FR3097875A1 - Lubricating composition for preventing corrosion and / or tribocorrosion of metal parts in an engine - Google Patents

Abstract

Lubricating composition for preventing corrosion and/or tribocorrosion of metal parts in an engine Lubricating composition comprising: - at least one base oil; and - from 0.1% to 30% by mass of a phosphorus ester compound of formula (A): in which s is 0 or 1; and the radicals X represent, independently of each other, groups -OR' or R', where R' represents a hydrogen or a hydrocarbon group, linear or branched, preferably having from 1 to 36 carbon atoms, provided that : when s is 0, the three X radicals represent -OR' groups and when s is 1, at least two of the three X radicals represent -OR' groups. Figure for abstract: None

Description

Lubricating composition for preventing corrosion and/or tribocorrosion of metal parts in an engine

The present invention relates to new lubricating compositions, in particular for engines, in particular useful for preventing corrosion and/or tribocorrosion of metal parts in an engine, and in particular in a two-stroke engine, such as a two-stroke marine engine. The present invention also relates to a process for passivating metal parts of an engine, in particular of a two-stroke engine, such as a two-stroke marine engine.

Since 2011, the presence of excessive corrosion, even uncontrolled, becomes preponderant when the engines are operated at very low load (25% or less of the maximum load). This excessive corrosion is also present with the latest existing engine designs because they are increasingly severe. Even if in the near future (2020), the sulfur levels of fuels for marine engines will be lowered in order to comply with regulations (SOx emissions), the problem of corrosion remains unresolved for many engine operators and more particularly for engines two-stroke.

The combustion of fuel oils generates the formation of acid gases, in particular sulfur oxides (SO ₃ , formed by oxidation of SO ₂ ), which are in contact with the metal parts of the engine. In the presence of water, SO ₃ hydrolyses into sulfuric acid H ₂ SO ₄ , responsible for the corrosion of engine parts. Other acids, such as nitric acid, compounds bearing one or more carboxylic acid functions, or combinations of these acids, can also be responsible for corrosion and/or tribocorrosion of engine parts.

Acid corrosion is located in the tribological system in the segment-piston-liner area. In this zone on a lubricated engine, the friction observed is of the alternating slip type.

In the case of marine engines, in particular two-stroke marine engines, the lubricating compositions are classified into two categories: cylinder oils, which ensure the lubrication of the piston-cylinder assembly, and system oils, which ensure the lubrication of all moving parts other than those of the piston-cylinder assembly.

When the engine is running, cylinder oil is spread over the cylinder and forms a thin, oily film between the piston and the cylinder wall. This film plays three roles:

- ensure the separation between the two surfaces in order to avoid adhesion wear,

- neutralize the drops of sulfuric acid formed in the combustion chamber before they reach the cylinder and cause its wear by corrosion and/or tribocorrosion, and

- disperse any deposit that may form on each surface to keep them clean.

The lubricating compositions for engines, and in particular for marine engines, currently used comprise a base oil to which are added dispersants and overbased detergents. These overbased detergents typically include a core of calcium carbonate CaCO₃coated with a layer of surfactant. calcium carbonate reacts with sulfuric acid to form calcium sulphate (CaSO₄). The drop in sulfuric acid in the medium allows parts to be protected against corrosion and/or tribocorrosion.

In order to ensure this protection, the lubricating compositions used must be sufficiently basic (in particular to neutralize the acid), which implies increasing the quantity of detergents included in these compositions.

Thus, the lubricating compositions currently on the market have Basicity Indexes (BN) greater than 70.

However, the increase in the quantity of detergents in these lubricating compositions leads to an increase in the number of CaCO ₃ and CaSO ₄ particles responsible for surface wear by polishing (or abrasive wear) of the metal parts of the engine, and in particular of the two-stroke engine cylinders, such as two-stroke marine engines. On the other hand, the use of currently available lubricating compositions does not completely protect the metal parts of the engine from corrosion and/or tribocorrosion, and in particular the metal parts of the two-stroke engine against tribocorrosion, when friction is of the reciprocating slip type.

There is therefore an interest in providing lubricating compositions which make it possible to improve the protection of the metal parts of an engine, in particular of a two-stroke engine, such as a two-stroke marine engine, against corrosion and/or tribocorrosion.

There is also an interest in providing lubricating compositions which make it possible to reduce their Basicity Index.

