Which statement best describes general (uniform) corrosion?

• A. General (uniform) corrosion is uniform material loss across a metal surface.
• B. Pitting corrosion forms discrete pits.
• C. SCC is always transgranular.
• D. Erosion is caused by chemical attack.

Answer: (A)

General uniform corrosion means the metal surface is attacked more or less evenly, leading to material loss that is spread across the entire exposed area rather than localized spots. This even thinning happens because the electrochemical reactions occur fairly uniformly on the surface, so the entire surface wears away at a similar rate. That’s why the statement that best describes general corrosion is that it results in uniform material loss across a metal surface.

Pitting corrosion, by contrast, creates discrete pits rather than a smooth, even thinning, so it isn’t uniform. Stress corrosion cracking can occur in various modes and is not restricted to being transgranular, so it isn’t described as always transgranular. Erosion is mainly a mechanical process driven by fluid flow removing material, not a chemical attack; erosion- corrosion is a different combined phenomenon, but erosion alone isn’t chemical corrosion.