A pit may terminate due to which of the following?

• A. Increased internal resistance of the local cell caused by filling with corrosion products, filming of the cathode, etc.
• B. Lower ambient temperature
• C. Higher local oxygen concentration
• D. Improved coating quality at the pit

Answer: (B)

Lower ambient temperature slows the electrochemical reactions and the diffusion of ions that drive pit growth. When the temperature drops, both the rate of metal dissolution inside the pit and the transport of corrosive species to and from the pit mouth decrease, reducing the driving force for continued attack. Protective films are more likely to reform or persist under cooler conditions, allowing the pit to repassivate and stop progressing.

Other factors don’t as reliably cause termination across common scenarios. Increased buildup of corrosion products can hinder growth but isn’t as universally effective at stopping a pit. A higher local oxygen concentration tends to keep the cathodic reaction going and can support continued corrosion. Improved coating quality at the pit reduces ingress of corrosive species but doesn’t inherently explain why an existing pit would terminate unless temperature effects are also present.