An objective of the present invention is to provide lubricating compositions which make it possible to improve the protection of the metal parts of an engine, typically of a two-stroke engine, in particular of a two-stroke marine engine, against corrosion and/ or tribocorrosion.

The present invention relates more particularly to the supply of cylinder oils for two-stroke engines, in particular for two-stroke marine engines.

Another object of the present invention is to provide lubricating compositions having a reduced Basicity Index.

Still other objectives will appear on reading the description of the invention which follows.

These objectives are fulfilled by the present invention which relates to a lubricating composition comprising:

- at least one base oil; And

- from 0.1% to 30%, preferably from 0.5% to 20%, advantageously from 1% to 10% by mass of a phosphorus ester compound of formula (A):

in which

s is 0 or 1; And

the radicals X represent, independently of each other, -OR' or R' groups, where R' represents a hydrogen or a linear or branched hydrocarbon group, preferably having from 1 to 36 carbon atoms, provided that:

when s is 0, the three radicals X represent -OR' groups and that,

when s is 1, at least two of the three X radicals represent -OR' groups.

Preferably, R' represents an alkyl group, linear or branched, comprising from 1 to 36 carbon atoms, preferentially from 2 to 30 carbon atoms, advantageously from 4 to 24 carbon atoms, or R', represents an alkenyl group, linear or branched, comprising from 2 to 36 carbon atoms, preferentially from 2 to 30 carbon atoms, advantageously from 4 to 24 carbon atoms.

Preferably, these objectives are fulfilled by the present invention which relates to a lubricating composition comprising:

- at least one base oil; And

- from 0.1% to 30%, preferably from 0.5% to 20%, advantageously from 1% to 10% by mass of a phosphorus ester compound of formula (B):

in which :

- R ¹ and R ² , identical or different, independently represent an alkyl group, linear or branched, comprising from 1 to 36 carbon atoms, preferably from 2 to 30 carbon atoms, advantageously from 4 to 24 carbon atoms, or R ¹ and R ² , which are identical or different, independently represent an alkenyl group, linear or branched, comprising from 2 to 36 carbon atoms, preferably from 2 to 30 carbon atoms, advantageously from 4 to 24 carbon atoms; And

- R ³ represents a hydrogen or a hydroxyl group (OH).

Preferably, the alkenyl group (R ¹ and/or R ² ) according to the invention comprises at least one double bond. Preferably, said double bond is located at C-9, C-10 of the alkenyl group with respect to the phosphorus ester function.

Preferably, the R ¹ , R ² or R ³ group does not comprise a sulfur or nitrogen atom.

According to the invention, a hydrocarbon group is a chain, linear or branched, saturated, partially or totally unsaturated, comprising from 1 to 36 carbon atoms, preferentially from 2 to 30 carbon atoms, advantageously from 4 to 24 carbon atoms.

According to a particular embodiment of the invention, the base oil included in the lubricating composition is chosen from oils of mineral, synthetic or vegetable origin as well as mixtures thereof.

The mineral or synthetic oils generally used in the application belong to one of the classes defined in the API classification as summarized in the table below.

Saturates content Sulfur content Viscosity index Group 1 Mineral oils < 90% > 0.03% 80  IV < 120 Group 2 Hydrocracked Oils  90%  0.03% 80  IV < 120 Group 3Hydro-isomerized oils  90%  0.03%  120 Group 4 Polyalphaolefins (PAO) Group 5 Other bases not included in bases of groups 1 to 4

Table 1: API Classification of Base Oils

Group 1 mineral oils can be obtained by distillation of selected naphthenic or paraffinic crudes, followed by purification of these distillates by processes such as solvent extraction, solvent or catalytic dewaxing, hydrotreating or hydrogenation.

Group 2 and 3 oils are obtained by more severe purification processes, for example a combination of hydrotreating, hydrocracking, hydrogenation and catalytic dewaxing.

Examples of Group 4 and 5 synthetic bases include poly-alpha olefins, polybutenes, polyisobutenes, alkylbenzenes.

These base oils can be used alone or in a mixture. A mineral oil can be combined with a synthetic oil.

Cylinder oils for 2-stroke diesel marine engines have a viscometric grade SAE-40 to SAE-60, generally SAE-50 equivalent to a kinematic viscosity at 100°C between 16.3 and 21.9 mm²/s.

Grade 40 oils have a kinematic viscosity at 100°C of between 12.5 and 16.3 mm²/s.

