Transmission electron microscopy of plan and sectional views of porous
anodic films formed on an Al-1.86%Cu alloy in sulphuric acid have rev
ealed the general and local processes occurring during anodic oxidatio
n of the alloy matrix and theta' platelets. In particular, the latter
give rise to oxygen generation, film cracking, platelet dissolution an
d extra porosity in the porous film before re-initiation of anodic oxi
dation of the matrix proceeds. (C) 1997 Elsevier Science Ltd.