Use of a boron-containing additive as an inhibitor of lead corrosion

1. A method of improving anti-corrosion properties of a non-aqueous lubricant composition comprising admixing (a) the non-aqueous lubricant composition comprising an ashless, organic ester, anti-wear additive and/or friction modifier with (b) a boron-containing additive in an amount so that the total boron content of the non-aqueous lubricant composition is at least 250 ppm by weight, wherein the boron-containing additive reduces corrosion as measured by High temperature Corrosion Bench Tests (HTCBT) according to ASTM D6594.

2. The method of claim 1 , wherein the non-aqueous lubricant composition is used to lubricate an internal combustion engine.

3. The method of claim 2 , wherein an ashless, organic ester, anti-wear additive and/or friction modifier is provided in a liquid fuel composition used to operate the internal combustion engine, and a portion of said ashless, organic ester, anti-wear and/or friction modifier ingresses into the non-aqueous lubricant composition during operation of said engine.

4. The method of claim 1 , wherein the boron-containing additive is a borated dispersant.

5. The method of claim 4 . wherein the borated dispersant is a borated ester.

6. The method of claim 5 , wherein the borated ester is a borated succinate ester or a borated succinate ester amide.

7. The method of claim 1 wherein the ashless, organic ester, anti- wear additive and/or friction modifier is

i) at least one fatty acid ester of a polyol,

ii) at least one oil-soluble mono, di-, or tri-glyceride of at least one hydroxy polycarboxylic acid;

iii) at least one long chain fatty acid ester of a hydroxy carboxylic acid in which the long chain fatty acid has at least 4 carbon atoms and the ester is an oil-soluble ester of a mono- or poly- hydroxy carboxylic acid containing 1 to 4 groups which are independently carboxylic acid groups or lower hydrocarbyl esters thereof and in which, when the hydroxy carboxylic acid is a mono-hydroxy carboxylic acid, the ester has a long chain fatty acid ester moiety of the hydroxy group of the hydroxy carboxylic acid and, when the hydroxy carboxylic acid is a poly-hydroxy carboxylic acid, the ester has independently long chain fatty acid ester moieties of one or two of the hydroxy groups of the poly-hydroxy carboxylic acid; or

iv) a mixture thereof.

8. The method of claim 7 , wherein the at least one fatty acid ester of a polyol is an ester of a fatty acid containing 12 to 24 carbon atoms.

9. The method of claim 7 , wherein the hydroxy polycarboxylic acid. has at least one hydroxy group which is in an alpha position with respect to a carboxylic moiety.

10. The method of claim 9 , wherein the hydroxy polycarboxylic acid is citric acid.

11. The method of claim 7 , wherein the glyceride is a glyceride of citric acid and oleic acid, a glyceride of citric acid and linoleic acid or a mixture thereof.

12. The method of claim 7 , wherein the oil-soluble ester has at least one long chain fatty acid ester moiety in an alpha position with respect to a carboxylic acid group or lower hydrocarbyl ester thereof.

13. The method of claim 7 , wherein the oil-soluble ester is triethyl citrate butyrate, triethyl citrate oleate, triethyl citrate octanoate, triethyl citrate myristate, diethyl tartrate dibutyrate or diethyl tartrate dioleate.

14. The method of claim 1 , wherein the method inhibits lead corrosion associated with the ashless, organic ester, anti-wear additive and/or friction modifier.

15. The method of claim 1 , wherein the amount of boron-containing additive is selected so that the total boron content of the non-aqueous lubricant composition is at least 280 ppm by weight.

16. The method of claim 1 , wherein the boron-containing additive reduces corrosion as measured by Sequence VIII corrosion tests according to ASTM D6709-13.

17. The method of claim 1 , wherein the total lead content is no more than 120 ppm after High temperature Corrosion Bench Tests (HTCBT) according to ASTM D6594.

18. The method of claim 1 , wherein the amount of boron-containing additive is selected so that the total boron content of the non-aqueous lubricant composition is at least 300 ppm by weight.