Explain the difference between dry and wet corrosion on aluminum components.

• A. Dry corrosion forms oxide in air
• B. Wet corrosion occurs only in vacuum
• C. Dry corrosion forms oxide when exposed to air; wet corrosion occurs in the presence of moisture and electrolytes
• D. Dry corrosion is the same as wet corrosion

Answer: (C)

Dry corrosion happens when aluminum is exposed to air with little or no moisture; the metal reacts with oxygen to form a surface oxide, which tends to grow slowly and act as a protective layer, keeping the damage relatively uniform in dry conditions. Wet corrosion, on the other hand, requires moisture and an electrolyte (like water with dissolved salts); the protective oxide film becomes part of an electrochemical cell, allowing anodic dissolution at exposed areas while a cathodic reaction occurs somewhere else. This accelerates corrosion and often leads to localized damage such as pitting or crevice corrosion, especially with chlorides or other ions present. So the key difference is the environment and mechanism: dry corrosion is oxidation in air forming a protective oxide, while wet corrosion is electrochemical attack in the presence of moisture and electrolytes.