Definition
An aluminum alloy sheet that has a thin layer of pure aluminum bonded to one or both sides of a stronger aluminum alloy core. The pure aluminum surface protects the underlying alloy from corrosion, while the alloy core provides structural strength.
Plain English
A sandwich-style aluminum sheet: a strong alloy in the middle with a thin layer of pure, corrosion-resistant aluminum on the outside.
Context Anchor
Seen in airframe sheet-metal construction, corrosion inspection, and aircraft repair discussions.
Derivation
Clad comes from the Old English clathian, meaning to clothe or cover. The strong alloy core is literally clothed in a protective layer of pure aluminum.
Why Pilots Care
Strong aluminum alloys corrode quickly when exposed to the elements. Clad aluminum gives the airframe both the strength of an alloy and the corrosion resistance of pure aluminum. When repairing or drilling into clad sheet, the protective layer must be preserved or properly treated, or corrosion can begin underneath.
Intuition Check
Clad aluminum does not mean the whole piece is pure aluminum. It means a stronger aluminum material is covered with a thin protective aluminum layer.
Example Sentence 1
The wing skins on most light aircraft are made from clad aluminum to resist corrosion.
Example Sentence 2
During the preflight walk-around the pilot noticed a small scratch through the outer layer of the clad aluminum wing and reported it for inspection.