| Abstract: | A wide range of literature hs been published in the period 1950–2000 concerning emerging concepts of the action mechanisms of boundary lubrication additives. Some aspects of these additives in terms of chemical nature, surface adsorption, surface film generation, thermal stability, thermodynamics of contact surfaces, and rise in surface temperature, as reported in this literature, are reviewed in the present paper. 1 Part I of this paper appeared in Lubrication Science, 16, 4 (2004) 405–19. It has been observed that the chemical constituents of boundary lubrication additives, particularly of organosulphur and organo‐sulphur‐phosphorus origin, are very complex in nature and no comprehensive details are readily available. Regarding action mechanisms, researchers have suggested different mechanisms for different conditions. However, information on the thermodynamics of surfaces and thermal stability of additives is not easily obtainable. Other details, such as the effect of sliding speed, operating load, surface roughness, and material design, are not covered here. Overall, the literature reveals that attempts to correlate additive characteristics with boundary lubrication activity have met with limited success, and efforts aimed at achieving ever‐increasing performance levels continue. In the first part, the authors examined the chemical nature of boundary lubrication additives, surface films, and surface temperature. In this second part, they look at thermal stability, and antiwear and extreme‐pressure activity. |
