Rates of uniform corrosion of aluminum can be very high in which environments?

• A. Neutral
• B. Alkaline
• C. Acidic
• D. Saline

Answer: (B)

Aluminum’s surface is protected by a thin oxide film that slows down corrosion in many environments. In neutral or mildly acidic environments, this film stays relatively stable, so uniform corrosion remains slow. In alkaline environments, however, the oxide layer is not stable and reacts to form soluble aluminate species. This dissolves the protective barrier and leaves new aluminum exposed to the environment, allowing the metal to corrode uniformly across the surface at a high rate. Saline environments tend to promote localized attack (pitting) rather than uniform dissolution because chloride ions disrupt the film at specific spots rather than across the whole surface. So, the high rates of uniform corrosion occur in alkaline environments.