About an anionic-radical concept of the lubrication mechanism of alcohols

To understand the chemical behaviour of alcohols in sliding contacts, especially in the boundary lubrication of aluminium-steel surfaces, the concept of a negative-ion-radical action mechanism of these compounds has been proposed. The lubrication model is based upon the ionization mechanism of alcohols caused by the action of exoelectrons. It has been shown that alcohols may produce ions and radical anions that react with a metal surface. This fact explains well the formation of a product of waxy appearance during sliding of an aluminium—steel system in the presence of fatty alcohols. The generation of radical and biradical anions elucidates the results that alcohol groups favour the production of an adherent coating composed of many components, including alkynes, dialkynes, alkenes and dialkenes, on sliding surfaces. Furthermore, the proposed action mechanism explains the chemisorption of alcohols on a clean aluminium surface prepared by cutting under high vacuum. Finally, this mechanism makes clear other findings related to pentaerythritol partial ester. The ester, which contains both hydroxyl and ester groups, reacts with the surface aluminium atoms to form amorphous substances such as aluminium complexes.