Pitting occurs at random pits; location cannot be predicted.

• A. Pitting occurs at random pits; location cannot be predicted
• B. Pitting occurs uniformly across surfaces
• C. Pitting cannot occur in aluminum
• D. Pitting is always easy to detect

Answer: (A)

Pitting is a localized form of corrosion that starts where the protective oxide film on the metal breaks down at a tiny, discrete spot. In environments with aggressive ions like chlorides, this film can be damaged at micro-sites such as inclusions, grain boundaries, or surface defects. Because many potential initiation sites exist and the exact triggering conditions are uneven and stochastic, pits form at unpredictable, random locations rather than spreading uniformly across the surface.

That’s why the idea that pits appear uniformly across the surface is not correct—pitting does not attack broadly and evenly. It can occur in aluminum too, so saying pitting cannot occur in aluminum is inaccurate. And pits aren’t always easy to detect; some can be very small or hidden beneath surface features, requiring careful inspection to reveal.

Thus, the description that pits form at random locations with unpredictable placement best captures how pitting behaves.