5. JQ1 sample
5.1. IGSCC on electropolished surface
    After the LIST test, the electropolished surface was covered by an oxide film. Because the surface was electropolished, there were no deep scratches on the surface. The surface oxide was removed by a gentle polish using 1200 grit silicon paper and a fine polish using diamond paste. The sample was etched using 2% nital and observed using SEM. IGSCC was obvious as shown in Fig. 9. Stress corrosion cracks had initi- ated at ferrite grain boundaries and had grown to a size of several grains. Not all grain boundaries were attacked, as would be expected if there was just intergranular corrosion. Thus it is concluded that there was intergranular stress corrosion cracking rather than just intergranular corrosion.
5.2. IGSCC observations on cross-section
    After surface observation, the sample was cross-sectioned using a slow speed saw. The cross section surface was polished using 220–1200 grit silicon paper and fine polished using diamond paste, and etched using 2% nital. A typical section is shown in Fig. 10. The surface was covered by an oxide film. Breaks in the oxide film corresponded to intergranular cracks. The cracks initiated at ferrite grain boundaries, and grew to a depth of below 10 mm. A layer of oxide film could be seen at the sample surface, but not at the surface of the cracks.