What are the four stages of pitting?

• A. Initiation, propagation, termination, reinitiation
• B. Initiation, propagation, reinitiation, termination
• C. Initiation, termination, propagation, reinitiation
• D. Activation, propagation, termination, reinitiation

Answer: (C)

Pitting corrosion develops in cycles where a tiny defect becomes an initiation site, then growth can pause before it resumes, and new pits can form at other sites as conditions stay aggressive.

After initiation, the local film can redeposit and shield the metal again (a termination of growth), or the local environment can become depleted of oxidants, temporarily halting further dissolution. When conditions shift back to favor attack—due to changes in chemistry, chloride concentration, or film breakdown— propagation resumes and the pit deepens. As the surface remains damaged, new initiation sites can become active or dormant pits can reawaken, which is described as reinitiation.

This sequence captures how a pit can start, briefly stop growing, continue to deepen, and then new pits can begin as the environment remains hostile.