Examination of surface films on aluminium and its alloys by low-voltage scanning and scanning transmission electron microscopy

The potential of low-voltage, high-resolution scanning and scanning transmission electron microscopy (SEM/STEM) for morphological characterization of various surface insulating films on aluminium and its alloys has been assessed by examination of porous anodic films, barrier anodic films and corrosion product layers. The characterization shows clearly the value of the approaches, particularly the ability to image directly fine details of appropriately-prepared aluminium surfaces that have usually required examination by transmission electron microscopy (TEM). Such ready characterization assists mechanistic understanding of the contributions of the macroscopic surface and flaws or second phase to the filming and corrosion processes. Further, the approaches are applicable to other materials where such understanding was limited by the sample preparation routes available for TEM.