ANODIC FILM FORMATION ON SPUTTER-DEPOSITED AMORPHOUS AL-ZR ALLOYS

The anodic oxidation of amorphous Al-32 at% Zr alloy films at high cur rent efficiency results in amorphous anodic films, comprising a mixtur e of Al2O3 and ZrO2 units, of uniform composition and thickness. The u se of an immobile xenon marker reveals that the films develop, under t he high field, at the alloy/film and film/electrolyte interfaces by th e inward transport of O2- and OH- ions and the outward transport of ca tions respectively. This mechanism is typical of growth of amorphous a nodic films involving the cooperative transport of cations and anions. The total transport number of cations is about 0.35. Zirconium and al uminium are incorporated into the anodic films, in their alloy proport ions, without the development of significant enrichments or depletions of zirconium at the alloy/film interface. Zr4+ ions, which are immobi le in the usual crystalline anodic zirconia, migrate outwards at about the same rate as Al3+ ions. Boron species, incorporated into the film s from the electrolyte, are immobile and are distributed uniformly in the film material formed at the film/electrolyte interface by outward migration of cations.