Grade 50 oils have a kinematic viscosity at 100°C of between 16.3 and 21.9 mm²/s.

Grade 60 oils have a kinematic viscosity at 100°C of between 21.9 and 26.1 mm²/s.

According to the practices of the profession, it is preferred to formulate cylinder oils for two-stroke diesel marine engines having a kinematic viscosity at 100° C. of between 18 and 21.5, preferably between 19 and 21.5 mm ² /s.

This viscosity can be obtained by mixing additives and base oils, for example containing Group 1 mineral bases such as Neutral Solvent bases (for example 500 NS or 600 NS) and Brightstock. Any other combination of mineral, synthetic or plant-based bases having, when mixed with additives, a viscosity compatible with SAE-50 grade can be used.

Typically, a conventional formulation of cylinder lubricant for slow 2-stroke marine diesel engines is of grade SAE-40 to SAE-60, preferably SAE-50 (according to the SAE J300 classification) and comprises at least 50% by mass of lubricating base of mineral and/or synthetic origin, suitable for use in a marine engine, for example, of API Group 1 class, that is to say obtained by distillation of selected crude oils followed by purification of these distillates by processes such as solvent extraction, solvent or catalytic dewaxing, hydrotreating or hydrogenation. Their Viscosity Index (VI) is between 80 and 120; their sulfur content is greater than 0.03% and their saturated content is less than 90%.

Advantageously, the lubricating composition according to the invention comprises at least 50% by mass of base oil(s) relative to the total mass of the composition.

More advantageously, the lubricating composition according to the invention comprises at least 60% by mass, or even at least 70% by mass, of base oil(s) relative to the total mass of the composition.

More particularly advantageously, the lubricating composition according to the invention comprises from 60% to 99.9% by mass of base oils, preferably from 70% to 98% by mass of base oils, with respect to the total mass of the composition.

Preferably, the lubricating composition according to the invention further comprises at least one additive chosen from detergents, dispersants and mixtures thereof.

The detergents used in the lubricating compositions according to the present invention are well known to those skilled in the art.

In the context of the present invention, the detergents commonly used in the formulation of lubricating compositions are anionic compounds comprising a long lipophilic hydrocarbon chain and a hydrophilic head. The associated cation is a metal cation of an alkali or alkaline earth metal.

The detergents are preferably chosen from alkali or alkaline-earth metal salts of carboxylic acids, sulfonates, salicylates, naphthenates, as well as phenate salts.

The alkali metals and alkaline earth metals are preferably calcium, magnesium, sodium or barium.

These metal salts may contain the metal in an approximately stoichiometric amount. In this case, we speak of non-overbased or “neutral” detergents, although they also provide a certain basicity. These "neutral" detergents typically have a BN, measured according to ASTM D2896, of less than 150 mg KOH/g, or less than 100, or even less than 80 mg KOH/g.

This type of so-called neutral detergents can contribute in part to the BN of the lubricants according to the present invention. Use will be made, for example, of neutral detergents of the carboxylate, sulphonate, salicylate, phenate, naphthenate type of alkali metals and alkaline earth metals, for example of calcium, sodium, magnesium, barium.

When the metal is in excess (in an amount greater than the stoichiometric amount), we are dealing with so-called overbased detergents. Their BN is high, for example greater than 150 mg KOH/g, typically between 200 and 700 mg KOH/g, generally between 250 and 450 mg KOH/g.

The excess metal providing the overbased character to the detergent is in the form of metal salts insoluble in oil, for example carbonate, hydroxide, oxalate, acetate, glutamate, preferentially carbonate.

In the same overbased detergent, the metals of these insoluble salts may be the same as those of oil-soluble detergents or they may be different. They are preferably chosen from calcium, magnesium, sodium or barium.

Overbased detergents thus come in the form of micelles composed of insoluble metal salts held in suspension in the lubricating composition by the detergents in the form of oil-soluble metal salts.

Overbased detergents with only one type of detergent soluble metal salt will generally be named after the nature of the hydrophobic chain of the latter detergent.

Thus, they will be said to be of the carboxylate, phenate, salicylate, sulfonate, naphthenate type depending on whether this detergent is respectively a carboxylate, phenate, salicylate, sulfonate, or naphthenate.

The overbased detergents will be said to be of mixed type if the micelles comprise several types of detergents, different from each other by the nature of their hydrophobic chain.

