LUBRICANT COMPOSITION FOR PREVENTING CORROSION AND/OR TRIBOCORROSION OF METALPARTS IN AN ENGINE

Abstract

A lubricant composition comprising: at least one base oil; and from 0.1% to 30% by weight of a phosphorus ester compound of formula (A):

##STR00001## in which s is 0 or 1; and the radicals X represent, independently of each other, —OR′ or R′ moieties, where R′ represents hydrogen or a linear or branched hydrocarbon moiety, preferably having from 1 to 36 carbon atoms, with the proviso that: when s is 0, the three X radicals represent —OR′ moieties, and when s is 1, at least two of the three X radicals are —OR′ moieties.

Claims

1. A lubricant composition comprising: at least one base oil; and from 0.1% to 30% by weight of a phosphorus ester compound of formula (A): ##STR00008## in which s is 0 or 1; and the radicals X represent, independently of each other, —OR′ or R′ moieties, where R′ represents hydrogen or a linear or branched hydrocarbon moiety, with the proviso that: when s is 0, the three X radicals represent —OR′ moieties, and when s is 1, at least two of the three X radicals are —OR′ moieties.

2. The lubricant composition according to claim 1, wherein the compound of formula (A) is a compound of formula (B): ##STR00009## defined as: R.sup.1 and R.sup.2, which may be the same or different, independently represent a linear or branched alkyl moiety comprising from 1 to 36 carbon atoms, or R.sup.1 and R.sup.2, which may be the same or different, independently represent a linear or branched alkenyl moiety comprising from 2 to 36 carbon atoms; and R.sup.3 represents hydrogen or a hydroxyl moiety.

3. The composition according to claim 1, further comprising at least one additive selected from detergents, dispersants and mixtures thereof.

4. The composition according to claim 3, wherein: the amount of detergent varies from 3% to 40% by weight, based on the total weight of the lubricant composition; and/or the amount of dispersant varies from 0.01% to 10% by weight, based on the total weight of the lubricant composition.

5. The composition according to claim 3, wherein the detergents are calcium carbonate overbased detergents selected from carboxylates, phenates, sulphonates, salicylates and mixed phenate-sulphonate-salicylate detergents.

6. The composition according to claim 1, wherein the compound of formula (A) corresponds to the compound of formula (I) defined by the following formula: ##STR00010##

7. The composition according to claim 1, wherein the compound of formula (A) corresponds to the compound of formula (II) defined by the following formula: ##STR00011##

8. Method for preventing and/or reducing corrosion and/or tribocorrosion of at least one metal part of an engine, comprising the addition in a lubricating composition comprising at least one base oil of a compound of formula (A) as defined in claim 1.

9. Method of preventing and/or reducing corrosion and/or tribocorrosion of at least one metal part of an engine, comprising lubricating said metal part with a lubricating composition according to claim 1.

10. A method of passivating at least one metal part of an engine, comprising at least one step of bringing said metal part into contact with a lubricating composition defined according to claim 1.

Description

BRIEF DESCRIPTION OF DRAWING

[0138] FIG. 1 shows the depth profiles of cast-iron plates obtained after a tribological test conducted in the presence of the lubricant composition according to the invention CL2 and the comparative composition CC1.

DETAILED DESCRIPTION

[0139] The present invention will now be described with the help of non-limiting examples.

Example 1: Lubricant Compositions

[0140] The compositions in Table 2 (CL: lubricant composition according to the invention; CC: comparative lubricant composition) were prepared by mixing the dispersant and/or detergents and the additive in a base oil at 60° C.

TABLE-US-00002 TABLE 2 Table 2: Lubricant compositions according to the invention and comparative lubricant compositions Phenate Sulphonate Base oil Dispersant detergent detergent Additive Lubricating (% by (% by (% by (% by (% by composition weight) weight) weight) weight) weight) CL1 mixture of Polyisobutylene phenate sulphonate Compound two group I succinimide with a BN with a of base oils (1.1%) of 250 BN of 400 formula (I) (75.3%) (13.6%) (5.3%) (5%) CL2 mixture of Polyisobutylene phenate sulphonate Compound two group I succinimide with a BN with a of base oils (1.1%) of 250 BN of 400 formula (II) (75.3%) (13.6%) (5.3%) (5%) CC1 mixture of Polyisobutylene phenate sulphonate — two group I succinimide with a BN with a base oils (1.2%) of 250 BN of 400 (79.2%) (14.3%) (5.3%)

Example 2: Wear Depth Test Results

[0141] 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 platens (FT 25) polished with 800 grit SiC sandpaper. The steel rods were also polished to a roughness Ra of between 50 and 100 nm. In addition, the areas of the cast-iron plates outside the friction zone have been coated with a resin. This resin is removed at the end of the tests. In this way, the resin-coated areas are not corroded during testing and serve as a standard for measuring the depth of wear marks due to corrosion phenomena.

[0142] Prior to each test, the lubricant composition was heated to 100° C. and brought into contact with a 5 M sulphuric acid solution (27% by weight) at room temperature using a “T” arrangement. The lubricant composition is fed through the main channel and the acid solution is fed through a channel perpendicular to the main channel.

[0143] The conditions for these tests are as follows: [0144] Temperature: 100° C. [0145] Pressure: 0.67 GPa [0146] Speed: 0.02 m/s [0147] Trace length: 5 mm [0148] Duration: 6 hrs.

[0149] At the end of each test, the corrosion products are removed with anethylenediaminetetraacetic acid (EDTA) solution, and the wear of the cast iron plates is analysed by white light interferometry, which allows a 3D profile of the wear scar produced by corrosion and/or tribocorrosion to be obtained.

[0150] These 3D profiles provide depth profiles of the wear scar. FIG. 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 lubricant composition according to the invention CL2 and the comparative composition 001.

[0151] The results of these tests show that in the absence of an additive, the cast-iron plate corrodes in the areas not in contact with the steel rod (non-contact areas), and tribocorrosion wear is also observed in the area in contact with the rod. The presence of additives improves the 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 neutralisation of the acid drops by the detergent by forming a physical barrier between the surface of the metal part and the oil of the lubricant composition, which prevents corrosion phenomena.

[0152] The lubricant 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 protect the cast-iron plate effectively against both corrosion (non-contact zones) and tribocorrosion (contact zone).