From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Chemical analysis and comparison of lubricating oils, focusing on sulphur and chlorine content and their corrosive properties.
| Identifier | ExFiles\Box 114\1\ scan0187 | |
| Date | 31th March 1939 guessed | |
| (2). thrown down by Hypoid oil, a moderate amount by GX, a small amount by Wakefield's oil, and none at all by T.E.X.. These deposits consisted mainly of tarry or carbonaceous matter, but that deposited by Hypoid oil contained lead and sulphur compounds. In this connection, it should be noted that the figures given under "corrosion tests" take into account any such deposits formed on the test specimens in addition to corrosion products, the latter however, were predominant. With regard to the substances added to the oils to induce extreme pressure properties, sulphur compounds were present in all four oils, comparatively large amounts of chlorine compounds were present in GX and Wakefield's oils, and small amounts in T.E.X. and Hypoid; the latter oil differed from the others inasmuch that it contained lead. In GX oil, the sulphur and chlorine existed in combination with each other as sulphur chloride. In Wakefield's oil, part of the sulphur was combined with all the chlorine as sulphur chloride, and the remainder existed in the free, or elementary condition, which is not surprising in view of the fact that sulphur chloride dissolves sulphur. With respect to the Hypoid oil, our tests shewed that the lead and a part of the sulphur were present as a lead sulphonate, the remaining sulphur probably existing in the free condition, or as one or more of the numerous sulphonic acid compounds, such as would be the case had the oil been "sulphonated". Our tests were not conclusive on this latter point, it being a matter of much time to isolate, purify, and identify small amounts of substances of this description. Similar remarks apply to the T.E.X. oil, in which our brief tests, although not conclusive, pointed to the presence of one or more of the thio ethers. Accordingly we considered it sufficient to estimate the total sulphur present. With regard to the suitability of these oils for use, it appears that apart from their lubricating properties, strict attention is needed with regard to corrosion and the ability of the oils when heated, to throw down deposits. We do not favour the presence of sulphur chloride in oils, because the chloride radical in this compound, has a strong tendency to form chlorides with metals, which are then converted into sulphides by the sulphur present, moreover, the presence of moisture will enhance the corrosion, by reason of the sulphurous and hydrochloric acids formed when sulphur chloride comes into contact with water. We would expect GX oil to be particularly bad in this respect and therefore cannot recommend it. Wakefield's Hi-press, containing nearly as much sulphur as GX, has the advantage that most of the sulphur exists in the free condition; free sulphur is not likely to cause more corrosion than harmless sulphide stains, on the other hand, the sulphur chloride, although present in small amounts, may give rise to corrosion troubles. | ||