For use in the lubricating compositions according to the present invention, the oil-soluble metal salts will preferably be carboxylates, phenates, sulfonates, salicylates, and mixed phenate-sulfonate detergents and/or calcium, magnesium, sodium salicylates. or barium.

The insoluble metal salts providing the overbased character are alkali metal and alkaline earth metal carbonates, preferably calcium carbonate.

Preferably, the detergents used in the lubricating compositions according to the present invention are detergents overbased with calcium carbonate chosen from carboxylates, phenates, sulfonates, salicylates and mixed phenate-sulfonate-salicylate detergents.

Advantageously, the lubricating composition according to the invention may comprise from 3% to 40%, preferably from 5% to 30%, advantageously from 10% to 25% by mass of detergent(s) relative to the total mass of the lubricating composition.

Dispersants are well-known additives used in the formulation of lubricating compositions, in particular for application in the marine field. Their primary role is to maintain in suspension the particles present initially or appearing in the lubricating composition during its use in the engine. They prevent their agglomeration by playing on steric hindrance. They may also exhibit a synergistic effect on neutralization.

In the context of the present invention, the dispersants used as lubricant additives contain a polar group, associated with a relatively long hydrocarbon chain, generally containing from 50 to 400 carbon atoms. The polar group typically contains at least one nitrogen or oxygen element.

Compounds derived from succinic acid are dispersants particularly used as lubricating additives. In particular, succinimides are used, obtained by condensation of succinic anhydrides and amines, succinic esters obtained by condensation of succinic anhydrides and alcohols or polyols.

These compounds can then be treated with various compounds, in particular sulphur, oxygen, formaldehyde, carboxylic acids and compounds containing boron or zinc to produce, for example, borated succinimides or zinc-blocked succinimides.

Mannich bases, obtained by polycondensation of phenols substituted with alkyl groups, formaldehyde and primary or secondary amines, are also compounds used as dispersants in lubricants.

Preferably, the dispersants according to the invention are chosen from succinimides, such as polyisobutylene bis-succinimides, optionally borated or blocked with zinc.

Advantageously, the lubricating composition according to the invention may comprise from 0.01% to 10%, preferably from 0.1% to 5%, advantageously from 0.5% to 3% by mass of dispersant(s) relative to the total mass of the lubricating composition.

The lubricating composition may also comprise at least one anti-wear additive.

Preferably, the anti-wear additive is zinc di-thiophosphate or DTPZn. This category also includes various phosphorus, sulphur, nitrogen, chlorine and boron compounds.

There are a wide variety of anti-wear additives, but the most widely used category is that of phospho-sulfur additives such as metal alkylthiophosphates, in particular zinc alkylthiophosphates, and more specifically zinc dialkyldithiophosphates or DTPZn.

Amine phosphates, polysulfides, especially sulfur olefins, are also commonly used anti-wear additives.

Anti-wear and extreme pressure additives of the nitrogen and sulfur type are also usually found in the lubricating compositions, such as, for example, metal dithiocarbamates, in particular molybdenum dithiocarbamate. Glycerol esters are also anti-wear additives. Mention may be made, for example, of mono, di- and trioleates, monopalmitates and monomyristates.

• de 50 % à 96.9% en poids, de préférence de 60 à 95% en poids, de préférence encore de 70 à 90% en poids, d’huile(s) de base,
• de 0,1 % à 30% en poids, de préférence de 0,5 à 20% en poids, de préférence encore de 1 à 10% en poids, d’un ou plusieurs composés ester phosphoré de formule (A), et
• de 3 % à 40% en poids, de préférence de 5 à 30% en poids, de préférence encore de 10 % à 25% en poids, de détergent(s), et
• éventuellement de 0,01 % à 10% en poids, de préférence de 0,1 à 5% en poids, de préférence encore de 0,5 % à 3% en poids, de dispersant(s).

According to a particular embodiment, the lubricating composition comprises, relative to the total weight of the lubricating composition:

• from 50% to 96.9% by weight, preferably from 60 to 95% by weight, more preferably from 70 to 90% by weight, of base oil(s),
• from 0.1% to 30% by weight, preferably from 0.5 to 20% by weight, more preferably from 1 to 10% by weight, of one or more phosphorus ester compounds of formula (A), and
• from 3% to 40% by weight, preferably from 5 to 30% by weight, more preferably from 10% to 25% by weight, of detergent(s), and
• optionally from 0.01% to 10% by weight, preferably from 0.1 to 5% by weight, more preferably from 0.5% to 3% by weight, of dispersant(s).

