CORROSION INHIBITION

Abstract

The present invention relates to a method of inhibiting corrosion experienced during use of a base oil or lubricant by the addition of a polyester corrosion inhibitor. More especially, the polyester corrosion inhibitor is the reaction product of an alk(en)yl substituted succinic anhydride wherein the average number of succinic groups per alk(en)yl group is less than 3.0, and at least one polyol. There is also provided a composition comprising such a polyester corrosion inhibitor and use of such a composition as a corrosion inhibitor, as well as a base oil or lubricant comprising such a polyester corrosion inhibitor.

Claims

1. A method of inhibiting corrosion by adding to a base oil or lubricant an effective amount of a polyester corrosion inhibitor obtained by reacting an alk(en)yl substituted succinic anhydride wherein the average number of succinic groups per alk(en)yl group is less than 3.0, with at least one polyol.

2. The method according to claim 1 wherein the effective amount of the polyester corrosion inhibitor is between 0.01 wt % and 1.0 wt % based on the total weight of the base oil or lubricant.

3. The method according to claim 1 wherein the average number of succinic groups per alk(en)yl group is less than 2.5.

4. The method according to claim 3 wherein the average number of succinic groups per alk(en)yl group is less than 2.0.

5. The method according to claim 1 wherein the alk(en)yl group is a polyolefin.

6. The method according to claim 5 wherein the alk(en)yl group is polyisobutylene.

7. The method according to claim 1 wherein the alk(en)yl group has an average molecular weight of 100 to 15,000.

8. The method according to claim 1 wherein the average number of succinic groups per alk(en)yl group is 2.5 to 30.

9. The method according to claim 8 wherein the average number of succinic groups per alk(en)yl group is 3 to 15.

10. The method according to claim 1 wherein the polyester has an average molecular weight Mn of 1,500 to 500,000 and/or an average molecular weight Mw of 3,000 to 1,000,000.

11. The method according to claim 1 wherein the polyester comprises the reaction residue of at least 2 alk(en)yl substituted succinic anhydride groups.

12. The method according to claim 1 wherein the polyester comprises the reaction residue of 2 to 30 polyol groups.

13. The method according to claim 1 wherein the polyol is sorbitol.

14. A composition comprising a polyester corrosion inhibitor as described in claim 1.

15. A composition according to claim 14 further comprising a diluent.

16. A base oil or lubricant composition comprising between 0.01 wt % and 1.0 wt % of a polyester corrosion inhibitor as described in claim 1 based on the total weight of the base oil or lubricant.

17. A corrosion inhibitor present in a base oil or lubricant wherein the corrosion inhibitor comprises a polyester obtained by reacting an alk(en)yl substituted succinic anhydride wherein the average number of succinic groups per alk(en)yl group is less than 3.0, with at least one polyol.

Description

EXAMPLES

[0043] The present invention will now be further explained with reference to the enclosed examples provided below and the Figures in which:

[0044] FIG. 1—test data for corrosion inhibitors in a Group I base oil

[0045] FIG. 2—test data for corrosion inhibitors in a Group II base oil

[0046] FIG. 3—test data for corrosion inhibitors in a Group III base oil

[0047] FIG. 4—test data for corrosion inhibitors in a Group IV base oil

[0048] FIG. 5—test data for corrosion inhibitors in a Group V environmentally acceptable base oil

[0049] FIG. 6—independent test house test data for corrosion inhibitors in a Group V environmentally acceptable base oil.

[0050] In the following Examples the standard test method ASTM D665B for corrosion inhibition of mineral oil in presence of synthetic seawater is used.

Example 1

[0051] Four base oils (one form each of Group I-IV) were selected for the testing as shown in Table 1, below.

TABLE-US-00001 TABLE 1 Base Oil Oil Group I ExxonMobil Americas Core 100 Group II ExxonMobil EHC45 Group III SK Lubricants YuBase 4 Group IV ExxonMobil PAO4

[0052] The corrosion inhibitors as detailed in Table 2 where the polyester is the reaction product of the alk(en)yl substituted succinic anhydride PIBSA with a varied carbon length polyol as indicated (C3, C5, or C6), were evaluated in each of the base oils detailed in Table 1, including a range of polyesters in accordance with the present invention and an imidazoline-based product used as an industry relevant reference.

