Which of the listed conditions is NOT one of the requirements for corrosion to occur?

• A. The presence of an electrolyte
• B. Electrical contact between anodic and cathodic areas
• C. The presence of a passive oxide film
• D. Moisture presence

Answer: (C)

Corrosion is an electrochemical process that needs three things to happen: an electrolyte that allows ions to move, electrical contact between an anodic area and a cathodic area so electrons can flow, and a moist or aqueous environment to support the chemical reactions. The presence of a passive oxide film, however, is not something required for corrosion to occur; in fact, it often blocks the reaction. That protective film acts as a barrier, slowing or preventing electron transfer and oxidation. When such a film is intact, corrosion is greatly reduced or stopped; when it’s damaged, corrosion can resume. So the passive oxide film is not a necessary condition for corrosion.