylated (s);

 Step 3: obtaining MEL (s) tri-acylated (s);

 Step 4: the recovery of MEL (s) tri-acylated (s).

 Step 1 :

 Strains from which it is possible to obtain di-acylated MELs are well known to those skilled in the art. By way of example, it is known to use strains of the family Basidiomycetes, preferably of the genus Pseudozyma, such as Pseudozyma antarctica, Pseudozyma Parantartica, Pseudozyma aphidis, Pseudozyma rugulosa, Pseudozyma graminicola, Pseudozyma siamensis, Pseudozyma hubeiensis, Pseudozyma tsukubaensis, Pseudozyma crassa, or the genus Ustilago, such as Ustilago maydis, Ustilago cynodontis and Ustilago scitaminea.

In general, depending on the strain, a class of MELs, MELs-A, MELs-B, MELs-C or MELs-D, is produced mainly or even exclusively compared to other classes of MELs. By way of example, Pseudozyma antarctica, Pseudozyma aphidis, Pseudozyma rugulosa and Pseudozyma parantarctica predominantly produce MELs-A of formula (II). Pseudozyma graminicola, Pseudozyma siamensis and Pseudozyma hubeiensis predominantly produce MELs-C of formula (II). Pseudozyma tsukubaensis produces MELs-B of formula (III) and Pseudozyma crassa produced in most of the MELs-A of formula (III).

 Advantageously, the di-acylated MELs are obtained by a fermentation process using a strain producing di-acylated MELs of formula (II).

 More particularly, the di-acylated MELs are obtained by a fermentation process using a strain selected from Pseudozyma aphidis, Pseudozyma rugulosa, Pseudozyma antarctica or Pseudozyma parantarctica, preferentially from Pseudozyma aphidis, Pseudozyma antarctica or Pseudozyma parantarctica, more preferably the strain. is Pseudozyma aphidis.

 The carbonaceous substrate is typically a glycerol, an n-alkane or an oil, in particular of renewable origin.

 Any oil, composed of triglycerides and liquid at the temperature of the fermentation process, can be used as a carbon substrate.

 Preferably, the renewable oil is a vegetable or animal oil, more preferably a vegetable oil. In particular, the vegetable oil is selected from the group consisting of soybean oil, sunflower oil, olive oil and rapeseed oil. More particularly, the vegetable oil is a soybean oil or a rapeseed oil, more particularly, a rapeseed oil.

 These renewable oils are particularly rich in acyl groups having a carbon chain containing 18 carbon atoms, such as acyl groups derived from oleic, linoleic and / or linolenic acid.

 The fermentation process generally lasts at least 3 days, preferably at least 7 days.

 According to a preferred embodiment, the di-acylated MELs are obtained by a fermentation process using:

 a strain of the genus Pseudozyma, preferentially Pseudozyma antartica, Pseudozyma parantarctica, or Pseudozyma aphidis,

 a vegetable oil, preferably a rapeseed oil or a soybean oil, as a carbon substrate.

Such a strain is usually grown in a reactor in a medium comprising glucose, water and / or salts (such as magnesium sulfate, monopotassium phosphate, sodium nitrate, and / or ammonium nitrate ). This culture medium is also used in the fermentation process. In fact, in general, the fermentation medium of the fermentation process, comprises a culture medium and the carbon substrate.

 Advantageously, the various components of the medium (glucose and strain in particular) are sterilized separately before introduction into the reactor.

 The temperature of the medium is preferably between 20 ° C and 40 ° C, more preferably between 25 ° C and 35 ° C.

 The reaction crude obtained at the end of the fermentation process, is what is called in the present application, the crude fermentation.

 The fermentation crude generally comprises at least two di-acylated MELs, at least the residual carbonaceous substrate and / or a by-product of the carbonaceous substrate, the strain and water, the by-product of the carbonaceous substrate resulting from the fermentation. .

 2nd step :

 The step of recovering MEL (s) di-acylated (s) subsequent to the fermentation process, aims to separate a di-acylated MEL (s) from one or more of the other components of the fermentation crude, such as residual carbonaceous substrate and / or a by-product of the carbonaceous substrate, a strain, and / or water.

 According to the preferred embodiment above, the crude fermentation product comprises at least two di-acylated MELs, at least one triglyceride and / or at least one fatty acid, water and a strain of the genus Pseudozyma.

 Indeed, when the carbon substrate is an oil of renewable origin, a by-product of the carbonaceous substrate is a fatty acid. In addition, since a vegetable oil is mainly (greater than 90% by weight) consisting of triglycerides, the residual vegetable oil is therefore composed of at least one triglyceride.

 The separation of one or more di-acylated MEL (s) from one or more of the other components of the fermentation crude can be carried out by any separation method known to those skilled in the art.

 Advantageously, the separation of one or more di-acylated MEL (s) from one or more of the other components may comprise one or more of the following methods:

 - decantation,

 - centrifugation,

 - filtration,

 - evaporation,

 - liquid / liquid extraction,

 - passage over a mineral substrate or a resin.

In particular : the strain can be separated by decantation, filtration, and / or centrifugation;

the water can be separated by decantation, evaporation, centrifugation, and / or passage over a mineral substrate which is an adsorbent;

 the fatty acids and the triglycerides can be separated by liquid / liquid extraction and / or by passage over a mineral substrate or a resin.

 The di-acylated MELs recovered can therefore comprise:

 at least one triglyceride and / or at least one fatty acid, and

 optionally, a strain.

 By "fatty acid" is meant a free fatty acid and / or salt form.

 The amount of fatty acid (s) and / or triglyceride (s) present in the di-acylated MELs recovered may be between 0.5 and 60% by weight, preferably between 1 and 50% by weight, relative to to the total weight of di-acylated MELs recovered.

 More particularly, the di-acylated MELs recovered comprise at least one triglyceride and at least one fatty acid.

 In this case, the amount of fatty acid (s) and triglyceride (s) present in the

MELs di-acyls recovered may be between 25 and 60% by weight, preferably between 30 and 50% by weight, more preferably between 35 and 45% by weight relative to the total weight of di-acylated MELs recovered.

 Advantageously, the fatty acid (s) comprises (s) a carbon chain comprising between 8 and 24 carbon atoms, preferably between 8 and 20 carbon atoms.

