How does galvanic corrosion differ from uniform corrosion?

• A. Uniform corrosion occurs across a surface
• B. Galvanic corrosion is localized to one metal in contact with a more anodic partner; uniform corrosion occurs evenly across a surface
• C. Galvanic corrosion is always slower than uniform corrosion
• D. They are the same

Answer: (B)

Galvanic corrosion occurs when two dissimilar metals are in electrical contact in an electrolyte, causing a potential difference that drives current between the metals. The metal with the more negative (anodic) potential acts as the anode and corrodes, while the more noble (cathodic) metal is protected. This makes the corrosion localized to the anodic metal, often at the interface or in small, specific areas, and the rate can be high if a small anodic area is coupled to a large cathodic area.

Uniform corrosion, on the other hand, is a general chemical or electrochemical attack that affects the exposed surface evenly, thinning the metal across the entire area over time.

So the main distinction is localization caused by galvanic coupling versus uniform thinning from a uniform environment.