US2218918A - Lubricating oil - Google Patents

Description

Reece it i Shoemaker, Hammond, Ind., assignors to Stand- -t ard Oil Company, Chicago, Ill, a corporation of 1 Indiana No Drawing.

Application August 31, 1935, Serial No. 98,734

7' Claims. (01. 252-41) This invention relates to improvements in lubricating oils, and particularly, to corrosion inhibited lubricating oils.

In order to obtain increased acceleration and ii increased speed in present day internal combustion engines it has become necessary to increase both the thermal and mechanical stresses 18 metal bearings, suchas copper-lead, cadmiumnickel and cadmium silver bearings have, to a large extent, replaced Babbitt metal bearings.

While mechanically the new type of metal bearings has proven satisfactory, there have been 20 an unusually large number of bearing failures due to corrosion. It has also been noted that the corrosion of hard metal alloy bearings has been more markedwith highly refined lubricatingoils. i 26 By highly refined lubricating oils we mean oils which have been subjected to such a refining process, for example, solvent extraction, that the paraffinicity of the .oil is markedly increased.

It has been found that highly refined lubri- 30 eating oils cause corrosion of cadmium-silvervalloy bearings to the extend of 5 mgs. per cm. and even greater when bearing-s'are submerged for 25 hours or less in an airagitated oil which has been preoxidized at about 340 -F. for 25 to 50 I, hours.

These highly refined lubricating oils have a minimum viscosity range of a5. A. E. 10 oil. Our

invention contemplates the use of highly" re--' fined lubricating oils per se or mixtures of high- 40 1y refined lubricating oils, or mixtures of-corrosi ve oils and non-corrosive oils, such as a corrosive oil andlubricating oil fractions from-.Winkler Crude or crudes of the Winkler type.

It is, therefore, an object of our invention to provide a highly refined motor oil which will not corrode bearings of the cadmium-silver and copper-lead type. Another object of our invention is to provide a corrosion inhibitor, which, when added to a highly refined lubricating oil, will prevent the corrosion.- of hard metal bearings suchas 'copper-lead and/or cadmium-silver metal bearings and which will not be detrimental to other desir-- able properties of the motor oil.

A further object of our invention is to provide dodecyl thiocyanate predominates.

a motor oil containing a very small amount of an organic material which will inhibit the'cor rosion of bearings in internal combustion en gines., g Wehave found that the foregoing objects may ,8 be attained by adding toa highly refined motor 011 up to 1%, but preferably 0.01% to 0.75% of certain organic materials, particularly, long straight chain alkyl thiocyanates and/or long straight chain allgvl isothiocyanates having the 10 general formula RSCN or RNC S where R is an alkyl group. Our invention contemplates the use of alkyl thiocyanates having 8 to 14 carbon atoms and preferably the alkyl thiocyanates having 12 carbonatoms in the alkyl radical, or a mixture 15 of alkyl thiocyanates such as dodecyl, octyl, decyl and tetradecyl thiocyanates, but in which the Our invention also contemplates the use of alkyl isothiocyanates having 8 to 14 carbon atoms in the alkyl go radical and preferably'the alkyl isothiocyanates having 12' carbon atoms in the alkyl radical, or a mixture of alkyl isothiocyanates such as dodecyl, octyl, decyl and tetradecyl isothiocyanates, .but in which the dodecyl isothiocyanate 25 predominates.

We have found that a very effective corrosion inhibitor is obtained when dodecyl thiocyanate or a mixture of allsvl thiocyanates, in which the dodecyl thiocyanate predominates besides small 30 amounts of octyl, decyl, and tetradecyl thiocyanates, is heated in a sealed tube at a tempera;- ture of about 350 F. for about three days. The resultant product may be used as such or fractions thereof may be employed. The product 35 may be vacuum distilled under about 1 pressure and the first ninety percent over used as the corrosion inhibitor or we may extract the product with hot alcohol at about -180 F. and the alcohol insoluble portion used, although 4 the alcohol soluble portion may also be used as corrosion inhibitor. Other-solvents, particularly very-low boiling hydrocarbons such as propane may be used. g

