Pits develop at weak spots in the surface film and at sites where self repair will occur.

• A. True
• B. False: Pits develop at weak spots in the surface film and at sites where self repair will NOT occur.
• C. False: Pits do not form at weak spots
• D. False: Pits form only under high temperature

Answer: (B)

Pitting corrosion starts where the protective surface film is locally weakened or damaged and cannot re-form quickly enough. These weak spots—such as scratches, inclusions, grain boundaries, or other defects—become anodic and initiate a pit. Once a pit begins, the environment inside becomes aggressive (acidic, chloride-rich), which impedes repassivation, so the pit can continue to grow while the surrounding surface stays protected. Therefore pits develop at weak spots in the surface film and at sites where self repair will NOT occur. If self repair were effective, repassivation would seal the defect and pit growth would be arrested.