• de 50 % à 96.9% en poids, de préférence de 60 à 95% en poids, de préférence encore de 70 à 90% en poids, d’huile(s) de base,
• de 0,1 % à 30% en poids, de préférence de 0,5 à 20% en poids, de préférence encore de 1 à 10% en poids, d’un ou plusieurs composés ester phosphoré de formule (B), et
• de 3 % à 40% en poids, de préférence de 5 à 30% en poids, de préférence encore de 10 % à 25% en poids, de détergent(s), et
• éventuellement de 0,01 % à 10% en poids, de préférence de 0,1 à 5% en poids, de préférence encore de 0,5 % à 3% en poids, de dispersant(s).

According to a particular embodiment, the lubricating composition comprises, relative to the total weight of the lubricating composition:

• from 50% to 96.9% by weight, preferably from 60 to 95% by weight, more preferably from 70 to 90% by weight, of base oil(s),
• from 0.1% to 30% by weight, preferably from 0.5 to 20% by weight, more preferably from 1 to 10% by weight, of one or more phosphorus ester compounds of formula (B), and
• from 3% to 40% by weight, preferably from 5 to 30% by weight, more preferably from 10% to 25% by weight, of detergent(s), and
• optionally from 0.01% to 10% by weight, preferably from 0.1 to 5% by weight, more preferably from 0.5% to 3% by weight, of dispersant(s).

• de 60 à 99% en poids, de préférence de 60 à 95% en poids, de préférence encore de 70 à 90% en poids, d’huile(s) de base,
• de 0,1 à 30% en poids, de préférence de 0,5 à 20% en poids, de préférence encore de 1 à 10% en poids, d’un ou plusieurs composés ester phosphoré de formule (A), et
• de 0,01 à 10% en poids, de préférence de 0,1 à 5% en poids, de préférence encore de 0,5 à 3% en poids, de dispersant(s), et
• éventuellement de 3 à 40% en poids, de préférence de 5 à 30% en poids, de préférence encore de 10 à 25% en poids, de détergent(s).

According to a particular embodiment, the lubricating composition comprises, relative to the total weight of the lubricating composition:

• from 60 to 99% by weight, preferably from 60 to 95% by weight, more preferably from 70 to 90% by weight, of base oil(s),
• from 0.1 to 30% by weight, preferably from 0.5 to 20% by weight, more preferably from 1 to 10% by weight, of one or more phosphorus ester compounds of formula (A), and
• from 0.01 to 10% by weight, preferably from 0.1 to 5% by weight, more preferably from 0.5 to 3% by weight, of dispersant(s), and
• optionally from 3 to 40% by weight, preferably from 5 to 30% by weight, more preferably from 10 to 25% by weight, of detergent(s).

• de 60 à 99% en poids, de préférence de 60 à 95% en poids, de préférence encore de 70 à 90% en poids, d’huile(s) de base,
• de 0,1 à 30% en poids, de préférence de 0,5 à 20% en poids, de préférence encore de 1 à 10% en poids, d’un ou plusieurs composés ester phosphoré de formule (B), et
• de 0,01 à 10% en poids, de préférence de 0,1 à 5% en poids, de préférence encore de 0,5 à 3% en poids, de dispersant(s), et
• éventuellement de 3 à 40% en poids, de préférence de 5 à 30% en poids, de préférence encore de 10 à 25% en poids, de détergent(s).

According to a particular embodiment, the lubricating composition comprises, relative to the total weight of the lubricating composition:

• from 60 to 99% by weight, preferably from 60 to 95% by weight, more preferably from 70 to 90% by weight, of base oil(s),
• from 0.1 to 30% by weight, preferably from 0.5 to 20% by weight, more preferably from 1 to 10% by weight, of one or more phosphorus ester compounds of formula (B), and
• from 0.01 to 10% by weight, preferably from 0.1 to 5% by weight, more preferably from 0.5 to 3% by weight, of dispersant(s), and
• optionally from 3 to 40% by weight, preferably from 5 to 30% by weight, more preferably from 10 to 25% by weight, of detergent(s).

The lubricating composition can also comprise all types of functional additives suitable for their use, for example anti-foam additives which can be, for example, polar polymers such as polymethylsiloxanes, polyacrylates, antioxidant additives, for example of the phenolic or amine type. and/or anti-rust additives, for example organo-metallic compounds or thiadiazoles. These are known to those skilled in the art.