We believe that by heating the thiocyanates in 45 the above manner, the same are converted to a substantial degree to the isothiocyanates. However, other products may be formed in the'heat-.

mentioned compounds as corrosion inhibitors in motor oils we have tested the same in a highly refined motor oil under severe engine operating agitating the same at about 341 F. The corrosion inhibitor and the weighed bearings are placed in the preoxidized oil and the oil air-agi-- tated at about 341 F. The bearings are removed at periodic intervals, washed free of oil and the loss in weight determined.

Test 2.-In this test the weighed bearings are placed in a highly refined oil containing the inhibitor and is air agitated at about 341 F. At periodic intervals the bearings are removed from the oil bath, washed free of oil and the loss in weight determined. Each time before being replaced in the oil bath the bearings are polished bright and reweighed and again tested for predetermined periods. This test differs from test No. 1 in that the test is started with an unoxidized highly refined oil and the test bearings are polished at predetermined intervals.

Test 3'.In this test the oil containing the corrosion inhibitor is tested in a six cylinder internal combustion engine operating under severe conditions of 2500 R. P. M. at 25 B. H. P. output with a water outlet temperature of about F. and

an oil sump temperature of about 320 F. The length of operation before bearing failure is a measure of the effectiveness of the corrosion inhibitor.

In each of the above tests the oil used was a motor oil refined to such an extent that a loss in weight of more than 5 mg. per cm. is obtained in 25 hours or less on a cadmium-silver alloy bearing submerged in an air agitated oil at 340 R, which oil has been preoxidized for 25-50 hours at about 340 F.

Table I shows the effectiveness of 0.2% of lauryl thiocyanate in a highly refined motor oil as evaluated by Test 1 described above.

Table I Hours of test Loss in mga [cm 1 Control (preoxidized 50 hrs.) 6. 0 41. Control+0.2%lauryl thiocyanate. 0. 0 0.0 0. 9 5. 7

In Table II are tabulated the results obtained with lauryl thiocyanate and lauryl isothiocyanate as evaluated by Test 1 with a 25 hour preoxidi'zed oil.

The above results demonstrate the efiectiveness of the alkyl thiocyanates and alkyl isothiocyanates of the, hereinbefore mentioned type in preventing the corrosion of cadmium-silver bearings.

Test 1.-.In this test a highly refined 011, to which the corrosion inhibitor is tobeadded, is preoxidized for either 25 hours or 50 hours by air In Table III we have tabulated results obtained by test method No- 2 described above.

In the engine tests described above as Test No. 3 the efiectiveness of the corrosion inhibitors in an oil has been tested in a six cylinder engine operating at 2500 R. P. M. with a 25 B. H. P. output and a water outlet temperature of about 180 F. The oil sump was maintained at a temperature of about 320 F. Using a highly refined S- A. E. 20 oil containing 0.5% of lauryl thiocyanate the bearing failed in 19 hours. With 0.5% of lauryl isothiocyanate in a sample of the same oil the engine ran for 35 hours without bearing failure. With a sample of the same oil containing no corrosion inhibitor the bearings failed in 12 hours. It should be observed that the above operating conditions are much more severe than those encountered under average actual driving conditions. Under average driving conditions the bearings would last much longer.

While we have illustrated our invention in connection with the foregoing examples, we do not wish to limit our invention to the same. These examples are merely illustrative and not a limitation upon the scope of our invention.

Where used hereinbefore and in the appended claims, the term lauryl thiocyanate is used to define an alkyl thiocyanate having 8 to 14 carbon atoms in the alkyl chain but predominantly a dodecyl thiocyanate with small amounts of octyl, decyl, and tetra decyl thiocyanate. The term lauryl isothiocyanate as used hereinbefore and in the appended claims is used to define the isothiocyanate of the above compounds.

