Graphite is a form of carbon and is silvery black in colour. The lamellar structure of graphite, which is in the form of dry powder, makes it ideal to reduce friction. Graphite can also serve as a liquid based lubricant.
The liquid carbon graphite lubricants are of different types. The graphite grease is designed to stick to the surface, where the grease will prevent the graphite from falling off the work surface. Another combination with liquid base is such that the liquid will evaporate when the mixture is painted on the surface, leaving the graphite to work to reduce friction.
Graphite may be used as an additive in lubricating oil to increase the thermal tolerance. They are also used as components of polymer based composite anti-friction coatings and form the second phase particles of metal based composite anti-friction coatings. They are used as molds for continuous casting and solid lubricant in metal forming.
Graphite lubricant is also used in continuous casting molds. The molds are fabricated from iso-statically pressed graphite. The low friction between the mold surface and solidifying metal ensures smooth extraction of the casting. The crystal structure of graphite provides low friction without the requirement of additional lubrication.
Graphite is characterized as natural and synthetic. Natural graphite is derived from mining. The refined graphite contains carbon, sulfur, SiO2 and Ash. The crystallizing quality of graphite is determined by the higher content of carbon, and better the lubricity and resistance to oxidation. Synthetic graphite is sintered from high temperature and has very high carbon content of up to 99.5-99.9%, and is therefore very good as a lubricant.
While the conventional automotive oils cannot withstand the high temperatures, graphite powder can serve as lubricants in automotive engines. The commercially available graphite lubricants are a colloidal dispersion of billions of microscopic particles of graphite. When this is added to the crankcase of an engine, it works with the motor oil to reduce friction. It also penetrates effectively into areas where oil cannot reach, keeps oil from thickening, improves compression and helps energy consumption and fuel economy.