IN order to discuss the manner in which colloidal graphite aids lubrication it is necessary to consider a piece of metal, the surface of which has been recently finished by some machining process. A material is only held together by reason of the attraction that the atoms of which the material is composed have for each other. In the body of the material each atom is surrounded by several other atoms to which it is attracted, but it cannot move under the influence of these attractions, because they balance. The atom at the surface of metal, however, has attracting atoms on the material side only; consequently there is a tendency for such an atom to be pulled inwards. The state of stress produced in this way is known as surface tension. This explanation could perhaps be better followed by picturing the atomic structure of a material in which two atoms only go to form the molecule, as in salt, where each atom of chlorine has its corresponding or companion atom of sodium, as pictured in Fig. 1.
Higinbotham, H. (1935), "Colloidal Graphite in Oils: An Institution of Automobile Engineers Paper on this Substance as an Adjunct Lubricant", Aircraft Engineering and Aerospace Technology, Vol. 7 No. 4, pp. 95-98. https://doi.org/10.1108/eb029924
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