What effect does contact between dissimilar metals in the presence of moisture have on aircraft components?

• A. Accelerates galvanic corrosion
• B. Improves conductivity
• C. Reduces corrosion
• D. Prevents rust

Answer: (A)

When two different metals touch in the presence of moisture, they form a galvanic cell. The moisture acts as an electrolyte, allowing ions to move between the metals. The metal that is more anodic (less noble) will corrode faster, while the more cathodic metal is relatively protected. So the touching dissimilar metals accelerates corrosion of the anodic metal on aircraft components. This is why isolation, compatible material choices, protective coatings, or insulating barriers are used to prevent such contact. The other options don’t fit because moisture doesn’t purposefully improve conductivity, corrosion isn’t reduced, and “rust” is specific to iron; it doesn’t describe the general effect of dissimilar metals in aviation alloys.