 Advantageously, the triglyceride (s) comprise (s) acyl groups whose acyclic carbon chain, saturated or unsaturated, contains between 8 and 24 carbon atoms, preferably between 16 and 18 carbon atoms. More particularly, the carbon chain is linear and contains only carbon and hydrogen atoms, optionally substituted by a hydroxyl (OH) function.

 The di-acylated MELs recovered can therefore be in a more or less purified form, that is to say in a mixture with other components of the fermentation medium.

 More particularly, in the present application, and in particular in the examples, when the di-acylated MELs recovered, are in admixture with at least one fatty acid and / or at least one triglyceride, optionally water and / or a strain this mixture is called a "mixture of di-acylated MELs".

A first mixture of di-acylated MELs is a fermentation crude, that is to say at least two MELs di-acylated with the other components of the crude fermentation. The fermentation crude may be subjected to one or more separation methods, leading to other preferred di-acylated MEL mixtures having the following characteristics:

 a content of di-acylated MELs greater than or equal to 30% by weight, preferably greater than or equal to 40% by weight, more preferably greater than or equal to 50% by weight;

 a content of other components (including fatty acid (s), triglyceride (s), water, and / or strain) less than or equal to 70% by weight, preferably less than or equal to 60% by weight, more preferably less than or equal to at 50% by weight;

 the percentages by weight being given relative to the weight of the mixture of di-acylated MELs.

 More particularly, according to the method (s) of separation as described above, mixtures of di-acylated MELs more or less concentrated di-acylated MELs can be obtained.

 According to a first embodiment, the mixture of di-acylated MELs has the following characteristics:

 a di-acylated MEL content greater than or equal to 55% by weight;

 - a content of other components (including fatty acid (s), triglyceride (s), water, and / or strain) less than or equal to 45% by weight;

 the percentages by weight being given relative to the weight of the mixture of di-acylated MELs.

 Advantageously, in this first embodiment, the content of water and / or strain is less than or equal to 10% by weight, preferably less than or equal to 5% by weight, relative to the weight of the mixture of di-acylated MELs.

 According to a second embodiment, the mixture of di-acylated MELs has the following characteristics:

 a content of di-acylated MELs greater than or equal to 90% by weight, preferably greater than or equal to 95% by weight, more preferably greater than or equal to 98% by weight;

 - a content of other components (including fatty acid (s), triglyceride (s), water, and / or strain) less than or equal to 10% by weight, preferably less than or equal to 5% by weight, more preferably less than or equal to at 2% by weight;

the percentages by weight being given in relation to the weight of the mixture of MELs di-acylated.

 Advantageously, in this second embodiment, the content of water and / or strain is less than or equal to 2% by weight, relative to the weight of the mixture of di-acylated MELs.

 Such a mixture of di-acylated MELs may, for example, be obtained using a fermentation process as described in step 1 above followed by several separation steps as described above, these separation steps preferably including a liquid / liquid extraction and / or a passage on a mineral substrate.

 The passage over a mineral substrate may be a chromatography, such as adsorption chromatography on a silica column, carried out using suitable solvents. Such solvents are known to those skilled in the art.

 Examples of mixtures of di-acylated MELs and their method of production are also described in the following publication: "Downstream processing of mannosylerythritol lipids produced by Pseudozyma aphidis"; Rau et al .; European

Journal of Lipids Science and Technology (2005), 107, 373-380.

 Advantageously, the di-acylated MELs that can be recovered comprise

Di-acylated MELs of different classes, selected from the group consisting of MELs-A,

MELs-B, MELs-C and MELs-D.

 According to a first advantageous embodiment, the di-acylated MELs recovered include MELs-A, MELs-B, MELs-C and optionally MELs-D, more preferably MELs-A, MELs-B, MELs-C and MELs-D.

 Advantageously, the di-acylated MELs recovered comprise MELs-A and

MELs-B at a content of between 50% to 95% by weight, preferably 60% to 85% by weight, the percentages by weight being indicated relative to the weight of the total amount of di-acylated MELs.

 Advantageously, the di-acylated MELs recovered comprise one or more MELs.

C at a content greater than or equal to 5% by weight, preferentially greater than

10% by weight, the percentages by weight being indicated relative to the weight of the total amount of di-acylated MELs.

 More particularly, the di-acylated MELs recovered comprise MELs-A and

MELs-B at a content between 60% and 80% by weight and MELs-C at a content greater than or equal to 20% by weight, the percentages by weight being indicated relative to the weight of the total amount of MELs di- acylated.

According to a second advantageous embodiment, the di-acylated MELs recovered contain MELs-D at a content of between 75% and 100% by weight, preferably between 90% and 100% by weight, the percentages by weight being indicated relative to the weight of the total amount of di-acylated MELs.

 MELs-D can be obtained by deacetylation of MELs-A, MELs-B and MELs-C. An example of a deacetylation reaction of MELs-A, MELs-B and MELs-C using a hydrolysing enzyme is described in the following publication: "Enzymatic synthesis of a novel glycolipid biosurfactant, mannosylerythritol lipid-D and its aqueous phase behavior"; Fukuoka et al .; Carbohydrate Research (201 1), 346, 266-271.

 Step 3:

 Step 3 allows the production of MEL (s) tri-acylated (s) from the di-acylated MEL (s) (or a mixture of di-acylated MELs) recovered (s) to step 2.

 This step includes:

 dissolving the di-acylated MEL (s) in an organic solvent in the presence of an enzyme; and

 - The addition of at least one vegetable oil, at least one fatty acid of vegetable origin or at least one fatty acid ester of vegetable origin; under conditions allowing either a transesterification reaction between the di-acylated MEL (s) and the triglycerides present in the vegetable oil or the fatty acid ester of vegetable origin, or a reaction of esterification between the di-acylated MEL (s) and the fatty acid of vegetable origin, thereby allowing the production of tri-acylated MEL (s).

 Advantageously, the organic solvent is chosen from methanol, ethanol, propanol, butanol, acetone, propanone, butanone, pentan-2-one, 1,2-ethanediol, butanediol, dioxane, acetonitrile, 2-methylbutan-2-ol, tert-butanol, 2-methylpropanol, 4-hydroxy-2-methylpentanone, tetrahydrofuran, hexane, dimethylformamide ( DMF), dimethylsulfoxide (DMSO) and / or pyridine.

