A Kinetic Study of the Reaction of Labeled Sulfur Compounds in Binary Additive Systems During Boundary Lubrication

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Abstract
A kinetic investigation of the reaction of steel surfaces and labeled sulfur compounds under boundary lubrication with line contact was carried out. The active sulfur compound was examined with an accompanying compound, such as a sulfur or chlorine compound, in a binary additive system in cetane solution. In the friction tests for the solutions containing two kinds of sulfur compounds, elementary sulfur showed the highest reactivity among the sulfur compounds used, didodecyl disulfide the lowest. Dibenzyl disulfide reduced the wear rate of the frictional surface, although it produced no disturbance of the reaction between the frictional surface and elementary sulfur, which is simultaneously used in the sample solution. It was suggested that a dynamic model rather than a static model be considered for the lubricant film functioning under boundary lubrication, and also that any deficiency of an additive could be made up by addition of the second compound used simultaneously in oil. In the friction tests using a mixture of chlorine compound and sulfur compound, it was found that the reaction of sulfur compounds with iron surface was suppressed by the addition of chlorine compound. This suppression depends on the surface activity of the sulfur compound.