An Understanding of How Lubricating Systems Work Is Crucial to the Selection of a Lubricant for a Particular Application

An understanding of how lubricating systems work is crucial to the selection of a lubricant for a particular application. This essay could be summarized in one sentence: lubricants provide a protective film that separates the two rubbing surfaces and reduces the level of friction in the two rubbing surfaces.

         Any surface contains irregularities, even when polished to a mirror finish. These irregularities may not be visible, except under a microscope. When two highly-polished surfaces are brought gently together, only some points on the surfaces will make contact. These contacts will be brought closer together when a force is applied at right angles to the surfaces (this force is referred to as a ‘normal load, and the number of contact points will increase If a protective film were present on each of the surfaces, the surfaces could be separated The protective film must adhere to each surface in order not to be sheared off or pushed aside by the movement of the surfaces, particularly under a load. The most commonly available lubricants today are manufactured from petroleum. A typical lubricant molecule consists of a long chain of carbon and hydrogen atoms; called alkane .An oil usually has between 15 and 20 carbon atoms. A grease has between 20 and 25 carbon atoms. The hydrogen atoms form very weak bonds with the surfaces. In the cases of brass and steel, metals consist of atomic nuclei surrounded by a sea of electrons. The hydrogen atoms are bonded to the carbon atoms by a pair of shared electrons, which face the carbon atoms: since there are no electrons on the other side of each hydrogen atom, the other side has a slightly positive charge because of the hydrogen nucleus. This positive charge attracts the hydrogen atoms to the sea of electrons of the metals. While the bonding is very weak, the total bonding caused by a large number of hydrogen atoms in a long carbon chain is considerably greater than in a short carbon chain. A shorter carbon chain...