Pitting location cannot be predicted. True or false?

• A. True
• B. False
• C. It occurs only in stainless steel
• D. It is always visible

Answer: (A)

Pitting corrosion starts at tiny, localized defects in the protective film or at inclusions and stresses on the metal surface. Because these initiation sites depend on random, microscopic surface conditions and local chemistry (such as slight differences in oxygen access or chloride concentration), you can’t know in advance exactly where a pit will begin. That makes the location of pits unpredictable on a given component exposed to a corrosive environment.

So the statement is true: the exact spot where pitting will occur cannot be predicted. Note that pits aren’t exclusive to stainless steel; other metals can pit under chloride exposure, and pits may be too small or hidden to be seen initially.