 Preferably, the organic solvent is selected from acetone, tetrahydrofuran, tert-butanol, acetonitrile, and / or dioxane.

 Preferentially, the vegetable oil is chosen from the group consisting of a soybean oil, a sunflower oil, an olive oil and a rapeseed oil. More particularly, the vegetable oil is a soybean oil or a rapeseed oil, more particularly, a rapeseed oil.

Advantageously, the fatty acid of vegetable origin or the fatty acid ester of vegetable origin comes from a soybean oil, a sunflower oil, an olive oil or a vegetable oil. rapeseed. More particularly, the plant-derived fatty acid or vegetable fatty acid ester is derived from a soybean oil or a vegetable oil. rapeseed, more particularly, a rapeseed oil.

 These vegetable oils are particularly rich in acyl groups comprising a carbon chain containing 18 carbon atoms, such as acyl groups derived from oleic, linoleic and / or linolenic acid.

 The fatty acid of vegetable origin is therefore preferably chosen from oleic, linoleic and / or linolenic acid.

 The fatty acid ester of vegetable origin is preferably chosen from esters of oleic, linoleic and / or linolenic acid.

 Preferably, the fatty acid ester of plant origin is an ester of oleic acid, more preferably a methyl ester of oleic acid.

 The enzyme may be selected from lipases, proteases, and / or esterases, preferably from lipases and / or esterases, more preferably from lipases.

 Advantageously, the esterification or transesterification reaction is carried out for about 12 to 72 hours at a temperature close to (+/- 10 ° C.) of the optimum temperature of activity of the enzyme, preferably for about 24 to 48 hours at a temperature between 20 and 30 ° C, more preferably at 25 ° C.

 Step 4:

 The tri-acylated MEL (s) may then be recovered from the reaction medium of step 3 by separation methods known to those skilled in the art.

 Among these separation methods is, for example, chromatography, such as silica column absorption chromatography.

 Among these separation methods is also the liquid / liquid extraction. Advantageously, the liquid / liquid extraction separation method further comprises a filtration, in order to eliminate the enzyme used in step 3, and / or an evaporation of the solvent (s), such as ) that for example the solvent used for the liquid / liquid extraction and / or any residual organic solvent of step 3.

 Advantageously, the tri-acylated MEL (s) recovered have a purity of at least 70%.

 Preferably, the tri-acylated MEL (s) recovered have a purity of at least 90%, more preferably at least 95%.

 Tri-acylated MELs are weakly toxic and biodegradable.

In addition, the tri-acylated MELs, when they are produced by the process for producing tri-acylated MELs described above using a vegetable oil are bio-renewable.

 However, the inventors have demonstrated that the tri-acylated MELs have a particularly high corrosion inhibiting capacity, as is more fully described in Example 1 and in Figures 1 to 5.

 By "corrosion inhibitor" is meant any compound aimed at preventing or reducing a phenomenon of corrosion.

 More particularly, the tri-acylated MELs have an inhibitory effect on the corrosion of the metal.

 Preferably, according to the invention, a tri-acylated MEL is used as an inhibitor of rust formation.

 Preferably, according to the invention, tri-acylated MELs are used as inhibitors of rust formation.

 A "rust inhibitor" is also commonly referred to as an "antirust".

 Indeed, tri-acylated MELs have an inhibitory capacity for the formation of rust on ferrous metals.

 By "rust" is meant the product, generally of red-brown color, which can be formed by oxidation on the surface of ferrous metals when these are in contact with water and air.

 "Ferrous metals" refers to metals composed in whole or in part of iron.

In the context of the present application, the corrosion-inhibiting power of a compound is advantageously evaluated in the same way or similar to that described in ASTM standard D665-03 ("Standard Test Method for Rust-Preventing Characteristics of Inhibited"). Ore Oil in the Presence of Water ").

 In this application, any reference to a standard is a reference to the standard in effect on the filing date.

Tri-acylated MELs can be used as a corrosion inhibitor in various industrial applications. They can especially be used in any type of composition where it is usual to add a corrosion inhibitor, such as lubricating compositions (motor oil, hydraulic oil, gear oil, metal working oil), petroleum and certain its derivatives (gasoline, liquefied petroleum gas (LPG), diesel, domestic fuel oil, jet fuels, heavy fuels, fuels for marine diesel engines, special fuels such as liquefied petroleum gases, bitumens, paraffins, petroleum jellies, waxes), or coatings (paints, varnishes, lacquers, protective coatings, and in particular rust).

 According to the invention, a tri-acylated MEL advantageously has the following general formula (I):

 in which :

R ¹ and R ² , which are identical or different, represent an acyl group comprising an unsaturated or saturated acyclic carbon chain,

R ³ and R ⁴ , which are identical or different, represent an acetyl group or a hydrogen atom, and

- R ⁵ represents an acyl group comprising an unsaturated or saturated acyclic carbon chain containing from 8 to 24 carbon atoms.

 Preferably, a tri-acylated MEL is represented by the following general formula (II):

 in which :

R ¹ and R ² , which are identical or different, represent an acyl group comprising an unsaturated or saturated acyclic carbon chain,

R ³ and R ⁴ , which are identical or different, represent an acetyl group or a hydrogen atom, and

- R ⁵ represents an acyl group comprising an unsaturated or saturated acyclic carbon chain containing from 8 to 24 carbon atoms.

Preferably, in formula (I) or (II), each carbon chain of the groups acyles is linear. In particular, the carbon chain comprises only carbon and hydrogen atoms, optionally substituted by a hydroxyl (OH) function. Advantageously, the acyl groups at R ¹ and R ² comprise a carbon chain comprising from 8 to 24 carbon atoms. More preferentially, the acyl groups at R ¹ and R ² are saturated and comprise a carbon chain comprising from 8 to 16 carbon atoms.

 Before use, a tri-acylated MEL may, according to the invention, be diluted in a suitable solvent, such as, for example, a vegetable oil, a fatty acid ester, propylene glycol, white spirit, or any other solvent. capable of dissolving tri-acylated MELs.

 As indicated above, tri-acylated mannosylerythritol lipids can be used as a corrosion inhibitor in various compositions, such as, for example, lubricating compositions.

 The invention therefore also relates to a composition, such as a lubricating composition, comprising a tri-acylated MEL and a mineral and / or synthetic oil.

