Due to increased demands on lubricants, there is a need to develop new lubricants and improved additives. Ionic liquids (ILs) are room temperature molten salts that have recently shown many advantages in this area. The application of ILs as lubricants in a diverse range of systems has found that these materials can show remarkable protection against wear and reduction of friction. ILs consists of large asymmetrical ions that can readily adsorb onto a metal surface and produce a protective film under boundary lubrication conditions. This article starts with a brief introduction to ILs and fluid lubrication, and then discusses in more detail the tribological properties of IL lubricants, either as base and synthetic oil additives. In this article the correlation between the IL structure and their performance in tribology applications is examined. Finally, some current problems and potential solutions are discussed.
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