List three common corrosion mechanisms affecting reactor materials.

• A. General (uniform) corrosion, pitting corrosion, and stress corrosion cracking (including IGSCC and IASCC).
• B. Erosion, galvanic rusting, photochemical corrosion.
• C. Oxidation, sulfidation, carburization.
• D. Crevice corrosion, intergranular corrosion, dealloying.

Answer: (A)

In reactor materials, you see three main ways corrosion manifests: general (uniform) corrosion, localized pitting, and cracking caused by the combination of tensile stress and a corrosive environment. General corrosion wears away the metal evenly over the surface as it dissolves in the coolant, influenced by temperature and chemistry. Pitting corrosion is when small spots of the protective film fail, creating pits that can become deep and penetrate the metal even with little overall loss. Stress corrosion cracking arises when a material under tensile stress is exposed to a corrosive medium, causing cracks to form and grow; in reactors this is especially significant for stainless steels and nickel-based alloys, with irradiation contributing to susceptibility in forms known as IGSCC and IASCC. These three mechanisms are the most representative and impactful for reactor materials, guiding how we select materials and control water chemistry. Other listed processes describe specific or less common phenomena (like erosion, photochemical effects, or carburization/sulfidation) that are not the primary corrosion modes you'll typically manage in reactor service.