 Advantageously, this composition comprises tri-acylated MELs.

 Mineral oils are oils from petroleum refining. They consist essentially of carbon and hydrogen atoms, such as paraffinic oils, hydrorefined oils, hydrocracked oils and hydro-isomerized oils.

 The mineral oil is preferably a mineral oil for a lubricating composition.

 Mineral oils for lubricating composition are categorized according to three groups:

 Group I oils: these oils have a saturated hydrocarbon content of less than 90% by mass, an aromatic hydrocarbon content of greater than 1.7% by mass, a sulfur content of greater than 0.03% by weight, and a viscosity number of 80 to 120;

 group II oils: these oils have a saturated hydrocarbon content of greater than 90% by mass, an aromatic hydrocarbon content of less than 1.7% by weight and a sulfur content of less than 0.03% by weight, and a viscosity number of 80 to 120;

group III oils: these oils have a saturated hydrocarbon content content of greater than 90% by mass, an aromatic hydrocarbon content of less than 1 7% by mass, a content in sulfur less than 0.03% by weight, and a viscosity number of greater than 120;

 the percentages by mass being given in relation to the mass of the oil. Group II mineral oils are widely used in the metalworking industry. Also, advantageously, the oil of the composition according to the invention is a Group II mineral oil.

 Synthetic oils are obtained by chemical reaction between molecules of petrochemical origin and / or of renewable origin, with the exception of the usual chemical reactions that make it possible to obtain mineral oils (such as hydrorefining, hydrocracking, hydrocracking). hydroisomerization, etc.). Among the different chemical families of synthetic oil, there may be mentioned in particular esters, polyalkylene glycols (PAG) and polyalphaolefins (PAO).

 Advantageously, the composition according to the invention is a lubricating composition, and preferably is a motor oil, a hydraulic oil, a gear oil, or an oil for working metals.

 The composition according to the invention, and in particular the engine, hydraulic, gearing or metalworking oils mentioned above, may be used to protect the metals.

 A composition according to the invention in the form of a motor oil may, for example, be used to protect an engine (and more particularly the metals constituting it) from corrosion, and more particularly from the formation of rust.

 Advantageously, the composition comprising a tri-acylated MEL and a mineral and / or synthetic oil according to the invention comprises at least 0.005% by weight, preferably at least 0.1% by weight of MEL (s) tri-acylated (s) ), on the total weight of said composition.

 Preferably, the composition comprising a tri-acylated MEL and a mineral and / or synthetic oil according to the invention comprises between 0.005 and 5% by weight, more preferably between 0.01 and 3% by weight of MEL (s) tri- acylated (s), on the total weight of said composition.

 Advantageously, the composition comprising a tri-acylated MEL and a mineral and / or synthetic oil according to the invention comprises between 1 and 99% by weight, preferably between 5 and 95% by weight of mineral and / or synthetic oil, on the total weight of said composition.

Advantageously, the composition according to the invention further comprises an additive. "Additive" means a compound intended to strengthen one or more intrinsic property (s) of a composition and / or provide one or more additional property (s).

 Advantageously, the additive is chosen from the additives used in the field of lubricants, that is to say among the antioxidants, the anti-wear, the improvers of the viscosity index, the friction modifiers, the extreme pressure , pour point depressants, defoamers, demulsifiers, corrosion inhibitors, thickeners, detergents and dispersants.

 The skilled person knows how to choose the additive (s) best suited (s) depending on the chosen application, such as a lubricant application.

 Preferably, the additive is selected from antioxidants and / or anti-wear.

The antioxidant can slow or even suppress the oxidation of the product with which it is in mixture.

 Advantageously, the antioxidant may be chosen from dialkyl-dithiophosphates, substituted phenols, aromatic amines or mixtures thereof.

 The anti-wear makes it possible to reinforce the anti-wear action exerted on a composition, such as a lubricating composition, vis-à-vis the elements with which it is in contact. Advantageously, the antiwear may be selected from zinc dialkyl dithiophosphates, phosphorus derivatives or mixtures thereof.

 In particular, the composition may comprise one or more antioxidant (s) and / or one or more anti-wear (s).

 Advantageously, the composition comprises at least one antioxidant and at least one antiwear.

 The composition may further comprise at least one other additive, which may be chosen from:

 viscosity index improvers, such as polymers of olefin copolymer type (OCP), polyisobutenes, polymethacrylates, diene polymers, polyalkylstyrenes and / or molybdenum derivatives;

 friction modifiers, such as glycerol monooleate (GMO);

 extreme pressure, such as organometallic molybdenum derivatives, fatty acid derivative compounds, phosphosulphurized molecules and / or borates;

 pour point depressants, such as metal soaps, carboxylic acids, polymethacrylates, alkylphenols, dialkylaryl esters of phthalic acid, maleate-styrene copolymers, naphthalene paraffins and / or polyesters of the type vinyl fumarate acetate;

antifoams, such as silicone oils, silicone polymers and / or alkyl acrylates;

 demulsifiers, such as propylene oxide copolymers;

 corrosion inhibitors, other than tri-acylated mannosylerythritol lipids, such as alkali metal and / or alkaline earth metal sulfonates (Na, Mg, Ca salts), fatty acids, fatty amines, and phenylsuccinic acids and / or their derivatives, benzotriazole, tolyltriazole, and / or di-acylated MELs;

 thickeners, such as fatty esters;

 detergents, such as the calcium and / or magnesium salts of alkylarylsulfonates, alkylphenates, alkylsalicylates and / or their derivatives;

 dispersants, such as alkenylsuccinimides, succinic esters and / or their derivatives, and / or Mannich bases;

 metal deactivators, such as heterocyclic compounds containing nitrogen and / or sulfur, for example triazole, tolutriazole, and benzotriazole;

 or their mixtures.

 Note that an additive may have several properties, for example antioxidant and anti-wear, such as zinc dialkyl-dithiophosphate which is an antioxidant, anti-wear, anti-corrosion and slightly dispersing additive.

 Tri-acylated MELs can also be used as a corrosion inhibitor in coatings.

 The invention therefore also relates to a composition, such as a coating composition, comprising a tri-acylated MEL and a binder.

 Advantageously, this composition comprises tri-acylated MELs.

 "Binder" means a compound intended to ensure cohesion between the various components of a coating.

