Which of the following is used as a lubricant?
- A. Graphite
- B. Silica
- C. Iron Oxide
- D. Diamond
Graphite is best suited for lubrication in air. Water vapor is a necessary component for graphite lubrication. The adsorption of water reduces the bonding energy between the hexagonal planes of the graphite to a lower level than the adhesion energy between a substrate and the graphite.