Heat of Preferential Adsorption of Surfactants on Porous Solids and Its Relation to Wear of Sliding Steel Surfaces

Abstract

A description is given of a method for the determination of the heats of preferential adsorption of various wear reducing agents, including lubricating oil fractions, on different types of solid surfaces covered with either n-heptane or benzene. The surfaces studied are those of silica gel, alumina, activated carbon, and iron. A proportion of the agents is adsorbed from the solutions on the surfaces, the process being accompanied by a heat effect. This heat effect is examined in relation to the wear produced by the lubricants in the Four Ball Machine operated under different loads for 60 min intervals. An attempt is then made to correlate the wear reduction of sliding steel surfaces and the heats of preferential adsorption of the lubricants from two different hydrocarbons on selected solids possessing high specific areas. From the results obtained it is concluded that the heats of adsorption of the lubricant solutions in benzene on iron, wetted with the same solvent, offer the best correlation with their wear reducing action determined by the Four Ball Machine. In general the results indicate that the method used has a great potential use in the field of correlation between the heat of adsorptions and wear for many different combinations of rubbing surfaces and lubricants.