“…Several papers report on comparisons of the tribological efficiency of organosulfur additives as a function of number of sulfur atoms, alkyl-or aryl-chains [1]. In tribotests, involving ferrous materials and S-containing additives, the formation of the FeS x compound has been detected in superficial layers by different surface analysis techniques [2,3]. FeS, also known as troilite, has a layered hexagonal structure, low shear strength and high melting point (1100°C), so it is an effective solid lubricant like graphite and MoS 2 [4].…”