Studies of Surface Films Formed by Adsorption of Polar Organic Molecules on Activated Metal Surfaces

The investigation of adsorption has been a valuable aid in under­ standing the properties of metal surfaces. The surface of a metal differs from the interior of the material due to unsatisfied valence forces which impart an affinity for adsorbed materials. This high sur­face energy is illustrated by the fact that when two clean metal sur­faces are placed in contact, that is, when there is no intervening adsorbed film, cold welding results. The resulting bond is equivalent to the bonding in the rest of the metal. This has been demonstrated by Bowden and Young,l who showed that mere contact of iron, nickel, and platinum surfaces, which had been cleaned in vacuo, resulted in seizing and welding. Since adsorbed films destroy this property, adsorption is important in friction and lubrication phenomena.