Mobility of lithium ions in anodic alumina formed on an Al–Li alloy

The mobility of lithium species in the barrier anodic film formed on an Al-3 at% Li alloy in ammonium pentaborate electrolyte has been determined from measurements of film composition by glow discharge optical emission spectroscopy and elastic recoil detection analysis. The results reveal the presence of lithium species throughout the thickness of the anodic film, with a reduced amount of lithium in the film compared with that in the alloy. The level of reduction in lithium content indicates that lithium species migrate outward about eight times faster than Al 3+ ions. The lithium species are lost to the electrolyte on reaching the film/electrolyte interface, leading to a slight loss in the eAciency of film growth. In contrast, aluminium species are retained within the film, as revealed by the distribution of boron in the outer 040% of the film thickness. Determination of hydrogen profiles indicates insignificant amounts of hydrogen in the film. # 2000 Elsevier Science Ltd. All rights reserved.