EP additives with a total sulfur content of approx. 15% are often used for forming processes. This class of additives was therefore studied very carefully.
The results for four commercially available products are presented below as an example:
- SC 1 geschwefelter Ester / Olefin
- SC 2 Polysulfid / Ester , 15% Gesamtschwefel
- SC 3 konventionell geschwefeltes Lardöl, 15% S
- SC 4 Additin RC 2515
Reference paraffinic basic oil, ISO VG 220
Although these additives are similar according to the information in the data sheet, the tests revealed significant differences: Fig. 1 shows the press-in force as a function of the press-in path. Fig. 2 describes the relative surface wear.
SC 1 showed the highest frictional forces and 80% surface wear/cold welding. Low viscosity and high active sulfur content resulted in poorly developed film-forming properties and therefore poor lubricant film formation on the metal surface.
SC 2 demonstrated poorer antifriction values than the base oil. The polysulfide content was responsible for the high frictional forces: polysulfide molecules contain a high proportion of active sulfur. This active sulfur is responsible for the increased friction in lubricant systems.
SC 3 is a conventional additive with moderate anti-friction performance.
SC 4 Additin RC 2515 shows the lowest surface wear and the lowest frictional force of all the oils tested. Its excellent adsorptive properties gives it high affinity to the metal surface, providing excellent protection against adhesive wear.
Reference paraffinic basic oil, ISO VG 220