 Among the binders, mention may be made in particular of:

 vinyl resins;

 polyvinyl acetals;

 cellulosic resins;

 drying oils;

 - the alkyd resins;

 acrylic resins;

 - amino resins;

 phenolic resins;

epoxy resins, - polyesters (other than alkyd resins);

 polyurethanes;

 - natural gums and resins;

 - bitumens, pitches and tars;

- coumarone-indene resins;

 vinylstyrene-butadiene copolymers;

 cyclized rubbers;

 - chlorinated rubber;

 halogenated polyolefins;

silicones;

 - inorganic organic mixed binders;

 fluorinated resins.

 According to an advantageous embodiment, the binder is chosen from:

 vinyl resins;

polyvinyl acetals;

 cellulosic resins;

 drying oils;

 - the alkyd resins;

 acrylic resins;

- amino resins;

 phenolic resins;

 epoxy resins,

 - polyesters (other than alkyd resins);

 polyurethanes;

- natural gums and resins;

 coumarone-indene resins;

 vinylstyrene-butadiene copolymers;

 cyclized rubbers;

 - chlorinated rubber;

halogenated polyolefins;

 silicones;

 - inorganic organic mixed binders;

 fluorinated resins.

According to a particular embodiment of this advantageous embodiment, is a liquid binder under normal pressure temperature conditions. (STP). After application of the composition according to the invention, in particular when this composition is a coating composition, the binder hardens.

 Preferably, the binder is a resin in aqueous phase and is chosen from acrylic resins, polyurethanes or polyesters (other than alkyd resins).

 Preferably, the composition comprising a tri-acylated MEL and a binder according to the invention is homogeneous.

 By "homogeneous" is meant a solid or liquid composition whose components can not be distinguished during an observation with the naked eye.

 Advantageously, the composition comprising a tri-acylated MEL and a binder according to the invention comprises at least 0.005% by weight, preferably at least 0.1% by weight of MEL (s) tri-acylated (s), on the weight total of said composition.

 Preferably, the composition comprising a tri-acylated MEL and a binder according to the invention comprises between 0.005 and 5% by weight, more preferably between 0.01 and 3% by weight of MEL (s) tri-acylated (s), on the total weight of said composition.

 The composition comprising a tri-acylated MEL and a binder according to the invention may further comprise a solvent.

 "Solvent" means a liquid under normal conditions of temperature and pressure (CNTP), which has the property of dissolving, diluting or extracting other substances without causing chemical modification of these substances and without it - even change.

 Among the solvents generally used in the field of coatings, there may be mentioned in particular:

 hydrocarbons such as aromatic hydrocarbons (toluene, xylene), petroleum solvents (white spirit, solvent naphtha, kerosene), turpentine oil, chlorinated hydrocarbons, nitrohydrocarbons;

 alcohols such as ethyl, isopropyl, n-butyl, isobutyl, ethyl-2-hexyl, isodecyl, isononyl, benzyl, hexylene glycol alcohols;

 glycol ethers such as butylglycol, methyldiglycol, ethyldiglycol, butyldiglycol, propylene glycol ethers;

 esters such as ethyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate, amyl acetate and butyl glycol acetate.

Advantageously, this composition is a coating such as a paint, a varnish, a lacquer or a protective coating such as an antirust coating. The composition comprising a tri-acylated MEL and a binder according to the invention may comprise an additive, such as an additive used in the coating field.

 The person skilled in the art knows how to choose the additive (s) best adapted to an application in the coating field.

 Tri-acylated MELs can also be used as a corrosion inhibitor in a fossil fuel (petroleum, coal, peat, natural gas) and / or a derivative thereof, for example to inhibit corrosion of the equipment (storage tank, pipeline, pump, valve) intended to be in contact with said fossil fuel.

 The term "fossil fuel derivative" refers to products derived from the refining of fossil fuels.

 In particular, tri-acylated mannosylerythritol lipids can be used as a corrosion inhibitor in petroleum and / or a derivative thereof.

 The invention therefore also relates to a composition comprising a tri-acylated MEL and oil and / or one of its derivatives.

 Advantageously, this composition comprises tri-acylated MELs.

 By "petroleum" is meant a mixture of hydrocarbons, also containing organic compounds sulfur, oxygenated and / or nitrogenous. It can be both crude oil, that is to say, coming directly from a deposit, that a synthetic oil, that is to say a petroleum reconstituted from hydrocarbon fractions and or compounds obtained by a synthesis process (and not by distillation or extraction), or mixtures thereof, such as, for example, a crude oil diluted with another crude oil or a crude oil diluted with a synthetic oil.

 The term "petroleum derivative" refers to products derived from petroleum refining, generally referred to as petroleum products, such as those listed below:

 - the essences;

 - liquefied petroleum gas (LPG) as a fuel;

 - diesel and domestic fuel oil (FOD);

 - jet fuels such as kerosene, high flash point kerosene and large cut;

 - heavy fuels and fuels for marine diesel engines;

 - special fuels such as liquefied petroleum gases;

 - bitumens;

 paraffins, petroleum jelly and waxes.

The "petroleum derivatives" targeted in particular are: - the essences;

 - liquefied petroleum gas (LPG) as a fuel;

 - diesel and domestic fuel oil (FOD);

 - jet fuels such as kerosene, high flash point kerosene and large cut;

 - heavy fuels and fuels for marine diesel engines;

 - special fuels such as liquefied petroleum gases.

 Advantageously, the composition comprising a tri-acylated MEL and oil and / or one of its derivatives according to the invention comprises at least 0.005% by weight, preferably at least 0.1% by weight of MEL (s) tri -acylated (s), on the total weight of said composition.

 Preferably, the composition comprising a tri-acylated MEL and oil and / or one of its derivatives according to the invention comprises between 0.005 and 5% by weight, more preferably between 0.01 and 3% by weight of MEL ( s) tri-acylated (s), on the total weight of said composition.

 Advantageously, the composition comprising a tri-acylated MEL and oil and / or one of its derivatives according to the invention comprises at least 20% by weight, preferably at least 50% by weight of oil and / or one of its derivatives, on the total weight of said composition.

It is particularly advantageous to use tri-acylated MELs as a corrosion inhibitor in substances rich in chlorides, sulphides, carbon dioxide (C0 ₂ ), organic acids such as naphthenic acids, or in microorganisms at the same time. origin of the formation of these compounds, as for example in crude oil.

