Oil-Soluble Sulfur-Containing Organic Molybdenum as Lubricant Additives: A Review

Abstract In situ formation of MoS2 from oil-soluble sulfur-containing organic molybdenum (SOM) additives in lubricating oils is an alternative route of adding MoS2 into oils directly, which is difficult to disperse homogeneously. In this advanced technology, the structures of SOM and the formation of MoS2 during friction determine the efficiencies of SOM additives on the tribological properties of oils. Given the fact that SOM additives have been used intensively in both laboratory researches and industrial applications, this review discusses their molecular structures, tribological behaviors, compatibility with the other additives, and some bottlenecks in practical applications. Moreover, some routes for overcoming the bottlenecks are suggested. This review also concludes the basic lubrication mechanisms of SOM additives and provides some suggestions for utilizing SOM in advanced lubrication systems. Finally, the future development of SOM as oil additives is proposed and summarized.