Tribocatalysis reaction during antiwear synergism between borates and Sn(IV) compounds in boundary lubrication

The combination of an oil-soluble Sn(IV) compound such as dibutyl tin dilaurate and organic borates gave better antiwear protection to an oil than either component separately. The surface examination of the rubbing zone indicated that the atomic concentration of tin produced on the boundary layers by such combinations was greater than those without borates. Based on this, an antiwear synergistic mechanism can be postulated in which borates with electron-deficient p orbits in boron catalyse the triboreduction of Sn(IV) compounds on rubbing surfaces.