On the surface acid-base properties of titanium sheets

Metals are usually covered by a thin metal oxide. Surface acid-base reactiv ity of this surface layer is still an open problem. In this work, this prob lem has been approached by wettability measurements and by chemical reactiv ity on titanium sheets. Wettability is an average surface property measured on a macroscopic scale. Chemical reactivity, which depends on surface site s, has been explored by adsorption of basic and acid molecules, acting as p robes, and has been subsequently analysed by XPS. Both analysis suggest tha t titanium sheets show basic reactivity. A comparison is made with the reac tivity of a thermally oxidised specimen where the thick oxide layer produce d showed a weak acid reactivity. Surface reactivity of titanium sheets is s uggested to depend on the oxide thickness. (C) 2000 Elsevier Science B.V. A ll rights reserved.