For years antiwear additives for high-performance oils have been phosphorous compounds, particularly zinc dialkyldithiophosphate (ZDDP), that work by forming a polyphosphate film on engine parts that reduces wear. Unfortunately phosphorus is a chemical poison for automobile catalytic converters, reducing their effectiveness and life span, so industry chemists have been searching for ways to replace or reduce the use of ZDDP. It’s not a simple problem because the additive has several useful functions in addition to wear resistance.
Titanium, a protean element with applications from pigments to aerospace alloys, could step into the role of environmentally friendly additive for automotive oil, thanks to work by materials scientists from Afton Chemical Corporation (Richmond, Va.) and the National Institute of Standards and Technology (NIST).
In a recent paper, the researchers established that a titanium compound added to engine oil creates a wear-resistant nanoscale layer bound to the surface of vulnerable engine parts, making it a credible substitute for older compounds that do not coexist well with antipollution equipment.