Definition
An aluminum alloy that does not have a thin protective layer of pure aluminum bonded to its surface. The alloy is exposed directly, so it must rely on other means -- such as anodizing, paint, or applied coatings -- for corrosion protection.
Plain English
A piece of aluminum alloy with no built-in pure-aluminum coating on the outside. Because the alloy itself is exposed, it has to be protected from corrosion by paint or another finish.
Context Anchor
Seen in aircraft sheet-metal maintenance, corrosion control, and material selection for repairs.
Derivation
Clad' comes from the Old English 'clathian,' meaning 'to clothe' or 'cover.' A clad alloy is 'clothed' in a layer of pure aluminum. 'Nonclad' simply means it is not clothed -- the alloy has no protective outer layer.
Why Pilots Care
Mechanics must apply separate corrosion protection to these alloys during repairs to avoid material degradation.
Intuition Check
Nonclad does not mean the part is simply unpainted or unfinished. It means the aluminum alloy has no thin protective aluminum layer bonded to its surface.
Example Sentence 1
The technician applied a primer and topcoat to the nonclad aluminum alloy panel before installing it on the fuselage.
Example Sentence 2
Inspectors examined the nonclad aluminum alloy skin for corrosion during the annual inspection.