Which type of corrosion is caused by a crack or crevice that creates a potential difference and can be mitigated by controlling dissolved oxygen levels?

• A. Crevice corrosion
• B. Pitting corrosion
• C. Stress corrosion
• D. Microbiologic corrosion

Answer: (A)

Crevice corrosion occurs when a crack or crevice forms a restricted space where diffusion of oxygen is limited. This creates a differential aeration cell: the outside surface is exposed to higher oxygen, while the interior of the crevice becomes oxygen-depleted. The result is a local potential difference that makes the inside of the crevice anodic and prone to dissolution, while the exterior acts as the cathode. Reducing the dissolved oxygen level lowers this difference in oxygen concentration, weakening the electrochemical driving force and slowing or preventing the anodic dissolution inside the crevice. This is why controlling dissolved oxygen is an effective mitigation strategy. Pitting corrosion involves localized film breakdown, which is not driven by a crevice-induced potential difference; stress corrosion requires applied stress to promote crack growth; microbiologic corrosion stems from microbial activity.