According to one embodiment of the invention, the compound of formula (A) is the following compound (I):

According to one embodiment of the invention, the compound of formula (B) is the following compound (I):

According to another embodiment of the invention, the compound of formula (A) is the following compound (II):

According to another embodiment of the invention, the compound of formula (B) is the following compound (II):

• de 50 à 96,9% en poids, de préférence de 60 à 95% en poids, de préférence encore de 70 à 90% en poids, d’huile(s) de base,
• de 0,1 à 30% en poids, de préférence de 0,5 à 20% en poids, de préférence encore de 1 à 10% en poids, d’un ou plusieurs composés ester phosphoré dont au moins un composé de formule (I) ou de formule (II) définies ci-dessus, et
• de 3 à 40% en poids, de préférence de 5 à 30% en poids, de préférence encore de 10 à 25% en poids, de détergent(s) comprenant au moins un détergent surbasé de type phénate ou sulphonate, et
• éventuellement de 0,01 à 10% en poids, de préférence de 0,1 à 5% en poids, de préférence encore de 0,5 à 3% en poids, de dispersant(s).

According to a particular embodiment, the lubricating composition comprises, relative to the total weight of the lubricating composition:

• from 50 to 96.9% by weight, preferably from 60 to 95% by weight, more preferably from 70 to 90% by weight, of base oil(s),
• from 0.1 to 30% by weight, preferably from 0.5 to 20% by weight, more preferably from 1 to 10% by weight, of one or more phosphorus ester compounds including at least one compound of formula (I ) or of formula (II) defined above, and
• from 3 to 40% by weight, preferably from 5 to 30% by weight, more preferably from 10 to 25% by weight, of detergent(s) comprising at least one overbased detergent of the phenate or sulphonate type, and
• optionally from 0.01 to 10% by weight, preferably from 0.1 to 5% by weight, more preferably from 0.5 to 3% by weight, of dispersant(s).

• de 60 à 99% en poids, de préférence de 60 à 95% en poids, de préférence encore de 70 à 90% en poids, d’huile(s) de base,
• de 0,1 à 30% en poids, de préférence de 0,5 à 20% en poids, de préférence encore de 1 à 10% en poids, d’un ou plusieurs composés ester phosphoré dont au moins un composé de formule (I) ou de formule (II) définies ci-dessus, et
• de 0,01 à 10% en poids, de préférence de 0,1 à 5% en poids, de préférence encore de 0,5 à 3% en poids, de dispersant(s) choisi(s) parmi les succinimides, et
• éventuellement de 3 à 40% en poids, de préférence de 5 à 30% en poids, de préférence encore de 10 à 25% en poids, de détergent(s).

According to a particular embodiment, the lubricating composition comprises, relative to the total weight of the lubricating composition:

• from 60 to 99% by weight, preferably from 60 to 95% by weight, more preferably from 70 to 90% by weight, of base oil(s),
• from 0.1 to 30% by weight, preferably from 0.5 to 20% by weight, more preferably from 1 to 10% by weight, of one or more phosphorus ester compounds including at least one compound of formula (I ) or of formula (II) defined above, and
• from 0.01 to 10% by weight, preferably from 0.1 to 5% by weight, more preferably from 0.5 to 3% by weight, of dispersant(s) chosen from succinimides, and
• optionally from 3 to 40% by weight, preferably from 5 to 30% by weight, more preferably from 10 to 25% by weight, of detergent(s).

The present invention also relates to the use of the lubricating composition according to the invention for lubricating at least one metal part of an engine, such as a two-stroke engine and in particular a two-stroke marine engine.

Preferably, the use of the lubricating composition according to the invention makes it possible to prevent and/or reduce corrosion and/or tribocorrosion of said metal part of said engine.

The present invention also relates to a method for lubricating at least one metal part of an engine, such as a two-stroke engine and in particular a two-stroke marine engine, comprising bringing said part of an engine into contact with the lubricating composition according to the invention.

The present invention also relates to the use of a compound of formula (A) according to the invention in a lubricating composition comprising at least one base oil for preventing and/or reducing corrosion and/or tribocorrosion of at least one metal part of an engine, such as a two-stroke engine and in particular a two-stroke marine engine.

