Silver-organic oil additive for high-temperature applications

Modern lubricants face the task of providing lubrication over a wide range of temperatures, and extreme engine temperatures can exceed the thermal degradation limits of many engine oils. Soft metal additives can extend the life of engine oils at very high temperatures by providing solid lubrication to contacting surfaces. We report a new silver–organic complex which contains a high metal content and minimal supporting organic ligands. This silver pyrazole–pyridine complex is evaluated as a friction-reducing and anti-wear additive in engine oil at testing temperatures which thermally degrade the base oil. Two sets of ball-on-disk tests are performed: the first at a constant temperature of 200 °C and the second while increasing the chamber temperature from 180 to 330 °C. At 200 °C, the wear is considerably reduced compared with the base oil when the silver-organic additive is present at 2.5–5.0 wt%. Furthermore, the silver-based additive at 20 wt% in oil induces a remarkable friction reduction during the temperature ramp test, so much, so that the tribological transition from the oil as the primary lubricant to its degradation, and to the silver additive as the primary lubricant, is imperceptible.