LUBRICANT COMPOSITION FOR PREVENTING CORROSION AND/OR TRIBO-CORROSION OF METAL PARTS IN AN ENGINE

Abstract

Lubricant composition comprising:

at least one base oil; and

0.1 to 30% by weight of an imidazoline compound of formula (A):

##STR00001##

defined such that:

R.sup.1 represents a linear or branched alkyl or alkenyl group comprising 1 to 16 carbon atoms, optionally substituted at the end of the chain by a group selected from among NH.sub.2, OH or SH; and

R.sup.2 represents a linear or branched alkyl or alkenyl group comprising 1 to 36 carbon atoms.

Claims

1. A lubricant composition comprising: at least one base oil; and 0.1 to 30% by weight of an imidazoline compound of formula (A): ##STR00004## defined such that: R.sup.1 represents a linear or branched alkyl group comprising 1 to 16 carbon atoms, optionally substituted at the end of the chain by a group selected from among NH.sub.2 or SH, or R.sup.1 represents a linear or branched alkenyl group comprising 2 to 16 carbon atoms, optionally substituted at the end of the chain by a group selected from among NH.sub.2 or SH; and R.sup.2 represents a linear or branched alkyl group comprising 1 to 36 carbon atoms, or R.sup.2 represents a linear or branched alkenyl group comprising 2 to 36 carbon atoms.

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

3. The composition according to claim 2, wherein: the amount of detergent varies from 3 to 40%; by weight, relative to the total weight of the lubricant composition; and/or the amount of dispersant varies from 0.01% to 10%, by weight, relative to the total weight of the lubricant composition.

4. The composition according to claim 2, wherein the dispersants are selected from among succinimides.

5. The composition according claim 2, wherein the detergents are calcium carbonate overbased detergents chosen in the group consisting of carboxylates, phenates, sulfonates, salicylates, and mixed phenate-sulfonate-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: ##STR00005##

7. 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.

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

9. The method according to claim 8 wherein the metal part is a cylinder.

10. A method for passivating at least one metal part of an engine, comprising at least one step to place said metal part in contact with a lubricant composition defined according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0113] FIG. 1 illustrates the depth profiles of cast iron plates obtained after a tribological test conducted in the presence of the composition of the invention CL and a comparative composition CC.

DETAILED DESCRIPTION

[0114] The present invention will now be described with the support of nonlimiting examples.

Example 1: Lubricant Compositions

[0115] The compositions in Table 2 (CL: lubricant composition of 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 Lubricant composition of the invention and comparative lubricant composition. Detergent Lubri- Detergent of cant of phenate sulfonate compo- Base oil Dispersant type type Additive sition (wt. %) (wt. %) (wt. %) (wt. %) (wt. %) CL Mixture of Polyisobutylene Phenate Sulfonate Formula two Group succinimide having a having a (I) 1 base oils (1.1%) BN of 250 BN of 400 compound (75.3%) (13.6%) (5%) (5%) CC Mixture of Polyisobutylene Phenate Sulfonate — two Group succinimide having a having a 1 base oils (1.2%) BN of 250 BN of 400 (79.2%) (14.3%) (5.3%)

Example 2: Results of Wear Depth Tests

[0116] Tribological tests were conducted on a reciprocating Biceri tribometer using steel pins (EN31) 6 mm in diameter with a radius of curvature of 50 mm, and cast iron plates (FT 25) polished with SiC grinding paper, Grit 800. The steel pins were also polished to obtain roughness Ra of between 50 and 100 nm. In addition, the zones of the cast iron plates outside the friction zone were coated with a resin. This resin was removed after the tests. The zones coated with resin were therefore not corroded during the tests and could be used as calibration to measure the depth of the wear marks due to corrosion phenomena.

[0117] Before each test, the lubricant composition was heated to 100° C. and placed in contact with 5 M sulfuric acid solution (27 weight %) at ambient temperature by means of a «T» assembly. The lubricant composition was conveyed via the main channel and the acid solution fed by a channel perpendicular to the main channel.

[0118] The conditions for these tests were as follows: [0119] Temperature: 100° C. [0120] Pressure: 0.67 GPa [0121] Speed: 0.02 m/s [0122] Track length: 5 mm [0123] Duration: 6 h.

[0124] At the end of each test, the corrosion products were removed with a solution of ethylenediaminetetraacetic acid (EDTA), and wear of the cast iron plates was analyzed by white light interferometry, allowing a 3D profile to be obtained of the wear mark produced by corrosion and/or tribocorrosion.

[0125] These 3D profiles allow depth profiles to be obtained of the wear mark. FIG. 1 shows the depth profiles of the cast iron plates obtained after a tribological test such as described above and conducted in the presence of the lubricant composition of the invention CL, and the comparative composition CC.

[0126] The results of these tests show that in the absence of the formula (I) compound, the cast iron plate is corroded at the zones which are not in contact with the steel pin (contact-free zones) and wear due to tribocorrosion can also be seen at the zone in contact with the pin. The presence of the formula (I) compound improves protection against corrosion and tribocorrosion. Without wishing to be bound by any theory, the additives allow a second protection layer to be created, adding to neutralization of acid drops by the detergent, by forming a physical barrier between the surface of the metal part and the oil of the lubricant composition, thereby preventing corrosion phenomena.