The present invention also relates to the use of a compound of formula (B) according to the invention in a lubricating composition comprising at least one base oil for preventing and/or reducing corrosion and/or tribocorrosion of at least one metal part of an engine, such as a two-stroke engine and in particular a two-stroke marine engine.

The present invention also relates to a method for preventing and/or reducing corrosion and/or tribocorrosion of at least one metal part of an engine, such as a two-stroke engine and in particular a two-stroke marine engine. time, comprising the lubrication of said metal part with a lubricating composition according to the invention.

The present invention also relates to the use of the lubricating composition according to the invention for the passivation of at least one metal part of an engine, such as a two-stroke engine and in particular a two-stroke marine engine.

The present invention also relates to a method for passivating at least one metal part of an engine comprising at least one step of bringing said metal part into contact with the lubricating composition according to the invention.

The present invention also relates to the use of a compound of formula (A) according to the invention in a lubricating composition comprising at least one base oil for the passivation of at least one metal part of an engine, such as a two-stroke engine and in particular a two-stroke marine engine.

The present invention also relates to the use of a compound of formula (B) according to the invention in a lubricating composition comprising at least one base oil for the passivation of at least one metal part of an engine, such as a two-stroke engine and in particular a two-stroke marine engine.

Preferably, the metal part according to the invention is a cylinder or a piston.

Advantageously, the metal part is made of cast iron.

Preferably, the engine according to the invention is a two-stroke engine. Preferably, the engine is a two-stroke marine engine.

Preferably, the engine is an engine consuming heavy fuel oil. By “heavy fuel oil”, is meant within the meaning of the present invention the heavy cuts resulting from the distillation of petroleum, optionally containing additives.

Within the meaning of the present invention, the term "corrosion" means an alteration of a material, preferably metallic, by chemical reaction with an oxidant. Preferably, this oxidant is an acid. Preferably, this acid is sulfuric acid H ₂ SO ₄ .

Within the meaning of the present invention, "tribocorrosion" means a process leading to the degradation and wear of a metallic material under the combined action of friction and corrosion as defined above.

Advantageously, the compound of formula (A) defined in the present invention is used in a cylinder lubricating composition to reduce acid tribocorrosion on the cylinders and pistons of a two-stroke engine, such as a two-stroke marine engine. .

Even more advantageously, the compound of formula (B) defined in the present invention is used in a cylinder lubricating composition to reduce acid tribocorrosion on the cylinders and pistons of a two-stroke engine, such as a two-stroke marine engine. -time.

FIG. 1 represents the depth profiles of the cast iron plates obtained after a tribological test carried out in the presence of the lubricating composition according to the invention CL2 and of the comparative composition CC1.

The present invention will now be described using non-limiting examples.

Example 1: Lubricating compositions

The compositions in Table 2 (CL: lubricating composition according to the invention; CC: comparative lubricating composition) were prepared by mixing the dispersant and/or the detergents and the additive in a base oil at 60°C.

Lubricant composition Base oil(% by mass) Dispersant(% by mass) Phenate type detergent(% by mass) Sulphonate detergent(% by mass) Additive(% by mass) CL1 blend of two Group I base oils (75.3%) Polyisobutylene succinimide (1.1%) phenate having a BN of 250 (13.6%) sulphonate having a BN of 400 (5.3%) Compound of formula (I)(5%) CL2 blend of two Group I base oils (75.3%) Polyisobutylene succinimide (1.1%) phenate having a BN of 250 (13.6%) sulphonate having a BN of 400 (5.3%) Compound of formula (II) (5%) CC1 blend of two Group I base oils (79.2%) Polyisobutylene succinimide (1.2%) phenate having a BN of 250 (14.3%) sulphonate having a BN of 400 (5.3%) -

Table 2: Lubricating compositions according to the invention and comparative lubricating compositions

Example 2: Wear depth test results

The tribological tests were carried out on an alternative Biceri tribometer using steel rods (EN31) with a diameter of 6 mm and a radius of curvature of 50 mm, and cast iron plates (FT 25) polished with 800 grit sandpaper. SiC. The steel rods were also polished to obtain a roughness Ra between 50 and 100 nm. In addition, the areas of the cast iron plates outside the friction zone have been covered with a resin. This resin is removed at the end of the tests. In this way, the areas covered by the resin are not corroded during the tests and serve as a standard to measure the depth of the wear marks due to corrosion phenomena.

