Pitting isolated

The early stage erosion surface of material SiC-C resulting from SiC erosion at 90° impact is shown in Fig. 20.9. A few isolated pits similar to those shown in Fig. 20.9(a), marked by arrows, were found in these regions. Interestingly, detailed examination revealed that damage features associated with individual impact sites were quite different. In the impact crater marked... 

Figures 5.6-5.9 correspond to coupon 1100/77. Figure 5.6 shows the corrosion produced inside the square zone covered by a Teflon separator. Figure 5.7 shows the massive pitting that can be encountered inside, at a higher magnification. Figures 5.8 and 5.9 show the cross-section metallography of one of the isolated pits encountered that were associated with dust particles. Figures 5.10-5.12 show the attack affecting sample 6063/64 inside the artificial crevice between coupons 6063/63 and 64, at three different...

Single 1100 77 Top 95% of surface stained brown, with several isolated pits. Three squared sections that were in contact with the Teflon separators and the central portion, where the A1 support FRL-027-14 was located, show signs of crevice corrosion, with white deposits... 

Single 6061 69 Top Dark and white stains mainly in the central part (contact with alumina). Small isolated pits... 

By assembling these technologies, isolated pits of 20 nm-diameter at 30 nm-pitch were successfully written on a storage disk, corresponding to a storage density of 1.5 Tb in.(Fig. 1.4). These technical developments realized a storage density... 

Isolated pitting—Pits that stand alone with unaffected metal between pits. Isolated pits of small diameter and shallow depth do not weaken the cylinder. (See Fig. 10-3.)... 

Line corrosion—Pits connected to others in a narrow band or line. This condition is more serious than isolated pitting. (See Fig. 10-4.)... 

A cylinder must be condemned when the remaining wall thickness in an area having isolated pitting is less than one-third of the original minimum allowable wall thickness. 

Unlike uniform corrosion, the intensity and rate of pitting corrosion can be assessed neither by determining the mass loss, nor by measuring released hydrogen. In fact, these measurements do not make sense because a very deep and isolated pit results only in a small mass loss, whereas a very large number of superficial pits can lead to a larger mass loss. 

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