FAA Aviation Mechanic Airframe (AMA)Airframe StructuresEasy
A technician inspecting a 2024-T3 aluminum wing skin notices a very thin layer of pure (unalloyed) aluminum bonded to the outer surface of the sheet. What is the primary purpose of this cladding layer?
- ATo reduce the overall weight of the skin panel
- BTo provide corrosion protection to the high-strength core alloy
- CTo increase the tensile strength of the sheet
- DTo improve rivet shear strength at fastener holes
Show answer & explanationAnswer & explanation
Correct answer: B. To provide corrosion protection to the high-strength core alloy
Alclad sheet consists of a high-strength aluminum alloy core coated with a thin layer of pure aluminum, which is much more corrosion resistant and sacrificially protects the core from corrosion. It does not add strength since pure aluminum is weaker than the alloy core.
Why the other options are wrong
- A. The cladding adds negligible weight and is not a weight-saving feature.
- C. Pure aluminum cladding is weaker, not stronger, than the alloy core.
- D. Cladding has no effect on rivet shear strength.
Alclad Aluminum
Aluminum alloy sheet with a thin coating of pure aluminum bonded to one or both surfaces for corrosion protection.
- Pure aluminum layer is anodic and sacrificially protects the alloy core
- Used extensively for aircraft skins (e.g., 2024, 7075 alloys)
- Cladding is soft and can be worn through by excessive polishing or sanding
Memory trick: Alclad = Aluminum's coat of armor