A NOVEL TECHNIQUE FOR READY DETERMINATION OF CATHODIC ACTIVITY OF INTERMETALLIC COMPOUNDS DURING CORROSION OF ALUMINUM

Electron transparent sections of aluminium and its alloys can be gener ated readily by ultramicrotomy, revealing matrix and second phase mate rial upon direct observation in the transmission electron microscope. Detailed examination of the sections, after retrieval from a water bat h located at the rear of the diamond knife used for sectioning, reveal s various textures in the aluminium matrix closely adjacent to second phase material of different compositions. Such texture, associated wit h different extents of Al(OH)3 development, result from local alkalini ty generated at cathodically active second phase material and its cons equent effects on the adjacent, filming aluminium matrix. This direct approach thus enables rapid assessment of the cathodic activity of var ious second phase material in aluminium alloys.