The heats of adsorption of various surface active substances from n-heptane and benzene onto iron oxides and iron sulfide were measured using flow microcalorimeter. The relation between their chemical structures and anti-wear properties was investigated.
The anti-wear properties and heats of adsorption of pentaerythritol caprylates increased with an increase of the number of hydroxyl groups involved in an ester molecule. The lubricities and heats of adsorption of the alkyl derivatives of pyridine were dependent on the position of the substituent on the ring. Stearic acid formed the close packing adsorbed film to give the greater antiwear properties than isostearic acid. It was found that the films such as FeS and Fe₃O₄ formed on the metal surface under extreme pressure lubrication are very active for the adsorption of the polar compounds.