Surface analytical science and automotive lubrication

This paper discusses the role surface analytical science has played in understanding the complex phenomena occurring during lubrication of modern internal combustion engines. The interactions between the multi-functional lubricant additives and the various metallic surfaces present in the tribological contacts are complex and lead to the formation of inhomogenous multi-layer protective surface films. Surface analysis by ultra-high vacuum (UHV) techniques such as x-ray photoelectron spectroscopy, Auger electron spectroscopy and secondary ion mass spectrometry has allowed model structures for these films to be derived through which the behaviour of the contact can be understood. Non-UHV probes have elucidated the role played by the soluble, partly reacted or degraded film precursors that occupy the interfacial region between the solid surface and the liquid lubricant, and have allowed the mechanical properties of the films to be investigated on a micro- and nano-scale. The use of surface analytical techniques to study interactions between lubricant species and combustion soot is also discussed.