What does the term Alclad mean?

• A. Sheets that consist of an aluminium alloy core coated with a layer of pure aluminium on both sides to a depth of approximately 1.5% to 5% of the total sheet thickness.
• B. A coating of warm-colored lacquer applied to aluminum surfaces.
• C. An alloy of aluminum and magnesium used in aircraft skins.
• D. A surface treatment that increases hardness of aluminum.

Answer: (A)

Alclad refers to aluminum-clad sheet metal: a core aluminum alloy sheet with a thin layer of pure aluminum on both faces. Those outer pure aluminum layers protect the weaker or more corrosion-susceptible alloy core from corrosion, while the core provides the needed strength for structural use. The clad layers are a small fraction of the total thickness, typically around a few percent, which keeps the overall sheet still strong and workable. So the definition describes the metal structure rather than a coating, a different alloy, or a surface hardening treatment.

The other ideas aren’t right because a lacquer coating is a decorative/ protective paint, not a metal cladding; an aluminum-magnesium alloy is a specific alloy, not a clad sheet; and a surface treatment that increases hardness is a processing step, not the layered clad construction.