 The composition comprising a tri-acylated MEL and oil and / or one of its derivatives according to the invention may comprise an additive, such as an additive used in the petroleum field, for example during the refining of oil, storage or the transport of oil or any of its derivatives.

 The person skilled in the art knows how to choose the additive (s) best adapted to an application in the oil field, for example for the refining of oil.

 The compositions according to the invention may also comprise other compounds, such as a vegetable oil.

The tri-acylated MEL can also be used as an anticorrosive additive in a composition for cleaning and / or degreasing metals, for example to protect equipment such as degreasing machines which contain metal parts. Such compositions include a cleaning and / or degreasing solvent.

 The invention therefore also relates to a composition comprising a tri-acylated MEL and a solvent for cleaning and / or degreasing, in particular a solvent for cleaning and / or degreasing the metals.

 Such a solvent may be selected from the group consisting of aliphatic hydrocarbons, dipropylene glycol n-butyl ether, diisobutyl adipate, methyl linoleate, methyl oleate, methyl stearate, beta-pinene.

 Advantageously, the composition comprising a tri-acylated MEL and a cleaning and / or degreasing solvent according to the invention comprises at least 0.005% by weight, preferably at least 0.1% by weight of tri-acylated MEL (s). (s), on the total weight of said composition.

 Preferably, the composition comprising a tri-acylated MEL and a cleaning and / or degreasing solvent according to the invention comprises between 0.005 and 5% by weight, more preferably between 0.1 and 3% by weight, more preferably between 0.5 and 2% by weight of MEL (s) tri-acylated (s), on the total weight of said composition.

 Advantageously, the composition comprising a tri-acylated MEL and a cleaning and / or degreasing solvent according to the invention comprises between 50 and 99.9% by weight, preferably between 75 and 99.5% by weight of cleaning solvent and or degreasing, on the total weight of said composition.

 More particularly, the invention relates to a composition comprising a tri-acylated MEL and a cleaning and / or degreasing solvent selected from the group consisting of dipropylene glycol n-butyl ether, diisobutyl adipate, methyl linoleate methyl oleate, methyl stearate, beta-pinene.

 The invention furthermore relates to a process for the preparation of a composition comprising a tri-acylated MEL and a mineral and / or synthetic oil according to the invention, comprising a step of mixing a mineral oil and / or an oil synthetic, with a tri-acylated MEL.

 The invention also relates to a process for preparing a composition comprising a tri-acylated MEL and a binder according to the invention, comprising a step of mixing a solvent and a binder, with a tri-acylated MEL.

The invention also relates to a process for preparing a composition comprising a tri-acylated MEL and oil and / or one of its derivatives according to the invention, comprising a step of mixing oil and / or one of its derivatives, with a tri-acylated MEL. The invention also relates to a process for preparing a composition comprising a tri-acylated MEL and a cleaning and / or degreasing solvent comprising a step of mixing the cleaning and / or degreasing solvent with a tri-acylated MEL.

 The invention relates more particularly to a process for the preparation of a composition comprising a tri-acylated MEL and a cleaning and / or degreasing solvent chosen from the group consisting of dipropylene glycol n-butyl ether, diisobutyl adipate, methyl linoleate, methyl oleate, methyl stearate, beta- pinene, comprising a step of mixing a cleaning and / or degreasing solvent selected from the group consisting of dipropylene glycol n-butyl ether, diisobutyl adipate, methyl linoleate, methyl oleate, methyl stearate, beta-pinene, with a tri-acylated MEL.

 These methods may also comprise a preliminary step of diluting a tri-acylated MEL in a suitable solvent, such as for example a vegetable oil, a fatty acid ester, propylene glycol, white spirit or any other solvent capable of to dissolve tri-acylated MELs.

 The compositions according to the invention are easily prepared by simply mixing their components.

 Advantageously, the mixing is carried out at room temperature under normal conditions of temperature and pressure (CNTP).

 Advantageously, the components have the preferred characteristics as described above.

 The present invention finally provides a method of protecting a metal against corrosion, comprising contacting a tri-acylated MEL, a composition comprising a tri-acylated MEL and a mineral and / or synthetic oil, d. a composition comprising a tri-acylated MEL and a binder, a composition comprising a tri-acylated MEL and oil and / or a derivative thereof, or a composition comprising a tri-acylated MEL and a solvent cleaning and / or degreasing, with said metal.

 The tri-acylated MELs and the compositions in particular according to the invention may be used so as to protect a metal with which they are intended to be in contact.

 In the case of a coating, and more particularly an antirust coating, the latter is advantageously applied to the metal to be protected.

This application can be done, for example, with the aid of a brush or by spraying, for example using an aerosol. Preferably the metal is a ferrous metal, preferably iron or steel.

 Advantageously, the process is therefore a method of protecting a metal against rust formation.

 Advantageously, the processes according to the invention described above implement tri-acylated MELs.

 The invention will be better understood from the following examples, given by way of illustration, with reference to:

 Figure 1, which includes two photographs (Fig. 1A and 1B) showing the corrosion state of a metal test rod following prolonged contact with air, water and MELs. tri-acylated;

 Figure 2, which includes two photographs (Fig. 2A and 2B) depicting the corrosion state of a metal test rod following prolonged contact with air, water and MELs. acylated (mixture of MELs 1A);

 - Figure 3, which includes a photograph showing the state of corrosion of a metal test rod following prolonged contact with air, water and di-acylated MELs (mixture of MELs 1 B);

 Figure 4, which includes a photograph showing the corrosion state of a metal test rod following prolonged contact with air, water and Perlastan® O; and

 Figure 5, which includes a photograph showing the state of corrosion of a metal test rod following prolonged contact with only air and water. Example 1: Determination of the ability of tri-acylated MELs and comparative compounds to inhibit corrosion

 The ability to inhibit the corrosion of tri-acylated MEL metals and comparative compounds, and in particular to protect steel from rust formation, was evaluated in a manner similar to that described in ASTM D665- 03 ("Standard Test Method for Rust-Preventing Characteristics of Inhibited Mineral Oil in the Presence of Water").

