FIG. 1. FIB secondary electron image (SEI) of the terminus of grain boundary corrosion (which appears black as it is an insulator) in a Ni-based alloy. Field of view = 80mm.

FIG. 2. FIB secondary ion image (SII) of the region shown in Figure 1. Oxygen enhanced ionization yield increases the signal from the corroded regions making them appear white.

FIG. 3. FIB SII after a thin protective layer of FIB tungsten is deposited over the region of interest. This tungsten also serves as a marker of the original surface. FOV = 80 mm.

FIGs. 4 & 5. Top and off-axis views (FIB SEI) of the "inverted barn" milled free of the surrounding material. A small support (top right) holds the barn in place until final trimming just prior to lift-out. The region to be removed is 25mm x 20mm at its base which is still covered by a protective tungsten coating.

FIG. 6. FIB SEI of the "barn" glued down on the carrier, ready for thinning to electron transparency.

FIG. 7. TEM BF image (originally 1,500X) of the final specimen mounted on the carrier. Compare to FIGs. 2 & 3.

FIG. 8. TEM BF image (originally 3,810X) of the tip of the corrosion and the unattacked portion of the g.b.