We claim:

1. The method of preventing the corrosion of bearing metal alloys selected from the group consisting of cadmium-silver, cadmium-nickel and copper-lead alloys in the presence of a highly refined lubricating oil normally corrosive to said metal alloys in internal combustion engines which comprises adding to said lubricating oil a substantial amount but not more than 1% of an alkyl thiocyanate' having 8 to 14 carbon atoms in the alkyl radical.

2. The method of preventing the corrosion of bearing metal alloys having the corrosive susceptibility of alloys of the class consisting of cadmium-silver, cadmium-nickel and copper-lead alloys in the presence of a highly refined l'ubrlcating oil normally corrosive to said bearing metal alloys in internal combustion engines which comprises adding to said lubricating oil from about 0.01% to about 1% of an alkyl isothiocyanate having 8 to 14 carbon atoms in the alkyl radical, whereby said highly refined lubricating oil is rendered non-corrosive to said bearing metal alloys. 1

3. The. method of preventing the corrosion of bearing metal alloys having the corrosive susceptibility of alloys of the class consisting ofcadmium-silver, cadmium-nickel and copperlead alloys in the presence of a. highly refined tibility of alloys of the classconsisting or cadmium-silver, cadmium-nickel and copper-lead alloys in' the presence 01' a highly refined lubricating oil normally corrosive to said bearing metal alloys in internal combustion engines which comprises adding to saidlubricating oil from about 0.01% to 1%of a mixture of alkyl isothiocyanates having more than seven carbonatoms in each alkyl radical, said mixture of alkyl isothiocyanates comprising predominantly dodecyl isothiocyanates and small amounts of octyl, decyl, and tetradecyl isothiocyanates, whereby said highly refined lubricating oil is made non-- corrosive to said bearing metal alloys.

5. The method of preventing the corrosion ofbearing metal alloys having the corrosive susceptibility of alloys of the class consisting of cadmium-silver, cadmium-nickel and copperlead alloys in the presence of a highly refined o isothiocyanate having 8 to 14 carbon atoms inlubricating oil normally corrosive to said bearing= metal alloys in internal combustion engines which comprises adding to said lubricating oil a sub-. stantial amount but not more than about 1% of an organic compound selected from the group consisting of an alkyl 'thiocyanate having 8 to 14 carbon atoms in the alkyl radical and an alkyl the alkyl radical'whereby corrosion of said bearinhibited.

7; A method of lubricating bearing surfaces" ing metal alloys by said highly refined lubricating oil is inhibited.

6. The method of preventing the corrosion of bearing metal alloys having the corrosive sus; ceptibility of alloys of the class consisting of cadmium-silver, cadmium-nickel and copper-lead alloys in the presence of a highly refined lubricating oil normally corrosive to said bearing metal alloys in internal combustion engines which comprises adding to said lubricating oil from about 0.01% to 1% of an organic compound selected from the group consisting of a mixture of alkyl thiocyanates having more than seven carbon atoms in each alkyl radical, said mixture of alkyl thiocyanates comprising predominately dodecyl thiocyanates and small amounts of octyl, decyl and tetradecyl thiocyanates, and a mixture of alkyl isothiocyanates having more than seven carbon atoms in each alkyl' radical, said mixture of alkyl isothiocyanates comprising predominately dodecyl isothiocyanates and small amounts of octyl, decyl and tetradecyl isothioalloys by said highly refined lubricating'oil is which comprises maintaining between metallic bearing surfaces, one of which is an'all'oy containing a characterizing proportion of a,metal selected from cadmium-silver, copper,-lead and nickel, a film of lubricating oil normally eifectiive to provide lubrication of the bearing surfaces but whichswould normally tend to corrode the surface of the aforesaid alloy, said lubricating oil having incorporated therein dodecyl isothiocyanate, in small amount suflicient substantially to retard corrosion of the surfaces of said alloys by said oils.

CLARENCE M. LOANE.

BERNARD H. SHOEMAKER.

' cyanates whereby corrosion to said bearing metal