 1. Material and methods

 at. Equipment

An apparatus for evaluating rust formation, such as that described in ASTM D665-03, has been used (LT / RP-194000-4 / M, Linetronic Technologies). This apparatus is in particular composed of a thermostatically controlled oil bath, a beaker in which is poured the test compound and water, a lid for beaker (perforated) and a shank. steel test that can be immersed in the water / test compound mixture (passing through the lid to beak through one of the perforations). The water / test compound mixture is in contact with the air, in order to allow any rust to appear.

 The tested products are:

 tri-acylated MELs;

 di-acylated MELs;

 - Perlastan® O (N-Oleoyl Sarcosine, which is a common corrosion inhibitor);

moderately hard water at 100 ppm CaCO ₃ , as described in ASTM D 4627-92.

 b. Methods

 Preparation of tri-acylated MELs

 The tri-acylated MELs were obtained by a process for producing tri-acylated MELs comprising the following steps:

 Step 1: Conversion of a carbonaceous substrate such as a vegetable oil (rapeseed) with a yeast strain such as Pseudozyma aphidis to obtain di-acylated MELs Step 2: Recovery of di-acylated MEL mixtures

 The recovery step of the di-acylated MELs can be carried out initially by separation by filtration, centrifugation and evaporation.

 A first mixture comprising di-acylated MELs (mixture of MELs di-acylated 1A) is obtained, which has the following characteristics:

 · Content of di-acylated MELs: 55% by weight

 • Content of other components: 45% by weight (including 42% by weight of fatty acids and triglycerides and 3% by weight of water and strain),

 the percentages by weight being given relative to the total weight of the mixture obtained.

 An additional separation step applied to the mixture of 1A di-alkylated MELs was then carried out by adsorption chromatography on a silica column. A second mixture of di-acylated MELs (mixture of di-acylated MELs 1 B) has thus been obtained, which has the following characteristics:

· Content of di-acylated MELs:> 98% by weight • Content of other components: <2% by weight (including fatty acids and triglycerides).

 The composition of the di-acylated MELs in the mixture of di-acylated MELs 1 B was analyzed by high performance liquid chromatography (HPLC).

For this assay, 50 mg of the di-acylated MEL mixture was weighed and 3 mL of 0.2% acid chloroform to 80% formic acid was added. Once the mixture of di-acylated MELs dissolves, the solution is filtered on a 0.2 μm filter or on three 0.45 μm diameter filters. 50 μl of clear filtrate is taken to which is added 950 μl of acidified chloroform in a 2 ml analytical vial. 10 μl of this solution is injected into a Shimadzu LC-20 AD HPLC system equipped with an ELSD Sedex 90 detector, equipped with a 60A silica Nova-Pak column, 150 ^* 3.9mm 4μηι and a Novel Pre-column. Pak silica 60A, 20 ^* 3.9mm 4μηι. The analysis temperature is 30 ° C.

 The di-acylated MELs include MELs-A (52 wt%), MELs-B (12 wt%), MELs-C (35 wt%), and D-MELs (1 wt%). , the percentages by weight being given relative to the weight of the total amount of MELs.

The di-acylated MELs are MELs of formula (I) as described above, in which the acyl groups at R ¹ and R ² predominantly comprise a saturated carbon chain containing 10 carbon atoms, and the R ⁵ group is a hydrogen atom.

 The amount of di-acylated MELs in the MEL mixtures 1A and 1B is greater than 98% by weight based on the weight of the total amount of MELs.

 Step 3: Obtaining tri-acylated MELs

 In this step, the mixture of di-acylated MELs 1 B recovered in step 2 was dissolved in acetone in the presence of a lipase (Novozym® 435) and methyl oleate, under conditions allowing esterification reaction between di-acylated MELs and methyl oleate. The reaction medium was stirred for 48 h at 25 ° C.

 Tri-acylated MELs have thus been produced.

 Step 4: Recovery of tri-acylated MELs

 The tri-acylated MELs were then recovered from the reaction medium by silica column absorption chromatography.

 The tri-acylated MELs recovered have a degree of purity of about 95%.

The tri-acylated MELs recovered are MELs of formula (I) as described above, in which the acyl groups at R ⁵ predominantly comprise an unsaturated carbon chain containing 18 carbon atoms. Preparation of di-acylated MELs

 Mixtures of di-acylated MELs 1A and 1B as described above were prepared.

 tests

 In the beaker, 1% by weight of a test compound (tri-acylated MELs, mixture of di-acylated MELs 1A, mixture of di-acylated MELs 1B or Perlastan® O) and 99% by weight of water are added, the percentages by weight being indicated relative to the total weight of the water / test compound mixture. This mixture is stirred at a temperature of 60 +/- 1 ° C. A cylindrical steel test rod is immersed in the water / test compound mixture. The test is performed for 4 hours. At the end of the test, the appearance of signs of rust formation on the test rod is evaluated with the naked eye.

 A control test without test compound (test rod immersed in water only) was also performed.

 Table 1 below summarizes the different tests implemented.

 Table 1: Tests implemented in Example 1.

 2. Results

 The results of tests 1 to 5 are shown in Figures 1 to 5, respectively. Concerning test 5, the degree of corrosion of the test rod is very important, as evidenced by the almost black color of the test rod in Figure 5.

 With regard to tests 1 to 4, Figures 1 to 4 show that the degree of corrosion of the test rods of tests 1 to 4 is less important than that of the test rod of test 5, which shows the inhibitory power of corrosion of tri-acylated and di-acylated MELs and Perlastan® O.

 More particularly, the degree of corrosion of the test rod of the test 1 is very low, as shown in FIG. 1, which shows the high inhibitory power of the corrosion of the tri-acylated MELs.

In addition, when assessing the degree of corrosion of the test rods shown in FIGS. 1 to 4, it can be observed that the inhibitory power of the corrosion of the tri-acylated MELs (FIG. 1) is greater than that of the MELs di -acylated (Figures 2 and 3), and that of Perlastan® O (Figure 4). Example 2 Preparation of compositions according to the invention

 1. Obtaining tri-acylated MELs

 The tri-acylated MELs were obtained by the method of producing tri-acylated MELs as described in Example 1.

 2. Oil

 - Group I oils: CORE 150 and / or CORE 600 from ExxonMobil Group II oil: EHC 50 from ExxonMobil

 - TMPTO (trimethylolpropane tri-oleate): Oleon Radialube 7364 3. Binder

 A polyurethane resin was used.