Before each test, the lubricating composition is heated to 100°C and brought into contact with a 5M sulfuric acid solution (27% by weight) at room temperature using a “T” assembly. The lubricating composition arrives through the main channel and the acid solution is fed through a channel perpendicular to the main channel.

The conditions for these tests are as follows:

- Temperature: 100°C

- Pressure: 0.67GPa

- Speed: 0.02m/s

- Trace length: 5 mm

- Duration: 6 hours.

At the end of each test, the corrosion products are eliminated with an ethylenediaminetetraacetic acid (EDTA) solution, and the wear of the cast iron plates is analyzed by white light interferometry, which makes it possible to obtain a 3D profile. the wear scar produced by corrosion and/or tribocorrosion.

These 3D profiles make it possible to obtain depth profiles of the wear scar. Figure 1 shows the depth profiles of the cast iron plates obtained after a tribological test as described above and conducted in the presence of the lubricating composition according to the invention CL2 and the comparative composition CC1.

The results of these tests show that in the absence of additive, the cast iron plate corrodes at the level of the zones which are not in contact with the steel rod (out-of-contact zones), and wear due to the Tribocorrosion is also observed at the area in contact with the rod. The presence of additives improves protection against corrosion and tribocorrosion. Indeed, without wishing to be bound by any theory, the additives make it possible to create a second layer of protection which is added to the neutralization of the acid drops by the detergent by forming a physical barrier between the surface of the metal part and the oil of the lubricating composition, which prevents corrosion phenomena.

The lubricating compositions according to the invention, and more particularly the compositions comprising the compounds of formula (I) or (II) (CL1 and CL2), make it possible to effectively protect the cast iron plate, both against corrosion (zones off-contact) and tribocorrosion (contact area).

Claims (10)

Lubricant composition comprising:
- at least one base oil; And
- from 0.1% to 30% by mass of a phosphorus ester compound of formula (A):

in which
s is 0 or 1; And
the radicals X represent, independently of each other, -OR' or R' groups, where R' represents a hydrogen or a linear or branched hydrocarbon group, preferably having from 1 to 36 carbon atoms, provided that:
when s is 0, the three X radicals represent -OR' groups and that,
when s is 1, at least two of the three X radicals represent —OR′ groups. A lubricating composition according to claim 1, comprising:
- at least one base oil; And
- from 0.1% to 30% by mass of a phosphorus ester compound of formula (B):

defined as:
- R ¹ and R ² , identical or different, independently represent an alkyl group, linear or branched, comprising from 1 to 36 carbon atoms, or R ¹ and R ² , identical or different, independently represent an alkenyl group, linear or branched , comprising from 2 to 36 carbon atoms; And
- R ³ represents a hydrogen or a hydroxyl group. Composition according to claim 1 or 2, further comprising at least one additive selected from detergents, dispersants and mixtures thereof. Composition according to Claim 3, in which:
- the amount of detergent varies from 3% to 40%, preferably from 5% to 30%, advantageously from 10% to 25% by mass, relative to the total mass of the lubricating composition; and or
- the amount of dispersant varies from 0.01% to 10%, preferably from 0.1% to 5%, advantageously from 0.5% to 3% by mass, relative to the total mass of the lubricating composition. A composition according to claim 3 or 4, wherein the detergents are calcium carbonate overbased detergents selected from carboxylates, phenates, sulfonates, salicylates and mixed phenate-sulfonate-salicylate detergents. Composition according to any one of the preceding claims, in which the compound of formula (A) or the compound of formula (B) corresponds to the compound of formula (I) defined by the following formula:
Composition according to any one of Claims 1 to 5, in which the compound of formula (A) or the compound of formula (B) corresponds to the compound of formula (II) defined by the following formula:
Use of a compound of formula (A) or of formula (B) as defined in claims 1, 2, 6 or 7 in a lubricating composition comprising at least one base oil for preventing and/or reducing corrosion and/ or the tribocorrosion of at least one metal part of an engine, in particular a two-stroke engine, for example a two-stroke marine engine. Use of the composition according to any one of Claims 1 to 7 for preventing and/or reducing corrosion and/or tribocorrosion of at least one metal part of an engine, in particular a two-stroke engine, for example a two-stroke marine engine. Process for passivating at least one metal part of an engine, in particular a two-stroke engine, for example a two-stroke marine engine, comprising at least one step of bringing said metal part into contact with a lubricating composition defined according to any of claims 1 to 7.