The application of ultramicrotomy to the electronoptical examination of surface films on aluminium

Ultramicrotomy has been used to produce thin sections of surface films on aluminium after different treatments and these have been examined by transmission electron microscopy. Films studied are those produced by electropolishing, outdoor exposure, a hydrothermal treatment, immersion in sodium hydroxide, a chemical conversion process, an a.c. treatment and cathodic polarization. Anodic films including porous and barrier-type films and the thick coating on a superplastic ZnAl alloy have been examined. It has been found that the application of ultramicrotomy enables observation of the thickness and morphology of both very thin and friable surface films on aluminium, and it is useful in the study of certain phenomena concerning thicker porous-type anodic films. Various novel features are visible that have not been observed previously, and it is apparent that ultramicrotomy may be used advantageously to examine surface films on aluminium.