1.5.4 Pitting Corrosion Localized attack in an otherwise resistant surface produces pitting corrosion. The pits may be deep, shallow, or undercut, as shown schematically in Figure 1 The stainless steels and nickel alloys with chromium depend on a passive film for cor rosion resistance and are especially susceptible to pitting by local breakdown of the film at isolated sites. A deep pit causing wall penetration and leaking is shown in Figure 1.9.