The essential facts
Pitting perforates equipment whose average wall thickness looks healthy — the deepest pit, not the mean loss, governs failure. Passive-film alloys (stainless steels, aluminum) are the classic victims, chlorides the classic agent, and stagnation, deposits and crevices the classic accelerators. Inspection matters: averaging thickness grids miss narrow pits between measurement points, so where pitting is credible, technique and coverage must be chosen for localized attack.
Related decisions
Alloy selection against pitting is screened with PREN; repair of pitted equipment typically means pit filling and resurfacing with engineered polymer systems once the mechanism is arrested, plus a lining where the service warrants it. The full mechanism — initiation, the self-acidifying pit, and the defenses that work — is in the parent article below.