TABLE-US-00002 TABLE 2 Corrosion Inhibitor Wt. % in Base Oil Imidazoline-based product 0.05 Polyester with C3 polyol 0.05 Polyester with C5 polyol 0.05 Polyester with C6 polyol 0.05

[0053] For each evaluation/test performed a mixture of 300 mL of base oil of interest with or without a corrosion inhibitor was stirred with 30 mL of synthetic seawater for 4 hours at 60° C. (in accordance with ASTM D665B). A cylindrical steel rod was fully submerged in the solution to be evaluated for the entire duration of the test and was then analysed for rust (corrosion) and degree of rusting.

[0054] After performance of the ASTM D665B procedure, the steel rods were rated for corrosion in comparison to the rod submerged in the base oil of interest with no corrosion inhibitor present. Results are ranked from 1 to 5, with 1 being the least corroded (best) and 5 being the most corroded (worst).

[0055] In the Group I base oil (Core 100), the imidazoline-based product exhibited the best corrosion inhibition, followed by the C5 polyol polyester corrosion inhibitor in accordance with the present invention. The results obtained are provided in FIG. 1.

[0056] In the Group II base oil (EHC45), the imidazoline-based product exhibited the best corrosion inhibition, followed by the C5 polyol polyester corrosion inhibitor in accordance with the present invention. The results obtained are provided in FIG. 2.

[0057] In the Group III base oil (YuBase 4), the imidazoline-based product exhibited the best corrosion inhibition, followed by the C6 polyol polyester corrosion inhibitor in accordance with the present invention. The results obtained are provided in FIG. 3.

[0058] In the Group IV base oil (PAO 4), the imidazoline-based product exhibited the best corrosion inhibition, followed by the C6 polyol polyester corrosion inhibitor in accordance with the present invention. The results obtained are provided in FIG. 4.

[0059] For all the tests within this example, the imidazoline-based corrosion inhibitor performed the best. However, this performance was closely followed by the polyester chemistries in accordance with the present invention (and particularly the polyol C5 and polyol C6 containing polyester corrosion inhibitors) which provided significant improvement in corrosion inhibition compared to the base oils that had no corrosion inhibitor added. The polyester corrosion inhibitors in accordance with the present invention provide an advantage over the commonly used imidazoline-based corrosion inhibitors, as they are less hazardous.

Example 2

[0060] The polyester corrosion inhibitors identified as C5 polyol and C6 polyol above were also evaluated/tested as corrosion inhibitors in a Group V environmentally acceptable base oil using the ASTM D665B procedure. In this case a blend of Priolube™ 1973 and Priolube™ 3987 (well-known industry accredited environmentally acceptable base oils) at a blend ratio of 1:1 was used as the base oil. The polyester corrosion inhibitors were added at a level of 0.05 wt. % and 0.10 wt. % in the base oil and compared to an imidazoline-based industry-relevant reference provided at a level of 0.05 wt. % in the oil. Results are ranked from 1 to 5, with 1 being the least corroded (best) and 5 being the most corroded (worst).

[0061] In this Group 5 base oil, the polyester corrosion inhibitor comprising the C6 polyol exhibited the best corrosion inhibition at both 0.05 wt. % and 0.10 wt. % inclusion in the oil and provided a better performance than the imidazoline-based reference. The results obtained are provided in FIG. 5. As such, the polyester corrosion inhibitors of the present invention may be particularly suited to use in Group V environmentally acceptable base oils.

Example 3

[0062] In addition to the tests performed above, an independent test house (SGS) was employed to verify the effect using the same ASTM D665B test method with Priolube™ 1973 being used as the Group 5 environmentally acceptable base oil. The polyester corrosion inhibitor comprising C6 polyol was tested as a corrosion inhibitor in the selected base oil at a level of 0.1 wt. % inclusion. An oleyl sarcosine industry benchmark comparative example (Crodasinic™ O) was also tested at a level of 0.1 wt. % inclusion in the base oil.

[0063] The polyester corrosion inhibitor of the present invention performs equivalently to the oleyl sarcosine industry benchmark as a corrosion inhibitor such that no corrosion was evident on the steel rods at the end of the test. The polyester corrosion inhibitor of the present invention, however, is less hazardous and less toxic than oleyl sarcosine which brings an added advantage to its use.