Unlike general corrosion, which occurs at discrete sites on a metal surface?

• A. Uniform corrosion
• B. Localized corrosion
• C. Galvanic corrosion
• D. Intergranular corrosion

Answer: (B)

Localized corrosion refers to attack that concentrates in small, discrete spots on the surface—pits, crevices, or inclusions—while the rest of the surface remains relatively intact. This contrasts with uniform corrosion, which progresses evenly across the entire exposed area. The reason this pattern fits is that a few weak points or local electrochemical cells drive most of the material loss, so the damage shows up as isolated areas rather than a blanket thinning.

Galvanic corrosion is driven by an electrical potential difference between two metals in contact, causing preferential attack at the anodic metal; intergranular corrosion is a specific form of localized attack along grain boundaries. Both are types of localized attack, but the simplest and most general description for a pattern that occurs at discrete sites is localized corrosion.