 4. Process for the preparation of the compositions according to the invention

 Composition 1 A

 The composition 1A according to the invention was prepared by mixing the oil of group I CORE 150 with the tri-acylated MELs. It is also possible to prepare a composition with the oil of group I CORE 600 or a mixture of the two oils of group I CORE 150 and CORE 600.

 Composition 1 B

 Composition 1B according to the invention was prepared by mixing the Group II oil with the tri-acylated MELs.

 Composition 2

 The composition 2 according to the invention was prepared by mixing the polyurethane resin with the tri-acylated MELs. Example 3 Determination of the ability of tri-acylated MELs to inhibit corrosion

 The ability to inhibit metal corrosion of tri-acylated MELs, and in particular to protect iron against rust formation, was evaluated in a manner similar to that described in ASTM D665-03 ("Standard Test Method"). for Rust-Preventing Characteristics of Inhibited Ore Oil in the Presence of Water ").

 1. Material and methods

 at. Equipment

 an apparatus for evaluating rust formation similar to that used in Example 1, but composed of an iron rod;

The products used are: tri-acylated MELs;

 a mineral oil (Escaid ™ 1 10 from ExxonMobil);

 - North Dakota crude oil;

 - Bakken brine brine from North Dakota. b. Methods

 Preparation of tri-acylated MELs

 The tri-acylated MELs were obtained by a process for producing tri-acylated MELs comprising the following steps:

 Steps 1 to 3: These steps are identical to those described in Example 1. Step 4: Recovery of tri-acylated MELs

 The tri-acylated MELs were recovered from the reaction medium by liquid / liquid extraction (hexane). Filtration (microfilter) was then performed to remove the lipase, followed by evaporation of the solvents.

 The tri-acylated MELs recovered have a degree of purity of about 75%.

The tri-acylated MELs recovered are MELs of formula (I) as described above, in which the acyl groups at R ⁵ predominantly comprise an unsaturated carbon chain containing 18 carbon atoms.

 Brine preparation

In a beaker comprising 1 liter of demineralized water, are added, under magnetic stirring, 60 g of CaCl _2, 5 g of MgCl _2, 5 g of NH ₄ Cl, 3g SRCI _2, 120 g of NaCl and 10 g of KCI.

 tests

 30 g of brine and 3 g of tri-acylated MELs are introduced into the beaker of the apparatus enabling evaluation of rust formation, then 240 g of mineral oil (test 7) or 240 g of crude oil (test 9).

 These mixtures are stirred at a temperature of 60 +/- 1 ° C for 5 minutes. A cylindrical iron test rod is weighed before being immersed in each of the mixtures. The tests are carried out for 24 hours. At the end of the tests, the appearance of signs of rust formation on the test stems is evaluated with the naked eye. The stems are also weighed. The mass difference for each rod is calculated by subtracting the mass of the rod after the rod test before testing. Thus, a negative mass difference indicates that the rod has been corroded.

 Comparative tests without tri-acylated MELs (test rod immersed in brine, and mineral oil or oil) were also performed.

Table 2 below summarizes the different tests implemented. Escaid 1 10 ™ Crude oil from

 Tri-Acylated MELs from ExxonMobil North Dakota Brine (g)

 (boy Wut)

(g) (g)

 Test 6

 240 - 30 0 (comparative)

 Test 7 240 - 30 3

Test 8

 - 240 30 0 (comparative)

 Test 9 - 240 30 3

 Table 2: Tests 6 to 9 implemented in Example 3.

 2. Results

 The results of tests 6 to 9 are presented in the following Table 3.

 Table 3: Test Results 6 to 9

 The results in Table 3 show that the iron rods immersed in the mixtures of comparative tests 6 and 8 (without tri-acylated MELs) have both been corroded.

 On the contrary, the iron rods immersed in the mixtures of tests 7 and 9 (with tri-acylated MELs) were not corroded.

 This attests the inhibitory power of the corrosion of tri-acylated MELs, even in the presence of a very hard water, very rich in calcium and magnesium.

Claims

Use of a tri-acylated mannosylerythritol lipid as a corrosion inhibitor. Use of a tri-acylated MEL according to claim 1 as an inhibitor of rust formation. Use according to one of claims 1 or 2, wherein the tri-acylated MEL is represented by the following general formula (I):

 in which : R ¹ and R ² , which are identical or different, represent an acyl group comprising an unsaturated or saturated acyclic carbon chain, R ³ and R ⁴ , which are identical or different, represent an acetyl group or a hydrogen atom, and - R ⁵ represents an acyl group comprising an unsaturated or saturated acyclic carbon chain containing from 8 to 24 carbon atoms. 4. Composition comprising a tri-acylated MEL and a mineral and / or synthetic oil. 5. Composition comprising a tri-acylated MEL and a binder. 6. Composition comprising a tri-acylated MEL and oil and / or one of its derivatives. 7. A composition comprising a tri-acylated MEL and a cleaning and / or degreasing solvent selected from the group consisting of dipropylene glycol n-butyl ether, diisobutyl adipate, methyl linoleate, methyl oleate, methyl stearate, beta-pinene. 8. Composition according to any one of claims 4 to 7, further comprising an additive. 9. Process for the preparation of a composition according to claim 4, comprising a step of mixing a mineral oil and / or a synthetic oil with a tri-acylated MEL. A process for preparing a composition according to claim 5 comprising a step of mixing a binder with a tri-acylated MEL. 1 1. A process for the preparation of a composition according to claim 6 comprising a step of mixing petroleum and / or a derivative thereof with a tri-acylated MEL. 12. Process for the preparation of a composition according to claim 7, comprising a step of mixing a cleaning and / or degreasing solvent selected from the group consisting of dipropylene glycol n-butyl ether, diisobutyl adipate, methyl linoleate, methyl oleate, methyl stearate, beta-pinene, with a tri-acylated MEL. A method of protecting a metal against corrosion, comprising contacting a tri-acylated MEL, a composition comprising a tri-acylated MEL and a mineral and / or synthetic oil, with a composition comprising a tri-acylated MEL and a binder, a composition comprising a tri-acylated MEL and oil and / or one of its derivatives, or a composition comprising a tri-acylated MEL and a cleaning solvent and / or degreasing, with said metal. 14. The method of claim 13, wherein the composition further comprises an additive.