A LOOK AT THE EFFECTS OF LUBRICANT ADDITIVES ON SURFACES 580111
This paper presents the results of an interference microscope study of the action of oil additives on metal surfaces in sliding contact and indicates that valuable information can be obtained from a study of the worn surface.
It is shown that the operation of engine cams and valve lifters on oils containing zinc dithiophosphate additives can result in an increase in the small-scale roughness of the lifter-foot surface over that obtained by operation of the same parts on oils which do not contain the additive. In addition, the development of this surface roughness is also influenced by operating time, stability and concentration of the additive, and composition of the contacting surfaces.
Although the mechanism involved is far from being completely understood, the increase in small-scale roughness is believed to result from a reaction of additive decomposition products and the surface.